feat(llm-security)!: v7.0.0 commit 2 — context-aware entropy scanner

Observed 70% false-positive rate on renderer/shader codebases (hyperframes):
GLSL, CSS-in-JS, inline HTML/SVG, ffmpeg filter-strings, hardcoded
User-Agent strings all matched base64-like entropy thresholds. This
commit adds two suppression layers before classification.

Layer A — file-extension skip: .glsl/.frag/.vert/.shader/.wgsl (shaders),
.css/.scss/.sass/.less (stylesheets), .svg (markup), .min.js/.min.css
(minified bundles). Tracked via new calibration.files_skipped_by_extension
field on scanner envelope for synthesizer stats.

Layer B — seven new line-level suppression rules in isFalsePositive()
(rules 11-17): GLSL/WGSL keywords, CSS-in-JS (styled/emotion/@keyframes),
inline HTML/SVG markup, ffmpeg filter-graph syntax, browser User-Agent,
SQL DDL/DML, error-message templates with embedded HTML.

Existing entropy.test.mjs: 9/9 still green — known bad base64 payload in
telemetry.mjs fixture still detected. Policy-driven thresholds wired in
Commit 3.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugins/llm-security/scanners/entropy-scanner.mjs

@@ -15,6 +15,31 @@ import { finding, scannerResult } from './lib/output.mjs';
 import { SEVERITY } from './lib/severity.mjs';
 import { shannonEntropy, extractStringLiterals, isBase64Like, isHexBlob, redact } from './lib/string-utils.mjs';
 
+// ---------------------------------------------------------------------------
+// File-extension suppression (context-aware, v7.0.0+)
+// ---------------------------------------------------------------------------
+
+/**
+ * Extensions whose contents are almost always benign high-entropy noise:
+ * GPU shaders, stylesheets, SVG markup. Scanning these produces massive
+ * false-positive rates (observed 70% FP on hyperframes renderer codebase).
+ */
+const ENTROPY_SKIP_EXTENSIONS = new Set([
+  '.glsl', '.frag', '.vert', '.shader', '.wgsl',  // GPU shaders
+  '.css', '.scss', '.sass', '.less',              // stylesheets
+  '.svg',                                          // SVG markup
+]);
+
+/**
+ * @param {{ relPath: string, ext: string }} fileInfo
+ * @returns {boolean} true if the file should be skipped entirely
+ */
+function shouldSkipByExtension(fileInfo) {
+  const lowerPath = (fileInfo.relPath || '').toLowerCase();
+  if (lowerPath.endsWith('.min.js') || lowerPath.endsWith('.min.css')) return true;
+  return ENTROPY_SKIP_EXTENSIONS.has((fileInfo.ext || '').toLowerCase());
+}
+
 // ---------------------------------------------------------------------------
 // Constants
 // ---------------------------------------------------------------------------
@@ -75,6 +100,27 @@ const UUID_PATTERN = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{
 /** Pure lowercase hex that could be a hash digest (not obfuscated code). */
 const HEX_HASH_PATTERN = /^[a-f0-9]{32,128}$/i;
 
