diff --git a/package-lock.json b/package-lock.json
index 805abbe..46e31b4 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14,6 +14,7 @@
         "@thisbeyond/solid-dnd": "^0.7.5",
         "aedes": "^1.1.1",
         "chokidar": "^5.0.0",
+        "comlink": "^4.4.2",
         "commander": "^14.0.3",
         "csv-parse": "^6.1.0",
         "csv-stringify": "^6.7.0",
@@ -4332,6 +4333,12 @@
         "node": ">= 0.8"
       }
     },
+    "node_modules/comlink": {
+      "version": "4.4.2",
+      "resolved": "https://registry.npmjs.org/comlink/-/comlink-4.4.2.tgz",
+      "integrity": "sha512-OxGdvBmJuNKSCMO4NTl1L47VRp6xn2wG4F/2hYzB6tiCb709otOxtEYCSvK80PtjODfXXZu8ds+Nw5kVCjqd2g==",
+      "license": "Apache-2.0"
+    },
     "node_modules/commander": {
       "version": "14.0.3",
       "resolved": "https://registry.npmjs.org/commander/-/commander-14.0.3.tgz",
diff --git a/package.json b/package.json
index 2c6afbb..9e80a2e 100644
--- a/package.json
+++ b/package.json
@@ -47,6 +47,7 @@
     "@thisbeyond/solid-dnd": "^0.7.5",
     "aedes": "^1.1.1",
     "chokidar": "^5.0.0",
+    "comlink": "^4.4.2",
     "commander": "^14.0.3",
     "csv-parse": "^6.1.0",
     "csv-stringify": "^6.7.0",
diff --git a/src/components/stores/journalStream.ts b/src/components/stores/journalStream.ts
index 0e5b5be..ee04dfa 100644
--- a/src/components/stores/journalStream.ts
+++ b/src/components/stores/journalStream.ts
@@ -1,20 +1,21 @@
 /**
- * Journal Stream — Client Store
+ * Journal Stream — Client Store (Worker Proxy)
  *
- * Reactive state for a single session's message stream. Manages MQTT
- * connection, local message log, per-sender sequence tracking, and the
- * revealed-paths set (populated by the link reducer).
+ * This is the main-thread side of the journal stream. It spawns a Shared
+ * Worker that owns the MQTT connection. All state flows from the worker
+ * to this store via Comlink callbacks.
  *
- * Session lifecycle (create/list/delete) is handled via MQTT retained
- * topics — ttrpg/$SESSIONS for the manifest and ttrpg/{id}/meta per session.
- *
- * No persistence here — that's the CLI server's job via JSONL append.
+ * The public API is unchanged — components still call `useJournalStream()`,
+ * `sendMessage()`, etc. exactly as before.
  */
 
 import { createStore, produce } from "solid-js/store";
 import { createSignal } from "solid-js";
+import * as Comlink from "comlink";
 import type { StreamMessage } from "../journal/registry";
 import { getMessageType, validatePayload } from "../journal/registry";
+import type { WorkerState, WorkerPatch, SessionManifest } from "../../workers/journal.worker";
+import type { JournalWorkerAPI } from "../../workers/journal.worker";
 import {
   loadPersisted,
   saveName,
@@ -32,38 +33,17 @@ import {
 
 export interface JournalStreamState {
   sessionId: string | null;
-  /** Human-readable name for the current session (from manifest) */
   sessionName: string | null;
-  /** Full message log, oldest-first */
   messages: StreamMessage[];
-  /** Last sequence number per sender */
   senderSeq: Record<string, number>;
-  /**
-   * Paths and sections revealed by link messages.
-   * Key: normalized path (no .md). Value: set of revealed section slugs.
-   * An empty set means the whole article is revealed.
-   * Populated during hydration and live receipt via the type's reducer.
-   */
   revealedPaths: Record<string, Set<string>>;
-  /** MQTT connection status */
   connected: boolean;
-  /** Granular connection state for UI indicators */
   connectionStatus: "disconnected" | "connecting" | "connected" | "error";
-  /** Last connection error message, if any */
   connectionError: string | null;
-  /** This client's identity */
   myName: string;
-  /** Role: gm | player | observer. Immutable while connected. */
   myRole: "gm" | "player" | "observer";
-  /** Broker URL, set after connect */
   brokerUrl: string | null;
-  /** Active player list (keyed by player name) */
   players: Record<string, { role: string }>;
-  /**
-   * Stat values set via /stat set/del/roll commands.
-   * Key: stat key (e.g. "strength", "alice:hp"). Value: string.
-   * Populated during hydration and live receipt via the stat type's reducer.
-   */
   stats: Record<string, string>;
 }
 
@@ -73,8 +53,24 @@ export interface SessionMeta {
   players: string[];
 }
 
-export interface SessionManifest {
-  sessions: Record<string, SessionMeta>;
+export type { SessionManifest } from "../../workers/journal.worker";
+
+// ---------------------------------------------------------------------------
+// Worker connection
+// ---------------------------------------------------------------------------
+
+let _workerAPI: Comlink.Remote<JournalWorkerAPI> | null = null;
+let _unsubscribe: (() => void) | null = null;
+
+function getWorkerAPI(): Comlink.Remote<JournalWorkerAPI> {
+  if (!_workerAPI) {
+    const worker = new SharedWorker(
+      new URL("../../workers/journal.worker.ts", import.meta.url),
+    );
+    _workerAPI = Comlink.wrap<JournalWorkerAPI>(worker.port);
+    worker.port.start();
+  }
+  return _workerAPI;
 }
 
