Merge pull request #499 from aakhter/pr/mobile-ime-preview

feat(terminal): preview IME composition text on iOS Safari

# Conflicts:
#	CLAUDE.md

src/web/public/index.html

@@ -3838,6 +3838,8 @@
   <script defer src="notification-manager.js"></script>
   <script defer src="keyboard-accessory.js"></script>
   <script defer src="input-cjk.js"></script>
+  <!-- Shows iOS Safari IME composition text inside the terminal. Must precede terminal-ui.js. -->
+  <script defer src="mobile-ime-preview.js"></script>
   <!-- Forwards committed input events that xterm drops on Android/GBoard soft keyboards. Must precede terminal-ui.js. -->
   <script defer src="terminal-keycode229-recovery.js"></script>
   <!-- Hardened markdown HTML sanitizer (wires DOMPurify). Must precede app.js. -->

src/web/public/mobile-ime-preview.js

@@ -0,0 +1,297 @@
+/**
+ * @fileoverview In-terminal preview of IME composition text on iOS Safari.
+ *
+ * On iOS WebKit touch devices the text an IME is composing (Japanese, Chinese,
+ * Korean, dictation) is not visible inside the terminal until it commits, so
+ * the user types blind. The controller listens to the helper textarea's
+ * composition events and asks the caller to render the latest composition
+ * (`phase: 'provisional'`), coalesced to one render per animation frame and
+ * capped at 2048 characters. When xterm emits the committed text through
+ * onData, the caller hands it to `consumeTerminalData()`, which switches the
+ * preview to `phase: 'committed'` until something else shows the text: the
+ * local echo overlay or a prediction (`completeCommit`), authoritative
+ * terminal output (`noteAuthoritativeOutput`), or a 2 s fallback timer. The
+ * same 2 s bound applies while waiting for a commit that never reaches onData
+ * (the user deleted the whole composition), so a later unrelated chunk is never
+ * mistaken for it.
+ *
+ * Keydown ordering: xterm registers its textarea keydown listener in the
+ * capture phase inside terminal.open() and finalizes the composition there
+ * (CompositionHelper.keydown), emitting the commit through onData
+ * synchronously. The controller therefore observes keydown in the capture
+ * phase on an ANCESTOR (`keydownTarget`, the terminal element), which runs
+ * before any listener on the textarea itself, and finalizes on exactly the
+ * keys xterm does.
+ *
+ * VISUAL ONLY: the controller never sends, consumes or reorders input bytes,
+ * and every callback is wrapped so a failing render cannot block the wire.
+ * `isIosWebKitTouch()` gates creation; other platforms keep xterm's own
+ * composition view untouched.
+ *
+ * @dependency none (standalone IIFE; consumed by terminal-ui.js)
+ * @loadorder 5.52 (before app.js/terminal-ui.js, which create the controller)
+ */
+(function (global) {
+  'use strict';
+
+  const COMMITTED_VISUAL_TTL = 2000;
+  const PREVIEW_CAP = 2048;
+  // keyCodes on which xterm 6's CompositionHelper.keydown keeps composing
+  // (CapsLock, the IME "composition character", Shift/Ctrl/Alt). Any other
+  // keydown during a composition finalizes it.
+  const KEEP_COMPOSING_KEYCODES = new Set([20, 229, 16, 17, 18]);
+  const CONTROL_OR_LINE_BREAK = /[\u0000-\u001f\u007f-\u009f\u2028\u2029]/;
+
+  function isIosWebKitTouch(nav = navigator) {
+    const userAgent = String(nav && nav.userAgent ? nav.userAgent : '');
+    const platform = String(nav && nav.platform ? nav.platform : '');
+    const touchPoints = Number(nav && nav.maxTouchPoints ? nav.maxTouchPoints : 0);
+    const iosDevice = /iPhone|iPad|iPod/.test(userAgent);
+    const desktopIpad = platform === 'MacIntel' && touchPoints > 1;
+    return touchPoints > 0 && /AppleWebKit/.test(userAgent) && (iosDevice || desktopIpad);
+  }
+
+  function create(options) {
+    const textarea = options.textarea;
+    // Must be the textarea or an ancestor of it, so its capture listener runs
