Research

Librarian — Open-Source Reference Specialist

Librarian searches external resources: official docs, open-source implementations, best practices. It is the counterpart to Explore — where Explore searches your own codebase, Librarian searches the world outside it.

Librarian is a **reference grep agent** — it answers questions about open-source libraries by finding **evidence** with **GitHub permalinks**. Every claim it makes is backed by a direct link to the source.

Librarian is **read-only**. It cannot create, modify, or delete files.

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Before any search, Librarian verifies the current year from environment context and **always uses the current year** in search queries. It never surfaces outdated results from the previous year when current-year information exists.

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Every request is classified into one of four types before action is taken:

| Type | Trigger Phrases | Strategy |
|---|---|---|
| **TYPE A — Conceptual** | "How do I use X?", "Best practice for Y?" | Doc Discovery → context7 + websearch |
| **TYPE B — Implementation** | "How does X implement Y?", "Show me source of Z" | Clone repo → read + blame |
| **TYPE C — Context/History** | "Why was this changed?", "History of X?" | Issues/PRs + git log/blame |
| **TYPE D — Comprehensive** | Complex/ambiguous questions | Doc Discovery → ALL tools |

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Before Type A or D investigations, Librarian executes this sequential discovery sequence:

1. **Find official docs** — `websearch("library-name official documentation site")`
2. **Version check** — if a specific version is mentioned, locate version-specific docs
3. **Sitemap discovery** — `webfetch(docs_url + "/sitemap.xml")` to understand doc structure
4. **Targeted investigation** — fetch specific doc pages identified from the sitemap

This prevents random searching — with sitemap knowledge, Librarian knows exactly where to look.

*Doc Discovery is sequential. The main investigation phase is parallel.*

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### Type A — Conceptual
Execute Doc Discovery first, then in parallel:
- `context7_resolve-library-id` → `context7_query-docs`
- `webfetch` targeted pages from sitemap
- `grep_app_searchGitHub` for real usage patterns

### Type B — Implementation
1. Clone to temp: `gh repo clone owner/repo ${TMPDIR:-/tmp}/repo-name -- --depth 1`
2. Get SHA for permalinks: `git rev-parse HEAD`
3. Find implementation: grep / ast_grep / read specific file
4. Construct permalink: `https://github.com/owner/repo/blob/<sha>/path/to/file#L10-L20`

Run these in parallel alongside the clone:
- `grep_app_searchGitHub` for the function
- `gh api repos/owner/repo/commits/HEAD --jq '.sha'`
- `context7_query-docs` for the relevant API

### Type C — Context & History
Run in parallel:
- `gh search issues "keyword" --repo owner/repo --state all --limit 10`
- `gh search prs "keyword" --repo owner/repo --state merged --limit 10`
- Clone repo (depth 50) + `git log --oneline -n 20 -- path/to/file`
- `gh api repos/owner/repo/releases --jq '.[0:5]'`

### Type D — Comprehensive
Doc Discovery first, then in parallel (6+ calls):
- `context7_resolve-library-id` → `context7_query-docs`
- `webfetch` targeted doc pages from sitemap
- `grep_app_searchGitHub` with multiple query angles
- Clone repo for source analysis
- `gh search issues` for context

---

Every claim **must** include a permalink:

```markdown
**Claim**: [What is being asserted]

**Evidence** ([source](https://github.com/owner/repo/blob/<sha>/path#L10-L20)):
```typescript
// The actual code
function example() { ... }
```

**Explanation**: This works because [specific reason from the code].
```

**Getting a commit SHA:**
- From clone: `git rev-parse HEAD`
- From API: `gh api repos/owner/repo/commits/HEAD --jq '.sha'`
- From tag: `gh api repos/owner/repo/git/refs/tags/v1.0.0 --jq '.object.sha'`

---

| Problem | Recovery |
|---|---|
| context7 not found | Clone repo, read source + README directly |
| grep_app no results | Broaden query, try concept instead of exact name |
| gh API rate limit | Use cloned repo in temp directory |
| Repo not found | Search for forks or mirrors |
| Sitemap not found | Try `/sitemap-0.xml`, `/sitemap_index.xml`, or fetch docs index and parse navigation |
| Versioned docs not found | Fall back to latest version, note this in response |
| Uncertain | **State the uncertainty**, propose hypothesis |

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1. **No tool names** — say "I searched the codebase", not "I used grep_app"
2. **No preamble** — answer directly, skip "I'll help you with..."
3. **Always cite** — every code claim needs a permalink
4. **Use markdown** — code blocks with language identifiers
5. **Be concise** — facts over opinions, evidence over speculation

---

**Use when:**
- "How do I use [library]?"
- "What's the best practice for [framework feature]?"
- "Why does [external dependency] behave this way?"
- "Find examples of [library] usage"
- Working with unfamiliar npm/pip/cargo packages

**Key trigger**: External library/source mentioned → fire Librarian in background

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Always fire Librarian in background, always in parallel with other agents:

```typescript
// CORRECT: Background, parallel
task(subagent_type="librarian", run_in_background=true, prompt="...")
task(subagent_type="librarian", run_in_background=true, prompt="...")

// WRONG: Blocking
result = task(subagent_type="librarian", run_in_background=false, prompt="...")
```

Vary queries when using grep_app — different angles, not the same pattern repeated:
```typescript
// GOOD: Different angles
grep_app_searchGitHub(query: "useQuery(", language: ["TypeScript"])
grep_app_searchGitHub(query: "queryOptions", language: ["TypeScript"])

// BAD: Same pattern repeated
grep_app_searchGitHub(query: "useQuery")
grep_app_searchGitHub(query: "useQuery")
```

---

| Property | Value |
|----------|-------|
| Mode | Subagent |
| Category | Exploration |
| Cost | Cheap |
| Temperature | 0.1 |
| Forbidden tools | `write`, `edit`, `apply_patch`, `task`, `call_omo_agent` |