diff --git a/packages/fs/tool-fs-search/src/search-core.ts b/packages/fs/tool-fs-search/src/search-core.ts
index b73c31bd1f..a47adfa7c3 100644
--- a/packages/fs/tool-fs-search/src/search-core.ts
+++ b/packages/fs/tool-fs-search/src/search-core.ts
@@ -158,7 +158,11 @@ async function completeStdout(toolName: string, result: BashRunResult, rawOutput
  * success with zero results (`noMatches`), anything else throws a
  * {@link SearchError} (abort/timeout → `SEARCH_ABORTED`, invalid pattern →
  * `SEARCH_INVALID_PATTERN`, the rest → `SEARCH_FAILED` /
- * `SEARCH_RAW_OUTPUT_OVERFLOW`).
+ * `SEARCH_RAW_OUTPUT_OVERFLOW`). A `run()` REJECTION — the seam's
+ * infrastructure failures (pre-aborted signal, unusable workdir, missing
+ * shell) — is translated into the same taxonomy: a pre-aborted signal becomes
+ * `SEARCH_ABORTED`, everything else `SEARCH_FAILED`, with the original as
+ * `cause`.
  *
  * @param ctx - the plugin context; execution uses its `bash` service.
  * @param exec - the tool-execution context; supplies the session cwd and the abort signal.
@@ -180,7 +184,18 @@ export async function runRipgrep(
     ...cwd !== undefined ? { workdir: cwd } : {},
     ...exec.signal ? { signal: exec.signal } : {},
   })
-  const result = await ctx.bash.run(spec)
+  let result: BashRunResult
+  try {
+    result = await ctx.bash.run(spec)
+  } catch (error: unknown) {
+    // The seam contract: run() REJECTS only for infrastructure failures — a
+    // pre-aborted signal, an unusable workdir, a missing shell. Translate them
+    // so these failures stay machine-routable under the SEARCH_* taxonomy.
+    if (spec.signal?.aborted === true) {
+      throw new SearchError(`${toolName} was aborted before completion (tool timeout or caller cancellation)`, 'SEARCH_ABORTED', { cause: error })
+    }
+    throw new SearchError(`${toolName} could not start its search command (unusable working directory or missing shell)`, 'SEARCH_FAILED', { cause: error })
+  }
   if (result.aborted) {
     throw new SearchError(`${toolName} was aborted before completion (tool timeout or caller cancellation)`, 'SEARCH_ABORTED')
   }
diff --git a/packages/fs/tool-fs-search/tests/integration.spec.ts b/packages/fs/tool-fs-search/tests/integration.spec.ts
index 74a418238b..481d3af620 100644
--- a/packages/fs/tool-fs-search/tests/integration.spec.ts
+++ b/packages/fs/tool-fs-search/tests/integration.spec.ts
@@ -158,4 +158,27 @@ describe.skipIf(!hasRg)('search tools over the real bash executor + real rg', ()
       }
     })
   })
+
+  describe('bash-start infrastructure failures stay in the SEARCH_* taxonomy', () => {
+    it('a pre-aborted exec.signal (real executor rejects before spawn) is SEARCH_ABORTED', async () => {
+      const controller = new AbortController()
+      controller.abort()
+      const result = await ctx.tools.execute({
+        callId: CallId(`it-${++callCounter}`),
+        name: 'grep',
+        arguments: { pattern: 'x' },
+        signal: controller.signal,
+      })
+      expect(result.isError).toBe(true)
+      expect(result.error).toMatchObject({ name: 'SearchError', code: 'SEARCH_ABORTED' })
+    })
+
+    it('an unusable session cwd (spawn failure) is SEARCH_FAILED', async () => {
+      const gone = join(dir, 'deleted-session-dir')
+      const result = await call('glob', { pattern: '*' }, { session: { header: { id: 'session-int', cwd: gone } } })
+      expect(result.isError).toBe(true)
+      expect(result.error).toMatchObject({ name: 'SearchError', code: 'SEARCH_FAILED' })
+      expect(text(result)).toContain('could not start')
+    })
+  })
 })
diff --git a/packages/fs/tool-fs-search/tests/tools.spec.ts b/packages/fs/tool-fs-search/tests/tools.spec.ts
index 55b54555ae..6afca54efd 100644
--- a/packages/fs/tool-fs-search/tests/tools.spec.ts
+++ b/packages/fs/tool-fs-search/tests/tools.spec.ts
@@ -279,6 +279,27 @@ describe('workdir derivation and signal forwarding', () => {
     expect(result.error).toMatchObject({ code: 'SEARCH_ABORTED' })
     expect(text(result)).toContain('timed out after 1234ms')
   })
+
+  it('translates a run() rejection under a pre-aborted signal into SEARCH_ABORTED', async () => {
+    // The seam contract: run() REJECTS for a pre-aborted signal (it never
+    // spawns). The plain rejection must not escape the SEARCH_* taxonomy.
+    const { ctx, bash } = await setup()
+    const controller = new AbortController()
+    controller.abort()
+    bash.handler = () => { throw new Error('aborted before spawn') }
+    const result = await call(ctx, 'grep', { pattern: 'x' }, { signal: controller.signal })
+    expect(result.isError).toBe(true)
+    expect(result.error).toMatchObject({ name: 'SearchError', code: 'SEARCH_ABORTED' })
+  })
+
+  it('translates a run() rejection without an abort (unusable workdir) into SEARCH_FAILED', async () => {
+    const { ctx, bash } = await setup()
+    bash.handler = () => { throw new Error('spawn bash ENOENT') }
+    const result = await call(ctx, 'glob', { pattern: '*' })
+    expect(result.isError).toBe(true)
+    expect(result.error).toMatchObject({ name: 'SearchError', code: 'SEARCH_FAILED' })
+    expect(text(result)).toContain('could not start')
+  })
 })
 
 describe('exit semantics and failure classification', () => {