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keep the terminal scrolled to the bottom across resizes if it was at the bottom #2941

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Merged
sawka merged 1 commit into from
Feb 26, 2026
Merged

keep the terminal scrolled to the bottom across resizes if it was at the bottom #2941

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3 changes: 3 additions & 0 deletions frontend/app/view/term/term.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -311,6 +311,9 @@ const TerminalView = ({ blockId, model }: ViewComponentProps<TermViewModel>) =>
model.termRef.current = termWrap;
setTermWrapInst(termWrap);
const rszObs = new ResizeObserver(() => {
if (termWrap.cachedAtBottomForResize == null) {
termWrap.cachedAtBottomForResize = termWrap.wasRecentlyAtBottom();
}
termWrap.handleResize_debounced();
});
rszObs.observe(connectElemRef.current);
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44 changes: 44 additions & 0 deletions frontend/app/view/term/termwrap.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,9 @@ export class TermWrap {
// xterm.js paste() method triggers onData event, which can cause duplicate sends
lastPasteData: string = "";
lastPasteTime: number = 0;
lastAtBottomTime: number = Date.now();
lastScrollAtBottom: boolean = true;
cachedAtBottomForResize: boolean | null = null;

constructor(
tabId: string,
Expand Down Expand Up @@ -226,6 +229,19 @@ export class TermWrap {
this.connectElem.removeEventListener("paste", pasteHandler, true);
},
});
const viewportElem = this.connectElem.querySelector(".xterm-viewport") as HTMLElement;
if (viewportElem) {
const scrollHandler = () => {
const atBottom = viewportElem.scrollTop + viewportElem.clientHeight >= viewportElem.scrollHeight - 20;
this.setAtBottom(atBottom);
};
viewportElem.addEventListener("scroll", scrollHandler);
this.toDispose.push({
dispose: () => {
viewportElem.removeEventListener("scroll", scrollHandler);
},
});
}
}

getZoneId(): string {
Expand Down Expand Up @@ -465,9 +481,30 @@ export class TermWrap {
}
}

setAtBottom(atBottom: boolean) {
if (this.lastScrollAtBottom && !atBottom) {
this.lastAtBottomTime = Date.now();
}
this.lastScrollAtBottom = atBottom;
if (atBottom) {
this.lastAtBottomTime = Date.now();
}
}

wasRecentlyAtBottom(): boolean {
if (this.lastScrollAtBottom) {
return true;
}
return Date.now() - this.lastAtBottomTime <= 1000;
}

handleResize() {
const oldRows = this.terminal.rows;
const oldCols = this.terminal.cols;
const atBottom = this.cachedAtBottomForResize ?? this.wasRecentlyAtBottom();
if (!atBottom) {
this.cachedAtBottomForResize = null;
}
this.fitAddon.fit();
if (oldRows !== this.terminal.rows || oldCols !== this.terminal.cols) {
const termSize: TermSize = { rows: this.terminal.rows, cols: this.terminal.cols };
Expand All @@ -478,6 +515,13 @@ export class TermWrap {
this.hasResized = true;
this.resyncController("initial resize");
}
if (atBottom) {
setTimeout(() => {
this.cachedAtBottomForResize = null;
this.terminal.scrollToBottom();
this.setAtBottom(true);
}, 20);
}
Comment on lines +518 to +524
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@coderabbitai coderabbitai bot Feb 26, 2026

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⚠️ Potential issue | 🟠 Major

Clear pending resize timeout to prevent post-dispose terminal mutations.

Line 519 schedules async work, but the timer handle is not tracked or canceled. If dispose happens before it fires, callback code can still run and touch terminal state after teardown.

Suggested patch 
 export class TermWrap {
@@
     cachedAtBottomForResize: boolean | null = null;
+    private resizeBottomTimeout: ReturnType<typeof window.setTimeout> | null = null;
@@
     dispose() {
+        if (this.resizeBottomTimeout != null) {
+            clearTimeout(this.resizeBottomTimeout);
+            this.resizeBottomTimeout = null;
+        }
         this.promptMarkers.forEach((marker) => {
             try {
                 marker.dispose();
@@
         if (atBottom) {
-            setTimeout(() => {
+            if (this.resizeBottomTimeout != null) {
+                clearTimeout(this.resizeBottomTimeout);
+            }
+            this.resizeBottomTimeout = window.setTimeout(() => {
                 this.cachedAtBottomForResize = null;
                 this.terminal.scrollToBottom();
                 this.setAtBottom(true);
+                this.resizeBottomTimeout = null;
             }, 20);
         }
     }
🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@frontend/app/view/term/termwrap.ts` around lines 518 - 524, The scheduled
resize timeout in the atBottom branch uses setTimeout but does not store the
timer id, allowing its callback to run after the terminal is disposed; update
the code around cachedAtBottomForResize so you assign the result of setTimeout
to a field (e.g., this.resizeTimeoutId or reuse cachedAtBottomForResize to hold
the timer id), clear any existing timeout before creating a new one, and ensure
the dispose/cleanup path clears that timer (clearTimeout(this.resizeTimeoutId))
so the callback (which calls this.terminal.scrollToBottom() and
this.setAtBottom(true)) cannot run after teardown.

}

processAndCacheData() {
Expand Down
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