+    // before xterm's capture listener on the textarea.
+    const keydownTarget = options.keydownTarget || textarea;
+    const render = typeof options.render === 'function' ? options.render : function () {};
+    const clear = typeof options.clear === 'function' ? options.clear : function () {};
+    const onCommit = typeof options.onCommit === 'function' ? options.onCommit : function () {};
+    const scheduleFrame = options.scheduleFrame || global.requestAnimationFrame.bind(global);
+    const cancelFrame = options.cancelFrame || global.cancelAnimationFrame.bind(global);
+    const setTimer = options.setTimer || global.setTimeout.bind(global);
+    const clearTimer = options.clearTimer || global.clearTimeout.bind(global);
+
+    let generation = 0;
+    let composing = false;
+    let awaitingCommit = false;
+    let committed = false;
+    let latestValue = '';
+    let renderPhase = null;
+    let frameToken = null;
+    let timerToken = null;
+    let finalizedByKeydown = false;
+    let destroyed = false;
+    let invokingClear = false;
+
+    function safely(callback, ...args) {
+      try {
+        return callback(...args);
+      } catch (_error) {
+        return undefined;
+      }
+    }
+
+    function cancelScheduledFrame() {
+      const token = frameToken;
+      frameToken = null;
+      if (token && token.id !== undefined) safely(cancelFrame, token.id);
+    }
+
+    function cancelCommittedTimer() {
+      const token = timerToken;
+      timerToken = null;
+      if (token && token.id !== undefined) safely(clearTimer, token.id);
+    }
+
+    function clearVisual() {
+      if (invokingClear) return;
+      invokingClear = true;
+      safely(clear);
+      invokingClear = false;
+    }
+
+    function cleanup() {
+      generation += 1;
+      cancelScheduledFrame();
+      cancelCommittedTimer();
+      composing = false;
+      awaitingCommit = false;
+      committed = false;
+      latestValue = '';
+      renderPhase = null;
+      finalizedByKeydown = false;
+      clearVisual();
+    }
+
+    function scheduleLatestPreview(phase) {
+      if (destroyed) return;
+      renderPhase = phase;
+      if (frameToken) return;
+      const token = { generation, id: undefined };
+      frameToken = token;
+      const callback = function () {
+        if (destroyed || frameToken !== token || token.generation !== generation || renderPhase === null) return;
+        frameToken = null;
+        const value = latestValue.slice(0, PREVIEW_CAP);
+        const phaseToRender = renderPhase;
+        safely(render, { text: value, phase: phaseToRender });
+      };
+      const id = safely(scheduleFrame, callback);
+      if (frameToken === token) {
+        if (id === undefined) frameToken = null;
+        else token.id = id;
+      }
+    }
+
+    function beginComposition() {
+      cleanup();
+      if (destroyed) return;
+      composing = true;
+    }
+
+    function updateComposition(event) {
+      if (!composing) return;
+      latestValue = event.data == null ? '' : String(event.data);
+      scheduleLatestPreview('provisional');
+    }
+
+    function onComposingInput(event) {
+      if (!event.isComposing) return;
+      updateComposition({ data: event.data == null ? textarea.value : event.data });
+    }
+
+    function armFallbackTimer(isCurrent) {
+      const token = { generation, id: undefined };
+      timerToken = token;
+      const callback = function () {
+        if (destroyed || timerToken !== token || token.generation !== generation || !isCurrent()) return;
+        timerToken = null;
+        cleanup();
+      };
+      const id = safely(setTimer, callback, COMMITTED_VISUAL_TTL);
+      if (timerToken === token) {
+        if (id === undefined) {
+          timerToken = null;
+          return false;
+        }
+        token.id = id;
+      }
+      return true;
+    }
+
