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-rw-r--r--tvix/Cargo.lock33
-rw-r--r--tvix/Cargo.nix147
-rw-r--r--tvix/Cargo.toml1
-rw-r--r--tvix/castore/Cargo.toml42
-rw-r--r--tvix/castore/build.rs38
-rw-r--r--tvix/castore/default.nix5
-rw-r--r--tvix/castore/protos/LICENSE21
-rw-r--r--tvix/castore/protos/castore.go (renamed from tvix/store/protos/castore.go)2
-rw-r--r--tvix/castore/protos/castore.pb.go580
-rw-r--r--tvix/castore/protos/castore.proto (renamed from tvix/store/protos/castore.proto)14
-rw-r--r--tvix/castore/protos/castore_test.go (renamed from tvix/store/protos/castore_test.go)140
-rw-r--r--tvix/castore/protos/go.mod19
-rw-r--r--tvix/castore/protos/go.sum96
-rw-r--r--tvix/castore/protos/rpc_blobstore.pb.go (renamed from tvix/store/protos/rpc_blobstore.pb.go)178
-rw-r--r--tvix/castore/protos/rpc_blobstore.proto (renamed from tvix/store/protos/rpc_blobstore.proto)4
-rw-r--r--tvix/castore/protos/rpc_blobstore_grpc.pb.go (renamed from tvix/store/protos/rpc_blobstore_grpc.pb.go)14
-rw-r--r--tvix/castore/protos/rpc_directory.pb.go273
-rw-r--r--tvix/castore/protos/rpc_directory.proto (renamed from tvix/store/protos/rpc_directory.proto)6
-rw-r--r--tvix/castore/protos/rpc_directory_grpc.pb.go (renamed from tvix/store/protos/rpc_directory_grpc.pb.go)12
-rw-r--r--tvix/castore/src/blobservice/from_addr.rs (renamed from tvix/store/src/blobservice/from_addr.rs)0
-rw-r--r--tvix/castore/src/blobservice/grpc.rs (renamed from tvix/store/src/blobservice/grpc.rs)2
-rw-r--r--tvix/castore/src/blobservice/memory.rs (renamed from tvix/store/src/blobservice/memory.rs)0
-rw-r--r--tvix/castore/src/blobservice/mod.rs (renamed from tvix/store/src/blobservice/mod.rs)0
-rw-r--r--tvix/castore/src/blobservice/naive_seeker.rs (renamed from tvix/store/src/blobservice/naive_seeker.rs)0
-rw-r--r--tvix/castore/src/blobservice/sled.rs (renamed from tvix/store/src/blobservice/sled.rs)0
-rw-r--r--tvix/castore/src/blobservice/tests.rs (renamed from tvix/store/src/blobservice/tests.rs)2
-rw-r--r--tvix/castore/src/digests.rs (renamed from tvix/store/src/digests.rs)0
-rw-r--r--tvix/castore/src/directoryservice/from_addr.rs (renamed from tvix/store/src/directoryservice/from_addr.rs)0
-rw-r--r--tvix/castore/src/directoryservice/grpc.rs (renamed from tvix/store/src/directoryservice/grpc.rs)6
-rw-r--r--tvix/castore/src/directoryservice/memory.rs (renamed from tvix/store/src/directoryservice/memory.rs)0
-rw-r--r--tvix/castore/src/directoryservice/mod.rs (renamed from tvix/store/src/directoryservice/mod.rs)0
-rw-r--r--tvix/castore/src/directoryservice/sled.rs (renamed from tvix/store/src/directoryservice/sled.rs)0
-rw-r--r--tvix/castore/src/directoryservice/traverse.rs (renamed from tvix/store/src/directoryservice/traverse.rs)6
-rw-r--r--tvix/castore/src/directoryservice/utils.rs (renamed from tvix/store/src/directoryservice/utils.rs)0
-rw-r--r--tvix/castore/src/errors.rs (renamed from tvix/store/src/errors.rs)0
-rw-r--r--tvix/castore/src/fixtures.rs95
-rw-r--r--tvix/castore/src/import.rs (renamed from tvix/store/src/import.rs)48
-rw-r--r--tvix/castore/src/lib.rs15
-rw-r--r--tvix/castore/src/proto/grpc_blobservice_wrapper.rs (renamed from tvix/store/src/proto/grpc_blobservice_wrapper.rs)0
-rw-r--r--tvix/castore/src/proto/grpc_directoryservice_wrapper.rs (renamed from tvix/store/src/proto/grpc_directoryservice_wrapper.rs)0
-rw-r--r--tvix/castore/src/proto/mod.rs279
-rw-r--r--tvix/castore/src/proto/tests/directory.rs (renamed from tvix/store/src/proto/tests/directory.rs)0
-rw-r--r--tvix/castore/src/proto/tests/directory_nodes_iterator.rs (renamed from tvix/store/src/proto/tests/directory_nodes_iterator.rs)0
-rw-r--r--tvix/castore/src/proto/tests/grpc_blobservice.rs (renamed from tvix/store/src/proto/tests/grpc_blobservice.rs)4
-rw-r--r--tvix/castore/src/proto/tests/grpc_directoryservice.rs (renamed from tvix/store/src/proto/tests/grpc_directoryservice.rs)4
-rw-r--r--tvix/castore/src/proto/tests/mod.rs4
-rw-r--r--tvix/castore/src/tests/import.rs (renamed from tvix/store/src/tests/import.rs)11
-rw-r--r--tvix/castore/src/tests/mod.rs1
-rw-r--r--tvix/castore/src/utils.rs19
-rw-r--r--tvix/cli/Cargo.toml1
-rw-r--r--tvix/cli/src/main.rs4
-rw-r--r--tvix/cli/src/tvix_store_io.rs11
-rw-r--r--tvix/default.nix34
-rw-r--r--tvix/proto/default.nix22
-rw-r--r--tvix/store/Cargo.toml13
-rw-r--r--tvix/store/README.md14
-rw-r--r--tvix/store/build.rs4
-rw-r--r--tvix/store/protos/castore.pb.go450
-rw-r--r--tvix/store/protos/default.nix16
-rw-r--r--tvix/store/protos/pathinfo.pb.go233
-rw-r--r--tvix/store/protos/pathinfo.proto12
-rw-r--r--tvix/store/protos/rpc_directory.pb.go271
-rw-r--r--tvix/store/protos/rpc_pathinfo.pb.go74
-rw-r--r--tvix/store/protos/rpc_pathinfo.proto3
-rw-r--r--tvix/store/protos/rpc_pathinfo_grpc.pb.go13
-rw-r--r--tvix/store/src/bin/tvix-store.rs23
-rw-r--r--tvix/store/src/fs/inode_tracker.rs30
-rw-r--r--tvix/store/src/fs/inodes.rs42
-rw-r--r--tvix/store/src/fs/mod.rs15
-rw-r--r--tvix/store/src/fs/tests.rs44
-rw-r--r--tvix/store/src/lib.rs9
-rw-r--r--tvix/store/src/nar/mod.rs7
-rw-r--r--tvix/store/src/nar/renderer.rs33
-rw-r--r--tvix/store/src/pathinfoservice/from_addr.rs15
-rw-r--r--tvix/store/src/pathinfoservice/grpc.rs45
-rw-r--r--tvix/store/src/pathinfoservice/memory.rs25
-rw-r--r--tvix/store/src/pathinfoservice/mod.rs19
-rw-r--r--tvix/store/src/pathinfoservice/sled.rs29
-rw-r--r--tvix/store/src/proto/grpc_pathinfoservice_wrapper.rs3
-rw-r--r--tvix/store/src/proto/mod.rs293
-rw-r--r--tvix/store/src/proto/tests/grpc_pathinfoservice.rs8
-rw-r--r--tvix/store/src/proto/tests/mod.rs4
-rw-r--r--tvix/store/src/proto/tests/pathinfo.rs76
-rw-r--r--tvix/store/src/tests/fixtures.rs85
-rw-r--r--tvix/store/src/tests/mod.rs1
-rw-r--r--tvix/store/src/tests/nar_renderer.rs20
-rw-r--r--tvix/store/src/tests/utils.rs16
87 files changed, 2306 insertions, 1832 deletions
diff --git a/tvix/Cargo.lock b/tvix/Cargo.lock
index ba0c4d9af87b..174c68d4d2d8 100644
--- a/tvix/Cargo.lock
+++ b/tvix/Cargo.lock
@@ -2731,6 +2731,37 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3528ecfd12c466c6f163363caf2d02a71161dd5e1cc6ae7b34207ea2d42d81ed"
 
 [[package]]
+name = "tvix-castore"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "async-stream",
+ "blake3",
+ "bytes",
+ "data-encoding",
+ "futures",
+ "lazy_static",
+ "pin-project-lite",
+ "prost",
+ "prost-build",
+ "sled",
+ "tempfile",
+ "test-case",
+ "thiserror",
+ "tokio",
+ "tokio-stream",
+ "tokio-util",
+ "tonic",
+ "tonic-build",
+ "tonic-mock",
+ "tonic-reflection",
+ "tower",
+ "tracing",
+ "url",
+ "walkdir",
+]
+
+[[package]]
 name = "tvix-cli"
 version = "0.1.0"
 dependencies = [
@@ -2742,6 +2773,7 @@ dependencies = [
  "thiserror",
  "tokio",
  "tracing",
+ "tvix-castore",
  "tvix-eval",
  "tvix-store",
  "wu-manber",
@@ -2832,6 +2864,7 @@ dependencies = [
  "tower",
  "tracing",
  "tracing-subscriber",
+ "tvix-castore",
  "url",
  "walkdir",
 ]
diff --git a/tvix/Cargo.nix b/tvix/Cargo.nix
index 947f8ab825e1..2f01a9473263 100644
--- a/tvix/Cargo.nix
+++ b/tvix/Cargo.nix
@@ -53,6 +53,16 @@ rec {
       # File a bug if you depend on any for non-debug work!
       debug = internal.debugCrate { inherit packageId; };
     };
+    "tvix-castore" = rec {
+      packageId = "tvix-castore";
+      build = internal.buildRustCrateWithFeatures {
+        packageId = "tvix-castore";
+      };
+
+      # Debug support which might change between releases.
+      # File a bug if you depend on any for non-debug work!
+      debug = internal.debugCrate { inherit packageId; };
+    };
     "tvix-cli" = rec {
       packageId = "tvix-cli";
       build = internal.buildRustCrateWithFeatures {
@@ -8115,6 +8125,135 @@ rec {
         ];
 
       };
+      "tvix-castore" = rec {
+        crateName = "tvix-castore";
+        version = "0.1.0";
+        edition = "2021";
+        # We can't filter paths with references in Nix 2.4
+        # See https://github.com/NixOS/nix/issues/5410
+        src =
+          if (lib.versionOlder builtins.nixVersion "2.4pre20211007")
+          then lib.cleanSourceWith { filter = sourceFilter; src = ./castore; }
+          else ./castore;
+        dependencies = [
+          {
+            name = "anyhow";
+            packageId = "anyhow";
+          }
+          {
+            name = "async-stream";
+            packageId = "async-stream";
+          }
+          {
+            name = "blake3";
+            packageId = "blake3";
+            features = [ "rayon" "std" ];
+          }
+          {
+            name = "bytes";
+            packageId = "bytes";
+          }
+          {
+            name = "data-encoding";
+            packageId = "data-encoding";
+          }
+          {
+            name = "futures";
+            packageId = "futures";
+          }
+          {
+            name = "lazy_static";
+            packageId = "lazy_static";
+          }
+          {
+            name = "pin-project-lite";
+            packageId = "pin-project-lite";
+          }
+          {
+            name = "prost";
+            packageId = "prost";
+          }
+          {
+            name = "sled";
+            packageId = "sled";
+            features = [ "compression" ];
+          }
+          {
+            name = "thiserror";
+            packageId = "thiserror";
+          }
+          {
+            name = "tokio";
+            packageId = "tokio";
+            features = [ "fs" "net" "rt-multi-thread" "signal" ];
+          }
+          {
+            name = "tokio-stream";
+            packageId = "tokio-stream";
+            features = [ "fs" "net" ];
+          }
+          {
+            name = "tokio-util";
+            packageId = "tokio-util";
+            features = [ "io" "io-util" ];
+          }
+          {
+            name = "tonic";
+            packageId = "tonic";
+          }
+          {
+            name = "tonic-reflection";
+            packageId = "tonic-reflection";
+            optional = true;
+          }
+          {
+            name = "tower";
+            packageId = "tower";
+          }
+          {
+            name = "tracing";
+            packageId = "tracing";
+          }
+          {
+            name = "url";
+            packageId = "url";
+          }
+          {
+            name = "walkdir";
+            packageId = "walkdir";
+          }
+        ];
+        buildDependencies = [
+          {
+            name = "prost-build";
+            packageId = "prost-build";
+          }
+          {
+            name = "tonic-build";
+            packageId = "tonic-build";
+          }
+        ];
+        devDependencies = [
+          {
+            name = "tempfile";
+            packageId = "tempfile";
+          }
+          {
+            name = "test-case";
+            packageId = "test-case";
+          }
+          {
+            name = "tonic-mock";
+            packageId = "tonic-mock";
+          }
+        ];
+        features = {
+          "default" = [ "reflection" ];
+          "reflection" = [ "tonic-reflection" ];
+          "tonic-reflection" = [ "dep:tonic-reflection" ];
+        };
+        resolvedDefaultFeatures = [ "default" "reflection" "tonic-reflection" ];
+      };
       "tvix-cli" = rec {
         crateName = "tvix-cli";
         version = "0.1.0";
@@ -8167,6 +8306,10 @@ rec {
             packageId = "tracing";
           }
           {
+            name = "tvix-castore";
+            packageId = "tvix-castore";
+          }
+          {
             name = "tvix-eval";
             packageId = "tvix-eval";
           }
@@ -8510,6 +8653,10 @@ rec {
             features = [ "json" ];
           }
           {
+            name = "tvix-castore";
+            packageId = "tvix-castore";
+          }
+          {
             name = "url";
             packageId = "url";
           }
diff --git a/tvix/Cargo.toml b/tvix/Cargo.toml
index 938364fc26b6..645aac362738 100644
--- a/tvix/Cargo.toml
+++ b/tvix/Cargo.toml
@@ -19,6 +19,7 @@
 resolver = "2"
 
 members = [
+  "castore",
   "cli",
   "eval",
   "eval/builtin-macros",
diff --git a/tvix/castore/Cargo.toml b/tvix/castore/Cargo.toml
new file mode 100644
index 000000000000..8bef5bb147bc
--- /dev/null
+++ b/tvix/castore/Cargo.toml
@@ -0,0 +1,42 @@
+[package]
+name = "tvix-castore"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1.0.68"
+async-stream = "0.3.5"
+blake3 = { version = "1.3.1", features = ["rayon", "std"] }
+bytes = "1.4.0"
+data-encoding = "2.3.3"
+futures = "0.3.28"
+lazy_static = "1.4.0"
+pin-project-lite = "0.2.13"
+prost = "0.11.2"
+sled = { version = "0.34.7", features = ["compression"] }
+thiserror = "1.0.38"
+tokio-stream = { version = "0.1.14", features = ["fs", "net"] }
+tokio-util = { version = "0.7.8", features = ["io", "io-util"] }
+tokio = { version = "1.28.0", features = ["fs", "net", "rt-multi-thread", "signal"] }
+tonic = "0.8.2"
+tower = "0.4.13"
+tracing = "0.1.37"
+url = "2.4.0"
+walkdir = "2.4.0"
+
+[dependencies.tonic-reflection]
+optional = true
+version = "0.5.0"
+
+[build-dependencies]
+prost-build = "0.11.2"
+tonic-build = "0.8.2"
+
+[dev-dependencies]
+test-case = "2.2.2"
+tempfile = "3.3.0"
+tonic-mock = { git = "https://github.com/brainrake/tonic-mock", branch = "bump-dependencies" }
+
+[features]
+default = ["reflection"]
+reflection = ["tonic-reflection"]
\ No newline at end of file
diff --git a/tvix/castore/build.rs b/tvix/castore/build.rs
new file mode 100644
index 000000000000..9f06c8833319
--- /dev/null
+++ b/tvix/castore/build.rs
@@ -0,0 +1,38 @@
+use std::io::Result;
+
+fn main() -> Result<()> {
+    #[allow(unused_mut)]
+    let mut builder = tonic_build::configure();
+
+    #[cfg(feature = "reflection")]
+    {
+        let out_dir = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
+        let descriptor_path = out_dir.join("tvix.castore.v1.bin");
+
+        builder = builder.file_descriptor_set_path(descriptor_path);
+    };
+
+    // https://github.com/hyperium/tonic/issues/908
+    let mut config = prost_build::Config::new();
+    config.bytes(["."]);
+
+    builder
+        .build_server(true)
+        .build_client(true)
+        .compile_with_config(
+            config,
+            &[
+                "tvix/castore/protos/castore.proto",
+                "tvix/castore/protos/rpc_blobstore.proto",
+                "tvix/castore/protos/rpc_directory.proto",
+            ],
+            // If we are in running `cargo build` manually, using `../..` works fine,
+            // but in case we run inside a nix build, we need to instead point PROTO_ROOT
+            // to a sparseTree containing that structure.
+            &[match std::env::var_os("PROTO_ROOT") {
+                Some(proto_root) => proto_root.to_str().unwrap().to_owned(),
+                None => "../..".to_string(),
+            }],
+        )?;
+    Ok(())
+}
diff --git a/tvix/castore/default.nix b/tvix/castore/default.nix
new file mode 100644
index 000000000000..09f6c0bea343
--- /dev/null
+++ b/tvix/castore/default.nix
@@ -0,0 +1,5 @@
+{ depot, pkgs, ... }:
+
+depot.tvix.crates.workspaceMembers.tvix-castore.build.override {
+  runTests = true;
+}
diff --git a/tvix/castore/protos/LICENSE b/tvix/castore/protos/LICENSE
new file mode 100644
index 000000000000..2034ada6fd9a
--- /dev/null
+++ b/tvix/castore/protos/LICENSE
@@ -0,0 +1,21 @@
+Copyright ยฉ The Tvix Authors
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+โ€œSoftwareโ€), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED โ€œAS ISโ€, WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
diff --git a/tvix/store/protos/castore.go b/tvix/castore/protos/castore.go
index 4ab7ab42887a..102ba4bff75d 100644
--- a/tvix/store/protos/castore.go
+++ b/tvix/castore/protos/castore.go
@@ -1,4 +1,4 @@
-package storev1
+package castorev1
 
 import (
 	"bytes"
diff --git a/tvix/castore/protos/castore.pb.go b/tvix/castore/protos/castore.pb.go
new file mode 100644
index 000000000000..5323d6c923a8
--- /dev/null
+++ b/tvix/castore/protos/castore.pb.go
@@ -0,0 +1,580 @@
+// SPDX-FileCopyrightText: edef <edef@unfathomable.blue>
+// SPDX-License-Identifier: OSL-3.0 OR MIT OR Apache-2.0
+
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.31.0
+// 	protoc        (unknown)
+// source: tvix/castore/protos/castore.proto
+
+package castorev1
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+// A Directory can contain Directory, File or Symlink nodes.
+// Each of these nodes have a name attribute, which is the basename in that directory
+// and node type specific attributes.
+// The name attribute:
+//   - MUST not contain slashes or null bytes
+//   - MUST not be '.' or '..'
+//   - MUST be unique across all three lists
+//
+// Elements in each list need to be lexicographically ordered by the name
+// attribute.
+type Directory struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	Directories []*DirectoryNode `protobuf:"bytes,1,rep,name=directories,proto3" json:"directories,omitempty"`
+	Files       []*FileNode      `protobuf:"bytes,2,rep,name=files,proto3" json:"files,omitempty"`
+	Symlinks    []*SymlinkNode   `protobuf:"bytes,3,rep,name=symlinks,proto3" json:"symlinks,omitempty"`
+}
+
+func (x *Directory) Reset() {
+	*x = Directory{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_castore_proto_msgTypes[0]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *Directory) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Directory) ProtoMessage() {}
+
+func (x *Directory) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_castore_proto_msgTypes[0]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use Directory.ProtoReflect.Descriptor instead.
+func (*Directory) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_castore_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *Directory) GetDirectories() []*DirectoryNode {
+	if x != nil {
+		return x.Directories
+	}
+	return nil
+}
+
+func (x *Directory) GetFiles() []*FileNode {
+	if x != nil {
+		return x.Files
+	}
+	return nil
+}
+
+func (x *Directory) GetSymlinks() []*SymlinkNode {
+	if x != nil {
+		return x.Symlinks
+	}
+	return nil
+}
+
+// A DirectoryNode represents a directory in a Directory.
+type DirectoryNode struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// The (base)name of the directory
+	Name []byte `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
+	// The blake3 hash of a Directory message, serialized in protobuf canonical form.
+	Digest []byte `protobuf:"bytes,2,opt,name=digest,proto3" json:"digest,omitempty"`
+	// Number of child elements in the Directory referred to by `digest`.
+	// Calculated by summing up the numbers of `directories`, `files` and
+	// `symlinks`, and for each directory, its size field. Used for inode
+	// number calculation.
+	// This field is precisely as verifiable as any other Merkle tree edge.
+	// Resolve `digest`, and you can compute it incrementally. Resolve the
+	// entire tree, and you can fully compute it from scratch.
+	// A credulous implementation won't reject an excessive size, but this is
+	// harmless: you'll have some ordinals without nodes. Undersizing is
+	// obvious and easy to reject: you won't have an ordinal for some nodes.
+	Size uint32 `protobuf:"varint,3,opt,name=size,proto3" json:"size,omitempty"`
+}
+
+func (x *DirectoryNode) Reset() {
+	*x = DirectoryNode{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_castore_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *DirectoryNode) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*DirectoryNode) ProtoMessage() {}
+
+func (x *DirectoryNode) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_castore_proto_msgTypes[1]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use DirectoryNode.ProtoReflect.Descriptor instead.
+func (*DirectoryNode) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_castore_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *DirectoryNode) GetName() []byte {
+	if x != nil {
+		return x.Name
+	}
+	return nil
+}
+
+func (x *DirectoryNode) GetDigest() []byte {
+	if x != nil {
+		return x.Digest
+	}
+	return nil
+}
+
+func (x *DirectoryNode) GetSize() uint32 {
+	if x != nil {
+		return x.Size
+	}
+	return 0
+}
+
+// A FileNode represents a regular or executable file in a Directory.
+type FileNode struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// The (base)name of the file
+	Name []byte `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
+	// The blake3 digest of the file contents
+	Digest []byte `protobuf:"bytes,2,opt,name=digest,proto3" json:"digest,omitempty"`
+	// The file content size
+	Size uint32 `protobuf:"varint,3,opt,name=size,proto3" json:"size,omitempty"`
+	// Whether the file is executable
+	Executable bool `protobuf:"varint,4,opt,name=executable,proto3" json:"executable,omitempty"`
+}
+
+func (x *FileNode) Reset() {
+	*x = FileNode{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_castore_proto_msgTypes[2]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *FileNode) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*FileNode) ProtoMessage() {}
+
+func (x *FileNode) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_castore_proto_msgTypes[2]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use FileNode.ProtoReflect.Descriptor instead.
+func (*FileNode) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_castore_proto_rawDescGZIP(), []int{2}
+}
+
+func (x *FileNode) GetName() []byte {
+	if x != nil {
+		return x.Name
+	}
+	return nil
+}
+
+func (x *FileNode) GetDigest() []byte {
+	if x != nil {
+		return x.Digest
+	}
+	return nil
+}
+
+func (x *FileNode) GetSize() uint32 {
+	if x != nil {
+		return x.Size
+	}
+	return 0
+}
+
+func (x *FileNode) GetExecutable() bool {
+	if x != nil {
+		return x.Executable
+	}
+	return false
+}
+
+// A SymlinkNode represents a symbolic link in a Directory.
+type SymlinkNode struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// The (base)name of the symlink
+	Name []byte `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
+	// The target of the symlink.
+	Target []byte `protobuf:"bytes,2,opt,name=target,proto3" json:"target,omitempty"`
+}
+
+func (x *SymlinkNode) Reset() {
+	*x = SymlinkNode{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_castore_proto_msgTypes[3]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *SymlinkNode) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*SymlinkNode) ProtoMessage() {}
+
+func (x *SymlinkNode) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_castore_proto_msgTypes[3]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use SymlinkNode.ProtoReflect.Descriptor instead.
+func (*SymlinkNode) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_castore_proto_rawDescGZIP(), []int{3}
+}
+
+func (x *SymlinkNode) GetName() []byte {
+	if x != nil {
+		return x.Name
+	}
+	return nil
+}
+
+func (x *SymlinkNode) GetTarget() []byte {
+	if x != nil {
+		return x.Target
+	}
+	return nil
+}
+
+// A Node is either a DirectoryNode, FileNode or SymlinkNode.
+type Node struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// Types that are assignable to Node:
+	//
+	//	*Node_Directory
+	//	*Node_File
+	//	*Node_Symlink
+	Node isNode_Node `protobuf_oneof:"node"`
+}
+
+func (x *Node) Reset() {
+	*x = Node{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_castore_proto_msgTypes[4]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *Node) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Node) ProtoMessage() {}
+
+func (x *Node) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_castore_proto_msgTypes[4]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use Node.ProtoReflect.Descriptor instead.
+func (*Node) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_castore_proto_rawDescGZIP(), []int{4}
+}
+
+func (m *Node) GetNode() isNode_Node {
+	if m != nil {
+		return m.Node
+	}
+	return nil
+}
+
+func (x *Node) GetDirectory() *DirectoryNode {
+	if x, ok := x.GetNode().(*Node_Directory); ok {
+		return x.Directory
+	}
+	return nil
+}
+
+func (x *Node) GetFile() *FileNode {
+	if x, ok := x.GetNode().(*Node_File); ok {
+		return x.File
+	}
+	return nil
+}
+
+func (x *Node) GetSymlink() *SymlinkNode {
+	if x, ok := x.GetNode().(*Node_Symlink); ok {
+		return x.Symlink
+	}
+	return nil
+}
+
+type isNode_Node interface {
+	isNode_Node()
+}
+
+type Node_Directory struct {
+	Directory *DirectoryNode `protobuf:"bytes,1,opt,name=directory,proto3,oneof"`
+}
+
+type Node_File struct {
+	File *FileNode `protobuf:"bytes,2,opt,name=file,proto3,oneof"`
+}
+
+type Node_Symlink struct {
+	Symlink *SymlinkNode `protobuf:"bytes,3,opt,name=symlink,proto3,oneof"`
+}
+
+func (*Node_Directory) isNode_Node() {}
+
+func (*Node_File) isNode_Node() {}
+
+func (*Node_Symlink) isNode_Node() {}
+
+var File_tvix_castore_protos_castore_proto protoreflect.FileDescriptor
+
+var file_tvix_castore_protos_castore_proto_rawDesc = []byte{
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+	0x31, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
+}
+
+var (
+	file_tvix_castore_protos_castore_proto_rawDescOnce sync.Once
+	file_tvix_castore_protos_castore_proto_rawDescData = file_tvix_castore_protos_castore_proto_rawDesc
+)
+
+func file_tvix_castore_protos_castore_proto_rawDescGZIP() []byte {
+	file_tvix_castore_protos_castore_proto_rawDescOnce.Do(func() {
+		file_tvix_castore_protos_castore_proto_rawDescData = protoimpl.X.CompressGZIP(file_tvix_castore_protos_castore_proto_rawDescData)
+	})
+	return file_tvix_castore_protos_castore_proto_rawDescData
+}
+
+var file_tvix_castore_protos_castore_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
+var file_tvix_castore_protos_castore_proto_goTypes = []interface{}{
+	(*Directory)(nil),     // 0: tvix.castore.v1.Directory
+	(*DirectoryNode)(nil), // 1: tvix.castore.v1.DirectoryNode
+	(*FileNode)(nil),      // 2: tvix.castore.v1.FileNode
+	(*SymlinkNode)(nil),   // 3: tvix.castore.v1.SymlinkNode
+	(*Node)(nil),          // 4: tvix.castore.v1.Node
+}
+var file_tvix_castore_protos_castore_proto_depIdxs = []int32{
+	1, // 0: tvix.castore.v1.Directory.directories:type_name -> tvix.castore.v1.DirectoryNode
+	2, // 1: tvix.castore.v1.Directory.files:type_name -> tvix.castore.v1.FileNode
+	3, // 2: tvix.castore.v1.Directory.symlinks:type_name -> tvix.castore.v1.SymlinkNode
+	1, // 3: tvix.castore.v1.Node.directory:type_name -> tvix.castore.v1.DirectoryNode
+	2, // 4: tvix.castore.v1.Node.file:type_name -> tvix.castore.v1.FileNode
+	3, // 5: tvix.castore.v1.Node.symlink:type_name -> tvix.castore.v1.SymlinkNode
+	6, // [6:6] is the sub-list for method output_type
+	6, // [6:6] is the sub-list for method input_type
+	6, // [6:6] is the sub-list for extension type_name
+	6, // [6:6] is the sub-list for extension extendee
+	0, // [0:6] is the sub-list for field type_name
+}
+
+func init() { file_tvix_castore_protos_castore_proto_init() }
+func file_tvix_castore_protos_castore_proto_init() {
+	if File_tvix_castore_protos_castore_proto != nil {
+		return
+	}
+	if !protoimpl.UnsafeEnabled {
+		file_tvix_castore_protos_castore_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*Directory); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_tvix_castore_protos_castore_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*DirectoryNode); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_tvix_castore_protos_castore_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*FileNode); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_tvix_castore_protos_castore_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*SymlinkNode); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_tvix_castore_protos_castore_proto_msgTypes[4].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*Node); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+	}
+	file_tvix_castore_protos_castore_proto_msgTypes[4].OneofWrappers = []interface{}{
+		(*Node_Directory)(nil),
+		(*Node_File)(nil),
+		(*Node_Symlink)(nil),
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: file_tvix_castore_protos_castore_proto_rawDesc,
+			NumEnums:      0,
+			NumMessages:   5,
+			NumExtensions: 0,
+			NumServices:   0,
+		},
+		GoTypes:           file_tvix_castore_protos_castore_proto_goTypes,
+		DependencyIndexes: file_tvix_castore_protos_castore_proto_depIdxs,
+		MessageInfos:      file_tvix_castore_protos_castore_proto_msgTypes,
+	}.Build()
+	File_tvix_castore_protos_castore_proto = out.File
+	file_tvix_castore_protos_castore_proto_rawDesc = nil
+	file_tvix_castore_protos_castore_proto_goTypes = nil
+	file_tvix_castore_protos_castore_proto_depIdxs = nil
+}
diff --git a/tvix/store/protos/castore.proto b/tvix/castore/protos/castore.proto
index 347815107198..d99df43857ac 100644
--- a/tvix/store/protos/castore.proto
+++ b/tvix/castore/protos/castore.proto
@@ -3,9 +3,9 @@
 
 syntax = "proto3";
 
