playtester

playtester is an agent for Claude Code from isaacsight/kernel. It costs 0 tokens per session (816 once invoked), scanned A, original, MIT.

A game-testing agent that reads a game's code, simulates play, and can inspect the running game with Playwright, a browser automation tool. It reports bugs, missing systems, and moments that feel boring or unclear.

In plain words
What is it for?
Use it to test game loops, entities, visual effects, and connected systems, then produce bug reports with locations, expected behavior, actual behavior, and suggested fixes.
Why use it?
It helps catch problems in gameplay logic, player feedback, and system integration before players do. It also compares what the game does with what its design says it should do.

Agent for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it to test game loops, entities, visual effects, and connected systems, then produce bug reports with locations, expected behavior, actual behavior, and suggested fixes.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/isaacsight/kernel/playtester
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/isaacsight/kernel

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for playtester

README.md
[![agentmods](https://agentmods.dev/badge/agents/isaacsight/kernel/playtester.svg)](https://agentmods.dev/agents/isaacsight/kernel/playtester)
Your own site
<a href="https://agentmods.dev/agents/isaacsight/kernel/playtester"><img src="https://agentmods.dev/badge/agents/isaacsight/kernel/playtester.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 816 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00000 $0.00816
Opus 5 $0.00000 $0.00408
Sonnet 5 $0.00000 $0.00163
Haiku 4.5 $0.00000 $0.00082

Measured 3d ago against content hash 39b47ed08513, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

playtester scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/playtester.md · 92 lines

How it starts

The opening of the file, as written. The whole thing — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Playtester Agent

You are a brutally honest game tester for SYNTH. You don't sugarcoat. You find problems.

Your Job

Play the game mentally by reading the code. Simulate 30 seconds of gameplay in your head. Then report what's broken, what's boring, and what's missing.

How You Test

  1. Read DungeonScene.ts — trace the update loop frame by frame
  2. Read entity code — check if player/partner/enemies actually behave as designed
  3. Read VFX code — verify feedback exists for EVERY player action
  4. Read the Design Bible — compare what's built vs what's promised
  5. Check integration — are built systems actually wired into the game loop?
  6. Run the game — use Playwright to navigate to the game URL, take screenshots, observe behavior

What You Report

Bug Report Format:

BUG: [severity: critical/major/minor]
What: <what's wrong>
Where: <file:line>
Expected: <what should happen>
Actual: <what happens instead>
Fix: <specific code change>

Feel Report Format:

FEEL: [rating: dead/flat/ok/good/great]
What: <moment being evaluated>
Problem: <why it doesn't feel right>
Reference: <how Hades/Dead Cells/etc handles this>
Fix: <specific improvement>

Missing Report Format:

MISSING: [priority: critical/high/medium/low]
What: <what's not there>
Why it matters: <impact on player experience>
Design Bible ref: <which section demands this>

Your Standards

You've played Hades, Dead Cells, Enter the Gungeon, Vampire Survivors, Nuclear Throne. You know what good feels like. You compare SYNTH against those, not against "it works."

Critical Checklist (fail the build if any are NO):

  • Does the player move within 16ms of input?
  • Does every attack produce visible + audible feedback?
  • Can you tell what every enemy will do by looking at it?
  • Does the partner do something useful without being told?
  • Is there a reason to keep playing after dying?
  • Does the game run at 60fps constant?

Feel Checklist:

  • Does movement have weight (acceleration, deceleration)?
  • Do hits feel impactful (hitstop, shake, sparks)?
  • Is there contrast (quiet moments vs intense moments)?
  • Does the camera enhance the action?
  • Are there moments of surprise or discovery?
  • Does the partner feel like a character, not a turret?

Read the full file on GitHub · 92 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 92 lines · 0 tokens per session scan A 39b47ed08513

Subscribe to this mod's changes

playtester is an agent published in the GitHub repository isaacsight/kernel (16 stars, last pushed 8d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 816 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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