+    function finalizeComposition(value, fromKeydown) {
+      if (!composing) return;
+      composing = false;
+      awaitingCommit = true;
+      committed = false;
+      finalizedByKeydown = fromKeydown;
+      latestValue = value == null ? latestValue : String(value);
+      scheduleLatestPreview('provisional');
+      // A commit that never reaches onData (the composition was deleted, so
+      // xterm emits nothing) must not leave the controller waiting forever.
+      cancelCommittedTimer();
+      const owner = generation;
+      armFallbackTimer(function () {
+        return awaitingCommit && generation === owner;
+      });
+    }
+
+    function onCompositionEnd(event) {
+      if (finalizedByKeydown) {
+        finalizedByKeydown = false;
+        return;
+      }
+      finalizeComposition(event.data, false);
+    }
+
+    // Mirrors CompositionHelper.keydown in @xterm/xterm 6.0.0
+    // (src/browser/input/CompositionHelper.ts:94-108): while composing, keyCode
+    // 20/229 and 16/17/18 keep the composition open and every other keyCode
+    // finalizes it. `isComposing` and `key` are deliberately not consulted,
+    // because xterm does not consult them.
+    function onKeydown(event) {
+      if (keydownTarget !== textarea && event.target !== textarea) return;
+      if (!composing || KEEP_COMPOSING_KEYCODES.has(event.keyCode)) return;
+      finalizeComposition(latestValue, true);
+    }
+
+    function reset() {
+      if (destroyed) return;
+      cleanup();
+    }
+
+    function consumeTerminalData(data) {
+      if (
+        destroyed ||
+        !awaitingCommit ||
+        typeof data !== 'string' ||
+        data.length === 0 ||
+        CONTROL_OR_LINE_BREAK.test(data)
+      ) {
+        return false;
+      }
+
+      generation += 1;
+      const owner = generation;
+      cancelScheduledFrame();
+      cancelCommittedTimer();
+      composing = false;
+      awaitingCommit = false;
+      committed = true;
+      latestValue = data;
+      renderPhase = 'committed';
+      safely(onCommit, data);
+      if (destroyed || generation !== owner || !committed) return true;
+
+      scheduleLatestPreview('committed');
+      if (destroyed || generation !== owner || !committed) return true;
+
+      const armed = armFallbackTimer(function () {
+        return committed;
+      });
+      if (!armed && !destroyed && generation === owner && committed) cleanup();
+      return true;
+    }
+
+    function completeCommit(result) {
+      if (destroyed || !result || result.predicted !== true || !committed) return;
+      cleanup();
+    }
+
+    function noteAuthoritativeOutput() {
+      if (destroyed || !committed) return;
+      cleanup();
+    }
+
+    const listeners = [
+      [textarea, 'compositionstart', beginComposition],
+      [textarea, 'compositionupdate', updateComposition],
+      [textarea, 'input', onComposingInput],
+      [textarea, 'compositionend', onCompositionEnd],
+      [keydownTarget, 'keydown', onKeydown, true],
+      [textarea, 'blur', reset],
+    ];
+    for (const [target, type, listener, capture] of listeners) target.addEventListener(type, listener, capture);
+
+    function destroy() {
+      if (destroyed) return;
+      destroyed = true;
+      for (const [target, type, listener, capture] of listeners) target.removeEventListener(type, listener, capture);
+      cleanup();
+    }
+
+    return {
+      consumeTerminalData,
+      completeCommit,
+      noteAuthoritativeOutput,
+      reset,
+      destroy,
+      get state() {
+        return {
+          generation,
+          composing,
+          awaitingCommit,
+          committed,
+          latest: latestValue,
+          framePending: frameToken !== null,
+          timerPending: timerToken !== null,
+        };
+      },
+    };
+  }
+
+  global.MobileImePreview = { create, isIosWebKitTouch };
+})(globalThis);

