diff --git a/packages/client/src/promise/generated/types.ts b/packages/client/src/promise/generated/types.ts
index 13dab421d59..f2aa6a3ff6e 100644
--- a/packages/client/src/promise/generated/types.ts
+++ b/packages/client/src/promise/generated/types.ts
@@ -3690,7 +3690,7 @@ export type CommandListOutput = {
     readonly description?: string
     readonly agent?: string
     readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string }
-    readonly subtask?: boolean
+    readonly subagent?: boolean
   }>
 }
 
diff --git a/packages/core/src/config.ts b/packages/core/src/config.ts
index 9d03d09c38d..8ffd12e0ef6 100644
--- a/packages/core/src/config.ts
+++ b/packages/core/src/config.ts
@@ -155,7 +155,7 @@ const layer = Layer.effect(
       const info = Option.getOrUndefined(
         ConfigMigrateV1.isV1(input)
           ? decodeV1Info(input).pipe(Option.map(ConfigMigrateV1.migrate), Option.flatMap(decodeInfo))
-          : decodeInfo(input),
+          : decodeInfo(normalizeCommandAliases(input)),
       )
       if (!info) return
       return new Document({ type: "document", path: filepath, info })
@@ -223,3 +223,21 @@ export const node = makeLocationNode({
   layer,
   deps: [FSUtil.node, Global.node, Location.node, Policy.node],
 })
+
+function normalizeCommandAliases(input: unknown) {
+  if (typeof input !== "object" || input === null || Array.isArray(input)) return input
+  const commands = (input as Record<string, unknown>).commands
+  if (typeof commands !== "object" || commands === null || Array.isArray(commands)) return input
+  return {
+    ...input,
+    commands: Object.fromEntries(
+      Object.entries(commands).map(([name, command]) => {
+        if (typeof command !== "object" || command === null || Array.isArray(command)) return [name, command]
+        const data = command as Record<string, unknown>
+        if (data.subagent !== undefined || typeof data.subtask !== "boolean") return [name, command]
+        const { subtask, ...rest } = data
+        return [name, { ...rest, subagent: subtask }]
+      }),
+    ),
+  }
+}
diff --git a/packages/core/src/config/command.ts b/packages/core/src/config/command.ts
index 394079b1e98..a98f8898e7d 100644
--- a/packages/core/src/config/command.ts
+++ b/packages/core/src/config/command.ts
@@ -8,5 +8,5 @@ export class Info extends Schema.Class<Info>("ConfigV2.Command")({
   agent: Schema.String.pipe(Schema.optional),
   model: Schema.String.pipe(Schema.optional),
   variant: Schema.String.pipe(Schema.optional),
-  subtask: Schema.Boolean.pipe(Schema.optional),
+  subagent: Schema.Boolean.pipe(Schema.optional),
 }) {}
diff --git a/packages/core/src/config/plugin/command.ts b/packages/core/src/config/plugin/command.ts
index f9b31f8e45a..0ba1459b971 100644
--- a/packages/core/src/config/plugin/command.ts
+++ b/packages/core/src/config/plugin/command.ts
@@ -40,7 +40,7 @@ export const Plugin = define({
               if (command.variant !== undefined && item.model !== undefined) {
                 item.model.variant = ModelV2.VariantID.make(command.variant)
               }
-              if (command.subtask !== undefined) item.subtask = command.subtask
+              if (command.subagent !== undefined) item.subagent = command.subagent
             })
           }
         }
@@ -70,7 +70,9 @@ function loadDirectory(fs: FSUtil.Interface, directory: string) {
 function decode(directory: string, filepath: string, content: string) {
   const markdown = ConfigMarkdown.parseOption(content)
   if (!markdown) return
-  const info = Option.getOrUndefined(decodeCommand({ ...markdown.data, template: markdown.content.trim() }))
+  const info = Option.getOrUndefined(
+    decodeCommand({ ...normalizeFrontmatter(markdown.data), template: markdown.content.trim() }),
+  )
   if (!info) return
   return {
     name: path
@@ -81,3 +83,9 @@ function decode(directory: string, filepath: string, content: string) {
     info,
   }
 }
+
+function normalizeFrontmatter(data: Record<string, unknown>) {
+  if (data.subagent !== undefined || typeof data.subtask !== "boolean") return data
+  const { subtask, ...rest } = data
+  return { ...rest, subagent: subtask }
+}
diff --git a/packages/core/src/plugin/command.ts b/packages/core/src/plugin/command.ts
index 19896412380..36e9497b3a8 100644
--- a/packages/core/src/plugin/command.ts
+++ b/packages/core/src/plugin/command.ts
@@ -18,6 +18,7 @@ export const Plugin = define({
       draft.update("review", (command) => {
         command.template = PROMPT_REVIEW.replace("${path}", location.project.directory)
         command.description = "review changes [commit|branch|pr], defaults to uncommitted"
+        command.subagent = true
       })
     })
   }),
diff --git a/packages/core/src/plugin/skill/customize-opencode.md b/packages/core/src/plugin/skill/customize-opencode.md
index 6932dbfd54c..4732d133d70 100644
--- a/packages/core/src/plugin/skill/customize-opencode.md
+++ b/packages/core/src/plugin/skill/customize-opencode.md
@@ -303,7 +303,8 @@ model: anthropic/claude-sonnet-4-6
 
