feat: add User-Agent customization support#19881
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Sameerlite merged 6 commits intoBerriAI:mainfrom Feb 2, 2026
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Add litellm.disable_default_user_agent global flag to control whether the automatic User-Agent header is injected into HTTP requests.
Modify http_handler.py and httpx_handler.py to check the disable_default_user_agent flag and return empty headers when disabled. This allows users to override the User-Agent header completely.
Add 8 tests covering: - Default User-Agent behavior - Disabling default User-Agent - Custom User-Agent via extra_headers - Environment variable support - Async handler support - Override without disabling - Claude Code use case - Backwards compatibility
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Summary
This PR lets you fully override LiteLLM’s default outbound
User-Agentby settingLITELLM_USER_AGENT.Problem
Some Anthropic/Claude credentials are only allowed when the request
User-Agentmatches an allowlist (e.g.Claude Code). LiteLLM currently sendsUser-Agent: litellm/{version}, which can trigger the block.Fix
LITELLM_USER_AGENTis set, LiteLLM sends exactly that value asUser-Agent(nolitellm/{version}appended).litellm/{version}).Usage
LITELLM_USER_AGENT="Claude Code"User-Agentstill works via request headers and will override the client default.Tests
tests/test_litellm/llms/custom_httpx/test_http_handler.pytests/test_litellm/proxy/auth/test_handle_jwt.pytests/test_litellm/llms/databricks/test_databricks_partner_integration.pytests/test_litellm/litellm_core_utils/test_litellm_logging.pyFixes #19017