diff --git a/internal/translator/codex/claude/codex_claude_request.go b/internal/translator/codex/claude/codex_claude_request.go
index d9f889e2704..9cb18ad8e5a 100644
--- a/internal/translator/codex/claude/codex_claude_request.go
+++ b/internal/translator/codex/claude/codex_claude_request.go
@@ -261,7 +261,7 @@ func ConvertClaudeRequestToCodex(modelName string, inputRawJSON []byte, _ bool)
 		for i := 0; i < len(toolResults); i++ {
 			toolResult := toolResults[i]
 			// Special handling: map Claude web search tool to Codex web_search
-			if isClaudeWebSearchToolType(toolResult.Get("type").String()) {
+			if isClaudeWebSearchTool(toolResult) {
 				template, _ = sjson.SetRawBytes(template, "tools.-1", convertClaudeWebSearchToolToCodex(toolResult))
 				continue
 			}
@@ -355,6 +355,44 @@ func isClaudeWebSearchToolType(toolType string) bool {
 	return toolType == "web_search_20250305" || toolType == "web_search_20260209"
 }
 
+// isClaudeWebSearchTool reports whether a Claude tool declaration should be
+// mapped to the Codex Responses builtin web_search tool. It matches both the
+// typed Anthropic server tools (web_search_20250305 / web_search_20260209) and
+// the plain function-style "WebSearch" tool emitted by recent Claude Code
+// releases (2.1.177+), which declares a normal input_schema instead of a typed
+// tool and would otherwise be forwarded to Codex as a regular function tool.
+func isClaudeWebSearchTool(tool gjson.Result) bool {
+	if isClaudeWebSearchToolType(tool.Get("type").String()) {
+		return true
+	}
+	return isClaudeCodeWebSearchFunctionTool(tool)
+}
+
+// isClaudeCodeWebSearchFunctionTool detects the function-style WebSearch tool
+// that Claude Code declares as {"name":"WebSearch","input_schema":{...}}. The
+// schema is fingerprinted by its query plus allowed_domains / blocked_domains
+// filter properties so unrelated custom tools (for example a user tool named
+// "web_search") are not misclassified as the builtin web search tool.
+func isClaudeCodeWebSearchFunctionTool(tool gjson.Result) bool {
+	if tool.Get("name").String() != "WebSearch" {
+		return false
+	}
+	// Typed server tools carry an explicit type and are handled separately;
+	// only plain custom/function declarations reach this branch.
+	switch tool.Get("type").String() {
+	case "", "custom":
+	default:
+		return false
+	}
+	props := tool.Get("input_schema.properties")
+	if !props.IsObject() {
+		return false
+	}
+	return props.Get("query").Exists() &&
+		props.Get("allowed_domains").Exists() &&
+		props.Get("blocked_domains").Exists()
+}
+
 func buildClaudeWebSearchToolNameSet(tools gjson.Result) map[string]struct{} {
 	names := map[string]struct{}{}
 	if !tools.IsArray() {
@@ -362,8 +400,7 @@ func buildClaudeWebSearchToolNameSet(tools gjson.Result) map[string]struct{} {
 	}
 
 	tools.ForEach(func(_, tool gjson.Result) bool {
-		toolType := tool.Get("type").String()
-		if !isClaudeWebSearchToolType(toolType) {
+		if !isClaudeWebSearchTool(tool) {
 			return true
 		}
 
diff --git a/internal/translator/codex/claude/codex_claude_request_test.go b/internal/translator/codex/claude/codex_claude_request_test.go
index eab12e4764d..56785d9d4ae 100644
--- a/internal/translator/codex/claude/codex_claude_request_test.go
+++ b/internal/translator/codex/claude/codex_claude_request_test.go
@@ -332,6 +332,97 @@ func TestConvertClaudeRequestToCodex_WebSearchToolChoiceUsesDeclaredTypedToolNam
 	}
 }
 
