diff --git a/e2e/search.spec.ts b/e2e/search.spec.ts
index 21d2b31..d64ec3e 100644
--- a/e2e/search.spec.ts
+++ b/e2e/search.spec.ts
@@ -1,4 +1,28 @@
-import { test, expect } from '@playwright/test';
+import { test, expect, Page } from '@playwright/test';
+
+const SEARCH_QUEUE_KEY = 'obsiviewer.searchdiag.queue';
+
+async function clearDiagnostics(page: Page): Promise<void> {
+  await page.evaluate(key => {
+    localStorage.removeItem(key);
+  }, SEARCH_QUEUE_KEY);
+}
+
+async function readDiagnostics(page: Page): Promise<any[]> {
+  const raw = await page.evaluate(key => localStorage.getItem(key), SEARCH_QUEUE_KEY);
+  if (!raw) {
+    return [];
+  }
+  try {
+    return JSON.parse(raw);
+  } catch {
+    return [];
+  }
+}
+
+function findStage(events: any[], stage: string): any | undefined {
+  return events.find(event => event?.stage === stage);
+}
 
 test.describe('Search Functionality', () => {
   test.beforeEach(async ({ page }) => {
@@ -69,16 +93,43 @@ test.describe('Search Functionality', () => {
   });
 
   test('should filter by tag', async ({ page }) => {
+    await clearDiagnostics(page);
     const searchInput = page.locator('input[type="text"]').first();
-    
+
     await searchInput.fill('tag:#work');
     await searchInput.press('Enter');
-    
+
     await page.waitForTimeout(1000);
     
     // Should show results with #work tag
     const results = page.locator('.search-result');
     await expect(results.first()).toBeVisible({ timeout: 5000 });
+
+    const events = await readDiagnostics(page);
+    const summary = findStage(events, 'SEARCH_DIAG_SUMMARY');
+    expect(summary).toBeTruthy();
+    expect(summary.data?.counts?.displayed).toBeGreaterThan(0);
+    expect(summary.data?.userVisible?.emptyStateShown).toBe(false);
+  });
+
+  test('should record diagnostics when tag search misses index', async ({ page }) => {
+    await clearDiagnostics(page);
+    const searchInput = page.locator('input[type="text"]').first();
+
+    await searchInput.fill('tag:#home');
+    await searchInput.press('Enter');
+
+    await page.waitForTimeout(500);
+
+    const events = await readDiagnostics(page);
+    const summary = findStage(events, 'SEARCH_DIAG_SUMMARY');
+    expect(summary).toBeTruthy();
+    expect(summary.data?.counts?.displayed ?? 0).toBe(0);
+    expect(summary.data?.userVisible?.emptyStateShown).toBe(true);
+
+    const resultMap = findStage(events, 'SEARCH_DIAG_RESULT_MAP');
+    expect(resultMap).toBeTruthy();
+    expect(resultMap.data?.reasonsEmpty).toEqual(expect.arrayContaining(['tagNotInIndex']));
   });
 
