commit 5c5bb04daa2c08b70429732a7e1b05c26b20c343
Author: Zhongwei Li <lizhongwei.nkcs@gmail.com>
Date:   Sun Nov 30 08:36:18 2025 +0800

    Initial commit

diff --git a/.claude-plugin/plugin.json b/.claude-plugin/plugin.json
new file mode 100644
index 0000000..400c345
--- /dev/null
+++ b/.claude-plugin/plugin.json
@@ -0,0 +1,15 @@
+{
+  "name": "claude-bumper-lanes",
+  "description": "Enforces git diff thresholds to promote disciplined code review during AI agent sessions",
+  "version": "1.2.0",
+  "author": {
+    "name": "Kyle Snow Schwartz",
+    "email": "kyle.snowschwartz@gmail.com"
+  },
+  "commands": [
+    "./commands"
+  ],
+  "hooks": [
+    "./hooks"
+  ]
+}
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..0a165b3
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# claude-bumper-lanes
+
+Enforces git diff thresholds to promote disciplined code review during AI agent sessions
diff --git a/commands/bumper-pause.md b/commands/bumper-pause.md
new file mode 100644
index 0000000..a35a4fc
--- /dev/null
+++ b/commands/bumper-pause.md
@@ -0,0 +1,9 @@
+---
+description: Temporarily suspend threshold enforcement while continuing to track changes
+---
+
+/claude-bumper-lanes:bumper-pause
+
+Pausing enforcement... (This command is handled by the UserPromptSubmit hook)
+
+Additional user arguments: $ARGUMENTS
diff --git a/commands/bumper-reset.md b/commands/bumper-reset.md
new file mode 100644
index 0000000..797779c
--- /dev/null
+++ b/commands/bumper-reset.md
@@ -0,0 +1,9 @@
+---
+description: Reset the diff baseline and restore threshold budget
+---
+
+/claude-bumper-lanes:bumper-reset
+
+Resetting baseline... (This command is handled by the UserPromptSubmit hook)
+
+Additional user arguments: $ARGUMENTS
diff --git a/commands/bumper-resume.md b/commands/bumper-resume.md
new file mode 100644
index 0000000..39e8fa3
--- /dev/null
+++ b/commands/bumper-resume.md
@@ -0,0 +1,9 @@
+---
+description: Re-enable threshold enforcement after a pause
+---
+
+/claude-bumper-lanes:bumper-resume
+
+Resuming enforcement... (This command is handled by the UserPromptSubmit hook)
+
+Additional user arguments: $ARGUMENTS
diff --git a/hooks/entrypoints/pause-baseline.sh b/hooks/entrypoints/pause-baseline.sh
new file mode 100755
index 0000000..1d75caa
--- /dev/null
+++ b/hooks/entrypoints/pause-baseline.sh
@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# pause-baseline.sh - Pause threshold enforcement (NOT a hook)
+# Purpose: Temporarily suspend Write/Edit blocking while continuing to track changes
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+
+# Read command-line argument (sessionId passed from command)
+session_id=${1:-}
+
+if [[ -z "$session_id" ]]; then
+  echo "Warning: No session ID provided"
+  exit 1
+fi
+
+# Load session state
+if ! session_state=$(read_session_state "$session_id" 2>/dev/null); then
+  echo "Warning: No active session found. Cannot pause."
+  exit 0
+fi
+
+# Check if already paused
+paused=$(echo "$session_state" | jq -r '.paused // false')
+if [[ "$paused" == "true" ]]; then
+  echo "Bumper lanes already paused. Use /bumper-resume to re-enable enforcement."
+  exit 0
+fi
+
+# Get current score for status message
+accumulated_score=$(echo "$session_state" | jq -r '.accumulated_score // 0')
+threshold_limit=$(echo "$session_state" | jq -r '.threshold_limit')
+
+# Set paused flag
+set_paused "$session_id" true
+
+cat <<EOF
+Bumper lanes: Enforcement paused ($accumulated_score/$threshold_limit pts)
+
+Edit/Write operations will proceed without threshold checks.
+Score tracking continues in the background.
+
+Use /bumper-resume to re-enable enforcement.
