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Project	Deployment	Actions	Updated (UTC)
litellm	Ready	Preview, Comment	Mar 31, 2026 2:30am

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Merging this PR will not alter performance

✅ 16 untouched benchmarks

_{Comparing litellm_/dazzling-jackson (3308fb9) with main (632beb0)}

Greptile Summary

This PR fixes a real bug where callable failure callbacks (both sync and async) were silently skipped whenever customLogger — a module-level global initialized to None — had not yet been set by a prior success path or set_callbacks. The fix applies on-demand lazy initialization of customLogger in both the sync and async failure handlers, matching the pattern already present in the async success handler.

Key changes:

• failure_handler (sync): replaced if callable(callback) and customLogger is not None with if callable(callback): + lazy customLogger = CustomLogger() guard
• async_failure_handler (async): same change applied

Remaining inconsistencies (not introduced by this PR):

• pre_call (line 1077) and the sync success handler (line 2421) still use the old customLogger is not None pattern, which can silently skip callable callbacks under the same conditions this PR addresses
• No test files were modified in this PR — the referenced passing tests (test_call_router_callbacks_on_failure) are separate evidence of correctness

Confidence Score: 4/5

Safe to merge; the targeted fix is correct, but two analogous silent-skip sites remain unfixed in pre_call and the sync success handler

The fix is correct and directly addresses the stated bug with the appropriate lazy-init pattern. Score is 4 rather than 5 because two peer code paths (pre_call at line 1077 and sync success at line 2421) retain the same customLogger is not None pattern that this PR was created to eliminate, leaving them susceptible to the same class of silent callback skipping.

litellm/litellm_core_utils/litellm_logging.py — lines 1077 and 2421 still use the unfixed pattern

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Request fails] --> B[failure_handler / async_failure_handler]
    B --> C{Iterate callbacks}
    C --> D{isinstance CustomLogger?}
    D -- Yes --> E[callback.log_failure_event / async_log_failure_event]
    D -- No --> F{callable callback?}
    F -- No --> C
    F -- Yes --> G{customLogger is None?}
    G -- Yes BEFORE FIX --> H[❌ Silent skip]
    G -- Yes AFTER FIX --> I[customLogger = CustomLogger]
    I --> J[customLogger.log_event / async_log_event]
    G -- No --> J
    E --> C
    J --> C

    style H fill:#f44,color:#fff
    style I fill:#4a4,color:#fff
    style J fill:#4a4,color:#fff

_{Reviews (2): Last reviewed commit: "Merge remote-tracking branch 'origin/mai..." | Re-trigger Greptile}

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