Instant Prompt compatibility with prompt-modifying themes

Answer to the question

Oh My Zsh does not publish a formal, exhaustive compatibility matrix for Instant Prompt. The only documented guidance is that a theme must keep its final PROMPT (and RPROMPT) static after oh‑my‑zsh.sh has finished loading, and it must not mutate prompt components via hooks or command substitutions that run after the placeholder is captured.

Categories of risky prompt escape patterns

• Dynamic command substitutions – any $(…) or `…` inside the prompt that invoke external commands (git, kubectl, python, etc.) will produce different output at placeholder time versus after initialization.
• Precmd/Preexec rewriting – hooks that rebuild PROMPT on each command can change the escape‑sequence structure after the placeholder has been displayed.
• Terminal‑capability dependencies – themes that rely on color codes, powerline glyphs, or OSC 133 sequences that are not yet set up when the placeholder is rendered.
• Plugin‑dependent variables – references to variables that plugins populate later (e.g. $VIRTUAL_ENV, $KUBECONFIG) will differ between the placeholder and the final prompt.

When Instant Prompt is safe to enable by default

• Built‑in OMZ themes that have been explicitly tested for Instant Prompt (e.g. robbyrussell, agnoster) and declare no dynamic modifications.
• Custom themes that only assign a static string to PROMPT/RPROMPT in the theme file and do not touch those variables after oh‑my‑zsh.sh loads.
• Powerlevel10k when used with its own p10k instant-prompt wizard, which replaces OMZ’s mechanism entirely.

Practical verification steps

1. Add ZSH_THEME_INSTANT_PROMPT=verbose to ~/.zshrc before source $ZSH/oh‑my‑zsh.sh.
2. Restart the shell and observe the first prompt: it should match the final prompt without flicker or misalignment.
3. Temporarily insert print -P "Before: $PROMPT" and print -P "After: $PROMPT" around oh‑my‑zsh.sh to compare escape‑sequence structures.
4. Review the theme’s source for any precmd, preexec, or command substitutions inside the prompt. Remove or defer them if present.
5. For third‑party themes, check the repository README or issue tracker for any mention of Instant Prompt support.
6. When using Powerlevel10k, run p10k configure and enable the instant‑prompt wizard instead of relying on OMZ’s setting.

Missing diagnostic detail

If you encounter a prompt that flickers or shows stale information after enabling Instant Prompt, please share the exact theme name and whether it uses any of the risky patterns listed above. That will help narrow down the specific incompatibility.