diff --git a/src/web/public/app.js b/src/web/public/app.js
index 01537caa..e1e6fc78 100644
--- a/src/web/public/app.js
+++ b/src/web/public/app.js
@@ -1362,6 +1362,8 @@ class CodemanApp {
     this.writeFrameScheduled = false;
     this._isLoadingBuffer = false;
     this._loadBufferQueue = null;
+    // Abort any in-flight chunkedTerminalWrite (SSE reconnect reloads buffers)
+    this._chunkedWriteGen = (this._chunkedWriteGen || 0) + 1;
     // Preserve local echo overlay text across SSE reconnect — just hide until
     // terminal buffer reloads and prompt is visible again.  _render() re-scans
     // for the ❯ prompt on every call, so rerender() after buffer load repositions it.
@@ -2020,6 +2022,10 @@ class CodemanApp {
     this.writeFrameScheduled = false;
     this._isLoadingBuffer = false;
     this._loadBufferQueue = null;
+    // Abort any in-flight chunkedTerminalWrite from the previous session.
+    // Without this, old rAF-scheduled chunks continue writing stale data
+    // into the terminal, interleaving with the new session's buffer.
+    this._chunkedWriteGen = (this._chunkedWriteGen || 0) + 1;
     // End any in-flight IME composition.
     // iOS Safari keeps autocorrect composing; switching tabs without ending it
     // leaves xterm's _compositionHelper._isComposing stuck true, which blocks
@@ -2136,6 +2142,11 @@ class CodemanApp {
     this._isLoadingBuffer = true;
     this._loadBufferQueue = [];
     try {
+      // Fit terminal to container BEFORE writing any buffer data.
+      // If the browser was resized while viewing another session, the terminal
+      // canvas may be at stale dimensions — content would render at wrong width.
+      if (this.fitAddon) this.fitAddon.fit();
+
       // Instant cache restore — show previous buffer via chunked write to avoid WebGL GPU stalls.
       // Direct terminal.write() of large cached buffers (256KB+) can block the main thread
       // for 5+ seconds while the WebGL renderer processes ReadPixels synchronously.
diff --git a/src/web/public/terminal-ui.js b/src/web/public/terminal-ui.js
index 0b206f24..df00b1b4 100644
--- a/src/web/public/terminal-ui.js
+++ b/src/web/public/terminal-ui.js
@@ -219,6 +219,9 @@ Object.assign(CodemanApp.prototype, {
     // Welcome message
     this.showWelcome();
 
+    // Generation counter for chunkedTerminalWrite — aborts stale writes on tab switch
+    this._chunkedWriteGen = 0;
+
     // Handle resize with throttling for performance
     this._resizeTimeout = null;
     this._lastResizeDims = null;
@@ -1033,6 +1036,10 @@ Object.assign(CodemanApp.prototype, {
    * @returns {Promise<void>} - Resolves when all chunks written
    */
   chunkedTerminalWrite(buffer, chunkSize = TERMINAL_CHUNK_SIZE) {
+    // Generation counter: if a newer chunkedTerminalWrite starts (tab switch),
+    // older writes abort instead of continuing to push stale data into the terminal.
+    const writeGen = ++this._chunkedWriteGen;
+
     return new Promise((resolve) => {
       if (!buffer || buffer.length === 0) {
         this._finishBufferLoad();
@@ -1049,7 +1056,10 @@ Object.assign(CodemanApp.prototype, {
       const cleanBuffer = buffer.replace(DEC_SYNC_STRIP_RE, '');
 
       const finish = () => {
-        this._finishBufferLoad();
+        // Only finish if we're still the active write — a newer write owns buffer load state
+        if (this._chunkedWriteGen === writeGen) {
+          this._finishBufferLoad();
+        }
         resolve();
       };
 
@@ -1067,6 +1077,12 @@ Object.assign(CodemanApp.prototype, {
       const _chunkStart = performance.now();
       let _chunkCount = 0;
       const writeChunk = () => {
+        // Abort if a newer chunked write started (user switched tabs)
+        if (this._chunkedWriteGen !== writeGen) {
+          resolve();
+          return;
+        }
+
         if (offset >= cleanBuffer.length) {
           const _totalMs = performance.now() - _chunkStart;
           console.log(`[CRASH-DIAG] chunkedTerminalWrite complete: ${cleanBuffer.length} bytes in ${_chunkCount} chunks, ${_totalMs.toFixed(0)}ms total`);
@@ -1240,6 +1256,9 @@ Object.assign(CodemanApp.prototype, {
    * @returns {Promise<void>}
    */
   async sendResize(sessionId) {
+    // Fit terminal to container before reading dimensions — ensures local
+    // terminal size matches what we report to the server PTY.
+    if (this.fitAddon) this.fitAddon.fit();
     const dims = this.getTerminalDimensions();
     if (!dims) return;
     // Fast path: WebSocket resize