🤖 fix: use correct tool policy for continue message after compaction (#1270)

When a `/compact` command includes a continue message, the continue
message was being queued with the compaction mode's tool policy (all
tools disabled) instead of the intended execution mode's tool policy.

## Root Cause

The bug existed since the feature was first implemented in PR #650 (Nov
21). The code spread compaction options into the queued message, which
included the disabled-all tool policy from compact mode.

## Fix

Add `mode` field to `ContinueMessage` type so the backend can derive the
correct tool policy via `modeToToolPolicy()` instead of inheriting from
compaction options.

## Changes

- `src/common/types/message.ts`: Add `mode` field to `ContinueMessage`
- `src/browser/utils/chatCommands.ts`: Set mode when building
continueMessage
- `src/browser/hooks/useResumeManager.ts`: Preserve mode during resume
- `src/node/services/agentSession.ts`: Use
`modeToToolPolicy(continueMessage.mode)`
- `src/node/services/agentSession.continueMessageToolPolicy.test.ts`:
Regression test

---
_Generated with `mux` • Model: `anthropic:claude-opus-4-5` • Thinking:
`high`_

Author: ammar-agent

src/browser/hooks/useResumeManager.ts

@@ -180,6 +180,7 @@ export function useResumeManager() {
               text: lastUserMsg.compactionRequest.parsed.continueMessage?.text ?? "",
               imageParts: lastUserMsg.compactionRequest.parsed.continueMessage?.imageParts,
               model: lastUserMsg.compactionRequest.parsed.continueMessage?.model ?? options.model,
+              mode: lastUserMsg.compactionRequest.parsed.continueMessage?.mode ?? "exec",
             },
           });
         }

src/browser/utils/chatCommands.ts

@@ -655,6 +655,9 @@ export function prepareCompactionMessage(options: CompactionOptions): {
   // Create compaction metadata (will be stored in user message)
   // Only include continueMessage if there's text, images, or reviews to queue after compaction
   const hasText = continueText;
+  // Determine mode for continue message - use mode from sendMessageOptions if it's exec/plan, otherwise default to exec
+  const continueMode = options.sendMessageOptions.mode === "plan" ? "plan" : "exec";
+
   const compactData: CompactionRequestData = {
     model: effectiveModel,
     maxOutputTokens: options.maxOutputTokens,
@@ -664,6 +667,7 @@ export function prepareCompactionMessage(options: CompactionOptions): {
             text: options.continueMessage?.text ?? "",
             imageParts: options.continueMessage?.imageParts,
             model: options.continueMessage?.model ?? options.sendMessageOptions.model,
+            mode: continueMode,
             reviews: options.continueMessage?.reviews,
           }
         : undefined,

src/common/types/message.ts

@@ -26,10 +26,12 @@ export interface UserMessageContent {
 
 /**
  * Message to continue with after compaction.
- * Extends UserMessageContent with model preference.
+ * Extends UserMessageContent with model and mode preferences.
  */
 export interface ContinueMessage extends UserMessageContent {
   model?: string;
+  /** Mode for the continue message (determines tool policy). Defaults to 'exec'. */
+  mode?: "exec" | "plan";
 }
 
 // Parsed compaction request data (shared type for consistency)