+EOF
+
+exit 0
diff --git a/hooks/entrypoints/post-tool-use.sh b/hooks/entrypoints/post-tool-use.sh
new file mode 100755
index 0000000..c4b8ee8
--- /dev/null
+++ b/hooks/entrypoints/post-tool-use.sh
@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# post-tool-use.sh - PostToolUse hook for auto-reset after git commit
+# Purpose: Reset bumper-lanes baseline after successful git commits
+# Hook: PostToolUse with Bash matcher
+# Trigger: After Bash tool completes successfully
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+
+# Read hook input from stdin
+input=$(cat)
+session_id=$(echo "$input" | jq -r '.session_id')
+tool_name=$(echo "$input" | jq -r '.tool_name')
+hook_event_name=$(echo "$input" | jq -r '.hook_event_name')
+command=$(echo "$input" | jq -r '.tool_input.command // empty')
+
+# Validate hook event (defensive check)
+if [[ "$hook_event_name" != "PostToolUse" ]]; then
+  exit 0
+fi
+
+# Only process Bash tool calls
+if [[ "$tool_name" != "Bash" ]]; then
+  exit 0
+fi
+
+# Detect git commit commands (various formats)
+# Pattern: git, optional flags (like -C /path), then commit subcommand
+# Matches: git commit, git -C /path commit, git --git-dir=/x commit
+# Rejects: prose like "use git to commit" (non-flag words between git and commit)
+if ! echo "$command" | grep -qE 'git\s+(-{1,2}[A-Za-z-]+([ =]("[^"]*"|\S+))?\s+)*commit\b'; then
+  exit 0
+fi
+
+# Check if session state exists (session-only enforcement)
+if ! session_state=$(read_session_state "$session_id" 2>/dev/null); then
+  # No session state - not enforcing, no reset needed (fail-open)
+  exit 0
+fi
+
+# Capture tree SHA from the commit that just happened
+# Use HEAD^{tree} to get the tree from the commit, not current index state
+# This ensures we capture exactly what was committed, not what's staged
+if ! current_tree=$(git rev-parse HEAD^{tree} 2>/dev/null); then
+  # Failed to get commit tree - fail open (don't break git workflow)
+  exit 0
+fi
+
+# Reset baseline to current tree (committed state)
+if ! reset_baseline_after_commit "$session_id" "$current_tree" 2>/dev/null; then
+  # Reset failed - fail open
+  exit 0
+fi
+
+# Output structured feedback for Claude Code
+# PostToolUse hooks return JSON with systemMessage to inform the agent
+jq -n '{
+    systemMessage: "✓ Bumper lanes: Auto-reset after commit. Fresh budget: 400 pts."
+  }'
+
+exit 0
diff --git a/hooks/entrypoints/pre-tool-use.sh b/hooks/entrypoints/pre-tool-use.sh
new file mode 100755
index 0000000..7e4dc20
--- /dev/null
+++ b/hooks/entrypoints/pre-tool-use.sh
@@ -0,0 +1,168 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# pre-tool-use.sh - PreToolUse hook for threshold enforcement
+# Purpose: Block file modification tools when diff threshold is exceeded
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+source "$SCRIPT_DIR/../lib/threshold-calculator.sh"
+
+# Read hook input from stdin
+input=$(cat)
+session_id=$(echo "$input" | jq -r '.session_id')
+tool_name=$(echo "$input" | jq -r '.tool_name')
+hook_event_name=$(echo "$input" | jq -r '.hook_event_name')
+
+# Validate hook event (defensive check)
+if [[ "$hook_event_name" != "PreToolUse" ]]; then
+  exit 0
+fi
+
+# Check if tool is a modification tool (early return optimization)
+case "$tool_name" in
+Write | Edit)
+  # This is a file modification tool - proceed with threshold check
+  ;;
+*)
+  # Not a file modification tool - allow it immediately
+  exit 0
+  ;;
+esac
+
+# Load session state
+if ! session_state=$(read_session_state "$session_id" 2>/dev/null); then
+  # No session state - fail open (allow tool)
+  exit 0
+fi
+
+# Extract state
+baseline_tree=$(echo "$session_state" | jq -r '.baseline_tree')
+threshold_limit=$(echo "$session_state" | jq -r '.threshold_limit')
+stop_triggered=$(echo "$session_state" | jq -r '.stop_triggered // false')
+previous_tree=$(echo "$session_state" | jq -r '.previous_tree // .baseline_tree')
+accumulated_score=$(echo "$session_state" | jq -r '.accumulated_score // 0')
+paused=$(echo "$session_state" | jq -r '.paused // false')
+
+# Capture current working tree (need this for both paths)
+if ! current_tree=$(capture_tree 2>/dev/null); then
+  # Failed to capture tree - fail open
+  exit 0
+fi
+
+# Check for branch switch BEFORE threshold calculation
+# This catches branch changes that Stop hook missed (e.g., switch and immediately edit)
+baseline_branch=$(echo "$session_state" | jq -r '.baseline_branch // ""')
+current_branch=$(get_current_branch)
+
+if [[ -n "$baseline_branch" ]] && [[ -n "$current_branch" ]] && [[ "$baseline_branch" != "$current_branch" ]]; then
+  # Branch switched - reset baseline and allow this tool (fresh start)
+  reset_baseline_stale "$session_id" "$current_tree" "$current_branch"
+
+  # Output notification and allow tool
+  jq -n \
+    --arg baseline_branch "$baseline_branch" \
+    --arg current_branch "$current_branch" \
+    '{
+      hookSpecificOutput: { hookEventName: "PreToolUse", permissionDecision: "allow" },
+      systemMessage: "↪ Bumper lanes: Branch changed (\($baseline_branch) → \($current_branch)) — baseline auto-reset."
