feedback5: merge CB5 — community reports (match / UI): module 特性追加 shown after the base trait (text only), a shop upgrade fills its new slot at once, spectators follow the player they picked through every phase (g.watch carries the playerId — PR #189's idea), the boss shows in boss-round prep scouting, the final-boss prep shows the pair together with green avatar frames (PR #191's idea, official colour); §25.19 after the hotkeys' §25.15; golden: the 18 bot matches (the upgrade's new card), battles unchanged

docs/design/client.md

@@ -37,7 +37,7 @@ Visuals: oblique perspective board (tilted ~30°, trapezoid tiles), raised highl
 
 Look & feel: research 06 §11–§12 (near-black green-grey panels, mint `#4ed8af` accents, gold prices, bracket frames, hexagon badges, bond discs, 7-segment countdown). Fonts: Noto Sans SC (Google Fonts with local fallback), Bender/Novecento self-hosted for numerals and Latin micro-labels.
 
-Screens: **Title** (season art backdrop, 开始 → nickname), **Lobby** (独立模拟 / 同盟模拟 → create or join; recent rooms), **Room** (4 seats, invite code + copy link, difficulty picker (host), add/remove AI, ready, start), **Briefing** (INFO_CHECK: stage, factions, disabled bonds, banned chess, boss silhouette, ready x/4), **Band draft** (grid of 40 bands with icon/name/LP/effect; turn order list; skip; 查看禁用盟约与干员 under the order list opens the briefing's bond rows, legend and banned operators again in a read-only dialog — one component, `ui/matchInfo.js`, §21.28), **Game** (Pixi field + DOM HUD: top bar with round/phase capsule/LP (live during the own battle, §17.5)/timer/ready; bond strip + popups; left team panel with LP/status/emote bubbles, click to watch; bottom shop bar (level card, 3–5 chess cards, item card, funds, refresh, freeze, collapse); detail panel on click/hover (header with bonds, then 特质 — the operator's own effect — right under it, 特性, stats (live: the battle's own numbers / the start-of-battle ones in prep, §18.5), skill, module, equipped items, talents: §17.5); enemy preview drawer (next round enemies with counts, factions; its 本局信息 tab lists the briefing's disabled bonds and banned operators, §21.28); 机变 overlay (the official card: framed icon + name, the effect text — data `descRaw` — under it, the taker's round avatar at the top-right; two taps, §18.2, §20.7); merge reward overlay (the promotion reward, or a special offer — 凯瑟琳's 定向投放 … — as item / chess cards under its source's label, with the count of offers queued behind it, §21.2); phase banners; ticker (by broadcast priority, highest first; a leader-damage line plays only in its round and a player's newer one replaces the older, §21.10); toasts; emote wheel; settings (volume, quality, show damage numbers)), **Result** (victory/defeat, rounds, per-player lineup, stats, titles, back to room).
+Screens: **Title** (season art backdrop, 开始 → nickname), **Lobby** (独立模拟 / 同盟模拟 → create or join; recent rooms), **Room** (4 seats, invite code + copy link, difficulty picker (host), add/remove AI, ready, start), **Briefing** (INFO_CHECK: stage, factions, disabled bonds, banned chess, boss silhouette, ready x/4), **Band draft** (grid of 40 bands with icon/name/LP/effect; turn order list; skip; 查看禁用盟约与干员 under the order list opens the briefing's bond rows, legend and banned operators again in a read-only dialog — one component, `ui/matchInfo.js`, §21.28), **Game** (Pixi field + DOM HUD: top bar with round/phase capsule/LP (live during the own battle, §17.5)/timer/ready; bond strip + popups; left team panel with LP/status/emote bubbles, click to watch (a boss round frames the viewer's pair in green, §15); bottom shop bar (level card, 3–5 chess cards, item card, funds, refresh, freeze, collapse); detail panel on click/hover (header with bonds, then 特质 — the operator's own effect — right under it, 特性, stats (live: the battle's own numbers / the start-of-battle ones in prep, §18.5), skill, module, equipped items, talents: §17.5); enemy preview drawer (next round enemies with counts, factions; its 本局信息 tab lists the briefing's disabled bonds and banned operators, §21.28); 机变 overlay (the official card: framed icon + name, the effect text — data `descRaw` — under it, the taker's round avatar at the top-right; two taps, §18.2, §20.7); merge reward overlay (the promotion reward, or a special offer — 凯瑟琳's 定向投放 … — as item / chess cards under its source's label, with the count of offers queued behind it, §21.2); phase banners; ticker (by broadcast priority, highest first; a leader-damage line plays only in its round and a player's newer one replaces the older, §21.10); toasts; emote wheel; settings (volume, quality, show damage numbers)), **Result** (victory/defeat, rounds, per-player lineup, stats, titles, back to room).
 
