Clarify call state, recording, and fallback for dial SIP transfers

fern/tools/transfer-call/blind-transfer.mdx

@@ -129,6 +129,17 @@ The SIP verb affects only calls running on SIP telephony. Other telephony provid
 
 Do not use `bye` when you expect Vapi to dial the destination. It intentionally places no destination call.
 
+## Call state after a SIP transfer
+
+The `refer` and `dial` verbs leave the call in different states once the transfer starts.
+
+- **`refer`** hands the call off with a SIP REFER. Vapi leaves the call when the transfer starts, and the destination continues the call without Vapi.
+- **`dial`** bridges a new outbound leg to the destination. The SIP layer keeps the caller and destination connected until either side hangs up, but the assistant leaves the call when the transfer starts. You can't unbridge a connected `dial` transfer and return the caller to the original assistant.
+
+With either verb, Vapi's recording and transcript stop when the transfer starts. To capture the rest of the call, record it in a system that stays in the media path, such as your SIP provider or PBX.
+
+If a `refer` or `dial` transfer is busy, unanswered, or fails, the caller doesn't return to the original assistant by default. If SIP transfer fallback is enabled and the destination's `transferPlan` has a `fallbackPlan`, the assistant speaks the fallback message. It then ends the call or keeps helping the caller. See [Understand transfer outcomes and fallback](/tools/transfer-call#understand-transfer-outcomes-and-fallback).
+
 ## Verify the transfer
 
 Place a test call and trigger the transfer. Confirm that the destination rings and that the customer and destination can hear each other.
@@ -144,6 +155,8 @@ An `assistant-forwarded-call` ended reason confirms that Vapi initiated the tran
 | The original call ends, but the destination never rings | The SIP system rejected or did not receive the REFER | Check the affected call's **Logs** tab in [**Logs → Calls**](/observability/logs/call-logs), then inspect the provider or PBX SIP logs and packet capture. Confirm required SIP signaling addresses are allowed. |
 | The call ends without dialing a destination | `sipVerb` is set to `bye` | Use `refer` or `dial` when Vapi should place or initiate the transfer. |
 | A dial transfer stops ringing too soon | `dialTimeout` is too short | Increase `dialTimeout` within the 1–600 second range. |
+| The caller doesn't return to the assistant after a failed transfer | The destination has no `fallbackPlan`, or SIP transfer fallback isn't enabled | Add a `fallbackPlan` to the destination's `transferPlan`. See [Understand transfer outcomes and fallback](/tools/transfer-call#understand-transfer-outcomes-and-fallback). |
+| The recording or transcript stops at the transfer | Vapi's recording and transcript end when the transfer starts for both `refer` and `dial` | Record the full call in your SIP provider or PBX. |
 | The summary header is missing | The standard blind mode is selected or summary generation is disabled | Use `blind-transfer-add-summary-to-sip-header` and enable `summaryPlan`. Inspect the receiving SIP system rather than the audio transcript. |
 | The summary contains the wrong information | The summary prompt is broad or uses the wrong template variable | Give `summaryPlan.messages` a focused instruction and include `{{transcript}}` in the user message. |
 | Vapi shows `assistant-forwarded-call`, but the transfer failed | Vapi initiated the downstream transfer but did not observe its final result | Use the telephony provider's call detail record and SIP signaling as the source of truth for downstream completion. |