src/web/public/styles.css

@@ -460,6 +460,31 @@ textarea:focus-visible {
   font-size: 16px !important; /* prevent iOS auto-zoom on focus */
 }
 
+.xterm-helpers .codeman-ime-preview {
+  position: absolute;
+  left: var(--xterm-helper-left, 0px);
+  top: var(--xterm-helper-top, 0px);
+  z-index: 6;
+  pointer-events: none;
+  white-space: pre;
+  color: var(--terminal-foreground, var(--text, #fff));
+  font-family: var(--font-mono, monospace);
+  font-size: 14px;
+  font-weight: 400;
+  font-style: normal;
+  line-height: 1.2;
+  height: 1.2em;
+}
+
+.xterm-helpers .codeman-ime-preview[data-phase='provisional'] {
+  text-decoration: underline;
+  text-decoration-style: dotted;
+}
+
+.touch-device .xterm-helpers.codeman-ime-preview-owned .composition-view.active {
+  display: none;
+}
+
 /* Session tab focus */
 .session-tab:focus-visible {
   outline: 2px solid var(--accent);

src/web/public/terminal-ui.js

@@ -250,6 +250,235 @@ Object.assign(CodemanApp.prototype, {
     this._keyCode229Recovery = null;
   },
 
+  _destroyMobileImePreview() {
+    try {
+      this._mobileImePreview?.destroy?.();
+    } catch {
+      // The preview is visual-only; terminal replacement must continue.
+    }
+    this._mobileImePreview = null;
+    this._mobileImePreviewSessionId = null;
+    this._mobileImeCommitOutputSeq = null;
+    try {
+      this._mobileImePreviewNode?.remove?.();
+    } catch {
+      // Best-effort node cleanup only.
+    }
+    try {
+      this._mobileImePreviewHelpers?.classList?.remove('codeman-ime-preview-owned');
+    } catch {
+      // Best-effort ownership cleanup only.
+    }
+    this._mobileImePreviewNode = null;
+    this._mobileImePreviewHelpers = null;
+    try {
+      if (this._mobileImePreviewOfflineHandler) {
+        window.removeEventListener('offline', this._mobileImePreviewOfflineHandler);
+      }
+      if (this._mobileImePreviewPagehideHandler) {
+        window.removeEventListener('pagehide', this._mobileImePreviewPagehideHandler);
+      }
+    } catch {
+      // Best-effort listener cleanup only.
+    }
+    this._mobileImePreviewOfflineHandler = null;
+    this._mobileImePreviewPagehideHandler = null;
+  },
+
+  /**
+   * iOS Safari IME preview (mobile-ime-preview.js). WebKit does not show the
+   * text an IME is composing inside the terminal, so the user types blind.
+   *
+   * Two homes, chosen per render:
+   * - Local echo on: typed text sits in the LocalEchoOverlay and the PTY
+   *   cursor stays at the prompt start, under the overlay's opaque text (z 7,
+   *   `.xterm-screen`). So the overlay draws the composition itself, as an
+   *   underlined tail after its pending text (`setComposition`).
+   * - Otherwise (a shell, or the overlay could not place it): a span inside
+   *   `.xterm-helpers`, positioned by the same --xterm-helper-left/top vars as
+   *   the helper textarea, which follow the PTY cursor.
+   *
+   * Visual only: nothing here touches the input path, and every failure
+   * leaves no DOM behind.
+   */
+  _initMobileImePreview() {
+    this._destroyMobileImePreview();
+    let preview = null;
+    let helpers = null;
+    try {
+      if (typeof MobileImePreview === 'undefined' || !MobileImePreview?.isIosWebKitTouch?.()) return;
+      const textarea = this.terminal?.textarea;
+      helpers = this.terminal?.element?.querySelector?.('.xterm-helpers');
+      if (!textarea || !helpers) return;
+
+      preview = document.createElement('span');
+      this._mobileImePreviewNode = preview;
+      this._mobileImePreviewHelpers = helpers;
+      preview.className = 'codeman-ime-preview';
