fix(app): submit callback commands as actions

packages/app/src/components/prompt-input/submit.ts

@@ -67,32 +67,18 @@ export async function sendFollowupDraft(input: FollowupSendInput) {
     cmd &&
     input.data.location.command.list({ directory: input.draft.sessionDirectory })?.some((item) => item.name === cmd)
   ) {
-    setBusy()
-    try {
-      const messageID = Identifier.ascending("message")
-      await input.api.command({
-        sessionID: input.draft.sessionID,
-        id: messageID,
-        command: cmd,
-        arguments: tail.join(" "),
-        agent: input.draft.agent,
-        model: {
-          id: input.draft.model.modelID,
-          providerID: input.draft.model.providerID,
-          variant: input.draft.variant,
-        },
-        files: await Promise.all(
-          images.map(async (attachment) => ({
-            uri: await blobDataUrl(attachment.blob, attachment.mime),
-            name: attachment.filename,
-          })),
-        ),
-      })
-      return true
-    } catch (err) {
-      setIdle()
-      throw err
-    }
+    await input.api.command({
+      sessionID: input.draft.sessionID,
+      command: cmd,
+      text: tail.join(" "),
+      files: await Promise.all(
+        images.map(async (attachment) => ({
+          uri: await blobDataUrl(attachment.blob, attachment.mime),
+          name: attachment.filename,
+        })),
+      ),
+    })
+    return true
   }
 
   const messageID = input.messageID ?? Identifier.ascending("message")
@@ -446,16 +432,11 @@ export function createPromptSubmit(input: PromptSubmitInput) {
           ?.find((command) => command.name === commandName)
         if (customCommand) {
           clearInput()
-          const messageID = Identifier.ascending("message")
-          submissionData.session.setStatus(session.id, "running")
           void submissionServerSDK.api.session
             .command({
               sessionID: session.id,
-              id: messageID,
               command: commandName,
-              arguments: args.join(" "),
-              agent,
-              model: { id: model.modelID, providerID: model.providerID, variant },
+              text: args.join(" "),
               files: await Promise.all(
                 images.map(async (attachment) => ({
                   uri: await blobDataUrl(attachment.blob, attachment.mime),
@@ -464,7 +445,6 @@ export function createPromptSubmit(input: PromptSubmitInput) {
               ),
             })
             .catch((err) => {
-              submissionData.session.setStatus(session.id, "idle")
               showToast({
                 title: language.t("prompt.toast.commandSendFailed.title"),
                 description: formatServerError(err, language.t, language.t("common.requestFailed")),

packages/cli/src/acp/event.ts

@@ -76,6 +76,7 @@ export async function streamTurn(input: {
   readonly cwd: string
   readonly start: TurnStart
   readonly writeTextFile: boolean
+  readonly action?: boolean
   readonly submit: (signal: AbortSignal) => Promise<unknown>
   readonly control: TurnControl
   readonly childSessionUpdate?: (update: ChildSessionUpdate) => Promise<void>
@@ -345,6 +346,11 @@ export async function streamTurn(input: {
     await input.submit(control.admission.signal).catch((error) => {
       if (!control.cancelled) throw error
     })
+    if (input.action) {
+      streamController.abort()
+      await completed.catch(() => {})
+      return response(undefined, undefined, "succeeded", control.cancelled, undefined)
+    }
     if (control.cancelled) {
       await input.client.session.interrupt({ sessionID: input.sessionID }).catch(() => {})
       if (!started) {

packages/cli/src/acp/service.ts

@@ -326,6 +326,7 @@ export function make(input: { readonly client: OpenCodeClient; readonly connecti
         cwd: state.cwd,
         start: prepared.start,
         writeTextFile: capabilities.writeTextFile,
+        action: prepared.command !== undefined,
         control,
         connectionSignal: input.connection.signal,
         sessionSignal: state.abort.signal,
@@ -377,9 +378,8 @@ async function submitPrompt(client: OpenCodeClient, session: Attached, prompt: P
     return client.session.command(
       {
         sessionID: session.id,
-        id: prompt.start.id,
         command: prompt.command.name,
-        arguments: prompt.slash?.args,
+        text: prompt.slash?.args ?? "",
         files: prompt.files,
         delivery: "steer",
       },

packages/cli/test/acp/event.test.ts

@@ -121,3 +121,42 @@ test("acp prompt resolves after ordered turn updates", async () => {
     controller.enqueue(encoder.encode(`data: ${JSON.stringify(event)}\n\n`))
   }
 })
+
+test("acp action resolves without prompt lifecycle events", async () => {
+  const encoder = new TextEncoder()
+  const server = Bun.serve({
+    port: 0,
+    fetch(request) {
+      if (new URL(request.url).pathname !== "/api/event") return new Response(null, { status: 404 })
+      return new Response(
+        new ReadableStream<Uint8Array>({
+          start(controller) {
+            controller.enqueue(encoder.encode(`data: ${JSON.stringify({ type: "server.connected", data: {} })}\n\n`))
+          },
+        }),
+        { headers: { "content-type": "text/event-stream" } },
+      )
+    },
+  })
+
+  try {
+    const response = await streamTurn({
+      client: OpenCode.make({ baseUrl: server.url.toString() }),
+      connection: {
+        sessionUpdate: async () => {},
+        requestPermission: async () => ({ outcome: { outcome: "cancelled" } }),
+      },
+      sessionID: "ses_test",
+      cwd: "/workspace",
+      start: { type: "input", id: "msg_action" },
+      writeTextFile: false,
+      action: true,
+      control: { cancelled: false, admission: new AbortController() },
+      submit: async () => {},
+    })
+
+    expect(response).toMatchObject({ stopReason: "end_turn" })
+  } finally {
+    await server.stop(true)
+  }
+})

packages/cli/test/acp/service-fixture.ts

@@ -87,7 +87,6 @@ export const planAgent = {
 export const reviewCommand = {
   name: "review",
   description: "Review changes",
-  template: "",
 } satisfies CommandInfo
 
 export const verifySkill = {

packages/client/src/effect/api/api.ts

@@ -184,18 +184,14 @@ export type SessionPromptOperation<E = never> = (input: Endpoint5_12Input) => Ef
 
 export type Endpoint5_13Input = {
   readonly sessionID: Session.ID
-  readonly id?: SessionMessage.ID | undefined
   readonly command: string
-  readonly arguments?: string | undefined
-  readonly agent?: Agent.ID | undefined
-  readonly model?: Model.Ref | undefined
+  readonly text: string
   readonly files?: ReadonlyArray<PromptInput.FileAttachment> | undefined
   readonly agents?: ReadonlyArray<AgentAttachment> | undefined
   readonly skills?: ReadonlyArray<PromptInput.SkillAttachment> | undefined
   readonly delivery?: SessionInbox.Delivery | undefined
-  readonly resume?: boolean | undefined
 }
-export type Endpoint5_13Output = SessionInbox.User
+export type Endpoint5_13Output = void
 export type SessionCommandOperation<E = never> = (input: Endpoint5_13Input) => Effect.Effect<Endpoint5_13Output, E>
 
 export type Endpoint5_14Input = {

packages/client/src/effect/generated/client.ts

@@ -415,21 +415,14 @@ const Endpoint5_13 = (raw: RawClient["server.session"]) => (input: Endpoint5_13I
     raw["session.command"]({
       params: { sessionID: input["sessionID"] },
       payload: {
-        id: input["id"],
         command: input["command"],
-        arguments: input["arguments"],
-        agent: input["agent"],
-        model: input["model"],
+        text: input["text"],
         files: input["files"],
         agents: input["agents"],
         skills: input["skills"],
         delivery: input["delivery"],
-        resume: input["resume"],
       },
-    }).pipe(
-      Effect.mapError(mapClientError),
-      Effect.map((value) => value.data),
-    ),
+    }).pipe(Effect.mapError(mapClientError)),
   )
 
 const Endpoint5_14 = (raw: RawClient["server.session"]) => (input: Endpoint5_14Input) =>

packages/client/src/promise/generated/client.ts

@@ -607,28 +607,24 @@ export function make(options: ClientOptions) {
           requestOptions,
         ).then((value) => value.data),
       command: (input: SessionCommandInput, requestOptions?: RequestOptions) =>
-        request<{ readonly data: SessionCommandOutput }>(
+        request<SessionCommandOutput>(
           {
             method: "POST",
             path: `/api/session/${encodeURIComponent(input.sessionID)}/command`,
             body: {
-              id: input["id"],
               command: input["command"],
-              arguments: input["arguments"],
-              agent: input["agent"],
-              model: input["model"],
+              text: input["text"],
               files: input["files"],
               agents: input["agents"],
               skills: input["skills"],
               delivery: input["delivery"],
-              resume: input["resume"],
             },
-            successStatus: 200,
-            declaredStatuses: [409, 400, 404, 500, 401],
-            empty: false,
+            successStatus: 204,
+            declaredStatuses: [404, 500, 400, 401],
+            empty: true,
           },
           requestOptions,
-        ).then((value) => value.data),
+        ),
       skill: (input: SessionSkillInput, requestOptions?: RequestOptions) =>
         request<SessionSkillOutput>(
           {

packages/client/src/promise/generated/types.ts

@@ -118,6 +118,8 @@ export type PermissionSavedInfo = { id: string; projectID: string; action: strin
 
 export type FileSystemEntry = { path: string; type: "file" | "directory" }
 
+export type CommandInfo = { name: string; description?: string }
+
 export type SkillInfo = {
   id: string
   name: string
@@ -183,15 +185,6 @@ export type WebSearchProvider = { id: string; name: string }
 
 export type WebSearchResult = { url: string; title?: string; content?: string; time: { published?: number } }
 
-export type CommandInfo = {
-  name: string
-  template: string
-  description?: string
-  agent?: string
-  model?: ModelRef
-  subtask?: boolean
-}
-
 export type ProviderRequest = {
   settings: ProviderSettings
   headers: { [x: string]: string }
@@ -2174,13 +2167,13 @@ export type CommandNotFoundError = {
 export const isCommandNotFoundError = (value: unknown): value is CommandNotFoundError =>
   typeof value === "object" && value !== null && "_tag" in value && value["_tag"] === "CommandNotFoundError"
 
