fix(web): renumber following items when inserting into a numbered list

apps/web/src/components/chat/ChatComposer.tsx

@@ -4051,14 +4051,9 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
             : listIndentForTab(snapshot.value, selection.start, selection.end);
         if (
           edit &&
-          applyPromptReplacement(
-            edit.start,
-            edit.end,
-            edit.replacement,
-            key === "Tab"
-              ? { expandedCursorAfterReplace: selection.start + edit.replacement.length }
-              : undefined,
-          )
+          applyPromptReplacement(edit.start, edit.end, edit.replacement, {
+            expandedCursorAfterReplace: edit.cursorAfter,
+          })
         ) {
           return true;
         }

apps/web/src/composer-list-continuation.test.ts

@@ -66,3 +66,58 @@ describe("composer list continuation", () => {
     expect(listIndentForTab("- foo", 1, 3)).toBeNull();
   });
 });
+
+describe("composer list renumbering", () => {
+  const enterAt = (value: string, cursor: number) => {
+    const edit = listContinuationForEnter(value, cursor)!;
+    return applyEdit(value, edit);
+  };
+
+  it("renumbers following items when an item is inserted mid-list", () => {
+    const value = "1. one\n2. two\n3. three";
+    // Enter at the start of "two" text pushes it down to a new item 3.
+    expect(enterAt(value, value.indexOf("two"))).toBe("1. one\n2. \n3. two\n4. three");
+    expect(enterAt(value, 6)).toBe("1. one\n2. \n3. two\n4. three");
+  });
+
+  it("puts the caret after the new marker when renumbering", () => {
+    const value = "1. one\n2. two";
+    const edit = listContinuationForEnter(value, 6)!;
+    expect(edit.cursorAfter).toBe(6 + "\n2. ".length);
+  });
+
+  it("leaves items that are already in sequence and other content alone", () => {
+    expect(enterAt("1. a\n\n5. b", 4)).toBe("1. a\n2. \n\n5. b");
+    expect(enterAt("1. a\ntext\n2. b", 4)).toBe("1. a\n2. \ntext\n2. b");
+    expect(enterAt("1. a\n1) b", 4)).toBe("1. a\n2. \n1) b");
+  });
+
+  it("renumbers past nested children but not past shallower lines", () => {
+    expect(enterAt("1. a\n  - x\n2. b", 4)).toBe("1. a\n2. \n  - x\n3. b");
+    expect(enterAt("  1. a\n2. b", 6)).toBe("  1. a\n  2. \n2. b");
+  });
+
+  it("keeps zero padding when renumbering", () => {
+    expect(enterAt("01. a\n02. b", 5)).toBe("01. a\n02. \n03. b");
+  });
+
+  it("does not add zero padding to wider unpadded numbers", () => {
+    expect(enterAt("1. a\n10. b", 4)).toBe("1. a\n2. \n3. b");
+  });
+
+  it("compares indentation by width so tab-indented children are skipped", () => {
+    expect(enterAt("  1. a\n\t- child\n  2. b", 6)).toBe("  1. a\n  2. \n\t- child\n  3. b");
+  });
+
+  it("leaves lines inside a multiline quoted mention alone", () => {
+    const value = '1. @"file\n2. name" \n2. b';
+    expect(enterAt(value, 3)).toBe('1. \n2. @"file\n2. name" \n3. b');
+  });
+
+  it("returns an expanded caret offset when a chip precedes the caret", () => {
+    const value = "1. @README.md go\n2. next";
+    const edit = listContinuationForEnter(value, value.indexOf(" go"))!;
+    expect(applyEdit(value, edit)).toBe("1. @README.md\n2.  go\n3. next");
+    expect(edit.cursorAfter).toBe(value.indexOf(" go") + "\n2. ".length);
+  });
+});

apps/web/src/composer-list-continuation.ts

@@ -15,6 +15,8 @@ export interface ComposerListEdit {
   start: number;
   end: number;
   replacement: string;
+  /** Expanded caret offset after the edit is applied. */
+  cursorAfter: number;
 }
 
 type ListMarker =
@@ -69,22 +71,96 @@ function nextMarkerText(marker: ListMarker): string {
   return `${marker.indent}${marker.bullet} `;
 }
 
