Roundup

Best tools to understand a codebase in 2026

For engineers starting on a codebase they didn’t write, and for leads choosing a tool to speed that up. We make Enhanciar, which is one of the options below. We’ve tried to be fair: several of these are better choices than ours for some teams, and the first section costs nothing.

A roundup, including free options and tools we don’t make · Updated 11 November 2026

Start with what’s free

Your IDE’s navigation. Go to definition, find references, call hierarchy. Still the fastest way to follow a request through the code.
Tests and a debugger. Tests tell you what the authors expected; stepping through one real request tells you what actually happens. These were the most repeated tips in Ask HN: How to understand the large codebase of an open-source project?.
Git history. git log -L, the pickaxe and blame with the right flags. See git blame alternatives.
An AI coding agent (Claude Code, Cursor, Copilot, Amp) pointed at the repo. Good at “what does this do?”. It sees the code, not the PR or Slack thread where a decision was argued.

Side by side

The tools, compared.

Tool	What it does	Where it answers	Cites PRs?	Pricing (as of Sep 2026)	Self-hosting
Enhanciar	Answers “why is this code like this?” from code, PRs, review comments, Slack and docs. Then does the follow-up: opens the GitHub issue or Linear ticket you approve, and reviews pull requests on repos where you turn it on	Web, Slack, MCP (Claude Code, Cursor)	Yes: file:line plus the PR, review comment or Slack message	$35 per person/mo (cancel anytime), or $315 per person/year paid once, bring your own LLM key, $0 inference markup. Open sign-up, paid plans	No; hosted
Unblocked	Codebase Q&A and a context layer for AI agents across code, conversations, issues and docs (source)	Web, Mac app, Slack, Microsoft Teams, MCP, CLI, API (source)	Says “every answer ships with source links”	$29/user/mo annual or $35 monthly; Enterprise custom; 21-day free trial (source)	On-prem options on Enterprise
Sourcegraph (Cody)	Enterprise code search, Deep Search and Cody; Cody Free/Pro ended July 2025 (source)	Web, IDE, MCP server, API, CLI	Cites code; built around search, not PR discussions	Enterprise from $16,000/yr minimum (source)	Yes: self-hosted or single-tenant cloud
Glean	Company-wide enterprise search and assistant; its GitHub connector indexes code, PRs, reviews and comments (source)	Web, Slack, MCP (docs)	References source documents, including PRs	Not published; sales-led (source)	Not stated on pricing page
Greptile	Mainly AI pull-request review now; codebase context over MCP (source)	PR comments, MCP (Cursor, Claude Code, VS Code, Codex)	Reviews PRs; not a history-of-decisions tool	Free Starter (1 dev, 50 credits a month); Pro $1 per credit, no seat fees; Enterprise custom (source)	Enterprise only
Swimm	Code-coupled docs; now sells modernization of large legacy estates as a delivered service (source)	IDE (VS Code, JetBrains), web, feeds AI tools via MCP (docs)	Checks docs against code on PRs; not a PR-history Q&A tool	Not public; the pricing page now redirects to the How it works page, which offers a scoping call (source)	Yes: on-prem and air-gapped
Amp	Agentic coding tool; spun out of Sourcegraph as its own company in Dec 2025	Editor / CLI	It writes code rather than explaining history	Free Hobby tier (BYOK); $20/mo Individual; Enterprise custom (source)	Not listed

Competitor details come from each vendor’s public pages as of September 2026 and are summarised, not quoted. Prices change; check the linked page before you buy. If we got something wrong, email us and we’ll fix it.

