GRAMMAC1 · GRAMMAC1 · Jul 7, 2026 · Jul 7, 2026
diff --git a/benchmarks/reports/report.md b/benchmarks/reports/report.md
@@ -2,15 +2,15 @@
 
 - Cases: 7
 - Signal matches: 21/26
-- Average reduction: 60.8%
-- Average total MCP ratio: 39.2%
+- Average reduction: 59.3%
+- Average total MCP ratio: 40.7%
 
 | Case | Raw KB | Brief KB | Evidence KB | Total MCP KB | Reduction | Tool Calls | Confidence | Signal Hit | File Hit | Code Hit |
 |---|---:|---:|---:|---:|---:|---:|---:|---:|---:|---:|
-| dipper-react-module-not-found | 2.1 | 1.3 | 0.0 | 1.3 | 37.8% | 1 | 0.80 | 2/3 | 1/1 | n/a |
-| filament-tailwind-vite-build-failure | 4.5 | 1.8 | 0.0 | 1.8 | 60.8% | 1 | 0.80 | 3/3 | 1/1 | n/a |
+| dipper-react-module-not-found | 2.1 | 1.4 | 0.0 | 1.4 | 33.2% | 1 | 0.90 | 2/3 | 1/1 | n/a |
+| filament-tailwind-vite-build-failure | 4.5 | 1.9 | 0.0 | 1.9 | 57.3% | 1 | 0.90 | 3/3 | 1/1 | n/a |
 | frappe-hrms-vite-pwa-build-failure | 5.1 | 2.0 | 0.0 | 2.0 | 60.3% | 1 | 0.80 | 4/4 | 1/1 | n/a |
-| react-scan-next-build-failure | 5.0 | 1.3 | 0.0 | 1.3 | 74.9% | 1 | 0.90 | 0/4 | 2/2 | n/a |
+| react-scan-next-build-failure | 5.0 | 1.4 | 0.0 | 1.4 | 73.0% | 1 | 0.90 | 0/4 | 2/2 | n/a |
 | satellite-js-vite-build-failure | 13.1 | 3.4 | 0.0 | 3.4 | 73.7% | 1 | 0.90 | 4/4 | 1/1 | 1/1 |
 | svelte-vite-bindable-build-failure | 1.1 | 0.6 | 0.0 | 0.6 | 47.7% | 1 | 0.80 | 4/4 | 1/1 | 1/1 |
-| tanstack-vite-devtools-build-failure | 4.9 | 1.4 | 0.0 | 1.4 | 70.6% | 1 | 0.90 | 4/4 | 1/1 | n/a |
+| tanstack-vite-devtools-build-failure | 4.9 | 1.5 | 0.0 | 1.5 | 70.0% | 1 | 0.90 | 4/4 | 1/1 | n/a |
diff --git a/packages/core/src/plugin/registry.ts b/packages/core/src/plugin/registry.ts
@@ -1,4 +1,5 @@
 import { genericPlugin } from '../plugins/generic.js';
+import { reactPlugin } from '../plugins/react.js';
 import { typescriptPlugin } from '../plugins/typescript.js';
 import type { Error2FixPlugin, PluginRegistry } from '../types/plugin.js';
 
