feat: integrate background_task system into agents

[vtemian]

Summary

• Fix background_task system issues (memory leak, silent errors, missing types)
• Integrate background_task into 3 agents for true async parallelism

Changes

Background Task System Fixes

• Remove unused field: Removed progress.lastMessage (defined but never populated)
• Add error logging: Replaced 4 silent .catch(() => {}) with proper console.error logging
• Add task cleanup: TTL-based cleanup (1 hour) to prevent memory leak
• Add response types: Proper TypeScript interfaces for session API responses
• Add unit tests: 17 test cases covering all BackgroundTaskManager functionality

Agent Prompt Updates

Agent	Pattern	Benefit
project-initializer	Fire-and-collect	Run glob/read while 5 agents work in background
planner	Fire-and-collect	Run context7/btca_ask while 4 agents work
executor	Fire-and-check	Start reviewer immediately when its implementer finishes

Testing

• All 40 tests passing
• TypeScript compiles cleanly

Design Document

See thoughts/shared/designs/2026-01-01-background-task-integration-design.md (gitignored)

---

Summary by cubic

Integrated the background_task system into executor, planner, and project-initializer for real async parallelism, and fixed stability issues in the task manager. This speeds up execution and prevents memory leaks and silent failures.

• New Features

  • Executor uses a fire-and-check pattern: fire implementers, poll, start reviewers immediately; includes fallback to Task.
  • Planner and project-initializer use fire-and-collect: fire background research, then collect results; includes fallback rules.
  • Added background tools usage in agent prompts: background_task, background_output, background_list.

• Bug Fixes

  • Added 1h TTL cleanup to remove completed/error tasks and stop memory leak.
  • Replaced silent catch blocks with console.error logging.
  • Added TypeScript response types for session APIs; removed unused progress.lastMessage.
  • Added tests for manager behavior, error logging, cleanup, response typing, and agent prompt integration.

^{Written for commit 23f96a5. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 13 files

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="tests/tools/background-task-error-logging.test.ts">

<violation number="1" location="tests/tools/background-task-error-logging.test.ts:16">
P2: Test doesn&#39;t verify what its name claims. The assertion only checks that catch blocks have a named parameter, not that `console.error` is actually called. A catch like `.catch((err) =&gt; {})` would pass this test despite not logging anything. Consider parsing the full catch block body and verifying it contains `console.error`.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

P2: Test doesn't verify what its name claims. The assertion only checks that catch blocks have a named parameter, not that console.error is actually called. A catch like .catch((err) => {}) would pass this test despite not logging anything. Consider parsing the full catch block body and verifying it contains console.error.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At tests/tools/background-task-error-logging.test.ts, line 16:

<comment>Test doesn&#39;t verify what its name claims. The assertion only checks that catch blocks have a named parameter, not that `console.error` is actually called. A catch like `.catch((err) =&gt; {})` would pass this test despite not logging anything. Consider parsing the full catch block body and verifying it contains `console.error`.</comment>

<file context>
@@ -0,0 +1,23 @@
+    const fs = await import(&quot;node:fs/promises&quot;);
+    const source = await fs.readFile(&quot;src/tools/background-task/manager.ts&quot;, &quot;utf-8&quot;);
+
+    // All .catch blocks should have console.error
+    const catchBlocks = source.match(/\.catch\s*\([^)]+\)/g) || [];
+    for (const block of catchBlocks) {
</file context>