Show HN: I Built a Capture the Flag Arena for Agents

yuvvantalreja1 pts0 comments

ClaySeal Arena — Prompt-Injection CTF

Sign in

Sign in to author challenges and appear on the leaderboard.

Sign in

New here?<br>Create an account

Challenges

Choose a target

Target model

Sent to this server only to relay each turn to<br>the provider. Held in memory for this tab, never stored.

Switching restarts the current challenge.

No server key configured.<br>Pick a — your key target above and paste your Anthropic or OpenAI key to play,<br>or set ANTHROPIC_API_KEY / OPENAI_API_KEY on the server.

Pick a challenge to begin

Each one is an AI agent guarding a secret flag. You get chat messages and<br>nothing else. Break its rule, read the flag, capture it.

Target:

Need a nudge? Show hint

🚩 Flag captured<br>What just happened

Send

Reset

Captured the flag? Submit it:

Capture

Community challenges

Sort

Newest<br>Most played<br>Hardest (lowest crack-rate)<br>Still unbroken

Agents authored by other players. Break them, capture the flag, climb the board.

No published challenges yet. Be the first — hit Create .

Create a challenge

Build a guarded agent around a secret flag, prove you can break it, then publish it for others.

Name<br>Difficulty

1 · warm-up2<br>34<br>5 · brutal

Agent name<br>Category

Tagline<br>Briefing (public)<br>Objective (public)<br>Opening message (public)<br>Hint (public, optional)

Secrets — never shown to players

Flag<br>System prompt<br>Takeaway (shown after capture)

Guards — optional

Input keyword firewall

Output flag-redaction filter

Custom tools — optional, runs sandboxed

+ Add tool

Handler code<br>— Python, runs in a WASM sandbox

Your code runs with no filesystem, network, or host access — only (name, args, flag, state).

Dry-run

args (JSON)

Run

Tool state<br>— JSON, optional

Save draft<br>Test in playground<br>New / clear

My challenges

Leaderboard

Score = sum of solved-challenge difficulties. First blood counts double the glory.

No solves yet. Go crack something.

Profile

flag capture challenges target challenge public

Related Articles