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

2 files changed, 50 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,
     ]
   })