Environment variables

The following environment variables control runtime behaviour without requiring code changes.

Download and cache

Variable	Description
LTP_PATH	Directory used to store downloaded LanguageTool packages. Default: ~/.cache/language_tool_python/.
LTP_JAR_DIR_PATH	Path to an existing local LanguageTool installation directory. When set, the automatic download is skipped entirely.
LTP_DOWNLOAD_HOST_SNAPSHOT	Override the snapshot download host. Default: https://internal1.languagetool.org/snapshots/.
LTP_DOWNLOAD_HOST_NEW_RELEASES	Override the release download host for LanguageTool ≥ 6.7. Default: https://github.com/jxmorris12/language_tool_python/releases/download/LanguageTool-{version}/.
LTP_DOWNLOAD_HOST_RELEASE	Override the release download host for LanguageTool 6.0–6.6. Default: https://languagetool.org/download/.
LTP_DOWNLOAD_HOST_ARCHIVE	Override the archive download host for LanguageTool 4.0–5.9. Default: https://languagetool.org/download/archive/.
LTP_MAX_DOWNLOAD_BYTES	Maximum ZIP download size in bytes. Default: 536870912 (512 MiB).

Integrity verification

Downloaded ZIPs are verified with SHA-256 when a checksum is available. Checksums are resolved in this order:

1. LTP_DOWNLOAD_SHA256_<VERSION> - version-specific checksum. Non-alphanumeric characters in the version string are replaced with _ and uppercased (e.g. LTP_DOWNLOAD_SHA256_6_8 for version 6.8).

2. LTP_DOWNLOAD_SHA256 - fallback checksum applied to any version.

3. The bundled language_tool_python/_ressources/integrity.toml manifest, which covers release and archive downloads. Snapshots are not included.

If none of the above resolves to a checksum, the download proceeds without verification.

Variable	Description
LTP_DOWNLOAD_SHA256_<VERSION>	Expected SHA-256 for a specific LanguageTool version (e.g. LTP_DOWNLOAD_SHA256_6_8=<hash>).
LTP_DOWNLOAD_SHA256	Fallback SHA-256 for any downloaded archive.
LTP_BYPASS_VERIFIED_DOWNLOADS	Set to true to skip SHA-256 verification entirely.

Safe ZIP extraction limits

Variable	Description
LTP_SAFE_ZIP_MAX_ARCHIVE_BYTES	Maximum total compressed size in bytes. Default: 536870912 (512 MiB).
LTP_SAFE_ZIP_MAX_EXTRACTED_BYTES	Maximum total extracted size in bytes. Default: 805306368 (768 MiB).
LTP_SAFE_ZIP_MAX_MEMBERS	Maximum number of members in the ZIP archive. Default: 5000.
LTP_SAFE_ZIP_MAX_MEMBER_EXTRACTED_BYTES	Maximum extracted size for a single member in bytes. Default: 134217728 (128 MiB).
LTP_SAFE_ZIP_MAX_MEMBER_COMPRESSION_RATIO	Maximum compression ratio for a single member. Default: 100.0.
LTP_SAFE_ZIP_MAX_TOTAL_COMPRESSION_RATIO	Maximum compression ratio for the whole archive. Default: 10.0.

Example

# Use a custom cache directory
export LTP_PATH=/path/to/cache

# Skip download and use an existing installation
export LTP_JAR_DIR_PATH=/path/to/LanguageTool-6.8

# Verify a specific release
export LTP_DOWNLOAD_SHA256_6_8=<sha256>

# Or bypass verification entirely (not recommended)
export LTP_BYPASS_VERIFIED_DOWNLOADS=true