// Investigate the history, usage, and liveness of code using search and git blame/log. Use when determining if code is dead, understanding why something exists, finding all callers before refactoring, or deciding whether something is safe to remove. Also useful for answering "who added this and why" or "is anything still using this".
| name | code-history |
| description | Investigate the history, usage, and liveness of code using search and git blame/log. Use when determining if code is dead, understanding why something exists, finding all callers before refactoring, or deciding whether something is safe to remove. Also useful for answering "who added this and why" or "is anything still using this". |
| allowed-tools | Read, Grep, Glob, Bash(git *) |
Figure out if code is still used and whether it's safe to remove. Pick whichever techniques below are useful -- you don't need all of them.
Search for callers with grep -rn 'symbol' --include='*.rs' across the whole repo. Classify hits as definition, test, re-export, or real caller. Zero real callers usually means dead. Also check pub use re-exports -- if nothing imports the re-export, it's still dead.
Find the introducing commit with git log --all --oneline --diff-filter=A -S 'symbol' -- '*.rs'. Then git show <commit> --stat to see what else was part of that change.
Trace the lifecycle with git log --all --oneline -S 'symbol' -- '*.rs' to see every commit that added or removed lines with the symbol. Look for commits that deleted callers without deleting the code they called -- that's usually how dead code happens.
Blame with git blame path/to/file.rs -L 100,120. If a function hasn't been touched since the original commit but surrounding code has evolved, it's probably orphaned.
Check transitive usage -- a symbol with zero direct callers might still be reachable through pub use re-exports or trait impls (impl Trait for). If nothing outside the crate uses the re-export, it's dead.
| Evidence | Verdict |
|---|---|
| Zero real callers, only definition + tests | Dead. Remove with its tests. |
| Re-exported but no external imports | Dead. Remove re-export too. |
| Caller was deleted in a later commit | Dead from incomplete refactor. |
| Only caller is itself dead | Transitively dead. Remove both. |
| One caller | Candidate for inlining. |
| 2+ callers | Alive. |
git log --all --oneline --diff-filter=A -S 'symbol' -- '*.rs' # first appearance
git log --all --oneline -S 'symbol' -- '*.rs' # all touches
git log --all --oneline -20 -- path/to/file.rs # file history
git show <commit>:path/to/file.rs # file at commit
git show <commit> -- path/to/file.rs # diff for one file
git show <commit> --stat # files changed
git blame path/to/file.rs -L 100,120 # blame range
git blame -w path/to/file.rs -L 100,120 # blame ignoring whitespace
git log -1 -S 'deleted_line' -- path/to/file.rs # find deletion
git log --all --merges --oneline -S 'symbol' # merge commits
Query the GitLab Knowledge Graph (Orbit) via `glab orbit remote` CLI subcommands or run a local copy with `glab orbit local`. Use for code-structure questions (who calls this function, where is this symbol defined), cross-project dependency and blast-radius analysis, merge-request and contributor queries, and any question answerable by traversing GitLab's unified entity graph (projects, users, MRs, issues, pipelines, files, definitions, vulnerabilities).
Audit and update documentation after code changes. Use when architecture, APIs, or behavior changed and docs may have drifted.
Investigate query evaluation failures in the Knowledge Graph synthetic data pipeline. Use when queries fail or return unexpected results after running the evaluate binary.
Profile GKG queries against ClickHouse with the query-profiler CLI. For optimizing query performance, comparing query plans, investigating slow queries, or checking ClickHouse resource usage.
AST-based code search and rewrite via tree-sitter patterns. Use instead of Grep/Edit for structural matching, batch rewrites, or context-aware queries (e.g. "unwrap inside impl blocks").
GitLab Pajamas Design System expert for building UIs with Pajamas components and patterns. Use when: (1) implementing UI that should follow GitLab's Pajamas design system, (2) selecting or configuring Pajamas/GlComponent components (GlButton, GlAlert, GlModal, etc.), (3) translating Figma designs into Pajamas-compliant code, (4) questions about Pajamas component usage, variants, categories, or accessibility, (5) building GitLab-style interfaces, or (6) the user mentions "Pajamas", "GitLab UI", "Gl components", or "design system" in a GitLab context. Works hand-in-hand with the implement-design skill and Figma MCP tools.