Incorrect Model Version 'Opus 4.1' and System Date Issues

Bug Report: Incorrect Model Version Information in Claude Code

Environment

• Claude Code Version: 2.1.81
• Platform: Windows (win32)
• Date: 2026-03-23 (Note: This date itself appears incorrect)
• Entrypoint: claude-vscode

Issue Description

Claude Code is reporting incorrect and non-existent model version information:

What's Being Reported:

• Model Name: "Opus 4.1"
• Model ID: claude-opus-4-1-20250805
• Knowledge Cutoff: January 2025
• System Date: 2026-03-23

Problems:

1. Non-existent Model: "Opus 4.1" is not an official Anthropic model name. Official naming follows patterns like "Claude 3 Opus", "Claude 3.5 Sonnet", etc.
2. Future Date in Model ID: The model ID includes "20250805" (August 5, 2025) which hasn't occurred yet
3. System Date Issue: The system is showing March 23, 2026, which seems incorrect
4. Inconsistent Information: Model dated 2025-08-05 but system shows 2026-03-23

Steps to Reproduce

1. Start Claude Code session
2. The assistant reports using "Opus 4.1" model
3. System environment shows date as 2026-03-23

Investigation Results

• claude --version returns: 2.1.81 (Claude Code)
• No model information in ~/.claude/settings.json
• Environment variables don't contain model info
• System date command shows: "2026년 03월 23일"

Expected Behavior

• Correct model name (e.g., "Claude 3 Opus" or "Claude 3.5 Sonnet")
• Accurate system date
• Consistent version information

Impact

• User confusion about which model is actually being used
• Inability to verify actual model capabilities
• Trust issues with system information

Additional Context

The assistant itself acknowledges this information is incorrect but cannot determine the source of the incorrect data injection.