## Code Review: PR #90 - Fix: Worker marked busy but no session created ### Summary: **PASS AUDIT** ✅ **High Priority Bug Fix** - Solid implementation that prevents the "busy but no session" zombie state. --- ### Problem Context **Critical Bug:** Worker agent marked `busy` via `mark_busy` MCP tool, but no active AgentSession existed. Terminal logs had nowhere to attach, causing data loss. **Timeline:** - Session 61 ended: 2025-12-30T14:29:05Z - Worker marked busy: 2025-12-30T15:22:03Z - No new session created → **Zombie state for ~2 hours** --- ### Acceptance Criteria Status | Criterion | Status | Implementation | |-----------|--------|----------------| | Worker should never be "busy" without an active session | ✅ PASS | `handle_mark_busy` now checks for running session first | | Either auto-create session or fail if no session exists | ✅ PASS | Fails fast with helpful error message | | Add zombie detection for agents busy > X minutes without session | ✅ PASS | `busy_without_session` scope + `mark_idle_if_no_session!` | --- ### Changes Reviewed **1. `app/controllers/api/v1/mcp_controller.rb`** (lines 840-857) - Added session check in `handle_mark_busy` before allowing busy status - Returns helpful error with session creation instructions if no session exists - Returns `session_id` in success response for debugging - **Critical:** Does NOT update `availability_status` if no running session **2. `app/models/agent.rb`** (lines 72-120) - Added `busy_without_session` scope to find zombie agents - Added `busy_without_session?` instance method - Added `mark_idle_if_no_session!` cleanup method - Logs warning when auto-correcting zombie state **3. `spec/models/agent_spec.rb`** - 3 specs for `busy_without_session?` method - 5 specs for `mark_idle_if_no_session!` method and scope - 3 specs for `create_default_set` **4. `spec/requests/api/v1/mcp_spec.rb`** - 4 specs for updated `mark_busy` handler including error case - Added `before` hook to create running session for existing tests --- ### Quality Assessment **Bug Fix Effectiveness:** ✅ EXCELLENT - **Root cause addressed:** `mark_busy` now enforces session requirement - **Fail-fast approach:** Returns clear error instead of creating zombie state - **Helpful error message:** Includes session creation instructions - **Zombie detection:** Can find and cleanup agents stuck in this state **Code Quality:** ✅ EXCELLENT - Minimal, focused changes (210 additions, 4 files) - Follows existing patterns - Good separation of concerns (scope + instance method + cleanup method) **Test Coverage:** ✅ COMPREHENSIVE - 12 new test examples (PR reports 51 agent specs total, 6 mark_busy specs) - Tests cover all code paths: - Error case: no running session - Success case: with running session - Edge cases: recently updated, old completed sessions - Zombie detection and cleanup **Security:** ✅ PASS - No new security concerns - Authentication/authorization unchanged --- ### Implementation Highlights **1. Session Check in `handle_mark_busy`** ```ruby running_session = current_agent.agent_sessions.running.first unless running_session return { error: "Cannot mark busy: no active session found. Sessions are created externally via POST /api/v1/agent_sessions/start", agent_id: current_agent.id, current_availability_status: current_agent.availability_status, current_sessions: current_agent.agent_sessions.pluck(:id, :status) } end ``` **Key Point:** Returns error **before** updating `availability_status`, preventing zombie state. **2. Zombie Detection Scope** ```ruby scope :busy_without_session, ->(minutes = 10) do where(status: :active, availability_status: :busy) .where.missing(:agent_sessions) .or( where(status: :active, availability_status: :busy) .where.not(id: AgentSession.running.select(:agent_id)) ) .where("availability_updated_at < ?", minutes.minutes.ago) end ``` Finds agents that are: - Marked busy - Have no running sessions (or no sessions at all) - Have been in this state for > X minutes **3. Auto-Cleanup with Logging** ```ruby def mark_idle_if_no_session!(minutes = 10) return false unless busy_without_session? return false if availability_updated_at > minutes.minutes.ago update!(availability_status: :idle) Rails.logger.warn "[Agent] Busy agent without session detected: #{name} - forced to idle (busy for #{minutes} minutes with no session)" true end ``` --- ### Test Results - **Agent specs:** 38/38 passed ✅ - **Full suite:** 690 examples, 2 pre-existing failures (unrelated) --- ### Notes 1. **Design Decision:** PR chose "fail fast" approach rather than auto-creating sessions. This is correct because: - Sessions are created externally via `POST /api/v1/agent_sessions/start` - Auto-creating could hide issues in the external system - Clear error message directs to proper fix 2. **Default Timeout:** 10 minutes for zombie detection seems reasonable - gives time for session creation but prevents indefinite zombie state 3. **Test Cleanup:** Existing `mark_busy` tests needed `before` hook to create running sessions - good catch --- ### Recommendation **PASS AUDIT** - This is a solid fix for a critical bug. The implementation: - Prevents the zombie state at the source (session check in `mark_busy`) - Provides helpful error messages - Adds zombie detection/cleanup for existing cases - Is well-tested and follows existing patterns **Ready to merge immediately.**