   test('should toggle case sensitivity', async ({ page }) => {
diff --git a/src/app/core/logging/log.service.ts b/src/app/core/logging/log.service.ts
new file mode 100644
index 0000000..280b07f
--- /dev/null
+++ b/src/app/core/logging/log.service.ts
@@ -0,0 +1,513 @@
+import { Injectable, PLATFORM_ID, inject } from '@angular/core';
+import { isPlatformBrowser } from '@angular/common';
+import { environment } from '../../../core/logging/environment';
+import { SearchDiagEvent, SearchDiagRecord } from './search-log.model';
+
+const SESSION_STORAGE_KEY = 'obsiviewer.searchdiag.sessionId';
+const LOCAL_STORAGE_QUEUE_KEY = 'obsiviewer.searchdiag.queue';
+const SAMPLE_DECISIONS_LIMIT = 1000;
+const MAX_DATA_SIZE = 5 * 1024; // 5KB
+const LARGE_ARRAY_LIMIT = 200;
+
+type SearchLogLevel = 'info' | 'warn' | 'error';
+
+interface SanitizedDictionary {
+  [key: string]: SanitizedValue;
+}
+
+type SanitizedValue =
+  | string
+  | number
+  | boolean
+  | null
+  | undefined
+  | SanitizedValue[]
+  | SanitizedDictionary;
+
+type Dictionary<T = unknown> = Record<string, T>;
+
+@Injectable({ providedIn: 'root' })
+export class SearchLogService {
+  private readonly platformId = inject(PLATFORM_ID);
+  private readonly isBrowser = isPlatformBrowser(this.platformId);
+
+  private readonly config = environment.logging;
+  private readonly sessionId = this.ensureSessionId();
+
+  private queue: SearchDiagRecord[] = [];
+  private flushTimer?: ReturnType<typeof setTimeout>;
+  private consecutiveFailures = 0;
+  private circuitBreakerOpenUntil = 0;
+  private isFlushing = false;
+
+  private readonly correlationQueries = new Map<string, string>();
+  private readonly sampleDecisions = new Map<string, boolean>();
+
+  constructor() {
+    if (this.isBrowser) {
+      this.loadQueueFromStorage();
+      if (typeof window !== 'undefined') {
+        window.addEventListener('online', () => this.scheduleFlush());
+        window.addEventListener('beforeunload', () => this.flushSync());
+      }
+    }
+  }
+
+  logSearch(
+    stage: SearchDiagEvent,
+    data: Record<string, unknown>,
+    level: SearchLogLevel = 'info',
+    correlationId?: string
+  ): string {
+    if (!this.isBrowser || !this.config.enabled) {
+      return correlationId ?? '';
+    }
+
+    const effectiveCorrelationId = correlationId || this.generateUUID();
+
+    if (!this.shouldSample(effectiveCorrelationId)) {
+      return effectiveCorrelationId;
+    }
+
+    const queryRaw = this.extractQueryRaw(effectiveCorrelationId, stage, data);
+
+    const record: SearchDiagRecord = {
+      ts: new Date().toISOString(),
+      app: 'ObsiViewer',
+      sessionId: this.sessionId,
+      level,
+      correlationId: effectiveCorrelationId,
+      queryRaw,
+      context: this.buildContext(),
+      stage,
+      data: this.prepareData(stage, data),
+      userAgent: this.getUserAgent(),
+    };
+
+    this.enqueue(record);
+    return effectiveCorrelationId;
+  }
+
+  async flush(): Promise<void> {
+    if (!this.isBrowser) {
+      return;
+    }
+
+    clearTimeout(this.flushTimer);
+    this.flushTimer = undefined;
+
+    await this.processQueue();
+  }
+
+  private flushSync(): void {
+    if (!this.isBrowser || this.queue.length === 0) {
+      return;
+    }
+
+    const payload = this.queue.slice();
+    this.queue = [];
+    this.persistQueue();
+
+    if ('sendBeacon' in navigator) {
+      const blob = new Blob([JSON.stringify(payload)], { type: 'application/json' });
+      navigator.sendBeacon(this.config.endpoint, blob);
+    }
+  }
+
+  private enqueue(record: SearchDiagRecord): void {
+    this.queue.push(record);
+    this.persistQueue();
+
+    if (this.queue.length >= this.config.batchSize) {
+      this.scheduleFlush(0);
+    } else {
+      this.scheduleFlush();
+    }
+  }
+
+  private scheduleFlush(delayMs = this.config.debounceMs): void {
+    if (!this.isBrowser) {
+      return;
+    }
+
+    if (this.flushTimer) {
+      return;
+    }
+
+    this.flushTimer = setTimeout(() => {
+      this.flushTimer = undefined;
+
+      if (typeof window !== 'undefined' && 'requestIdleCallback' in window) {
+        requestIdleCallback(() => this.processQueue());
+      } else {
+        this.processQueue();
+      }
+    }, delayMs);
+  }
+
+  private async processQueue(): Promise<void> {
+    if (!this.isBrowser) {
+      return;
+    }
+
+    if (this.isFlushing || this.queue.length === 0) {
+      return;
+    }
+
+    if (Date.now() < this.circuitBreakerOpenUntil) {
+      return;
+    }
+
+    if (typeof navigator !== 'undefined' && !navigator.onLine) {
+      return;
+    }
+
+    this.isFlushing = true;
+    const batch = [...this.queue];
+
+    try {
+      await this.sendWithRetry(batch);
+      this.queue = [];
+      this.consecutiveFailures = 0;
+      this.persistQueue();
+    } catch (error) {
+      this.consecutiveFailures++;
+
+      if (this.consecutiveFailures >= this.config.circuitBreakerThreshold) {
+        this.circuitBreakerOpenUntil = Date.now() + this.config.circuitBreakerResetMs;
+      }
+
+      console.warn('[SearchLogService] Failed to send diagnostics batch', error);
+    } finally {
+      this.isFlushing = false;
+    }
+  }
+
+  private async sendWithRetry(batch: SearchDiagRecord[]): Promise<void> {
+    let lastError: unknown;
+
+    for (let attempt = 0; attempt < this.config.maxRetries; attempt++) {
+      try {
+        await this.postBatch(batch);
+        return;
+      } catch (error) {
+        lastError = error;
+
+        if (attempt < this.config.maxRetries - 1) {
+          const delayMs = 500 * Math.pow(2, attempt);
+          await this.delay(delayMs);
+        }
+      }
+    }
+
+    throw lastError;
+  }
+
+  private async postBatch(batch: SearchDiagRecord[]): Promise<void> {
+    if (batch.length === 0) {
+      return;
+    }
+
+    const payload = batch.length === 1 ? batch[0] : batch;
+
+    const response = await fetch(this.config.endpoint, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+      body: JSON.stringify(payload),
+      keepalive: true,
+    });
+
+    if (!response.ok) {
+      throw new Error(`HTTP ${response.status}: ${response.statusText}`);
+    }
+  }
+
+  private buildContext(): SearchDiagRecord['context'] {
+    const context: SearchDiagRecord['context'] = {
+      version: environment.appVersion,
+    };
+
+    if (!this.isBrowser) {
+      return context;
+    }
+
+    if (typeof window !== 'undefined' && window.location) {
+      context.route = window.location.pathname + window.location.search;
+    }
+
+    if (typeof document !== 'undefined' && document.documentElement) {
+      const theme = document.documentElement.getAttribute('data-theme');
+      if (theme === 'light' || theme === 'dark') {
+        context.theme = theme;
+      }
+    }
+
+    try {
+      const vault = localStorage.getItem('obsiviewer.vaultName');
+      if (vault) {
+        context.vault = vault;
+      }
+    } catch {
+      // ignore storage errors
+    }
+
+    return context;
+  }
+
+  private getUserAgent(): string | undefined {
+    if (!this.isBrowser || typeof navigator === 'undefined') {
+      return undefined;
+    }
+    return navigator.userAgent;
+  }
+
+  private prepareData(stage: SearchDiagEvent, data: Record<string, unknown>): Dictionary {
+    const cloned = this.cloneData(data);
+    delete cloned.queryRaw;
+    delete cloned['noteContent'];
+
+    const sanitized = this.sanitizeValue(cloned, [stage]) as Dictionary;
+    return this.enforceSizeLimit(sanitized);
+  }
+
+  private sanitizeValue(value: unknown, path: string[], seen = new WeakSet<object>()): SanitizedValue {
+    if (value === null || value === undefined) {
+      return value as SanitizedValue;
+    }
+
+    if (typeof value === 'number' || typeof value === 'boolean') {
+      return value;
+    }
+
+    if (typeof value === 'string') {
+      return this.sanitizeString(value, path);
+    }
+
+    if (Array.isArray(value)) {
+      if (seen.has(value)) {
+        return '[Circular]' as SanitizedValue;
+      }
+      seen.add(value);
+
+      const limited = value.slice(0, LARGE_ARRAY_LIMIT);
+      const sanitizedArray = limited.map((entry, index) => this.sanitizeValue(entry, [...path, String(index)], seen));
+
+      if (value.length > LARGE_ARRAY_LIMIT) {
+        sanitizedArray.push('[Truncated]' as unknown as SanitizedValue);
+      }
+
+      seen.delete(value);
+      return sanitizedArray;
+    }
+
+    if (typeof value === 'object') {
+      if (seen.has(value as object)) {
+        return '[Circular]' as SanitizedValue;
+      }
+
+      seen.add(value as object);
+      const result: Dictionary<SanitizedValue> = {};
+
+      for (const [key, entry] of Object.entries(value as Dictionary)) {
+        const lowerKey = key.toLowerCase();
+
+        if (this.isContentKey(lowerKey)) {
+          result[key] = '[REDACTED_CONTENT]';
+          continue;
+        }
+
+        if (this.isSensitivePathKey(lowerKey)) {
+          result[key] = this.maskPath(String(entry));
+          continue;
+        }
+
+        result[key] = this.sanitizeValue(entry, [...path, key], seen);
+      }
+
+      seen.delete(value as object);
+      return result;
+    }
+
+    return String(value);
+  }
+
+  private sanitizeString(value: string, path: string[]): string {
+    const lowerPath = path[path.length - 1]?.toLowerCase() ?? '';
+
+    if (this.isContentKey(lowerPath)) {
+      return '[REDACTED_CONTENT]';
+    }
+
+    if (this.isSensitivePathKey(lowerPath)) {
+      return this.maskPath(value);
+    }
+
+    if (value.length > MAX_DATA_SIZE) {
+      return `${value.slice(0, 512)}…[TRUNCATED_${value.length}]`;
+    }
+
+    return value;
+  }
+
+  private enforceSizeLimit<T>(value: T): T {
+    try {
+      const serialized = JSON.stringify(value);
+      if (serialized.length > MAX_DATA_SIZE) {
+        return {
+          _truncated: true,
+          _originalSize: serialized.length,
+          _message: 'Payload truncated due to size limit',
+        } as unknown as T;
+      }
+    } catch (error) {
+      return {
+        _error: 'Failed to serialize payload',
+        _message: String(error),
+      } as unknown as T;
+    }
+
+    return value;
+  }
+
+  private isContentKey(key: string): boolean {
+    return key.includes('content') || key.includes('raw') || key.includes('body') || key.includes('html');
+  }
+
+  private isSensitivePathKey(key: string): boolean {
+    return key.includes('path') || key.includes('filepath') || key.includes('folder');
+  }
+
+  private maskPath(value: string): string {
+    if (!value) {
+      return value;
+    }
+
+    const segments = value.split(/[\\/]+/).filter(Boolean);
+    if (segments.length === 0) {
+      return value;
+    }
+
+    const tail = segments.slice(-2).join('/');
+    return segments.length > 2 ? `…/${tail}` : tail;
+  }
+
+  private cloneData(data: Record<string, unknown>): Dictionary {
+    return JSON.parse(JSON.stringify(data ?? {})) as Dictionary;
+  }
+
+  private ensureSessionId(): string {
+    if (!this.isBrowser) {
+      return this.generateUUID();
+    }
+
+    try {
+      let id = sessionStorage.getItem(SESSION_STORAGE_KEY);
