add x-cashu support

routstr/proxy.py

@@ -2,6 +2,7 @@ import asyncio
 import inspect
 import json
 from typing import Any
+from urllib.parse import urlsplit
 
 from fastapi import APIRouter, Depends, HTTPException, Request
 from fastapi.responses import Response, StreamingResponse
@@ -38,9 +39,17 @@ from .payment.models import Model
 from .upstream import BaseUpstreamProvider
 from .upstream.ehbp import forward_ehbp_request, forward_ehbp_x_cashu_request
 from .upstream.helpers import init_upstreams
+from .upstream.model_paths import (
+    ModelPathSelector,
+    decode_model_path,
+    public_model_id,
+    public_provider_url,
+)
 from .upstream.request_correction import correct_request, extract_error_message
 
 logger = get_logger(__name__)
+
+MODEL_PATH_HEADER = "x-routstr-model-path"
 proxy_router = APIRouter()
 
 _upstreams: list[BaseUpstreamProvider] = []
@@ -113,6 +122,25 @@ def get_candidates(
     return None
 
 
+def _model_ids_match(requested: str, selected: str) -> bool:
+    if requested.lower() == selected.lower():
+        return True
+    return public_model_id(requested).lower() == public_model_id(selected).lower()
+
+
+def _candidate_for_selector(
+    selector: ModelPathSelector,
+    candidates: list[tuple[Model, BaseUpstreamProvider]],
+) -> tuple[Model, BaseUpstreamProvider] | None:
+    for model_obj, upstream in candidates:
+        if (
+            upstream.db_id == selector.provider_id
+            and public_provider_url(upstream.base_url) == selector.base_url
+        ):
+            return model_obj, upstream
+    return None
+
+
 def get_model_instance(model_id: str) -> Model | None:
     """Get the best-ranked Model instance for a model ID."""
     candidates = get_candidates(model_id)
@@ -424,6 +452,13 @@ async def _proxy(
     # without model/cost/auth lookups. Do not prefix-match here: paths such as
     # /attestationjunk must continue through normal authentication.
     if request.method == "GET" and _is_tinfoil_attestation_path(path):
+        if MODEL_PATH_HEADER in headers:
+            return create_error_response(
+                "unsupported_request",
+                "Model paths do not apply to attestation",
+                400,
+                request=request,
+            )
         selected_upstreams = _select_unauthenticated_get_upstreams(path, _upstreams)
         if not selected_upstreams:
             return create_error_response(
@@ -464,6 +499,41 @@ async def _proxy(
             "upstream_error", "All upstreams failed", 502, request=request
         )
 
+    selector: ModelPathSelector | None = None
+    if MODEL_PATH_HEADER in headers:
+        selector = decode_model_path(headers[MODEL_PATH_HEADER])
+        if (
+            selector is None
+            or sum(
+                name.lower() == MODEL_PATH_HEADER for name, _ in request.headers.items()
+            )
+            != 1
+        ):
+            return create_error_response(
+                "invalid_request",
+                f"Malformed {MODEL_PATH_HEADER} header",
+                400,
+                request=request,
+            )
+        if not isinstance(model_id, str) or not _model_ids_match(
+            model_id, selector.model_id
+        ):
+            return create_error_response(
+                "invalid_request",
+                f"{MODEL_PATH_HEADER} selects model '{selector.model_id}' but the "
+                f"request asks for '{model_id}'",
+                400,
+                request=request,
+            )
+        if "models" in request_body_dict:
+            return create_error_response(
+                "invalid_request",
+                "Model paths cannot be combined with model fallbacks",
+                400,
+                request=request,
+            )
+        model_id = selector.model_id
+
     candidates = get_candidates(model_id)
 
     if not candidates:
@@ -471,6 +541,51 @@ async def _proxy(
             "invalid_model", f"Model '{model_id}' not found", 400, request=request
         )
 
