feedback5 CB5: the boss round's prep shows both players of a pair together — the partner's pieces on the other half, as the battle places them — and frames the pair's two avatars in the official green (community report of 2026-10-06, item 51)

The own half was already the official one (the right-hand player on the right half with the
right_boss_*_camera_param camera, its layout mirrored col c -> 20 - c with RIGHT <-> LEFT, so its operators
face the leader as before: research 09 §1.2, DESIGN §15); the partner's half stood empty and nothing framed
the pair.
Server: in a boss round's prep m.private.bossMate { playerId, side, units } = the partner's board as UnitInfo
on its half (Match.bossMateView, finalAssault.js bossFieldPlacement); markPrivate marks the partner's
m.private with the mover's, so it follows live; a scout of either player (Match.prepFieldMeta) carries both
halves (`mate`), and its signature covers the partner's board.
Client: render/app.js syncMates draws the partner's units read-only ('m:<uid>' views: never picked, dragged
or swept with the own pieces) and the whole boss field is lit; the team panel frames the pair's avatars
(gameLogic teamFrameIds: the players still in by seat, two by two, as prepCamera — the boss field in the
fight) from the round start through the Final Assault / Hidden Core, with the official ui/battle
bg_team_border tinted the autochess green (#4ed8af; a plain ring without the local art); none for a lone
player, an eliminated player, a spectator seat, or 联防.
Overlap with PR #191 (same-field frames, issue #190; not merged): it published m.public bossPairing and
framed the partner alone in gold, 联防 included, plus a banner naming the partner; here the pairing is read
as the prep camera already does, both avatars get the official green frame, boss rounds only.
[ASSUMED] the partner's bench is not shown; one frame per avatar.

Golden unchanged. Tests: test/match/feedback5-boss-pair-prep.test.js (new, 4), the item 55 test now checks
the scouted player's own pieces (the partner's stand on the other half); SP_E2E
test/ui/feedback5-boss-pair.e2e.test.js (new, 2: both halves and the frames in prep and fight; item 55's
eliminated guest on the boss field with the leader). Docs: design/client.md §10 / §15, design/network.md,
PLAYING.md.

server/match/match/messaging.js

@@ -52,8 +52,17 @@ export class MatchMessaging {
   }
 
   markPublic() { this._pubDirty = true; }
-  /** A player's state changed: its m.private and (throttled, deduplicated) m.public (level, board, bonds…). */
-  markPrivate(ps) { if (ps) { this._privDirty.add(ps); this._pubDirty = true; } }
+  /**
+   * A player's state changed: its m.private and (throttled, deduplicated) m.public (level, board, bonds…) — in a boss
+   * round's prep also its pair partner's m.private, which shows this board on its other half (bossMate, item 51).
+   */
+  markPrivate(ps) {
+    if (!ps) return;
+    this._privDirty.add(ps);
+    this._pubDirty = true;
+    const m = this._bossMateOf(ps);
+    if (m) this._privDirty.add(m.mate);
+  }
 
   /** Send pending m.private (per player, only when changed) and m.public (throttled ≤ 10/s). */
   flush(forcePublic = false) {

server/match/match/views.js

@@ -184,17 +184,17 @@ export class MatchViews {
     return previewOf([...this.wave.spawns, ...bounty]);
   }
 