+      if (!id) {
+        id = this.generateUUID();
+        sessionStorage.setItem(SESSION_STORAGE_KEY, id);
+      }
+      return id;
+    } catch {
+      return this.generateUUID();
+    }
+  }
+
+  private shouldSample(correlationId: string): boolean {
+    const rate = this.config.sampleRateSearchDiag ?? 1;
+    if (rate >= 1) {
+      return true;
+    }
+
+    if (this.sampleDecisions.has(correlationId)) {
+      return this.sampleDecisions.get(correlationId) as boolean;
+    }
+
+    const decision = Math.random() < rate;
+    this.sampleDecisions.set(correlationId, decision);
+
+    if (this.sampleDecisions.size > SAMPLE_DECISIONS_LIMIT) {
+      const [firstKey] = this.sampleDecisions.keys();
+      if (firstKey) {
+        this.sampleDecisions.delete(firstKey);
+      }
+    }
+
+    return decision;
+  }
+
+  private extractQueryRaw(
+    correlationId: string,
+    stage: SearchDiagEvent,
+    data: Record<string, unknown>
+  ): string {
+    let query = '';
+    const maybeQuery = data['queryRaw'];
+    if (typeof maybeQuery === 'string') {
+      query = maybeQuery;
+    } else {
+      query = this.correlationQueries.get(correlationId) ?? '';
+    }
+
+    if (stage === 'SEARCH_DIAG_START' && query) {
+      this.correlationQueries.set(correlationId, query);
+    }
+
+    if (!query && typeof data['query'] === 'string') {
+      query = data['query'] as string;
+    }
+
+    return query;
+  }
+
+  private persistQueue(): void {
+    if (!this.isBrowser) {
+      return;
+    }
+
+    try {
+      localStorage.setItem(LOCAL_STORAGE_QUEUE_KEY, JSON.stringify(this.queue));
+    } catch {
+      // ignore
+    }
+  }
+
+  private loadQueueFromStorage(): void {
+    if (!this.isBrowser) {
+      return;
+    }
+
+    try {
+      const stored = localStorage.getItem(LOCAL_STORAGE_QUEUE_KEY);
+      if (!stored) {
+        return;
+      }
+      const parsed = JSON.parse(stored);
+      if (Array.isArray(parsed)) {
+        this.queue = parsed;
+        if (this.queue.length > 0) {
+          this.scheduleFlush();
+        }
+      }
+    } catch {
+      // ignore parse errors
+    }
+  }
+
+  private generateUUID(): string {
+    if (this.isBrowser && typeof window !== 'undefined' && 'crypto' in window && typeof crypto.randomUUID === 'function') {
+      return crypto.randomUUID();
+    }
+
+    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (char) => {
+      const random = (Math.random() * 16) | 0;
+      const value = char === 'x' ? random : (random & 0x3) | 0x8;
+      return value.toString(16);
+    });
+  }
+
+  private delay(ms: number): Promise<void> {
+    return new Promise((resolve) => setTimeout(resolve, ms));
+  }
+}
diff --git a/src/app/core/logging/search-log.model.ts b/src/app/core/logging/search-log.model.ts
new file mode 100644
index 0000000..32736e6
--- /dev/null
+++ b/src/app/core/logging/search-log.model.ts
@@ -0,0 +1,37 @@
+export type SearchDiagEvent =
+  | 'SEARCH_DIAG_START'
+  | 'SEARCH_DIAG_PARSE'
+  | 'SEARCH_DIAG_PLAN'
+  | 'SEARCH_DIAG_EXEC_PROVIDER'
+  | 'SEARCH_DIAG_RESULT_MAP'
+  | 'SEARCH_DIAG_SUMMARY'
+  | 'SEARCH_DIAG_ERROR';
+
+export interface SearchDiagRecord {
+  ts: string;
+  app: 'ObsiViewer';
+  sessionId: string;
+  level: 'info' | 'warn' | 'error';
+  correlationId: string;
+  queryRaw: string;
+  context: {
+    route?: string;
+    vault?: string;
+    theme?: 'dark' | 'light';
+    version?: string;
+  };
+  userAgent?: string;
+  stage: SearchDiagEvent;
+  data: Record<string, unknown>;
+}
+
+export interface SearchDiagContextMeta {
+  userAgent?: string;
+  sampleRate?: number;
+}
+
+export interface SearchDiagOptions {
+  correlationId?: string;
+  level?: 'info' | 'warn' | 'error';
+  queryRaw: string;
+}
diff --git a/src/core/logging/environment.ts b/src/core/logging/environment.ts
index 889a009..589132b 100644
--- a/src/core/logging/environment.ts
+++ b/src/core/logging/environment.ts
@@ -9,5 +9,6 @@ export const environment = {
     maxRetries: 5,
     circuitBreakerThreshold: 5,
     circuitBreakerResetMs: 30000,
+    sampleRateSearchDiag: 1.0,
   },
 };
diff --git a/src/core/search/__tests__/search-orchestrator.plan.spec.ts b/src/core/search/__tests__/search-orchestrator.plan.spec.ts
new file mode 100644
index 0000000..6cf9766
--- /dev/null
+++ b/src/core/search/__tests__/search-orchestrator.plan.spec.ts
@@ -0,0 +1,121 @@
+import { TestBed } from '@angular/core/testing';
+import { provideZonelessChangeDetection } from '@angular/core';
+import { SearchOrchestratorService } from '../search-orchestrator.service';
+import { SearchIndexService, SearchIndexDiagnosticsSnapshot, SearchIndexNormalizationRules } from '../search-index.service';
+import { ClientLoggingService } from '../../../services/client-logging.service';
+import { SearchLogService } from '../../../app/core/logging/log.service';
+import { ParseDiagnostics } from '../search-parser.types';
+import { SearchExecutionOptions } from '../search-orchestrator.service';
+
+describe('SearchOrchestratorService diagnostics planning', () => {
+  let service: SearchOrchestratorService;
+  let normalizationRules: SearchIndexNormalizationRules;
+
+  beforeEach(() => {
+    normalizationRules = {
+      tags: {
+        ensureHashPrefix: true,
+        preserveCase: true,
+        deduplicate: true,
+        stripHashOnMatch: true
+      },
+      paths: {
+        separator: '/',
+        caseSensitive: false
+      },
+      files: {
+        caseSensitive: false
+      }
+    };
+
+    const searchIndexStub = {
+      getAllContexts: jasmine.createSpy('getAllContexts').and.returnValue([]),
+      getIndexDiagnostics: jasmine.createSpy('getIndexDiagnostics').and.returnValue({})
+    } as unknown as SearchIndexService;
+
+    const clientLoggerStub = jasmine.createSpyObj<ClientLoggingService>('ClientLoggingService', ['info', 'debug', 'error', 'warn']);
+    const diagLoggerStub = {
+      logSearch: jasmine.createSpy('logSearch').and.returnValue('correlation-1')
+    } as unknown as SearchLogService;
+
+    TestBed.configureTestingModule({
+      providers: [
+        provideZonelessChangeDetection(),
+        SearchOrchestratorService,
+        { provide: SearchIndexService, useValue: searchIndexStub },
+        { provide: ClientLoggingService, useValue: clientLoggerStub },
+        { provide: SearchLogService, useValue: diagLoggerStub }
+      ]
+    });
+
+    service = TestBed.inject(SearchOrchestratorService);
+  });
+
+  it('builds plan with tag stages and no warnings when tag is indexed', () => {
+    const diagnostics: ParseDiagnostics = {
+      tokens: ['tag:#home'],
+      warnings: [],
+      filters: {
+        tag: ['#home'],
+        path: [],
+        file: [],
+        negative: [],
+        negativeDetails: [],
+        regex: false,
+        caseSensitive: false,
+        wholeWord: false
+      }
+    };
+    const options: SearchExecutionOptions = { caseSensitive: false, regexMode: false };
+    const indexSnapshot: SearchIndexDiagnosticsSnapshot = {
+      tagsIndexed: true,
+      pathIndexed: true,
+      filesIndexed: true,
+      totalContexts: 25,
+      tagCardinality: { home: 3 },
+      normalizeRules: normalizationRules
+    };
+
+    const plan = (service as any).buildExecutionPlan(diagnostics, options, indexSnapshot);
+
+    expect(plan.stages.length).toBeGreaterThan(0);
+    const tagStage = plan.stages.find((s: any) => s.name === 'candidateSetFromTag');
+    expect(tagStage).toBeDefined();
+    expect(tagStage.constraint).toBe('tag=home');
+    expect(tagStage.estimate).toBe(3);
+    expect(plan.warnings).toEqual([]);
+  });
+
+  it('flags missing tag index and negative filters in plan warnings', () => {
+    const diagnostics: ParseDiagnostics = {
+      tokens: ['tag:#home', '-path:"Archive"'],
+      warnings: [],
+      filters: {
+        tag: ['#home'],
+        path: ['Archive'],
+        file: [],
+        negative: ['Archive'],
+        negativeDetails: [{ type: 'path', value: 'Archive', wildcard: false }],
+        regex: false,
+        caseSensitive: false,
+        wholeWord: false
+      }
+    };
+    const options: SearchExecutionOptions = { caseSensitive: false, regexMode: false };
+    const indexSnapshot: SearchIndexDiagnosticsSnapshot = {
+      tagsIndexed: false,
+      pathIndexed: true,
+      filesIndexed: true,
+      totalContexts: 10,
+      tagCardinality: {},
+      normalizeRules: normalizationRules
+    };
+
+    const plan = (service as any).buildExecutionPlan(diagnostics, options, indexSnapshot);
+
+    expect(plan.warnings).toContain('TagIndexUnavailable');
+    const negativeStage = plan.stages.find((s: any) => s.name === 'applyNegative');
+    expect(negativeStage).toBeDefined();
+    expect(negativeStage.constraint).toBe('path:Archive');
+  });
+});
diff --git a/src/core/search/__tests__/search-parser.spec.ts b/src/core/search/__tests__/search-parser.spec.ts
new file mode 100644
index 0000000..2add675
--- /dev/null
+++ b/src/core/search/__tests__/search-parser.spec.ts
@@ -0,0 +1,40 @@
+import { parseSearchQuery } from '../search-parser';
+import { SearchOptions } from '../search-parser.types';
+
+describe('parseSearchQuery diagnostics', () => {
+  const baseOptions: SearchOptions = {
+    caseSensitive: false,
+    regexMode: false
+  };
+
+  it('captures filters for tag and file operators', () => {
+    const query = 'tag:#home file:"Project Plan.md"';
+    const parsed = parseSearchQuery(query, baseOptions);
+
+    expect(parsed.isEmpty).toBe(false);
+    expect(parsed.diagnostics).toBeDefined();
+    expect(parsed.diagnostics?.filters.tag).toEqual(['#home']);
+    expect(parsed.diagnostics?.filters.file).toEqual(['Project Plan.md']);
+    const negative = parsed.diagnostics?.filters.negative ?? [];
+    expect(negative.length).toBe(0);
+  });
+
+  it('tracks negative filters with metadata', () => {
+    const query = 'tag:#home -path:"Archive" -content:"secret"';
+    const parsed = parseSearchQuery(query, baseOptions);
+
+    expect(parsed.diagnostics?.filters.negative).toEqual(['Archive', 'secret']);
+    const negativeDetails = parsed.diagnostics?.filters.negativeDetails ?? [];
+    expect(negativeDetails.length).toBe(2);
+    expect(negativeDetails[0]).toEqual(jasmine.objectContaining({ type: 'path', value: 'Archive' }));
+    expect(negativeDetails[1]).toEqual(jasmine.objectContaining({ type: 'content', value: 'secret' }));
+  });
+
+  it('records warnings for unknown prefixes', () => {
+    const query = 'unknown:term -unknown:value';
+    const parsed = parseSearchQuery(query, baseOptions);
+
+    expect(parsed.diagnostics?.warnings).toContain('UnknownOperator:unknown');
+    expect(parsed.diagnostics?.filters.negative).toContain('unknown:value');
+  });
+});
diff --git a/src/core/search/search-index.service.ts b/src/core/search/search-index.service.ts
index 9860d73..38ec889 100644
--- a/src/core/search/search-index.service.ts
+++ b/src/core/search/search-index.service.ts
@@ -3,6 +3,31 @@ import { SearchContext, SectionContent, TaskInfo } from './search-parser.types';
 import { VaultService } from '../../services/vault.service';
 import { Note } from '../../types';
 