-export type CommandEvaluationError = {
-  readonly _tag: "CommandEvaluationError"
+export type CommandExecutionError = {
+  readonly _tag: "CommandExecutionError"
   readonly command: string
   readonly message: string
 }
-export const isCommandEvaluationError = (value: unknown): value is CommandEvaluationError =>
-  typeof value === "object" && value !== null && "_tag" in value && value["_tag"] === "CommandEvaluationError"
+export const isCommandExecutionError = (value: unknown): value is CommandExecutionError =>
+  typeof value === "object" && value !== null && "_tag" in value && value["_tag"] === "CommandExecutionError"
 
 export type SkillNotFoundError = {
   readonly _tag: "SkillNotFoundError"
@@ -3523,35 +3516,9 @@ export type SessionPromptOutput = { data: SessionInboxUser }["data"]
 
 export type SessionCommandInput = {
   readonly sessionID: { readonly sessionID: string }["sessionID"]
-  readonly id?: {
-    readonly id?: string | null
-    readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
-    readonly files?: ReadonlyArray<{
-      readonly uri: string
-      readonly name?: string
-      readonly description?: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly agents?: ReadonlyArray<{
-      readonly name: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly skills?: ReadonlyArray<{
-      readonly id: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
-  }["id"]
   readonly command: {
-    readonly id?: string | null
     readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
+    readonly text: string
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3567,14 +3534,10 @@ export type SessionCommandInput = {
       readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
     }>
     readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
   }["command"]
-  readonly arguments?: {
-    readonly id?: string | null
+  readonly text: {
     readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
+    readonly text: string
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3590,60 +3553,10 @@ export type SessionCommandInput = {
       readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
     }>
     readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
-  }["arguments"]
-  readonly agent?: {
-    readonly id?: string | null
-    readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
-    readonly files?: ReadonlyArray<{
-      readonly uri: string
-      readonly name?: string
-      readonly description?: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly agents?: ReadonlyArray<{
-      readonly name: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly skills?: ReadonlyArray<{
-      readonly id: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
-  }["agent"]
-  readonly model?: {
-    readonly id?: string | null
-    readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
-    readonly files?: ReadonlyArray<{
-      readonly uri: string
-      readonly name?: string
-      readonly description?: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly agents?: ReadonlyArray<{
-      readonly name: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly skills?: ReadonlyArray<{
-      readonly id: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
-  }["model"]
+  }["text"]
   readonly files?: {
-    readonly id?: string | null
     readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
+    readonly text: string
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3659,14 +3572,10 @@ export type SessionCommandInput = {
       readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
     }>
     readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
   }["files"]
   readonly agents?: {
-    readonly id?: string | null
     readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
+    readonly text: string
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3682,14 +3591,10 @@ export type SessionCommandInput = {
       readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
     }>
     readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
   }["agents"]
   readonly skills?: {
-    readonly id?: string | null
     readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
+    readonly text: string
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3705,14 +3610,10 @@ export type SessionCommandInput = {
       readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
     }>
     readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
   }["skills"]
   readonly delivery?: {
-    readonly id?: string | null
     readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
+    readonly text: string
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3728,34 +3629,10 @@ export type SessionCommandInput = {
       readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
     }>
     readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
   }["delivery"]
-  readonly resume?: {
-    readonly id?: string | null
-    readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
-    readonly files?: ReadonlyArray<{
-      readonly uri: string
-      readonly name?: string
-      readonly description?: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly agents?: ReadonlyArray<{
-      readonly name: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly skills?: ReadonlyArray<{
-      readonly id: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly delivery?: ("steer" | "queue") | null
-    readonly resume?: boolean | null
-  }["resume"]
 }
 
-export type SessionCommandOutput = { data: SessionInboxUser }["data"]
+export type SessionCommandOutput = void
 
 export type SessionSkillInput = {
   readonly sessionID: { readonly sessionID: string }["sessionID"]

packages/core/src/command.ts

@@ -1,28 +1,32 @@
 export * as Command from "./command.js"
 
-import { makeLocationNode } from "@opencode-ai/util/effect/app-node"
-import { Context, Effect, Layer, Schema, Types } from "effect"
 import { Command } from "@opencode-ai/schema/command"
-import { State } from "./state.js"
-import { MCP } from "./mcp/index.js"
+import type { PromptInput } from "@opencode-ai/schema/prompt-input"
+import type { Session } from "@opencode-ai/schema/session"
+import type { SessionInbox } from "@opencode-ai/schema/session-inbox"
+import { makeLocationNode } from "@opencode-ai/util/effect/app-node"
+import { Context, Effect, Layer, Schema } from "effect"
 import { Bus } from "./bus.js"
-import { AppProcess } from "@opencode-ai/util/process"
-import { ChildProcess } from "effect/unstable/process"
-import { Config } from "./config.js"
-import { Location } from "./location.js"
-import { ShellSelect } from "./shell/select.js"
-import { Global } from "@opencode-ai/util/global"
+import { State } from "./state.js"
 
 export const Info = Command.Info
 export type Info = Command.Info
 export { Event } from "@opencode-ai/schema/command"
 
-export type Evaluation = {
-  readonly text: string
+export interface Invocation {
+  readonly sessionID: Session.ID
+  readonly prompt: PromptInput.Prompt
+  readonly delivery: SessionInbox.Delivery
 }
 
-export type Data = {
-  commands: Map<string, Types.DeepMutable<Info>>
+export interface Definition {
+  readonly name: string
+  readonly description?: string
+  readonly execute: (input: Invocation) => Effect.Effect<void, unknown>
+}
+
+export type Draft = {
+  add: (definition: Definition) => void
 }
 
 export class NotFoundError extends Schema.TaggedError<NotFoundError>()("Command.NotFoundError", {
@@ -30,249 +34,73 @@ export class NotFoundError extends Schema.TaggedError<NotFoundError>()("Command.
   message: Schema.String,
 }) {}
 
-export class EvaluationError extends Schema.TaggedError<EvaluationError>()("Command.EvaluationError", {
+export class ExecutionError extends Schema.TaggedError<ExecutionError>()("Command.ExecutionError", {
   command: Schema.String,
   message: Schema.String,
 }) {}
 
-export type Draft = {
-  list: () => readonly Info[]
-  get: (name: string) => Info | undefined
-  update: (name: string, update: (command: Types.DeepMutable<Info>) => void) => void
-  remove: (name: string) => void
-}
-
 export interface Interface extends State.Transformable<Draft> {
   readonly get: (name: string) => Effect.Effect<Info | undefined>
   readonly list: () => Effect.Effect<Info[]>
-  readonly evaluate: (input: {
+  readonly execute: (input: {
     readonly name: string
-    readonly arguments?: string
-  }) => Effect.Effect<Evaluation, NotFoundError | EvaluationError>
+    readonly invocation: Invocation
+  }) => Effect.Effect<void, NotFoundError | ExecutionError>
 }
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/Command") {}
 
-export const layer = (options?: ShellSelect.Options) =>
-  Layer.effect(
-    Service,
-    Effect.gen(function* () {
-      const mcp = yield* MCP.Service
-      const bus = yield* Bus.Service
-      const processes = yield* AppProcess.Service
-      const config = yield* Config.Service
-      const location = yield* Location.Service
-      const global = yield* Global.Service
-      const state = State.create<Data, Draft>({
-        name: "command",
-        initial: () => ({ commands: new Map() }),
-        draft: (draft) => ({
-          list: () => Array.from(draft.commands.values()) as Info[],
-          get: (name) => draft.commands.get(name),
-          update: (name, update) => {
-            const current = draft.commands.get(name) ?? ({ name, template: "" } as Types.DeepMutable<Info>)
-            if (!draft.commands.has(name)) draft.commands.set(name, current)
-            update(current)
-            current.name = name
-          },
-          remove: (name) => {
-            draft.commands.delete(name)
-          },
-        }),
-        finalize: () => bus.publish(Command.Event.Updated, {}).pipe(Effect.asVoid),
-      })
-      const staticCommand = (name: string) => state.get().commands.get(name) as Info | undefined
-      const mcpCommands = Effect.fnUntraced(function* () {
-        return (yield* mcp.prompts()).map((prompt) =>
-          Info.make({
-            name: mcpCommandName(prompt.server, prompt.name),
-            template: "",
-            description: prompt.description,
-          }),
-        )
+export const layer = Layer.effect(
+  Service,
+  Effect.gen(function* () {
+    const bus = yield* Bus.Service
+    const state = State.create<Map<string, Definition>, Draft>({
+      name: "command",
+      initial: () => new Map(),
+      draft: (draft) => ({
+        add: (definition) => draft.set(definition.name, definition),
+      }),
+      finalize: () => bus.publish(Command.Event.Updated, {}).pipe(Effect.asVoid),
+    })
+    const info = (definition: Definition) =>
+      Info.make({
+        name: definition.name,
+        description: definition.description,
       })
 
