Defer `langsmith` and tracer imports in `callbacks/manager.py` and
`runnables/config.py` from module-level to function-level.
These imports pull in the full `langsmith` package (~132ms) at import
time but are only used inside `_configure()`, `trace_as_chain_group()`,
`_set_config_context()`, and `set_config_context()` — none of which run
during module initialization.
## Summary
- Replace `claude-3-5-haiku-20241022` and `claude-3-7-sonnet-20250219`
with `claude-haiku-4-5-20251001` and `claude-sonnet-4-5-20250929`
respectively
- Both models were retired by Anthropic on February 19, 2026, causing
all anthropic integration tests to fail
- Updates integration tests, a unit test, and docstring examples in
`langchain-core`
See:
https://platform.claude.com/docs/en/docs/resources/model-deprecations
it looks scary but i promise it is not
improving documentation consistency across core. primarily update
docstrings and comments for better formatting, readability, and
accuracy, as well as add minor clarifications and formatting
improvements to user-facing documentation.
## Summary
- Adds explicit `tags: list[str] | None = None` parameter to sync
`LLMManagerMixin` methods
- Aligns sync methods with their async counterparts in
`AsyncCallbackHandler`
## Changes
Added `tags` parameter to:
- `on_llm_new_token`
- `on_llm_end`
- `on_llm_error`
## Why
- Sync handlers receive `tags` via `**kwargs`, but it was undocumented
in the method signature
- Async handlers already have `tags` explicitly documented
- This improves IDE autocompletion and type hints for sync handlers
Closes#34720🤖 Generated with [Claude Code](https://claude.ai/claude-code)
Co-authored-by: skyvanguard <skyvanguard@gmail.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
## Description
Fixed `BaseCallbackManager.merge()` method to correctly preserve the
distinction between `handlers` and `inheritable_handlers` during merge
operations.
Previously, the merge method was using `add_handler()` which incorrectly
added handlers to both lists when `inherit=True`, causing
cross-contamination between regular and inheritable handlers.
The fix directly passes the combined handler lists to the constructor
instead of using `add_handler()`, ensuring proper separation is
maintained.
## Issue
Fixes#32028
## Dependencies
None
## Testing
- Modified existing test `test_merge_preserves_handler_distinction()` to
verify handlers remain properly separated after merge
## Checklist
- [x] **Breaking Changes**: No breaking changes - only fixes incorrect
behavior
- [x] **Type Hints**: All functions have complete type annotations
- [x] **Tests**: Fix is fully tested with existing unit test
- [x] **Security**: No security implications
- [x] **Documentation**: No documentation changes needed - bug fix only
- [x] **Code Quality**: Passes lint and format checks
- [x] **Commit Message**: Follows Conventional Commits format
---------
Co-authored-by: Mason Daugherty <mason@langchain.dev>
* Fixed a few TC
* Added a few Pydantic classes to
`flake8-type-checking.runtime-evaluated-base-classes` (not as much as I
would have imagined)
* Added a few `noqa: TC`
* Activated TC rules
The `@shielded` decorator in async callback managers was not preserving
context variables, breaking OpenTelemetry instrumentation and other
context-dependent functionality.
## Problem
When using async callbacks with the `@shielded` decorator (applied to
methods like `on_llm_end`, `on_chain_end`, etc.), context variables were
not being preserved across the shield boundary. This caused issues with:
- OpenTelemetry span context propagation
- Other instrumentation that relies on context variables
- Inconsistent context behavior between sync and async execution
The issue was reproducible with:
```python
from contextvars import copy_context
import asyncio
from langgraph.graph import StateGraph
# Sync case: context remains consistent
print("SYNC")
print(copy_context()) # Same object
graph.invoke({"result": "init"})
print(copy_context()) # Same object
# Async case: context was inconsistent (before fix)
print("ASYNC")
asyncio.run(graph.ainvoke({"result": "init"}))
print(copy_context()) # Different object than expected
```
## Root Cause
The original `shielded` decorator implementation:
```python
async def wrapped(*args: Any, **kwargs: Any) -> Any:
return await asyncio.shield(func(*args, **kwargs))
```
Used `asyncio.shield()` directly without preserving the current
execution context, causing context variables to be lost.
## Solution
Modified the `shielded` decorator to:
1. Capture the current context using `copy_context()`
2. Create a task with explicit context using `asyncio.create_task(coro,
context=ctx)` for Python 3.11+
3. Shield the context-aware task
4. Fallback to regular task creation for Python < 3.11
```python
async def wrapped(*args: Any, **kwargs: Any) -> Any:
# Capture the current context to preserve context variables
ctx = copy_context()
coro = func(*args, **kwargs)
try:
# Create a task with the captured context to preserve context variables
task = asyncio.create_task(coro, context=ctx)
return await asyncio.shield(task)
except TypeError:
# Python < 3.11 fallback
task = asyncio.create_task(coro)
return await asyncio.shield(task)
```
## Testing
- Added comprehensive test
`test_shielded_callback_context_preservation()` that validates context
variables are preserved across shielded callback boundaries
- Verified the fix resolves the original LangGraph context consistency
issue
- Confirmed all existing callback manager tests still pass
- Validated OpenTelemetry-like instrumentation scenarios work correctly
The fix is minimal, maintains backward compatibility, and ensures proper
context preservation for both modern Python versions and older ones.
Fixes#31398.