+export interface SearchIndexNormalizationRules {
+  tags: {
+    ensureHashPrefix: boolean;
+    preserveCase: boolean;
+    deduplicate: boolean;
+    stripHashOnMatch: boolean;
+  };
+  paths: {
+    separator: string;
+    caseSensitive: boolean;
+  };
+  files: {
+    caseSensitive: boolean;
+  };
+}
+
+export interface SearchIndexDiagnosticsSnapshot {
+  tagsIndexed: boolean;
+  pathIndexed: boolean;
+  filesIndexed: boolean;
+  totalContexts: number;
+  tagCardinality: Record<string, number>;
+  normalizeRules: SearchIndexNormalizationRules;
+}
+
 /**
  * Comprehensive search index for the vault
  * Indexes all content for fast searching with full Obsidian operator support
@@ -17,6 +42,7 @@ export class SearchIndexService {
   private pathsIndex = signal<string[]>([]);
   private filesIndex = signal<string[]>([]);
   private tagsIndex = signal<string[]>([]);
+  private tagCardinality = signal<Record<string, number>>({});
   private propertiesIndex = signal<Map<string, Set<string>>>(new Map());
   private headingsIndex = signal<Map<string, string[]>>(new Map());
 
@@ -56,6 +82,7 @@ export class SearchIndexService {
     const pathsSet = new Set<string>();
     const filesSet = new Set<string>();
     const tagsSet = new Set<string>();
+    const tagCounts = new Map<string, number>();
     const propertiesMap = new Map<string, Set<string>>();
     const headingsMap = new Map<string, string[]>();
 
@@ -78,7 +105,12 @@ export class SearchIndexService {
       filesSet.add(context.fileNameWithExt);
 
       // Index tags
-      context.tags.forEach(tag => tagsSet.add(tag));
+      context.tags.forEach(tag => {
+        tagsSet.add(tag);
+        const normalized = tag.startsWith('#') ? tag.substring(1) : tag;
+        const key = normalized.toLowerCase();
+        tagCounts.set(key, (tagCounts.get(key) ?? 0) + 1);
+      });
 
       // Index properties
       Object.keys(context.properties).forEach(key => {
@@ -104,6 +136,11 @@ export class SearchIndexService {
     this.pathsIndex.set(Array.from(pathsSet).sort());
     this.filesIndex.set(Array.from(filesSet).sort());
     this.tagsIndex.set(Array.from(tagsSet).sort());
+    const tagCardinalityObj: Record<string, number> = {};
+    tagCounts.forEach((count, key) => {
+      tagCardinalityObj[key] = count;
+    });
+    this.tagCardinality.set(tagCardinalityObj);
     this.propertiesIndex.set(propertiesMap);
     this.headingsIndex.set(headingsMap);
   }
@@ -286,6 +323,48 @@ export class SearchIndexService {
     return Array.from(new Set(all));
   }
 
+  getIndexDiagnostics(filters?: { tags?: string[] }): SearchIndexDiagnosticsSnapshot {
+    const tagSnapshot = this.tagCardinality();
+    const selectedTags = filters?.tags ?? Object.keys(tagSnapshot);
+    const tagCardinality: Record<string, number> = {};
+
+    selectedTags.forEach(tag => {
+      const normalized = tag.startsWith('#') ? tag.substring(1) : tag;
+      const key = normalized.toLowerCase();
+      const value = tagSnapshot[key];
+      if (value !== undefined) {
+        tagCardinality[normalized] = value;
+      }
+    });
+
+    return {
+      tagsIndexed: this.tagsIndex().length > 0,
+      pathIndexed: this.pathsIndex().length > 0,
+      filesIndexed: this.filesIndex().length > 0,
+      totalContexts: this.indexData().size,
+      tagCardinality,
+      normalizeRules: this.getNormalizationRules()
+    };
+  }
+
+  getNormalizationRules(): SearchIndexNormalizationRules {
+    return {
+      tags: {
+        ensureHashPrefix: true,
+        preserveCase: true,
+        deduplicate: true,
+        stripHashOnMatch: true
+      },
+      paths: {
+        separator: '/',
+        caseSensitive: false
+      },
+      files: {
+        caseSensitive: false
+      }
+    };
+  }
+
   /**
    * Extract tags from YAML frontmatter in raw markdown content.
    * Supports:
diff --git a/src/core/search/search-orchestrator.service.spec.ts b/src/core/search/search-orchestrator.service.spec.ts
index 59a3b4b..160698a 100644
--- a/src/core/search/search-orchestrator.service.spec.ts
+++ b/src/core/search/search-orchestrator.service.spec.ts
@@ -3,6 +3,8 @@ import { provideZonelessChangeDetection } from '@angular/core';
 import { SearchOrchestratorService } from './search-orchestrator.service';
 import { SearchIndexService } from './search-index.service';
 import { SearchContext } from './search-parser.types';
+import { ClientLoggingService } from '../../services/client-logging.service';
+import { SearchLogService } from '../../app/core/logging/log.service';
 
 describe('SearchOrchestratorService', () => {
   let service: SearchOrchestratorService;
@@ -38,14 +40,33 @@ describe('SearchOrchestratorService', () => {
     contexts = [mockContext];
 
     const indexServiceStub = {
-      getAllContexts: () => contexts
-    } as SearchIndexService;
+      getAllContexts: () => contexts,
+      getIndexDiagnostics: jasmine.createSpy('getIndexDiagnostics').and.returnValue({
+        tagsIndexed: true,
+        pathIndexed: true,
+        filesIndexed: true,
+        totalContexts: 1,
+        tagCardinality: { test: 1, example: 1 },
+        normalizeRules: {
+          tags: { ensureHashPrefix: true, preserveCase: true, deduplicate: true, stripHashOnMatch: true },
+          paths: { separator: '/', caseSensitive: false },
+          files: { caseSensitive: false }
+        }
+      })
+    } as unknown as SearchIndexService;
+
+    const clientLoggerStub = jasmine.createSpyObj<ClientLoggingService>('ClientLoggingService', ['info', 'debug', 'error', 'warn']);
+    const diagLoggerStub = {
+      logSearch: jasmine.createSpy('logSearch').and.returnValue('test-correlation-id')
+    } as unknown as SearchLogService;
 
     TestBed.configureTestingModule({
       providers: [
         provideZonelessChangeDetection(),
         SearchOrchestratorService,
-        { provide: SearchIndexService, useValue: indexServiceStub }
+        { provide: SearchIndexService, useValue: indexServiceStub },
+        { provide: ClientLoggingService, useValue: clientLoggerStub },
+        { provide: SearchLogService, useValue: diagLoggerStub }
       ]
     });
     service = TestBed.inject(SearchOrchestratorService);
diff --git a/src/core/search/search-orchestrator.service.ts b/src/core/search/search-orchestrator.service.ts
index 64373d4..c4989e5 100644
--- a/src/core/search/search-orchestrator.service.ts
+++ b/src/core/search/search-orchestrator.service.ts
@@ -1,8 +1,11 @@
 import { Injectable, inject } from '@angular/core';
 import { parseSearchQuery, queryToPredicate } from './search-parser';
 import { SearchOptions, SearchContext } from './search-parser.types';
-import { SearchIndexService } from './search-index.service';
+import { SearchIndexService, SearchIndexDiagnosticsSnapshot } from './search-index.service';
 import { ClientLoggingService } from '../../services/client-logging.service';
+import { SearchLogService } from '../../app/core/logging/log.service';
+import { SearchDiagEvent } from '../../app/core/logging/search-log.model';
+import { ParseDiagnostics } from './search-parser.types';
 
 /**
  * Match range for highlighting
@@ -43,6 +46,16 @@ export interface SearchExecutionOptions extends SearchOptions {
   contextLines?: number;
   /** Maximum number of results to return (default: unlimited) */
   maxResults?: number;
+  /** Diagnostic trigger source */
+  trigger?: 'submit' | 'debounce' | 'route' | string;
+  /** Diagnostic source identifier */
+  source?: string;
+  /** Paging page number for diagnostics */
+  page?: number;
+  /** Paging page size for diagnostics */
+  pageSize?: number;
+  /** Existing correlation id to reuse */
+  correlationId?: string;
 }
 
 /**
@@ -55,6 +68,7 @@ export interface SearchExecutionOptions extends SearchOptions {
 export class SearchOrchestratorService {
   private searchIndex = inject(SearchIndexService);
   private logger = inject(ClientLoggingService);
+  private diagnosticsLogger = inject(SearchLogService);
 
   /**
    * Execute a search query and return matching notes with highlights
@@ -64,87 +78,420 @@ export class SearchOrchestratorService {
       return [];
     }
 
