customizing-statusline

name	customizing-statusline
description	Creates, edits, and migrates Letta Code statusline extensions. Use when handling the /statusline command or continuing work started by /statusline.

Customizing Statusline

Use this skill to create or update the global Letta Code statusline extension:

~/.letta/extensions/statusline.tsx

The statusline is a full-row idle renderer. Host UI can still temporarily preempt it for safety confirmations and transient hints.

Statusline ownership model

safety preemption
else transient host hint
else custom statusline extension
else built-in default statusline

A custom statusline owns the whole idle row. Do not preserve legacy left/right split semantics in the new API.

Workflow

1. Check whether ~/.letta/extensions/statusline.tsx exists.
2. If it exists, read it before editing and preserve unrelated code.
3. If it does not exist, start from the built-in default template or synthesize a focused starter for the user's request.
4. If the user asks to migrate, import a .sh file, or match a shell prompt, read references/migration.md.
5. If API details or concrete patterns are needed, read references/api.md and references/examples.md.
6. If the request combines statusline work with commands, tools, events, panels, or stateful extension behavior, also use creating-extensions and its references/architecture.md.
7. Guard statusline-specific behavior with letta.capabilities.ui.customStatuslineRenderer when writing new files.
8. Edit ~/.letta/extensions/statusline.tsx.
9. Summarize the absolute file path changed and tell the user to run /reload unless the command can reload automatically.

Bare /statusline behavior

If the user ran /statusline without a specific request:

• If a custom statusline file exists, summarize what it appears to do and ask what they want to change.
• If no custom file exists, explain that Letta is using the built-in default statusline and offer focused next steps:
  1. start from the default Letta statusline
  2. add project info like git branch, worktree, or PR
  3. migrate an existing legacy statusline .sh file
  4. match shell prompt / PS1
  5. describe a custom statusline in their own words

Keep this conversational. Do not build a menu UI unless the product command explicitly asks for one.

Rules

• Global-only for now. Do not create project extensions.
• Keep the extension single-file for MVP.
• Do not assume extra npm packages are available.
• Do not use relative multi-file imports yet.
• Keep renderers synchronous. Do not shell, fetch, or await inside render.
• Do async work in setup code, intervals, subscriptions, or status providers.
• Use letta.ui.setStatus for data and setStatuslineRenderer for drawing that data.
• Guard optional APIs with letta.capabilities.ui.statusValues and letta.capabilities.ui.customStatuslineRenderer in new files.
• Return a disposer that clears timers/subscriptions.
• Preserve existing extension code unless the user asks to reset.
• Do not delete legacy command statusline files or settings unless the user explicitly asks.

Useful references

• references/api.md - extension API, render context, lifecycle rules
• references/examples.md - common statusline patterns
• references/migration.md - legacy command .sh and PS1 migration