diff --git a/packages/cli/src/commands/handlers/console/login.ts b/packages/cli/src/commands/handlers/console/login.ts
index 9025c67c21..99af278a35 100644
--- a/packages/cli/src/commands/handlers/console/login.ts
+++ b/packages/cli/src/commands/handlers/console/login.ts
@@ -35,7 +35,7 @@ const login = Effect.fn("cli.console.login.run")(function* (timeline: TimelineHo
   yield* request(() => timeline.intro("Log in"))
   yield* request(() => timeline.pending("Connecting to OpenCode..."))
 
-  const endpoint = yield* Service.start(yield* ServiceConfig.options())
+  const endpoint = yield* Service.ensure(yield* ServiceConfig.options())
   const client = OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) })
   const found = yield* request((signal) => client.integration.get({ integrationID, location }, { signal }))
   const integration = yield* required(found.data, "OpenCode Console integration is unavailable")
diff --git a/packages/cli/src/commands/handlers/debug/agents.ts b/packages/cli/src/commands/handlers/debug/agents.ts
index f3cd7c1b12..c178e90b45 100644
--- a/packages/cli/src/commands/handlers/debug/agents.ts
+++ b/packages/cli/src/commands/handlers/debug/agents.ts
@@ -11,7 +11,7 @@ export default Runtime.handler(
   Effect.fn("cli.debug.agents")(function* () {
     const options = yield* ServiceConfig.options()
     const found = yield* Service.discover(options)
-    const endpoint = found ?? (yield* Service.start(options))
+    const endpoint = found ?? (yield* Service.ensure(options))
     const client = OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) })
     const response = yield* Effect.promise(() => client.agent.list({ location: { directory: process.cwd() } }))
     process.stdout.write(
diff --git a/packages/cli/src/commands/handlers/mcp/auth.ts b/packages/cli/src/commands/handlers/mcp/auth.ts
index a6ebe09b47..32e728b435 100644
--- a/packages/cli/src/commands/handlers/mcp/auth.ts
+++ b/packages/cli/src/commands/handlers/mcp/auth.ts
@@ -19,7 +19,7 @@ export default Runtime.handler(
   Effect.fn("cli.mcp.auth")(function* (input) {
     const options = yield* ServiceConfig.options()
     const found = yield* Service.discover(options)
-    const endpoint = found ?? (yield* Service.start(options))
+    const endpoint = found ?? (yield* Service.ensure(options))
     const client = OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) })
 
     const integration = yield* resolveIntegration(client, input.name, location)
diff --git a/packages/cli/src/commands/handlers/mcp/list.ts b/packages/cli/src/commands/handlers/mcp/list.ts
index a44aa9af9c..590fb818c5 100644
--- a/packages/cli/src/commands/handlers/mcp/list.ts
+++ b/packages/cli/src/commands/handlers/mcp/list.ts
@@ -11,7 +11,7 @@ export default Runtime.handler(
   Effect.fn("cli.mcp.list")(function* () {
     const options = yield* ServiceConfig.options()
     const found = yield* Service.discover(options)
-    const endpoint = found ?? (yield* Service.start(options))
+    const endpoint = found ?? (yield* Service.ensure(options))
     const client = OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) })
     const response = yield* Effect.promise(() => client.mcp.list({ location: { directory: process.cwd() } }))
     const servers = response.data.toSorted((a, b) => a.name.localeCompare(b.name))
diff --git a/packages/cli/src/commands/handlers/mcp/logout.ts b/packages/cli/src/commands/handlers/mcp/logout.ts
index 7e1aaac1d2..47dc3052a6 100644
--- a/packages/cli/src/commands/handlers/mcp/logout.ts
+++ b/packages/cli/src/commands/handlers/mcp/logout.ts
@@ -14,7 +14,7 @@ export default Runtime.handler(
   Effect.fn("cli.mcp.logout")(function* (input) {
     const options = yield* ServiceConfig.options()
     const found = yield* Service.discover(options)
-    const endpoint = found ?? (yield* Service.start(options))
+    const endpoint = found ?? (yield* Service.ensure(options))
     const client = OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) })
 
