fix(scheduler): add duplicate-name and task-size checks to updateJob

Addresses PR ghostwright#87 feedback: updateJob now validates duplicate names
(skipping when unchanged for idempotency) and enforces the 32KB
MAX_TASK_BYTES cap at the service layer, matching createJob behavior.

Co-Authored-By: Claude Opus 4 (1M context) <noreply@anthropic.com>

Author: kagura-agent

src/scheduler/__tests__/service.test.ts

@@ -578,4 +578,48 @@ describe("Scheduler", () => {
 			scheduler.updateJob(job.id, { delivery: { channel: "slack", target: "invalid" } });
 		}).toThrow("invalid delivery.target");
 	});
+
+	test("updateJob rejects duplicate name belonging to another job", () => {
+		const scheduler = new Scheduler({ db, runtime: mockRuntime as never });
+		scheduler.createJob({
+			name: "Existing",
+			schedule: { kind: "every", intervalMs: 60_000 },
+			task: "Task A",
+		});
+		const jobB = scheduler.createJob({
+			name: "Other",
+			schedule: { kind: "every", intervalMs: 60_000 },
+			task: "Task B",
+		});
+
+		expect(() => {
+			scheduler.updateJob(jobB.id, { name: "Existing" });
+		}).toThrow('job with name "Existing" already exists');
+	});
+
+	test("updateJob allows renaming to current name (idempotent)", () => {
+		const scheduler = new Scheduler({ db, runtime: mockRuntime as never });
+		const job = scheduler.createJob({
+			name: "SameName",
+			schedule: { kind: "every", intervalMs: 60_000 },
+			task: "Task",
+		});
+
+		const updated = scheduler.updateJob(job.id, { name: "SameName" });
+		expect(updated?.name).toBe("SameName");
+	});
+
+	test("updateJob rejects task exceeding MAX_TASK_BYTES", () => {
+		const scheduler = new Scheduler({ db, runtime: mockRuntime as never });
+		const job = scheduler.createJob({
+			name: "BigTask",
+			schedule: { kind: "every", intervalMs: 60_000 },
+			task: "small",
+		});
+
+		const huge = "x".repeat(33 * 1024);
+		expect(() => {
+			scheduler.updateJob(job.id, { task: huge });
+		}).toThrow("byte limit");
+	});
 });

src/scheduler/service.ts

@@ -2,7 +2,7 @@ import type { Database } from "bun:sqlite";
 import { randomUUID } from "node:crypto";
 import type { AgentRuntime } from "../agent/runtime.ts";
 import type { SlackTransport } from "../channels/slack-transport.ts";
-import { validateCreateInput } from "./create-validation.ts";
+import { MAX_TASK_BYTES, validateCreateInput } from "./create-validation.ts";
 import { executeJob } from "./executor.ts";
 import { type SchedulerHealthSummary, computeHealthSummary } from "./health.ts";
 import { cleanupOldTerminalJobs, staggerMissedJobs } from "./recovery.ts";
@@ -151,6 +151,24 @@ export class Scheduler {
 			}
 		}
 
+		// Duplicate name detection: skip if unchanged (idempotent rename).
+		if (input.name !== undefined && input.name.toLowerCase() !== job.name.toLowerCase()) {
+			const dupe = this.db
+				.query("SELECT id FROM scheduled_jobs WHERE lower(name) = lower(?)")
+				.get(input.name) as { id: string } | null;
+			if (dupe) {
+				throw new Error(`job with name "${input.name}" already exists (id: ${dupe.id})`);
+			}
+		}
+
+		// Task size cap (mirrors validateCreateInput).
+		if (input.task !== undefined) {
+			const taskBytes = Buffer.byteLength(input.task, "utf8");
+			if (taskBytes > MAX_TASK_BYTES) {
+				throw new Error(`task text is ${taskBytes} bytes, exceeds ${MAX_TASK_BYTES} byte limit`);
+			}
+		}
+
 		// Build dynamic UPDATE statement
 		const updates: string[] = [];
 		const values: (string | number | null)[] = [];