+    if selector is not None:
+        pinned = _candidate_for_selector(selector, candidates)
+        if pinned is None:
+            return create_error_response(
+                "invalid_model_path",
+                f"Model '{selector.model_id}' is not routable through provider "
+                f"{selector.provider_id}",
+                404,
+                request=request,
+            )
+        # Explicit routes must never enter cross-provider failover.
+        candidates = [pinned]
+
+        if selector.endpoint_tag:
+            if (
+                is_ehbp
+                or not request_body_dict
+                or urlsplit(pinned[1].base_url).hostname != "openrouter.ai"
+                or _canonical_api_path(path)
+                not in {"chat/completions", "completions", "responses"}
+            ):
+                return create_error_response(
+                    "unsupported_request",
+                    "Endpoint pinning requires an OpenRouter completion or Responses JSON request",
+                    400,
+                    request=request,
+                )
+            provider_options = request_body_dict.get("provider", {})
+            if not isinstance(provider_options, dict):
+                return create_error_response(
+                    "invalid_request",
+                    "provider must be an object",
+                    400,
+                    request=request,
+                )
+            request_body_dict = {
+                **request_body_dict,
+                "provider": {
+                    **provider_options,
+                    "order": [selector.endpoint_tag],
+                    "allow_fallbacks": False,
+                },
+            }
+            request_body = json.dumps(request_body_dict).encode()
+
     if is_ehbp:
         candidates = [
             (model, upstream)
@@ -521,11 +636,21 @@ async def _proxy(
                     )
                 elif is_responses_api:
                     return await upstream.handle_x_cashu_responses(
-                        request, x_cashu, path, max_cost_for_model, model_obj
+                        request,
+                        x_cashu,
+                        path,
+                        max_cost_for_model,
+                        model_obj,
+                        request_body=request_body,
                     )
                 else:
                     return await upstream.handle_x_cashu(
-                        request, x_cashu, path, max_cost_for_model, model_obj
+                        request,
+                        x_cashu,
+                        path,
+                        max_cost_for_model,
+                        model_obj,
+                        request_body=request_body,
                     )
             except UpstreamError as e:
                 logger.warning(
@@ -728,7 +853,7 @@ async def _proxy(
                 # When the upstream 400s naming such a param, strip it from the
                 # body and retry the SAME upstream. ``already_stripped`` bounds
                 # this to one retry per distinct param so it always terminates.
-                if response.status_code == 400 and not is_ehbp:
+                if response.status_code == 400 and not is_ehbp and selector is None:
                     correction = correct_request(
                         request_body,
                         extract_error_message(response),

routstr/upstream/base.py

@@ -533,6 +533,7 @@ class BaseUpstreamProvider:
             "refund-lnurl",
             "key-expiry-time",
             "x-cashu",
+            "x-routstr-model-path",
         ]:
             if headers.pop(header, None) is not None:
                 removed_headers.append(header)
@@ -4244,6 +4245,8 @@ class BaseUpstreamProvider:
         max_cost_for_model: int,
         model_obj: Model,
         mint: str | None = None,
+        *,
+        request_body: bytes | None = None,
     ) -> Response | StreamingResponse:
         """Forward request paid with X-Cashu token to upstream service.
 
@@ -4263,7 +4266,8 @@ class BaseUpstreamProvider:
         if path.startswith("v1/"):
             path = path.replace("v1/", "")
 
-        request_body = await request.body()
+        if request_body is None:
+            request_body = await request.body()
 
         if (
             path.endswith("messages/count_tokens")
@@ -4459,6 +4463,8 @@ class BaseUpstreamProvider:
         path: str,
         max_cost_for_model: int,
         model_obj: Model,
+        *,
+        request_body: bytes | None = None,
     ) -> Response | StreamingResponse:
         """Handle X-Cashu payment for Responses API requests.
 
@@ -4523,6 +4529,7 @@ class BaseUpstreamProvider:
                 max_cost_for_model,
                 model_obj,
                 mint,
+                request_body=request_body,
             )
         except Exception as e:
             error_message = str(e)
@@ -4579,6 +4586,8 @@ class BaseUpstreamProvider:
         max_cost_for_model: int,
         model_obj: Model,
         mint: str | None = None,
+        *,
+        request_body: bytes | None = None,
     ) -> Response | StreamingResponse:
         """Forward Responses API request paid with X-Cashu token to upstream service.
 
@@ -4600,7 +4609,8 @@ class BaseUpstreamProvider:
 
         url = f"{self.base_url}/{path}"
 
-        request_body = await request.body()
+        if request_body is None:
+            request_body = await request.body()
         transformed_body = self.prepare_responses_request_body(request_body, model_obj)
 
         logger.debug(
@@ -5162,6 +5172,8 @@ class BaseUpstreamProvider:
         path: str,
         max_cost_for_model: int,
         model_obj: Model,
+        *,
+        request_body: bytes | None = None,
     ) -> Response | StreamingResponse:
         """Handle request with X-Cashu token payment, redeeming token and forwarding request.
 
