Explicit dependency constraints

In configuration/requirements files, make compatibility explicit: bound versions to prevent silent breakage across Python/platform build environments, and use environment markers for dependencies that differ by Python version, OS, implementation, or wheel availability.

Do:

• Prefer bounded ranges that preserve compatibility, e.g. package>=x.y,<x.(y+1) or ~=x.y when appropriate.
• Use environment markers when a dependency must vary by python_version, sys_platform, or platform_python_implementation.
• Constrain build-tooling for known breakpoints (e.g., setuptools<82.0.0 when source builds fail with newer setuptools).
• Justify pins (==) only when you must avoid known incompatibilities or missing wheels; otherwise prefer ranges.

Don’t:

• Rely on overly broad constraints that can change behavior between build environments.
• Swap <= to == without a clear motivation (it’s a silent change for users depending on transitive compatibility).

Example pattern:

# Tooling broken beyond a known version for certain builds
setuptools<82.0.0

# Different tooling versions per Python
pre-commit>=3.5.0,<3.8.0; python_version < '3.9'
pre-commit>=3.8.0; python_version >= '3.9'

# Platform/implementation gating for deps without universal wheels/support
pycurl>=7.43.0.5; sys_platform != 'win32' and platform_python_implementation=="CPython"

# Major-version safety constraints for runtime libs
cassandra-driver>=3.24,<4