 盟约栏支持「收起／展开盟约」（GitHub #142）：收起时隐藏完整列表并关闭由列表打开的浮层，让原图标区域的指针事件到达棋盘，只保留至少 44×44 CSS px 的恢复按钮。折叠状态在本局阶段变化、观看队友时保留；展开后仍按当前观看对象显示最新盟约。按钮支持 Enter / Space，聚焦按钮时 Space 不触发准备或暂停。
 
@@ -72,6 +72,6 @@ Target: a **real 3D board layer** rendered with three.js (vendored ESM, no CDN)
 - One camera model drives both layers: `public/js/render/projection.js` keeps its public API (`worldToScreen`, `screenToWorld`/tile picking, presets, transitions) but derives it from a three.js `PerspectiveCamera` initialised from the official configBlackBoard framing, so Spine units, FX, drag/drop and hit-testing stay aligned with the 3D board.
 - Must degrade gracefully: when local-client art or WebGL2 features are missing, fall back to the current 2D atlas board; keep 60 fps (static geometry merged into few draw calls; textures mipmapped; DPR-aware).
 - Implemented (`public/js/render/board3d/*`, `render/app.js`): three.js is downloaded only when the local-art manifest lists the board atlas; the built 3D area, the drawn 2D rows and the lit rect follow `viewKind(kind, {rect})` (the field the camera actually shows: a 'prep' camera on rows ≤ 6 = `bossPrep`); the background plane is extended with mirrored copies and the clear colour matches the fog (no visible edge at any aspect); battle crates live in their own group (survive scene rebuilds) and follow the board mode (`switchableBox`: 3D mesh ⇄ 2D box on a mode switch or a lost WebGL context); quality 'low' drops shadows; `?board=2d|3d` overrides. The direction wheel's range stripes sit between the board canvas and the unit canvas.
-- Done: Final Assault / Hidden Core prep takes place on your own half of the boss field (research 09 §1.2): pieces shown at boss-field positions (row − 7; right-hand player mirrored col → 20 − col, RIGHT ↔ LEFT), drop targets and wheel directions mapped back to board coordinates (`prepCamera` → `bossPrep` in public/js/ui/gameLogic.js; covered by the playtest2 browser tests).
+- Done: Final Assault / Hidden Core prep takes place on your own half of the boss field (research 09 §1.2): pieces shown at boss-field positions (row − 7; right-hand player mirrored col → 20 − col, RIGHT ↔ LEFT), drop targets and wheel directions mapped back to board coordinates (`prepCamera` → `bossPrep` in public/js/ui/gameLogic.js; covered by the playtest2 browser tests). A scout of such a board (`m.field` prep of a boss round) comes in boss-field coordinates with the player's `side` and is framed the same way, the leader standing at its spawn (0.2.0, community report item 55). Both players of a pair are shown together, as in the battle (0.2.0, community report item 51): the partner's board stands on the other half (`m.private.bossMate` units, already in boss-field coordinates: mirrored on the right half, RIGHT ↔ LEFT; read-only `m:<uid>` views of `render/app.js syncMates`), the whole boss field is lit, a scout carries both halves (`mate`), and the team panel frames the pair's avatars in the official green (`ui/battle bg_team_border` tinted, a plain ring without the local art; `gameLogic teamFrameIds`) from the round's start through the fight.
 
