fix(duckduckgo): decode & last in decodeHtmlEntities to avoid double-decoding (#96348)

* fix(duckduckgo): decode & last in decodeHtmlEntities to avoid double-decoding

decodeHtmlEntities decoded & FIRST, so result text that literally contains
an entity (e.g. a page title 'How to escape < in HTML', which DuckDuckGo
returns double-encoded as '<') was re-decoded into markup: '<'
became '<' instead of the literal '&lt;', corrupting the titles, snippets, and
URLs the web-search tool returns to the model.

Reorder so &amp; is decoded last, matching the established convention elsewhere
in the codebase (msteams/inbound.ts, openai-transport-stream.ts,
launchd-plist.ts, doctor-session-snapshots.ts all decode &amp; last).
Behavior-preserving for all singly-encoded input.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(duckduckgo): decode html entities in one pass

---------

Co-authored-by: ly-wang19 <ly-wang19@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

extensions/duckduckgo/src/ddg-client.ts

@@ -36,21 +36,49 @@ type DuckDuckGoResult = {
 };
 
 function decodeHtmlEntities(text: string): string {
-  return text
-    .replace(/&/g, "&")
-    .replace(/&lt;/g, "<")
-    .replace(/&gt;/g, ">")
-    .replace(/&quot;/g, '"')
-    .replace(/&apos;/g, "'")
-    .replace(/&#39;/g, "'")
-    .replace(/&#x27;/g, "'")
-    .replace(/&#x2F;/g, "/")
-    .replace(/&nbsp;/g, " ")
-    .replace(/&ndash;/g, "-")
-    .replace(/&mdash;/g, "--")
-    .replace(/&hellip;/g, "...")
-    .replace(/&#(\d+);/g, (_, code) => String.fromCodePoint(Number(code)))
-    .replace(/&#x([0-9a-f]+);/gi, (_, code) => String.fromCodePoint(Number.parseInt(code, 16)));
+  return text.replace(
+    /&(?:lt|gt|quot|apos|#39|#x27|#x2F|nbsp|ndash|mdash|hellip|amp|#\d+|#x[0-9a-f]+);/gi,
+    (entity) => {
+      const normalized = entity.toLowerCase();
+      if (normalized === "&lt;") {
+        return "<";
+      }
+      if (normalized === "&gt;") {
+        return ">";
+      }
+      if (normalized === "&quot;") {
+        return '"';
+      }
+      if (normalized === "&apos;" || normalized === "&#39;" || normalized === "&#x27;") {
+        return "'";
+      }
+      if (normalized === "&#x2f;") {
+        return "/";
+      }
+      if (normalized === "&nbsp;") {
+        return " ";
+      }
+      if (normalized === "&ndash;") {
+        return "-";
+      }
+      if (normalized === "&mdash;") {
+        return "--";
+      }
+      if (normalized === "&hellip;") {
+        return "...";
+      }
+      if (normalized === "&amp;") {
+        return "&";
+      }
+      if (normalized.startsWith("&#x")) {
+        return String.fromCodePoint(Number.parseInt(normalized.slice(3, -1), 16));
+      }
+      if (normalized.startsWith("&#")) {
+        return String.fromCodePoint(Number.parseInt(normalized.slice(2, -1), 10));
+      }
+      return entity;
+    },
+  );
 }
 
 function stripHtml(html: string): string {

extensions/duckduckgo/src/ddg-search-provider.test.ts

@@ -186,6 +186,17 @@ describe("duckduckgo web search provider", () => {
     );
   });
 
+  it("does not double-decode escaped entities (decodes & last)", () => {
+    // A result whose text literally shows "<" arrives double-encoded as
+    // "&amp;lt;". Decoding &amp; first would re-decode it into "<", corrupting
+    // the snippet; &amp; must be decoded last.
+    expect(ddgClientTesting.decodeHtmlEntities("How to escape &amp;lt; in HTML")).toBe(
+      "How to escape &lt; in HTML",
+    );
+    expect(ddgClientTesting.decodeHtmlEntities("a&amp;#39;b")).toBe("a&#39;b");
+    expect(ddgClientTesting.decodeHtmlEntities("a&#x26;amp;b")).toBe("a&amp;b");
+  });
+
   it("parses results when href appears before class", () => {
     const html = `
       <a href="https://duckduckgo.com/l/?uddg=https%3A%2F%2Fexample.com" class="result__a">