feat(phase-06): add reference file contract and submit payload helper

frontend/src/components/ai-elements/prompt-input.tsx

@@ -468,6 +468,16 @@ export const PromptInputActionAddAttachments = ({
 export type PromptInputMessage = {
   text: string;
   files: FileUIPart[];
+  references?: PromptInputReference[];
+};
+
+export type PromptInputReference = {
+  filename: string;
+  path?: string;
+  size?: number;
+  ref_kind: "mention";
+  ref_source: "artifact" | "upload";
+  stale?: boolean;
 };
 
 export type PromptInputProps = Omit<
@@ -866,6 +876,8 @@ export type PromptInputTextareaProps = ComponentProps<
 
 export const PromptInputTextarea = ({
   onChange,
+  onKeyDown,
+  onPaste,
   className,
   placeholder = "What would you like to know?",
   submitOnEnter = true,
@@ -876,6 +888,10 @@ export const PromptInputTextarea = ({
   const [isComposing, setIsComposing] = useState(false);
 
   const handleKeyDown: KeyboardEventHandler<HTMLTextAreaElement> = (e) => {
+    onKeyDown?.(e);
+    if (e.defaultPrevented) {
+      return;
+    }
     if (e.key === "Enter") {
       if (isComposing || e.nativeEvent.isComposing) {
         return;
@@ -940,6 +956,10 @@ export const PromptInputTextarea = ({
   };
 
   const handlePaste: ClipboardEventHandler<HTMLTextAreaElement> = (event) => {
+    onPaste?.(event);
+    if (event.defaultPrevented) {
+      return;
+    }
     const items = event.clipboardData?.items;
 
     if (!items) {

frontend/src/core/messages/utils.ts

@@ -332,6 +332,8 @@ export interface FileInMessage {
   size: number; // bytes
   path?: string; // virtual path, may not be set during upload
   status?: "uploading" | "uploaded";
+  ref_kind?: "mention";
+  ref_source?: "artifact" | "upload";
 }
 
 /**

frontend/src/core/threads/hooks.test.ts

@@ -1,29 +1,50 @@
 import assert from "node:assert/strict";
 import test from "node:test";
 
-const { resolveThreadQueryIntent } = await import(
-  new URL("./utils.ts", import.meta.url).href
+const { buildFilesForSubmit } = await import(
+  new URL("./submit-files.ts", import.meta.url).href
 );
 
-void test("uses /chats/new route as the only new-session signal", () => {
-  const intent = resolveThreadQueryIntent({
-    pathThreadId: "new",
-    queryThreadId: "thread-from-query",
-    isNewRoute: true,
-  });
+void test("buildFilesForSubmit keeps uploads and appends valid references", () => {
+  const result = buildFilesForSubmit(
+    [
+      {
+        filename: "uploaded.md",
+        size: 12,
+        virtual_path: "/mnt/user-data/uploads/uploaded.md",
+      },
+    ],
+    [
+      {
+        filename: "artifact.md",
+        path: "/mnt/user-data/artifacts/artifact.md",
+        ref_kind: "mention",
+        ref_source: "artifact",
+      },
+    ],
+  );
 
-  assert.equal(intent.isNewThread, true);
-  assert.equal(intent.showWelcomeStyle, true);
-  assert.equal(intent.threadId, "thread-from-query");
+  assert.equal(result.staleCount, 0);
+  assert.equal(result.files.length, 2);
+  assert.equal(result.files[0]?.filename, "uploaded.md");
+  assert.equal(result.files[1]?.ref_kind, "mention");
+  assert.equal(result.files[1]?.ref_source, "artifact");
 });
 
-void test("prefers path thread id over query thread id when not on /new", () => {
-  const intent = resolveThreadQueryIntent({
-    pathThreadId: "thread-from-path",
-    queryThreadId: "thread-from-query",
-    isNewRoute: false,
-  });
+void test("buildFilesForSubmit drops stale references without blocking submit", () => {
+  const result = buildFilesForSubmit(
+    [],
+    [
+      {
+        filename: "stale.md",
+        path: "/stale.md",
+        ref_kind: "mention",
+        ref_source: "upload",
+        stale: true,
+      },
+    ],
+  );
 
-  assert.equal(intent.isNewThread, false);
-  assert.equal(intent.threadId, "thread-from-path");
+  assert.equal(result.staleCount, 1);
+  assert.equal(result.files.length, 0);
 });

frontend/src/core/threads/submit-files.ts

@@ -0,0 +1,46 @@
+import type { FileInMessage } from "../messages/utils";
+import type { UploadedFileInfo } from "../uploads/api";
+
+export type MentionReference = {
+  filename: string;
+  path?: string;
+  size?: number;
+  ref_kind: "mention";
+  ref_source: "artifact" | "upload";
+  stale?: boolean;
+};
+
+export function buildFilesForSubmit(
+  uploadedFileInfo: UploadedFileInfo[],
+  references: MentionReference[] = [],
+) {
+  const uploadedFiles: FileInMessage[] = uploadedFileInfo.map((info) => ({
+    filename: info.filename,
+    size: info.size,
+    path: info.virtual_path,
+    status: "uploaded" as const,
+  }));
+
+  const referenceFiles: FileInMessage[] = [];
+  let staleCount = 0;
+
+  for (const reference of references) {
+    if (reference.stale) {
+      staleCount += 1;
+      continue;
+    }
+    referenceFiles.push({
+      filename: reference.filename,
+      size: reference.size ?? 0,
+      path: reference.path,
+      status: "uploaded" as const,
+      ref_kind: "mention",
+      ref_source: reference.ref_source,
+    });
+  }
+
+  return {
+    files: [...uploadedFiles, ...referenceFiles],
+    staleCount,
+  };
+}