-package tvix.store.v1;
+package tvix.castore.v1;
 
-option go_package = "code.tvl.fyi/tvix/store/protos;storev1";
+option go_package = "code.tvl.fyi/tvix/castore/protos;castorev1";
 
 // A Directory can contain Directory, File or Symlink nodes.
 // Each of these nodes have a name attribute, which is the basename in that directory
@@ -60,3 +60,13 @@ message SymlinkNode {
     // The target of the symlink.
     bytes target = 2;
 }
+
+// A Node is either a DirectoryNode, FileNode or SymlinkNode.
+message Node {
+    oneof node {
+        DirectoryNode directory = 1;
+        FileNode file = 2;
+        SymlinkNode symlink = 3;
+    }
+}
+
diff --git a/tvix/store/protos/castore_test.go b/tvix/castore/protos/castore_test.go
index 15a2554bbb57..958d399d76cc 100644
--- a/tvix/store/protos/castore_test.go
+++ b/tvix/castore/protos/castore_test.go
@@ -1,9 +1,9 @@
-package storev1_test
+package castorev1_test
 
 import (
 	"testing"
 
-	storev1pb "code.tvl.fyi/tvix/store/protos"
+	castorev1pb "code.tvl.fyi/tvix/castore/protos"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -17,63 +17,63 @@ var (
 
 func TestDirectorySize(t *testing.T) {
 	t.Run("empty", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{},
-			Files:       []*storev1pb.FileNode{},
-			Symlinks:    []*storev1pb.SymlinkNode{},
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{},
+			Files:       []*castorev1pb.FileNode{},
+			Symlinks:    []*castorev1pb.SymlinkNode{},
 		}
 
 		assert.Equal(t, uint32(0), d.Size())
 	})
 
 	t.Run("containing single empty directory", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{{
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{{
 				Name:   []byte([]byte("foo")),
 				Digest: dummyDigest,
 				Size:   0,
 			}},
-			Files:    []*storev1pb.FileNode{},
-			Symlinks: []*storev1pb.SymlinkNode{},
+			Files:    []*castorev1pb.FileNode{},
+			Symlinks: []*castorev1pb.SymlinkNode{},
 		}
 
 		assert.Equal(t, uint32(1), d.Size())
 	})
 
 	t.Run("containing single non-empty directory", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{{
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{{
 				Name:   []byte("foo"),
 				Digest: dummyDigest,
 				Size:   4,
 			}},
-			Files:    []*storev1pb.FileNode{},
-			Symlinks: []*storev1pb.SymlinkNode{},
+			Files:    []*castorev1pb.FileNode{},
+			Symlinks: []*castorev1pb.SymlinkNode{},
 		}
 
 		assert.Equal(t, uint32(5), d.Size())
 	})
 
 	t.Run("containing single file", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{},
-			Files: []*storev1pb.FileNode{{
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{},
+			Files: []*castorev1pb.FileNode{{
 				Name:       []byte("foo"),
 				Digest:     dummyDigest,
 				Size:       42,
 				Executable: false,
 			}},
-			Symlinks: []*storev1pb.SymlinkNode{},
+			Symlinks: []*castorev1pb.SymlinkNode{},
 		}
 
 		assert.Equal(t, uint32(1), d.Size())
 	})
 
 	t.Run("containing single symlink", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{},
-			Files:       []*storev1pb.FileNode{},
-			Symlinks: []*storev1pb.SymlinkNode{{
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{},
+			Files:       []*castorev1pb.FileNode{},
+			Symlinks: []*castorev1pb.SymlinkNode{{
 				Name:   []byte("foo"),
 				Target: []byte("bar"),
 			}},
@@ -84,10 +84,10 @@ func TestDirectorySize(t *testing.T) {
 
 }
 func TestDirectoryDigest(t *testing.T) {
-	d := storev1pb.Directory{
-		Directories: []*storev1pb.DirectoryNode{},
-		Files:       []*storev1pb.FileNode{},
-		Symlinks:    []*storev1pb.SymlinkNode{},
+	d := castorev1pb.Directory{
+		Directories: []*castorev1pb.DirectoryNode{},
+		Files:       []*castorev1pb.FileNode{},
+		Symlinks:    []*castorev1pb.SymlinkNode{},
 	}
 
 	dgst, err := d.Digest()
@@ -101,10 +101,10 @@ func TestDirectoryDigest(t *testing.T) {
 
 func TestDirectoryValidate(t *testing.T) {
 	t.Run("empty", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{},
-			Files:       []*storev1pb.FileNode{},
-			Symlinks:    []*storev1pb.SymlinkNode{},
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{},
+			Files:       []*castorev1pb.FileNode{},
+			Symlinks:    []*castorev1pb.SymlinkNode{},
 		}
 
 		assert.NoError(t, d.Validate())
@@ -112,50 +112,50 @@ func TestDirectoryValidate(t *testing.T) {
 
 	t.Run("invalid names", func(t *testing.T) {
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{{
 					Name:   []byte{},
 					Digest: dummyDigest,
 					Size:   42,
 				}},
-				Files:    []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{},
+				Files:    []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{},
 			}
 
 			assert.ErrorContains(t, d.Validate(), "invalid name")
 		}
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{{
 					Name:   []byte("."),
 					Digest: dummyDigest,
 					Size:   42,
 				}},
-				Files:    []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{},
+				Files:    []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{},
 			}
 
 			assert.ErrorContains(t, d.Validate(), "invalid name")
 		}
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{},
-				Files: []*storev1pb.FileNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{},
+				Files: []*castorev1pb.FileNode{{
 					Name:       []byte(".."),
 					Digest:     dummyDigest,
 					Size:       42,
 					Executable: false,
 				}},
-				Symlinks: []*storev1pb.SymlinkNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{},
 			}
 
 			assert.ErrorContains(t, d.Validate(), "invalid name")
 		}
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{},
-				Files:       []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{},
+				Files:       []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{{
 					Name:   []byte("\x00"),
 					Target: []byte("foo"),
 				}},
@@ -164,10 +164,10 @@ func TestDirectoryValidate(t *testing.T) {
 			assert.ErrorContains(t, d.Validate(), "invalid name")
 		}
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{},
-				Files:       []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{},
+				Files:       []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{{
 					Name:   []byte("foo/bar"),
 					Target: []byte("foo"),
 				}},
@@ -178,14 +178,14 @@ func TestDirectoryValidate(t *testing.T) {
 	})
 
 	t.Run("invalid digest", func(t *testing.T) {
-		d := storev1pb.Directory{
-			Directories: []*storev1pb.DirectoryNode{{
+		d := castorev1pb.Directory{
+			Directories: []*castorev1pb.DirectoryNode{{
 				Name:   []byte("foo"),
 				Digest: nil,
 				Size:   42,
 			}},
-			Files:    []*storev1pb.FileNode{},
-			Symlinks: []*storev1pb.SymlinkNode{},
+			Files:    []*castorev1pb.FileNode{},
+			Symlinks: []*castorev1pb.SymlinkNode{},
 		}
 
 		assert.ErrorContains(t, d.Validate(), "invalid digest length")
@@ -194,8 +194,8 @@ func TestDirectoryValidate(t *testing.T) {
 	t.Run("sorting", func(t *testing.T) {
 		// "b" comes before "a", bad.
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{{
 					Name:   []byte("b"),
 					Digest: dummyDigest,
 					Size:   42,
@@ -204,35 +204,35 @@ func TestDirectoryValidate(t *testing.T) {
 					Digest: dummyDigest,
 					Size:   42,
 				}},
-				Files:    []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{},
+				Files:    []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{},
 			}
 			assert.ErrorContains(t, d.Validate(), "is not in sorted order")
 		}
 
 		// "a" exists twice, bad.
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{{
 					Name:   []byte("a"),
 					Digest: dummyDigest,
 					Size:   42,
 				}},
-				Files: []*storev1pb.FileNode{{
+				Files: []*castorev1pb.FileNode{{
 					Name:       []byte("a"),
 					Digest:     dummyDigest,
 					Size:       42,
 					Executable: false,
 				}},
-				Symlinks: []*storev1pb.SymlinkNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{},
 			}
 			assert.ErrorContains(t, d.Validate(), "duplicate name")
 		}
 
 		// "a" comes before "b", all good.
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{{
 					Name:   []byte("a"),
 					Digest: dummyDigest,
 					Size:   42,
@@ -241,16 +241,16 @@ func TestDirectoryValidate(t *testing.T) {
 					Digest: dummyDigest,
 					Size:   42,
 				}},
-				Files:    []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{},
+				Files:    []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{},
 			}
 			assert.NoError(t, d.Validate(), "shouldn't error")
 		}
 
 		// [b, c] and [a] are both properly sorted.
 		{
-			d := storev1pb.Directory{
-				Directories: []*storev1pb.DirectoryNode{{
+			d := castorev1pb.Directory{
+				Directories: []*castorev1pb.DirectoryNode{{
 					Name:   []byte("b"),
 					Digest: dummyDigest,
 					Size:   42,
@@ -259,8 +259,8 @@ func TestDirectoryValidate(t *testing.T) {
 					Digest: dummyDigest,
 					Size:   42,
 				}},
-				Files: []*storev1pb.FileNode{},
-				Symlinks: []*storev1pb.SymlinkNode{{
+				Files: []*castorev1pb.FileNode{},
+				Symlinks: []*castorev1pb.SymlinkNode{{
 					Name:   []byte("a"),
 					Target: []byte("foo"),
 				}},
diff --git a/tvix/castore/protos/go.mod b/tvix/castore/protos/go.mod
new file mode 100644
index 000000000000..35219aba5c1b
--- /dev/null
+++ b/tvix/castore/protos/go.mod
@@ -0,0 +1,19 @@
+module code.tvl.fyi/tvix/castore/protos
+
+go 1.19
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.8.1 // indirect
+	golang.org/x/net v0.0.0-20220722155237-a158d28d115b // indirect
+	golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f // indirect
+	golang.org/x/text v0.4.0 // indirect
+	google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013 // indirect
+	google.golang.org/grpc v1.51.0 // indirect
+	google.golang.org/protobuf v1.28.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+	lukechampine.com/blake3 v1.1.7 // indirect
+)
diff --git a/tvix/castore/protos/go.sum b/tvix/castore/protos/go.sum
new file mode 100644
index 000000000000..7a603cdb120d
--- /dev/null
+++ b/tvix/castore/protos/go.sum
@@ -0,0 +1,96 @@
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
+github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
+github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
+github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
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+github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
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+github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
+github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
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+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
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+github.com/klauspost/cpuid/v2 v2.0.9 h1:lgaqFMSdTdQYdZ04uHyN2d/eKdOMyi2YLSvlQIBFYa4=
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+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
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diff --git a/tvix/store/protos/rpc_blobstore.pb.go b/tvix/castore/protos/rpc_blobstore.pb.go
index 987d75e3b997..1afc82674451 100644
--- a/tvix/store/protos/rpc_blobstore.pb.go
+++ b/tvix/castore/protos/rpc_blobstore.pb.go
@@ -5,9 +5,9 @@
 // versions:
 // 	protoc-gen-go v1.31.0
 // 	protoc        (unknown)
-// source: tvix/store/protos/rpc_blobstore.proto
+// source: tvix/castore/protos/rpc_blobstore.proto
 
-package storev1
+package castorev1
 
 import (
 	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
@@ -35,7 +35,7 @@ type StatBlobRequest struct {
 func (x *StatBlobRequest) Reset() {
 	*x = StatBlobRequest{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[0]
+		mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[0]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -48,7 +48,7 @@ func (x *StatBlobRequest) String() string {
 func (*StatBlobRequest) ProtoMessage() {}
 
 func (x *StatBlobRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[0]
+	mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[0]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -61,7 +61,7 @@ func (x *StatBlobRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use StatBlobRequest.ProtoReflect.Descriptor instead.
 func (*StatBlobRequest) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_blobstore_proto_rawDescGZIP(), []int{0}
+	return file_tvix_castore_protos_rpc_blobstore_proto_rawDescGZIP(), []int{0}
 }
 
 func (x *StatBlobRequest) GetDigest() []byte {
@@ -80,7 +80,7 @@ type BlobMeta struct {
 func (x *BlobMeta) Reset() {
 	*x = BlobMeta{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[1]
+		mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[1]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -93,7 +93,7 @@ func (x *BlobMeta) String() string {
 func (*BlobMeta) ProtoMessage() {}
 
 func (x *BlobMeta) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[1]
+	mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[1]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -106,7 +106,7 @@ func (x *BlobMeta) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use BlobMeta.ProtoReflect.Descriptor instead.
 func (*BlobMeta) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_blobstore_proto_rawDescGZIP(), []int{1}
+	return file_tvix_castore_protos_rpc_blobstore_proto_rawDescGZIP(), []int{1}
 }
 
 type ReadBlobRequest struct {
@@ -121,7 +121,7 @@ type ReadBlobRequest struct {
 func (x *ReadBlobRequest) Reset() {
 	*x = ReadBlobRequest{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[2]
+		mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[2]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -134,7 +134,7 @@ func (x *ReadBlobRequest) String() string {
 func (*ReadBlobRequest) ProtoMessage() {}
 
 func (x *ReadBlobRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[2]
+	mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[2]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -147,7 +147,7 @@ func (x *ReadBlobRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use ReadBlobRequest.ProtoReflect.Descriptor instead.
 func (*ReadBlobRequest) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_blobstore_proto_rawDescGZIP(), []int{2}
+	return file_tvix_castore_protos_rpc_blobstore_proto_rawDescGZIP(), []int{2}
 }
 
 func (x *ReadBlobRequest) GetDigest() []byte {
@@ -170,7 +170,7 @@ type BlobChunk struct {
 func (x *BlobChunk) Reset() {
 	*x = BlobChunk{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[3]
+		mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[3]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -183,7 +183,7 @@ func (x *BlobChunk) String() string {
 func (*BlobChunk) ProtoMessage() {}
 
 func (x *BlobChunk) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[3]
+	mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[3]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -196,7 +196,7 @@ func (x *BlobChunk) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use BlobChunk.ProtoReflect.Descriptor instead.
 func (*BlobChunk) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_blobstore_proto_rawDescGZIP(), []int{3}
+	return file_tvix_castore_protos_rpc_blobstore_proto_rawDescGZIP(), []int{3}
 }
 
 func (x *BlobChunk) GetData() []byte {
@@ -218,7 +218,7 @@ type PutBlobResponse struct {
 func (x *PutBlobResponse) Reset() {
 	*x = PutBlobResponse{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[4]
+		mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[4]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -231,7 +231,7 @@ func (x *PutBlobResponse) String() string {
 func (*PutBlobResponse) ProtoMessage() {}
 
 func (x *PutBlobResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_blobstore_proto_msgTypes[4]
+	mi := &file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[4]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -244,7 +244,7 @@ func (x *PutBlobResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use PutBlobResponse.ProtoReflect.Descriptor instead.
 func (*PutBlobResponse) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_blobstore_proto_rawDescGZIP(), []int{4}
+	return file_tvix_castore_protos_rpc_blobstore_proto_rawDescGZIP(), []int{4}
 }
 
 func (x *PutBlobResponse) GetDigest() []byte {
@@ -254,69 +254,71 @@ func (x *PutBlobResponse) GetDigest() []byte {
 	return nil
 }
 
-var File_tvix_store_protos_rpc_blobstore_proto protoreflect.FileDescriptor
-
-var file_tvix_store_protos_rpc_blobstore_proto_rawDesc = []byte{
-	0x0a, 0x25, 0x74, 0x76, 0x69, 0x78, 0x2f, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f,
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+var File_tvix_castore_protos_rpc_blobstore_proto protoreflect.FileDescriptor
+
+var file_tvix_castore_protos_rpc_blobstore_proto_rawDesc = []byte{
+	0x0a, 0x27, 0x74, 0x76, 0x69, 0x78, 0x2f, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70,
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-	0x12, 0x18, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2e, 0x76, 0x31,
-	0x2e, 0x42, 0x6c, 0x6f, 0x62, 0x43, 0x68, 0x75, 0x6e, 0x6b, 0x1a, 0x1e, 0x2e, 0x74, 0x76, 0x69,
-	0x78, 0x2e, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2e, 0x76, 0x31, 0x2e, 0x50, 0x75, 0x74, 0x42, 0x6c,
-	0x6f, 0x62, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x28, 0x01, 0x42, 0x28, 0x5a, 0x26,
+	0x52, 0x06, 0x64, 0x69, 0x67, 0x65, 0x73, 0x74, 0x32, 0xe1, 0x01, 0x0a, 0x0b, 0x42, 0x6c, 0x6f,
+	0x62, 0x53, 0x65, 0x72, 0x76, 0x69, 0x63, 0x65, 0x12, 0x43, 0x0a, 0x04, 0x53, 0x74, 0x61, 0x74,
+	0x12, 0x20, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2e,
+	0x76, 0x31, 0x2e, 0x53, 0x74, 0x61, 0x74, 0x42, 0x6c, 0x6f, 0x62, 0x52, 0x65, 0x71, 0x75, 0x65,
+	0x73, 0x74, 0x1a, 0x19, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72,
+	0x65, 0x2e, 0x76, 0x31, 0x2e, 0x42, 0x6c, 0x6f, 0x62, 0x4d, 0x65, 0x74, 0x61, 0x12, 0x46, 0x0a,
+	0x04, 0x52, 0x65, 0x61, 0x64, 0x12, 0x20, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x63, 0x61, 0x73,
+	0x74, 0x6f, 0x72, 0x65, 0x2e, 0x76, 0x31, 0x2e, 0x52, 0x65, 0x61, 0x64, 0x42, 0x6c, 0x6f, 0x62,
+	0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x1a, 0x1a, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x63,
+	0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2e, 0x76, 0x31, 0x2e, 0x42, 0x6c, 0x6f, 0x62, 0x43, 0x68,
+	0x75, 0x6e, 0x6b, 0x30, 0x01, 0x12, 0x45, 0x0a, 0x03, 0x50, 0x75, 0x74, 0x12, 0x1a, 0x2e, 0x74,
+	0x76, 0x69, 0x78, 0x2e, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2e, 0x76, 0x31, 0x2e, 0x42,
+	0x6c, 0x6f, 0x62, 0x43, 0x68, 0x75, 0x6e, 0x6b, 0x1a, 0x20, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e,
+	0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2e, 0x76, 0x31, 0x2e, 0x50, 0x75, 0x74, 0x42, 0x6c,
+	0x6f, 0x62, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x28, 0x01, 0x42, 0x2c, 0x5a, 0x2a,
 	0x63, 0x6f, 0x64, 0x65, 0x2e, 0x74, 0x76, 0x6c, 0x2e, 0x66, 0x79, 0x69, 0x2f, 0x74, 0x76, 0x69,
-	0x78, 0x2f, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x73, 0x3b, 0x73,
-	0x74, 0x6f, 0x72, 0x65, 0x76, 0x31, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
+	0x78, 0x2f, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x73,
+	0x3b, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x76, 0x31, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74,
+	0x6f, 0x33,
 }
 
 var (
-	file_tvix_store_protos_rpc_blobstore_proto_rawDescOnce sync.Once
-	file_tvix_store_protos_rpc_blobstore_proto_rawDescData = file_tvix_store_protos_rpc_blobstore_proto_rawDesc
+	file_tvix_castore_protos_rpc_blobstore_proto_rawDescOnce sync.Once
+	file_tvix_castore_protos_rpc_blobstore_proto_rawDescData = file_tvix_castore_protos_rpc_blobstore_proto_rawDesc
 )
 
-func file_tvix_store_protos_rpc_blobstore_proto_rawDescGZIP() []byte {
-	file_tvix_store_protos_rpc_blobstore_proto_rawDescOnce.Do(func() {
-		file_tvix_store_protos_rpc_blobstore_proto_rawDescData = protoimpl.X.CompressGZIP(file_tvix_store_protos_rpc_blobstore_proto_rawDescData)
+func file_tvix_castore_protos_rpc_blobstore_proto_rawDescGZIP() []byte {
+	file_tvix_castore_protos_rpc_blobstore_proto_rawDescOnce.Do(func() {
+		file_tvix_castore_protos_rpc_blobstore_proto_rawDescData = protoimpl.X.CompressGZIP(file_tvix_castore_protos_rpc_blobstore_proto_rawDescData)
 	})
-	return file_tvix_store_protos_rpc_blobstore_proto_rawDescData
-}
-
-var file_tvix_store_protos_rpc_blobstore_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
-var file_tvix_store_protos_rpc_blobstore_proto_goTypes = []interface{}{
-	(*StatBlobRequest)(nil), // 0: tvix.store.v1.StatBlobRequest
-	(*BlobMeta)(nil),        // 1: tvix.store.v1.BlobMeta
-	(*ReadBlobRequest)(nil), // 2: tvix.store.v1.ReadBlobRequest
-	(*BlobChunk)(nil),       // 3: tvix.store.v1.BlobChunk
-	(*PutBlobResponse)(nil), // 4: tvix.store.v1.PutBlobResponse
-}
-var file_tvix_store_protos_rpc_blobstore_proto_depIdxs = []int32{
-	0, // 0: tvix.store.v1.BlobService.Stat:input_type -> tvix.store.v1.StatBlobRequest
-	2, // 1: tvix.store.v1.BlobService.Read:input_type -> tvix.store.v1.ReadBlobRequest
-	3, // 2: tvix.store.v1.BlobService.Put:input_type -> tvix.store.v1.BlobChunk
-	1, // 3: tvix.store.v1.BlobService.Stat:output_type -> tvix.store.v1.BlobMeta
-	3, // 4: tvix.store.v1.BlobService.Read:output_type -> tvix.store.v1.BlobChunk
-	4, // 5: tvix.store.v1.BlobService.Put:output_type -> tvix.store.v1.PutBlobResponse
+	return file_tvix_castore_protos_rpc_blobstore_proto_rawDescData
+}
+
+var file_tvix_castore_protos_rpc_blobstore_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
+var file_tvix_castore_protos_rpc_blobstore_proto_goTypes = []interface{}{
+	(*StatBlobRequest)(nil), // 0: tvix.castore.v1.StatBlobRequest
+	(*BlobMeta)(nil),        // 1: tvix.castore.v1.BlobMeta
+	(*ReadBlobRequest)(nil), // 2: tvix.castore.v1.ReadBlobRequest
+	(*BlobChunk)(nil),       // 3: tvix.castore.v1.BlobChunk
+	(*PutBlobResponse)(nil), // 4: tvix.castore.v1.PutBlobResponse
+}
+var file_tvix_castore_protos_rpc_blobstore_proto_depIdxs = []int32{
+	0, // 0: tvix.castore.v1.BlobService.Stat:input_type -> tvix.castore.v1.StatBlobRequest
+	2, // 1: tvix.castore.v1.BlobService.Read:input_type -> tvix.castore.v1.ReadBlobRequest
+	3, // 2: tvix.castore.v1.BlobService.Put:input_type -> tvix.castore.v1.BlobChunk
+	1, // 3: tvix.castore.v1.BlobService.Stat:output_type -> tvix.castore.v1.BlobMeta
+	3, // 4: tvix.castore.v1.BlobService.Read:output_type -> tvix.castore.v1.BlobChunk
+	4, // 5: tvix.castore.v1.BlobService.Put:output_type -> tvix.castore.v1.PutBlobResponse
 	3, // [3:6] is the sub-list for method output_type
 	0, // [0:3] is the sub-list for method input_type
 	0, // [0:0] is the sub-list for extension type_name
@@ -324,13 +326,13 @@ var file_tvix_store_protos_rpc_blobstore_proto_depIdxs = []int32{
 	0, // [0:0] is the sub-list for field type_name
 }
 
-func init() { file_tvix_store_protos_rpc_blobstore_proto_init() }
-func file_tvix_store_protos_rpc_blobstore_proto_init() {
-	if File_tvix_store_protos_rpc_blobstore_proto != nil {
+func init() { file_tvix_castore_protos_rpc_blobstore_proto_init() }
+func file_tvix_castore_protos_rpc_blobstore_proto_init() {
+	if File_tvix_castore_protos_rpc_blobstore_proto != nil {
 		return
 	}
 	if !protoimpl.UnsafeEnabled {
-		file_tvix_store_protos_rpc_blobstore_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
+		file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*StatBlobRequest); i {
 			case 0:
 				return &v.state
@@ -342,7 +344,7 @@ func file_tvix_store_protos_rpc_blobstore_proto_init() {
 				return nil
 			}
 		}
-		file_tvix_store_protos_rpc_blobstore_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+		file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*BlobMeta); i {
 			case 0:
 				return &v.state
@@ -354,7 +356,7 @@ func file_tvix_store_protos_rpc_blobstore_proto_init() {
 				return nil
 			}
 		}
-		file_tvix_store_protos_rpc_blobstore_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
+		file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*ReadBlobRequest); i {
 			case 0:
 				return &v.state
@@ -366,7 +368,7 @@ func file_tvix_store_protos_rpc_blobstore_proto_init() {
 				return nil
 			}
 		}
-		file_tvix_store_protos_rpc_blobstore_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
+		file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*BlobChunk); i {
 			case 0:
 				return &v.state
@@ -378,7 +380,7 @@ func file_tvix_store_protos_rpc_blobstore_proto_init() {
 				return nil
 			}
 		}
-		file_tvix_store_protos_rpc_blobstore_proto_msgTypes[4].Exporter = func(v interface{}, i int) interface{} {
+		file_tvix_castore_protos_rpc_blobstore_proto_msgTypes[4].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*PutBlobResponse); i {
 			case 0:
 				return &v.state
@@ -395,18 +397,18 @@ func file_tvix_store_protos_rpc_blobstore_proto_init() {
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
-			RawDescriptor: file_tvix_store_protos_rpc_blobstore_proto_rawDesc,
+			RawDescriptor: file_tvix_castore_protos_rpc_blobstore_proto_rawDesc,
 			NumEnums:      0,
 			NumMessages:   5,
 			NumExtensions: 0,
 			NumServices:   1,
 		},
-		GoTypes:           file_tvix_store_protos_rpc_blobstore_proto_goTypes,
-		DependencyIndexes: file_tvix_store_protos_rpc_blobstore_proto_depIdxs,
-		MessageInfos:      file_tvix_store_protos_rpc_blobstore_proto_msgTypes,
+		GoTypes:           file_tvix_castore_protos_rpc_blobstore_proto_goTypes,
+		DependencyIndexes: file_tvix_castore_protos_rpc_blobstore_proto_depIdxs,
+		MessageInfos:      file_tvix_castore_protos_rpc_blobstore_proto_msgTypes,
 	}.Build()
-	File_tvix_store_protos_rpc_blobstore_proto = out.File
-	file_tvix_store_protos_rpc_blobstore_proto_rawDesc = nil
-	file_tvix_store_protos_rpc_blobstore_proto_goTypes = nil
-	file_tvix_store_protos_rpc_blobstore_proto_depIdxs = nil
+	File_tvix_castore_protos_rpc_blobstore_proto = out.File
+	file_tvix_castore_protos_rpc_blobstore_proto_rawDesc = nil
+	file_tvix_castore_protos_rpc_blobstore_proto_goTypes = nil
+	file_tvix_castore_protos_rpc_blobstore_proto_depIdxs = nil
 }
diff --git a/tvix/store/protos/rpc_blobstore.proto b/tvix/castore/protos/rpc_blobstore.proto
index 2ca3df60a81b..6ee9a80f0afc 100644
--- a/tvix/store/protos/rpc_blobstore.proto
+++ b/tvix/castore/protos/rpc_blobstore.proto
@@ -2,9 +2,9 @@
 // Copyright ยฉ 2022 The Tvix Authors
 syntax = "proto3";
 