@@ -16,5 +17,5 @@ export function registerPlugin(
 }
 
 export function getDefaultPluginRegistry(): PluginRegistry {
-  return createPluginRegistry([typescriptPlugin, genericPlugin]);
+  return createPluginRegistry([typescriptPlugin, reactPlugin, genericPlugin]);
 }
diff --git a/packages/core/src/plugins/react.ts b/packages/core/src/plugins/react.ts
@@ -0,0 +1,272 @@
+import type { CoreAnalysisInput } from '../types/core.js';
+import type { Error2FixPlugin } from '../types/plugin.js';
+import {
+  normalizeDiagnosticMessage,
+  readAnalysisLogText,
+  unique,
+} from '../utils/text.js';
+
+type ReactFailureKind =
+  | 'hook_rule'
+  | 'hydration_mismatch'
+  | 'server_client_boundary'
+  | 'invalid_component'
+  | 'jsx_runtime'
+  | 'next_runtime'
+  | 'react_runtime';
+
+interface ReactDiagnostic {
+  kind: ReactFailureKind;
+  message: string;
+  file?: string;
+}
+
+interface ReactContext {
+  framework: 'react' | 'next' | 'unknown';
+  configFiles: string[];
+  componentFiles: string[];
+}
+
+interface ReactData {
+  diagnostics: ReactDiagnostic[];
+  failureKinds: ReactFailureKind[];
+}
+
+const REACT_FILE_PATTERN = /\.(tsx|jsx)$/;
+const FRONTEND_SOURCE_PATTERN = /\.(ts|tsx|js|jsx|mjs|cjs)$/;
+const REACT_CONFIG_PATTERN =
+  /^(next|vite|vitest|jest|tailwind|postcss)\.config\.(ts|mts|cts|js|mjs|cjs)$/;
+
+function isProjectSourceFile(file: string): boolean {
+  return (
+    FRONTEND_SOURCE_PATTERN.test(file) &&
+    !/node_modules|\.next|dist|build/.test(file)
+  );
+}
+
+function hasReactSignal(input: CoreAnalysisInput): boolean {
+  const text = readAnalysisLogText(input);
+  return (
+    /\b(?:React|Next\.js|Next|JSX|hydration|Hydration|hook|Hook|Server Component|Client Component)\b/.test(
+      text,
+    ) ||
+    /ReactServerComponentsError|Invalid hook call|Objects are not valid as a React child|Element type is invalid/.test(
+      text,
+    ) ||
+    (input.signals.relatedFiles.some((file) => REACT_FILE_PATTERN.test(file)) &&
+      /\b(?:render|component|props|hook|hydration|jsx)\b/i.test(text)) ||
+    input.workspace.files.some((file) => file.startsWith('next.config.'))
+  );
+}
+
+function detectFramework(input: CoreAnalysisInput): ReactContext['framework'] {
+  const text = readAnalysisLogText(input);
+  if (
+    /\b(?:Next\.js|next\/|ReactServerComponentsError|Server Component|Client Component)\b/.test(
+      text,
+    ) ||
+    input.workspace.files.some((file) => file.startsWith('next.config.'))
+  ) {
+    return 'next';
+  }
+  if (/\bReact\b/.test(text)) {
+    return 'react';
+  }
+  return 'unknown';
+}
+
+function firstRelatedSourceFile(input: CoreAnalysisInput): string | undefined {
+  return (
+    input.signals.relatedFiles.find((file) => REACT_FILE_PATTERN.test(file)) ??
+    input.signals.relatedFiles.find(isProjectSourceFile)
+  );
+}
+
+function addDiagnostic(
+  diagnostics: ReactDiagnostic[],
+  input: CoreAnalysisInput,
+  kind: ReactFailureKind,
+  pattern: RegExp,
+): void {
+  const text = readAnalysisLogText(input);
+  const match = text.match(pattern);
+  if (!match) {
+    return;
+  }
+
+  diagnostics.push({
+    kind,
+    message: normalizeDiagnosticMessage(match[0]),
+    file: firstRelatedSourceFile(input),
+  });
+}
+
+function extractDiagnostics(input: CoreAnalysisInput): ReactDiagnostic[] {
+  const diagnostics: ReactDiagnostic[] = [];
+
+  addDiagnostic(
+    diagnostics,
+    input,
+    'hook_rule',
+    /(?:Invalid hook call|Hooks can only be called inside[^.\n]*|React Hook [^\n]+(?:is called conditionally|has a missing dependency|cannot be called))/i,
+  );
+  addDiagnostic(
+    diagnostics,
+    input,
+    'hydration_mismatch',
+    /(?:Hydration failed[^\n]*|hydration mismatch[^\n]*|Text content did not match[^\n]*|server rendered HTML didn't match[^\n]*)/i,
+  );
+  addDiagnostic(
+    diagnostics,
+    input,
+    'server_client_boundary',
+    /(?:(?:You're importing|You are importing)[^\n]+(?:useState|useEffect|useLayoutEffect|useReducer)[^\n]*|needs ["']use client["'][^\n]*|Event handlers cannot be passed to Client Component props[^\n]*|ReactServerComponentsError[^\n]*)/i,
+  );
+  addDiagnostic(
+    diagnostics,
+    input,
+    'invalid_component',
+    /(?:Element type is invalid[^\n]*|Objects are not valid as a React child[^\n]*|Functions are not valid as a React child[^\n]*|Minified React error #\d+[^\n]*)/i,
+  );
+  addDiagnostic(
+    diagnostics,
+    input,
+    'jsx_runtime',
+    /(?:React is not defined[^\n]*|jsx-runtime[^\n]*|Cannot use JSX[^\n]*|Adjacent JSX elements must be wrapped[^\n]*)/i,
+  );
+  addDiagnostic(
+    diagnostics,
+    input,
+    'next_runtime',
+    /(?:next\/(?:font|image|navigation|headers)[^\n]*|Failed to compile[^\n]*Next[^\n]*|Error occurred prerendering page[^\n]*)/i,
+  );
+
+  if (diagnostics.length === 0 && hasReactSignal(input)) {
