feat: add session_child_toggle key command

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -382,6 +382,22 @@ export function Session() {
     }
   }
 
+  function toggleChildSession() {
+    if (session()?.parentID) {
+      // Currently in child, go to parent
+      const parentID = session()?.parentID
+      if (parentID) {
+        navigate({
+          type: "session",
+          sessionID: parentID,
+        })
+      }
+    } else {
+      // Currently in primary, go to first child
+      moveFirstChild()
+    }
+  }
+
   function childSessionHandler(func: (dialog: DialogContext) => void) {
     return (dialog: DialogContext) => {
       if (!session()?.parentID || dialog.stack.length > 0) return
@@ -985,6 +1001,16 @@ export function Session() {
         dialog.clear()
       }),
     },
+    {
+      title: session()?.parentID ? "Return to parent session" : "Show child sessions",
+      value: "session.child.toggle",
+      keybind: "session_child_toggle",
+      category: "Session",
+      onSelect: (dialog) => {
+        toggleChildSession()
+        dialog.clear()
+      },
+    },
     {
       title: "Next child session",
       value: "session.child.next",

packages/opencode/src/config/keybinds.ts

@@ -107,6 +107,7 @@ const KeybindsSchema = Schema.Struct({
   session_child_cycle: keybind("right", "Go to next child session"),
   session_child_cycle_reverse: keybind("left", "Go to previous child session"),
   session_parent: keybind("up", "Go to parent session"),
+  session_child_toggle: keybind("none", "Toggle between primary and child sessions"),
   // `terminal_suspend` was formerly `.default("ctrl+z").transform((v) => win32 ? "none" : v)`,
   // but `tui.ts` already forces the binding to "none" on win32 before calling
   // `Keybinds.parse(...)`, so the schema-level transform was redundant.