 - `template` is the command body — everything below the frontmatter — and is required: it is the prompt opencode runs when the command is invoked. Do not also put a `template:` key in the frontmatter.
 - `$ARGUMENTS` is replaced with everything the user typed after the command; `$1`, `$2`, … pull individual positional arguments.
-- Optional: `description`, `agent`, `model`, `variant`, `subtask`.
+- Optional: `description`, `agent`, `model`, `variant`, `subagent`.
+- `subtask` is still accepted for older commands and is treated like `subagent`.
 
 ## Plugins
 
diff --git a/packages/core/src/session.ts b/packages/core/src/session.ts
index 108d36707a2..11dbf7454cc 100644
--- a/packages/core/src/session.ts
+++ b/packages/core/src/session.ts
@@ -45,6 +45,10 @@ import { Identifier } from "./util/identifier"
 import { Shell } from "./shell"
 import { KeyedMutex } from "./effect/keyed-mutex"
 
+const SUBAGENT_COMMAND_STARTED =
+  "The command is running in a background subagent session. You will be notified automatically when it finishes. DO NOT sleep, poll, or proactively check on its progress."
+const SUBAGENT_COMMAND_NO_TEXT = "Subagent command completed without a text response."
+
 export const RevertState = Revert.State
 export type RevertState = Revert.State
 
