fix: stop centering the viewport on mouse line clicks in diffs

src/browser/components/pr-review.tsx

@@ -2494,7 +2494,7 @@ const DiffViewer = memo(function DiffViewer({
         if (state.selectionAnchor === null) {
           store.setSelectionAnchor(state.focusedLine, side);
         }
-        store.setFocusedLine(lineNum, side);
+        store.setFocusedLine(lineNum, side, "mouse");
         const startLine = Math.min(anchor, lineNum);
         const endLine = Math.max(anchor, lineNum);
         if (startLine !== endLine) {
@@ -2510,7 +2510,7 @@ const DiffViewer = memo(function DiffViewer({
       isDraggingRef.current = true;
       dragAnchorRef.current = lineNum;
       dragSideRef.current = side;
-      store.setFocusedLine(lineNum, side);
+      store.setFocusedLine(lineNum, side, "mouse");
       store.setSelectionAnchor(lineNum, side);
       setIsDraggingState(true);
     },
@@ -2667,7 +2667,7 @@ const DiffViewer = memo(function DiffViewer({
       }
 
       if (closestLine !== null) {
-        store.setFocusedLine(closestLine, dragSide);
+        store.setFocusedLine(closestLine, dragSide, "mouse");
       }
     };
 
@@ -2702,6 +2702,7 @@ const DiffViewer = memo(function DiffViewer({
   // Selection state for CSS-based highlighting (no per-row subscriptions)
   const focusedLine = usePRReviewSelector((s) => s.focusedLine);
   const focusedLineSide = usePRReviewSelector((s) => s.focusedLineSide);
+  const focusSource = usePRReviewSelector((s) => s.focusSource);
   const selectionAnchor = usePRReviewSelector((s) => s.selectionAnchor);
   const selectionAnchorSide = usePRReviewSelector((s) => s.selectionAnchorSide);
 
@@ -2756,8 +2757,10 @@ const DiffViewer = memo(function DiffViewer({
         }
       }
 
-      // 2. Scroll to focused line (after selection update)
-      if (focusedLine && !isDraggingState) {
+      // 2. Scroll to focused line (after selection update). Only for
+      // keyboard/programmatic focus — re-centering on mouse clicks breaks
+      // double-click word selection.
+      if (focusedLine && !isDraggingState && focusSource !== "mouse") {
         const rowIndex = getRowIndexForLine(focusedLine, focusedLineSide);
         if (rowIndex !== undefined) {
           virtualizer.scrollToIndex(rowIndex, {
@@ -2775,6 +2778,7 @@ const DiffViewer = memo(function DiffViewer({
   }, [
     focusedLine,
     focusedLineSide,
+    focusSource,
     selectionAnchor,
     selectionAnchorSide,
     isDraggingState,
@@ -3125,7 +3129,7 @@ const DiffLineRow = memo(function DiffLineRow({
             state.focusedLineSide ?? lineSide
           );
         }
-        store.setFocusedLine(lineNum, lineSide);
+        store.setFocusedLine(lineNum, lineSide, "mouse");
         const startLine = Math.min(anchor, lineNum);
         const endLine = Math.max(anchor, lineNum);
         if (startLine !== endLine) {
@@ -3154,7 +3158,7 @@ const DiffLineRow = memo(function DiffLineRow({
       }
 
       // Normal click: focus the line (clear any selection)
-      store.setFocusedLine(lineNum, lineSide);
+      store.setFocusedLine(lineNum, lineSide, "mouse");
       store.setSelectionAnchor(null, null);
     },
     [lineNum, lineSide, store]
@@ -3693,6 +3697,20 @@ const InlineCommentForm = memo(function InlineCommentForm({
   textRef.current = text;
 
   const [submitting, setSubmitting] = useState(false);
+  const formRef = useRef<HTMLDivElement>(null);
+
+  // Make sure the freshly opened form is fully visible with the smallest
+  // possible scroll (no re-centering).
+  useEffect(() => {
+    requestAnimationFrame(() => {
+      formRef.current?.scrollIntoView({
+        block: "nearest",
+        behavior: "instant",
+      });
+    });
+    // Only on mount, when the form is opened
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
 
   // Persist draft text when the form unmounts without submitting
   useEffect(() => {
@@ -3799,6 +3817,7 @@ const InlineCommentForm = memo(function InlineCommentForm({
 
   return (
     <div
+      ref={formRef}
       data-inline-comment-form
       className="mx-4 my-3 rounded-lg border border-border bg-card overflow-hidden shadow-sm"
       style={{ fontFamily: "var(--font-sans)" }}

src/browser/contexts/pr-review/index.test.ts

@@ -343,6 +343,18 @@ test("setFocusedLine updates line focus", () => {
   const state = store.getSnapshot();
   expect(state.focusedLine).toBe(42);
   expect(state.focusedLineSide).toBe("new");
+  expect(state.focusSource).toBe("keyboard");
+});
+
+test("setFocusedLine records mouse source", () => {
+  const store = createStore();
+  store.selectFile("src/index.ts");
+
+  store.setFocusedLine(42, "new", "mouse");
+  expect(store.getSnapshot().focusSource).toBe("mouse");
+
+  store.setFocusedLine(43, "new");
+  expect(store.getSnapshot().focusSource).toBe("keyboard");
 });
 
 test("setFocusedLine clears skip block focus", () => {

src/browser/contexts/pr-review/index.tsx

@@ -314,6 +314,9 @@ interface PRReviewState {
   // Line selection
   focusedLine: number | null;
   focusedLineSide: "old" | "new" | null; // 'old' for delete lines, 'new' for insert/context
+  // How the current focus was set, so the UI can react differently (e.g. only
+  // keyboard focus gets scrolled to center)
+  focusSource: "mouse" | "keyboard";
   selectionAnchor: number | null;
   selectionAnchorSide: "old" | "new" | null;
   focusedSkipBlockIndex: number | null; // Index of focused skip block for keyboard navigation
@@ -613,6 +616,7 @@ export class PRReviewStore {
       ...initialState,
       files: sortedFiles,
       viewerCanMergeAsAdmin: false,
+      focusSource: "keyboard",
 