+      preview.setAttribute('aria-hidden', 'true');
+      preview.hidden = true;
+      helpers.appendChild(preview);
+      const syncPreviewTypography = () => {
+        try {
+          const compositionView =
+            helpers.querySelector?.('.composition-view') || this.terminal?.element?.querySelector?.('.composition-view');
+          if (!compositionView || !preview.style) return;
+          const style = typeof getComputedStyle === 'function' ? getComputedStyle(compositionView) : compositionView.style;
+          for (const property of ['fontFamily', 'fontSize', 'fontWeight', 'fontStyle', 'lineHeight', 'height']) {
+            const value = style?.[property] || compositionView.style?.[property];
+            if (value) preview.style[property] = value;
+          }
+          const theme = this.terminal?.options?.theme;
+          let foreground = theme?.foreground;
+          let background = theme?.background;
+          if (!foreground || !background) {
+            try {
+              const current = window.codemanCurrentXtermTheme?.();
+              foreground = foreground || current?.foreground;
+              background = background || current?.background;
+            } catch {
+              // Theme lookup is best-effort; retain the safe terminal fallback.
+            }
+          }
+          preview.style.color = foreground || '#e0e0e0';
+          // Opaque, like xterm's own composition view, so the preview does not
+          // overprint whatever sits at the cursor (a dim composer placeholder).
+          preview.style.backgroundColor = background || '#0d0d0d';
+        } catch {
+          // Typography matching is visual-only and must not block input.
+        }
+      };
+      // The overlay only when it is what shows typed text right now (local echo
+      // on, and not handed back to plain PTY echo by a composer nav key).
+      const localEchoOverlay = () =>
+        this._localEchoEnabled && !this._echoPassthroughSessions?.has(this.activeSessionId)
+          ? this._localEchoOverlay || null
+          : null;
+      const clearOverlayComposition = () => {
+        try {
+          if (this._localEchoOverlay?.composition) this._localEchoOverlay.setComposition('');
+        } catch {}
+      };
+      const hideSpan = () => {
+        try {
+          preview.hidden = true;
+        } catch {}
+        try {
+          preview.textContent = '';
+        } catch {}
+        try {
+          delete preview.dataset.phase;
+        } catch {}
+        try {
+          helpers.classList.remove('codeman-ime-preview-owned');
+        } catch {}
+      };
+      const clearPreview = () => {
+        clearOverlayComposition();
+        hideSpan();
+      };
+      const controller = MobileImePreview.create({
+        textarea,
+        // An ancestor of the textarea: its capture-phase keydown listener runs
+        // before xterm's capture listener on the textarea, which finalizes the
+        // composition and emits the commit synchronously.
+        keydownTarget: this.terminal.element,
+        render: ({ text, phase }) => {
+          try {
+            const overlay = localEchoOverlay();
+            if (overlay && typeof overlay.setComposition === 'function') {
+              overlay.setComposition(text);
+              // No prompt found = nothing drawn: fall back to the span.
+              if (!text || overlay.state?.visible) {
+                hideSpan();
+                helpers.classList.toggle('codeman-ime-preview-owned', !!text);
+                return;
+              }
