feat(tui): navigate child sessions (subagents)

packages/opencode/src/config/config.ts

@@ -218,6 +218,12 @@ export namespace Config {
       session_unshare: z.string().optional().default("none").describe("Unshare current session"),
       session_interrupt: z.string().optional().default("esc").describe("Interrupt current session"),
       session_compact: z.string().optional().default("<leader>c").describe("Compact the session"),
+      session_child_cycle: z.string().optional().default("ctrl+right").describe("Cycle to next child session"),
+      session_child_cycle_reverse: z
+        .string()
+        .optional()
+        .default("ctrl+left")
+        .describe("Cycle to previous child session"),
       messages_page_up: z.string().optional().default("pgup").describe("Scroll messages up by one page"),
       messages_page_down: z.string().optional().default("pgdown").describe("Scroll messages down by one page"),
       messages_half_page_up: z.string().optional().default("ctrl+alt+u").describe("Scroll messages up by half page"),

packages/opencode/src/server/server.ts

@@ -293,8 +293,18 @@ export namespace Server {
             },
           },
         }),
+        zValidator(
+          "json",
+          z
+            .object({
+              parentID: z.string().optional(),
+              title: z.string().optional(),
+            })
+            .optional(),
+        ),
         async (c) => {
-          const session = await Session.create()
+          const body = c.req.valid("json") ?? {}
+          const session = await Session.create(body.parentID, body.title)
           return c.json(session)
         },
       )

packages/opencode/src/session/index.ts

@@ -163,12 +163,12 @@ export namespace Session {
     },
   )
 
-  export async function create(parentID?: string) {
+  export async function create(parentID?: string, title?: string) {
     const result: Info = {
       id: Identifier.descending("session"),
       version: Installation.VERSION,
       parentID,
-      title: createDefaultTitle(!!parentID),
+      title: title ?? createDefaultTitle(!!parentID),
       time: {
         created: Date.now(),
         updated: Date.now(),

packages/opencode/src/tool/task.ts

@@ -23,11 +23,11 @@ export const TaskTool = Tool.define("task", async () => {
       subagent_type: z.string().describe("The type of specialized agent to use for this task"),
     }),
     async execute(params, ctx) {
-      const session = await Session.create(ctx.sessionID)
-      const msg = await Session.getMessage(ctx.sessionID, ctx.messageID)
-      if (msg.info.role !== "assistant") throw new Error("Not an assistant message")
       const agent = await Agent.get(params.subagent_type)
       if (!agent) throw new Error(`Unknown agent type: ${params.subagent_type} is not a valid agent type`)
+      const session = await Session.create(ctx.sessionID, params.description + ` (@${agent.name} subagent)`)
+      const msg = await Session.getMessage(ctx.sessionID, ctx.messageID)
+      if (msg.info.role !== "assistant") throw new Error("Not an assistant message")
       const messageID = Identifier.ascending("message")
       const parts: Record<string, MessageV2.ToolPart> = {}
       const unsub = Bus.subscribe(MessageV2.Event.PartUpdated, async (evt) => {