diff --git a/frameworks/sinatra/Dockerfile b/frameworks/sinatra/Dockerfile
new file mode 100644
index 0000000..0e79e34
--- /dev/null
+++ b/frameworks/sinatra/Dockerfile
@@ -0,0 +1,16 @@
+FROM ruby:3.4-slim
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends build-essential libsqlite3-dev && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY Gemfile .
+RUN bundle install --jobs=$(nproc)
+
+COPY . .
+
+EXPOSE 8080
+
+CMD ["bundle", "exec", "puma", "-C", "puma.rb"]
diff --git a/frameworks/sinatra/Gemfile b/frameworks/sinatra/Gemfile
new file mode 100644
index 0000000..a8f853d
--- /dev/null
+++ b/frameworks/sinatra/Gemfile
@@ -0,0 +1,6 @@
+source 'https://rubygems.org'
+
+gem 'sinatra', '~> 4.1'
+gem 'puma', '~> 6.5'
+gem 'sqlite3', '~> 2.6'
+gem 'json'
diff --git a/frameworks/sinatra/app.rb b/frameworks/sinatra/app.rb
new file mode 100644
index 0000000..be794af
--- /dev/null
+++ b/frameworks/sinatra/app.rb
@@ -0,0 +1,142 @@
+require 'sinatra/base'
+require 'json'
+require 'zlib'
+require 'stringio'
+require 'sqlite3'
+
+class App < Sinatra::Base
+  configure do
+    set :server, :puma
+    set :logging, false
+    set :show_exceptions, false
+
+    # Load dataset
+    dataset_path = ENV.fetch('DATASET_PATH', '/data/dataset.json')
+    if File.exist?(dataset_path)
+      raw = JSON.parse(File.read(dataset_path))
+      items = raw.map do |d|
+        d.merge('total' => (d['price'] * d['quantity'] * 100).round / 100.0)
+      end
+      set :dataset_items, raw
+      set :json_payload, JSON.generate({ 'items' => items, 'count' => items.length })
+    else
+      set :dataset_items, nil
+      set :json_payload, nil
+    end
+
+    # Large dataset for compression
+    large_path = '/data/dataset-large.json'
+    if File.exist?(large_path)
+      raw = JSON.parse(File.read(large_path))
+      items = raw.map do |d|
+        d.merge('total' => (d['price'] * d['quantity'] * 100).round / 100.0)
+      end
+      payload = JSON.generate({ 'items' => items, 'count' => items.length })
+      # Pre-compress with gzip level 1
+      sio = StringIO.new
+      gz = Zlib::GzipWriter.new(sio, 1)
+      gz.write(payload)
+      gz.close
+      set :compressed_payload, sio.string
+    else
+      set :compressed_payload, nil
+    end
+
+    # SQLite
+    set :db_available, File.exist?('/data/benchmark.db')
+  end
+
+  DB_QUERY = 'SELECT id, name, category, price, quantity, active, tags, rating_score, rating_count FROM items WHERE price BETWEEN ? AND ? LIMIT 50'
+
+  helpers do
+    def get_db
+      Thread.current[:sinatra_db] ||= begin
+        db = SQLite3::Database.new('/data/benchmark.db', readonly: true)
+        db.execute('PRAGMA mmap_size=268435456')
+        db.results_as_hash = true
+        db
+      end
+    end
+  end
+
+  get '/pipeline' do
+    content_type 'text/plain'
+    headers 'Server' => 'sinatra'
+    'ok'
+  end
+
+  def handle_baseline11
+    total = 0
+    request.GET.each do |_k, v|
+      total += v.to_i if v =~ /\A-?\d+\z/
+    end
+    if request.post?
