diff --git a/open-sse/services/webSearchFallback.ts b/open-sse/services/webSearchFallback.ts
index 62f3f06ca5..61fe2355c3 100644
--- a/open-sse/services/webSearchFallback.ts
+++ b/open-sse/services/webSearchFallback.ts
@@ -130,6 +130,7 @@ function buildFallbackTool(tool: JsonRecord, targetFormat?: string | null): Json
 }
 
 export function supportsNativeWebSearchFallbackBypass({
+  sourceFormat,
   targetFormat,
   nativeCodexPassthrough,
 }: {
@@ -138,8 +139,16 @@ export function supportsNativeWebSearchFallbackBypass({
   targetFormat: string | null | undefined;
   nativeCodexPassthrough: boolean;
 }): boolean {
+  // Native Codex (OpenAI Responses) passthrough: the upstream runs web search itself.
   if (nativeCodexPassthrough) return true;
-  return targetFormat === FORMATS.GEMINI;
+  // Gemini target: the Gemini translator maps built-in web search to googleSearch natively.
+  if (targetFormat === FORMATS.GEMINI) return true;
+  // Claude -> Claude passthrough: the Anthropic Messages upstream (e.g. a Claude
+  // subscription driven by Claude Code) natively runs web_search_20250305. Forward the
+  // native tool untouched instead of rewriting it to omniroute_web_search. Mirrors the
+  // Codex/Gemini bypasses so every native-web-search provider is treated symmetrically.
+  if (sourceFormat === FORMATS.CLAUDE && targetFormat === FORMATS.CLAUDE) return true;
+  return false;
 }
 
 export function prepareWebSearchFallbackBody<T extends JsonRecord>(
diff --git a/tests/unit/web-search-fallback-format.test.ts b/tests/unit/web-search-fallback-format.test.ts
index 605aa1f7dd..8941eb7a2f 100644
--- a/tests/unit/web-search-fallback-format.test.ts
+++ b/tests/unit/web-search-fallback-format.test.ts
@@ -1,8 +1,11 @@
 import test from "node:test";
 import assert from "node:assert/strict";
 
-const { prepareWebSearchFallbackBody, OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME } =
-  await import("../../open-sse/services/webSearchFallback.ts");
+const {
+  prepareWebSearchFallbackBody,
+  supportsNativeWebSearchFallbackBypass,
+  OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME,
+} = await import("../../open-sse/services/webSearchFallback.ts");
 