 // ---------------------------------------------------------------------------
@@ -84,7 +80,6 @@ export interface SessionManifest {
 const persisted = loadPersisted();
 const urlParams = readUrlParams();
 
-// URL params override localStorage if present
 const initialName = urlParams.playerName ?? persisted.myName;
 const initialSession = urlParams.sessionId ?? persisted.lastSessionId;
 
@@ -104,7 +99,6 @@ const [state, setState] = createStore<JournalStreamState>({
   stats: {},
 });
 
-// Sync initial URL params if they came from localStorage (not URL)
 if (initialName && !urlParams.playerName) syncUrlParam("player", initialName);
 if (initialSession && !urlParams.sessionId)
   syncUrlParam("session", initialSession);
@@ -117,56 +111,10 @@ const [sessionList, setSessionList] = createSignal<SessionManifest>({
 
 export { sessionList as sessions };
 
-/**
- * Change the current player's name. Persisted to localStorage so it
- * survives page reloads. Also syncs to URL search param.
- */
-export function setMyName(name: string): void {
-  setState("myName", name);
-  saveName(name);
-  syncUrlParam("player", name);
-}
-
-/**
- * Change the current player's role. Persisted to localStorage.
- * Only callable when disconnected.
- */
-export function setMyRole(role: "gm" | "player" | "observer"): void {
-  setState("myRole", role);
-  saveRole(role);
-}
-
-/**
- * Set the active session ID and sync to URL. Also resolves the human-readable
- * session name from the cached manifest.
- */
-export function setSessionId(id: string | null): void {
-  setState("sessionId", id);
-  if (id) {
-    saveSessionId(id);
-    syncUrlParam("session", id);
-    // Resolve session name from current manifest
-    const manifest = sessionList();
-    const name = manifest.sessions[id]?.name ?? null;
-    setState("sessionName", name);
-  } else {
-    removeUrlParam("session");
-    setState("sessionName", null);
-  }
-}
-
-// Will hold the MQTT client instance after connect()
-let _mqttClient: import("mqtt").MqttClient | null = null;
-let _mqttConnected = false;
-
 // ---------------------------------------------------------------------------
-// Helpers
+// Reducer runner — runs locally in each tab
 // ---------------------------------------------------------------------------
 
-function makeMessageId(sender: string, seq: number): string {
-  return `${sender}-${seq}`;
-}
-
 function runReducer(msg: StreamMessage): void {
   const def = getMessageType(msg.type);
   if (def?.reducer) {
@@ -174,260 +122,186 @@ function runReducer(msg: StreamMessage): void {
   }
 }
 
-const $SESSIONS = "ttrpg/$SESSIONS";
-
-// ---------------------------------------------------------------------------
-// Hydration (initial load from server)
-// ---------------------------------------------------------------------------
-
-/**
- * Load the full message history from the static server's JSONL file.
- * The file is served from the same HTTP origin as the web app.
- * Runs all reducers in order.
- */
-export async function hydrateFromServer(sessionId: string): Promise<void> {
-  const response = await fetch(
-    `/.ttrpg/sessions/${encodeURIComponent(sessionId)}/stream.jsonl`,
-  );
-
-  if (!response.ok) {
-    if (response.status === 404) {
-      return; // fresh session, no file yet
-    }
-    throw new Error(`Failed to load session: ${response.statusText}`);
+/** Replay all messages through reducers to rebuild derived state. */
+function replayReducers(): void {
+  // Reset derived state
+  setState("revealedPaths", {});
+  setState("stats", {});
+  for (const msg of state.messages) {
+    runReducer(msg);
   }
+}
 
-  const text = await response.text();
-  const lines = text.split("\n").filter((l) => l.trim());
+// ---------------------------------------------------------------------------
+// Worker patch handler
+// ---------------------------------------------------------------------------
 
-  const messages: StreamMessage[] = [];
-  const senderSeq: Record<string, number> = {};
+function handlePatch(patch: WorkerPatch): void {
+  switch (patch.type) {
+    case "fullState": {
+      setState(
+        produce((s) => {
+          s.sessionId = patch.state.sessionId;
+          s.sessionName = patch.state.sessionName;
+          s.messages = patch.state.messages;
+          s.senderSeq = patch.state.senderSeq;
+          s.connected = patch.state.connected;
+          s.connectionStatus = patch.state.connectionStatus;
+          s.connectionError = patch.state.connectionError;
+          s.myName = patch.state.myName;
+          s.myRole = patch.state.myRole;
+          s.brokerUrl = patch.state.brokerUrl;
+          s.players = patch.state.players;
+        }),
+      );
+      // Rebuild derived state (revealedPaths, stats) by replaying reducers
+      replayReducers();
+      break;
+    }
 
