fix(checkout): malformed-402 re-challenge must run pre_validate -> v2.5.8 (#90)

Parity hotfix for 2.5.7 (mirrors node-commerce 2.7.1).
Malformed-credential 402 re-challenge skipped pre_validate, 500ing for
dynamic-pricing merchants. Fix: strip the credential + re-enter handle()
(full discovery flow). Regression test added. Gate green:
ruff/ty/vulture/pytest (1835, 95.48%).

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

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

Author: vvillait88

agentscore_commerce/checkout.py

@@ -1076,16 +1076,16 @@ async def handle(self, request: CheckoutRequest) -> CheckoutResult:
                 else self.compose_mppx is not None
             )
             if enforced and malformed is not None:
-                # Protocol-correct recovery: a junk credential gets a FRESH 402
-                # challenge (same shape as the discovery leg) so an x402/MPP
-                # client re-pays, instead of a dead-end 400 it cannot act on.
-                # Strip the malformed credential first (``_discovery_view``) so
-                # recipient minting + MPP compose take their fresh-mint /
-                # fresh-challenge path rather than binding the garbage and
-                # raising another 400. pre_validate and the gate/assess are
-                # skipped by construction here (a junk credential must never burn
-                # the merchant's paid probe or an identity API call).
-                result = await self._emit_fresh_challenge(self._discovery_view(ctx))
+                # A junk credential is treated as a discovery request: strip it
+                # and re-enter handle() so pre_validate + pricing + recipient
+                # minting + compose all run their fresh path exactly as for a
+                # no-credential request. That yields a fresh 402 the agent
+                # re-pays against, not a dead-end 400, and not a 500 when
+                # compute_pricing reads state that pre_validate populates. The
+                # gate/assess and settle are skipped by construction: after
+                # stripping there is no payment header, so no re-trigger of this
+                # check (max one level of recursion) and no identity call.
+                result = await self.handle(self._strip_payment_headers(request))
                 return dataclasses.replace(result, settle_phase="credential_malformed")
 
         # Pre-validate (optional): resolve merchant-specific per-request state
@@ -2658,11 +2658,11 @@ async def _handle_mppx(self, ctx: CheckoutContext) -> CheckoutResult:
         )
 
     async def _emit_fresh_challenge(self, ctx: CheckoutContext) -> CheckoutResult:
-        """Emit a fresh 402 challenge (the discovery leg).
+        """Emit the discovery-leg 402.
 
-        Factored out so the malformed-credential path can reuse it. Idempotent on
-        already-computed pricing / resolved recipients (``_emit_402`` resolves
-        recipients), so the normal discovery leg pays nothing extra.
+        pre_validate + pricing already ran in the main flow before this is
+        reached; idempotent on already-computed pricing / resolved recipients
+        (``_emit_402`` resolves recipients), so it primes nothing twice.
         """
         if ctx.pricing is None:
             ctx.pricing = await _maybe_await(self.compute_pricing(ctx))
@@ -2679,24 +2679,26 @@ async def _emit_fresh_challenge(self, ctx: CheckoutContext) -> CheckoutResult:
                 pass
         return await self._emit_402(ctx, mppx_headers=mppx_headers)
 
-    def _discovery_view(self, ctx: CheckoutContext) -> CheckoutContext:
-        """Return a copy of ``ctx`` with payment-credential headers removed.
+    def _strip_payment_headers(self, request: CheckoutRequest) -> CheckoutRequest:
+        """Return a copy of the request with payment-credential headers removed.
 
-        Recipient minting and MPP compose then take their discovery (fresh-mint,
-        fresh-challenge) path instead of binding the inbound credential, turning a
-        malformed-credential request into a clean 402 re-challenge. Pricing and
-        recipients are reset so they mint fresh.
+        Re-entering handle() with it treats the request as a discovery
+        (no-credential) request: pre_validate + pricing + minting + compose run
+        their fresh path, and the gate/assess and settle are skipped. Turns a
+        malformed-credential request into a clean 402 re-challenge. The raw
+        request is left intact; compose_mppx reads it only best-effort under a
+        try/except, while the stripped headers are what the shape check, gate
+        dispatch, and recipient minting read.
         """
         headers = {
             k: v
-            for k, v in ctx.request.headers.items()
+            for k, v in request.headers.items()
             if not (
                 k.lower() in ("payment-signature", "x-payment")
                 or (k.lower() == "authorization" and v.startswith("Payment "))
             )
         }
-        request = dataclasses.replace(ctx.request, headers=headers)
-        return dataclasses.replace(ctx, request=request, pricing=None, recipients={})
+        return dataclasses.replace(request, headers=headers)
 
     async def _emit_402(
         self,

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "agentscore-commerce"
-version = "2.5.7"
+version = "2.5.8"
 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_credential_precheck.py

@@ -47,7 +47,7 @@ def test_malformed_payment_credential_classifies_channels() -> None:
 
 
 @pytest.mark.asyncio
-async def test_junk_mpp_header_rechallenges_with_fresh_402_no_pre_validate() -> None:
+async def test_junk_mpp_header_rechallenges_with_fresh_402_discovery_flow() -> None:
     calls: list[str] = []
 
     async def _pre_validate(_ctx: Any) -> dict[str, Any]:
@@ -69,12 +69,12 @@ async def _compose(_ctx: Any) -> MppxComposeOutcome:
     assert result.status == 402
     assert result.settle_phase == "credential_malformed"
     assert result.headers["www-authenticate"] == 'Payment realm="fresh"'
-    # The junk credential must not burn the merchant's paid probe.
-    assert "pre_validate" not in calls
+    # Treated as a discovery request: pre_validate runs (pricing depends on its state).
+    assert "pre_validate" in calls
 
 
 @pytest.mark.asyncio
-async def test_junk_x402_header_rechallenges_with_fresh_402_no_pre_validate() -> None:
+async def test_junk_x402_header_rechallenges_with_fresh_402_discovery_flow() -> None:
     calls: list[str] = []
 
     async def _pre_validate(_ctx: Any) -> dict[str, Any]:
@@ -93,8 +93,31 @@ async def _pre_validate(_ctx: Any) -> dict[str, Any]:
     # A fresh challenge the agent can re-pay against, not a bare error body.
     assert result.body["accepted_methods"] is not None
     assert result.settle_phase == "credential_malformed"
-    # Junk must not burn the merchant's paid probe.
-    assert calls == []
+    # Discovery flow: pre_validate runs.
+    assert calls == ["pre_validate"]
+
+
+@pytest.mark.asyncio
+async def test_malformed_credential_runs_pre_validate_so_stateful_pricing_survives() -> None:
+    # Regression: compute_pricing reads state that pre_validate populates (the
+    # martin-estate shape). The malformed re-challenge must run pre_validate
+    # first, or pricing dereferences missing state and 500s.
+    async def _pre_validate(_ctx: Any) -> dict[str, Any]:
+        return {"product": {"price_cents": 4800}}
+
+    def _compute_pricing(ctx: Any) -> PricingResult:
+        return PricingResult(amount_usd=ctx.state["product"]["price_cents"] / 100)
+
+    checkout = Checkout(
+        rails={"x402_base": X402BaseRailSpec(recipient="0x" + "00" * 19 + "dEaD")},
+        url="https://api.example/purchase",
+        pre_validate=_pre_validate,
+        compute_pricing=_compute_pricing,
+        x402_server=object(),
+    )
+    result = await checkout.handle(_req({"x-payment": "not-decodable"}))
+    assert result.status == 402
+    assert result.body["accepted_methods"] is not None
 
 
 @pytest.mark.asyncio