-package tvix.store.v1;
+package tvix.castore.v1;
 
-option go_package = "code.tvl.fyi/tvix/store/protos;storev1";
+option go_package = "code.tvl.fyi/tvix/castore/protos;castorev1";
 
 service BlobService {
     // In the future, Stat will expose more metadata about a given blob,
diff --git a/tvix/store/protos/rpc_blobstore_grpc.pb.go b/tvix/castore/protos/rpc_blobstore_grpc.pb.go
index 531ebcd2c637..0876bcc4e95a 100644
--- a/tvix/store/protos/rpc_blobstore_grpc.pb.go
+++ b/tvix/castore/protos/rpc_blobstore_grpc.pb.go
@@ -5,9 +5,9 @@
 // versions:
 // - protoc-gen-go-grpc v1.3.0
 // - protoc             (unknown)
-// source: tvix/store/protos/rpc_blobstore.proto
+// source: tvix/castore/protos/rpc_blobstore.proto
 
-package storev1
+package castorev1
 
 import (
 	context "context"
@@ -22,9 +22,9 @@ import (
 const _ = grpc.SupportPackageIsVersion7
 
 const (
-	BlobService_Stat_FullMethodName = "/tvix.store.v1.BlobService/Stat"
-	BlobService_Read_FullMethodName = "/tvix.store.v1.BlobService/Read"
-	BlobService_Put_FullMethodName  = "/tvix.store.v1.BlobService/Put"
+	BlobService_Stat_FullMethodName = "/tvix.castore.v1.BlobService/Stat"
+	BlobService_Read_FullMethodName = "/tvix.castore.v1.BlobService/Read"
+	BlobService_Put_FullMethodName  = "/tvix.castore.v1.BlobService/Put"
 )
 
 // BlobServiceClient is the client API for BlobService service.
@@ -250,7 +250,7 @@ func (x *blobServicePutServer) Recv() (*BlobChunk, error) {
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
 var BlobService_ServiceDesc = grpc.ServiceDesc{
-	ServiceName: "tvix.store.v1.BlobService",
+	ServiceName: "tvix.castore.v1.BlobService",
 	HandlerType: (*BlobServiceServer)(nil),
 	Methods: []grpc.MethodDesc{
 		{
@@ -270,5 +270,5 @@ var BlobService_ServiceDesc = grpc.ServiceDesc{
 			ClientStreams: true,
 		},
 	},
-	Metadata: "tvix/store/protos/rpc_blobstore.proto",
+	Metadata: "tvix/castore/protos/rpc_blobstore.proto",
 }
diff --git a/tvix/castore/protos/rpc_directory.pb.go b/tvix/castore/protos/rpc_directory.pb.go
new file mode 100644
index 000000000000..f658c6b60cc0
--- /dev/null
+++ b/tvix/castore/protos/rpc_directory.pb.go
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: MIT
+// Copyright ยฉ 2022 The Tvix Authors
+
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.31.0
+// 	protoc        (unknown)
+// source: tvix/castore/protos/rpc_directory.proto
+
+package castorev1
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+type GetDirectoryRequest struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// Types that are assignable to ByWhat:
+	//
+	//	*GetDirectoryRequest_Digest
+	ByWhat isGetDirectoryRequest_ByWhat `protobuf_oneof:"by_what"`
+	// If set to true, recursively resolve all child Directory messages.
+	// Directory messages SHOULD be streamed in a recursive breadth-first walk,
+	// but other orders are also fine, as long as Directory messages are only
+	// sent after they are referred to from previously sent Directory messages.
+	Recursive bool `protobuf:"varint,2,opt,name=recursive,proto3" json:"recursive,omitempty"`
+}
+
+func (x *GetDirectoryRequest) Reset() {
+	*x = GetDirectoryRequest{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_rpc_directory_proto_msgTypes[0]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *GetDirectoryRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*GetDirectoryRequest) ProtoMessage() {}
+
+func (x *GetDirectoryRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_rpc_directory_proto_msgTypes[0]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use GetDirectoryRequest.ProtoReflect.Descriptor instead.
+func (*GetDirectoryRequest) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_rpc_directory_proto_rawDescGZIP(), []int{0}
+}
+
+func (m *GetDirectoryRequest) GetByWhat() isGetDirectoryRequest_ByWhat {
+	if m != nil {
+		return m.ByWhat
+	}
+	return nil
+}
+
+func (x *GetDirectoryRequest) GetDigest() []byte {
+	if x, ok := x.GetByWhat().(*GetDirectoryRequest_Digest); ok {
+		return x.Digest
+	}
+	return nil
+}
+
+func (x *GetDirectoryRequest) GetRecursive() bool {
+	if x != nil {
+		return x.Recursive
+	}
+	return false
+}
+
+type isGetDirectoryRequest_ByWhat interface {
+	isGetDirectoryRequest_ByWhat()
+}
+
+type GetDirectoryRequest_Digest struct {
+	// The blake3 hash of the (root) Directory message, serialized in
+	// protobuf canonical form.
+	// Keep in mind this can be a subtree of another root.
+	Digest []byte `protobuf:"bytes,1,opt,name=digest,proto3,oneof"`
+}
+
+func (*GetDirectoryRequest_Digest) isGetDirectoryRequest_ByWhat() {}
+
+type PutDirectoryResponse struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	RootDigest []byte `protobuf:"bytes,1,opt,name=root_digest,json=rootDigest,proto3" json:"root_digest,omitempty"`
+}
+
+func (x *PutDirectoryResponse) Reset() {
+	*x = PutDirectoryResponse{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_tvix_castore_protos_rpc_directory_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *PutDirectoryResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*PutDirectoryResponse) ProtoMessage() {}
+
+func (x *PutDirectoryResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_tvix_castore_protos_rpc_directory_proto_msgTypes[1]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use PutDirectoryResponse.ProtoReflect.Descriptor instead.
+func (*PutDirectoryResponse) Descriptor() ([]byte, []int) {
+	return file_tvix_castore_protos_rpc_directory_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *PutDirectoryResponse) GetRootDigest() []byte {
+	if x != nil {
+		return x.RootDigest
+	}
+	return nil
+}
+
+var File_tvix_castore_protos_rpc_directory_proto protoreflect.FileDescriptor
+
+var file_tvix_castore_protos_rpc_directory_proto_rawDesc = []byte{
+	0x0a, 0x27, 0x74, 0x76, 0x69, 0x78, 0x2f, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70,
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+	0x72, 0x79, 0x52, 0x65, 0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x28, 0x01, 0x42, 0x2c, 0x5a, 0x2a,
+	0x63, 0x6f, 0x64, 0x65, 0x2e, 0x74, 0x76, 0x6c, 0x2e, 0x66, 0x79, 0x69, 0x2f, 0x74, 0x76, 0x69,
+	0x78, 0x2f, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x73,
+	0x3b, 0x63, 0x61, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x76, 0x31, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74,
+	0x6f, 0x33,
+}
+
+var (
+	file_tvix_castore_protos_rpc_directory_proto_rawDescOnce sync.Once
+	file_tvix_castore_protos_rpc_directory_proto_rawDescData = file_tvix_castore_protos_rpc_directory_proto_rawDesc
+)
+
+func file_tvix_castore_protos_rpc_directory_proto_rawDescGZIP() []byte {
+	file_tvix_castore_protos_rpc_directory_proto_rawDescOnce.Do(func() {
+		file_tvix_castore_protos_rpc_directory_proto_rawDescData = protoimpl.X.CompressGZIP(file_tvix_castore_protos_rpc_directory_proto_rawDescData)
+	})
+	return file_tvix_castore_protos_rpc_directory_proto_rawDescData
+}
+
+var file_tvix_castore_protos_rpc_directory_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
+var file_tvix_castore_protos_rpc_directory_proto_goTypes = []interface{}{
+	(*GetDirectoryRequest)(nil),  // 0: tvix.castore.v1.GetDirectoryRequest
+	(*PutDirectoryResponse)(nil), // 1: tvix.castore.v1.PutDirectoryResponse
+	(*Directory)(nil),            // 2: tvix.castore.v1.Directory
+}
+var file_tvix_castore_protos_rpc_directory_proto_depIdxs = []int32{
+	0, // 0: tvix.castore.v1.DirectoryService.Get:input_type -> tvix.castore.v1.GetDirectoryRequest
+	2, // 1: tvix.castore.v1.DirectoryService.Put:input_type -> tvix.castore.v1.Directory
+	2, // 2: tvix.castore.v1.DirectoryService.Get:output_type -> tvix.castore.v1.Directory
+	1, // 3: tvix.castore.v1.DirectoryService.Put:output_type -> tvix.castore.v1.PutDirectoryResponse
+	2, // [2:4] is the sub-list for method output_type
+	0, // [0:2] is the sub-list for method input_type
+	0, // [0:0] is the sub-list for extension type_name
+	0, // [0:0] is the sub-list for extension extendee
+	0, // [0:0] is the sub-list for field type_name
+}
+
+func init() { file_tvix_castore_protos_rpc_directory_proto_init() }
+func file_tvix_castore_protos_rpc_directory_proto_init() {
+	if File_tvix_castore_protos_rpc_directory_proto != nil {
+		return
+	}
+	file_tvix_castore_protos_castore_proto_init()
+	if !protoimpl.UnsafeEnabled {
+		file_tvix_castore_protos_rpc_directory_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*GetDirectoryRequest); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_tvix_castore_protos_rpc_directory_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*PutDirectoryResponse); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+	}
+	file_tvix_castore_protos_rpc_directory_proto_msgTypes[0].OneofWrappers = []interface{}{
+		(*GetDirectoryRequest_Digest)(nil),
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: file_tvix_castore_protos_rpc_directory_proto_rawDesc,
+			NumEnums:      0,
+			NumMessages:   2,
+			NumExtensions: 0,
+			NumServices:   1,
+		},
+		GoTypes:           file_tvix_castore_protos_rpc_directory_proto_goTypes,
+		DependencyIndexes: file_tvix_castore_protos_rpc_directory_proto_depIdxs,
+		MessageInfos:      file_tvix_castore_protos_rpc_directory_proto_msgTypes,
+	}.Build()
+	File_tvix_castore_protos_rpc_directory_proto = out.File
+	file_tvix_castore_protos_rpc_directory_proto_rawDesc = nil
+	file_tvix_castore_protos_rpc_directory_proto_goTypes = nil
+	file_tvix_castore_protos_rpc_directory_proto_depIdxs = nil
+}
diff --git a/tvix/store/protos/rpc_directory.proto b/tvix/castore/protos/rpc_directory.proto
index 0aeed5c3c0e1..8d4c22828547 100644
--- a/tvix/store/protos/rpc_directory.proto
+++ b/tvix/castore/protos/rpc_directory.proto
@@ -2,11 +2,11 @@
 // Copyright ยฉ 2022 The Tvix Authors
 syntax = "proto3";
 
-package tvix.store.v1;
+package tvix.castore.v1;
 
-import "tvix/store/protos/castore.proto";
+import "tvix/castore/protos/castore.proto";
 
-option go_package = "code.tvl.fyi/tvix/store/protos;storev1";
+option go_package = "code.tvl.fyi/tvix/castore/protos;castorev1";
 
 service DirectoryService {
   // Get retrieves a stream of Directory messages, by using the lookup
diff --git a/tvix/store/protos/rpc_directory_grpc.pb.go b/tvix/castore/protos/rpc_directory_grpc.pb.go
index a578dbd89d39..f19e457d867b 100644
--- a/tvix/store/protos/rpc_directory_grpc.pb.go
+++ b/tvix/castore/protos/rpc_directory_grpc.pb.go
@@ -5,9 +5,9 @@
 // versions:
 // - protoc-gen-go-grpc v1.3.0
 // - protoc             (unknown)
-// source: tvix/store/protos/rpc_directory.proto
+// source: tvix/castore/protos/rpc_directory.proto
 
-package storev1
+package castorev1
 
 import (
 	context "context"
@@ -22,8 +22,8 @@ import (
 const _ = grpc.SupportPackageIsVersion7
 
 const (
-	DirectoryService_Get_FullMethodName = "/tvix.store.v1.DirectoryService/Get"
-	DirectoryService_Put_FullMethodName = "/tvix.store.v1.DirectoryService/Put"
+	DirectoryService_Get_FullMethodName = "/tvix.castore.v1.DirectoryService/Get"
+	DirectoryService_Put_FullMethodName = "/tvix.castore.v1.DirectoryService/Put"
 )
 
 // DirectoryServiceClient is the client API for DirectoryService service.
@@ -219,7 +219,7 @@ func (x *directoryServicePutServer) Recv() (*Directory, error) {
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
 var DirectoryService_ServiceDesc = grpc.ServiceDesc{
-	ServiceName: "tvix.store.v1.DirectoryService",
+	ServiceName: "tvix.castore.v1.DirectoryService",
 	HandlerType: (*DirectoryServiceServer)(nil),
 	Methods:     []grpc.MethodDesc{},
 	Streams: []grpc.StreamDesc{
@@ -234,5 +234,5 @@ var DirectoryService_ServiceDesc = grpc.ServiceDesc{
 			ClientStreams: true,
 		},
 	},
-	Metadata: "tvix/store/protos/rpc_directory.proto",
+	Metadata: "tvix/castore/protos/rpc_directory.proto",
 }
diff --git a/tvix/store/src/blobservice/from_addr.rs b/tvix/castore/src/blobservice/from_addr.rs
index 2e0a30697d75..2e0a30697d75 100644
--- a/tvix/store/src/blobservice/from_addr.rs
+++ b/tvix/castore/src/blobservice/from_addr.rs
diff --git a/tvix/store/src/blobservice/grpc.rs b/tvix/castore/src/blobservice/grpc.rs
index ae84f4ce0ff7..db9d4a9c00f0 100644
--- a/tvix/store/src/blobservice/grpc.rs
+++ b/tvix/castore/src/blobservice/grpc.rs
@@ -289,8 +289,8 @@ mod tests {
     use tokio_stream::wrappers::UnixListenerStream;
 
     use crate::blobservice::MemoryBlobService;
+    use crate::fixtures;
     use crate::proto::GRPCBlobServiceWrapper;
-    use crate::tests::fixtures;
 
     use super::BlobService;
     use super::GRPCBlobService;
diff --git a/tvix/store/src/blobservice/memory.rs b/tvix/castore/src/blobservice/memory.rs
index 383127344a17..383127344a17 100644
--- a/tvix/store/src/blobservice/memory.rs
+++ b/tvix/castore/src/blobservice/memory.rs
diff --git a/tvix/store/src/blobservice/mod.rs b/tvix/castore/src/blobservice/mod.rs
index 5ecf25ac1337..5ecf25ac1337 100644
--- a/tvix/store/src/blobservice/mod.rs
+++ b/tvix/castore/src/blobservice/mod.rs
diff --git a/tvix/store/src/blobservice/naive_seeker.rs b/tvix/castore/src/blobservice/naive_seeker.rs
index e65a82c7f45a..e65a82c7f45a 100644
--- a/tvix/store/src/blobservice/naive_seeker.rs
+++ b/tvix/castore/src/blobservice/naive_seeker.rs
diff --git a/tvix/store/src/blobservice/sled.rs b/tvix/castore/src/blobservice/sled.rs
index 209f0b76fc7a..209f0b76fc7a 100644
--- a/tvix/store/src/blobservice/sled.rs
+++ b/tvix/castore/src/blobservice/sled.rs
diff --git a/tvix/store/src/blobservice/tests.rs b/tvix/castore/src/blobservice/tests.rs
index 501270780cf4..fe390b537eb8 100644
--- a/tvix/store/src/blobservice/tests.rs
+++ b/tvix/castore/src/blobservice/tests.rs
@@ -9,7 +9,7 @@ use super::B3Digest;
 use super::BlobService;
 use super::MemoryBlobService;
 use super::SledBlobService;
-use crate::tests::fixtures;
+use crate::fixtures;
 
 // TODO: avoid having to define all different services we test against for all functions.
 // maybe something like rstest can be used?
diff --git a/tvix/store/src/digests.rs b/tvix/castore/src/digests.rs
index 4df11b389e93..4df11b389e93 100644
--- a/tvix/store/src/digests.rs
+++ b/tvix/castore/src/digests.rs
diff --git a/tvix/store/src/directoryservice/from_addr.rs b/tvix/castore/src/directoryservice/from_addr.rs
index 776cf061096c..776cf061096c 100644
--- a/tvix/store/src/directoryservice/from_addr.rs
+++ b/tvix/castore/src/directoryservice/from_addr.rs
diff --git a/tvix/store/src/directoryservice/grpc.rs b/tvix/castore/src/directoryservice/grpc.rs
index 6257a8e81485..0f0305341265 100644
--- a/tvix/store/src/directoryservice/grpc.rs
+++ b/tvix/castore/src/directoryservice/grpc.rs
@@ -348,12 +348,10 @@ mod tests {
 
     use crate::{
         directoryservice::DirectoryService,
+        fixtures::{DIRECTORY_A, DIRECTORY_B},
         proto,
         proto::{directory_service_server::DirectoryServiceServer, GRPCDirectoryServiceWrapper},
-        tests::{
-            fixtures::{DIRECTORY_A, DIRECTORY_B},
-            utils::gen_directory_service,
-        },
+        utils::gen_directory_service,
     };
 
     #[test]
diff --git a/tvix/store/src/directoryservice/memory.rs b/tvix/castore/src/directoryservice/memory.rs
index ac67c999d01b..ac67c999d01b 100644
--- a/tvix/store/src/directoryservice/memory.rs
+++ b/tvix/castore/src/directoryservice/memory.rs
diff --git a/tvix/store/src/directoryservice/mod.rs b/tvix/castore/src/directoryservice/mod.rs
index 3b26f4baf79b..3b26f4baf79b 100644
--- a/tvix/store/src/directoryservice/mod.rs
+++ b/tvix/castore/src/directoryservice/mod.rs
diff --git a/tvix/store/src/directoryservice/sled.rs b/tvix/castore/src/directoryservice/sled.rs
index 0dc5496803cb..0dc5496803cb 100644
--- a/tvix/store/src/directoryservice/sled.rs
+++ b/tvix/castore/src/directoryservice/sled.rs
diff --git a/tvix/store/src/directoryservice/traverse.rs b/tvix/castore/src/directoryservice/traverse.rs
index 5043439e9de5..4f011c963c06 100644
--- a/tvix/store/src/directoryservice/traverse.rs
+++ b/tvix/castore/src/directoryservice/traverse.rs
@@ -84,10 +84,8 @@ pub async fn descend_to(
 mod tests {
     use std::path::PathBuf;
 
-    use crate::tests::{
-        fixtures::{DIRECTORY_COMPLICATED, DIRECTORY_WITH_KEEP},
-        utils::gen_directory_service,
-    };
+    use crate::fixtures::{DIRECTORY_COMPLICATED, DIRECTORY_WITH_KEEP};
+    use crate::utils::gen_directory_service;
 
     use super::descend_to;
 
diff --git a/tvix/store/src/directoryservice/utils.rs b/tvix/castore/src/directoryservice/utils.rs
index 4c5e7cfde37c..4c5e7cfde37c 100644
--- a/tvix/store/src/directoryservice/utils.rs
+++ b/tvix/castore/src/directoryservice/utils.rs
diff --git a/tvix/store/src/errors.rs b/tvix/castore/src/errors.rs
index 3b23f972b045..3b23f972b045 100644
--- a/tvix/store/src/errors.rs
+++ b/tvix/castore/src/errors.rs
diff --git a/tvix/castore/src/fixtures.rs b/tvix/castore/src/fixtures.rs
new file mode 100644
index 000000000000..ed3d1ca6e855
--- /dev/null
+++ b/tvix/castore/src/fixtures.rs
@@ -0,0 +1,95 @@
+use crate::{
+    proto::{self, Directory, DirectoryNode, FileNode, SymlinkNode},
+    B3Digest,
+};
+use lazy_static::lazy_static;
+
+pub const HELLOWORLD_BLOB_CONTENTS: &[u8] = b"Hello World!";
+pub const EMPTY_BLOB_CONTENTS: &[u8] = b"";
+
+lazy_static! {
+    pub static ref DUMMY_DIGEST: B3Digest = {
+        let u: &[u8; 32] = &[
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00,
+        ];
+        u.into()
+    };
+    pub static ref DUMMY_DIGEST_2: B3Digest = {
+        let u: &[u8; 32] = &[
+            0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00,
+        ];
+        u.into()
+    };
+    pub static ref DUMMY_DATA_1: bytes::Bytes = vec![0x01, 0x02, 0x03].into();
+    pub static ref DUMMY_DATA_2: bytes::Bytes = vec![0x04, 0x05].into();
+
+    pub static ref HELLOWORLD_BLOB_DIGEST: B3Digest =
+        blake3::hash(HELLOWORLD_BLOB_CONTENTS).as_bytes().into();
+    pub static ref EMPTY_BLOB_DIGEST: B3Digest =
+        blake3::hash(EMPTY_BLOB_CONTENTS).as_bytes().into();
+
+    // 2 bytes
+    pub static ref BLOB_A: bytes::Bytes = vec![0x00, 0x01].into();
+    pub static ref BLOB_A_DIGEST: B3Digest = blake3::hash(&BLOB_A).as_bytes().into();
+
+    // 1MB
+    pub static ref BLOB_B: bytes::Bytes = (0..255).collect::<Vec<u8>>().repeat(4 * 1024).into();
+    pub static ref BLOB_B_DIGEST: B3Digest = blake3::hash(&BLOB_B).as_bytes().into();
+
+    // Directories
+    pub static ref DIRECTORY_WITH_KEEP: proto::Directory = proto::Directory {
+        directories: vec![],
+        files: vec![FileNode {
+            name: b".keep".to_vec().into(),
+            digest: EMPTY_BLOB_DIGEST.clone().into(),
+            size: 0,
+            executable: false,
+        }],
+        symlinks: vec![],
+    };
+    pub static ref DIRECTORY_COMPLICATED: proto::Directory = proto::Directory {
+        directories: vec![DirectoryNode {
+            name: b"keep".to_vec().into(),
+            digest: DIRECTORY_WITH_KEEP.digest().into(),
+            size: DIRECTORY_WITH_KEEP.size(),
+        }],
+        files: vec![FileNode {
+            name: b".keep".to_vec().into(),
+            digest: EMPTY_BLOB_DIGEST.clone().into(),
+            size: 0,
+            executable: false,
+        }],
+        symlinks: vec![SymlinkNode {
+            name: b"aa".to_vec().into(),
+            target: b"/nix/store/somewhereelse".to_vec().into(),
+        }],
+    };
+    pub static ref DIRECTORY_A: Directory = Directory::default();
+    pub static ref DIRECTORY_B: Directory = Directory {
+        directories: vec![DirectoryNode {
+            name: b"a".to_vec().into(),
+            digest: DIRECTORY_A.digest().into(),
+            size: DIRECTORY_A.size(),
+        }],
+        ..Default::default()
+    };
+    pub static ref DIRECTORY_C: Directory = Directory {
+        directories: vec![
+            DirectoryNode {
+                name: b"a".to_vec().into(),
+                digest: DIRECTORY_A.digest().into(),
+                size: DIRECTORY_A.size(),
+            },
+            DirectoryNode {
+                name: b"a'".to_vec().into(),
+                digest: DIRECTORY_A.digest().into(),
+                size: DIRECTORY_A.size(),
+            }
+        ],
+        ..Default::default()
+    };
+}
diff --git a/tvix/store/src/import.rs b/tvix/castore/src/import.rs
index 6eebe500d275..92f792bfe704 100644
--- a/tvix/store/src/import.rs
+++ b/tvix/castore/src/import.rs
@@ -1,6 +1,12 @@
 use crate::blobservice::BlobService;
+use crate::directoryservice::DirectoryPutter;
 use crate::directoryservice::DirectoryService;
-use crate::{directoryservice::DirectoryPutter, proto};
+use crate::proto::node::Node;
+use crate::proto::Directory;
+use crate::proto::DirectoryNode;
+use crate::proto::FileNode;
+use crate::proto::SymlinkNode;
+use crate::Error as CastoreError;
 use std::os::unix::ffi::OsStrExt;
 use std::sync::Arc;
 use std::{
@@ -15,7 +21,7 @@ use walkdir::WalkDir;
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
     #[error("failed to upload directory at {0}: {1}")]
-    UploadDirectoryError(PathBuf, crate::Error),
+    UploadDirectoryError(PathBuf, CastoreError),
 
     #[error("invalid encoding encountered for entry {0:?}")]
     InvalidEncoding(PathBuf),
@@ -30,11 +36,11 @@ pub enum Error {
     UnableToRead(PathBuf, std::io::Error),
 }
 
-impl From<super::Error> for Error {
-    fn from(value: super::Error) -> Self {
+impl From<CastoreError> for Error {
+    fn from(value: CastoreError) -> Self {
         match value {
-            crate::Error::InvalidRequest(_) => panic!("tvix bug"),
-            crate::Error::StorageError(_) => panic!("error"),
+            CastoreError::InvalidRequest(_) => panic!("tvix bug"),
+            CastoreError::StorageError(_) => panic!("error"),
         }
     }
 }
@@ -59,8 +65,8 @@ async fn process_entry(
     blob_service: Arc<dyn BlobService>,
     directory_putter: &mut Box<dyn DirectoryPutter>,
     entry: &walkdir::DirEntry,
-    maybe_directory: Option<proto::Directory>,
-) -> Result<proto::node::Node, Error> {
+    maybe_directory: Option<Directory>,
+) -> Result<Node, Error> {
     let file_type = entry.file_type();
 
     if file_type.is_dir() {
@@ -75,7 +81,7 @@ async fn process_entry(
             .await
             .map_err(|e| Error::UploadDirectoryError(entry.path().to_path_buf(), e))?;
 
-        return Ok(proto::node::Node::Directory(proto::DirectoryNode {
+        return Ok(Node::Directory(DirectoryNode {
             name: entry.file_name().as_bytes().to_owned().into(),
             digest: directory_digest.into(),
             size: directory_size,
@@ -90,7 +96,7 @@ async fn process_entry(
             .to_owned()
             .into();
 
-        return Ok(proto::node::Node::Symlink(proto::SymlinkNode {
+        return Ok(Node::Symlink(SymlinkNode {
             name: entry.file_name().as_bytes().to_owned().into(),
             target,
         }));
@@ -113,7 +119,7 @@ async fn process_entry(
 
         let digest = writer.close().await?;
 
-        return Ok(proto::node::Node::File(proto::FileNode {
+        return Ok(Node::File(FileNode {
             name: entry.file_name().as_bytes().to_vec().into(),
             digest: digest.into(),
             size: metadata.len() as u32,
@@ -132,17 +138,17 @@ async fn process_entry(
 /// It does not follow symlinks at the root, they will be ingested as actual
 /// symlinks.
 ///
-/// It's not interacting with a
-/// [PathInfoService](crate::pathinfoservice::PathInfoService), it's up to the
-/// caller to possibly register it somewhere (and potentially rename it based on
-/// some naming scheme.
+/// It's not interacting with a PathInfoService (from tvix-store), or anything
+/// else giving it a "non-content-addressed name".
+/// It's up to the caller to possibly register it somewhere (and potentially
+/// rename it based on some naming scheme)
 #[instrument(skip(blob_service, directory_service), fields(path=?p))]
 pub async fn ingest_path<P: AsRef<Path> + Debug>(
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
     p: P,
-) -> Result<proto::node::Node, Error> {
-    let mut directories: HashMap<PathBuf, proto::Directory> = HashMap::default();
+) -> Result<Node, Error> {
+    let mut directories: HashMap<PathBuf, Directory> = HashMap::default();
 