+              overlay.setComposition('');
+            } else {
+              clearOverlayComposition();
+            }
+            syncPreviewTypography();
+            preview.textContent = text;
+            preview.dataset.phase = phase;
+            preview.hidden = !text;
+            helpers.classList.toggle('codeman-ime-preview-owned', !!text);
+          } catch {
+            clearPreview();
+          }
+        },
+        clear: clearPreview,
+      });
+      this._mobileImePreview = controller;
+      this._mobileImePreviewSessionId = this.activeSessionId;
+
+      // Offline and pagehide only reset: initTerminal() runs once per page
+      // load, so destroying on pagehide would leave the preview off for good
+      // after a back-forward cache restore (iOS Safari keeps pages there).
+      this._mobileImePreviewOfflineHandler = () => {
+        try {
+          this._mobileImePreview?.reset?.();
+        } catch {
+          // Disconnect cleanup is visual-only.
+        }
+      };
+      this._mobileImePreviewPagehideHandler = this._mobileImePreviewOfflineHandler;
+      window.addEventListener('offline', this._mobileImePreviewOfflineHandler);
+      window.addEventListener('pagehide', this._mobileImePreviewPagehideHandler);
+    } catch {
+      this._destroyMobileImePreview();
+    }
+  },
+
+  /**
+   * Tell the IME preview about a chunk xterm emitted through onData. Returns
+   * true when the chunk is the IME's committed text, in which case the preview
+   * holds it (phase 'committed') until something else shows it. Never throws.
+   */
+  _consumeMobileImeTerminalData(data) {
+    let isImeCommit = false;
+    try {
+      isImeCommit = this._mobileImePreview?.consumeTerminalData?.(data) === true;
+    } catch {
+      // The preview is visual-only; normal terminal input must continue.
+    }
+    // Output accepted from here on can carry the echo of this commit.
+    if (isImeCommit) this._mobileImeCommitOutputSeq = this._terminalOutputSeq || 0;
+    return isImeCommit;
+  },
+
+  /**
+   * Clear a committed IME preview once terminal output accepted AFTER the
+   * commit has been parsed. `flushedOutputSeq` is the output sequence a fully
+   * written flush covered (null when part of it was deferred), so output that
+   * was already queued before the commit can never clear it early.
+   */
+  _noteMobileImeAuthoritativeOutput(flushedOutputSeq, sessionId) {
+    try {
+      const commitSeq = this._mobileImeCommitOutputSeq;
+      if (commitSeq === null || commitSeq === undefined || flushedOutputSeq === null) return;
+      if (sessionId !== this.activeSessionId || !(flushedOutputSeq > commitSeq)) return;
+      this._mobileImeCommitOutputSeq = null;
+      this._mobileImePreview?.noteAuthoritativeOutput?.();
+    } catch {
+      // Authoritative output is never delayed or consumed by the preview.
+    }
+  },
+
+  /**
+   * The local echo overlay has just taken a committed IME chunk through the
+   * ordinary printable/paste branch, so it now shows the text: release the
+   * preview instead of waiting for terminal output.
+   */
+  _transferMobileImeCommitToLocalEcho() {
+    this._mobileImeCommitOutputSeq = null;
+    try {
+      this._mobileImePreview?.completeCommit?.({ predicted: true });
+    } catch {
+      // Ownership transfer is visual-only.
+    }
+  },
+
   initTerminal() {
     // Load scrollback setting from localStorage, treating DEFAULT_SCROLLBACK as a floor
     // so users who picked up the previous (smaller) default get the new minimum on upgrade.
@@ -307,6 +536,7 @@ Object.assign(CodemanApp.prototype, {
 
