diff --git a/README.md b/README.md
index ae4e889..b1827ea 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,7 @@ Scan your codebase to detect which environment variables are used in your code.
 Optimized for SvelteKit and Next.js. </br>
 Also works well in modern JavaScript/TypeScript projects and frameworks like Node.js, Nuxt, and Vue — or any other setup where you want reliable .env file comparison / scanning.
 
+![CI](https://github.com/chrilleweb/dotenv-diff/actions/workflows/ci.yml/badge.svg)
 [![npm version](https://img.shields.io/npm/v/dotenv-diff.svg)](https://www.npmjs.com/package/dotenv-diff)
 [![npm downloads](https://img.shields.io/npm/dt/dotenv-diff.svg)](https://www.npmjs.com/package/dotenv-diff)
 
@@ -347,12 +348,19 @@ This makes it quick to set up environment files without manually copying or rety
 `dotenv-diff` will warn you if your `.env` file is **not** ignored by Git.  
 This helps prevent accidentally committing sensitive environment variables.
 
+## Exit codes
+
+- `0` → No errors (warnings may be present unless `--strict`)
+- `1` → Errors found (or warnings when using `--strict`)
+
 ## 🤝 Contributing
 
-Contributions are welcome! Feel free to open an issue or a pull request.
+Issues, feature requests and pull requests are welcome.
+
+If you plan a larger change, please open an issue first to discuss scope and approach.
 
 ## License
 
-MIT
+Licensed under the [MIT](LICENSE) license.
 
 ### Created by [chrilleweb](https://github.com/chrilleweb)
\ No newline at end of file
diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000..2981dc9
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,5 @@
+# Security Policy
+
+If you discover a security vulnerability, please report it responsibly.
+
+Send us an email to christian.munknissen@gmail.com and **don't** open a public issue.
diff --git a/package.json b/package.json
index 11f0eaa..f8e36bf 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "dotenv-diff",
   "version": "2.3.11",
   "type": "module",
-  "description": "Scan your codebase to find environment variables in use.",
+  "description": "Detects environment variable issues, usage, and potential security risks.",
   "bin": {
     "dotenv-diff": "dist/bin/dotenv-diff.js"
   },
@@ -40,11 +40,17 @@
     "dotenv",
     "env",
     "dotenv-diff",
+    "env-check",
+    "env-validate",
+    "env-scan",
     "cli",
-    "compare",
-    "environment variables",
-    "dotenv validator",
-    "scan codebase"
+    "config",
+    "security",
+    "ci",
+    "monorepo",
+    "sveltekit",
+    "nextjs",
+    "node"
   ],
   "repository": {
     "type": "git",
diff --git a/src/cli/run.ts b/src/cli/run.ts
index ea0c23b..3119bbf 100644
--- a/src/cli/run.ts
+++ b/src/cli/run.ts
@@ -3,7 +3,7 @@ import fs from 'fs';
 import path from 'path';
 import { normalizeOptions } from '../config/options.js';
 import { discoverEnvFiles } from '../services/envDiscovery.js';
-import { pairWithExample } from '../services/envPairing.js';
+import { pairWithExample } from '../core/envPairing.js';
 import { ensureFilesOrPrompt } from '../services/ensureFilesOrPrompt.js';
 import { compareMany } from '../commands/compare.js';
 import {
diff --git a/src/core/determineComparisonFile.ts b/src/core/determineComparisonFile.ts
index 7518e01..5785251 100644
--- a/src/core/determineComparisonFile.ts
+++ b/src/core/determineComparisonFile.ts
@@ -3,14 +3,26 @@ import path from 'path';
 import { type ScanUsageOptions } from '../config/types.js';
 import { resolveFromCwd } from './helpers/resolveFromCwd.js';
 
+type ComparisonFile = {
+  path: string;
+  name: string;
+};
+
+const DEFAULT_ENV_FILES = [
+  '.env',
+  '.env.example',
+  '.env.local',
+  '.env.production',
+] as const;
+
 /**
  * Determines which file to use for comparison based on provided options
  * @param {ScanUsageOptions} opts - Scan configuration options
- * @returns {Object|null} - The comparison file information or undefined if not found
+ * @returns Comparison file info with absolute path and basename, or undefined if not found
  */
 export function determineComparisonFile(
   opts: ScanUsageOptions,
-): { path: string; name: string } | undefined {
+): ComparisonFile | undefined {
   // Priority: explicit flags first, then auto-discovery
 
   if (opts.examplePath) {
@@ -28,8 +40,7 @@ export function determineComparisonFile(
   }
 
   // Auto-discovery: look for common env files relative to cwd
-  const candidates = ['.env', '.env.example', '.env.local', '.env.production'];
-  for (const candidate of candidates) {
+  for (const candidate of DEFAULT_ENV_FILES) {
     const fullPath = path.resolve(opts.cwd, candidate);
     if (fs.existsSync(fullPath)) {
       return { path: fullPath, name: candidate };
diff --git a/src/services/envPairing.ts b/src/core/envPairing.ts
similarity index 81%
rename from src/services/envPairing.ts
rename to src/core/envPairing.ts
index 9679d28..9267d57 100644
--- a/src/services/envPairing.ts
+++ b/src/core/envPairing.ts
@@ -1,20 +1,15 @@
 import fs from 'fs';
 import path from 'path';
-import type { Discovery } from './envDiscovery.js';
+import type { Discovery } from '../services/envDiscovery.js';
+import type { FilePair } from '../config/types.js';
 