     const integration = yield* resolveIntegration(client, input.name, location)
diff --git a/packages/cli/src/commands/handlers/pair.ts b/packages/cli/src/commands/handlers/pair.ts
index be4c8d97fc..edbae68f6c 100644
--- a/packages/cli/src/commands/handlers/pair.ts
+++ b/packages/cli/src/commands/handlers/pair.ts
@@ -10,7 +10,7 @@ import { ServiceConfig } from "../../services/service-config"
 export default Runtime.handler(
   Commands.commands.pair,
   Effect.fn("cli.pair")(function* () {
-    const endpoint = yield* Service.start(yield* ServiceConfig.options())
+    const endpoint = yield* Service.ensure(yield* ServiceConfig.options())
     const password = yield* ServiceConfig.password()
     const server = yield* Effect.tryPromise(() =>
       OpenCode.make({ baseUrl: endpoint.url, headers: Service.headers(endpoint) }).server.get(),
diff --git a/packages/cli/src/commands/handlers/service/restart.ts b/packages/cli/src/commands/handlers/service/restart.ts
index fbe1ecca63..fe306dcb02 100644
--- a/packages/cli/src/commands/handlers/service/restart.ts
+++ b/packages/cli/src/commands/handlers/service/restart.ts
@@ -10,7 +10,7 @@ export default Runtime.handler(
   Effect.fn("cli.service.restart")(function* () {
     const options = yield* ServiceConfig.options()
     yield* Service.stop(options)
-    const transport = yield* Service.start(options)
+    const transport = yield* Service.ensure(options)
     process.stdout.write(transport.url + EOL)
   }),
 )
diff --git a/packages/cli/src/commands/handlers/service/start.ts b/packages/cli/src/commands/handlers/service/start.ts
index 8dff91376f..dfdbac3997 100644
--- a/packages/cli/src/commands/handlers/service/start.ts
+++ b/packages/cli/src/commands/handlers/service/start.ts
@@ -8,7 +8,7 @@ import { ServiceConfig } from "../../../services/service-config"
 export default Runtime.handler(
   Commands.commands.service.commands.start,
   Effect.fn("cli.service.start")(function* () {
-    const transport = yield* Service.start(yield* ServiceConfig.options())
+    const transport = yield* Service.ensure(yield* ServiceConfig.options())
     process.stdout.write(transport.url + EOL)
   }),
 )
diff --git a/packages/cli/src/services/server-connection.ts b/packages/cli/src/services/server-connection.ts
index 87b2c81e7c..4eccc95bc9 100644
--- a/packages/cli/src/services/server-connection.ts
+++ b/packages/cli/src/services/server-connection.ts
@@ -1,4 +1,4 @@
-import { Service, type Endpoint, type StartOptions } from "@opencode-ai/client/effect/service"
+import { Service, type Endpoint, type EnsureOptions } from "@opencode-ai/client/effect/service"
 import { ClientError, isUnauthorizedError, OpenCode } from "@opencode-ai/client/promise"
 import { InstallationVersion } from "@opencode-ai/core/installation/version"
 import { Effect, Redacted } from "effect"
@@ -10,7 +10,7 @@ export type Args = {
   readonly server?: string
   readonly standalone?: boolean
   readonly mismatch?: "replace" | "ignore" | "error"
-  readonly onStart?: StartOptions["onStart"]
+  readonly onStart?: EnsureOptions["onStart"]
 }
 
 export type Resolved = {
@@ -49,31 +49,31 @@ export const resolve = Effect.fn("cli.server-connection.resolve")(function* (arg
   } satisfies Resolved
 })
 
-function managedService(options: StartOptions) {
+function managedService(options: EnsureOptions) {
   const reconnectOptions = { ...options, version: undefined }
   return {
-    reconnect: () => Service.start(reconnectOptions),
+    reconnect: () => Service.ensure(reconnectOptions),
     restart: () =>
       Effect.gen(function* () {
         yield* Service.stop(options)
-        yield* Service.start(options)
+        yield* Service.ensure(options)
       }),
   }
 }
 
