Hotspots

Website: https://hotspots.dev  |  Docs: https://docs.hotspots.dev  |  Crates.io:

Install: cargo install hotspots-cli  |  curl -fsSL https://raw.githubusercontent.com/Stephen-Collins-tech/hotspots/main/install.sh | sh

Find the code that's actually causing problems.

Your codebase has thousands of functions. Some are messy but never break. Others are complex AND change constantly—those are your hotspots, the 20% of code causing 80% of your bugs, incidents, and slowdowns.

Stop refactoring code that doesn't matter. Focus on what's hurting you right now.

---

The Problem

You know your codebase has tech debt. But which code should you actually refactor?

❌ Refactor by gut feeling → Waste weeks on code that rarely causes issues ❌ Refactor everything → Impossible, and you'll rewrite stable code that doesn't need touching ❌ Refactor nothing → Tech debt compounds until "fix this bug" becomes "rewrite everything"

The real question: Which functions are both complex AND frequently changed?

Those are the functions causing production incidents, slowing down features, and burning out your team.

---

The Solution

Hotspots analyzes your codebase and git history to find functions that are:

1. Complex - High cyclomatic complexity, deep nesting, lots of branching
2. Volatile - Changed frequently in recent commits
3. Risky - The dangerous combination of both

Instead of guessing what to refactor, you get a prioritized list:

Risk Landscape from a real 7,911-function codebase: 284 Critical (red), 491 High (orange). Each dot is a function — top-right are your hotspots.

hotspots analyze src/

# Output:
Critical (LRS ≥ 9.0):
processPlanUpgrade    src/api/billing.ts:142    LRS 12.4  CC 15  ND 4  FO 8  NS 3

High (6.0 ≤ LRS < 9.0):
validateSession       src/auth/session.ts:67    LRS 9.8   CC 11  ND 3  FO 7  NS 2
applySchema           src/db/migrations.ts:203  LRS 8.1   CC 10  ND 2  FO 5  NS 2

Now you know exactly where to focus.

---

What You Get

✅ Refactor What Actually Matters

Stop wasting time on code that "looks messy" but never causes problems. Focus on the 20% of functions responsible for 80% of your incidents.

✅ Block Complexity Regressions in CI

Catch risky changes before they merge:

# Run in CI with policy checks
hotspots analyze src/ --mode delta --policy
# Exit code 1 if policies fail → CI fails

Your CI fails if someone introduces high-risk code. No manual review needed.

GitHub Action coming soon. A native hotspots-action for GitHub Actions is not yet available. Use the CLI directly in your workflows in the meantime.

✅ Ship with Confidence, Not Crossed Fingers

Know which files are landmines before you touch them. See complexity trends over time. Make informed decisions about refactoring vs rewriting vs leaving it alone.

✅ Get AI-Assisted Refactoring

Hotspots integrates with Claude Code, Cursor, and GitHub Copilot. Point your AI at the hottest functions and get refactoring suggestions that actually improve your codebase.

# Analyze changes in your project
hotspots analyze . --mode delta --format json

# Get agent-optimized output (quadrant buckets + action text)
hotspots analyze . --mode delta --all-functions --format json

---

Quick Start

1. Install

cargo (Rust toolchain):

cargo install hotspots-cli

macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/Stephen-Collins-tech/hotspots/main/install.sh | sh

Installs to ~/.local/bin/hotspots. Verify with hotspots --version.

GitHub Action: Coming soon. Use the CLI directly in your workflows for now.

2. Analyze Your Code

# Find your hotspots
hotspots analyze src/

# Filter to critical functions only
hotspots analyze src/ --min-lrs 9.0

# Get per-function explanations with driver labels
hotspots analyze . --mode snapshot --format text --explain --top 10

# Get JSON for tooling/AI
hotspots analyze src/ --format json

# Stream JSONL for pipeline processing
hotspots analyze src/ --format jsonl

# Compare with previous commit (delta mode)
hotspots analyze src/ --mode delta --policy

3. Act on Results

Critical functions (LRS ≥ 9.0): Refactor now. These are your top priority. High functions (LRS 6.0-9.0): Watch closely. Refactor before they become critical. Moderate functions (LRS 3.0-6.0): Keep an eye on them. Block complexity increases. Low functions (LRS < 3.0): You're good. Don't overthink these.

