Coding labs that actually grade themselves.

Flame is an interactive coding platform for classrooms. Teachers post problems with hidden tests. Students write code in 28 languages and submit — graded in seconds, no install, no setup.

Start coding See a lab

Writing

{}solution.ts

Explorer

{}solution.ts

ttests.ts

{}package.json

##README.md

typescript

2 tests waiting

Labs

Write, run, test. No setup, ever.

A real editor, a real runtime, a real test runner — in the browser. Every problem ships with hidden grader tests so students learn by proving it.

{} solution.ts

typescript

grader statusAll Passed

returns doubled for small list
expect[6, 14, 4]
--
handles empty input
expect[]
--
preserves order
expect[2, 4, 6, 8]
--
rejects non-number values
expectTypeError
--
handles 10k entries under 50ms
expect<= 50ms
--

❯ flame test ./solution.ts

auto-run

28 languages out of the box

Python
TypeScript
Go
Rust
Java
C++
SQL
Ruby

Why Flame

A platform that shows its work.

Flame is the surface area of a real coding tool — fast, sandboxed, multi-language — wrapped in a runtime view that actually teaches.

Autosave everything

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Autosave everything

Every keystroke saved. Resume mid-thought from any device — drafts never disappear.

28 languages

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28 languages

Python, TS, Go, Rust, Java, C++, SQL — one editor, one shortcut set, one workflow.

Leaderboards

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Leaderboards

Per-batch rankings by score, speed, and coverage. Healthy competition, private to your class.

Progressive hints

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Progressive hints

Stuck? Teachers drop tiered hints that reveal only what a student has earned.

Shareable runs

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Shareable runs

Export a submission as a replayable link. Perfect for code review and office hours.

Classroom analytics

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Classroom analytics

See where the class stalls, which tests fail most, and which concepts need re-teaching.

Sandboxed runtime

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Sandboxed runtime

Every run executes in an isolated container. Safe for schools, strict for grading.

Keyboard first

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Keyboard first

Vim, emacs, VSCode bindings, command palette, snippets — editor feels like home.

Execution engine

Live runtime

Execution engine

A full distributed runtime under the hood — every run is observable, replayable, and traceable step by step.

Visual Trace

See exactly how it ran.

The execution engine records every branch decision and memory mutation. Students replay runs step-by-step — not just whether it passed, but why.

sort.ts

step 1 / 5

1function sort(arr: number[]) {

2 if (arr[0] > arr[1]) {

3 const temp = arr[0];

4 arr[0] = arr[1];

5 arr[1] = temp;

6 }

7 return arr;

10sort([8, 3]);

Execution log1 / 5 events

0.001sCALLsort([8, 3])

─BRANCH

─ASSIGN

─MUTATE

─RETURN

Memory

arr=[8, 3]

[

]

Flow graphcall tree

CALLsort([8, 3])

BRANCHarr[0] > arr[1]

ASSIGNtemp ← arr[0]

MUTATEarr[0]=3 arr[1]=8

RETURNreturn [3, 8]

BRANCHreturn arr

Batches

Teachers run the class. Students run the code.

Batches are how classrooms live on Flame. One container per student per run, hidden tests stay hidden, rubrics enforce partial credit, time limits enforce reality.

Teacherrole · teacher

Own the curriculum

Draft problems with starter code, edge-case tests, and rubric weights. Clone last term's batch in one click.

Create a batchName it, share the join link
01
Post problemswith hidden tests + rubric
02
Auto-gradepass/fail in seconds
03

Studentrole · student

Prove it by running it

Write, test, submit. See exactly which tests passed and what your code actually did.

Join with codeno signup friction
01
Solve in browserreal editor, real runtime
02
Submit & see flowgraded with feedback
03

Hidden tests stay hidden Rubric-weighted scoring Per-problem time limits

Roadmap

Built in the open. What's next.

We ship in public. Here's what's live, what's being built, and what's queued up next.

LiveQ1 2026

Shipping this quarter

Hidden-test graderRubric weights, time limits

Batches & rosterJoin codes, SSO ready

28-language editorVim, emacs, VSCode bindings

Phase 013 items

BuildingQ2 2026

In active development

Current focus

Submission replaysStep through any past run

Plagiarism clustersNear-duplicate detection

Teacher analyticsPer-problem failure modes

Phase 023 items

PlannedQ3 2026+

On the roadmap

Live class modeShared cursors, live grading

LMS bridgesCanvas, Moodle, Google Classroom

Premium runtimeAdvanced visualization layer

Phase 03

Use cases

One platform, four classrooms.

Flame is built around a single primitive — the batch — but it bends to whatever your classroom looks like.

Universities

Replace the patchwork

One tool for problem authoring, hidden tests, auto-grading and analytics. Drop the Replit-Classroom-spreadsheet stack.

Roster sync · SSO
TA review queues
Per-section batches

Bootcamps

Ship cohorts faster

Clone last cohort's batch, swap in this week's problems, ship by Monday. Hidden grader runs at scale without flake.

Cohort cloning
Rubric reuse
Time-limit enforcement

Interview prep

Real timing, real tests

Practice against grader tests that match the constraints of real interviews — not just whether the code compiles.

Difficulty filters
Speed leaderboards
Replay your runs

Hackathons

Run a fair contest

Spin up a one-off batch, share a join code, freeze the leaderboard at the end. Auto-grading keeps the judges honest.

Single-link join
Leaderboard freeze
CSV export

How Flame compares

What the old toolchain doesn 't do.

Most classrooms cobble together an editor, a Google Form, a sheet, and a TA. Flame replaces all of it.

FeatureFlameLegacy stack

Hidden tests stay hidden from students
Auto-graded with rubric weights
manual
Real sandboxed runtime per submission
shared
Per-problem time + memory limits
Clone a cohort in one click
copy-paste
Replayable submissions
28 languages, one editor
varies
SSO + roster sync
premium

From the classroom

Built with educators who actually teach.

“The batch grader replaced our patchwork of Google Classroom, Replit, and a TA spreadsheet. One tool, auditable, fast.”

Marcus HollowayProgram Lead · Scholars Code Academy

“We run 400-student cohorts and auto-grading stays under 30 seconds. The hidden-test workflow is exactly what we needed.”

Ana RuizCurriculum Director · Codeworks MX

“Students stopped asking how to set up the toolchain on Tuesday. They started writing actual code on Tuesday.”

Dr. Priya IyerCS Lecturer · IIT Delhi

“Cloning last term's batch in one click saved my Sunday. The rubric weights survived the migration. That used to take hours.”

Elena ParkTeaching Assistant · Stanford CS106

Pricing

Pay for runs. Own every language.

Every pack unlocks the full platform — all languages, exact-engine animation, real sandboxed execution. Packs differ only in how many NeonFlow runs you get, and runs never expire. Start with 3 free runs, no card needed.