     // TODO: pass this one instead?
     let mut directory_putter = directory_service.put_multiple_start();
@@ -157,7 +163,7 @@ pub async fn ingest_path<P: AsRef<Path> + Debug>(
 
         // process_entry wants an Option<Directory> in case the entry points to a directory.
         // make sure to provide it.
-        let maybe_directory: Option<proto::Directory> = {
+        let maybe_directory: Option<Directory> = {
             if entry.file_type().is_dir() {
                 Some(
                     directories
@@ -188,9 +194,9 @@ pub async fn ingest_path<P: AsRef<Path> + Debug>(
             // record node in parent directory, creating a new [proto:Directory] if not there yet.
             let parent_directory = directories.entry(parent_path).or_default();
             match node {
-                proto::node::Node::Directory(e) => parent_directory.directories.push(e),
-                proto::node::Node::File(e) => parent_directory.files.push(e),
-                proto::node::Node::Symlink(e) => parent_directory.symlinks.push(e),
+                Node::Directory(e) => parent_directory.directories.push(e),
+                Node::File(e) => parent_directory.files.push(e),
+                Node::Symlink(e) => parent_directory.symlinks.push(e),
             }
         }
     }
diff --git a/tvix/castore/src/lib.rs b/tvix/castore/src/lib.rs
new file mode 100644
index 000000000000..76490fb7e6ef
--- /dev/null
+++ b/tvix/castore/src/lib.rs
@@ -0,0 +1,15 @@
+mod digests;
+mod errors;
+
+pub mod blobservice;
+pub mod directoryservice;
+pub mod fixtures;
+pub mod import;
+pub mod proto;
+pub mod utils;
+
+pub use digests::B3Digest;
+pub use errors::Error;
+
+#[cfg(test)]
+mod tests;
diff --git a/tvix/store/src/proto/grpc_blobservice_wrapper.rs b/tvix/castore/src/proto/grpc_blobservice_wrapper.rs
index 93db1deef69a..93db1deef69a 100644
--- a/tvix/store/src/proto/grpc_blobservice_wrapper.rs
+++ b/tvix/castore/src/proto/grpc_blobservice_wrapper.rs
diff --git a/tvix/store/src/proto/grpc_directoryservice_wrapper.rs b/tvix/castore/src/proto/grpc_directoryservice_wrapper.rs
index 5e143a7bd7a8..5e143a7bd7a8 100644
--- a/tvix/store/src/proto/grpc_directoryservice_wrapper.rs
+++ b/tvix/castore/src/proto/grpc_directoryservice_wrapper.rs
diff --git a/tvix/castore/src/proto/mod.rs b/tvix/castore/src/proto/mod.rs
new file mode 100644
index 000000000000..2a44383fdd85
--- /dev/null
+++ b/tvix/castore/src/proto/mod.rs
@@ -0,0 +1,279 @@
+#![allow(clippy::derive_partial_eq_without_eq, non_snake_case)]
+// https://github.com/hyperium/tonic/issues/1056
+use data_encoding::BASE64;
+use std::{collections::HashSet, iter::Peekable};
+use thiserror::Error;
+
+use prost::Message;
+
+mod grpc_blobservice_wrapper;
+mod grpc_directoryservice_wrapper;
+
+pub use grpc_blobservice_wrapper::GRPCBlobServiceWrapper;
+pub use grpc_directoryservice_wrapper::GRPCDirectoryServiceWrapper;
+
+use crate::B3Digest;
+
+tonic::include_proto!("tvix.castore.v1");
+
+#[cfg(feature = "reflection")]
+/// Compiled file descriptors for implementing [gRPC
+/// reflection](https://github.com/grpc/grpc/blob/master/doc/server-reflection.md) with e.g.
+/// [`tonic_reflection`](https://docs.rs/tonic-reflection).
+pub const FILE_DESCRIPTOR_SET: &[u8] = tonic::include_file_descriptor_set!("tvix.castore.v1");
+
+#[cfg(test)]
+mod tests;
+
+/// Errors that can occur during the validation of Directory messages.
+#[derive(Debug, PartialEq, Eq, Error)]
+pub enum ValidateDirectoryError {
+    /// Elements are not in sorted order
+    #[error("{} is not sorted", std::str::from_utf8(.0).unwrap_or(&BASE64.encode(.0)))]
+    WrongSorting(Vec<u8>),
+    /// Multiple elements with the same name encountered
+    #[error("{0:?} is a duplicate name")]
+    DuplicateName(Vec<u8>),
+    /// Invalid name encountered
+    #[error("Invalid name in {0:?}")]
+    InvalidName(Vec<u8>),
+    /// Invalid digest length encountered
+    #[error("Invalid Digest length: {0}")]
+    InvalidDigestLen(usize),
+}
+
+/// Checks a Node name for validity as an intermediate node, and returns an
+/// error that's generated from the supplied constructor.
+///
+/// We disallow slashes, null bytes, '.', '..' and the empty string.
+fn validate_node_name<E>(name: &[u8], err: fn(Vec<u8>) -> E) -> Result<(), E> {
+    if name.is_empty()
+        || name == b".."
+        || name == b"."
+        || name.contains(&0x00)
+        || name.contains(&b'/')
+    {
+        return Err(err(name.to_vec()));
+    }
+    Ok(())
+}
+
+/// NamedNode is implemented for [FileNode], [DirectoryNode] and [SymlinkNode]
+/// and [node::Node], so we can ask all of them for the name easily.
+pub trait NamedNode {
+    fn get_name(&self) -> &[u8];
+}
+
+impl NamedNode for &FileNode {
+    fn get_name(&self) -> &[u8] {
+        &self.name
+    }
+}
+
+impl NamedNode for &DirectoryNode {
+    fn get_name(&self) -> &[u8] {
+        &self.name
+    }
+}
+
+impl NamedNode for &SymlinkNode {
+    fn get_name(&self) -> &[u8] {
+        &self.name
+    }
+}
+
+impl NamedNode for node::Node {
+    fn get_name(&self) -> &[u8] {
+        match self {
+            node::Node::File(node_file) => &node_file.name,
+            node::Node::Directory(node_directory) => &node_directory.name,
+            node::Node::Symlink(node_symlink) => &node_symlink.name,
+        }
+    }
+}
+
+impl node::Node {
+    /// Returns the node with a new name.
+    pub fn rename(self, name: bytes::Bytes) -> Self {
+        match self {
+            node::Node::Directory(n) => node::Node::Directory(DirectoryNode { name, ..n }),
+            node::Node::File(n) => node::Node::File(FileNode { name, ..n }),
+            node::Node::Symlink(n) => node::Node::Symlink(SymlinkNode { name, ..n }),
+        }
+    }
+}
+
+/// Accepts a name, and a mutable reference to the previous name.
+/// If the passed name is larger than the previous one, the reference is updated.
+/// If it's not, an error is returned.
+fn update_if_lt_prev<'n>(
+    prev_name: &mut &'n [u8],
+    name: &'n [u8],
+) -> Result<(), ValidateDirectoryError> {
+    if *name < **prev_name {
+        return Err(ValidateDirectoryError::WrongSorting(name.to_vec()));
+    }
+    *prev_name = name;
+    Ok(())
+}
+
+/// Inserts the given name into a HashSet if it's not already in there.
+/// If it is, an error is returned.
+fn insert_once<'n>(
+    seen_names: &mut HashSet<&'n [u8]>,
+    name: &'n [u8],
+) -> Result<(), ValidateDirectoryError> {
+    if seen_names.get(name).is_some() {
+        return Err(ValidateDirectoryError::DuplicateName(name.to_vec()));
+    }
+    seen_names.insert(name);
+    Ok(())
+}
+
+impl Directory {
+    /// The size of a directory is the number of all regular and symlink elements,
+    /// the number of directory elements, and their size fields.
+    pub fn size(&self) -> u32 {
+        self.files.len() as u32
+            + self.symlinks.len() as u32
+            + self
+                .directories
+                .iter()
+                .fold(0, |acc: u32, e| (acc + 1 + e.size))
+    }
+
+    /// Calculates the digest of a Directory, which is the blake3 hash of a
+    /// Directory protobuf message, serialized in protobuf canonical form.
+    pub fn digest(&self) -> B3Digest {
+        let mut hasher = blake3::Hasher::new();
+
+        hasher
+            .update(&self.encode_to_vec())
+            .finalize()
+            .as_bytes()
+            .into()
+    }
+
+    /// validate checks the directory for invalid data, such as:
+    /// - violations of name restrictions
+    /// - invalid digest lengths
+    /// - not properly sorted lists
+    /// - duplicate names in the three lists
+    pub fn validate(&self) -> Result<(), ValidateDirectoryError> {
+        let mut seen_names: HashSet<&[u8]> = HashSet::new();
+
+        let mut last_directory_name: &[u8] = b"";
+        let mut last_file_name: &[u8] = b"";
+        let mut last_symlink_name: &[u8] = b"";
+
+        // check directories
+        for directory_node in &self.directories {
+            validate_node_name(&directory_node.name, ValidateDirectoryError::InvalidName)?;
+            // ensure the digest has the appropriate size.
+            if TryInto::<B3Digest>::try_into(directory_node.digest.clone()).is_err() {
+                return Err(ValidateDirectoryError::InvalidDigestLen(
+                    directory_node.digest.len(),
+                ));
+            }
+
+            update_if_lt_prev(&mut last_directory_name, &directory_node.name)?;
+            insert_once(&mut seen_names, &directory_node.name)?;
+        }
+
+        // check files
+        for file_node in &self.files {
+            validate_node_name(&file_node.name, ValidateDirectoryError::InvalidName)?;
+            if TryInto::<B3Digest>::try_into(file_node.digest.clone()).is_err() {
+                return Err(ValidateDirectoryError::InvalidDigestLen(
+                    file_node.digest.len(),
+                ));
+            }
+
+            update_if_lt_prev(&mut last_file_name, &file_node.name)?;
+            insert_once(&mut seen_names, &file_node.name)?;
+        }
+
+        // check symlinks
+        for symlink_node in &self.symlinks {
+            validate_node_name(&symlink_node.name, ValidateDirectoryError::InvalidName)?;
+
+            update_if_lt_prev(&mut last_symlink_name, &symlink_node.name)?;
+            insert_once(&mut seen_names, &symlink_node.name)?;
+        }
+
+        Ok(())
+    }
+
+    /// Allows iterating over all three nodes ([DirectoryNode], [FileNode],
+    /// [SymlinkNode]) in an ordered fashion, as long as the individual lists
+    /// are sorted (which can be checked by the [Directory::validate]).
+    pub fn nodes(&self) -> DirectoryNodesIterator {
+        return DirectoryNodesIterator {
+            i_directories: self.directories.iter().peekable(),
+            i_files: self.files.iter().peekable(),
+            i_symlinks: self.symlinks.iter().peekable(),
+        };
+    }
+}
+
+/// Struct to hold the state of an iterator over all nodes of a Directory.
+///
+/// Internally, this keeps peekable Iterators over all three lists of a
+/// Directory message.
+pub struct DirectoryNodesIterator<'a> {
+    // directory: &Directory,
+    i_directories: Peekable<std::slice::Iter<'a, DirectoryNode>>,
+    i_files: Peekable<std::slice::Iter<'a, FileNode>>,
+    i_symlinks: Peekable<std::slice::Iter<'a, SymlinkNode>>,
+}
+
+/// looks at two elements implementing NamedNode, and returns true if "left
+/// is smaller / comes first".
+///
+/// Some(_) is preferred over None.
+fn left_name_lt_right<A: NamedNode, B: NamedNode>(left: Option<&A>, right: Option<&B>) -> bool {
+    match left {
+        // if left is None, right always wins
+        None => false,
+        Some(left_inner) => {
+            // left is Some.
+            match right {
+                // left is Some, right is None - left wins.
+                None => true,
+                Some(right_inner) => {
+                    // both are Some - compare the name.
+                    return left_inner.get_name() < right_inner.get_name();
+                }
+            }
+        }
+    }
+}
+
+impl Iterator for DirectoryNodesIterator<'_> {
+    type Item = node::Node;
+
+    // next returns the next node in the Directory.
+    // we peek at all three internal iterators, and pick the one with the
+    // smallest name, to ensure lexicographical ordering.
+    // The individual lists are already known to be sorted.
+    fn next(&mut self) -> Option<Self::Item> {
+        if left_name_lt_right(self.i_directories.peek(), self.i_files.peek()) {
+            // i_directories is still in the game, compare with symlinks
+            if left_name_lt_right(self.i_directories.peek(), self.i_symlinks.peek()) {
+                self.i_directories
+                    .next()
+                    .cloned()
+                    .map(node::Node::Directory)
+            } else {
+                self.i_symlinks.next().cloned().map(node::Node::Symlink)
+            }
+        } else {
+            // i_files is still in the game, compare with symlinks
+            if left_name_lt_right(self.i_files.peek(), self.i_symlinks.peek()) {
+                self.i_files.next().cloned().map(node::Node::File)
+            } else {
+                self.i_symlinks.next().cloned().map(node::Node::Symlink)
+            }
+        }
+    }
+}
diff --git a/tvix/store/src/proto/tests/directory.rs b/tvix/castore/src/proto/tests/directory.rs
index eed49b2b593c..eed49b2b593c 100644
--- a/tvix/store/src/proto/tests/directory.rs
+++ b/tvix/castore/src/proto/tests/directory.rs
diff --git a/tvix/store/src/proto/tests/directory_nodes_iterator.rs b/tvix/castore/src/proto/tests/directory_nodes_iterator.rs
index 68f147a33210..68f147a33210 100644
--- a/tvix/store/src/proto/tests/directory_nodes_iterator.rs
+++ b/tvix/castore/src/proto/tests/directory_nodes_iterator.rs
diff --git a/tvix/store/src/proto/tests/grpc_blobservice.rs b/tvix/castore/src/proto/tests/grpc_blobservice.rs
index 497893f03dd7..0d7b340b4409 100644
--- a/tvix/store/src/proto/tests/grpc_blobservice.rs
+++ b/tvix/castore/src/proto/tests/grpc_blobservice.rs
@@ -1,7 +1,7 @@
+use crate::fixtures::{BLOB_A, BLOB_A_DIGEST};
 use crate::proto::blob_service_server::BlobService as GRPCBlobService;
 use crate::proto::{BlobChunk, GRPCBlobServiceWrapper, ReadBlobRequest, StatBlobRequest};
-use crate::tests::fixtures::{BLOB_A, BLOB_A_DIGEST};
-use crate::tests::utils::gen_blob_service;
+use crate::utils::gen_blob_service;
 use tokio_stream::StreamExt;
 
 fn gen_grpc_blob_service() -> GRPCBlobServiceWrapper {
diff --git a/tvix/store/src/proto/tests/grpc_directoryservice.rs b/tvix/castore/src/proto/tests/grpc_directoryservice.rs
index a5300039fb9f..6e8cf1e4a7a4 100644
--- a/tvix/store/src/proto/tests/grpc_directoryservice.rs
+++ b/tvix/castore/src/proto/tests/grpc_directoryservice.rs
@@ -1,9 +1,9 @@
+use crate::fixtures::{DIRECTORY_A, DIRECTORY_B, DIRECTORY_C};
 use crate::proto::directory_service_server::DirectoryService as GRPCDirectoryService;
 use crate::proto::get_directory_request::ByWhat;
 use crate::proto::{Directory, DirectoryNode, SymlinkNode};
 use crate::proto::{GRPCDirectoryServiceWrapper, GetDirectoryRequest};
-use crate::tests::fixtures::{DIRECTORY_A, DIRECTORY_B, DIRECTORY_C};
-use crate::tests::utils::gen_directory_service;
+use crate::utils::gen_directory_service;
 use tokio_stream::StreamExt;
 use tonic::Status;
 
diff --git a/tvix/castore/src/proto/tests/mod.rs b/tvix/castore/src/proto/tests/mod.rs
new file mode 100644
index 000000000000..8b62fadeb5a6
--- /dev/null
+++ b/tvix/castore/src/proto/tests/mod.rs
@@ -0,0 +1,4 @@
+mod directory;
+mod directory_nodes_iterator;
+mod grpc_blobservice;
+mod grpc_directoryservice;
diff --git a/tvix/store/src/tests/import.rs b/tvix/castore/src/tests/import.rs
index 3f7f7dff9db1..77ed6d21c07a 100644
--- a/tvix/store/src/tests/import.rs
+++ b/tvix/castore/src/tests/import.rs
@@ -1,8 +1,7 @@
-use super::utils::{gen_blob_service, gen_directory_service};
+use crate::fixtures::*;
 use crate::import::ingest_path;
 use crate::proto;
-use crate::tests::fixtures::DIRECTORY_COMPLICATED;
-use crate::tests::fixtures::*;
+use crate::utils::{gen_blob_service, gen_directory_service};
 use tempfile::TempDir;
 
 #[cfg(target_family = "unix")]
@@ -29,7 +28,7 @@ async fn symlink() {
     .expect("must succeed");
 
     assert_eq!(
-        crate::proto::node::Node::Symlink(proto::SymlinkNode {
+        proto::node::Node::Symlink(proto::SymlinkNode {
             name: "doesntmatter".into(),
             target: "/nix/store/somewhereelse".into(),
         }),
@@ -54,7 +53,7 @@ async fn single_file() {
     .expect("must succeed");
 
     assert_eq!(
-        crate::proto::node::Node::File(proto::FileNode {
+        proto::node::Node::File(proto::FileNode {
             name: "root".into(),
             digest: HELLOWORLD_BLOB_DIGEST.clone().into(),
             size: HELLOWORLD_BLOB_CONTENTS.len() as u32,
@@ -94,7 +93,7 @@ async fn complicated() {
 
     // ensure root_node matched expectations
     assert_eq!(
-        crate::proto::node::Node::Directory(proto::DirectoryNode {
+        proto::node::Node::Directory(proto::DirectoryNode {
             name: tmpdir
                 .path()
                 .file_name()
diff --git a/tvix/castore/src/tests/mod.rs b/tvix/castore/src/tests/mod.rs
new file mode 100644
index 000000000000..d016f3e0aa55
--- /dev/null
+++ b/tvix/castore/src/tests/mod.rs
@@ -0,0 +1 @@
+mod import;
diff --git a/tvix/castore/src/utils.rs b/tvix/castore/src/utils.rs
new file mode 100644
index 000000000000..660cb2f4b084
--- /dev/null
+++ b/tvix/castore/src/utils.rs
@@ -0,0 +1,19 @@
+//! A crate containing constructors to provide instances of a BlobService and
+//! DirectoryService.
+//! Only used for testing purposes, but across crates.
+//! Should be removed once we have a better concept of a "Service registry".
+
+use std::sync::Arc;
+
+use crate::{
+    blobservice::{BlobService, MemoryBlobService},
+    directoryservice::{DirectoryService, MemoryDirectoryService},
+};
+
+pub fn gen_blob_service() -> Arc<dyn BlobService> {
+    Arc::new(MemoryBlobService::default())
+}
+
+pub fn gen_directory_service() -> Arc<dyn DirectoryService> {
+    Arc::new(MemoryDirectoryService::default())
+}
diff --git a/tvix/cli/Cargo.toml b/tvix/cli/Cargo.toml
index cb795976a971..577ee8bb9e87 100644
--- a/tvix/cli/Cargo.toml
+++ b/tvix/cli/Cargo.toml
@@ -9,6 +9,7 @@ path = "src/main.rs"
 
 [dependencies]
 nix-compat = { path = "../nix-compat" }
+tvix-castore = { path = "../castore" }
 tvix-store = { path = "../store", features = []}
 tvix-eval = { path = "../eval" }
 bytes = "1.4.0"
diff --git a/tvix/cli/src/main.rs b/tvix/cli/src/main.rs
index 65970e1d1cd8..ebcfe4b800b8 100644
--- a/tvix/cli/src/main.rs
+++ b/tvix/cli/src/main.rs
@@ -13,10 +13,10 @@ use std::{fs, path::PathBuf};
 use clap::Parser;
 use known_paths::KnownPaths;
 use rustyline::{error::ReadlineError, Editor};
+use tvix_castore::blobservice::MemoryBlobService;
+use tvix_castore::directoryservice::MemoryDirectoryService;
 use tvix_eval::observer::{DisassemblingObserver, TracingObserver};
 use tvix_eval::Value;
-use tvix_store::blobservice::MemoryBlobService;
-use tvix_store::directoryservice::MemoryDirectoryService;
 use tvix_store::pathinfoservice::MemoryPathInfoService;
 use tvix_store_io::TvixStoreIO;
 
diff --git a/tvix/cli/src/tvix_store_io.rs b/tvix/cli/src/tvix_store_io.rs
index ef112858b1bc..cc69357282fd 100644
--- a/tvix/cli/src/tvix_store_io.rs
+++ b/tvix/cli/src/tvix_store_io.rs
@@ -6,14 +6,17 @@ use tokio::io::AsyncReadExt;
 use tracing::{error, instrument, warn};
 use tvix_eval::{EvalIO, FileType, StdIO};
 
-use tvix_store::{
+use tvix_castore::{
     blobservice::BlobService,
     directoryservice::{self, DirectoryService},
     import,
+    proto::{node::Node, NamedNode},
+    B3Digest,
+};
+use tvix_store::{
     nar::calculate_size_and_sha256,
     pathinfoservice::PathInfoService,
-    proto::{node::Node, NamedNode, NarInfo, PathInfo},
-    B3Digest,
+    proto::{NarInfo, PathInfo},
 };
 
 /// Implements [EvalIO], asking given [PathInfoService], [DirectoryService]
@@ -330,7 +333,7 @@ async fn import_path_with_pathinfo(
 
     // assemble the [PathInfo] object.
     let path_info = PathInfo {
-        node: Some(tvix_store::proto::Node {
+        node: Some(tvix_castore::proto::Node {
             node: Some(root_node),
         }),
         // There's no reference scanning on path contents ingested like this.
diff --git a/tvix/default.nix b/tvix/default.nix
index 8082a13155c8..84d9730d1907 100644
--- a/tvix/default.nix
+++ b/tvix/default.nix
@@ -36,8 +36,13 @@ let
         nativeBuildInputs = protobufDep prev;
       };
 
+      tvix-castore = prev: {
+        PROTO_ROOT = depot.tvix.proto;
+        nativeBuildInputs = protobufDep prev;
+      };
+
       tvix-store = prev: {
-        PROTO_ROOT = depot.tvix.store.protos;
+        PROTO_ROOT = depot.tvix.proto;
         nativeBuildInputs = protobufDep prev;
       };
     };
@@ -103,20 +108,26 @@ in
     ] ++ iconvDarwinDep;
   };
 
-  # Builds and tests the code in store/protos.
-  store-protos-go = pkgs.buildGoModule {
-    name = "store-golang";
-    src = depot.third_party.gitignoreSource ./store/protos;
+  # Builds and tests the code in castore/protos.
+  # castore-protos-go = pkgs.buildGoModule {
+  #   name = "castore-golang";
+  #   src = depot.third_party.gitignoreSource ./store/protos;
+  #   vendorHash = "sha256-00000000000000000000000000000000000000000000";
+  # };
 
-    vendorHash = "sha256-7xfXBBU3xJz7ifjk7Owm/byTfCQ8oaZtqXzBKhLqo00=";
-  };
+  # Builds and tests the code in store/protos.
+  # store-protos-go = pkgs.buildGoModule {
+  #   name = "store-golang";
+  #   src = depot.third_party.gitignoreSource ./store/protos;
+  #   vendorHash = "sha256-00000000000000000000000000000000000000000000";
+  # };
 
   # Build the Rust documentation for publishing on docs.tvix.dev.
   rust-docs = pkgs.stdenv.mkDerivation {
     inherit cargoDeps;
     name = "tvix-rust-docs";
     src = depot.third_party.gitignoreSource ./.;
-    PROTO_ROOT = depot.tvix.store.protos;
+    PROTO_ROOT = depot.tvix.proto;
 
     buildInputs = [
       pkgs.fuse
@@ -135,5 +146,10 @@ in
     '';
   };
 
-  meta.ci.targets = [ "store-protos-go" "shell" "rust-docs" ];
+  meta.ci.targets = [
+    # "castore-protos-go"
+    # "store-protos-go"
+    "shell"
+    "rust-docs"
+  ];
 }
diff --git a/tvix/proto/default.nix b/tvix/proto/default.nix
index 35e2eba7fed4..0ee102e4f958 100644
--- a/tvix/proto/default.nix
+++ b/tvix/proto/default.nix
@@ -1,9 +1,15 @@
-# Build protocol buffer definitions to ensure that protos are valid in
-# CI. Note that the output of this build target is not actually used
-# anywhere, it just functions as a CI check for now.
-{ pkgs, ... }:
+# Target containing just the proto files used in tvix
 
-pkgs.runCommand "tvix-cc-proto" { } ''
-  mkdir $out
-  ${pkgs.protobuf}/bin/protoc -I ${./.} evaluator.proto --cpp_out=$out
-''
+{ depot, lib, ... }:
+
+depot.nix.sparseTree {
+  name = "tvix-protos";
+  root = depot.path.origSrc;
+  paths = [
+    ../castore/protos/castore.proto
+    ../castore/protos/rpc_blobstore.proto
+    ../castore/protos/rpc_directory.proto
+    ../store/protos/pathinfo.proto
+    ../store/protos/rpc_pathinfo.proto
+  ];
+}
diff --git a/tvix/store/Cargo.toml b/tvix/store/Cargo.toml
index 81f9d7e75b48..a2e143de7014 100644
--- a/tvix/store/Cargo.toml
+++ b/tvix/store/Cargo.toml
@@ -7,28 +7,29 @@ edition = "2021"
 anyhow = "1.0.68"
 async-stream = "0.3.5"
 blake3 = { version = "1.3.1", features = ["rayon", "std"] }
+bytes = "1.4.0"
 clap = { version = "4.0", features = ["derive", "env"] }
 count-write = "0.1.0"
 data-encoding = "2.3.3"
+futures = "0.3.28"
 lazy_static = "1.4.0"
 nix-compat = { path = "../nix-compat" }
 parking_lot = "0.12.1"
+pin-project-lite = "0.2.13"
 prost = "0.11.2"
 sha2 = "0.10.6"
 sled = { version = "0.34.7", features = ["compression"] }
 thiserror = "1.0.38"
 tokio-stream = { version = "0.1.14", features = ["fs"] }
+tokio-util = { version = "0.7.8", features = ["io", "io-util"] }
 tokio = { version = "1.28.0", features = ["fs", "net", "rt-multi-thread", "signal"] }
 tonic = "0.8.2"
+tower = "0.4.13"
 tracing = "0.1.37"
 tracing-subscriber = { version = "0.3.16", features = ["json"] }
-walkdir = "2.4.0"
-tokio-util = { version = "0.7.8", features = ["io", "io-util"] }
-tower = "0.4.13"
-futures = "0.3.28"
-bytes = "1.4.0"
+tvix-castore = { path = "../castore" }
 url = "2.4.0"
-pin-project-lite = "0.2.13"
+walkdir = "2.4.0"
 
 [dependencies.fuse-backend-rs]
 optional = true
diff --git a/tvix/store/README.md b/tvix/store/README.md
index ca64cd249c1e..8fa4cf5a67c5 100644
--- a/tvix/store/README.md
+++ b/tvix/store/README.md
@@ -14,9 +14,12 @@ However, enough information is preserved to still be able to render NAR and
 NARInfo when needed.
 
 ## More Information
-Check the `protos/` subfolder for the definition of the exact RPC methods and
-messages.
+The store consists out of two different gRPC services, `tvix.castore.v1` for
+the low-level content-addressed bits, and `tvix.store.v1` for the Nix and
+`StorePath`-specific bits.
 
+Check the `protos/` subfolder both here and in `castore` for the definition of
+the exact RPC methods and messages.
 
