Opencode Effect

OpenCode V2 Development

Use OpenCode V2 and its Effect-native APIs unless the user explicitly asks for V1, a Promise-only integration, or hybrid compatibility.

Source Rule

1. Read the relevant current V2 guide before writing code:
   • plugins: https://opencode.ai/v2/docs/build/plugins/effect
   • network client: https://opencode.ai/v2/docs/build/client/effect
   • embedded SDK: https://opencode.ai/v2/docs/build/sdk/effect
   • HTTP API: https://opencode.ai/v2/docs/api
   • V1 migration inputs: https://opencode.ai/v2/docs/migrate-v1
2. Check the target project's exact pinned OpenCode and Effect package versions. Inspect both published metadata and the installed package.json exports map before using a subpath. Confirm that every OpenCode package resolves to a mutually compatible release and that Effect platform packages use the same Effect release channel.
3. Treat moving tags in installation examples as discovery inputs, not package constraints. Resolve and lock exact versions. Do not assume separately moving plugin, client, and SDK tags form a compatible set, or replace a missing Effect export with a Promise/root entrypoint.
4. Do not infer V2 contracts from V1 docs or from https://opencode.ai/config.json.

Defaults

• Write plugins with @opencode-ai/plugin/effect, Plugin.define, and an effect function. Use the plugin Scope for registrations, finalizers, and scoped fibers instead of manual Promise cleanup.
• Connect applications with @opencode-ai/client/effect. Compose operations with Effect, consume subscriptions as Stream values, and use @opencode-ai/client/effect/service for the Node background service.
• Embed OpenCode with @opencode-ai/sdk/effect. Own the host with Effect.scoped or provide it through OpenCode.layer().
• Use the generated client instead of hand-written HTTP calls when an endpoint is available. For direct API work, verify the operation and schema in the V2 API reference or the running server's /openapi.json, use Effect's HttpClient, and decode request and response boundaries with Schema.
• Keep decoded branded values such as AbsolutePath, Location.Ref, and resource IDs. Do not cast plain strings or untrusted responses into them.
• Keep expected client failures in the Effect error channel. Use Effect.orDie only when the surrounding application deliberately treats that failure as a defect.

Plugin Example

import { Plugin } from "@opencode-ai/plugin/effect"
import { Effect } from "effect"

export default Plugin.define({
  id: "example",
  effect: (ctx) =>
    Effect.gen(function* () {
      yield* ctx.storage.set("loaded", true)
      yield* Effect.addFinalizer(() => ctx.storage.remove("loaded"))
    }),
})

Plugin hook callbacks and registered command, tool, integration, or websearch executors return Effect values. Tool inputs and outputs use Effect Schema rather than unchecked JSON Schema casts.

Client Example

import { AbsolutePath, Location, OpenCode } from "@opencode-ai/client/effect"
import { Effect } from "effect"
import { FetchHttpClient } from "effect/unstable/http"

const program = Effect.gen(function* () {
  const client = yield* OpenCode.make({ baseUrl: "http://localhost:4096" })
  return yield* client.session.create({
    location: Location.Ref.make({
      directory: AbsolutePath.make("/workspace"),
    }),
  })
})

const session = await Effect.runPromise(
  program.pipe(Effect.provide(FetchHttpClient.layer)),
)

Use Stream operators for client.event.subscribe() and other streaming operations. Provide the required HTTP, filesystem, and platform layers at the application boundary, not inside reusable workflows.

SDK Example

import { AbsolutePath, Location, OpenCode } from "@opencode-ai/sdk/effect"
import { Effect } from "effect"

const program = Effect.scoped(
  Effect.gen(function* () {
    const opencode = yield* OpenCode.create()
    return yield* opencode.sessions.create({
      location: Location.Ref.make({
        directory: AbsolutePath.make("/workspace"),
      }),
    })
  }),
)

const session = await Effect.runPromise(program)

Promise And V1 Exceptions

• Retain Promise plugin, client, or SDK code only when documenting migration input, maintaining a concrete Promise-only consumer, or providing an explicitly labelled hybrid compatibility path. Keep the Effect result as the recommended V2 output.
• Use @opencode-ai/client, @opencode-ai/client/service, or the Promise SDK only inside that documented exception. Do not present them as the default V2 starting point.
• Treat V1 plugin and server APIs as migration inputs only. V1 plugins do not run on V2, and V1 server integrations must move to the V2 API.
• Preserve supported V1 configuration only when compatibility is the goal; new native V2 configuration and code should use V2 shapes and entrypoints.

Verification

Typecheck examples against the target project's exact locked package set after verifying every imported subpath in published and installed package metadata. Exercise plugin load and cleanup, and run one real client or SDK operation. For direct HTTP work, verify the same operation with opencode2 api or the Effect-native generated client.