Use when the user wants to review a pull request, understand what a PR changes, assess risk of merging, or check for missing test coverage. Examples: "Review this PR", "What does PR #42 change?", "Is this PR safe to merge?"
1. gh pr diff <number> → Get the raw diff
2. gitnexus_detect_changes({scope: "compare", base_ref: "main"}) → Map diff to affected flows
3. For each changed symbol:
gitnexus_impact({target: "<symbol>", direction: "upstream"}) → Blast radius per change
4. gitnexus_context({name: "<key symbol>"}) → Understand callers/callees
5. READ gitnexus://repo/{name}/processes → Check affected execution flows
6. Summarize findings with risk assessment
If "Index is stale" → run npx gitnexus analyze in terminal before reviewing.
- [ ] Fetch PR diff (gh pr diff or git diff base...head)
- [ ] gitnexus_detect_changes to map changes to affected execution flows
- [ ] gitnexus_impact on each non-trivial changed symbol
- [ ] Review d=1 items (WILL BREAK) — are callers updated?
- [ ] gitnexus_context on key changed symbols to understand full picture
- [ ] Check if affected processes have test coverage
- [ ] Assess overall risk level
- [ ] Write review summary with findings
| Dimension | How GitNexus Helps |
|---|---|
| Correctness | context shows callers — are they all compatible with the change? |
| Blast radius | impact shows d=1/d=2/d=3 dependents — anything missed? |
| Completeness | detect_changes shows all affected flows — are they all handled? |
| Test coverage | impact({includeTests: true}) shows which tests touch changed code |
| Breaking changes | d=1 upstream items that aren't updated in the PR = potential breakage |
| Signal | Risk |
|---|---|
| Changes touch <3 symbols, 0-1 processes | LOW |
| Changes touch 3-10 symbols, 2-5 processes | MEDIUM |
| Changes touch >10 symbols or many processes | HIGH |
| Changes touch auth, payments, or data integrity code | CRITICAL |
| d=1 callers exist outside the PR diff | Potential breakage — flag it |
gitnexus_detect_changes — map PR diff to affected execution flows:
gitnexus_detect_changes({scope: "compare", base_ref: "main"})
→ Changed: 8 symbols in 4 files
→ Affected processes: CheckoutFlow, RefundFlow, WebhookHandler
→ Risk: MEDIUM
gitnexus_impact — blast radius per changed symbol:
gitnexus_impact({target: "validatePayment", direction: "upstream"})
→ d=1 (WILL BREAK):
- processCheckout (src/checkout.ts:42) [CALLS, 100%]
- webhookHandler (src/webhooks.ts:15) [CALLS, 100%]
→ d=2 (LIKELY AFFECTED):
- checkoutRouter (src/routes/checkout.ts:22) [CALLS, 95%]
gitnexus_impact with tests — check test coverage:
gitnexus_impact({target: "validatePayment", direction: "upstream", includeTests: true})
→ Tests that cover this symbol:
- validatePayment.test.ts [direct]
- checkout.integration.test.ts [via processCheckout]
gitnexus_context — understand a changed symbol's role:
gitnexus_context({name: "validatePayment"})
→ Incoming calls: processCheckout, webhookHandler
→ Outgoing calls: verifyCard, fetchRates
→ Processes: CheckoutFlow (step 3/7), RefundFlow (step 1/5)
1. gh pr diff 42 > /tmp/pr42.diff
→ 4 files changed: payments.ts, checkout.ts, types.ts, utils.ts
2. gitnexus_detect_changes({scope: "compare", base_ref: "main"})
→ Changed symbols: validatePayment, PaymentInput, formatAmount
→ Affected processes: CheckoutFlow, RefundFlow
→ Risk: MEDIUM
3. gitnexus_impact({target: "validatePayment", direction: "upstream"})
→ d=1: processCheckout, webhookHandler (WILL BREAK)
→ webhookHandler is NOT in the PR diff — potential breakage!
4. gitnexus_impact({target: "PaymentInput", direction: "upstream"})
→ d=1: validatePayment (in PR), createPayment (NOT in PR)
→ createPayment uses the old PaymentInput shape — breaking change!
5. gitnexus_context({name: "formatAmount"})
→ Called by 12 functions — but change is backwards-compatible (added optional param)
6. Review summary:
- MEDIUM risk — 3 changed symbols affect 2 execution flows
- BUG: webhookHandler calls validatePayment but isn't updated for new signature
- BUG: createPayment depends on PaymentInput type which changed
- OK: formatAmount change is backwards-compatible
- Tests: checkout.test.ts covers processCheckout path, but no webhook test
Structure your review as:
## PR Review: <title>
**Risk: LOW / MEDIUM / HIGH / CRITICAL**
### Changes Summary
- <N> symbols changed across <M> files
- <P> execution flows affected
### Findings
1. **[severity]** Description of finding
- Evidence from GitNexus tools
- Affected callers/flows
### Missing Coverage
- Callers not updated in PR: ...
- Untested flows: ...
### Recommendation
APPROVE / REQUEST CHANGES / NEEDS DISCUSSION