Codeck

Markdown decks with live Codex built in

Create Markdown teaching decks, run Codex prompts on slides, ask the Deck Assistant for edits, and present from one native Mac app.

View on GitHub Read the format

.mdeck: Markdown files that macOS opens in Codeck.
Live cards: Run fenced Codex blocks from the slide itself.
Assistant: Turn slide critique into selectable Markdown edits.

Codeck showing a Markdown editor and the Deck Assistant proposing slide changes

Write, run, present, repeat.

Codeck keeps the lesson source, rendered slide, and live assistant output in one editing loop so prompting demos stay reproducible.

Author in Markdown

Plain slides, YAML deck settings, images, GIFs, and fenced code blocks.

Run Codex cards

Each prompt block has model, reasoning, sandbox, and a dedicated run button.

Preview the lesson

The slide updates beside the editor with syntax highlighting and rendered Markdown.

Teach full screen

Launch presentation mode and move through the deck with familiar arrow keys.

Prompting demos that actually run.

A fenced codex block becomes a live card on the slide. Deck defaults keep model, reasoning, and sandbox choices consistent, while individual sessions can override them when a lesson needs more precision.

Run one card or run every Codex session on the current slide.
Stream Markdown output into the rendered slide as the answer arrives.
Keep stable session IDs for repeatable lessons and demos.

```codex id=first-demo
title: First example
reasoning: xhigh
sandbox: read-only

Explain three practical ways to make
a prompt more testable.
```

First example ready

Explain three practical ways to make a prompt more testable.

Click run to simulate a streamed Markdown response.

Deck Assistant

Turn a rough deck into proposed edits.

The Deck Assistant sits beside the editor, reads the selected slide or the whole deck, and asks Codex for focused changes. You keep control: review replacements and insertions, select the ones that fit, then apply them back to the Markdown.

Choose Slide for a local pass or Deck for a full presentation audit.
Run quick actions for gaps, shortening, polish, research, and data-backed evidence.
Enable web research when current facts, benchmarks, or citations matter.

Deck Assistant Slide 1: What's new in GPT-5.5

Slide Deck

Add useful data, benchmarks, comparisons, or evidence that would strengthen the argument. Cite sources when external facts are used.

Find Gaps Shorten Polish Research Add Data

Use web Ask Codex

Add benchmark evidence 2 selected

Add benchmark proof points Slide 1

Replace broad positioning with concrete signals so the opening claim is easier to trust.

Add one comparison slide Insert at 2

Insert a focused slide that separates the biggest improvements from the smaller ones.

---
format: codeck.mdeck
version: 1
theme: studio
codex:
  sandbox: read-only
  model: "gpt-5.5"
  reasoning: medium
---

# First Slide

Teach the workflow, then run it live.

A deck format you can read in a diff.

Codeck keeps decks as Markdown with YAML front matter. Slides are separated by a simple divider, and the document stays friendly to source control, review, and examples.

Markdown body YAML settings Theme metadata Codex defaults

Five moods for one lesson.

Switch the rendered deck between Studio, Midnight, Chalk, Solar, and Atelier without changing the source Markdown.

Studio

Prompt shape

Ask for observable behavior, name the verification path, then narrow the change.

```swift
let prompt = "Make this change testable"
```

Build lessons that can run in front of the room.

Codeck gives Markdown presentations a native editing loop, gives Codex prompts a stage where the result is part of the slide, and gives rough drafts an assistant that can propose the next useful edit.

Open the project