+      request.body.rewind
+      body_str = request.body.read.strip
+      total += body_str.to_i if body_str =~ /\A-?\d+\z/
+    end
+    content_type 'text/plain'
+    headers 'Server' => 'sinatra'
+    total.to_s
+  end
+
+  get('/baseline11') { handle_baseline11 }
+  post('/baseline11') { handle_baseline11 }
+
+  get '/baseline2' do
+    total = 0
+    request.GET.each do |_k, v|
+      total += v.to_i if v =~ /\A-?\d+\z/
+    end
+    content_type 'text/plain'
+    headers 'Server' => 'sinatra'
+    total.to_s
+  end
+
+  get '/json' do
+    payload = settings.json_payload
+    halt 500, 'No dataset' unless payload
+    content_type 'application/json'
+    headers 'Server' => 'sinatra'
+    payload
+  end
+
+  get '/compression' do
+    compressed = settings.compressed_payload
+    halt 500, 'No dataset' unless compressed
+    content_type 'application/json'
+    headers 'Content-Encoding' => 'gzip', 'Server' => 'sinatra'
+    compressed
+  end
+
+  get '/db' do
+    unless settings.db_available
+      content_type 'application/json'
+      headers 'Server' => 'sinatra'
+      return '{"items":[],"count":0}'
+    end
+    min_val = (params['min'] || 10).to_f
+    max_val = (params['max'] || 50).to_f
+    db = get_db
+    rows = db.execute(DB_QUERY, [min_val, max_val])
+    items = rows.map do |r|
+      {
+        'id' => r['id'], 'name' => r['name'], 'category' => r['category'],
+        'price' => r['price'], 'quantity' => r['quantity'], 'active' => r['active'] == 1,
+        'tags' => JSON.parse(r['tags']),
+        'rating' => { 'score' => r['rating_score'], 'count' => r['rating_count'] }
+      }
+    end
+    content_type 'application/json'
+    headers 'Server' => 'sinatra'
+    JSON.generate({ 'items' => items, 'count' => items.length })
+  end
+
+  post '/upload' do
+    request.body.rewind
+    data = request.body.read
+    content_type 'text/plain'
+    headers 'Server' => 'sinatra'
+    data.bytesize.to_s
+  end
+end
diff --git a/frameworks/sinatra/config.ru b/frameworks/sinatra/config.ru
new file mode 100644
index 0000000..14935f3
--- /dev/null
+++ b/frameworks/sinatra/config.ru
@@ -0,0 +1,21 @@
+require_relative 'app'
+
+# Rack middleware to handle unknown HTTP methods before Puma/Sinatra
+class MethodGuard
+  KNOWN = %w[GET POST PUT DELETE PATCH HEAD OPTIONS TRACE CONNECT].freeze
+
+  def initialize(app)
+    @app = app
+  end
+
+  def call(env)
+    if KNOWN.include?(env['REQUEST_METHOD'])
+      @app.call(env)
+    else
+      [405, { 'content-type' => 'text/plain', 'server' => 'sinatra' }, ['Method Not Allowed']]
+    end
+  end
+end
+
+use MethodGuard
+run App
diff --git a/frameworks/sinatra/meta.json b/frameworks/sinatra/meta.json
new file mode 100644
index 0000000..314b2ea
--- /dev/null
+++ b/frameworks/sinatra/meta.json
@@ -0,0 +1,19 @@
+{
+  "display_name": "Sinatra",
+  "language": "Ruby",
+  "type": "framework",
+  "engine": "puma",
+  "description": "Sinatra DSL web framework on Puma, multi-threaded with one worker per CPU core.",
+  "repo": "https://github.com/sinatra/sinatra",
+  "enabled": true,
+  "tests": [
+    "baseline",
+    "pipelined",
+    "noisy",
+    "limited-conn",
+    "json",
+    "upload",
+    "compression",
+    "mixed"
+  ]
+}
diff --git a/frameworks/sinatra/puma.rb b/frameworks/sinatra/puma.rb
new file mode 100644
index 0000000..6c31965
--- /dev/null
+++ b/frameworks/sinatra/puma.rb
@@ -0,0 +1,16 @@
+require 'etc'
+
+cores = Etc.nprocessors
+workers cores
+threads 4, 4
+
+bind 'tcp://0.0.0.0:8080'
+
+# Allow all HTTP methods so unknown ones reach Rack middleware (returned as 405)
+supported_http_methods :any
+
+preload_app!
+
+before_fork do
+  # Close any inherited DB connections
+end