aether-models/aether-kit-gpt2

GPT-2 124M for Aether Kit

A macOS Core AI conversion of openai-community/gpt2, using upstream revision 607a30d783dfa663caf39e06633721c8d4cfcd7e. Built with the GPT-2 port spike for Aether Kit v0.0.6, source commit 20bbc96.

Bundle

mac/ is an Aether language bundle: language-model.json, model.aimodel/, tokenizer/, and export-report.json. It requires Apple silicon and macOS 27 with Core AI. There is no qualified iOS bundle in this repository.

The model uses fp16 weights and KV caches, float32 scaled dot-product attention, and the bucketed cache contract. The maximum context is 1,024 tokens, including prompt and generated tokens; the exported prefill bound is 64 tokens.

GPT-2 is a base completion model without a chat template. Use plain text/token prompts with AetherLanguageCoreAI.LanguageGenerationSession; the chat facade reports unsupportedTemplate. This conversion adds no instruction tuning.

import AetherLanguageCoreAI
import AetherLanguageTokenizers

let tokenizer = try await LanguageTokenizer.open(bundle: bundle)
let session = try await LanguageGenerationSession.open(bundle: bundle, platform: .macos)
let result = try await session.generate(
    prompt: tokenizer.encode("The future of artificial intelligence is"),
    maximumTokens: 64)
print(tokenizer.decode(result.tokens))
await session.unload()

Download mac/ at an immutable Hub commit and pass that local directory as bundle. A pinned Aether catalog entry is maintained in Spikes/gpt2/catalog-macos.json. The bundle's model SHA-256 is f04fefaa3a7e69f3e4da783ce1ac5aef7f80e0bc70e441db452ec691e7429316.

Qualification and limits

Evidence is included under verification/; commands and architecture notes are in Spikes/gpt2. The converter used Torch 2.11.0, Transformers 4.57.3 and coreai-torch 0.4.2. Tests ran on macOS build 26B123, Core AI device architecture h17c.

• The float32 eager port matches all 64 reference argmax rows on both a six-token prompt and a 600-token prompt, under both running and bucketed cache contracts.
• The full converted checkpoint passes its Core AI CPU logits/cache self-check.
• Both registered-bundle native GPU cases pass Aether's fp16 numerical policy: per-row cosine >= 0.995; differing choices require a reference probability margin below 0.1 and a native choice within the reference top five. Prefill widths 7 and 16 produce identical native continuations.
• The 600-token prompt matches the full 64-token upstream greedy continuation. The short prompt has one near-tie among 64 teacher-forced rows and first diverges in free generation at token index 40: native rank 2, reference probability margin approximately 0.00139. This conversion does not promise bit-exact float32 output.

This is an experimental v0.0.6 spike asset. Qualification covers these synthetic prompts on one Mac, not general task quality, every Apple device, or iOS. GPT-2 retains the capabilities and limitations described in its upstream model card.

License and provenance

The original GPT-2 assets retain the Modified MIT terms in LICENSE, Copyright (c) 2019 OpenAI. NOTICE identifies conversion and architecture sources. The Aether Kit conversion tooling is Apache-2.0. This repository distributes a Core AI conversion and tokenizer assets; it is not an OpenAI-hosted model service.