Forthsky

AT Protocol / Bluesky client in gforth. The interpreter is the UI.

forthsky 0.1 — AT Protocol client in gforth
Former Lab. GPL v3. Type `help` for words, `login` to begin.

ok login
handle: formerlab.bsky.social
app password: ****
✓ session established for @formerlab.bsky.social

ok 5 timeline

[1] @nintendolife.com  2026-05-15T10:25:01+01:00
    Tomodachi Life: Living The Dream Updated To Version 1.0.2,
    Here Are The Full Patch Notes. (Repost)
    ♥ 0  ↻ 0

[2] @patak.cat  2026-05-15T09:24:49.365Z
    oh, thanks! I reposted it in english. I have no idea why the
    mobile app defaulted to german
    ♥ 0  ↻ 0
...

ok 1 like
✓ liked.

ok s" hello from Forth and Forthsky" post
✓ posted.
  at://did:plc:.../app.bsky.feed.post/3mluvf...

ok bye

There is no main loop. There are no menus. Words compose. Lists on screen are addressable by index. 1 like likes the first thing you just rendered — like Forth always works, the previous thing becomes input to the next thing.

Design

┌────────────────┐  plain HTTP/1.0   ┌──────────────────┐  HTTPS   ┌──────────────┐
│ gforth bsky.fs │ ─────────────────▶│ forthsky-bridge  │ ───────▶ │  PDS         │
│  (Forthsky)    │                   │ (socat+OpenSSL)  │          │  bsky.social │
└────────────────┘  127.0.0.1:8443   └──────────────────┘  :443    └──────────────┘

Forth handles the application protocol. A short socat sidecar terminates TLS and forwards bytes to the PDS. Honest about what it is — no embedded crypto stack yet, just a clean line between protocol logic (Forth) and ciphers (OpenSSL via socat).

Status

v0.1 Posts to the live network. Read and write paths verified against bsky.social.

Implemented: login, whoami, logout, N timeline, s" text" post, N like, N repost, real ISO-8601 timestamps via date -u.

Coming next:

• N thread — show a post and its replies
• N reply <text> — reply to a feed item
• N profile — author profile of an item
• N follow / N unfollow
• notifications / search
• Better repost/quote-post detection in timeline parse
• Pure-Forth ed25519 + DPoP + full OAuth (replaces app passwords)
• Firehose subscriber + sine-scroller demoscene moment

Running

Tested on Ubuntu 25.10. Should work anywhere gforth and socat run.

# 1. install deps
sudo apt install -y gforth socat libtool libtool-bin libc6-dev build-essential

# 2. clone
git clone https://github.com/FormerLab/forthsky.git
cd forthsky

# 3. make the bridge executable
chmod +x bridge/forthsky-bridge.sh

# 4. start the TLS bridge in one terminal
./bridge/forthsky-bridge.sh

# 5. start forthsky in another
LC_ALL=en_US.UTF-8 gforth bsky.fs

The LC_ALL matters: gforth 0.7.3 needs a UTF-8 locale active for xc@+ to decode codepoints correctly.

For credentials, use a Bluesky app password (Settings → App Passwords), not your main account password.

Vocabulary

session:    login    whoami    logout
reading:    N timeline   (planned: N thread, N profile)
writing:    s" text" post     N like     N repost
            (planned: N reply <text>)
misc:       help    bye

N is the 1-based index from the last rendered list.

Notes for hackers

gforth 0.7.3 quirks worth knowing if you want to extend Forthsky:

• xc@+ ( addr -- addr' xc ) — single address in, manage byte counts with xc-size.
• require utf-8.fs + set-encoding-utf-8 is mandatory for codepoint mode.
• +to doesn't exist; use dup to or plain variables with +!.
• \ starts a line comment; for a backslash byte literal use 92 (its ASCII).
• Names are case-insensitive — don't define FOO constant and foo variable.
• [char] X foo not foo [char] X — literal-then-word, as for any Forth word.
• cmove ( src dst u -- ), easy to flip with the addr u string convention.
• Locals ({ ... -- ... }) save you from stack juggling; use them in any word with more than three live values.
• bsky.social returns chunked HTTP/1.1 by default; Forthsky speaks HTTP/1.0 to avoid implementing chunk decoding.

The hardest parts (display width + word wrap, JSON SAX, JSON-path matching, the field-extraction routing in xrpc.fs) are done and verified against the live network. New verbs are short additions to xrpc.fs.

License

GPL v3.

Former Lab

Forthsky is one of an esoteric/retro AT Protocol client series from Former Lab — building sovereign computing infrastructure. Other clients in the series:

• Fortransky — Fortran 2018, dithering and DM support
• Cobolsky — GnuCOBOL 3.1, Floyd-Steinberg in pure COBOL (COMING SOON)
• Assemblersky500 — 68000 assembly, Linux m68k + AmigaOS dual target (COMING SOON)
• INTERCALsky — yes, really
• Malbolgesky — yes, really
• Adatalksky - Ada and Smalltalk

The series is proof-of-work for a broader thesis: anything that touches the network should be expressible in any sufficient language, on any sufficient machine, including the deliberately inadequate ones.