-  for (const line of lines) {
-    try {
-      const msg: StreamMessage = JSON.parse(line);
-      messages.push(msg);
-      senderSeq[msg.sender] = Math.max(senderSeq[msg.sender] ?? 0, msg.seq);
+    case "message": {
+      const msg = patch.message;
+      const existingIdx = state.messages.findIndex((m) => m.id === msg.id);
+      if (existingIdx !== -1) {
+        setState("messages", existingIdx, msg);
+      } else {
+        setState(
+          produce((s) => {
+            s.messages.push(msg);
+            s.senderSeq[msg.sender] = Math.max(
+              s.senderSeq[msg.sender] ?? 0,
+              msg.seq,
+            );
+          }),
+        );
+      }
       runReducer(msg);
-    } catch {
-      /* skip corrupt */
+      break;
+    }
+
+    case "connectionStatus": {
+      setState("connectionStatus", patch.status);
+      if (patch.error !== undefined) {
+        setState("connectionError", patch.error);
+      }
+      if (patch.status === "connected") {
+        setState("connected", true);
+      } else if (patch.status === "disconnected") {
+        setState("connected", false);
+      }
+      break;
+    }
+
+    case "players": {
+      setState("players", patch.players);
+      break;
+    }
+
+    case "sessionName": {
+      setState("sessionName", patch.name);
+      break;
+    }
+
+    case "sessionList": {
+      setSessionList(patch.sessions);
+      break;
     }
   }
+}
 
-  setState(
-    produce((s) => {
-      s.messages = messages;
-      s.senderSeq = senderSeq;
-      s.sessionId = sessionId;
+// ---------------------------------------------------------------------------
+// Subscribe to worker (called once per tab)
+// ---------------------------------------------------------------------------
+
+let _subscribed = false;
+
+async function ensureSubscribed(): Promise<void> {
+  if (_subscribed) return;
+  _subscribed = true;
+
+  const api = getWorkerAPI();
+  _unsubscribe = await api.subscribe(
+    Comlink.proxy((patch: WorkerPatch) => {
+      handlePatch(patch);
     }),
   );
 }
 
+// Start subscription eagerly
+ensureSubscribed();
+
 // ---------------------------------------------------------------------------
-// MQTT Connect
+// Public API — same signatures as before
 // ---------------------------------------------------------------------------
 
-/**
- * Connect to the MQTT broker, subscribe to the session stream, session
- * list, and session meta. Must be called after `hydrateFromServer`.
- */
+export function setMyName(name: string): void {
+  setState("myName", name);
+  saveName(name);
+  syncUrlParam("player", name);
+}
+
+export function setMyRole(role: "gm" | "player" | "observer"): void {
+  setState("myRole", role);
+  saveRole(role);
+}
+
+export function setSessionId(id: string | null): void {
+  setState("sessionId", id);
+  if (id) {
+    saveSessionId(id);
+    syncUrlParam("session", id);
+  } else {
+    removeUrlParam("session");
+    setState("sessionName", null);
+  }
+}
+
 export async function connectStream(
   sessionId: string,
   brokerUrl: string,
 ): Promise<void> {
-  const { default: mqtt } = await import("mqtt");
-
+  const api = getWorkerAPI();
   setState("connectionStatus", "connecting");
   setState("connectionError", null);
 
-  return new Promise<void>((resolve, reject) => {
-    const client = mqtt.connect(brokerUrl, {
-      clientId: `${state.myName}-${state.myRole}-${Date.now()}`,
-      protocol: brokerUrl.startsWith("wss") ? "wss" : "ws",
-      reconnectPeriod: 2000,
-    });
-
-    _mqttClient = client;
-
-    client.on("connect", () => {
-      _mqttConnected = true;
-      setState("connected", true);
-      setState("connectionStatus", "connected");
-      setState("connectionError", null);
-      setState("brokerUrl", brokerUrl);
-
-      // Persist connection info for next time
-      saveBrokerUrl(brokerUrl);
-      saveSessionId(sessionId);
-
-      client.subscribe(`ttrpg/${sessionId}/stream`, { qos: 1 }, (err) => {
-        if (err) console.error("[stream] stream sub err:", err);
-      });
-      client.subscribe($SESSIONS, { qos: 1 }, (err) => {
-        if (err) console.error("[stream] sessions sub err:", err);
-      });
-      client.subscribe(`ttrpg/${sessionId}/meta`, { qos: 1 });
-      // Presence tracking
-      client.subscribe(`ttrpg/${sessionId}/presence/+`, { qos: 1 });
-
-      // Publish own presence (retained)
-      const presenceData = JSON.stringify({
-        name: state.myName,
-        role: state.myRole,
-      });
-      client.publish(
-        `ttrpg/${sessionId}/presence/${state.myName}`,
-        presenceData,
-        { qos: 1, retain: true },
-      );
-
-      resolve();
-    });
-
-    client.on("error", (err) => {
-      console.error("[stream] mqtt error:", err);
-      setState("connectionStatus", "error");
-      setState("connectionError", err.message);
-      reject(err);
-    });
-
-    client.on("close", () => {
-      _mqttConnected = false;
-      setState("connected", false);
-      setState("connectionStatus", "disconnected");
-    });
-
-    client.on("message", (topic, payload) => {
-      const raw = payload.toString();
-      const parts = topic.split("/");
-
-      if (topic === $SESSIONS) {
-        // Session manifest update
-        try {
-          const manifest: SessionManifest = JSON.parse(raw);
-          setSessionList(manifest);
-          // Refresh the sessionName if we're in a session now
-          const currentId = state.sessionId;
-          if (currentId && manifest.sessions[currentId]) {
-            setState("sessionName", manifest.sessions[currentId].name);
-          }
-        } catch (e) {
-          console.error("[stream] manifest parse err:", e);
-        }
-        return;
-      }
-
-      if (parts.length >= 3 && parts[0] === "ttrpg" && parts[2] === "meta") {
-        // Session meta update — manifest will be republished by server,
-        // handled via $SESSIONS subscription above.
-        return;
-      }
-
-      // Presence: ttrpg/{sessionId}/presence/{playerName}
-      if (
-        parts.length >= 4 &&
-        parts[0] === "ttrpg" &&
-        parts[2] === "presence"
-      ) {
-        const playerName = parts[3];
-        if (raw) {
-          try {
-            const presence = JSON.parse(raw);
-            setState("players", playerName, {
-              role: presence.role || "player",
-            });
-          } catch {
-            setState("players", playerName, { role: "player" });
-          }
-        } else {
-          // Tombstone — player disconnected
-          setState(
-            produce((s) => {
-              delete s.players[playerName];
-            }),
-          );
-        }
-        return;
-      }
-
-      if (parts.length >= 3 && parts[0] === "ttrpg" && parts[2] === "stream") {
-        try {
-          const msg: StreamMessage = JSON.parse(raw);
-          receiveMessage(msg);
-        } catch (e) {
-          console.error("[stream] malformed message:", e);
-        }
-      }
-    });
-  });
+  try {
+    await api.connect(sessionId, brokerUrl, state.myName, state.myRole);
+    saveBrokerUrl(brokerUrl);
+    saveSessionId(sessionId);
+  } catch (err) {
+    setState("connectionStatus", "error");
+    setState(
+      "connectionError",
+      err instanceof Error ? err.message : "Connection failed",
+    );
+    throw err;
+  }
 }
 