 const resolveManaged = Effect.fnUntraced(function* (
-  options: StartOptions,
+  options: EnsureOptions,
   mismatch: NonNullable<Args["mismatch"]>,
 ) {
-  if (mismatch === "replace") return yield* Service.start(options)
-  if (mismatch === "ignore") return yield* Service.start({ ...options, version: undefined })
+  if (mismatch === "replace") return yield* Service.ensure(options)
+  if (mismatch === "ignore") return yield* Service.ensure({ ...options, version: undefined })
 
   const compatible = yield* Service.discover(options)
   if (compatible !== undefined) return compatible
   const existing = yield* Service.discover({ ...options, version: undefined })
   if (existing !== undefined)
     return yield* Effect.fail(new Error("Background server version does not match this client"))
-  return yield* Service.start(options)
+  return yield* Service.ensure(options)
 })
 
 function connectError(endpoint: Endpoint, cause: unknown) {
diff --git a/packages/cli/src/services/service-config.ts b/packages/cli/src/services/service-config.ts
index 80e0fb42b0..2446d30730 100644
--- a/packages/cli/src/services/service-config.ts
+++ b/packages/cli/src/services/service-config.ts
@@ -6,7 +6,7 @@ import { Effect, FileSystem, Option, Schema } from "effect"
 import { randomBytes } from "crypto"
 import path from "path"
 
-// The CLI's service configuration file, plus the Service.StartOptions binding that
+// The CLI's service configuration file, plus the Service.EnsureOptions binding that
 // points the client package's service operations at this CLI: which
 // registration file (by channel), which version, and how to spawn opencode.
 
diff --git a/packages/client/src/effect/service.ts b/packages/client/src/effect/service.ts
index aad67dba3c..e4bf5bbefb 100644
--- a/packages/client/src/effect/service.ts
+++ b/packages/client/src/effect/service.ts
@@ -6,7 +6,7 @@ import { join } from "node:path"
 import type {
   DiscoverOptions,
   Endpoint,
-  StartOptions,
+  EnsureOptions,
   StopOptions,
 } from "../service.js"
 
@@ -28,7 +28,7 @@ type Contender = {
 }
 
 // Read-only lookup: registration file plus health check and version gate.
-// Never spawns; escalation to start() is the caller's policy.
+// Never spawns; escalation to ensure() is the caller's policy.
 /** Discover a healthy, compatible local service without starting one. */
 export const discover = Effect.fn("service.discover")(function* (options: DiscoverOptions = {}) {
   return (yield* discoverLocal(options))?.endpoint
@@ -45,7 +45,7 @@ const discoverLocal = Effect.fnUntraced(function* (options: DiscoverOptions) {
 // version-mismatched one, and otherwise spawns small contenders until a server
 // becomes discoverable. A contender is never killed merely for slow startup.
 /** Ensure a healthy, compatible local service is running. */
-export const start = Effect.fn("service.start")(function* (options: StartOptions = {}) {
+export const ensure = Effect.fn("service.ensure")(function* (options: EnsureOptions = {}) {
   const contenders = new Set<Contender>()
   let announced = false
   let lastSpawn = 0
@@ -219,7 +219,7 @@ const find = Effect.fnUntraced(function* (options: { readonly file?: string }) {
   return (yield* registered(options.file, true)).service
 })
 
-// 50ms cadence bounded at ~5s, shared by stop escalation and each start
+// 50ms cadence bounded at ~5s, shared by stop escalation and each ensure
 // discovery window.
 const poll = Schedule.spaced("50 millis").pipe(Schedule.both(Schedule.recurs(100)))
 
@@ -280,4 +280,4 @@ const requestStop = Effect.fnUntraced(function* (service: LocalService) {
 })
 
 /** Effect-based local service lifecycle operations. */
-export const Service = { discover, start, stop, headers, Info }
+export const Service = { discover, ensure, stop, headers, Info }
diff --git a/packages/client/src/promise/service.ts b/packages/client/src/promise/service.ts
index e6037e387b..aecaf95f4f 100644
--- a/packages/client/src/promise/service.ts
+++ b/packages/client/src/promise/service.ts
@@ -6,7 +6,7 @@ import type {
   DiscoverOptions,
   Endpoint,
   Info,
-  StartOptions,
+  EnsureOptions,
   StopOptions,
 } from "../service.js"
 import type { ServiceHealth, ServiceStopResponse } from "./generated/types.js"
@@ -37,7 +37,7 @@ async function discoverLocal(options: DiscoverOptions) {
 }
 
