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Nexus-skills

by Haaaiawd · Haaaiawd/Nexus-skills

Codebase intelligence skills — build a persistent .nexus-map/ knowledge base and query file structure, dependencies, and change impact.

Nexus Skills makes Claude Code and other agents codebase-aware. Run it once to generate a .nexus-map/ knowledge base with file structure, dependency graphs, and call sites. After that, queries like 'what breaks if I change this function?' get precise answers instead of guesses. Useful in large, unfamiliar repos.

▶ Watch demo 📦 Install 💡 Use Cases

Why use it

Key features

Live Demo

What it looks like in practice

nexus-skill.replay ▶ ready
0/0

Install

Author repository · Claude Skills documentation

Use Cases

Real-world ways to use Nexus-skills

How to onboard to an unfamiliar codebase fast

👤 Engineers joining a new team or team inheriting a codebase ⏱ ~60 min intermediate

When to use: Day one in a repo you've never seen; you want a map before making changes.

Flow
  1. Build the map
    Use nexus-skills to scan this repo and build .nexus-map/.✓ Copied
    → Progress output + map files produced
  2. Get the tour
    Using .nexus-map, tell me: entry points, top 10 most-imported modules, and any orphaned files.✓ Copied
    → Repo overview keyed to actual files
  3. Dig into a subsystem
    Show me the payments subsystem — files, dependencies, external calls.✓ Copied
    → Scoped subsystem view

Outcome: A factual mental model of the repo built in under an hour.

Pitfalls
  • Map goes stale after big merges — Re-run nexus update; it's incremental

Check blast radius before changing a core function

👤 Engineers about to touch a widely-used utility ⏱ ~30 min intermediate

When to use: You're about to rename or change the signature of a function and want to see every call site.

Prerequisites
  • .nexus-map/ already built — Run once per repo; incremental after
Flow
  1. Query impact
    What calls formatCurrency(), and what would break if I change the signature to accept a locale?✓ Copied
    → Call-site list with each caller's likely break mode
  2. Generate migration
    Produce the minimal diff across all call sites to add the new locale param with a sensible default.✓ Copied
    → Multi-file patch

Outcome: A change with known blast radius and a prepared diff.

Find dead code and unused exports

👤 Engineers cleaning up before a refactor ⏱ ~40 min intermediate

When to use: Before a refactor you want to know what's truly unused.

Flow
  1. Query map
    Using .nexus-map, list files with no imports from elsewhere, and exports with no external references.✓ Copied
    → Ranked list with confidence per finding
  2. Verify
    For the top 10 candidates, double-check by searching for string-based usage (reflection, dynamic imports).✓ Copied
    → Filtered list with false-positive caveats

Outcome: A dead-code delete list you can actually ship.

Pitfalls
  • Dynamic imports look dead statically — Always run the string-based sweep before deleting

Combinations

Pair with other MCPs for X10 leverage

nexus-skill + claude-code-owasp-skill

Security-impact queries: where does tainted input flow?

Using nexus-map, trace every call path from the /ingest endpoint into the DB layer. Then OWASP review those paths.✓ Copied

Tools

What this MCP exposes

ToolInputsWhen to callCost
build_map repo_root Once per repo initially compute (local)
update_map changed_files After large merges compute (local)
query_structure question Answering structure questions Claude tokens
change_impact symbol or file Before breaking changes Claude tokens
dead_code - Pre-refactor cleanup Claude tokens

Cost & Limits

What this costs to run

API quota
None
Tokens per call
Map build is local compute (fast); queries consume Claude tokens
Monetary
Free
Tip
Build once, query often. Re-build only when repo shape changes materially.

Security

Permissions, secrets, blast radius

Credential storage: No credentials. .nexus-map/ is local by default.
Data egress: Map building is local. Querying sends map snippets to Claude.

Troubleshooting

Common errors and fixes

Map build crashes on monorepos

Run per-package rather than on the root; nexus supports a scope flag

Queries return stale results after edits

Run nexus update on the changed files; incremental is cheap

Language not recognized

Check supported languages in nexus docs; some frameworks need explicit parser config

Alternatives

Nexus-skills vs others

AlternativeWhen to use it insteadTradeoff
SourceGraph / CodyYou need hosted code intelligence at org scalePaid; not local
tree-sitter + custom queriesYou want full controlMuch more build time

More

Resources

📖 Read the official README on GitHub

🐙 Browse open issues

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