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---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mdrxy <61371264+mdrxy@users.noreply.github.com>
Co-authored-by: Mason Daugherty <github@mdrxy.com>
Co-authored-by: Mason Daugherty <mason@langchain.dev>
- standardize on using model IDs, no more aliases - makes future
maintenance easier
- use latest models in docstrings to highlight support
- remove remaining sonnet 3-7 usage due to deprecation
Depends on #33751
Largely:
- Remove explicit `"Default is x"` since new refs show default inferred
from sig
- Inline code (useful for eventual parsing)
- Fix code block rendering (indentations)
Ensures proper reStructuredText formatting by adding the required blank
line before closing docstring quotes, which resolves the "Block quote
ends without a blank line; unexpected unindent" warning.
**Description:**
I traced the kwargs starting at `.invoke()` and it was not clear where
they go. it was clarified to two layers down. so I changed it to make it
more documented for the next person.
**Issue:**
No related issue.
**Dependencies:**
No dependency changes.
**Twitter handle:**
Nah. We're good.
If no one reviews your PR within a few days, please @-mention one of
baskaryan, eyurtsev, ccurme, vbarda, hwchase17.
---------
Co-authored-by: Mason Daugherty <mason@langchain.dev>
Recommend using context manager for FileCallbackHandler to avoid opening
too many file descriptors
---------
Co-authored-by: Mason Daugherty <github@mdrxy.com>
1. Remove `shielded` decorator from non-end event handlers
2. Exit early with a `self.handlers` check instead of doing unnecessary
asyncio work
Using a benchmark that processes ~200k chunks (a poem about broccoli).
Before: ~15s
Circled in blue is unnecessary event handling time. This is addressed by
point 2 above
<img width="1347" alt="Screenshot 2025-05-14 at 7 37 53 AM"
src="https://github.com/user-attachments/assets/675e0fed-8f37-46c0-90b3-bef3cb9a1e86"
/>
After: ~4.2s
The total time is largely reduced by the removal of the `shielded`
decorator, which holds little significance for non-end handlers.
<img width="1348" alt="Screenshot 2025-05-14 at 7 37 22 AM"
src="https://github.com/user-attachments/assets/54be8a3e-5827-4136-a87b-54b0d40fe331"
/>
Most easily reviewed with the "hide whitespace" option toggled.
Seeing 10-50% speed ups in import time for common structures 🚀
The general purpose of this PR is to lazily import structures within
`langchain_core.XXX_module.__init__.py` so that we're not eagerly
importing expensive dependencies (`pydantic`, `requests`, etc).
Analysis of flamegraphs generated with `importtime` motivated these
changes. For example, the one below demonstrates that importing
`HumanMessage` accidentally triggered imports for `importlib.metadata`,
`requests`, etc.
There's still much more to do on this front, and we can start digging
into our own internal code for optimizations now that we're less
concerned about external imports.
<img width="1210" alt="Screenshot 2025-04-11 at 1 10 54 PM"
src="https://github.com/user-attachments/assets/112a3fe7-24a9-4294-92c1-d5ae64df839e"
/>
I've tracked the improvements with some local benchmarks:
## `pytest-benchmark` results
| Name | Before (s) | After (s) | Delta (s) | % Change |
|-----------------------------|------------|-----------|-----------|----------|
| Document | 2.8683 | 1.2775 | -1.5908 | -55.46% |
| HumanMessage | 2.2358 | 1.1673 | -1.0685 | -47.79% |
| ChatPromptTemplate | 5.5235 | 2.9709 | -2.5526 | -46.22% |
| Runnable | 2.9423 | 1.7793 | -1.163 | -39.53% |
| InMemoryVectorStore | 3.1180 | 1.8417 | -1.2763 | -40.93% |
| RunnableLambda | 2.7385 | 1.8745 | -0.864 | -31.55% |
| tool | 5.1231 | 4.0771 | -1.046 | -20.42% |
| CallbackManager | 4.2263 | 3.4099 | -0.8164 | -19.32% |
| LangChainTracer | 3.8394 | 3.3101 | -0.5293 | -13.79% |
| BaseChatModel | 4.3317 | 3.8806 | -0.4511 | -10.41% |
| PydanticOutputParser | 3.2036 | 3.2995 | 0.0959 | 2.99% |
| InMemoryRateLimiter | 0.5311 | 0.5995 | 0.0684 | 12.88% |
Note the lack of change for `InMemoryRateLimiter` and
`PydanticOutputParser` is just random noise, I'm getting comparable
numbers locally.
## Local CodSpeed results
We're still working on configuring CodSpeed on CI. The local usage
produced similar results.
Looks like `pyupgrade` was already used here but missed some docs and
tests.
This helps to keep our docs looking professional and up to date.
Eventually, we should lint / format our inline docs.
**Description:**
Fixed a bug in `BaseCallbackManager.remove_handler()` that caused a
`ValueError` when removing a handler added via the constructor's
`handlers` parameter. The issue occurred because handlers passed to the
constructor were added only to the `handlers` list and not automatically
to `inheritable_handlers` unless explicitly specified. However,
`remove_handler()` attempted to remove the handler from both lists
unconditionally, triggering a `ValueError` when it wasn't in
`inheritable_handlers`.
The fix ensures the method checks for the handler’s presence in each
list before attempting removal, making it more robust while preserving
its original behavior.
**Issue:** Fixes#30640
**Dependencies:** None
---------
Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
