Fix(messages): Properly format non-primitive tool arguments in AIMessage.toFormattedString()

[shubham-021]

Description:

Fixed an issue in AIMessage.toFormattedString() where nested objects in tool call arguments were being displayed as [object Object] instead of their actual JSON representation.

Changes

• Modified convertToPrettyString() in libs/langchain-core/src/messages/format.ts to use JSON.stringify() for object values when formatting tool call arguments

Testing

Added a new test case "formats an AI message with nested objects in tool call args" that verifies:

• Nested objects are serialized as JSON strings
• The output does not contain [object Object]

Fixes #9504

[changeset-bot]

🦋 Changeset detected

Latest commit: d16c7e5

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

This PR includes changesets to release 10 packages

Name	Type
@langchain/core	Patch
@langchain/standard-tests	Patch
langchain	Patch
@langchain/google-cloud-sql-pg	Patch
@langchain/google-common	Patch
@langchain/google-genai	Patch
@langchain/google-webauth	Patch
@langchain/google-vertexai-web	Patch
@langchain/google-vertexai	Patch
@langchain/google-gauth	Patch

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