 ---

docs/design/network.md

@@ -15,10 +15,10 @@ Platform additions (implemented): `welcome.{resumed, version}`, `welcome.diyKitt
 **Spectator seats** (a remake feature — the official room has none; community report #26, owner's decision 2026-10-04; the spectator-seat subsection of §23): `room.spectate {code}` takes one of a co-op room's `MAX_SPECTATORS` (2) spectator seats, in its lobby or during its match; `room.removeSpectator {playerId}` (host) frees one (`room.closed {reason:'kicked'}` to it); `room.state.spectators: [{playerId, name, connected}]`. A spectator is never a player (not in `seats`, not counted for the start, never host, keeps no room alive — `room.closed {empty}` when the last human leaves), receives the room's broadcasts and watches like an eliminated player (`Match.addSpectator`: `b.start` watch / `m.field`, never `m.private`); it may only `g.watch`, leave, and store a `room.loadout` — anything else answers `error SPECTATOR`. Its seat is kept and given back on reconnect like a player's.
 
 ### 8.2 Match
-C→S (all carry `rid`): `g.infoReady` · `g.band {bandId}` · `g.bandSkip` · `g.bandFocus {bandId?}` (the strategy highlighted in the draft screen — what a timed-out turn takes; absent / null clears it; `WRONG_PHASE` outside BAND_DRAFT, `ALREADY` after the pick, `BAD_TARGET` for a band not allowed; §18.2) · `g.buy {slot}` · `g.refresh` · `g.freeze` · `g.levelUp` · `g.sell {uid}` · `g.move {uid, to:{area:'board', row, col}|{area:'hand', idx}, dir?}` · `g.equip {itemUid, targetUid, replaceUid?}` (`replaceUid`: which equipped item a third one replaces, §6.2) · `g.art {itemUid, row, col, dir?}` (`dir` ∈ UP|RIGHT|DOWN|LEFT from the deploy wheel, §3; absent ⇒ `to.dir`, then RIGHT; `g.move` onto the piece's own tile re-orients it; board pieces in `m.private` / `m.field {prep:true}` carry `dir`) · `g.destroy {uid}` (hand / temp items only; equipped items are locked, §6.2) · `g.reward {idx}` · `g.choice {idx}` · `g.ready {ready}` · `g.emote {id}` · `g.watch {fieldId}` · `g.autoplay {on}` · `g.pause {on}` (solo battles only, §14 Solo pause) · `g.unitStats {seq?}` (ROUND_START / SP_DRAFT / PREP, else `WRONG_PHASE`; eliminated: `ELIMINATED`) → push `m.unitStats` (§18.5) · `g.leave`
+C→S (all carry `rid`): `g.infoReady` · `g.band {bandId}` · `g.bandSkip` · `g.bandFocus {bandId?}` (the strategy highlighted in the draft screen — what a timed-out turn takes; absent / null clears it; `WRONG_PHASE` outside BAND_DRAFT, `ALREADY` after the pick, `BAD_TARGET` for a band not allowed; §18.2) · `g.buy {slot}` · `g.refresh` · `g.freeze` · `g.levelUp` · `g.sell {uid}` · `g.move {uid, to:{area:'board', row, col}|{area:'hand', idx}, dir?}` · `g.equip {itemUid, targetUid, replaceUid?}` (`replaceUid`: which equipped item a third one replaces, §6.2) · `g.art {itemUid, row, col, dir?}` (`dir` ∈ UP|RIGHT|DOWN|LEFT from the deploy wheel, §3; absent ⇒ `to.dir`, then RIGHT; `g.move` onto the piece's own tile re-orients it; board pieces in `m.private` / `m.field {prep:true}` carry `dir`) · `g.destroy {uid}` (hand / temp items only; equipped items are locked, §6.2) · `g.reward {idx}` · `g.choice {idx}` · `g.ready {ready}` · `g.emote {id}` · `g.watch {fieldId, playerId?}` (`playerId`: the player tapped — a shared 联防 / boss pair field shows two; what an eliminated viewer follows, §25) · `g.autoplay {on}` · `g.pause {on}` (solo battles only, §14 Solo pause) · `g.unitStats {seq?}` (ROUND_START / SP_DRAFT / PREP, else `WRONG_PHASE`; eliminated: `ELIMINATED`) → push `m.unitStats` (§18.5) · `g.leave`
