Phaser Debugger

Phaser 4 Debugger

Use this skill to diagnose and fix Phaser 4 issues from evidence rather than guessing.

Workflow

1. Collect the exact symptom, error text, stack trace, browser/device context, and reproduction steps when available.
2. Read the relevant code before editing. For black screens, inspect src/main.ts, scene registration, scene transitions, preload paths, and browser console/network errors.
3. Trace likely root causes using Phaser lifecycle order: config, preload, create, update, asset keys, physics body creation, collisions, input, scene start/stop state, and rendering depth.
4. Make the smallest fix that addresses the root cause.
5. Verify with npx tsc --noEmit for TypeScript projects and, when practical, a local dev-server smoke test.

Debugging Checklist

• Asset 404s and mismatched texture keys
• Scene not registered or wrong scene key
• this.physics, this.input, or this.anims used before scene initialization
• Arcade body missing because object was created without physics
• Collider/overlap registered with the wrong object or group
• Animation key/frame mismatch
• Depth/alpha/camera bounds hiding an object
• Phaser 3 API usage after upgrading to Phaser 4
• Per-frame allocations, unbounded groups, and missing object pooling
• Timer events not tracked — time.addEvent() without a stored reference accumulates across scene restarts
• Physics groups not explicitly destroyed — evolved weapon groups and spawn-phase groups leak if not clear(true,true) + destroy()'d
• Stat mutations without base+modifiers — two systems writing the same stat in the same frame produce race-condition values
• Notification dedup by string equality — drops legitimate rapid repeat events (e.g. two coin pickups in 200 ms); use a time-window dedup instead
• Overlay/panel backdrops sized from module-level constants — freeze at boot size; use this.cameras.main.width/height + resize listener

Common Silent Failure Categories

When the game freezes or behaves incorrectly with no console error, use these fast diagnostic paths before reaching for the full guide in references/agent-guidance.md.

Silent freeze (no error):

// Add to main.ts BEFORE new Phaser.Game(config)
window.onerror = (msg, _src, _line, _col, err) => {
  console.error('GLOBAL ERROR:', msg, err?.stack);
};
window.onunhandledrejection = (ev) => {
  console.error('UNHANDLED REJECTION:', ev.reason);
};

Then hard-refresh. Any previously silent failure will now log. See references/agent-guidance.md → Silent Freeze for the full checklist.

Spawns stop mid-session (no error): Pool slot leak — entities leaving the camera view without recycling their slot. Add console.log('pool free:', pool.getTotalFree()) in your spawn call. If it hits zero and stays there, a slot is being held. See references/agent-guidance.md → Pool Slot Leak.

Forced animation plays one frame then reverts: Entity update() overwrites forced animation one tick later. Fix with cinematicMode flag. See skills/phaser-animation/references/state-machine-patterns.md.

Speed or stat jumps to wrong value intermittently: Two systems mutate the same stat on the same frame. Use base+modifiers pattern. See references/agent-guidance.md → Race Between Two Systems.

Stuck entity detection fires incorrectly (false positives or negatives): body.velocity returns 0 when pushing against a wall. Use position-delta sampling instead. See references/agent-guidance.md → Stuck Detection Fails.

Full Guidance

For the complete diagnostic playbook, read references/agent-guidance.md. It is copied from the Claude subagent definition but should be applied as a portable skill; ignore Claude-only fields such as model, color, and tools.