+/** GLSL/WGSL shader keywords — suppress inline shader source (gl_Position, vec3, uniform, ...). */
+const GLSL_KEYWORDS = /\b(?:gl_(?:Position|FragColor|FragCoord|PointSize|PointCoord)|vec[234]|mat[234]|uniform|varying|attribute|precision\s+(?:high|medium|low)p|smoothstep|mix|clamp|texture2D|textureCube|sampler[123]D)\b/;
+
+/** CSS-in-JS patterns (styled-components, emotion, vanilla-extract, @keyframes). */
+const CSS_IN_JS_PATTERN = /\b(?:styled\.[a-z]+|css)\s*`|@(?:keyframes|media|supports)\s|:\s*(?:hover|focus|active|before|after|visited|root)\b/;
+
+/** Inline HTML/SVG markup in source (tags with attributes on the same line). */
+const INLINE_MARKUP = /<(?:svg|path|defs|g\s|rect\s|circle\s|polygon|polyline|ellipse|line\s|use\s|symbol\s|clipPath|linearGradient|radialGradient|div\s+[a-z-]+|span\s+[a-z-]+|style>|script>|template\s)/i;
+
+/** ffmpeg filter-graph syntax (stream selectors + filter chains). */
+const FFMPEG_SYNTAX = /\[\d+:[avs]\]|(?:scale|crop|concat|overlay|psnr|drawtext|setpts|atempo|filter_complex|format|pad|trim|setdar|setsar)\s*=/;
+
+/** Browser User-Agent strings (hardcoded in source — long but structured, not encoded). */
+const USER_AGENT_PATTERN = /Mozilla\/\d|AppleWebKit|Chrome\/\d+|Safari\/\d+|Firefox\/\d+|Edg\/\d+|OPR\/\d+/;
+
+/** SQL DDL/DML statements (long structured strings, not encoded payloads). */
+const SQL_STATEMENT = /^\s*(?:SELECT|INSERT|UPDATE|DELETE|CREATE|ALTER|WITH|DROP|TRUNCATE|GRANT|REVOKE)\s+/i;
+
+/** Error-message templates with embedded HTML/markup (throw new Error("<div>...</div>")). */
+const ERROR_TEMPLATE = /(?:throw\s+new\s+(?:Error|TypeError|RangeError|SyntaxError)|new\s+Error\s*\()\s*[`'"]/;
+
 // ---------------------------------------------------------------------------
 // False-positive suppression helpers
 // ---------------------------------------------------------------------------
@@ -133,6 +179,27 @@ function isFalsePositive(str, line, absPath) {
     if (str.startsWith(prefix)) return true;
   }
 
+  // 11. GLSL/WGSL shader keywords on the line — inline shader source
+  if (GLSL_KEYWORDS.test(line)) return true;
+
+  // 12. CSS-in-JS (styled-components, emotion, vanilla-extract)
+  if (CSS_IN_JS_PATTERN.test(line)) return true;
+
+  // 13. Inline HTML/SVG markup — React/Vue components, email templates
+  if (INLINE_MARKUP.test(line)) return true;
+
+  // 14. ffmpeg filter-graph syntax — long structured strings, not encoded
+  if (FFMPEG_SYNTAX.test(line)) return true;
+
+  // 15. Browser User-Agent strings — hardcoded but structured, not a payload
+  if (USER_AGENT_PATTERN.test(line)) return true;
+
+  // 16. SQL DDL/DML — long SELECT/INSERT/... lines
+  if (SQL_STATEMENT.test(line)) return true;
+
+  // 17. Error-message templates (throw new Error("<html>...</html>"))
+  if (ERROR_TEMPLATE.test(line)) return true;
+
   return false;
 }
 
@@ -298,8 +365,17 @@ export async function scan(targetPath, discovery) {
   const allFindings = [];
   let filesScanned = 0;
 
+  let filesSkippedByExtension = 0;
+
   try {
     for (const fileInfo of discovery.files) {
+      // Context-aware skip: GPU shaders, stylesheets, SVG, minified bundles.
+      // These file types produce ~70% false-positive rate on real codebases.
+      if (shouldSkipByExtension(fileInfo)) {
+        filesSkippedByExtension++;
+        continue;
+      }
+
       const content = await readTextFile(fileInfo.absPath);
 
       // readTextFile returns null for binary files or unreadable paths — skip silently
@@ -314,7 +390,13 @@ export async function scan(targetPath, discovery) {
     const durationMs = Date.now() - startMs;
     const status = 'ok';
 
-    return scannerResult('entropy-scanner', status, allFindings, filesScanned, durationMs);
+    const result = scannerResult('entropy-scanner', status, allFindings, filesScanned, durationMs);
+    // Calibration stats for synthesizer — how many files the ext-policy excluded.
+    result.calibration = {
+      files_skipped_by_extension: filesSkippedByExtension,
+      skip_extensions: [...ENTROPY_SKIP_EXTENSIONS, '.min.js', '.min.css'],
+    };
+    return result;
   } catch (err) {
     const durationMs = Date.now() - startMs;
     return scannerResult(