diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..6142d1b
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,18 @@
+# Changelog
+
+All notable changes to this project are documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## Unreleased
+
+## 0.4.1 - 2026-09-30
+
+### Fixed
+
+- Encode non-Latin-1 route metadata before placing it in the `x-askr-head`
+  response header, preventing HTTP 500 responses for Unicode titles and
+  descriptions.
+- Percent-encode Unicode redirect locations while preserving existing percent
+  escapes, so internationalized paths produce valid `Location` headers.
diff --git a/package-lock.json b/package-lock.json
index cff42bc..1f15347 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@askrjs/server",
-  "version": "0.4.0",
+  "version": "0.4.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@askrjs/server",
-      "version": "0.4.0",
+      "version": "0.4.1",
       "license": "Apache-2.0",
       "dependencies": {
         "@askrjs/auth": ">=0.4.0 <0.5.0",
diff --git a/package.json b/package.json
index ca79175..ba6abbe 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@askrjs/server",
-  "version": "0.4.0",
+  "version": "0.4.1",
   "description": "Transport-neutral HTTP application core built on Web Request and Response",
   "keywords": [
     "askr",
diff --git a/src/askr/page-handler.ts b/src/askr/page-handler.ts
index 71e7b4e..f5e8c48 100644
--- a/src/askr/page-handler.ts
+++ b/src/askr/page-handler.ts
@@ -33,6 +33,22 @@ function headerValue(value: string): string {
   return output;
 }
 
+function encodeHeaderText(value: string): string {
+  const bytes = new TextEncoder().encode(value);
+  let binary = "";
+  for (let offset = 0; offset < bytes.length; offset += 0x8000) {
+    binary += String.fromCharCode(...bytes.subarray(offset, offset + 0x8000));
+  }
+  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/g, "");
+}
+
+function requiresUtf8HeaderEncoding(...values: (string | undefined)[]): boolean {
+  return values.some(
+    (value) =>
+      value !== undefined && [...value].some((character) => character.charCodeAt(0) > 0xff),
+  );
+}
+
 function escapeStyleRawText(value: string): string {
   return value.replace(/<\/style/gi, "<\\/style");
 }
@@ -88,12 +104,14 @@ export async function translateAskrPageResult(
   const headers = new Headers({ "content-type": "text/html; charset=utf-8; askr-fragment=1" });
   if (result.record) {
     const metadata = await resolveRouteMeta(result.record, routeContext(context, result.params));
-    const head = headerValue(serializeRouteMeta(metadata));
-    if (head) headers.set("x-askr-head", head);
-    if (metadata.html?.lang) {
-      headers.set("x-askr-html-lang", headerValue(metadata.html.lang));
-    }
-    if (metadata.html?.dir) headers.set("x-askr-html-dir", metadata.html.dir);
+    const head = serializeRouteMeta(metadata);
+    const lang = metadata.html?.lang;
+    const dir = metadata.html?.dir;
+    const encode = requiresUtf8HeaderEncoding(head, lang, dir);
+    if (encode) headers.set("x-askr-encoding", "base64url-v1");
+    if (head) headers.set("x-askr-head", encode ? encodeHeaderText(head) : headerValue(head));
+    if (lang) headers.set("x-askr-html-lang", encode ? encodeHeaderText(lang) : headerValue(lang));
+    if (dir) headers.set("x-askr-html-dir", encode ? encodeHeaderText(dir) : dir);
   }
   const carrier = styleCarrier(result.styles, cspNonce);
   const body = result.stream ?? result.html;
diff --git a/src/http/responses.ts b/src/http/responses.ts
index 43c4e8f..633c526 100644
--- a/src/http/responses.ts
+++ b/src/http/responses.ts
@@ -37,7 +37,10 @@ export function text(value: string, init?: ResponseInit): Response {
 
 /** Builds a redirect response with an empty body and a `Location` header. Defaults to `302 Found`. */
 export function redirect(location: string, status: 301 | 302 | 303 | 307 | 308 = 302): Response {
-  return new Response(null, { status, headers: { location } });
+  const headerLocation = location.replace(/[\u0080-\u{10FFFF}]/gu, (character) =>
+    encodeURIComponent(character),
+  );
+  return new Response(null, { status, headers: { location: headerLocation } });
 }
 