 ## Interacting with the GRPC service manually
 The shell environment in `//tvix` provides `evans`, which is an interactive
@@ -37,15 +40,16 @@ $ evans --host localhost --port 8000 -r repl
  more expressive universal gRPC client
 
 
-tvix.store.v1@localhost:8000> service BlobService
+localhost:8000> package tvix.castore.v1
+tvix.castore.v1@localhost:8000> service BlobService
 
-tvix.store.v1.BlobService@localhost:8000> call Put --bytes-from-file
+tvix.castore.v1.BlobService@localhost:8000> call Put --bytes-from-file
 data (TYPE_BYTES) => /run/current-system/system
 {
   "digest": "KOM3/IHEx7YfInAnlJpAElYezq0Sxn9fRz7xuClwNfA="
 }
 
-tvix.store.v1.BlobService@localhost:8000> call Get --bytes-as-base64
+tvix.castore.v1.BlobService@localhost:8000> call Get --bytes-as-base64
 digest (TYPE_BYTES) => KOM3/IHEx7YfInAnlJpAElYezq0Sxn9fRz7xuClwNfA=
 {
   "data": "eDg2XzY0LWxpbnV4"
diff --git a/tvix/store/build.rs b/tvix/store/build.rs
index a021dc328af6..9a7356f84eec 100644
--- a/tvix/store/build.rs
+++ b/tvix/store/build.rs
@@ -15,6 +15,7 @@ fn main() -> Result<()> {
     // https://github.com/hyperium/tonic/issues/908
     let mut config = prost_build::Config::new();
     config.bytes(["."]);
+    config.extern_path(".tvix.castore.v1", "::tvix_castore::proto");
 
     builder
         .build_server(true)
@@ -22,10 +23,7 @@ fn main() -> Result<()> {
         .compile_with_config(
             config,
             &[
-                "tvix/store/protos/castore.proto",
                 "tvix/store/protos/pathinfo.proto",
-                "tvix/store/protos/rpc_blobstore.proto",
-                "tvix/store/protos/rpc_directory.proto",
                 "tvix/store/protos/rpc_pathinfo.proto",
             ],
             // If we are in running `cargo build` manually, using `../..` works fine,
diff --git a/tvix/store/protos/castore.pb.go b/tvix/store/protos/castore.pb.go
deleted file mode 100644
index 074b39d548e3..000000000000
--- a/tvix/store/protos/castore.pb.go
+++ /dev/null
@@ -1,450 +0,0 @@
-// SPDX-FileCopyrightText: edef <edef@unfathomable.blue>
-// SPDX-License-Identifier: OSL-3.0 OR MIT OR Apache-2.0
-
-// Code generated by protoc-gen-go. DO NOT EDIT.
-// versions:
-// 	protoc-gen-go v1.31.0
-// 	protoc        (unknown)
-// source: tvix/store/protos/castore.proto
-
-package storev1
-
-import (
-	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
-	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
-	reflect "reflect"
-	sync "sync"
-)
-
-const (
-	// Verify that this generated code is sufficiently up-to-date.
-	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
-	// Verify that runtime/protoimpl is sufficiently up-to-date.
-	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
-)
-
-// A Directory can contain Directory, File or Symlink nodes.
-// Each of these nodes have a name attribute, which is the basename in that directory
-// and node type specific attributes.
-// The name attribute:
-//   - MUST not contain slashes or null bytes
-//   - MUST not be '.' or '..'
-//   - MUST be unique across all three lists
-//
-// Elements in each list need to be lexicographically ordered by the name
-// attribute.
-type Directory struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	Directories []*DirectoryNode `protobuf:"bytes,1,rep,name=directories,proto3" json:"directories,omitempty"`
-	Files       []*FileNode      `protobuf:"bytes,2,rep,name=files,proto3" json:"files,omitempty"`
-	Symlinks    []*SymlinkNode   `protobuf:"bytes,3,rep,name=symlinks,proto3" json:"symlinks,omitempty"`
-}
-
-func (x *Directory) Reset() {
-	*x = Directory{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_castore_proto_msgTypes[0]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *Directory) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*Directory) ProtoMessage() {}
-
-func (x *Directory) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_castore_proto_msgTypes[0]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use Directory.ProtoReflect.Descriptor instead.
-func (*Directory) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_castore_proto_rawDescGZIP(), []int{0}
-}
-
-func (x *Directory) GetDirectories() []*DirectoryNode {
-	if x != nil {
-		return x.Directories
-	}
-	return nil
-}
-
-func (x *Directory) GetFiles() []*FileNode {
-	if x != nil {
-		return x.Files
-	}
-	return nil
-}
-
-func (x *Directory) GetSymlinks() []*SymlinkNode {
-	if x != nil {
-		return x.Symlinks
-	}
-	return nil
-}
-
-// A DirectoryNode represents a directory in a Directory.
-type DirectoryNode struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	// The (base)name of the directory
-	Name []byte `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
-	// The blake3 hash of a Directory message, serialized in protobuf canonical form.
-	Digest []byte `protobuf:"bytes,2,opt,name=digest,proto3" json:"digest,omitempty"`
-	// Number of child elements in the Directory referred to by `digest`.
-	// Calculated by summing up the numbers of `directories`, `files` and
-	// `symlinks`, and for each directory, its size field. Used for inode
-	// number calculation.
-	// This field is precisely as verifiable as any other Merkle tree edge.
-	// Resolve `digest`, and you can compute it incrementally. Resolve the
-	// entire tree, and you can fully compute it from scratch.
-	// A credulous implementation won't reject an excessive size, but this is
-	// harmless: you'll have some ordinals without nodes. Undersizing is
-	// obvious and easy to reject: you won't have an ordinal for some nodes.
-	Size uint32 `protobuf:"varint,3,opt,name=size,proto3" json:"size,omitempty"`
-}
-
-func (x *DirectoryNode) Reset() {
-	*x = DirectoryNode{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_castore_proto_msgTypes[1]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *DirectoryNode) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*DirectoryNode) ProtoMessage() {}
-
-func (x *DirectoryNode) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_castore_proto_msgTypes[1]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use DirectoryNode.ProtoReflect.Descriptor instead.
-func (*DirectoryNode) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_castore_proto_rawDescGZIP(), []int{1}
-}
-
-func (x *DirectoryNode) GetName() []byte {
-	if x != nil {
-		return x.Name
-	}
-	return nil
-}
-
-func (x *DirectoryNode) GetDigest() []byte {
-	if x != nil {
-		return x.Digest
-	}
-	return nil
-}
-
-func (x *DirectoryNode) GetSize() uint32 {
-	if x != nil {
-		return x.Size
-	}
-	return 0
-}
-
-// A FileNode represents a regular or executable file in a Directory.
-type FileNode struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	// The (base)name of the file
-	Name []byte `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
-	// The blake3 digest of the file contents
-	Digest []byte `protobuf:"bytes,2,opt,name=digest,proto3" json:"digest,omitempty"`
-	// The file content size
-	Size uint32 `protobuf:"varint,3,opt,name=size,proto3" json:"size,omitempty"`
-	// Whether the file is executable
-	Executable bool `protobuf:"varint,4,opt,name=executable,proto3" json:"executable,omitempty"`
-}
-
-func (x *FileNode) Reset() {
-	*x = FileNode{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_castore_proto_msgTypes[2]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *FileNode) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*FileNode) ProtoMessage() {}
-
-func (x *FileNode) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_castore_proto_msgTypes[2]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use FileNode.ProtoReflect.Descriptor instead.
-func (*FileNode) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_castore_proto_rawDescGZIP(), []int{2}
-}
-
-func (x *FileNode) GetName() []byte {
-	if x != nil {
-		return x.Name
-	}
-	return nil
-}
-
-func (x *FileNode) GetDigest() []byte {
-	if x != nil {
-		return x.Digest
-	}
-	return nil
-}
-
-func (x *FileNode) GetSize() uint32 {
-	if x != nil {
-		return x.Size
-	}
-	return 0
-}
-
-func (x *FileNode) GetExecutable() bool {
-	if x != nil {
-		return x.Executable
-	}
-	return false
-}
-
-// A SymlinkNode represents a symbolic link in a Directory.
-type SymlinkNode struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	// The (base)name of the symlink
-	Name []byte `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
-	// The target of the symlink.
-	Target []byte `protobuf:"bytes,2,opt,name=target,proto3" json:"target,omitempty"`
-}
-
-func (x *SymlinkNode) Reset() {
-	*x = SymlinkNode{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_castore_proto_msgTypes[3]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *SymlinkNode) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*SymlinkNode) ProtoMessage() {}
-
-func (x *SymlinkNode) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_castore_proto_msgTypes[3]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use SymlinkNode.ProtoReflect.Descriptor instead.
-func (*SymlinkNode) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_castore_proto_rawDescGZIP(), []int{3}
-}
-
-func (x *SymlinkNode) GetName() []byte {
-	if x != nil {
-		return x.Name
-	}
-	return nil
-}
-
-func (x *SymlinkNode) GetTarget() []byte {
-	if x != nil {
-		return x.Target
-	}
-	return nil
-}
-
-var File_tvix_store_protos_castore_proto protoreflect.FileDescriptor
-
-var file_tvix_store_protos_castore_proto_rawDesc = []byte{
-	0x0a, 0x1f, 0x74, 0x76, 0x69, 0x78, 0x2f, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f,
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-	0x03, 0x28, 0x0b, 0x32, 0x1c, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x73, 0x74, 0x6f, 0x72, 0x65,
-	0x2e, 0x76, 0x31, 0x2e, 0x44, 0x69, 0x72, 0x65, 0x63, 0x74, 0x6f, 0x72, 0x79, 0x4e, 0x6f, 0x64,
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-}
-
-var (
-	file_tvix_store_protos_castore_proto_rawDescOnce sync.Once
-	file_tvix_store_protos_castore_proto_rawDescData = file_tvix_store_protos_castore_proto_rawDesc
-)
-
-func file_tvix_store_protos_castore_proto_rawDescGZIP() []byte {
-	file_tvix_store_protos_castore_proto_rawDescOnce.Do(func() {
-		file_tvix_store_protos_castore_proto_rawDescData = protoimpl.X.CompressGZIP(file_tvix_store_protos_castore_proto_rawDescData)
-	})
-	return file_tvix_store_protos_castore_proto_rawDescData
-}
-
-var file_tvix_store_protos_castore_proto_msgTypes = make([]protoimpl.MessageInfo, 4)
-var file_tvix_store_protos_castore_proto_goTypes = []interface{}{
-	(*Directory)(nil),     // 0: tvix.store.v1.Directory
-	(*DirectoryNode)(nil), // 1: tvix.store.v1.DirectoryNode
-	(*FileNode)(nil),      // 2: tvix.store.v1.FileNode
-	(*SymlinkNode)(nil),   // 3: tvix.store.v1.SymlinkNode
-}
-var file_tvix_store_protos_castore_proto_depIdxs = []int32{
-	1, // 0: tvix.store.v1.Directory.directories:type_name -> tvix.store.v1.DirectoryNode
-	2, // 1: tvix.store.v1.Directory.files:type_name -> tvix.store.v1.FileNode
-	3, // 2: tvix.store.v1.Directory.symlinks:type_name -> tvix.store.v1.SymlinkNode
-	3, // [3:3] is the sub-list for method output_type
-	3, // [3:3] is the sub-list for method input_type
-	3, // [3:3] is the sub-list for extension type_name
-	3, // [3:3] is the sub-list for extension extendee
-	0, // [0:3] is the sub-list for field type_name
-}
-
-func init() { file_tvix_store_protos_castore_proto_init() }
-func file_tvix_store_protos_castore_proto_init() {
-	if File_tvix_store_protos_castore_proto != nil {
-		return
-	}
-	if !protoimpl.UnsafeEnabled {
-		file_tvix_store_protos_castore_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*Directory); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-		file_tvix_store_protos_castore_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*DirectoryNode); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-		file_tvix_store_protos_castore_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*FileNode); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-		file_tvix_store_protos_castore_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*SymlinkNode); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-	}
-	type x struct{}
-	out := protoimpl.TypeBuilder{
-		File: protoimpl.DescBuilder{
-			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
-			RawDescriptor: file_tvix_store_protos_castore_proto_rawDesc,
-			NumEnums:      0,
-			NumMessages:   4,
-			NumExtensions: 0,
-			NumServices:   0,
-		},
-		GoTypes:           file_tvix_store_protos_castore_proto_goTypes,
-		DependencyIndexes: file_tvix_store_protos_castore_proto_depIdxs,
-		MessageInfos:      file_tvix_store_protos_castore_proto_msgTypes,
-	}.Build()
-	File_tvix_store_protos_castore_proto = out.File
-	file_tvix_store_protos_castore_proto_rawDesc = nil
-	file_tvix_store_protos_castore_proto_goTypes = nil
-	file_tvix_store_protos_castore_proto_depIdxs = nil
-}
diff --git a/tvix/store/protos/default.nix b/tvix/store/protos/default.nix
deleted file mode 100644
index d5c44842229d..000000000000
--- a/tvix/store/protos/default.nix
+++ /dev/null
@@ -1,16 +0,0 @@
-# Target containing just the proto files.
-
-{ depot, lib, ... }:
-
-let
-  inherit (lib.strings) hasSuffix;
-  inherit (builtins) attrNames filter readDir;
-
-  protoFileNames = filter (hasSuffix ".proto") (attrNames (readDir ./.));
-  protoFiles = map (f: ./. + ("/" + f)) protoFileNames;
-in
-depot.nix.sparseTree {
-  name = "tvix-store-protos";
-  root = depot.path.origSrc;
-  paths = protoFiles;
-}
diff --git a/tvix/store/protos/pathinfo.pb.go b/tvix/store/protos/pathinfo.pb.go
index 126fc34af27d..1e5479ac8f75 100644
--- a/tvix/store/protos/pathinfo.pb.go
+++ b/tvix/store/protos/pathinfo.pb.go
@@ -10,6 +10,7 @@
 package storev1
 
 import (
+	protos "code.tvl.fyi/tvix/castore/protos"
 	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
 	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
 	reflect "reflect"
@@ -31,7 +32,7 @@ type PathInfo struct {
 	unknownFields protoimpl.UnknownFields
 
 	// The path can be a directory, file or symlink.
-	Node *Node `protobuf:"bytes,1,opt,name=node,proto3" json:"node,omitempty"`
+	Node *protos.Node `protobuf:"bytes,1,opt,name=node,proto3" json:"node,omitempty"`
 	// List of references (output path hashes)
 	// This really is the raw *bytes*, after decoding nixbase32, and not a
 	// base32-encoded string.
@@ -72,7 +73,7 @@ func (*PathInfo) Descriptor() ([]byte, []int) {
 	return file_tvix_store_protos_pathinfo_proto_rawDescGZIP(), []int{0}
 }
 
-func (x *PathInfo) GetNode() *Node {
+func (x *PathInfo) GetNode() *protos.Node {
 	if x != nil {
 		return x.Node
 	}
@@ -93,101 +94,6 @@ func (x *PathInfo) GetNarinfo() *NARInfo {
 	return nil
 }
 
-type Node struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	// Types that are assignable to Node:
-	//
-	//	*Node_Directory
-	//	*Node_File
-	//	*Node_Symlink
-	Node isNode_Node `protobuf_oneof:"node"`
-}
-
-func (x *Node) Reset() {
-	*x = Node{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[1]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *Node) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*Node) ProtoMessage() {}
-
-func (x *Node) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[1]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use Node.ProtoReflect.Descriptor instead.
-func (*Node) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_pathinfo_proto_rawDescGZIP(), []int{1}
-}
-
-func (m *Node) GetNode() isNode_Node {
-	if m != nil {
-		return m.Node
-	}
-	return nil
-}
-
-func (x *Node) GetDirectory() *DirectoryNode {
-	if x, ok := x.GetNode().(*Node_Directory); ok {
-		return x.Directory
-	}
-	return nil
-}
-
-func (x *Node) GetFile() *FileNode {
-	if x, ok := x.GetNode().(*Node_File); ok {
-		return x.File
-	}
-	return nil
-}
-
-func (x *Node) GetSymlink() *SymlinkNode {
-	if x, ok := x.GetNode().(*Node_Symlink); ok {
-		return x.Symlink
-	}
-	return nil
-}
-
-type isNode_Node interface {
-	isNode_Node()
-}
-
-type Node_Directory struct {
-	Directory *DirectoryNode `protobuf:"bytes,1,opt,name=directory,proto3,oneof"`
-}
-
-type Node_File struct {
-	File *FileNode `protobuf:"bytes,2,opt,name=file,proto3,oneof"`
-}
-
-type Node_Symlink struct {
-	Symlink *SymlinkNode `protobuf:"bytes,3,opt,name=symlink,proto3,oneof"`
-}
-
-func (*Node_Directory) isNode_Node() {}
-
-func (*Node_File) isNode_Node() {}
-
-func (*Node_Symlink) isNode_Node() {}
-
 // Nix C++ uses NAR (Nix Archive) as a format to transfer store paths,
 // and stores metadata and signatures in NARInfo files.
 // Store all these attributes in a separate message.
@@ -219,7 +125,7 @@ type NARInfo struct {
 func (x *NARInfo) Reset() {
 	*x = NARInfo{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[2]
+		mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[1]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -232,7 +138,7 @@ func (x *NARInfo) String() string {
 func (*NARInfo) ProtoMessage() {}
 
 func (x *NARInfo) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[2]
+	mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[1]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -245,7 +151,7 @@ func (x *NARInfo) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use NARInfo.ProtoReflect.Descriptor instead.
 func (*NARInfo) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_pathinfo_proto_rawDescGZIP(), []int{2}
+	return file_tvix_store_protos_pathinfo_proto_rawDescGZIP(), []int{1}
 }
 
 func (x *NARInfo) GetNarSize() uint64 {
@@ -289,7 +195,7 @@ type NARInfo_Signature struct {
 func (x *NARInfo_Signature) Reset() {
 	*x = NARInfo_Signature{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[3]
+		mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[2]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -302,7 +208,7 @@ func (x *NARInfo_Signature) String() string {
 func (*NARInfo_Signature) ProtoMessage() {}
 
 func (x *NARInfo_Signature) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[3]
+	mi := &file_tvix_store_protos_pathinfo_proto_msgTypes[2]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -315,7 +221,7 @@ func (x *NARInfo_Signature) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use NARInfo_Signature.ProtoReflect.Descriptor instead.
 func (*NARInfo_Signature) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_pathinfo_proto_rawDescGZIP(), []int{2, 0}
+	return file_tvix_store_protos_pathinfo_proto_rawDescGZIP(), []int{1, 0}
 }
 
 func (x *NARInfo_Signature) GetName() string {
@@ -338,46 +244,35 @@ var file_tvix_store_protos_pathinfo_proto_rawDesc = []byte{
 	0x0a, 0x20, 0x74, 0x76, 0x69, 0x78, 0x2f, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f,
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+	0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -392,28 +287,22 @@ func file_tvix_store_protos_pathinfo_proto_rawDescGZIP() []byte {
 	return file_tvix_store_protos_pathinfo_proto_rawDescData
 }
 
-var file_tvix_store_protos_pathinfo_proto_msgTypes = make([]protoimpl.MessageInfo, 4)
+var file_tvix_store_protos_pathinfo_proto_msgTypes = make([]protoimpl.MessageInfo, 3)
 var file_tvix_store_protos_pathinfo_proto_goTypes = []interface{}{
 	(*PathInfo)(nil),          // 0: tvix.store.v1.PathInfo
-	(*Node)(nil),              // 1: tvix.store.v1.Node
-	(*NARInfo)(nil),           // 2: tvix.store.v1.NARInfo
-	(*NARInfo_Signature)(nil), // 3: tvix.store.v1.NARInfo.Signature
-	(*DirectoryNode)(nil),     // 4: tvix.store.v1.DirectoryNode
-	(*FileNode)(nil),          // 5: tvix.store.v1.FileNode
-	(*SymlinkNode)(nil),       // 6: tvix.store.v1.SymlinkNode
+	(*NARInfo)(nil),           // 1: tvix.store.v1.NARInfo
+	(*NARInfo_Signature)(nil), // 2: tvix.store.v1.NARInfo.Signature
+	(*protos.Node)(nil),       // 3: tvix.castore.v1.Node
 }
 var file_tvix_store_protos_pathinfo_proto_depIdxs = []int32{
-	1, // 0: tvix.store.v1.PathInfo.node:type_name -> tvix.store.v1.Node
-	2, // 1: tvix.store.v1.PathInfo.narinfo:type_name -> tvix.store.v1.NARInfo
-	4, // 2: tvix.store.v1.Node.directory:type_name -> tvix.store.v1.DirectoryNode
-	5, // 3: tvix.store.v1.Node.file:type_name -> tvix.store.v1.FileNode
-	6, // 4: tvix.store.v1.Node.symlink:type_name -> tvix.store.v1.SymlinkNode
-	3, // 5: tvix.store.v1.NARInfo.signatures:type_name -> tvix.store.v1.NARInfo.Signature
-	6, // [6:6] is the sub-list for method output_type
-	6, // [6:6] is the sub-list for method input_type
-	6, // [6:6] is the sub-list for extension type_name
-	6, // [6:6] is the sub-list for extension extendee
-	0, // [0:6] is the sub-list for field type_name
+	3, // 0: tvix.store.v1.PathInfo.node:type_name -> tvix.castore.v1.Node
+	1, // 1: tvix.store.v1.PathInfo.narinfo:type_name -> tvix.store.v1.NARInfo
+	2, // 2: tvix.store.v1.NARInfo.signatures:type_name -> tvix.store.v1.NARInfo.Signature
+	3, // [3:3] is the sub-list for method output_type
+	3, // [3:3] is the sub-list for method input_type
+	3, // [3:3] is the sub-list for extension type_name
+	3, // [3:3] is the sub-list for extension extendee
+	0, // [0:3] is the sub-list for field type_name
 }
 
 func init() { file_tvix_store_protos_pathinfo_proto_init() }
@@ -421,7 +310,6 @@ func file_tvix_store_protos_pathinfo_proto_init() {
 	if File_tvix_store_protos_pathinfo_proto != nil {
 		return
 	}
-	file_tvix_store_protos_castore_proto_init()
 	if !protoimpl.UnsafeEnabled {
 		file_tvix_store_protos_pathinfo_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*PathInfo); i {
@@ -436,18 +324,6 @@ func file_tvix_store_protos_pathinfo_proto_init() {
 			}
 		}
 		file_tvix_store_protos_pathinfo_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*Node); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-		file_tvix_store_protos_pathinfo_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*NARInfo); i {
 			case 0:
 				return &v.state
@@ -459,7 +335,7 @@ func file_tvix_store_protos_pathinfo_proto_init() {
 				return nil
 			}
 		}
-		file_tvix_store_protos_pathinfo_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
+		file_tvix_store_protos_pathinfo_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*NARInfo_Signature); i {
 			case 0:
 				return &v.state
@@ -472,18 +348,13 @@ func file_tvix_store_protos_pathinfo_proto_init() {
 			}
 		}
 	}
-	file_tvix_store_protos_pathinfo_proto_msgTypes[1].OneofWrappers = []interface{}{
-		(*Node_Directory)(nil),
-		(*Node_File)(nil),
-		(*Node_Symlink)(nil),
-	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_tvix_store_protos_pathinfo_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   4,
+			NumMessages:   3,
 			NumExtensions: 0,
 			NumServices:   0,
 		},
diff --git a/tvix/store/protos/pathinfo.proto b/tvix/store/protos/pathinfo.proto
index 896d4aa225ac..aa98c6df9a2d 100644
--- a/tvix/store/protos/pathinfo.proto
+++ b/tvix/store/protos/pathinfo.proto
@@ -4,7 +4,7 @@ syntax = "proto3";
 
 package tvix.store.v1;
 
-import "tvix/store/protos/castore.proto";
+import "tvix/castore/protos/castore.proto";
 
 option go_package = "code.tvl.fyi/tvix/store/protos;storev1";
 
@@ -12,7 +12,7 @@ option go_package = "code.tvl.fyi/tvix/store/protos;storev1";
 // That's a single element inside /nix/store.
 message PathInfo {
     // The path can be a directory, file or symlink.
-    Node node = 1;
+    tvix.castore.v1.Node node = 1;
 
     // List of references (output path hashes)
     // This really is the raw *bytes*, after decoding nixbase32, and not a
@@ -23,14 +23,6 @@ message PathInfo {
     NARInfo narinfo = 3;
 }
 
