Llama.ttf: A font which is also an LLM

Original Article ↗ Hacker News Discussion ↗

Core idea and implementation

  • A TrueType font embeds a tiny LLM plus inference engine, using Harfbuzz’s experimental WebAssembly (WASM) shaper.
  • Specific character sequences (e.g., runs of !) are “shaped” into model output at render time; the underlying text data stays unchanged.
  • This does not use classic TrueType hinting bytecode but a separate WASM shaper path in Harfbuzz.
  • The demo model is ~15M parameters (≈60–90 MB font file); a 70B-parameter variant would be ~280–290 GB and is shown only conceptually.

Determinism, UX, and copying text

  • Identical generations across apps come from fixed seeding and temperature 0, making inference deterministic given the same input.
  • Some suggest input-controlled seeds, regeneration symbols, and letting typed letters override suggestions to act like a custom autocomplete.
  • Because only the visual shaping changes, copy/paste returns the original punctuation, not the rendered prose.
  • Users note this feels like a built‑in “DRM”: readable but not trivially copiable; OCR (including OS‑level OCR APIs and tools) is proposed as the workaround.

Security, sandboxing, and complexity

  • Several posters are alarmed that fonts can execute code at all, citing:
    • Long history of font-based exploits and that Windows once parsed TTF in the kernel.
    • Increased attack surface: now a WASM runtime is needed just to render text.
    • Risks of misleading displays (text says one thing, glyphs show another) for phishing and content scanning.
  • Others argue:
    • WASM is strongly sandboxed, with limited APIs, and comparable in risk to web JS/WASM.
    • Harfbuzz’s WASM shaper is experimental and not enabled in mainstream browsers.
    • WASM is preferable to ad‑hoc VMs (TrueType, Graphite2) that already exist in font stacks.
  • Concerns remain about DoS, side channels, quotas, and the general “compute-mad” trend of putting Turing-complete layers everywhere.

Typographic and broader implications

  • Complex scripts (e.g., Urdu with tens of thousands of ligatures) are cited as justification for powerful shaping logic.
  • Some find the project “terrifying” yet “awesome”; others see it as a proof‑of‑concept hack rather than something that should become common.
  • Ideas raised include animated or game fonts, Doom-in-a-font, text-adventure interpreters, and model‑per‑font “personalities” for richer UIs.