ACS Call Automation playToAll silent in Teams Online Meeting (CallConnected + PlayCompleted, list_participants=0)

Comience con el endpoint de callback de ACS documentado /api/teams/copilot-acs-media/events y la evidencia de reproducción de CallConnected, PlayCompleted y list_participants=0. Revise MICROSOFT_SUPPORT_TICKET_PORTAL_WALKTHROUGH_2026-06-30.md y el resumen del ADR de arquitectura referenciado. Se considera terminado cuando exista un acuerdo sobre una arquitectura de producción compatible para audio bidireccional de Teams y, posteriormente, vídeo, no cuando se realice un cambio de código en el repositorio.

Microsoft Azure Support Ticket — Teams Bidirectional Media (Voice + Live Avatar)

Stand: 2026-06-30
Sprache Ticket: Englisch (Copy-Paste unten)
Portal: Azure Portal → Help + support → Create a support request
Schritt-für-Schritt (Deutsch): MICROSOFT_SUPPORT_TICKET_PORTAL_WALKTHROUGH_2026-06-30.md
Issue type: Technical → Azure Communication Services (primary) + cross-reference Microsoft Teams / Graph Cloud Communications

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Kurz (Deutsch, intern)

Wir bauen STELLA — einen KI-Copilot für Teams-Meetings mit bidirektionaler Kommunikation:

Phase	Ziel
1 — Voice only	STELLA spricht hörbar in der Meeting-Leitung (TTS), hört Teilnehmer (STT), antwortet intelligent
2 — Voice + Video	Live-Avatar (Runway) als sichtbare Kachel im Meeting-Grid, synchron zu Audio

Blocker: ACS Call Automation (playToAll) meldet CallConnected + PlayCompleted, aber list_participants=0 → kein hörbares Audio (Ghost Leg). Das bleibt bestehen auch nach native onlineMeetings-Erstellung + Application Access Policy.

Bitte an Microsoft: Empfohlener Architekturpfad für produktionsreife Bot-Media in Teams (Audio rein/raus, später Video) — ACS vs Application-hosted Media vs andere.

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Copy-Paste: Support Request (English)

Title

ACS Call Automation playToAll silent in Teams Online Meeting (PlayCompleted, participants=0) — guidance for bidirectional voice + live avatar video

Problem description

We are building STELLA, a multi-tenant AI meeting copilot integrated with Microsoft Teams. Our production stack uses:

• Azure Communication Services (ACS) resource: cdtech-communication (region: Europe)
• Microsoft 365 tenant: fe87c2f4-700c-4a68-9bd7-218fde87a857 (C&D Technologies GmbH)
• Organizer UPN: [email protected] (also [email protected])
• Backend: Python/FastAPI on Azure Railway (https://api.cdtechnologies.de)
• Teams Graph App (application permissions): Client ID 4b1d32ba-6c39-4a0b-b320-31981ce0654b (GRAPH_CLIENT_ID_TEAMS)

We need guidance on the correct Microsoft-recommended architecture for:

1. Outbound audio (Phase 1): Bot TTS audible to all meeting participants (not operator-only Sidecar/browser audio).
2. Inbound audio (Phase 1): Bot receives participant speech for STT / conversational AI (bidirectional voice).
3. Outbound video (Phase 2): Live AI avatar (H.264) as a visible participant tile in the Teams meeting grid, lip-synced to TTS.
4. Scalable multi-tenant SaaS: Each customer uses their own M365 tenant; we orchestrate via delegated/app permissions and tenant-specific organizer mailboxes.

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Current architecture (what we built)

┌─────────────────────────────────────────────────────────────────────────────┐
│ STELLA Backend (Railway, Linux, Python)                                      │
│  • Meeting create: Graph POST /users/{org}/onlineMeetings (native)           │
│  • Copilot session, TTS (Azure Speech de-DE-KatjaNeural → WAV)               │
│  • ACS Call Automation: connect_call(groupCallId) + playToAll(audioUrl)    │
│  • Callbacks: POST /api/teams/copilot-acs-media/events                       │
│  • Bot Framework: meeting chat text (works)                                    │
│  • Sidecar UI: browser STT chunks → backend (works, not meeting-wide)        │
└───────────────┬───────────────────────────────┬─────────────────────────────┘
                │ HTTPS                          │ Graph / Bot Framework
                ▼                                ▼
┌───────────────────────────┐    ┌────────────────────────────────────────────┐
│ ACS (cdtech-communication)│    │ Teams Online Meeting                        │
│ Call Automation API       │───▶│ groupCall / thread v2                       │
│ (invisible bot leg)       │    │ Human participants + meeting chat           │
└───────────────────────────┘    └────────────────────────────────────────────┘