@@ -5241,6 +5253,7 @@ class BaseUpstreamProvider:
                 max_cost_for_model,
                 model_obj,
                 mint,
+                request_body=request_body,
             )
         except Exception as e:
             error_message = str(e)

routstr/upstream/model_paths.py

@@ -1,9 +1,6 @@
 """Model-path discovery service.
 
 Exposes every selectable upstream route a Routstr model is reachable through.
-This PR remains discovery-only: request-side routing will consume the opaque
-selectors in a follow-up.
-
 A path is a standard percent-encoded query string containing the configured
 upstream URL, provider ID, client-visible model ID and, for an exact OpenRouter
 endpoint, its machine-readable tag::
@@ -20,7 +17,7 @@ import random
 import time
 from dataclasses import dataclass
 from typing import TYPE_CHECKING, Any, Callable
-from urllib.parse import urlencode, urlsplit
+from urllib.parse import parse_qsl, urlencode, urlsplit
 
 import httpx
 from sqlalchemy.dialects.sqlite import insert
@@ -132,6 +129,57 @@ def encode_model_path(
     return urlencode(components)
 
 
+@dataclass(frozen=True)
+class ModelPathSelector:
+    """Decoded client-supplied route selector."""
+
+    base_url: str
+    provider_id: int
+    model_id: str
+    endpoint_tag: str | None = None
+
+
+def decode_model_path(path: str) -> ModelPathSelector | None:
+    """Inverse of ``encode_model_path``; ``None`` when the selector is malformed."""
+    try:
+        pairs = parse_qsl(
+            path,
+            keep_blank_values=True,
+            strict_parsing=True,
+            max_num_fields=4,
+            errors="strict",
+        )
+    except ValueError:
+        return None
+    params = dict(pairs)
+    if len(params) != len(pairs) or params.keys() - {
+        "url",
+        "provider-id",
+        "model-id",
+        "endpoint",
+    }:
+        return None
+    if any(not value.strip() for value in params.values()):
+        return None
+    base_url = params.get("url", "")
+    model_id = params.get("model-id", "")
+    raw_provider_id = params.get("provider-id", "")
+    if not base_url or not model_id or not raw_provider_id:
+        return None
+    try:
+        provider_id = int(raw_provider_id)
+    except ValueError:
+        return None
+    if provider_id <= 0:
+        return None
+    return ModelPathSelector(
+        base_url=base_url,
+        provider_id=provider_id,
+        model_id=model_id,
+        endpoint_tag=params.get("endpoint") or None,
+    )
+
+
 def _make_http_client() -> httpx.AsyncClient:
     """Client factory, separated so tests can substitute a mock transport."""
     return httpx.AsyncClient()

