Updating config doesn’t create missing windows/panes or re-run start command

Description

I’ve been experimenting with tmuxinator and ran into an issue when updating an existing project config.

If I modify a config to add new windows or panes, or if I’ve closed an existing pane and then re-run tmuxinator start <project>, tmuxinator just attaches me to the existing session. It doesn’t create the missing windows/panes, nor does it re-run the commands defined in the config.

Steps to Reproduce

1. Create a simple config, e.g. ~/.tmuxinator/sample.yml:

name: sample
root: ~/

windows:
  - editor:
      layout: main-vertical
      panes:
        - editor:
          - vim
        - guard

1. Run tmuxinator start sample. Everything works as expected.

2. Update the config to add new windows/panes or close the guard pane:

name: sample
root: ~/

windows:
  - editor:
      layout: main-vertical
      panes:
        - editor:
          - vim
        - guard
  - server: bundle exec rails s
  - logs: tail -f log/development.log

1. Run tmuxinator start sample again.

Expected Behaviour (My Expectation)

• If new windows/panes are added in the config, they should be created when starting the project again.
• If a pane has been closed, it should be recreated and run the command from the config.
• Already running processes in existing panes should remain untouched.

Actual Behaviour

• tmuxinator start sample only attaches to the existing session.
• New windows/panes are not created.
• Closed panes are not recreated.
• Commands from the updated config are not re-run.

Notes

• I do not want to stop and restart the entire project/session, because that kills existing processes (e.g. a running server).
• My use case: I may already be running a Ruby API server in one pane. Later, I want to add a watcher in another pane. I don’t want to stop the running server just to have the watcher created.

Additional Info:

I'm running following versions of the softwares.

• tmux v3.5a
• tmuxinator v3.3.5
• ruby v2.6.10p210
• macOS v15.5 arm64
• zsh v5.9
• HomeBrew v4.6.4