+    }'
+  exit 0
+fi
+
+# Helper: Output fuel gauge JSON if approaching threshold
+output_fuel_gauge() {
+  local score="$1"
+  local limit="$2"
+
+  local message
+  message=$(get_fuel_gauge_message "$score" "$limit")
+
+  if [[ -n "$message" ]]; then
+    jq -n --arg msg "$message" '{
+      hookSpecificOutput: { hookEventName: "PreToolUse", permissionDecision: "allow" },
+      systemMessage: $msg
+    }'
+  fi
+}
+
+# Check if enforcement is paused
+# When paused, we still track changes but don't enforce thresholds
+if [[ "$paused" == "true" ]]; then
+  threshold_data=$(calculate_incremental_threshold "$previous_tree" "$current_tree" "$accumulated_score")
+  new_accumulated_score=$(echo "$threshold_data" | jq -r '.accumulated_score')
+  update_incremental_state "$session_id" "$current_tree" "$new_accumulated_score"
+
+  jq -n \
+    --argjson score "$new_accumulated_score" \
+    --argjson limit "$threshold_limit" \
+    '{
+      hookSpecificOutput: { hookEventName: "PreToolUse", permissionDecision: "allow" },
+      systemMessage: "Bumper lanes paused (\($score)/\($limit) pts)"
+    }'
+  exit 0
+fi
+
+# Check if Stop hook has been triggered
+# PreToolUse only blocks AFTER Stop hook has fired once
+if [[ "$stop_triggered" != "true" ]]; then
+  # Stop hasn't triggered yet - allow tool to proceed
+  # BUT update incremental state for next check
+  threshold_data=$(calculate_incremental_threshold "$previous_tree" "$current_tree" "$accumulated_score")
+  new_accumulated_score=$(echo "$threshold_data" | jq -r '.accumulated_score')
+  update_incremental_state "$session_id" "$current_tree" "$new_accumulated_score"
+
+  # Output fuel gauge if approaching threshold
+  output_fuel_gauge "$new_accumulated_score" "$threshold_limit"
+  exit 0
+fi
+
+# Stop has triggered - now enforce blocking on Write/Edit tools
+# Use incremental calculation
+threshold_data=$(calculate_incremental_threshold "$previous_tree" "$current_tree" "$accumulated_score")
+weighted_score=$(echo "$threshold_data" | jq -r '.accumulated_score')
+
+# Check threshold
+if [[ $weighted_score -le $threshold_limit ]]; then
+  # Under threshold - allow tool and update state
+  update_incremental_state "$session_id" "$current_tree" "$weighted_score"
+
+  # Output fuel gauge if approaching threshold
+  output_fuel_gauge "$weighted_score" "$threshold_limit"
+  exit 0
+fi
+
+# Over threshold - deny tool call
+# Format breakdown for user message
+# Note: threshold_data contains both weighted_score (delta) and accumulated_score (total)
+# For user display, we need to show the accumulated total, not just this turn's delta
+threshold_data_for_display=$(echo "$threshold_data" | jq '.weighted_score = .accumulated_score')
+breakdown=$(format_threshold_breakdown "$threshold_data_for_display" "$threshold_limit")
+
+# Build denial reason
+reason="
+
+🚫 Bumper lanes: Diff threshold exceeded
+
+$breakdown
+
+Cannot modify files while over threshold.
+
+Review your changes and run /bumper-reset to continue.
