feat(tui): allow backgrounding synchronous subagents (#30488)

packages/opencode/test/server/httpapi-exercise/index.ts

@@ -568,6 +568,17 @@ 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
+    .post("/experimental/session/{sessionID}/background", "experimental.session.background")
+    .mutating()
+    .seeded((ctx) => ctx.session({ title: "Background route owner" }))
+    .at((ctx) => ({
+      path: route("/experimental/session/{sessionID}/background", { sessionID: ctx.state.id }),
+      headers: ctx.headers(),
+    }))
+    .json(200, (body) => {
+      check(body === false, "background route should be a no-op without running subagents")
+    }),
   http.protected.get("/experimental/resource", "experimental.resource.list").json(),
   http.protected
     .post("/sync/history", "sync.history.list")

packages/opencode/test/server/session-actions.test.ts

@@ -90,4 +90,23 @@ describe("session action routes", () => {
       }),
     { git: true },
   )
+
+  it.instance(
+    "experimental background route is a no-op without synchronous subagents",
+    () =>
+      Effect.gen(function* () {
+        const test = yield* TestInstance
+        const session = yield* Effect.acquireRelease(SessionNs.use.create({}), (created) =>
+          SessionNs.use.remove(created.id).pipe(Effect.ignore),
+        )
+
+        const res = yield* requestInDirectory(`/experimental/session/${session.id}/background`, test.directory, {
+          method: "POST",
+        })
+
+        expect(res.status).toBe(200)
+        expect(yield* res.json).toBe(false)
+      }),
+    { git: true },
+  )
 })

packages/opencode/test/server/workspace-routing.test.ts

@@ -41,6 +41,11 @@ describe("getWorkspaceRouteSessionID", () => {
     expect(getWorkspaceRouteSessionID(url)).toBe(SessionID.make("ses_xyz"))
   })
 
+  test("extracts session ID from experimental background path", () => {
+    const url = new URL("http://localhost/experimental/session/ses_bg/background")
+    expect(getWorkspaceRouteSessionID(url)).toBe(SessionID.make("ses_bg"))
+  })
+
   test("returns null for /session/status", () => {
     const url = new URL("http://localhost/session/status")
     expect(getWorkspaceRouteSessionID(url)).toBeNull()