diff --git a/src/agents/index.ts b/src/agents/index.ts
index f29a86d..7b4621f 100644
--- a/src/agents/index.ts
+++ b/src/agents/index.ts
@@ -3,7 +3,11 @@ import {
   OneCLIRequestError,
   toOneCLIError,
 } from "../errors.js";
-import type { CreateAgentInput, CreateAgentResponse } from "./types.js";
+import type {
+  CreateAgentInput,
+  CreateAgentResponse,
+  EnsureAgentResponse,
+} from "./types.js";
 
 export class AgentsClient {
   private baseUrl: string;
@@ -57,4 +61,26 @@ export class AgentsClient {
       throw toOneCLIError(error);
     }
   };
+
+  /**
+   * Ensure an agent exists. Creates it if missing, returns normally if it already exists.
+   * Unlike `createAgent`, this method treats a 409 conflict as success.
+   */
+  ensureAgent = async (
+    input: CreateAgentInput,
+  ): Promise<EnsureAgentResponse> => {
+    try {
+      await this.createAgent(input);
+      return { name: input.name, identifier: input.identifier, created: true };
+    } catch (error) {
+      if (error instanceof OneCLIRequestError && error.statusCode === 409) {
+        return {
+          name: input.name,
+          identifier: input.identifier,
+          created: false,
+        };
+      }
+      throw error;
+    }
+  };
 }
diff --git a/src/agents/types.ts b/src/agents/types.ts
index 24d86ac..d2913ed 100644
--- a/src/agents/types.ts
+++ b/src/agents/types.ts
@@ -12,3 +12,10 @@ export interface CreateAgentResponse {
   identifier: string;
   createdAt: string;
 }
+
+export interface EnsureAgentResponse {
+  name: string;
+  identifier: string;
+  /** Whether the agent was newly created. `false` if it already existed. */
+  created: boolean;
+}
diff --git a/src/client.ts b/src/client.ts
index 2bfcccb..6b3e87c 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -8,6 +8,7 @@ import type {
 import type {
   CreateAgentInput,
   CreateAgentResponse,
+  EnsureAgentResponse,
 } from "./agents/types.js";
 
 const DEFAULT_URL = "https://app.onecli.sh";
@@ -50,4 +51,11 @@ export class OneCLI {
   createAgent = (input: CreateAgentInput): Promise<CreateAgentResponse> => {
     return this.agentsClient.createAgent(input);
   };
+
+  /**
+   * Ensure an agent exists. Creates it if missing, returns normally if it already exists.
+   */
+  ensureAgent = (input: CreateAgentInput): Promise<EnsureAgentResponse> => {
+    return this.agentsClient.ensureAgent(input);
+  };
 }
diff --git a/src/index.ts b/src/index.ts
index 01219ca..1c6fb97 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -11,4 +11,5 @@ export type {
 export type {
   CreateAgentInput,
   CreateAgentResponse,
+  EnsureAgentResponse,
 } from "./agents/types.js";
diff --git a/test/agents/client.test.ts b/test/agents/client.test.ts
index e949055..94ec54e 100644
--- a/test/agents/client.test.ts
+++ b/test/agents/client.test.ts
@@ -162,7 +162,7 @@ describe("AgentsClient", () => {
       ).rejects.toThrow("fetch failed");
     });
 
-    it("re-throws OneCLIRequestError without wrapping", async () => {
+    it("re-throws OneCLIRequestError on 500 without wrapping", async () => {
       fetchSpy = vi.spyOn(globalThis, "fetch").mockResolvedValue(
         new Response("", { status: 500, statusText: "Internal Server Error" }),
       );
@@ -180,4 +180,88 @@ describe("AgentsClient", () => {
       expect((err as OneCLIRequestError).name).toBe("OneCLIRequestError");
     });
   });
+
+  describe("ensureAgent", () => {
+    it("returns created: true when agent is newly created", async () => {
+      fetchSpy = vi.spyOn(globalThis, "fetch").mockResolvedValue(
+        new Response(JSON.stringify(MOCK_AGENT), { status: 201 }),
+      );
+
+      const client = new AgentsClient(
+        "http://localhost:3000",
+        "oc_test",
+        5000,
+      );
+      const result = await client.ensureAgent({
+        name: "My Agent",
+        identifier: "my-agent",
+      });
+
+      expect(result).toEqual({
+        name: "My Agent",
+        identifier: "my-agent",
+        created: true,
+      });
+    });
+
+    it("returns created: false when agent already exists (409)", async () => {
+      fetchSpy = vi.spyOn(globalThis, "fetch").mockResolvedValue(
+        new Response(
+          JSON.stringify({ error: "identifier already exists" }),
+          { status: 409, statusText: "Conflict" },
+        ),
+      );
+
+      const client = new AgentsClient(
+        "http://localhost:3000",
+        "oc_test",
+        5000,
+      );
+      const result = await client.ensureAgent({
+        name: "My Agent",
+        identifier: "my-agent",
+      });
+
+      expect(result).toEqual({
+        name: "My Agent",
+        identifier: "my-agent",
+        created: false,
+      });
+    });
+
+    it("throws on non-409 errors", async () => {
+      fetchSpy = vi.spyOn(globalThis, "fetch").mockResolvedValue(
+        new Response(JSON.stringify({ error: "Unauthorized" }), {
+          status: 401,
+          statusText: "Unauthorized",
+        }),
+      );
+
+      const client = new AgentsClient(
+        "http://localhost:3000",
+        "oc_bad",
+        5000,
+      );
+
+      await expect(
+        client.ensureAgent({ name: "Test", identifier: "test" }),
+      ).rejects.toThrow(OneCLIRequestError);
+    });
+
+    it("throws on network errors", async () => {
+      fetchSpy = vi
+        .spyOn(globalThis, "fetch")
+        .mockRejectedValue(new TypeError("fetch failed"));
+
+      const client = new AgentsClient(
+        "http://localhost:3000",
+        "oc_test",
+        5000,
+      );
+
+      await expect(
+        client.ensureAgent({ name: "Test", identifier: "test" }),
+      ).rejects.toThrow(OneCLIError);
+    });
+  });
 });