fix(core): Always inherit parent run id onto callback manager from context

[jacoblee93]

If a LangChainTracer instance were already present in the callback manager, the if statement here would never trigger:

      if (
        tracingEnabled &&
        !callbackManager.handlers.some(
          (handler) => handler.name === "langchain_tracer"
        )
      ) {
        ...
      }

And the parent/child relationship would break.

[changeset-bot]

🦋 Changeset detected

Latest commit: d7f67c1

The changes in this PR will be included in the next version bump.

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Preview	Comments	Updated (UTC)
langchainjs-docs	Ready	Preview	Comment	Sep 4, 2025 9:37pm

1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
langchainjs-api-refs	Ignored			Sep 4, 2025 9:37pm