       // PR data (loaded separately)
       reviews: [],
@@ -1890,11 +1894,13 @@ export class PRReviewStore {
 
   setFocusedLine = (
     line: number | null,
-    side: "old" | "new" | null = "new"
+    side: "old" | "new" | null = "new",
+    source: "mouse" | "keyboard" = "keyboard"
   ) => {
     this.set({
       focusedLine: line,
       focusedLineSide: line !== null ? side : null,
+      focusSource: source,
       focusedSkipBlockIndex: null, // Clear skip block focus when focusing a line
     });
   };
@@ -2184,6 +2190,7 @@ export class PRReviewStore {
           this.set({
             focusedLine: nextItem.lineNum,
             focusedLineSide: nextItem.side,
+            focusSource: "keyboard",
             focusedSkipBlockIndex: null,
             selectionAnchor: null,
             selectionAnchorSide: null,
@@ -2231,6 +2238,7 @@ export class PRReviewStore {
           this.set({
             focusedLine: nextNav.lineNum,
             focusedLineSide: nextNav.side,
+            focusSource: "keyboard",
             focusedPendingCommentId: null,
             focusedCommentId: null,
             selectionAnchor: null,
@@ -2248,6 +2256,7 @@ export class PRReviewStore {
         this.set({
           focusedLine: pendingLine,
           focusedLineSide: "new",
+          focusSource: "keyboard",
           focusedPendingCommentId: null,
           selectionAnchor: null,
           selectionAnchorSide: null,
@@ -2284,6 +2293,7 @@ export class PRReviewStore {
             this.set({
               focusedLine: nextNav.lineNum,
               focusedLineSide: nextNav.side,
+              focusSource: "keyboard",
               focusedCommentId: null,
               selectionAnchor: null,
               selectionAnchorSide: null,
@@ -2311,6 +2321,7 @@ export class PRReviewStore {
           this.set({
             focusedLine: commentLine,
             focusedLineSide: "new",
+            focusSource: "keyboard",
             focusedCommentId: null,
             selectionAnchor: null,
             selectionAnchorSide: null,
@@ -2458,6 +2469,7 @@ export class PRReviewStore {
             focusedSkipBlockIndex: nextPair.skipIndex,
             focusedLine: null,
             focusedLineSide: null,
+            focusSource: "keyboard",
             selectionAnchor: null,
             selectionAnchorSide: null,
             focusedCommentId: null,
@@ -2522,6 +2534,7 @@ export class PRReviewStore {
             this.set({
               focusedLine: nextLine,
               focusedLineSide: nextSide,
+              focusSource: "keyboard",
               selectionAnchor: selectionAnchor ?? focusedLine ?? nextLine,
               selectionAnchorSide:
                 selectionAnchorSide ?? focusedLineSide ?? nextSide,
@@ -2533,6 +2546,7 @@ export class PRReviewStore {
             this.set({
               focusedLine: nextLine,
               focusedLineSide: nextSide,
+              focusSource: "keyboard",
               selectionAnchor: null,
               selectionAnchorSide: null,
               focusedSkipBlockIndex: null,
@@ -2629,6 +2643,7 @@ export class PRReviewStore {
       this.set({
         focusedLine: nextLine,
         focusedLineSide: nextSide,
+        focusSource: "keyboard",
         selectionAnchor: selectionAnchor ?? focusedLine ?? nextLine,
         selectionAnchorSide: selectionAnchorSide ?? focusedLineSide ?? nextSide,
         focusedSkipBlockIndex: null,
@@ -2639,6 +2654,7 @@ export class PRReviewStore {
       this.set({
         focusedLine: nextLine,
         focusedLineSide: nextSide,
+        focusSource: "keyboard",
         selectionAnchor: null,
         selectionAnchorSide: null,
         focusedSkipBlockIndex: null,
@@ -3039,6 +3055,7 @@ export class PRReviewStore {
       // Focus the line the comment was on so user can continue with keyboard
       focusedLine: commentLine ?? null,
       focusedLineSide: commentLine ? "new" : null,
+      focusSource: "keyboard",
     });
     this.recomputeCommentRangeLookup();
   };
@@ -3109,6 +3126,7 @@ export class PRReviewStore {
       // Focus the line the comment was on so user can continue with keyboard
       focusedLine: commentLine ?? null,
       focusedLineSide: commentLine ? "new" : null,
+      focusSource: "keyboard",
     });
   };
 
@@ -3369,6 +3387,7 @@ export class PRReviewStore {
         this.set({
           focusedLine: end,
           focusedLineSide: "new",
+          focusSource: "keyboard",
           selectionAnchor: start,
           selectionAnchorSide: "new",
           focusedSkipBlockIndex: null,
@@ -3381,6 +3400,7 @@ export class PRReviewStore {
           this.set({
             focusedLine: line,
             focusedLineSide: "new",
+            focusSource: "keyboard",
             selectionAnchor: null,
             selectionAnchorSide: null,
             focusedSkipBlockIndex: null,