bug-detection

Bug Detection Patterns

Playbook Anti-Patterns (catch these in review)

Anti-Pattern	What to Look For	Fix
Monolithic tool	Single MCP tool doing 3+ distinct operations	Split into granular single-purpose tools
Fragile enum expansion	Enum types growing with each edge case	Add "other" + detail field
Sequential file reading	Read tool loading all files one by one	Grep → pinpoint → Read specific
Context contamination	A/B exploration in single thread	Use fork_session for divergent branches
Emphatic prompt compliance	"CRITICAL POLICY: NEVER..." in system prompt	Application-layer hook intercept
Stale tool results	Resuming session with hours-old data	Filter out old tool_result on resume
Self-review bias	Same session reviews its own generated code	Independent review instance
Generic error strings	MCP returning "Operation failed"	Structured {isError, errorCategory, isRetryable}

Edge Cases to Test

Agent Orchestration

• Coordinator receives empty result from subagent
• Subagent exceeds turn limit
• Parallel subagent spawning — race condition in result aggregation
• Tool call returns isError: true but isRetryable: false

MCP Integration

• MCP server disconnects mid-tool-call
• Tool returns valid empty result (no matches) vs access failure
• Token expires between consecutive tool calls
• Tool description keyword conflicts with system prompt instructions

Data Pipeline

• OTel event with null session_id
• Duplicate events (same event_id, different recorded_at)
• Token usage event with 0 cost (cache hit)
• Schema migration applied twice (idempotency)

Plugin System

• Plugin installed at both user and project scope — which wins?
• Marketplace update overwrites local changes
• Skill invoked with no arguments when argument-hint expects one
• Two plugins define skills with same name

Mobile/Integration

• Network drops during Remote Control session
• Dispatch task sent while Desktop is sleeping
• Channel message from non-allowlisted sender
• Scheduled task fires while Claude is mid-response

Regression Triggers

Watch these areas after changes:

• Any change to CLAUDE.md → verify all plugins still load correctly
• Any change to .mcp.json → verify all MCP servers connect
• Any change to hooks/ → verify pre/post tool behavior
• Any schema migration → verify Cube.js models still query correctly
• Any package version bump → verify versions.json in sync