diff --git a/src/config/zod-schema.agent-params.test.ts b/src/config/zod-schema.agent-params.test.ts
new file mode 100644
index 00000000000..83b712c2d00
--- /dev/null
+++ b/src/config/zod-schema.agent-params.test.ts
@@ -0,0 +1,36 @@
+import { describe, expect, it } from "vitest";
+import { AgentEntrySchema } from "./zod-schema.agent-runtime.js";
+
+describe("AgentEntrySchema params field", () => {
+  it("accepts agents.list[].params with cacheRetention", () => {
+    const result = AgentEntrySchema.safeParse({
+      id: "main",
+      params: { cacheRetention: "none" },
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.params).toEqual({ cacheRetention: "none" });
+    }
+  });
+
+  it("accepts agents.list[].params with arbitrary model overrides", () => {
+    const result = AgentEntrySchema.safeParse({
+      id: "main",
+      params: { temperature: 0.7, maxTokens: 4096 },
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.params).toEqual({ temperature: 0.7, maxTokens: 4096 });
+    }
+  });
+
+  it("accepts agents.list[] without params (optional)", () => {
+    const result = AgentEntrySchema.safeParse({
+      id: "main",
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.params).toBeUndefined();
+    }
+  });
+});
diff --git a/src/config/zod-schema.agent-runtime.ts b/src/config/zod-schema.agent-runtime.ts
index d7b1dd393e7..f4ac349e68b 100644
--- a/src/config/zod-schema.agent-runtime.ts
+++ b/src/config/zod-schema.agent-runtime.ts
@@ -751,6 +751,8 @@ export const AgentEntrySchema = z
     heartbeat: HeartbeatSchema,
     identity: IdentitySchema,
     groupChat: GroupChatSchema,
+    /** Per-agent model params (e.g. cacheRetention, temperature). Merged on top of agents.defaults.models[...].params. */
+    params: z.record(z.string(), z.unknown()).optional(),
     subagents: z
       .object({
         allowAgents: z.array(z.string()).optional(),