+func TestConvertClaudeRequestToCodex_ClaudeCodeWebSearchFunctionToolMapping(t *testing.T) {
+	// Recent Claude Code (>= 2.1.177) declares WebSearch as a plain function tool
+	// with an input_schema instead of a typed web_search_* server tool. It must
+	// still map to the Codex Responses builtin web_search tool, while ordinary
+	// function tools alongside it are preserved.
+	inputJSON := `{
+		"model": "gpt-5.5",
+		"tools": [
+			{
+				"name": "Bash",
+				"description": "Run a shell command",
+				"input_schema": {"type":"object","properties":{"command":{"type":"string"}},"required":["command"]}
+			},
+			{
+				"name": "WebSearch",
+				"description": "Search the web. Returns result blocks with titles and URLs.",
+				"input_schema": {
+					"type": "object",
+					"additionalProperties": false,
+					"properties": {
+						"query": {"type": "string", "minLength": 2, "description": "The search query to use"},
+						"allowed_domains": {"type": "array", "items": {"type": "string"}},
+						"blocked_domains": {"type": "array", "items": {"type": "string"}}
+					},
+					"required": ["query"]
+				}
+			}
+		],
+		"messages": [{"role": "user", "content": "search the latest Go release"}]
+	}`
+
+	result := ConvertClaudeRequestToCodex("test-model", []byte(inputJSON), false)
+	resultJSON := gjson.ParseBytes(result)
+
+	if got := resultJSON.Get("tools.#").Int(); got != 2 {
+		t.Fatalf("tools length = %d, want 2. Output: %s", got, string(result))
+	}
+	webSearchTool := resultJSON.Get(`tools.#(type=="web_search")`)
+	if !webSearchTool.Exists() {
+		t.Fatalf("expected a builtin web_search tool. Output: %s", string(result))
+	}
+	// The builtin tool must not leak the function schema fields.
+	if webSearchTool.Get("parameters").Exists() || webSearchTool.Get("input_schema").Exists() || webSearchTool.Get("name").Exists() {
+		t.Fatalf("builtin web_search tool should not carry name/parameters/input_schema. Output: %s", string(result))
+	}
+	if resultJSON.Get(`tools.#(name=="WebSearch")`).Exists() {
+		t.Fatalf("WebSearch must not be forwarded as a function tool. Output: %s", string(result))
+	}
+	// The ordinary Bash tool must still be forwarded as a function tool.
+	bashTool := resultJSON.Get(`tools.#(name=="Bash")`)
+	if !bashTool.Exists() {
+		t.Fatalf("expected Bash to remain a function tool. Output: %s", string(result))
+	}
+	if got := bashTool.Get("type").String(); got != "function" {
+		t.Fatalf("Bash tool type = %q, want function. Output: %s", got, string(result))
+	}
+	if got := bashTool.Get("parameters.properties.command.type").String(); got != "string" {
+		t.Fatalf("Bash tool parameters not preserved. Output: %s", string(result))
+	}
+}
+
+func TestConvertClaudeRequestToCodex_ClaudeCodeWebSearchToolChoiceMapsToBuiltin(t *testing.T) {
+	inputJSON := `{
+		"model": "gpt-5.5",
+		"tools": [
+			{
+				"name": "WebSearch",
+				"description": "Search the web.",
+				"input_schema": {
+					"type": "object",
+					"properties": {
+						"query": {"type": "string"},
+						"allowed_domains": {"type": "array", "items": {"type": "string"}},
+						"blocked_domains": {"type": "array", "items": {"type": "string"}}
+					},
+					"required": ["query"]
+				}
+			}
+		],
+		"tool_choice": {"type": "tool", "name": "WebSearch"},
+		"messages": [{"role": "user", "content": "hello"}]
+	}`
+
+	result := ConvertClaudeRequestToCodex("test-model", []byte(inputJSON), false)
+	resultJSON := gjson.ParseBytes(result)
+
+	if got := resultJSON.Get("tool_choice.type").String(); got != "web_search" {
+		t.Fatalf("tool_choice.type = %q, want web_search. Output: %s", got, string(result))
+	}
+}
+
 func TestConvertClaudeRequestToCodex_AssistantThinkingSignatureToReasoningItem(t *testing.T) {
 	signature := validCodexReasoningSignature()
 	inputJSON := `{