 S→C:
 - `m.public` — full public state on every change (throttled ≤ 10/s): `{ phase, round, lastRound, deadline, serverNow, modeId, difficulty, stageId, factions, disabledBonds, bannedChess, bossId, hiddenBossId?, teamLp?, bossHp?:{hp,max}, overtimeAt? /* FA / HC: ms epoch the overtime drain starts, §4 */, paused /* solo pause, §14 */, draft?:{order,turn,picks,skipsLeft,turnDeadline,turnSeconds /* one turn's length, 0 untimed; deadline = turnDeadline (§18.2) */,untimed}, sp?:{family,cards /* bounty cards carry descRaw?, §20.6 */,turn,picks}, players:[{playerId, seat, name, isBot, connected, alive, lp, bandId, shopLevel, boardCount, ready, bonds:[{bondId,count,active,tier,layers,harmony? /* 调和's +1 is in count, §21.26 */}], fieldId, status, pendingLp? /* COMBAT / 联防 of a normal round: the LP the player's own battle will cost at settlement so far, min(lpCapPerRound, counted leaks) — in 联防 min(lpCapPerRound, uniteLeft) — omitted when 0 and in every other phase (§17.5 live LP) */, uniteLeft? /* 联防: the leaker's enemies still standing — not spawned yet + alive + counted leaks, uncapped, live (§20.6) */}] , fields:[{fieldId, kind, players:[playerId...]}] }`
-- `m.private` — the recipient's full PlayerState view (§6.2 minus server-only data) on every change.
+- `m.private` — the recipient's full PlayerState view (§6.2 minus server-only data) on every change; in a boss round's prep also `bossMate { playerId, side, units }` — the pair partner's board on its half of the boss field (UnitInfo, mirrored on the right half), re-sent when the partner moves (0.2.0, community report item 51).
 - `m.field` — field meta when watching starts: `{ fieldId, kind, rect, stageId, units: [UnitInfo], effects? }` (the units on the field, knocked-out operators waiting to redeploy included — `Battle.fieldMeta`, §18.3). The prep-scouting field (`Match.prepFieldMeta`) puts the scouted player's **hand (整备区) and 临时整备区 into `units` as well**: held pieces as units on the hand row (row 7, col = hand slot) and temp pieces on the temp row (row 8, cols 4..8 = the temp slots; PRTS 帮助 counts the temp area with the hand; a held item is a `kind: 'item'` unit the client draws as its floating plate) — the scout renders exactly like the own prep bench, for every watcher alike, the spectator seat's copy equal to a teammate's (§23.19's "never a private view" stays the no-`m.private` rule); the scout signature `_prepScoutSig` carries the hand / temp slots, so a piece moved to another slot is a change — and carries `effects`: the scouted player's effects view (策略 / 机变 / 悬赏 …), the watched player's effects column ready-made
 - NOTE: game time in `b.snap`/`b.ev` is carried as **`gt`** (the frame's `t` is the message type).
 - Active finite zero-SP timed skills display `sp=timeLeft`, `spMax=duration` and `UF.SKILL`; after end they display
@@ -75,7 +75,7 @@ Piece = { uid, kind: 'chess'|'item'|'token', id, golden: bool, tier, items: [ {
 
