Bumper Lanes

Bumper lanes gives you two features native to Claude-Code:

1. A 'Heads Up Display' of the changes Claude makes via unique git-diff visualizations in the status line
2. A configurable circuit breaker that blocks Claude from continuing until you review and approve the accumulated changes

What It Does

Bumper-Lanes tracks how much code Claude has written or edited, blocking further edits when a threshold is exceeded. 600 points corresponds roughly to that many lines of code added, depending on the mix of new files vs edits.

When the threshold is exceeded:

1. Fuel gauge warnings show escalating alerts after each Write/Edit (70% NOTICE → 90% WARNING) to you and to Claude
2. Stop hook blocks Claude from continuing when threshold exceeded
3. Reset command (/bumper-reset) restores the budget after you review

Installation

claude plugin marketplace add kylesnowschwartz/claude-bumper-lanes
claude plugin install claude-bumper-lanes

Requirements: Go 1.21+ (binaries are built automatically on first session start)

Usage

Work normally with Claude. If the configurable threshold is exceeded:

1. Claude will be blocked from continuing
2. Review your changes
3. Optionally commit: git add -u && git commit -m "message" (resets the baseline automatically)
4. Or Manually reset the baseline: /bumper-reset
5. Continue working with restored budget

Commands

Command	Description
/bumper-reset	Reset baseline after reviewing changes
/bumper-pause	Pause threshold enforcement (session only)
/bumper-resume	Resume threshold enforcement
/bumper-config	Show current configuration
/bumper-config <n>	Set repo threshold (0=disabled, 50-2000)

View Modes

Command	Description
/bumper-tree	Indented file tree with +/- stats
/bumper-smart	Multi-column table sorted by magnitude
/bumper-sparkline-tree	Rainbow sidebar tree with sparkline bars
/bumper-hotpath	Hot trail view (follows largest child)
/bumper-icicle	Horizontal area chart
/bumper-brackets	Nested [dir file] single-line
/bumper-gauge	Progress gauge showing change magnitude
/bumper-depth	Nested gauges by depth level
/bumper-stat	Native git diff --stat output

Status Line Setup

Status line is auto-configured on first session. No manual setup needed, though you may want to tweak if you use a custom setup.

If you need to configure manually:

Auto-setup writes this to ~/.claude/settings.json:

{
  "statusLine": {
    "type": "command",
    "command": "/path/to/.claude/plugins/cache/.../bumper-lanes status",
    "padding": 0
  }
}

The path is versioned and changes on plugin updates—auto-setup handles this automatically.

Want just the diff visualization? Install diff-viz globally:

go install github.com/kylesnowschwartz/diff-viz/v2/cmd/git-diff-tree@latest

Then use git-diff-tree directly in your custom status line scripts. This optionally gives you the tree visualization without the threshold enforcement as well.

Opting Out of Auto-Setup

To prevent bumper-lanes from modifying your statusline script, add this comment anywhere in your script:

# BUMPER_HANDS_OFF

This tells bumper-lanes to leave your configuration alone. The plugin will not wrap, update, or regenerate any script containing this marker.

Configuration

Config files (in precedence order):

1. .bumper-lanes.json at repo root (highest priority)
2. ~/.config/bumper-lanes/config.json (global fallback)
3. Built-in defaults

{
  "threshold": 400,
  "default_view_mode": "tree",
  "default_view_opts": "--width 80 --depth 3",
  "show_diff_viz": true
}

Field	Description
threshold	Points limit. 0 = disabled, 50-2000 = active (default: 600)
default_view_mode	Visualization mode (default: tree)
default_view_opts	Options passed to diff-viz renderer (e.g., --width 80 --depth 3)
show_diff_viz	Show diff visualization in status line (default: true)

Available view modes: tree, smart, sparkline-tree, hotpath, icicle, brackets, gauge, depth, stat

Viz-Only Mode (Global Config)

Want the diff visualization without threshold enforcement? Create a global config:

mkdir -p ~/.config/bumper-lanes
echo '{"threshold": 0}' > ~/.config/bumper-lanes/config.json

This disables enforcement across all repos while keeping the status line diff visualization. Individual repos can override with their own .bumper-lanes.json.

Run /bumper-config to see which config files are active.

Other Options

Disabling per-repo: Set "threshold": 0 in .bumper-lanes.json to disable for a specific repo.

Hiding diff visualization: Set "show_diff_viz": false to hide the diff tree from the status line. Running any view command (/bumper-tree, etc.) restores it for the current session.

Weighted Scoring

• New file additions: 1.0x weight
• Edits to existing files: 1.3x weight (harder to review)
• Scatter penalty: Extra points when touching many files
• Deletions: Not counted (removing code is good)

Requirements

• Go 1.21+ (for automatic binary compilation)
• Git 2.x+
• Claude Code with hooks support

Project Structure

bumper-lanes-plugin/
├── bin/                    # Built binaries (auto-generated)
│   ├── bumper-lanes        # Hook handler
│   └── git-diff-tree       # Diff visualization (from diff-viz)
├── scripts/
│   └── ensure-binaries.sh  # Auto-builds on first run
├── tools/
│   └── bumper-lanes/       # Hook handler source (Go)
├── commands/               # Slash command definitions
└── hooks/
    └── hooks.json          # Hook configuration

Diff visualization is provided by diff-viz.