Impact Analysis with GitNexus

When to Use

• "Is it safe to change this function?"
• "What will break if I modify X?"
• "Show me the blast radius"
• "Who uses this code?"
• Before making non-trivial code changes
• Before committing — to understand what your changes affect

Workflow

1. impact({target: "X", direction: "upstream"})  → What depends on this
2. READ gitnexus://repo/{name}/processes                   → Check affected execution flows
3. detect_changes()                               → Map current git changes to affected flows
4. Assess risk and report to user

If "Index is stale" → run node .gitnexus/run.cjs analyze in terminal.

Checklist

- [ ] impact({target, direction: "upstream"}) to find dependents
- [ ] Review d=1 items first (these WILL BREAK)
- [ ] Check high-confidence (>0.8) dependencies
- [ ] READ processes to check affected execution flows
- [ ] detect_changes() for pre-commit check
- [ ] Assess risk level and report to user

Understanding Output

Depth	Risk Level	Meaning
d=1	WILL BREAK	Direct callers/importers
d=2	LIKELY AFFECTED	Indirect dependencies
d=3	MAY NEED TESTING	Transitive effects

Risk Assessment

Affected	Risk
<5 symbols, few processes	LOW
5-15 symbols, 2-5 processes	MEDIUM
>15 symbols or many processes	HIGH
Critical path (auth, payments)	CRITICAL

Tools

impact — the primary tool for symbol blast radius:

impact({
  target: "validateUser",
  direction: "upstream",
  minConfidence: 0.8,
  maxDepth: 3
})

→ d=1 (WILL BREAK):
  - loginHandler (src/auth/login.ts:42) [CALLS, 100%]
  - apiMiddleware (src/api/middleware.ts:15) [CALLS, 100%]

→ d=2 (LIKELY AFFECTED):
  - authRouter (src/routes/auth.ts:22) [CALLS, 95%]

detect_changes — git-diff based impact analysis:

detect_changes({scope: "staged"})

→ Changed: 5 symbols in 3 files
→ Affected: LoginFlow, TokenRefresh, APIMiddlewarePipeline
→ Risk: MEDIUM

Example: "What breaks if I change validateUser?"

1. impact({target: "validateUser", direction: "upstream"})
   → d=1: loginHandler, apiMiddleware (WILL BREAK)
   → d=2: authRouter, sessionManager (LIKELY AFFECTED)

2. READ gitnexus://repo/my-app/processes
   → LoginFlow and TokenRefresh touch validateUser

3. Risk: 2 direct callers, 2 processes = MEDIUM