 **Protocol (additions; `shared/protocol.js` is normative).**
 - `battleId` = `<prefix>.<round>.<seq>.<fieldId>` (`Match._ccField`; `<prefix>` = the match seed in base 36 plus `-<matchNo>`, the room's match number the lobby passes as `opts.matchNo`; `<seq>` counts every battle of the match; the informational `.<fieldId>` is dropped when the id would exceed the protocol's 64 chars): unique for the whole match although field ids repeat (`n:<pid>` every round, `u`, `b1`/`b2` in both boss rounds), and across the matches of one room. The client runner keys its local battles by it (the same id again = the same battle, no rebuild) and the server matches reports by it, so a late `b.progress` / `b.result` of a finished battle — or one that crossed into the room's next match on the same socket — is ignored instead of being credited to another battle.
-- S→C `b.start { battleId, fieldId, kind, spec, authoritative, startAt, serverNow, elapsed, speed, watch, done }` — sent at COMBAT/UNITE/FINAL_ASSAULT/HIDDEN start to every human in the field (联防: to every human; COMBAT and boss rounds: eliminated humans get the first field as a display replica — research 09 "keep-watching auto-observes the first available field"), on `g.watch`, and on reconnect/resync. `elapsed` = game seconds on the field clock (a finished field: its end time); the client fast-forwards to it. `speed` = game seconds per real second (2; tests/tools may speed up).
+- S→C `b.start { battleId, fieldId, kind, spec, authoritative, startAt, serverNow, elapsed, speed, watch, done }` — sent at COMBAT/UNITE/FINAL_ASSAULT/HIDDEN start to every human in the field (联防: to every human; COMBAT and boss rounds: eliminated humans and spectator seats get the field of the player they follow as a display replica — the one they last watched with `g.watch`, else the first player still in; research 09 "keep-watching auto-observes the first available field", 0.2.0 item 56), on `g.watch`, and on reconnect/resync. `elapsed` = game seconds on the field clock (a finished field: its end time); the client fast-forwards to it. `speed` = game seconds per real second (2; tests/tools may speed up).
 - C→S `b.progress { battleId, gt, killed, total, leaks?, left?, bossDmg?, by?, done? }` — authoritative clients, ~1 Hz (boss fields 4 Hz). Normal/联防: `leaks` = counted leaks so far; 联防: `left` = per leaker its enemies still standing (`spec.js uniteLeft`, clamped by the server to `fields.js uniteBillBounds`; §20.6). Boss: `bossDmg` = cumulative damage of this field to the shared pool, `by` = the same per player, `leaks` = the field's cumulative LP cost (leaks × `lpr` + leader "扣除目标生命" effects; `spec.js attachLpMeter`). The server applies deltas (never twice). Stale reports (unknown battle, not the authority, after the match ended) are ignored, never answered with an error; the platform never answers a rid-less `b.progress` with an error frame (it would surface as a toast).
 - C→S `b.result { battleId, result }` — authoritative client at battle end; `result` = `compactResult(BattleResult)` (the fields the match consumes; ≤ 4 players, ≤ 400 leaks, ≤ 64 unitsEnd, ≤ 160 unitStats, ≤ 40 layer gains; `fitResult` keeps the frame ≤ 60 KB: unit statistics, then leak mods, then — boss only — leak entries go first). Structural checks in `isBattleResult`; `server/net.js` routes `b.*` frames to the match (lobby `routeGame`).
 - S→C `b.pool { hp, max, teamLp, acked: { [fieldId]: cumulative damage counted } }` (boss rounds, ≤ 4 Hz; exact numbers, never rounded) — clients reconcile their `LocalBossPool`: displayed pool = server hp − (local cumulative damage − acked). Pools never hold less than 1 HP (`BOSS_POOL_MIN_HP`: `SharedBossPool` and `LocalBossPool`; a browser pool reads any finite rest below 1 as 0 — §20.5); the 'cleared'-result dust rule (a boss field whose client result is `'cleared'` while < 1 HP is left on the server empties the pool) only catches noise at that boundary.
@@ -89,7 +89,7 @@ Piece = { uid, kind: 'chess'|'item'|'token', id, golden: bool, tier, items: [ {
 
