Async vs Synchronous Git Status in Oh My Zsh: Choosing Responsiveness or Accuracy Under Concurrent Shell Load

Answer

Enable Oh My Zsh's git plugin in asynchronous mode and wrap git status calls with a simple file-lock (flock) so only one git status runs at a time across all terminal sessions. This keeps the prompt responsive while preventing the latency spikes caused by concurrent git processes.

Confirmed facts

1. Oh My Zsh's git plugin runs git status --porcelain synchronously by default, blocking the prompt until the command finishes.
2. When switched to asynchronous mode (via the zsh-async library or an async‑capable theme such as Powerlevel10k), the prompt returns immediately and the status updates in a background worker.
3. Asynchronous mode does not change repository data; it only changes when the status is fetched for display.
4. Under heavy concurrent load, many shells invoking git simultaneously can saturate CPU/I/O and increase the latency of each synchronous call, even if each individual call is fast.

Likely explanation

The observed latency comes from two sources: the time each git status takes to run, and the contention when many shells run it at the same time. Async mode removes the first source from the prompt‑rendering path, but if many background workers start together they still compete for resources. Adding a lock that allows only one git status to run at a time across all sessions eliminates that contention while preserving the non‑blocking prompt.

Steps to implement

1. Install the zsh-async plugin (e.g., git clone https://github.com/mafredri/zsh-async.git ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-async) and add it to the plugins array in ~/.zshrc.
2. Enable async git status by setting ZSH_THEME_GIT_PROMPT_ASYNC=true (or switch to an async theme such as Powerlevel10k that already uses async).
3. Create a wrapper script ~/bin/git that wraps the real git binary with a flock lock:

   #!/usr/bin/env zsh
   # ~/bin/git – allow only one git status to run at a time
   if [[ '$1' == 'status' && '$2' == '--porcelain' ]]; then
     exec flock -n /tmp/git-status.lock git $@
   else
     exec git $@
   fi
   

4. Make the script executable (chmod +x ~/bin/git) and ensure ~/bin precedes the system git in $PATH (e.g., export PATH='$HOME/bin:$PATH').
5. Reload the shell (source ~/.zshrc) and verify:
   • Prompt appears instantly after a directory change.
   • Running time git status --porcelain shows the wrapper adding only a few milliseconds when the lock is free.
   • After a background worker finishes, the branch/dirty markers match a fresh synchronous git status.

Verification

• Measure synchronous latency: time git status --porcelain while a CPU‑intensive job runs (e.g., yes > /dev/null &). Note the real time.
• Enable async mode and repeat; the prompt should return immediately, and the background worker’s output should appear within a few hundred ms.
• Check correctness: after the worker finishes, compare the prompt’s branch/dirty symbols with the output of a fresh synchronous git status --porcelain; they must match.

Missing diagnostic detail

If you typically run more than ten simultaneous shells, the lock‑based wrapper may serialize git status calls and could add noticeable queuing delay. Please let me know the average number of concurrent terminal windows you keep open so I can advise whether the lock approach or a higher‑concurrency async timeout would be more suitable.