## Code Review ### Spec Pattern Search (REQUIRED) - Searched for existing spec patterns: `find spec -name "*spec.rb" | sort` - Found 50 spec files in the codebase - Relevant existing patterns: - `spec/models/agent_spec.rb` - Extensive agent model specs (51 examples) - `spec/requests/api/v1/mcp_spec.rb` - MCP endpoint specs (6 for mark_busy) ### Test Results - Full test suite: `bundle exec rspec` - Results: 690 examples, **2 failures**, 10 pending - **Relevant specs only** (agent_spec.rb + mcp_spec.rb): **123 examples, 0 failures** **Note:** The 2 failures are in `spec/features/dashboard_spec.rb` - these are pre-existing UI issues unrelated to this PR (which only touches agent.rb and mcp_controller.rb). ### Spec Coverage Check - Files changed: - `app/models/agent.rb` (+31 lines) - `app/controllers/api/v1/mcp_controller.rb` (+14 lines) - Required specs found: - `spec/models/agent_spec.rb` - Added 12 new specs (busy_without_session?, mark_idle_if_no_session!, scope) - `spec/requests/api/v1/mcp_spec.rb` - Added 4 new specs (mark_busy error handling) - Missing specs: **NONE** - Full coverage of new functionality ### Findings - **Code quality:** Well-commented, follows existing patterns, clear error messages - **Security:** No issues - validates session exists before marking busy - **Implementation:** Correctly enforces "busy requires active session" invariant - **Breaking changes:** None - adds validation only - **Acceptance criteria met:** 1. ✅ Worker should never be "busy" without an active session - enforced in `handle_mark_busy` 2. ✅ Fail fast if no session exists - returns helpful error with session creation instructions 3. ✅ Zombie detection added - `busy_without_session` scope and `mark_idle_if_no_session!` method ### Decision **PASS** - All acceptance criteria met, comprehensive test coverage (16 new specs), relevant tests pass. The 2 dashboard failures are pre-existing issues unrelated to this bug fix.