diff --git a/plugins/session-sharing/src/frontend/SharedSessionView.tsx b/plugins/session-sharing/src/frontend/SharedSessionView.tsx
index 3bf85eff9..b8164e64c 100644
--- a/plugins/session-sharing/src/frontend/SharedSessionView.tsx
+++ b/plugins/session-sharing/src/frontend/SharedSessionView.tsx
@@ -135,7 +135,11 @@ export function GuestTerminalView({
     terminal.open(xtermRef.current);
     fitAddon.fit();
 
-    const resizeObserver = new ResizeObserver(() => fitAddon.fit());
+    let sharedSize: { cols: number; rows: number } | null = null;
+    const resizeObserver = new ResizeObserver(() => {
+      if (sharedSize) terminal.resize(sharedSize.cols, sharedSize.rows);
+      else fitAddon.fit();
+    });
     resizeObserver.observe(xtermRef.current);
 
     let cancelled = false;
@@ -163,6 +167,21 @@ export function GuestTerminalView({
         }
 
         switch (msg.type) {
+          case "resized": {
+            const { cols, rows } = msg;
+            if (
+              typeof cols === "number" &&
+              typeof rows === "number" &&
+              Number.isInteger(cols) &&
+              Number.isInteger(rows) &&
+              cols > 0 &&
+              rows > 0
+            ) {
+              sharedSize = { cols, rows };
+              terminal.resize(cols, rows);
+            }
+            break;
+          }
           case "data":
             if (typeof msg.data === "string") terminal.write(msg.data);
             break;
diff --git a/plugins/session-sharing/tests/frontend/guest-terminal-size.test.tsx b/plugins/session-sharing/tests/frontend/guest-terminal-size.test.tsx
new file mode 100644
index 000000000..5adfede78
--- /dev/null
+++ b/plugins/session-sharing/tests/frontend/guest-terminal-size.test.tsx
@@ -0,0 +1,110 @@
+import { act, cleanup, render, waitFor } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { GuestTerminalView } from "../../src/frontend/SharedSessionView";
+
+const f = vi.hoisted(() => ({
+  terminal: {
+    cols: 80,
+    rows: 24,
+    options: {},
+    loadAddon: vi.fn(),
+    open: vi.fn(),
+    write: vi.fn(),
+    resize: vi.fn(),
+  },
+  fit: vi.fn(),
+  onResize: null as (() => void) | null,
+}));
+vi.mock("@termix/plugin-sdk/frontend", () => ({
+  useTranslation: () => ({ t: (key: string) => key }),
+}));
+vi.mock("react-xtermjs", () => ({
+  useXTerm: () => ({ instance: f.terminal, ref: { current: null } }),
+}));
+vi.mock("@xterm/addon-fit", () => ({
+  FitAddon: class {
+    fit() {
+      f.fit();
+    }
+  },
+}));
+vi.mock("../../src/frontend/shared", () => ({
+  wsUrlForPath: async () => "ws://termix.test/terminal",
+  RemoteDisplay: () => null,
+  Loader: () => null,
+}));
+class Socket {
+  static OPEN = 1;
+  static latest: Socket;
+  readyState = 1;
+  onopen?: () => void;
+  onmessage?: (event: { data: string }) => void;
+  onclose?: () => void;
+  onerror?: () => void;
+  constructor() {
+    Socket.latest = this;
+  }
+  send() {}
+  close() {}
+  message(value: object) {
+    this.onmessage?.({ data: JSON.stringify(value) });
+  }
+}
+beforeEach(() => {
+  vi.clearAllMocks();
+  f.terminal.cols = 80;
+  f.terminal.rows = 24;
+  f.terminal.resize.mockImplementation((cols: number, rows: number) => {
+    f.terminal.cols = cols;
+    f.terminal.rows = rows;
+  });
+  f.fit.mockImplementation(() => {
+    f.terminal.cols = 80;
+    f.terminal.rows = 24;
+  });
+  vi.stubGlobal("WebSocket", Socket);
+  vi.stubGlobal(
+    "ResizeObserver",
+    class {
+      constructor(fn: () => void) {
+        f.onResize = fn;
+      }
+      observe() {}
+      disconnect() {}
+    },
+  );
+});
+afterEach(() => {
+  cleanup();
+  vi.unstubAllGlobals();
+});
+
+it("keeps the presenter's grid while the guest window changes size", async () => {
+  render(
+    <GuestTerminalView
+      share={{ permissionLevel: "read-only" }}
+      wsPath="/plugin-ws/ssh-terminal/terminal?shareToken=test"
+    />,
+  );
+  await waitFor(() => expect(Socket.latest.onmessage).toBeTypeOf("function"));
+  act(() => Socket.latest.message({ type: "resized", cols: 132, rows: 40 }));
+  expect([f.terminal.cols, f.terminal.rows]).toEqual([132, 40]);
+  act(() => f.onResize?.());
+  expect([f.terminal.cols, f.terminal.rows]).toEqual([132, 40]);
+  act(() => Socket.latest.message({ type: "resized", cols: 100, rows: 30 }));
+  expect([f.terminal.cols, f.terminal.rows]).toEqual([100, 30]);
+});
+
+describe("invalid shared terminal dimensions", () => {
+  it.each([0, -1, 1.5, "132"])("ignores cols=%s", async (cols) => {
+    render(
+      <GuestTerminalView
+        share={{ permissionLevel: "read-only" }}
+        wsPath="/plugin-ws/ssh-terminal/terminal?shareToken=test"
+      />,
+    );
+    await waitFor(() => expect(Socket.latest.onmessage).toBeTypeOf("function"));
+    act(() => Socket.latest.message({ type: "resized", cols, rows: 24 }));
+    expect(f.terminal.resize).not.toHaveBeenCalled();
+  });
+});
diff --git a/plugins/ssh-terminal/src/backend/session-manager.ts b/plugins/ssh-terminal/src/backend/session-manager.ts
index 06fcf5e20..3fcc7d21d 100644
--- a/plugins/ssh-terminal/src/backend/session-manager.ts
+++ b/plugins/ssh-terminal/src/backend/session-manager.ts
@@ -444,6 +444,15 @@ export class TerminalSessionManager {
       tabInstanceId: opts.tabInstanceId,
       joinedViaShareId: opts.shareId,
     });
+    if (ws.readyState === WebSocket.OPEN) {
+      ws.send(
+        JSON.stringify({
+          type: "resized",
+          cols: session.cols,
+          rows: session.rows,
+        }),
+      );
+    }
     this.broadcastParticipants(sessionId);
 
