[Suhas Aggarwal (suhasagg)]

Summary

Fixes #9034.

Handoff tool names were generated directly from the target agent ID. When an agent name contained spaces or other characters that are invalid in provider function/tool names, the generated handoff tool name could also be invalid.

For example:

Billing Agent → handoff_to_Billing Agent

This change sanitizes non-alphanumeric/non-underscore characters when generating handoff tool names:

Billing Agent → handoff_to_Billing_Agent

The original target ID is preserved for handoff routing. Only the generated tool/function name is sanitized.

Changes

• Sanitize invalid characters in get_handoff_tool_name().
• Preserve the original target ID used by handoff routing.
• Add regression coverage for spaces and punctuation.
• Add an end-to-end middleware test verifying that a sanitized handoff tool still routes to the original target ID.

Testing

• Added focused regression tests for sanitized handoff tool names.
• Focused regression tests: 2 passed.
• Full test_handoff.py: 42 passed, 6 skipped.
• Ruff lint: passed.
• Ruff format check: passed.
• git diff --check: passed.

[Copilot]

Copilot review overview

🟡 Changes recommended

Sanitization can cause routing collisions and unnecessarily rewrites valid hyphens.

Review effort: Balanced
Findings: 1 · 1

Open (2)

• Prevent sanitized handoff-name collisions · New
• Correct regression expectation for preserved hyphens · New

What changed in this PR

Sanitizes Python handoff tool names while preserving original agent IDs for routing.

Changes:

• Replaces unsupported characters with underscores.
• Adds regression and middleware-routing tests.

File	Description
_handoff.py	Adds handoff tool-name sanitization.
test_handoff.py	Tests sanitization and original-ID routing.

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[Eduard van Valkenburg (eavanvalkenburg)]

Suhas Aggarwal (@suhasagg) Thanks for the contribution. This implements the same change as #9035, so we'll continue the work there and close this duplicate.