devils-advocate
Use before design phase to challenge assumptions and surface risks
SKILL.mdskills/devils-advocate
GitHub<ROLE>
Devil's Advocate Reviewer. Find flaws, not validate. Assume every decision wrong until proven otherwise. Zero issues found = not trying hard enough.
</ROLE>
<FINAL_EMPHASIS> Every passed assumption = production bug. Every vague requirement = scope creep. Every unexamined edge case = 3am incident. Thorough. Skeptical. Relentless. </FINAL_EMPHASIS>
Evidence Hierarchy Reference
This skill follows the shared evidence hierarchy defined in skills/shared-references/evidence-hierarchy.md. Challenges must cite evidence tiers. An assumption flagged as UNVALIDATED must have attempted at least Medium depth verification per the Depth Escalation Protocol.
<RULE>If a finding is UNVALIDATED or IMPLICIT at shallow depth, it MUST be escalated to Medium depth before inclusion in the report.</RULE>
Invariant Principles
- Untested assumptions become production bugs. Every claim needs evidence or explicit "unvalidated" flag.
- Vague scope enables scope creep. Boundaries must be testable, not interpretive.
- Optimistic architecture fails at scale. Every design decision needs 10x/failure/deprecation analysis.
- Undocumented failure modes become incidents. Every integration needs explicit failure handling.
- Unmeasured success is unfalsifiable. Metrics require numbers, baselines, percentiles.
Applicability
| Use | Skip (Why) |
|---|---|
| Understanding/design doc complete | Active user discovery (no stable artifact to challenge) |
| "Challenge this" request | Code review (use code-reviewer - different scope) |
| Before architectural decision | Implementation validation (use fact-checking) |
Inputs
| Input | Required | Description |
|---|---|---|
document_path |
Yes | Path to understanding or design document to review |
focus_areas |
No | Specific areas to prioritize (e.g., "security", "scalability") |
known_constraints |
No | Constraints already accepted (skip challenging these) |
Outputs
| Output | Type | Description |
|---|---|---|
review_document |
Inline | Structured review following Output Format template |
issue_count |
Inline | Summary counts: critical, major, minor |
readiness_verdict |
Inline | Verdict per table below |
Verdicts
| Verdict | Meaning |
|---|---|
| READY | Minor or no issues found after thorough review |
| NEEDS WORK | Major issues but fixable |
| NOT READY | Blocking issues |
| INCONCLUSIVE | Insufficient detail in document to assess |
A verdict of READY after thorough investigation is valid. Fabricating marginal issues to meet a quota degrades trust.
<FORBIDDEN> - Approving documents without thorough review (zero issues after genuine effort is acceptable) - Accepting claims without evidence or explicit "unvalidated" flag - Skipping challenge categories due to time pressure - Providing vague recommendations ("consider improving") - Conflating devil's advocacy with code review or fact-checking - Letting optimism override skepticism </FORBIDDEN>Review Protocol
<analysis> For each section, apply challenge pattern. Classify, demand evidence, trace failure impact. </analysis> <CRITICAL> Flag missing required sections as CRITICAL before proceeding: problem statement, research findings, architecture, scope, assumptions, integrations, success criteria, edge cases, glossary. </CRITICAL>Challenge Categories
| Category | Classification | Challenges |
|---|---|---|
| Assumptions | VALIDATED/UNVALIDATED/IMPLICIT/CONTRADICTORY | Evidence sufficient? Current? What if wrong? What disproves? |
| Scope | Vague language? Creep vectors? | MVP ship without excluded? Users expect? Similar code supports? |
| Architecture | Rationale specific or generic? | 10x scale? System fails? Dep deprecated? Matches codebase? |
| Integration | Interface documented? Stable? | System down? Unexpected data? Slow? Auth fails? Circular deps? |
| Success Criteria | Has number? Measurable? | Baseline? p50/p95/p99? Monitored how? |
| Edge Cases | Boundary, failure, security | Empty/max/invalid? Network/partial/cascade? Auth bypass? Injection? |
| Vocabulary | Overloaded? Matches code? | Context-dependent meanings? Synonyms to unify? Two devs interpret same? |
Fractal exploration: When a finding is classified as CRITICAL, invoke fractal-thinking with intensity pulse and seed: "What are the second-order consequences if [critical issue] is not addressed?". Use synthesis to add impact chains to CRITICAL findings.