tests/unit/test_model_path_routing.py

@@ -0,0 +1,537 @@
+"""Model-path routing and fail-closed behavior."""
+
+import json
+from typing import Any
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+from routstr import proxy as proxy_module
+from routstr.auth import ReservationSnapshot
+from routstr.core.db import ApiKey
+from routstr.upstream.model_paths import decode_model_path, encode_model_path
+
+MODEL_ID = "test-model"
+
+
+def _make_upstream(db_id: int, status_code: int = 200) -> MagicMock:
+    upstream = MagicMock()
+    upstream.db_id = db_id
+    upstream.base_url = "http://localhost"
+    upstream.provider_type = f"provider-{db_id}"
+    upstream.supports_ehbp = False
+    upstream.prepare_headers = MagicMock(side_effect=lambda h: h)
+    upstream.on_upstream_error_redirect = AsyncMock()
+    upstream.forward_request = AsyncMock(
+        return_value=MagicMock(status_code=status_code, body=b"{}")
+    )
+    return upstream
+
+
+def _make_request(headers: dict[str, str], body: bytes) -> MagicMock:
+    request = MagicMock()
+    request.method = "POST"
+    request.headers = headers
+    request.body = AsyncMock(return_value=body)
+    request.state = MagicMock()
+    request.state.request_id = "req-model-path"
+    return request
+
+
+async def _run_proxy(
+    request: MagicMock,
+    candidates: list[tuple[Any, Any]],
+    path: str = "v1/chat/completions",
+) -> Any:
+    key = ApiKey(hashed_key="mpkey", balance=10_000)
+    reservation = ReservationSnapshot(
+        release_id="model-path-release",
+        key_hash=key.hashed_key,
+        billing_key_hash=key.hashed_key,
+        reserved_msats=1_000,
+    )
+    with (
+        patch.object(proxy_module, "get_candidates", return_value=candidates),
+        patch.object(
+            proxy_module, "get_max_cost_for_model", AsyncMock(return_value=1_000)
+        ),
+        patch.object(
+            proxy_module,
+            "calculate_discounted_max_cost",
+            AsyncMock(return_value=1_000),
+        ),
+        patch.object(proxy_module, "check_token_balance", MagicMock()),
+        patch.object(proxy_module, "get_bearer_token_key", AsyncMock(return_value=key)),
+        patch.object(proxy_module, "pay_for_request", AsyncMock(return_value=1_000)),
+        patch.object(
+            proxy_module,
+            "get_reservation_snapshot",
+            AsyncMock(return_value=reservation),
+        ),
+        patch.object(proxy_module, "revert_pay_for_request", AsyncMock()),
+    ):
+        return await proxy_module.proxy(request, path, session=MagicMock())
+
+
+def test_decode_model_path_round_trips_encode() -> None:
+    selector = decode_model_path(
+        encode_model_path("https://openrouter.ai/api/v1", 7, MODEL_ID, "deepinfra/fp8")
+    )
+    assert selector is not None
+    assert selector.base_url == "https://openrouter.ai/api/v1"
+    assert selector.provider_id == 7
+    assert selector.model_id == MODEL_ID
+    assert selector.endpoint_tag == "deepinfra/fp8"
+
+
+def test_decode_model_path_without_endpoint_has_no_tag() -> None:
+    selector = decode_model_path(encode_model_path("http://localhost", 1, MODEL_ID))
+    assert selector is not None
+    assert selector.endpoint_tag is None
+
+
+@pytest.mark.parametrize(
+    "path",
+    [
+        "",
+        "url=http://localhost&model-id=test-model",
+        "url=http://localhost&provider-id=abc&model-id=test-model",
+        "provider-id=1&model-id=test-model",
+        "url=http://localhost&provider-id=1",
+    ],
+)
+def test_decode_model_path_rejects_malformed_selectors(path: str) -> None:
+    assert decode_model_path(path) is None
+
+
+@pytest.mark.asyncio
+async def test_model_path_routes_to_the_selected_provider() -> None:
+    first, selected = _make_upstream(1), _make_upstream(2)
+    request = _make_request(
+        {
+            "authorization": "Bearer sk-mpkey",
+            "x-routstr-model-path": encode_model_path("http://localhost", 2, MODEL_ID),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+
+    await _run_proxy(request, [(MagicMock(), first), (MagicMock(), selected)])
+
+    selected.forward_request.assert_awaited_once()
+    first.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("status_code", [400, 429, 500, 502, 503])
+async def test_model_path_failure_is_returned_without_falling_back(
+    status_code: int,
+) -> None:
+    selected = _make_upstream(1, status_code=status_code)
+    fallback = _make_upstream(2)
+    request = _make_request(
+        {
+            "authorization": "Bearer sk-mpkey",
+            "x-routstr-model-path": encode_model_path("http://localhost", 1, MODEL_ID),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+
