diff --git a/packages/workflow-utils/src/hermes-agent.ts b/packages/workflow-utils/src/hermes-agent.ts
index 61620dc..0d76dd6 100644
--- a/packages/workflow-utils/src/hermes-agent.ts
+++ b/packages/workflow-utils/src/hermes-agent.ts
@@ -9,8 +9,8 @@ import { type SpawnEnv, type SpawnError, spawnSafe } from "./spawn-safe.js";
  */
 export type HermesAgentOptions = {
   prompt: string;
-  model: string;
-  provider: string;
+  model: string | null;
+  provider: string | null;
   skills: string[];
   /** When true, suppresses interactive UI noise. */
   quiet: boolean;
@@ -38,13 +38,15 @@ export async function hermesAgent(
     "-q",
     options.prompt,
     "--yolo",
-    "--model",
-    options.model,
-    "--provider",
-    options.provider,
     "--max-turns",
     String(options.maxTurns),
   ];
+  if (options.model) {
+    args.push("--model", options.model);
+  }
+  if (options.provider) {
+    args.push("--provider", options.provider);
+  }
   for (const s of options.skills) {
     args.push("-s", s);
   }
diff --git a/packages/workflow-utils/src/hermes-options.ts b/packages/workflow-utils/src/hermes-options.ts
index 44e788c..dfb866c 100644
--- a/packages/workflow-utils/src/hermes-options.ts
+++ b/packages/workflow-utils/src/hermes-options.ts
@@ -1,8 +1,8 @@
 import type { HermesRoleDefaults, HermesRoleRequired } from "./role-types.js";
 
 const HERMES_DEFAULTS: HermesRoleDefaults = {
-  model: "auto",
-  provider: "auto",
+  model: null,
+  provider: null,
   skills: [],
   quiet: true,
   maxTurns: 90,
diff --git a/packages/workflow-utils/src/role-types.ts b/packages/workflow-utils/src/role-types.ts
index f011582..ca8c63a 100644
--- a/packages/workflow-utils/src/role-types.ts
+++ b/packages/workflow-utils/src/role-types.ts
@@ -40,8 +40,8 @@ export type HermesRoleRequired<T> = {
 };
 
 export type HermesRoleDefaults = {
-  model: string;
-  provider: string;
+  model: string | null;
+  provider: string | null;
   skills: string[];
   quiet: boolean;
   maxTurns: number;