Verify Runtime Behavior

After changing data-flow code, verify it works at runtime — not just that it compiles.

When to Use

• Modified files in **/api/** or **/shared/api/**
• Changed dual-write, shadow-read, or mutation logic
• Fixed a data-flow bug and need evidence it's resolved

Prerequisites

The Vite dev server must be running (npm run dev) for logs to be captured. devLog() POSTs to /__dev/log which the Vite plugin writes to .logs/dev-*.jsonl. Without the server, no entries are recorded.

Verification Flow

digraph verify {
  "Code change made" -> "Type-check passes?";
  "Type-check passes?" -> "Fix types" [label="no"];
  "Type-check passes?" -> "Tests pass?" [label="yes"];
  "Tests pass?" -> "Fix tests" [label="no"];
  "Tests pass?" -> "Dev server running?" [label="yes"];
  "Dev server running?" -> "npm run dev" [label="no"];
  "Dev server running?" -> "Trigger action in browser" [label="yes"];
  "npm run dev" -> "Trigger action in browser";
  "Trigger action in browser" -> "Run devlog:check";
  "Run devlog:check" -> "Errors found?";
  "Errors found?" -> "Diagnose from logs" [label="yes"];
  "Diagnose from logs" -> "Code change made";
  "Errors found?" -> "Warnings present?" [label="no"];
  "Warnings present?" -> "Review mismatches" [label="yes"];
  "Warnings present?" -> "Verified" [label="no"];
  "Review mismatches" -> "Verified";
}

Commands

npm run type-check      # Static types
npm run test:run        # Unit tests
npm run devlog:check    # Runtime verification (exit 1 on errors, exit 0 on warnings)
npm run devlog:errors   # Show warnings + errors
npm run devlog          # Show recent events
npm run devlog:trace ID # Trace one action by correlationId

Quick HTTP checks (dev server running)

curl localhost:PORT/__dev/logs          # JSON array of recent entries
curl localhost:PORT/__dev/logs?limit=5  # Last 5 entries
curl localhost:PORT/__dev/logs/path     # Current log file path

What to Check

Category	Good Signal	Bad Signal
dual-write	write-success for your entity	write-error or unexpected write-skipped
shadow-read	compare-match	compare-mismatch with missing IDs
Any	Events present for your change	Zero events (code path not hit)

Note: devlog:check exits 0 on warnings (mismatches), exits 1 only on errors. Always review warnings — shadow-read mismatches may indicate backfill gaps.

Red Flags

• "It compiles, so it works" — Dual-write can compile and silently fail at runtime.
• "No errors in the log" — Check that events WERE logged. Zero events means the code path wasn't exercised.
• "I can't start the dev server" — Note the verification gap. Run devlog:check after available test runs.

Log Format

Files: .logs/dev-*.jsonl — one JSON object per line.

Each entry has: timestamp, category, event, level (info/warn/error), correlationId, optional data and duration.

Grep patterns:

• All errors: grep '"level":"error"' .logs/dev-*.jsonl
• Dual-write issues: grep '"category":"dual-write"' .logs/dev-*.jsonl
• Mismatches: grep '"event":"compare-mismatch"' .logs/dev-*.jsonl