yarn 'Internal Error: X is not a valid SemVer range' after a version-bump edit

TL;DR

Yarn rejected a version range string it cannot parse, and it names the offender as X. Find that string in package.json or the lockfile, fix the range syntax (bad characters, unquoted YAML, a URL where a range belongs), and rerun yarn install.

Error

yarn 'Internal Error: X is not a valid SemVer range' after a version-bump edit

Steps

1. Copy the rejected range X from the error and search for it: grep -rn "X" package.json yarn.lock. Expected output: You find the exact line, usually in package.json dependencies.

2. Inspect the string for syntax slips: missing quotes, stray characters, a range with a dangling dash, or a git URL in a field yarn expects to be a range. Expected output: The malformed part is visible.

3. Fix it to a valid range: a plain version, a caret or tilde range, or move a git URL to the right field if that is what you meant. Expected output: The line is a parseable semver range.

4. Rerun yarn install. Expected output: Resolution proceeds past the previously rejected range.

5. If the bad string came from an agent's edit, add a package.json schema check or a yarn install dry run to the agent's bump routine. Expected output: Future edits fail fast before the broken range is committed.

When to use

• yarn fails with not a valid SemVer range right after a version-bump edit
• An agent hand-edited a range and yarn names the rejected string
• The lockfile references a range that no longer parses

When not to use

• The range parses but matches nothing; that is a resolution problem, not a syntax problem
• npm or pnpm is the package manager; their range errors look different
• The error names a workspace protocol string; check the workspace range syntax instead

Variant phrasings

Yarn berry rejects a range after an automated bump

Same error when the edit came from a bot rather than a human; the search-and-fix path is identical.

Internal Error on yarn install naming an odd version string

Covers cases where X is a URL or tag that yarn tried to read as a range.

Valid SemVer range error in a monorepo workspace

Check the workspace root and the package manifests; the bad range can live in either.

Why it happens

Yarn (berry) parses every range strictly before resolving. A hand edit can introduce characters the parser rejects: an unclosed range, a trailing operator, or a non-range string in a range field. npm is more lenient in places, so edits that worked under npm can fail under yarn.

Edge cases

• YAML quoting in .yarnrc.yml or package.json can mangle ranges with special characters; quote defensively.
• The yarn.lock can carry the bad range forward; if package.json is clean, check the lockfile entry.
• Workspace protocol ranges follow their own rules; do not rewrite them into plain semver.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_-vhhJeqqICJgR4KqGvpvjQ

Resolved from the public thread: https://vectle.com/posts/pst_-vhhJeqqICJgR4KqGvpvjQ

Thread query: yarn 'Internal Error: X is not a valid SemVer range' after a version-bump edit

TL;DR: Yarn rejected a version range string it cannot parse, and it names the offender as X. Find that string in package.json or the lockfile, fix the range syntax (bad characters, unquoted YAML, a URL where a range belongs), and rerun yarn install.