marimo-grader¶

Assignments that are real notebooks, graded without anybody touching Git.

marimo-grader is a grading service for coursework written as marimo notebooks. A student opens a notebook, works through it, presses Check for instant feedback, signs in with their university account from inside the notebook, and presses Submit. Teaching staff grade in a web app. Grades export to Canvas.

Be a student for five minutes

Try an assignment — a real one, in your browser, on this site. Nothing to install, nothing submitted anywhere.

The loop¶

read → experiment → check → submit → get feedback

That is the whole student-facing design, and everything else exists to protect it. Students never touch Git, tokens, servers, virtual environments, or a submission portal. They press two buttons, and the difference between them is the thing worth learning:

	Check	Submit
Runs	in the student's notebook	on the grader
When	as often as they like	when they are ready
Speed	instant	a score back in about a minute
Counts?	no — it is for learning	yes — it records an attempt
Sees	the visible tests	the visible tests and the hidden ones

The same notebook, wherever it runs¶

Environment	What it is	Typical use
Browser (WASM)	the notebook runs in the page itself, no server	light assignments: Python basics, pandas, plotting
MoLab	marimo's hosted notebooks, a full Python environment	most data-science assignments
A cluster (Open OnDemand)	marimo on institutional HPC	large datasets, neuroimaging, GPUs
A laptop	`marimo edit --sandbox assignment.py`	anyone who prefers local work

Execution and grading are independent. Whatever the kernel runs on, the widget's JavaScript runs in the student's browser, so the only network requirement is that the browser can reach the grader. A notebook on a cluster behind a VPN submits perfectly well.

How the pieces fit¶

private assignments repo          instructor notebooks: solutions, hidden tests, marks
        |  grader publish
        v
marimo-grader server              versions, student notebooks, grading, roster, exports
        |  student notebook served at /a/{course}/{term}/{slug}/student.py
        v
course website / MoLab / cluster  students open the assignment
        ^
student's browser  ---  sign-in handshake and submit, from the notebook widget

Every submission stores the whole notebook as an immutable attempt against the exact assignment version the student opened. A worker autogrades it inside a sandbox with no network and renders it to HTML for the grading view. Written answers wait in a queue for a person. The life of a submission follows one all the way through.

The autograding itself is MoGrader, James Kermode's open-source grading engine for marimo notebooks, used as a library. It supplies the authoring markers, the checks, the integrity hashes and the sandboxed runner; marimo-grader supplies single sign-on, the multi-course service around it, and the notebook widget. See The grading engine.

What the staff side looks like¶

The course page leads with the only question that matters on a Tuesday — who needs my attention? — and puts the class grid underneath.

The course page: a Needs attention list above the class progress grid, one column per question

Hand-graded questions have a queue: the student's rendered notebook on the left, score and feedback on the right, j/k to move, Cmd+Enter to save. Student code never runs in a grader's browser.

The grading queue: the rendered notebook on the left, score, feedback, and the student's written answer on the right

Where to start¶

New here — Try an assignment, then What the instructor wrote. Fifteen minutes and you will know whether this fits your course.
Students — Open an assignment · Sign in and submit · Feedback and grades
Instructors and TAs — Author an assignment · Publish · Roster and staff · Grading · Canvas export
Understanding it — Concepts · The life of a submission · The grading engine
Authentication — How sign-in works, then the notebook handshake, SAML, email links, and sessions and tokens.
Running a server — Overview · Deploy · Security model, which is written to be handed to an institutional review as is.
Reference — command line · configuration · notebook metadata · HTTP API · design document

Status¶

A pilot. It runs one course — DartBrains at Dartmouth — and is built to run more. The code is at github.com/ljchang/marimo-grader, MIT licensed. Things that are planned rather than done are labelled as such on the page where they belong; the design document has the roadmap.

This site and the DartBrains course book are built with marimo-book, a static-site generator for marimo notebooks (source). A book publishes the student version of an assignment as an ordinary page and links it here — the drawer on Try an assignment is that feature. See marimo-book's Assignments and grading.

MoGrader (James Kermode, University of Warwick, MIT license) is the grading engine. If you publish work that used this system, please cite it alongside marimo-grader.