docs: log E2EE key-sync issues (KE-1..4) + tester checklist

LOTUS_BUGS.md: new Encryption/E2EE section tagged EXTREME complexity +
planning-session-required for a senior-engineer deep dive — OTK upload
conflict storm (KE-1), Element Call media-key distribution failures causing
audio/video dropouts (KE-2), a timeline decryption error (KE-3), and
MatrixRTC delayed-event timeouts (KE-4). All observed live 2026-06-30; not
caused by the EC fork work. Plus a non-developer ELEMENT_CALL_TEST_CHECKLIST.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ELEMENT_CALL_TEST_CHECKLIST.md

@@ -0,0 +1,122 @@
+# Voice/Video Call — Testing Checklist 🎧
+
+Thanks for helping test! We just upgraded the voice/video call system. Please run
+through the checks below and tell us what happened.
+
+**What you need:**
+
+- 2 people (you + a friend), each on their own device, in the same call. A few
+  checks need one of you to have a **camera** and to **share your screen**.
+- About 15–20 minutes.
+
+**How to report:** for each item just say ✅ (worked) or ❌ (didn't), and for any
+❌ tell us what you saw. If something looks broken, a screenshot helps a lot.
+
+---
+
+## ⭐ Most important — please do these first
+
+### 1. Your microphone keeps working after a connection hiccup
+
+This is the biggest thing we changed, so test it carefully.
+
+1. Join a call with your friend and talk for a few seconds (make sure they hear you).
+2. Now **turn off your WiFi / internet for about 10 seconds**, then turn it back on.
+   (The call will show a "Connection lost / reconnecting" message — that's expected.)
+3. Once it reconnects, **start talking again.**
+
+- ✅ **Good if:** your friend can still hear you normally after it reconnects, without
+  you having to leave and rejoin the call.
+- ❌ **Tell us if:** your friend can't hear you after reconnecting, or your voice
+  sounds broken/robotic/muffled, until you leave and rejoin.
+
+### 2. Microphone quality / noise removal sounds normal
+
+1. In a call, just talk normally for a bit.
+2. If there's background noise (fan, typing, TV), notice whether it's reduced.
+
+- ✅ **Good if:** your voice is clear and there's no silence, echo, or robotic warble.
+- ❌ **Tell us if:** there are dropouts, echo, a "underwater"/metallic sound, or your
+  mic is silent even though you're talking.
+
+### 3. Switching your microphone mid-call
+
+1. While in a call, open call **Settings** and change your microphone to a
+   different one (e.g. headset ↔ built-in), then back.
+2. Talk after each switch.
+
+- ✅ **Good if:** your friend keeps hearing you after each switch.
+- ❌ **Tell us if:** your audio cuts out or doesn't come back after switching.
+
+### 4. All the call buttons still work
+
+Go down the call control bar and tap each one, checking it actually does the thing:
+
+- [ ] **Mute / unmute mic** (icon changes AND your friend stops/starts hearing you)
+- [ ] **Camera on / off**
+- [ ] **Deafen / sound** toggle (you stop/start hearing others)
+- [ ] **Share screen** start and stop (including the "Share your screen?" prompt)
+- [ ] **Full screen** on and off
+- [ ] **"More" (⋮) menu** → the **Reactions**, **Settings**, and **Grid/Spotlight**
+      options each open the right thing
+- [ ] **Leave / End call** — leaves cleanly
+
+- ❌ **Tell us if:** any button does nothing when you tap it (tell us which one).
+
+---
+
+## 👀 Please also check these
+
+### 5. The "who's talking" highlight points at the right person
+
+1. In a call, have your friend talk, then you talk.
+
+- ✅ **Good if:** the highlight / glow appears around the person who is actually
+  talking (and the right person, not someone else).
+- ❌ **Tell us if:** the wrong person lights up, or nobody lights up when talking.
+
+### 6. Mute badges show on the right person
+
+1. Have your friend mute their mic.
+
+- ✅ **Good if:** any "muted" indicator shows next to the person who is muted.
+- ❌ **Tell us if:** it shows on the wrong person or doesn't update.
+
+### 7. Focus a camera while someone is sharing their screen
+
+_(Needs: one person sharing screen, another with camera on.)_
+
+1. Person A **shares their screen.**
+2. Person B turns their **camera on.**
+3. Use the **"Focus camera"** option (from a participant's menu) on Person B.
+
+- ✅ **Good if:** Person B's camera becomes the highlighted/spotlighted view
+  **alongside or over** the shared screen.
+- ❌ **Tell us if:** nothing happens, or it throws you out of the screen share, or
+  you get an error.
+
+### 8. Avatar decorations show on call tiles
+
+_(Needs: someone in the call has an avatar decoration set in Settings → Profile.)_
+
+1. Have a person with a **profile decoration** join with their **camera off** (so
+   their avatar/picture shows instead of video).
+
+- ✅ **Good if:** their decoration (the frame/ring/effect around their picture)
+  shows on their tile **inside the call**, like it does elsewhere in the app.
+- ❌ **Tell us if:** the decoration is missing, cut off, or in the wrong place.
+
+### 9. The call screen looks right
+
+1. Just look at the overall call screen.
+
+- ✅ **Good if:** backgrounds, colors, and layout look normal — nothing is a weird
+  black box, see-through in a bad way, or overlapping.
+- ❌ **Tell us if:** anything looks visually broken or out of place.
+
+---
+
+## 🙏 Thank you!
+
+If a call ever sounds bad for **everyone** (not just you), let us know right away —
+that's the one we most want to hear about quickly, and we can switch back fast.