+
+"
+
+# Output denial decision using modern JSON format
+jq -n \
+  --arg reason "$reason" \
+  '{
+    hookSpecificOutput: {
+      hookEventName: "PreToolUse",
+      permissionDecision: "deny",
+      permissionDecisionReason: $reason
+    }
+  }'
+
+exit 0
diff --git a/hooks/entrypoints/reset-baseline.sh b/hooks/entrypoints/reset-baseline.sh
new file mode 100755
index 0000000..6066b26
--- /dev/null
+++ b/hooks/entrypoints/reset-baseline.sh
@@ -0,0 +1,86 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# reset-baseline.sh - Reset baseline script (NOT a hook)
+# Purpose: Reset baseline tree to current working tree state, update session state
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+
+# Read command-line argument (sessionId passed from command)
+session_id=${1:-}
+
+if [[ -z "$session_id" ]]; then
+  echo "⚠ Bumper Lanes: Error - No session ID provided"
+  exit 1
+fi
+
+# Load session state
+if ! session_state=$(read_session_state "$session_id" 2>/dev/null); then
+  # No active session - print error message
+  echo "⚠ Bumper Lanes: No active session found. Baseline reset skipped."
+  exit 0
+fi
+
+old_baseline=$(echo "$session_state" | jq -r '.baseline_tree')
+threshold_limit=$(echo "$session_state" | jq -r '.threshold_limit')
+created_at=$(echo "$session_state" | jq -r '.created_at')
+
+# Compute final diff stats (for reporting accepted changes)
+current_tree=$(capture_tree)
+if [[ -z "$current_tree" ]]; then
+  echo "⚠ Bumper Lanes: Failed to reset baseline. Please try again."
+  exit 1
+fi
+
+diff_output=$(compute_diff "$old_baseline" "$current_tree")
+
+# Parse diff stats inline (git diff-tree --shortstat format)
+# Format: "N files changed, X insertions(+), Y deletions(-)"
+files_changed=0
+lines_added=0
+lines_deleted=0
+
+if [[ "$diff_output" =~ ([0-9]+)\ file ]]; then
+  files_changed=${BASH_REMATCH[1]}
+fi
+if [[ "$diff_output" =~ ([0-9]+)\ insertion ]]; then
+  lines_added=${BASH_REMATCH[1]}
+fi
+if [[ "$diff_output" =~ ([0-9]+)\ deletion ]]; then
+  lines_deleted=${BASH_REMATCH[1]}
+fi
+
+total_lines=$((lines_added + lines_deleted))
+
+# Update session state with new baseline and clear incremental tracking
+new_baseline="$current_tree"
+write_session_state "$session_id" "$new_baseline"
+set_stop_triggered "$session_id" false
+# Reset incremental tracking: previous_tree = baseline, accumulated_score = 0
+update_incremental_state "$session_id" "$new_baseline" 0
+
+# Build confirmation message
+# Format timestamps for display
+old_timestamp=$(date -r "$(date -j -f "%Y-%m-%dT%H:%M:%SZ" "$created_at" +%s)" "+%Y-%m-%d %H:%M:%S" 2>/dev/null || echo "$created_at")
+new_timestamp=$(date "+%Y-%m-%d %H:%M:%S")
+
+# Truncate SHAs for display
+old_baseline_short="${old_baseline:0:7}"
+new_baseline_short="${new_baseline:0:7}"
+
+# Build multi-line confirmation message
+cat <<EOF
+✓ Baseline reset complete.
+
+Previous baseline: $old_baseline_short (captured $old_timestamp)
+New baseline: $new_baseline_short (captured $new_timestamp)
+
+Changes accepted: $files_changed files, $lines_added insertions(+), $lines_deleted deletions(-) [$total_lines lines total]
+
+You now have a fresh diff budget of $threshold_limit points. Pick up where we left off?
+EOF
+
+exit 0
diff --git a/hooks/entrypoints/resume-baseline.sh b/hooks/entrypoints/resume-baseline.sh
new file mode 100755
index 0000000..f627b1f
--- /dev/null
+++ b/hooks/entrypoints/resume-baseline.sh
@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# resume-baseline.sh - Resume threshold enforcement (NOT a hook)
+# Purpose: Re-enable Write/Edit blocking after a pause
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+
+# Read command-line argument (sessionId passed from command)
+session_id=${1:-}
+
+if [[ -z "$session_id" ]]; then
+  echo "Warning: No session ID provided"
+  exit 1
+fi
+
+# Load session state
+if ! session_state=$(read_session_state "$session_id" 2>/dev/null); then
+  echo "Warning: No active session found. Cannot resume."
+  exit 0
+fi
+
+# Check if already unpaused
+paused=$(echo "$session_state" | jq -r '.paused // false')
+if [[ "$paused" != "true" ]]; then
+  echo "Bumper lanes not paused. Enforcement is already active."