@@ -524,14 +528,77 @@ const layer = Layer.effect(
           })
         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 agents = yield* AgentV2.Service.pipe(Effect.provide(locations.get(session.location)))
+        const commandAgent = command.agent ? yield* agents.get(AgentV2.ID.make(command.agent)) : undefined
+        const model = command.model ?? commandAgent?.model ?? input.model ?? session.model
+        const subagent = command.subagent ?? false
+
+        if (subagent) {
+          const childAgent = AgentV2.ID.make(command.agent ?? "general")
+          const childAgentInfo = yield* agents.get(childAgent)
+          const title = command.description ?? input.command
+          const child = yield* result.create({
+            parentID: input.sessionID,
+            title,
+            agent: childAgent,
+            model: command.model ?? childAgentInfo?.model ?? input.model ?? session.model,
+          })
+          const completion = (state: "completed" | "error" | "cancelled", text: string) =>
+            result.synthetic({
+              sessionID: input.sessionID,
+              text: `<subagent id="${child.id}" state="${state}" description="${title}">\n${text}\n</subagent>`,
+              description: command.description,
+              metadata: { command: input.command, subagent: true, sessionID: child.id },
+            })
+          const admitted = yield* result.prompt({
+            id: input.id,
+            sessionID: child.id,
+            prompt: { text: evaluated.text, files: input.files, agents: input.agents },
+            delivery: input.delivery,
+            resume: false,
+          })
+          yield* jobs.start({
+            id: child.id,
+            type: "subagent",
+            title,
+            metadata: { command: input.command, parentID: input.sessionID, agent: childAgent.toString() },
+            run: Effect.gen(function* () {
+              yield* result.resume(child.id)
+              const messages = yield* result.messages({ sessionID: child.id, order: "desc", limit: 20 })
+              const assistant = messages.find(
+                (message) =>
+                  message.type === "assistant" && message.time.completed !== undefined && message.error === undefined,
+              )
+              if (assistant === undefined || assistant.type !== "assistant") return SUBAGENT_COMMAND_NO_TEXT
+              const text = assistant.content
+                .filter((part): part is Extract<typeof part, { type: "text" }> => part.type === "text")
+                .map((part) => part.text)
+                .join("")
+              return text.length > 0 ? text : SUBAGENT_COMMAND_NO_TEXT
+            }).pipe(Effect.onInterrupt(() => result.interrupt(child.id))),
+          })
+          yield* jobs.background(child.id)
+          yield* jobs.wait({ id: child.id }).pipe(
+            Effect.flatMap((result) => {
+              if (result.info?.status === "completed")
+                return completion("completed", result.info.output ?? SUBAGENT_COMMAND_NO_TEXT)
+              if (result.info?.status === "error")
+                return completion("error", result.info.error ?? "Subagent command failed")
+              if (result.info?.status === "cancelled") return completion("cancelled", "Subagent command cancelled")
+              return Effect.void
+            }),
+            Effect.forkIn(scope, { startImmediately: true }),
+          )
+          yield* result.synthetic({
+            sessionID: input.sessionID,
+            text: `<subagent id="${child.id}" state="running" description="${title}">\n${SUBAGENT_COMMAND_STARTED}\n</subagent>`,
+            description: command.description,
+            metadata: { command: input.command, subagent: true, sessionID: child.id },
+          })
+          return admitted
+        }
+
         const agent = command.agent ?? input.agent
-        const commandAgent = yield* Effect.gen(function* () {
-          if (!command.agent) return undefined
-          const agents = yield* AgentV2.Service.pipe(Effect.provide(locations.get(session.location)))
-          return yield* agents.get(AgentV2.ID.make(command.agent))
-        })
-        const model = command.model ?? commandAgent?.model ?? input.model
         if (agent !== undefined && session.agent !== AgentV2.ID.make(agent))
           yield* result.switchAgent({ sessionID: input.sessionID, agent })
         if (model !== undefined) yield* result.switchModel({ sessionID: input.sessionID, model })
diff --git a/packages/core/src/v1/config/migrate.ts b/packages/core/src/v1/config/migrate.ts
index 2a9e1c73832..8404e9b68c6 100644
--- a/packages/core/src/v1/config/migrate.ts
+++ b/packages/core/src/v1/config/migrate.ts
@@ -72,7 +72,7 @@ export function migrate(info: typeof ConfigV1.Info.Type) {
       buffer: info.compaction.reserved,
     },
     skills: info.skills && [...(info.skills.paths ?? []), ...(info.skills.urls ?? [])],
-    commands: info.command,
+    commands: commands(info.command),
     instructions: info.instructions,
     references: info.references ?? info.reference,
     plugins: info.plugin?.map((plugin) =>
@@ -83,6 +83,17 @@ export function migrate(info: typeof ConfigV1.Info.Type) {
   }
 }
 
