$5-a-day demo recipe: the agent buys until the budget says no (#29 pattern)

[hellno]

Standalone; the x402-track demo deliverable in the full #29 shape. Depends on #34 (budget primitive + fixtures), #206 (local facilitator recipe), #208 (agent 402 client); #207 provides the visible gauge (the transcript notes which beats are GUI vs headless).

The demo, audience view

1. Policy: policy.x402-daily.json — USDC allowed (asset_allow), a 5.00 USDC/day token_budget, a per-payment cap (e.g. $2.50), everything else default-deny. Dollar framing throughout: the pitch is "$5 a day", not wei.
2. Agent hits a paid API (the local x402 server fixture from x402 phase 2: exact/EIP-3009 payments on the Ethereum reference path, fully local demo loop #34, facilitator per Spike: x402 build shape — hand-rolled EIP-3009 vs x402-rs, and prove the fully-local facilitator loop #206). First call: 402 → the daemon authorizes $2.00 within budget → content returned. The gauge reads $2.00 / $5.00.
3. Second call: $2.50 → $4.50 / $5.00.
4. Third call ($2.00): would breach the daily budget → typed budget-exhausted deny (x402 phase 2: exact/EIP-3009 payments on the Ethereum reference path, fully local demo loop #34's X-series reason) → the agent reports "out of budget until tomorrow (UTC rollover)". Optional approval beat: the human raises the budget in-app, the retry succeeds.
5. Lockdown (Rename the global stop to Lockdown #203) ends the session.

Deliverables (the #29 triple)

• policy.x402-daily.json.
• The transcript: exact prompts, expected tool results, expected UI states.
• An acceptance test (mock daemon) asserting the three decisions — allow, allow, budget-deny — and the UTC-rollover reset.
• just demo-x402: wires fork world + x402 server fixture + facilitator + agent env in one target.

Acceptance

1. just demo-x402 + transcript reproduce end-to-end on a fresh clone.
2. Acceptance test green in CI.
3. Screenshots: the payment card, the gauge at $4.50, and the budget-deny (GUI beats via x402 payment surfaces in the GUI: authorization card, per-asset budget gauge, paid-domain activity rows #207).
4. DoD green: cargo fmt --all --check, just check, cargo test --workspace, no new/changed deps without approval.