+    const pipelineStart = this.now();
+    let stageAtFailure: SearchDiagEvent = 'SEARCH_DIAG_START';
+    const timings = {
+      parse: 0,
+      plan: 0,
+      exec: 0,
+      map: 0,
+      render: 0
+    };
+    let results: SearchResult[] = [];
+    let allContextsCount = 0;
+    let combinedCount = 0;
+    let planInfo: ReturnType<typeof this.buildExecutionPlan> | undefined;
+    let indexDiagnostics: SearchIndexDiagnosticsSnapshot | undefined;
+
+    const correlationId = this.diagnosticsLogger.logSearch('SEARCH_DIAG_START', {
+      source: options?.source ?? 'ui',
+      trigger: options?.trigger ?? 'submit',
+      queryRaw: query,
+      options: {
+        caseSensitive: options?.caseSensitive ?? false,
+        regex: options?.regexMode ?? false,
+        wholeWord: (options as any)?.wholeWord ?? false
+      },
+      paging: {
+        page: options?.page ?? 1,
+        pageSize: options?.pageSize ?? options?.maxResults ?? 0
+      }
+    }, 'info');
+
     const contextLines = options?.contextLines ?? 2;
     const maxResults = options?.maxResults;
 
-    // Parse the query into an AST
-    this.logger.info('SearchOrchestrator', 'Parsing query', { query, options });
-    const parsed = parseSearchQuery(query, options);
-    if (parsed.isEmpty) {
-      this.logger.debug('SearchOrchestrator', 'Parsed query is empty');
+    try {
+      stageAtFailure = 'SEARCH_DIAG_PARSE';
+      this.logger.info('SearchOrchestrator', 'Parsing query', { query, options });
+      const parseStart = this.now();
+      const parsed = parseSearchQuery(query, options);
+      timings.parse = this.now() - parseStart;
+
+      if (parsed.diagnostics) {
+        this.diagnosticsLogger.logSearch('SEARCH_DIAG_PARSE', {
+          queryRaw: query,
+          tokens: parsed.diagnostics.tokens,
+          filters: parsed.diagnostics.filters,
+          parseWarnings: parsed.diagnostics.warnings
+        }, 'info', correlationId);
+      }
+
+      if (parsed.isEmpty) {
+        this.logger.debug('SearchOrchestrator', 'Parsed query is empty');
+        return [];
+      }
+
+      stageAtFailure = 'SEARCH_DIAG_PLAN';
+      this.logger.debug('SearchOrchestrator', 'Building predicate');
+      const predicate = queryToPredicate(parsed, options);
+
+      this.logger.debug('SearchOrchestrator', 'Extracting search terms');
+      const searchTerms = this.extractSearchTerms(parsed.ast);
+
+      const planStart = this.now();
+      indexDiagnostics = this.searchIndex.getIndexDiagnostics({ tags: parsed.diagnostics?.filters.tag });
+      planInfo = this.buildExecutionPlan(parsed.diagnostics, options, indexDiagnostics);
+      timings.plan = this.now() - planStart;
+
+      this.diagnosticsLogger.logSearch('SEARCH_DIAG_PLAN', {
+        queryRaw: query,
+        stages: planInfo.stages,
+        indexStats: planInfo.indexStats,
+        warnings: planInfo.warnings,
+        normalizeRules: planInfo.normalizeRules
+      }, planInfo.warnings.length > 0 ? 'warn' : 'info', correlationId);
+
+      stageAtFailure = 'SEARCH_DIAG_EXEC_PROVIDER';
+      results = [];
+      const allContexts = this.searchIndex.getAllContexts();
+      allContextsCount = allContexts.length;
+      this.logger.info('SearchOrchestrator', 'Evaluating contexts', {
+        contextCount: allContextsCount
+      });
+
+      const execStart = this.now();
+      for (const context of allContexts) {
+        this.logger.debug('SearchOrchestrator', 'Evaluating context', {
+          noteId: context.noteId,
+          filePath: context.filePath
+        });
+
+        if (!predicate(context)) {
+          this.logger.debug('SearchOrchestrator', 'Context filtered out', {
+            noteId: context.noteId
+          });
+          continue;
+        }
+
+        this.logger.debug('SearchOrchestrator', 'Context matched predicate, finding highlights', {
+          noteId: context.noteId
+        });
+        const { matches, allRanges } = this.findMatchesWithRanges(
+          context,
+          searchTerms,
+          options,
+          contextLines
+        );
+
+        const score = this.calculateScore(context, query, matches);
+        this.logger.debug('SearchOrchestrator', 'Context scored', {
+          noteId: context.noteId,
+          matchCount: matches.length,
+          score
+        });
+
+        results.push({
+          noteId: context.noteId,
+          matches,
+          score,
+          allRanges
+        });
+      }
+      timings.exec = this.now() - execStart;
+
+      const providerOutputCount = results.length;
+      combinedCount = providerOutputCount;
+      this.diagnosticsLogger.logSearch('SEARCH_DIAG_EXEC_PROVIDER', {
+        queryRaw: query,
+        provider: 'localIndex',
+        inputCount: allContextsCount,
+        filterApplied: this.buildFilterApplied(parsed.diagnostics),
+        outputCount: providerOutputCount,
+        timingMs: timings.exec,
+        cache: { hit: false }
+      }, 'info', correlationId);
+
+      stageAtFailure = 'SEARCH_DIAG_RESULT_MAP';
+      const mapStart = this.now();
+      this.logger.debug('SearchOrchestrator', 'Sorting results', {
+        resultCount: results.length
+      });
+
+      if (maxResults && maxResults > 0) {
+        this.logger.debug('SearchOrchestrator', 'Applying maxResults slice', { maxResults });
+        results.splice(maxResults);
+      }
+
+      const providerResults = [{ provider: 'localIndex', count: providerOutputCount }];
+      const afterUIFiltersCount = combinedCount;
+      const reasonsEmpty = indexDiagnostics && planInfo
+        ? this.collectEmptyReasons(results.length, planInfo, indexDiagnostics)
+        : [];
+      timings.map = this.now() - mapStart;
+
+      this.diagnosticsLogger.logSearch('SEARCH_DIAG_RESULT_MAP', {
+        queryRaw: query,
+        providerResults,
+        combinedCount,
+        afterUIFiltersCount,
+        reasonsEmpty
+      }, reasonsEmpty.length > 0 ? 'warn' : 'info', correlationId);
+
+      this.logger.info('SearchOrchestrator', 'Returning results', {
+        resultCount: results.length
+      });
+
+      stageAtFailure = 'SEARCH_DIAG_SUMMARY';
+      const totalMs = this.now() - pipelineStart;
+      timings.render = Math.max(0, totalMs - (timings.parse + timings.plan + timings.exec + timings.map));
+      const summaryLevel: 'info' | 'warn' = results.length === 0 || (planInfo?.warnings.length ?? 0) > 0 ? 'warn' : 'info';
+
+      this.diagnosticsLogger.logSearch('SEARCH_DIAG_SUMMARY', {
+        queryRaw: query,
+        totalMs,
+        stagesMs: timings,
+        counts: {
+          beforeFilters: allContextsCount,
+          afterFilters: combinedCount,
+          displayed: results.length
+        },
+        index: indexDiagnostics ? {
+          tagsIndexed: indexDiagnostics.tagsIndexed,
+          tagCardinality: indexDiagnostics.tagCardinality
+        } : undefined,
+        userVisible: {
+          emptyStateShown: results.length === 0,
+          helperSuggestions: planInfo ? this.buildHelperSuggestions(planInfo, results.length) : []
+        }
+      }, summaryLevel, correlationId);
+
+      return results;
+    } catch (error) {
+      const errorKind = this.inferErrorKind(stageAtFailure, error);
+      this.diagnosticsLogger.logSearch('SEARCH_DIAG_ERROR', {
+        queryRaw: query,
+        kind: errorKind,
+        message: error instanceof Error ? error.message : String(error),
+        code: (error as any)?.code,
+        safeStack: this.extractSafeStack(error),
+        stageAtFailure,
+        partialCounts: {
+          beforeFilters: allContextsCount,
+          afterFilters: combinedCount
+        }
+      }, 'error', correlationId);
+      this.logger.error('SearchOrchestrator', 'Search pipeline failed', {
+        stage: stageAtFailure,
+        error
+      });
+      throw error;
+    }
+  }
+
+  private inferErrorKind(stage: SearchDiagEvent, error: unknown): 'ParseError' | 'IndexError' | 'ProviderError' | 'Timeout' | 'Unknown' {
+    if ((error as any)?.name === 'TimeoutError') {
+      return 'Timeout';
+    }
+
+    switch (stage) {
+      case 'SEARCH_DIAG_PARSE':
+        return 'ParseError';
+      case 'SEARCH_DIAG_PLAN':
+        return 'IndexError';
+      case 'SEARCH_DIAG_EXEC_PROVIDER':
+        return 'ProviderError';
+      default:
+        return 'Unknown';
+    }
+  }
+
+  private extractSafeStack(error: unknown): string | undefined {
+    if (error instanceof Error && typeof error.stack === 'string') {
+      return error.stack.split('\n').slice(0, 5).join('\n');
+    }
+    return undefined;
+  }
+
+  private now(): number {
+    if (typeof performance !== 'undefined' && typeof performance.now === 'function') {
+      return performance.now();
+    }
+    return Date.now();
+  }
+
+  private buildExecutionPlan(
+    diagnostics: ParseDiagnostics | undefined,
+    options: SearchExecutionOptions | undefined,
+    indexDiagnostics: SearchIndexDiagnosticsSnapshot
+  ): {
+    stages: Array<{ name: string; estimate: number; constraint: string }>;
+    warnings: string[];
+    indexStats: {
+      tagsIndexed: boolean;
+      tagCardinality: Record<string, number>;
+      pathIndexed: boolean;
+      filesIndexed: boolean;
+    };
+    normalizeRules: SearchIndexDiagnosticsSnapshot['normalizeRules'];
+  } {
+    const stages: Array<{ name: string; estimate: number; constraint: string }> = [];
+    const warnings: string[] = [];
+    const filters = diagnostics?.filters;
+
+    if (filters?.tag?.length) {
+      filters.tag.forEach(tag => {
+        const normalized = tag.startsWith('#') ? tag.substring(1) : tag;
+        const key = normalized.toLowerCase();
+        const count = indexDiagnostics.tagCardinality[key];
+        stages.push({
+          name: 'candidateSetFromTag',
+          estimate: count ?? 0,
+          constraint: `tag=${normalized}`
+        });
+        if (!indexDiagnostics.tagsIndexed) {
+          warnings.push('TagIndexUnavailable');
+        } else if (count === undefined) {
+          warnings.push(`TagNotInIndex:${normalized}`);
+        } else if (count === 0) {
+          warnings.push(`TagEmpty:${normalized}`);
+        }
+      });
+    }
+
+    if (filters?.path?.length) {
+      filters.path.forEach(path => {
+        stages.push({
+          name: 'intersectPath',
+          estimate: Math.max(0, Math.floor(indexDiagnostics.totalContexts / 4)),
+          constraint: `path=${path}`
+        });
+      });
+    }
+
+    if (filters?.file?.length) {
+      filters.file.forEach(file => {
+        stages.push({
+          name: 'intersectFile',
+          estimate: Math.max(0, Math.floor(indexDiagnostics.totalContexts / 6)),
+          constraint: `file=${file}`
+        });
+      });
+    }
+
+    if (filters?.negativeDetails?.length) {
+      const constraint = filters.negativeDetails.map(n => `${n.type}:${n.value}`).join(', ');
+      stages.push({
+        name: 'applyNegative',
+        estimate: Math.max(0, Math.floor(indexDiagnostics.totalContexts / 8)),
+        constraint
+      });
+    }
+
+    if (options?.regexMode || filters?.regex) {
+      stages.push({
+        name: 'postFilterRegex',
+        estimate: Math.max(0, Math.floor(indexDiagnostics.totalContexts / 3)),
+        constraint: `regex=${options?.regexMode ?? filters?.regex}`
+      });
+    }
+
+    if (filters?.caseSensitive) {
+      stages.push({
+        name: 'postFilterCaseSensitive',
+        estimate: Math.max(0, Math.floor(indexDiagnostics.totalContexts / 2)),
+        constraint: 'caseSensitive=true'
+      });
+    }
+
+    if (!stages.length) {
+      stages.push({
+        name: 'fullScan',
+        estimate: indexDiagnostics.totalContexts,
+        constraint: 'none'
+      });
+    }
+
+    if (!indexDiagnostics.tagsIndexed && filters?.tag?.length) {
+      warnings.push('E_TAG_INDEX_DISABLED');
+    }
+
+    return {
+      stages,
+      warnings,
+      indexStats: {
+        tagsIndexed: indexDiagnostics.tagsIndexed,
+        tagCardinality: indexDiagnostics.tagCardinality,
+        pathIndexed: indexDiagnostics.pathIndexed,
+        filesIndexed: indexDiagnostics.filesIndexed
+      },
+      normalizeRules: indexDiagnostics.normalizeRules
+    };
+  }
+
+  private buildFilterApplied(diagnostics: ParseDiagnostics | undefined): Record<string, unknown> {
+    if (!diagnostics) {
+      return {};
+    }
+
+    return {
+      tag: diagnostics.filters.tag,
+      path: diagnostics.filters.path,
+      file: diagnostics.filters.file,
+      negative: diagnostics.filters.negative
+    };
+  }
+
+  private collectEmptyReasons(
+    resultCount: number,
+    planInfo: ReturnType<typeof this.buildExecutionPlan>,
+    indexDiagnostics: SearchIndexDiagnosticsSnapshot
+  ): string[] {
+    if (resultCount > 0) {
       return [];
     }
 