-      return Service.of({
-        reload: state.reload,
-        transform: state.transform,
-        get: Effect.fn("Command.get")(function* (name) {
-          const command = staticCommand(name)
-          if (command) return command
-          return (yield* mcpCommands()).find((command) => command.name === name)
+    return Service.of({
+      reload: state.reload,
+      transform: state.transform,
+      get: Effect.fn("Command.get")((name) =>
+        Effect.sync(() => {
+          const definition = state.get().get(name)
+          return definition ? info(definition) : undefined
         }),
-        list: Effect.fn("Command.list")(function* () {
-          const commands = Array.from(state.get().commands.values()) as Info[]
-          const names = new Set(commands.map((command) => command.name))
-          return [...commands, ...(yield* mcpCommands()).filter((command) => !names.has(command.name))]
-        }),
-        evaluate: Effect.fn("Command.evaluate")(function* (input) {
-          const command = staticCommand(input.name)
-          if (command)
-            return yield* evaluateTemplate(input.name, command.template, input.arguments ?? "", {
-              config,
-              location,
-              processes,
-              shell: options,
-              bin: global.bin,
-            })
-
-          const prompt = (yield* mcp.prompts()).find(
-            (prompt) => mcpCommandName(prompt.server, prompt.name) === input.name,
-          )
-          if (!prompt)
-            return yield* new NotFoundError({ command: input.name, message: `Command not found: ${input.name}` })
-          const result = yield* mcp
-            .prompt({
-              server: prompt.server,
-              name: prompt.name,
-              args: Object.fromEntries(
-                (prompt.arguments ?? []).map((argument, index) => [
-                  argument.name,
-                  parseArguments(input.arguments ?? "")[index] ?? "",
-                ]),
-              ),
-            })
-            .pipe(
-              Effect.catchTag("MCP.NotFoundError", () =>
-                Effect.fail(
-                  new EvaluationError({
-                    command: input.name,
-                    message: `MCP server could not be found while evaluating prompt: ${prompt.server}`,
-                  }),
-                ),
-              ),
-            )
-          if (!result)
-            return yield* new EvaluationError({
-              command: input.name,
-              message: `MCP prompt could not be evaluated: ${prompt.server}:${prompt.name}`,
-            })
-          return {
-            text: result.messages
-              .map((message) => promptMessageText(message.content))
-              .join("\n")
-              .trim(),
-          }
-        }),
-      })
-    }),
-  )
-
-function evaluateTemplate(
-  command: string,
-  template: string,
-  input: string,
-  services: {
-    readonly config: Config.Interface
-    readonly location: Location.Info
-    readonly processes: AppProcess.Interface
-    readonly shell?: ShellSelect.Options
-    readonly bin: string
-  },
-) {
-  return Effect.gen(function* () {
-    const expanded = evaluateArguments(template, input)
-    return { text: yield* evaluateShell(command, expanded, services) }
-  })
-}
-
-function evaluateArguments(template: string, input: string) {
-  const args = parseArguments(input)
-  const placeholders = template.match(placeholderRegex) ?? []
-  const last = Math.max(0, ...placeholders.map((item) => Number(item.slice(1))))
-  const expanded = template.replaceAll(placeholderRegex, (_, index) => {
-    const position = Number(index)
-    const argIndex = position - 1
-    if (argIndex >= args.length) return ""
-    if (position === last) return args.slice(argIndex).join(" ")
-    return args[argIndex]
-  })
-  const withArguments = expanded.replaceAll("$ARGUMENTS", input)
-  if (placeholders.length === 0 && !template.includes("$ARGUMENTS") && input.trim())
-    return `${withArguments}\n\n${input}`.trim()
-  return withArguments.trim()
-}
-
-const evaluateShell = Effect.fnUntraced(function* (
-  command: string,
-  text: string,
-  services: {
-    readonly config: Config.Interface
-    readonly location: Location.Info
-    readonly processes: AppProcess.Interface
-    readonly shell?: ShellSelect.Options
-    readonly bin: string
-  },
-) {
-  const matches = Array.from(text.matchAll(shellRegex))
-  if (matches.length === 0) return text
-  const shell = ShellSelect.preferred(
-    Config.latest(yield* services.config.entries(), "shell"),
-    services.shell,
-    services.bin,
-  )
-  const outputs = yield* Effect.forEach(
-    matches,
-    (match) => {
-      const source = match[1] ?? ""
-      return services.processes
-        .run(
-          ChildProcess.make(shell, ShellSelect.args(shell, source), {
-            cwd: services.location.directory,
-            stdin: "ignore",
-          }),
-          {
-            combineOutput: true,
-          },
+      ),
+      list: Effect.fn("Command.list")(() => Effect.sync(() => Array.from(state.get().values(), info))),
+      execute: Effect.fn("Command.execute")(function* (input) {
+        const definition = state.get().get(input.name)
+        if (!definition)
+          return yield* new NotFoundError({ command: input.name, message: `Command not found: ${input.name}` })
+        return yield* definition.execute(input.invocation).pipe(
+          Effect.tapError((error) => Effect.logError("command execution failed", { command: input.name, error })),
+          Effect.mapError((error) => new ExecutionError({ command: input.name, message: errorMessage(error) })),
         )
-        .pipe(
-          Effect.map((result) => (result.output ?? Buffer.concat([result.stdout, result.stderr])).toString("utf8")),
-          Effect.mapError(
-            (error) =>
-              new EvaluationError({
-                command,
-                message: `Shell interpolation failed for ${JSON.stringify(source)}: ${error.message}`,
-              }),
-          ),
-        )
-    },
-    { concurrency: 2 },
-  )
-  const iterator = outputs[Symbol.iterator]()
-  return text.replace(shellRegex, () => iterator.next().value ?? "")
+      }),
+    })
+  }),
+)
+
+export const node = makeLocationNode({
+  service: Service,
+  layer,
+  deps: [Bus.node],
 })
 
-function parseArguments(input: string) {
-  return (input.match(argsRegex) ?? []).map((arg) => arg.replace(quoteTrimRegex, ""))
+function errorMessage(error: unknown) {
+  if (error instanceof Error) return error.message
+  if (typeof error === "string") return error
+  if (error && typeof error === "object" && "message" in error && typeof error.message === "string")
+    return error.message
+  return "Command execution failed"
 }
-
-function promptMessageText(content: unknown) {
-  if (typeof content === "string") return content
-  if (!content || typeof content !== "object") return ""
-  if (!("type" in content) || content.type !== "text") return ""
-  if (!("text" in content) || typeof content.text !== "string") return ""
-  return content.text
-}
-
-function mcpCommandName(server: string, prompt: string) {
-  return `${sanitize(server)}:${sanitize(prompt)}`
-}
-
-function sanitize(value: string) {
-  return value.replace(/[^a-zA-Z0-9_-]/g, "_")
-}
-
-const argsRegex = /(?:\[Image\s+\d+\]|"[^"]*"|'[^']*'|[^\s"']+)/gi
-const placeholderRegex = /\$(\d+)/g
-const quoteTrimRegex = /^["']|["']$/g
-const shellRegex = /!`([^`]+)`/g
-
-export function configured(options?: ShellSelect.Options) {
-  return makeLocationNode({
-    service: Service,
-    layer: layer(options),
-    deps: [MCP.node, Bus.node, AppProcess.node, Config.node, Location.node, Global.node],
-  })
-}
-
-export const node = configured()

packages/core/src/config/plugin/command.ts

@@ -1,12 +1,19 @@
 export * as ConfigCommandPlugin from "./command.js"
 
 import { define } from "@opencode-ai/plugin/effect/plugin"
+import { Agent } from "@opencode-ai/schema/agent"
 import { Info, type Entry } from "@opencode-ai/schema/config"
 import { ConfigCommand } from "@opencode-ai/schema/config/command"
+import { Model } from "@opencode-ai/schema/model"
+import { Provider } from "@opencode-ai/schema/provider"
+import { AppProcess } from "@opencode-ai/util/process"
 import path from "path"
 import { Effect, Option, Schema, Stream } from "effect"
-import { Command } from "../../command.js"
+import { ChildProcess } from "effect/unstable/process"
 import { Config } from "../../config.js"
+import { Location } from "../../location.js"
+import { Shell } from "../../shell.js"
+import { ShellSelect } from "../../shell/select.js"
 import { FSUtil } from "@opencode-ai/util/fs-util"
 import { ConfigMarkdown } from "../markdown.js"
 
@@ -17,6 +24,9 @@ export const Plugin = define({
   effect: Effect.fn(function* (ctx) {
     const config = yield* Config.Service
     const fs = yield* FSUtil.Service
+    const location = yield* Location.Service
+    const processes = yield* AppProcess.Service
+    const shell = yield* Shell.Service
     const load = Effect.fn("ConfigCommandPlugin.load")(function* () {
       return yield* Effect.forEach(yield* config.entries(), (entry) => {
         if (entry.type === "document") return Effect.succeed([{ commands: entry.info.commands }])
@@ -53,17 +63,41 @@ export const Plugin = define({
     yield* ctx.command.transform((draft) => {
       for (const document of loaded.documents) {
         for (const [name, command] of Object.entries(document.commands ?? {})) {
-          draft.update(name, (item) => {
-            item.template = command.template
-            if (command.description !== undefined) item.description = command.description
-            if (command.agent !== undefined) item.agent = command.agent
-            if (command.model !== undefined)
-              item.model = {
-                id: command.model.model,
-                providerID: command.model.providerID,
-                ...(command.model.variant === undefined ? {} : { variant: command.model.variant }),
-              }
-            if (command.subtask !== undefined) item.subtask = command.subtask
+          draft.add({
+            name,
+            description: command.description,
+            execute: (input) =>
+              Effect.gen(function* () {
+                const agent = command.agent === undefined ? undefined : Agent.ID.make(command.agent)
+                const commandAgent = yield* Effect.gen(function* () {
+                  if (agent === undefined) return
+                  const session = yield* ctx.session.get({ sessionID: input.sessionID })
+                  if (session.agent !== agent) yield* ctx.session.switchAgent({ sessionID: input.sessionID, agent })
+                  return (yield* ctx.agent.get({ agentID: agent })).data
+                })
+                const model =
+                  command.model === undefined
+                    ? commandAgent?.model
+                    : {
+                        id: Model.ID.make(command.model.model),
+                        providerID: Provider.ID.make(command.model.providerID),
+                        ...(command.model.variant === undefined
+                          ? {}
+                          : { variant: Model.VariantID.make(command.model.variant) }),
+                      }
+                if (model !== undefined) yield* ctx.session.switchModel({ sessionID: input.sessionID, model })
+                yield* ctx.session.prompt({
+                  ...input.prompt,
+                  sessionID: input.sessionID,
+                  text: yield* evaluateTemplate(command.template, input.prompt.text, {
+                    config,
+                    location,
+                    processes,
+                    shell,
+                  }),
+                  delivery: input.delivery,
+                })
+              }).pipe(Effect.asVoid),
           })
         }
       }
@@ -116,3 +150,67 @@ function decode(directory: string, filepath: string, content: string) {
     info,
   }
 }
+
+function evaluateTemplate(
+  template: string,
+  input: string,
+  services: {
+    readonly config: Config.Interface
+    readonly location: Location.Info
+    readonly processes: AppProcess.Interface
+    readonly shell: Shell.Interface
+  },
+) {
+  return Effect.gen(function* () {
+    const args = parseArguments(input)
+    const placeholders = template.match(placeholderRegex) ?? []
+    const last = Math.max(0, ...placeholders.map((item) => Number(item.slice(1))))
+    const expanded = template.replaceAll(placeholderRegex, (_, index) => {
+      const position = Number(index)
+      const argIndex = position - 1
+      if (argIndex >= args.length) return ""
+      if (position === last) return args.slice(argIndex).join(" ")
+      return args[argIndex]
+    })
+    const withArguments = expanded.replaceAll("$ARGUMENTS", input)
+    const text =
+      placeholders.length === 0 && !template.includes("$ARGUMENTS") && input.trim()
+        ? `${withArguments}\n\n${input}`.trim()
+        : withArguments.trim()
+    const matches = Array.from(text.matchAll(shellRegex))
+    if (matches.length === 0) return text
+    const shell = yield* services.shell.name()
+    const outputs = yield* Effect.forEach(
+      matches,
+      (match) => {
+        const source = match[1] ?? ""
+        return services.processes
+          .run(
+            ChildProcess.make(shell, ShellSelect.args(shell, source), {
+              cwd: services.location.directory,
+              stdin: "ignore",
+            }),
+            { combineOutput: true },
+          )
+          .pipe(
+            Effect.map((result) => (result.output ?? Buffer.concat([result.stdout, result.stderr])).toString("utf8")),
+            Effect.mapError((error) =>
+              new Error(`Shell interpolation failed for ${JSON.stringify(source)}: ${error.message}`),
+            ),
+          )
+      },
+      { concurrency: 2 },
+    )
+    const iterator = outputs[Symbol.iterator]()
+    return text.replace(shellRegex, () => iterator.next().value ?? "")
+  })
+}
+
+function parseArguments(input: string) {
+  return (input.match(argsRegex) ?? []).map((arg) => arg.replace(quoteTrimRegex, ""))
+}
+
+const argsRegex = /(?:\[Image\s+\d+\]|"[^"]*"|'[^']*'|[^\s"']+)/gi
+const placeholderRegex = /\$(\d+)/g
+const quoteTrimRegex = /^["']|["']$/g
+const shellRegex = /!`([^`]+)`/g

