docs: update next session — Kookoo dial to SIP extension is the blocker

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/next-session.md

@@ -1,5 +1,25 @@
 # Next Session — Outbound Call UI + Remaining Work
 
+## Priority 0: Kookoo Dial to SIP Extension
+
+**Status:** Kookoo IVR endpoint works. When customer answers, Kookoo hits /kookoo/ivr, we respond with `<dial>523590</dial>`. But Kookoo tries to call 523590 as a PSTN number — status=not_answered.
+
+**The Voice URL in Kookoo dashboard has been changed to:** `https://engage-api.srv1477139.hstgr.cloud/kookoo/ivr`
+
+**Formats to try in the `<dial>` tag:**
+1. `523590` — current, fails (treated as PSTN)
+2. `0523590` — with STD prefix
+3. `sip:523590@blr-pub-rtc4.ozonetel.com` — full SIP URI
+4. `523590@blr-pub-rtc4.ozonetel.com` — SIP without scheme
+5. Use `<conference>` tag instead — put customer in room, have browser SIP join same room
+
+**Alternative approach:** Instead of `<dial>`, use `<conference>` tag:
+- Customer answers → put in conference room "call-{sid}"
+- Meanwhile, browser SIP joins the same conference room
+- Both connected
+
+**Files:** `helix-engage-server/src/ozonetel/kookoo-ivr.controller.ts` line where we return `<dial>523590</dial>`
+
 ## Priority 1: Outbound Call UI
 
 **Problem:** When agent clicks Call, a toast appears and the call happens in the background. No call screen shows.