fix: Fix warm transfer not working

[manas-narra]

Summary by CodeRabbit

• Bug Fixes
  • Fixed an issue where callers could be unexpectedly disconnected during warm transfers to live agents with certain VoIP providers.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b6a3fa2b-84ce-454f-83d6-8f28d87692f0

📥 Commits

Reviewing files that changed from the base of the PR and between df477de and 205783c.

📒 Files selected for processing (1)

• app/ai/voice/agents/breeze_buddy/handlers/internal/warm_transfer.py

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Walkthrough

The change adds Plivo-specific handling to the warm transfer handler. After a successful conference transfer is created, the code now checks if the call provider is Plivo and attempts to suppress the serializer's automatic hang-up logic by setting an internal flag, with graceful error handling.

Changes

Plivo Serializer Hang-up Prevention

Layer / File(s)	Summary
Plivo serializer hang-up suppression app/ai/voice/agents/breeze_buddy/handlers/internal/warm_transfer.py	After successful conference transfer, the handler checks for CallProvider.PLIVO, accesses the Plivo serializer via context.bot.transport.output()._params.serializer, and sets _hangup_attempted = True to prevent automatic hang-up from disconnecting the caller; failures are caught and logged as warnings.

Estimated Code Review Effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 A transfer so warm, a conference born,
Plivo's hang-up no longer will mourn,
Set the flag, let callers stay,
No premature drops today!
The serializer now keeps the thread,
Friends together, never misled. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly describes the main change: fixing warm transfer functionality by preventing automatic hang-up during agent transfer.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[Copilot]

Pull request overview

This PR fixes warm transfer functionality for Plivo-based calls. Previously, when transferring to a live agent, the Pipecat EndFrame would cause the Plivo serializer to invoke _hang_up_call() and drop the caller from the conference. The fix preemptively sets _hangup_attempted=True on the Plivo serializer so it skips its automatic hang-up API call, allowing the customer leg to stay connected in the conference.

Changes:

• Before ending the AI conversation on a successful transfer, set the Plivo serializer's _hangup_attempted flag to suppress its auto hang-up.
• Wrapped in try/except with warning-level logging so any failure to access the serializer is non-fatal.
• Only applied when context.provider == CallProvider.PLIVO.