fix(x402): strip extensions/resource from paymentPayload before facilitator (parity with node 2.7.5) (#92)

## Parity with node-commerce 2.7.5

x402 clients echo the 402 challenge's `extensions` (Bazaar input schema)
+ `resource` into the payload alongside the signed `payload` +
`accepted`. The Coinbase facilitator's `/x402/verify` validates the
payment payload against its `x402V2PaymentPayload` schema, which is `{
x402Version, payload, accepted }` and admits neither `extensions` nor
`resource`: their presence makes the payload match no union branch
(`must match one of [x402V2PaymentPayload, x402V1PaymentPayload]`) and
settle fails. Routes with a large echoed Bazaar schema fail while small
ones slip through.

## Fix

`process_x402_settle` now runs `strip_unsigned_x402_payload_fields`
before coercing to the typed model whose `model_dump(by_alias,
exclude_none)` reaches the facilitator, dropping only `extensions` +
`resource` and keeping `accepted` (which CDP requires, and which
`verify_x402_request` reads for network/payTo). Neither stripped block
is part of the EIP-3009 signature.

Confirmed against the live CDP facilitator: the stripped accepted-nested
payload passes schema and reaches signature verify; a flat `{
x402Version, scheme, network, payload }` is rejected with `requires
'accepted'`.

## Tests

Unit: drop-both / keep-accepted, unchanged-when-absent (same object),
single-field strip, non-dict passthrough. Integration:
`process_x402_settle` forwards a payload to BOTH verify and settle with
`accepted` kept and `extensions`/`resource` gone.

Full suite green (1840 passed, 95.36% coverage), ruff + ty clean.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: vvillait88

agentscore_commerce/payment/__init__.py

@@ -76,6 +76,7 @@
     coerce_resource_config,
     process_x402_settle,
     settle_result_to_json_bytes,
+    strip_unsigned_x402_payload_fields,
 )
 from agentscore_commerce.payment.x402_validation import (
     X402_SUPPORTED_BASE_NETWORKS,
@@ -164,6 +165,7 @@
     "resolve_recipient",
     "settle_result_to_json_bytes",
     "settlement_override_header",
+    "strip_unsigned_x402_payload_fields",
     "usd_to_atomic",
     "validate_x402_network_config",
     "verify_x402_request",

agentscore_commerce/payment/x402_settle.py

@@ -301,6 +301,31 @@ def coerce_payment_payload(payload: Any) -> Any:
         return payload
 
 
+def strip_unsigned_x402_payload_fields(payload: Any) -> Any:
+    """Drop the non-signed ``extensions`` + ``resource`` blocks from a decoded X-Payment payload.
+
+    x402 clients echo the 402 challenge's ``extensions`` (Bazaar input schema) and ``resource``
+    into the payload alongside the signed ``payload`` + ``accepted``. Neither is part of the
+    EIP-3009 signature (which covers only ``payload.authorization``). The Coinbase facilitator's
+    ``/x402/verify`` validates the payment payload against its ``x402V2PaymentPayload`` schema,
+    which is ``{x402Version, payload, accepted}`` and admits neither ``extensions`` nor
+    ``resource``: their presence makes the payload match no union branch and CDP rejects it
+    (``must match one of [x402V2PaymentPayload, x402V1PaymentPayload]``). Routes whose echoed
+    Bazaar schema is large fail while small ones slip through, so it presents as route-dependent
+    but is one shape bug.
+
+    ``accepted`` (which ``verify_x402_request`` reads for network/payTo, and which CDP requires)
+    and every other field stay intact; only the two echoed challenge blocks are dropped, before
+    the payload is coerced to the typed model whose ``model_dump`` reaches the facilitator.
+    Non-dict payloads, and payloads carrying neither field, pass through unchanged.
+    """
+    if not isinstance(payload, dict):
+        return payload
+    if "extensions" not in payload and "resource" not in payload:
+        return payload
+    return {k: v for k, v in payload.items() if k not in ("extensions", "resource")}
+
+
 async def process_x402_settle(
     *,
     x402_server: Any,
@@ -322,7 +347,9 @@ async def process_x402_settle(
     """
     server = x402_server
     coerced_config = coerce_resource_config(resource_config)
-    coerced_payload = coerce_payment_payload(payload)
+    # Drop the echoed extensions/resource blocks before coercion: CDP's verify schema admits
+    # neither, so their presence makes the payload match no union branch and settle fails.
+    coerced_payload = coerce_payment_payload(strip_unsigned_x402_payload_fields(payload))
 
     try:
         built_requirements = server.build_payment_requirements(coerced_config)

