docs(agents): BYO SIP cold transfers need PSTN transfers enabled on the trunk

[Him188]

Summary

• Twilio walkthrough: the "Allow transfers" step now says to also allow transfers to the PSTN. A trunk limited to SIP transfers rejects every transfer to a phone number, so transfers to phone numbers do not work.
• Transfers prerequisites: the imported SIP number bullet names the same two Twilio settings.
• Transfers limitations: removed the "Transfer-capable numbers" bullet. It said only purchased numbers can transfer, which contradicted the prerequisites, and the prerequisites already cover which numbers support transfers.

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Summary by CodeRabbit

• Documentation
  • Clarified Twilio trunk settings required for transfers to phone numbers, including enabling Call Transfer (SIP REFER) and allowing PSTN transfers.
  • Updated transfer guidance to explain when imported SIP numbers support cold transfers and when warm transfers are supported.
  • Clarified that transfer availability depends on the number involved in the call supporting transfers.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: d17b3c29-a48b-4d0d-b714-8b9afbe3edaa

📥 Commits

Reviewing files that changed from the base of the PR and between 47b4451 and f7cf66f.

📒 Files selected for processing (2)

• agents/telephony/byo-sip.mdx
• agents/telephony/transfers.mdx

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📝 Walkthrough

Walkthrough

The telephony transfer docs clarify cold-transfer requirements for SIP numbers, Twilio settings for SIP REFER and PSTN transfers, and the limitation for call numbers that support transfers.

Changes

SIP transfer documentation

Layer / File(s)	Summary
Transfer requirements and limitations agents/telephony/transfers.mdx, agents/telephony/byo-sip.mdx	The prerequisites specify that SIP REFER must be honored to the destination and describe the Twilio settings for cold transfers. The Twilio walkthrough notes that restricting transfers to SIP destinations causes phone-number transfers to be rejected. The limitation now applies to call numbers that support transfers.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to f7cf6

The documentation clarifies cold-transfer setup and which numbers support transfers. No actionable merge risk is evident; the change is ready after normal checks.

Architecture Summary

Architecture risk: 🔵 Low · up to f7cf6

The change affects 1 system.

Changed systems: agents

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — agents (service) was modified; 2 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in agents/telephony/byo-sip.mdx: The Twilio transfer instructions now require enabling PSTN transfers as well as SIP REFER. They state that if transfers are restricted to SIP destinations, transfers to phone numbers are rejected and the caller remains with the agent; the removed instruction only said to enable SIP REFER so Twilio honors the handoff.
• observed — Modified behavior in agents/telephony/transfers.mdx: The prerequisite now specifies that SIP REFER must be honored to the destination and adds the Twilio settings required for cold transfers; the warm-transfer termination requirement is unchanged.
• observed — Modified behavior in agents/telephony/transfers.mdx: The limitation now applies to any call number that supports transfers, as described in the prerequisites, replacing the requirement that the caller-dialed number use the twilio provider.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main documentation change: BYO SIP cold transfers require PSTN transfers to be enabled on the trunk.

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