     const container = document.getElementById('terminalContainer');
     this.terminal.open(container);
+    this._initMobileImePreview();
     this._installMobileTapMouseGuard();
     this._installShiftDragSelection();
     this._installTouchSelectionFocusGuard();
@@ -1215,6 +1445,8 @@ Object.assign(CodemanApp.prototype, {
     // survives tab switches and reconnects.
 
     const handleTerminalData = (data) => {
+      // Before anything can rewrite `data`: is this chunk the IME's commit?
+      const isImeCommit = this._consumeMobileImeTerminalData(data);
       // Mouse SGR reports (tap-to-position) are NOT IME input — they must reach
       // the PTY even while the CJK input field owns focus. Without this exception
       // tapping to move the cursor silently does nothing whenever Chinese input
@@ -1292,6 +1524,8 @@ Object.assign(CodemanApp.prototype, {
         // When enabled, keystrokes are buffered locally in the overlay for
         // instant visual feedback.  Nothing is sent to the PTY until Enter
         // (or a control char) is pressed — avoids out-of-order char delivery.
+        // An IME commit takes the same printable/paste branch as typed text,
+        // and the overlay then shows it in place of the preview.
         if (this._localEchoEnabled && !echoPassthrough) {
           if (data === '\x7f') {
             const source = this._localEchoOverlay?.removeChar();
@@ -1348,6 +1582,7 @@ Object.assign(CodemanApp.prototype, {
           if (data.length > 1 && data.charCodeAt(0) >= 32) {
             // Paste: append to overlay only (sent on Enter)
             this._localEchoOverlay?.appendText(data);
+            if (isImeCommit && this._localEchoOverlay) this._transferMobileImeCommitToLocalEcho();
             return;
           }
           if (data.charCodeAt(0) < 32) {
@@ -1493,6 +1728,7 @@ Object.assign(CodemanApp.prototype, {
           if (data.length === 1 && data.charCodeAt(0) >= 32) {
             // Printable char: add to overlay only (sent on Enter)
             this._localEchoOverlay?.addChar(data);
+            if (isImeCommit && this._localEchoOverlay) this._transferMobileImeCommitToLocalEcho();
             return;
           }
         }
@@ -3528,6 +3764,9 @@ Object.assign(CodemanApp.prototype, {
   },
 
   batchTerminalWrite(data) {
+    // Arrival order of output, so the IME preview can tell output that
+    // followed a commit from output that was already queued before it.
+    this._terminalOutputSeq = (this._terminalOutputSeq || 0) + 1;
     // Feed the renderer watchdog. Recorded before the buffer-load early return
     // below: a write that is queued rather than written still means the pipeline
     // owes us a frame once it drains.
@@ -3591,6 +3830,7 @@ Object.assign(CodemanApp.prototype, {
 
     // Accumulate raw data (may contain DEC 2026 markers)
     this.pendingWrites.push(data);
+    this._pendingWritesOutputSeq = this._terminalOutputSeq;
     this._scheduleTerminalWriteFlush();
   },
 
@@ -3622,6 +3862,7 @@ Object.assign(CodemanApp.prototype, {
 
     // Transfer buffered data to normal pending writes
     this.pendingWrites.push(this.flickerFilterBuffer);
+    this._pendingWritesOutputSeq = this._terminalOutputSeq;
     this.flickerFilterBuffer = '';
     this.flickerFilterActive = false;
 
@@ -3652,6 +3893,15 @@ Object.assign(CodemanApp.prototype, {
    * Position is tracked dynamically by _findPrompt() on every render.
    */
   _updateLocalEchoState() {
+    if (this._mobileImePreviewSessionId !== this.activeSessionId) {
+      this._mobileImePreviewSessionId = this.activeSessionId;
+      this._mobileImeCommitOutputSeq = null;
+      try {
+        this._mobileImePreview?.reset?.();
+      } catch {
+        // The preview is visual-only; session switching must continue.
+      }
+    }
     const settings = this.loadAppSettingsFromStorage();
     const session = this.activeSessionId ? this.sessions.get(this.activeSessionId) : null;
     const echoEnabled = settings.localEchoEnabled ?? MobileDetection.isTouchDevice();
@@ -3857,6 +4107,9 @@ Object.assign(CodemanApp.prototype, {
       this.pendingWrites.push(joined.slice(MAX_FRAME_BYTES));
       deferred = true;
     }
+    // Newest output this chunk fully contains, for the IME preview. A split
+    // chunk may not hold that output yet, so it reports nothing.
+    const flushedOutputSeq = deferred ? null : (this._pendingWritesOutputSeq ?? null);
     this._terminalWriteInFlight = true;
     this._terminalWriteInFlightBytes = writeChunk.length;
     try {
@@ -3874,6 +4127,7 @@ Object.assign(CodemanApp.prototype, {
         // because the test's write mock moved the viewport synchronously.)
         this._restoreTerminalViewport(preserveViewportY, flushSessionId);
         this._scheduleTerminalWriteFlush();
+        this._noteMobileImeAuthoritativeOutput(flushedOutputSeq, flushSessionId);
       });
     } catch (err) {
       this._terminalWriteInFlight = false;