Implementation:Wandb Weave Implicit Patch

Knowledge Sources	Wandb Weave Weave Docs
Domains	Instrumentation, Monkey_Patching
Last Updated	2026-02-14 00:00 GMT

Overview

Concrete tool for automatically patching LLM provider SDKs at initialization provided by the Wandb Weave library.

Description

implicit_patch() scans sys.modules for known integration module names and applies tracing patches. register_import_hook() installs a WeaveImportHook (MetaPathFinder) at sys.meta_path[0] that intercepts future imports and patches them via PatchingLoader.

The INTEGRATION_MODULE_MAPPING dict maps 25+ module names to their patch functions, supporting OpenAI, Anthropic, Mistral, Cohere, Google GenAI, Groq, LiteLLM, HuggingFace, LangChain, LlamaIndex, DSPy, CrewAI, and more.

Usage

These functions are called automatically by weave.init(). Call unregister_import_hook() to disable automatic patching of future imports.

Code Reference

Source Location

Repository: wandb/weave
File: weave/integrations/patch.py
Lines: L438-496 (implicit_patch, register_import_hook, unregister_import_hook)
Lines: L306-334 (INTEGRATION_MODULE_MAPPING)
Lines: L337-419 (WeaveImportHook, PatchingLoader)

Signature

def implicit_patch() -> None:
    """Check sys.modules and patch any already-imported integrations.
    Called during weave.init() to enable implicit patching.
    """

def register_import_hook() -> None:
    """Register import hook to auto-patch integrations imported after weave.init().
    Respects the implicitly_patch_integrations setting.
    """

def unregister_import_hook() -> None:
    """Unregister the import hook (for testing or cleanup)."""

class WeaveImportHook(MetaPathFinder):
    """Import hook that auto-patches supported integrations when imported."""
    def find_spec(self, fullname, path, target=None) -> None | ModuleSpec: ...

class PatchingLoader:
    """Loader wrapper that patches an integration after it's imported."""
    def __init__(self, original_loader, module_name: str) -> None: ...
    def exec_module(self, module): ...

Import

from weave.integrations.patch import implicit_patch, register_import_hook, unregister_import_hook

I/O Contract

Inputs

Name	Type	Required	Description
(none)	—	—	Reads from sys.modules and INTEGRATION_MODULE_MAPPING

Outputs

Name	Type	Description
side_effect	patch	Already-imported LLM libraries are monkey-patched
side_effect	hook	WeaveImportHook installed at sys.meta_path[0]

Usage Examples

Automatic (via weave.init)

import openai  # Already imported before init
import weave

# implicit_patch() will detect openai in sys.modules and patch it
# register_import_hook() will catch any future imports
client = weave.init("my-team/my-project")

# OpenAI calls are now automatically traced
response = openai.chat.completions.create(
    model="gpt-4", messages=[{"role": "user", "content": "Hello"}]
)

Related Pages

Implements Principle

Principle:Wandb_Weave_Auto_Patching

Requires Environment

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Principle

Implementation

Heuristic

Environment