+  exit 0
+fi
+
+# Get current score for status message
+accumulated_score=$(echo "$session_state" | jq -r '.accumulated_score // 0')
+threshold_limit=$(echo "$session_state" | jq -r '.threshold_limit')
+stop_triggered=$(echo "$session_state" | jq -r '.stop_triggered // false')
+
+# Clear paused flag
+set_paused "$session_id" false
+
+# Calculate percentage for status
+pct=$((accumulated_score * 100 / threshold_limit))
+
+# Check if over threshold and warn
+if [[ $accumulated_score -gt $threshold_limit ]]; then
+  cat <<EOF
+Warning: Bumper lanes resumed — OVER THRESHOLD ($accumulated_score/$threshold_limit pts, ${pct}%)
+
+Write/Edit operations will be blocked until /bumper-reset.
+Review your changes before resetting.
+EOF
+elif [[ $pct -ge 75 ]]; then
+  cat <<EOF
+Bumper lanes: Enforcement resumed ($accumulated_score/$threshold_limit pts, ${pct}%)
+
+Approaching threshold. Consider committing working state soon.
+EOF
+else
+  cat <<EOF
+Bumper lanes: Enforcement resumed ($accumulated_score/$threshold_limit pts)
+
+Threshold checks active.
+EOF
+fi
+
+exit 0
diff --git a/hooks/entrypoints/session-end.sh b/hooks/entrypoints/session-end.sh
new file mode 100755
index 0000000..644fafd
--- /dev/null
+++ b/hooks/entrypoints/session-end.sh
@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# session-end.sh - SessionEnd hook for checkpoint cleanup
+# Purpose: Remove session-specific checkpoint file when Claude session terminates
+
+# Read hook input from stdin
+input=$(cat)
+session_id=$(echo "$input" | jq -r '.session_id // ""')
+
+# Validate session_id
+if [[ -z "$session_id" ]]; then
+  echo "ERROR: No session_id provided to SessionEnd hook" >&2
+  exit 0 # Fail open - SessionEnd can't block anyway
+fi
+
+# Check if git repo (checkpoint dir won't exist otherwise)
+if ! git rev-parse --git-dir &>/dev/null; then
+  exit 0
+fi
+
+checkpoint_dir=".git/bumper-checkpoints"
+state_file="$checkpoint_dir/session-$session_id"
+
+# Remove this session's checkpoint file
+if [[ -f "$state_file" ]]; then
+  rm -f "$state_file" 2>/dev/null || true
+fi
+
+# Optional: Clean stale checkpoints (files older than 30 days)
+# Uncomment the line below to enable automatic stale file cleanup:
+# find "$checkpoint_dir" -type f -name "session-*" -mtime +30 -delete 2>/dev/null || true
+
+exit 0
diff --git a/hooks/entrypoints/session-start.sh b/hooks/entrypoints/session-start.sh
new file mode 100755
index 0000000..7fe394d
--- /dev/null
+++ b/hooks/entrypoints/session-start.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# session-start.sh - SessionStart hook for baseline capture
+# Purpose: Capture working tree state as baseline when Claude session starts
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+
+# Read hook input from stdin
+input=$(cat)
+session_id=$(echo "$input" | jq -r '.session_id')
+
+# Hook is already executed in project directory (cwd field in JSON)
+
+# Check if this is a git repository
+if ! git rev-parse --git-dir &>/dev/null; then
+  # Not a git repo - disable plugin gracefully
+  exit 0
+fi
+
+# Capture baseline tree
+baseline_tree=$(capture_tree)
+if [[ -z "$baseline_tree" ]]; then
+  echo "ERROR: Failed to capture baseline tree" >&2
+  exit 0 # Fail open
+fi
+
+# Capture current branch name for staleness detection
+baseline_branch=$(get_current_branch)
+
+# Write session state (with branch tracking)
+write_session_state "$session_id" "$baseline_tree" "$baseline_branch"
+
+# Allow session start
+exit 0
diff --git a/hooks/entrypoints/stop.sh b/hooks/entrypoints/stop.sh
new file mode 100755
index 0000000..8c884d9
--- /dev/null
+++ b/hooks/entrypoints/stop.sh
@@ -0,0 +1,141 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# stop.sh - Stop hook for threshold enforcement
+# Purpose: Check diff threshold when agent stops, block if exceeded
+
+# Source library functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/../lib/git-state.sh"
+source "$SCRIPT_DIR/../lib/state-manager.sh"
+source "$SCRIPT_DIR/../lib/threshold-calculator.sh"
+
+# Read hook input from stdin
+input=$(cat)
+session_id=$(echo "$input" | jq -r '.session_id')