src/node/services/agentSession.continueMessageToolPolicy.test.ts

@@ -0,0 +1,76 @@
+import { describe, expect, test } from "bun:test";
+import { modeToToolPolicy } from "@/common/utils/ui/modeUtils";
+
+/**
+ * Regression test for continue message tool policy bug.
+ *
+ * Bug: When a /compact command includes a continue message, the continue message
+ * was being queued with the compaction mode's tool policy (all tools disabled)
+ * instead of the intended execution mode's tool policy.
+ *
+ * Fix: Continue message now carries its own mode field, and the backend uses
+ * modeToToolPolicy(continueMessage.mode) instead of copying options.toolPolicy.
+ *
+ * This test verifies that the mode-to-policy transformation produces the expected
+ * tool policies for continue messages. The actual integration of this logic into
+ * agentSession.ts is verified by the type system and manual testing.
+ */
+describe("Continue message tool policy derivation", () => {
+  test("exec mode enables tools (not disabled-all like compaction)", () => {
+    const execPolicy = modeToToolPolicy("exec");
+    const compactionPolicy = [{ regex_match: ".*", action: "disable" }];
+
+    // Exec mode should NOT disable all tools like compaction does
+    expect(execPolicy).not.toEqual(compactionPolicy);
+
+    // Exec mode specifically disables propose_plan (the plan mode tool)
+    expect(execPolicy).toEqual([{ regex_match: "propose_plan", action: "disable" }]);
+  });
+
+  test("plan mode has different policy than compaction", () => {
+    const planPolicy = modeToToolPolicy("plan");
+    const compactionPolicy = [{ regex_match: ".*", action: "disable" }];
+
+    // Plan mode should NOT disable all tools like compaction does
+    expect(planPolicy).not.toEqual(compactionPolicy);
+
+    // Plan mode enables propose_plan
+    expect(planPolicy).toEqual([{ regex_match: "propose_plan", action: "enable" }]);
+  });
+
+  test("verifies fix: mode field determines policy, not inherited compaction policy", () => {
+    // This test documents the fix behavior:
+    // Before fix: continueMessage used options.toolPolicy (compaction's disabled-all)
+    // After fix: continueMessage.mode determines the policy via modeToToolPolicy()
+
+    // Simulating the fixed logic from agentSession.ts:
+    // const continueMode = continueMessage.mode ?? "exec";
+    // toolPolicy: modeToToolPolicy(continueMode)
+
+    const simulateContinueMessagePolicy = (mode?: "exec" | "plan") => {
+      const continueMode = mode ?? "exec"; // Default to exec as in the fix
+      return modeToToolPolicy(continueMode);
+    };
+
+    // Explicit exec mode
+    expect(simulateContinueMessagePolicy("exec")).toEqual([
+      { regex_match: "propose_plan", action: "disable" },
+    ]);
+
+    // Explicit plan mode
+    expect(simulateContinueMessagePolicy("plan")).toEqual([
+      { regex_match: "propose_plan", action: "enable" },
+    ]);
+
+    // No mode specified (defaults to exec)
+    expect(simulateContinueMessagePolicy(undefined)).toEqual([
+      { regex_match: "propose_plan", action: "disable" },
+    ]);
+
+    // None of these should be the compaction policy
+    const compactionPolicy = [{ regex_match: ".*", action: "disable" }];
+    expect(simulateContinueMessagePolicy("exec")).not.toEqual(compactionPolicy);
+    expect(simulateContinueMessagePolicy("plan")).not.toEqual(compactionPolicy);
+    expect(simulateContinueMessagePolicy(undefined)).not.toEqual(compactionPolicy);
+  });
+});

src/node/services/agentSession.ts

@@ -39,6 +39,7 @@ import type { PostCompactionAttachment, PostCompactionExclusions } from "@/commo
 import { TURNS_BETWEEN_ATTACHMENTS } from "@/common/constants/attachments";
 import { extractEditedFileDiffs } from "@/common/utils/messages/extractEditedFiles";
 import { isValidModelFormat } from "@/common/utils/ai/models";
+import { modeToToolPolicy } from "@/common/utils/ui/modeUtils";
 
 /**
  * Tracked file state for detecting external edits.
@@ -525,13 +526,15 @@ export class AgentSession {
       const { finalText, metadata } = prepareUserMessageForSend(continueMessage);
 
       // Build options for the queued message (strip compaction-specific fields)
+      // Use the mode from continueMessage to derive correct tool policy, not the compaction mode's disabled-all policy
+      const continueMode = continueMessage.mode ?? "exec";
       const sanitizedOptions: Omit<
         SendMessageOptions,
         "muxMetadata" | "mode" | "editMessageId" | "imageParts" | "maxOutputTokens"
       > & { imageParts?: typeof continueMessage.imageParts; muxMetadata?: typeof metadata } = {
         model: continueMessage.model ?? options.model,
         thinkingLevel: options.thinkingLevel,
-        toolPolicy: options.toolPolicy,
+        toolPolicy: modeToToolPolicy(continueMode),
         additionalSystemInstructions: options.additionalSystemInstructions,
         providerOptions: options.providerOptions,
         experiments: options.experiments,