Optional (scaffold, Windows VM — not production-ready):
┌─────────────────────────────────────────────────────────────────────────────┐
│ teams-media-bot (.NET 8, Azure Windows VM)                                   │
│  • Target: Microsoft.Graph.Communications.Calls.Media (Application-hosted)   │
│  • StellaBridge HTTP: push PCM + H.264 frames                                │
│  • Today: ACS relay fallback only; GraphCommunicationsService = deferred     │
│  • URL: https://teams-media-bot.cdtechnologies.de (health often timeout)     │
└─────────────────────────────────────────────────────────────────────────────┘

Live avatar source (Phase 2):
┌─────────────────────────────────────────────────────────────────────────────┐
│ Runway Live API → WebRTC/video frames → transcode → Media Bot VideoSocket    │
│ (Sidecar bridge today: operator-only video; not in Teams grid)               │
└─────────────────────────────────────────────────────────────────────────────┘

Separate channels (important):

Channel	Technology	Status
Meeting chat (text, @mentions)	Bot Framework + Graph	✅ Works
Meeting audio broadcast (TTS to all)	ACS playToAll	❌ Ghost Leg — silent
Operator Sidecar TTS	Browser audio	✅ Operator hears only
Transcript post-meeting	Graph onlineMeeting transcript	✅ (after meeting ends)
Live STT from all participants	Not implemented	❌ Need inbound media path
Visible avatar tile	Graph Application-hosted media (planned)	❌ Not wired

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Symptom (Ghost Leg)

When joining a native Teams online meeting (created via Graph onlineMeetings, not calendar fallback):

• ACS connect_call succeeds; webhook CallConnected received.
• ACS playToAll with publicly reachable HTTPS WAV URL succeeds; webhook PlayCompleted received.
• ACS list_participants returns count=0 consistently after connect.
• No audible media in Teams client for human participants.
• Sidecar/browser TTS works for operator only (not acceptable for product).

Application Access Policy (Teams PowerShell) already applied:

• Policy: Tag:STELLA-Graph-OnlineMeetings → AppId 4b1d32ba-6c39-4a0b-b320-31981ce0654b
• Granted to: [email protected], [email protected], [email protected]
• Meeting create returns _source: onlineMeetings (MS… meeting ID) — Ghost Leg persists.

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Reproduction evidence (2026-06-30, Policy Test)

Field	Value
Meeting subject	STELLA onlineMeetings Policy Test 2026-06-30
onlineMeeting ID	MSplYzJiODRlNy01MTJlLTQyMzUtOTYzYi01YjJlOTA0MjNhNmMqMCoqMTk6bWVldGluZ19OalpqTkdVek5HVXROVEkxT1MwMFlXRTVMVGt3Wm1FdE1HSTFNbUZpWlRZek1HRTFAdGhyZWFkLnYy
groupCallId (thread)	66c4e34e-5259-4aa9-90fa-0b52abe630a5
ACS call_connection_id	6d003a80-a129-48b2-a1ec-22e979b71feb
Join URL thread	19:meeting_NjZjNGUzNGUtNTI1OS00YWE5LTkwZmEtMGI1MmFiZTYzMGE1@thread.v2
Callback URL	https://api.cdtechnologies.de/api/teams/copilot-acs-media/events
Backend flags	TEAMS_COPILOT_AUDIO_PREFER_RAILWAY_ACS=true, Runway broadcast off
Human in call	Yes (Teams desktop, mic bar active, second machine)
Result	PlayCompleted, no audible output in meeting

Earlier retest (calendar fallback, same symptom):

• groupCallId: e6613890-2b4e-4b2d-80b9-1b716e146e36
• ACS call: 1e003a80-2f9a-4348-a143-3b8206013c61

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Graph / Entra permissions (Teams app 4b1d32ba…)

Application permissions (admin consented), including:

• Calls.JoinGroupCall.All, Calls.InitiateGroupCall.All
• OnlineMeetings.ReadWrite.All, OnlineMeetings.Read.All
• Calendars.ReadWrite, Calendars.Read
• Chat.ReadWrite.All, TeamsAppInstallation.ReadWriteForChat.All (auto-install still 403 without Consent variant)
• User.Read.All, CallRecords.Read.All, etc.

