> ## Documentation Index
> Fetch the complete documentation index at: https://docs.checkfu.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Skills

> Reuse versioned instructions and files in Session context.

A **Skill** is Workspace-owned instructions plus optional files. It is content
the Agent reads from the sandbox filesystem. It has no input schema or
transport binding and does not itself grant permission to call a Tool.

## Reuse and version instructions

Skills can be instructional or executable and follow the Agent Skills
directory shape. Each committed edit creates an immutable SkillVersion.
Session admission freezes the Agent's Skill references. At each turn, an exact
version resolves that immutable content; an omitted or `latest` version resolves
the current Skill and records its version and content digest for that turn.
Pin an exact version when later edits must not change future turns.

Start with [Install a Skill](/guides/install-a-skill). The
[Skill format and version details](/concepts/capabilities#skills) cover
import, export, frontmatter, and exact-version retrieval.

## Maintain Skills in a repository

A SkillSource uses a Git FileTree as its authoring home. Sync reports created,
updated, unchanged, invalid, or missing Skills; it does not delete a Skill
just because the file disappeared upstream.

A SkillProposal can turn Session experience into a candidate Skill, verify it
in a separate child Session, and publish a branch for human review. Merging
and syncing remain deliberate steps before the content becomes an ordinary
versioned Skill. Follow [Ship a self-authored Skill](/guides/ship-a-self-authored-skill)
and read the [proposal lifecycle](/concepts/capabilities#skills-that-improve-themselves).

Check [capability status](/getting-started/status) for availability. Skills,
[Files](/concepts/file-trees), and [Memory](/concepts/memory) are distinct
resources within the [context model](/concepts/context).


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