Tern

A guided walkthrough for any GitHub PR, in your editor.

Paste a PR URL into the Tern sidebar. You get an explanation alongside the diff: the change broken down by what it's actually doing, with pointers to the lines that prove the point.

Read it by intent, not by file.

A 47-file PR isn't 47 unrelated edits. Tern groups the diff by what's changing together: the auth refactor, the new error path, the test fixture update. Each group gets a paragraph of context. You read the PR as a few connected ideas instead of a wall of files.

See what carries the change.

Some hunks do the work. Most are mechanical: renames, formatting, import shuffles. Tern points at the lines that actually explain each piece, so you spend your attention where it matters. Click a pointer, your editor jumps straight to the file.

Walkthrough, diff, and code in one window.

If your workspace is checked out at the PR's commit, gutter marks show the diff next to the live code. The explanation, the inline diff, and the source you'd actually edit are all next to each other.

Works on individual commits too. Hit Refresh after new pushes.

Migrations

Tern also runs repo-wide migrations: auth swaps, framework upgrades, deprecation cleanup. Tern's agents produce a spreadsheet of every location that needs to change, classified by pattern and grouped by owner. The full spreadsheet lives at app.tern.sh; this extension shows those rows in the sidebar so you can click one and land in the file.

Getting started

Install the extension and open the Tern sidebar. Click Create new account. No email, no form: the extension provisions a local identity for you.

Then find your repo in the Repos view and click Tour PR/Commit.

If you already use Tern at app.tern.sh, click Sign In as Existing User instead. You'll get your team's migrations alongside the PR walkthroughs.