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3db82d5b6d
Add `StateGraph.set_node_defaults()` — a fluent builder method for
setting graph-wide node policies in one place. Per-node values from
`add_node()` always take precedence. Defaults are applied at `compile()`
time.
```python
graph = (
StateGraph(State)
.set_node_defaults(
retry_policy=RetryPolicy(max_attempts=3),
error_handler=my_fallback_handler,
timeout=TimeoutPolicy(run_timeout=30),
)
.add_node("a", node_a)
.add_node("b", node_b, retry_policy=custom) # overrides default
.add_edge(START, "a")
.compile()
)
```
Error handlers are never invoked on error-handler nodes themselves —
handler failures fail the run. Not inherited by subgraphs.
## Supported defaults
| `set_node_defaults()` kwarg | Fallback for `add_node(...)` kwarg |
Applies to error-handler nodes? |
|---|---|---|
| `retry_policy` | `retry_policy` | Yes |
| `cache_policy` | `cache_policy` | No — caching handler results is
unsafe |
| `error_handler` | `error_handler` | No — handlers must never catch
themselves |
| `timeout` | `timeout` | Yes |
## Changes
- `libs/langgraph/langgraph/graph/state.py` — new `_NodeDefaults`
dataclass, `set_node_defaults()` method on `StateGraph`; `compile()`
applies builder defaults to node specs with per-branch rules for which
defaults apply to error-handler nodes.
- `libs/langgraph/tests/test_retry.py` — 14 new tests covering all four
policy types, per-node override precedence, chaining, combined
retry+handler, handler exclusion, `RunnableConfig` injection, and name
collision.
## Verification
`make format`, `make lint`, `make test` all passing in `libs/langgraph`.
---------
Co-authored-by: Sydney Runkle <sydneymarierunkle@gmail.com>