diff --git a/src/agents/pi-embedded-helpers.validate-turns.test.ts b/src/agents/pi-embedded-helpers.validate-turns.test.ts
index a073d5b1f3d..7730844dc0a 100644
--- a/src/agents/pi-embedded-helpers.validate-turns.test.ts
+++ b/src/agents/pi-embedded-helpers.validate-turns.test.ts
@@ -525,6 +525,52 @@ describe("validateAnthropicTurns strips dangling tool_use blocks", () => {
     ]);
   });
 
+  it("preserves assistant turns that include signed thinking blocks", () => {
+    const msgs = asMessages([
+      { role: "user", content: [{ type: "text", text: "Use tool" }] },
+      {
+        role: "assistant",
+        content: [
+          { type: "thinking", thinking: "internal", thinkingSignature: "sig_1" },
+          { type: "toolCall", id: "tool-1", name: "gateway", arguments: {} },
+        ],
+      },
+      { role: "user", content: [{ type: "text", text: "Continue" }] },
+    ]);
+
+    const result = validateAnthropicTurns(msgs);
+
+    expect(result).toHaveLength(3);
+    const assistantContent = (result[1] as { content?: unknown[] }).content;
+    expect(assistantContent).toEqual([
+      { type: "thinking", thinking: "internal", thinkingSignature: "sig_1" },
+      { type: "toolCall", id: "tool-1", name: "gateway", arguments: {} },
+    ]);
+  });
+
+  it("preserves assistant turns that include redacted thinking blocks", () => {
+    const msgs = asMessages([
+      { role: "user", content: [{ type: "text", text: "Use tool" }] },
+      {
+        role: "assistant",
+        content: [
+          { type: "redacted_thinking", data: "blob", thinkingSignature: "sig_1" },
+          { type: "toolUse", id: "tool-1", name: "gateway", arguments: {} },
+        ],
+      },
+      { role: "user", content: [{ type: "text", text: "Continue" }] },
+    ]);
+
+    const result = validateAnthropicTurns(msgs);
+
+    expect(result).toHaveLength(3);
+    const assistantContent = (result[1] as { content?: unknown[] }).content;
+    expect(assistantContent).toEqual([
+      { type: "redacted_thinking", data: "blob", thinkingSignature: "sig_1" },
+      { type: "toolUse", id: "tool-1", name: "gateway", arguments: {} },
+    ]);
+  });
+
   it("is replay-safe across repeated validation passes", () => {
     const msgs = makeDualToolAnthropicTurns([
       {
diff --git a/src/agents/pi-embedded-helpers/turns.ts b/src/agents/pi-embedded-helpers/turns.ts
index e5687faa83d..43bcf77e79e 100644
--- a/src/agents/pi-embedded-helpers/turns.ts
+++ b/src/agents/pi-embedded-helpers/turns.ts
@@ -15,6 +15,14 @@ function isToolCallBlock(block: AnthropicContentBlock): boolean {
   return block.type === "toolUse" || block.type === "toolCall" || block.type === "functionCall";
 }
 
+function isThinkingLikeBlock(block: unknown): boolean {
+  if (!block || typeof block !== "object") {
+    return false;
+  }
+  const type = (block as { type?: unknown }).type;
+  return type === "thinking" || type === "redacted_thinking";
+}
+
 function isAbortedAssistantTurn(message: AgentMessage): boolean {
   const stopReason = (message as { stopReason?: unknown }).stopReason;
   return stopReason === "aborted" || stopReason === "error";
@@ -117,6 +125,10 @@ function stripDanglingAnthropicToolUses(messages: AgentMessage[]): AgentMessage[
       result.push(msg);
       continue;
     }
+    if (originalContent.some((block) => isThinkingLikeBlock(block))) {
+      result.push(msg);
+      continue;
+    }
     if (
       extractToolCallsFromAssistant(msg as Extract<AgentMessage, { role: "assistant" }>).length ===
       0