What demur is

demur is a code reviewer with a fixed stance: it grants every fact in the pull request and then argues why the change still must not be merged. It runs on your own provider key, and it cannot merge anything.

The name is the legal sense of the word. A demurrer does not dispute the facts. It says that even if every one of them is true, there is no case. That is the review demur performs.

What it does

• Reads the pull request diff, the title, and the description.
• Triages the changed hunks, deep dives the risky clusters through the lenses you enabled, and on the deep profile cross-examines the change as a whole.
• Publishes one review event and one check run, with findings ranked by the harm they argue and anchored to exact lines.
• Records what it spent, what it covered, and anything it had to cut.

What it refuses to do

• It never merges and never edits. The strongest actions available to it are REQUEST_CHANGES and a failed check run. There is no auto-fix commit and no auto-merge, and no configuration setting adds one.
• It never praises. A finding that cannot name a file, a line range, and a concrete harm is dropped at synthesis rather than padded into the review.
• It never comments on style unless you enable a style lens.
• It never hides reduced coverage behind a green check. If the budget cut a pass, the review says which pass and what went unreviewed.
• It never takes custody of your key. There is no hosted component, no proxy, and nowhere for a key to go except the endpoint you configured.

What it is not

demur is not a linter and not a replacement for one. It will not tell you that a name is unclear or that a function is long. Those are your formatter's job and your own. demur exists to find the reason a change should not ship, and to say so in a form a human reviewer can check against the diff.

It is also not a consensus machine. It argues one side on purpose. A finding you disagree with is meant to be dismissed, and a dismissed finding stays dismissed on every later run.

Where to go next

• Setup installs the GitHub Action.
• Local CLI reviews a pull request or a local range from your terminal without publishing anything.
• The review pipeline explains the passes and what each one costs you.