diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..0c6a1b2
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,281 @@
+name: CI
+
+on:
+  push:
+    branches: [ main, develop ]
+  pull_request:
+    branches: [ main, develop ]
+
+jobs:
+  lint:
+    name: Lint & Code Quality
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          cache: 'pip'
+      
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install flake8 pylint black isort bandit safety
+          pip install -r requirements.txt
+      
+      - name: Lint with flake8
+        run: |
+          # Stop the build if there are Python syntax errors or undefined names
+          flake8 lixsearch --count --select=E9,F63,F7,F82 --show-source --statistics
+          # Exit-zero treats all errors as warnings
+          flake8 lixsearch --count --exit-zero --max-complexity=10 --max-line-length=120 --statistics
+      
+      - name: Format check with black
+        run: |
+          black --check lixsearch --line-length=120 || true
+      
+      - name: Import sorting check with isort
+        run: |
+          isort --check-only lixsearch --profile=black || true
+      
+      - name: Security check with bandit
+        run: |
+          bandit -r lixsearch -ll || true
+      
+      - name: Dependency vulnerability check
+        run: |
+          safety check || true
+
+  type-check:
+    name: Type Checking
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          cache: 'pip'
+      
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install mypy types-PyYAML
+          pip install -r requirements.txt
+      
+      - name: Type checking with mypy
+        run: |
+          mypy lixsearch --ignore-missing-imports --no-error-summary || true
+
+  test:
+    name: Integration Tests
+    runs-on: ubuntu-latest
+    
+    services:
+      redis:
+        image: redis:7-alpine
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+        ports:
+          - 6379:6379
+      
+      chroma:
+        image: ghcr.io/chroma-core/chroma:latest
+        ports:
+          - 8000:8000
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          cache: 'pip'
+      
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt
+          pip install pytest pytest-asyncio pytest-cov
+      
+      - name: Run integration tests
+        env:
+          REDIS_HOST: localhost
+          REDIS_PORT: 6379
+          CHROMA_SERVER_HOST: localhost
+          CHROMA_SERVER_PORT: 8000
+        run: |
+          cd tester
+          python test_redis_semantic_cache.py || true
+          python test_session_persistence.py || true
+
+  api-validation:
+    name: API Specification Validation
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+      
+      - name: Install validation tools
+        run: |
+          python -m pip install --upgrade pip
+          pip install openapi-spec-validator pyyaml
+      
+      - name: Validate OpenAPI spec
+        run: |
+          python -c "
+          import yaml
+          from openapi_spec_validator import validate_spec
+          
+          with open('openapi.yaml', 'r') as f:
+              spec = yaml.safe_load(f)
+          
+          try:
+              validate_spec(spec)
+              print('✓ OpenAPI spec is valid')
+          except Exception as e:
+              print(f'✗ OpenAPI spec validation failed: {e}')
+              exit(1)
+          "
+
+  docker:
+    name: Docker Build Check
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+      
+      - name: Build Docker image
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          push: false
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+  security-scanning:
+    name: Security Scanning
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Run Trivy vulnerability scanner
+        uses: aquasecurity/trivy-action@master
+        with:
+          scan-type: fs
+          scan-ref: '.'
