[Feature Request]: Auto-backup config.toml before edits to prevent crash loops

[akaeba]

Component

CLI

Problem statement

When config.toml becomes corrupted (bad TOML syntax, invalid config values, or malformed settings), Vibe CLI can crash on startup. Users must manually repair the configuration file from memory or from external backups.

This is particularly problematic when:

• Experimenting with custom MCP server configurations
• Testing new provider or model settings
• Editing complex TOML structures that are prone to syntax errors

Proposed solution

• Backup location: Same directory as config.toml (either ~/.vibe/ or project-local .vibe/)
• Backup naming: config.toml.bak for current, config.toml.1.bak, config.toml.2.bak for rotations
• Rotation: Keep last 5 backups, delete oldest on new backup
• Atomic writes: Write backup before modifying original to prevent partial writes

Use Case Example

User adds a custom MCP server with incorrect configuration:

[[mcp_servers]]
name = "my-server"
transport = "stdio"
command = "npx"
args = ["-y", "@my/mcp-server"]
# Missing required field causes crash

Vibe crashes on next startup. User must:

1. Remember what they changed
2. Manually edit the file to fix it
3. Or restore from external backup

With auto-backup: User can simply run a restore command or Vibe auto-detects the crash and offers to restore.

Impact

• Reliability: Prevents crash loops from config errors
• User Experience: Reduces friction during configuration experiments
• Recovery: Easy rollback without manual file recovery
• Safety Net: Encourages users to try new configurations without fear

Additional context

Submitted by: Vibe CLI user