PR Review with GitNexus

When to Use

• "Review this PR"

• "What does PR #42 change?"

• "Is this safe to merge?"

• "What's the blast radius of this PR?"

• "Are there missing tests for this PR?"

• Reviewing someone else's code changes before merge

Workflow

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.

Checklist

• 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

Review Dimensions

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

Risk Assessment

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

Tools

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)

Example: "Review PR #42"

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

Review Output Format

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