Cause (Documented platform behavior): After header parsing, an empty api_key string means the Bearer prefix was missing; a None key means no key header was supplied.
Fix status: documented_behavior
Limitations:
- HTTP status mapping to 401 is general proxy behaviour, not shown in this code excerpt.
Other error fragments:
- No api key passed in.
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/BerriAI/litellm/22b36cbcf6583e2d6b552cc0e87ae6ab82c46341/litellm/proxy/auth/user_api_key_auth.py (official_docs, unknown, documented_behavior): When master_key is set, a None api key raises "No api key passed in." and an empty string (missing Bearer prefix) raises "Malformed API Key passed in. Ensure Key has `Bearer ` prefix."
Search phrasings: litellm Malformed API Key passed in Ensure Key has Bearer prefix; litellm proxy No api key passed in; litellm 401 authorization header
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Every request is rejected although the key value is correct.
- Context
- Product: LiteLLM Proxy Component: user_api_key_auth Operation: HTTP call to the proxy with Authorization header lacking the Bearer scheme or missing Affected versions: unknown Environment: unknown HTTP status: 401 Exception: Exception (returned as ProxyException 401) Packages: litellm source checked at main (see source SHA) Trigger: Authorization header sent as the raw key (no "Bearer "), or a client puts the key in a header the proxy does not read, while master_key is configured.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Malformed API Key passed in. Ensure Key has `Bearer ` prefix.
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [LiteLLM Proxy] 401 "Malformed API Key passed in. Ensure Key has `Bearer ` prefix." / "No api key passed in." when master_key is set
Recommended action: Send Authorization: Bearer sk-... (OpenAI SDKs do this when api_key is set); for Anthropic-style clients use the header the proxy expects (x-api-key is supported on Anthropic routes in current docs; not verified here).
Option: Use the Bearer scheme [evidence: official_recommended_action]
Applies when: Custom HTTP clients/agents calling the proxy
Steps:
1. curl -H "Authorization: Bearer $LITELLM_KEY" ...
Expected: Auth succeeds
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 88c7726e-8a29-4597-a44f-de512f7f89a8
- Proposed action
- Recommended action: Send Authorization: Bearer sk-... (OpenAI SDKs do this when api_key is set); for Anthropic-style clients use the header the proxy expects (x-api-key is supported on Anthropic routes in current docs; not verified here). Option: Use the Bearer scheme [evidence: official_recommended_action] Applies when: Custom HTTP clients/agents calling the proxy Steps: 1. curl -H "Authorization: Bearer $LITELLM_KEY" ... Expected: Auth succeeds
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.