feat: Add AsyncAPI spec support for WebSocket client code generation

Add end-to-end support for generating typed WebSocket clients from AsyncAPI 3.0
specifications, enabling auto-generation of realtime clients (ElevenLabs STT,
OpenAI Realtime, etc.) that were previously hand-written.

Key components:
- AsyncAPI spec parser with JSON Schema to OpenAPI bridge for model reuse
- WebSocket client class generation (ClientWebSocket wrapper with Connect,
  Send, Receive, Dispose, auth constructors, partial hooks)
- Typed send methods (SendXxxAsync with JSON serialization)
- Async enumerable receive method (ReceiveUpdatesAsync → IAsyncEnumerable<T>)
- Source generator and CLI integration with new MSBuild properties
- Snapshot tests for ElevenLabs realtime STT AsyncAPI spec

All 160 unit tests and 94 snapshot tests pass. No existing generation affected.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: HavenDV

specs/elevenlabs-realtime-stt.json

@@ -0,0 +1,268 @@
+{
+  "asyncapi": "3.0.0",
+  "info": {
+    "title": "ElevenLabs Realtime Speech-to-Text",
+    "version": "1.0.0",
+    "description": "ElevenLabs realtime speech-to-text WebSocket API for streaming audio transcription."
+  },
+  "servers": {
+    "production": {
+      "host": "api.elevenlabs.io",
+      "pathname": "/v1/speech-to-text/realtime",
+      "protocol": "wss",
+      "description": "ElevenLabs production WebSocket server"
+    }
+  },
+  "channels": {
+    "realtime": {
+      "address": "/v1/speech-to-text/realtime",
+      "messages": {
+        "inputAudioChunk": {
+          "$ref": "#/components/messages/InputAudioChunk"
+        },
+        "sessionStarted": {
+          "$ref": "#/components/messages/SessionStarted"
+        },
+        "partialTranscript": {
+          "$ref": "#/components/messages/PartialTranscript"
+        },
+        "committedTranscript": {
+          "$ref": "#/components/messages/CommittedTranscript"
+        },
+        "error": {
+          "$ref": "#/components/messages/Error"
+        }
+      }
+    }
+  },
+  "operations": {
+    "sendAudioChunk": {
+      "action": "send",
+      "channel": {
+        "$ref": "#/channels/realtime"
+      },
+      "summary": "Send an audio chunk to the server for transcription.",
+      "messages": [
+        {
+          "$ref": "#/channels/realtime/messages/inputAudioChunk"
+        }
+      ]
+    },
+    "receiveSessionStarted": {
+      "action": "receive",
+      "channel": {
+        "$ref": "#/channels/realtime"
+      },
+      "summary": "Receive session started event.",
+      "messages": [
+        {
+          "$ref": "#/channels/realtime/messages/sessionStarted"
+        }
+      ]
+    },
+    "receivePartialTranscript": {
+      "action": "receive",
+      "channel": {
+        "$ref": "#/channels/realtime"
+      },
+      "summary": "Receive partial transcript event.",
+      "messages": [
+        {
+          "$ref": "#/channels/realtime/messages/partialTranscript"
+        }
+      ]
+    },
+    "receiveCommittedTranscript": {
+      "action": "receive",
+      "channel": {
+        "$ref": "#/channels/realtime"
+      },
+      "summary": "Receive committed transcript event.",
+      "messages": [
+        {
+          "$ref": "#/channels/realtime/messages/committedTranscript"
+        }
+      ]
+    },
+    "receiveError": {
+      "action": "receive",
+      "channel": {
+        "$ref": "#/channels/realtime"
+      },
+      "summary": "Receive error event.",
+      "messages": [
+        {
+          "$ref": "#/channels/realtime/messages/error"
+        }
+      ]
+    }
+  },
+  "components": {
+    "schemas": {
+      "InputAudioChunkPayload": {
+        "type": "object",
+        "description": "Audio chunk sent by the client.",
+        "required": ["message_type", "audio_base_64", "commit", "sample_rate"],
+        "properties": {
+          "message_type": {
+            "type": "string",
+            "description": "Must be 'input_audio_chunk'.",
+            "enum": ["input_audio_chunk"]
+          },
+          "audio_base_64": {
+            "type": "string",
+            "description": "Base64-encoded audio data."
+          },
+          "commit": {
+            "type": "boolean",
+            "description": "Whether to commit the audio buffer."
+          },
+          "sample_rate": {
+            "type": "integer",
+            "description": "Audio sample rate in Hz."