Bot Framework app (separate registration) handles /api/teams/bot/messages — chat works; does not provide meeting media.

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What we need from Microsoft

Please advise on the recommended production path for our goals:

A) Outbound meeting audio (Phase 1 — voice only)

1. Is ACS Call Automation playToAll into Teams native online meetings a supported scenario? If yes, why would list_participants=0 + silent audio occur despite CallConnected/PlayCompleted?
2. Should we use Graph Cloud Communications / Application-hosted media bot instead (Windows VM + Calls.AccessMedia.All + media platform certificate)?
3. Is there a service-hosted media bot or Teams Real-time API path that avoids Windows VM ops but still delivers audible mixed audio?
4. Any tenant-level enablement required beyond Application Access Policy (e.g. Cloud Communications error 7504, policy flags)?

B) Inbound audio — bidirectional voice (Phase 1)

5. How should a bot receive participant audio for STT in a Teams meeting?
   • Graph AudioSocket / subscribed media?
   • ACS receive path?
   • Teams transcription API (too high latency for live dialog)?
6. Minimum architecture for full-duplex voice (human speaks → bot hears → bot responds with TTS in meeting)?

C) Outbound video — live avatar (Phase 2)

7. Recommended approach to inject live H.264 video (AI avatar, ~25 fps) as a visible meeting participant:
   • Application-hosted media only?
   • Can ACS carry video into Teams grid or audio-only?
8. Can audio and video use the same Graph call leg, or must they be separate?
9. Licensing / SKU requirements (Teams Premium, Copilot, etc.)?

D) Multi-tenant SaaS

10. For customer tenants (not our own): recommended onboarding — Application Access Policy per tenant, consent model, hosted vs customer-deployed media bot?
11. Any certification or Teams store requirements for a copilot with media injection?

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Alternatives we are evaluating (please comment)

Option	Our understanding	Question for Microsoft
ACS Call Automation	Simple HTTP, Linux-friendly; current Ghost Leg	Supported for Teams meetings? Fix for participants=0?
Application-hosted Media Bot	Windows VM, Graph Communications SDK, AudioSocket/VideoSocket	Is this the only supported path for grid video + reliable audio?
Service-hosted media bot	Microsoft hosts media stack	Available for our scenario / tenant size?
Teams RTMP / live events	Not interactive meeting	Not suitable — need 2-way
Screen share / computer sound	Operator workaround only	Not productizable
Azure OpenAI Realtime + ACS	Voice AI patterns	Overlap with Teams meeting join?

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Business context

• Product: STELLA — AI copilot for regulated industries (energy consulting, sales meetings).
• Use case: AI assistant joins customer Teams meetings, introduces itself (ISB compliance script), answers questions audibly, later with live avatar.
• Requirement: Bidirectional communication; voice-first MVP, video avatar second phase.
• Scale: Multi-tenant; each customer brings their own M365 tenant.

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Severity / impact

• Severity: High — blocks core product capability (audible AI in Teams meetings).
• Workaround: Operator shares "computer sound" from browser Sidecar — not acceptable for customers.

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Attachments / logs we can provide on request

• ACS webhook event sequence (CallConnected, PlayCompleted timestamps)
• Redacted Railway logs for call_connection_id above
• Graph meeting create response (onlineMeetings)
• Architecture ADR: docs/architecture/TEAMS_LIVE_AVATAR_MEDIA_BOT_DECISION_2026-06.md (private repo — summary included above)

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Contact

• Primary: Markus Jaszczyk — [email protected] / [email protected]
• Organization: C&D Technologies GmbH
• Tenant ID: fe87c2f4-700c-4a68-9bd7-218fde87a857

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Nach dem Absenden

1. Correlation IDs aus Azure Portal notieren und in docs/ops/TEAMS_ACS_GHOST_LEG_INCIDENT_2026-06-30.md ergänzen.
2. Antwort mit Architektur-Empfehlung → ADR aktualisieren + P1 Media Bot Scope anpassen.
3. Falls 7504 / tenant enablement nötig: separates Enablement-Ticket referenzieren.

Verwandte interne Docs

• TEAMS_ACS_GHOST_LEG_INCIDENT_2026-06-30.md
• TEAMS_GRAPH_MEDIA_BOT_P1_HANDOFF_2026-06-30.md
• TEAMS_VOICE_AUDIO_TEST_HANDOVER_2026-06-29.md
• services/teams-media-bot/README.md