jestatsio/codebase-mentor

Give your coding agent a repeatable way to answer “How does this work?” and “Where do I make this change?” Codebase Mentor asks it to read current source, cite the relevant files and symbols, and call out missing evidence. A short ONBOARDING.md adds the rationale and gotchas your team knows.

Start in any repo. An onboarding doc is optional. The skills need no API key, database, background service, or separate runtime beyond your coding agent.

Install

Claude Code

Run in Claude Code:

/plugin marketplace add jestatsio/codebase-mentor
/plugin install codebase-mentor@codebase-mentor

Codex

Run in your terminal with a current Codex CLI:

codex plugin marketplace add jestatsio/codebase-mentor
codex plugin add codebase-mentor@codebase-mentor

In the Codex app, add jestatsio/codebase-mentor as a plugin marketplace and install Codebase Mentor. If your version does not support plugins, use the skills fallback.

IBM Bob

From the repository you want to understand:

curl -fsSL https://raw.githubusercontent.com/jestatsio/codebase-mentor/main/install.sh | bash -s -- --agent bob --project

This installs both skills in .bob/skills/. Reopen your workspace if they do not appear, then ask Bob to use Codebase Mentor. See Bob setup and troubleshooting for a download-and-review alternative.

Other agents: npx skills add jestatsio/codebase-mentor installs the open skills format. Cursor, Copilot, AGENTS.md, and all installation options →

Try it

Open a repo in your agent and paste:

Use Codebase Mentor to trace one important execution path in this repo.
Explain it to a new contributor. Cite the files and symbols you read,
and flag anything you cannot verify.

Then put it to work:

In Claude Code, invoke the generator directly with /codebase-mentor:onboard. In other agents, select onboard from their skills menu or ask for it by name.

An answer should make its evidence inspectable. For example, in this repository:

Where do I change the mentor’s behavior? Edit core/mentor-protocol.md, then run scripts/sync-adapters.sh to regenerate the distributed copies. Update core/mentor-protocol-compact.md when the rule also applies to compact adapters. Run scripts/sync-adapters.sh --check to check for drift.

Evidence: the full and compact protocol files, plus the generation and check paths in scripts/sync-adapters.sh.

The protocol is an instruction set, not a correctness guarantee. Results depend on your agent and its source access. Review its evidence before acting.

A map your team can maintain

ONBOARDING.md is a short, human-owned guide: purpose, layers, execution path, vocabulary, change recipes, useful files, and known gotchas. The agent uses it to find the code, then checks what the code actually does.

1. Draft: use the onboard skill, or start with the template.
2. Review: add the design decisions and pitfalls only your team knows.
3. Share: commit it alongside your code. Follow the team setup guide.
4. Maintain: ask for a freshness scan after refactors, or opt into the scheduled scan.

Browse real example maps for Python libraries, Java services, and a Python/React application. Examples are snapshots, so verify their anchors against the version you use.

Evidence and limitations

The project began with a five-task, author-scored case study on the Stargate Data API:

This is an exploratory case study, not an independent benchmark. The first comparison changes both source access and instructions. Published responses include normalized excerpts, and independent judging has not been completed. Read the design, rubrics, responses, and limitations.

Go further

The MCP package is not currently published to npm. Use its documented local build. Native plugin and skill installs do not need it.

Repository layout