+function formatOrderedNumber(value: number, numberText: string): string {
+  if (!Number.isSafeInteger(value)) return numberText;
+  // Keep the width only for explicitly zero-padded markers ("01.").
+  return numberText.startsWith("0")
+    ? String(value).padStart(numberText.length, "0")
+    : String(value);
+}
+
+/** Visual indent width with tabs expanded to four-column stops, as in CommonMark. */
+function indentWidth(indent: string): number {
+  let width = 0;
+  for (const char of indent) width = char === "\t" ? width + 4 - (width % 4) : width + 1;
+  return width;
+}
+
+/**
+ * Renumber the ordered items that follow `afterLineEnd` so a newly inserted
+ * item does not leave duplicates below it. Walks the contiguous run of
+ * same-indent, same-delimiter items (skipping deeper-indented children) and
+ * stops at the first line that is not part of that run. Returns the end
+ * offset of the last renumbered marker and the replacement for the text
+ * between `afterLineEnd` and that offset.
+ */
+function renumberFollowingItems(
+  value: string,
+  afterLineEnd: number,
+  marker: Extract<ListMarker, { kind: "ordered" }>,
+  firstNumber: number,
+): { end: number; text: string } | null {
+  const tokens = inlineTokenRanges(value);
+  const baseWidth = indentWidth(marker.indent);
+  let expected = firstNumber;
+  let position = afterLineEnd;
+  let end = -1;
+  let text = "";
+  let copiedUntil = afterLineEnd;
+  while (position < value.length) {
+    const lineStart = position + 1;
+    const nextBreak = value.indexOf("\n", lineStart);
+    const lineEnd = nextBreak === -1 ? value.length : nextBreak;
+    position = lineEnd;
+    // A line that starts inside a multiline chip is part of that chip's text.
+    if (tokens.some((token) => lineStart > token.start && lineStart < token.end)) continue;
+    const line = value.slice(lineStart, lineEnd);
+    const parsed = parseListMarker(line);
+    const width = indentWidth(line.match(/^[ \t]*/)?.[0] ?? "");
+    if (
+      parsed?.marker.kind === "ordered" &&
+      width === baseWidth &&
+      parsed.marker.delimiter === marker.delimiter
+    ) {
+      const current = parsed.marker;
+      const numberStart = lineStart + current.indent.length;
+      const numberEnd = numberStart + current.numberText.length;
+      const replacement = formatOrderedNumber(expected, current.numberText);
+      if (replacement !== current.numberText) {
+        text += value.slice(copiedUntil, numberStart) + replacement;
+        copiedUntil = numberEnd;
+        end = numberEnd;
+      }
+      expected += 1;
+    } else if (line.trim() === "" || width <= baseWidth) {
+      break;
+    }
+  }
+  return end === -1 ? null : { end, text };
+}
+
 function segmentSource(
   segment: ReturnType<typeof splitPromptIntoComposerSegments>[number],
 ): string {
   if (segment.type === "text") return segment.text;
   return segment.source;
 }
 
-/** True when splitting at the caret would cut an inline chip in two. */
-function isInsideInlineToken(value: string, cursor: number): boolean {
+/** Expanded offsets of every inline chip in the prompt. */
+function inlineTokenRanges(value: string): Array<{ start: number; end: number }> {
+  const ranges: Array<{ start: number; end: number }> = [];
   let offset = 0;
   for (const segment of splitPromptIntoComposerSegments(value)) {
     const end = offset + segmentSource(segment).length;
-    if (segment.type !== "text" && cursor > offset && cursor < end) return true;
+    if (segment.type !== "text") ranges.push({ start: offset, end });
     offset = end;
   }
-  return false;
+  return ranges;
+}
+
+/** True when splitting at the caret would cut an inline chip in two. */
+function isInsideInlineToken(value: string, cursor: number): boolean {
+  return inlineTokenRanges(value).some((range) => cursor > range.start && cursor < range.end);
 }
 
 function currentLine(value: string, cursor: number): { start: number; end: number; text: string } {
@@ -95,8 +171,8 @@ function currentLine(value: string, cursor: number): { start: number; end: numbe
 }
 
 /**
- * Enter on a list item line: continue the list, or exit it when the item is
- * empty. Returns null for non-list lines, carets inside the marker, and
+ * Enter on a list item line: continue the list (renumbering the ordered items
+ * below), or exit it when the item is empty. Returns null for non-list lines, carets inside the marker, and
  * carets inside an inline chip — all fall through to a plain newline.
  */
 export function listContinuationForEnter(value: string, cursor: number): ComposerListEdit | null {
@@ -109,13 +185,33 @@ export function listContinuationForEnter(value: string, cursor: number): Compose
   if (isInsideInlineToken(value, cursor)) return null;
   if (value.slice(markerEnd, line.end).trim() === "") {
     // Empty item: Enter exits the list by removing the marker.
-    return { start: line.start, end: Math.max(cursor, markerEnd), replacement: "" };
+    return {
+      start: line.start,
+      end: Math.max(cursor, markerEnd),
+      replacement: "",
+      cursorAfter: line.start,
+    };
+  }
+  const insertion = `\n${nextMarkerText(parsed.marker)}`;
+  const cursorAfter = cursor + insertion.length;
+  const { marker } = parsed;
+  if (marker.kind === "ordered") {
+    const number = Number.parseInt(marker.numberText, 10);
+    const renumbered = Number.isSafeInteger(number)
+      ? renumberFollowingItems(value, line.end, marker, number + 2)
+      : null;
+    if (renumbered) {
+      // The caret splits the current line, so its remainder is re-emitted
+      // after the new marker, followed by the renumbered lines below.
+      return {
+        start: cursor,
+        end: renumbered.end,
+        replacement: insertion + value.slice(cursor, line.end) + renumbered.text,
+        cursorAfter,
+      };
+    }
   }
-  return {
-    start: cursor,
-    end: cursor,
-    replacement: `\n${nextMarkerText(parsed.marker)}`,
-  };
+  return { start: cursor, end: cursor, replacement: insertion, cursorAfter };
 }
 
 /**
@@ -132,5 +228,5 @@ export function listIndentForTab(
   const line = currentLine(value, start);
   if (!parseListMarker(line.text)) return null;
   if (isInsideInlineToken(value, start)) return null;
-  return { start: line.start, end: line.start, replacement: "  " };
+  return { start: line.start, end: line.start, replacement: "  ", cursorAfter: start + 2 };
 }