[Sidharth Rajmohan (dumko2001)]

Description:
This PR fixes an issue where injection types (like ToolRuntime) were not recognized by ToolNode when used with generic type arguments (e.g., ToolRuntime[MyContext]).

Previously, the _is_injection check relied solely on isinstance and issubclass, which fail for typing._GenericAlias objects. This update adds a check using typing.get_origin() to correctly identify the base class of generic types, ensuring the runtime is injected correctly even when type hints are present.

Issue: Fixes #6465

Dependencies: None

Twitter handle: @SidharthRajmoh2

[vercel]

Sidharth Rajmohan (@dumko2001) is attempting to deploy a commit to the LangChain Team on Vercel.

A member of the Team first needs to authorize it.

[Sydney Runkle (sydney-runkle)]

Thanks so much. This is consistent w/ the logic we have for checking the origin in langchain-core as well.

It's actually a bit odd that these functions aren't unified.

[Sidharth Rajmohan (dumko2001)]

Welcome Sydney! . I’m already digging into the core for some other PRs (#6511 , #6512 ), so I’m happy to take a stab at cleaning this up. Let me know if you'd like me to open a PR for it!

[Sourav Nandy (Sourav-Nandy-ai)]

Hi Sidharth,

I ran a real before-and-after test on this. First, I caught an error in my own notes. I had this PR's merge date wrong (I had 2025-11-27, which is actually when it was opened; it merged on 2026-01-12). I corrected this before testing.

I installed real langgraph-prebuilt==1.0.5 (pre-fix) and 1.0.6 (post-fix, the actual first release with your fix). I then built a tool with a ToolRuntime[MyContext]-annotated parameter and dispatched it through a real ToolNode.invoke() call, running it 10 times for each version.

The Results

• Pre-fix: Every single call fails with a real rt: Field required validation error. The generic-parameterized annotation is not recognized, so ToolNode tries to treat it as an LLM-supplied argument.
• Post-fix: Every call succeeds, and the runtime object is correctly injected.

I confirmed this at the source level as well. The _is_injection() function in 1.0.5 has no generic-origin branch, whereas 1.0.6 adds exactly the check needed for get_origin(ToolRuntime[MyContext]) to match.

I maintain agent-eval (agent_regress). You can find the full scripts and raw output here: https://github.com/RudrenduPaul/agent-eval

Given you are doing more ToolRuntime generic-type work, I am curious whether this reproduction matches the real-world case that prompted the fix, or if there is a related generic-type edge case worth testing next.

Best,
Sourav