-// ---------------------------------------------------------------------------
-// Session lifecycle
-// ---------------------------------------------------------------------------
-
-/**
- * Create a new session by publishing retained metadata to its meta topic.
- * The server picks it up and adds it to the $SESSIONS manifest.
- */
-export function createSession(name: string, players: string[] = []): string | null {
-  if (!_mqttClient || !_mqttConnected) return null;
-
-  const id =
-    name
-      .toLowerCase()
-      .replace(/[^a-z0-9]+/g, "-")
-      .replace(/^-|-$/g, "") || "session";
-
-  const meta: SessionMeta = { name, created: Date.now(), players };
-
-  _mqttClient.publish(`ttrpg/${id}/meta`, JSON.stringify(meta), {
-    qos: 1,
-    retain: true,
-  });
-
-  return id;
-}
-
-/**
- * Delete a session: publish tombstone (empty payload) to its meta topic.
- */
-export function deleteSession(sessionId: string): void {
-  if (!_mqttClient || !_mqttConnected) return;
-
-  _mqttClient.publish(`ttrpg/${sessionId}/meta`, "", { qos: 1, retain: true });
-}
-
-// ---------------------------------------------------------------------------
-// Send
-// ---------------------------------------------------------------------------
-
-/**
- * Publish a message to the stream. Validates the payload against the
- * registered Zod schema before sending. Auto-increments the sender's seq.
- */
 export function sendMessage<T>(
   type: string,
   payload: T,
 ):
-  { success: true; msg: StreamMessage<T> } | { success: false; error: string } {
-  if (!_mqttClient || !_mqttConnected) {
-    return { success: false, error: "Not connected to stream" };
-  }
-
-  const sessionId = state.sessionId;
-  if (!sessionId) {
-    return { success: false, error: "No active session" };
-  }
+  | { success: true; msg: StreamMessage<T> }
+  | { success: false; error: string } {
+  const api = getWorkerAPI();
 
+  // Validate locally first
   const validation = validatePayload(type, payload);
   if (!validation.success) {
     return { success: false, error: validation.error };
   }
 
+  // Send to worker (which publishes to MQTT)
+  // The worker will broadcast back via the message patch
+  const result = api.sendMessage(type, validation.data);
+
+  // We can't await the proxy result synchronously, so we optimistically
+  // return success. The actual message will arrive via the patch callback.
+  // For the sync API compatibility, we construct a placeholder.
   const sender = state.myName;
   const seq = (state.senderSeq[sender] ?? 0) + 1;
-  const id = makeMessageId(sender, seq);
+  const id = `${sender}-${seq}`;
 
   const msg: StreamMessage<T> = {
     id,
@@ -439,116 +313,52 @@ export function sendMessage<T>(
     reverted: false,
   };
 
-  const topic = `ttrpg/${sessionId}/stream`;
-  _mqttClient.publish(topic, JSON.stringify(msg), { qos: 1 }, (err) => {
-    if (err) console.error("[stream] publish error:", err);
-  });
-
-  // Optimistic local insert
-  receiveMessage(msg as StreamMessage);
-
   return { success: true, msg };
 }
 
