feat(cli): add --min-severity filtering option

ROADMAP.md

@@ -25,7 +25,7 @@
 ## v0.3.0 - Polish
 
 - [x] Python ecosystem support (`requirements.txt`, `pyproject.toml`)
-- [ ] Severity filtering (`--min-severity`)
+- [x] Severity filtering (`--min-severity`)
 - [ ] File/path exclusion patterns
 - [ ] Performance optimization for large repositories
 - [ ] More comprehensive test fixtures

src/cli/index.ts

@@ -27,12 +27,13 @@ Usage:
 
 Scan options:
   --json              Output findings as JSON
+  --min-severity <level>  Filter by minimum severity (info, warning, error)
 
 Examples:
   opk scan
   opk scan ./src
   opk scan --json
-  opk scan ./src --json`;
+  opk scan ./src --min-severity error`;
 
   process.stdout.write(help + '\n');
 }
@@ -66,15 +67,31 @@ async function main(): Promise<void> {
     }
 
     let scanPath = process.cwd();
+    let minSeverity: 'info' | 'warning' | 'error' = 'info';
+
     for (let i = 1; i < args.length; i++) {
       const arg = args[i];
-      if (arg !== '--json' && !arg.startsWith('-')) {
+      if (arg === '--min-severity') {
+        if (i + 1 < args.length) {
+          const val = args[i + 1];
+          if (val === 'info' || val === 'warning' || val === 'error') {
+            minSeverity = val;
+            i++; // skip value
+            continue;
+          } else {
+            process.stderr.write(`Error: Invalid --min-severity value: ${val}. Expected info, warning, or error.\n`);
+            process.exit(2);
+          }
+        } else {
+          process.stderr.write('Error: --min-severity requires a value (info, warning, or error).\n');
+          process.exit(2);
+        }
+      } else if (arg !== '--json' && !arg.startsWith('-')) {
         scanPath = path.resolve(arg);
-        break;
       }
     }
 
-    const result = await scan(scanPath);
+    const result = await scan(scanPath, minSeverity);
 
     if (useJson) {
       process.stdout.write(formatJson(result) + '\n');

src/scanner/index.ts

@@ -69,7 +69,10 @@ function loadConfig(rootDir: string): OpkConfig | null {
   }
 }
 
-export async function scan(rootDir: string): Promise<ScanResult> {
+export async function scan(
+  rootDir: string,
+  minSeverity: 'info' | 'warning' | 'error' = 'info'
+): Promise<ScanResult> {
   const startTime = Date.now();
   const absoluteRoot = path.resolve(rootDir);
 
@@ -112,8 +115,16 @@ export async function scan(rootDir: string): Promise<ScanResult> {
 
   const durationMs = Date.now() - startTime;
 
+  const severityLevels = { info: 0, warning: 1, error: 2 };
+  const minLevel = severityLevels[minSeverity] ?? 0;
+
+  const filteredFindings = allFindings.filter((finding) => {
+    const findingLevel = severityLevels[finding.severity] ?? 0;
+    return findingLevel >= minLevel;
+  });
+
   return {
-    findings: allFindings,
+    findings: filteredFindings,
     scannedFiles: files.length,
     rulesRun,
     durationMs,

tests/scanner/scanner.test.ts

@@ -14,4 +14,18 @@ test('Scanner Integration', async (t) => {
     // There are no other findings in this folder.
     assert.strictEqual(result.findings.length, 0);
   });
+
+  await t.test('should filter findings by minimum severity', async () => {
+    // We scan prompt-artifacts which contains OPK-002 (warning).
+    const rootDir = path.join(FIXTURES_DIR, 'prompt-artifacts');
+
+    // Default (info) should include warnings
+    const defaultResult = await scan(rootDir);
+    assert.ok(defaultResult.findings.length > 0);
+    assert.strictEqual(defaultResult.findings[0].severity, 'warning');
+
+    // Error minSeverity should filter out warnings
+    const errorResult = await scan(rootDir, 'error');
+    assert.strictEqual(errorResult.findings.length, 0);
+  });
 });