+stop_hook_active=$(echo "$input" | jq -r '.stop_hook_active // false')
+
+# Hook is already executed in project directory (cwd field in JSON)
+
+# If already blocked once, allow stop this time to prevent infinite loop
+if [[ "$stop_hook_active" == "true" ]]; then
+  exit 0
+fi
+
+# Load session state
+if ! session_state=$(read_session_state "$session_id" 2>/dev/null); then
+  # No baseline - allow stop (fail open)
+  exit 0
+fi
+
+# Exit early if bumper lanes already tripped - allow review collaboration
+stop_triggered=$(echo "$session_state" | jq -r '.stop_triggered // false')
+if [[ "$stop_triggered" == "true" ]]; then
+  # PreToolUse is actively blocking Write/Edit - no need to block stop
+  exit 0
+fi
+
+# Exit early if enforcement is paused - allow work to continue
+paused=$(echo "$session_state" | jq -r '.paused // false')
+if [[ "$paused" == "true" ]]; then
+  # Still need to track changes while paused
+  current_tree=$(capture_tree)
+  if [[ -n "$current_tree" ]]; then
+    previous_tree=$(echo "$session_state" | jq -r '.previous_tree // .baseline_tree')
+    accumulated_score=$(echo "$session_state" | jq -r '.accumulated_score // 0')
+    threshold_data=$(calculate_incremental_threshold "$previous_tree" "$current_tree" "$accumulated_score")
+    weighted_score=$(echo "$threshold_data" | jq -r '.accumulated_score')
+    update_incremental_state "$session_id" "$current_tree" "$weighted_score"
+  fi
+  exit 0
+fi
+
+baseline_tree=$(echo "$session_state" | jq -r '.baseline_tree')
+baseline_branch=$(echo "$session_state" | jq -r '.baseline_branch // ""')
+threshold_limit=$(echo "$session_state" | jq -r '.threshold_limit')
+previous_tree=$(echo "$session_state" | jq -r '.previous_tree // .baseline_tree')
+accumulated_score=$(echo "$session_state" | jq -r '.accumulated_score // 0')
+
+# Capture current working tree
+current_tree=$(capture_tree)
+if [[ -z "$current_tree" ]]; then
+  echo "ERROR: Failed to capture current tree" >&2
+  exit 0 # Fail open
+fi
+
+# Detect branch switch - auto-reset baseline to keep diffs meaningful
+current_branch=$(get_current_branch)
+
+if [[ -n "$baseline_branch" ]] && [[ -n "$current_branch" ]] && [[ "$baseline_branch" != "$current_branch" ]]; then
+  # Branch switched - reset baseline (score to 0, stop_triggered to false, update branch)
+  reset_baseline_stale "$session_id" "$current_tree" "$current_branch"
+
+  # Allow stop via JSON API (continue: true)
+  jq -n \
+    --arg baseline_branch "$baseline_branch" \
+    --arg current_branch "$current_branch" \
+    '{
+      continue: true,
+      systemMessage: "↪ Bumper lanes: Branch changed (\($baseline_branch) → \($current_branch)) — baseline auto-reset.",
+      suppressOutput: false
+    }'
+
+  # Exit after JSON response (avoid threshold check)
+  exit 0
+fi
+
+# Compute incremental threshold (previous → current + accumulated)
+threshold_data=$(calculate_incremental_threshold "$previous_tree" "$current_tree" "$accumulated_score")
+weighted_score=$(echo "$threshold_data" | jq -r '.accumulated_score')
+
+if [[ $weighted_score -le $threshold_limit ]]; then
+  # Under threshold - allow stop and update incremental state
+  update_incremental_state "$session_id" "$current_tree" "$weighted_score"
+  exit 0
+fi
+
+# Over threshold - set stop_triggered flag to activate PreToolUse blocking
+set_stop_triggered "$session_id" true
+# Also update incremental state
+update_incremental_state "$session_id" "$current_tree" "$weighted_score"
+
+# Format breakdown for user message
+# Note: threshold_data contains both weighted_score (delta) and accumulated_score (total)
+# For user display, we need to show the accumulated total, not just this turn's delta
+threshold_data_for_display=$(echo "$threshold_data" | jq '.weighted_score = .accumulated_score')
+breakdown=$(format_threshold_breakdown "$threshold_data_for_display" "$threshold_limit")
+
+# Build reason message
+reason="
+
+⚠️  Bumper lanes: Diff threshold exceeded
+
+$breakdown
+
+Ask the User: Would you like to conduct a structured, manual review?
+
+This workflow ensures incremental code review at predictable checkpoints.