+function commands(info?: typeof ConfigV1.Info.Type.command) {
+  if (!info) return undefined
+  return Object.fromEntries(
+    Object.entries(info).map(([name, command]) => {
+      if (command?.subtask === undefined) return [name, command]
+      const { subtask, ...rest } = command
+      return [name, { ...rest, subagent: subtask }]
+    }),
+  )
+}
+
 function permissions(info?: ConfigPermissionV1.Info, tools?: Readonly<Record<string, boolean>>) {
   const rules: Array<{ action: string; resource: string; effect: ConfigPermissionV1.Action }> = Object.entries(
     tools ?? {},
diff --git a/packages/core/test/config/command.test.ts b/packages/core/test/config/command.test.ts
index 362a8e5da5f..35c9b08f2ab 100644
--- a/packages/core/test/config/command.test.ts
+++ b/packages/core/test/config/command.test.ts
@@ -44,9 +44,16 @@ description: File review
 agent: reviewer
 model: anthropic/claude
 variant: high
-subtask: true
+subagent: true
 ---
 Review files`,
+            )
+            await fs.writeFile(
+              path.join(tmp.path, "commands", "legacy.md"),
+              `---
+subtask: true
+---
+Legacy review`,
             )
             await fs.writeFile(path.join(tmp.path, "commands", "nested", "docs.md"), "Write docs")
             await fs.writeFile(path.join(tmp.path, "commands", "empty.md"), "")
@@ -80,9 +87,10 @@ Review files`,
                 id: ModelV2.ID.make("claude"),
                 variant: ModelV2.VariantID.make("high"),
               },
-              subtask: true,
+              subagent: true,
             }),
             CommandV2.Info.make({ name: "empty", template: "" }),
+            CommandV2.Info.make({ name: "legacy", template: "Legacy review", subagent: true }),
             CommandV2.Info.make({ name: "nested/docs", template: "Write docs" }),
           ])
         }),
diff --git a/packages/core/test/config/config.test.ts b/packages/core/test/config/config.test.ts
index e46644abaee..66eaf09e8fa 100644
--- a/packages/core/test/config/config.test.ts
+++ b/packages/core/test/config/config.test.ts
@@ -149,7 +149,7 @@ describe("Config", () => {
           agent: "reviewer",
           model: "anthropic/claude",
           variant: "high",
-          subtask: true,
+          subagent: true,
         },
       })
     }),
diff --git a/packages/core/test/plugin/command.test.ts b/packages/core/test/plugin/command.test.ts
index be84975f644..fa08b26351f 100644
--- a/packages/core/test/plugin/command.test.ts
+++ b/packages/core/test/plugin/command.test.ts
@@ -40,6 +40,7 @@ describe("CommandPlugin.Plugin", () => {
       expect(yield* command.get("review")).toMatchObject({
         name: "review",
         description: "review changes [commit|branch|pr], defaults to uncommitted",
+        subagent: true,
       })
     }),
   )
diff --git a/packages/core/test/session-command.test.ts b/packages/core/test/session-command.test.ts
new file mode 100644
index 00000000000..32450e43163
--- /dev/null
+++ b/packages/core/test/session-command.test.ts
@@ -0,0 +1,134 @@
+import { describe, expect } from "bun:test"
+import { Effect, Layer } from "effect"
+import { AgentV2 } from "@opencode-ai/core/agent"
+import { CommandV2 } from "@opencode-ai/core/command"
+import { Database } from "@opencode-ai/core/database/database"
+import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
+import { LayerNode } from "@opencode-ai/core/effect/layer-node"
+import { EventV2 } from "@opencode-ai/core/event"
+import { Job } from "@opencode-ai/core/job"
+import { Location } from "@opencode-ai/core/location"
+import { LocationServiceMap } from "@opencode-ai/core/location-service-map"
+import { ModelV2 } from "@opencode-ai/core/model"
+import { ProjectV2 } from "@opencode-ai/core/project"
+import { ProviderV2 } from "@opencode-ai/core/provider"
+import { AbsolutePath } from "@opencode-ai/core/schema"
+import { SessionV2 } from "@opencode-ai/core/session"
+import { SessionExecution } from "@opencode-ai/core/session/execution"
+import { SessionProjector } from "@opencode-ai/core/session/projector"
+import { SessionStore } from "@opencode-ai/core/session/store"
+import { tmpdir } from "./fixture/tmpdir"
+import { testEffect } from "./lib/effect"
+
+const projects = Layer.succeed(
+  ProjectV2.Service,
+  ProjectV2.Service.of({
+    resolve: (directory) => Effect.succeed({ id: ProjectV2.ID.global, directory }),
+    directories: () => Effect.succeed([]),
+    commit: () => Effect.void,
+  }),
+)
+
+const it = testEffect(
+  AppNodeBuilder.build(
+    LayerNode.group([
+      Database.node,
+      EventV2.node,
+      Job.node,
+      SessionProjector.node,
+      SessionStore.node,
+      SessionV2.node,
+      LocationServiceMap.node,
+    ]),
+    [
+      [ProjectV2.node, projects],
