| name | investigation |
| description | Scaffolds a structured investigation in scratch/ for empirical research and documentation. Use when the user says "start an investigation" or wants to: trace code paths or data flow ("trace from X to Y", "what touches X", "follow the wiring"), document system architecture comprehensively ("document how the system works", "archeology"), investigate bugs ("figure out why X happens"), explore technical feasibility ("can we do X?"), or explore design options ("explore the API", "gather context", "design alternatives"). Creates dated folder with README. NOT for simple code questions or single-file searches.
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Set up an investigation
Instructions
- Create a folder in
{REPO_ROOT}/scratch/ with the format {YYYY-MM-DD}-{descriptive-name}.
- Create a
README.md in this folder with: task description, background context, task checklist. Update with findings as you progress.
- Create scripts and data files as needed for empirical work.
- For complex investigations, split into sub-documents as patterns emerge.
Investigation Patterns
These are common patterns, not rigid categories. Most investigations blend multiple patterns.
Tracing - "trace from X to Y", "what touches X", "follow the wiring"
- Follow call stack or data flow from a focal component to its connections
- Can trace forward (X → where does it go?) or backward (what leads to X?)
- Useful for: assessing impact of changes, understanding coupling
System Architecture Archeology - "document how the system works", "archeology"
- Comprehensive documentation of an entire system or flow for reusable reference
- Start from entry points, trace through all layers, document relationships exhaustively
- For complex systems, consider numbered sub-documents (01-cli.md, 02-data.md, etc.)
Bug Investigation - "figure out why X happens", "this is broken"
- Reproduce → trace root cause → propose fix
- For cross-repo bugs, consider per-repo task breakdowns
Technical Exploration - "can we do X?", "is this possible?", "figure out how to"
- Feasibility testing with proof-of-concept scripts
- Document what works AND what doesn't
Design Research - "explore the API", "gather context", "design alternatives"
- Understand systems and constraints before building
- Compare alternatives, document trade-offs
- Include visual artifacts (mockups, screenshots) when relevant
- For iterative decisions, use numbered "Design Questions" (DQ1, DQ2...) to structure review
Best Practices
- Use
uv with inline dependencies for standalone scripts; for scripts importing local project code, use python directly (or uv run python if env not activated)
- Use subagents for parallel exploration to save context
- Write small scripts to explore APIs interactively
- Generate figures/diagrams and reference inline in markdown
- For web servers:
npx serve -p 8080 --cors --no-clipboard &
- For screenshots: use Playwright MCP for web, Qt's grab() for GUI
- For external package API review: clone to
scratch/repos/ for direct source access
Important: Scratch is Gitignored
The scratch/ directory is in .gitignore and will NOT be committed.
- NEVER delete anything from scratch - it doesn't need cleanup
- When distilling findings into PRs, include all relevant info inline
- Copy key findings, code, and data directly into PR descriptions
- PRs must be self-contained; don't reference scratch files
