diff --git a/extensions/anthropic/src/anthropic-native-search-wrapper.test.ts b/extensions/anthropic/src/anthropic-native-search-wrapper.test.ts
new file mode 100644
index 00000000000..06978c4befc
--- /dev/null
+++ b/extensions/anthropic/src/anthropic-native-search-wrapper.test.ts
@@ -0,0 +1,53 @@
+import { describe, expect, it, vi } from "vitest";
+import { createAnthropicNativeSearchStreamWrapper } from "./anthropic-native-search-wrapper.js";
+
+describe("createAnthropicNativeSearchStreamWrapper", () => {
+  it("injects web_search server tool into anthropic-messages payloads", () => {
+    const capturedPayloads: any[] = [];
+    const fakeStream = vi.fn((_model: any, _context: any, options: any) => {
+      // Simulate calling onPayload
+      if (options?.onPayload) {
+        const payload = { tools: [{ type: "function", name: "other_tool" }] };
+        options.onPayload(payload);
+        capturedPayloads.push(payload);
+      }
+      return { type: "stream", events: [] } as any;
+    });
+
+    const wrapped = createAnthropicNativeSearchStreamWrapper(fakeStream as any);
+    wrapped({ api: "anthropic-messages" } as any, {} as any, {} as any);
+
+    expect(fakeStream).toHaveBeenCalledOnce();
+    expect(capturedPayloads[0].tools).toHaveLength(2);
+    expect(capturedPayloads[0].tools[1].type).toMatch(/^web_search_/);
+    expect(capturedPayloads[0].tools[1].name).toBe("web_search");
+  });
+
+  it("does not inject if web_search server tool already present", () => {
+    const capturedPayloads: any[] = [];
+    const fakeStream = vi.fn((_model: any, _context: any, options: any) => {
+      if (options?.onPayload) {
+        const payload = { tools: [{ type: "web_search_20260209", name: "web_search" }] };
+        options.onPayload(payload);
+        capturedPayloads.push(payload);
+      }
+      return { type: "stream", events: [] } as any;
+    });
+
+    const wrapped = createAnthropicNativeSearchStreamWrapper(fakeStream as any);
+    wrapped({ api: "anthropic-messages" } as any, {} as any, {} as any);
+
+    expect(capturedPayloads[0].tools).toHaveLength(1);
+  });
+
+  it("passes through non-anthropic API calls unchanged", () => {
+    const fakeStream = vi.fn(() => ({ type: "stream" }) as any);
+    const wrapped = createAnthropicNativeSearchStreamWrapper(fakeStream as any);
+
+    wrapped({ api: "openai-chat" } as any, {} as any, { onPayload: vi.fn() } as any);
+
+    // onPayload should be the original, not our wrapper
+    const passedOptions = fakeStream.mock.calls[0][2];
+    expect(passedOptions.onPayload).toBeDefined();
+  });
+});
diff --git a/extensions/anthropic/src/anthropic-web-search.test.ts b/extensions/anthropic/src/anthropic-web-search.test.ts
new file mode 100644
index 00000000000..0268bb6d6b5
--- /dev/null
+++ b/extensions/anthropic/src/anthropic-web-search.test.ts
@@ -0,0 +1,122 @@
+import { describe, expect, it } from "vitest";
+import { __testing, buildAnthropicWebSearchServerTool } from "./anthropic-web-search-provider.js";
+
+const { resolveAnthropicWebSearchConfig, resolveToolVersion, DEFAULT_TOOL_VERSION } = __testing;
+
+describe("resolveAnthropicWebSearchConfig", () => {
+  it("returns empty object when no config", () => {
+    expect(resolveAnthropicWebSearchConfig(undefined)).toEqual({});
+    expect(resolveAnthropicWebSearchConfig({})).toEqual({});
+  });
+
+  it("returns empty object for non-object anthropic value", () => {
+    expect(resolveAnthropicWebSearchConfig({ anthropic: "invalid" } as any)).toEqual({});
+    expect(resolveAnthropicWebSearchConfig({ anthropic: [] } as any)).toEqual({});
+  });
+
+  it("passes through anthropic config object", () => {
+    const config = { anthropic: { maxUses: 5, allowedDomains: ["example.com"] } };
+    expect(resolveAnthropicWebSearchConfig(config as any)).toEqual({
+      maxUses: 5,
+      allowedDomains: ["example.com"],
+    });
+  });
+});
+
+describe("resolveToolVersion", () => {
+  it("defaults to latest version", () => {
+    expect(resolveToolVersion({})).toBe(DEFAULT_TOOL_VERSION);
+  });
+
+  it("accepts valid versions", () => {
+    expect(resolveToolVersion({ toolVersion: "web_search_20250305" })).toBe("web_search_20250305");
+    expect(resolveToolVersion({ toolVersion: "web_search_20260209" })).toBe("web_search_20260209");
+  });
+
+  it("falls back to default for invalid versions", () => {
+    expect(resolveToolVersion({ toolVersion: "invalid" })).toBe(DEFAULT_TOOL_VERSION);
+    expect(resolveToolVersion({ toolVersion: "  " })).toBe(DEFAULT_TOOL_VERSION);
+  });
+});
+
+describe("buildAnthropicWebSearchServerTool", () => {
+  it("builds minimal tool with defaults", () => {
+    const tool = buildAnthropicWebSearchServerTool();
+    expect(tool).toEqual({
+      type: DEFAULT_TOOL_VERSION,
+      name: "web_search",
+    });
+  });
+
+  it("includes allowed_domains when configured", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: { allowedDomains: ["example.com", "docs.dev"] },
+    } as any);
+    expect(tool.allowed_domains).toEqual(["example.com", "docs.dev"]);
+  });
+
+  it("includes blocked_domains when configured", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: { blockedDomains: ["spam.com"] },
+    } as any);
+    expect(tool.blocked_domains).toEqual(["spam.com"]);
+  });
+
+  it("includes max_uses when positive", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: { maxUses: 3 },
+    } as any);
+    expect(tool.max_uses).toBe(3);
+  });
+
+  it("excludes max_uses when zero or negative", () => {
+    expect(
+      buildAnthropicWebSearchServerTool({ anthropic: { maxUses: 0 } } as any).max_uses,
+    ).toBeUndefined();
+    expect(
+      buildAnthropicWebSearchServerTool({ anthropic: { maxUses: -1 } } as any).max_uses,
+    ).toBeUndefined();
+  });
+
+  it("includes user_location when configured", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: {
+        userLocation: {
+          type: "approximate",
+          city: "Denver",
+          region: "Colorado",
+          country: "US",
+          timezone: "America/Denver",
+        },
+      },
+    } as any);
+    expect(tool.user_location).toEqual({
+      type: "approximate",
+      city: "Denver",
+      region: "Colorado",
+      country: "US",
+      timezone: "America/Denver",
+    });
+  });
+
+  it("omits user_location when empty", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: { userLocation: {} },
+    } as any);
+    expect(tool.user_location).toBeUndefined();
+  });
+
+  it("respects custom tool version", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: { toolVersion: "web_search_20250305" },
+    } as any);
+    expect(tool.type).toBe("web_search_20250305");
+  });
+
+  it("omits empty allowed_domains array", () => {
+    const tool = buildAnthropicWebSearchServerTool({
+      anthropic: { allowedDomains: [] },
+    } as any);
+    expect(tool.allowed_domains).toBeUndefined();
+  });
+});