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

# Dynamic skills

> Per-user skill resolution — cache layers, fallbacks, and bind-mounts.

<Frame>
  <img src="https://mintcdn.com/yambr/AQ23_2YQrfJDjXh_/images/diagrams/dynamic-skills.svg?fit=max&auto=format&n=AQ23_2YQrfJDjXh_&q=85&s=da06e22f28cdb38a8b27d2ca383cadc6" alt="Dynamic skill injection architecture" width="750" height="420" data-path="images/diagrams/dynamic-skills.svg" />
</Frame>

## Resolution pipeline

On every chat start, the server calls `skill_manager.get_user_skills(email)`. The result resolves through **three fallback levels**:

1. **Memory cache** — 60-second TTL. Same `(email)` hit twice in a minute = dict lookup.
2. **Settings Wrapper API** — if `MCP_TOKENS_URL` is set, fetches the user's enabled skills.
3. **Disk cache** — if the API is down but we cached last known good, reuse it.
4. **Hardcoded defaults** — all 13 public skills.

Without the Settings Wrapper, step 4 always wins — everyone gets the full public set.

## System prompt injection

The skill list becomes an `<available_skills>` XML block injected into the system prompt:

```xml theme={null}
<available_skills>
  <skill>
    <name>docx</name>
    <description>Create and edit Word documents with tracked changes</description>
    <path>/mnt/skills/public/docx/</path>
  </skill>
  <!-- ... -->
</available_skills>
```

The model reads this once per chat and then consults `SKILL.md` files on demand.

## User skill mounts

User-uploaded skills (ZIPs from the Settings Wrapper) are:

1. Downloaded and extracted atomically: unzip to temp, rename to final.
2. Cached under `/data/skills-cache/{name}/` on the host.
3. Tracked in `.manifest.json` (name → SHA-256 + timestamp).
4. Bind-mounted into the sandbox at `/mnt/skills/user/{name}/` — **read-only**.

Stale cache reuse: if the API or download fails but old cache exists, use it. Docker daemon needs host paths for bind mounts — configured via `SKILLS_CACHE_HOST_PATH`.

## Core functions (`skill_manager.py`)

| Function                              | Purpose                                                          |
| ------------------------------------- | ---------------------------------------------------------------- |
| `get_user_skills(email)`              | Async — full resolution with all fallbacks                       |
| `get_user_skills_sync(email)`         | Sync — reads cache only (called from the Docker-creation thread) |
| `ensure_skill_cached(skill)`          | Download + extract user-uploaded ZIP                             |
| `build_available_skills_xml(skills)`  | `<available_skills>` for the system prompt                       |
| `build_sub_agent_skills_text(skills)` | Skill list for the sub-agent prompt                              |
| `get_skill_mounts(skills)`            | Dict of bind mounts for user skills                              |

## HTTP endpoints

| Endpoint                                    | Returns                                    |
| ------------------------------------------- | ------------------------------------------ |
| `GET /system-prompt?user_email=X&chat_id=Y` | Rendered per-user prompt                   |
| `GET /skill-mounts?user_email=X`            | Bind-mount descriptors for user skills     |
| `GET /skill-list?user_email=X`              | Formatted skill list for sub-agent prompts |

## Configuration

| Var                      | Default              | Purpose                     |
| ------------------------ | -------------------- | --------------------------- |
| `MCP_TOKENS_URL`         | *(empty)*            | Settings Wrapper URL        |
| `MCP_TOKENS_API_KEY`     | *(empty)*            | Internal API key            |
| `SKILLS_CACHE_DIR`       | `/data/skills-cache` | In-container cache path     |
| `SKILLS_CACHE_HOST_PATH` | `/tmp/skills-cache`  | Host path for Docker mounts |

## Verify

```bash theme={null}
# System prompt should list skills
curl "http://localhost:8081/system-prompt?user_email=admin@open-computer-use.dev&chat_id=test" | head -50

# Bind mounts
curl "http://localhost:8081/skill-mounts?user_email=admin@open-computer-use.dev"

# Skill list
curl "http://localhost:8081/skill-list?user_email=admin@open-computer-use.dev"
```