Groundline

A hallucination firewall for personal AI agents. Before your agent tells you something or commits code, Groundline buys independent checks from Telegraph's ranked miners and marks each claim ✓ verified, ? uncertain or ✗ contradicted, with sources and a verifiable receipt for every check.

Built for Telegraph Hackathon Season II, Apps & Agents track. Missions: 09 Personal Agent and 10 Model Economy. Runs on Telegraph beta 2 (Ethereum Sepolia, test USDC).

# abbreviated output from a real testnet run
$ groundline verify "GPT-3 was released by OpenAI in 2020 and has 175 billion parameters. BERT was introduced by Meta in 2012."

UNRELIABLE  trust 49  ·  paid checks · $0.16
 ✓ GPT-3 was released by OpenAI in 2020 and has 175 billion parameters.   VERIFIED 80%  (TxLens: True)
 ✗ BERT was introduced by Meta in 2012.   CONTRADICTED 85%
     "BERT was introduced in October 2018 by researchers at Google, not by Meta in 2012."

How it works

Every purchase goes into ~/.groundline/ledger.jsonl with intent, miner, cost, latency, signal_hash and receipt_hash. Anyone can re-verify a check:

curl -s https://devnode.telegraphprotocol.com/engine/v1/signal/<signal_hash> | jq .verification
# {"algorithm":"keccak256","commitment":"payload","verified":true}

Related MCP server: VerifyAPI MCP Server

Where it runs

• MCP server (groundline-mcp), for Claude Code, Cursor, OpenClaw, Hermes, Goose or any MCP client. Tools: groundline_verify_answer, groundline_verify_claim, groundline_code_guard, groundline_spend, groundline_status.

• CLI: groundline verify | claim | guard | extract | spend | status | serve | hook install.

• Local API + live spend dashboard at http://127.0.0.1:8787, showing a spend leaderboard per intent and per miner, recent receipts, and a "verify an answer" box.

• Browser extension (extension/) that adds Verify with Groundline under ChatGPT, Claude and Gemini answers, plus a floating Check whole answer / Check selection dock, highlights each claim in place and lists every link with its status.

Quick start

Requires Node 20+.

git clone https://github.com/AadithyaAle/groundline && cd groundline
npm install && npx tsc

Once published to npm, the package will be groundline-ai (commands groundline and groundline-mcp): npx -y -p groundline-ai groundline serve. Until then, use the clone and node dist/cli.js … as below.

1. Wallet (testnet only, no real money). Create a fresh burner wallet and put its key in .env. Never use a wallet that holds real funds.

cat > .env <<'EOF'
TELEGRAPH_PRIVATE_KEY=0x<burner private key>
GROUNDLINE_MAX_SPEND_USD=1.00
EOF
chmod 600 .env

Send it a little free Sepolia ETH from a faucet. Then mint test USDC and move part of it into Telegraph escrow:

node scripts/fund.mjs 10 2      # mint 10 test USDC, deposit 2 into escrow
node dist/cli.js status

2. Try it.

node dist/cli.js extract "The transformer was introduced in 2017. GPT-3 has 175 billion parameters."   # free
node dist/cli.js claim "BERT was introduced by Meta in 2012."                                          # ~$0.02-0.05
git diff --cached | node dist/cli.js guard                                                             # ~$0.03
node dist/cli.js serve        # dashboard at http://127.0.0.1:8787

3. Add it to your agent (MCP).

claude mcp add groundline -e GROUNDLINE_ENV_FILE=$PWD/.env -- node $PWD/dist/mcp.js

Other clients use the same command / args / env block, as in the Telegraph MCP examples.

4. Browser extension. Run node dist/cli.js serve. Then open chrome://extensions, enable Developer mode, click Load unpacked and select extension/. See extension/README.md.

5. Pre-commit guard. In any repo, run node /path/to/groundline/dist/cli.js hook install.

Settings

Safety

• The private key stays in the local process. It is never sent to the model, the browser or the logs.

• Spend limits are checked before each payment is signed. A failed ask is never billed: escrow isn't charged, and x402 payments are credited back to escrow.

• The local server binds to 127.0.0.1 only. It accepts only the chat sites, the extension and loopback origins, checks the Host header against DNS rebinding, and limits request bodies to 200KB.

Limitations (honest)

• Testnet only (Telegraph beta 2). Prices and miners change as the network evolves.

• Network fact checkers often abstain. Moving down the ranking helps, but some claims honestly end up UNCERTAIN.

• Claim extraction is heuristic unless the calling agent passes its own claims, which the MCP tool asks it to do.

• The extension's site selectors may need updating when ChatGPT, Claude or Gemini change their DOM.

Development

npx tsc           # build
npm test          # 118 unit tests, mocked network, no spending

The payment flow is adapted from telegraphprotocol/Telegraph-MCP (MIT). License: MIT.