-  /** UnitInfo list of a player's board and hand (prep scouting): board pieces on their tiles, held pieces on the
-   *   hand row (row 7) — the scout renders like the own prep bench. */
-  prepFieldMeta(ps) {
+  /** A 自选 piece's pick (like the sim's UnitInfo.diy): a scout's card composes the operator from it (shared/diy.js). */
+  _diyInfo(ps, piece) {
+    const p = piece.kind === 'chess' && typeof ps.diyPickOf === 'function' ? ps.diyPickOf(piece.id) : null;
+    return p ? { charId: p.charId, skillIndex: p.skillIndex, uniEquipId: p.uniEquipId } : undefined;
+  }
+
+  /** UnitInfo of a player's board pieces on their (board) tiles — a prep scout's board, the boss partner's (bossMateView). */
+  _prepBoardUnits(ps) {
     const units = [];
-    // the scouted player's own view of the data (0.2.0 自选编队: its slotted DIY slots are its operators — player/diy.js)
+    // the player's own view of the data (0.2.0 自选编队: its slotted DIY slots are its operators — player/diy.js)
     const gd = ps.gd || this.gd;
-    // a 自选 piece's pick (like the sim's UnitInfo.diy): the scout's card composes the operator from it (shared/diy.js)
-    const diyOf = (piece) => {
-      const p = piece.kind === 'chess' && typeof ps.diyPickOf === 'function' ? ps.diyPickOf(piece.id) : null;
-      return p ? { charId: p.charId, skillIndex: p.skillIndex, uniEquipId: p.uniEquipId } : undefined;
-    };
     for (const { r, c, piece } of boardOrder(ps.board)) {
       const chess = piece.kind === 'token' ? null : gd.chess(piece.id);
       // 0.2.0 补位: a chess this player fields as its stand-in is deployed with the stand-in's body — name, art, max HP,
@@ -214,9 +214,42 @@ export class MatchViews {
         // the equipped items (like the sim's UnitInfo): a 变形同构体 wearer shows as a member of the bond it grants
         items: piece.kind === 'chess' && Array.isArray(piece.items) && piece.items.length ? piece.items.map((it) => it.id) : undefined,
         standInFor: rec && rec.standInFor ? rec.standInFor : undefined,
-        diy: diyOf(piece),
+        diy: this._diyInfo(ps, piece),
       });
     }
+    return units;
+  }
+
+  /**
+   * A boss round's prep (最终攻势 / 隐秘核心: the pairing planned, no field up yet): the other player of `ps`'s pair as
+   * { mate: PlayerState, side: its half 'L' | 'R' }, else null (a lone player, any other phase).
+   */
+  _bossMateOf(ps) {
+    if (!ps || !this.bossWaves || this.fields.length) return null;
+    const g = this.bossGroupOf(ps);
+    const pid = g && g.players.length > 1 ? g.players.find((x) => x !== ps.playerId) : null;
+    const mate = pid ? this.players.get(pid) : null;
+    return mate ? { mate, side: g.side === 'R' ? 'L' : 'R' } : null;
+  }
+
+  /**
+   * m.private `bossMate` (community report of 2026-10-06, item 51): in a boss round's prep the partner's board on its
+   * half of the boss field, as the battle will place it (bossFieldPlacement: the right half mirrored, RIGHT ↔ LEFT) — the
+   * own prep view draws it beside the own half, read-only, as the official prep shows both players of a pair together
+   * (the official client knows every board: ChangePositionDn { boardStatus }, research 09). Null otherwise.
+   * @returns {{ playerId: string, side: 'L'|'R', units: object[] } | null}
+   */
+  bossMateView(ps) {
+    const m = ps && ps.alive ? this._bossMateOf(ps) : null;
+    if (!m) return null;
+    return { playerId: m.mate.playerId, side: m.side, units: this._prepBoardUnits(m.mate).map((u) => this._onBossHalf(u, m.side)) };
+  }
+
+  /** UnitInfo list of a player's board and hand (prep scouting): board pieces on their tiles, held pieces on the
+   *   hand row (row 7) — the scout renders like the own prep bench. */
+  prepFieldMeta(ps) {
+    const units = this._prepBoardUnits(ps);
+    const gd = ps.gd || this.gd;
     // the hand (整备区) and the 临时整备区 scout exactly like the own prep bench renders them: pieces as units on
     // their rows (hand row 7, col = hand slot; temp row 8, cols 4..8 = temp slots; no dir — bench pieces face right),
     // items included (the client draws their floating plates). PRTS 帮助 counts the temp area with the hand (review of
@@ -240,7 +273,7 @@ export class MatchViews {
         moduleId: lo && typeof lo.moduleId === 'string' ? lo.moduleId : undefined,
         items: piece.kind === 'chess' && Array.isArray(piece.items) && piece.items.length ? piece.items.map((it) => it.id) : undefined,
         standInFor: standIn && standIn.standInFor ? standIn.standInFor : undefined,
-        diy: diyOf(piece),
+        diy: this._diyInfo(ps, piece),
       });
     };
     for (let i = 0; i < ps.hand.length; i++) {
@@ -261,9 +294,12 @@ export class MatchViews {
     // round's leader at its spawn tile (nextEnemies `start`), framed by the boss-field prep camera of the player's side
     // (`side`). Until 0.2.0 an eliminated player or a spectator seat scouting a player then saw the normal board and no
     // leader at all (community report of 2026-10-06, item 55).
+    // The pair's other player stands on the other half (item 51: both players of a pair together, as in the battle).
     const g = this.fields.length ? null : this.bossGroupOf(ps);
-    if (g) return { ...meta, kind: 'boss', rect: { ...GEO.BOSS_RECT }, side: g.side, units: units.map((u) => this._onBossHalf(u, g.side)) };
-    return meta;
+    if (!g) return meta;
+    const mate = this.bossMateView(ps);
+    const own = units.map((u) => this._onBossHalf(u, g.side));
+    return { ...meta, kind: 'boss', rect: { ...GEO.BOSS_RECT }, side: g.side, units: mate ? [...own, ...mate.units] : own, ...(mate ? { mate: { playerId: mate.playerId, side: mate.side } } : {}) };
   }
 
