# gitnexus-pr-review

## Summary

gitnexus-pr-review helps reviewers quickly assess pull requests by mapping diffs to affected execution flows, identifying impacted symbols, and estimating blast radius and test coverage. Key features include extracting raw diffs (gh pr diff), gitnexus_detect_changes to map changes to flows, gitnexus_impact to enumerate upstream/downstream dependents (including d=1/d=2/d=3), gitnexus_context to show callers/callees, and an includeTests option to surface which tests touch changed code. Typical use cases: safety checks before merging, identifying missing tests, prioritizing high-risk changes, and writing focused review summaries. Advantages: reduces manual trace analysis, highlights likely breakages (unupdated callers), surfaces affected processes, and speeds consistent risk assessments. Notes: if the index is stale run npx gitnexus analyze before review.

# PR Review with GitNexus

## When to Use

- "Review this PR"
- "What does PR [#42](https://github.com/lobehub/lobehub/issues/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

```plaintext
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
```

## Checklist

```plaintext
- [ ] 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:

```plaintext
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:

```plaintext
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:

```plaintext
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:

```plaintext
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](https://github.com/lobehub/lobehub/issues/42)"

```plaintext
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:

```markdown
## 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
```