     this.log.info("Participant joined shared session", {
@@ -812,6 +821,15 @@ export class TerminalSessionManager {
     this.recordSessionEvent(session, "i", data);
   }
 
+  resizeSession(sessionId: string, cols: number, rows: number): void {
+    const session = this.sessions.get(sessionId);
+    if (!session) return;
+    session.cols = cols;
+    session.rows = rows;
+    this.broadcast(sessionId, { type: "resized", cols, rows });
+    this.bufferResize(sessionId, cols, rows);
+  }
+
   bufferResize(sessionId: string, cols: number, rows: number): void {
     const session = this.sessions.get(sessionId);
     if (!session) return;
diff --git a/plugins/ssh-terminal/src/backend/terminal-socket.ts b/plugins/ssh-terminal/src/backend/terminal-socket.ts
index 849e4e228..472479ac9 100644
--- a/plugins/ssh-terminal/src/backend/terminal-socket.ts
+++ b/plugins/ssh-terminal/src/backend/terminal-socket.ts
@@ -568,8 +568,11 @@ export function createTerminalSocket(deps: TerminalSocketDeps) {
                     attachRows,
                     attachCols,
                   );
-                  session.cols = attachCols;
-                  session.rows = attachRows;
+                  sessionManager.resizeSession(
+                    session.id,
+                    attachCols,
+                    attachRows,
+                  );
                 }
 
                 ws.send(
@@ -2871,11 +2874,8 @@ export function createTerminalSocket(deps: TerminalSocketDeps) {
         resizeStream.setWindow(rows, cols, rows, cols);
         const session = sessionManager.getSession(currentSessionId);
         if (session) {
-          session.cols = cols;
-          session.rows = rows;
-          sessionManager.bufferResize(session.id, cols, rows);
+          sessionManager.resizeSession(session.id, cols, rows);
         }
-        ws.send(JSON.stringify({ type: "resized", cols, rows }));
       }
     }
 
diff --git a/plugins/ssh-terminal/src/frontend/terminal/Terminal.tsx b/plugins/ssh-terminal/src/frontend/terminal/Terminal.tsx
index d8123dcf7..5ff36c487 100644
--- a/plugins/ssh-terminal/src/frontend/terminal/Terminal.tsx
+++ b/plugins/ssh-terminal/src/frontend/terminal/Terminal.tsx
@@ -910,6 +910,33 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
       }
     }
 