+    response = await _run_proxy(
+        request, [(MagicMock(), selected), (MagicMock(), fallback)]
+    )
+
+    assert response.status_code == status_code
+    selected.forward_request.assert_awaited_once()
+    fallback.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_unknown_provider_in_model_path_is_rejected() -> None:
+    upstream = _make_upstream(1)
+    request = _make_request(
+        {
+            "authorization": "Bearer sk-mpkey",
+            "x-routstr-model-path": encode_model_path("http://localhost", 99, MODEL_ID),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+
+    response = await _run_proxy(request, [(MagicMock(), upstream)])
+
+    assert response.status_code == 404
+    assert json.loads(bytes(response.body))["error"]["type"] == "invalid_model_path"
+    upstream.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_model_path_disagreeing_with_the_body_model_is_rejected() -> None:
+    upstream = _make_upstream(1)
+    request = _make_request(
+        {
+            "authorization": "Bearer sk-mpkey",
+            "x-routstr-model-path": encode_model_path(
+                "http://localhost", 1, "other-model"
+            ),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+
+    response = await _run_proxy(request, [(MagicMock(), upstream)])
+
+    assert response.status_code == 400
+    upstream.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_malformed_model_path_header_is_rejected() -> None:
+    upstream = _make_upstream(1)
+    request = _make_request(
+        {
+            "authorization": "Bearer sk-mpkey",
+            "x-routstr-model-path": "not-a-model-path",
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+
+    response = await _run_proxy(request, [(MagicMock(), upstream)])
+
+    assert response.status_code == 400
+    upstream.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_endpoint_tag_pins_the_upstream_subprovider() -> None:
+    upstream = _make_upstream(1)
+    upstream.base_url = "https://openrouter.ai/api/v1"
+    request = _make_request(
+        {
+            "authorization": "Bearer sk-mpkey",
+            "x-routstr-model-path": encode_model_path(
+                "https://openrouter.ai/api/v1", 1, MODEL_ID, "deepinfra/fp8"
+            ),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+
+    await _run_proxy(request, [(MagicMock(), upstream)])
+
+    forwarded_body = upstream.forward_request.await_args.args[3]
+    assert json.loads(forwarded_body)["provider"] == {
+        "order": ["deepinfra/fp8"],
+        "allow_fallbacks": False,
+    }
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "raw",
+    ["", " ", "url=http://localhost&provider-id=1&model-id=test-model&provider-id=2"],
+)
+async def test_ambiguous_headers_do_not_route(raw: str) -> None:
+    upstream = _make_upstream(1)
+    request = _make_request(
+        {"authorization": "Bearer key", "x-routstr-model-path": raw},
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+    response = await _run_proxy(request, [(MagicMock(), upstream)])
+    assert response.status_code == 400
+    upstream.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_selector_url_must_match_configured_provider() -> None:
+    upstream = _make_upstream(1)
+    request = _make_request(
+        {
+            "authorization": "Bearer key",
+            "x-routstr-model-path": encode_model_path(
+                "http://169.254.169.254", 1, MODEL_ID
+            ),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+    response = await _run_proxy(request, [(MagicMock(), upstream)])
+    assert response.status_code == 404
+    upstream.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_endpoint_pin_cannot_be_stripped_on_retry() -> None:
+    upstream = _make_upstream(1, 400)
+    upstream.base_url = "https://openrouter.ai/api/v1"
+    upstream.forward_request.return_value.body = (
+        b'{"error":{"message":"provider is not supported"}}'
+    )
+    request = _make_request(
+        {
+            "authorization": "Bearer key",
+            "x-routstr-model-path": encode_model_path(
+                upstream.base_url, 1, MODEL_ID, "deepinfra/fp8"
+            ),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+    response = await _run_proxy(request, [(MagicMock(), upstream)])
+    assert response.status_code == 400
+    upstream.forward_request.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "path,handler",
+    [
+        ("v1/chat/completions", "handle_x_cashu"),
+        ("v1/responses", "handle_x_cashu_responses"),
+    ],
+)
+async def test_cashu_receives_endpoint_pinned_body(path: str, handler: str) -> None:
+    upstream = _make_upstream(1)