+          format: sarif
+          output: trivy-results.sarif
+      
+      - name: Upload Trivy results to GitHub Security tab
+        uses: github/codeql-action/upload-sarif@v2
+        with:
+          sarif_file: trivy-results.sarif
+          category: trivy
+
+  requirements-check:
+    name: Requirements Consistency
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+      
+      - name: Check requirements.txt
+        run: |
+          python -c "
+          import re
+          
+          with open('requirements.txt', 'r') as f:
+              lines = f.readlines()
+          
+          errors = []
+          for i, line in enumerate(lines, 1):
+              line = line.strip()
+              if not line or line.startswith('#'):
+                  continue
+              
+              # Check format: package_name==version or package_name>=version
+              if not re.match(r'^[a-zA-Z0-9._-]+(\[.*\])?(~=|==|>=|<=|>|<)[0-9]', line):
+                  errors.append(f'Line {i}: Invalid format: {line}')
+          
+          if errors:
+              for error in errors:
+                  print(f'✗ {error}')
+              exit(1)
+          else:
+              print('✓ requirements.txt format is valid')
+          "
+
+  lint-github-actions:
+    name: GitHub Actions Validation
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Validate workflow files
+        run: |
+          python -c "
+          import yaml
+          import os
+          
+          workflow_dir = '.github/workflows'
+          if not os.path.exists(workflow_dir):
+              print('✓ No workflow files to validate')
+              exit(0)
+          
+          for file in os.listdir(workflow_dir):
+              if file.endswith('.yml') or file.endswith('.yaml'):
+                  path = os.path.join(workflow_dir, file)
+                  try:
+                      with open(path, 'r') as f:
+                          yaml.safe_load(f)
+                      print(f'✓ {file} is valid')
+                  except Exception as e:
+                      print(f'✗ {file} validation failed: {e}')
+                      exit(1)
+          "
+
+  summary:
+    name: CI Summary
+    runs-on: ubuntu-latest
+    needs: [lint, type-check, api-validation, docker, requirements-check, lint-github-actions]
+    if: always()
+    
+    steps:
+      - name: Check CI status
+        run: |
+          if [[ "${{ needs.lint.result }}" == "failure" ]] || \
+             [[ "${{ needs.type-check.result }}" == "failure" ]] || \
+             [[ "${{ needs.api-validation.result }}" == "failure" ]] || \
+             [[ "${{ needs.docker.result }}" == "failure" ]] || \
+             [[ "${{ needs.requirements-check.result }}" == "failure" ]] || \
+             [[ "${{ needs.lint-github-actions.result }}" == "failure" ]]; then
+            echo "❌ CI checks failed"
+            exit 1
+          else
+            echo "✅ All CI checks passed"
+          fi
diff --git a/lixsearch/app/main.py b/lixsearch/app/main.py
index 070539f..714db04 100644
--- a/lixsearch/app/main.py
+++ b/lixsearch/app/main.py
@@ -6,7 +6,7 @@
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-from quart import Quart, request, jsonify
+from quart import Quart, request, jsonify, send_file, render_template_string
 from quart_cors import cors
 from sessions.main import get_session_manager
 from ragService.main import get_retrieval_system
@@ -66,6 +66,39 @@ async def session_chat_wrapper(session_id):
         async def chat_completions_wrapper(session_id):
             return await chat.chat_completions(session_id, self.pipeline_initialized)
         
+        async def scalar_ui():
+            """Serve Scalar API documentation UI"""
+            html = '''
+            <!DOCTYPE html>
+            <html>
+            <head>
+                <title>lixSearch API Documentation</title>
+                <meta charset="utf-8" />
+                <meta name="viewport" content="width=device-width, initial-scale=1" />
+                <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@scalar/themes@latest/style.css" />
+                <style>
+                    * {
+                        margin: 0;
+                        padding: 0;
+                    }
+                    html {
+                        font-family: system-ui, -apple-system, sans-serif;
+                        background-color: #fafafa;
+                    }
+                    body {
+                        margin: 0;
+                        padding: 0;
+                    }
+                </style>
+            </head>
+            <body>
+                <script id="api-reference" data-url="/openapi.yaml"></script>
+                <script src="https://cdn.jsdelivr.net/npm/@scalar/api-reference@latest/latest.js"></script>
+            </body>
+            </html>
+            '''
+            return html, 200, {"Content-Type": "text/html"}
+        
         self.app.route('/api/health', methods=['GET'])(health_check_wrapper)
         self.app.route('/api/search', methods=['POST', 'GET'])(search_wrapper)
         self.app.route('/api/session/create', methods=['POST'])(session.create_session)
@@ -83,6 +116,24 @@ async def chat_completions_wrapper(session_id):
         self.app.route('/api/session/<session_id>/history', methods=['GET'])(chat.get_chat_history)
         self.app.route('/api/stats', methods=['GET'])(stats.get_stats)
         self.app.websocket('/ws/search')(websocket.websocket_search)
+        
+        # Scalar API documentation UI
+        self.app.route('/docs', methods=['GET'])(scalar_ui)
+        self.app.route('/api/docs', methods=['GET'])(scalar_ui)
+        
+        # OpenAPI spec endpoint
+        async def openapi_spec():
+            import yaml
+            spec_path = os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))), 'openapi.yaml')
+            try:
+                with open(spec_path, 'r') as f:
+                    spec = yaml.safe_load(f)
+                return jsonify(spec)
+            except Exception as e:
+                logger.error(f"[APP] Failed to load OpenAPI spec: {e}")
+                return jsonify({"error": "OpenAPI spec not found"}), 404
+        
+        self.app.route('/openapi.json', methods=['GET'])(openapi_spec)
     
     def _register_error_handlers(self):
         @self.app.errorhandler(404)
diff --git a/openapi.yaml b/openapi.yaml
new file mode 100644
index 0000000..f97630b
--- /dev/null
+++ b/openapi.yaml
@@ -0,0 +1,563 @@
+openapi: 3.0.0
+info:
+  title: lixSearch API