packages/core/src/mcp/index.ts

@@ -2,7 +2,7 @@ export * as MCP from "./index.js"
 
 import { Mcp } from "@opencode-ai/schema/mcp"
 import { McpEvent } from "@opencode-ai/schema/mcp-event"
-import { Command } from "@opencode-ai/schema/command"
+import { ephemeral } from "@opencode-ai/schema/event"
 import { createHash } from "node:crypto"
 import { isDeepStrictEqual } from "node:util"
 import { Cause, Context, Deferred, Effect, Exit, FiberSet, Layer, Schema, Scope, Stream, Types } from "effect"
@@ -19,6 +19,7 @@ import { State } from "../state.js"
 import type { MCPClient } from "./client.js"
 
 export const ServerName = Schema.String.pipe(Schema.brand("MCP.ServerName"))
+export const PromptsChanged = ephemeral({ type: "mcp.prompts.changed", schema: { server: Schema.String } })
 export type ServerName = typeof ServerName.Type
 
 // The status union is a public wire contract, so it lives in @opencode-ai/schema and is re-exported here.
@@ -428,7 +429,7 @@ export const layer = (options?: Options) =>
           Effect.map((defs) => {
             entry.prompts = defs.map((def) => toPrompt(name, def))
           }),
-          Effect.andThen(bus.publish(Command.Event.Updated, {})),
+          Effect.andThen(bus.publish(PromptsChanged, { server: name })),
         )
 
       // Runs a connection callback under the server lock, dropping it if the connection is no longer
@@ -547,7 +548,7 @@ export const layer = (options?: Options) =>
         yield* Scope.close(scope, Exit.void)
         yield* bus.publish(McpEvent.ToolsChanged, { server: name }).pipe(Effect.ignore)
         yield* bus.publish(McpEvent.ResourcesChanged, { server: name }).pipe(Effect.ignore)
-        yield* bus.publish(Command.Event.Updated, {}).pipe(Effect.ignore)
+        yield* bus.publish(PromptsChanged, { server: name }).pipe(Effect.ignore)
       })
 
       const disposeServer = Effect.fnUntraced(function* (name: ServerName, entry: ServerEntry) {

packages/core/src/plugin/command.ts

@@ -1,8 +1,10 @@
 export * as CommandPlugin from "./command.js"
 
 import { define } from "@opencode-ai/plugin/effect/plugin"
-import { Effect } from "effect"
+import { Effect, Stream } from "effect"
+import { Bus } from "../bus.js"
 import { Location } from "../location.js"
+import { MCP } from "../mcp/index.js"
 import PROMPT_INITIALIZE from "./command/initialize.txt"
 import PROMPT_REVIEW from "./command/review.txt"
 
@@ -10,15 +12,104 @@ export const Plugin = define({
   id: "opencode.command",
   effect: Effect.fn(function* (ctx) {
     const location = yield* Location.Service
+    const mcp = yield* MCP.Service
+    const bus = yield* Bus.Service
+    const loaded = { prompts: [] as MCP.Prompt[] }
+    yield* bus
+      .subscribe(MCP.PromptsChanged)
+      .pipe(
+        Stream.runForEach(() =>
+          mcp.prompts().pipe(
+            Effect.tap((prompts) => Effect.sync(() => (loaded.prompts = prompts))),
+            Effect.andThen(ctx.command.reload()),
+          ),
+        ),
+        Effect.forkScoped({ startImmediately: true }),
+      )
+    loaded.prompts = yield* mcp.prompts()
     yield* ctx.command.transform((draft) => {
-      draft.update("init", (command) => {
-        command.template = PROMPT_INITIALIZE.replace("${path}", location.project.directory)
-        command.description = "guided AGENTS.md setup"
+      draft.add({
+        name: "init",
+        description: "guided AGENTS.md setup",
+        execute: (input) =>
+          ctx.session
+            .prompt({
+              ...input.prompt,
+              sessionID: input.sessionID,
+              text: append(PROMPT_INITIALIZE.replace("${path}", location.project.directory), input.prompt.text),
+              delivery: input.delivery,
+            })
+            .pipe(Effect.asVoid),
       })
-      draft.update("review", (command) => {
-        command.template = PROMPT_REVIEW.replace("${path}", location.project.directory)
-        command.description = "review changes [commit|branch|pr], defaults to uncommitted"
+      draft.add({
+        name: "review",
+        description: "review changes [commit|branch|pr], defaults to uncommitted",
+        execute: (input) =>
+          ctx.session
+            .prompt({
+              ...input.prompt,
+              sessionID: input.sessionID,
+              text: append(PROMPT_REVIEW.replace("${path}", location.project.directory), input.prompt.text),
+              delivery: input.delivery,
+            })
+            .pipe(Effect.asVoid),
       })
+      for (const prompt of loaded.prompts) {
+        draft.add({
+          name: mcpCommandName(prompt.server, prompt.name),
+          description: prompt.description,
+          execute: (input) =>
+            Effect.gen(function* () {
+              const result = yield* mcp.prompt({
+                server: prompt.server,
+                name: prompt.name,
+                args: Object.fromEntries(
+                  (prompt.arguments ?? []).map((argument, index) => [
+                    argument.name,
+                    parseArguments(input.prompt.text)[index] ?? "",
+                  ]),
+                ),
+              })
+              if (!result) return yield* Effect.fail(new Error(`MCP prompt not found: ${prompt.server}:${prompt.name}`))
+              yield* ctx.session.prompt({
+                ...input.prompt,
+                sessionID: input.sessionID,
+                text: result.messages
+                  .map((message) => promptMessageText(message.content))
+                  .join("\n")
+                  .trim(),
+                delivery: input.delivery,
+              })
+            }).pipe(Effect.asVoid),
+        })
+      }
     })
   }),
 })
+
+function append(template: string, input: string) {
+  return [template, input.trim()].filter(Boolean).join("\n\n")
+}
+
+function parseArguments(input: string) {
+  return (input.match(argsRegex) ?? []).map((argument) => argument.replace(quoteTrimRegex, ""))
+}
+
+function promptMessageText(content: unknown) {
+  if (typeof content === "string") return content
+  if (!content || typeof content !== "object") return ""
+  if (!("type" in content) || content.type !== "text") return ""
+  if (!("text" in content) || typeof content.text !== "string") return ""
+  return content.text
+}
+
+function mcpCommandName(server: string, prompt: string) {
+  return `${sanitize(server)}:${sanitize(prompt)}`
+}
+
+function sanitize(value: string) {
+  return value.replace(/[^a-zA-Z0-9_-]/g, "_")
+}
+
+const argsRegex = /(?:\[Image\s+\d+\]|"[^"]*"|'[^']*'|[^\s"']+)/gi
+const quoteTrimRegex = /^["']|["']$/g

packages/core/src/plugin/host.ts

@@ -395,6 +395,8 @@ export const make = Effect.fn("PluginHost.make")(function* (plugin: import("../p
             input?.location ?? Location.Ref.make({ directory: location.directory, workspaceID: location.workspaceID }),
         }),
       get: (input) => runtime.session.get(input.sessionID),
+      switchAgent: runtime.session.switchAgent,
+      switchModel: runtime.session.switchModel,
       prompt: runtime.session.prompt,
       generate: (input) => runtime.session.generate(input).pipe(Effect.map((text) => ({ text }))),
       command: runtime.session.command,