+    upstream.base_url = "https://openrouter.ai/api/v1"
+    captured: dict[str, Any] = {}
+
+    async def handle(request: Any, *args: Any, **kwargs: Any) -> Any:
+        captured.update(json.loads(kwargs.get("request_body") or await request.body()))
+        return MagicMock(status_code=200)
+
+    setattr(upstream, handler, AsyncMock(side_effect=handle))
+    request = _make_request(
+        {
+            "x-cashu": "test-token",
+            "x-routstr-model-path": encode_model_path(
+                upstream.base_url, 1, MODEL_ID, "deepinfra/fp8"
+            ),
+        },
+        json.dumps(
+            {
+                "model": MODEL_ID,
+                "provider": {
+                    "order": ["other"],
+                    "allow_fallbacks": True,
+                    "data_collection": "deny",
+                },
+            }
+        ).encode(),
+    )
+    await _run_proxy(request, [(MagicMock(), upstream)], path)
+    assert captured["provider"] == {
+        "order": ["deepinfra/fp8"],
+        "allow_fallbacks": False,
+        "data_collection": "deny",
+    }
+
+
+def test_model_path_header_is_not_forwarded() -> None:
+    from routstr.upstream.base import BaseUpstreamProvider
+
+    upstream = BaseUpstreamProvider("http://localhost", "upstream-key")
+    headers = upstream.prepare_headers({"x-routstr-model-path": "private-routing-data"})
+    assert "x-routstr-model-path" not in headers
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("path", ["v1/chat/completions", "v1/responses"])
+@pytest.mark.parametrize("status_code", [200, 429, 502])
+async def test_cashu_pin_reaches_http_transport(path: str, status_code: int) -> None:
+    import httpx
+    from fastapi.responses import Response
+
+    from routstr.upstream.openrouter import OpenRouterUpstreamProvider
+
+    upstream = OpenRouterUpstreamProvider(api_key="upstream-key")
+    upstream.db_id = 1
+    fallback = _make_upstream(2)
+    fallback.handle_x_cashu = AsyncMock()
+    fallback.handle_x_cashu_responses = AsyncMock()
+    sent: list[httpx.Request] = []
+
+    def respond(request: httpx.Request) -> httpx.Response:
+        sent.append(request)
+        return httpx.Response(status_code, json={"error": "test"})
+
+    client = httpx.AsyncClient(transport=httpx.MockTransport(respond))
+    model = MagicMock(id=MODEL_ID, forwarded_model_id=None, canonical_slug=None)
+    request = _make_request(
+        {
+            "x-cashu": "test-token",
+            "x-routstr-model-path": encode_model_path(
+                upstream.base_url, 1, MODEL_ID, "deepinfra/fp8"
+            ),
+        },
+        json.dumps({"model": MODEL_ID, "provider": {"allow_fallbacks": True}}).encode(),
+    )
+    request.query_params = {}
+    with (
+        patch("routstr.upstream.base.httpx.AsyncClient", return_value=client),
+        patch(
+            "routstr.upstream.base.recieve_token",
+            AsyncMock(return_value=(1000, "msat", "https://mint.test")),
+        ) as redeem,
+        patch("routstr.upstream.base.store_cashu_transaction", AsyncMock()),
+        patch.object(upstream, "send_refund", AsyncMock(return_value="refund")),
+        patch.object(
+            upstream,
+            "handle_x_cashu_chat_completion",
+            AsyncMock(return_value=Response(status_code=200)),
+        ),
+        patch.object(
+            upstream,
+            "handle_x_cashu_responses_completion",
+            AsyncMock(return_value=Response(status_code=200)),
+        ),
+    ):
+        response = await _run_proxy(
+            request, [(model, upstream), (model, fallback)], path
+        )
+    assert response.status_code == status_code
+    redeem.assert_awaited_once()
+    assert len(sent) == 1
+    assert sent[0].url.host == "openrouter.ai"
+    assert json.loads(sent[0].content)["provider"] == {
+        "order": ["deepinfra/fp8"],
+        "allow_fallbacks": False,
+    }
+    assert "x-routstr-model-path" not in sent[0].headers
+    fallback.handle_x_cashu.assert_not_awaited()
+    fallback.handle_x_cashu_responses.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_unpinned_requests_still_fall_back() -> None:
+    first, fallback = _make_upstream(1, 502), _make_upstream(2)
+    request = _make_request(
+        {"authorization": "Bearer key"}, json.dumps({"model": MODEL_ID}).encode()
+    )
+    response = await _run_proxy(
+        request, [(MagicMock(), first), (MagicMock(), fallback)]
+    )
+    assert response.status_code == 200
+    first.forward_request.assert_awaited_once()
+    fallback.forward_request.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_pinned_exception_does_not_fall_back() -> None:
