Fortransky#

Yes, that Fortran.

A terminal-only Bluesky / AT Protocol client written in Fortran. Posts, timelines, notifications, dithered image posting, DMs, and terminal image rendering — all from an amber terminal (if you run it in cool-retro-term), all the way down to the protocol

Project blog: https://www.patreon.com/posts/153457794

Architecture#

Fortran TUI  (src/)
  └─ C libcurl bridge  (cshim/)
  └─ Fortran iso_c_binding module  (src/atproto/firehose_bridge.f90)
       └─ Rust staticlib  (bridge/firehose-bridge/)
            envelope → CAR → DAG-CBOR → NormalizedEvent → JSONL

relay-raw stream path:
  relay_raw_tail.py
    └─ assemblersky_cli  (bridge/assemblersky/bin/)  ← x86-64 assembly decoder
    └─ firehose_bridge_cli  (bridge/firehose-bridge/target/release/)  ← Rust fallback
    └─ Python cbor2  ← live stream decode (CBORTag/CIDv1 aware)

image post path  (d <imagepath>):
  dither_prep.py    image → greyscale flat pixel file
  dither.f90        Floyd-Steinberg error diffusion in Fortran
  pixels_to_png.py  pixel file → PNG
  uploadBlob        PNG → AT Protocol blob
  createRecord      post with app.bsky.embed.images

image view path  (v on a post with image):
  CDN blob fetch    download fullsize image via http_get_to_file
  dither_prep.py    greyscale + resize to 80×48 for terminal
  dither.f90        Floyd-Steinberg in Fortran
  render            Unicode half-block chars (▀ ▄ █) — 80×48 effective pixels

DM path  (dm <handle>, i):
  getConvoForMembers  resolve or create conversation
  getMessages         fetch message thread
  sendMessage         send a DM
  All routed via atproto-proxy header to did:web:api.bsky.chat
  PDS host resolved automatically from plc.directory on login

Session state is saved to ~/.fortransky/session.json. Use an app password with DM access enabled, not your main Bluesky password.

Build dependencies#

System packages (Ubuntu/Debian)#

sudo apt install -y gfortran cmake pkg-config libcurl4-openssl-dev

System packages (Arch/Garuda)#

sudo pacman -S gcc-fortran cmake pkgconf curl python-pillow python-cbor2 python-websockets

Rust toolchain#

Requires rustc >= 1.78 (Cargo.lock v4). Latest stable recommended. Install via rustup if not present:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Python deps#

Required for relay-raw stream path, image posting, and image viewing:

sudo pip install cbor2 websockets Pillow --break-system-packages

Or with a venv (run Fortransky with the venv active):

python3 -m venv .venv && source .venv/bin/activate
pip install cbor2 websockets Pillow

Assemblersky integrated in Fortransky (relay-raw native decoder)#

Assemblersky decodes raw AT Protocol firehose frames in x86-64 assembly. If present at bridge/assemblersky/bin/assemblersky_cli, it is preferred automatically.

Assemblersky module repo is not public yet, but here is how to do it later when shipped separately:

Build from source: https://github.com/FormerLab/assemblersky

cd /path/to/assemblersky && make
mkdir -p /path/to/fortransky/bridge/assemblersky/bin
cp rust-harness/target/release/assemblersky-harness \
   /path/to/fortransky/bridge/assemblersky/bin/assemblersky_cli

Check detection: ./scripts/check_assemblersky.sh

Build#

chmod and

./scripts/build.sh
./build/fortransky

Login#

Use an app password with DM access enabled. At the home prompt:

l
Identifier: yourhandle.bsky.social
Password/app password: <app password>

Session is saved to ~/.fortransky/session.json and restored on next launch. Your real PDS host is resolved from plc.directory on first login and stored in the session — required for DMs and other PDS-proxied endpoints. To log out: x

TUI commands (only TUI here)#

Home view#

Post list view#

DM thread view#

Stream view#

Image posting#

The d command dithers any image using Bill Atkinson's Floyd-Steinberg algorithm — the same algorithm used in MacPaint in 1984 — and posts it to Bluesky as an image embed.

d /path/to/image.jpg

The image is converted to greyscale, resized to 576×720 (the original MacPaint canvas dimensions), dithered to 1-bit in Fortran, converted to PNG, and posted via com.atproto.repo.uploadBlob + createRecord. Pillow is required.