 /** Ensure a healthy, compatible local service is running. */
-export async function start(options: StartOptions = {}): Promise<Endpoint> {
+export async function ensure(options: EnsureOptions = {}): Promise<Endpoint> {
   const contenders = new Set<Contender>()
   let announced = false
   let lastSpawn = 0
@@ -249,4 +249,4 @@ function delay(milliseconds: number) {
 }
 
 /** Promise-based local service lifecycle operations. */
-export const Service = { discover, start, stop, headers }
+export const Service = { discover, ensure, stop, headers }
diff --git a/packages/client/src/service.ts b/packages/client/src/service.ts
index 11254fc843..96d54871f6 100644
--- a/packages/client/src/service.ts
+++ b/packages/client/src/service.ts
@@ -21,15 +21,15 @@ export type DiscoverOptions = {
   readonly version?: string
 }
 
-/** Reason a new service process must be started. */
-export type StartReason = "missing" | "version-mismatch"
+/** Reason ensuring the service requires a new process. */
+export type EnsureReason = "missing" | "version-mismatch"
 
 /** Options used to ensure the local OpenCode service is running. */
-export type StartOptions = DiscoverOptions & {
+export type EnsureOptions = DiscoverOptions & {
   /** Service command and arguments. Defaults to `opencode serve --service`. */
   readonly command?: ReadonlyArray<string>
   /** Called once before spawning a new service process. */
-  readonly onStart?: (reason: StartReason, previousVersion?: string) => void
+  readonly onStart?: (reason: EnsureReason, previousVersion?: string) => void
 }
 
 /** Options used to stop the local OpenCode service. */
diff --git a/packages/client/test/promise-service.test.ts b/packages/client/test/promise-service.test.ts
index dc422f07bc..1cf6757a78 100644
--- a/packages/client/test/promise-service.test.ts
+++ b/packages/client/test/promise-service.test.ts
@@ -2,7 +2,7 @@ import { afterEach, expect, test } from "bun:test"
 import { mkdtemp, rm } from "node:fs/promises"
 import { tmpdir } from "node:os"
 import { join } from "node:path"
-import { Service, type StartReason } from "../src/promise/service"
+import { Service, type EnsureReason } from "../src/promise/service"
 
 const fixture = join(import.meta.dir, "fixture/service.ts")
 const processes: Bun.Subprocess[] = []
@@ -23,12 +23,12 @@ test("discovers a registered service", async () => {
   expect(await Service.discover({ file: registration, version: "other" })).toBeUndefined()
 })
 
-test("starts a missing service with native promises", async () => {
+test("ensures a missing service with native promises", async () => {
   const directory = await temp()
   const registration = join(directory, "service.json")
-  const starts: StartReason[] = []
+  const starts: EnsureReason[] = []
 
-  const endpoint = await Service.start({
+  const endpoint = await Service.ensure({
     file: registration,
     version: "test",
     command: [process.execPath, fixture, registration, "coordinated"],
@@ -47,7 +47,7 @@ test("starts a missing service with native promises", async () => {
 test("reports a failed registered service", async () => {
   const registration = await setup("failed-owner")
 
-  await expect(Service.start({ file: registration, version: "test", command: [] })).rejects.toThrow(
+  await expect(Service.ensure({ file: registration, version: "test", command: [] })).rejects.toThrow(
     "Background service failed to start",
   )
 })
diff --git a/packages/client/test/service.test.ts b/packages/client/test/service.test.ts
index c3ebcb1580..8e73536bca 100644
--- a/packages/client/test/service.test.ts
+++ b/packages/client/test/service.test.ts
@@ -4,7 +4,7 @@ import { Effect } from "effect"
 import { mkdtemp, rm, writeFile } from "node:fs/promises"
 import { tmpdir } from "node:os"
 import { join } from "node:path"
-import { Service, type StartReason } from "../src/effect/service"
+import { Service, type EnsureReason } from "../src/effect/service"
 
 const fixture = join(import.meta.dir, "fixture/service.ts")
 const processes: Bun.Subprocess[] = []
@@ -23,9 +23,9 @@ test("a concurrent same-version start cannot invalidate a resolved endpoint", as
   await waitForFile(registration)
   const original = await Bun.file(registration).json()
 
