TL;DR
Users report that the Claude Code command‑line client fails to start after upgrading to version 2.1.0, producing an "Invalid Version: 2.1.0 (2026-01-07)" error. Community troubleshooting has identified the release's date suffix in the version string as the probable cause and several local workarounds have been shared.
What happened
A widely viewed GitHub issue filed on Jan. 7, 2026, documents that installing Claude Code 2.1.0 prevents the CLI from launching on macOS. Start-up logs include an "Invalid Version: 2.1.0 (2026-01-07)" error and a short stack trace; contributors observed that the semver parser fails when the version string contains the trailing date. Multiple users reproduced the failure and reported related symptoms: sessions crashing during debugging, install or reinstall errors such as permission denials, and a warning that another install process was running. Community members proposed and tested temporary remedies: editing or truncating the cached changelog file in ~/.claude/cache/changelog.md, changing its permissions, or removing the dated entry from a cachedChangelog key in a .claude.json file. Some users noted that the native installer was temporarily pointing back to 2.0.76 and a later 2.1.1 report worked for a few people.
Why it matters
- CLI users cannot start Claude Code after the 2.1.0 update, interrupting workflows including debugging.
- The fault appears to come from how the release version is formatted, which can break downstream tooling that expects strict semver.
- Affected users must apply manual workarounds or revert to earlier installers, adding operational overhead and risk.
- The issue produced a high volume of reports and reactions, indicating broad user impact for this repository.
Key facts
- Issue opened on GitHub for anthropics/claude-code on 2026-01-07 (issue #16673).
- Error visible on startup: "Invalid Version: 2.1.0 (2026-01-07)" with a short stack trace.
- Community diagnosis: the semver parser rejects the date suffix in the version string; suggestion to coerce or strip the date.
- Workarounds shared include editing ~/.claude/cache/changelog.md to remove the date, making that file read-only, or modifying cachedChangelog in .claude.json.
- Some users reported reinstall or permission errors (e.g., "zsh: permission denied: claude") when attempting to remove or reinstall the CLI.
- Several commenters said the native installer was reverted to 2.0.76 for them; at least one user reported 2.1.1 worked locally.
- The repository is actively used (repository metadata shows thousands of forks and tens of thousands of stars).
- GitHub's actions bot identified possible duplicate issues and slated automatic duplicate closure behavior.
What to watch next
- Whether maintainers publish an official patch or guidance addressing version-string parsing (not confirmed in the source).
- Community reports confirming that 2.1.1 or another subsequent release reliably fixes the startup error (not confirmed in the source).
- Persistence of the temporary rollback to 2.0.76 via the native installer for affected users.
Quick glossary
- CLI: Command-line interface: a text-based way to interact with software using typed commands.
- semver: Semantic Versioning: a convention for version numbers (major.minor.patch) that many tools parse to determine compatibility.
- changelog: A file or document that lists notable changes, fixes, and updates between software versions.
- chmod: A Unix command to change file permissions, often used to make files read-only or executable.
Reader FAQ
Is Claude Code 2.1.0 confirmed to be broken?
Multiple users reported the CLI fails to start after upgrading to 2.1.0 and filed a GitHub issue documenting the problem.
Is there a workaround I can try now?
Users shared temporary fixes such as removing the dated header from ~/.claude/cache/changelog.md, making that file read-only, or editing cachedChangelog in .claude.json.
Has the project released a fix?
Not confirmed in the source.
Will reinstalling solve the issue?
Some users reported installer rollbacks to 2.0.76 or that 2.1.1 worked for them, but reinstall attempts also produced permission and "another process" errors for others.
anthropics / claude-code Public Notifications Fork 3.8k Star 52.9k Code Issues 5k+ Pull requests 97 Actions Security 13 [BUG] Invalid Version: 2.1.0 (2026-01-07) #16673 New issue Closed as duplicate of #16682…
Sources
- Claude Code CLI was broken
- [BUG] Claude Code 2.1.0 crashes on startup
- [BUG] Claude Code CLI: Severe Connection Errors (65 …
Related posts
- Go.sum is not a lockfile — stop parsing it to analyze dependency graphs
- Lean 4 proof argues SSOT needs definition-time hooks and introspection
- Go authors: stop treating go.sum as a lockfile — use go.mod instead