Summary

• Fixes type inconsistency where ToolLoopAgentOnFinishCallback had experimental_context as optional (?) while StreamTextOnFinishCallback and GenerateTextOnFinishCallback had it as required
• Adds type tests to verify callback type compatibility between agent and streamText/generateText callbacks
• Updates JSDoc comment to use "tool execution" wording for consistency with other callbacks

Problem

As reported in #12195, ToolLoopAgentOnFinishCallback defines experimental_context?: unknown (optional), but StreamTextOnFinishCallback and GenerateTextOnFinishCallback define experimental_context: unknown (required).

Since ToolLoopAgent delegates to streamText/generateText, and both always pass experimental_context when invoking the callback (stream-text.ts#L1011, generate-text.ts#L940), the types should match.

This inconsistency causes type errors when trying to use a StreamTextOnFinishCallback where ToolLoopAgentOnFinishCallback is expected (or vice versa).

Solution

Changed experimental_context?: unknown to experimental_context: unknown in ToolLoopAgentOnFinishCallback to match the other callback types.

Testing

• All 1812 tests pass including new type tests
• Added 2 new type tests verifying bidirectional type compatibility between StreamTextOnFinishCallback and ToolLoopAgentOnFinishCallback
• Full type check passes with no errors

Fixes #12195