diff --git a/lib/ruby_llm/provider.rb b/lib/ruby_llm/provider.rb
index 5540e907..67e40a6b 100644
--- a/lib/ruby_llm/provider.rb
+++ b/lib/ruby_llm/provider.rb
@@ -7,7 +7,8 @@ module RubyLLM
   module Provider
     # Common functionality for all LLM providers. Implements the core provider
     # interface so specific providers only need to implement a few key methods.
-    module Methods # rubocop:disable Metrics/ModuleLength
+    # rubocop:disable Metrics/ModuleLength
+    module Methods
       extend Streaming
 
       def complete(messages, tools:, temperature:, model:, &block) # rubocop:disable Metrics/MethodLength
@@ -40,14 +41,14 @@ def list_models
 
       def embed(text, model:)
         payload = render_embedding_payload text, model: model
-        response = post embedding_url, payload
+        response = post embedding_url, payload, model_id: model
         parse_embedding_response response
       end
 
       def paint(prompt, model:, size:)
         payload = render_image_payload(prompt, model:, size:)
 
-        response = post(images_url, payload)
+        response = post(images_url, payload, model_id: model)
         parse_image_response(response)
       end
 
@@ -78,13 +79,21 @@ def ensure_configured!
       end
 
       def sync_response(payload)
-        response = post completion_url, payload
+        model_id = payload[:model]
+        response = post completion_url, payload, model_id: model_id
         parse_completion_response response
       end
 
-      def post(url, payload)
+      def post(url, payload, model_id: nil)
+        request_headers = headers
+
+        if model_id && capabilities.respond_to?(:additional_headers_for_model)
+          additional_headers = capabilities.additional_headers_for_model(model_id)
+          request_headers = request_headers.merge(additional_headers) unless additional_headers.empty?
+        end
+
         connection.post url, payload do |req|
-          req.headers.merge! headers
+          req.headers.merge! request_headers
           yield req if block_given?
         end
       end
@@ -190,5 +199,6 @@ def configured_providers
         providers.select { |_name, provider| provider.configured? }.values
       end
     end
+    # rubocop:enable Metrics/ModuleLength
   end
 end
diff --git a/lib/ruby_llm/providers/anthropic/capabilities.rb b/lib/ruby_llm/providers/anthropic/capabilities.rb
index 4e07afec..a835b4ad 100644
--- a/lib/ruby_llm/providers/anthropic/capabilities.rb
+++ b/lib/ruby_llm/providers/anthropic/capabilities.rb
@@ -68,6 +68,18 @@ def supports_extended_thinking?(model_id)
           model_id.match?(/claude-3-7-sonnet/)
         end
 
+        # Returns additional request headers for a specific model
+        # @param model_id [String] the model identifier
+        # @return [Hash] additional headers to include in the request
+        def additional_headers_for_model(model_id)
+          case model_id
+          when 'claude-3-7-sonnet-20250219'
+            { 'anthropic-beta' => 'output-128k-2025-02-19' }
+          else
+            {}
+          end
+        end
+
         # Determines the model family for a given model ID
         # @param model_id [String] the model identifier
         # @return [Symbol] the model family identifier
diff --git a/lib/ruby_llm/providers/bedrock.rb b/lib/ruby_llm/providers/bedrock.rb
index 7db44a9a..aff0bdcc 100644
--- a/lib/ruby_llm/providers/bedrock.rb
+++ b/lib/ruby_llm/providers/bedrock.rb
@@ -24,7 +24,7 @@ def api_base
         @api_base ||= "https://bedrock-runtime.#{RubyLLM.config.bedrock_region}.amazonaws.com"
       end
 
-      def post(url, payload)
+      def post(url, payload, model_id: nil) # rubocop:disable Lint/UnusedMethodArgument
         signature = sign_request("#{connection.url_prefix}#{url}", payload:)
         connection.post url, payload do |req|
           req.headers.merge! build_headers(signature.headers, streaming: block_given?)
diff --git a/lib/ruby_llm/streaming.rb b/lib/ruby_llm/streaming.rb
index 442aa014..43cf7e44 100644
--- a/lib/ruby_llm/streaming.rb
+++ b/lib/ruby_llm/streaming.rb
@@ -10,8 +10,9 @@ module Streaming
 
     def stream_response(payload, &block)
       accumulator = StreamAccumulator.new
+      model_id = payload[:model]
 
