code-trace

<essential_principles>

How Code Tracing Works

This skill traces code execution paths interactively, letting you navigate through the codebase like a debugger stepping through code - but with rich explanations at each step.

Principle 1: Application Boundary

Trace ONLY application code. External dependencies (node_modules, vendor/) receive:

• A summary of what they do
• Link to official documentation
• NOT deep-traced into their internals

Why: External libraries can be 100K+ lines. Tracing into them wastes context and obscures the actual application logic. The goal is understanding YOUR code, not library internals.

Principle 2: Interactive Navigation

Every conditional branch becomes a user choice:

| Code Pattern | Presentation | |--------------|--------------| | if/else | "Path A: condition true" vs "Path B: condition false" | | switch | One choice per case | | try/catch | "Success path" vs "Error path" | | async/await | Option to trace into called functions |

Why: Linear traces miss important paths. Interactive navigation lets users explore exactly what they're interested in.

Principle 3: Progressive Explanation

Each step includes:

1. Location: File + line range + function name
2. Code: Full source (no abbreviation)
3. What: Brief summary of what the code does
4. Why: Why this step exists in the flow
5. Next: What happens next (or choices if branching)

Use thinking markers (🤔🎯⚡📊💡🔐) for clarity.

Principle 4: State Persistence

Trace state is stored in Serena Memory to enable:

• Resuming interrupted traces
• Backtracking to previous decision points
• Saving completed traces for future reference </essential_principles>

<intake> ## What would you like to trace?

1. Trace a request flow - Follow HTTP request from receipt to response
2. Trace a function call - Follow a specific function through the codebase
3. Resume previous trace - Continue from where you left off

Please provide additional context:

• For request tracing: Which endpoint? (e.g., "POST /api/users")
• For function tracing: Which function? (e.g., "validateUser" or "src/utils/auth.ts:checkToken")

Wait for response before proceeding. </intake>

<routing> | Response | Workflow | |----------|----------| | 1, "request", "HTTP", "route", "API", "endpoint", "POST", "GET" | `workflows/trace-request.md` | | 2, "function", "call", specific function name | `workflows/trace-function.md` | | 3, "resume", "continue", "previous" | Read Serena memory for `trace_session_*` |

Before Starting Any Workflow

1. Detect Framework: Run scripts/detect-framework.sh to identify:

   • Express, Next.js (App/Pages), Fastify, Hono, NestJS, Koa, or generic

2. Load Framework Patterns: Read references/framework-patterns.md section for detected framework

3. Prepare Serena: Ensure Serena MCP is available for:

   • find_symbol() - Locate functions/handlers
   • find_referencing_symbols() - Find callers
   • get_symbols_overview() - Map module structure
   • write_memory() / read_memory() - State persistence

After determining intent and framework, read the appropriate workflow and follow it. </routing>

<reference_index>

References

All in references/:

| File | Content | |------|---------| | framework-patterns.md | Entry point detection and request flow for Express, Next.js, Fastify, etc. | | control-flow-types.md | How to present if/switch/try/loops as interactive choices | | explanation-style.md | Thinking markers, step format, summary format | | mermaid-templates.md | Mermaid.js flowchart generation from trace path_history | </reference_index>

<workflows_index>

Workflows

All in workflows/:

| Workflow | Purpose | |----------|---------| | trace-request.md | Trace HTTP request from entry to response | | trace-function.md | Trace a specific function's call chain | </workflows_index>

<scripts_index>

Scripts

| Script | Purpose | |--------|---------| | detect-framework.sh | Auto-detect project framework from package.json |

Usage:

./scripts/detect-framework.sh /path/to/project
# Output: express | nextjs-app | nextjs-pages | fastify | hono | nestjs | koa | generic

</scripts_index>

<success_criteria> A successful code trace:

• [ ] Entry point correctly identified and explained
• [ ] Framework detected and appropriate patterns applied
• [ ] At least one branch point presented as interactive choice
• [ ] External dependencies summarized (not deep-traced)
• [ ] User navigated to terminal point OR chose to stop
• [ ] Path history shown in ASCII flowchart format
• [ ] Mermaid flowchart offered as output option (if trace completed)
• [ ] Key insights collected and displayed
• [ ] Trace state available for resume (if user chose to save) </success_criteria>

<boundaries> ## Boundaries

Will:

• Trace application code with full source display
• Explain each step with thinking markers
• Present conditional branches as interactive choices
• Summarize external dependencies at the boundary
• Persist trace state for resume capability

Will Not:

• Deep-trace into node_modules or external libraries
• Execute or run the code (read-only analysis)
• Modify any source files
• Make assumptions about runtime values (present all branches)

</boundaries>