diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts
index 378e0b721..52c714a5a 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts
@@ -25,6 +25,10 @@ const ConsoleStateResponse = Schema.Struct({
   switchableOrgCount: NonNegativeInt,
 }).annotate({ identifier: "ConsoleState" })
 
+const CapabilitiesResponse = Schema.Struct({
+  backgroundSubagents: Schema.Boolean,
+}).annotate({ identifier: "ExperimentalCapabilities" })
+
 const ConsoleOrgOption = Schema.Struct({
   accountID: Schema.String,
   accountEmail: Schema.String,
@@ -84,6 +88,7 @@ export const SessionListQuery = Schema.Struct({
 })
 
 export const ExperimentalPaths = {
+  capabilities: "/experimental/capabilities",
   console: "/experimental/console",
   consoleOrgs: "/experimental/console/orgs",
   consoleSwitch: "/experimental/console/switch",
@@ -100,6 +105,16 @@ export const ExperimentalApi = HttpApi.make("experimental")
   .add(
     HttpApiGroup.make("experimental")
       .add(
+        HttpApiEndpoint.get("capabilities", ExperimentalPaths.capabilities, {
+          query: WorkspaceRoutingQuery,
+          success: described(CapabilitiesResponse, "Experimental capabilities"),
+        }).annotateMerge(
+          OpenApi.annotations({
+            identifier: "experimental.capabilities.get",
+            summary: "Get experimental capabilities",
+            description: "Get experimental features enabled on the OpenCode server.",
+          }),
+        ),
         HttpApiEndpoint.get("console", ExperimentalPaths.console, {
           query: WorkspaceRoutingQuery,
           success: described(ConsoleStateResponse, "Active Console provider metadata"),
diff --git a/packages/opencode/src/server/routes/instance/httpapi/handlers/experimental.ts b/packages/opencode/src/server/routes/instance/httpapi/handlers/experimental.ts
index 57d6464d9..caed54400 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/handlers/experimental.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/handlers/experimental.ts
@@ -36,6 +36,10 @@ export const experimentalHandlers = HttpApiBuilder.group(InstanceHttpApi, "exper
     const background = yield* BackgroundJob.Service
     const flags = yield* RuntimeFlags.Service
 
+    const capabilities = Effect.fn("ExperimentalHttpApi.capabilities")(function* () {
+      return { backgroundSubagents: flags.experimentalBackgroundSubagents }
+    })
+
     const getConsole = Effect.fn("ExperimentalHttpApi.console")(function* () {
       const [state, groups] = yield* Effect.all(
         [
@@ -171,6 +175,7 @@ export const experimentalHandlers = HttpApiBuilder.group(InstanceHttpApi, "exper
     })
 
     return handlers
+      .handle("capabilities", capabilities)
       .handle("console", getConsole)
       .handle("consoleOrgs", listConsoleOrgs)
       .handle("consoleSwitch", switchConsole)
diff --git a/packages/opencode/test/server/httpapi-exercise/index.ts b/packages/opencode/test/server/httpapi-exercise/index.ts
index 3860d742d..e8fdadd8e 100644
--- a/packages/opencode/test/server/httpapi-exercise/index.ts
+++ b/packages/opencode/test/server/httpapi-exercise/index.ts
@@ -578,6 +578,12 @@ const scenarios: Scenario[] = [
     .get("/experimental/session", "experimental.session.list")
     .at((ctx) => ({ path: "/experimental/session?roots=false&archived=false", headers: ctx.headers() }))
     .json(200, array),
+  http.protected
+    .get("/experimental/capabilities", "experimental.capabilities.get")
+    .json(200, (body) => {
+      check(typeof body === "object" && body !== null, "capabilities should be an object")
+      check("backgroundSubagents" in body, "capabilities should report background subagents")
+    }),
   http.protected
     .post("/experimental/session/{sessionID}/background", "experimental.session.background")
     .mutating()
diff --git a/packages/sdk/js/src/v2/gen/sdk.gen.ts b/packages/sdk/js/src/v2/gen/sdk.gen.ts
index 0b72e620a..7c1c9108d 100644
--- a/packages/sdk/js/src/v2/gen/sdk.gen.ts
+++ b/packages/sdk/js/src/v2/gen/sdk.gen.ts
@@ -29,6 +29,8 @@ import type {
   EventTuiPromptAppend,
   EventTuiSessionSelect,
   EventTuiToastShow,
+  ExperimentalCapabilitiesGetErrors,
+  ExperimentalCapabilitiesGetResponses,
   ExperimentalConsoleGetErrors,
   ExperimentalConsoleGetResponses,
   ExperimentalConsoleListOrgsErrors,
@@ -627,6 +629,42 @@ export class ControlPlane extends HeyApiClient {
   }
 }
 