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "agentscore-commerce"
-version = "2.5.9"
+version = "2.5.10"
 description = "Agent commerce SDK for Python — identity middleware (FastAPI, Flask, Django, AIOHTTP, Sanic, ASGI) + payment helpers + 402 builders + discovery + Stripe multichain. The full merchant-side toolkit for AgentScore-powered agent commerce."
 readme = "README.md"
 license = "MIT"

tests/test_x402_settle_extra.py

@@ -11,6 +11,7 @@
     classify_x402_settle_result,
     process_x402_settle,
     settle_result_to_json_bytes,
+    strip_unsigned_x402_payload_fields,
 )
 
 
@@ -123,3 +124,55 @@ def test_settle_result_to_json_bytes() -> None:
     out = settle_result_to_json_bytes({"a": 1, "b": "two"})
     assert isinstance(out, bytes)
     assert b'"a"' in out
+
+
+_ACCEPTED = {"scheme": "exact", "network": "eip155:8453", "payTo": "0xabc"}
+_INNER = {"authorization": {"from": "0xsigner", "to": "0xabc"}, "signature": "0xdeadbeef"}
+_WIRE = {
+    "x402Version": 2,
+    "payload": _INNER,
+    "accepted": _ACCEPTED,
+    "extensions": {"bazaar": {"schema": {"type": "object", "properties": {"phone": {"type": "string"}}}}},
+    "resource": {"url": "https://x/person/base/no-pii", "description": "d" * 600, "tags": ["person"]},
+}
+
+
+def test_strip_drops_extensions_and_resource_keeps_accepted() -> None:
+    assert strip_unsigned_x402_payload_fields(_WIRE) == {
+        "x402Version": 2,
+        "payload": _INNER,
+        "accepted": _ACCEPTED,
+    }
+
+
+def test_strip_returns_same_object_when_neither_field_present() -> None:
+    lean = {"x402Version": 2, "payload": _INNER, "accepted": _ACCEPTED}
+    assert strip_unsigned_x402_payload_fields(lean) is lean
+
+
+def test_strip_handles_single_field_and_non_dict() -> None:
+    assert strip_unsigned_x402_payload_fields({"payload": _INNER, "resource": {"url": "x"}}) == {"payload": _INNER}
+    assert strip_unsigned_x402_payload_fields({"payload": _INNER, "extensions": {"bazaar": {}}}) == {"payload": _INNER}
+    assert strip_unsigned_x402_payload_fields(None) is None
+    assert strip_unsigned_x402_payload_fields("not-a-dict") == "not-a-dict"
+
+
+@pytest.mark.asyncio
+async def test_process_x402_settle_strips_bloat_before_facilitator() -> None:
+    # Incomplete `accepted` makes coerce_payment_payload leave the payload a plain dict, so we
+    # can assert directly on what reaches verify_payment / settle_payment. The strip must have
+    # removed extensions/resource and kept accepted (which CDP's v2 schema requires).
+    server = _make_server()
+    result = await process_x402_settle(
+        x402_server=server,
+        payload=_WIRE,
+        resource_config={"scheme": "exact", "network": "eip155:8453", "payTo": "0xabc"},
+        resource_meta={"url": "https://x/person/base/no-pii", "description": "t", "mimeType": "application/json"},
+    )
+    assert isinstance(result, ProcessX402SettleSuccess)
+    for mock in (server.verify_payment, server.settle_payment):
+        forwarded = mock.call_args[0][0]
+        assert forwarded == {"x402Version": 2, "payload": _INNER, "accepted": _ACCEPTED}
+        assert "accepted" in forwarded
+        assert "extensions" not in forwarded
+        assert "resource" not in forwarded