feat: Cancel workflow by id via the client

packages/openworkflow/client.test.ts

@@ -412,6 +412,33 @@ describe("OpenWorkflow", () => {
     expect(workflowRun?.finishedAt).not.toBeNull();
   });
 
+  test("cancels workflow run via client by ID", async () => {
+    const backend = await createBackend();
+    const client = new OpenWorkflow({ backend });
+
+    const workflow = client.defineWorkflow({ name: "cancel-test" }, noopFn);
+    const handle = await workflow.run({ value: 1 });
+
+    await client.cancelWorkflowRun(handle.workflowRun.id);
+
+    const workflowRun = await backend.getWorkflowRun({
+      workflowRunId: handle.workflowRun.id,
+    });
+    expect(workflowRun?.status).toBe("canceled");
+    expect(workflowRun?.finishedAt).not.toBeNull();
+  });
+
+  test("throws when canceling a non-existent workflow run", async () => {
+    const backend = await createBackend();
+    const client = new OpenWorkflow({ backend });
+
+    const nonExistentId = randomUUID();
+
+    await expect(client.cancelWorkflowRun(nonExistentId)).rejects.toThrow(
+      `Workflow run ${nonExistentId} does not exist`,
+    );
+  });
+
   describe("defineWorkflowSpec / implementWorkflow API", () => {
     test("defineWorkflowSpec returns a spec that can be used to schedule runs", async () => {
       const backend = await createBackend();

packages/openworkflow/client.ts

@@ -157,6 +157,20 @@ export class OpenWorkflow {
 
     return new RunnableWorkflow(this, workflow);
   }
+
+  /**
+   * Cancels the workflow run with the given ID. Only workflow runs in pending, running, or sleeping
+   * status can be canceled.
+   * @param workflowRunId - The ID of the workflow run to cancel
+   * @returns Promise<void>
+   * @example
+   * ```ts
+   * await ow.cancelWorkflowRun("123");
+   * ```
+   */
+  async cancelWorkflowRun(workflowRunId: string): Promise<void> {
+    await this.backend.cancelWorkflowRun({ workflowRunId });
+  }
 }
 
 /**