+export class Capabilities extends HeyApiClient {
+  /**
+   * Get experimental capabilities
+   *
+   * Get experimental features enabled on the OpenCode server.
+   */
+  public get<ThrowOnError extends boolean = false>(
+    parameters?: {
+      directory?: string
+      workspace?: string
+    },
+    options?: Options<never, ThrowOnError>,
+  ) {
+    const params = buildClientParams(
+      [parameters],
+      [
+        {
+          args: [
+            { in: "query", key: "directory" },
+            { in: "query", key: "workspace" },
+          ],
+        },
+      ],
+    )
+    return (options?.client ?? this.client).get<
+      ExperimentalCapabilitiesGetResponses,
+      ExperimentalCapabilitiesGetErrors,
+      ThrowOnError
+    >({
+      url: "/experimental/capabilities",
+      ...options,
+      ...params,
+    })
+  }
+}
+
 export class Console extends HeyApiClient {
   /**
    * Get active Console provider metadata
@@ -1180,6 +1218,11 @@ export class Experimental extends HeyApiClient {
     return (this._controlPlane ??= new ControlPlane({ client: this.client }))
   }
 
+  private _capabilities?: Capabilities
+  get capabilities(): Capabilities {
+    return (this._capabilities ??= new Capabilities({ client: this.client }))
+  }
+
   private _console?: Console
   get console(): Console {
     return (this._console ??= new Console({ client: this.client }))
diff --git a/packages/sdk/js/src/v2/gen/types.gen.ts b/packages/sdk/js/src/v2/gen/types.gen.ts
index 093c1894a..e2add116e 100644
--- a/packages/sdk/js/src/v2/gen/types.gen.ts
+++ b/packages/sdk/js/src/v2/gen/types.gen.ts
@@ -2144,6 +2144,10 @@ export type Provider = {
   }
 }
 
+export type ExperimentalCapabilities = {
+  backgroundSubagents: boolean
+}
+
 export type ConsoleState = {
   consoleManagedProviders: Array<string>
   activeOrgName?: string
@@ -5549,6 +5553,36 @@ export type ConfigProvidersResponses = {
 
 export type ConfigProvidersResponse = ConfigProvidersResponses[keyof ConfigProvidersResponses]
 
+export type ExperimentalCapabilitiesGetData = {
+  body?: never
+  path?: never
+  query?: {
+    directory?: string
+    workspace?: string
+  }
+  url: "/experimental/capabilities"
+}
+
+export type ExperimentalCapabilitiesGetErrors = {
+  /**
+   * Bad request
+   */
+  400: BadRequestError
+}
+
+export type ExperimentalCapabilitiesGetError =
+  ExperimentalCapabilitiesGetErrors[keyof ExperimentalCapabilitiesGetErrors]
+
+export type ExperimentalCapabilitiesGetResponses = {
+  /**
+   * Experimental capabilities
+   */
+  200: ExperimentalCapabilities
+}
+
+export type ExperimentalCapabilitiesGetResponse =
+  ExperimentalCapabilitiesGetResponses[keyof ExperimentalCapabilitiesGetResponses]
+
 export type ExperimentalConsoleGetData = {
   body?: never
   path?: never
diff --git a/packages/tui/src/context/sync.tsx b/packages/tui/src/context/sync.tsx
index 4882c1392..d6c6a40eb 100644
--- a/packages/tui/src/context/sync.tsx
+++ b/packages/tui/src/context/sync.tsx
@@ -65,6 +65,9 @@ export const {
       provider_default: Record<string, string>
       provider_next: ProviderListResponse
       console_state: ConsoleState
+      capabilities: {
+        experimentalBackgroundSubagents: boolean
+      }
       provider_auth: Record<string, ProviderAuthMethod[]>
       agent: Agent[]
       command: Command[]
@@ -107,6 +110,9 @@ export const {
         connected: [],
       },
       console_state: emptyConsoleState,
+      capabilities: {
+        experimentalBackgroundSubagents: false,
+      },
       provider_auth: {},
       config: {},
       status: "loading",
@@ -434,6 +440,10 @@ export const {
       // blocking - include session.list when continuing a session
       const providersPromise = sdk.client.config.providers({ workspace }, { throwOnError: true })
       const providerListPromise = sdk.client.provider.list({ workspace }, { throwOnError: true })
+      const capabilitiesPromise = sdk.client.experimental.capabilities
+        .get({ workspace }, { throwOnError: true })
+        .then((x) => x.data)
+        .catch(() => undefined)
       const consoleStatePromise = sdk.client.experimental.console
         .get({ workspace }, { throwOnError: true })
         .then((x) => x.data)
@@ -443,6 +453,7 @@ export const {
       await Promise.all([
         providersPromise,
         providerListPromise,
+        capabilitiesPromise,
         agentsPromise,
         configPromise,
         projectPromise,
@@ -451,6 +462,7 @@ export const {
         .then(async () => {
           const providersResponse = providersPromise.then((x) => x.data!)
           const providerListResponse = providerListPromise.then((x) => x.data!)
+          const capabilitiesResponse = capabilitiesPromise
           const consoleStateResponse = consoleStatePromise
           const agentsResponse = agentsPromise.then((x) => x.data ?? [])
           const configResponse = configPromise.then((x) => x.data!)
@@ -459,6 +471,7 @@ export const {
           return Promise.all([
             providersResponse,
             providerListResponse,
+            capabilitiesResponse,
             consoleStateResponse,
             agentsResponse,
             configResponse,
@@ -466,15 +479,21 @@ export const {
           ]).then((responses) => {
             const providers = responses[0]
             const providerList = responses[1]
-            const consoleState = responses[2]
-            const agents = responses[3]
-            const config = responses[4]
-            const sessions = responses[5]
+            const capabilities = responses[2]
+            const consoleState = responses[3]
+            const agents = responses[4]
+            const config = responses[5]
+            const sessions = responses[6]
 
