From 2d1f4af67ab45c09157e2fbf1aa675c7039fcbab Mon Sep 17 00:00:00 2001
From: Shakker <shakkerdroid@gmail.com>
Date: Sun, 12 Apr 2026 03:35:25 +0100
Subject: [PATCH] fix: preserve thinking turns during transcript repair

---
 src/agents/session-transcript-repair.test.ts | 34 ++++++++++++++++++++
 src/agents/session-transcript-repair.ts      | 16 +++++++++
 2 files changed, 50 insertions(+)

diff --git a/src/agents/session-transcript-repair.test.ts b/src/agents/session-transcript-repair.test.ts
index 3fa01fb1de0..3f460c40d80 100644
--- a/src/agents/session-transcript-repair.test.ts
+++ b/src/agents/session-transcript-repair.test.ts
@@ -380,6 +380,40 @@ describe("sanitizeToolCallInputs", () => {
     expect(types).toEqual(["text", "toolUse"]);
   });
 
+  it("preserves assistant turns that include thinking blocks", () => {
+    const input = castAgentMessages([
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "thinking",
+            thinking: "Let me check the gateway config.",
+            thinkingSignature: "sig_gateway",
+          },
+          {
+            type: "toolCall",
+            id: "call_gateway",
+            name: "gateway",
+            arguments: {
+              action: "config.get",
+              path: "channels.telegram",
+            },
+          },
+        ],
+      },
+    ]);
+
+    const out = sanitizeToolCallInputs(input, { allowedToolNames: ["read"] });
+
+    expect(out).toBe(input);
+    const assistant = out[0] as Extract<AgentMessage, { role: "assistant" }>;
+    const types = Array.isArray(assistant.content)
+      ? assistant.content.map((block) => (block as { type?: unknown }).type)
+      : [];
+    expect(types).toEqual(["thinking", "toolCall"]);
+    expect((assistant.content?.[1] as { name?: unknown })?.name).toBe("gateway");
+  });
+
   it.each([
     {
       name: "trims leading whitespace from tool names",
diff --git a/src/agents/session-transcript-repair.ts b/src/agents/session-transcript-repair.ts
index dcb8661f742..044fa9731e1 100644
--- a/src/agents/session-transcript-repair.ts
+++ b/src/agents/session-transcript-repair.ts
@@ -17,6 +17,14 @@ type RawToolCallBlock = {
   arguments?: unknown;
 };
 
+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 isRawToolCallBlock(block: unknown): block is RawToolCallBlock {
   if (!block || typeof block !== "object") {
     return false;
@@ -239,6 +247,14 @@ export function repairToolCallInputs(
       continue;
     }
 
+    // Preserve provider-owned thinking turns verbatim. Anthropic replays can
+    // reject any historical assistant turn whose signed thinking block no
+    // longer matches the original response, including sibling tool calls.
+    if (msg.content.some((block) => isThinkingLikeBlock(block))) {
+      out.push(msg);
+      continue;
+    }
+
     const nextContent: typeof msg.content = [];
     let droppedInMessage = 0;
     let messageChanged = false;