diff --git a/src/config/zod-schema.agent-defaults.ts b/src/config/zod-schema.agent-defaults.ts
index d655a797ad2..302335a1d52 100644
--- a/src/config/zod-schema.agent-defaults.ts
+++ b/src/config/zod-schema.agent-defaults.ts
@@ -1,6 +1,7 @@
 import { z } from "zod";
 import {
   HeartbeatSchema,
+  AgentModelSchema,
   MemorySearchSchema,
   SandboxBrowserSchema,
   SandboxDockerSchema,
@@ -160,17 +161,7 @@ export const AgentDefaultsSchema = z
             "Maximum number of active children a single agent session can spawn (default: 5).",
           ),
         archiveAfterMinutes: z.number().int().positive().optional(),
-        model: z
-          .union([
-            z.string(),
-            z
-              .object({
-                primary: z.string().optional(),
-                fallbacks: z.array(z.string()).optional(),
-              })
-              .strict(),
-          ])
-          .optional(),
+        model: AgentModelSchema.optional(),
         thinking: z.string().optional(),
       })
       .strict()
diff --git a/src/config/zod-schema.agent-model.ts b/src/config/zod-schema.agent-model.ts
new file mode 100644
index 00000000000..3a6bac05c24
--- /dev/null
+++ b/src/config/zod-schema.agent-model.ts
@@ -0,0 +1,11 @@
+import { z } from "zod";
+
+export const AgentModelSchema = z.union([
+  z.string(),
+  z
+    .object({
+      primary: z.string().optional(),
+      fallbacks: z.array(z.string()).optional(),
+    })
+    .strict(),
+]);
diff --git a/src/config/zod-schema.agent-runtime.ts b/src/config/zod-schema.agent-runtime.ts
index bab2b645115..197f29368ca 100644
--- a/src/config/zod-schema.agent-runtime.ts
+++ b/src/config/zod-schema.agent-runtime.ts
@@ -1,5 +1,6 @@
 import { z } from "zod";
 import { parseDurationMs } from "../cli/parse-duration.js";
+import { AgentModelSchema } from "./zod-schema.agent-model.js";
 import {
   GroupChatSchema,
   HumanDelaySchema,
@@ -450,15 +451,7 @@ export const MemorySearchSchema = z
   })
   .strict()
   .optional();
-export const AgentModelSchema = z.union([
-  z.string(),
-  z
-    .object({
-      primary: z.string().optional(),
-      fallbacks: z.array(z.string()).optional(),
-    })
-    .strict(),
-]);
+export { AgentModelSchema };
 export const AgentEntrySchema = z
   .object({
     id: z.string(),