Fix Claude Code Plugin Install EJSONPARSE Error from Corrupted Cache File

What this error means

EJSONPARSE: Unexpected non-whitespace character after JSON at position (Claude Code plugin cache) is a Claude Code failure pattern reported for developers trying to fix ejsonparse error when installing or updating claude code plugins. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

File write bug: package.json cache file not truncated before write, causing JSON parse errors. Users must manually delete the file to recover. Affects all plugin install/update operations.

Common causes

• Claude Code plugin install/update writes ~/.claude/plugins/npm-cache/package.json without truncating, leaving trailing bytes from previous content. Subsequent operations fail with EJSONPARSE, locking users out of plugin management.
• File write bug: package.json cache file not truncated before write, causing JSON parse errors. Users must manually delete the file to recover. Affects all plugin install/update operations.

Quick fixes

1. Confirm the exact error signature matches EJSONPARSE: Unexpected non-whitespace character after JSON at position (Claude Code plugin cache).
2. Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/anthropics/claude-code/issues/58935

Evidence note: File write bug: package.json cache file not truncated before write, causing JSON parse errors. Users must manually delete the file to recover. Affects all plugin install/update operations.

Related errors

• Claude Code plugin install fails
• npm cache corruption Claude Code

FAQ

What should I check first?

Start with the exact EJSONPARSE: Unexpected non-whitespace character after JSON at position (Claude Code plugin cache) text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Claude Code workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without EJSONPARSE: Unexpected non-whitespace character after JSON at position (Claude Code plugin cache).