             batch(() => {
               setStore("provider", reconcile(providers.providers))
               setStore("provider_default", reconcile(providers.default))
               setStore("provider_next", reconcile(providerList))
+              setStore(
+                "capabilities",
+                "experimentalBackgroundSubagents",
+                capabilities?.backgroundSubagents === true,
+              )
               setStore("console_state", reconcile(consoleState))
               setStore("agent", reconcile(agents))
               setStore("config", reconcile(config))
diff --git a/packages/tui/src/routes/session/index.tsx b/packages/tui/src/routes/session/index.tsx
index 1a1eb0fcc..4d983ee99 100644
--- a/packages/tui/src/routes/session/index.tsx
+++ b/packages/tui/src/routes/session/index.tsx
@@ -206,15 +206,17 @@ export function Session() {
   })
   const messages = createMemo(() => sync.data.message[route.sessionID] ?? [])
   const foregroundTasks = createMemo(() =>
-    messages().flatMap((message) =>
-      (sync.data.part[message.id] ?? []).filter(
-        (part): part is ToolPart =>
-          part.type === "tool" &&
-          part.tool === "task" &&
-          part.state.status === "running" &&
-          part.state.metadata?.background !== true,
-      ),
-    ),
+    sync.data.capabilities.experimentalBackgroundSubagents
+      ? messages().flatMap((message) =>
+          (sync.data.part[message.id] ?? []).filter(
+            (part): part is ToolPart =>
+              part.type === "tool" &&
+              part.tool === "task" &&
+              part.state.status === "running" &&
+              part.state.metadata?.background !== true,
+          ),
+        )
+      : [],
   )
   const userMessageIDs = createMemo(
     () =>
@@ -1510,13 +1512,16 @@ function AssistantMessage(props: { message: AssistantMessage; parts: Part[]; las
             {childShortcut()}
             <span style={{ fg: theme.textMuted }}> view subagents</span>
             <Show
-              when={props.parts.some(
-                (x) =>
-                  x.type === "tool" &&
-                  x.tool === "task" &&
-                  x.state.status === "running" &&
-                  x.state.metadata?.background !== true,
-              )}
+              when={
+                sync.data.capabilities.experimentalBackgroundSubagents &&
+                props.parts.some(
+                  (x) =>
+                    x.type === "tool" &&
+                    x.tool === "task" &&
+                    x.state.status === "running" &&
+                    x.state.metadata?.background !== true,
+                )
+              }
             >
               <span style={{ fg: theme.textMuted }}> · </span>
               {backgroundShortcut()}
diff --git a/packages/tui/test/fixture/tui-sdk.ts b/packages/tui/test/fixture/tui-sdk.ts
index 1d3bdd575..ed18b7acd 100644
--- a/packages/tui/test/fixture/tui-sdk.ts
+++ b/packages/tui/test/fixture/tui-sdk.ts
@@ -58,6 +58,7 @@ export function createFetch(override?: FetchHandler) {
       return json({})
     if (url.pathname === "/config/providers") return json({ providers: {}, default: {} })
     if (url.pathname === "/experimental/console") return json({ consoleManagedProviders: [], switchableOrgCount: 0 })
+    if (url.pathname === "/experimental/capabilities") return json({ backgroundSubagents: false })
     if (url.pathname === "/path") return json({ home: "", state: "", config: "", worktree, directory })
     if (url.pathname === "/api/location") return json({ directory, project: { id: "proj_test", directory: worktree } })
     if (