-message Node {
-    oneof node {
-        DirectoryNode directory = 1;
-        FileNode file = 2;
-        SymlinkNode symlink = 3;
-    }
-}
-
 // Nix C++ uses NAR (Nix Archive) as a format to transfer store paths,
 // and stores metadata and signatures in NARInfo files.
 // Store all these attributes in a separate message.
diff --git a/tvix/store/protos/rpc_directory.pb.go b/tvix/store/protos/rpc_directory.pb.go
deleted file mode 100644
index ac5384677b1e..000000000000
--- a/tvix/store/protos/rpc_directory.pb.go
+++ /dev/null
@@ -1,271 +0,0 @@
-// SPDX-License-Identifier: MIT
-// Copyright ยฉ 2022 The Tvix Authors
-
-// Code generated by protoc-gen-go. DO NOT EDIT.
-// versions:
-// 	protoc-gen-go v1.31.0
-// 	protoc        (unknown)
-// source: tvix/store/protos/rpc_directory.proto
-
-package storev1
-
-import (
-	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
-	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
-	reflect "reflect"
-	sync "sync"
-)
-
-const (
-	// Verify that this generated code is sufficiently up-to-date.
-	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
-	// Verify that runtime/protoimpl is sufficiently up-to-date.
-	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
-)
-
-type GetDirectoryRequest struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	// Types that are assignable to ByWhat:
-	//
-	//	*GetDirectoryRequest_Digest
-	ByWhat isGetDirectoryRequest_ByWhat `protobuf_oneof:"by_what"`
-	// If set to true, recursively resolve all child Directory messages.
-	// Directory messages SHOULD be streamed in a recursive breadth-first walk,
-	// but other orders are also fine, as long as Directory messages are only
-	// sent after they are referred to from previously sent Directory messages.
-	Recursive bool `protobuf:"varint,2,opt,name=recursive,proto3" json:"recursive,omitempty"`
-}
-
-func (x *GetDirectoryRequest) Reset() {
-	*x = GetDirectoryRequest{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_directory_proto_msgTypes[0]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *GetDirectoryRequest) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*GetDirectoryRequest) ProtoMessage() {}
-
-func (x *GetDirectoryRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_directory_proto_msgTypes[0]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use GetDirectoryRequest.ProtoReflect.Descriptor instead.
-func (*GetDirectoryRequest) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_directory_proto_rawDescGZIP(), []int{0}
-}
-
-func (m *GetDirectoryRequest) GetByWhat() isGetDirectoryRequest_ByWhat {
-	if m != nil {
-		return m.ByWhat
-	}
-	return nil
-}
-
-func (x *GetDirectoryRequest) GetDigest() []byte {
-	if x, ok := x.GetByWhat().(*GetDirectoryRequest_Digest); ok {
-		return x.Digest
-	}
-	return nil
-}
-
-func (x *GetDirectoryRequest) GetRecursive() bool {
-	if x != nil {
-		return x.Recursive
-	}
-	return false
-}
-
-type isGetDirectoryRequest_ByWhat interface {
-	isGetDirectoryRequest_ByWhat()
-}
-
-type GetDirectoryRequest_Digest struct {
-	// The blake3 hash of the (root) Directory message, serialized in
-	// protobuf canonical form.
-	// Keep in mind this can be a subtree of another root.
-	Digest []byte `protobuf:"bytes,1,opt,name=digest,proto3,oneof"`
-}
-
-func (*GetDirectoryRequest_Digest) isGetDirectoryRequest_ByWhat() {}
-
-type PutDirectoryResponse struct {
-	state         protoimpl.MessageState
-	sizeCache     protoimpl.SizeCache
-	unknownFields protoimpl.UnknownFields
-
-	RootDigest []byte `protobuf:"bytes,1,opt,name=root_digest,json=rootDigest,proto3" json:"root_digest,omitempty"`
-}
-
-func (x *PutDirectoryResponse) Reset() {
-	*x = PutDirectoryResponse{}
-	if protoimpl.UnsafeEnabled {
-		mi := &file_tvix_store_protos_rpc_directory_proto_msgTypes[1]
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		ms.StoreMessageInfo(mi)
-	}
-}
-
-func (x *PutDirectoryResponse) String() string {
-	return protoimpl.X.MessageStringOf(x)
-}
-
-func (*PutDirectoryResponse) ProtoMessage() {}
-
-func (x *PutDirectoryResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_tvix_store_protos_rpc_directory_proto_msgTypes[1]
-	if protoimpl.UnsafeEnabled && x != nil {
-		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
-		if ms.LoadMessageInfo() == nil {
-			ms.StoreMessageInfo(mi)
-		}
-		return ms
-	}
-	return mi.MessageOf(x)
-}
-
-// Deprecated: Use PutDirectoryResponse.ProtoReflect.Descriptor instead.
-func (*PutDirectoryResponse) Descriptor() ([]byte, []int) {
-	return file_tvix_store_protos_rpc_directory_proto_rawDescGZIP(), []int{1}
-}
-
-func (x *PutDirectoryResponse) GetRootDigest() []byte {
-	if x != nil {
-		return x.RootDigest
-	}
-	return nil
-}
-
-var File_tvix_store_protos_rpc_directory_proto protoreflect.FileDescriptor
-
-var file_tvix_store_protos_rpc_directory_proto_rawDesc = []byte{
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-}
-
-var (
-	file_tvix_store_protos_rpc_directory_proto_rawDescOnce sync.Once
-	file_tvix_store_protos_rpc_directory_proto_rawDescData = file_tvix_store_protos_rpc_directory_proto_rawDesc
-)
-
-func file_tvix_store_protos_rpc_directory_proto_rawDescGZIP() []byte {
-	file_tvix_store_protos_rpc_directory_proto_rawDescOnce.Do(func() {
-		file_tvix_store_protos_rpc_directory_proto_rawDescData = protoimpl.X.CompressGZIP(file_tvix_store_protos_rpc_directory_proto_rawDescData)
-	})
-	return file_tvix_store_protos_rpc_directory_proto_rawDescData
-}
-
-var file_tvix_store_protos_rpc_directory_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
-var file_tvix_store_protos_rpc_directory_proto_goTypes = []interface{}{
-	(*GetDirectoryRequest)(nil),  // 0: tvix.store.v1.GetDirectoryRequest
-	(*PutDirectoryResponse)(nil), // 1: tvix.store.v1.PutDirectoryResponse
-	(*Directory)(nil),            // 2: tvix.store.v1.Directory
-}
-var file_tvix_store_protos_rpc_directory_proto_depIdxs = []int32{
-	0, // 0: tvix.store.v1.DirectoryService.Get:input_type -> tvix.store.v1.GetDirectoryRequest
-	2, // 1: tvix.store.v1.DirectoryService.Put:input_type -> tvix.store.v1.Directory
-	2, // 2: tvix.store.v1.DirectoryService.Get:output_type -> tvix.store.v1.Directory
-	1, // 3: tvix.store.v1.DirectoryService.Put:output_type -> tvix.store.v1.PutDirectoryResponse
-	2, // [2:4] is the sub-list for method output_type
-	0, // [0:2] is the sub-list for method input_type
-	0, // [0:0] is the sub-list for extension type_name
-	0, // [0:0] is the sub-list for extension extendee
-	0, // [0:0] is the sub-list for field type_name
-}
-
-func init() { file_tvix_store_protos_rpc_directory_proto_init() }
-func file_tvix_store_protos_rpc_directory_proto_init() {
-	if File_tvix_store_protos_rpc_directory_proto != nil {
-		return
-	}
-	file_tvix_store_protos_castore_proto_init()
-	if !protoimpl.UnsafeEnabled {
-		file_tvix_store_protos_rpc_directory_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*GetDirectoryRequest); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-		file_tvix_store_protos_rpc_directory_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*PutDirectoryResponse); i {
-			case 0:
-				return &v.state
-			case 1:
-				return &v.sizeCache
-			case 2:
-				return &v.unknownFields
-			default:
-				return nil
-			}
-		}
-	}
-	file_tvix_store_protos_rpc_directory_proto_msgTypes[0].OneofWrappers = []interface{}{
-		(*GetDirectoryRequest_Digest)(nil),
-	}
-	type x struct{}
-	out := protoimpl.TypeBuilder{
-		File: protoimpl.DescBuilder{
-			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
-			RawDescriptor: file_tvix_store_protos_rpc_directory_proto_rawDesc,
-			NumEnums:      0,
-			NumMessages:   2,
-			NumExtensions: 0,
-			NumServices:   1,
-		},
-		GoTypes:           file_tvix_store_protos_rpc_directory_proto_goTypes,
-		DependencyIndexes: file_tvix_store_protos_rpc_directory_proto_depIdxs,
-		MessageInfos:      file_tvix_store_protos_rpc_directory_proto_msgTypes,
-	}.Build()
-	File_tvix_store_protos_rpc_directory_proto = out.File
-	file_tvix_store_protos_rpc_directory_proto_rawDesc = nil
-	file_tvix_store_protos_rpc_directory_proto_goTypes = nil
-	file_tvix_store_protos_rpc_directory_proto_depIdxs = nil
-}
diff --git a/tvix/store/protos/rpc_pathinfo.pb.go b/tvix/store/protos/rpc_pathinfo.pb.go
index 293cb5a7c321..8a3c10a82101 100644
--- a/tvix/store/protos/rpc_pathinfo.pb.go
+++ b/tvix/store/protos/rpc_pathinfo.pb.go
@@ -10,6 +10,7 @@
 package storev1
 
 import (
+	protos "code.tvl.fyi/tvix/castore/protos"
 	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
 	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
 	reflect "reflect"
@@ -205,39 +206,42 @@ var file_tvix_store_protos_rpc_pathinfo_proto_rawDesc = []byte{
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+	0x75, 0x65, 0x73, 0x74, 0x1a, 0x17, 0x2e, 0x74, 0x76, 0x69, 0x78, 0x2e, 0x73, 0x74, 0x6f, 0x72,
+	0x65, 0x2e, 0x76, 0x31, 0x2e, 0x50, 0x61, 0x74, 0x68, 0x49, 0x6e, 0x66, 0x6f, 0x30, 0x01, 0x42,
+	0x28, 0x5a, 0x26, 0x63, 0x6f, 0x64, 0x65, 0x2e, 0x74, 0x76, 0x6c, 0x2e, 0x66, 0x79, 0x69, 0x2f,
+	0x74, 0x76, 0x69, 0x78, 0x2f, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f,
+	0x73, 0x3b, 0x73, 0x74, 0x6f, 0x72, 0x65, 0x76, 0x31, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f,
+	0x33,
 }
 
 var (
@@ -258,12 +262,12 @@ var file_tvix_store_protos_rpc_pathinfo_proto_goTypes = []interface{}{
 	(*ListPathInfoRequest)(nil),  // 1: tvix.store.v1.ListPathInfoRequest
 	(*CalculateNARResponse)(nil), // 2: tvix.store.v1.CalculateNARResponse
 	(*PathInfo)(nil),             // 3: tvix.store.v1.PathInfo
-	(*Node)(nil),                 // 4: tvix.store.v1.Node
+	(*protos.Node)(nil),          // 4: tvix.castore.v1.Node
 }
 var file_tvix_store_protos_rpc_pathinfo_proto_depIdxs = []int32{
 	0, // 0: tvix.store.v1.PathInfoService.Get:input_type -> tvix.store.v1.GetPathInfoRequest
 	3, // 1: tvix.store.v1.PathInfoService.Put:input_type -> tvix.store.v1.PathInfo
-	4, // 2: tvix.store.v1.PathInfoService.CalculateNAR:input_type -> tvix.store.v1.Node
+	4, // 2: tvix.store.v1.PathInfoService.CalculateNAR:input_type -> tvix.castore.v1.Node
 	1, // 3: tvix.store.v1.PathInfoService.List:input_type -> tvix.store.v1.ListPathInfoRequest
 	3, // 4: tvix.store.v1.PathInfoService.Get:output_type -> tvix.store.v1.PathInfo
 	3, // 5: tvix.store.v1.PathInfoService.Put:output_type -> tvix.store.v1.PathInfo
diff --git a/tvix/store/protos/rpc_pathinfo.proto b/tvix/store/protos/rpc_pathinfo.proto
index e1d6cd774144..1930e87de004 100644
--- a/tvix/store/protos/rpc_pathinfo.proto
+++ b/tvix/store/protos/rpc_pathinfo.proto
@@ -5,6 +5,7 @@ syntax = "proto3";
 package tvix.store.v1;
 
 import "tvix/store/protos/pathinfo.proto";
+import "tvix/castore/protos/castore.proto";
 
 option go_package = "code.tvl.fyi/tvix/store/protos;storev1";
 
@@ -40,7 +41,7 @@ service PathInfoService {
     //
     // It can also be used to calculate arbitrary NAR hashes of output paths,
     // in case a legacy Nix Binary Cache frontend is provided.
-    rpc CalculateNAR(Node) returns (CalculateNARResponse);
+    rpc CalculateNAR(tvix.castore.v1.Node) returns (CalculateNARResponse);
 
     // Return a stream of PathInfo messages matching the criteria specified in
     // ListPathInfoRequest.
diff --git a/tvix/store/protos/rpc_pathinfo_grpc.pb.go b/tvix/store/protos/rpc_pathinfo_grpc.pb.go
index d7b6711c0310..10d8a7ffa49c 100644
--- a/tvix/store/protos/rpc_pathinfo_grpc.pb.go
+++ b/tvix/store/protos/rpc_pathinfo_grpc.pb.go
@@ -10,6 +10,7 @@
 package storev1
 
 import (
+	protos "code.tvl.fyi/tvix/castore/protos"
 	context "context"
 	grpc "google.golang.org/grpc"
 	codes "google.golang.org/grpc/codes"
@@ -60,7 +61,7 @@ type PathInfoServiceClient interface {
 	//
 	// It can also be used to calculate arbitrary NAR hashes of output paths,
 	// in case a legacy Nix Binary Cache frontend is provided.
-	CalculateNAR(ctx context.Context, in *Node, opts ...grpc.CallOption) (*CalculateNARResponse, error)
+	CalculateNAR(ctx context.Context, in *protos.Node, opts ...grpc.CallOption) (*CalculateNARResponse, error)
 	// Return a stream of PathInfo messages matching the criteria specified in
 	// ListPathInfoRequest.
 	List(ctx context.Context, in *ListPathInfoRequest, opts ...grpc.CallOption) (PathInfoService_ListClient, error)
@@ -92,7 +93,7 @@ func (c *pathInfoServiceClient) Put(ctx context.Context, in *PathInfo, opts ...g
 	return out, nil
 }
 
-func (c *pathInfoServiceClient) CalculateNAR(ctx context.Context, in *Node, opts ...grpc.CallOption) (*CalculateNARResponse, error) {
+func (c *pathInfoServiceClient) CalculateNAR(ctx context.Context, in *protos.Node, opts ...grpc.CallOption) (*CalculateNARResponse, error) {
 	out := new(CalculateNARResponse)
 	err := c.cc.Invoke(ctx, PathInfoService_CalculateNAR_FullMethodName, in, out, opts...)
 	if err != nil {
@@ -165,7 +166,7 @@ type PathInfoServiceServer interface {
 	//
 	// It can also be used to calculate arbitrary NAR hashes of output paths,
 	// in case a legacy Nix Binary Cache frontend is provided.
-	CalculateNAR(context.Context, *Node) (*CalculateNARResponse, error)
+	CalculateNAR(context.Context, *protos.Node) (*CalculateNARResponse, error)
 	// Return a stream of PathInfo messages matching the criteria specified in
 	// ListPathInfoRequest.
 	List(*ListPathInfoRequest, PathInfoService_ListServer) error
@@ -182,7 +183,7 @@ func (UnimplementedPathInfoServiceServer) Get(context.Context, *GetPathInfoReque
 func (UnimplementedPathInfoServiceServer) Put(context.Context, *PathInfo) (*PathInfo, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method Put not implemented")
 }
-func (UnimplementedPathInfoServiceServer) CalculateNAR(context.Context, *Node) (*CalculateNARResponse, error) {
+func (UnimplementedPathInfoServiceServer) CalculateNAR(context.Context, *protos.Node) (*CalculateNARResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method CalculateNAR not implemented")
 }
 func (UnimplementedPathInfoServiceServer) List(*ListPathInfoRequest, PathInfoService_ListServer) error {
@@ -238,7 +239,7 @@ func _PathInfoService_Put_Handler(srv interface{}, ctx context.Context, dec func
 }
 
 func _PathInfoService_CalculateNAR_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
-	in := new(Node)
+	in := new(protos.Node)
 	if err := dec(in); err != nil {
 		return nil, err
 	}
@@ -250,7 +251,7 @@ func _PathInfoService_CalculateNAR_Handler(srv interface{}, ctx context.Context,
 		FullMethod: PathInfoService_CalculateNAR_FullMethodName,
 	}
 	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
-		return srv.(PathInfoServiceServer).CalculateNAR(ctx, req.(*Node))
+		return srv.(PathInfoServiceServer).CalculateNAR(ctx, req.(*protos.Node))
 	}
 	return interceptor(ctx, in, info, handler)
 }
diff --git a/tvix/store/src/bin/tvix-store.rs b/tvix/store/src/bin/tvix-store.rs
index 7761855cccb1..474a48c9fd1a 100644
--- a/tvix/store/src/bin/tvix-store.rs
+++ b/tvix/store/src/bin/tvix-store.rs
@@ -8,18 +8,18 @@ use std::path::Path;
 use std::path::PathBuf;
 use tokio::task::JoinHandle;
 use tracing_subscriber::prelude::*;
-use tvix_store::blobservice;
-use tvix_store::directoryservice;
-use tvix_store::import;
+use tvix_castore::blobservice;
+use tvix_castore::directoryservice;
+use tvix_castore::import;
+use tvix_castore::proto::blob_service_server::BlobServiceServer;
+use tvix_castore::proto::directory_service_server::DirectoryServiceServer;
+use tvix_castore::proto::node::Node;
+use tvix_castore::proto::GRPCBlobServiceWrapper;
+use tvix_castore::proto::GRPCDirectoryServiceWrapper;
+use tvix_castore::proto::NamedNode;
 use tvix_store::pathinfoservice;
-use tvix_store::proto::blob_service_server::BlobServiceServer;
-use tvix_store::proto::directory_service_server::DirectoryServiceServer;
-use tvix_store::proto::node::Node;
 use tvix_store::proto::path_info_service_server::PathInfoServiceServer;
-use tvix_store::proto::GRPCBlobServiceWrapper;
-use tvix_store::proto::GRPCDirectoryServiceWrapper;
 use tvix_store::proto::GRPCPathInfoServiceWrapper;
-use tvix_store::proto::NamedNode;
 use tvix_store::proto::NarInfo;
 use tvix_store::proto::PathInfo;
 
@@ -30,6 +30,8 @@ use tvix_store::fs::TvixStoreFs;
 use tvix_store::fs::fuse::FuseDaemon;
 
 #[cfg(feature = "reflection")]
+use tvix_castore::proto::FILE_DESCRIPTOR_SET as CASTORE_FILE_DESCRIPTOR_SET;
+#[cfg(feature = "reflection")]
 use tvix_store::proto::FILE_DESCRIPTOR_SET;
 
 use clap::Parser;
@@ -185,6 +187,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             #[cfg(feature = "reflection")]
             {
                 let reflection_svc = tonic_reflection::server::Builder::configure()
+                    .register_encoded_file_descriptor_set(CASTORE_FILE_DESCRIPTOR_SET)
                     .register_encoded_file_descriptor_set(FILE_DESCRIPTOR_SET)
                     .build()?;
                 router = router.add_service(reflection_svc);
@@ -248,7 +251,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
                         // assemble the [crate::proto::PathInfo] object.
                         let path_info = PathInfo {
-                            node: Some(tvix_store::proto::Node {
+                            node: Some(tvix_castore::proto::Node {
                                 node: Some(root_node),
                             }),
                             // There's no reference scanning on path contents ingested like this.
diff --git a/tvix/store/src/fs/inode_tracker.rs b/tvix/store/src/fs/inode_tracker.rs
index ad1ef859a2f3..daf6b4ee79c2 100644
--- a/tvix/store/src/fs/inode_tracker.rs
+++ b/tvix/store/src/fs/inode_tracker.rs
@@ -1,8 +1,8 @@
 use std::{collections::HashMap, sync::Arc};
 
-use crate::{proto, B3Digest};
-
 use super::inodes::{DirectoryInodeData, InodeData};
+use tvix_castore::proto as castorepb;
+use tvix_castore::B3Digest;
 
 /// InodeTracker keeps track of inodes, stores data being these inodes and deals
 /// with inode allocation.
@@ -139,21 +139,21 @@ impl InodeTracker {
     // Consume a list of children with zeroed inodes, and allocate (or fetch existing) inodes.
     fn allocate_inodes_for_children(
         &mut self,
-        children: Vec<(u64, proto::node::Node)>,
-    ) -> Vec<(u64, proto::node::Node)> {
+        children: Vec<(u64, castorepb::node::Node)>,
+    ) -> Vec<(u64, castorepb::node::Node)> {
         // allocate new inodes for all children
-        let mut children_new: Vec<(u64, proto::node::Node)> = Vec::new();
+        let mut children_new: Vec<(u64, castorepb::node::Node)> = Vec::new();
 
         for (child_ino, ref child_node) in children {
             debug_assert_eq!(0, child_ino, "expected child inode to be 0");
             let child_ino = match child_node {
-                proto::node::Node::Directory(directory_node) => {
+                castorepb::node::Node::Directory(directory_node) => {
                     // Try putting the sparse data in. If we already have a
                     // populated version, it'll not update it.
                     self.put(directory_node.into())
                 }
-                proto::node::Node::File(file_node) => self.put(file_node.into()),
-                proto::node::Node::Symlink(symlink_node) => self.put(symlink_node.into()),
+                castorepb::node::Node::File(file_node) => self.put(file_node.into()),
+                castorepb::node::Node::Symlink(symlink_node) => self.put(symlink_node.into()),
             };
 
             children_new.push((child_ino, child_node.clone()))
@@ -198,8 +198,8 @@ impl InodeTracker {
 #[cfg(test)]
 mod tests {
     use crate::fs::inodes::DirectoryInodeData;
-    use crate::proto;
     use crate::tests::fixtures;
+    use tvix_castore::proto as castorepb;
 
     use super::InodeData;
     use super::InodeTracker;
@@ -304,7 +304,7 @@ mod tests {
                 let (child_ino, child_node) = children.first().unwrap();
                 assert_ne!(dir_ino, *child_ino);
                 assert_eq!(
-                    &proto::node::Node::File(
+                    &castorepb::node::Node::File(
                         fixtures::DIRECTORY_WITH_KEEP.files.first().unwrap().clone()
                     ),
                     child_node
@@ -362,7 +362,9 @@ mod tests {
                     let (child_ino, child_node) = &children[0];
                     assert!(!seen_inodes.contains(child_ino));
                     assert_eq!(
-                        &proto::node::Node::File(fixtures::DIRECTORY_COMPLICATED.files[0].clone()),
+                        &castorepb::node::Node::File(
+                            fixtures::DIRECTORY_COMPLICATED.files[0].clone()
+                        ),
                         child_node
                     );
                     seen_inodes.push(*child_ino);
@@ -373,7 +375,7 @@ mod tests {
                     let (child_ino, child_node) = &children[1];
                     assert!(!seen_inodes.contains(child_ino));
                     assert_eq!(
-                        &proto::node::Node::Symlink(
+                        &castorepb::node::Node::Symlink(
                             fixtures::DIRECTORY_COMPLICATED.symlinks[0].clone()
                         ),
                         child_node
@@ -386,7 +388,7 @@ mod tests {
                     let (child_ino, child_node) = &children[2];
                     assert!(!seen_inodes.contains(child_ino));
                     assert_eq!(
-                        &proto::node::Node::Directory(
+                        &castorepb::node::Node::Directory(
                             fixtures::DIRECTORY_COMPLICATED.directories[0].clone()
                         ),
                         child_node
@@ -439,7 +441,7 @@ mod tests {
                 let (child_node_inode, child_node) = children.first().unwrap();
                 assert_ne!(dir_complicated_ino, *child_node_inode);
                 assert_eq!(
-                    &proto::node::Node::File(
+                    &castorepb::node::Node::File(
                         fixtures::DIRECTORY_WITH_KEEP.files.first().unwrap().clone()
                     ),
                     child_node
diff --git a/tvix/store/src/fs/inodes.rs b/tvix/store/src/fs/inodes.rs
index e8959ce3629b..928f51059002 100644
--- a/tvix/store/src/fs/inodes.rs
+++ b/tvix/store/src/fs/inodes.rs
@@ -1,6 +1,7 @@
 //! This module contains all the data structures used to track information
 //! about inodes, which present tvix-store nodes in a filesystem.
-use crate::{proto, B3Digest};
+use tvix_castore::proto as castorepb;
+use tvix_castore::B3Digest;
 
 #[derive(Clone, Debug)]
 pub enum InodeData {
@@ -10,33 +11,33 @@ pub enum InodeData {
 }
 
 /// This encodes the two different states of [InodeData::Directory].
-/// Either the data still is sparse (we only saw a [proto::DirectoryNode], but
-/// didn't fetch the [proto::Directory] struct yet,
-/// or we processed a lookup and did fetch the data.
+/// Either the data still is sparse (we only saw a [castorepb::DirectoryNode],
+/// but didn't fetch the [castorepb::Directory] struct yet, or we processed a
+/// lookup and did fetch the data.
 #[derive(Clone, Debug)]
 pub enum DirectoryInodeData {
-    Sparse(B3Digest, u32),                              // digest, size
-    Populated(B3Digest, Vec<(u64, proto::node::Node)>), // [(child_inode, node)]
+    Sparse(B3Digest, u32),                                  // digest, size
+    Populated(B3Digest, Vec<(u64, castorepb::node::Node)>), // [(child_inode, node)]
 }
 
-impl From<&proto::node::Node> for InodeData {
-    fn from(value: &proto::node::Node) -> Self {
+impl From<&castorepb::node::Node> for InodeData {
+    fn from(value: &castorepb::node::Node) -> Self {
         match value {
-            proto::node::Node::Directory(directory_node) => directory_node.into(),
-            proto::node::Node::File(file_node) => file_node.into(),
-            proto::node::Node::Symlink(symlink_node) => symlink_node.into(),
+            castorepb::node::Node::Directory(directory_node) => directory_node.into(),
+            castorepb::node::Node::File(file_node) => file_node.into(),
+            castorepb::node::Node::Symlink(symlink_node) => symlink_node.into(),
         }
     }
 }
 
-impl From<&proto::SymlinkNode> for InodeData {
-    fn from(value: &proto::SymlinkNode) -> Self {
+impl From<&castorepb::SymlinkNode> for InodeData {
+    fn from(value: &castorepb::SymlinkNode) -> Self {
         InodeData::Symlink(value.target.clone())
     }
 }
 
-impl From<&proto::FileNode> for InodeData {
-    fn from(value: &proto::FileNode) -> Self {
+impl From<&castorepb::FileNode> for InodeData {
+    fn from(value: &castorepb::FileNode) -> Self {
         InodeData::Regular(
             value.digest.clone().try_into().unwrap(),
             value.size,
@@ -46,8 +47,8 @@ impl From<&proto::FileNode> for InodeData {
 }
 
 /// Converts a DirectoryNode to a sparsely populated InodeData::Directory.
-impl From<&proto::DirectoryNode> for InodeData {
-    fn from(value: &proto::DirectoryNode) -> Self {
+impl From<&castorepb::DirectoryNode> for InodeData {
+    fn from(value: &castorepb::DirectoryNode) -> Self {
         InodeData::Directory(DirectoryInodeData::Sparse(
             value.digest.clone().try_into().unwrap(),
             value.size,
@@ -57,11 +58,12 @@ impl From<&proto::DirectoryNode> for InodeData {
 
 /// converts a proto::Directory to a InodeData::Directory(DirectoryInodeData::Populated(..)).
 /// The inodes for each child are 0, because it's up to the InodeTracker to allocate them.
-impl From<proto::Directory> for InodeData {
-    fn from(value: proto::Directory) -> Self {
+impl From<castorepb::Directory> for InodeData {
+    fn from(value: castorepb::Directory) -> Self {
         let digest = value.digest();
 
-        let children: Vec<(u64, proto::node::Node)> = value.nodes().map(|node| (0, node)).collect();
+        let children: Vec<(u64, castorepb::node::Node)> =
+            value.nodes().map(|node| (0, node)).collect();
 
         InodeData::Directory(DirectoryInodeData::Populated(digest, children))
     }
diff --git a/tvix/store/src/fs/mod.rs b/tvix/store/src/fs/mod.rs
index 02d3bb3221ad..59b8f0d0854f 100644
--- a/tvix/store/src/fs/mod.rs
+++ b/tvix/store/src/fs/mod.rs
@@ -8,13 +8,8 @@ pub mod fuse;
 #[cfg(test)]
 mod tests;
 
-use crate::{
-    blobservice::{BlobReader, BlobService},
-    directoryservice::DirectoryService,
-    pathinfoservice::PathInfoService,
-    proto::{node::Node, NamedNode},
-    B3Digest, Error,
-};
+use crate::pathinfoservice::PathInfoService;
+
 use fuse_backend_rs::api::filesystem::{Context, FileSystem, FsOptions, ROOT_ID};
 use futures::StreamExt;
 use nix_compat::store_path::StorePath;
@@ -32,6 +27,12 @@ use tokio::{
     sync::mpsc,
 };
 use tracing::{debug, info_span, warn};
+use tvix_castore::{
+    blobservice::{BlobReader, BlobService},
+    directoryservice::DirectoryService,
+    proto::{node::Node, NamedNode},
+    B3Digest, Error,
+};
 
 use self::{
     file_attr::{gen_file_attr, ROOT_FILE_ATTR},
diff --git a/tvix/store/src/fs/tests.rs b/tvix/store/src/fs/tests.rs
index 6837f8aa293a..2adea0ceb3a9 100644
--- a/tvix/store/src/fs/tests.rs
+++ b/tvix/store/src/fs/tests.rs
@@ -5,17 +5,17 @@ use std::path::Path;
 use std::sync::Arc;
 use tokio::{fs, io};
 use tokio_stream::wrappers::ReadDirStream;
+use tvix_castore::blobservice::BlobService;
+use tvix_castore::directoryservice::DirectoryService;
 
 use tempfile::TempDir;
 
-use crate::blobservice::BlobService;
-use crate::directoryservice::DirectoryService;
 use crate::fs::{fuse::FuseDaemon, TvixStoreFs};
 use crate::pathinfoservice::PathInfoService;
-use crate::proto;
-use crate::proto::{DirectoryNode, FileNode, PathInfo};
+use crate::proto::PathInfo;
 use crate::tests::fixtures;
 use crate::tests::utils::{gen_blob_service, gen_directory_service, gen_pathinfo_service};
+use tvix_castore::proto as castorepb;
 
 const BLOB_A_NAME: &str = "00000000000000000000000000000000-test";
 const BLOB_B_NAME: &str = "55555555555555555555555555555555-test";
@@ -67,8 +67,8 @@ async fn populate_blob_a(
 
     // Create a PathInfo for it
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::File(FileNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::File(castorepb::FileNode {
                 name: BLOB_A_NAME.into(),
                 digest: fixtures::BLOB_A_DIGEST.clone().into(),
                 size: fixtures::BLOB_A.len() as u32,
@@ -97,8 +97,8 @@ async fn populate_blob_b(
 
     // Create a PathInfo for it
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::File(FileNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::File(castorepb::FileNode {
                 name: BLOB_B_NAME.into(),
                 digest: fixtures::BLOB_B_DIGEST.clone().into(),
                 size: fixtures::BLOB_B.len() as u32,
@@ -131,8 +131,8 @@ async fn populate_helloworld_blob(
 
     // Create a PathInfo for it
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::File(FileNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::File(castorepb::FileNode {
                 name: HELLOWORLD_BLOB_NAME.into(),
                 digest: fixtures::HELLOWORLD_BLOB_DIGEST.clone().into(),
                 size: fixtures::HELLOWORLD_BLOB_CONTENTS.len() as u32,
@@ -154,8 +154,8 @@ async fn populate_symlink(
 ) {
     // Create a PathInfo for it
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::Symlink(proto::SymlinkNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Symlink(castorepb::SymlinkNode {
                 name: SYMLINK_NAME.into(),
                 target: BLOB_A_NAME.into(),
             })),
@@ -177,8 +177,8 @@ async fn populate_symlink2(
 ) {
     // Create a PathInfo for it
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::Symlink(proto::SymlinkNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Symlink(castorepb::SymlinkNode {
                 name: SYMLINK_NAME2.into(),
                 target: "/nix/store/somewhereelse".into(),
             })),
@@ -211,8 +211,8 @@ async fn populate_directory_with_keep(
 
