diff --git a/packages/opencode/src/server/instance.ts b/packages/opencode/src/server/instance.ts
index 4bb6efaf9b05..1647ce427044 100644
--- a/packages/opencode/src/server/instance.ts
+++ b/packages/opencode/src/server/instance.ts
@@ -25,6 +25,7 @@ import { ConfigRoutes } from "./routes/config"
 import { ExperimentalRoutes } from "./routes/experimental"
 import { ProviderRoutes } from "./routes/provider"
 import { EventRoutes } from "./routes/event"
+import { TriggerRoutes } from "./routes/trigger"
 import { errorHandler } from "./middleware"
 
 const log = Log.create({ service: "server" })
@@ -51,6 +52,7 @@ export const InstanceRoutes = (app?: Hono) =>
     .route("/permission", PermissionRoutes())
     .route("/question", QuestionRoutes())
     .route("/provider", ProviderRoutes())
+    .route("/trigger", TriggerRoutes())
     .route("/", FileRoutes())
     .route("/", EventRoutes())
     .route("/mcp", McpRoutes())
diff --git a/packages/opencode/src/server/routes/trigger.ts b/packages/opencode/src/server/routes/trigger.ts
new file mode 100644
index 000000000000..bfdbf3343d06
--- /dev/null
+++ b/packages/opencode/src/server/routes/trigger.ts
@@ -0,0 +1,53 @@
+import { Hono } from "hono"
+import { describeRoute, resolver, validator } from "hono-openapi"
+import { Trigger } from "@/trigger"
+import { errors } from "../error"
+import { lazy } from "../../util/lazy"
+
+export const TriggerRoutes = lazy(() =>
+  new Hono()
+    .get(
+      "/",
+      describeRoute({
+        summary: "List triggers",
+        description: "List lightweight scheduled triggers for the current instance.",
+        operationId: "trigger.list",
+        responses: {
+          200: {
+            description: "Triggers",
+            content: {
+              "application/json": {
+                schema: resolver(Trigger.Info.array()),
+              },
+            },
+          },
+        },
+      }),
+      async (c) => {
+        return c.json(await Trigger.list())
+      },
+    )
+    .post(
+      "/",
+      describeRoute({
+        summary: "Create trigger",
+        description: "Register a lightweight scheduled trigger for the current instance.",
+        operationId: "trigger.create",
+        responses: {
+          200: {
+            description: "Trigger",
+            content: {
+              "application/json": {
+                schema: resolver(Trigger.Info),
+              },
+            },
+          },
+          ...errors(400),
+        },
+      }),
+      validator("json", Trigger.CreateInput),
+      async (c) => {
+        return c.json(await Trigger.create(c.req.valid("json")))
+      },
+    ),
+)
diff --git a/packages/opencode/src/trigger/index.ts b/packages/opencode/src/trigger/index.ts
new file mode 100644
index 000000000000..fc54a12f78f6
--- /dev/null
+++ b/packages/opencode/src/trigger/index.ts
@@ -0,0 +1,151 @@
+import { randomUUID } from "node:crypto"
+import { Bus } from "@/bus"
+import { BusEvent } from "@/bus/bus-event"
+import { InstanceState } from "@/effect/instance-state"
+import { makeRuntime } from "@/effect/run-service"
+import { Cause, Duration, Effect, Layer, Schedule, ServiceMap } from "effect"
+import z from "zod"
+import { Log } from "../util/log"
+
+export namespace Trigger {
+  const log = Log.create({ service: "trigger" })
+
+  export const Info = z
+    .object({
+      id: z.string(),
+      schedule: z.object({
+        type: z.literal("interval"),
+        interval: z.number().int().positive(),
+      }),
+      runs: z.number().int().nonnegative(),
+      time: z.object({
+        created: z.number().int().nonnegative(),
+        last: z.number().int().nonnegative().optional(),
+        next: z.number().int().nonnegative(),
+      }),
+    })
+    .meta({
+      ref: "Trigger",
+    })
+  export type Info = z.infer<typeof Info>
+
+  export const CreateInput = z.object({
+    interval: z.number().int().min(10).max(86_400_000),
+  })
+  export type CreateInput = z.infer<typeof CreateInput>
+
+  export const Event = {
+    Fired: BusEvent.define(
+      "trigger.fired",
+      z.object({
+        triggerID: z.string(),
+        runs: z.number().int().nonnegative(),
+        at: z.number().int().nonnegative(),
+      }),
+    ),
+  }
+
+  type State = {
+    create: (input: CreateInput) => Effect.Effect<Info>
+    list: () => Effect.Effect<Info[]>
+  }
+
+  export interface Interface {
+    readonly create: (input: CreateInput) => Effect.Effect<Info>
+    readonly list: () => Effect.Effect<Info[]>
+  }
+
+  export class Service extends ServiceMap.Service<Service, Interface>()("@opencode/Trigger") {}
+
+  export const layer = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const state = yield* InstanceState.make<State>(
+        Effect.fn("Trigger.state")(function* () {
+          const data = new Map<string, Info>()
+
+          const tick = Effect.fnUntraced(function* () {
+            const now = Date.now()
+            yield* Effect.forEach(
+              Array.from(data.values()).filter((item) => item.time.next <= now),
+              (item) =>
+                Effect.gen(function* () {
+                  const at = Date.now()
+                  const next = {
+                    ...item,
+                    runs: item.runs + 1,
