Compound — Capture Solutions as Knowledge

After fixing a problem, capture the solution as searchable institutional documentation.

Usage

phx-compound Fixed N+1 query in user listing
phx-compound Resolved LiveView timeout in dashboard
phx-compound   # Auto-detects from recent session context

Philosophy

Each unit of engineering work should make subsequent units easier — not harder.

Workflow

Step 1: Detect Context

1. If $ARGUMENTS provided, use as description
2. If no args, check scratchpad DEAD-END/DECISION entries, git diff, .claude/plans/{slug}/progress.md for recent completions
3. If unclear, ask: "What problem did you just solve?"

Only document non-trivial problems that required investigation.

Step 2: Search Existing Solutions

Create .claude/solutions/ directory if it doesn't exist (run mkdir -p .claude/solutions). Then search .claude/solutions/ for relevant keywords using Grep.

If found: Create new (different root cause), Update existing (same root cause, new symptom), or Skip.

Step 3: Gather Details and Create Solution

Extract from session context: module, symptoms, investigation steps, root cause, solution code, and prevention advice.

Validate frontmatter against ../compound-docs/references/schema.md, then create file using ../compound-docs/references/resolution-template.md.

Write-blocked fallback: if writing to .claude/solutions/ is denied by permissions, do NOT silently drop the solution. Output the full solution doc inline (fenced markdown the user can paste), then suggest phx-permissions to allow .claude/solutions/ writes for next time.

Step 4: Decision Menu

1. Continue (default)
2. Promote to Iron Law check — Add to iron-law-judge
3. Update skill reference — Add to relevant skill
4. Update CLAUDE.md — Add prevention rule

Auto-Trigger Phrases

When user says "that worked", "it's fixed", "problem solved", "the fix was" — suggest phx-compound.

Supply-chain finding auto-feed (Phase 3)

When phx-deps-audit produces a BLOCK-severity finding that the user investigates and confirms is a real malicious pattern (not a false positive), suggest:

Caught a high-severity finding in <pkg>@<version>. Run phx-compound to capture this for future audits?

If accepted, the resulting solution doc goes to .claude/solutions/supply-chain/<pkg>-<cve_or_pattern>.md and includes the exact rule-id + snippet + diff window that triggered the finding. This compounds the audit corpus: future runs of phx-deps-audit grep solutions/supply-chain/ for snippet matches and pre-elevate severity on known-bad patterns.

Always prompt; never auto-write. Solution docs are durable and shape future trust calls — the user reviews before committing.

Iron Laws

1. YAML frontmatter validates or STOP
2. Symptoms must be specific — not "it broke"
3. Root cause is WHY, not WHAT
4. One problem per file
5. NEVER document a fix before verifying it works — run mix compile && mix test first; unverified solutions poison the knowledge base

Integration with Workflow

phx-review → Complete → phx-compound  ← YOU ARE HERE
                              │
                 .claude/solutions/{category}/{fix}.md
                              │
              phx-investigate and phx-plan search here

References

• references/compound-workflow.md — Detailed step-by-step
• See also: compound-docs skill for schema and templates