     // upload pathinfo
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::Directory(DirectoryNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Directory(castorepb::DirectoryNode {
                 name: DIRECTORY_WITH_KEEP_NAME.into(),
                 digest: fixtures::DIRECTORY_WITH_KEEP.digest().into(),
                 size: fixtures::DIRECTORY_WITH_KEEP.size(),
@@ -235,8 +235,8 @@ async fn populate_pathinfo_without_directory(
 ) {
     // upload pathinfo
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::Directory(DirectoryNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Directory(castorepb::DirectoryNode {
                 name: DIRECTORY_WITH_KEEP_NAME.into(),
                 digest: fixtures::DIRECTORY_WITH_KEEP.digest().into(),
                 size: fixtures::DIRECTORY_WITH_KEEP.size(),
@@ -258,8 +258,8 @@ async fn populate_blob_a_without_blob(
 ) {
     // Create a PathInfo for blob A
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::File(FileNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::File(castorepb::FileNode {
                 name: BLOB_A_NAME.into(),
                 digest: fixtures::BLOB_A_DIGEST.clone().into(),
                 size: fixtures::BLOB_A.len() as u32,
@@ -300,8 +300,8 @@ async fn populate_directory_complicated(
 
     // upload pathinfo
     let path_info = PathInfo {
-        node: Some(proto::Node {
-            node: Some(proto::node::Node::Directory(DirectoryNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Directory(castorepb::DirectoryNode {
                 name: DIRECTORY_COMPLICATED_NAME.into(),
                 digest: fixtures::DIRECTORY_COMPLICATED.digest().into(),
                 size: fixtures::DIRECTORY_COMPLICATED.size(),
diff --git a/tvix/store/src/lib.rs b/tvix/store/src/lib.rs
index 6270812d47fc..c59121453352 100644
--- a/tvix/store/src/lib.rs
+++ b/tvix/store/src/lib.rs
@@ -1,18 +1,9 @@
-mod digests;
-mod errors;
-
 #[cfg(feature = "fs")]
 pub mod fs;
 
-pub mod blobservice;
-pub mod directoryservice;
-pub mod import;
 pub mod nar;
 pub mod pathinfoservice;
 pub mod proto;
 
-pub use digests::B3Digest;
-pub use errors::Error;
-
 #[cfg(test)]
 mod tests;
diff --git a/tvix/store/src/nar/mod.rs b/tvix/store/src/nar/mod.rs
index 5a8bc21ae953..fc6805e9e758 100644
--- a/tvix/store/src/nar/mod.rs
+++ b/tvix/store/src/nar/mod.rs
@@ -1,16 +1,15 @@
-use crate::B3Digest;
 use data_encoding::BASE64;
-use thiserror::Error;
+use tvix_castore::{B3Digest, Error};
 
 mod renderer;
 pub use renderer::calculate_size_and_sha256;
 pub use renderer::write_nar;
 
 /// Errors that can encounter while rendering NARs.
-#[derive(Debug, Error)]
+#[derive(Debug, thiserror::Error)]
 pub enum RenderError {
     #[error("failure talking to a backing store client: {0}")]
-    StoreError(crate::Error),
+    StoreError(Error),
 
     #[error("unable to find directory {}, referred from {:?}", .0, .1)]
     DirectoryNotFound(B3Digest, bytes::Bytes),
diff --git a/tvix/store/src/nar/renderer.rs b/tvix/store/src/nar/renderer.rs
index f1392472a50e..55dce911ee1a 100644
--- a/tvix/store/src/nar/renderer.rs
+++ b/tvix/store/src/nar/renderer.rs
@@ -1,20 +1,21 @@
 use super::RenderError;
-use crate::{
-    blobservice::BlobService,
-    directoryservice::DirectoryService,
-    proto::{self, NamedNode},
-};
 use count_write::CountWrite;
 use nix_compat::nar;
 use sha2::{Digest, Sha256};
 use std::{io, sync::Arc};
 use tokio::{io::BufReader, task::spawn_blocking};
 use tracing::warn;
+use tvix_castore::{
+    blobservice::BlobService,
+    directoryservice::DirectoryService,
+    proto::{self as castorepb, NamedNode},
+    Error,
+};
 
 /// Invoke [write_nar], and return the size and sha256 digest of the produced
 /// NAR output.
 pub async fn calculate_size_and_sha256(
-    root_node: &proto::node::Node,
+    root_node: &castorepb::node::Node,
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
 ) -> Result<(u64, [u8; 32]), RenderError> {
@@ -26,9 +27,9 @@ pub async fn calculate_size_and_sha256(
     Ok((cw.count(), cw.into_inner().finalize().into()))
 }
 
-/// Accepts a [proto::node::Node] pointing to the root of a (store) path,
-/// and uses the passed blob_service and directory_service to
-/// perform the necessary lookups as it traverses the structure.
+/// Accepts a [castorepb::node::Node] pointing to the root of a (store) path,
+/// and uses the passed blob_service and directory_service to perform the
+/// necessary lookups as it traverses the structure.
 /// The contents in NAR serialization are writen to the passed [std::io::Write].
 ///
 /// The writer is passed back in the return value. This is done because async Rust
@@ -39,7 +40,7 @@ pub async fn calculate_size_and_sha256(
 /// This will panic if called outside the context of a Tokio runtime.
 pub async fn write_nar<W: std::io::Write + Send + 'static>(
     mut w: W,
-    proto_root_node: &proto::node::Node,
+    proto_root_node: &castorepb::node::Node,
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
 ) -> Result<W, RenderError> {
@@ -69,24 +70,24 @@ pub async fn write_nar<W: std::io::Write + Send + 'static>(
 fn walk_node(
     tokio_handle: tokio::runtime::Handle,
     nar_node: nar::writer::Node,
-    proto_node: &proto::node::Node,
+    proto_node: &castorepb::node::Node,
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
 ) -> Result<(), RenderError> {
     match proto_node {
-        proto::node::Node::Symlink(proto_symlink_node) => {
+        castorepb::node::Node::Symlink(proto_symlink_node) => {
             nar_node
                 .symlink(&proto_symlink_node.target)
                 .map_err(RenderError::NARWriterError)?;
         }
-        proto::node::Node::File(proto_file_node) => {
+        castorepb::node::Node::File(proto_file_node) => {
             let digest = proto_file_node.digest.clone().try_into().map_err(|_e| {
                 warn!(
                     file_node = ?proto_file_node,
                     "invalid digest length in file node",
                 );
 
-                RenderError::StoreError(crate::Error::StorageError(
+                RenderError::StoreError(Error::StorageError(
                     "invalid digest len in file node".to_string(),
                 ))
             })?;
@@ -110,13 +111,13 @@ fn walk_node(
                 )
                 .map_err(RenderError::NARWriterError)?;
         }
-        proto::node::Node::Directory(proto_directory_node) => {
+        castorepb::node::Node::Directory(proto_directory_node) => {
             let digest = proto_directory_node
                 .digest
                 .clone()
                 .try_into()
                 .map_err(|_e| {
-                    RenderError::StoreError(crate::Error::StorageError(
+                    RenderError::StoreError(Error::StorageError(
                         "invalid digest len in directory node".to_string(),
                     ))
                 })?;
diff --git a/tvix/store/src/pathinfoservice/from_addr.rs b/tvix/store/src/pathinfoservice/from_addr.rs
index 36b30aecdcf5..93cb487f29b9 100644
--- a/tvix/store/src/pathinfoservice/from_addr.rs
+++ b/tvix/store/src/pathinfoservice/from_addr.rs
@@ -1,10 +1,9 @@
+use super::{GRPCPathInfoService, MemoryPathInfoService, PathInfoService, SledPathInfoService};
+
 use std::sync::Arc;
+use tvix_castore::{blobservice::BlobService, directoryservice::DirectoryService, Error};
 use url::Url;
 
-use crate::{blobservice::BlobService, directoryservice::DirectoryService};
-
-use super::{GRPCPathInfoService, MemoryPathInfoService, PathInfoService, SledPathInfoService};
-
 /// Constructs a new instance of a [PathInfoService] from an URI.
 ///
 /// The following URIs are supported:
@@ -26,9 +25,9 @@ pub fn from_addr(
     uri: &str,
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
-) -> Result<Arc<dyn PathInfoService>, crate::Error> {
-    let url = Url::parse(uri)
-        .map_err(|e| crate::Error::StorageError(format!("unable to parse url: {}", e)))?;
+) -> Result<Arc<dyn PathInfoService>, Error> {
+    let url =
+        Url::parse(uri).map_err(|e| Error::StorageError(format!("unable to parse url: {}", e)))?;
 
     Ok(if url.scheme() == "memory" {
         Arc::new(MemoryPathInfoService::from_url(
@@ -49,7 +48,7 @@ pub fn from_addr(
             directory_service,
         )?)
     } else {
-        Err(crate::Error::StorageError(format!(
+        Err(Error::StorageError(format!(
             "unknown scheme: {}",
             url.scheme()
         )))?
diff --git a/tvix/store/src/pathinfoservice/grpc.rs b/tvix/store/src/pathinfoservice/grpc.rs
index c116ddbc8905..6883c56104a6 100644
--- a/tvix/store/src/pathinfoservice/grpc.rs
+++ b/tvix/store/src/pathinfoservice/grpc.rs
@@ -1,14 +1,13 @@
 use super::PathInfoService;
-use crate::{
-    blobservice::BlobService,
-    directoryservice::DirectoryService,
-    proto::{self, ListPathInfoRequest},
-};
+use crate::proto::{self, ListPathInfoRequest, PathInfo};
 use async_stream::try_stream;
 use futures::Stream;
 use std::{pin::Pin, sync::Arc};
 use tokio::net::UnixStream;
 use tonic::{async_trait, transport::Channel, Code};
+use tvix_castore::{
+    blobservice::BlobService, directoryservice::DirectoryService, proto as castorepb, Error,
+};
 
 /// Connects to a (remote) tvix-store PathInfoService over gRPC.
 #[derive(Clone)]
@@ -40,16 +39,14 @@ impl PathInfoService for GRPCPathInfoService {
         url: &url::Url,
         _blob_service: Arc<dyn BlobService>,
         _directory_service: Arc<dyn DirectoryService>,
-    ) -> Result<Self, crate::Error> {
+    ) -> Result<Self, tvix_castore::Error> {
         // Start checking for the scheme to start with grpc+.
         match url.scheme().strip_prefix("grpc+") {
-            None => Err(crate::Error::StorageError("invalid scheme".to_string())),
+            None => Err(Error::StorageError("invalid scheme".to_string())),
             Some(rest) => {
                 if rest == "unix" {
                     if url.host_str().is_some() {
-                        return Err(crate::Error::StorageError(
-                            "host may not be set".to_string(),
-                        ));
+                        return Err(Error::StorageError("host may not be set".to_string()));
                     }
                     let path = url.path().to_string();
                     let channel = tonic::transport::Endpoint::try_from("http://[::]:50051") // doesn't matter
@@ -63,7 +60,7 @@ impl PathInfoService for GRPCPathInfoService {
                 } else {
                     // ensure path is empty, not supported with gRPC.
                     if !url.path().is_empty() {
-                        return Err(crate::Error::StorageError(
+                        return Err(tvix_castore::Error::StorageError(
                             "path may not be set".to_string(),
                         ));
                     }
@@ -89,7 +86,7 @@ impl PathInfoService for GRPCPathInfoService {
         }
     }
 
-    async fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, crate::Error> {
+    async fn get(&self, digest: [u8; 20]) -> Result<Option<PathInfo>, Error> {
         // Get a new handle to the gRPC client.
         let mut grpc_client = self.grpc_client.clone();
 
@@ -104,18 +101,18 @@ impl PathInfoService for GRPCPathInfoService {
         match path_info {
             Ok(path_info) => Ok(Some(path_info.into_inner())),
             Err(e) if e.code() == Code::NotFound => Ok(None),
-            Err(e) => Err(crate::Error::StorageError(e.to_string())),
+            Err(e) => Err(Error::StorageError(e.to_string())),
         }
     }
 
-    async fn put(&self, path_info: proto::PathInfo) -> Result<proto::PathInfo, crate::Error> {
+    async fn put(&self, path_info: PathInfo) -> Result<PathInfo, Error> {
         // Get a new handle to the gRPC client.
         let mut grpc_client = self.grpc_client.clone();
 
         let path_info = grpc_client
             .put(path_info)
             .await
-            .map_err(|e| crate::Error::StorageError(e.to_string()))?
+            .map_err(|e| Error::StorageError(e.to_string()))?
             .into_inner();
 
         Ok(path_info)
@@ -123,36 +120,36 @@ impl PathInfoService for GRPCPathInfoService {
 
     async fn calculate_nar(
         &self,
-        root_node: &proto::node::Node,
-    ) -> Result<(u64, [u8; 32]), crate::Error> {
+        root_node: &castorepb::node::Node,
+    ) -> Result<(u64, [u8; 32]), Error> {
         // Get a new handle to the gRPC client.
         let mut grpc_client = self.grpc_client.clone();
         let root_node = root_node.clone();
 
         let path_info = grpc_client
-            .calculate_nar(proto::Node {
+            .calculate_nar(castorepb::Node {
                 node: Some(root_node),
             })
             .await
-            .map_err(|e| crate::Error::StorageError(e.to_string()))?
+            .map_err(|e| Error::StorageError(e.to_string()))?
             .into_inner();
 
         let nar_sha256: [u8; 32] = path_info
             .nar_sha256
             .to_vec()
             .try_into()
-            .map_err(|_e| crate::Error::StorageError("invalid digest length".to_string()))?;
+            .map_err(|_e| Error::StorageError("invalid digest length".to_string()))?;
 
         Ok((path_info.nar_size, nar_sha256))
     }
 
-    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<proto::PathInfo, crate::Error>> + Send>> {
+    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<PathInfo, Error>> + Send>> {
         let mut grpc_client = self.grpc_client.clone();
 
         let stream = try_stream! {
             let resp = grpc_client.list(ListPathInfoRequest::default()).await;
 
-            let mut stream = resp.map_err(|e| crate::Error::StorageError(e.to_string()))?.into_inner();
+            let mut stream = resp.map_err(|e| Error::StorageError(e.to_string()))?.into_inner();
 
             loop {
                 match stream.message().await {
@@ -160,7 +157,7 @@ impl PathInfoService for GRPCPathInfoService {
                         Some(pathinfo) => {
                             // validate the pathinfo
                             if let Err(e) = pathinfo.validate() {
-                                Err(crate::Error::StorageError(format!(
+                                Err(Error::StorageError(format!(
                                     "pathinfo {:?} failed validation: {}",
                                     pathinfo, e
                                 )))?;
@@ -171,7 +168,7 @@ impl PathInfoService for GRPCPathInfoService {
                             return;
                         },
                     },
-                    Err(e) => Err(crate::Error::StorageError(e.to_string()))?,
+                    Err(e) => Err(Error::StorageError(e.to_string()))?,
                 }
             }
         };
diff --git a/tvix/store/src/pathinfoservice/memory.rs b/tvix/store/src/pathinfoservice/memory.rs
index 4cdc411ffb28..dbb4b02dd013 100644
--- a/tvix/store/src/pathinfoservice/memory.rs
+++ b/tvix/store/src/pathinfoservice/memory.rs
@@ -1,8 +1,5 @@
 use super::PathInfoService;
-use crate::{
-    blobservice::BlobService, directoryservice::DirectoryService, nar::calculate_size_and_sha256,
-    proto, Error,
-};
+use crate::{nar::calculate_size_and_sha256, proto::PathInfo};
 use futures::{stream::iter, Stream};
 use std::{
     collections::HashMap,
@@ -10,9 +7,12 @@ use std::{
     sync::{Arc, RwLock},
 };
 use tonic::async_trait;
+use tvix_castore::proto as castorepb;
+use tvix_castore::Error;
+use tvix_castore::{blobservice::BlobService, directoryservice::DirectoryService};
 
 pub struct MemoryPathInfoService {
-    db: Arc<RwLock<HashMap<[u8; 20], proto::PathInfo>>>,
+    db: Arc<RwLock<HashMap<[u8; 20], PathInfo>>>,
 
     blob_service: Arc<dyn BlobService>,
     directory_service: Arc<dyn DirectoryService>,
@@ -43,17 +43,17 @@ impl PathInfoService for MemoryPathInfoService {
         directory_service: Arc<dyn DirectoryService>,
     ) -> Result<Self, Error> {
         if url.scheme() != "memory" {
-            return Err(crate::Error::StorageError("invalid scheme".to_string()));
+            return Err(Error::StorageError("invalid scheme".to_string()));
         }
 
         if url.has_host() || !url.path().is_empty() {
-            return Err(crate::Error::StorageError("invalid url".to_string()));
+            return Err(Error::StorageError("invalid url".to_string()));
         }
 
         Ok(Self::new(blob_service, directory_service))
     }
 
-    async fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, Error> {
+    async fn get(&self, digest: [u8; 20]) -> Result<Option<PathInfo>, Error> {
         let db = self.db.read().unwrap();
 
         match db.get(&digest) {
@@ -62,7 +62,7 @@ impl PathInfoService for MemoryPathInfoService {
         }
     }
 
-    async fn put(&self, path_info: proto::PathInfo) -> Result<proto::PathInfo, Error> {
+    async fn put(&self, path_info: PathInfo) -> Result<PathInfo, Error> {
         // Call validate on the received PathInfo message.
         match path_info.validate() {
             Err(e) => Err(Error::InvalidRequest(format!(
@@ -81,7 +81,10 @@ impl PathInfoService for MemoryPathInfoService {
         }
     }
 
-    async fn calculate_nar(&self, root_node: &proto::node::Node) -> Result<(u64, [u8; 32]), Error> {
+    async fn calculate_nar(
+        &self,
+        root_node: &castorepb::node::Node,
+    ) -> Result<(u64, [u8; 32]), Error> {
         calculate_size_and_sha256(
             root_node,
             self.blob_service.clone(),
@@ -91,7 +94,7 @@ impl PathInfoService for MemoryPathInfoService {
         .map_err(|e| Error::StorageError(e.to_string()))
     }
 
-    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<proto::PathInfo, Error>> + Send>> {
+    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<PathInfo, Error>> + Send>> {
         let db = self.db.read().unwrap();
 
         // Copy all elements into a list.
diff --git a/tvix/store/src/pathinfoservice/mod.rs b/tvix/store/src/pathinfoservice/mod.rs
index b436ad0b16dc..af7bbc9f88e4 100644
--- a/tvix/store/src/pathinfoservice/mod.rs
+++ b/tvix/store/src/pathinfoservice/mod.rs
@@ -8,10 +8,12 @@ use std::sync::Arc;
 
 use futures::Stream;
 use tonic::async_trait;
+use tvix_castore::blobservice::BlobService;
+use tvix_castore::directoryservice::DirectoryService;
+use tvix_castore::proto as castorepb;
+use tvix_castore::Error;
 
-use crate::blobservice::BlobService;
-use crate::directoryservice::DirectoryService;
-use crate::{proto, Error};
+use crate::proto::PathInfo;
 
 pub use self::from_addr::from_addr;
 pub use self::grpc::GRPCPathInfoService;
@@ -34,16 +36,19 @@ pub trait PathInfoService: Send + Sync {
         Self: Sized;
 
     /// Retrieve a PathInfo message by the output digest.
-    async fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, Error>;
+    async fn get(&self, digest: [u8; 20]) -> Result<Option<PathInfo>, Error>;
 
     /// Store a PathInfo message. Implementations MUST call validate and reject
     /// invalid messages.
-    async fn put(&self, path_info: proto::PathInfo) -> Result<proto::PathInfo, Error>;
+    async fn put(&self, path_info: PathInfo) -> Result<PathInfo, Error>;
 
     /// Return the nar size and nar sha256 digest for a given root node.
     /// This can be used to calculate NAR-based output paths,
     /// and implementations are encouraged to cache it.
-    async fn calculate_nar(&self, root_node: &proto::node::Node) -> Result<(u64, [u8; 32]), Error>;
+    async fn calculate_nar(
+        &self,
+        root_node: &castorepb::node::Node,
+    ) -> Result<(u64, [u8; 32]), Error>;
 
     /// Iterate over all PathInfo objects in the store.
     /// Implementations can decide to disallow listing.
@@ -52,5 +57,5 @@ pub trait PathInfoService: Send + Sync {
     /// and the box allows different underlying stream implementations to be returned since
     /// Rust doesn't support this as a generic in traits yet. This is the same thing that
     /// [async_trait] generates, but for streams instead of futures.
-    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<proto::PathInfo, Error>> + Send>>;
+    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<PathInfo, Error>> + Send>>;
 }
diff --git a/tvix/store/src/pathinfoservice/sled.rs b/tvix/store/src/pathinfoservice/sled.rs
index a9d0b029ee6b..bac384ea0912 100644
--- a/tvix/store/src/pathinfoservice/sled.rs
+++ b/tvix/store/src/pathinfoservice/sled.rs
@@ -1,13 +1,13 @@
 use super::PathInfoService;
-use crate::{
-    blobservice::BlobService, directoryservice::DirectoryService, nar::calculate_size_and_sha256,
-    proto, Error,
-};
+use crate::nar::calculate_size_and_sha256;
+use crate::proto::PathInfo;
 use futures::{stream::iter, Stream};
 use prost::Message;
 use std::{path::PathBuf, pin::Pin, sync::Arc};
 use tonic::async_trait;
 use tracing::warn;
+use tvix_castore::proto as castorepb;
+use tvix_castore::{blobservice::BlobService, directoryservice::DirectoryService, Error};
 
 /// SledPathInfoService stores PathInfo in a [sled](https://github.com/spacejam/sled).
 ///
@@ -63,11 +63,11 @@ impl PathInfoService for SledPathInfoService {
         directory_service: Arc<dyn DirectoryService>,
     ) -> Result<Self, Error> {
         if url.scheme() != "sled" {
-            return Err(crate::Error::StorageError("invalid scheme".to_string()));
+            return Err(Error::StorageError("invalid scheme".to_string()));
         }
 
         if url.has_host() {
-            return Err(crate::Error::StorageError(format!(
+            return Err(Error::StorageError(format!(
                 "invalid host: {}",
                 url.host().unwrap()
             )));
@@ -78,7 +78,7 @@ impl PathInfoService for SledPathInfoService {
             Self::new_temporary(blob_service, directory_service)
                 .map_err(|e| Error::StorageError(e.to_string()))
         } else if url.path() == "/" {
-            Err(crate::Error::StorageError(
+            Err(Error::StorageError(
                 "cowardly refusing to open / with sled".to_string(),
             ))
         } else {
@@ -87,10 +87,10 @@ impl PathInfoService for SledPathInfoService {
         }
     }
 
-    async fn get(&self, digest: [u8; 20]) -> Result<Option<proto::PathInfo>, Error> {
+    async fn get(&self, digest: [u8; 20]) -> Result<Option<PathInfo>, Error> {
         match self.db.get(digest) {
             Ok(None) => Ok(None),
-            Ok(Some(data)) => match proto::PathInfo::decode(&*data) {
+            Ok(Some(data)) => match PathInfo::decode(&*data) {
                 Ok(path_info) => Ok(Some(path_info)),
                 Err(e) => {
                     warn!("failed to decode stored PathInfo: {}", e);
@@ -110,7 +110,7 @@ impl PathInfoService for SledPathInfoService {
         }
     }
 
-    async fn put(&self, path_info: proto::PathInfo) -> Result<proto::PathInfo, Error> {
+    async fn put(&self, path_info: PathInfo) -> Result<PathInfo, Error> {
         // Call validate on the received PathInfo message.
         match path_info.validate() {
             Err(e) => Err(Error::InvalidRequest(format!(
@@ -131,7 +131,10 @@ impl PathInfoService for SledPathInfoService {
         }
     }
 
-    async fn calculate_nar(&self, root_node: &proto::node::Node) -> Result<(u64, [u8; 32]), Error> {
+    async fn calculate_nar(
+        &self,
+        root_node: &castorepb::node::Node,
+    ) -> Result<(u64, [u8; 32]), Error> {
         calculate_size_and_sha256(
             root_node,
             self.blob_service.clone(),
@@ -141,11 +144,11 @@ impl PathInfoService for SledPathInfoService {
         .map_err(|e| Error::StorageError(e.to_string()))
     }
 
-    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<proto::PathInfo, Error>> + Send>> {
+    fn list(&self) -> Pin<Box<dyn Stream<Item = Result<PathInfo, Error>> + Send>> {
         Box::pin(iter(self.db.iter().values().map(|v| match v {
             Ok(data) => {
                 // we retrieved some bytes
-                match proto::PathInfo::decode(&*data) {
+                match PathInfo::decode(&*data) {
                     Ok(path_info) => Ok(path_info),
                     Err(e) => {
                         warn!("failed to decode stored PathInfo: {}", e);
diff --git a/tvix/store/src/proto/grpc_pathinfoservice_wrapper.rs b/tvix/store/src/proto/grpc_pathinfoservice_wrapper.rs
index 14ceb34c3af7..7632614291dc 100644
--- a/tvix/store/src/proto/grpc_pathinfoservice_wrapper.rs
+++ b/tvix/store/src/proto/grpc_pathinfoservice_wrapper.rs
@@ -7,6 +7,7 @@ use tokio::task;
 use tokio_stream::wrappers::ReceiverStream;
 use tonic::{async_trait, Request, Response, Result, Status};
 use tracing::{debug, instrument, warn};
+use tvix_castore::proto as castorepb;
 
 pub struct GRPCPathInfoServiceWrapper {
     path_info_service: Arc<dyn PathInfoService>,
@@ -67,7 +68,7 @@ impl proto::path_info_service_server::PathInfoService for GRPCPathInfoServiceWra
     #[instrument(skip(self))]
     async fn calculate_nar(
         &self,
-        request: Request<proto::Node>,
+        request: Request<castorepb::Node>,
     ) -> Result<Response<proto::CalculateNarResponse>> {
         match request.into_inner().node {
             None => Err(Status::invalid_argument("no root node sent")),
diff --git a/tvix/store/src/proto/mod.rs b/tvix/store/src/proto/mod.rs
index 97a2694ac3de..6924b023c942 100644
--- a/tvix/store/src/proto/mod.rs
+++ b/tvix/store/src/proto/mod.rs
@@ -1,23 +1,13 @@
 #![allow(clippy::derive_partial_eq_without_eq, non_snake_case)]
 // https://github.com/hyperium/tonic/issues/1056
-use data_encoding::BASE64;
-use std::{collections::HashSet, iter::Peekable};
-use thiserror::Error;
-
-use prost::Message;
-
 use nix_compat::store_path::{self, StorePath};
+use thiserror::Error;
+use tvix_castore::{proto as castorepb, B3Digest};
 
-mod grpc_blobservice_wrapper;
-mod grpc_directoryservice_wrapper;
 mod grpc_pathinfoservice_wrapper;
 
-pub use grpc_blobservice_wrapper::GRPCBlobServiceWrapper;
-pub use grpc_directoryservice_wrapper::GRPCDirectoryServiceWrapper;
 pub use grpc_pathinfoservice_wrapper::GRPCPathInfoServiceWrapper;
 
-use crate::B3Digest;
-
 tonic::include_proto!("tvix.store.v1");
 
 #[cfg(feature = "reflection")]
@@ -29,23 +19,6 @@ pub const FILE_DESCRIPTOR_SET: &[u8] = tonic::include_file_descriptor_set!("tvix
 #[cfg(test)]
 mod tests;
 
-/// Errors that can occur during the validation of Directory messages.
-#[derive(Debug, PartialEq, Eq, Error)]
-pub enum ValidateDirectoryError {
-    /// Elements are not in sorted order
-    #[error("{} is not sorted", std::str::from_utf8(.0).unwrap_or(&BASE64.encode(.0)))]
-    WrongSorting(Vec<u8>),
-    /// Multiple elements with the same name encountered
-    #[error("{0:?} is a duplicate name")]
-    DuplicateName(Vec<u8>),
-    /// Invalid name encountered
-    #[error("Invalid name in {0:?}")]
-    InvalidName(Vec<u8>),
-    /// Invalid digest length encountered
-    #[error("Invalid Digest length: {0}")]
-    InvalidDigestLen(usize),
-}
-
 /// Errors that can occur during the validation of PathInfo messages.
 #[derive(Debug, Error, PartialEq)]
 pub enum ValidatePathInfoError {
@@ -67,31 +40,6 @@ pub enum ValidatePathInfoError {
     InconsistentNumberOfReferences(usize, usize),
 }
 
