feat: name byte-path file downloads via Content-Disposition

CHANGELOG.md

@@ -7,6 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.11.6] - 2026-08-23
+
+### Added
+
+- Remote file downloads carry a `Content-Disposition` filename: the byte
+  path's URL basename is always "file" (the real name lives in a query
+  param), so browser direct-downloads saved nameless. Responses now send
+  `inline; filename="…"; filename*=UTF-8''…` (RFC 6266/5987 — non-ASCII
+  names survive via the `filename*` form, the ASCII fallback degrades to
+  underscores). Line windows (viewer-internal partial views) stay unnamed.
+
 ## [0.11.5] - 2026-08-22
 
 ### Fixed

package.json

@@ -1,6 +1,6 @@
 {
   "name": "zcode-acp-server",
-  "version": "0.11.5",
+  "version": "0.11.6",
   "description": "Agent Client Protocol (ACP) server bridging headless ZCode to editors like Zed and JetBrains.",
   "type": "module",
   "license": "Apache-2.0",

src/remote/file-endpoint.ts

@@ -91,6 +91,17 @@ function mimeFor(file: string): string {
   return MIME_BY_EXT[path.extname(file).toLowerCase()] ?? "application/octet-stream";
 }
 
+/**
+ * Content-Disposition for the byte path. The URL's basename is "file" (the
+ * real name lives in a query param), so without this header browsers save
+ * direct-link downloads nameless. `inline` keeps previewable types rendering
+ * in-browser; the filename* form preserves non-ASCII names (RFC 6266/5987).
+ */
+function contentDisposition(name: string): string {
+  const ascii = name.replace(/["\\]/g, "_").replace(/[^\x20-\x7e]/g, "_");
+  return `inline; filename="${ascii}"; filename*=UTF-8''${encodeURIComponent(name)}`;
+}
+
 function sendText(res: ServerResponse, code: number, message: string): void {
   if (res.writableEnded) return;
   res.writeHead(code, { "Content-Type": "text/plain" });
@@ -335,7 +346,10 @@ async function handleFile(
 
   if (head) {
     // Same headers the GET would send, no body.
-    const headers: Record<string, string> = { "Content-Type": mime };
+    const headers: Record<string, string> = {
+      "Content-Type": mime,
+      "Content-Disposition": contentDisposition(path.basename(file)),
+    };
     if (hasByte) {
       headers["Content-Range"] = `bytes ${start}-${end}/${s.size}`;
       headers["Content-Length"] = String(end! - start + 1);
@@ -354,7 +368,10 @@ async function handleFile(
     res.destroy();
   });
   req.on("close", () => stream.destroy());
-  const headers: Record<string, string> = { "Content-Type": mime };
+  const headers: Record<string, string> = {
+    "Content-Type": mime,
+    "Content-Disposition": contentDisposition(path.basename(file)),
+  };
   if (hasByte) {
     headers["Content-Range"] = `bytes ${start}-${end}/${s.size}`;
     headers["Content-Length"] = String(end! - start + 1);

tests/remote-file-endpoint.test.ts

@@ -152,6 +152,32 @@ describe("session files over the hub proxy", () => {
     expect(await res.text()).toBe(content.slice(2, 6));
   });
 
+  it("names byte-path downloads via Content-Disposition", async () => {
+    const { base, dir } = await spawnFixture();
+    await writeFile(path.join(dir, "年度报告.md"), "# 总结\n");
+
+    const res = await fsFetch(base, "/file?sessionId=s-fs&path=README.md");
+    expect(res.status).toBe(200);
+    expect(res.headers.get("content-disposition")).toBe(
+      `inline; filename="README.md"; filename*=UTF-8''README.md`,
+    );
+
+    // Non-ASCII names survive via the RFC 5987 filename* form; the ASCII
+    // fallback degrades to underscores instead of mojibake.
+    const zh = await fsFetch(
+      base,
+      `/file?sessionId=s-fs&path=${encodeURIComponent("年度报告.md")}`,
+    );
+    expect(zh.status).toBe(200);
+    expect(zh.headers.get("content-disposition")).toBe(
+      `inline; filename="____.md"; filename*=UTF-8''${encodeURIComponent("年度报告.md")}`,
+    );
+
+    // Line windows are viewer-internal partial views — no download name.
+    const win = await fsFetch(base, "/file?sessionId=s-fs&path=README.md&line=1&limit=1");
+    expect(win.headers.get("content-disposition")).toBeNull();
+  });
+
   it("serves text line windows with X-Zcode-First-Line", async () => {
     const { base } = await spawnFixture();
     const res = await fsFetch(base, "/file?sessionId=s-fs&path=README.md&line=2&limit=1");