fix(proxy/hooks): populate llm_provider on budget/iterations 429s

Final batch of internal raise sites — the user/session-budget and
max-iterations hooks. Same pattern: resolve data['model'] once at
raise time, attach to ProxyHTTPRateLimitError so Prometheus and
observability callbacks can attribute the 429.

Hooks updated:
* max_budget_limiter (per-user max_budget exceeded)
* max_iterations_limiter (per-session agent iteration cap)
* max_budget_per_session_limiter (per-session dollar cap)

All three fall back to llm_provider='litellm_proxy' when data['model']
is missing or unparseable. Drops the now-unused HTTPException import
from each module.

Co-authored-by: Mateo Wang <mateo-berri@users.noreply.github.com>

litellm/proxy/hooks/max_budget_limiter.py

@@ -5,6 +5,10 @@ from litellm._logging import verbose_proxy_logger
 from litellm.caching.caching import DualCache
 from litellm.integrations.custom_logger import CustomLogger
 from litellm.proxy._types import UserAPIKeyAuth
+from litellm.proxy.hooks.rate_limiter_utils import (
+    ProxyHTTPRateLimitError,
+    resolve_llm_provider_for_rate_limit,
+)
 
 
 class _PROXY_MaxBudgetLimiter(CustomLogger):
@@ -63,7 +67,15 @@ class _PROXY_MaxBudgetLimiter(CustomLogger):
 
             # CHECK IF REQUEST ALLOWED
             if curr_spend >= max_budget:
-                raise HTTPException(status_code=429, detail="Max budget limit reached.")
+                resolved_model, llm_provider = resolve_llm_provider_for_rate_limit(
+                    data.get("model") if data else None
+                )
+                raise ProxyHTTPRateLimitError(
+                    status_code=429,
+                    detail="Max budget limit reached.",
+                    model=resolved_model,
+                    llm_provider=llm_provider,
+                )
         except HTTPException as e:
             raise e
         except Exception as e:

litellm/proxy/hooks/max_budget_per_session_limiter.py

@@ -17,12 +17,14 @@ Follows the same pattern as max_iterations_limiter.py.
 import os
 from typing import TYPE_CHECKING, Any, Optional, Union
 
-from fastapi import HTTPException
-
 from litellm import DualCache
 from litellm._logging import verbose_proxy_logger
 from litellm.integrations.custom_logger import CustomLogger
 from litellm.proxy._types import UserAPIKeyAuth
+from litellm.proxy.hooks.rate_limiter_utils import (
+    ProxyHTTPRateLimitError,
+    resolve_llm_provider_for_rate_limit,
+)
 
 if TYPE_CHECKING:
     from litellm.proxy.utils import InternalUsageCache as _InternalUsageCache
@@ -112,13 +114,18 @@ class _PROXY_MaxBudgetPerSessionHandler(CustomLogger):
         )
 
         if current_spend >= max_budget:
-            raise HTTPException(
+            resolved_model, llm_provider = resolve_llm_provider_for_rate_limit(
+                data.get("model") if data else None
+            )
+            raise ProxyHTTPRateLimitError(
                 status_code=429,
                 detail=(
                     f"Session budget exceeded for session {session_id}. "
                     f"Current spend: ${current_spend:.4f}, "
                     f"max_budget_per_session: ${max_budget:.2f}."
                 ),
+                model=resolved_model,
+                llm_provider=llm_provider,
             )
 
         return None

litellm/proxy/hooks/max_iterations_limiter.py

@@ -13,12 +13,14 @@ Follows the same pattern as parallel_request_limiter_v3.py.
 import os
 from typing import TYPE_CHECKING, Any, Optional, Union
 
-from fastapi import HTTPException
-
 from litellm import DualCache
 from litellm._logging import verbose_proxy_logger
 from litellm.integrations.custom_logger import CustomLogger
 from litellm.proxy._types import UserAPIKeyAuth
+from litellm.proxy.hooks.rate_limiter_utils import (
+    ProxyHTTPRateLimitError,
+    resolve_llm_provider_for_rate_limit,
+)
 
 if TYPE_CHECKING:
     from litellm.proxy.utils import InternalUsageCache as _InternalUsageCache
@@ -116,12 +118,17 @@ class _PROXY_MaxIterationsHandler(CustomLogger):
         current_count = await self._increment_and_get(cache_key)
 
         if current_count > max_iterations:
-            raise HTTPException(
+            resolved_model, llm_provider = resolve_llm_provider_for_rate_limit(
+                data.get("model") if data else None
+            )
+            raise ProxyHTTPRateLimitError(
                 status_code=429,
                 detail=(
                     f"Max iterations exceeded for session {session_id}. "
                     f"Current count: {current_count}, max_iterations: {max_iterations}."
                 ),
+                model=resolved_model,
+                llm_provider=llm_provider,
             )
 
         verbose_proxy_logger.debug(