   /** A prep UnitInfo (board, bench or temp row) placed on side 'L' | 'R' of the boss field (bossFieldPlacement). */

server/match/match/watch.js

@@ -240,13 +240,18 @@ export class MatchWatch {
 
   /** Board signature of a prep scout view (board, hand and temp rows: a shop or funds change is not a board change).
    *  Hand / temp entries carry their slot — `prepFieldMeta` draws x from it, so a piece moved to another slot is a
-   *  change (review of PR #129). */
+   *  change (review of PR #129). In a boss round's prep the pair partner's board is part of the view (item 51). */
   _prepScoutSig(ps) {
     const parts = [];
-    for (const { r, c, piece } of boardOrder(ps.board)) {
-      const items = piece.kind === 'chess' && Array.isArray(piece.items) ? piece.items.map((it) => `${it.uid}:${it.id}`).join(',') : '';
-      parts.push(`${piece.uid}:${piece.id}@${r},${c}:${pieceDir(piece)}:${items}`);
-    }
+    const boardSig = (q) => {
+      for (const { r, c, piece } of boardOrder(q.board)) {
+        const items = piece.kind === 'chess' && Array.isArray(piece.items) ? piece.items.map((it) => `${it.uid}:${it.id}`).join(',') : '';
+        parts.push(`${piece.uid}:${piece.id}@${r},${c}:${pieceDir(piece)}:${items}`);
+      }
+    };
+    boardSig(ps);
+    const m = this._bossMateOf(ps);
+    if (m) { parts.push(`|mate:${m.mate.playerId}:${m.side}`); boardSig(m.mate); }
     for (let i = 0; i < ps.hand.length; i++) {
       const piece = ps.hand[i];
       if (!piece) continue;

server/match/player/views.js

@@ -55,6 +55,8 @@ export class PlayerViews {
     const free = this.shop.freeRefreshes > 0;
     const board = [];
     for (const { r, c, piece } of boardOrder(this.board)) board.push(this.pieceView(piece, [r, c]));
+    // a boss round's prep: the partner's board on its half of the boss field (Match.bossMateView, item 51)
+    const bossMate = typeof this.m.bossMateView === 'function' ? this.m.bossMateView(this) : null;
     return {
       t: 'm.private',
       playerId: this.playerId,
@@ -98,6 +100,10 @@ export class PlayerViews {
       // switched off)
       diy: this.diy,
       diyBanned: this.diyBanned,
+      // 最终攻势 / 隐秘核心 prep (community report of 2026-10-06, item 51): `{ playerId, side, units }` — the pair partner's
+      // board pieces as UnitInfo on its half of the boss field (mirrored on the right half, as the battle places them);
+      // the own prep view draws them beside the own half, read-only. Absent otherwise.
+      ...(bossMate ? { bossMate } : {}),
       stats: {
         dmgDealt: Math.round(this.stats.dmgDealt), kills: this.stats.kills, leaks: this.stats.leaks, gold: this.stats.gold,
         refreshes: this.stats.refreshes, merges: this.stats.merges,