Fixes #24817 (#24864)

### What does this PR do?

Fixes #24817

### How did you verify your code works?
Test

---------

Co-authored-by: taylor.fish <contact@taylor.fish>

src/bun.js/api/server/StaticRoute.zig

@@ -29,9 +29,11 @@ pub const InitFromBytesOptions = struct {
 /// Ownership of `blob` is transferred to this function.
 pub fn initFromAnyBlob(blob: *const AnyBlob, options: InitFromBytesOptions) *StaticRoute {
     var headers = bun.handleOom(Headers.from(options.headers, bun.default_allocator, .{ .body = blob }));
-    if (options.mime_type) |mime_type| {
-        if (headers.getContentType() == null) {
+    if (headers.getContentType() == null) {
+        if (options.mime_type) |mime_type| {
             bun.handleOom(headers.append("Content-Type", mime_type.value));
+        } else if (blob.hasContentTypeFromUser()) {
+            bun.handleOom(headers.append("Content-Type", blob.contentType()));
         }
     }
 
@@ -92,6 +94,7 @@ pub fn fromJS(globalThis: *jsc.JSGlobalObject, argument: jsc.JSValue) bun.JSErro
         // The user may want to pass in the same Response object multiple endpoints
         // Let's let them do that.
         const bodyValue = response.getBodyValue();
+        const was_string = bodyValue.wasString();
         bodyValue.toBlobIfPossible();
 
         const blob: AnyBlob = brk: {
@@ -151,6 +154,10 @@ pub fn fromJS(globalThis: *jsc.JSGlobalObject, argument: jsc.JSValue) bun.JSErro
                 .allocator = bun.default_allocator,
             };
 
+        if (was_string and headers.getContentType() == null) {
+            bun.handleOom(headers.append("Content-Type", bun.http.MimeType.Table.@"text/plain; charset=utf-8".slice()));
+        }
+
         // Generate ETag if not already present
         if (headers.get("etag") == null) {
             if (blob.slice().len > 0) {

src/bun.js/webcore/Body.zig

@@ -272,6 +272,14 @@ pub const Value = union(Tag) {
         };
     }
 
+    pub fn wasString(this: *const Value) bool {
+        return switch (this.*) {
+            .InternalBlob => |*blob| blob.was_string,
+            .WTFStringImpl => true,
+            else => false,
+        };
+    }
+
     pub const heap_breakdown_label = "BodyValue";
     pub const ValueError = union(enum) {
         AbortReason: jsc.CommonAbortReason,

src/http/MimeType.zig

@@ -246,7 +246,6 @@ pub const html = MimeType.initComptime("text/html;charset=utf-8", .html);
 pub const json = MimeType.initComptime("application/json;charset=utf-8", .json);
 pub const transpiled_json = javascript;
 pub const text = MimeType.initComptime("text/plain;charset=utf-8", .html);
-pub const text_plain = MimeType.initComptime("text/plain;charset=utf-8", .text);
 pub const wasm = MimeType.initComptime(
     "application/wasm",
     .wasm,

test/regression/issue/24817.test.ts

@@ -0,0 +1,62 @@
+// https://github.com/oven-sh/bun/issues/24817
+// Unicode not working with static route
+import { expect, test } from "bun:test";
+
+test("static routes should handle unicode correctly", async () => {
+  using server = Bun.serve({
+    port: 0,
+    routes: {
+      "/dynamic": () => new Response("▲"),
+      "/static": new Response("▲"),
+      "/unicode-string": new Response("こんにちは世界"),
+      "/emoji": new Response("🎉🚀✨"),
+    },
+  });
+
+  const baseUrl = server.url.href;
+
+  // Test basic unicode character
+  {
+    const staticResp = await fetch(`${baseUrl}/static`);
+
+    const staticText = await staticResp.text();
+    expect(staticText).toBe("▲");
+    expect(staticResp.headers.get("content-type")).toBe("text/plain; charset=utf-8");
+  }
+
+  // Test Japanese characters
+  {
+    const resp = await fetch(`${baseUrl}/unicode-string`);
+    const text = await resp.text();
+
+    expect(text).toBe("こんにちは世界");
+    expect(resp.headers.get("content-type")).toBe("text/plain; charset=utf-8");
+  }
+
+  // Test emoji
+  {
+    const resp = await fetch(`${baseUrl}/emoji`);
+    const text = await resp.text();
+
+    expect(text).toBe("🎉🚀✨");
+    expect(resp.headers.get("content-type")).toBe("text/plain; charset=utf-8");
+  }
+});
+
+test("static routes with explicit content-type should not override", async () => {
+  using server = Bun.serve({
+    port: 0,
+    routes: {
+      "/custom": new Response("▲", { headers: { "content-type": "text/html" } }),
+    },
+  });
+
+  const baseUrl = server.url.href;
+
+  const resp = await fetch(`${baseUrl}/custom`);
+  const text = await resp.text();
+
+  expect(text).toBe("▲");
+  // Should respect the explicit content-type
+  expect(resp.headers.get("content-type")).toBe("text/html");
+});