ewan's projects — docs
← all docs

Platinum

November 2, 2026 5 min read
macos9retrocatprotoblueskydesktop

Platinum is a Bluesky client for Classic Mac OS 9. It is the Mac OS 9 member of the same family as Cobalt on the Wii U and Indigo on the 3DS, built on Wolfram for the AT Protocol work. It is not a browser pointed at a web app: it is a C89 application named after the Platinum appearance, intended to look like it belongs in a System Folder.

There is no packaged release of the Mac application yet. Releases are paused until Platinum has been run on Mac OS 9 itself.

How it fits together

Mac OS 9 has no modern TLS, OAuth or DID resolution, so Platinum currently has two parts:

Today:   Classic Mac OS 9  --HTTP + JSON-->  Platinum Bridge  --AT Protocol-->  PDS / AppView
Target:  Classic Mac OS 9  --HTTPS + XRPC------------------------------->  PDS / AppView
  • The bridge is a small Node.js service that does OAuth pairing, issues and revokes tokens, and serves a profile, timeline, notifications and posting. It can update itself from this repository's releases when asked.
  • The native client is the Mac application. It is being migrated off the bridge a route at a time, using Wolfram's Open Transport and macTLS transport directly.

The first native modules (URLs, identity and session parsing) live in macos9/atproto_*.c and are host-tested. docs/architecture/native-client-migration.md maps every route to its native replacement and records what is not done.

Status

Early, and stated plainly:

  • The bridge works. It does OAuth pairing, issues and revokes tokens, and serves a profile, a timeline, notifications and posting. App-password sign-in exists but is off unless enabled.
  • The native bridge is being built. native/ is a C bridge on Wolfram meant to replace the Node service, and every route family is implemented. Its CI job builds Wolfram from a pinned commit and runs the C tests and Wolfram-backed routes against a mock PDS; it has not run against a live PDS or on a Mac.
  • The Mac client is written but unproven. It has a window, menus, a timeline, threads, profiles, people lists, search, notifications, compose (with replies, quotes and reply limits), and preferences. CI compiles every source as strict C89 against declaration-only Mac SDK stubs and runs the pairing and JSON tests; that checks dialect and types, not a CodeWarrior build or a run on real hardware.
  • Much is missing. The timeline, notifications, likes and reposts now use the native session; replies, quotes, profile actions, search, conversations and compose still use the bridge. Images and native post publishing are unfinished. docs/PARITY.md lists every gap against Cobalt and Indigo, and CI checks the table against the code.

Recent native work includes opening threads through the Mac's own session first, flattening app.bsky.feed.getPostThread in C, filtering the native timeline with the account's muted words, and a native app-password sign-in window with shared keyboard rules. The bridge path remains for anything not yet migrated.

Installing

There is no packaged Mac application yet. The bridge can be run from this repository or from a release archive.

Requirements for the bridge: Node.js 22 or newer, and a public HTTPS address if you want OAuth outside your own machine. The bridge's update manifest, its parsing, SHA-256 and signature verification, and the OAuth pairing parsers are Wolfram's own C, loaded through Wolfram's Node addon at the commit pinned in ci.yml.

The Mac client targets CodeWarrior-era tools, Wolfram 0.26.0 or newer for the transport, and macTLS.

Using the bridge

cd bridge
cp .env.example .env
npm install
npm run build
npm start

It listens on 127.0.0.1:8787. For OAuth, set PLATINUM_BRIDGE_PUBLIC_URL to the externally reachable HTTPS address; the client metadata and callback are derived from it. Do not put the bridge on an untrusted network without HTTPS and access control.

Pairing is done in a browser, once:

  1. Open /login?handle=you.example.com on the bridge.
  2. Complete the OAuth flow.
  3. The bridge shows a six-character code, good for ten minutes and one use.
  4. Type it into Platinum. The Mac stores a bridge token, your DID and an installation ID.

OAuth refresh credentials never leave the bridge. Tokens are revocable with POST /v1/revoke; treat them as credentials and keep them out of logs and bug reports. App-password sign-in is possible if PLATINUM_BRIDGE_ALLOW_APP_PASSWORD=1 is set, but over plain HTTP the password crosses the network in the clear. The Mac client exposes this path through its dedicated sign-in window.

The wire protocol is in docs/BRIDGE_PROTOCOL.md; the window and menu design is in docs/UI_DESIGN.md.

Building

Bridge:

cd bridge
npm run check
# The tests need Wolfram's Node addon; build it from a Wolfram checkout
# (the commit pinned in .github/workflows/ci.yml) into bridge/build/ first.
tools/build-addon.sh ../wolfram
npm test
npm run build

Mac client: build Wolfram's Mac OS 9 transport against macTLS first.

cmake -S . -B build-macos9-transport \
  -DWOLFRAM_BUILD_MACOS9_TRANSPORT=ON \
  -DWOLFRAM_MACTLS_ROOT=/path/to/macTLS
cmake --build build-macos9-transport --target wolfram-macos9-transport

Then build the application with Retro68, a GCC-based cross-compiler for Classic Mac OS (68k and PowerPC):

docker run --rm -v "$PWD":/root -v /path/to/wolfram:/root/wolfram \
  ghcr.io/autc04/retro68 tools/build-macos9.sh [68k|ppc|both]

That produces a MacBinary application file in build-macos9-*/Platinum.bin, with the compiled resource fork carried inside it. Take the .bin copy to a Mac OS 9 volume — real hardware or an emulator such as BasiliskII, SheepShaver or Mini vMac — and double-click.

The CI build links a test transport stub because the Wolfram transport needs Open Transport and macTLS. A real build links the transport libraries with -DPLATINUM_LINK_TRANSPORT_STUB=OFF -DPLATINUM_TRANSPORT_LIBS=...; a stub binary cannot reach the bridge and must not be distributed.

Testing

The Mac target has four validation layers, described in docs/TESTING_MACOS9.md: the C89 source sweep, host UI logic tests for layout and interaction, the Retro68 68k and PowerPC builds, and a QEMU harness that boots a Mac OS 9 guest headlessly for screenshots and synthetic input. Only the first three run on public CI; the runtime layer needs an owner-supplied Mac OS 9 installation that is never committed.

Licence

AGPL-3.0 — see LICENSE.

← all docs