Type the blob-write response hash as fabro_types::BlobHash

Promote BlobHash to a named OpenAPI schema with the ^[0-9a-f]{64}$
pattern, reference it from WriteBlobResponse.hash and the blobHash path
parameter, and map it to fabro_types::BlobHash via with_replacement.
The server now serializes the domain type directly and the client gets
a parsed BlobHash by construction, removing the to_string/parse adapter
pair across the wire boundary. Adds the JSON-parity test required for
new replacements.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/public/api-reference/fabro-api.yaml

@@ -5980,8 +5980,7 @@ components:
       required: true
       description: Content-addressed blob hash.
       schema:
-        type: string
-        pattern: '^[0-9a-f]{64}$'
+        $ref: "#/components/schemas/BlobHash"
       example: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
 
     ArtifactFilename:
@@ -10283,6 +10282,12 @@ components:
           description: Assigned event sequence number.
           example: 42
 
+    BlobHash:
+      description: Content-addressed SHA-256 hash of a stored blob.
+      type: string
+      pattern: "^[0-9a-f]{64}$"
+      example: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
+
     WriteBlobResponse:
       description: Content-addressed hash of a stored blob.
       type: object
@@ -10290,9 +10295,7 @@ components:
         - hash
       properties:
         hash:
-          type: string
-          description: Content-addressed hash of the stored blob.
-          example: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
+          $ref: "#/components/schemas/BlobHash"
 
     CommandTermination:
       description: Terminal state for a command execution.

lib/apps/fabro-server/src/server/handler/artifacts.rs

@@ -105,10 +105,7 @@ async fn write_run_blob(
     }
     match state.stores.runs.open_run(&id).await {
         Ok(run_store) => match run_store.write_blob(&body).await {
-            Ok(blob_hash) => Json(WriteBlobResponse {
-                hash: blob_hash.to_string(),
-            })
-            .into_response(),
+            Ok(blob_hash) => Json(WriteBlobResponse { hash: blob_hash }).into_response(),
             Err(err) => {
                 ApiError::new(StatusCode::INTERNAL_SERVER_ERROR, err.to_string()).into_response()
             }

lib/foundation/fabro-api/build.rs

@@ -725,6 +725,7 @@ fn main() {
         ("WorkflowVersion", "fabro_types::WorkflowVersion", &[]),
         ("WorkflowPath", "fabro_types::WorkflowPath", &[]),
         ("WorkflowVersionId", "fabro_types::WorkflowVersionId", &[]),
+        ("BlobHash", "fabro_types::BlobHash", &[]),
         ("CostSource", "fabro_model::CostSource", &[]),
     ];
     for (name, path, impls) in replacements {

lib/foundation/fabro-api/src/lib.rs

@@ -42,7 +42,7 @@ pub mod types {
     pub use fabro_types::{
         ActivatedSkill, AgentControlState, AgentMcpToolSummary, AgentSkillActivationSource,
         AgentSkillSummary, AgentToolCategory, AgentToolSource, AgentToolSummary,
-        AgentToolsAvailableProps, AskFabro, AuthMethod, AutomationRef, BilledTokenCounts,
+        AgentToolsAvailableProps, AskFabro, AuthMethod, AutomationRef, BilledTokenCounts, BlobHash,
         CommandTermination, Conclusion, ContentPart, CreateVariableRequest, DiffStats, DiffSummary,
         DirtyStatus, EventEnvelope, ExecOutputTail, FailureCategory, FailureDetail,
         FailureSignature, GitContext, IdpIdentity, IntegrationConnectionKind,

lib/foundation/fabro-api/tests/blob_hash_round_trip.rs

@@ -0,0 +1,50 @@
+use std::any::{TypeId, type_name};
+
+use fabro_api::types::{BlobHash as ApiBlobHash, WriteBlobResponse};
+use fabro_types::BlobHash;
+use serde_json::json;
+
+const BLOB_HASH: &str = "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824";
+
+#[test]
+fn blob_hash_schema_reuses_domain_type() {
+    assert_same_type::<ApiBlobHash, BlobHash>();
+}
+
+#[test]
+fn write_blob_response_round_trips_exact_wire_shape() {
+    let value = json!({ "hash": BLOB_HASH });
+
+    let response: WriteBlobResponse = serde_json::from_value(value.clone()).unwrap();
+    assert_eq!(serde_json::to_value(&response).unwrap(), value);
+}
+
+#[test]
+fn blob_hash_emits_the_documented_lowercase_pattern() {
+    // Serialization must match the OpenAPI schema pattern `^[0-9a-f]{64}$`.
+    let hash: ApiBlobHash = serde_json::from_value(json!(BLOB_HASH)).unwrap();
+    let emitted = serde_json::to_value(hash).unwrap();
+    assert_eq!(emitted, json!(BLOB_HASH));
+
+    let text = emitted.as_str().unwrap();
+    assert_eq!(text.len(), 64);
+    assert!(
+        text.bytes()
+            .all(|byte| matches!(byte, b'0'..=b'9' | b'a'..=b'f'))
+    );
+}
+
+#[test]
+fn blob_hash_rejects_non_hex_values() {
+    assert!(serde_json::from_value::<ApiBlobHash>(json!("not-a-blob-hash")).is_err());
+}
+
+fn assert_same_type<Api: 'static, Domain: 'static>() {
+    assert_eq!(
+        TypeId::of::<Api>(),
+        TypeId::of::<Domain>(),
+        "{} must be the domain type {}",
+        type_name::<Api>(),
+        type_name::<Domain>()
+    );
+}

lib/foundation/fabro-client/src/client.rs

@@ -1839,11 +1839,7 @@ impl Client {
                     .await
             })
             .await?;
-        response
-            .into_inner()
-            .hash
-            .parse()
-            .context("write_run_blob returned invalid blob hash")
+        Ok(response.into_inner().hash)
     }
 
     pub async fn read_run_blob(
@@ -1856,7 +1852,7 @@ impl Client {
             .client
             .read_run_blob()
             .id(run_id.to_string())
-            .blob_hash(blob_hash.to_string())
+            .blob_hash(*blob_hash)
             .send()
             .await;
         match response {

lib/packages/fabro-api-client/src/models/write-blob-response.ts

@@ -19,7 +19,7 @@
  */
 export interface WriteBlobResponse {
     /**
-     * Content-addressed hash of the stored blob.
+     * Content-addressed SHA-256 hash of a stored blob.
      */
     'hash': string;
 }