[BUG] Startup failure due to malformed telemetry files in ~/.claude/telemetry/

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code fails to start when telemetry files accumulate in ~/.claude/telemetry/.
Files named 1p_failed_events.*.json contain JSON Lines format (multiple JSON objects
per file) but have .json extension, causing a JSON parse error on startup.

What Should Happen?

Claude Code should start successfully even when telemetry files are present.
Either the files should use .jsonl extension, or the startup process should
handle malformed telemetry files gracefully instead of crashing.

Error Messages/Logs

Steps to Reproduce

1. Use Claude Code normally for a period of time
2. Work in a corporate proxy environment (telemetry transmission fails and events accumulate in ~/.claude/telemetry/)
3. Exit Claude Code
4. Try to restart Claude Code
5. Application fails to start with authentication error (401)

Workaround

rm -rf ~/.claude/telemetry

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.69

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

generated report by Claude Code CLI

Claude Code Bug Report: Startup Failure due to Malformed Telemetry Files

Summary

Claude Code fails to start when telemetry files in ~/.claude/telemetry/ are present. These files are in JSON Lines format (.jsonl) but have .json file extensions, causing JSON parsing errors during startup.

Environment

• OS: Windows 11
• Shell: Git Bash (MINGW64_NT-10.0-22631)
• Claude Code Version: 2.1.69 (based on telemetry data)
• Node Version: v24.3.0

Steps to Reproduce

1. Use Claude Code normally for a period of time (telemetry files accumulate)
2. Exit Claude Code
3. Try to restart Claude Code
4. Application fails to start

Root Cause

Files in ~/.claude/telemetry/ directory with pattern 1p_failed_events.*.json contain multiple JSON objects (JSON Lines format) but have .json extension. Example:

~/.claude/telemetry/1p_failed_events.01635425-b1f2-4a29-9277-fead101ee290.0ca514d6-5422-4d3b-9492-fd119d5910b9.json

File contents (multiple JSON objects on separate lines):

{"event_type":"ClaudeCodeInternalEvent","event_data":{...}}
{"event_type":"ClaudeCodeInternalEvent","event_data":{...}}
{"event_type":"ClaudeCodeInternalEvent","event_data":{...}}

When parsed as standard JSON (based on .json extension), this causes:

Error: Extra data: line 2 column 1 (char 1353)

Affected Files

27 telemetry files were found with this issue in my installation:

• 1p_failed_events.01635425-b1f2-4a29-9277-fead101ee290.0ca514d6-5422-4d3b-9492-fd119d5910b9.json
• 1p_failed_events.04cb5e6b-c2b6-4441-a0cd-d8f72cdd84c3.690caded-5b0b-4bf2-925a-002e9feeb2ac.json
• (... and 25 more files with similar naming pattern)

Workaround

Delete or move the ~/.claude/telemetry/ directory:

rm -rf ~/.claude/telemetry
# or
mv ~/.claude ~/.claude-backup

Claude Code will start successfully after removing these files.

Suggested Fixes

Option 1: Use correct file extension

Rename files to .jsonl to properly indicate JSON Lines format:

1p_failed_events.*.jsonl

Option 2: Write valid JSON

If .json extension is required, wrap multiple events in a JSON array:

[
  {"event_type":"ClaudeCodeInternalEvent","event_data":{...}},
  {"event_type":"ClaudeCodeInternalEvent","event_data":{...}}
]

Option 3: Skip malformed files

Add error handling during startup to skip or delete corrupted telemetry files rather than failing the entire application launch.

Impact

• Severity: High - Prevents application from starting
• Frequency: Occurs after normal usage once telemetry files accumulate
• User Impact: Complete loss of functionality until manual intervention

Additional Notes

• All other files in ~/.claude/ directory structure were validated as correct JSON
• Only files in telemetry/ subdirectory had this issue
• The telemetry files appear to be "failed events" based on the filename pattern, suggesting they may be edge cases in error handling

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Reproduction timestamp: 2026-03-05
Reporter environment: Windows 11, Git Bash