ADR-016: Team-Besprechung — separate side room per open enquiry, hard close at acceptance

• Status: Accepted — Frank, 2026-07-18 (grill-with-docs session)
• Date: 2026-07-18
• Deciders: Frank (product) + AI (engineering)
• Related: ADR-002 (silent membership / access curtain), ADR-008 (supervision side-channel = separate room), CONTEXT-conversation-types.md (Team-Besprechung overlay), ORISO-Frontend/CONTEXT.md (full glossary entry), memory oriso-team-besprechung-design

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Context

Counsellor teams want to coordinate on an incoming enquiry ("who takes this, what do you think?") before anyone accepts it — invisible to the advice seeker — and then continue the normal 1:1. The tempting implementation is "hidden messages / a team thread inside the client's conversation", but Matrix delivers every event to every room member's device: in-room hiding was exactly the U25 safeguarding leak ADR-008 removed. Verified on origin/pre-dev: the ADR-008 side-room primitive is alive (per-session Matrix room the client is never invited to, leak-abort on the send path), but it attaches at acceptance and assumes an assigned consultant; the old Caritas Feedback-Chat was physically removed (changeset 0046).

Decision

1. Team-Besprechung = a separate Matrix room attached to one open Agency-Counselling enquiry, generalizing the ADR-008 side-room principle to the pre-assignment phase. Guardrail (hard rule): team coordination never happens in the client's room — not even "hidden".
2. Hard close at acceptance. The moment the enquiry is accepted, the Besprechung is archived — it is not carried into the active case. Post-acceptance coordination uses the existing mechanisms: Supervision (read-only accompaniment) or Case Handover (co-access/takeover). This keeps three cleanly separated coordination tools instead of one blurry one.
3. Archive re-access is read-only (hard rule); access rules stay loose for now (team members may look without a co-access ceremony); retention rides the existing archive auto-deletion — no new TTL mechanism.
4. Participation right = enquiry visibility right. Exactly the counsellors who can see (and could accept) the enquiry may discuss; no new permission layer. A tenant-level feature toggle guards the whole feature.
5. The discussion is flat — the side room is already scoped to one enquiry, so it is the one "thread on the enquiry"; no thread machinery inside it. Scope: Agency Counselling only (Live Chat is anonymous/ephemeral and excluded per ADR-002; the other modalities have no request area).
6. UI: a panel/tab on the enquiry in the request area, with a post-count badge and a permanent "team-only — invisible to the advice seeker" marker, so a counsellor is never unsure which side they are writing on.

Considered options

• Thread in the client's room, hidden client-side. Rejected: impossible to hide on Matrix; re-opens the ADR-008 leak class.
• Carry the side room into the active case. Rejected by product decision: post-accept coordination belongs to Supervision/Case Handover; a room that lives on blurs that boundary. Context continuity is served by read-only archive access instead ("frozen, on demand" rather than "open forever").
• Wait for Megolm per-recipient subsets (one room, cryptographic hiding). Deferred in ADR-008 already; unrealistic before go-live 2026-10-01.

Consequences

Positive: reuses a shipped, leak-guarded primitive; no new permission model; clean lifecycle boundary matching the existing mechanism taxonomy. Cost: room provisioning at enquiry time (pre-assignment operator handling — today's facade assumes an assigned consultant); notification recipient fan-out must be built (current message producers hardcode user+consultant); archived-room re-access UI.