Complete implementation: Solidity AgentEscrow contract with timeout/refund + Python payment client + comprehensive tests. Trustless escrow flow with payer/payee confirmation.

Author: @D2758695161

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

)

Closes #5. Tracks cumulative gas spent per wallet over rolling
hour + day windows, auto-pauses the wallet when a limit is
crossed, and exposes status/reset/resume controls.

- switchboard/gas_budget.py — tracker, limits, BudgetExhausted
- tests/test_gas_budget.py — 14 pytest cases incl. thread-safety
  and window-roll assertions using an injectable clock

No new runtime deps. Rolling windows (not calendar buckets) so a
burst at 23:59 cannot reset one minute later.

Adds web/index.html — zero-build explorer of the 2026 agent-
payment landscape and how switchboard fits alongside.

- Tab-switcher across five rails: x402 (Linux Foundation / USDC
  HTTP 402), MPP (Stripe × Tempo sessions), AP2 (Google A2A +
  Verifiable Intent), Circle Nanopayments, switchboard's own on-
  chain AgentEscrow.sol.
- For each: 4-step sequence diagram (SVG, swim-lane per actor,
  active-step highlight) + wire-level code snippet (HTTP, JSON
  body, Solidity call) that updates as you click through steps.
- Side-by-side compatibility matrix: transport, settlement
  asset, agent↔agent vs agent↔server, streaming, dispute
  resolution, fiat rails, license.
- "How switchboard fits" section explaining the gap the open
  rails leave (agent-side keys, nonces, gas budgets, escrow)
  and pointing at the open issues.

Single file, no build, no backend. Same dark palette as the
other kcolbchain dashboards.

Co-authored-by: Abhishek Krishna <[email protected]>

fix: Add gas budget tracker with configurable limits

…19)

Adds X402Middleware that intercepts HTTP 402 responses and automatically
pays on-chain via PaymentClient, then retries with X-Payment-Proof header.

- Supports exact (direct transfer) and escrow payment schemes
- Policy enforcement: max payment cap, recipient allowlist, gas budget
- Payment history tracking and spend summaries
- 15 tests covering offer parsing, validation, payment execution

Closes #16

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

Adds switchboard/zap_transport.py — encode/decode PaymentOffer and
PaymentProof over the ZAP wire format (luxfi/zap, port 9999) as a
zero-allocation alternative to the existing JSON-in-HTTP-headers path.

Why: switchboard's HTTP/JSON transport is fine for HTTP/REST agents
but expensive for high-volume agent-to-agent traffic (every offer
parsed, allocated, copied). When two agents sit on the same Lux
network, ZAP lets them exchange offers/proofs with zero parse-time
allocation and ~10x smaller payloads.

zap_py is an optional dependency. If it isn't installed, the module
still imports cleanly and encode/decode raise ZapNotAvailable so
callers can fall back to the JSON path. Tests use pytest.importorskip
so the suite stays green either way.

Wire layout uses zap_py.StructBuilder so the schema is pinned and a
Go counterpart can mirror it exactly:

  PaymentOffer:
    scheme(u8) | chain_id(u64) | expires_at(u64, 0=null)
    | recipient(address) | amount(bytes,uint256-be) | currency(text)
    | description(text) | endpoint(text) | nonce(text)

  PaymentProof:
    chain_id(u64) | timestamp(u64) | payer(address) | tx_hash(hash32)
    | amount(bytes,uint256-be) | nonce(text)

amount is a 32-byte big-endian uint256 rather than a uint64 so realistic
on-chain values aren't truncated.

11 tests cover: schema layout sanity, minimal+full offer roundtrip,
each PaymentScheme value, uint256-max amount, overflow/negative
rejection, proof roundtrip, invalid tx_hash length, ZapNotAvailable
gating, and a wire-size-vs-JSON sanity check.

Existing 40-test switchboard suite remains green. Two pre-existing
test files (test_nonce_manager.py, test_payment_protocol.py) had
collection-time syntax errors before this branch; they remain
unchanged.