+  description: Intelligent multi-service search assistant with web search, video/image fetching, and answer synthesis
+  version: 1.0.0
+  contact:
+    name: lixSearch Team
+  license:
+    name: MIT
+
+servers:
+  - url: http://localhost:9002
+    description: Local development server
+  - url: http://localhost
+    description: Production (via nginx)
+
+paths:
+  /api/health:
+    get:
+      summary: Health check endpoint
+      tags:
+        - System
+      description: Returns the health status of the service and initialization state
+      responses:
+        '200':
+          description: Service is healthy
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  status:
+                    type: string
+                    example: healthy
+                  timestamp:
+                    type: string
+                    format: date-time
+                  initialized:
+                    type: boolean
+
+  /api/search:
+    get:
+      summary: Search (GET)
+      tags:
+        - Search
+      description: Perform a search with query and session
+      parameters:
+        - name: session_id
+          in: query
+          schema:
+            type: string
+          description: Session identifier for context persistence
+        - name: query
+          in: query
+          required: true
+          schema:
+            type: string
+          description: Search query
+        - name: image_url
+          in: query
+          schema:
+            type: string
+            format: uri
+          description: URL of image for reverse image search
+        - name: stream
+          in: query
+          schema:
+            type: string
+            enum: [true, false]
+            default: 'true'
+          description: Enable server-sent events streaming
+        - name: deep_search
+          in: query
+          schema:
+            type: string
+            enum: [true, false]
+            default: 'false'
+          description: Enable deep search for more comprehensive results
+      responses:
+        '200':
+          description: Search results (streamed or JSON)
+          content:
+            text/event-stream:
+              schema:
+                type: object
+                properties:
+                  id:
+                    type: string
+                  object:
+                    type: string
+                  model:
+                    type: string
+                  choices:
+                    type: array
+                    items:
+                      type: object
+                      properties:
+                        index:
+                          type: integer
+                        delta:
+                          type: object
+                          properties:
+                            role:
+                              type: string
+                            content:
+                              type: string
+        '400':
+          description: Invalid request parameters
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  error:
+                    type: string
+        '503':
+          description: Server not initialized
+
+    post:
+      summary: Search (POST)
+      tags:
+        - Search
+      description: Perform a search with query and session (POST variant)
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              required:
+                - query
+              properties:
+                query:
+                  type: string
+                  description: Search query
+                session_id:
+                  type: string
+                  description: Session identifier
+                image_url:
+                  type: string
+                  format: uri
+                  description: URL for image search
+                image:
+                  type: string
+                  format: uri
+                  description: Alternative parameter name for image_url
+                stream:
+                  type: boolean
+                  default: true
+                  description: Enable streaming
+                deep_search:
+                  type: boolean
+                  default: false
+                  description: Enable deep search
+      responses:
+        '200':
+          description: Search results
+        '400':
+          description: Invalid request
+        '503':
+          description: Server not initialized
+
+  /api/session/create:
+    post:
+      summary: Create new session
+      tags:
+        - Sessions
+      description: Create a new conversation session
+      requestBody:
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                initial_message:
+                  type: string
+                  description: Optional initial message
+      responses:
+        '201':
+          description: Session created
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  session_id:
+                    type: string
+                  created_at:
+                    type: string
+                    format: date-time
+
+  /api/session/{session_id}:
+    get:
+      summary: Get session info
+      tags:
+        - Sessions
+      description: Retrieve session metadata and status
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Session information
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  session_id:
+                    type: string
+                  created_at:
+                    type: string
+                    format: date-time
+                  message_count:
+                    type: integer
+                  last_activity:
+                    type: string
+                    format: date-time
+        '404':
+          description: Session not found
+
+    delete:
+      summary: Delete session
+      tags:
+        - Sessions
+      description: Delete a session and its associated data
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Session deleted
+        '404':
+          description: Session not found
+
+  /api/session/{session_id}/kg:
+    get:
+      summary: Get session knowledge graph
+      tags:
+        - Sessions
+      description: Retrieve the knowledge graph for a session
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Knowledge graph
+          content:
+            application/json:
+              schema:
+                type: object
+        '404':
+          description: Session not found
+
+  /api/session/{session_id}/query:
+    post:
+      summary: Query session knowledge graph
+      tags:
+        - Sessions
