## Summary
Removes the `add_handler()` overrides on `_GraphCallbackManager` and
`_AsyncGraphCallbackManager` that reject handlers not inheriting from
`GraphCallbackHandler`. This fixes a regression in 1.1.7 where
`opentelemetry-instrumentation-langchain` (and likely other libraries
that patch `BaseCallbackManager.__init__`) crash with `TypeError:
handlers must inherit GraphCallbackHandler` at invocation time.
## Why this is safe
The strict type check is redundant — `_configure_graph_callbacks` and
`_filter_graph_handlers` already filter handlers to
`GraphCallbackHandler` instances at construction time. Non-graph
handlers that enter via external patches (like OTel's monkey-patch) are
harmless because `handle_event("on_interrupt", ...)` /
`handle_event("on_resume", ...)` will simply no-op on handlers that
don't implement those methods.
## What changed
- Deleted `add_handler()` override from `_GraphCallbackManager` (was
lines 248-255)
- Deleted `add_handler()` override from `_AsyncGraphCallbackManager`
(was lines 324-331)
- No other changes — 18 lines removed, 0 added
## Test plan
- [x] All 8 existing `test_graph_callbacks.py` tests pass (`make test
TEST=tests/test_graph_callbacks.py`)
- [x] `make lint` passes
- [x] `make format` passes (no changes needed)
- [x] Verified fix locally: `LangchainInstrumentor().instrument()` +
`create_react_agent()` + `graph.ainvoke()` no longer raises `TypeError`
- [x] Verified the graph lifecycle callbacks (`on_interrupt`,
`on_resume`) still work correctly
Closes#7543
---------
Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
## Summary
This change adds first-class graph lifecycle callbacks to LangGraph so
interrupt and resume transitions can be observed without overloading the
existing LangChain custom event system. It introduces a dedicated graph
callback manager and wires lifecycle emission through Pregel execution
in both sync and async paths.
## Changes
- **`libs/langgraph/langgraph/callbacks.py`**: Adds
`GraphCallbackHandler` and `GraphCallbackManager` (built on LangChain
base callback classes), plus config plumbing via `graph_callbacks` and
`get_graph_callback_manager_for_config`.
- **`libs/langgraph/langgraph/pregel/_loop.py`**: Introduces
`GraphLifecycleEvent` and records lifecycle transitions (`resume`,
`interrupt`) into an internal FIFO queue with
`shift_graph_lifecycle_event()`.
- **`libs/langgraph/langgraph/pregel/main.py`**: Resolves graph callback
manager from config and drains lifecycle events while loop execution
progresses, dispatching `on_resume` and `on_interrupt` consistently in
sync and async runtimes.
- **`libs/langgraph/tests/test_graph_callbacks.py`**: Adds sync and
async coverage verifying lifecycle callbacks fire correctly and remain
distinct from LangChain `on_custom_event` handlers.
---------
Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
