Face room: a peer's multi-paragraph line arrives empty (3+ lines lose first/last line) — room.message viewed twice #302

Summary

In a Face-to-face room, a peer line with two paragraphs arrives on the other home as an empty bubble. A line with three or more lines loses its first and last line. Single-line text and plain two-line text arrive intact. The text is complete on Bot Social, so this is a FlyBot client bug. The cause is proven below; it is not the new mentions field.

Environment

• FlyBot main a003044 (after fix(ui,host): stable tool mask, one Main Bot term, own Bots only as Main Bot, short typed-line header, display name in People with access #292, Face rooms: sender-side explicit mention list (handles) on typed lines, receiver resolves by handle first (follow-up to #287) #293/feat(face-rooms): explicit mention list: typed lines carry target handles, receiver resolves by handle first (#293) #294, Face rooms: a plain line should let every Bot in the room answer (one round, capped), not only the first (follow-up to #287) #295/feat(face-rooms): a plain line lets every Bot in the room answer, one pass, capped (#295) #296), core + plugins/social + plugins/tree on @deepseek-ai/dsh@0.2.0-rc.2, Node 24.
• Two fresh installs on one Linux box: A :3090 (SelfA1622, @selfa1622.home) and B :3091 (SelfB1622, @selfb1622.home). Both Chiefs run ark/deepseek-v4-flash. A's Chief is shared with B by a per-Bot invite.
• Bot Social prod https://47-80-69-220.sslip.io (deploy 1870786, features typed_by_owner, mentions).
• Scheduled product self-test, focus: Face-to-face room, 2026-10-18 16:27–16:33 Asia/Shanghai.

Repro

1. A: + → Face-to-face group → Chief → number 482913. B joins the same number with Chief. Enter chat.
2. A types hi from A (a plain line, so both Chiefs answer, Face rooms: a plain line should let every Bot in the room answer (one round, capped), not only the first (follow-up to #287) #295). Approve A's Chief's reply on A.
3. A's Chief's reply has two paragraphs: Hi from A's side 👋 I'm Chief, A's assistant here. … nice face-to-face setup. + blank line + Anything you'd like us to work on together while we're here? @SelfB1622's Chief, want to say hello from B's side?
4. Look at that line on B.

Actual

• On A the reply shows in full.
• On B it is an empty grey bubble under SelfA1622's Chief @chief.selfa1622.home. It stays empty after a reload and in Past rooms → Open (read-only). B's sidebar preview reads SelfA1622's Chief： with nothing after it. Screenshot: B's room with the empty bubble between B's own Chief line and the user's next line.
• The short reply later (2 + 2 = 4 😄) arrives fine.
• B's stored transcript has the line with "text": "" (room log seq 6, no eventId). B's room Session got [Group post from Chief · SelfA1622]\n with nothing after it, so B's Chief also saw an empty post.

Evidence (read-only)

• Bot Social has the full text. GET /v1/face-rooms/frm_01M571ZK5FZCKPS54G5J27B4ZS?after=0 (as A; B had left, so it got 404) returns event 199 with untrusted_content: { text: "Hi from A's side …\n\nAnything … from B's side?" } (240 chars). That event has no mentions field. Mentions only appear on B's typed line 201, and that line arrived fine.
• Root cause: the event is "viewed" twice. faceApi.get() → viewFaceRoom() → viewFaceEvent() turns untrusted_content into a plain string untrustedText. applyFaceSnapshot() (plugins/social/src/social.js L2211) then calls renderFaceEvent(event), which calls viewFaceEvent() again. On that second pass untrusted_content is absent, so faceUntrustedText(untrustedText) takes the string branch. That branch (face-rooms.js L64–69, UNTRUSTED = /^[\s\S]*?\n([\s\S]*)\n[^\n]*$/) assumes a wrapped <marker>\n…\n<marker> string. It drops the first and last line of any plain text with ≥ 2 newlines.
• Reproduced with the real server payload (node, on a003044):

  viewFaceRoom(serverBody) → renderFaceEvent(ev, { attested: true }).text
  198 "hi from A"            → "hi from A"
  199 (240 chars, 2 paras)  → ""
  202 "2 + 2 = 4 😄"          → "2 + 2 = 4 😄"
  "line1\nline2\nline3"     → "line2"
  

• The same path handles every received room.message: Bot lines, people's typed lines, and Past rooms replay. Any multi-paragraph message from another home is blanked or cut.

Expected

• Every home shows a peer's line exactly as Bot Social delivered it, including paragraphs and line breaks (docs/subsystems/social.md: peer text is fenced, not rewritten).
• The receiving Bot sees the same fenced text.
• A regression test feeds a multi-paragraph room.message through viewFaceRoom → applyFaceSnapshot/renderFaceEvent.

Fix direction (not done here)

Make viewFaceEvent idempotent: keep an already-viewed untrustedText string as-is, or have renderFaceEvent accept a viewed event without viewing it again. Apply the marker regex only to strings that really carry the begin/end markers.