-/// Checks a Node name for validity as an intermediate node, and returns an
-/// error that's generated from the supplied constructor.
-///
-/// We disallow slashes, null bytes, '.', '..' and the empty string.
-fn validate_node_name<E>(name: &[u8], err: fn(Vec<u8>) -> E) -> Result<(), E> {
-    if name.is_empty()
-        || name == b".."
-        || name == b"."
-        || name.contains(&0x00)
-        || name.contains(&b'/')
-    {
-        return Err(err(name.to_vec()));
-    }
-    Ok(())
-}
-
-/// Checks a digest for validity.
-/// Digests are 32 bytes long, as we store blake3 digests.
-fn validate_digest<E>(digest: &bytes::Bytes, err: fn(usize) -> E) -> Result<(), E> {
-    if digest.len() != 32 {
-        return Err(err(digest.len()));
-    }
-    Ok(())
-}
-
 /// Parses a root node name.
 ///
 /// On success, this returns the parsed [StorePath].
@@ -129,16 +77,17 @@ impl PathInfo {
             None => {
                 return Err(ValidatePathInfoError::NoNodePresent());
             }
-            Some(Node { node }) => match node {
+            Some(castorepb::Node { node }) => match node {
                 None => {
                     return Err(ValidatePathInfoError::NoNodePresent());
                 }
-                Some(node::Node::Directory(directory_node)) => {
+                Some(castorepb::node::Node::Directory(directory_node)) => {
                     // ensure the digest has the appropriate size.
-                    validate_digest(
-                        &directory_node.digest,
-                        ValidatePathInfoError::InvalidDigestLen,
-                    )?;
+                    if TryInto::<B3Digest>::try_into(directory_node.digest.clone()).is_err() {
+                        return Err(ValidatePathInfoError::InvalidDigestLen(
+                            directory_node.digest.len(),
+                        ));
+                    }
 
                     // parse the name
                     parse_node_name_root(
@@ -146,14 +95,18 @@ impl PathInfo {
                         ValidatePathInfoError::InvalidNodeName,
                     )?
                 }
-                Some(node::Node::File(file_node)) => {
+                Some(castorepb::node::Node::File(file_node)) => {
                     // ensure the digest has the appropriate size.
-                    validate_digest(&file_node.digest, ValidatePathInfoError::InvalidDigestLen)?;
+                    if TryInto::<B3Digest>::try_into(file_node.digest.clone()).is_err() {
+                        return Err(ValidatePathInfoError::InvalidDigestLen(
+                            file_node.digest.len(),
+                        ));
+                    }
 
                     // parse the name
                     parse_node_name_root(&file_node.name, ValidatePathInfoError::InvalidNodeName)?
                 }
-                Some(node::Node::Symlink(symlink_node)) => {
+                Some(castorepb::node::Node::Symlink(symlink_node)) => {
                     // parse the name
                     parse_node_name_root(
                         &symlink_node.name,
@@ -167,217 +120,3 @@ impl PathInfo {
         Ok(root_nix_path)
     }
 }
-
-/// NamedNode is implemented for [FileNode], [DirectoryNode] and [SymlinkNode]
-/// and [node::Node], so we can ask all of them for the name easily.
-pub trait NamedNode {
-    fn get_name(&self) -> &[u8];
-}
-
-impl NamedNode for &FileNode {
-    fn get_name(&self) -> &[u8] {
-        &self.name
-    }
-}
-
-impl NamedNode for &DirectoryNode {
-    fn get_name(&self) -> &[u8] {
-        &self.name
-    }
-}
-
-impl NamedNode for &SymlinkNode {
-    fn get_name(&self) -> &[u8] {
-        &self.name
-    }
-}
-
-impl NamedNode for node::Node {
-    fn get_name(&self) -> &[u8] {
-        match self {
-            node::Node::File(node_file) => &node_file.name,
-            node::Node::Directory(node_directory) => &node_directory.name,
-            node::Node::Symlink(node_symlink) => &node_symlink.name,
-        }
-    }
-}
-
-impl node::Node {
-    /// Returns the node with a new name.
-    pub fn rename(self, name: bytes::Bytes) -> Self {
-        match self {
-            node::Node::Directory(n) => node::Node::Directory(DirectoryNode { name, ..n }),
-            node::Node::File(n) => node::Node::File(FileNode { name, ..n }),
-            node::Node::Symlink(n) => node::Node::Symlink(SymlinkNode { name, ..n }),
-        }
-    }
-}
-
-/// Accepts a name, and a mutable reference to the previous name.
-/// If the passed name is larger than the previous one, the reference is updated.
-/// If it's not, an error is returned.
-fn update_if_lt_prev<'n>(
-    prev_name: &mut &'n [u8],
-    name: &'n [u8],
-) -> Result<(), ValidateDirectoryError> {
-    if *name < **prev_name {
-        return Err(ValidateDirectoryError::WrongSorting(name.to_vec()));
-    }
-    *prev_name = name;
-    Ok(())
-}
-
-/// Inserts the given name into a HashSet if it's not already in there.
-/// If it is, an error is returned.
-fn insert_once<'n>(
-    seen_names: &mut HashSet<&'n [u8]>,
-    name: &'n [u8],
-) -> Result<(), ValidateDirectoryError> {
-    if seen_names.get(name).is_some() {
-        return Err(ValidateDirectoryError::DuplicateName(name.to_vec()));
-    }
-    seen_names.insert(name);
-    Ok(())
-}
-
-impl Directory {
-    /// The size of a directory is the number of all regular and symlink elements,
-    /// the number of directory elements, and their size fields.
-    pub fn size(&self) -> u32 {
-        self.files.len() as u32
-            + self.symlinks.len() as u32
-            + self
-                .directories
-                .iter()
-                .fold(0, |acc: u32, e| (acc + 1 + e.size))
-    }
-
-    /// Calculates the digest of a Directory, which is the blake3 hash of a
-    /// Directory protobuf message, serialized in protobuf canonical form.
-    pub fn digest(&self) -> B3Digest {
-        let mut hasher = blake3::Hasher::new();
-
-        hasher
-            .update(&self.encode_to_vec())
-            .finalize()
-            .as_bytes()
-            .into()
-    }
-
-    /// validate checks the directory for invalid data, such as:
-    /// - violations of name restrictions
-    /// - invalid digest lengths
-    /// - not properly sorted lists
-    /// - duplicate names in the three lists
-    pub fn validate(&self) -> Result<(), ValidateDirectoryError> {
-        let mut seen_names: HashSet<&[u8]> = HashSet::new();
-
-        let mut last_directory_name: &[u8] = b"";
-        let mut last_file_name: &[u8] = b"";
-        let mut last_symlink_name: &[u8] = b"";
-
-        // check directories
-        for directory_node in &self.directories {
-            validate_node_name(&directory_node.name, ValidateDirectoryError::InvalidName)?;
-            validate_digest(
-                &directory_node.digest,
-                ValidateDirectoryError::InvalidDigestLen,
-            )?;
-
-            update_if_lt_prev(&mut last_directory_name, &directory_node.name)?;
-            insert_once(&mut seen_names, &directory_node.name)?;
-        }
-
-        // check files
-        for file_node in &self.files {
-            validate_node_name(&file_node.name, ValidateDirectoryError::InvalidName)?;
-            validate_digest(&file_node.digest, ValidateDirectoryError::InvalidDigestLen)?;
-
-            update_if_lt_prev(&mut last_file_name, &file_node.name)?;
-            insert_once(&mut seen_names, &file_node.name)?;
-        }
-
-        // check symlinks
-        for symlink_node in &self.symlinks {
-            validate_node_name(&symlink_node.name, ValidateDirectoryError::InvalidName)?;
-
-            update_if_lt_prev(&mut last_symlink_name, &symlink_node.name)?;
-            insert_once(&mut seen_names, &symlink_node.name)?;
-        }
-
-        Ok(())
-    }
-
-    /// Allows iterating over all three nodes ([DirectoryNode], [FileNode],
-    /// [SymlinkNode]) in an ordered fashion, as long as the individual lists
-    /// are sorted (which can be checked by the [Directory::validate]).
-    pub fn nodes(&self) -> DirectoryNodesIterator {
-        return DirectoryNodesIterator {
-            i_directories: self.directories.iter().peekable(),
-            i_files: self.files.iter().peekable(),
-            i_symlinks: self.symlinks.iter().peekable(),
-        };
-    }
-}
-
-/// Struct to hold the state of an iterator over all nodes of a Directory.
-///
-/// Internally, this keeps peekable Iterators over all three lists of a
-/// Directory message.
-pub struct DirectoryNodesIterator<'a> {
-    // directory: &Directory,
-    i_directories: Peekable<std::slice::Iter<'a, DirectoryNode>>,
-    i_files: Peekable<std::slice::Iter<'a, FileNode>>,
-    i_symlinks: Peekable<std::slice::Iter<'a, SymlinkNode>>,
-}
-
-/// looks at two elements implementing NamedNode, and returns true if "left
-/// is smaller / comes first".
-///
-/// Some(_) is preferred over None.
-fn left_name_lt_right<A: NamedNode, B: NamedNode>(left: Option<&A>, right: Option<&B>) -> bool {
-    match left {
-        // if left is None, right always wins
-        None => false,
-        Some(left_inner) => {
-            // left is Some.
-            match right {
-                // left is Some, right is None - left wins.
-                None => true,
-                Some(right_inner) => {
-                    // both are Some - compare the name.
-                    return left_inner.get_name() < right_inner.get_name();
-                }
-            }
-        }
-    }
-}
-
-impl Iterator for DirectoryNodesIterator<'_> {
-    type Item = node::Node;
-
-    // next returns the next node in the Directory.
-    // we peek at all three internal iterators, and pick the one with the
-    // smallest name, to ensure lexicographical ordering.
-    // The individual lists are already known to be sorted.
-    fn next(&mut self) -> Option<Self::Item> {
-        if left_name_lt_right(self.i_directories.peek(), self.i_files.peek()) {
-            // i_directories is still in the game, compare with symlinks
-            if left_name_lt_right(self.i_directories.peek(), self.i_symlinks.peek()) {
-                self.i_directories
-                    .next()
-                    .cloned()
-                    .map(node::Node::Directory)
-            } else {
-                self.i_symlinks.next().cloned().map(node::Node::Symlink)
-            }
-        } else {
-            // i_files is still in the game, compare with symlinks
-            if left_name_lt_right(self.i_files.peek(), self.i_symlinks.peek()) {
-                self.i_files.next().cloned().map(node::Node::File)
-            } else {
-                self.i_symlinks.next().cloned().map(node::Node::Symlink)
-            }
-        }
-    }
-}
diff --git a/tvix/store/src/proto/tests/grpc_pathinfoservice.rs b/tvix/store/src/proto/tests/grpc_pathinfoservice.rs
index 114e89cacc10..c0b953d0f2e9 100644
--- a/tvix/store/src/proto/tests/grpc_pathinfoservice.rs
+++ b/tvix/store/src/proto/tests/grpc_pathinfoservice.rs
@@ -1,9 +1,8 @@
 use crate::proto::get_path_info_request::ByWhat::ByOutputHash;
-use crate::proto::node::Node::Symlink;
 use crate::proto::path_info_service_server::PathInfoService as GRPCPathInfoService;
 use crate::proto::GRPCPathInfoServiceWrapper;
+use crate::proto::GetPathInfoRequest;
 use crate::proto::PathInfo;
-use crate::proto::{GetPathInfoRequest, Node, SymlinkNode};
 use crate::tests::fixtures::DUMMY_OUTPUT_HASH;
 use crate::tests::utils::gen_blob_service;
 use crate::tests::utils::gen_directory_service;
@@ -11,6 +10,7 @@ use crate::tests::utils::gen_pathinfo_service;
 use std::sync::Arc;
 use tokio_stream::wrappers::ReceiverStream;
 use tonic::Request;
+use tvix_castore::proto as castorepb;
 
 /// generates a GRPCPathInfoService out of blob, directory and pathinfo services.
 ///
@@ -48,8 +48,8 @@ async fn put_get() {
     let service = gen_grpc_service();
 
     let path_info = PathInfo {
-        node: Some(Node {
-            node: Some(Symlink(SymlinkNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Symlink(castorepb::SymlinkNode {
                 name: "00000000000000000000000000000000-foo".into(),
                 target: "doesntmatter".into(),
             })),
diff --git a/tvix/store/src/proto/tests/mod.rs b/tvix/store/src/proto/tests/mod.rs
index 0a96ea3a0d59..bff885624380 100644
--- a/tvix/store/src/proto/tests/mod.rs
+++ b/tvix/store/src/proto/tests/mod.rs
@@ -1,6 +1,2 @@
-mod directory;
-mod directory_nodes_iterator;
-mod grpc_blobservice;
-mod grpc_directoryservice;
 mod grpc_pathinfoservice;
 mod pathinfo;
diff --git a/tvix/store/src/proto/tests/pathinfo.rs b/tvix/store/src/proto/tests/pathinfo.rs
index 779b46ed168e..dfbeb831d7d2 100644
--- a/tvix/store/src/proto/tests/pathinfo.rs
+++ b/tvix/store/src/proto/tests/pathinfo.rs
@@ -1,31 +1,10 @@
-use crate::proto::{self, Node, PathInfo, ValidatePathInfoError};
-use crate::B3Digest;
+use crate::proto::{NarInfo, PathInfo, ValidatePathInfoError};
+use crate::tests::fixtures::*;
 use bytes::Bytes;
-use lazy_static::lazy_static;
 use nix_compat::store_path::{self, StorePath};
 use std::str::FromStr;
 use test_case::test_case;
-
-lazy_static! {
-    static ref DUMMY_DIGEST: B3Digest = {
-        let u: &[u8; 32] = &[
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00, 0x00, 0x00,
-        ];
-        u.into()
-    };
-    static ref DUMMY_DIGEST_2: B3Digest = {
-        let u: &[u8; 32] = &[
-            0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00, 0x00, 0x00,
-        ];
-        u.into()
-    };
-}
-
-const DUMMY_NAME: &str = "00000000000000000000000000000000-dummy";
+use tvix_castore::proto as castorepb;
 
 #[test_case(
     None,
@@ -33,12 +12,12 @@ const DUMMY_NAME: &str = "00000000000000000000000000000000-dummy";
     "No node"
 )]
 #[test_case(
-    Some(Node { node: None }),
+    Some(castorepb::Node { node: None }),
     Err(ValidatePathInfoError::NoNodePresent());
     "No node 2"
 )]
 fn validate_no_node(
-    t_node: Option<proto::Node>,
+    t_node: Option<castorepb::Node>,
     t_result: Result<StorePath, ValidatePathInfoError>,
 ) {
     // construct the PathInfo object
@@ -50,7 +29,7 @@ fn validate_no_node(
 }
 
 #[test_case(
-    proto::DirectoryNode {
+    castorepb::DirectoryNode {
         name: DUMMY_NAME.into(),
         digest: DUMMY_DIGEST.clone().into(),
         size: 0,
@@ -59,7 +38,7 @@ fn validate_no_node(
     "ok"
 )]
 #[test_case(
-    proto::DirectoryNode {
+    castorepb::DirectoryNode {
         name: DUMMY_NAME.into(),
         digest: Bytes::new(),
         size: 0,
@@ -68,7 +47,7 @@ fn validate_no_node(
     "invalid digest length"
 )]
 #[test_case(
-    proto::DirectoryNode {
+    castorepb::DirectoryNode {
         name: "invalid".into(),
         digest: DUMMY_DIGEST.clone().into(),
         size: 0,
@@ -80,13 +59,13 @@ fn validate_no_node(
     "invalid node name"
 )]
 fn validate_directory(
-    t_directory_node: proto::DirectoryNode,
+    t_directory_node: castorepb::DirectoryNode,
     t_result: Result<StorePath, ValidatePathInfoError>,
 ) {
     // construct the PathInfo object
     let p = PathInfo {
-        node: Some(Node {
-            node: Some(proto::node::Node::Directory(t_directory_node)),
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Directory(t_directory_node)),
         }),
         ..Default::default()
     };
@@ -94,7 +73,7 @@ fn validate_directory(
 }
 
 #[test_case(
-    proto::FileNode {
+    castorepb::FileNode {
         name: DUMMY_NAME.into(),
         digest: DUMMY_DIGEST.clone().into(),
         size: 0,
@@ -104,7 +83,7 @@ fn validate_directory(
     "ok"
 )]
 #[test_case(
-    proto::FileNode {
+    castorepb::FileNode {
         name: DUMMY_NAME.into(),
         digest: Bytes::new(),
         ..Default::default()
@@ -113,7 +92,7 @@ fn validate_directory(
     "invalid digest length"
 )]
 #[test_case(
-    proto::FileNode {
+    castorepb::FileNode {
         name: "invalid".into(),
         digest: DUMMY_DIGEST.clone().into(),
         ..Default::default()
@@ -124,11 +103,14 @@ fn validate_directory(
     ));
     "invalid node name"
 )]
-fn validate_file(t_file_node: proto::FileNode, t_result: Result<StorePath, ValidatePathInfoError>) {
+fn validate_file(
+    t_file_node: castorepb::FileNode,
+    t_result: Result<StorePath, ValidatePathInfoError>,
+) {
     // construct the PathInfo object
     let p = PathInfo {
-        node: Some(Node {
-            node: Some(proto::node::Node::File(t_file_node)),
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::File(t_file_node)),
         }),
         ..Default::default()
     };
@@ -136,7 +118,7 @@ fn validate_file(t_file_node: proto::FileNode, t_result: Result<StorePath, Valid
 }
 
 #[test_case(
-    proto::SymlinkNode {
+    castorepb::SymlinkNode {
         name: DUMMY_NAME.into(),
         ..Default::default()
     },
@@ -144,7 +126,7 @@ fn validate_file(t_file_node: proto::FileNode, t_result: Result<StorePath, Valid
     "ok"
 )]
 #[test_case(
-    proto::SymlinkNode {
+    castorepb::SymlinkNode {
         name: "invalid".into(),
         ..Default::default()
     },
@@ -155,13 +137,13 @@ fn validate_file(t_file_node: proto::FileNode, t_result: Result<StorePath, Valid
     "invalid node name"
 )]
 fn validate_symlink(
-    t_symlink_node: proto::SymlinkNode,
+    t_symlink_node: castorepb::SymlinkNode,
     t_result: Result<StorePath, ValidatePathInfoError>,
 ) {
     // construct the PathInfo object
     let p = PathInfo {
-        node: Some(Node {
-            node: Some(proto::node::Node::Symlink(t_symlink_node)),
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Symlink(t_symlink_node)),
         }),
         ..Default::default()
     };
@@ -172,8 +154,8 @@ fn validate_symlink(
 fn validate_references() {
     // create a PathInfo without narinfo field.
     let path_info = PathInfo {
-        node: Some(Node {
-            node: Some(proto::node::Node::Directory(proto::DirectoryNode {
+        node: Some(castorepb::Node {
+            node: Some(castorepb::node::Node::Directory(castorepb::DirectoryNode {
                 name: DUMMY_NAME.into(),
                 digest: DUMMY_DIGEST.clone().into(),
                 size: 0,
@@ -186,7 +168,7 @@ fn validate_references() {
 
     // create a PathInfo with a narinfo field, but an inconsistent set of references
     let path_info_with_narinfo_missing_refs = PathInfo {
-        narinfo: Some(proto::NarInfo {
+        narinfo: Some(NarInfo {
             nar_size: 0,
             nar_sha256: DUMMY_DIGEST.clone().into(),
             signatures: vec![],
@@ -204,7 +186,7 @@ fn validate_references() {
 
     // create a pathinfo with the correct number of references, should suceed
     let path_info_with_narinfo = PathInfo {
-        narinfo: Some(proto::NarInfo {
+        narinfo: Some(NarInfo {
             nar_size: 0,
             nar_sha256: DUMMY_DIGEST.clone().into(),
             signatures: vec![],
diff --git a/tvix/store/src/tests/fixtures.rs b/tvix/store/src/tests/fixtures.rs
index c362744a34a7..4d820af1578e 100644
--- a/tvix/store/src/tests/fixtures.rs
+++ b/tvix/store/src/tests/fixtures.rs
@@ -1,90 +1,9 @@
-use crate::{
-    proto::{self, Directory, DirectoryNode, FileNode, SymlinkNode},
-    B3Digest,
-};
 use lazy_static::lazy_static;
+pub use tvix_castore::fixtures::*;
 
-pub const HELLOWORLD_BLOB_CONTENTS: &[u8] = b"Hello World!";
-pub const EMPTY_BLOB_CONTENTS: &[u8] = b"";
+pub const DUMMY_NAME: &str = "00000000000000000000000000000000-dummy";
 
 lazy_static! {
-    pub static ref DUMMY_DIGEST: B3Digest = {
-        let u: &[u8; 32] = &[
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00,
-        ];
-        u.into()
-    };
-    pub static ref DUMMY_DATA_1: bytes::Bytes = vec![0x01, 0x02, 0x03].into();
-    pub static ref DUMMY_DATA_2: bytes::Bytes = vec![0x04, 0x05].into();
-
-    pub static ref HELLOWORLD_BLOB_DIGEST: B3Digest =
-        blake3::hash(HELLOWORLD_BLOB_CONTENTS).as_bytes().into();
-    pub static ref EMPTY_BLOB_DIGEST: B3Digest =
-        blake3::hash(EMPTY_BLOB_CONTENTS).as_bytes().into();
-
-    // 2 bytes
-    pub static ref BLOB_A: bytes::Bytes = vec![0x00, 0x01].into();
-    pub static ref BLOB_A_DIGEST: B3Digest = blake3::hash(&BLOB_A).as_bytes().into();
-
-    // 1MB
-    pub static ref BLOB_B: bytes::Bytes = (0..255).collect::<Vec<u8>>().repeat(4 * 1024).into();
-    pub static ref BLOB_B_DIGEST: B3Digest = blake3::hash(&BLOB_B).as_bytes().into();
-
-    // Directories
-    pub static ref DIRECTORY_WITH_KEEP: proto::Directory = proto::Directory {
-        directories: vec![],
-        files: vec![FileNode {
-            name: b".keep".to_vec().into(),
-            digest: EMPTY_BLOB_DIGEST.clone().into(),
-            size: 0,
-            executable: false,
-        }],
-        symlinks: vec![],
-    };
-    pub static ref DIRECTORY_COMPLICATED: proto::Directory = proto::Directory {
-        directories: vec![DirectoryNode {
-            name: b"keep".to_vec().into(),
-            digest: DIRECTORY_WITH_KEEP.digest().into(),
-            size: DIRECTORY_WITH_KEEP.size(),
-        }],
-        files: vec![FileNode {
-            name: b".keep".to_vec().into(),
-            digest: EMPTY_BLOB_DIGEST.clone().into(),
-            size: 0,
-            executable: false,
-        }],
-        symlinks: vec![SymlinkNode {
-            name: b"aa".to_vec().into(),
-            target: b"/nix/store/somewhereelse".to_vec().into(),
-        }],
-    };
-    pub static ref DIRECTORY_A: Directory = Directory::default();
-    pub static ref DIRECTORY_B: Directory = Directory {
-        directories: vec![DirectoryNode {
-            name: b"a".to_vec().into(),
-            digest: DIRECTORY_A.digest().into(),
-            size: DIRECTORY_A.size(),
-        }],
-        ..Default::default()
-    };
-    pub static ref DIRECTORY_C: Directory = Directory {
-        directories: vec![
-            DirectoryNode {
-                name: b"a".to_vec().into(),
-                digest: DIRECTORY_A.digest().into(),
-                size: DIRECTORY_A.size(),
-            },
-            DirectoryNode {
-                name: b"a'".to_vec().into(),
-                digest: DIRECTORY_A.digest().into(),
-                size: DIRECTORY_A.size(),
-            }
-        ],
-        ..Default::default()
-    };
-
     // output hash
     pub static ref DUMMY_OUTPUT_HASH: bytes::Bytes = vec![
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
diff --git a/tvix/store/src/tests/mod.rs b/tvix/store/src/tests/mod.rs
index 8ceea01e3190..daea048deddf 100644
--- a/tvix/store/src/tests/mod.rs
+++ b/tvix/store/src/tests/mod.rs
@@ -1,4 +1,3 @@
 pub mod fixtures;
-mod import;
 mod nar_renderer;
 pub mod utils;
diff --git a/tvix/store/src/tests/nar_renderer.rs b/tvix/store/src/tests/nar_renderer.rs
index e0163dc7bd93..485d7d115ff5 100644
--- a/tvix/store/src/tests/nar_renderer.rs
+++ b/tvix/store/src/tests/nar_renderer.rs
@@ -1,12 +1,12 @@
 use crate::nar::calculate_size_and_sha256;
 use crate::nar::write_nar;
-use crate::proto::DirectoryNode;
-use crate::proto::FileNode;
-use crate::proto::SymlinkNode;
 use crate::tests::fixtures::*;
 use crate::tests::utils::*;
 use sha2::{Digest, Sha256};
 use std::io;
+use tvix_castore::proto::DirectoryNode;
+use tvix_castore::proto::FileNode;
+use tvix_castore::proto::{self as castorepb, SymlinkNode};
 
 #[tokio::test]
 async fn single_symlink() {
@@ -14,7 +14,7 @@ async fn single_symlink() {
 
     let buf = write_nar(
         buf,
-        &crate::proto::node::Node::Symlink(SymlinkNode {
+        &castorepb::node::Node::Symlink(SymlinkNode {
             name: "doesntmatter".into(),
             target: "/nix/store/somewhereelse".into(),
         }),
@@ -35,7 +35,7 @@ async fn single_file_missing_blob() {
 
     let e = write_nar(
         buf,
-        &crate::proto::node::Node::File(FileNode {
+        &castorepb::node::Node::File(FileNode {
             name: "doesntmatter".into(),
             digest: HELLOWORLD_BLOB_DIGEST.clone().into(),
             size: HELLOWORLD_BLOB_CONTENTS.len() as u32,
@@ -82,7 +82,7 @@ async fn single_file_wrong_blob_size() {
 
         let e = write_nar(
             buf,
-            &crate::proto::node::Node::File(FileNode {
+            &castorepb::node::Node::File(FileNode {
                 name: "doesntmatter".into(),
                 digest: HELLOWORLD_BLOB_DIGEST.clone().into(),
                 size: 42, // <- note the wrong size here!
@@ -109,7 +109,7 @@ async fn single_file_wrong_blob_size() {
 
         let e = write_nar(
             buf,
-            &crate::proto::node::Node::File(FileNode {
+            &castorepb::node::Node::File(FileNode {
                 name: "doesntmatter".into(),
                 digest: HELLOWORLD_BLOB_DIGEST.clone().into(),
                 size: 2, // <- note the wrong size here!
@@ -152,7 +152,7 @@ async fn single_file() {
 
     let buf = write_nar(
         buf,
-        &crate::proto::node::Node::File(FileNode {
+        &castorepb::node::Node::File(FileNode {
             name: "doesntmatter".into(),
             digest: HELLOWORLD_BLOB_DIGEST.clone().into(),
             size: HELLOWORLD_BLOB_CONTENTS.len() as u32,
@@ -199,7 +199,7 @@ async fn test_complicated() {
 
     let buf = write_nar(
         buf,
-        &crate::proto::node::Node::Directory(DirectoryNode {
+        &castorepb::node::Node::Directory(DirectoryNode {
             name: "doesntmatter".into(),
             digest: DIRECTORY_COMPLICATED.digest().into(),
             size: DIRECTORY_COMPLICATED.size(),
@@ -216,7 +216,7 @@ async fn test_complicated() {
     let bs = blob_service.clone();
     let ds = directory_service.clone();
     let (nar_size, nar_digest) = calculate_size_and_sha256(
-        &crate::proto::node::Node::Directory(DirectoryNode {
+        &castorepb::node::Node::Directory(DirectoryNode {
             name: "doesntmatter".into(),
             digest: DIRECTORY_COMPLICATED.digest().into(),
             size: DIRECTORY_COMPLICATED.size(),
diff --git a/tvix/store/src/tests/utils.rs b/tvix/store/src/tests/utils.rs
index 9ccd3dcc65b7..961be6e7ac07 100644
--- a/tvix/store/src/tests/utils.rs
+++ b/tvix/store/src/tests/utils.rs
@@ -1,18 +1,8 @@
+use crate::pathinfoservice::{MemoryPathInfoService, PathInfoService};
 use std::sync::Arc;
+use tvix_castore::{blobservice::BlobService, directoryservice::DirectoryService};
 
-use crate::{
-    blobservice::{BlobService, MemoryBlobService},
-    directoryservice::{DirectoryService, MemoryDirectoryService},
-    pathinfoservice::{MemoryPathInfoService, PathInfoService},
-};
-
-pub fn gen_blob_service() -> Arc<dyn BlobService> {
-    Arc::new(MemoryBlobService::default())
-}
-
-pub fn gen_directory_service() -> Arc<dyn DirectoryService> {
-    Arc::new(MemoryDirectoryService::default())
-}
+pub use tvix_castore::utils::*;
 
 pub fn gen_pathinfo_service(
     blob_service: Arc<dyn BlobService>,