+          },
+          "previous_text": {
+            "type": "string",
+            "description": "Optional previous text context.",
+            "nullable": true
+          }
+        }
+      },
+      "SessionConfig": {
+        "type": "object",
+        "description": "Session configuration returned by the server.",
+        "properties": {
+          "model_id": {
+            "type": "string",
+            "description": "The model used for transcription."
+          },
+          "audio_format": {
+            "type": "string",
+            "description": "Audio format being used."
+          }
+        }
+      },
+      "SessionStartedPayload": {
+        "type": "object",
+        "description": "Event sent when a session is started.",
+        "required": ["message_type", "session_id"],
+        "properties": {
+          "message_type": {
+            "type": "string",
+            "description": "Must be 'session_started'.",
+            "enum": ["session_started"]
+          },
+          "session_id": {
+            "type": "string",
+            "description": "Unique session identifier."
+          },
+          "config": {
+            "$ref": "#/components/schemas/SessionConfig"
+          }
+        }
+      },
+      "PartialTranscriptPayload": {
+        "type": "object",
+        "description": "Event sent when a partial transcript is available.",
+        "required": ["message_type", "text"],
+        "properties": {
+          "message_type": {
+            "type": "string",
+            "description": "Must be 'partial_transcript'.",
+            "enum": ["partial_transcript"]
+          },
+          "text": {
+            "type": "string",
+            "description": "The partial transcript text."
+          }
+        }
+      },
+      "CommittedTranscriptPayload": {
+        "type": "object",
+        "description": "Event sent when a transcript is committed.",
+        "required": ["message_type", "text"],
+        "properties": {
+          "message_type": {
+            "type": "string",
+            "description": "Must be 'committed_transcript'.",
+            "enum": ["committed_transcript"]
+          },
+          "text": {
+            "type": "string",
+            "description": "The committed transcript text."
+          }
+        }
+      },
+      "ErrorPayload": {
+        "type": "object",
+        "description": "Error event.",
+        "required": ["message_type", "error_type", "error"],
+        "properties": {
+          "message_type": {
+            "type": "string",
+            "description": "Must be 'error'.",
+            "enum": ["error"]
+          },
+          "error_type": {
+            "type": "string",
+            "description": "Type of error."
+          },
+          "error": {
+            "type": "string",
+            "description": "Error message."
+          }
+        }
+      }
+    },
+    "messages": {
+      "InputAudioChunk": {
+        "name": "InputAudioChunk",
+        "summary": "Audio chunk for transcription.",
+        "contentType": "application/json",
+        "payload": {
+          "$ref": "#/components/schemas/InputAudioChunkPayload"
+        }
+      },
+      "SessionStarted": {
+        "name": "SessionStarted",
+        "summary": "Session started event.",
+        "contentType": "application/json",
+        "payload": {
+          "$ref": "#/components/schemas/SessionStartedPayload"
+        }
+      },
+      "PartialTranscript": {
+        "name": "PartialTranscript",
+        "summary": "Partial transcript event.",
+        "contentType": "application/json",
+        "payload": {
+          "$ref": "#/components/schemas/PartialTranscriptPayload"
+        }
+      },
+      "CommittedTranscript": {
+        "name": "CommittedTranscript",
+        "summary": "Committed transcript event.",
+        "contentType": "application/json",
+        "payload": {
+          "$ref": "#/components/schemas/CommittedTranscriptPayload"
+        }
+      },
+      "Error": {
+        "name": "Error",
+        "summary": "Error event.",
+        "contentType": "application/json",
+        "payload": {
+          "$ref": "#/components/schemas/ErrorPayload"
+        }
+      }
+    },
+    "securitySchemes": {
+      "apiKey": {
+        "type": "httpApiKey",
+        "name": "xi-api-key",
+        "in": "header",
+        "description": "ElevenLabs API key"
+      }
+    }
+  }
+}