+
+"
+
+threshold_pct=$(awk "BEGIN {printf \"%.0f\", ($weighted_score / $threshold_limit) * 100}")
+
+# Output block decision to STDOUT (JSON API pattern with exit code 0)
+jq -n \
+  --arg decision "block" \
+  --arg reason "$reason" \
+  --argjson continue true \
+  --arg systemMessage "/bumper-reset after code review." \
+  --argjson threshold_data "$threshold_data" \
+  --argjson threshold_limit "$threshold_limit" \
+  --argjson threshold_percentage "$threshold_pct" \
+  '{
+    continue: $continue,
+    systemMessage: $systemMessage,
+    suppressOutput: true,
+    decision: $decision,
+    reason: $reason,
+    threshold_data: ($threshold_data + {threshold_limit: $threshold_limit, threshold_percentage: $threshold_percentage})
+  }'
+
+exit 0
diff --git a/hooks/entrypoints/user-prompt-submit.sh b/hooks/entrypoints/user-prompt-submit.sh
new file mode 100755
index 0000000..85dfe0a
--- /dev/null
+++ b/hooks/entrypoints/user-prompt-submit.sh
@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# user-prompt-submit.sh - UserPromptSubmit hook for /bumper-reset command
+# Purpose: Watch for /bumper-reset in user prompt and execute reset-baseline.sh
+
+# Source library functions (for potential future use)
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Read hook input from stdin
+input=$(cat)
+prompt=$(echo "$input" | jq -r '.prompt // ""')
+session_id=$(echo "$input" | jq -r '.session_id')
+
+# Helper function to output command result as JSON
+output_command_result() {
+  local output="$1"
+  jq -n \
+    --arg output "$output" \
+    '{
+      hookSpecificOutput: {
+        hookEventName: "UserPromptSubmit",
+        additionalContext: $output
+      }
+    }'
+}
+
+# Check if user typed /claude-bumper-lanes:bumper-reset
+if [[ "$prompt" == *"/claude-bumper-lanes:bumper-reset"* ]]; then
+  reset_output=$("$SCRIPT_DIR/reset-baseline.sh" "$session_id" 2>&1)
+  output_command_result "$reset_output"
+  exit 0
+fi
+
+# Check if user typed /claude-bumper-lanes:bumper-pause
+if [[ "$prompt" == *"/claude-bumper-lanes:bumper-pause"* ]]; then
+  pause_output=$("$SCRIPT_DIR/pause-baseline.sh" "$session_id" 2>&1)
+  output_command_result "$pause_output"
+  exit 0
+fi
+
+# Check if user typed /claude-bumper-lanes:bumper-resume
+if [[ "$prompt" == *"/claude-bumper-lanes:bumper-resume"* ]]; then
+  resume_output=$("$SCRIPT_DIR/resume-baseline.sh" "$session_id" 2>&1)
+  output_command_result "$resume_output"
+  exit 0
+fi
+
+exit 0
diff --git a/hooks/hooks.json b/hooks/hooks.json
new file mode 100644
index 0000000..614e8f9
--- /dev/null
+++ b/hooks/hooks.json
@@ -0,0 +1,67 @@
+{
+  "description": "Bumper Lanes hook configuration for threshold enforcement",
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/hooks/entrypoints/session-start.sh"
+          }
+        ]
+      }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/hooks/entrypoints/stop.sh"
+          }
+        ]
+      }
+    ],
+    "UserPromptSubmit": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/hooks/entrypoints/user-prompt-submit.sh"
+          }
+        ]
+      }
+    ],
+    "PreToolUse": [
+      {
+        "matcher": "Edit|Write",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/hooks/entrypoints/pre-tool-use.sh"
+          }
+        ]
+      }
+    ],
+    "PostToolUse": [
+      {
+        "matcher": "Bash",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/hooks/entrypoints/post-tool-use.sh"
+          }
+        ]
+      }
+    ],
+    "SessionEnd": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "${CLAUDE_PLUGIN_ROOT}/hooks/entrypoints/session-end.sh"
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/plugin.lock.json b/plugin.lock.json
new file mode 100644
index 0000000..5ca9828
--- /dev/null
+++ b/plugin.lock.json
@@ -0,0 +1,105 @@
+{
+  "$schema": "internal://schemas/plugin.lock.v1.json",