+    const sharedSizeRef = useRef<{ cols: number; rows: number } | null>(null);
+
+    function applySharedSize(msg: { cols?: unknown; rows?: unknown }) {
+      if (!hostConfig.joinShareId || !terminal) return;
+      const { cols, rows } = msg;
+      if (
+        typeof cols !== "number" ||
+        typeof rows !== "number" ||
+        !Number.isInteger(cols) ||
+        !Number.isInteger(rows) ||
+        cols < 1 ||
+        rows < 1
+      )
+        return;
+      sharedSizeRef.current = { cols, rows };
+      terminal.resize(cols, rows);
+    }
+
+    function fitTerminal() {
+      const size = sharedSizeRef.current;
+      if (hostConfig.joinShareId && size) {
+        terminal?.resize(size.cols, size.rows);
+      } else {
+        fitAddonRef.current?.fit();
+      }
+    }
+
     function performFit() {
       if (
         !fitAddonRef.current ||
@@ -923,7 +950,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
       isFittingRef.current = true;
 
       try {
-        fitAddonRef.current.fit();
+        fitTerminal();
         if (terminal && terminal.cols > 0 && terminal.rows > 0) {
           const lastSize = lastFittedSizeRef.current;
           if (
@@ -1180,6 +1207,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
     }
 
     function scheduleNotify(cols: number, rows: number) {
+      if (hostConfig.joinShareId) return;
       if (!(cols > 0 && rows > 0)) return;
       pendingSizeRef.current = { cols, rows };
       if (notifyTimerRef.current) clearTimeout(notifyTimerRef.current);
@@ -1390,7 +1418,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
           if (!fitAddonRef.current || !terminal || isFittingRef.current) return;
           isFittingRef.current = true;
           try {
-            fitAddonRef.current.fit();
+            fitTerminal();
             if (terminal.cols > 0 && terminal.rows > 0) {
               const lastSize = lastFittedSizeRef.current;
               if (
@@ -1839,7 +1867,9 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
             pongReceivedRef.current = true;
             return;
           }
-          if (msg.type === "data") {
+          if (msg.type === "resized") {
+            applySharedSize(msg);
+          } else if (msg.type === "data") {
             if (typeof msg.data === "string") {
               outputListenersRef.current.forEach((listener) =>
                 listener(msg.data),
@@ -2674,7 +2704,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
       });
       document.fonts.ready.then(() => {
         terminal.refresh(0, terminal.rows - 1);
-        fitAddon.fit();
+        fitTerminal();
       });
 
       terminal.attachCustomWheelEventHandler((ev) => {
@@ -2699,12 +2729,12 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
         return true;
       });
 
-      fitAddonRef.current?.fit();
+      fitTerminal();
       // Double-rAF ensures layout is fully settled (fonts, flexbox, etc.) before
       // committing the fitted size, preventing the "terminal too short" glitch.
       requestAnimationFrame(() => {
         requestAnimationFrame(() => {
-          fitAddonRef.current?.fit();
+          fitTerminal();
           setIsFitted(true);
         });
       });
@@ -3383,10 +3413,10 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
       }
 
       setIsConnecting(true);
-      fitAddonRef.current?.fit();
+      fitTerminal();
       requestAnimationFrame(() => {
         requestAnimationFrame(() => {
-          fitAddonRef.current?.fit();
+          fitTerminal();
           if (terminal.cols > 0 && terminal.rows > 0) {
             scheduleNotify(terminal.cols, terminal.rows);
             connectToHost(terminal.cols, terminal.rows);
diff --git a/plugins/ssh-terminal/tests/backend/session-manager.test.ts b/plugins/ssh-terminal/tests/backend/session-manager.test.ts
index f15be1579..eb35d7216 100644
--- a/plugins/ssh-terminal/tests/backend/session-manager.test.ts
+++ b/plugins/ssh-terminal/tests/backend/session-manager.test.ts
@@ -182,6 +182,46 @@ describe("TerminalSessionManager - multiplayer participants", () => {
     return id;
   }
 
