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.claude/skills/gitnexus/gitnexus-debugging/SKILL.md

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+---
+name: gitnexus-debugging
+description: "Use when the user is debugging a bug, tracing an error, or asking why something fails. Examples: \"Why is X failing?\", \"Where does this error come from?\", \"Trace this bug\""
+---
+
+# 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
+```