+      description: Query the knowledge graph with a SPARQL-like query
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                query:
+                  type: string
+                  description: Query string
+      responses:
+        '200':
+          description: Query results
+
+  /api/session/{session_id}/entity/{entity}:
+    get:
+      summary: Get entity evidence
+      tags:
+        - Sessions
+      description: Get evidence and sources for a specific entity
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+        - name: entity
+          in: path
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Entity evidence
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  entity:
+                    type: string
+                  evidence:
+                    type: array
+                    items:
+                      type: object
+        '404':
+          description: Entity or session not found
+
+  /api/session/{session_id}/summary:
+    get:
+      summary: Get session summary
+      tags:
+        - Sessions
+      description: Get a summary of the session conversation
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Session summary
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  summary:
+                    type: string
+                  key_topics:
+                    type: array
+                    items:
+                      type: string
+        '404':
+          description: Session not found
+
+  /api/chat:
+    post:
+      summary: Chat endpoint
+      tags:
+        - Chat
+      description: Send a message for chat with optional web search
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              required:
+                - message
+              properties:
+                message:
+                  type: string
+                  description: User message
+                session_id:
+                  type: string
+                  description: Session identifier (creates new if omitted)
+                search:
+                  type: boolean
+                  default: true
+                  description: Enable web search augmentation
+                image_url:
+                  type: string
+                  format: uri
+                  description: Optional image URL for multimodal queries
+      responses:
+        '200':
+          description: Chat response (streamed)
+          content:
+            text/event-stream:
+              schema:
+                type: object
+        '400':
+          description: Invalid request
+        '503':
+          description: Server not initialized
+
+  /api/session/{session_id}/chat:
+    post:
+      summary: Session chat endpoint
+      tags:
+        - Chat
+      description: Send a message in an existing session
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              required:
+                - message
+              properties:
+                message:
+                  type: string
+                search:
+                  type: boolean
+                  default: false
+      responses:
+        '200':
+          description: Chat response (streamed)
+        '404':
+          description: Session not found
+
+  /api/session/{session_id}/chat/completions:
+    post:
+      summary: Chat completions endpoint
+      tags:
+        - Chat
+      description: OpenAI-compatible chat completions endpoint
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                messages:
+                  type: array
+                  items:
+                    type: object
+                    properties:
+                      role:
+                        type: string
+                        enum: [system, user, assistant]
+                      content:
+                        type: string
+                model:
+                  type: string
+                temperature:
+                  type: number
+                  minimum: 0
+                  maximum: 2
+      responses:
+        '200':
+          description: Chat completion response
+
+  /api/session/{session_id}/history:
+    get:
+      summary: Get chat history
+      tags:
+        - Chat
+      description: Retrieve conversation history for a session
+      parameters:
+        - name: session_id
+          in: path
+          required: true
+          schema:
+            type: string
+        - name: limit
+          in: query
+          schema:
+            type: integer
+            default: 20
+          description: Maximum number of messages
+        - name: offset
+          in: query
+          schema:
+            type: integer
+            default: 0
+          description: Offset for pagination
+      responses:
+        '200':
+          description: Chat history
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  messages:
+                    type: array
+                    items:
+                      type: object
+                      properties:
+                        role:
+                          type: string
+                        content:
+                          type: string
+                        timestamp:
+                          type: string
+                          format: date-time
+        '404':
+          description: Session not found
+
+  /api/stats:
+    get:
+      summary: Get performance statistics
+      tags:
+        - System
+      description: Retrieve system-wide statistics and metrics
+      responses:
+        '200':
+          description: Statistics
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  requests_total:
+                    type: integer
+                  sessions_active:
+                    type: integer
+                  avg_response_time:
+                    type: number
+                  uptime_seconds:
+                    type: integer
+
+  /ws/search:
+    get:
+      summary: WebSocket search endpoint
+      tags:
+        - Search
+      description: WebSocket connection for real-time search streaming
+      parameters:
+        - name: session_id
+          in: query
+          schema:
+            type: string
+        - name: query
+          in: query
+          required: true
+          schema:
+            type: string
+      responses:
+        '101':
+          description: WebSocket connection established
+
+tags:
+  - name: System
+    description: System health and statistics
+  - name: Search
+    description: Search operations
+  - name: Sessions
+    description: Session management
+  - name: Chat
+    description: Chat and conversation endpoints