-    // Convert to predicate function
-    this.logger.debug('SearchOrchestrator', 'Building predicate');
-    const predicate = queryToPredicate(parsed, options);
-
-    // Extract search terms for highlighting
-    this.logger.debug('SearchOrchestrator', 'Extracting search terms');
-    const searchTerms = this.extractSearchTerms(parsed.ast);
-
-    // Evaluate against all indexed contexts
-    const results: SearchResult[] = [];
-    const allContexts = this.searchIndex.getAllContexts();
-    this.logger.info('SearchOrchestrator', 'Evaluating contexts', {
-      contextCount: allContexts.length
-    });
-
-    for (const context of allContexts) {
-      this.logger.debug('SearchOrchestrator', 'Evaluating context', {
-        noteId: context.noteId,
-        filePath: context.filePath
-      });
-
-      // Apply the predicate filter (if it doesn't match, skip this context)
-      if (!predicate(context)) {
-        this.logger.debug('SearchOrchestrator', 'Context filtered out', {
-          noteId: context.noteId
-        });
-        continue;
+    const reasons = new Set<string>();
+    planInfo.warnings.forEach(warning => {
+      if (warning.startsWith('TagNotInIndex')) {
+        reasons.add('tagNotInIndex');
+      } else if (warning.startsWith('TagEmpty')) {
+        reasons.add('noMatchesForTag');
+      } else if (warning === 'TagIndexUnavailable' || warning === 'E_TAG_INDEX_DISABLED') {
+        reasons.add('tagIndexUnavailable');
       }
-
-      // Find matches and ranges for highlighting (may be empty for file/path/property queries)
-      this.logger.debug('SearchOrchestrator', 'Context matched predicate, finding highlights', {
-        noteId: context.noteId
-      });
-      const { matches, allRanges } = this.findMatchesWithRanges(
-        context,
-        searchTerms,
-        options,
-        contextLines
-      );
-
-      const score = this.calculateScore(context, query, matches);
-      this.logger.debug('SearchOrchestrator', 'Context scored', {
-        noteId: context.noteId,
-        matchCount: matches.length,
-        score
-      });
-
-      results.push({
-        noteId: context.noteId,
-        matches,
-        score,
-        allRanges
-      });
-    }
-
-    // Sort by score (descending)
-    this.logger.debug('SearchOrchestrator', 'Sorting results', {
-      resultCount: results.length
     });
 
-    // Apply max results limit if specified
-    if (maxResults && maxResults > 0) {
-      this.logger.debug('SearchOrchestrator', 'Applying maxResults slice', { maxResults });
-      return results.slice(0, maxResults);
+    if (!indexDiagnostics.filesIndexed) {
+      reasons.add('fileIndexUnavailable');
+    }
+    if (!indexDiagnostics.pathIndexed) {
+      reasons.add('pathIndexUnavailable');
     }
 
-    this.logger.info('SearchOrchestrator', 'Returning results', {
-      resultCount: results.length
-    });
-    return results;
+    if (!reasons.size) {
+      reasons.add('intersectionEmpty');
+    }
+
+    return Array.from(reasons);
+  }
+
+  private buildHelperSuggestions(planInfo: ReturnType<typeof this.buildExecutionPlan>, resultCount: number): string[] {
+    const suggestions: string[] = [];
+
+    if (resultCount === 0) {
+      if (planInfo.warnings.some(w => w.startsWith('TagNotInIndex'))) {
+        suggestions.push('Vérifier que le tag existe dans le vault');
+      }
+      if (planInfo.warnings.includes('TagIndexUnavailable') || planInfo.warnings.includes('E_TAG_INDEX_DISABLED')) {
+        suggestions.push('Reconstruire l’index des tags');
+      }
+      if (!suggestions.length) {
+        suggestions.push('Assouplir les filtres ou retirer les exclusions');
+      }
+    }
+
+    return suggestions.slice(0, 3);
   }
   /**
    * Extract search terms from AST for highlighting
diff --git a/src/core/search/search-parser.ts b/src/core/search/search-parser.ts
index 8786efd..c475252 100644
--- a/src/core/search/search-parser.ts
+++ b/src/core/search/search-parser.ts
@@ -13,7 +13,9 @@ import {
   SearchContext,
   SearchOptions,
   SectionContent,
-  TaskInfo
+  TaskInfo,
+  ParseDiagnostics,
+  SearchFilterDiagnostics
 } from './search-parser.types';
 