 **Solo pause (official `PauseUp` / `ResumeUp`; `Match.setPause`).** C→S `g.pause { on }`: solo matches only (co-op → `WRONG_PHASE 'co-op battles never pause'`), and `on: true` only while a battle runs (COMBAT / FINAL_ASSAULT / HIDDEN_CORE with a live field, not once the Final Assault is ending — else `WRONG_PHASE 'no battle running'`); `on: false` is always accepted. While `m.public.paused` is true everything of the battle is frozen: the field clock (`b.start elapsed`, the boss plausibility budgets and the overtime drain), the authority deadline and the server-run release timers, the boss clock, the HUD `deadline` / `overtimeAt` (shifted by the paused time on resume) and the server-run pacers (FieldRunner / HeadlessPacer skip their intervals); the browser's runner stops its local clock. In solo battles the top bar shows a 暂停 / 继续作战 button (`ui/hud.js PauseButton`, `ui/matchStatus.js pauseAvailable`; `Space` toggles it), a paused overlay offers 继续作战 / 放弃模拟, and the HUD clocks freeze at the pause moment. A disconnect or leave resumes (the server takes the field over — nobody is left to resume it); the battle phase ending drops the pause.
 
-**Spectating (research 09 §3.1 / §6.3).** No live spectating while your own normal battle runs (`g.watch` → `WRONG_PHASE 'own battle running'`; the UI toasts "作战中无法查看队友"). After your own battle ends you see "⌛ 作战结束，等待队友完成作战" with each teammate's live progress (`m.public.fields[].progress`); tapping a teammate's avatar expands **前往查看** → `g.watch` → `b.start` (display replica fast-forwarded to the field clock); the own row shows **返回战场**. Prep: the same flow shows the teammate's board (`m.field` with `prep: true`) and sends it again when that board changes (GitHub #87). The scout is framed by the prep camera in its shop-folded form and renders the teammate’s hand (整备区) and 临时整备区 as units on their rows — the own prep bench’s exact look (user playtest #2 item 1, the GitHub #44 suggestion; the spectator seat's scout view is the same, §23.19's never-a-private-view staying the no-`m.private` rule). While scouting, the 本局信息 drawer shows the watched player's 策略 in place of one's own (`game.js scoutPid` → `enemyDrawer.js InfoTab bandId / bandOwner`, labelled "X 的策略"; user playtest #2 item 2), and the right effects column follows the watched field too: the scout meta carries the player's effects view, a display-replica battle derives it from the spec's `playerEffects` (`battle/observe.js spectateEffects`) — undefined (empty column, never one's own) for 联防 / boss pair fields and server-run watched fields. 联防: every human receives the unite spec (helpers + observers). Final Assault: each human sees its own pair field; the other pair → `BAD_TARGET 'other group hidden'`. In 联防/FA fields the ‹ › pill switches the camera LEFT half / 全景 / RIGHT half ("你自己" / "👁 name" / "全景" / "无人在家"); there is **no** view switcher during normal combat. Eliminated players start each combat phase on the first field (auto-observe) and may watch any field.
+**Spectating (research 09 §3.1 / §6.3).** No live spectating while your own normal battle runs (`g.watch` → `WRONG_PHASE 'own battle running'`; the UI toasts "作战中无法查看队友"). After your own battle ends you see "⌛ 作战结束，等待队友完成作战" with each teammate's live progress (`m.public.fields[].progress`); tapping a teammate's avatar expands **前往查看** → `g.watch` → `b.start` (display replica fast-forwarded to the field clock); the own row shows **返回战场**. Prep: the same flow shows the teammate's board (`m.field` with `prep: true`) and sends it again when that board changes (GitHub #87). In a boss round's prep that board is built on the boss field — the player's half (rows − 7, the right half mirrored with RIGHT ↔ LEFT, `server/match/finalAssault.js bossFieldPlacement`), `kind: 'boss'`, `side`, the leader in `nextEnemies` at its spawn tile — and framed by the boss-field prep camera of that side, so a watcher sees the leader as the players do (0.2.0, community report item 55). The scout is framed by the prep camera in its shop-folded form and renders the teammate’s hand (整备区) and 临时整备区 as units on their rows — the own prep bench’s exact look (user playtest #2 item 1, the GitHub #44 suggestion; the spectator seat's scout view is the same, §23.19's never-a-private-view staying the no-`m.private` rule). While scouting, the 本局信息 drawer shows the watched player's 策略 in place of one's own (`game.js scoutPid` → `enemyDrawer.js InfoTab bandId / bandOwner`, labelled "X 的策略"; user playtest #2 item 2), and the right effects column follows the watched field too: the scout meta carries the player's effects view, a display-replica battle derives it from the spec's `playerEffects` (`battle/observe.js spectateEffects`) — undefined (empty column, never one's own) for 联防 / boss pair fields and server-run watched fields. 联防: every human receives the unite spec (helpers + observers). Final Assault: each human sees its own pair field; the other pair → `BAD_TARGET 'other group hidden'`. In 联防/FA fields the ‹ › pill switches the camera LEFT half / 全景 / RIGHT half ("你自己" / "👁 name" / "全景" / "无人在家"); there is **no** view switcher during normal combat. Eliminated players and spectator seats follow a player through every phase reset (0.2.0, community report item 56; the official DeadAutoObDn { obIndex, state, preparation }; the idea of PR #189): the player they last watched with a manual `g.watch` (`Match.watchPref`; a shared field records the `playerId` tapped, else nobody), else the first player still in (seat order, AI seats included) — the round start pushes that player's prep board (`Match._followScout`, adopted by the screen like a 前往查看 tap: `battle/observe.js followedScout`; kept through 机变 and 休整期), each battle starts on that player's field, a resync / a spectator joining in prep gets the board again; they may watch any field.
 