packages/core/src/session.ts

@@ -235,26 +235,14 @@ export interface Interface {
     prompt: string
   }) => Effect.Effect<string, NotFoundError | SessionGenerate.Error>
   readonly command: (input: {
-    id?: SessionMessage.ID
     sessionID: SessionSchema.ID
     command: string
-    arguments?: string
-    agent?: Agent.ID
-    model?: Model.Ref
+    text: string
     files?: PromptInput.Prompt["files"]
     agents?: PromptInput.Prompt["agents"]
     skills?: PromptInput.Prompt["skills"]
     delivery?: SessionInbox.Delivery
-    resume?: boolean
-  }) => Effect.Effect<
-    SessionInbox.User,
-    | NotFoundError
-    | PromptConflictError
-    | AttachmentError
-    | SkillNotFoundError
-    | Command.NotFoundError
-    | Command.EvaluationError
-  >
+  }) => Effect.Effect<void, NotFoundError | Command.NotFoundError | Command.ExecutionError>
   readonly shell: (input: {
     id?: Event.ID
     sessionID: SessionSchema.ID
@@ -629,35 +617,19 @@ const layer = Layer.effect(
       command: Effect.fn("Session.command")(function* (input) {
         const session = yield* result.get(input.sessionID)
         const commands = yield* Command.Service.pipe(Effect.provide(locations.get(session.location)))
-        const command = yield* commands.get(input.command)
-        if (!command)
-          return yield* new Command.NotFoundError({
-            command: input.command,
-            message: `Command not found: ${input.command}`,
-          })
-        const evaluated = yield* commands.evaluate({ name: input.command, arguments: input.arguments })
-
-        // TODO(v2 commands): decide whether command-level subtask/background execution belongs in v2 commands.
-        const agent = command.agent ?? input.agent
-        const commandAgent = yield* Effect.gen(function* () {
-          if (!command.agent) return undefined
-          const agents = yield* Agent.Service.pipe(Effect.provide(locations.get(session.location)))
-          return yield* agents.get(Agent.ID.make(command.agent))
-        })
-        const model = command.model ?? commandAgent?.model ?? input.model
-        if (agent !== undefined && session.agent !== Agent.ID.make(agent))
-          yield* result.switchAgent({ sessionID: input.sessionID, agent: Agent.ID.make(agent) })
-        if (model !== undefined) yield* result.switchModel({ sessionID: input.sessionID, model })
-
-        return yield* result.prompt({
-          id: input.id,
-          sessionID: input.sessionID,
-          text: evaluated.text,
-          files: input.files,
-          agents: input.agents,
-          skills: input.skills,
-          delivery: input.delivery,
-          resume: input.resume,
+        const delivery = input.delivery ?? "steer"
+        yield* commands.execute({
+          name: input.command,
+          invocation: {
+            sessionID: input.sessionID,
+            prompt: {
+              text: input.text,
+              files: input.files,
+              agents: input.agents,
+              skills: input.skills,
+            },
+            delivery,
+          },
         })
       }),
       shell: Effect.fn("Session.shell")(function* (input) {

packages/core/test/command.test.ts

@@ -1,79 +1,71 @@
 import { describe, expect } from "bun:test"
-import { Effect } from "effect"
 import { Command } from "@opencode-ai/core/command"
-import { Config } from "@opencode-ai/core/config"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
-import { Location } from "@opencode-ai/core/location"
-import { MCP } from "@opencode-ai/core/mcp/index"
-import { Model } from "@opencode-ai/core/model"
-import { Provider } from "@opencode-ai/core/provider"
-import { emptyConfigLayer, emptyMcpLayer, testLocationLayer } from "./fixture/mcp"
+import { Session } from "@opencode-ai/schema/session"
+import { Effect } from "effect"
 import { testEffect } from "./lib/effect"
 
-const it = testEffect(
-  AppNodeBuilder.build(Command.node, [
-    [MCP.node, emptyMcpLayer],
-    [Config.node, emptyConfigLayer],
-    [Location.node, testLocationLayer],
-  ]),
-)
+const it = testEffect(AppNodeBuilder.build(Command.node))
 
 describe("Command", () => {
-  it.effect("applies command transforms and preserves later overrides", () =>
+  it.effect("registers and executes callback commands", () =>
     Effect.gen(function* () {
       const command = yield* Command.Service
-      yield* command.transform((editor) => {
-        editor.update("review", (command) => {
-          command.template = "First"
-          command.description = "Review code"
-        })
-        editor.update("review", (command) => {
-          command.template = "Second"
-          command.model = {
-            id: Model.ID.make("claude"),
-            providerID: Provider.ID.make("anthropic"),
-            variant: Model.VariantID.make("high"),
-          }
+      const calls: Command.Invocation[] = []
+      yield* command.transform((draft) => {
+        draft.add({
+          name: "goal",
+          description: "Manage the session goal",
+          execute: (input) => Effect.sync(() => calls.push(input)),
         })
       })
 
-      expect(yield* command.get("review")).toEqual(
-        Command.Info.make({
-          name: "review",
-          template: "Second",
-          description: "Review code",
-          model: {
-            id: Model.ID.make("claude"),
-            providerID: Provider.ID.make("anthropic"),
-            variant: Model.VariantID.make("high"),
-          },
-        }),
+      expect(yield* command.get("goal")).toEqual(
+        Command.Info.make({ name: "goal", description: "Manage the session goal" }),
       )
-      expect(yield* command.list()).toEqual([
-        Command.Info.make({
-          name: "review",
-          template: "Second",
-          description: "Review code",
-          model: {
-            id: Model.ID.make("claude"),
-            providerID: Provider.ID.make("anthropic"),
-            variant: Model.VariantID.make("high"),
-          },
-        }),
-      ])
+      const invocation = {
+        sessionID: Session.ID.make("ses_test"),
+        prompt: { text: "ship it", files: [{ uri: "file:///tmp/plan.md" }] },
+        delivery: "steer" as const,
+      }
+      yield* command.execute({ name: "goal", invocation })
+      expect(calls).toEqual([invocation])
     }),
   )
 
-  it.effect("evaluates command template shell blocks", () =>
+  it.effect("replaces commands with later definitions", () =>
     Effect.gen(function* () {
       const command = yield* Command.Service
-      yield* command.transform((editor) => {
-        editor.update("review", (command) => {
-          command.template = "Output: !`echo command-output`"
+      yield* command.transform((draft) => {
+        draft.add({ name: "goal", description: "First", execute: () => Effect.void })
+        draft.add({ name: "goal", description: "Second", execute: () => Effect.void })
+      })
+
+      expect(yield* command.list()).toEqual([Command.Info.make({ name: "goal", description: "Second" })])
+    }),
+  )
+
+  it.effect("returns callback error messages without stack traces", () =>
+    Effect.gen(function* () {
+      const command = yield* Command.Service
+      yield* command.transform((draft) => {
+        draft.add({
+          name: "fail",
+          execute: () => Effect.fail(new Error("command failed")),
         })
       })
 
-      expect((yield* command.evaluate({ name: "review" })).text.replace(/\r?\n$/, "")).toEqual("Output: command-output")
+      const error = yield* command
+        .execute({
+          name: "fail",
+          invocation: {
+            sessionID: Session.ID.make("ses_test"),
+            prompt: { text: "" },
+            delivery: "steer",
+          },
+        })
+        .pipe(Effect.flip)
+      expect(error).toMatchObject({ _tag: "Command.ExecutionError", message: "command failed" })
     }),
   )
 })

packages/core/test/config/command.test.ts

@@ -1,11 +1,13 @@
 import fs from "fs/promises"
 import path from "path"
 import { describe, expect } from "bun:test"
-import { Deferred, Effect, Fiber, Layer, Option, PubSub, Schema, Stream } from "effect"
+import { DateTime, Deferred, Effect, Fiber, Layer, Option, PubSub, Schema, Stream } from "effect"
 import { advance, drain } from "../lib/clock"
 import { Directory, Document, Event, Info } from "@opencode-ai/schema/config"
+import { Session } from "@opencode-ai/schema/session"
+import { SessionInbox } from "@opencode-ai/schema/session-inbox"
+import { SessionMessage } from "@opencode-ai/schema/session-message"
 import { Command } from "@opencode-ai/core/command"
-import { Agent } from "@opencode-ai/core/agent"
 import { Config } from "@opencode-ai/core/config"
 import { ConfigCommandPlugin } from "@opencode-ai/core/config/plugin/command"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
@@ -15,11 +17,11 @@ import { Bus } from "@opencode-ai/core/bus"
 import { Credential } from "@opencode-ai/core/credential"
 import { WellKnown } from "@opencode-ai/core/wellknown"
 import { Global } from "@opencode-ai/util/global"
+import { AppProcess } from "@opencode-ai/util/process"
 import { Location } from "@opencode-ai/core/location"
 import { MCP } from "@opencode-ai/core/mcp/index"
-import { Model } from "@opencode-ai/core/model"
-import { Provider } from "@opencode-ai/core/provider"
 import { AbsolutePath } from "@opencode-ai/core/schema"
+import { Shell } from "@opencode-ai/core/shell"
 import { Watcher } from "@opencode-ai/core/filesystem/watcher"
 import { emptyCredentialNode, emptyWellknownNode } from "../fixture/config-nodes"
 import { emptyConfigLayer, emptyMcpLayer, testLocationLayer } from "../fixture/mcp"
@@ -28,12 +30,30 @@ import { tmpdir } from "../fixture/tmpdir"
 import { testEffect } from "../lib/effect"
 import { host } from "../plugin/host"
 
+const shellLayer = Layer.succeed(
+  Shell.Service,
+  Shell.Service.of({
+    name: () => Effect.succeed("sh"),
+    create: () => Effect.die("unused shell.create"),
+    list: () => Effect.die("unused shell.list"),
+    get: () => Effect.die("unused shell.get"),
+    wait: () => Effect.die("unused shell.wait"),
+    timeout: () => Effect.die("unused shell.timeout"),
+    output: () => Effect.die("unused shell.output"),
+    remove: () => Effect.die("unused shell.remove"),
+  }),
+)
+
 const it = testEffect(
-  AppNodeBuilder.build(LayerNode.group([Command.node, Bus.node, FSUtil.node]), [
-    [MCP.node, emptyMcpLayer],
-    [Config.node, emptyConfigLayer],
-    [Location.node, testLocationLayer],
-  ]),
+  AppNodeBuilder.build(
+    LayerNode.group([Command.node, Bus.node, FSUtil.node, AppProcess.node, Location.node, Shell.node]),
+    [
+      [MCP.node, emptyMcpLayer],
+      [Config.node, emptyConfigLayer],
+      [Location.node, testLocationLayer],
+      [Shell.node, shellLayer],
+    ],
+  ),
 )
 const decode = Schema.decodeUnknownSync(Info)
 