 // Re-export types for convenience
@@ -26,16 +28,27 @@ export function parseSearchQuery(query: string, options?: SearchOptions): Parsed
   if (!query || !query.trim()) {
     return {
       ast: { type: 'group', operator: 'AND', terms: [] },
-      isEmpty: true
+      isEmpty: true,
+      diagnostics: {
+        tokens: [],
+        filters: createEmptyDiagnosticsFilters(options),
+        warnings: []
+      }
     };
   }
 
   const tokens = tokenize(query);
-  const ast = parseTokens(tokens, options);
+  const diagnostics: ParseDiagnostics = {
+    tokens: [...tokens],
+    filters: createEmptyDiagnosticsFilters(options),
+    warnings: []
+  };
+  const ast = parseTokens(tokens, options, diagnostics);
 
   return {
     ast,
-    isEmpty: false
+    isEmpty: false,
+    diagnostics
   };
 }
 
@@ -63,21 +76,39 @@ function tokenize(query: string): string[] {
 
     // Handle quoted strings
     if (char === '"') {
-      if (current) {
-        tokens.push(current);
-        current = '';
-      }
-      let quoted = '';
-      i++;
-      while (i < query.length && query[i] !== '"') {
-        quoted += query[i];
+      // If we are inside a prefix token like file: or path:, attach the quoted part to current
+      if (current.includes(':') && !current.includes(' ')) {
+        let quoted = '"';
         i++;
+        while (i < query.length && query[i] !== '"') {
+          quoted += query[i];
+          i++;
+        }
+        if (i < query.length && query[i] === '"') {
+          quoted += '"';
+          i++;
+        }
+        current += quoted;
+        continue;
+      } else {
+        if (current) {
+          tokens.push(current);
+          current = '';
+        }
+        let quoted = '';
+        i++;
+        while (i < query.length && query[i] !== '"') {
+          quoted += query[i];
+          i++;
+        }
+        if (i < query.length && query[i] === '"') {
+          i++;
+        }
+        if (quoted) {
+          tokens.push(`"${quoted}"`);
+        }
+        continue;
       }
-      if (quoted) {
-        tokens.push(`"${quoted}"`);
-      }
-      i++;
-      continue;
     }
 
     // Handle regex patterns /.../ 
@@ -137,7 +168,7 @@ function tokenize(query: string): string[] {
 /**
  * Parse tokens into AST
  */
-function parseTokens(tokens: string[], options?: SearchOptions): SearchNode {
+function parseTokens(tokens: string[], options: SearchOptions | undefined, diagnostics: ParseDiagnostics): SearchNode {
   const terms: SearchNode[] = [];
   let i = 0;
 
@@ -158,14 +189,14 @@ function parseTokens(tokens: string[], options?: SearchOptions): SearchNode {
 
     // Handle parentheses
     if (token === '(') {
-      const { node, endIndex } = parseGroup(tokens, i + 1, options);
+      const { node, endIndex } = parseGroup(tokens, i + 1, options, diagnostics);
       terms.push(node);
       i = endIndex + 1;
       continue;
     }
 
     // Parse term
-    const term = parseTerm(token, options);
+    const term = parseTerm(token, options, diagnostics);
     if (term) {
       terms.push(term);
     }
@@ -186,7 +217,12 @@ function parseTokens(tokens: string[], options?: SearchOptions): SearchNode {
 /**
  * Parse a group enclosed in parentheses
  */
-function parseGroup(tokens: string[], startIndex: number, options?: SearchOptions): { node: SearchNode; endIndex: number } {
+function parseGroup(
+  tokens: string[],
+  startIndex: number,
+  options: SearchOptions | undefined,
+  diagnostics: ParseDiagnostics
+): { node: SearchNode; endIndex: number } {
   const terms: SearchNode[] = [];
   let i = startIndex;
   let depth = 1;
@@ -204,7 +240,7 @@ function parseGroup(tokens: string[], startIndex: number, options?: SearchOption
     }
 
     if (token.toUpperCase() !== 'OR' && token.toUpperCase() !== 'AND' && token !== '(' && token !== ')') {
-      const term = parseTerm(token, options);
+      const term = parseTerm(token, options, diagnostics);
       if (term) {
         terms.push(term);
       }
@@ -229,30 +265,34 @@ function parseGroup(tokens: string[], startIndex: number, options?: SearchOption
 /**
  * Parse a single search term
  */
-function parseTerm(token: string, options?: SearchOptions): SearchTerm | null {
-  if (!token) return null;
+function parseTerm(token: string, options: SearchOptions | undefined, diagnostics: ParseDiagnostics): SearchTerm | null {
+  if (!token) {
+    return null;
+  }
 
   let negated = false;
   let value = token;
 
-  // Handle negation
   if (value.startsWith('-')) {
     negated = true;
     value = value.substring(1);
   }
 
+  let term: SearchTerm | null = null;
+  let negativeValue: string | undefined;
+
   // Support property form: [key]:value (Obsidian compatibility)
   if (value.startsWith('[') && value.includes(']:')) {
     const closeBracket = value.indexOf(']');
     if (closeBracket > 0) {
       const propertyKey = value.substring(1, closeBracket);
-      let propertyValue = value.substring(closeBracket + 2); // after ]:
+      let propertyValue = value.substring(closeBracket + 2);
       let propValueQuoted = false;
       if (propertyValue.startsWith('"') && propertyValue.endsWith('"')) {
         propValueQuoted = true;
         propertyValue = propertyValue.substring(1, propertyValue.length - 1);
       }
-      return {
+      term = {
         type: 'property',
         value: propertyValue,
         propertyKey,
@@ -260,96 +300,132 @@ function parseTerm(token: string, options?: SearchOptions): SearchTerm | null {
         quoted: propValueQuoted,
         wildcard: propertyValue.includes('*')
       };
+      negativeValue = propertyValue || propertyKey;
     }
   }
 
-  // Handle regex patterns /.../ 
-  if (value.startsWith('/') && value.endsWith('/') && value.length > 2) {
+  if (!term && value.startsWith('/') && value.endsWith('/') && value.length > 2) {
     const regexPattern = value.substring(1, value.length - 1);
-    return { type: 'regex', value: regexPattern, negated, quoted: false, wildcard: false };
+    term = { type: 'regex', value: regexPattern, negated, quoted: false, wildcard: false };
+    diagnostics.filters.regex = true;
+    negativeValue = regexPattern;
   }
 
-  // Handle quoted strings
   let quoted = false;
-  if (value.startsWith('"') && value.endsWith('"')) {
+  if (!term && value.startsWith('"') && value.endsWith('"')) {
     quoted = true;
     value = value.substring(1, value.length - 1);
   }
 
-  // Handle wildcards
   const wildcard = value.includes('*');
 
-  // Check for prefixes
-  const colonIndex = value.indexOf(':');
-  if (colonIndex > 0) {
-    const prefix = value.substring(0, colonIndex).toLowerCase();
-    const searchValue = value.substring(colonIndex + 1);
+  if (!term) {
+    const colonIndex = value.indexOf(':');
+    if (colonIndex > 0) {
+      const prefix = value.substring(0, colonIndex).toLowerCase();
+      const searchValueRaw = value.substring(colonIndex + 1);
+      let cleanValue = searchValueRaw;
+      let valueQuoted = false;
+      if (cleanValue.startsWith('"') && cleanValue.endsWith('"')) {
+        valueQuoted = true;
+        cleanValue = cleanValue.substring(1, cleanValue.length - 1);
+      }
 