+      [
+        SessionExecution.node,
+        Layer.succeed(
+          SessionExecution.Service,
+          SessionExecution.Service.of({
+            active: Effect.succeed(new Set()),
+            resume: () => Effect.never,
+            wake: () => Effect.void,
+            interrupt: () => Effect.void,
+            awaitIdle: () => Effect.void,
+          }),
+        ),
+      ],
+    ],
+  ),
+)
+
+const model = ModelV2.Ref.make({ id: ModelV2.ID.make("sonnet"), providerID: ProviderV2.ID.make("anthropic") })
+
+function withTmp<A, E, R>(f: (location: Location.Ref) => Effect.Effect<A, E, R>) {
+  return Effect.acquireRelease(
+    Effect.promise(() => tmpdir()),
+    (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+  ).pipe(Effect.flatMap((tmp) => f(Location.Ref.make({ directory: AbsolutePath.make(tmp.path) }))))
+}
+
+describe("SessionV2.command", () => {
+  it.effect("runs subagent commands as background child sessions", () =>
+    withTmp((location) =>
+      Effect.gen(function* () {
+        const sessions = yield* SessionV2.Service
+        const parent = yield* sessions.create({ location, model })
+        const locations = yield* LocationServiceMap.Service
+        const commands = yield* CommandV2.Service.pipe(Effect.provide(locations.get(parent.location)))
+        yield* commands.transform((draft) => {
+          draft.update("review", (command) => {
+            command.template = "Review this"
+            command.description = "review changes"
+            command.agent = "reviewer"
+            command.subagent = true
+          })
+        })
+
+        const admitted = yield* sessions.command({ sessionID: parent.id, command: "review" })
+        const children = yield* sessions.list({ parentID: parent.id })
+
+        expect(children.data).toHaveLength(1)
+        expect(children.data[0]).toMatchObject({
+          parentID: parent.id,
+          title: "review changes",
+          agent: AgentV2.ID.make("reviewer"),
+          model,
+        })
+        expect(admitted).toMatchObject({ sessionID: children.data[0]!.id, prompt: { text: "Review this" } })
+        expect(yield* Job.Service.use((jobs) => jobs.get(children.data[0]!.id))).toMatchObject({
+          id: children.data[0]!.id,
+          type: "subagent",
+          status: "running",
+        })
+        expect(yield* sessions.messages({ sessionID: parent.id })).toEqual([
+          expect.objectContaining({ type: "synthetic", text: expect.stringContaining(children.data[0]!.id) }),
+        ])
+      }),
+    ),
+  )
+
+  it.effect("defaults subagent commands without an agent to the general agent", () =>
+    withTmp((location) =>
+      Effect.gen(function* () {
+        const sessions = yield* SessionV2.Service
+        const parent = yield* sessions.create({ location })
+        const locations = yield* LocationServiceMap.Service
+        const commands = yield* CommandV2.Service.pipe(Effect.provide(locations.get(parent.location)))
+        yield* commands.transform((draft) => {
+          draft.update("research", (command) => {
+            command.template = "Legacy task"
+            command.subagent = true
+          })
+        })
+
+        const admitted = yield* sessions.command({ sessionID: parent.id, command: "research" })
+        const children = yield* sessions.list({ parentID: parent.id })
+
+        expect(children.data).toHaveLength(1)
+        expect(children.data[0]).toMatchObject({ agent: AgentV2.ID.make("general") })
+        expect(admitted).toMatchObject({ sessionID: children.data[0]!.id, prompt: { text: "Legacy task" } })
+      }),
+    ),
+  )
+})
diff --git a/packages/schema/src/command.ts b/packages/schema/src/command.ts
index 81e37157c6a..9b4a8efb6f7 100644
--- a/packages/schema/src/command.ts
+++ b/packages/schema/src/command.ts
@@ -14,7 +14,7 @@ export const Info = Schema.Struct({
   description: Schema.String.pipe(optional),
   agent: Schema.String.pipe(optional),
   model: Model.Ref.pipe(optional),
-  subtask: Schema.Boolean.pipe(optional),
+  subagent: Schema.Boolean.pipe(optional),
 }).annotate({ identifier: "CommandV2.Info" })
 
 export const Event = {
diff --git a/packages/sdk/js/src/v2/gen/types.gen.ts b/packages/sdk/js/src/v2/gen/types.gen.ts
index d97eb59298f..1681bb06c73 100644
--- a/packages/sdk/js/src/v2/gen/types.gen.ts
+++ b/packages/sdk/js/src/v2/gen/types.gen.ts
@@ -5506,7 +5506,7 @@ export type CommandV2Info = {
   description?: string
   agent?: string
   model?: ModelRef
-  subtask?: boolean
+  subagent?: boolean
 }
 
 export type SkillV2Info = {
@@ -9461,7 +9461,7 @@ export type CommandV2Info2 = {
   description?: string
   agent?: string
   model?: ModelRef2
-  subtask?: boolean
+  subagent?: boolean
 }
 
 export type SkillV2Info2 = {