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Academy → Developer guideOfficial documentation · clear explanation

Extending the CLI

Extending the CLI

Developer10 minutes3 questions✓ 2026-08-09
The idea in one minute

Start with meaning, then move to detail.

This lesson explains Extending the CLI as part of Hermes internals and extension points. You will learn what it does, when it matters, and the smallest safe test that proves it works.

If you are new

If you are new, do not memorize names. Focus on three questions: what problem does this solve, what access does it need, and how can you verify the result?

For hands-on use

For practice, inspect the first example, identify its effects, run it on test data, and compare the result with the source claim.

For specialists

For advanced readers, inspect Extension points, Quick start: a wrapper CLI, Hook reference, then verify failure modes and version compatibility.

What do you need first?

Know Python, Git, and basic project structure before changing code.

What will you know?

A clear outcome before you read.

  • Understand Extending the CLI without assumed prior knowledge.
  • Separate the source description from what still needs testing in your environment.
  • Read the first command and identify its inputs and outputs before copying it.
Official page description

Build wrapper CLIs that extend the Hermes TUI with custom widgets, keybindings, and layout changes

Topic map

What does the source say, and in what order?

  1. 01
    Extension points

    Start here to understand the core idea or structure.

  2. 02
    Quick start: a wrapper CLI

    Read this after the foundation, then connect it to the previous step.

  3. 03
    Hook reference

    Read this after the foundation, then connect it to the previous step.

  4. 04
    getextratuiwidgets()

    Read this after the foundation, then connect it to the previous step.

  5. 05
    registerextratuikeybindings(kb, , inputarea)

    Read this after the foundation, then connect it to the previous step.

  6. 06
    buildtuilayoutchildren(widgets)

    Read this after the foundation, then connect it to the previous step.

  7. 07
    Layout diagram

    Read this after the foundation, then connect it to the previous step.

  8. 08
    Tips

    Finish here to verify the result and special cases.

Examples from the official page

Copy only after you understand the effect.

Run it:
## Hook reference ### `_get_extra_tui_widgets()` Returns a list of prompt_toolkit widgets to insert into the TUI layout. Widgets appear **between the spacer and the status bar** — above the input area but below the main output.
Each widget should be a prompt_toolkit container (e.g., `Window`, `ConditionalContainer`, `HSplit`). Use `ConditionalContainer` or `filter=Condition(...)` to make widgets toggleable.
Try it now

Read the first command and identify its inputs and outputs before copying it.

Match every command to your installed Hermes version, review the files and accounts it can reach, and use non-sensitive data for the first test. If this explanation differs from the source, the official source wins.

Knowledge check

Three decisions before completion.

1. What is the source of truth when “Extending the CLI” changes?
2. What is the best way to apply this lesson?
3. What should happen before a step can modify files or an external account?