-    // Remove quotes from search value if present
-    let cleanValue = searchValue;
-    let valueQuoted = false;
-    if (cleanValue.startsWith('"') && cleanValue.endsWith('"')) {
-      valueQuoted = true;
-      cleanValue = cleanValue.substring(1, cleanValue.length - 1);
-    }
-
-    // Fallback: handle property form [key]:value (if missed previously)
-    if (prefix.startsWith('[') && prefix.endsWith(']')) {
-      const propertyKey = prefix.substring(1, prefix.length - 1);
-      return {
-        type: 'property',
-        value: cleanValue,
-        propertyKey,
-        negated,
-        quoted: valueQuoted,
-        wildcard: cleanValue.includes('*')
-      };
-    }
-
-    switch (prefix) {
-      case 'path':
-        return { type: 'path', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'file':
-        return { type: 'file', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'content':
-        return { type: 'content', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'tag':
-        return { type: 'tag', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'line':
-        return { type: 'line', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'block':
-        return { type: 'block', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'section':
-        return { type: 'section', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'task':
-        return { type: 'task', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'task-todo':
-        return { type: 'task-todo', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'task-done':
-        return { type: 'task-done', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
-      case 'match-case':
-        return { type: 'match-case', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*'), caseSensitive: true };
-      case 'ignore-case':
-        return { type: 'ignore-case', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*'), caseSensitive: false };
+      if (prefix.startsWith('[') && prefix.endsWith(']')) {
+        const propertyKey = prefix.substring(1, prefix.length - 1);
+        term = {
+          type: 'property',
+          value: cleanValue,
+          propertyKey,
+          negated,
+          quoted: valueQuoted,
+          wildcard: cleanValue.includes('*')
+        };
+        negativeValue = cleanValue || propertyKey;
+      } else {
+        switch (prefix) {
+          case 'path':
+            if (!negated) {
+              diagnostics.filters.path.push(cleanValue);
+            }
+            term = { type: 'path', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'file':
+            if (!negated) {
+              diagnostics.filters.file.push(cleanValue);
+            }
+            term = { type: 'file', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'content':
+            term = { type: 'content', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'tag':
+            if (!negated) {
+              diagnostics.filters.tag.push(cleanValue);
+            }
+            term = { type: 'tag', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'line':
+            term = { type: 'line', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'block':
+            term = { type: 'block', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'section':
+            term = { type: 'section', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'task':
+            term = { type: 'task', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'task-todo':
+            term = { type: 'task-todo', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'task-done':
+            term = { type: 'task-done', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*') };
+            negativeValue = cleanValue;
+            break;
+          case 'match-case':
+            diagnostics.filters.caseSensitive = true;
+            term = { type: 'match-case', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*'), caseSensitive: true };
+            negativeValue = cleanValue;
+            break;
+          case 'ignore-case':
+            diagnostics.filters.caseSensitive = false;
+            term = { type: 'ignore-case', value: cleanValue, negated, quoted: valueQuoted, wildcard: cleanValue.includes('*'), caseSensitive: false };
+            negativeValue = cleanValue;
+            break;
+          default:
+            diagnostics.warnings.push(`UnknownOperator:${prefix}`);
+            // treat as text with original value including prefix
+            term = { type: 'text', value, negated, quoted, wildcard };
+            negativeValue = value;
+            break;
+        }
+      }
     }
   }
 
-  // Check for property search [property:value] or [property]
-  if (value.startsWith('[') && value.endsWith(']')) {
+  if (!term && value.startsWith('[') && value.endsWith(']')) {
     const inner = value.substring(1, value.length - 1);
     const propColonIndex = inner.indexOf(':');
     if (propColonIndex > 0) {
       const propertyKey = inner.substring(0, propColonIndex);
       let propertyValue = inner.substring(propColonIndex + 1);
       let propValueQuoted = false;
-      
-      // Remove quotes from property value
       if (propertyValue.startsWith('"') && propertyValue.endsWith('"')) {
         propValueQuoted = true;
         propertyValue = propertyValue.substring(1, propertyValue.length - 1);
       }
-      
-      return {
+      term = {
         type: 'property',
         value: propertyValue,
         propertyKey,
@@ -357,20 +433,52 @@ function parseTerm(token: string, options?: SearchOptions): SearchTerm | null {
         quoted: propValueQuoted,
         wildcard: propertyValue.includes('*')
       };
+      negativeValue = propertyValue || propertyKey;
+    } else {
+      term = {
+        type: 'property',
+        value: '',
+        propertyKey: inner,
+        negated,
+        quoted: false,
+        wildcard: false
+      };
+      negativeValue = inner;
     }
-    // Property existence check [property]
-    return {
-      type: 'property',
-      value: '',
-      propertyKey: inner,
-      negated,
-      quoted: false,
-      wildcard: false
-    };
   }
 
-  // Default: text search
-  return { type: 'text', value, negated, quoted, wildcard };
+  if (!term) {
+    term = { type: 'text', value, negated, quoted, wildcard };
+    negativeValue = value;
+  }
+
+  if (negated && negativeValue && term) {
+    diagnostics.filters.negative.push(negativeValue);
+    diagnostics.filters.negativeDetails.push({
+      type: term.type,
+      value: negativeValue,
+      wildcard: 'wildcard' in term ? Boolean((term as any).wildcard) : undefined
+    });
+  }
+
+  if (term.type === 'regex') {
+    diagnostics.filters.regex = true;
+  }
+
+  return term;
+}
+
+function createEmptyDiagnosticsFilters(options?: SearchOptions): SearchFilterDiagnostics {
+  return {
+    tag: [],
+    path: [],
+    file: [],
+    negative: [],
+    negativeDetails: [],
+    regex: options?.regexMode ?? false,
+    caseSensitive: options?.caseSensitive ?? false,
+    wholeWord: (options as any)?.wholeWord ?? false
+  };
 }
 
 /**
diff --git a/src/core/search/search-parser.types.ts b/src/core/search/search-parser.types.ts
index d4cf689..2ae0dc2 100644
--- a/src/core/search/search-parser.types.ts
+++ b/src/core/search/search-parser.types.ts
@@ -41,9 +41,33 @@ export interface SearchGroup {
 
 export type SearchNode = SearchTerm | SearchGroup;
 
+export interface NegativeFilterDiagnostic {
+  type: SearchTermType;
+  value: string;
+  wildcard?: boolean;
+}
+
+export interface SearchFilterDiagnostics {
+  tag: string[];
+  path: string[];
+  file: string[];
+  negative: string[];
+  negativeDetails: NegativeFilterDiagnostic[];
+  regex: boolean;
+  caseSensitive: boolean;
+  wholeWord: boolean;
+}
+
+export interface ParseDiagnostics {
+  tokens: string[];
+  filters: SearchFilterDiagnostics;
+  warnings: string[];
+}
+
 export interface ParsedQuery {
   ast: SearchNode;
   isEmpty: boolean;
+  diagnostics?: ParseDiagnostics;
 }
 
 /** Predicate function to test if content matches the query */
diff --git a/src/test-setup.ts b/src/test-setup.ts
new file mode 100644
index 0000000..1e7853d
--- /dev/null
+++ b/src/test-setup.ts
@@ -0,0 +1,14 @@
+// Test setup file for Karma/Jasmine
+import 'zone.js';
+import 'zone.js/testing';
+import { getTestBed } from '@angular/core/testing';
+import {
+  BrowserDynamicTestingModule,
+  platformBrowserDynamicTesting
+} from '@angular/platform-browser-dynamic/testing';
+
+// First, initialize the Angular testing environment.
+getTestBed().initTestEnvironment(
+  BrowserDynamicTestingModule,
+  platformBrowserDynamicTesting(),
+);
diff --git a/test-parser-debug.js b/test-parser-debug.js
new file mode 100644
index 0000000..1109a91
--- /dev/null
+++ b/test-parser-debug.js
@@ -0,0 +1,19 @@
+// Quick test to debug parser behavior
+const { parseSearchQuery } = require('./dist/core/search/search-parser');
+
+const query1 = 'tag:#home file:"Project Plan.md"';
+const parsed1 = parseSearchQuery(query1, { caseSensitive: false, regexMode: false });
+
+console.log('Query 1:', query1);
+console.log('Tokens:', parsed1.diagnostics?.tokens);
+console.log('Tag filters:', parsed1.diagnostics?.filters.tag);
+console.log('File filters:', parsed1.diagnostics?.filters.file);
+console.log('---');
+
+const query2 = 'tag:#home -path:"Archive" -content:"secret"';
+const parsed2 = parseSearchQuery(query2, { caseSensitive: false, regexMode: false });
+
+console.log('Query 2:', query2);
+console.log('Tokens:', parsed2.diagnostics?.tokens);
+console.log('Negative filters:', parsed2.diagnostics?.filters.negative);
+console.log('Negative details:', parsed2.diagnostics?.filters.negativeDetails);
diff --git a/tsconfig.spec.json b/tsconfig.spec.json
index 3a86045..39b4b7d 100644
--- a/tsconfig.spec.json
+++ b/tsconfig.spec.json
@@ -9,6 +9,9 @@
     "allowJs": false,
     "types": ["jasmine", "node"]
   },
+  "files": [
+    "src/test-setup.ts"
+  ],
   "include": [
     "src/**/*.spec.ts",
     "src/**/*.d.ts"
diff --git a/vault/.obsidian/graph.json b/vault/.obsidian/graph.json
index 8bc5a09..339d3ce 100644
--- a/vault/.obsidian/graph.json
+++ b/vault/.obsidian/graph.json
@@ -1,22 +1,22 @@
 {
   "collapse-filter": false,
   "search": "",
-  "showTags": true,
+  "showTags": false,
   "showAttachments": false,
   "hideUnresolved": false,
-  "showOrphans": false,
+  "showOrphans": true,
   "collapse-color-groups": false,
   "colorGroups": [],
   "collapse-display": false,
   "showArrow": false,
-  "textFadeMultiplier": -3,
-  "nodeSizeMultiplier": 0.25,
-  "lineSizeMultiplier": 1.45,
+  "textFadeMultiplier": 0,
+  "nodeSizeMultiplier": 1,
+  "lineSizeMultiplier": 1,
   "collapse-forces": false,
-  "centerStrength": 0.27,
-  "repelStrength": 10,
-  "linkStrength": 0.15,
-  "linkDistance": 102,
-  "scale": 1.4019828977761002,
+  "centerStrength": 0.3,
+  "repelStrength": 17,
+  "linkStrength": 0.5,
+  "linkDistance": 200,
+  "scale": 1,
   "close": false
 }
\ No newline at end of file