 const statusTitles: Record<number, string> = {
diff --git a/tests/pack-result.d.ts b/tests/pack-result.d.ts
new file mode 100644
index 0000000..f815594
--- /dev/null
+++ b/tests/pack-result.d.ts
@@ -0,0 +1,5 @@
+export interface PackRecord {
+  files: Array<{ path: string }>;
+}
+
+export function readPackRecord(result: unknown): PackRecord;
diff --git a/tests/pack-result.js b/tests/pack-result.js
new file mode 100644
index 0000000..286f720
--- /dev/null
+++ b/tests/pack-result.js
@@ -0,0 +1,27 @@
+/** @typedef {{ files: Array<{ path: string }> }} PackRecord */
+
+/** Normalize the array and name-keyed object shapes used by npm pack --json. */
+export function readPackRecord(result) {
+  const records = Array.isArray(result)
+    ? result
+    : result !== null && typeof result === "object"
+      ? Object.values(result)
+      : [];
+
+  if (records.length !== 1)
+    throw new Error(`Expected one packed artifact, received ${records.length}.`);
+
+  const record = records[0];
+  if (
+    record === null ||
+    typeof record !== "object" ||
+    !Array.isArray(record.files) ||
+    !record.files.every(
+      (file) => file !== null && typeof file === "object" && typeof file.path === "string",
+    )
+  ) {
+    throw new Error("npm pack returned an invalid artifact record.");
+  }
+
+  return /** @type {PackRecord} */ (record);
+}
diff --git a/tests/pack-result.test.ts b/tests/pack-result.test.ts
new file mode 100644
index 0000000..cb4135a
--- /dev/null
+++ b/tests/pack-result.test.ts
@@ -0,0 +1,26 @@
+import { describe, expect, it } from "vitest";
+import { readPackRecord } from "./pack-result.js";
+
+const record = { filename: "package.tgz", files: [{ path: "dist/index.js" }] };
+
+describe("npm pack JSON normalization", () => {
+  it.each([[record], { "@askrjs/server": record }])(
+    "should read one artifact from the supported npm result shape",
+    (result) => {
+      expect(readPackRecord(result)).toBe(record);
+    },
+  );
+
+  it.each([[], [record, record], {}, null, "invalid"])(
+    "should reject a result without exactly one artifact",
+    (result) => {
+      expect(() => readPackRecord(result)).toThrow(/Expected one packed artifact/);
+    },
+  );
+
+  it("should reject malformed artifact records", () => {
+    expect(() => readPackRecord([{ files: [{ path: 1 }] }])).toThrow(
+      "npm pack returned an invalid artifact record.",
+    );
+  });
+});
diff --git a/tests/package-artifacts.js b/tests/package-artifacts.js
index 44464d1..33ac3fc 100644
--- a/tests/package-artifacts.js
+++ b/tests/package-artifacts.js
@@ -1,13 +1,16 @@
 import { execFileSync } from "node:child_process";
 import { readFileSync } from "node:fs";
 import { dirname, join, normalize } from "node:path";
+import { readPackRecord } from "./pack-result.js";
 
 const npmCli = process.env.npm_execpath;
 if (!npmCli) throw new Error("npm_execpath is unavailable; run this check through npm");
-const result = JSON.parse(
-  execFileSync(process.execPath, [npmCli, "pack", "--ignore-scripts", "--dry-run", "--json"], {
-    encoding: "utf8",
-  }),
+const result = readPackRecord(
+  JSON.parse(
+    execFileSync(process.execPath, [npmCli, "pack", "--ignore-scripts", "--dry-run", "--json"], {
+      encoding: "utf8",
+    }),
+  ),
 );
 
 const manifest = JSON.parse(readFileSync("package.json", "utf8"));
@@ -17,11 +20,7 @@ if (JSON.stringify(dependencies) !== JSON.stringify(allowedDependencies)) {
   throw new Error(`Unexpected production dependencies: ${dependencies.join(", ")}`);
 }
 
-if (result.length !== 1) {
-  throw new Error(`Expected one packed artifact, received ${result.length}.`);
-}
-
-const packedFiles = new Set(result[0].files.map(({ path }) => normalize(path)));
+const packedFiles = new Set(result.files.map(({ path }) => normalize(path)));
 for (const expected of ["dist/testing.js", "dist/testing.d.ts"]) {
   if (!packedFiles.has(normalize(expected))) {
     throw new Error(`Packed artifact is missing ${expected}.`);
@@ -46,7 +45,7 @@ for (const file of packedFiles) {
 }
 const sourceMappingPattern = /[#@]\s*sourceMappingURL=([^\s*]+)/gu;
 
-for (const file of result[0].files) {
+for (const file of result.files) {
   if (!/\.(?:css|d\.ts|js)$/u.test(file.path)) continue;
 
   const source = readFileSync(file.path, "utf8");
diff --git a/tests/server.test.ts b/tests/server.test.ts
index 0123387..b66df62 100644
--- a/tests/server.test.ts
+++ b/tests/server.test.ts
@@ -4,6 +4,7 @@ import {
   createRouter,
   defineRoutes,
   json,
+  redirect,
   setCookie,
   text,
   type Middleware,
@@ -21,6 +22,15 @@ const authenticated: AuthContext = {
 };
 
 describe("HTTP responses", () => {
+  it("should encode Unicode redirect locations as valid header values", () => {
+    const response = redirect("/tags/日本?q=東京#詳細");
+
+    expect(response.status).toBe(302);
+    expect(response.headers.get("location")).toBe(
+      "/tags/%E6%97%A5%E6%9C%AC?q=%E6%9D%B1%E4%BA%AC#%E8%A9%B3%E7%B4%B0",
+    );
+  });
+
   it.each([
     { headers: { "x-value": "object" } },
     { headers: [["x-value", "tuple"]] as [string, string][] },