Refactor: Centralize call_type Literal definitions into TypeAliases

[yashwantbezawada]

Problem

The call_type parameter's Literal type hint was duplicated across 36+ files (CustomLogger subclasses), causing:

1. DRY violation: Adding new call types (e.g., aembedding) required editing 36+ files manually
2. Liskov Substitution Principle violation: Some subclasses had more restrictive types than the base class, causing MyPy errors
3. Inconsistencies: Between CallTypes enum (singular: "embedding") and CustomLogger Literals (plural: "embeddings")
4. Maintenance burden: PR fix: Use valid CallTypes enum value in embeddings endpoint #16328 couldn't update all files to add "aembedding" support

Solution

Created centralized TypeAliases in litellm/types/callbacks.py:

• PreCallHookCallType: For async_pre_call_hook methods
• ModerationHookCallType: For async_moderation_hook methods

Updated 36 files to use these TypeAliases instead of duplicating Literal definitions.

Impact

Code reduction: -439 lines (603 deletions, 164 insertions)

Files changed:

• ✅ New: litellm/types/callbacks.py (centralized TypeAlias definitions)
• ✅ Updated: litellm/integrations/custom_logger.py (base class)
• ✅ Updated: 35 CustomLogger subclass files across:
  • litellm/proxy/guardrails/guardrail_hooks/ (24 files)
  • litellm/proxy/hooks/ (4 files)
  • litellm/proxy/example_config_yaml/ (2 files)
  • enterprise/ (6 files)

Benefits

✅ Single source of truth: All call_type definitions in one place
✅ Easier maintenance: Adding new call types requires editing 1 file instead of 36+
✅ Fixes LSP violations: All subclasses now accept the same types as base class
✅ Consistent type checking: MyPy will catch type errors consistently
✅ Adds aembedding support: Async embeddings now supported (from PR #16328)
✅ Future-proof: New call types can be added without touching 36+ files

Testing

This is a pure type system refactoring with no runtime changes:

• Type hints in Python are not enforced at runtime (they're just hints for IDEs/MyPy)
• All existing behavior is preserved
• CI will validate MyPy type checking

Related Issues

Fixes #16362
Related: #16240 (guardrail validation bug), #16328 (aembedding PR)

---

Checklist:

• Created centralized TypeAlias definitions
• Updated base class (CustomLogger)
• Updated all 36 subclass files
• Verified no remaining duplicate Literals
• Added aembedding to both TypeAliases
• Commit message follows conventional commits format

[vercel]

@yashwantbezawada is attempting to deploy a commit to the CLERKIEAI Team on Vercel.

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[krrishdholakia]

i think i already fixed a lot of this on main @yashwantbezawada

[yashwantbezawada]

Thanks for the heads up! Just checked and I see issue #16362 was already fixed via commit db378c4 using CallTypesLiteral from litellm.types.utils.

Closing this PR since the refactoring has been handled. Thanks for reviewing!