-  const starts: StartReason[] = []
+  const starts: EnsureReason[] = []
   const first = run(
-    Service.start({
+    Service.ensure({
       file: registration,
       version: "test",
       command: [],
@@ -34,7 +34,7 @@ test("a concurrent same-version start cannot invalidate a resolved endpoint", as
   )
   await waitForFile(registration + ".first-request")
 
-  const resolved = await run(Service.start({ file: registration, version: "test" }))
+  const resolved = await run(Service.ensure({ file: registration, version: "test" }))
   expect(resolved.url).toBe(original.url)
 
   await writeFile(registration + ".release", "")
@@ -50,7 +50,7 @@ test("waits for a registered service to finish starting", async () => {
   const registration = join(directory, "service.json")
   const process = spawn(registration, "starting")
   await waitForFile(registration)
-  const result = run(Service.start({ file: registration, version: "test", command: [] }))
+  const result = run(Service.ensure({ file: registration, version: "test", command: [] }))
 
   await Bun.sleep(500)
   expect(process.exitCode).toBe(null)
@@ -64,7 +64,7 @@ test("reports a failed registered service without spawning", async () => {
   const process = spawn(registration, "failed-owner")
   await waitForFile(registration)
 
-  await expect(run(Service.start({ file: registration, version: "test", command: [] }))).rejects.toThrow(
+  await expect(run(Service.ensure({ file: registration, version: "test", command: [] }))).rejects.toThrow(
     "Background service failed to start",
   )
   expect(process.exitCode).toBe(null)
@@ -90,7 +90,7 @@ test("does not spawn contenders while an incompatible service rejects replacemen
   await waitForFile(registration)
   const controller = new AbortController()
   const starting = Effect.runPromise(
-    Service.start({
+    Service.ensure({
       file: registration,
       version: "test",
       command: [process.execPath, fixture, contender, "record-start"],
@@ -113,8 +113,8 @@ test("a legacy health response is still replaced", async () => {
   const existing = spawn(registration, "legacy")
   await waitForFile(registration)
 
-  const starts: StartReason[] = []
-  const result = run(Service.start({ file: registration, command: [], onStart: (reason) => starts.push(reason) }))
+  const starts: EnsureReason[] = []
+  const result = run(Service.ensure({ file: registration, command: [], onStart: (reason) => starts.push(reason) }))
 
   await expect(result).rejects.toThrow("Missing service command")
   expect(starts).toEqual(["version-mismatch"])
@@ -125,7 +125,7 @@ test("waits for a slow winner while bounding lock probes", async () => {
   const directory = await temp()
   const registration = join(directory, "service.json")
   const endpoint = await run(
-    Service.start({
+    Service.ensure({
       file: registration,
       version: "test",
       command: [process.execPath, fixture, registration, "coordinated"],
@@ -146,7 +146,7 @@ test("reports a contender that fails to start", async () => {
   const registration = join(directory, "service.json")
   await expect(
     run(
-      Service.start({
+      Service.ensure({
         file: registration,
         version: "test",
         command: [process.execPath, fixture, registration, "failed"],
@@ -160,7 +160,7 @@ test("reports a contender terminated by a signal", async () => {
   const registration = join(directory, "service.json")
   await expect(
     run(
-      Service.start({
+      Service.ensure({
         file: registration,
         version: "test",
         command: [process.execPath, fixture, registration, "signal"],
@@ -174,7 +174,7 @@ test("reports a slow contender that eventually fails", async () => {
   const registration = join(directory, "service.json")
   await expect(
     run(
-      Service.start({
+      Service.ensure({
         file: registration,
         version: "test",
         command: [process.execPath, fixture, registration, "delayed-failed", "8000"],
@@ -187,7 +187,7 @@ test("replaces an incompatible owner that appears during startup", async () => {
   const directory = await temp()
   const registration = join(directory, "service.json")
   const starting = run(
-    Service.start({
+    Service.ensure({
       file: registration,
       version: "test",
       command: [process.execPath, fixture, registration, "delayed", "8000"],
diff --git a/packages/docs/build/client.mdx b/packages/docs/build/client.mdx
index f759e04d45..0465dd6fed 100644
--- a/packages/docs/build/client.mdx
+++ b/packages/docs/build/client.mdx
@@ -70,23 +70,23 @@ for await (const event of client.event.subscribe()) {
 }
 ```
 
-## Local service
+## Local background service
 
-`Service` discovers and manages the local OpenCode background service from a
-Node application. The Promise API uses Node APIs directly and does not require
-Effect or `@effect/platform-node`.
+The main client entrypoints are browser-compatible and do not include local
+process management. In a Node application, import the native Promise service
+API from `@opencode-ai/client/service`.
 
 - `Service.discover()` returns a healthy registered endpoint without starting
   a process.
-- `Service.start()` reuses a compatible service or starts one when needed.
-- `Service.stop()` stops the registered service.
+- `Service.ensure()` returns a compatible service, starting one when needed.
+- `Service.stop()` stops the exact registered service instance.
 - `Service.headers(endpoint)` creates the authentication headers for a client.
 