 /**
  * Pairs each environment file with its corresponding example file.
  * @param d - The discovery object containing environment and example file information.
  * @returns An array of objects containing the environment name, path, and example path.
  */
-export function pairWithExample(
-  d: Discovery,
-): Array<{ envName: string; envPath: string; examplePath: string }> {
-  const pairs: Array<{
-    envName: string;
-    envPath: string;
-    examplePath: string;
-  }> = [];
+export function pairWithExample(d: Discovery): Array<FilePair> {
+  const pairs: Array<FilePair> = [];
   const list = d.envFiles.length > 0 ? d.envFiles : [d.primaryEnv];
 
   for (const envName of list) {
diff --git a/src/services/duplicates.ts b/src/services/duplicates.ts
index 4b60cd8..c52ce08 100644
--- a/src/services/duplicates.ts
+++ b/src/services/duplicates.ts
@@ -1,4 +1,5 @@
 import fs from 'fs';
+import type { Duplicate } from '../config/types.js';
 
 /**
  * Scan a .env-like file for duplicate keys.
@@ -9,9 +10,7 @@ import fs from 'fs';
  * @param filePath - Path to the .env file to scan
  * @returns An array of objects representing duplicate keys and their counts.
  */
-export function findDuplicateKeys(
-  filePath: string,
-): Array<{ key: string; count: number }> {
+export function findDuplicateKeys(filePath: string): Array<Duplicate> {
   if (!fs.existsSync(filePath)) return [];
 
   const raw = fs.readFileSync(filePath, 'utf8');
@@ -32,7 +31,7 @@ export function findDuplicateKeys(
     counts.set(key, (counts.get(key) ?? 0) + 1);
   }
 
-  const duplicates: Array<{ key: string; count: number }> = [];
+  const duplicates: Array<Duplicate> = [];
   for (const [key, count] of counts) {
     if (count > 1) duplicates.push({ key, count });
   }
diff --git a/src/services/fileWalker.ts b/src/services/fileWalker.ts
index 1fb0ed2..1ea0c31 100644
--- a/src/services/fileWalker.ts
+++ b/src/services/fileWalker.ts
@@ -6,6 +6,12 @@ import {
   DEFAULT_EXCLUDE_PATTERNS,
 } from '../core/patterns.js';
 
+interface FindFilesOptions {
+  include?: string[];
+  exclude?: string[];
+  files?: string[];
+}
+
 /**
  * Recursively finds all files in the given directory matching the include patterns,
  * while excluding files and directories that match the exclude patterns.
@@ -15,7 +21,7 @@ import {
  */
 export async function findFiles(
   rootDir: string,
-  opts: { include: string[]; exclude: string[]; files?: string[] },
+  opts: FindFilesOptions,
 ): Promise<string[]> {
   // If --files provided, keep existing replacement behavior
   if (opts.files && opts.files.length > 0) {
@@ -24,7 +30,7 @@ export async function findFiles(
 
   const defaultPatterns = getDefaultPatterns();
   const rawInclude =
-    opts.include.length > 0
+    opts.include && opts.include.length > 0
       ? [...defaultPatterns, ...opts.include]
       : defaultPatterns;
   const includePatterns = rawInclude.flatMap(expandBraceSets);
@@ -69,7 +75,7 @@ export async function findFiles(
       if (
         shouldExclude(entry.name, relativeToRoot, [
           ...DEFAULT_EXCLUDE_PATTERNS,
-          ...opts.exclude,
+          ...(opts.exclude ?? []),
         ])
       ) {
         continue;
diff --git a/src/services/scanOutputToConsole.ts b/src/services/scanOutputToConsole.ts
index e95be8a..0565602 100644
--- a/src/services/scanOutputToConsole.ts
+++ b/src/services/scanOutputToConsole.ts
@@ -24,6 +24,13 @@ import { printHealthScore } from '../ui/scan/printHealthScore.js';
 import { printExpireWarnings } from '../ui/scan/printExpireWarnings.js';
 import { printInconsistentNamingWarning } from '../ui/scan/printInconsistentNamingWarning.js';
 
+interface FixContext {
+  fixApplied: boolean;
+  removedDuplicates: string[];
+  addedEnv: string[];
+  gitignoreUpdated: boolean;
+}
+
 /**
  * Outputs the scan results to the console.
  * @param scanResult - The result of the scan.
@@ -35,12 +42,7 @@ export function outputToConsole(
   scanResult: ScanResult,
   opts: ScanUsageOptions,
   comparedAgainst: string,
-  fixContext?: {
-    fixApplied: boolean;
-    removedDuplicates: string[];
-    addedEnv: string[];
-    gitignoreUpdated: boolean;
-  },
+  fixContext?: FixContext,
 ): { exitWithError: boolean } {
   let exitWithError = false;