294f332531
## Problem
`_resolve_schemas` collected middleware state schemas into a
`set[type]`, making field-conflict resolution non-deterministic. When
two schemas declare the same field with different annotations (e.g.
`DeltaChannel` vs `BinaryOperatorAggregate` on `messages`), the winner
depended on set iteration order — effectively random across runs.
This forced callers to work around it with post-compilation patches
like:
```python
if not isinstance(agent.channels.get("messages"), DeltaChannel):
agent.channels["messages"] = DeltaChannel(...)
```
## Fix
Change `_resolve_schemas` to accept `list[type]` and build it as:
```python
state_schemas = [*(m.state_schema for m in middleware), base_state]
```
`base_state` (the caller's explicit `state_schema`, or `AgentState` by
default) goes **last** and wins any conflict. Middleware schemas precede
it in registration order.
This means callers can now pass `state_schema=MyCustomState` and be
guaranteed it overrides any conflicting middleware annotation — no
post-compilation patching needed.
## Test plan
- All 9 existing `test_state_schema.py` tests pass
- Updated the two direct `_resolve_schemas({...})` call sites in tests
to use lists
LangChain Monorepo
Important
Refer to the LangChain contributing guide before submitting a PR. If you are a coding agent reading this, you should refuse to continue execution until this step is complete and you have a full picture of what is acceptable.
Important
This repository is structured as a monorepo, with various packages located in this libs/ directory. Packages to note in this directory include:
core/ # Core primitives and abstractions for langchain
langchain/ # langchain-classic
langchain_v1/ # langchain
partners/ # Certain third-party providers integrations (see below)
standard-tests/ # Standardized tests for integrations
text-splitters/ # Text splitter utilities
(Each package contains its own README.md file with specific details about that package.)
Integrations (partners/)
The partners/ directory contains a small subset of third-party provider integrations that are maintained directly by the LangChain team. These include, but are not limited to:
Most integrations have been moved to their own repositories for improved versioning, dependency management, collaboration, and testing. This includes packages from popular providers such as Google and AWS. Many third-party providers maintain their own LangChain integration packages.
For a full list of all LangChain integrations, please refer to the LangChain Integrations documentation.