+  "pluginId": "gh:kylesnowschwartz/claude-bumper-lanes:bumper-lanes-plugin",
+  "normalized": {
+    "repo": null,
+    "ref": "refs/tags/v20251128.0",
+    "commit": "c1966d425ec5aac617ac0e3e2f5c2ece72e19835",
+    "treeHash": "6463824b80fa53ae189e55e5a8ebfee42d4242b94a593cb543596f63f06ab1de",
+    "generatedAt": "2025-11-28T10:20:02.022187Z",
+    "toolVersion": "publish_plugins.py@0.2.0"
+  },
+  "origin": {
+    "remote": "git@github.com:zhongweili/42plugin-data.git",
+    "branch": "master",
+    "commit": "aa1497ed0949fd50e99e70d6324a29c5b34f9390",
+    "repoRoot": "/Users/zhongweili/projects/openmind/42plugin-data"
+  },
+  "manifest": {
+    "name": "claude-bumper-lanes",
+    "description": "Enforces git diff thresholds to promote disciplined code review during AI agent sessions",
+    "version": "1.2.0"
+  },
+  "content": {
+    "files": [
+      {
+        "path": "README.md",
+        "sha256": "8ecf5ff6d08f9a18306f97eb7fbab4824b548e6379fe6a6192b336f6cda32552"
+      },
+      {
+        "path": "hooks/hooks.json",
+        "sha256": "73687af1261fd167c5f694e2cb364e4d5e8747aa1902eb3111adcbb8474648f8"
+      },
+      {
+        "path": "hooks/lib/git-state.sh",
+        "sha256": "faedd43659d24a6cb3df1c1039bef011ee5b9272c8acd2a9d45c319aa9a41c14"
+      },
+      {
+        "path": "hooks/lib/state-manager.sh",
+        "sha256": "a8b286251b84080fced34b54c6febd846a652b4beae20eebe55e84217704f7d5"
+      },
+      {
+        "path": "hooks/lib/threshold-calculator.sh",
+        "sha256": "6d486b76a15e5c836bda9ecc730da7e209c059605d0c94f431dac5a5734e96e2"
+      },
+      {
+        "path": "hooks/entrypoints/user-prompt-submit.sh",
+        "sha256": "0b406abc15b70b9ff251c0cef998909b8361ffb18930019f18aad0ef7f460951"
+      },
+      {
+        "path": "hooks/entrypoints/pause-baseline.sh",
+        "sha256": "cd6a160ddf4fee8654be0d3cdf169551a4742a384b1411065b85a92cec1b36c4"
+      },
+      {
+        "path": "hooks/entrypoints/reset-baseline.sh",
+        "sha256": "3f43dfa791e54952d180b9d2a10a19b8dc43f409af978d695f198f2398952131"
+      },
+      {
+        "path": "hooks/entrypoints/pre-tool-use.sh",
+        "sha256": "58bca0058f4f1012fd22ddede7f7de45ce04431f296a9ab6c0b7b9d83912fd1c"
+      },
+      {
+        "path": "hooks/entrypoints/session-start.sh",
+        "sha256": "44622c20335effe57b8d79ffbd4a0c497a0151983992be428d2293411d91a2c3"
+      },
+      {
+        "path": "hooks/entrypoints/session-end.sh",
+        "sha256": "29d8ee18e4d45d66f9b97940dc9fc677bebd9ed47d0e61193953621aee016493"
+      },
+      {
+        "path": "hooks/entrypoints/post-tool-use.sh",
+        "sha256": "801d417179369d3e18741c5721f6fdfa28e52d9b3aad28fea491ced294772c76"
+      },
+      {
+        "path": "hooks/entrypoints/stop.sh",
+        "sha256": "8f875bfb76a88d6386a1860055598881858b4bce21a951adc10321718d234550"
+      },
+      {
+        "path": "hooks/entrypoints/resume-baseline.sh",
+        "sha256": "0536ec1561672b716f9bef0d1e68ff3eb067775b7af32f3b76d31e4cf862cbaa"
+      },
+      {
+        "path": ".claude-plugin/plugin.json",
+        "sha256": "9216794e8daea5816d25aab492a9c82c8b7318d840096d32a1b74587cf185724"
+      },
+      {
+        "path": "commands/bumper-reset.md",
+        "sha256": "cbaf768a331cb313ce600d77e166185b855b9d2070f447c16bbc0615250b37bc"
+      },
+      {
+        "path": "commands/bumper-resume.md",
+        "sha256": "e55729fa98e9f1342840ef500269163465fdecce95433102c9ee1fab3508a70d"
+      },
+      {
+        "path": "commands/bumper-pause.md",
+        "sha256": "a0c810c68d5ea2e743f333fcfd5de59b03125b8ecf8140e5d3f008a72f89ff32"
+      }
+    ],
+    "dirSha256": "6463824b80fa53ae189e55e5a8ebfee42d4242b94a593cb543596f63f06ab1de"
+  },
+  "security": {
+    "scannedAt": null,
+    "scannerVersion": null,
+    "flags": []
+  }
+}
\ No newline at end of file