diff --git a/apps/web/src/components/chat/ChatComposer.tsx b/apps/web/src/components/chat/ChatComposer.tsx
index 5f9aec837ca..e3a6198de25 100644
--- a/apps/web/src/components/chat/ChatComposer.tsx
+++ b/apps/web/src/components/chat/ChatComposer.tsx
@@ -123,6 +123,11 @@ import {
 } from "../../lib/contextWindow";
 import { formatProviderSkillDisplayName } from "../../providerSkillPresentation";
 import { searchProviderSkills } from "../../providerSkillSearch";
+import { projectEnvironment } from "~/state/projects";
+import { useAtomCommand } from "~/state/use-atom-command";
+import { resolvePathLinkTarget } from "~/terminal-links";
+
+const TEXT_ATTACHMENT_MAX_BYTES = 1024 * 1024;
 import { useMediaQuery } from "../../hooks/useMediaQuery";
 import type { ReviewCommentContext } from "../../reviewCommentContext";
 
@@ -613,6 +618,7 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
   // Store subscriptions (prompt / images / terminal contexts)
   // ------------------------------------------------------------------
   const composerDraft = useComposerThreadDraft(composerDraftTarget);
+  const writeProjectFile = useAtomCommand(projectEnvironment.writeFile, { reportFailure: false });
   const prompt = composerDraft.prompt;
   const composerImages = composerDraft.images;
   const composerTerminalContexts = composerDraft.terminalContexts;
@@ -1758,14 +1764,46 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
   };
 
   // ------------------------------------------------------------------
-  // Callbacks: images
+  // Callbacks: attachments
   // ------------------------------------------------------------------
-  const addComposerImages = (files: File[]) => {
+  const addComposerTextAttachment = async (file: File): Promise<string | null> => {
+    if (!gitCwd) return `Could not resolve the workspace path for '${file.name}'.`;
+    if (file.size > TEXT_ATTACHMENT_MAX_BYTES) {
+      return `'${file.name}' exceeds the 1 MB text attachment limit.`;
+    }
+    const safeName = file.name.replace(/[^a-zA-Z0-9._-]+/g, "-") || "context.md";
+    const relativePath = `.t3/attachments/${randomUUID()}/${safeName}`;
+    const result = await file
+      .arrayBuffer()
+      .then((buffer) => {
+        const bytes = new Uint8Array(buffer);
+        if (bytes.includes(0)) return null;
+        const contents = new TextDecoder("utf-8", { fatal: true }).decode(bytes);
+        return writeProjectFile({
+          environmentId,
+          input: { cwd: gitCwd, relativePath, contents },
+        });
+      })
+      .catch(() => null);
+    if (result === null) return `'${file.name}' is not a supported text file.`;
+    if (result._tag === "Failure") return `Could not attach '${file.name}'.`;
+
+    const currentPrompt = promptRef.current;
+    const separator = currentPrompt.length > 0 && !/\s$/.test(currentPrompt) ? " " : "";
+    applyPromptReplacement(
+      currentPrompt.length,
+      currentPrompt.length,
+      `${separator}${serializeComposerFileLink(resolvePathLinkTarget(relativePath, gitCwd))} `,
+    );
+    return null;
+  };
+
+  const addComposerAttachments = async (files: File[]) => {
     if (!activeThreadId || files.length === 0) return;
     if (pendingUserInputs.length > 0) {
       toastManager.add({
         type: "error",
-        title: "Attach images after answering plan questions.",
+        title: "Attach files after answering plan questions.",
       });
       return;
     }
@@ -1774,7 +1812,7 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
     let error: string | null = null;
     for (const file of files) {
       if (!file.type.startsWith("image/")) {
-        error = `Unsupported file type for '${file.name}'. Please attach image files only.`;
+        error = (await addComposerTextAttachment(file)) ?? error;
         continue;
       }
       if (file.size > PROVIDER_SEND_TURN_MAX_IMAGE_BYTES) {
@@ -1818,7 +1856,7 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
     const imageFiles = files.filter((file) => file.type.startsWith("image/"));
     if (imageFiles.length === 0) return;
     event.preventDefault();
-    addComposerImages(imageFiles);
+    void addComposerAttachments(imageFiles);
   };
 
