MdChat

Native macOS Markdown previewer and vim-keyed editor, with a Gemini chat panel
that answers questions about whatever part of the document you pick — and can
rewrite it in place, behind a diff you approve.

Requirements

• macOS 13 or newer
• Xcode command line tools, Swift 5.9+ — xcode-select --install if swift --version comes back empty
• An API key for at least one provider: Gemini or Meta Model API (Muse Spark)

No Xcode project and no SwiftPM dependencies. The only third-party code is
vendored JavaScript: markdown-it, Mermaid, and CodeMirror 5 with its vim keymap.

Setup

git clone <your-remote> MdChat
cd MdChat
chmod +x fetch-deps.sh build.sh
./fetch-deps.sh          # downloads the pinned JS into Resources/vendor
./build.sh               # -> MdChat.app
open MdChat.app

fetch-deps.sh needs network access and only has to run once — but it is
required, because vendor/ is gitignored and the app renders nothing without
it. build.sh takes debug or release (default release) and ad-hoc signs
the bundle so Keychain and network access behave.

The app icon comes from Icon/AppIcon.icns, which build.sh copies into the
bundle. To change the artwork, replace Icon/icon-1024.png and run
./make-icon.sh (which uses sips and iconutil).

Move MdChat.app wherever you like, or leave it in the tree. Rebuilding
replaces it, so keep it where build.sh puts it if you plan to iterate.

Providers and API keys

Two backends, one conversation. Press ⌘,, pick the provider tab, paste its
key, set a model ID, Save. The checkbox in that sheet is what makes a
provider active — saving a key doesn't switch to it, so you can keep both
configured and flip between them from the toolbar menu or the Chat menu.

	Gemini	Muse Spark
Key from	https://aistudio.google.com/apikey	Meta Model API (MODEL_API_KEY)
Endpoint	streamGenerateContent?alt=sse	https://api.meta.ai/v1/chat/completions
Auth header	x-goog-api-key	Authorization: Bearer
Default model	gemini-3.8-flash	muse-spark-1.3-contributor

Keys go into your login Keychain under service MdChat, one account per
provider — never a file in the project or a plist. Nothing in the repo will ever
contain one. To check or remove them outside the app:

security find-generic-password -s MdChat -a gemini -w