Fixing a Broken Prompt Theme After an Update

A prompt theme that suddenly breaks after updating Oh My Zsh, Powerlevel10k, Starship, or a similar tool almost always falls into one of three specific categories — a font issue, a stale configuration option, or an actual breaking change in the tool itself.

Step 1: identify exactly what “broken” looks like

Missing or garbled icons/symbols → likely a font issue
Shell errors on every startup → likely a config/version mismatch
Prompt shows but formatting looks wrong → likely a stale config option

The specific symptom narrows down which of the three categories you’re actually dealing with, rather than trying fixes for all three at once.

Step 2: for missing icons or garbled symbols, check your terminal font

Confirm your terminal emulator's configured font is
  a "Nerd Font" variant (or otherwise includes the
  specific glyph set your theme uses for icons)

Modern prompt themes rely on special glyphs (git branch icons, OS logos, powerline separators) that only exist in specific patched font sets — a terminal font that doesn’t include these glyphs will show broken boxes or question marks in their place, a font problem, not a shell or theme configuration problem.

Step 3: for startup errors, check the specific error message for a removed/renamed option

# read the exact error text — many theme updates rename
# specific configuration variables and print a
# specific deprecation or removal notice

Prompt frameworks and themes frequently rename or restructure configuration options between versions — the actual error message usually names the specific option involved, which is the fastest way to identify what needs updating in your own config file.

Step 4: check the tool’s own changelog for the specific version you updated to

starship --version
# check the corresponding GitHub releases page for
# breaking changes at that specific version

A breaking change is, definitionally, something the maintainers documented as intentional — checking release notes for the exact version you updated to (not just “the latest changes”) finds the specific, relevant breaking change quickly.

Step 5: temporarily revert to a minimal prompt to isolate the framework from the terminal

PS1='$ '

Setting a minimal, plain prompt temporarily confirms whether the shell itself is otherwise healthy — if commands run fine with this minimal prompt, the problem is isolated specifically to the theme/framework layer, not anything more fundamental.

Step 6: regenerate your configuration from the tool’s current defaults

p10k configure     # Powerlevel10k's interactive config wizard
starship preset    # Starship's built-in preset configurations

Rather than trying to manually patch an old configuration file against a new tool version, regenerating configuration through the tool’s own current setup wizard often resolves compatibility issues faster than manual repair.

Step 7: pin the tool to a known-working version if you need a quick, temporary fix

# via your package manager, install a specific
# previous version rather than "latest"

If the breaking change affects something you depend on and you need a working prompt immediately, temporarily pinning to the last known-good version buys time to properly update your configuration without an urgent broken-shell situation.

Step 8: verify the fix across a genuinely new shell session

exec zsh

Confirming the fix in a fresh shell session (not just the current one, which may have stale in-memory state) verifies the configuration file itself is correctly fixed, not just that the current session happens to be working.

Why isolating font, config, and version issues separately matters

These three failure categories look superficially similar (“my prompt looks wrong”) but have completely different fixes — chasing a font problem with configuration changes, or a genuine breaking change with a font reinstall, wastes time that identifying the specific category first would have saved.