Using Glean for Code Exploration
Glean indexes source code across the organization's connected repositories. Local tools (Grep, Glob, Read) see only the current repo; this skill is for everything else.
When to reach for this
- Finding the system — "Where does our payments code live?"
- Finding the patterns — "How do other teams handle rate limiting?"
- Finding the people — combining code authorship with
employee_search reveals real owners (not just titled ones)
- Prior art before designing — see reference/plan-prep.md for the research-before-plan workflow
- Cross-repo exploration — understanding systems, mapping breadth, finding contributors across the organization
The tool you'll mostly use
This skill drives the code_search MCP tool. For full param shape, inline filter syntax, and pitfalls (quoting names, the app: filter not applying, recency caveats), read ../using-glean/reference/code-search.md. That is the canonical reference; this skill carries the workflow on top.
For this skill's own workflow patterns, see:
- reference/exploration.md — exploring an unfamiliar system across repos: what to search for, what to filter, what to present
- reference/plan-prep.md — gathering enterprise context before entering plan mode for architectural / strategic work
Vetting
Not every match is worth surfacing. Code in legacy/, deprecated/, archive/, abandoned repos, or files with extensive TODO/FIXME comments will mislead the user. Apply the criteria in ../using-glean/reference/vetting.md and prefer 3 high-quality matches over 10 unfiltered ones.
Quality test
- Is this good code to reference?
- GOOD: Clean, tested, actively maintained
- ACCEPTABLE: Works but has caveats
- POOR: Hacky, deprecated, abandoned
Recency test
- Is this code maintained?
- ACTIVE: Commits in past 3 months
- SLOWING: 3–12 months since last commit
- STALE: 12+ months — likely outdated patterns
Relevance test
- Does this actually answer the question?
- RELEVANT: Directly addresses what was asked
- RELATED: Similar but different context
- TANGENTIAL: Keyword match only
Filter out: code in /deprecated/, /old/, /legacy/ paths; abandoned repositories; prototype/experimental code; code with extensive TODO/FIXME comments. Quality over quantity — 3 good examples beat 10 mediocre ones.
Key differentiator
Local tools (grep, glob) search only the current repo. Glean searches across all repositories in the organization. This is powerful for:
- Finding examples: "How do other teams handle authentication?"
- Understanding systems: "What repos touch the billing service?"
- Finding owners: "Who's been active in the payments codebase?"
Tool selection
| User intent |
Glean tool |
| Find code by content, pattern, or file |
code_search |
| Find related design docs or specs |
search |
| Identify code owners/contributors |
code_search + employee_search |
| Read full file content |
read_document |
Output expectations
When presenting code findings:
- Cite each file with its full URL so the user can open it directly
- Note last-update date when a result depends on currency (active patterns vs. archaeological digs)
- Group by repo when results span many repos — it shows the user the shape of the answer
- Flag drift when implementations disagree across teams — don't pretend consensus exists if it doesn't
Related skills
codebase-context — structured architecture rundown for an unfamiliar systemsimilar-code — find similar implementationsfind-examples — usage examples for an internal API or librarycode-owners — maintainers and contributorsplan-prep — the workflow described in reference/plan-prep.md
1---2name: using-glean-code3description: Search and analyze internal source code across the organization's repositories — use when asked how something is implemented, where the code for a system lives, who has been working on a codebase, or to find similar patterns across teams. Trigger phrases include how is X implemented, where is the code for, find the implementation of, what repos contain, who wrote the code for, how do other teams handle, find similar code to, examples of using, prior art for. Do not use for code in the current working directory (prefer local Grep/Glob), for design docs (use the using-glean skill's search reference), or for finding people without code context (use the using-glean skill's employee-search reference).4---56# Using Glean for Code Exploration78Glean indexes source code across the organization's connected repositories. Local tools (`Grep`, `Glob`, `Read`) see only the current repo; this skill is for everything else.910## When to reach for this1112- **Finding the system** — "Where does our payments code live?"13- **Finding the patterns** — "How do other teams handle rate limiting?"14- **Finding the people** — combining code authorship with `employee_search` reveals real owners (not just titled ones)15- **Prior art before designing** — see [reference/plan-prep.md](reference/plan-prep.md) for the research-before-plan workflow16- **Cross-repo exploration** — understanding systems, mapping breadth, finding contributors across the organization1718## The tool you'll mostly use1920This skill drives the `code_search` MCP tool. For full param shape, inline filter syntax, and pitfalls (quoting names, the `app:` filter not applying, recency caveats), read [`../using-glean/reference/code-search.md`](../using-glean/reference/code-search.md). That is the canonical reference; this skill carries the *workflow* on top.2122For this skill's own workflow patterns, see:2324- [reference/exploration.md](reference/exploration.md) — exploring an unfamiliar system across repos: what to search for, what to filter, what to present25- [reference/plan-prep.md](reference/plan-prep.md) — gathering enterprise context before entering plan mode for architectural / strategic work2627## Vetting2829Not every match is worth surfacing. Code in `legacy/`, `deprecated/`, `archive/`, abandoned repos, or files with extensive `TODO/FIXME` comments will mislead the user. Apply the criteria in [`../using-glean/reference/vetting.md`](../using-glean/reference/vetting.md) and prefer 3 high-quality matches over 10 unfiltered ones.3031**Quality test**32- Is this good code to reference?33- GOOD: Clean, tested, actively maintained34- ACCEPTABLE: Works but has caveats35- POOR: Hacky, deprecated, abandoned3637**Recency test**38- Is this code maintained?39- ACTIVE: Commits in past 3 months40- SLOWING: 3–12 months since last commit41- STALE: 12+ months — likely outdated patterns4243**Relevance test**44- Does this actually answer the question?45- RELEVANT: Directly addresses what was asked46- RELATED: Similar but different context47- TANGENTIAL: Keyword match only4849Filter out: code in `/deprecated/`, `/old/`, `/legacy/` paths; abandoned repositories; prototype/experimental code; code with extensive TODO/FIXME comments. Quality over quantity — 3 good examples beat 10 mediocre ones.5051## Key differentiator5253Local tools (grep, glob) search only the current repo. Glean searches across all repositories in the organization. This is powerful for:54- Finding examples: "How do other teams handle authentication?"55- Understanding systems: "What repos touch the billing service?"56- Finding owners: "Who's been active in the payments codebase?"5758## Tool selection5960| User intent | Glean tool |61|-------------|------------|62| Find code by content, pattern, or file | `code_search` |63| Find related design docs or specs | `search` |64| Identify code owners/contributors | `code_search` + `employee_search` |65| Read full file content | `read_document` |6667## Output expectations6869When presenting code findings:70711. **Cite each file with its full URL** so the user can open it directly722. **Note last-update date** when a result depends on currency (active patterns vs. archaeological digs)733. **Group by repo** when results span many repos — it shows the user the shape of the answer744. **Flag drift** when implementations disagree across teams — don't pretend consensus exists if it doesn't7576## Related skills7778- `codebase-context` — structured architecture rundown for an unfamiliar system79- `similar-code` — find similar implementations80- `find-examples` — usage examples for an internal API or library81- `code-owners` — maintainers and contributors82- `plan-prep` — the workflow described in [reference/plan-prep.md](reference/plan-prep.md)
gleanwork