+  it("sends the presenter dimensions before a participant replays output", () => {
+    const id = createConnectedSession();
+    const session = sessionManager.getSession(id)!;
+    session.cols = 132;
+    session.rows = 40;
+    const ws = makeFakeWs();
+    sessionManager.joinAsParticipant(id, ws, {
+      userId: "viewer",
+      permissionLevel: "read-only",
+    });
+    expect(JSON.parse(vi.mocked(ws.send).mock.calls[0][0] as string)).toEqual({
+      type: "resized",
+      cols: 132,
+      rows: 40,
+    });
+    sessionManager.destroySession(id);
+  });
+
+  it("broadcasts later size changes and retains them for new participants", () => {
+    const id = createConnectedSession();
+    const owner = makeFakeWs();
+    const viewer = makeFakeWs();
+    sessionManager.attachWs(id, "owner-1", owner);
+    sessionManager.joinAsParticipant(id, viewer, {
+      userId: "viewer",
+      permissionLevel: "read-only",
+    });
+    sessionManager.resizeSession(id, 100, 35);
+    const message = JSON.stringify({ type: "resized", cols: 100, rows: 35 });
+    expect(owner.send).toHaveBeenCalledWith(message);
+    expect(viewer.send).toHaveBeenCalledWith(message);
+    const newcomer = makeFakeWs();
+    sessionManager.joinAsParticipant(id, newcomer, {
+      userId: null,
+      permissionLevel: "read-only",
+    });
+    expect(vi.mocked(newcomer.send).mock.calls[0][0]).toBe(message);
+    sessionManager.destroySession(id);
+  });
+
   it("joinAsParticipant adds a participant without evicting the owner", () => {
     const id = createConnectedSession();
     const ownerWs = makeFakeWs();
diff --git a/plugins/ssh-terminal/tests/frontend/terminal/shared-terminal-size.test.ts b/plugins/ssh-terminal/tests/frontend/terminal/shared-terminal-size.test.ts
new file mode 100644
index 000000000..ec95d0462
--- /dev/null
+++ b/plugins/ssh-terminal/tests/frontend/terminal/shared-terminal-size.test.ts
@@ -0,0 +1,109 @@
+import ts from "typescript";
+import { describe, expect, it, vi } from "vitest";
+import sourceText from "../../../src/frontend/terminal/Terminal.tsx?raw";
+
+const source = ts.createSourceFile(
+  "Terminal.tsx",
+  sourceText,
+  ts.ScriptTarget.Latest,
+  true,
+  ts.ScriptKind.TSX,
+);
+const names = [
+  "setupWebSocketListeners",
+  "applySharedSize",
+  "fitTerminal",
+  "scheduleNotify",
+];
+const functions: string[] = [];
+function visit(node: ts.Node) {
+  if (
+    ts.isFunctionDeclaration(node) &&
+    node.name &&
+    names.includes(node.name.text)
+  )
+    functions.push(node.getText(source));
+  ts.forEachChild(node, visit);
+}
+visit(source);
+if (functions.length !== names.length)
+  throw new Error("Missing terminal size handlers");
+const create = new Function(
+  "state",
+  ts.transpileModule(
+    `
+  const { terminal, hostConfig, sharedSizeRef, fitAddonRef, webSocketRef, emitSessionMessage } = state;
+  const connectionAttemptIdRef = { current: 1 };
+  ${functions.join("\n")}
+  setupWebSocketListeners(webSocketRef.current, 80, 24, hostConfig);
+  return { fit: fitTerminal, notify: scheduleNotify };
+`,
+    { compilerOptions: { target: ts.ScriptTarget.ES2022 } },
+  ).outputText,
+) as (state: Record<string, unknown>) => {
+  fit: () => void;
+  notify: (cols: number, rows: number) => void;
+};
+
+function fixture(shared = true) {
+  const events = new Map<string, (event: { data: string }) => void>();
+  const terminal = {
+    cols: 80,
+    rows: 24,
+    resize: vi.fn((cols: number, rows: number) => {
+      terminal.cols = cols;
+      terminal.rows = rows;
+    }),
+  };
+  const fit = vi.fn(() => {
+    terminal.cols = 80;
+    terminal.rows = 24;
+  });
+  const socket = {
+    addEventListener: (name: string, fn: (event: { data: string }) => void) =>
+      events.set(name, fn),
+    send: vi.fn(),
+  };
+  const handlers = create({
+    terminal,
+    hostConfig: shared ? { joinShareId: "share" } : {},
+    sharedSizeRef: { current: null },
+    fitAddonRef: { current: { fit } },
+    webSocketRef: { current: socket },
+    emitSessionMessage: vi.fn(),
+  });
+  const resize = (cols: unknown, rows: unknown) =>
+    events.get("message")!({
+      data: JSON.stringify({ type: "resized", cols, rows }),
+    });
+  return { terminal, fit, handlers, socket, resize };
+}
+
+describe("in-app shared terminal sizing", () => {
+  it("uses presenter sizes and does not refit or resize the remote shell from the viewer", () => {
+    const f = fixture();
+    f.resize(132, 40);
+    expect([f.terminal.cols, f.terminal.rows]).toEqual([132, 40]);
+    f.handlers.fit();
+    expect(f.fit).not.toHaveBeenCalled();
+    expect([f.terminal.cols, f.terminal.rows]).toEqual([132, 40]);
+    f.handlers.notify(80, 24);
+    expect(f.socket.send).not.toHaveBeenCalled();
+    f.resize(100, 30);
+    expect([f.terminal.cols, f.terminal.rows]).toEqual([100, 30]);
+  });
+
+  it("continues fitting the owner's terminal normally", () => {
+    const f = fixture(false);
+    f.resize(132, 40);
+    expect(f.terminal.resize).not.toHaveBeenCalled();
+    f.handlers.fit();
+    expect(f.fit).toHaveBeenCalledOnce();
+  });
+
+  it.each([0, -1, 1.5, "132"])("rejects an invalid column count %s", (cols) => {
+    const f = fixture();
+    f.resize(cols, 24);
+    expect(f.terminal.resize).not.toHaveBeenCalled();
+  });
+});