fix(codex): preserve custom tools during request normalization

Add CODEX_PASSTHROUGH_TOOL_TYPES allowlist so Responses-native freeform
tools (e.g. grammar-backed apply_patch) survive normalizeCodexTools and
reach the upstream Codex Responses API intact.

Refs #1907

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/executors/codex.js

@@ -26,6 +26,9 @@ const CODEX_HOSTED_TOOL_TYPES = new Set([
   "tool_search"
 ]);
 
+// Responses-native freeform tools carry a name plus format payload and must pass through intact.
+const CODEX_PASSTHROUGH_TOOL_TYPES = new Set(["custom"]);
+
 // Allowlist of fields accepted by Codex Responses API — anything else is stripped
 const RESPONSES_API_ALLOWLIST = new Set([
   "model", "input", "instructions", "tools", "tool_choice", "stream", "store",
@@ -72,6 +75,7 @@ function normalizeCodexTools(body) {
       return true;
     }
     if (type !== "function") {
+      if (CODEX_PASSTHROUGH_TOOL_TYPES.has(type)) return true;
       if (!type || tool.function || typeof tool.name === "string") return false;
       return CODEX_HOSTED_TOOL_TYPES.has(type);
     }

tests/unit/codex-tool-normalization.test.js

@@ -0,0 +1,99 @@
+import { describe, expect, it } from "vitest";
+
+import { CodexExecutor } from "../../open-sse/executors/codex.js";
+
+function normalizeTools(tools) {
+  const executor = new CodexExecutor();
+  const body = {
+    model: "gpt-5.5",
+    input: [{ type: "message", role: "user", content: [{ type: "input_text", text: "probe" }] }],
+    tools,
+    stream: true,
+  };
+
+  executor.transformRequest("gpt-5.5", body, true, {
+    connectionId: "test-codex-tools",
+    providerSpecificData: {},
+  });
+
+  return body.tools;
+}
+
+describe("CodexExecutor tool normalization", () => {
+  it("preserves Responses-native tool_search tools", () => {
+    const tools = normalizeTools([
+      {
+        type: "tool_search",
+        execution: "sync",
+        description: "Discover deferred tools",
+        parameters: { type: "object", properties: {} },
+      },
+      {
+        type: "namespace",
+        name: "codex_app",
+        description: "app tools",
+        tools: [
+          {
+            type: "function",
+            name: "automation_update",
+            description: "automation",
+            parameters: { type: "object", properties: {} },
+            defer_loading: true,
+          },
+        ],
+      },
+      {
+        type: "function",
+        name: "plain_fn",
+        description: "plain",
+        parameters: { type: "object", properties: {} },
+      },
+    ]);
+
+    expect(tools.map((tool) => `${tool.type}:${tool.name || ""}`)).toEqual([
+      "tool_search:",
+      "namespace:codex_app",
+      "function:plain_fn",
+    ]);
+  });
+
+  it("preserves hosted Responses tools", () => {
+    const tools = normalizeTools([
+      { type: "web_search", search_context_size: "medium" },
+      { type: "image_generation", size: "1024x1024" },
+      { type: "mcp", server_label: "docs", server_url: "https://example.com/mcp" },
+      { type: "local_shell" },
+      { type: "code_interpreter", container: { type: "auto" } },
+      { type: "computer", display_width: 1024, display_height: 768, environment: "browser" },
+    ]);
+
+    expect(tools.map((tool) => tool.type)).toEqual([
+      "web_search",
+      "image_generation",
+      "mcp",
+      "local_shell",
+      "code_interpreter",
+      "computer",
+    ]);
+  });
+
+  it("preserves custom freeform tools with format payloads", () => {
+    const tools = normalizeTools([
+      {
+        type: "custom",
+        name: "apply_patch",
+        description: "patch",
+        format: { type: "grammar", syntax: "lark", definition: "start: /.+/" },
+      },
+    ]);
+
+    expect(tools).toEqual([
+      {
+        type: "custom",
+        name: "apply_patch",
+        description: "patch",
+        format: { type: "grammar", syntax: "lark", definition: "start: /.+/" },
+      },
+    ]);
+  });
+});