Graph Trace — Full System Flow

Trace connections from a target node through multiple edge types using BFS. Shows the complete chain: API endpoints → commands → entity events → bus messages → cross-service consumers.

When to Use

• "What happens when X is called/created/updated?" → --direction downstream
• "What calls/triggers X?" → --direction upstream
• "Show me the full flow through X" → --direction both (best when entry point is a middle file like a controller or command handler)
• Impact analysis — understand what's affected by a code change
• Cross-service tracing — follow MESSAGE_BUS edges to see which services consume events

Prerequisites

Graph must exist (.code-graph/graph.db). If missing, run /graph-build first.

Workflow

Step 1: Identify the target

If the user specifies a file path, use it directly. If the query is semantic:

1. Grep first to find entry point files related to the user's query
2. Use the discovered file as the trace target

Step 2: Choose direction

Step 3: Run trace

# Downstream trace (default) — what does this trigger?
python .claude/scripts/code_graph trace <target> --json

# Upstream trace — what calls/triggers this?
python .claude/scripts/code_graph trace <target> --direction upstream --json

# Bidirectional — full flow through this point
python .claude/scripts/code_graph trace <target> --direction both --json

# Custom depth (default: 3)
python .claude/scripts/code_graph trace <target> --direction both --depth 5 --json

# Filter to specific edge types
python .claude/scripts/code_graph trace <target> --edge-kinds CALLS,MESSAGE_BUS --json

Step 4: Present results

The trace returns a multi-level BFS tree:

{
  "status": "ok",
  "direction": "both",
  "levels": [
    { "depth": 0, "nodes": [...], "edges": [] },
    { "depth": 1, "nodes": [...], "edges": [{ "kind": "CALLS", ... }] },
    { "depth": 2, "nodes": [...], "edges": [{ "kind": "MESSAGE_BUS", ... }] }
  ]
}

Present results grouped by depth level. Highlight cross-service MESSAGE_BUS edges — these show the flow spreading to other microservices.

Step 5: Handle ambiguous targets

If trace returns status: "ambiguous", multiple nodes match the target name. Use search to find the exact qualified name:

python .claude/scripts/code_graph search <keyword> --kind Function --json

Then retry with the full qualified name.

Edge Types Traced

CLI Reference

trace <target> [--direction downstream|upstream|both] [--depth N] [--edge-kinds KIND1,KIND2] [--node-mode file|function|class|all] [--json]

Examples

# What happens when a user is created? (trace from command handler downstream)
python .claude/scripts/code_graph trace src/Services/Accounts/Commands/CreateUser/CreateUserCommandHandler.cs --json

# What calls this API controller? (trace upstream to find frontend callers)
python .claude/scripts/code_graph trace src/Services/Growth/Controllers/GoalController.cs --direction upstream --json

# Full flow through an entity event handler (upstream triggers + downstream consumers)
python .claude/scripts/code_graph trace src/Services/Employee/UseCaseEvents/EmployeeCreatedEventHandler.cs --direction both --json

# File-level overview (10-30x less noise — great first pass before drilling into functions)
python .claude/scripts/code_graph trace src/Services/Growth/Controllers/GoalController.cs --direction both --node-mode file --json

Anti-Patterns

• Don't trace without --json — structured output is needed for parsing
• Don't trace with depth > 5 — results get noisy; use edge-kinds filter instead
• Don't skip grep-first — if you don't know the file path, grep for it first
• Don't use for single-hop queries — use callers_of or importers_of instead (faster)

Related Skills

• /graph-query — Individual query patterns (callers_of, importers_of, etc.)
• /graph-blast-radius — Change-driven impact analysis from git diff
• /graph-build — Build or rebuild the graph
• /graph-connect-api — Frontend-to-backend API endpoint matching

Closing Reminders

• MUST break work into small todo tasks using TaskCreate BEFORE starting
• MUST search codebase for 3+ similar patterns before creating new code
• MUST cite file:line evidence for every claim (confidence >80% to act)
• MUST add a final review todo task to verify work quality