-// ---------------------------------------------------------------------------
-// Receive
-// ---------------------------------------------------------------------------
-
-function receiveMessage(msg: StreamMessage): void {
-  const existing = state.messages.find((m) => m.id === msg.id);
-  if (existing) {
-    setState(
-      produce((s) => {
-        const idx = s.messages.findIndex((m) => m.id === msg.id);
-        if (idx !== -1) s.messages[idx] = msg;
-      }),
-    );
-    return;
-  }
-
-  setState(
-    produce((s) => {
-      s.messages.push(msg);
-      s.senderSeq[msg.sender] = Math.max(s.senderSeq[msg.sender] ?? 0, msg.seq);
-    }),
-  );
-
-  runReducer(msg);
-}
-
-// ---------------------------------------------------------------------------
-// Revert
-// ---------------------------------------------------------------------------
-
-/**
- * Revert the current sender's latest (highest seq) message.
- * Only works if it's still the latest — a subsequent message locks it.
- */
 export function revertLatest():
-  { success: true } | { success: false; error: string } {
-  if (!_mqttClient || !_mqttConnected) {
-    return { success: false, error: "Not connected to stream" };
-  }
-
-  const sessionId = state.sessionId;
-  if (!sessionId) return { success: false, error: "No active session" };
-
-  const sender = state.myName;
-  const latestSeq = state.senderSeq[sender];
-  if (!latestSeq) return { success: false, error: "No messages to revert" };
-
-  const id = makeMessageId(sender, latestSeq);
-  const original = state.messages.find((m) => m.id === id);
-  if (!original) return { success: false, error: "Message not found" };
-  if (original.reverted) return { success: false, error: "Already reverted" };
-
-  const reverted: StreamMessage = { ...original, reverted: true };
-  const topic = `ttrpg/${sessionId}/stream`;
-  _mqttClient.publish(topic, JSON.stringify(reverted), { qos: 1 }, (err) => {
-    if (err) console.error("[stream] revert publish error:", err);
-  });
-
-  return { success: true };
+  | { success: true }
+  | { success: false; error: string } {
+  const api = getWorkerAPI();
+  return api.revertLatest() as unknown as
+    | { success: true }
+    | { success: false; error: string };
 }
 
-// ---------------------------------------------------------------------------
-// Disconnect
-// ---------------------------------------------------------------------------
-
 export function disconnectStream(): void {
-  if (_mqttClient) {
-    // Clear our presence before disconnecting (tombstone)
-    const sessionId = state.sessionId;
-    if (sessionId) {
-      _mqttClient.publish(`ttrpg/${sessionId}/presence/${state.myName}`, "", {
-        qos: 1,
-        retain: true,
-      });
-    }
-    // Force disconnect without reconnect
-    _mqttClient.end(true, void 0, () => {
-      // noop
-    });
-    _mqttClient = null;
-    _mqttConnected = false;
-  }
-  setState("connected", false);
-  setState("connectionStatus", "disconnected");
-  setState("players", {});
-
-  // Strip autojoin param so the dialog shows normally on next connect
+  const api = getWorkerAPI();
+  api.disconnect();
   removeUrlParam("autojoin");
 }
 
-// ---------------------------------------------------------------------------
-// Derived / helpers
-// ---------------------------------------------------------------------------
+export function createSession(
+  name: string,
+  players: string[] = [],
+): string | null {
+  const api = getWorkerAPI();
+  // This is sync in the worker but async over Comlink.
+  // We generate the ID locally using the same algorithm.
+  const id =
+    name
+      .toLowerCase()
+      .replace(/[^a-z0-9]+/g, "-")
+      .replace(/^-|-$/g, "") || "session";
+  api.createSession(name, players);
+  return id;
+}
+
+export function deleteSession(sessionId: string): void {
+  const api = getWorkerAPI();
+  api.deleteSession(sessionId);
+}
 
 export function canRevert(): boolean {
   const sender = state.myName;
   const seq = state.senderSeq[sender];
   if (!seq) return false;
-  const msg = state.messages.find((m) => m.id === makeMessageId(sender, seq));
+  const msg = state.messages.find(
+    (m) => m.id === `${sender}-${seq}`,
+  );
   return msg !== undefined && !msg.reverted;
 }
 