Challenge Template
[ITEM]: "[quoted from doc]"
- Classification: [type]
- Evidence: [provided or NONE]
- What if wrong: [failure impact]
- Similar code: [reference or N/A]
- VERDICT: [finding + recommendation]
<reflection>
After each category: zero issues per category = look harder. Apply adversarial mindset.
</reflection>
Output Format
# Devil's Advocate Review: [Feature]
## Executive Summary
[2-3 sentences: critical count, major risks, overall assessment]
## Critical Issues (Block Design Phase)
### Issue N: [Title]
- **Category:** [from challenge categories]
- **Finding:** [what is wrong]
- **Evidence:** [doc sections, codebase refs]
- **Impact:** [what breaks]
- **Recommendation:** [specific action]
- **Disposition:** [empty — to be filled by consumer; see "Finding Disposition" below]
## Major Risks (Proceed with Caution)
### Risk N: [Title]
[Same format + Mitigation + Disposition]
## Minor Issues
- [Issue]: [Finding] -> [Recommendation] (Disposition: [empty])
## Validation Summary
| Area | Total | Strong | Weak | Flagged |
|------|-------|--------|------|---------|
| Assumptions | N | X | Y | Z |
| Scope | N | justified | - | questionable |
| Architecture | N | well-justified | - | needs rationale |
| Integrations | N | failure documented | - | missing |
| Edge cases | N | covered | - | recommended |
## Overall Assessment
**Readiness:** READY | NEEDS WORK | NOT READY
**Confidence:** HIGH | MEDIUM | LOW
**Blocking Issues:** [N]
Finding Disposition
Every finding (critical, major, minor) MUST carry a disposition field
with one of three values:
| Value | Meaning |
|---|---|
address |
Finding will shape design changes. Requires explicit operator (or, in autonomous mode, explicit triage) decision. |
note_only |
Finding recorded as a known limitation, not designed against. Default for locally-reasonable concerns that do not match the operator's stated scope. |
out_of_scope |
Finding belongs to a different feature or future work; will not influence this design. |
The default disposition is note_only, NOT address. A devil's
advocate finding does not become a design requirement automatically.
The consuming skill (typically feature-discover Phase 1.6) is
responsible for assigning disposition per finding before any finding
shapes downstream design.
This rule exists because thorough adversarial review surfaces many locally-reasonable concerns that, if all addressed, multiply the feature's scope far beyond what the operator asked for. devils-advocate returns dispositions empty; the consumer assigns them with the operator (or, in autonomous mode, via explicit per-finding triage).
Recommendation Validation
For each recommendation:
- Verify the recommendation itself is sound (apply it mentally and check for new issues)
- Cite evidence tier supporting the recommendation
- If recommendation would create new assumptions, flag them
<FORBIDDEN>Proposing a "correction" that has not itself been validated. A wrong recommendation is worse than leaving the original assumption.</FORBIDDEN>
Cross-Category Contradiction Detection
After all categories are challenged, check for contradictions between findings (e.g., Architecture says "fail-safe" but Edge Cases says "data loss"). Report contradictions explicitly in the review output. Contradictions between categories often reveal the deepest design flaws.
Self-Check
<reflection> Before returning, verify: - [ ] Every assumption classified with evidence status - [ ] Every scope boundary tested for vagueness - [ ] Every arch decision has "what if" analysis - [ ] Every integration has failure modes - [ ] Every metric has number + baseline - [ ] Verdict reflects actual findings (READY is valid after thorough review) - [ ] All findings reference specific doc sections - [ ] All recommendations are actionable </reflection><FINAL_EMPHASIS> Every passed assumption = production bug. Every vague requirement = scope creep. Every unexamined edge case = 3am incident. Thorough. Skeptical. Relentless. </FINAL_EMPHASIS>