 ```ts
 import { OpenCode } from "@opencode-ai/client"
 import { Service } from "@opencode-ai/client/service"
 
-const endpoint = await Service.start()
+const endpoint = await Service.ensure()
 const client = OpenCode.make({
   baseUrl: endpoint.url,
   headers: Service.headers(endpoint),
@@ -95,7 +95,22 @@ const client = OpenCode.make({
 const health = await client.health.get()
 ```
 
-Import the native Promise service API from `@opencode-ai/client/service`.
+`Service.ensure()` accepts an optional registration file, required version,
+service command, and `onStart` callback:
+
+```ts
+const endpoint = await Service.ensure({
+  file: "/var/run/opencode/service.json",
+  version: "2.0.0",
+  command: ["opencode", "serve", "--service"],
+  onStart(reason, previousVersion) {
+    console.log(reason, previousVersion)
+  },
+})
+```
+
+Omit these options to use the standard registration path and
+`opencode serve --service` command.
 
 ## Effect
 
@@ -133,11 +148,11 @@ const session = await Effect.runPromise(
 Streaming operations, including `client.event.subscribe()` and
 `client.session.log(...)`, return Effect `Stream` values.
 
-### Local service
+### Local background service
 
-The Effect entrypoint exposes the same service lifecycle operations as Effect
-values. Add `@effect/platform-node` and provide its filesystem layer when
-running service operations.
+The Node-only `@opencode-ai/client/effect/service` entrypoint exposes the same
+operations as Effect values. Add `@effect/platform-node` and provide its
+filesystem layer when running them.
 
 ```sh
 bun add @effect/platform-node
@@ -151,7 +166,7 @@ import { Effect } from "effect"
 import { FetchHttpClient } from "effect/unstable/http"
 
 const program = Effect.gen(function* () {
-  const endpoint = yield* Service.start()
+  const endpoint = yield* Service.ensure()
   const client = yield* OpenCode.make({
     baseUrl: endpoint.url,
     headers: Service.headers(endpoint),
diff --git a/packages/www/content/docs/build/client.mdx b/packages/www/content/docs/build/client.mdx
index a306c8e271..ace8cc573b 100644
--- a/packages/www/content/docs/build/client.mdx
+++ b/packages/www/content/docs/build/client.mdx
@@ -113,7 +113,7 @@ Node application:
 
 - `Service.discover()` returns a healthy registered endpoint without starting
   a process.
-- `Service.start()` reuses a compatible service or starts one when needed.
+- `Service.ensure()` returns a compatible service, starting one when needed.
 - `Service.stop()` stops the registered service.
 - `Service.headers(endpoint)` creates the authentication headers for a client.
 
@@ -129,7 +129,7 @@ import { Effect } from "effect"
 import { FetchHttpClient } from "effect/unstable/http"
 
 const program = Effect.gen(function* () {
-  const endpoint = yield* Service.start()
+  const endpoint = yield* Service.ensure()
   const client = yield* OpenCode.make({
     baseUrl: endpoint.url,
     headers: Service.headers(endpoint),