fix(mcp): set LITELLM_MASTER_KEY env var in e2e tests

[jquinter]

Summary

• Fixes MCP e2e test failures where all tests fail with "User not allowed to call this tool"
• Root cause: The FastAPI lifespan event (proxy_startup_event) re-reads master_key from the LITELLM_MASTER_KEY env var, overriding whatever initialize() set from the YAML config. Without this env var set, master_key becomes None, causing all users to be treated as INTERNAL_USER with no MCP server access.
• Fix: Set LITELLM_MASTER_KEY=sk-1234 in the session-scoped test fixture so the lifespan event preserves the master key.

Root Cause Analysis

1. _initialize_proxy() calls initialize(config=config_path) which sets master_key = "sk-1234" from the YAML config
2. uvicorn.Server.serve() triggers the FastAPI lifespan handler proxy_startup_event
3. proxy_startup_event at line 768 does master_key = get_secret_str("LITELLM_MASTER_KEY") — since the env var isn't set, this returns None, wiping out the previously configured master key
4. All subsequent requests see master_key is None → auth returns user_role=INTERNAL_USER → get_allowed_mcp_servers() returns [] → 403 error

Test plan

• All 4 MCP e2e tests pass locally (pytest tests/mcp_tests/test_proxy_mcp_e2e.py)

Closes #22330

🤖 Generated with Claude Code

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
litellm	Building	Preview, Comment	Feb 28, 2026 5:49pm

[greptile-apps]

Greptile Summary

Fixes MCP e2e test failures by setting the LITELLM_MASTER_KEY env var in the session-scoped test fixture. The FastAPI lifespan handler (proxy_startup_event) re-reads master_key from the env var, overriding the value set by initialize() from the YAML config. Without the env var, master_key becomes None, causing all users to be treated as INTERNAL_USER with no MCP server access.

• Sets LITELLM_MASTER_KEY in the _clear_proxy_database_env fixture, matching the value in the test YAML config and the PROXY_AUTHORIZATION_HEADER constant
• Root cause verified: proxy_server.py:768 calls get_secret_str("LITELLM_MASTER_KEY") which returns None when the env var is not set
• No issues found in this change

Confidence Score: 5/5

• This PR is safe to merge — it's a minimal, well-targeted test fixture fix with no production code changes.
• The change is a single line addition to a test fixture that sets an environment variable. The value (sk-1234) is consistent with the existing YAML config and auth header. The root cause analysis is thorough and verified. No production code is modified.
• No files require special attention.

Important Files Changed

Filename	Overview
tests/mcp_tests/test_proxy_mcp_e2e.py	Adds LITELLM_MASTER_KEY env var to the session-scoped fixture to prevent proxy_startup_event from resetting the master key to None. Value is consistent with YAML config and auth header constant.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Test Fixture: _clear_proxy_database_env] --> B[Set LITELLM env var]
    B --> C[initialize from YAML config]
    C --> D[uvicorn.Server.serve triggers lifespan]
    D --> E[proxy_startup_event reads env var]
    E --> F{Env var set?}
    F -->|Yes - After Fix| G[Auth credentials preserved]
    F -->|No - Before Fix| H[Auth credentials reset to None]
    G --> I[MCP requests succeed with 200]
    H --> J[All users treated as INTERNAL_USER]
    J --> K[MCP access denied with 403]

Loading

_{Last reviewed commit: 456ad50}

[greptile-apps]

_{1 file reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}

[jquinter]

CI Failure Analysis: test_sse_mcp_handler_mock

The failing test tests/mcp_tests/test_mcp_server.py::test_sse_mcp_handler_mock is not related to this PR.

• This PR only modifies tests/mcp_tests/test_proxy_mcp_e2e.py (adds 4 lines to set LITELLM_MASTER_KEY env var)
• The failing test is in a completely different file (test_mcp_server.py)
• The test passes on both main and this branch when run locally
• This appears to be a flaky test (likely a race condition in the mock setup)

Retrying CI.