Image viewing#

The v command on any post with an image fetches the image from the Bluesky CDN, dithers it in Fortran, and renders it inline using Unicode half-block characters (▀ ▄ █).

Each terminal character represents two pixel rows — top half and bottom half — giving 80×48 effective pixels in a standard 80-column terminal. The same Floyd-Steinberg algorithm used for posting is used for display.

DMs#

Fortransky implements chat.bsky.convo.* — the same DM protocol used by the official Bluesky app. Requests are proxied through your PDS to did:web:api.bsky.chat via the atproto-proxy header.

Your app password must have DM access enabled (the "Allow access to your direct messages" toggle in Bluesky's app password settings).

PDS host is resolved automatically from plc.directory on login and stored in the session file — no manual configuration needed.

Stream modes#

jetstream — Bluesky's Jetstream WebSocket service. Lower bandwidth, JSON native, easiest to work with...

relay-raw — raw AT Protocol relay (com.atproto.sync.subscribeRepos). Binary CBOR frames over WebSocket, decoded in Python with cbor2. The native Assemblersky decoder (x86-64 assembly) is used when available for single-frame decode; the Rust firehose_bridge_cli is the fallback.

Native decoder detection order#

1. FORTRANSKY_RELAY_DECODER environment variable
2. FORTRANSKY_ASSEMBLERSKY_DECODER environment variable
3. bridge/assemblersky/bin/assemblersky_cli (bundled Assemblersky)
4. assemblersky_cli on PATH
5. FORTRANSKY_FIREHOSE_DECODER environment variable
6. bridge/firehose-bridge/target/release/firehose_bridge_cli
7. bridge/firehose-bridge/target/debug/firehose_bridge_cli
8. firehose_bridge_cli on PATH

Known issues / notes#

• JSON parser is hand-rolled — not a full schema-driven parser
• relay-raw only surfaces app.bsky.feed.post create ops
• DM thread view shows raw DIDs; handle resolution coming in a future version
• The TUI is line-based (type command + Enter), not raw keypress
• m and j for stream control are home view commands — go b back to home first if you are in the post list

Changelog#

v1.5 — Terminal image viewer via v command. Fetches image from Bluesky CDN, dithers with Floyd-Steinberg in Fortran, renders using Unicode half-block characters (80×48 effective pixels). Deep JSON key extraction added to json_extract_mod for nested embed fields.

v1.4 — DM support via chat.bsky.convo.*. dm <handle> opens or creates a conversation, i lists the inbox, r sends a reply. PDS host auto-resolved from plc.directory on login. atproto-proxy header routing to did:web:api.bsky.chat. App password requires DM access enabled.

v1.3 — Floyd-Steinberg dithering + image post via d <imagepath>. Bill Atkinson's algorithm (MacPaint, 1984) ported to Fortran. uploadBlob + createRecord with image embed. Requires Pillow.

v1.2 — Assemblersky integration. relay_raw_tail.py detects and prefers assemblersky_cli over the Rust bridge. Live relay-raw decode via Python cbor2 (CBOR tag / CIDv1 handling fixed). Decoder detection order documented.

v1.1 — Native Rust firehose decoder integrated. relay_raw_tail.py prefers firehose_bridge_cli when found. CMakeLists wires Rust staticlib into the Fortran link. JWT field lengths bumped to 1024. JSON key scanner depth-tracking fix.

v1.0 — Like, repost, quote-post actions. URL facet emission.

v0.9 — Typed decode layer (decode.f90). Richer post semantics in TUI.

v0.7 — C libcurl bridge replacing shell curl. Saved session support. Stream mode toggle (jetstream / relay-raw).