src/libs/AutoSDK.CLI/Commands/GenerateCommand.cs

@@ -137,8 +137,15 @@ internal sealed class GenerateCommand : Command
         Description = "OpenAPI override as 'path=action'. Actions: object, dictionary, remove. Repeatable.",
         AllowMultipleArgumentsPerToken = true,
     };
-    
-    public GenerateCommand() : base(name: "generate", description: "Generates client sdk using a OpenAPI spec.")
+
+    private Option<string> WebSocketClientClassName { get; } = new(
+        name: "--websocket-class-name")
+    {
+        DefaultValueFactory = _ => string.Empty,
+        Description = "Override class name for the generated WebSocket client (AsyncAPI specs only).",
+    };
+
+    public GenerateCommand() : base(name: "generate", description: "Generates client sdk using an OpenAPI or AsyncAPI spec.")
     {
         Arguments.Add(Input);
         Options.Add(Output);
@@ -157,6 +164,7 @@ internal sealed class GenerateCommand : Command
         Options.Add(SecuritySchemes);
         Options.Add(BaseUrl);
         Options.Add(OpenApiOverrides);
+        Options.Add(WebSocketClientClassName);
 
         SetAction(HandleAsync);
     }
@@ -188,6 +196,8 @@ private async Task HandleAsync(ParseResult parseResult)
             SecuritySchemes = parseResult.GetRequiredValue(SecuritySchemes).ToImmutableArray(),
             BaseUrl = parseResult.GetRequiredValue(BaseUrl),
             OpenApiOverrides = parseResult.GetRequiredValue(OpenApiOverrides).ToImmutableArray(),
+            GenerateWebSocketClient = true,
+            WebSocketClientClassName = parseResult.GetRequiredValue(WebSocketClientClassName),
         };
 
         Console.WriteLine($"Loading {input}...");
@@ -284,6 +294,16 @@ private async Task HandleAsync(ParseResult parseResult)
                 ? [Sources.ResponseStream(data.Converters.Settings)]
                 : [])
             .Concat([Sources.UnixTimestampJsonConverter(settings)])
+            // WebSocket client generation (from AsyncAPI specs)
+            .Concat(data.WebSocketClients
+                .SelectMany(x => new []
+                {
+                    Sources.WebSocketClient(x),
+                    Sources.WebSocketReceiveMethod(x),
+                }))
+            .Concat(data.WebSocketOperations
+                .Where(x => x.Direction == AutoSDK.Models.WebSocketDirection.Send)
+                .Select(x => Sources.WebSocketSendMethod(x)))
             .Where(x => !x.IsEmpty)
             .ToArray();
 

src/libs/AutoSDK.SourceGenerators/AutoSDK.SourceGenerators.props

@@ -102,10 +102,17 @@
     <CompilerVisibleProperty Include="AutoSDK_BaseUrl"/>
     <!-- OpenAPI overrides as 'path=action' separated by ;. Actions: object, dictionary, remove. Default: Empty -->
     <CompilerVisibleProperty Include="AutoSDK_OpenApiOverrides"/>
+
+    <!-- WebSocket client generation -->
+    <!-- true/false. Default: true (when AsyncAPI detected) -->
+    <CompilerVisibleProperty Include="AutoSDK_GenerateWebSocketClient"/>
+    <!-- Override class name for the generated WebSocket client. Default: auto from spec title -->
+    <CompilerVisibleProperty Include="AutoSDK_WebSocketClientClassName"/>
   </ItemGroup>
 