+    from routstr.core.exceptions import UpstreamError
+
+    first, fallback = _make_upstream(1), _make_upstream(2)
+    first.forward_request.side_effect = UpstreamError("unavailable", status_code=503)
+    request = _make_request(
+        {
+            "authorization": "Bearer key",
+            "x-routstr-model-path": encode_model_path(first.base_url, 1, MODEL_ID),
+        },
+        json.dumps({"model": MODEL_ID}).encode(),
+    )
+    response = await _run_proxy(
+        request, [(MagicMock(), first), (MagicMock(), fallback)]
+    )
+    assert response.status_code == 503
+    first.forward_request.assert_awaited_once()
+    fallback.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "path,is_ehbp", [("v1/messages", False), ("v1/chat/completions", True)]
+)
+async def test_unsupported_endpoint_pins_fail_before_payment(
+    path: str, is_ehbp: bool
+) -> None:
+    upstream = _make_upstream(1)
+    upstream.base_url = "https://openrouter.ai/api/v1"
+    headers = {
+        "x-cashu": "test-token",
+        "x-routstr-model-path": encode_model_path(
+            upstream.base_url, 1, MODEL_ID, "deepinfra/fp8"
+        ),
+    }
+    if is_ehbp:
+        headers.update({"ehbp-encapsulated-key": "sealed", "x-routstr-model": MODEL_ID})
+    request = _make_request(headers, json.dumps({"model": MODEL_ID}).encode())
+    with (
+        patch.object(proxy_module, "check_token_balance") as payment,
+        patch.object(
+            proxy_module, "get_candidates", return_value=[(MagicMock(), upstream)]
+        ),
+    ):
+        response = await proxy_module.proxy(request, path, MagicMock())
+    assert response.status_code == 400
+    assert json.loads(response.body)["error"]["type"] == "unsupported_request"
+    payment.assert_not_called()
+    upstream.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("cashu", [False, True])
+async def test_ehbp_pin_does_not_fall_back(cashu: bool) -> None:
+    from routstr.core.exceptions import UpstreamError
+
+    selected, fallback = _make_upstream(1), _make_upstream(2)
+    selected.supports_ehbp = fallback.supports_ehbp = True
+    headers = {
+        "ehbp-encapsulated-key": "sealed",
+        "x-routstr-model": MODEL_ID,
+        "x-routstr-model-path": encode_model_path(selected.base_url, 1, MODEL_ID),
+    }
+    headers.update({"x-cashu": "token"} if cashu else {"authorization": "Bearer key"})
+    request = _make_request(headers, b"encrypted-body")
+    handler = "forward_ehbp_x_cashu_request" if cashu else "forward_ehbp_request"
+    with patch.object(
+        proxy_module,
+        handler,
+        AsyncMock(side_effect=UpstreamError("unavailable", status_code=503)),
+    ) as forward:
+        response = await _run_proxy(
+            request, [(MagicMock(), selected), (MagicMock(), fallback)]
+        )
+    assert response.status_code == 503
+    forward.assert_awaited_once()
+    assert forward.await_args is not None
+    assert forward.await_args.kwargs["upstream"] is selected
+
+
+@pytest.mark.asyncio
+async def test_duplicate_header_fields_are_rejected() -> None:
+    from starlette.datastructures import Headers
+
+    selected = _make_upstream(1)
+    route = encode_model_path(selected.base_url, 1, MODEL_ID).encode()
+    request = _make_request({}, json.dumps({"model": MODEL_ID}).encode())
+    request.headers = Headers(
+        raw=[
+            (b"authorization", b"Bearer key"),
+            (b"x-routstr-model-path", route),
+            (b"x-routstr-model-path", route),
+        ]
+    )
+    response = await _run_proxy(request, [(MagicMock(), selected)])
+    assert response.status_code == 400
+    selected.forward_request.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_attestation_does_not_ignore_model_path() -> None:
+    request = _make_request(
+        {"x-routstr-model-path": encode_model_path("http://localhost", 1, MODEL_ID)},
+        b"",
+    )
+    request.method = "GET"
+    with patch.object(proxy_module, "_select_unauthenticated_get_upstreams") as select:
+        response = await _run_proxy(request, [], "attestation")
+    assert response.status_code == 400
+    select.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_model_fallback_list_is_rejected_when_pinned() -> None:
+    selected = _make_upstream(1)
+    request = _make_request(
+        {
+            "authorization": "Bearer key",
+            "x-routstr-model-path": encode_model_path(selected.base_url, 1, MODEL_ID),
+        },
+        json.dumps({"model": MODEL_ID, "models": ["other-model"]}).encode(),
+    )
+    response = await _run_proxy(request, [(MagicMock(), selected)])
+    assert response.status_code == 400
+    selected.forward_request.assert_not_awaited()