Fix Anthropic streaming and empty tool input errors (#299)

* Fix Anthropic streaming error for higher-level gem events

The anthropic gem (1.12+) emits higher-level convenience events
(TextEvent, ThinkingEvent, SignatureEvent, etc.) in addition to raw
streaming events when using MessageStream.

The :signature event was causing "Unexpected chunk type: signature"
errors because it lacks a :snapshot method, causing it to fall
through to the error handler.

Added explicit handling for all higher-level convenience events:
:text, :input_json, :citation, :thinking, :signature

These are safely ignored since the actual content is already
processed via the raw :content_block_delta events.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Fix empty tool input JSON parsing for parameterless tools

For tools with no parameters, the streaming API may send empty
partial_json, resulting in an empty string input that would fail
JSON.parse with a syntax error.

Changes:
- Use json_buf.present? instead of just json_buf to skip empty strings
- For string inputs, check .present? before parsing and default to {}

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: mattwebbio

lib/active_agent/providers/anthropic_provider.rb

@@ -189,9 +189,14 @@ def process_stream_chunk(api_response_chunk)
         when :ping
           # No-Op Keep Awake
         when :overloaded_error
-          # TODO: https://docs.claude.com/en/docs/build-with-claude/streaming#error-events
+        # TODO: https://docs.claude.com/en/docs/build-with-claude/streaming#error-events
+
+        # Higher-level convenience events from anthropic gem's MessageStream
+        when :text, :input_json, :citation, :thinking, :signature
+          # No-Op; Already handled via :content_block_delta
+
         else
-          # No-Op: Looks like internal tracking from gem wrapper
+          # No-Op; Internal tracking from gem wrapper
           return if api_response_chunk.respond_to?(:snapshot)
           raise "Unexpected chunk type: #{api_response_chunk.type}"
         end
@@ -296,11 +301,16 @@ def process_prompt_finished_extract_messages(api_response)
       def process_prompt_finished_extract_function_calls
         message_stack.pluck(:content).flatten.select { _1 in { type: "tool_use" } }.map do |api_function_call|
           json_buf = api_function_call.delete(:json_buf)
-          api_function_call[:input] = JSON.parse(json_buf, symbolize_names: true) if json_buf
+          api_function_call[:input] = JSON.parse(json_buf, symbolize_names: true) if json_buf.present?
 
           # Handle case where :input is still a JSON string (gem >= 1.14.0)
+          # For tools with no parameters, input may be an empty string
           if api_function_call[:input].is_a?(String)
-            api_function_call[:input] = JSON.parse(api_function_call[:input], symbolize_names: true)
+            if api_function_call[:input].present?
+              api_function_call[:input] = JSON.parse(api_function_call[:input], symbolize_names: true)
+            else
+              api_function_call[:input] = {}
+            end
           end
 
           api_function_call

test/providers/anthropic/empty_tool_input_test.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require_relative "../../../lib/active_agent/providers/anthropic_provider"
+
+module Providers
+  module Anthropic
+    class EmptyToolInputTest < ActiveSupport::TestCase
+      setup do
+        @provider = ActiveAgent::Providers::AnthropicProvider.new(
+          service: "Anthropic",
+          model: "claude-sonnet-4-5",
+          messages: [ { role: "user", content: "Hello" } ],
+          stream_broadcaster: ->(message, delta, event_type) { }
+        )
+      end
+
+      test "handles empty string input for tools with no parameters" do
+        @provider.send(:message_stack).push({
+          role: "assistant",
+          content: [
+            { type: "tool_use", id: "tool_123", name: "no_param_tool", input: "" }
+          ]
+        })
+
+        result = @provider.send(:process_prompt_finished_extract_function_calls)
+
+        assert_equal 1, result.size
+        assert_equal({}, result.first[:input])
+      end
+
+      test "handles empty json_buf gracefully" do
+        @provider.send(:message_stack).push({
+          role: "assistant",
+          content: [
+            { type: "tool_use", id: "tool_123", name: "no_param_tool", json_buf: "", input: nil }
+          ]
+        })
+
+        result = @provider.send(:process_prompt_finished_extract_function_calls)
+
+        assert_equal 1, result.size
+        assert_nil result.first[:input]
+      end
+    end
+  end
+end

test/providers/anthropic/streaming_events_test.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require_relative "../../../lib/active_agent/providers/anthropic_provider"
+
+module Providers
+  module Anthropic
+    class StreamingEventsTest < ActiveSupport::TestCase
+      setup do
+        @provider = ActiveAgent::Providers::AnthropicProvider.new(
+          service: "Anthropic",
+          model: "claude-sonnet-4-5",
+          messages: [ { role: "user", content: "Hello" } ],
+          stream_broadcaster: ->(message, delta, event_type) { }
+        )
+
+        @provider.send(:message_stack).push({
+          role: "assistant",
+          content: [ { type: "text", text: "" } ]
+        })
+      end
+
+      MockEvent = Struct.new(:type, keyword_init: true) do
+        def [](key)
+          send(key) if respond_to?(key)
+        end
+      end
+
+      test "handles :signature event without raising" do
+        event = MockEvent.new(type: :signature)
+
+        assert_nothing_raised do
+          @provider.send(:process_stream_chunk, event)
+        end
+      end
+
+      test "handles :thinking event without raising" do
+        event = MockEvent.new(type: :thinking)
+
+        assert_nothing_raised do
+          @provider.send(:process_stream_chunk, event)
+        end
+      end
+    end
+  end
+end