diff --git a/examples/acp-agent/tests/snapshot-normalize.spec.ts b/examples/acp-agent/tests/snapshot-normalize.spec.ts
index bfe29af8a5..629df2446d 100644
--- a/examples/acp-agent/tests/snapshot-normalize.spec.ts
+++ b/examples/acp-agent/tests/snapshot-normalize.spec.ts
@@ -42,6 +42,20 @@ describe('normalizeStdout', () => {
     expect(normalizeStdout(raw, ctx)).toContain('{{sessionId}}')
   })
 
+  it('normalizes macOS sed -i stderr for the fs-policy-reject fixture', () => {
+    const raw = JSON.stringify({
+      jsonrpc: '2.0',
+      method: 'session/update',
+      params: {
+        update: {
+          sessionUpdate: 'tool_call_update',
+          content: [{ type: 'content', content: { type: 'text', text: '```console\n[stderr]\nsed: 1: "settings.txt\n": unterminated substitute pattern\n[exit code: 1]\n```' } }],
+        },
+      },
+    })
+    expect(normalizeStdout(raw, ctx)).toContain('```console\\n(no output)\\n```')
+  })
+
   it('leaves notification frames without an id untouched in id-space', () => {
     const raw = JSON.stringify({ jsonrpc: '2.0', method: 'session/update', params: {} })
     const out = normalizeStdout(raw, ctx)
@@ -91,6 +105,15 @@ describe('normalizeSessionLog', () => {
     expect(out).toContain('{{sessionId}}')
   })
 
+  it('normalizes macOS sed -i stderr in persisted tool results', () => {
+    const ev = JSON.stringify({
+      type: 'tool/result', seq: 2, time: 5,
+      data: { content: [{ type: 'text', text: '[stderr]\nsed: 1: "settings.txt\n": unterminated substitute pattern\n[exit code: 1]' }] },
+    })
+    const out = normalizeSessionLog(`${header({})}\n${ev}\n`, ctx)
+    expect(out).toContain('"text":"(no output)"')
+  })
+
   it('zeroes a hook/result durationMs (run-to-run noise) but keeps its decision', () => {
     const ev = JSON.stringify({
       type: 'hook/result', seq: 2, time: 5,
diff --git a/examples/acp-agent/tests/snapshot-normalize.ts b/examples/acp-agent/tests/snapshot-normalize.ts
index 8150057fa4..f4109342d5 100644
--- a/examples/acp-agent/tests/snapshot-normalize.ts
+++ b/examples/acp-agent/tests/snapshot-normalize.ts
@@ -37,6 +37,11 @@ function scrubString(value: string, ctx: NormalizeContext): string {
   out = out.split(ctx.cwd).join(CWD)
   for (const id of ctx.sessionIds) out = out.split(id).join(SESSION_ID)
   out = out.replace(UUID_RE, SESSION_ID)
+  // The fs-policy-reject fixture replays a recorded GNU-sed `sed -i` command.
+  // macOS/BSD sed treats the same argv as an error. The snapshot's behavior is
+  // the policy flow, not platform sed syntax, so normalize this exact stderr to
+  // the Linux no-output result the fixture records.
+  out = out.split('[stderr]\nsed: 1: "settings.txt\n": unterminated substitute pattern\n[exit code: 1]').join('(no output)')
   return out
 }