From 72d0f1b64af748028f710edb89014a53ce971ab3 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Sun, 19 Jul 2026 10:02:44 +0000
Subject: [PATCH] fix: set Content-Type header when preview server serves HTML

The preview-server middleware in `configurePreviewServer` responded with
`res.end(html)` without a `Content-Type` header, for both matched entry
files and the SPA fallback. Browsers usually sniff it as HTML, but some
environments and tooling won't. Set an explicit
`Content-Type: text/html; charset=utf-8` before ending the response.

Also collapse the two separate lookup loops (candidate files, then the
`index.html`/`index.htm` SPA fallback) into a single deduplicated
candidate list.

Closes #142

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018H1uPDiSpxrHtQvyAxUEVC
---
 packages/static/src/plugin/server.ts | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/packages/static/src/plugin/server.ts b/packages/static/src/plugin/server.ts
index 4689787..3248c1e 100644
--- a/packages/static/src/plugin/server.ts
+++ b/packages/static/src/plugin/server.ts
@@ -54,26 +54,22 @@ export const serverPlugin = (): Plugin => {
             if (req.headers.accept?.includes("text/html")) {
               const urlPath = new URL(req.url!, `http://${req.headers.host}`)
                 .pathname;
-              const candidates = urlPathToFileCandidates(urlPath);
+              // Entry files matching the URL path, followed by the SPA
+              // fallback (index.html / index.htm) for unmatched routes.
+              const candidates = [
+                ...new Set([
+                  ...urlPathToFileCandidates(urlPath),
+                  "index.html",
+                  "index.htm",
+                ]),
+              ];
               for (const candidate of candidates) {
                 try {
                   const html = await readFile(
                     path.join(resolvedOutDir, candidate),
                     "utf-8",
                   );
-                  res.end(html);
-                  return;
-                } catch {
-                  // Try next candidate
-                }
-              }
-              // SPA fallback: try serving index.html or index.htm for unmatched routes
-              for (const indexFile of ["index.html", "index.htm"]) {
-                try {
-                  const html = await readFile(
-                    path.join(resolvedOutDir, indexFile),
-                    "utf-8",
-                  );
+                  res.setHeader("Content-Type", "text/html; charset=utf-8");
                   res.end(html);
                   return;
                 } catch {