@@ -65,6 +85,7 @@ Review files`,
           const bus = yield* Bus.Service
           const update = yield* bus.publish(Event.Updated, {})
           const updates = yield* PubSub.unbounded<typeof update>()
+          const prompts: { text: string; files?: readonly { readonly uri: string }[]; delivery?: string }[] = []
           yield* ConfigCommandPlugin.Plugin.effect(
             host({
               command: {
@@ -73,6 +94,20 @@ Review files`,
                 reload: command.reload,
               },
               event: { subscribe: () => Stream.fromPubSub(updates) },
+              session: {
+                prompt: (input) =>
+                  Effect.sync(() => {
+                    prompts.push({ text: input.text, files: input.files, delivery: input.delivery })
+                    return SessionInbox.User.make({
+                      id: SessionMessage.ID.make("msg_test"),
+                      sessionID: input.sessionID,
+                      timeCreated: DateTime.makeUnsafe(0),
+                      type: "user",
+                      payload: { text: input.text },
+                      delivery: input.delivery ?? "steer",
+                    })
+                  }),
+              },
             }),
           ).pipe(
             Effect.provide(
@@ -89,28 +124,46 @@ Review files`,
           expect(yield* command.list()).toEqual([
             Command.Info.make({
               name: "review",
-              template: "Review files",
               description: "File review",
-              agent: Agent.ID.make("reviewer"),
-              model: {
-                providerID: Provider.ID.make("anthropic"),
-                id: Model.ID.make("claude"),
-                variant: Model.VariantID.make("high"),
-              },
-              subtask: true,
             }),
-            Command.Info.make({ name: "empty", template: "" }),
-            Command.Info.make({ name: "nested/docs", template: "Write docs" }),
+            Command.Info.make({ name: "empty" }),
+            Command.Info.make({ name: "nested/docs" }),
+          ])
+          yield* command.execute({
+            name: "nested/docs",
+            invocation: {
+              sessionID: Session.ID.make("ses_test"),
+              prompt: { text: "details", files: [{ uri: "file:///tmp/context.md" }] },
+              delivery: "queue",
+            },
+          })
+          expect(prompts).toEqual([
+            {
+              text: "Write docs\n\ndetails",
+              files: [{ uri: "file:///tmp/context.md" }],
+              delivery: "queue",
+            },
           ])
 
-          yield* Effect.promise(() => fs.writeFile(path.join(tmp.path, "commands", "review.md"), "Review again"))
+          yield* Effect.promise(() =>
+            fs.writeFile(path.join(tmp.path, "commands", "review.md"), markdown("Review again", "Review again")),
+          )
           yield* Effect.sleep("10 millis")
           yield* PubSub.publish(updates, update)
           for (let attempt = 0; attempt < 100; attempt++) {
-            if ((yield* command.get("review"))?.template === "Review again") break
+            if ((yield* command.get("review"))?.description === "Review again") break
             yield* Effect.sleep("10 millis")
           }
-          expect((yield* command.get("review"))?.template).toBe("Review again")
+          expect((yield* command.get("review"))?.description).toBe("Review again")
+          yield* command.execute({
+            name: "review",
+            invocation: {
+              sessionID: Session.ID.make("ses_test"),
+              prompt: { text: "latest" },
+              delivery: "steer",
+            },
+          })
+          expect(prompts.at(-1)?.text).toBe("Review again\n\nlatest")
         }),
       ),
     ),
@@ -193,11 +246,13 @@ Review files`,
           yield* advance(() => reloads >= 1)
           expect(reloads).toBe(1)
 
-          yield* Effect.promise(() => fs.writeFile(path.join(directory, "review.md"), "Review twice"))
+          yield* Effect.promise(() =>
+            fs.writeFile(path.join(directory, "review.md"), markdown("Review twice", "Review twice")),
+          )
           yield* configTest.emitChange({ type: "update", path: path.join(directory, "review.md") })
           yield* advance(() => reloads >= 2)
           expect(reloads).toBe(2)
-          expect((yield* command.get("review"))?.template).toBe("Review twice")
+          expect((yield* command.get("review"))?.description).toBe("Review twice")
         }).pipe(Effect.provide(Config.testLayer([directoryEntry(tmp.path)]))),
       ),
     ),
@@ -232,10 +287,12 @@ Review files`,
           expect(reloads).toBe(0)
 
           // The feed stays live after unrelated updates.
-          yield* Effect.promise(() => fs.writeFile(path.join(directory, "review.md"), "Review related"))
+          yield* Effect.promise(() =>
+            fs.writeFile(path.join(directory, "review.md"), markdown("Review related", "Review related")),
+          )
           yield* configTest.emitChange({ type: "create", path: path.join(directory, "review.md") })
           yield* advance(() => reloads >= 1)
-          expect((yield* command.get("review"))?.template).toBe("Review related")
+          expect((yield* command.get("review"))?.description).toBe("Review related")
         }).pipe(Effect.provide(Config.testLayer([directoryEntry(tmp.path)]))),
       ),
     ),
@@ -272,28 +329,47 @@ describeNative("ConfigCommandPlugin native watcher", () => {
         yield* watchReady(config, global)
 
         const created = yield* nextCommandUpdate(bus)
-        yield* fs.writeFileString(path.join(global, "commands", "review.md"), "Review native")
+        yield* fs.writeFileString(
+          path.join(global, "commands", "review.md"),
+          markdown("Review native", "Review native"),
+        )
         yield* Fiber.join(created).pipe(Effect.timeout("10 seconds"))
-        expect((yield* command.get("review"))?.template).toBe("Review native")
+        expect((yield* command.get("review"))?.description).toBe("Review native")
 
         const updated = yield* nextCommandUpdate(bus)
-        yield* fs.writeFileString(path.join(global, "commands", "review.md"), "Review native again")
+        yield* fs.writeFileString(
+          path.join(global, "commands", "review.md"),
+          markdown("Review native again", "Review native again"),
+        )
         yield* Fiber.join(updated).pipe(Effect.timeout("10 seconds"))
-        expect((yield* command.get("review"))?.template).toBe("Review native again")
+        expect((yield* command.get("review"))?.description).toBe("Review native again")
       }).pipe(
         Effect.provide(
-          AppNodeBuilder.build(LayerNode.group([Command.node, Config.node, Bus.node, FSUtil.node]), [
-            [
+          AppNodeBuilder.build(
+            LayerNode.group([
+              Command.node,
+              Config.node,
+              Bus.node,
+              FSUtil.node,
+              AppProcess.node,
+              Global.node,
               Location.node,
-              Layer.succeed(
-                Location.Service,
-                Location.Service.of(location({ directory: AbsolutePath.make(path.join(tmp, "project")) })),
-              ),
+              Shell.node,
+            ]),
+            [
+              [
+                Location.node,
+                Layer.succeed(
+                  Location.Service,
+                  Location.Service.of(location({ directory: AbsolutePath.make(path.join(tmp, "project")) })),
+                ),
+              ],
+              [Global.node, Global.layerWith({ config: global, home: path.join(global, "home") })],
+              [Shell.node, shellLayer],
+              [Credential.node, emptyCredentialNode],
+              [WellKnown.node, emptyWellknownNode],
             ],
-            [Global.node, Global.layerWith({ config: global, home: path.join(global, "home") })],
-            [Credential.node, emptyCredentialNode],
-            [WellKnown.node, emptyWellknownNode],
-          ]),
+          ),
         ),
       )
     }),
@@ -337,6 +413,10 @@ function directoryEntry(directory: string) {
   return new Directory({ type: "directory", path: AbsolutePath.make(directory) })
 }
 
+function markdown(description: string, template: string) {
+  return `---\ndescription: ${description}\n---\n${template}`
+}
+
 function sourceCases() {
   return [
     {
@@ -345,33 +425,37 @@ function sourceCases() {
       mutate: (directory: string) =>
         Effect.promise(async () => {
           const file = path.join(directory, "review.md")
-          await fs.writeFile(file, "Review created")
+          await fs.writeFile(file, markdown("Review created", "Review created"))
           return [{ type: "create" as const, path: file }]
         }),
       verify: (command: Command.Interface) =>
         Effect.gen(function* () {
-          expect((yield* command.get("review"))?.template).toBe("Review created")
+          expect((yield* command.get("review"))?.description).toBe("Review created")
         }),
     },
     {
       name: "updated",
       prepare: (directory: string) =>
-        Effect.promise(() => fs.writeFile(path.join(directory, "review.md"), "Review first")),
+        Effect.promise(() =>
+          fs.writeFile(path.join(directory, "review.md"), markdown("Review first", "Review first")),
+        ),
       mutate: (directory: string) =>
         Effect.promise(async () => {
           const file = path.join(directory, "review.md")
-          await fs.writeFile(file, "Review updated")
+          await fs.writeFile(file, markdown("Review updated", "Review updated"))
           return [{ type: "update" as const, path: file }]
         }),
       verify: (command: Command.Interface) =>
         Effect.gen(function* () {
-          expect((yield* command.get("review"))?.template).toBe("Review updated")
+          expect((yield* command.get("review"))?.description).toBe("Review updated")
         }),
     },
     {
       name: "renamed",
       prepare: (directory: string) =>
-        Effect.promise(() => fs.writeFile(path.join(directory, "review.md"), "Review renamed")),
+        Effect.promise(() =>
+          fs.writeFile(path.join(directory, "review.md"), markdown("Review renamed", "Review renamed")),
+        ),
       mutate: (directory: string) =>
         Effect.promise(async () => {
           const previous = path.join(directory, "review.md")
@@ -385,7 +469,7 @@ function sourceCases() {
       verify: (command: Command.Interface) =>
         Effect.gen(function* () {
           expect(yield* command.get("review")).toBeUndefined()
-          expect((yield* command.get("release"))?.template).toBe("Review renamed")
+          expect((yield* command.get("release"))?.description).toBe("Review renamed")
         }),
     },
     {