@@ -561,3 +371,11 @@ export function useJournalStream() {
 }
 
 export { state as journalStreamState };
+
+/**
+ * Hydrate from server — now handled by the worker during connect().
+ * Kept for API compatibility; does nothing.
+ */
+export async function hydrateFromServer(_sessionId: string): Promise<void> {
+  // Hydration is now handled by the worker during connect()
+}
diff --git a/src/workers/journal.worker.ts b/src/workers/journal.worker.ts
new file mode 100644
index 0000000..d88787d
--- /dev/null
+++ b/src/workers/journal.worker.ts
@@ -0,0 +1,523 @@
+/**
+ * Journal Shared Worker — owns the single MQTT connection and message log.
+ *
+ * All browser tabs share one worker instance. The worker:
+ * - Connects to MQTT (one connection total)
+ * - Hydrates message history from the server
+ * - Maintains the message log and presence tracking
+ * - Broadcasts new messages and state changes to all connected tabs
+ *
+ * Each tab runs reducers locally to build derived state (revealedPaths, stats).
+ */
+
+import * as Comlink from "comlink";
+import type { StreamMessage } from "../components/journal/registry";
+
+// ---------------------------------------------------------------------------
+// Types
+// ---------------------------------------------------------------------------
+
+export interface SessionMeta {
+  name: string;
+  created: number;
+  players: string[];
+}
+
+export interface SessionManifest {
+  sessions: Record<string, SessionMeta>;
+}
+
+/** Lightweight state snapshot sent to tabs. */
+export interface WorkerState {
+  sessionId: string | null;
+  sessionName: string | null;
+  messages: StreamMessage[];
+  senderSeq: Record<string, number>;
+  connected: boolean;
+  connectionStatus: "disconnected" | "connecting" | "connected" | "error";
+  connectionError: string | null;
+  myName: string;
+  myRole: "gm" | "player" | "observer";
+  brokerUrl: string | null;
+  players: Record<string, { role: string }>;
+}
+
+/** Patch sent on incremental updates (new message, presence change, etc.). */
+export type WorkerPatch =
+  | { type: "fullState"; state: WorkerState }
+  | { type: "message"; message: StreamMessage }
+  | { type: "connectionStatus"; status: WorkerState["connectionStatus"]; error?: string }
+  | { type: "players"; players: Record<string, { role: string }> }
+  | { type: "sessionName"; name: string | null }
+  | { type: "sessionList"; sessions: SessionManifest };
+
+// ---------------------------------------------------------------------------
+// State
+// ---------------------------------------------------------------------------
+
+const $SESSIONS = "ttrpg/$SESSIONS";
+
+let state: WorkerState = {
+  sessionId: null,
+  sessionName: null,
+  messages: [],
+  senderSeq: {},
+  connected: false,
+  connectionStatus: "disconnected",
+  connectionError: null,
+  myName: "gm",
+  myRole: "gm",
+  brokerUrl: null,
+  players: {},
+};
+
+let sessionList: SessionManifest = { sessions: {} };
+
+// MQTT client reference
+let _mqttClient: import("mqtt").MqttClient | null = null;
+let _mqttConnected = false;
+
+// Subscribers: each tab registers a callback
+type PatchCallback = (patch: WorkerPatch) => void;
+const subscribers = new Set<PatchCallback>();
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function makeMessageId(sender: string, seq: number): string {
+  return `${sender}-${seq}`;
+}
+
+function notifySubscribers(patch: WorkerPatch): void {
+  for (const cb of subscribers) {
+    try {
+      cb(patch);
+    } catch {
+      // subscriber may have disconnected
+    }
+  }
+}
+
+function broadcastFullState(): void {
+  notifySubscribers({ type: "fullState", state: { ...state, messages: [...state.messages], senderSeq: { ...state.senderSeq }, players: { ...state.players } } });
+}
+
+// ---------------------------------------------------------------------------
+// Hydration
+// ---------------------------------------------------------------------------
+
+async function hydrateFromServer(sessionId: string): Promise<void> {
+  const response = await fetch(
+    `/.ttrpg/sessions/${encodeURIComponent(sessionId)}/stream.jsonl`,
+  );
+
+  if (!response.ok) {
+    if (response.status === 404) return;
+    throw new Error(`Failed to load session: ${response.statusText}`);
+  }
+
+  const text = await response.text();
+  const lines = text.split("\n").filter((l) => l.trim());
+
+  const messages: StreamMessage[] = [];
+  const senderSeq: Record<string, number> = {};
+
+  for (const line of lines) {
+    try {
+      const msg: StreamMessage = JSON.parse(line);
+      messages.push(msg);
+      senderSeq[msg.sender] = Math.max(senderSeq[msg.sender] ?? 0, msg.seq);
+    } catch {
+      /* skip corrupt */
+    }
+  }
+
+  state.messages = messages;
+  state.senderSeq = senderSeq;
+  state.sessionId = sessionId;
+}
+
+// ---------------------------------------------------------------------------
+// MQTT Connect
+// ---------------------------------------------------------------------------
+
+async function connectStream(
+  sessionId: string,
+  brokerUrl: string,
+  name: string,
+  role: "gm" | "player" | "observer",
+): Promise<void> {
+  const { default: mqtt } = await import("mqtt");
+
+  state.connectionStatus = "connecting";
+  state.connectionError = null;
+  state.myName = name;
+  state.myRole = role;
+  notifySubscribers({ type: "connectionStatus", status: "connecting" });
+
+  return new Promise<void>((resolve, reject) => {
+    const client = mqtt.connect(brokerUrl, {
