diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf81a987c57..1c43a94e26b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Tools/web_search Brave language-code validation: align `search_lang` handling with Brave-supported codes (including `zh-hans`, `zh-hant`, `en-gb`, and `pt-br`), map common alias inputs (`zh`, `ja`) to valid Brave values, and reject unsupported codes before upstream requests to prevent 422 failures. (#37260) Thanks @heyanming.
 - Models/openai-completions streaming compatibility: force `compat.supportsUsageInStreaming=false` for non-native OpenAI-compatible endpoints during model normalization, preventing usage-only stream chunks from triggering `choices[0]` parser crashes in provider streams. (#8714) Thanks @nonanon1.
 - Tools/xAI native web-search collision guard: drop OpenClaw `web_search` from tool registration when routing to xAI/Grok model providers (including OpenRouter `x-ai/*`) to avoid duplicate tool-name request failures against provider-native `web_search`. (#14749) Thanks @realsamrat.
 - TUI/token copy-safety rendering: treat long credential-like mixed alphanumeric tokens (including quoted forms) as copy-sensitive in render sanitization so formatter hard-wrap guards no longer inject visible spaces into auth-style values before display. (#26710) Thanks @jasonthane.
diff --git a/src/agents/tools/web-search.ts b/src/agents/tools/web-search.ts
index ee15b9c0773..eb7dc225ce9 100644
--- a/src/agents/tools/web-search.ts
+++ b/src/agents/tools/web-search.ts
@@ -40,7 +40,67 @@ const KIMI_WEB_SEARCH_TOOL = {
 const SEARCH_CACHE = new Map<string, CacheEntry<Record<string, unknown>>>();
 const BRAVE_FRESHNESS_SHORTCUTS = new Set(["pd", "pw", "pm", "py"]);
 const BRAVE_FRESHNESS_RANGE = /^(\d{4}-\d{2}-\d{2})to(\d{4}-\d{2}-\d{2})$/;
-const BRAVE_SEARCH_LANG_CODE = /^[a-z]{2}$/i;
+const BRAVE_SEARCH_LANG_CODES = new Set([
+  "ar",
+  "eu",
+  "bn",
+  "bg",
+  "ca",
+  "zh-hans",
+  "zh-hant",
+  "hr",
+  "cs",
+  "da",
+  "nl",
+  "en",
+  "en-gb",
+  "et",
+  "fi",
+  "fr",
+  "gl",
+  "de",
+  "el",
+  "gu",
+  "he",
+  "hi",
+  "hu",
+  "is",
+  "it",
+  "jp",
+  "kn",
+  "ko",
+  "lv",
+  "lt",
+  "ms",
+  "ml",
+  "mr",
+  "nb",
+  "pl",
+  "pt-br",
+  "pt-pt",
+  "pa",
+  "ro",
+  "ru",
+  "sr",
+  "sk",
+  "sl",
+  "es",
+  "sv",
+  "ta",
+  "te",
+  "th",
+  "tr",
+  "uk",
+  "vi",
+]);
+const BRAVE_SEARCH_LANG_ALIASES: Record<string, string> = {
+  ja: "jp",
+  zh: "zh-hans",
+  "zh-cn": "zh-hans",
+  "zh-hk": "zh-hant",
+  "zh-sg": "zh-hans",
+  "zh-tw": "zh-hant",
+};
 const BRAVE_UI_LANG_LOCALE = /^([a-z]{2})-([a-z]{2})$/i;
 const PERPLEXITY_RECENCY_VALUES = new Set(["day", "week", "month", "year"]);
 
@@ -127,7 +187,7 @@ function createWebSearchSchema(provider: (typeof SEARCH_PROVIDERS)[number]) {
       search_lang: Type.Optional(
         Type.String({
           description:
-            "Short ISO language code for search results (e.g., 'de', 'en', 'fr', 'tr'). Must be a 2-letter code, NOT a locale.",
+            "Brave language code for search results (e.g., 'en', 'de', 'en-gb', 'zh-hans', 'zh-hant', 'pt-br').",
         }),
       ),
       ui_lang: Type.Optional(
@@ -731,10 +791,14 @@ function normalizeBraveSearchLang(value: string | undefined): string | undefined
     return undefined;
   }
   const trimmed = value.trim();
-  if (!trimmed || !BRAVE_SEARCH_LANG_CODE.test(trimmed)) {
+  if (!trimmed) {
     return undefined;
   }
-  return trimmed.toLowerCase();
+  const canonical = BRAVE_SEARCH_LANG_ALIASES[trimmed.toLowerCase()] ?? trimmed.toLowerCase();
+  if (!BRAVE_SEARCH_LANG_CODES.has(canonical)) {
+    return undefined;
+  }
+  return canonical;
 }
 
 function normalizeBraveUiLang(value: string | undefined): string | undefined {
@@ -1473,7 +1537,7 @@ export function createWebSearchTool(options?: {
         return jsonResult({
           error: "invalid_search_lang",
           message:
-            "search_lang must be a 2-letter ISO language code like 'en' (not a locale like 'en-US').",
+            "search_lang must be a Brave-supported language code like 'en', 'en-gb', 'zh-hans', or 'zh-hant'.",
           docs: "https://docs.openclaw.ai/tools/web",
         });
       }
diff --git a/src/agents/tools/web-tools.enabled-defaults.test.ts b/src/agents/tools/web-tools.enabled-defaults.test.ts
index c42fb680002..53af4a5c8f3 100644
--- a/src/agents/tools/web-tools.enabled-defaults.test.ts
+++ b/src/agents/tools/web-tools.enabled-defaults.test.ts
@@ -155,6 +155,8 @@ describe("web_search country and language parameters", () => {
   async function runBraveSearchAndGetUrl(
     params: Partial<{
       country: string;
+      language: string;
+      search_lang: string;
       ui_lang: string;
       freshness: string;
     }>,
@@ -185,6 +187,30 @@ describe("web_search country and language parameters", () => {
     expect(url.searchParams.get("search_lang")).toBe("de");
   });
 
+  it("maps legacy zh language code to Brave zh-hans search_lang", async () => {
+    const url = await runBraveSearchAndGetUrl({ language: "zh" });
+    expect(url.searchParams.get("search_lang")).toBe("zh-hans");
+  });
+
+  it("maps ja language code to Brave jp search_lang", async () => {
+    const url = await runBraveSearchAndGetUrl({ language: "ja" });
+    expect(url.searchParams.get("search_lang")).toBe("jp");
+  });
+
+  it("passes Brave extended language code variants unchanged", async () => {
+    const url = await runBraveSearchAndGetUrl({ search_lang: "zh-hant" });
+    expect(url.searchParams.get("search_lang")).toBe("zh-hant");
+  });
+
+  it("rejects unsupported Brave search_lang values before upstream request", async () => {
+    const mockFetch = installMockFetch({ web: { results: [] } });
+    const tool = createWebSearchTool({ config: undefined, sandboxed: true });
+    const result = await tool?.execute?.("call-1", { query: "test", search_lang: "xx" });
+
+    expect(mockFetch).not.toHaveBeenCalled();
+    expect(result?.details).toMatchObject({ error: "invalid_search_lang" });
+  });
+
   it("rejects invalid freshness values", async () => {
     const mockFetch = installMockFetch({ web: { results: [] } });
     const tool = createWebSearchTool({ config: undefined, sandboxed: true });