packages/core/test/plugin/command.test.ts

@@ -1,10 +1,18 @@
 import { describe, expect } from "bun:test"
 import { Effect, Layer } from "effect"
 import { Command } from "@opencode-ai/core/command"
+import { Bus } from "@opencode-ai/core/bus"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { Location } from "@opencode-ai/core/location"
+import { MCP } from "@opencode-ai/core/mcp/index"
 import { CommandPlugin } from "@opencode-ai/core/plugin/command"
 import { AbsolutePath } from "@opencode-ai/core/schema"
+import { Session } from "@opencode-ai/schema/session"
+import { SessionInbox } from "@opencode-ai/schema/session-inbox"
+import { SessionMessage } from "@opencode-ai/schema/session-message"
+import { LayerNode } from "@opencode-ai/util/effect/layer-node"
+import { DateTime } from "effect"
+import { emptyMcpLayer } from "../fixture/mcp"
 import { location } from "../fixture/location"
 import { testEffect } from "../lib/effect"
 import { host } from "./host"
@@ -15,12 +23,18 @@ const locationLayer = Layer.succeed(
   Location.Service,
   Location.Service.of(location({ directory }, { projectDirectory: project })),
 )
-const it = testEffect(AppNodeBuilder.build(Command.node, [[Location.node, locationLayer]]))
+const it = testEffect(
+  AppNodeBuilder.build(LayerNode.group([Command.node, MCP.node, Bus.node]), [
+    [MCP.node, emptyMcpLayer],
+    [Location.node, locationLayer],
+  ]),
+)
 
 describe("CommandPlugin.Plugin", () => {
   it.effect("registers built-in init and review commands", () =>
     Effect.gen(function* () {
       const command = yield* Command.Service
+      const prompts: { text: string; files?: readonly { readonly uri: string }[] }[] = []
       yield* CommandPlugin.Plugin.effect(
         host({
           command: {
@@ -28,6 +42,20 @@ describe("CommandPlugin.Plugin", () => {
             transform: command.transform,
             reload: command.reload,
           },
+          session: {
+            prompt: (input) =>
+              Effect.sync(() => {
+                prompts.push({ text: input.text, files: input.files })
+                return SessionInbox.User.make({
+                  id: SessionMessage.ID.make("msg_test"),
+                  sessionID: input.sessionID,
+                  timeCreated: DateTime.makeUnsafe(0),
+                  type: "user",
+                  payload: { text: input.text },
+                  delivery: input.delivery ?? "steer",
+                })
+              }),
+          },
         }),
       ).pipe(
         Effect.provideService(
@@ -40,11 +68,24 @@ describe("CommandPlugin.Plugin", () => {
         name: "init",
         description: "guided AGENTS.md setup",
       })
-      expect((yield* command.get("init"))?.template).toContain("`/repo`")
       expect(yield* command.get("review")).toMatchObject({
         name: "review",
         description: "review changes [commit|branch|pr], defaults to uncommitted",
       })
+      yield* command.execute({
+        name: "init",
+        invocation: {
+          sessionID: Session.ID.make("ses_test"),
+          prompt: { text: "extra context", files: [{ uri: "file:///tmp/context.md" }] },
+          delivery: "queue",
+        },
+      })
+      expect(prompts).toEqual([
+        {
+          text: expect.stringContaining("extra context"),
+          files: [{ uri: "file:///tmp/context.md" }],
+        },
+      ])
     }),
   )
 })

packages/core/test/plugin/host.ts

@@ -111,6 +111,8 @@ export function host(overrides: Overrides = {}): Plugin.Context {
       hook: overrides.session?.hook ?? (() => Effect.die("unused session.hook")),
       create: overrides.session?.create ?? (() => Effect.die("unused session.create")),
       get: overrides.session?.get ?? (() => Effect.die("unused session.get")),
+      switchAgent: overrides.session?.switchAgent ?? (() => Effect.die("unused session.switchAgent")),
+      switchModel: overrides.session?.switchModel ?? (() => Effect.die("unused session.switchModel")),
       prompt: overrides.session?.prompt ?? (() => Effect.die("unused session.prompt")),
       generate: overrides.session?.generate ?? (() => Effect.die("unused session.generate")),
       command: overrides.session?.command ?? (() => Effect.die("unused session.command")),

packages/plugin/src/effect/command.ts

@@ -1,16 +1,27 @@
 import type { CommandApi } from "@opencode-ai/client/effect/api"
-import type { CommandInfo } from "@opencode-ai/client"
+import type { PromptInput } from "@opencode-ai/schema/prompt-input"
+import type { Session } from "@opencode-ai/schema/session"
+import type { SessionInbox } from "@opencode-ai/schema/session-inbox"
 import type { Effect } from "effect"
 import type { Transform } from "./registration.js"
 
-export interface CommandDraft {
-  list(): readonly CommandInfo[]
-  get(name: string): CommandInfo | undefined
-  update(name: string, update: (command: CommandInfo) => void): void
-  remove(name: string): void
+export interface CommandInvocation {
+  readonly sessionID: Session.ID
+  readonly prompt: PromptInput.Prompt
+  readonly delivery: SessionInbox.Delivery
 }
 
-export interface CommandDomain extends CommandApi<unknown> {
+export interface CommandDefinition {
+  readonly name: string
+  readonly description?: string
+  readonly execute: (input: CommandInvocation) => Effect.Effect<void, unknown>
+}
+
+export interface CommandDraft {
+  add(definition: CommandDefinition): void
+}
+
+export interface CommandDomain extends Pick<CommandApi<unknown>, "list"> {
   readonly transform: Transform<CommandDraft>
   readonly reload: () => Effect.Effect<void>
 }

packages/plugin/src/effect/session.ts

@@ -47,7 +47,17 @@ export interface SessionHooks {
 
 export type SessionDomain = Pick<
   SessionApi<unknown>,
-  "create" | "get" | "prompt" | "generate" | "command" | "synthetic" | "interrupt" | "rename" | "wait"
+  | "create"
+  | "get"
+  | "switchAgent"
+  | "switchModel"
+  | "prompt"
+  | "generate"
+  | "command"
+  | "synthetic"
+  | "interrupt"
+  | "rename"
+  | "wait"
 > & {
   readonly hook: ModelHooks<SessionHooks>
 }

packages/plugin/src/promise/adapter.ts

@@ -149,7 +149,19 @@ export function fromPromise(plugin: Plugin) {
           },
           command: {
             list: adaptApiMethod(CommandEndpoints["command.list"], host.command.list),
-            transform: transform(host.command),
+            transform: (callback) =>
+              register(
+                host.command.transform((draft) =>
+                  callback({
+                    add: (definition) =>
+                      draft.add({
+                        ...definition,
+                        execute: (input) =>
+                          Effect.tryPromise({ try: () => definition.execute(input), catch: (cause) => cause }),
+                      }),
+                  }),
+                ),
+              ),
             reload: () => run(host.command.reload()),
           },
           event: {
@@ -303,6 +315,8 @@ export function fromPromise(plugin: Plugin) {
               ),
             create: adaptApiMethod(SessionEndpoints["session.create"], host.session.create),
             get: adaptApiMethod(SessionEndpoints["session.get"], host.session.get),
+            switchAgent: adaptApiMethod(SessionEndpoints["session.switchAgent"], host.session.switchAgent),
+            switchModel: adaptApiMethod(SessionEndpoints["session.switchModel"], host.session.switchModel),
             prompt: adaptApiMethod(SessionEndpoints["session.prompt"], host.session.prompt),
             generate: adaptApiMethod(SessionEndpoints["session.generate"], host.session.generate),
             command: adaptApiMethod(SessionEndpoints["session.command"], host.session.command),

packages/plugin/src/promise/command.ts

@@ -1,15 +1,26 @@
 import type { CommandApi } from "@opencode-ai/client/promise/api"
-import type { CommandInfo } from "@opencode-ai/client"
+import type { PromptInput } from "@opencode-ai/schema/prompt-input"
+import type { Session } from "@opencode-ai/schema/session"
+import type { SessionInbox } from "@opencode-ai/schema/session-inbox"
 import type { Transform } from "./registration.js"
 
-export interface CommandDraft {
-  list(): readonly CommandInfo[]
-  get(name: string): CommandInfo | undefined
-  update(name: string, update: (command: CommandInfo) => void): void
-  remove(name: string): void
+export interface CommandInvocation {
+  readonly sessionID: Session.ID
+  readonly prompt: PromptInput.Prompt
+  readonly delivery: SessionInbox.Delivery
 }
 
-export interface CommandDomain extends CommandApi {
+export interface CommandDefinition {
+  readonly name: string
+  readonly description?: string
+  readonly execute: (input: CommandInvocation) => Promise<void>
+}
+
+export interface CommandDraft {
+  add(definition: CommandDefinition): void
+}
+
+export interface CommandDomain extends Pick<CommandApi, "list"> {
   readonly transform: Transform<CommandDraft>
   readonly reload: () => Promise<void>
 }

packages/plugin/src/promise/session.ts

@@ -47,7 +47,17 @@ export interface SessionHooks {
 
 export type SessionDomain = Pick<
   SessionApi,
-  "create" | "get" | "prompt" | "generate" | "command" | "synthetic" | "interrupt" | "rename" | "wait"
+  | "create"
+  | "get"
+  | "switchAgent"
+  | "switchModel"
+  | "prompt"
+  | "generate"
+  | "command"
+  | "synthetic"
+  | "interrupt"
+  | "rename"
+  | "wait"
 > & {
   readonly hook: ModelHooks<SessionHooks>
 }

packages/protocol/src/errors.ts

@@ -117,8 +117,8 @@ export class CommandNotFoundError extends Schema.TaggedError<CommandNotFoundErro
   { httpApiStatus: 404 },
 ) {}
 
