diff --git a/src/auto-reply/model.test.ts b/src/auto-reply/model.test.ts
new file mode 100644
index 000000000..f4dd64221
--- /dev/null
+++ b/src/auto-reply/model.test.ts
@@ -0,0 +1,115 @@
+import { describe, expect, it } from "vitest";
+import { extractModelDirective } from "./model.js";
+
+describe("extractModelDirective", () => {
+  describe("basic /model command", () => {
+    it("extracts /model with argument", () => {
+      const result = extractModelDirective("/model gpt-5");
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("gpt-5");
+      expect(result.cleaned).toBe("");
+    });
+
+    it("extracts /model with provider/model format", () => {
+      const result = extractModelDirective("/model anthropic/claude-opus-4-5");
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("anthropic/claude-opus-4-5");
+    });
+
+    it("extracts /model with profile override", () => {
+      const result = extractModelDirective("/model gpt-5@myprofile");
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("gpt-5");
+      expect(result.rawProfile).toBe("myprofile");
+    });
+
+    it("returns no directive for plain text", () => {
+      const result = extractModelDirective("hello world");
+      expect(result.hasDirective).toBe(false);
+      expect(result.cleaned).toBe("hello world");
+    });
+  });
+
+  describe("alias shortcuts", () => {
+    it("recognizes /gpt as model directive when alias is configured", () => {
+      const result = extractModelDirective("/gpt", { aliases: ["gpt", "sonnet", "opus"] });
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("gpt");
+      expect(result.cleaned).toBe("");
+    });
+
+    it("recognizes /sonnet as model directive", () => {
+      const result = extractModelDirective("/sonnet", { aliases: ["gpt", "sonnet", "opus"] });
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("sonnet");
+    });
+
+    it("recognizes alias mid-message", () => {
+      const result = extractModelDirective("switch to /opus please", {
+        aliases: ["opus"],
+      });
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("opus");
+      expect(result.cleaned).toBe("switch to please");
+    });
+
+    it("is case-insensitive for aliases", () => {
+      const result = extractModelDirective("/GPT", { aliases: ["gpt"] });
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("GPT");
+    });
+
+    it("does not match alias without leading slash", () => {
+      const result = extractModelDirective("gpt is great", { aliases: ["gpt"] });
+      expect(result.hasDirective).toBe(false);
+    });
+
+    it("does not match unknown aliases", () => {
+      const result = extractModelDirective("/unknown", { aliases: ["gpt", "sonnet"] });
+      expect(result.hasDirective).toBe(false);
+      expect(result.cleaned).toBe("/unknown");
+    });
+
+    it("prefers /model over alias when both present", () => {
+      const result = extractModelDirective("/model haiku", { aliases: ["gpt"] });
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("haiku");
+    });
+
+    it("handles empty aliases array", () => {
+      const result = extractModelDirective("/gpt", { aliases: [] });
+      expect(result.hasDirective).toBe(false);
+    });
+
+    it("handles undefined aliases", () => {
+      const result = extractModelDirective("/gpt");
+      expect(result.hasDirective).toBe(false);
+    });
+  });
+
+  describe("edge cases", () => {
+    it("handles alias with special regex characters", () => {
+      const result = extractModelDirective("/test.alias", {
+        aliases: ["test.alias"],
+      });
+      expect(result.hasDirective).toBe(true);
+      expect(result.rawModel).toBe("test.alias");
+    });
+
+    it("does not match partial alias", () => {
+      const result = extractModelDirective("/gpt-turbo", { aliases: ["gpt"] });
+      expect(result.hasDirective).toBe(false);
+    });
+
+    it("handles empty body", () => {
+      const result = extractModelDirective("", { aliases: ["gpt"] });
+      expect(result.hasDirective).toBe(false);
+      expect(result.cleaned).toBe("");
+    });
+
+    it("handles undefined body", () => {
+      const result = extractModelDirective(undefined, { aliases: ["gpt"] });
+      expect(result.hasDirective).toBe(false);
+    });
+  });
+});
diff --git a/src/auto-reply/reply.ts b/src/auto-reply/reply.ts
index c2bd3ecb3..e7a063ee4 100644
--- a/src/auto-reply/reply.ts
+++ b/src/auto-reply/reply.ts
@@ -31,7 +31,10 @@ import { clearCommandLane, getQueueSize } from "../process/command-queue.js";
 import { defaultRuntime } from "../runtime.js";
 import { resolveCommandAuthorization } from "./command-auth.js";
 import { hasControlCommand } from "./command-detection.js";
-import { shouldHandleTextCommands } from "./commands-registry.js";
+import {
+  listChatCommands,
+  shouldHandleTextCommands,
+} from "./commands-registry.js";
 import { getAbortMemory } from "./reply/abort.js";
 import { runReplyAgent } from "./reply/agent-runner.js";
 import { resolveBlockStreamingChunking } from "./reply/block-streaming.js";
@@ -312,9 +315,15 @@ export async function getReplyFromConfig(
     rawDrop: undefined,
     hasQueueOptions: false,
   });
+  const reservedCommands = new Set(
+    listChatCommands().flatMap((cmd) =>
+      cmd.textAliases.map((a) => a.replace(/^\//, "").toLowerCase()),
+    ),
+  );
   const configuredAliases = Object.values(cfg.agent?.models ?? {})
     .map((entry) => entry.alias)
-    .filter((alias): alias is string => Boolean(alias));
+    .filter((alias): alias is string => Boolean(alias))
+    .filter((alias) => !reservedCommands.has(alias.toLowerCase()));
   let parsedDirectives = parseInlineDirectives(rawBody, {
     modelAliases: configuredAliases,
   });