+                    time: {
+                      ...item.time,
+                      last: at,
+                      next: at + item.schedule.interval,
+                    },
+                  }
+                  data.set(item.id, next)
+                  yield* bus.publish(Event.Fired, {
+                    triggerID: item.id,
+                    runs: next.runs,
+                    at,
+                  })
+                }),
+              { discard: true },
+            )
+          })
+
+          yield* tick().pipe(
+            Effect.catchCause((cause) => {
+              log.error("tick loop failed", { cause: Cause.pretty(cause) })
+              return Effect.void
+            }),
+            Effect.repeat(Schedule.spaced(Duration.millis(10))),
+            Effect.forkScoped,
+          )
+
+          const create = Effect.fn("Trigger.create")(function* (input: CreateInput) {
+            const now = Date.now()
+            const item = {
+              id: `trg_${randomUUID().replaceAll("-", "")}`,
+              schedule: {
+                type: "interval" as const,
+                interval: input.interval,
+              },
+              runs: 0,
+              time: {
+                created: now,
+                next: now + input.interval,
+              },
+            } satisfies Info
+            data.set(item.id, item)
+            return item
+          })
+
+          const list = Effect.fn("Trigger.list")(() =>
+            Effect.succeed(Array.from(data.values()).sort((a, b) => a.time.created - b.time.created)),
+          )
+
+          return { create, list }
+        }),
+      )
+
+      return Service.of({
+        create: Effect.fn("Trigger.create")(function* (input: CreateInput) {
+          return yield* InstanceState.useEffect(state, (svc) => svc.create(input))
+        }),
+        list: Effect.fn("Trigger.list")(function* () {
+          return yield* InstanceState.useEffect(state, (svc) => svc.list())
+        }),
+      })
+    }),
+  )
+
+  const defaultLayer = layer.pipe(Layer.provide(Bus.layer))
+  const { runPromise } = makeRuntime(Service, defaultLayer)
+
+  export async function create(input: CreateInput) {
+    return runPromise((svc) => svc.create(input))
+  }
+
+  export async function list() {
+    return runPromise((svc) => svc.list())
+  }
+}
diff --git a/packages/opencode/test/server/trigger.test.ts b/packages/opencode/test/server/trigger.test.ts
new file mode 100644
index 000000000000..4a03a4e9a7d1
--- /dev/null
+++ b/packages/opencode/test/server/trigger.test.ts
@@ -0,0 +1,45 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import { Instance } from "../../src/project/instance"
+import { Server } from "../../src/server/server"
+import { tmpdir } from "../fixture/fixture"
+
+afterEach(async () => {
+  await Instance.disposeAll()
+})
+
+describe("trigger routes", () => {
+  test("creates and lists triggers", async () => {
+    await using tmp = await tmpdir({ git: true })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const app = Server.Default()
+
+        const create = await app.request("/trigger", {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({ interval: 20 }),
+        })
+
+        expect(create.status).toBe(200)
+        const item = await create.json()
+        expect(item).toMatchObject({
+          schedule: { interval: 20 },
+          runs: 0,
+        })
+
+        await Bun.sleep(80)
+
+        const list = await app.request("/trigger")
+        expect(list.status).toBe(200)
+        const body = await list.json()
+        expect(body).toHaveLength(1)
+        expect(body[0]).toMatchObject({
+          id: item.id,
+          schedule: { type: "interval", interval: 20 },
+        })
+        expect(body[0].runs).toBeGreaterThan(0)
+      },
+    })
+  })
+})
diff --git a/packages/opencode/test/trigger/trigger.test.ts b/packages/opencode/test/trigger/trigger.test.ts
new file mode 100644
index 000000000000..35d54b6e10b4
--- /dev/null
+++ b/packages/opencode/test/trigger/trigger.test.ts
@@ -0,0 +1,42 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import { Instance } from "../../src/project/instance"
+import { Trigger } from "../../src/trigger"
+import { tmpdir } from "../fixture/fixture"
+
+afterEach(async () => {
+  await Instance.disposeAll()
+})
+
+describe("trigger service", () => {
+  test("creates triggers per instance and fires them later", async () => {
+    await using a = await tmpdir({ git: true })
+    await using b = await tmpdir({ git: true })
+
+    await Instance.provide({
+      directory: a.path,
+      fn: async () => {
+        const item = await Trigger.create({ interval: 20 })
+        const list = await Trigger.list()
+        expect(list).toHaveLength(1)
+        expect(list[0]).toMatchObject({
+          id: item.id,
+          schedule: { interval: 20 },
+          runs: 0,
+        })
+
+        await Bun.sleep(80)
+
+        const next = (await Trigger.list())[0]
+        expect(next?.runs).toBeGreaterThan(0)
+        expect(next?.time.last).toBeGreaterThanOrEqual(next!.time.created)
+      },
+    })
+
+    await Instance.provide({
+      directory: b.path,
+      fn: async () => {
+        expect(await Trigger.list()).toEqual([])
+      },
+    })
+  })
+})