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PR Blackboard

Big PRs are hard to follow file by file. PR Blackboard lays a GitHub PR out as one Drawdy board.

Phureewat A
Phureewat A1
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PR Blackboard

Read any PR as one board.

PRs come in faster every month, and they keep getting bigger. A coding agent can open a thousand-line PR in a few minutes, and someone on the team still has to read it.

PR Blackboard pins a GitHub PR to your Drawdy board. Each changed function becomes a card. Labelled lines run from every call to the function it reaches, and from every test to the code it covers. The board reads left to right, from where the change starts to the code it calls, so you can walk through a big PR one card at a time.

honojs/hono#5513 on the board: step through it card by card, jump along a line from the panel, open the overview, then paste a PR link

Why a board

A diff lists the changed files in alphabetical order. Where the change starts, what calls it and which test covers it are left for you to piece together, and on a big PR that takes most of the review.

  • The whole change in one place. Where the change starts, then what it calls, then what that calls, from left to right.
  • Calls you can follow. A line runs from each call to the exact function it reaches, in whatever file it lives.
  • Callers included. Code that didn't change but calls into the change gets a card too.
  • Tests next to the code. Each test sits under the code it tests.
  • Big PRs too. Bun's 2,188-file rewrite in Rust opens as one board you can step through.

How it works

1. Paste a PR link, or pick an example. 2. PR Blackboard reads the changed files and links the code. 3. Follow the lines, step by step.

Made for

  • Getting through the review queue: see the shape of each PR in a few minutes, then read the lines that matter.
  • PRs from coding agents: see what the agent touched and how the pieces connect before you approve it.
  • Learning a new codebase: open a recent PR and watch a real change move through the project.
  • Walking your team through a change: step through the board card by card on a shared screen, and add sticky notes as you talk.

What's on the board

  • The PR card: the title, the author, what changed, and the whole description, rendered the way GitHub shows it.
  • Change cards: each changed function with its changes, and every call to another card marked →. Read all opens the full code right on the board; drag it anywhere, and it pans and zooms with the board.
  • Lines: calls, uses, tests and imports. Lines that cross or run close get different colours, so you can follow one across the board. PR Blackboard draws a line only when it can tell exactly where a call goes. It never guesses from a name.

Stepping through

  • › and ‹, or the arrow keys, step through the code in board order, and the camera follows.
  • For each card, the panel lists what calls it, what it calls and what tests it. Each name takes its line's colour; click one to go there.
  • Overview shows the whole board. Description goes to the PR card. Home takes you back to the examples, and your board stays. Rebuild reads the PR again after new commits.

Lines are drawn for JavaScript, TypeScript, Python, Go, Rust and Java. PRs in other languages get a card for every change.

Try it in 30 seconds

  1. Click the PR Blackboard button on the right edge of the board: the stack of cards.
  2. Paste a link like github.com/honojs/hono/pull/5513, or pick one of 14 examples from Hono, Vite, Node.js, Svelte, Bun, Prometheus, CPython and more.
  3. Press › and follow the lines.

Good to know

  • Works with public PRs on GitHub. No account or sign-in.
  • GitHub allows 60 requests an hour without signing in. Opening a PR uses 2, and a very big one more: Bun's 2,188-file rewrite takes 23.
  • The first PR in a language downloads that language's parser, once: 81 KB for the engine, then 37 KB for Go, 46 KB for JavaScript, 48 KB for Java, 63 KB for Python, 110 KB for Rust or 128 KB for TypeScript. It stays on your device after that.
  • The board is yours: move the cards, draw on them, add sticky notes.
  • PR Blackboard only reads. It never approves, comments on or changes anything on GitHub.
  • Links inside the description can't be opened from the board yet.
  • A board holds 32 cards, and PR Blackboard reads up to 40 code and 40 test files of a PR. When a PR has more, or GitHub's requests run low, the panel warns while it loads and keeps the warning on the PR card.

Permissions

  • Board: to pin cards and lines, and to find the boards it pinned before.
  • Interface: to show its panel, its button and the Read all pane.
  • Storage: to keep the PRs you open and the language parsers on your device.

Privacy

PR Blackboard reads the PR and its files from GitHub and downloads the language parsers from jsDelivr. Each parser must match a pinned SHA-256 hash before it runs. Apart from those requests it sends nothing, and it has no account or tracking.

License

MIT licensed.