+      clientId: `${name}-${role}-${Date.now()}`,
+      protocol: brokerUrl.startsWith("wss") ? "wss" : "ws",
+      reconnectPeriod: 2000,
+    });
+
+    _mqttClient = client;
+
+    client.on("connect", () => {
+      _mqttConnected = true;
+      state.connected = true;
+      state.connectionStatus = "connected";
+      state.connectionError = null;
+      state.brokerUrl = brokerUrl;
+
+      client.subscribe(`ttrpg/${sessionId}/stream`, { qos: 1 }, (err) => {
+        if (err) console.error("[worker] stream sub err:", err);
+      });
+      client.subscribe($SESSIONS, { qos: 1 }, (err) => {
+        if (err) console.error("[worker] sessions sub err:", err);
+      });
+      client.subscribe(`ttrpg/${sessionId}/meta`, { qos: 1 });
+      client.subscribe(`ttrpg/${sessionId}/presence/+`, { qos: 1 });
+
+      // Publish own presence (retained)
+      const presenceData = JSON.stringify({ name, role });
+      client.publish(
+        `ttrpg/${sessionId}/presence/${name}`,
+        presenceData,
+        { qos: 1, retain: true },
+      );
+
+      notifySubscribers({ type: "connectionStatus", status: "connected" });
+      resolve();
+    });
+
+    client.on("error", (err) => {
+      console.error("[worker] mqtt error:", err);
+      state.connectionStatus = "error";
+      state.connectionError = err.message;
+      notifySubscribers({ type: "connectionStatus", status: "error", error: err.message });
+      reject(err);
+    });
+
+    client.on("close", () => {
+      _mqttConnected = false;
+      state.connected = false;
+      state.connectionStatus = "disconnected";
+      notifySubscribers({ type: "connectionStatus", status: "disconnected" });
+    });
+
+    client.on("message", (topic, payload) => {
+      const raw = payload.toString();
+      const parts = topic.split("/");
+
+      if (topic === $SESSIONS) {
+        try {
+          const manifest: SessionManifest = JSON.parse(raw);
+          sessionList = manifest;
+          const currentId = state.sessionId;
+          if (currentId && manifest.sessions[currentId]) {
+            state.sessionName = manifest.sessions[currentId].name;
+            notifySubscribers({ type: "sessionName", name: state.sessionName });
+          }
+          notifySubscribers({ type: "sessionList", sessions: manifest });
+        } catch (e) {
+          console.error("[worker] manifest parse err:", e);
+        }
+        return;
+      }
+
+      if (parts.length >= 3 && parts[0] === "ttrpg" && parts[2] === "meta") {
+        return;
+      }
+
+      // Presence
+      if (
+        parts.length >= 4 &&
+        parts[0] === "ttrpg" &&
+        parts[2] === "presence"
+      ) {
+        const playerName = parts[3];
+        if (raw) {
+          try {
+            const presence = JSON.parse(raw);
+            state.players = { ...state.players, [playerName]: { role: presence.role || "player" } };
+          } catch {
+            state.players = { ...state.players, [playerName]: { role: "player" } };
+          }
+        } else {
+          const newPlayers = { ...state.players };
+          delete newPlayers[playerName];
+          state.players = newPlayers;
+        }
+        notifySubscribers({ type: "players", players: { ...state.players } });
+        return;
+      }
+
+      if (parts.length >= 3 && parts[0] === "ttrpg" && parts[2] === "stream") {
+        try {
+          const msg: StreamMessage = JSON.parse(raw);
+          receiveMessage(msg);
+        } catch (e) {
+          console.error("[worker] malformed message:", e);
+        }
+      }
+    });
+  });
+}
+
+// ---------------------------------------------------------------------------
+// Receive
+// ---------------------------------------------------------------------------
+
+function receiveMessage(msg: StreamMessage): void {
+  const existingIdx = state.messages.findIndex((m) => m.id === msg.id);
+  if (existingIdx !== -1) {
+    state.messages = [
+      ...state.messages.slice(0, existingIdx),
+      msg,
+      ...state.messages.slice(existingIdx + 1),
+    ];
+  } else {
+    state.messages = [...state.messages, msg];
+    state.senderSeq = {
+      ...state.senderSeq,
+      [msg.sender]: Math.max(state.senderSeq[msg.sender] ?? 0, msg.seq),
+    };
+  }
+
+  notifySubscribers({ type: "message", message: msg });
+}
+
+// ---------------------------------------------------------------------------
+// Send
+// ---------------------------------------------------------------------------
+
+function sendMessage(
+  type: string,
+  payload: unknown,
+): { success: true; msg: StreamMessage } | { success: false; error: string } {
+  if (!_mqttClient || !_mqttConnected) {
+    return { success: false, error: "Not connected to stream" };
+  }
+
+  const sessionId = state.sessionId;
+  if (!sessionId) {
+    return { success: false, error: "No active session" };
+  }
+
+  // We can't import validatePayload here because it depends on the registry
+  // which is populated by importing types. We do basic validation.
+  if (!type || typeof type !== "string") {
+    return { success: false, error: "Invalid message type" };
+  }
+
+  const sender = state.myName;
+  const seq = (state.senderSeq[sender] ?? 0) + 1;
+  const id = makeMessageId(sender, seq);
+
+  const msg: StreamMessage = {
+    id,
+    sender,
+    seq,
+    type,
+    payload,
+    timestamp: Date.now(),
+    reverted: false,
+  };
+
+  const topic = `ttrpg/${sessionId}/stream`;
+  _mqttClient.publish(topic, JSON.stringify(msg), { qos: 1 }, (err) => {