 // Regression for #2390: when the target is a Responses-API provider, the injected
 // omniroute_web_search tool must use the FLAT function shape ({ type, name }), not the
@@ -72,3 +75,153 @@ test("#2390 tool_choice matches the injected tool shape per target format", () =
   const cFn = cChoice.function as Record<string, unknown> | undefined;
   assert.equal(cFn?.name, OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME);
 });
+
+// ── Native web-search bypass: predicate coverage for every native path ──
+
+test("bypass predicate: true for native Codex passthrough", () => {
+  assert.equal(
+    supportsNativeWebSearchFallbackBypass({
+      provider: "openai",
+      sourceFormat: "openai-responses",
+      targetFormat: "openai-responses",
+      nativeCodexPassthrough: true,
+    }),
+    true
+  );
+});
+
+test("bypass predicate: true for Gemini target", () => {
+  assert.equal(
+    supportsNativeWebSearchFallbackBypass({
+      provider: "gemini",
+      sourceFormat: "openai",
+      targetFormat: "gemini",
+      nativeCodexPassthrough: false,
+    }),
+    true
+  );
+});
+
+test("bypass predicate: true for Claude -> Claude passthrough", () => {
+  assert.equal(
+    supportsNativeWebSearchFallbackBypass({
+      provider: "claude",
+      sourceFormat: "claude",
+      targetFormat: "claude",
+      nativeCodexPassthrough: false,
+    }),
+    true
+  );
+});
+
+test("bypass predicate: false for standard OpenAI -> OpenAI", () => {
+  assert.equal(
+    supportsNativeWebSearchFallbackBypass({
+      provider: "openai",
+      sourceFormat: "openai",
+      targetFormat: "openai",
+      nativeCodexPassthrough: false,
+    }),
+    false
+  );
+});
+
+test("bypass predicate: false when only the target is Claude (non-native tool must convert)", () => {
+  // An OpenAI-format client hitting a Claude target sends an OpenAI-shaped web_search
+  // tool that is NOT native Anthropic format, so it must still be converted. Only the
+  // Claude -> Claude passthrough (native body) is bypassed.
+  assert.equal(
+    supportsNativeWebSearchFallbackBypass({
+      provider: "claude",
+      sourceFormat: "openai",
+      targetFormat: "claude",
+      nativeCodexPassthrough: false,
+    }),
+    false
+  );
+});
+
+test("bypass predicate: false when only the source is Claude", () => {
+  assert.equal(
+    supportsNativeWebSearchFallbackBypass({
+      provider: "openai",
+      sourceFormat: "claude",
+      targetFormat: "openai",
+      nativeCodexPassthrough: false,
+    }),
+    false
+  );
+});
+
+// ── Native web-search bypass: end-to-end body behavior ──
+
+test("Claude -> Claude: native web_search_20250305 forwarded untouched", () => {
+  const inputBody = {
+    tools: [{ type: "web_search_20250305", name: "web_search", max_uses: 5 }],
+  };
+  const { body, fallback } = prepareWebSearchFallbackBody(inputBody, {
+    provider: "claude",
+    sourceFormat: "claude",
+    targetFormat: "claude",
+    nativeCodexPassthrough: false,
+  });
+
+  assert.equal(fallback.enabled, false);
+  assert.equal(fallback.toolName, null);
+  assert.equal(fallback.convertedToolCount, 0);
+  // Body forwarded verbatim — the native tool reaches the Anthropic upstream as-is.
+  assert.deepEqual(body, inputBody);
+});
+
+test("Claude -> Claude: bare web_search type also forwarded untouched", () => {
+  // Even the bare (unversioned) web_search type is forwarded on the Claude passthrough,
+  // because the Anthropic upstream owns web search. This is the explicit protection that
+  // no longer depends on the versioned type being absent from the matcher set.
+  const inputBody = { tools: [{ type: "web_search" }] };
+  const { body, fallback } = prepareWebSearchFallbackBody(inputBody, {
+    provider: "claude",
+    sourceFormat: "claude",
+    targetFormat: "claude",
+    nativeCodexPassthrough: false,
+  });
+
+  assert.equal(fallback.enabled, false);
+  assert.equal(fallback.toolName, null);
+  assert.deepEqual(body, inputBody);
+});
+
+test("native Codex passthrough: built-in web_search_preview forwarded untouched", () => {
+  // Symmetric end-to-end coverage for the Codex bypass.
+  const inputBody = { tools: [{ type: "web_search_preview" }] };
+  const { body, fallback } = prepareWebSearchFallbackBody(inputBody, {
+    provider: "openai",
+    sourceFormat: "openai-responses",
+    targetFormat: "openai-responses",
+    nativeCodexPassthrough: true,
+  });
+
+  assert.equal(fallback.enabled, false);
+  assert.equal(fallback.toolName, null);
+  assert.deepEqual(body, inputBody);
+});
+
+test("OpenAI -> Claude (non-passthrough): built-in web_search IS still converted", () => {
+  // Regression guard: the new Claude bypass must NOT swallow the conversion path for a
+  // non-native (OpenAI-format) client that merely targets a Claude provider.
+  const inputBody = {
+    tools: [{ type: "web_search", search_context_size: "low" }],
+  };
+  const { body, fallback } = prepareWebSearchFallbackBody(inputBody, {
+    provider: "claude",
+    sourceFormat: "openai",
+    targetFormat: "claude",
+    nativeCodexPassthrough: false,
+  });
+
+  assert.equal(fallback.enabled, true);
+  assert.equal(fallback.toolName, OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME);
+  assert.equal(fallback.convertedToolCount, 1);
+  const tools = (body.tools as Record<string, any>[]) || [];
+  const toolNames = tools.map((t) => (t.function ? t.function.name : t.name));
+  assert.ok(toolNames.includes(OMNIROUTE_WEB_SEARCH_FALLBACK_TOOL_NAME));
+});