diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
index 1d84dbca0c..2c74912a47 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
@@ -2373,6 +2373,71 @@ describe("Codex app-server provider", () => {
     });
   });
 
+  test("keeps an output field named properties as a field", () => {
+    const input = {
+      type: "object",
+      properties: { properties: { type: "string" } },
+      required: ["properties"],
+      additionalProperties: false,
+    };
+
+    expect(normalizeCodexOutputSchema(input)).toEqual(input);
+  });
+
+  test("normalizes schemas under keywords and leaves literal values alone", () => {
+    const literal = { type: "object", properties: { type: "string" } };
+    const input = {
+      type: "object",
+      properties: {
+        result: { $ref: "#/$defs/result" },
+        choice: { anyOf: [{ type: "object", properties: { id: { type: "string" } } }] },
+      },
+      $defs: {
+        properties: { type: "string" },
+        result: {
+          type: "object",
+          properties: { value: { type: "string" } },
+          default: literal,
+          examples: [literal],
+          enum: [literal],
+          const: literal,
+        },
+      },
+    };
+
+    expect(normalizeCodexOutputSchema(input)).toEqual({
+      type: "object",
+      properties: {
+        result: { $ref: "#/$defs/result" },
+        choice: {
+          anyOf: [
+            {
+              type: "object",
+              properties: { id: { type: "string" } },
+              required: ["id"],
+              additionalProperties: false,
+            },
+          ],
+        },
+      },
+      required: ["result", "choice"],
+      additionalProperties: false,
+      $defs: {
+        properties: { type: "string" },
+        result: {
+          type: "object",
+          properties: { value: { type: "string" } },
+          default: literal,
+          examples: [literal],
+          enum: [literal],
+          const: literal,
+          required: ["value"],
+          additionalProperties: false,
+        },
+      },
+    });
+  });
+
   test("passes a normalized output schema to turn/start", async () => {
     const session = createSession();
     const request = vi.fn(async (method: string) => {
diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.ts
index 1d0aca552c..f16c5fb6d8 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.ts
@@ -365,19 +365,67 @@ function isObjectSchemaNode(schema: Record<string, unknown>): boolean {
   );
 }
 
-function normalizeCodexOutputSchemaNode(schema: unknown, schemaPath: string): unknown {
+// Keywords whose value maps names to schemas.
+const SCHEMA_MAP_KEYWORDS = [
+  "properties",
+  "patternProperties",
+  "$defs",
+  "definitions",
+  "dependentSchemas",
+] as const;
+
+// Keywords whose value is a schema or an array of schemas.
+const SUBSCHEMA_KEYWORDS = [
+  "items",
+  "prefixItems",
+  "additionalItems",
+  "contains",
+  "additionalProperties",
+  "unevaluatedProperties",
+  "unevaluatedItems",
+  "propertyNames",
+  "allOf",
+  "anyOf",
+  "oneOf",
+  "not",
+  "if",
+  "then",
+  "else",
+] as const;
+
+function normalizeCodexOutputSubschema(schema: unknown, schemaPath: string): unknown {
   if (Array.isArray(schema)) {
     return schema.map((entry, index) =>
       normalizeCodexOutputSchemaNode(entry, `${schemaPath}[${index}]`),
     );
   }
+  return normalizeCodexOutputSchemaNode(schema, schemaPath);
+}
+
+function normalizeCodexOutputSchemaNode(schema: unknown, schemaPath: string): unknown {
   if (!isSchemaRecord(schema)) {
     return schema;
   }
 
-  const normalized: Record<string, unknown> = {};
-  for (const [key, value] of Object.entries(schema)) {
-    normalized[key] = normalizeCodexOutputSchemaNode(value, `${schemaPath}.${key}`);
+  const normalized: Record<string, unknown> = { ...schema };
+  for (const keyword of SCHEMA_MAP_KEYWORDS) {
+    const schemas = schema[keyword];
+    if (isSchemaRecord(schemas)) {
+      normalized[keyword] = Object.fromEntries(
+        Object.entries(schemas).map(([name, child]) => [
+          name,
+          normalizeCodexOutputSchemaNode(child, `${schemaPath}.${keyword}.${name}`),
+        ]),
+      );
+    }
+  }
+  for (const keyword of SUBSCHEMA_KEYWORDS) {
+    if (keyword in schema) {
+      normalized[keyword] = normalizeCodexOutputSubschema(
+        schema[keyword],
+        `${schemaPath}.${keyword}`,
+      );
+    }
   }
 
   if (!isObjectSchemaNode(normalized)) {