fix(budget-limiter): fall back to logging payload for custom_llm_provider

`/v1/chat/completions` injects `custom_llm_provider` into `litellm_params`, but
`/v1/messages` and `/v1/embeddings` do not. `RouterBudgetLimiting.async_log_success_event`
read it only from `litellm_params` and raised `ValueError("custom_llm_provider is
required")` before incrementing any spend counter, so provider budgets never
accrued on those routes. Deployment-level `max_budget` sits below the same guard,
so it was silently disabled too.

The standard logging payload already carries `custom_llm_provider` for every
route -- it is built from the top-level call details rather than from
`litellm_params` -- so fall back to it. `litellm_params` keeps precedence, and
the `ValueError` is preserved when neither source has a provider.

Fixes #26701

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015ftJdiLtpTbjoZaNuqX6dq

litellm/router_strategy/budget_limiter.py

@@ -408,7 +408,15 @@ class RouterBudgetLimiting(CustomLogger):
 
         response_cost: Final[float] = standard_logging_payload.get("response_cost", 0)
         model_id: Final[str] = str(standard_logging_payload.get("model_id", ""))
-        custom_llm_provider: Final[str] = kwargs.get("litellm_params", {}).get("custom_llm_provider", None)
+        # `/v1/chat/completions` injects `custom_llm_provider` into `litellm_params`,
+        # but `/v1/messages` and `/v1/embeddings` do not. The standard logging payload
+        # carries it for every route (it is built from the top-level call details), so
+        # fall back to that instead of raising before any spend counter is incremented.
+        # See https://github.com/BerriAI/litellm/issues/26701.
+        custom_llm_provider: Final[str | None] = (
+            kwargs.get("litellm_params", {}).get("custom_llm_provider", None)
+            or standard_logging_payload["custom_llm_provider"]
+        )
         if custom_llm_provider is None:
             raise ValueError("custom_llm_provider is required")
 

tests/test_litellm/router_strategy/test_budget_limiter_provider_derivation.py

@@ -0,0 +1,125 @@
+"""
+Regression tests for #26701.
+
+`/v1/chat/completions` injects `custom_llm_provider` into `litellm_params`, but
+`/v1/messages` and `/v1/embeddings` do not. Before the fix,
+`RouterBudgetLimiting.async_log_success_event` raised
+`ValueError("custom_llm_provider is required")` before incrementing any spend
+counter, so provider budgets (and deployment-level `max_budget`, which sits
+below the same guard) silently never accrued on those routes.
+
+The standard logging payload carries `custom_llm_provider` for every route --
+it is built from the top-level call details rather than from `litellm_params` --
+so the limiter falls back to it.
+"""
+
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from litellm.caching.caching import DualCache
+from litellm.router_strategy.budget_limiter import RouterBudgetLimiting
+
+
+def _make_limiter() -> RouterBudgetLimiting:
+    return RouterBudgetLimiting(
+        dual_cache=DualCache(),
+        provider_budget_config={
+            "anthropic": {"budget_limit": 5.0, "time_period": "24h"},
+            "openai": {"budget_limit": 5.0, "time_period": "24h"},
+        },
+    )
+
+
+def _payload(provider: str | None) -> dict:
+    return {
+        "response_cost": 0.001,
+        "model_id": "deployment-abc123",
+        "custom_llm_provider": provider,
+    }
+
+
+def _patched(limiter: RouterBudgetLimiting):
+    """Isolate the provider-budget path from deployment/tag budget lookups."""
+    return (
+        patch.object(limiter, "_increment_spend_for_key", new_callable=AsyncMock),
+        patch.object(limiter, "_get_budget_config_for_deployment", return_value=None),
+        patch.object(limiter, "_get_budget_config_for_tag", return_value=None),
+    )
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    ("route", "model", "provider"),
+    [
+        ("/v1/messages", "anthropic/claude-haiku-4-5-20251001", "anthropic"),
+        ("/v1/embeddings", "openai/text-embedding-3-small", "openai"),
+    ],
+)
+async def test_provider_falls_back_to_logging_payload(route: str, model: str, provider: str):
+    """
+    Routes that omit `custom_llm_provider` from `litellm_params` must still
+    accrue spend, using the provider recorded on the standard logging payload.
+    """
+    limiter = _make_limiter()
+    kwargs = {
+        "model": model,
+        # `litellm_params` on these routes carries no `custom_llm_provider`.
+        "litellm_params": {"model": model},
+        "standard_logging_object": _payload(provider),
+    }
+
+    increment, _dep, _tag = _patched(limiter)
+    with increment as mock_increment, _dep, _tag:
+        # Before the fix this raised ValueError before any counter moved.
+        await limiter.async_log_success_event(kwargs=kwargs, response_obj=None, start_time=None, end_time=None)
+
+    assert mock_increment.await_count >= 1, f"{route}: provider spend was never incremented"
+    spend_keys = [call.kwargs.get("spend_key", "") for call in mock_increment.await_args_list]
+    assert any(f"provider_spend:{provider}:" in key for key in spend_keys), (
+        f"{route}: expected a provider_spend key for {provider!r}, got {spend_keys}"
+    )
+
+
+@pytest.mark.asyncio
+async def test_litellm_params_provider_takes_precedence():
+    """
+    `/v1/chat/completions` already sets `custom_llm_provider` in `litellm_params`;
+    that value must keep winning over the payload so behaviour is unchanged.
+    """
+    limiter = _make_limiter()
+    kwargs = {
+        "model": "claude-haiku-direct",
+        "litellm_params": {
+            "model": "anthropic/claude-haiku-4-5-20251001",
+            "custom_llm_provider": "anthropic",
+        },
+        # Deliberately disagrees, to prove precedence rather than coincidence.
+        "standard_logging_object": _payload("openai"),
+    }
+
+    increment, _dep, _tag = _patched(limiter)
+    with increment as mock_increment, _dep, _tag:
+        await limiter.async_log_success_event(kwargs=kwargs, response_obj=None, start_time=None, end_time=None)
+
+    spend_keys = [call.kwargs.get("spend_key", "") for call in mock_increment.await_args_list]
+    assert any("provider_spend:anthropic:" in key for key in spend_keys), spend_keys
+    assert not any("provider_spend:openai:" in key for key in spend_keys), spend_keys
+
+
+@pytest.mark.asyncio
+async def test_missing_provider_everywhere_still_raises():
+    """
+    With no provider in `litellm_params` and none on the payload there is
+    nothing to attribute spend to; the existing contract must be preserved.
+    """
+    limiter = _make_limiter()
+    kwargs = {
+        "model": "totally-unresolvable-garbage-xyz-123",
+        "litellm_params": {},
+        "standard_logging_object": _payload(None),
+    }
+
+    increment, _dep, _tag = _patched(limiter)
+    with increment, _dep, _tag, pytest.raises(ValueError, match="custom_llm_provider is required"):
+        await limiter.async_log_success_event(kwargs=kwargs, response_obj=None, start_time=None, end_time=None)