-export class CommandEvaluationError extends Schema.TaggedError<CommandEvaluationError>()(
-  "CommandEvaluationError",
+export class CommandExecutionError extends Schema.TaggedError<CommandExecutionError>()(
+  "CommandExecutionError",
   {
     command: Schema.String,
     message: Schema.String,

packages/protocol/src/groups/session.ts

@@ -12,7 +12,7 @@ import { Context, Effect, Encoding, Result, Schema, SchemaGetter, Struct } from
 import { HttpApiEndpoint, HttpApiGroup, HttpApiMiddleware, HttpApiSchema, OpenApi } from "effect/unstable/httpapi"
 import {
   ConflictError,
-  CommandEvaluationError,
+  CommandExecutionError,
   CommandNotFoundError,
   InvalidCursorError,
   InvalidRequestError,
@@ -338,27 +338,19 @@ export const makeSessionGroup = <I extends HttpApiMiddleware.AnyId, S>(sessionLo
       HttpApiEndpoint.post("session.command", "/api/session/:sessionID/command", {
         params: { sessionID: Session.ID },
         payload: Schema.Struct({
-          id: SessionMessage.ID.pipe(Schema.optional),
           command: Schema.String,
-          arguments: Schema.String.pipe(Schema.optional),
-          agent: Agent.ID.pipe(Schema.optional),
-          model: Model.Ref.pipe(Schema.optional),
-          files: PromptInput.Prompt.fields.files,
-          agents: PromptInput.Prompt.fields.agents,
-          skills: PromptInput.Prompt.fields.skills,
+          ...PromptInput.Prompt.fields,
           delivery: SessionInbox.Delivery.pipe(Schema.optional),
-          resume: Schema.Boolean.pipe(Schema.optional),
         }),
-        success: Schema.Struct({ data: SessionInbox.User }),
-        error: [ConflictError, InvalidRequestError, SessionNotFoundError, CommandNotFoundError, CommandEvaluationError],
+        success: HttpApiSchema.NoContent,
+        error: [SessionNotFoundError, CommandNotFoundError, CommandExecutionError],
       })
         .middleware(sessionLocationMiddleware)
         .annotateMerge(
           OpenApi.annotations({
             identifier: "v2.session.command",
             summary: "Run command",
-            description:
-              "Resolve a slash command into prompt input, admit it durably, and schedule execution unless resume is false.",
+            description: "Execute a slash command callback immediately.",
           }),
         ),
     )

packages/schema/src/command.ts

@@ -3,19 +3,13 @@ export * as Command from "./command.js"
 import { Schema } from "effect"
 import { ephemeral, inventory } from "./event.js"
 import { optional } from "./schema.js"
-import { Model } from "./model.js"
-import { Agent } from "./agent.js"
 
 const Updated = ephemeral({ type: "command.updated", schema: {} })
 
 export interface Info extends Schema.Schema.Type<typeof Info> {}
 export const Info = Schema.Struct({
   name: Schema.String,
-  template: Schema.String,
   description: Schema.String.pipe(optional),
-  agent: Agent.ID.pipe(optional),
-  model: Model.Ref.pipe(optional),
-  subtask: Schema.Boolean.pipe(optional),
 }).annotate({ identifier: "Command.Info" })
 
 export const Event = {

packages/server/src/handlers/session.ts

@@ -7,7 +7,7 @@ import { Api } from "../api"
 import { SessionsCursor } from "@opencode-ai/protocol/groups/session"
 import {
   ConflictError,
-  CommandEvaluationError,
+  CommandExecutionError,
   CommandNotFoundError,
   InvalidRequestError,
   InvalidCursorError,
@@ -365,62 +365,42 @@ export const SessionHandler = HttpApiBuilder.group(Api, "server.session", (handl
       .handle(
         "session.command",
         Effect.fn(function* (ctx) {
-          return {
-            data: yield* session
-              .command({
-                sessionID: ctx.params.sessionID,
-                id: ctx.payload.id,
-                command: ctx.payload.command,
-                arguments: ctx.payload.arguments,
-                agent: ctx.payload.agent,
-                model: ctx.payload.model,
-                files: ctx.payload.files,
-                agents: ctx.payload.agents,
-                skills: ctx.payload.skills,
-                delivery: ctx.payload.delivery,
-                resume: ctx.payload.resume,
-              })
-              .pipe(
-                Effect.catchTag("Session.NotFoundError", (error) =>
-                  Effect.fail(
-                    new SessionNotFoundError({
-                      sessionID: error.sessionID,
-                      message: `Session not found: ${error.sessionID}`,
-                    }),
-                  ),
-                ),
-                Effect.catchTag("Command.NotFoundError", (error) =>
-                  Effect.fail(
-                    new CommandNotFoundError({
-                      command: error.command,
-                      message: error.message,
-                    }),
-                  ),
-                ),
-                Effect.catchTag("Command.EvaluationError", (error) =>
-                  Effect.fail(
-                    new CommandEvaluationError({
-                      command: error.command,
-                      message: error.message,
-                    }),
-                  ),
-                ),
-                Effect.catchTag("Session.PromptConflictError", (error) =>
-                  Effect.fail(
-                    new ConflictError({
-                      message: `Prompt message ID conflicts with an existing durable record: ${error.messageID}`,
-                      resource: error.messageID,
-                    }),
-                  ),
-                ),
-                Effect.catchTag("Session.AttachmentError", (error) =>
-                  Effect.fail(new InvalidRequestError({ message: error.message, field: "files" })),
-                ),
-                Effect.catchTag("Session.SkillNotFoundError", (error) =>
-                  Effect.fail(new InvalidRequestError({ message: `Skill not found: ${error.skill}`, field: "skills" })),
+          yield* session
+            .command({
+              sessionID: ctx.params.sessionID,
+              command: ctx.payload.command,
+              text: ctx.payload.text,
+              files: ctx.payload.files,
+              agents: ctx.payload.agents,
+              skills: ctx.payload.skills,
+              delivery: ctx.payload.delivery,
+            })
+            .pipe(
+              Effect.catchTag("Session.NotFoundError", (error) =>
+                Effect.fail(
+                  new SessionNotFoundError({
+                    sessionID: error.sessionID,
+                    message: `Session not found: ${error.sessionID}`,
+                  }),
                 ),
               ),
-          }
+              Effect.catchTag("Command.NotFoundError", (error) =>
+                Effect.fail(
+                  new CommandNotFoundError({
+                    command: error.command,
+                    message: error.message,
+                  }),
+                ),
+              ),
+              Effect.catchTag("Command.ExecutionError", (error) =>
+                Effect.fail(
+                  new CommandExecutionError({
+                    command: error.command,
+                    message: error.message,
+                  }),
+                ),
+              ),
+            )
         }),
       )
       .handle(

packages/server/src/routes.ts

@@ -115,7 +115,6 @@ function makeRoutes<AuthError, AuthServices>(
       }),
     ],
     [InstructionDiscovery.node, InstructionDiscovery.configured({ project: options.config?.project })],
-    [Command.node, Command.configured({ gitbash: options.windows?.gitbash })],
     [Pty.node, Pty.configured({ gitbash: options.windows?.gitbash })],
     [Shell.node, Shell.configured({ gitbash: options.windows?.gitbash })],
     [

packages/tui/src/component/prompt/index.tsx

@@ -1230,24 +1230,17 @@ export function Prompt(props: PromptProps) {
       })
       setStore("mode", "normal")
     } else if (slashHead && isCommand) {
-      move.startSubmit()
-      const model = { providerID: selection.providerID, id: selection.modelID, variant }
-      const cancelCommit = local.model.trackSessionCommit(sessionID, model)
-
       void client.api.session
         .command({
           sessionID,
           command: slashHead.name,
-          arguments: slashHead.arguments,
-          agent: agent.id,
-          model,
+          text: slashHead.arguments,
           files: store.prompt.files,
           agents: store.prompt.agents,
           skills: store.prompt.skills?.length ? store.prompt.skills : undefined,
           delivery,
         })
         .catch((error) => {
-          cancelCommit()
           toast.show({ title: "Failed to run command", message: errorMessage(error), variant: "error" })
         })
     } else if (isSkill) {

packages/tui/src/mini/stream-v2.transport.ts

@@ -1647,17 +1647,12 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
       )
     }
 
-    const selected = await resolveSelectedModel(input, client, next)
-    if (next.variant && !selected) throw new Error("Cannot select a variant before selecting a model")
     input.trace?.write("send.command", { sessionID: input.sessionID, messageID, command: command.name, delivery })
     return client.session.command(
       {
         sessionID: input.sessionID,
-        id: messageID,
         command: command.name,
-        arguments: command.arguments,
-        agent: next.agent,
-        model: selected,
+        text: command.arguments,
         files: attachments.files.length ? attachments.files : undefined,
         agents: agents.length ? agents : undefined,
         skills: skills.length ? skills : undefined,
@@ -1698,7 +1693,7 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
         throw new Error("This prompt cannot be queued")
       if (!state.connected) throw new Error("Event stream is reconnecting")
       const client = sdk
-      if (next.agent)
+      if (!next.prompt.command && next.agent)
         await client.session.switchAgent({ sessionID: input.sessionID, agent: next.agent }, { signal: next.signal })
       if (!next.prompt.command) {
         const selected = await resolveSelectedModel(input, client, next)
@@ -1706,7 +1701,8 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
         if (selected)
           await client.session.switchModel({ sessionID: input.sessionID, model: selected }, { signal: next.signal })
       }
-      mergePending(await admitPrompt(next, client, delivery))
+      const admitted = await admitPrompt(next, client, delivery)
+      if (admitted) mergePending(admitted)
       settlementClient = client
     },
     async waitForIdle() {
@@ -1744,13 +1740,8 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
         return
       }
       if (command) {
-        await runTurnWait(
-          next,
-          messageID,
-          client,
-          () => admitPrompt(next, client, next.prompt.delivery ?? "steer"),
-          admitted,
-        )
+        await admitPrompt(next, client, next.prompt.delivery ?? "steer")
+        admitted?.()
         return
       }
 

packages/tui/test/mini/stream-v2.transport.test.ts

@@ -2814,14 +2814,7 @@ describe("V2 mini transport", () => {
           data: { sessionID: "ses_1" },
         })
       })
-      return ok({
-        id: input.id ?? "msg_cmd",
-        sessionID: "ses_1",
-        type: "user" as const,
-        payload: { text: "evaluated template" },
-        delivery: "steer" as const,
-        timeCreated: 2,
-      })
+      return ok(undefined)
     })
 
     await transport.runPromptTurn({
@@ -2852,11 +2845,8 @@ describe("V2 mini transport", () => {
 
     expect(request).toMatchObject({
       sessionID: "ses_1",
-      id: "msg_cmd",
       command: "deploy",
-      arguments: "prod",
-      agent: "build",
-      model: { providerID: "test", id: "model" },
+      text: "prod",
       files: [
         { uri: "file:///tmp/context.txt", name: "context.txt" },
         {
@@ -2868,7 +2858,6 @@ describe("V2 mini transport", () => {
       skills: [{ id: "api-design", mention: { start: 13, end: 24, text: "/api-design" } }],
       delivery: "steer",
     })
-    // Selection rides the command payload; no separate client-side switch.
     expect(client.session.switchAgent).not.toHaveBeenCalled()
     expect(client.session.switchModel).not.toHaveBeenCalled()
     await transport.close()