-      post stream_url, payload do |req|
+      post stream_url, payload, model_id: model_id do |req|
         req.options.on_data = handle_stream do |chunk|
           accumulator.add chunk
           block.call chunk
diff --git a/spec/ruby_llm/providers/anthropic/capabilities_spec.rb b/spec/ruby_llm/providers/anthropic/capabilities_spec.rb
new file mode 100644
index 00000000..c5d239b6
--- /dev/null
+++ b/spec/ruby_llm/providers/anthropic/capabilities_spec.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe RubyLLM::Providers::Anthropic::Capabilities do
+  describe '.additional_headers_for_model' do
+    it 'returns the beta header for claude-3-7-sonnet-20250219' do
+      result = described_class.additional_headers_for_model('claude-3-7-sonnet-20250219')
+      expect(result).to eq('anthropic-beta' => 'output-128k-2025-02-19')
+    end
+
+    it 'returns an empty hash for other models' do
+      other_models = ['claude-3-5-sonnet-20241022', 'claude-3-haiku', 'claude-2']
+
+      other_models.each do |model|
+        result = described_class.additional_headers_for_model(model)
+        expect(result).to eq({})
+      end
+    end
+  end
+end
diff --git a/spec/ruby_llm/providers/anthropic/headers_spec.rb b/spec/ruby_llm/providers/anthropic/headers_spec.rb
new file mode 100644
index 00000000..13366178
--- /dev/null
+++ b/spec/ruby_llm/providers/anthropic/headers_spec.rb
@@ -0,0 +1,116 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Anthropic API Request Headers' do # rubocop:disable RSpec/DescribeClass
+  include_context 'with configured RubyLLM'
+
+  before do
+    WebMock.disable_net_connect!(allow_localhost: true)
+  end
+
+  after do
+    WebMock.allow_net_connect!
+  end
+
+  it 'includes the beta header for claude-3-7-sonnet-20250219' do # rubocop:disable RSpec/ExampleLength
+    # Setup the expected request with the beta header
+    stub_request(:post, 'https://api.anthropic.com/v1/messages')
+      .with(
+        headers: {
+          'Anthropic-Beta' => 'output-128k-2025-02-19'
+        }
+      )
+      .to_return(
+        status: 200,
+        body: {
+          id: 'msg_123',
+          model: 'claude-3-7-sonnet-20250219',
+          type: 'message',
+          role: 'assistant',
+          content: [{ type: 'text', text: 'Hello!' }],
+          usage: { input_tokens: 10, output_tokens: 20 }
+        }.to_json,
+        headers: { 'Content-Type' => 'application/json' }
+      )
+
+    # Make a request with the specific model
+    chat = RubyLLM.chat(model: 'claude-3-7-sonnet-20250219')
+    chat.ask('Hello')
+
+    # Verify that the request was made with the expected headers
+    expect(
+      a_request(:post, 'https://api.anthropic.com/v1/messages')
+        .with(headers: { 'Anthropic-Beta' => 'output-128k-2025-02-19' })
+    ).to have_been_made
+  end
+
+  it 'does not include the beta header for other Claude models' do # rubocop:disable RSpec/ExampleLength
+    # Setup the expected request without the beta header
+    stub_request(:post, 'https://api.anthropic.com/v1/messages')
+      .with { |request| !request.headers.key?('Anthropic-Beta') }
+      .to_return(
+        status: 200,
+        body: {
+          id: 'msg_456',
+          model: 'claude-3-5-sonnet-20241022',
+          type: 'message',
+          role: 'assistant',
+          content: [{ type: 'text', text: 'Hello!' }],
+          usage: { input_tokens: 10, output_tokens: 20 }
+        }.to_json,
+        headers: { 'Content-Type' => 'application/json' }
+      )
+
+    # Make a request with a different model
+    chat = RubyLLM.chat(model: 'claude-3-5-sonnet-20241022')
+    chat.ask('Hello')
+
+    # Verify that the request was made without the beta header
+    expect(
+      a_request(:post, 'https://api.anthropic.com/v1/messages')
+        .with { |request| !request.headers.key?('Anthropic-Beta') }
+    ).to have_been_made
+  end
+
+  it 'includes the beta header in streaming responses for claude-3-7-sonnet-20250219' do # rubocop:disable RSpec/ExampleLength
+    streaming_body = <<~STREAM_DATA
+      event: content_block_delta
+      data: {"type":"content_block_delta","delta":{"type":"text","text":"Hello"}}
+
+      event: content_block_delta
+      data: {"type":"content_block_delta","delta":{"type":"text","text":"!"}}
+
+      event: message_stop
+      data: {}
+    STREAM_DATA
+
+    # Setup the expected streaming request with the beta header
+    stub_request(:post, 'https://api.anthropic.com/v1/messages')
+      .with(
+        headers: {
+          'Anthropic-Beta' => 'output-128k-2025-02-19'
+        },
+        body: hash_including('stream' => true)
+      )
+      .to_return(
+        status: 200,
+        body: streaming_body,
+        headers: { 'Content-Type' => 'text/event-stream' }
+      )
+
+    # Make a streaming request with the specific model
+    chat = RubyLLM.chat(model: 'claude-3-7-sonnet-20250219')
+    chunks = []
+    chat.ask('Hello') { |chunk| chunks << chunk }
+
+    # Verify that the streaming request was made with the expected headers
+    expect(
+      a_request(:post, 'https://api.anthropic.com/v1/messages')
+        .with(
+          headers: { 'Anthropic-Beta' => 'output-128k-2025-02-19' },
+          body: hash_including('stream' => true)
+        )
+    ).to have_been_made
+  end
+end