---

Supported Languages

• TypeScript - .ts, .tsx, .mts, .cts
• JavaScript - .js, .jsx, .mjs, .cjs
• Go - .go
• Python - .py
• Rust - .rs
• Java - .java

Full language parity across all metrics and features. See docs/reference/language-support.md for details.

---

How It Works

Hotspots computes a Local Risk Score (LRS) for each function based on:

1. Cyclomatic Complexity (CC) - How many paths through the code?
2. Nesting Depth (ND) - How deeply nested are your if/for/while statements?
3. Fan-Out (FO) - How many other functions does this call?
4. Non-Structured Exits (NS) - How many early returns, breaks, throws?

These metrics combine into a single Local Risk Score (LRS). Higher LRS = higher risk of bugs, incidents, and developer confusion.

LRS is then combined with Activity Risk signals from git history and the call graph:

• Churn — lines changed in the last 30 days (volatile code)
• Touch frequency — commit count touching this function
• Recency — days since last change (branch-aware)
• Fan-in — how many other functions call this one (call graph)
• Cyclic dependency — SCC membership (tightly coupled code)
• Neighbor churn — lines changed in direct dependencies

The call graph engine resolves imports to detect fan-in, PageRank, betweenness centrality, and SCC membership. Functions that are both complex AND heavily depended upon by other changing code rise to the top.

Understanding Quadrants

Every function is placed in one of four quadrants based on its structural complexity and recent activity:

Quadrant	Complexity	Recent Activity	What it means
fire	High	High	Live regression risk — complex AND actively changing right now
debt	High	Low	Structural debt — complex but not recently touched; high blast radius when next changed
simple-active	Low	High	Active but manageable — monitor, low structural risk
simple-stable	Low	Low	Lowest priority

Important: The activity-weighted risk score (and lrs) is a decay function computed over git history — it never reaches zero even if a function hasn't been touched in months. A high risk score alone does not mean a function is actively changing. Always check quadrant and touches_30d to determine whether a function is a live regression risk (fire) or structural debt (debt).

• fire: Refactor now — every commit is landing on a complex function
• debt: Schedule proactively — refactor before the next development push into that area, not urgently
• simple-active: Watch closely but don't over-invest in refactoring
• simple-stable: Leave it alone unless metrics change

Example:

// LRS: 12.4 (Critical) - Complex AND frequently changed
function processPlanUpgrade(user, newPlan, paymentMethod) {
  if (!user.isActive) return false;
  if (user.plan === newPlan) return true;

  if (paymentMethod.type === "card") {
    if (paymentMethod.isExpired) {
      try {
        paymentMethod = renewPaymentMethod(user);
      } catch (error) {
        logError(error);
        notifyUser(user, "payment_failed");
        return false;
      }
    }

    if (newPlan.price > user.plan.price) {
      const prorated = calculateProration(user, newPlan);
      if (!chargeCard(paymentMethod, prorated)) {
        return false;
      }
    }
  } else if (paymentMethod.type === "invoice") {
    // Different logic for invoice customers...
  }

  updateDatabase(user, newPlan);
  sendConfirmation(user);
  return true;
}

This function:

• CC: 15 (lots of branching)
• ND: 4 (deeply nested)
• FO: 8 (calls many functions)
• NS: 3 (multiple early returns)
• LRS: 12.4 ← This is a hotspot

Refactor this before it causes a production incident.