Beyond answering	Enhanciar	The others
Takes actions	Yes, you approve first: Jira, Linear and GitHub issues, Slack posts, Gmail drafts, calendar events, Notion pages, Zendesk notes	Coding agents (Claude Code, Cursor, Amp, Unblocked Code) write code; the Q&A and search tools here do not state ticket or message actions
Reviews pull requests	Yes, posted on the PR with the whole codebase as context, on repos you turn it on for	Greptile: yes, its main job. Unblocked: yes, inline comments on each PR. Swimm: checks docs against the PR. The others: not a stated feature

How to choose

“Where is X?” across hundreds of repos: Sourcegraph.
“Why is it like this?” and “what breaks if I change it?”: Enhanciar or Unblocked. Enhanciar is $35 per person with your own model key and files the issue you approve; Unblocked is per user and offers on-prem on Enterprise.
“Where is anything at this company?”: Glean.
“Is this PR safe?”: Greptile, or Enhanciar’s review on the repos where you turn it on.
“We need written docs that stay current” or a mainframe migration: Swimm.
“Help me write the change”: an AI coding agent. Pair it with one of the above over MCP so it can see the history too.

When to pick something other than Enhanciar

If you need self-hosting, pick Sourcegraph, Swimm, or the Enterprise plans of Unblocked or Greptile; Enhanciar is hosted only. If you need SSO and procurement paperwork this quarter, the established vendors are further along. If your team won’t manage a model key, choose a tool that includes the model. And if your questions are mostly “where”, not “why”, code search is the better buy.

A setup that works for most teams

Fix the free basics first: .git-blame-ignore-revs for format commits, PR templates that ask “why”, and squash merges that keep the PR number.
Pick one tool for “why” questions and connect GitHub plus the chat tool where decisions happen.
Point your AI coding agent at that tool over MCP, so the agent’s changes respect past decisions.
For a new hire’s first week, have them ask the tool before asking a person, and check the cited source each time. The onboarding guide has a fuller plan.

What Enhanciar costs

It is $35 per person a month (cancel anytime), or $315 per person a year paid once, which works out to about $26 a month. You bring your own model key (Anthropic, OpenAI, Google or a compatible provider) and pay that provider directly; Enhanciar adds $0 on tokens. Sign-up is open: you pick a paid plan (no free trial) and get started right away. There is no self-hosted version.

Then hand it the follow-up

Understanding the code is step one.

After the answer, say what you need. It drafts the work and waits in your Actions queue for a person to approve; PR review runs on its own once you turn it on for a repo.

Review this PR Open a GitHub issue for the dead flag Turn the review notes into Linear tickets Write the decision up in Notion Post what you found to #eng

Orange dot: waits for your approval. Teal dot: pull-request review posts on its own, only on repos where you turn it on.

FAQ

Questions people ask.

What is the best tool to understand a large codebase?

There isn't one tool. IDE navigation and a debugger for how it works, code search (Sourcegraph) for where things are, and a tool that reads PRs and chat (Enhanciar, Unblocked) for why it's built that way. (Asked in: Ask HN: How to understand the large codebase of an open-source project?)

Are there AI tools that can make sense of a large repo?

Yes. Coding agents like Claude Code, Cursor and Amp can read a repo and explain it. Tools like Enhanciar, Unblocked and Glean also read PRs, tickets and chat, which is where the reasons live. (Asked in: Ask HN: Any AI tools that help you make sense of a large repo?)

Can I just give the whole codebase to ChatGPT?

For a small repo, roughly. For a large one it won't fit or stay current, and it won't include the review discussions. That's the gap these tools fill. (Asked in: Ask HN: How to share entire codebase with ChatGPT)

Is it safe to connect our private code to these tools?

Read each vendor's data policy. Self-hosted options (Sourcegraph, Swimm, some Enterprise plans) keep code on your infrastructure. With bring-your-own-key tools like Enhanciar, model calls go to the provider whose key you use. (Asked in: Launch HN: Greptile)

Which tools are free?

git, your IDE and a debugger. Greptile has a free Starter plan and Amp has a free Hobby tier (source; source). Unblocked has a 21-day trial.

How do I find why a decision was made in the code?

Go from the line to the commit, from the commit to the PR, and read the review thread and linked ticket. Our guide walks through it.

Get started

Ask the codebase why. Then hand it the ticket.

Sign-up is open. Pick a plan, add your own AI key and connect your first source.

Get started See pricing