 **Client runner.** `public/js/battle/runner.js` owns the local Battles: fixed-step clock at the battle speed (60 ticks per real second at 2×, at most `max(8, 4·speed)` ticks per frame, bounded fast-forward of ≤ 240 ticks per frame when far behind; a new battle is caught up silently before it is shown), feeds the existing renderer through the same `snapshot()`/`drainEvents()` wire formats every frame (`view.setLocalFeed` shrinks the interpolation buffer to ~2 frames), publishes the field meta (m.field shape + `local`, `battleId`, `players`, `sides`, `speed`) into `store.match.field` and its state into `store.match.battle` (with `leaks: { [fieldId]: counted leaks so far }` of every normal field it simulates and, while the 联防 field is on screen, `uniteLeft` per leaker (§20.6), authoritative or display replica — the settle rule's count, `/sim/spec.js battleProgress`; published in the frame a count changes: the live LP of §17.5), sends `b.progress`/`b.result` when authoritative (results retried once on timeout; a result lost with the socket — the request failed `DISCONNECTED` / `OFFLINE` or timed out twice — is kept and sent again when the session is back online and whenever a `b.start` still names that finished battle `authoritative: true`; the server answers a duplicate `ok` and changes nothing; a server refusal is final), follows `m.public.paused` (solo pause: every local clock stands still, resume shifts it by the paused time), handles `b.pool`/`b.end`, fast-forwards on reconnect/observe, and survives tab backgrounding (a 250 ms interval pump keeps authoritative battles on their clock while hidden; the server deadline + takeover cover extreme cases). Catch-up frames keep the state events and every enemy form fx (`keepsState`); while hidden, the battle on screen holds them for the first frame back (`hold`; past `HELD_MAX` the superseded status / skill toggles are dropped, `compactHeld`, and only a backlog still past it re-enters the view from the field meta), and a battle that ended while hidden delivers them when the tab is shown; a catch-up frame or a hidden step drains its events every `EV_SLICE` (15) ticks, each batch stamped with its own game time (`gt`), so a late form fx reaches the render engine as late as it is; the game screen's pre-entry buffer (`keepEarly`, also while a re-sent field meta re-enters the field on screen) and the render engine's event queue (`render/interp.js isCosmeticEvent`) never drop a form fx either (§21.4). Sim content errors are logged as console warnings (the server logs its own). The sim loader fetches the ten data files (one retry each) and fails when any is missing — a battle on partial data would report a plausible wrong result — so the next `b.start` retries and the server's deadline covers the field meanwhile. `public/js/battle/observe.js` holds the observing rules and labels.