feat(comments): support file mentions (#20447)

5 files changed, 60 insertions, 0 deletions

diff --git a/packages/app/src/components/prompt-input/build-request-parts.test.ts b/packages/app/src/components/prompt-input/build-request-parts.test.ts
index ce09ae921..06c377331 100644
--- a/packages/app/src/components/prompt-input/build-request-parts.test.ts
+++ b/packages/app/src/components/prompt-input/build-request-parts.test.ts
@@ -100,6 +100,30 @@ describe("buildRequestParts", () => {
     expect(synthetic).toHaveLength(1)
   })
 
+  test("adds file parts for @mentions inside comment text", () => {
+    const result = buildRequestParts({
+      prompt: [{ type: "text", content: "look", start: 0, end: 4 }],
+      context: [
+        {
+          key: "ctx:comment-mention",
+          type: "file",
+          path: "src/review.ts",
+          comment: "Compare with @src/shared.ts and @src/review.ts.",
+        },
+      ],
+      images: [],
+      text: "look",
+      messageID: "msg_comment_mentions",
+      sessionID: "ses_comment_mentions",
+      sessionDirectory: "/repo",
+    })
+
+    const files = result.requestParts.filter((part) => part.type === "file")
+    expect(files).toHaveLength(2)
+    expect(files.some((part) => part.type === "file" && part.url === "file:///repo/src/review.ts")).toBe(true)
+    expect(files.some((part) => part.type === "file" && part.url === "file:///repo/src/shared.ts")).toBe(true)
+  })
+
   test("handles Windows paths correctly (simulated on macOS)", () => {
     const prompt: Prompt = [{ type: "file", path: "src\\foo.ts", content: "@src\\foo.ts", start: 0, end: 11 }]
 
diff --git a/packages/app/src/components/prompt-input/build-request-parts.ts b/packages/app/src/components/prompt-input/build-request-parts.ts
index 4146fb484..a1076e60c 100644
--- a/packages/app/src/components/prompt-input/build-request-parts.ts
+++ b/packages/app/src/components/prompt-input/build-request-parts.ts
@@ -39,6 +39,16 @@ const absolute = (directory: string, path: string) => {
 const fileQuery = (selection: FileSelection | undefined) =>
   selection ? `?start=${selection.startLine}&end=${selection.endLine}` : ""
 
+const mention = /(^|[\s([{"'])@(\S+)/g
+
+const parseCommentMentions = (comment: string) => {
+  return Array.from(comment.matchAll(mention)).flatMap((match) => {
+    const path = (match[2] ?? "").replace(/[.,!?;:)}\]"']+$/, "")
+    if (!path) return []
+    return [path]
+  })
+}
+
 const isFileAttachment = (part: Prompt[number]): part is FileAttachmentPart => part.type === "file"
 const isAgentAttachment = (part: Prompt[number]): part is AgentPart => part.type === "agent"
 
@@ -138,6 +148,21 @@ export function buildRequestParts(input: BuildRequestPartsInput) {
 
     if (!comment) return [filePart]
 
+    const mentions = parseCommentMentions(comment).flatMap((path) => {
+      const url = `file://${encodeFilePath(absolute(input.sessionDirectory, path))}`
+      if (used.has(url)) return []
+      used.add(url)
+      return [
+        {
+          id: Identifier.ascending("part"),
+          type: "file",
+          mime: "text/plain",
+          url,
+          filename: getFilename(path),
+        } satisfies PromptRequestPart,
+      ]
+    })
+
     return [
       {
         id: Identifier.ascending("part"),
@@ -153,6 +178,7 @@ export function buildRequestParts(input: BuildRequestPartsInput) {
         }),
       } satisfies PromptRequestPart,
       filePart,
+      ...mentions,
     ]
   })
 
diff --git a/packages/app/src/pages/session.tsx b/packages/app/src/pages/session.tsx
index 917de35b1..18bae6e2d 100644
--- a/packages/app/src/pages/session.tsx
+++ b/packages/app/src/pages/session.tsx
@@ -1046,6 +1046,9 @@ export default function Page() {
         onLineCommentUpdate={updateCommentInContext}
         onLineCommentDelete={removeCommentFromContext}
         lineCommentActions={reviewCommentActions()}
+        commentMentions={{
+          items: file.searchFilesAndDirectories,
+        }}
         comments={comments.all()}
         focusedComment={comments.focus()}
         onFocusedCommentChange={comments.setFocus}
diff --git a/packages/app/src/pages/session/file-tabs.tsx b/packages/app/src/pages/session/file-tabs.tsx
index 8208b6c99..9430b7025 100644
--- a/packages/app/src/pages/session/file-tabs.tsx
+++ b/packages/app/src/pages/session/file-tabs.tsx
@@ -302,6 +302,9 @@ export function FileTabContent(props: { tab: string }) {
     comments: fileComments,
     label: language.t("ui.lineComment.submit"),
     draftKey: () => path() ?? props.tab,
+    mention: {
+      items: file.searchFilesAndDirectories,
+    },
     state: {
       opened: () => note.openedComment,
       setOpened: (id) => setNote("openedComment", id),
diff --git a/packages/app/src/pages/session/review-tab.tsx b/packages/app/src/pages/session/review-tab.tsx
index c073e6214..76b65a221 100644
--- a/packages/app/src/pages/session/review-tab.tsx
+++ b/packages/app/src/pages/session/review-tab.tsx
@@ -30,6 +30,9 @@ export interface SessionReviewTabProps {
   onFocusedCommentChange?: (focus: { file: string; id: string } | null) => void
   focusedFile?: string
   onScrollRef?: (el: HTMLDivElement) => void
+  commentMentions?: {
+    items: (query: string) => string[] | Promise<string[]>
+  }
   classes?: {
     root?: string
     header?: string
@@ -162,6 +165,7 @@ export function SessionReviewTab(props: SessionReviewTabProps) {
       onLineCommentUpdate={props.onLineCommentUpdate}
       onLineCommentDelete={props.onLineCommentDelete}
       lineCommentActions={props.lineCommentActions}
+      lineCommentMention={props.commentMentions}
       comments={props.comments}
       focusedComment={props.focusedComment}
       onFocusedCommentChange={props.onFocusedCommentChange}