---
name: phx-challenge
description: Challenge mode reviews - rigorous questioning before approving changes.
Use when you want thorough scrutiny of Ecto changes, LiveView events, OTP designs,
or PR readiness.
---
# Challenge Mode Reviews
Rigorous, critical review patterns inspired by Boris Cherny's "Grill me" approach. Push beyond first solutions to ensure quality.
## Iron Laws - Never Violate These
1. **No approval without verification** - Don't approve until all concerns addressed
2. **Assume bugs exist** - Look for edge cases, race conditions, missing handlers
3. **Question everything** - Even "obvious" code can hide issues
4. **Demand proof** - Ask for tests, show state transitions, verify behavior
## Adversarial Lenses (Apply to ALL Modes)
1. **"What Would Break This?"** — Production failure modes under load, during deploys, with unexpected data
2. **"Assumption Stress Test"** — List every assumption; which are most fragile?
3. **"Contradictions Finder"** — Find contradictions between tests/implementation, docs/behavior, or within the changeset
## Challenge Modes
### Ecto Challenge (`phx-challenge ecto`)
Grill the developer on database changes:
**Migration Safety**
- Will this migration lock the table in production?
- What happens to existing records without the new field?
- Is the migration reversible?
- Are there any unsafe operations (column removal, type change)?
**Query Performance**
- Have you introduced any N+1 queries?
- Are there missing indexes for new WHERE clauses?
- Will this query scale with data growth?
**Schema Integrity**
- Are all constraints enforced at database level?
- What happens during rolling deployment (old code, new schema)?
- Are foreign key cascades correct?
**Backward Compatibility**
- Will old code work during deployment?
- Are there any breaking changes to the context API?
### LiveView Challenge (`phx-challenge liveview`)
Prove the LiveView handles all cases:
**Event Coverage**
- List every `handle_event` clause and expected socket state
- What happens if socket assigns are missing when event fires?
- Are there race conditions between user events and server pushes?
**PubSub Handling**
- List every `handle_info` clause and when it's triggered
- Do all PubSub subscriptions have corresponding handlers?
- What happens if a message arrives before mount completes?
**State Transitions**
- Show the event → handler → state transition table
- Are all error states handled gracefully?
- What's the recovery path from each error state?
**Memory & Performance**
- Are large lists using streams?
- Is transient data using temporary_assigns?
- What's the memory footprint per connected user?
### PR Challenge (`phx-challenge pr`)
Senior engineer review checklist:
**Must Pass**
- [ ] No direct Repo calls in controllers/LiveViews
- [ ] All Ecto queries use explicit preloads
- [ ] Changesets validate all user input
- [ ] No atoms created from params
- [ ] Error cases handled (not just happy path)
- [ ] Tests cover new functionality
**Performance**
- [ ] No queries in Enum.map loops
- [ ] LiveView streams for lists > 100 items
- [ ] Indexes exist for WHERE clause columns
**OTP**
- [ ] GenServers have supervision
- [ ] Timeouts set for GenServer.call
- [ ] No unbounded process spawning
**Security**
- [ ] No SQL injection via raw queries
- [ ] No path traversal in file handling
- [ ] Authorization checks present
## Prior Findings Deduplication (MANDATORY)
CRITICAL: Prevents re-discovering identical issues across consecutive runs.
1. **Search** `.claude/plans/*/reviews/` and `.claude/reviews/` for prior findings
2. **Read ALL** prior findings before analyzing code
3. **Check each finding** against priors:
- Fixed → **SKIP** | Still present → **PERSISTENT** (one line) | New → **NEW** (full analysis) | Reintroduced → **REGRESSION**
4. **Present**: NEW first (full), then PERSISTENT (one-line), then REGRESSION
## Example Challenge Output
```markdown
## Challenge: Ecto — Orders Migration
### FINDING 1: Table lock risk (HIGH)
AddColumn on `orders` (2.1M rows) will lock table during deploy.
**Proof needed**: Run `SELECT count(*) FROM orders` — if >1M, use
`ALTER TABLE ... ADD COLUMN ... DEFAULT NULL` (no lock).
### FINDING 2: Missing index (MEDIUM)
New `WHERE status = ?` query on line 45 has no index.
**Action**: Add `create index(:orders, [:status])` to migration.
### Status: BLOCKED — 2 unresolved findings
```
## Usage
Run `phx-challenge [mode]` to initiate a rigorous review. The reviewer will not approve until all concerns are addressed with evidence.
Example workflow:
1. Run `phx-challenge ecto` after migration changes
2. Answer each question with code references or test results
3. Address all concerns before proceeding to PR