fix: keep debugger pane maximized

rvctl.py

@@ -4955,6 +4955,7 @@ def respawn_tmux_session_pane(
     shell_command: str | None,
     dry_run: bool = False,
     force: bool = False,
+    stem_instance: str | None = None,
 ) -> dict[str, str]:
     name, pane_id, _ = resolve_tmux_session_pane(raw_target, force=force)
     shell = os.environ.get("SHELL", "/bin/bash")
@@ -4972,12 +4973,42 @@ def respawn_tmux_session_pane(
     }
     if not dry_run:
         subprocess.run(command, check=True)
+        # A debugger session contains an inner tmux and Neovim.  If its host
+        # pane remains in a split, the inner client inherits only that short
+        # height and leaves an unusable empty area below the editor.  Zoom the
+        # replacement pane after every attach/refresh/reset so it receives the
+        # full host window height.  A later user Ctrl-a z simply restores the
+        # ordinary host-pane layout.
+        zoom_state = subprocess.run(
+            ["tmux", "display-message", "-p", "-t", pane_id, "#{window_zoomed_flag}"],
+            check=False,
+            text=True,
+            capture_output=True,
+        )
+        if zoom_state.returncode == 0 and zoom_state.stdout.strip() != "1":
+            subprocess.run(
+                ["tmux", "resize-pane", "-Z", "-t", pane_id],
+                check=False,
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL,
+            )
         subprocess.run(
             ["tmux", "set-option", "-p", "-t", pane_id, "@stem_role", "debugger" if shell_command else "shell"],
             check=False,
             stdout=subprocess.DEVNULL,
             stderr=subprocess.DEVNULL,
         )
+        instance_option = ["tmux", "set-option", "-p", "-t", pane_id]
+        if shell_command and stem_instance:
+            instance_option.extend(["@stem_instance", stem_instance])
+        else:
+            instance_option.extend(["-u", "@stem_instance"])
+        subprocess.run(
+            instance_option,
+            check=False,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
     return details
 
 
@@ -5216,6 +5247,7 @@ def run_session(config: WorkspaceConfig, args: argparse.Namespace) -> None:
             None,
             dry_run=args.dry_run,
             force=args.force_pane,
+            stem_instance=session.instance,
         )
         print_session_target(session)
         print_key_values(details)
@@ -5266,6 +5298,7 @@ def run_session(config: WorkspaceConfig, args: argparse.Namespace) -> None:
             debug_command,
             dry_run=args.dry_run,
             force=args.force_pane,
+            stem_instance=session.instance,
         )
         print_key_values(pane_details)
         if args.dry_run:
@@ -5300,6 +5333,7 @@ def run_session(config: WorkspaceConfig, args: argparse.Namespace) -> None:
             debug_command,
             dry_run=args.dry_run,
             force=args.force_pane,
+            stem_instance=session.instance,
         )
         print_key_values(pane_details)
         if args.dry_run:
@@ -5341,6 +5375,7 @@ def run_session(config: WorkspaceConfig, args: argparse.Namespace) -> None:
                 pane_command,
                 dry_run=args.dry_run,
                 force=args.force_pane,
+                stem_instance=session.instance,
             )
             print_key_values(pane_details)
         elif record is None and not args.dry_run and (prepared_stage is None or online):
@@ -5372,6 +5407,7 @@ def run_session(config: WorkspaceConfig, args: argparse.Namespace) -> None:
             attach_command,
             dry_run=args.dry_run,
             force=args.force_pane,
+            stem_instance=session.instance,
         )
         print_key_values(pane_details)
         if args.dry_run: