diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index 4ce3398aa0ef22fd0d7aa4b6be8946c9ff55f06f..565ce201ff2a2192f828984bfe5aa192ecbe4be0 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -3707,6 +3707,7 @@ export default function ChatView({ threadId }: ChatViewProps) {
               </div>
             ) : (
               <div
+                data-chat-composer-footer="true"
                 className={cn(
                   "flex items-center justify-between px-2.5 pb-2.5 sm:px-3 sm:pb-3",
                   isComposerFooterCompact ? "gap-1.5" : "flex-wrap gap-2 sm:flex-nowrap sm:gap-0",
@@ -3835,7 +3836,7 @@ export default function ChatView({ threadId }: ChatViewProps) {
                 </div>
 
                 {/* Right side: send / stop button */}
-                <div className="flex shrink-0 items-center gap-2">
+                <div data-chat-composer-actions="right" className="flex shrink-0 items-center gap-2">
                   {isPreparingWorktree ? (
                     <span className="text-muted-foreground/70 text-xs">Preparing worktree...</span>
                   ) : null}
diff --git a/apps/web/src/routes/_chat.$threadId.tsx b/apps/web/src/routes/_chat.$threadId.tsx
index 2593eb7605a11a529cee7966c844b77c14f189fe..ccd2002777272e91af88e02a5f773f169f65b8ad 100644
--- a/apps/web/src/routes/_chat.$threadId.tsx
+++ b/apps/web/src/routes/_chat.$threadId.tsx
@@ -15,6 +15,7 @@ const DIFF_INLINE_LAYOUT_MEDIA_QUERY = "(max-width: 1180px)";
 const DIFF_INLINE_SIDEBAR_WIDTH_STORAGE_KEY = "chat_diff_sidebar_width";
 const DIFF_INLINE_DEFAULT_WIDTH = "clamp(28rem,48vw,44rem)";
 const DIFF_INLINE_SIDEBAR_MIN_WIDTH = 26 * 16;
+const COMPOSER_COMPACT_MIN_LEFT_CONTROLS_WIDTH_PX = 208;
 
 const DiffPanelSheet = (props: {
   children: ReactNode;
@@ -91,8 +92,23 @@ const DiffPanelInlineSidebar = (props: {
         composerViewport.clientWidth - viewportPaddingLeft - viewportPaddingRight,
       );
       const formRect = composerForm.getBoundingClientRect();
+      const composerFooter = composerForm.querySelector<HTMLElement>("[data-chat-composer-footer='true']");
+      const composerRightActions = composerForm.querySelector<HTMLElement>(
+        "[data-chat-composer-actions='right']",
+      );
+      const composerRightActionsWidth = composerRightActions?.getBoundingClientRect().width ?? 0;
+      const composerFooterGap = composerFooter
+        ? Number.parseFloat(window.getComputedStyle(composerFooter).columnGap) ||
+          Number.parseFloat(window.getComputedStyle(composerFooter).gap) ||
+          0
+        : 0;
+      const minimumComposerWidth =
+        COMPOSER_COMPACT_MIN_LEFT_CONTROLS_WIDTH_PX +
+        composerRightActionsWidth +
+        composerFooterGap;
       const hasComposerOverflow = composerForm.scrollWidth > composerForm.clientWidth + 0.5;
       const overflowsViewport = formRect.width > viewportContentWidth + 0.5;
+      const violatesMinimumComposerWidth = composerForm.clientWidth + 0.5 < minimumComposerWidth;
 
       if (previousSidebarWidth.length > 0) {
         wrapper.style.setProperty("--sidebar-width", previousSidebarWidth);
@@ -100,7 +116,7 @@ const DiffPanelInlineSidebar = (props: {
         wrapper.style.removeProperty("--sidebar-width");
       }
 
-      return !hasComposerOverflow && !overflowsViewport;
+      return !hasComposerOverflow && !overflowsViewport && !violatesMinimumComposerWidth;
     },
     [],
   );