diff --git a/src/agents/pi-embedded-runner.anthropic-tool-replay.live.test.ts b/src/agents/pi-embedded-runner.anthropic-tool-replay.live.test.ts
index ab587fd38ba..1b2b0749a3d 100644
--- a/src/agents/pi-embedded-runner.anthropic-tool-replay.live.test.ts
+++ b/src/agents/pi-embedded-runner.anthropic-tool-replay.live.test.ts
@@ -76,6 +76,8 @@ describeLive("pi embedded anthropic replay sanitization (live)", () => {
       const wrapped = wrapStreamFnSanitizeMalformedToolCalls(baseFn as never, new Set(["noop"]), {
         validateGeminiTurns: false,
         validateAnthropicTurns: true,
+        preserveSignatures: false,
+        dropThinkingBlocks: false,
       });
 
       await Promise.resolve(wrapped(model as never, { messages } as never, {} as never));
diff --git a/src/agents/pi-embedded-runner.sanitize-session-history.test.ts b/src/agents/pi-embedded-runner.sanitize-session-history.test.ts
index 0252f7a6d15..fb5625d84b2 100644
--- a/src/agents/pi-embedded-runner.sanitize-session-history.test.ts
+++ b/src/agents/pi-embedded-runner.sanitize-session-history.test.ts
@@ -1010,6 +1010,34 @@ describe("sanitizeSessionHistory", () => {
     });
   });
 
+  it("uses immutable thinking replay for amazon-bedrock claude providers when policy preserves signatures", async () => {
+    setNonGoogleModelApi();
+
+    const messages = castAgentMessages([
+      makeUserMessage("retry"),
+      makeAssistantMessage([
+        {
+          type: "thinking",
+          thinking: "internal",
+          thinkingSignature: "sig_1",
+        },
+        { type: "toolCall", id: "call_1", name: " read ", arguments: {} },
+      ] as unknown as AssistantMessage["content"]),
+    ]);
+
+    const result = await sanitizeAnthropicHistory({
+      provider: "amazon-bedrock",
+      modelApi: "bedrock-converse-stream",
+      messages,
+    });
+
+    expect(result).toHaveLength(1);
+    expect(result[0]).toMatchObject({
+      role: "user",
+      content: "retry",
+    });
+  });
+
   it("keeps mutable thinking turns outside exact anthropic replay", async () => {
     setNonGoogleModelApi();
 
diff --git a/src/agents/pi-embedded-runner/run/attempt.test.ts b/src/agents/pi-embedded-runner/run/attempt.test.ts
index b96ff7e9533..5460876a3e3 100644
--- a/src/agents/pi-embedded-runner/run/attempt.test.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.test.ts
@@ -1006,6 +1006,50 @@ describe("wrapStreamFnSanitizeMalformedToolCalls", () => {
     ]);
   });
 
+  it("drops signed thinking turns for bedrock claude replay when sibling tool calls are not replay-safe", async () => {
+    const messages = [
+      {
+        role: "assistant",
+        content: [
+          { type: "thinking", thinking: "internal", thinkingSignature: "sig_1" },
+          { type: "toolCall", id: "toolu_legacy", name: "gateway", arguments: {} },
+        ],
+      },
+      {
+        role: "user",
+        content: [{ type: "text", text: "retry" }],
+      },
+    ];
+    const baseFn = vi.fn((_model, _context) =>
+      createFakeStream({ events: [], resultMessage: { role: "assistant", content: [] } }),
+    );
+
+    const wrapped = wrapStreamFnSanitizeMalformedToolCalls(
+      baseFn as never,
+      new Set(["read"]),
+      {
+        validateAnthropicTurns: true,
+        preserveSignatures: true,
+        dropThinkingBlocks: false,
+      } as never,
+    );
+    const stream = wrapped(
+      { api: "bedrock-converse-stream" } as never,
+      { messages } as never,
+      {} as never,
+    ) as FakeWrappedStream | Promise<FakeWrappedStream>;
+    await Promise.resolve(stream);
+
+    expect(baseFn).toHaveBeenCalledTimes(1);
+    const seenContext = baseFn.mock.calls[0]?.[1] as { messages: unknown[] };
+    expect(seenContext.messages).toEqual([
+      {
+        role: "user",
+        content: [{ type: "text", text: "retry" }],
+      },
+    ]);
+  });
+
   it("drops signed thinking turns when replay would expose inline sessions_spawn attachments", async () => {
     const attachmentContent = "SIGNED_THINKING_INLINE_ATTACHMENT";
     const messages = [
@@ -1588,6 +1632,8 @@ describe("wrapStreamFnSanitizeMalformedToolCalls", () => {
     const wrapped = wrapStreamFnSanitizeMalformedToolCalls(baseFn as never, new Set(["read"]), {
       validateGeminiTurns: false,
       validateAnthropicTurns: true,
+      preserveSignatures: false,
+      dropThinkingBlocks: false,
     });
     const stream = wrapped({} as never, { messages } as never, {} as never) as
       | FakeWrappedStream
@@ -1633,6 +1679,8 @@ describe("wrapStreamFnSanitizeMalformedToolCalls", () => {
     const wrapped = wrapStreamFnSanitizeMalformedToolCalls(baseFn as never, new Set(["read"]), {
       validateGeminiTurns: false,
       validateAnthropicTurns: true,
+      preserveSignatures: false,
+      dropThinkingBlocks: false,
     });
     const stream = wrapped({} as never, { messages } as never, {} as never) as
       | FakeWrappedStream
@@ -1682,6 +1730,8 @@ describe("wrapStreamFnSanitizeMalformedToolCalls", () => {
       const wrapped = wrapStreamFnSanitizeMalformedToolCalls(baseFn as never, new Set(["read"]), {
         validateGeminiTurns: false,
         validateAnthropicTurns: true,
+        preserveSignatures: false,
+        dropThinkingBlocks: false,
       });
       const stream = wrapped({} as never, { messages } as never, {} as never) as
         | FakeWrappedStream
@@ -1722,6 +1772,8 @@ describe("wrapStreamFnSanitizeMalformedToolCalls", () => {
     const wrapped = wrapStreamFnSanitizeMalformedToolCalls(baseFn as never, new Set(["read"]), {
       validateGeminiTurns: false,
       validateAnthropicTurns: true,
+      preserveSignatures: false,
+      dropThinkingBlocks: false,
     });
     const stream = wrapped({} as never, { messages } as never, {} as never) as
       | FakeWrappedStream