---

Features

🚦 Policy Enforcement (CI/CD)

Block risky code before it merges:

• Critical Introduction - Fail CI if new functions exceed LRS 9.0
• Excessive Regression - Fail CI if LRS increases by ≥1.0
• Watch/Attention Warnings - Warn about functions approaching thresholds
• Rapid Growth Detection - Catch functions growing >50% in complexity

# Run in CI with policy checks
hotspots analyze src/ --mode delta --policy
# Exit code 1 if policies fail → CI fails

🔍 Driver Labels & Explain Mode

Understand why a function is flagged and get concrete refactoring advice:

hotspots analyze . --mode snapshot --format text --explain --top 10

Each function shows its primary driver (high_complexity, deep_nesting, high_churn_low_cc, high_fanout_churning, high_fanin_complex, cyclic_dep, composite) plus an Action line with dimension-specific guidance:

processPayment             /src/billing.ts:89
   LRS: 14.52 | Band: critical | Driver: high_complexity
   CC: 15, ND: 4, FO: 8, NS: 3
   Action: Reduce branching; extract sub-functions

Use --level file or --level module for higher-level aggregated views.

📊 Multiple Output Formats

Terminal (human-readable):

Critical (LRS ≥ 9.0):
processPlanUpgrade    src/api/billing.ts:142    LRS 12.4  CC 15  ND 4  FO 8  NS 3

JSON (machine-readable):

{
  "schema_version": 2,
  "functions": [
    {
      "function_id": "src/api/billing.ts::processPlanUpgrade",
      "file": "src/api/billing.ts",
      "line": 142,
      "lrs": 12.4,
      "band": "critical",
      "driver": "high_complexity",
      "metrics": { "cc": 15, "nd": 4, "fo": 8, "ns": 3 }
    }
  ]
}

JSONL (streaming per-function):

hotspots analyze src/ --mode snapshot --format jsonl | grep '"band":"critical"'

One JSON object per line — ideal for large repos and shell pipeline processing.

HTML (interactive reports):

• Sortable, filterable tables
• Risk band visualization
• Shareable with stakeholders
• Upload as CI artifacts

🔇 Suppression Comments

Have complex code you can't refactor yet? Suppress warnings with a reason:

// hotspots-ignore: legacy payment processor, rewrite scheduled Q2 2026
function legacyBillingLogic() {
  // Complex but can't touch it yet
}

Functions with suppressions:

• ✅ Still appear in reports (visibility)
• ❌ Don't fail CI policies (pragmatism)
• 📝 Require a reason (accountability)

⚙️ Configuration

Customize thresholds, weights, and file patterns:

{
  "thresholds": {
    "moderate": 3.0,
    "high": 6.0,
    "critical": 9.0
  },
  "include": ["src/**/*.ts"],
  "exclude": ["**/*.test.ts", "**/__mocks__/**"]
}

See docs/guide/configuration.md for all options.

🤖 AI Integration

Claude Code:

# Analyze changes and feed to Claude Code
hotspots analyze . --mode delta --format json

# Get agent-optimized output
hotspots analyze . --mode delta --all-functions --format json

See docs/integrations/ai-agents.md for complete guide.

Cursor/GitHub Copilot:

hotspots analyze src/ --format json | jq '.functions[] | select(.lrs > 9)'
# Feed results to your AI coding assistant

📈 Git History Analysis

Track complexity over time:

# Create baseline snapshot
hotspots analyze src/ --mode snapshot

# Compare current code vs baseline
hotspots analyze src/ --mode delta

# Compare any two git refs (branches, tags, SHAs)
hotspots diff main HEAD
hotspots diff v1.0.0 v2.0.0 --format json
hotspots diff main HEAD --top 10 --policy

# See complexity trends
hotspots trends .

# Prune unreachable snapshots (after force-push or branch deletion)
hotspots prune --unreachable --older-than 30

# Compact snapshot history
hotspots compact --level 0

Delta mode and hotspots diff show:

• Functions that got more complex
• Functions that were simplified
• New high-complexity functions introduced
• Overall repository complexity trend

hotspots diff requires snapshots to exist for both refs (run hotspots analyze --mode snapshot at each ref first). Use --auto-analyze to generate missing snapshots automatically via git worktrees.