   const onComposerDragEnter = (event: React.DragEvent<HTMLDivElement>) => {
@@ -1852,7 +1890,7 @@ export const ChatComposer = memo(function ChatComposer(props: ChatComposerProps)
     dragDepthRef.current = 0;
     setIsDragOverComposer(false);
     const files = Array.from(event.dataTransfer.files);
-    addComposerImages(files);
+    void addComposerAttachments(files);
     focusComposer();
   };
   const handleInterruptPrimaryAction = useCallback(() => {
diff --git a/apps/web/src/components/chat/MessagesTimeline.test.tsx b/apps/web/src/components/chat/MessagesTimeline.test.tsx
index 0957e025311..b39ebee90dd 100644
--- a/apps/web/src/components/chat/MessagesTimeline.test.tsx
+++ b/apps/web/src/components/chat/MessagesTimeline.test.tsx
@@ -338,6 +338,29 @@ describe("MessagesTimeline", () => {
     expect(markup).toContain('data-user-message-collapsible="false"');
   });
 
+  it("does not collapse short visible prompts with long file-link destinations", async () => {
+    const { MessagesTimeline } = await import("./MessagesTimeline");
+    const fileLinks = Array.from(
+      { length: 15 },
+      (_, index) =>
+        `[test-${index}.ts](/Users/test/project/.t3/attachments/12345678-1234-1234-1234-123456789abc/test-${index}.ts)`,
+    );
+    const markup = renderToStaticMarkup(
+      <MessagesTimeline
+        {...buildProps()}
+        timelineEntries={[
+          buildUserTimelineEntry([...fileLinks, "tell me the contents of each file"].join(" ")),
+        ]}
+      />,
+    );
+
+    expect(markup).toContain("test-0.ts");
+    expect(markup).toContain("test-14.ts");
+    expect(markup).toContain("tell me the contents of each file");
+    expect(markup).toContain('data-user-message-body="true"');
+    expect(markup).not.toContain("Show full message");
+  });
+
   it("renders inline terminal labels with the composer chip UI", async () => {
     const { MessagesTimeline } = await import("./MessagesTimeline");
     const markup = renderToStaticMarkup(
diff --git a/apps/web/src/components/chat/MessagesTimeline.tsx b/apps/web/src/components/chat/MessagesTimeline.tsx
index 1a4dc6b6895..87173caba1f 100644
--- a/apps/web/src/components/chat/MessagesTimeline.tsx
+++ b/apps/web/src/components/chat/MessagesTimeline.tsx
@@ -1375,15 +1375,19 @@ const MAX_COLLAPSED_USER_MESSAGE_LINES = 8;
 const MAX_COLLAPSED_USER_MESSAGE_LENGTH = 600;
 const COLLAPSED_USER_MESSAGE_FADE_HEIGHT_REM = 1.75;
 const COLLAPSED_USER_MESSAGE_FADE_MASK = `linear-gradient(to bottom, black calc(100% - ${COLLAPSED_USER_MESSAGE_FADE_HEIGHT_REM}rem), transparent)`;
+const USER_MESSAGE_FILE_LINK_PATTERN = /\[((?:\\.|[^\]\\])*)\]\([^)\s]+\)/g;
 
 function shouldCollapseUserMessage(text: string): boolean {
-  if (text.trim().length === 0) {
+  const visibleText = text.replace(USER_MESSAGE_FILE_LINK_PATTERN, (_source, label: string) =>
+    label.replace(/\\(.)/g, "$1"),
+  );
+  if (visibleText.trim().length === 0) {
     return false;
   }
 
   return (
-    text.length > MAX_COLLAPSED_USER_MESSAGE_LENGTH ||
-    text.split("\n").length > MAX_COLLAPSED_USER_MESSAGE_LINES
+    visibleText.length > MAX_COLLAPSED_USER_MESSAGE_LENGTH ||
+    visibleText.split("\n").length > MAX_COLLAPSED_USER_MESSAGE_LINES
   );
 }