[help wanted] a2a-x402 adapter for switchboard transport

[abhicris]

What

Build a switchboard.adapters.a2a_x402 Python module that translates switchboard's binary-wire PaymentOffer / PaymentProof envelopes to and from the JSON shape used by google-agentic-commerce/a2a-x402 — Google's A2A + x402 bridge for agentic commerce. The adapter round-trips both directions: a switchboard agent should be able to satisfy an a2a-x402 payment challenge, and an a2a-x402 caller should be able to drive a switchboard-managed endpoint.

Why

Switchboard's transport (PR #21) is a tight binary envelope — it doesn't speak JSON-over-HTTP out of the box. a2a-x402 is the emerging Google-backed JSON protocol for agent-to-agent payment metadata layered over x402. The two formats encode the same idea (payment requirement → signed payment proof) but neither side will adopt the other's wire format. The fix is a thin Python adapter under switchboard.adapters.* plus a round-trip integration test against the a2a-x402 reference flow.

Scope

• switchboard/adapters/a2a_x402.py exposing to_a2a_request(offer: PaymentOffer) -> dict and from_a2a_response(payload: dict) -> PaymentProof.
• Round-trip pytest using a fixture taken from the a2a-x402 repo's examples/ flow — start the reference server in a fixture, drive it from a switchboard client, assert the proof verifies.
• docs/adapters/a2a-x402.md walking through one end-to-end call.
• No changes outside switchboard/adapters/* and docs/adapters/*.

Paid-project channel

This is in our paid-project queue. If you open a credible draft PR we'll talk paid contribution via our contributor page. There is no direct repo bounty on this issue — the contributor page explains how payouts actually work.

Receipts to read first

• switchboard PR zap_transport: binary wire encoding for PaymentOffer / PaymentProof #21 — zap_transport: binary wire encoding for PaymentOffer / PaymentProof
• a2a-x402 PR #90 — SpendingPolicy hook for spending limits + circuit breakers (our prior contribution to that codebase, useful context for how their executor flow is wired)

Out of scope

• Multi-chain settlement logic — the adapter is pure encoding/decoding.
• Non-Python adapters (TS / Go) — separate issues if/when needed.
• Anything outside switchboard.adapters.* and its docs.

[Treasure520520]

Hi, I can take a first implementation slice here if the paid-project path is still open.

Before I open a draft PR, can you confirm the expected payout range/process for this issue and whether you want contributors to proceed before being approved through the contributor page? I want to avoid sending a complete unpaid implementation if this needs assignment or a specific paid-work handshake first.

Proposed scoped plan:

• read switchboard PR zap_transport: binary wire encoding for PaymentOffer / PaymentProof #21 and the current PaymentOffer / PaymentProof binary envelope types
• add switchboard/adapters/a2a_x402.py with to_a2a_request(offer) and from_a2a_response(payload) mapping only the documented fields
• add a small fixture-based pytest that round-trips a representative a2a-x402 example payload through the adapter and verifies the resulting proof shape
• add docs/adapters/a2a-x402.md with one end-to-end call flow and the exact unsupported cases
• keep the PR limited to switchboard/adapters/*, tests/fixtures needed for that adapter, and docs/adapters/*

If that matches the paid-project process, I can proceed with a reviewable draft PR.

[newtempleee]

Hi — I saw the a2a-x402 adapter issue and can help with this.

I’d approach it as a small isolated Python module with round-trip tests for PaymentOffer / PaymentProof conversion both ways. First milestone would be:

1. define the mapping between switchboard envelopes and a2a-x402 JSON,
2. implement serializer/deserializer,
3. add fixture-based tests against sample payloads.

If useful, I can send a short implementation plan or open a first PR.