LOTUS_BUGS.md

@@ -80,6 +80,58 @@ Items from testing, with their fork-level fix path:
 
 - **N127 — ML denoise shim is never injected in `vite dev`.** The `lotusDenoise` plugin injects only on `closeBundle` (build), so ML noise suppression is silently inactive during local dev. Add a dev-mode injection (`configureServer` / `transformIndexHtml`). Dev-only impact. _Note: this **dissolves entirely** once denoise moves in-source in the fork (A7 fix) — there is then no build-time injection to be missing in dev._
 
+### 🧨 Encryption / E2EE — ⚠️ EXTREME COMPLEXITY · 🧠 PLANNING SESSION REQUIRED · 👤 SENIOR ENGINEER
+
+> **Observed live in prod 2026-06-30** on `chat.lotusguild.org` during a 2-person
+> **Element Call** (E2EE enabled). These span **client rust-crypto (via
+> `matrix-js-sdk@41.6.0-rc.0`) ↔ Synapse ↔ Element Call's MatrixRTC E2EE** and are
+> very likely **interrelated** (see KE-1 → KE-2). Do **not** spot-fix — they need
+> a dedicated cross-system planning session with the homeserver owner. Capture
+> full client console + a synapse-side trace for the same call before starting.
+> **None of these are caused by the EC fork work** (the issues reproduce on the
+> old build; the local mic/denoise path is unrelated to key distribution).
+
+- **KE-1 — One-time-key (OTK) upload conflict storm (CRITICAL, root-cause candidate).**
+  `POST /_matrix/client/v3/keys/upload` returns `400 M_UNKNOWN: One time key
+signed_curve25519:AAAAAAAAAGQ already exists. Old key: {…} new key: {…}` —
+  firing **continuously** (many/sec). The client repeatedly tries to publish an
+  OTK at a key id the server already holds **with a different value**, i.e. the
+  rust-crypto key store and Synapse have **diverged OTK state**. Impact: floods
+  the crypto outgoing-request loop and is the prime suspect for the downstream
+  missing-key failures (no fresh OTKs ⇒ no new Olm sessions ⇒ undecryptable
+  to-device key events). _Investigate:_ device/key-store reset-or-restore
+  mismatch, OTK id-counter desync, RC-SDK (`41.6.0-rc.0`) regression, or a
+  Synapse OTK bug. Repro signature: grep console for `already exists`.
+  **Extreme — planning session.**
+
+- **KE-2 — Element Call media keys not arriving/decrypting → audio & video cut out (CRITICAL).**
+  `MissingKey: missing key at index N for participant @user`, `skipping decryption
+due to missing key`, `MissingKey: key set not found for @user at index 0`, and
+  rust-crypto `WARN … Received an unexpected encrypted to-device event …
+event_type="io.element.call.encryption_keys"`. EC distributes per-participant
+  media keys as **encrypted to-device `io.element.call.encryption_keys`** events;
+  these aren't being received/decrypted in order, so remote LiveKit audio/video
+  can't be decrypted — **this is the "friend's audio cuts out occasionally"
+  symptom.** Almost certainly downstream of **KE-1** (broken Olm sessions). Spans
+  EC's MatrixRTC E2EE + rust-crypto to-device + Synapse. **Extreme — planning
+  session.**
+
+- **KE-3 — Timeline decryption error: missing `algorithm` field (HIGH).**
+  `Error decrypting event (… type=m.room.encrypted …): DecryptionError[msg:
+missing field 'algorithm' at line 1 column 138 …]`. A malformed/legacy
+  encrypted event (or a serialization mismatch in the RC SDK) that rust-crypto
+  can't parse. Lower frequency than KE-1/2 but a distinct decode-path failure —
+  capture the offending event id (`$SASBBzoqj…` seen) and inspect its raw content.
+
+- **KE-4 — MatrixRTC delayed-event / membership timeouts (MEDIUM-HIGH, reliability).**
+  `[MembershipManager] Network local timeout error while sending event, immediate
+retry … AbortError: Restart delayed event timed out before the HS responded`,
+  with repeated `org.matrix.msc4157.update_delayed_event`. MSC4140/4157
+  delayed-event reliability against `matrix.lotusguild.org` — can cause stale/ghost
+  call membership and missed leave events. May be partly **homeserver
+  responsiveness**; correlate with synapse latency/load. Include in the same
+  planning session since it shares the call-reliability + HS-interaction surface.
+
 ### Security & Privacy
 
 - **N97 — Access token stored in plaintext `localStorage`** (`state/sessions.ts`), vulnerable to XSS; device ID likewise. Architectural — needs a token-protection / session-storage redesign.