⚙️ Configuration Commands

# Show resolved configuration (weights, thresholds, filters)
hotspots config show

# Validate configuration file without running analysis
hotspots config validate

---

Documentation

• 🚀 Quick Start - Get started in 5 minutes
• 📖 CLI Reference - All commands and options
• 🎯 GitHub Action - CI/CD integration (coming soon)
• 🤖 AI Integration - Claude, Cursor, Copilot
• 🏗️ Architecture - How it works
• 🤝 Contributing - Add languages, fix bugs, improve docs

Full documentation: docs/index.md

---

Why Hotspots?

vs ESLint Complexity Rules

ESLint: Checks individual metrics (CC > 10). No context about change frequency or real-world risk. Hotspots: Combines multiple metrics into LRS. Integrates git history. Prioritizes based on actual risk.

vs SonarQube / CodeClimate

SonarQube: Enterprise platform, complex setup, slow scans, requires server infrastructure. Hotspots: Single binary, instant analysis, zero config, works offline, git history built-in.

vs Code Reviews

Reviews: Catch complexity subjectively. Miss gradual regressions. Don't track trends. Hotspots: Objective metrics. Catches every change. Shows trends over time. Enforces policies automatically.

Use both: Hotspots + code reviews = comprehensive quality control.

---

Real-World Use Cases

🔥 Incident Prevention

"We had 3 production incidents in Q1. All originated from the same 5 functions. Hotspots flagged all 5 as critical. We refactored them in Q2. Zero incidents since."

🚀 Faster Onboarding

"New engineers use Hotspots to identify risky code before touching it. 'This function is LRS 11.2, be careful' = instant context."

🎯 Refactoring Sprints

"We allocate 1 sprint per quarter to reduce our top 10 hotspots. Dropped average LRS from 6.2 to 4.1 over 6 months."

🤖 AI-Guided Refactoring

"Feed hotspots JSON to Claude. It suggests refactorings for critical functions. Accept, commit, verify LRS dropped. Repeat."

⚖️ Technical Debt Metrics

"Execs ask 'How's our tech debt?' I show them: 23 critical functions (down from 31), average LRS 4.8 (down from 5.3). Clear progress."

---

Installation

Quick Install

cargo (Rust toolchain):

cargo install hotspots-cli

macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/Stephen-Collins-tech/hotspots/main/install.sh | sh

Installs to ~/.local/bin/hotspots. Verify with hotspots --version.

Install a specific version:

HOTSPOTS_VERSION=v1.0.0 curl -fsSL https://raw.githubusercontent.com/Stephen-Collins-tech/hotspots/main/install.sh | sh

Build from Source

git clone https://github.com/Stephen-Collins-tech/hotspots.git
cd hotspots
cargo build --release
mkdir -p ~/.local/bin
cp target/release/hotspots ~/.local/bin/

Requirements: Rust 1.75 or later

---

Contributing

We welcome contributions!

• 🐛 Report bugs
• 💡 Request features
• 🔧 Submit PRs
• 📖 Improve docs

Want to add a language? See docs/contributing/adding-languages.md - we have a proven pattern for adding TypeScript, JavaScript, Go, Python, Rust, and Java.

---

License

MIT License - see LICENSE-MIT for details.

---

Next Steps

1. ⚡ Install Hotspots (2 minutes)
2. 🔍 Run your first analysis: hotspots analyze src/
3. 🎯 Identify your top 10 hotspots
4. 🛠️ Refactor the worst offender
5. 📊 Add to CI/CD: hotspots analyze src/ --mode delta --policy (GitHub Action coming soon)
6. 🤖 Integrate with AI: AI Integration Guide

Questions? Open a GitHub Discussion.

Found a bug? Open an issue.

---

Stop refactoring guesswork. Start with Hotspots.