gitnexus-debugging

---
name: gitnexus-debugging
description: "Optional GitNexus workflow. Use only when the user explicitly requests GitNexus; never a prerequisite for ordinary code work."
---

## Optional scope

Use this skill only when the user explicitly requests GitNexus. It is not a prerequisite for exploring, editing, refactoring, reviewing, or committing code. Do not invoke it or reindex automatically. Otherwise, trace direct callers and imports in source, inspect the diff, and run the relevant normal tests and checks.

# Debugging with GitNexus

## When to Use

- "Why is this function failing?"
- "Trace where this error comes from"
- "Who calls this method?"
- "This endpoint returns 500"
- Investigating bugs, errors, or unexpected behavior

## Workflow

```
1. gitnexus_query({query: "<error or symptom>"})            → Find related execution flows
2. gitnexus_context({name: "<suspect>"})                    → See callers/callees/processes
3. READ gitnexus://repo/{name}/process/{name}                → Trace execution flow
4. gitnexus_cypher({query: "MATCH path..."})                 → Custom traces if needed
```

> If "Index is stale" → run `npx gitnexus analyze` in terminal.

## Checklist

```
- [ ] Understand the symptom (error message, unexpected behavior)
- [ ] gitnexus_query for error text or related code
- [ ] Identify the suspect function from returned processes
- [ ] gitnexus_context to see callers and callees
- [ ] Trace execution flow via process resource if applicable
- [ ] gitnexus_cypher for custom call chain traces if needed
- [ ] Read source files to confirm root cause
```

## Debugging Patterns

| Symptom              | GitNexus Approach                                          |
| -------------------- | ---------------------------------------------------------- |
| Error message        | `gitnexus_query` for error text → `context` on throw sites |
| Wrong return value   | `context` on the function → trace callees for data flow    |
| Intermittent failure | `context` → look for external calls, async deps            |
| Performance issue    | `context` → find symbols with many callers (hot paths)     |
| Recent regression    | `detect_changes` to see what your changes affect           |

## Tools

**gitnexus_query** — find code related to error:

```
gitnexus_query({query: "payment validation error"})
→ Processes: CheckoutFlow, ErrorHandling
→ Symbols: validatePayment, handlePaymentError, PaymentException
```

**gitnexus_context** — full context for a suspect:

```
gitnexus_context({name: "validatePayment"})
→ Incoming calls: processCheckout, webhookHandler
→ Outgoing calls: verifyCard, fetchRates (external API!)
→ Processes: CheckoutFlow (step 3/7)
```

**gitnexus_cypher** — custom call chain traces:

```cypher
MATCH path = (a)-[:CodeRelation {type: 'CALLS'}*1..2]->(b:Function {name: "validatePayment"})
RETURN [n IN nodes(path) | n.name] AS chain
```

## Example: "Payment endpoint returns 500 intermittently"

```
1. gitnexus_query({query: "payment error handling"})
   → Processes: CheckoutFlow, ErrorHandling
   → Symbols: validatePayment, handlePaymentError

2. gitnexus_context({name: "validatePayment"})
   → Outgoing calls: verifyCard, fetchRates (external API!)

3. READ gitnexus://repo/my-app/process/CheckoutFlow
   → Step 3: validatePayment → calls fetchRates (external)

4. Root cause: fetchRates calls external API without proper timeout
```