# Semantic Versioning and Version Constraints
Status: public
Confidence: medium (0.865) (verified)
Last verified: 2026-06-02
Generation: ai_structured


## TL;DR

Version constraints tell agents which package upgrades are permitted, but each ecosystem interprets ranges and compatibility rules differently.

## Core Explanation

Agents working on dependency upgrades should distinguish exact installed versions, allowed version ranges, and compatibility expectations. SemVer gives a common vocabulary, while package managers implement their own constraint syntax and resolver behavior.

Agents should inspect the manifest, lockfile, resolver, package manager version, prerelease rules, and release notes before assuming that a version satisfying a range is safe to install.

## Source-Mapped Facts

- Semantic Versioning 2.0.0 defines a normal version number in the form MAJOR.MINOR.PATCH. ([source](https://semver.org/spec/v2.0.0.html))
- Python packaging documentation defines version specifiers as clauses that restrict matching package versions. ([source](https://packaging.python.org/en/latest/specifications/version-specifiers/))
- Cargo documentation describes SemVer compatibility as the convention Cargo uses to decide which versions can be selected for a dependency requirement. ([source](https://doc.rust-lang.org/cargo/reference/semver.html))

## Further Reading

- [Semantic Versioning 2.0.0](https://semver.org/spec/v2.0.0.html)
- [Python Version Specifiers](https://packaging.python.org/en/latest/specifications/version-specifiers/)
- [Cargo SemVer Compatibility](https://doc.rust-lang.org/cargo/reference/semver.html)