| 1 | # 🤖 Instance contexts — one engine, different social defaults |
| 2 | |
| 3 | Status: **design** (not built). Builds on `docs/threads-and-dms.md` and |
| 4 | `docs/invite-redesign.md`. Nothing here weakens the E2EE invariant: the server |
| 5 | still only ever stores ciphertext and key-blobs it cannot open. |
| 6 | |
| 7 | ## The idea |
| 8 | |
| 9 | Different kinds of instances — a family, a friend group, a community — share |
| 10 | ~80% of what they need and differ in ~20%. The shared 80% is the **messaging |
| 11 | core**: threads, per-thread AES-GCM keys, the instance key, DMs, attachments, |
| 12 | mini-apps, the whole crypto model. None of it changes across kinds. |
| 13 | |
| 14 | The 20% that differs is entirely **social structure**: who may cross the trust |
| 15 | boundary, who can see whom, and which channels exist by default. So "context" is |
| 16 | **not a mode the engine branches on** — it's a *named preset* over a handful of |
| 17 | orthogonal knobs, plus tailored onboarding copy and channel scaffolding. |
| 18 | |
| 19 | - **A context is a template chosen at instance creation.** It expands into |
| 20 | concrete values on the knobs below, seeds a channel or two, and sets the |
| 21 | onboarding language. |
| 22 | - **We store the resolved knobs, not the context.** Real instances drift — a |
| 23 | family later wants a General; a friend group wants restricted DMs for the one |
| 24 | kid. The admin console exposes the dials directly; the context only seeds them. |
| 25 | - **"Other / Custom" always exists** — the dials with no preset. Future contexts |
| 26 | (Team, Club, Business) are new template rows, not engine changes. |
| 27 | |
| 28 | ## The knobs |
| 29 | |
| 30 | | Knob | Options | Backing | |
| 31 | |---|---|---| |
| 32 | | **1. Admission** — who adds a *person* to the instance | admin-only · members-can-invite · open join-link | `usersCanInvite` / `user_invites_enabled` (exists); open join-link is new | |
| 33 | | **2. Default channels** | none · one "General" · several topic channels | instance-key–encrypted threads, auto-created | |
| 34 | | **3. Member-created open channels** | off · on | deferred *"group join links, instance-members-only"* (`threads-and-dms.md`) | |
| 35 | | **4. Discovery / roster visibility** | full-open · restricted (e.g. kids ↔ parents only) | deferred *"restricted discovery"* | |
| 36 | | **5. Who can DM whom** | anyone ↔ anyone · restricted | same restricted-discovery lever | |
| 37 | |
| 38 | Everything else (composing, reactions, attachments, mini-apps) is the shared |
| 39 | core and is identical in every context. |
| 40 | |
| 41 | ## Contexts as presets |
| 42 | |
| 43 | | | Admission | Default channels | Member open channels | Discovery / DMs | |
| 44 | |---|---|---|---|---| |
| 45 | | **Family** | admin-only (parents) | none | off | restricted (kids ↔ parents), else open | |
| 46 | | **Friends** | members-can-invite | one General | maybe | full-open | |
| 47 | | **Community** | members-invite or open-link | several topic channels | on | full-open (role-gated later) | |
| 48 | | **Other** | fully custom | — | — | — | |
| 49 | | *Team (later)* | domain/SSO-gated | per-project | on | open within org | |
| 50 | | *Business (later)* | admin/SSO | departmental | on | + retention/audit ⚠️ (see below) | |
| 51 | | *Club (later)* | invite or open-link | few | on | open | |
| 52 | |
| 53 | Each row is a starting point on those five dials, nothing more. |
| 54 | |
| 55 | ## Two knobs that aren't cosmetic |
| 56 | |
| 57 | Most knobs are defaults you can flip freely. Two change the **trust model** and |
| 58 | must be designed as first-class features, not preset side effects. |
| 59 | |
| 60 | ### Admission is the security posture |
| 61 | |
| 62 | Family's "admin-only" *is* the safety model: a parent vets everyone who can read |
| 63 | anything. Community's "open join-link" means unvetted people get keys wrapped to |
| 64 | them. That is not a preference — it changes who you are trusting. The open |
| 65 | join-link is its own carefully-gated feature (expiring links, optional |
| 66 | admin-approval step), never something a preset silently turns on. |
| 67 | |
| 68 | ### Open channels: subscription vs. access |
| 69 | |
| 70 | An "open" channel (General, topic channels) is cleanest **encrypted with the |
| 71 | instance key**: every member already holds it, and new members get it |
| 72 | auto-granted via the existing nudge-and-wrap flow (`instance-key/nudge` → |
| 73 | `grantInstanceKeyTo`), so the channel is instantly readable with zero per-member |
| 74 | re-wrap. That gives a clean split: |
| 75 | |
| 76 | - **Open channels** → instance-key encrypted. *Any member can read* (even browse |
| 77 | before joining). Membership here is a **subscription** — it controls what's in |
| 78 | your list and what notifies you, not access. |
| 79 | - **Private groups / DMs** → per-thread key. Membership is **access** — you |
| 80 | cannot decrypt without being wrapped in. |
| 81 | |
| 82 | Honest limitation: an open channel is cryptographically readable by every |
| 83 | current and future instance member, forever. "Leaving" one is unsubscribing, not |
| 84 | losing the ability to decrypt. For a community that is usually the intended |
| 85 | meaning of "open." A channel that is open-to-join but revocable-on-leave needs a |
| 86 | per-channel key + rekey-on-leave, which costs an online key-holder and O(members) |
| 87 | re-wraps — a bill that grows with size. |
| 88 | |
| 89 | ## Cross-cutting concerns (not knobs) |
| 90 | |
| 91 | - **Scale is the silent axis.** Family (~5) and Friends (~20) sit in the model's |
| 92 | sweet spot. Community (100s) strains two mechanics: the nudge-and-grant |
| 93 | instance-key handshake assumes a holder is reachable, and remove-a-member rekey |
| 94 | is O(members) and needs someone online. Decide how far up the size curve each |
| 95 | context is meant to go before designing it. |
| 96 | - **Business bends the model.** Team and Club are basically Community + roles. |
| 97 | Business drags in retention, compliance, and admin-visible audit — several of |
| 98 | which *directly conflict* with E2EE (you cannot hand a compliance officer |
| 99 | plaintext the server never sees). Business needs its own trust-model |
| 100 | conversation; it is not a preset. |
| 101 | |
| 102 | ## Status / next steps |
| 103 | |
| 104 | Design only — nothing here is built. Natural build order once we commit: |
| 105 | |
| 106 | 1. Land the knobs as instance config + admin-console dials (extends the existing |
| 107 | `user_invites_enabled` pattern). |
| 108 | 2. Instance-key–encrypted "General" / open channels + the subscription-vs-access |
| 109 | split. |
| 110 | 3. Member-created open channels (the deferred group-join-links design). |
| 111 | 4. Restricted discovery (kids ↔ parents). |
| 112 | 5. Context templates + onboarding copy on top, once the dials exist. |
| 113 | |
amadan