   <ItemGroup>
     <CompilerVisibleItemMetadata Include="AdditionalFiles" MetadataName="AutoSDK_OpenApiSpecification" />
+    <CompilerVisibleItemMetadata Include="AdditionalFiles" MetadataName="AutoSDK_AsyncApiSpecification" />
     <CompilerVisibleItemMetadata Include="AdditionalFiles" MetadataName="AutoSDK_Namespace" />
     <CompilerVisibleItemMetadata Include="AdditionalFiles" MetadataName="AutoSDK_ClassName" />
   </ItemGroup>

src/libs/AutoSDK.SourceGenerators/OptionsExtensions.cs

@@ -80,7 +80,9 @@ public static Settings GetSettings(
                               []).ToImmutableArray(),
             BaseUrl: options.GetGlobalOption(nameof(Settings.BaseUrl), prefix) ?? string.Empty,
             OpenApiOverrides: (options.GetGlobalOption(nameof(Settings.OpenApiOverrides), prefix)?.Split(';') ??
-                               []).Where(static x => !string.IsNullOrWhiteSpace(x)).ToImmutableArray());
+                               []).Where(static x => !string.IsNullOrWhiteSpace(x)).ToImmutableArray(),
+            GenerateWebSocketClient: options.GetBoolGlobalOption(nameof(Settings.GenerateWebSocketClient), prefix, defaultValue: Settings.Default.GenerateWebSocketClient),
+            WebSocketClientClassName: options.GetGlobalOption(nameof(Settings.WebSocketClientClassName), prefix) ?? string.Empty);
 
         string? GetOptionFromAdditionalText(string name)
         {

src/libs/AutoSDK.SourceGenerators/SdkGenerator.cs

@@ -47,7 +47,8 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
         var data = context.AdditionalTextsProvider
             .Combine(context.AnalyzerConfigOptionsProvider)
             .Where(static pair =>
-                pair.Right.GetOption(pair.Left, "OpenApiSpecification", prefix: "AutoSDK")?.ToUpperInvariant() == "TRUE")
+                pair.Right.GetOption(pair.Left, "OpenApiSpecification", prefix: "AutoSDK")?.ToUpperInvariant() == "TRUE" ||
+                pair.Right.GetOption(pair.Left, "AsyncApiSpecification", prefix: "AutoSDK")?.ToUpperInvariant() == "TRUE")
             .Select((pair, cancellationToken) => (
                 GetContent(pair.Left, cancellationToken),
                 pair.Right.GetSettings(prefix: "AutoSDK", additionalText: pair.Left)))
@@ -155,6 +156,24 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             .SelectAndReportExceptions((x, c) => Sources.JsonSerializerContextConverters(x, c)
                 .AsFileWithName(), context, Id)
             .AddSource(context);
+
+        // WebSocket client generation (from AsyncAPI specs)
+        data
+            .SelectMany(static (x, _) => x.WebSocketClients)
+            .SelectAndReportExceptions((x, c) => Sources.WebSocketClient(x, c)
+                .AsFileWithName(), context, Id)
+            .AddSource(context);
+        data
+            .SelectMany(static (x, _) => x.WebSocketOperations)
+            .Where(static x => x.Direction == AutoSDK.Models.WebSocketDirection.Send)
+            .SelectAndReportExceptions((x, c) => Sources.WebSocketSendMethod(x, c)
+                .AsFileWithName(), context, Id)
+            .AddSource(context);
+        data
+            .SelectMany(static (x, _) => x.WebSocketClients)
+            .SelectAndReportExceptions((x, c) => Sources.WebSocketReceiveMethod(x, c)
+                .AsFileWithName(), context, Id)
+            .AddSource(context);
     }
 
     private static string GetContent(AdditionalText additionalText, CancellationToken cancellationToken = default)