+    const fallbackLine = readAnalysisLogText(input)
+      .split(/\r?\n/)
+      .map((line) => line.trim())
+      .find((line) =>
+        /\b(?:React|Next|JSX|component|render|hydration|hook)\b/i.test(line),
+      );
+    diagnostics.push({
+      kind: 'react_runtime',
+      message: normalizeDiagnosticMessage(
+        fallbackLine ?? 'React-related failure detected.',
+      ),
+      file: firstRelatedSourceFile(input),
+    });
+  }
+
+  return unique(
+    diagnostics.map((diagnostic) =>
+      JSON.stringify({
+        kind: diagnostic.kind,
+        message: diagnostic.message,
+        file: diagnostic.file,
+      }),
+    ),
+  )
+    .map((diagnostic) => JSON.parse(diagnostic) as ReactDiagnostic)
+    .slice(0, 5);
+}
+
+function formatDiagnostic(diagnostic: ReactDiagnostic): string {
+  const location = diagnostic.file ? ` in ${diagnostic.file}` : '';
+  return `React ${diagnostic.kind.replaceAll('_', ' ')}${location}: ${diagnostic.message}`;
+}
+
+function buildKeySnippet(
+  input: CoreAnalysisInput,
+  diagnostics: ReactDiagnostic[],
+): string | undefined {
+  const first = diagnostics[0];
+  if (!first) {
+    return input.signals.snippet;
+  }
+
+  const lines = readAnalysisLogText(input).split(/\r?\n/);
+  const diagnosticIndex = lines.findIndex((line) =>
+    line.toLowerCase().includes(first.message.toLowerCase().slice(0, 48)),
+  );
+  if (diagnosticIndex === -1) {
+    return input.signals.snippet;
+  }
+
+  return lines
+    .slice(diagnosticIndex, diagnosticIndex + 4)
+    .map((line) => line.trimEnd())
+    .join('\n')
+    .trim();
+}
+
+function buildSuggestions(diagnostics: ReactDiagnostic[]): string[] {
+  const suggestions = diagnostics.map((diagnostic) => {
+    switch (diagnostic.kind) {
+      case 'hook_rule':
+        return 'Check that hooks run unconditionally inside React function components or custom hooks, not inside callbacks, branches, or module scope.';
+      case 'hydration_mismatch':
+        return 'Compare server-rendered and client-rendered output, especially browser-only state, dates, randomness, locale formatting, and conditional markup.';
+      case 'server_client_boundary':
+        return 'Move interactive React code behind a client component boundary or add the required "use client" directive at the correct component entry.';
+      case 'invalid_component':
+        return 'Check component imports/exports and rendered children; this often comes from default/named import mismatches or rendering plain objects.';
+      case 'jsx_runtime':
+        return 'Check JSX runtime configuration, React import expectations, and framework compiler settings.';
+      case 'next_runtime':
+        return 'Inspect the referenced Next.js route, app/page component, or Next-specific API usage before chasing framework stack frames.';
+      default:
+        return 'Open the first referenced React component and inspect the component boundary, props, and render path.';
+    }
+  });
+
+  return unique([
+    ...suggestions,
+    'Prefer the first application component frame over React or Next.js internals.',
+  ]).slice(0, 5);
+}
+
+export const reactPlugin: Error2FixPlugin<ReactContext, ReactData> = {
+  meta: {
+    name: 'builtin-react',
+    displayName: 'React',
+  },
+  detect(input) {
+    return hasReactSignal(input);
+  },
+  collectContext(input) {
+    return {
+      framework: detectFramework(input),
+      configFiles: input.workspace.files.filter((file) =>
+        REACT_CONFIG_PATTERN.test(file),
+      ),
+      componentFiles: input.signals.relatedFiles
+        .filter((file) => REACT_FILE_PATTERN.test(file))
+        .slice(0, 8),
+    };
+  },
+  analyze(input, context) {
+    const diagnostics = extractDiagnostics(input);
+    const relatedFiles = unique([
+      ...diagnostics.flatMap((diagnostic) =>
+        diagnostic.file ? [diagnostic.file] : [],
+      ),
+      ...input.signals.relatedFiles.filter(isProjectSourceFile),
+    ]).slice(0, 8);
+
+    return {
+      plugin: 'builtin-react',
+      matched: true,
+      summary: diagnostics[0]
+        ? formatDiagnostic(diagnostics[0])
+        : 'React-related failure detected from frontend log evidence.',
+      keySnippet: buildKeySnippet(input, diagnostics),
+      relatedFiles,
+      context,
+      data: {
+        diagnostics,
+        failureKinds: unique(diagnostics.map((diagnostic) => diagnostic.kind)),
+      },
+      suggestions: buildSuggestions(diagnostics),
+    };
+  },
+};
diff --git a/packages/core/src/plugins/typescript.ts b/packages/core/src/plugins/typescript.ts
@@ -1,5 +1,10 @@
 import type { CoreAnalysisInput } from '../types/core.js';
 import type { Error2FixPlugin } from '../types/plugin.js';
+import {
+  normalizeDiagnosticMessage,
+  readAnalysisLogText,
+  unique,
+} from '../utils/text.js';
 
