@hy-sde-org/dsh-zstd-frame

Zstandard frame primitives shared by the DeepSeek Harness session persistence backend (session.jsonl.zstd) and the project memory bank (bank.jsonl.zstd). Both store append-only, checksummed, per-batch zstd frames; this package owns the structural scan, the one-shot compress / decompress API with checksum, torn-frame recovery, and the interchangeable multi-frame decoders, so consumers never reimplement frame layout or Node-private decoder lifecycle.

Published standalone as @hy-sde-org/dsh-zstd-frame; it mirrors @deepseek-ai/dsh-zstd-frame in the hy-sde deepseek-harness fork.

Backed entirely by node:zlib — no native module, works in-process.

API

import {
  compressZstdFrame,
  decompressZstdFrame,
  decompressZstdFrameSync,
  decompressZstdPrefix,
  scanZstdFrames,
  createZstdFrameDecoder,
} from '@hy-sde-org/dsh-zstd-frame'

• scanZstdFrames(buffer, maxFrames?) → { frames: ZstdFrameRange[], tornStart? } — locate complete frames without decompressing their blocks; EOF inside the final frame returns its start for repair.
• compressZstdFrame(input) — one independently decodable, checksummed frame.
• decompressZstdFrame(input, maxOutput?) / decompressZstdFrameSync(...) — one-frame decompression with optional plaintext bound.
• decompressZstdPrefix(input) — recover available plaintext from a structurally incomplete final frame.
• createZstdFrameDecoder() — NodePrivateZstdFrameDecoder when the running Node shape is compatible, else PublicZstdFrameDecoder; both implement the common ZstdFrameDecoder interface (decode(source, frames) generator + close()).

Known Limitations and Deferred Work

• The private-handle decoder (NodePrivateZstdFrameDecoder) depends on the private zlib._handle.writeSync shape, which the public Node API does not document; the decoder feature-probes at load and falls back to the one-shot-based PublicZstdFrameDecoder when the shape is incompatible, so correctness never depends on private internals.
• No streaming incremental compressor; frames are written whole per batch.
• Only checksummed frames are produced by compressZstdFrame (ZSTD_c_checksumFlag), and decompressZstdPrefix deliberately suppresses final-frame/checksum completion — callers must establish the torn boundary themselves before using it.

License

MIT. Derived from the DeepSeek Harness codebase; see THIRD-PARTY-NOTICES.md for provenance.