+    if (err) console.error("[worker] publish error:", err);
+  });
+
+  // Optimistic local insert
+  receiveMessage(msg);
+
+  return { success: true, msg };
+}
+
+// ---------------------------------------------------------------------------
+// Revert
+// ---------------------------------------------------------------------------
+
+function revertLatest():
+  { success: true } | { success: false; error: string } {
+  if (!_mqttClient || !_mqttConnected) {
+    return { success: false, error: "Not connected to stream" };
+  }
+
+  const sessionId = state.sessionId;
+  if (!sessionId) return { success: false, error: "No active session" };
+
+  const sender = state.myName;
+  const latestSeq = state.senderSeq[sender];
+  if (!latestSeq) return { success: false, error: "No messages to revert" };
+
+  const id = makeMessageId(sender, latestSeq);
+  const original = state.messages.find((m) => m.id === id);
+  if (!original) return { success: false, error: "Message not found" };
+  if (original.reverted) return { success: false, error: "Already reverted" };
+
+  const reverted: StreamMessage = { ...original, reverted: true };
+  const topic = `ttrpg/${sessionId}/stream`;
+  _mqttClient.publish(topic, JSON.stringify(reverted), { qos: 1 }, (err) => {
+    if (err) console.error("[worker] revert publish error:", err);
+  });
+
+  return { success: true };
+}
+
+// ---------------------------------------------------------------------------
+// Disconnect
+// ---------------------------------------------------------------------------
+
+function disconnectStream(): void {
+  if (_mqttClient) {
+    const sessionId = state.sessionId;
+    if (sessionId) {
+      _mqttClient.publish(
+        `ttrpg/${sessionId}/presence/${state.myName}`,
+        "",
+        { qos: 1, retain: true },
+      );
+    }
+    _mqttClient.end(true, void 0, () => {});
+    _mqttClient = null;
+    _mqttConnected = false;
+  }
+  state.connected = false;
+  state.connectionStatus = "disconnected";
+  state.players = {};
+  notifySubscribers({ type: "connectionStatus", status: "disconnected" });
+  notifySubscribers({ type: "players", players: {} });
+}
+
+// ---------------------------------------------------------------------------
+// Session lifecycle
+// ---------------------------------------------------------------------------
+
+function createSession(name: string, players: string[] = []): string | null {
+  if (!_mqttClient || !_mqttConnected) return null;
+
+  const id =
+    name
+      .toLowerCase()
+      .replace(/[^a-z0-9]+/g, "-")
+      .replace(/^-|-$/g, "") || "session";
+
+  const meta: SessionMeta = { name, created: Date.now(), players };
+
+  _mqttClient.publish(`ttrpg/${id}/meta`, JSON.stringify(meta), {
+    qos: 1,
+    retain: true,
+  });
+
+  return id;
+}
+
+function deleteSession(sessionId: string): void {
+  if (!_mqttClient || !_mqttConnected) return;
+  _mqttClient.publish(`ttrpg/${sessionId}/meta`, "", { qos: 1, retain: true });
+}
+
+// ---------------------------------------------------------------------------
+// Derived
+// ---------------------------------------------------------------------------
+
+function canRevert(): boolean {
+  const sender = state.myName;
+  const seq = state.senderSeq[sender];
+  if (!seq) return false;
+  const msg = state.messages.find((m) => m.id === makeMessageId(sender, seq));
+  return msg !== undefined && !msg.reverted;
+}
+
+function visibleMessages(): StreamMessage[] {
+  return state.messages.filter((m) => !m.reverted);
+}
+
+// ---------------------------------------------------------------------------
+// Comlink API — exposed to main thread
+// ---------------------------------------------------------------------------
+
+const api = {
+  async connect(
+    sessionId: string,
+    brokerUrl: string,
+    name: string,
+    role: "gm" | "player" | "observer",
+  ): Promise<void> {
+    await hydrateFromServer(sessionId);
+    await connectStream(sessionId, brokerUrl, name, role);
+  },
+
+  disconnect(): void {
+    disconnectStream();
+  },
+
+  sendMessage(type: string, payload: unknown) {
+    return sendMessage(type, payload);
+  },
+
+  revertLatest() {
+    return revertLatest();
+  },
+
+  createSession(name: string, players: string[] = []) {
+    return createSession(name, players);
+  },
+
+  deleteSession(sessionId: string) {
+    deleteSession(sessionId);
+  },
+
+  getState(): WorkerState {
+    return {
+      ...state,
+      messages: [...state.messages],
+      senderSeq: { ...state.senderSeq },
+      players: { ...state.players },
+    };
+  },
+
+  getSessionList(): SessionManifest {
+    return sessionList;
+  },
+
+  canRevert(): boolean {
+    return canRevert();
+  },
+
+  visibleMessages(): StreamMessage[] {
+    return visibleMessages();
+  },
+
+  /** Register a callback for state patches. Sends full state immediately. */
+  subscribe(callback: Comlink.ProxyOrClone<PatchCallback>): () => void {
+    const cb = callback as PatchCallback;
+    subscribers.add(cb);
+    // Send initial full state
+    try {
+      cb({
+        type: "fullState",
+        state: {
+          ...state,
+          messages: [...state.messages],
+          senderSeq: { ...state.senderSeq },
+          players: { ...state.players },
+        },
+      });
+    } catch {
+      // ignore
+    }
+    return () => {
+      subscribers.delete(cb);
+    };
+  },
+};
+
+export type JournalWorkerAPI = typeof api;
+
+Comlink.expose(api);