 type TypeScriptFailureKind =
   | 'module_resolution'
@@ -37,34 +42,19 @@ const TS_CODE_PATTERN = /\bTS\d{3,5}\b/;
 const FRONTEND_TS_CONFIG_PATTERN =
   /^(vite|next|nuxt|vitest|jest|tailwind|postcss)\.config\.(ts|mts|cts|js|mjs|cjs)$/;
 
-function unique<T>(values: T[]): T[] {
-  return [...new Set(values)];
-}
-
-function readLogText(input: CoreAnalysisInput): string {
-  return [input.capture.stderr, input.capture.stdout, input.signals.snippet]
-    .filter(Boolean)
-    .join('\n');
-}
-
 function hasTypeScriptSignal(input: CoreAnalysisInput): boolean {
-  const text = readLogText(input);
+  const text = readAnalysisLogText(input);
   return (
     TS_CODE_PATTERN.test(text) ||
     /\b(?:tsc|vue-tsc|tsserver|typescript)\b/i.test(text) ||
     input.signals.keywords.some((keyword) => /^TS\d{3,5}$/.test(keyword)) ||
-    input.signals.relatedFiles.some((file) => TS_FILE_PATTERN.test(file)) ||
-    input.workspace.files.some((file) => file === 'tsconfig.json')
+    (input.signals.relatedFiles.some((file) => TS_FILE_PATTERN.test(file)) &&
+      /\b(?:type|typescript|tsc|TS\d{3,5})\b/i.test(text)) ||
+    (input.workspace.files.some((file) => file === 'tsconfig.json') &&
+      /\b(?:type|typescript|tsc|TS\d{3,5})\b/i.test(text))
   );
 }
 
-function normalizeMessage(message: string): string {
-  return message
-    .trim()
-    .replace(/\s+/g, ' ')
-    .replace(/[.;\s]+$/g, '.');
-}
-
 function classifyDiagnostic(
   code: string,
   message: string,
@@ -172,15 +162,15 @@ function parseLocation(
 }
 
 function extractDiagnostics(input: CoreAnalysisInput): TypeScriptDiagnostic[] {
-  const text = readLogText(input);
+  const text = readAnalysisLogText(input);
   const diagnostics: TypeScriptDiagnostic[] = [];
   const seen = new Set<string>();
   const diagnosticPattern =
     /(?:(?<location>(?:\.{0,2}\/)?(?:[\w@%+=:,.-]+\/)*[\w@%+=,.-]+\.(?:ts|tsx|mts|cts|vue)(?::\d+:\d+|\(\d+,\d+\)))\s*(?:-|:)?\s*)?(?:error\s+)?(?<code>TS\d{3,5}):\s*(?<message>[^\n]+)/gi;
 
   for (const match of text.matchAll(diagnosticPattern)) {
     const code = match.groups?.code.toUpperCase();
-    const message = normalizeMessage(match.groups?.message ?? '');
+    const message = normalizeDiagnosticMessage(match.groups?.message ?? '');
     if (!code || !message) {
       continue;
     }
@@ -241,7 +231,7 @@ function buildKeySnippet(
   input: CoreAnalysisInput,
   diagnostics: TypeScriptDiagnostic[],
 ): string | undefined {
-  const text = readLogText(input);
+  const text = readAnalysisLogText(input);
   const first = diagnostics[0];
   if (!first) {
     return input.signals.snippet;