v1.4.0

Added

• New max_decompressed_size keyword on AsyncGzipBinaryFile and AsyncGzipTextFile: when set, reads abort with OSError once the cumulative decompressed output exceeds the cap. Intended as a decompression-bomb guard for untrusted input.
• New strict_size keyword on AsyncGzipBinaryFile and AsyncGzipTextFile: when true, writes that would push the uncompressed member size past the gzip ISIZE field's 4 GiB limit raise OSError instead of producing a trailer with a silently-truncated size. Default remains false so spec-compliant wrapping (matching gzip.open()) is preserved.

Fixed

• Detect truncated gzip streams. A member that ended before the decompressor consumed its trailer previously caused read() and seek(0, SEEK_END) to silently return the partial bytes already emitted. Both paths now raise gzip.BadGzipFile. Behavior change: callers that were (often unknowingly) relying on silent truncation will now see an exception — this is a data-integrity fix.
• Keep write accounting consistent after a failed underlying write(). _crc, _input_size, and _position now update only after the compressed bytes are durably handed to the file object, and the CRC accumulator is explicitly masked to 32 bits. A mid-write OSError marks the stream broken so follow-up writes refuse rather than silently producing a torn gzip member, and close() skips emitting a trailer that would lie about bytes never written.
• _cleanup_failed_enter now nulls _file in a finally block, so a raising close during setup-failure cleanup no longer leaves a reachable handle on the instance.
• Add an upper bound (128 MiB) to _validate_chunk_size and to AsyncGzipBinaryFile.peek(size=…), so a caller passing an unsanitized integer cannot accidentally allocate gigabytes of buffer.

Performance

• Offload zlib compress/decompress calls to the default executor when the input is ≥ 256 KiB. zlib releases the GIL internally, so multiple gzip streams on the same event loop now run their CPU work in parallel. The repo's concurrent-I/O benchmark improves ~4x; single-stream latency is unchanged within noise.

Documentation

• README now describes append-mode multi-member semantics, backward-seek cost, the 4 GiB ISIZE caveat (and strict_size), and max_decompressed_size as a decompression-bomb guard.

Tooling

• Add a scripts/check_py38_compat.py pre-commit hook that rejects PEP 585 generic subscripts (tuple[...], list[...], PathLike[...], ...) and PEP 604 union operators in src/. mypy ≥ 1.15 no longer accepts python_version = "3.8", so this grep-based check guards the library's declared Python 3.8+ support.
• /release-prep skill now refuses to run when the current branch has commits ahead of origin/main that are not yet merged, preventing silent exclusion of feature work from the release.