From ee3aa0e036f476270169b2fb6b19d4d7c0d1be1b Mon Sep 17 00:00:00 2001
From: Vinh Nguyen <vinhnt36@fpt.com>
Date: Sun, 3 May 2026 14:36:24 +0700
Subject: [PATCH] test(session-file-repair): add regression for trailing
 stop-assistant after tool-result
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Adds a test covering the exact bug scenario described in the fix document:
user → assistant(toolCall) → toolResult → assistant(text, stopReason=stop).

The repair pass must leave this sequence untouched; previously, overly broad
trimming logic could drop the final text response, breaking multi-turn context
for the next user message. The test verifies repaired=false and byte-identity
of the session file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 src/agents/session-file-repair.test.ts | 54 ++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/src/agents/session-file-repair.test.ts b/src/agents/session-file-repair.test.ts
index f0151e96843..1efb6fc6c41 100644
--- a/src/agents/session-file-repair.test.ts
+++ b/src/agents/session-file-repair.test.ts
@@ -465,6 +465,60 @@ describe("repairSessionFileIfNeeded", () => {
     expect(after).toBe(original);
   });
 
+  it("preserves final text assistant turn that follows a tool-call/tool-result pair", async () => {
+    // Regression: a trailing assistant message with stopReason "stop" that follows a
+    // tool-call turn and its matching tool-result must never be trimmed by the repair
+    // pass. This is the exact sequence produced by any agent run that calls at least
+    // one tool before returning a final text response, and it must survive intact so
+    // subsequent user messages are parented to the correct leaf node.
+    const { file } = await createTempSessionPath();
+    const { header, message } = buildSessionHeaderAndMessage();
+    const toolCallAssistant = {
+      type: "message",
+      id: "msg-asst-tc",
+      parentId: "msg-1",
+      timestamp: new Date().toISOString(),
+      message: {
+        role: "assistant",
+        content: [{ type: "toolCall", id: "call_1", name: "get_tasks", input: {} }],
+        stopReason: "toolUse",
+      },
+    };
+    const toolResult = {
+      type: "message",
+      id: "msg-tool-result",
+      parentId: "msg-asst-tc",
+      timestamp: new Date().toISOString(),
+      message: {
+        role: "toolResult",
+        toolCallId: "call_1",
+        toolName: "get_tasks",
+        content: [{ type: "text", text: "Task A, Task B" }],
+        isError: false,
+      },
+    };
+    const finalAssistant = {
+      type: "message",
+      id: "msg-asst-final",
+      parentId: "msg-tool-result",
+      timestamp: new Date().toISOString(),
+      message: {
+        role: "assistant",
+        content: [{ type: "text", text: "Here are your tasks: Task A, Task B." }],
+        stopReason: "stop",
+      },
+    };
+    const original = `${JSON.stringify(header)}\n${JSON.stringify(message)}\n${JSON.stringify(toolCallAssistant)}\n${JSON.stringify(toolResult)}\n${JSON.stringify(finalAssistant)}\n`;
+    await fs.writeFile(file, original, "utf-8");
+
+    const result = await repairSessionFileIfNeeded({ sessionFile: file });
+
+    expect(result.repaired).toBe(false);
+
+    const after = await fs.readFile(file, "utf-8");
+    expect(after).toBe(original);
+  });
+
   it("preserves assistant-only session history after the header", async () => {
     const { file } = await createTempSessionPath();
     const { header } = buildSessionHeaderAndMessage();