Generated the JSON contracts of the providers at compile time

app/MindWork AI Studio/Provider/Anthropic/AnthropicContentBlockBuilder.cs

@@ -117,8 +117,8 @@ public sealed class AnthropicContentBlockBuilder
             case TYPE_TEXT:
                 return this.BuildFromSeed(new()
                 {
-                    ["type"] = JsonSerializer.Serialize(TYPE_TEXT),
-                    ["text"] = JsonSerializer.Serialize(this.text.ToString()),
+                    ["type"] = JsonSerializer.Serialize(TYPE_TEXT, ProviderJsonOptions.OPTIONS),
+                    ["text"] = JsonSerializer.Serialize(this.text.ToString(), ProviderJsonOptions.OPTIONS),
                 });
             
             case TYPE_THINKING:
@@ -129,9 +129,9 @@ public sealed class AnthropicContentBlockBuilder
                 //
                 return this.BuildFromSeed(new()
                 {
-                    ["type"] = JsonSerializer.Serialize(TYPE_THINKING),
-                    ["thinking"] = JsonSerializer.Serialize(this.thinking.ToString()),
-                    ["signature"] = JsonSerializer.Serialize(this.signature),
+                    ["type"] = JsonSerializer.Serialize(TYPE_THINKING, ProviderJsonOptions.OPTIONS),
+                    ["thinking"] = JsonSerializer.Serialize(this.thinking.ToString(), ProviderJsonOptions.OPTIONS),
+                    ["signature"] = JsonSerializer.Serialize(this.signature, ProviderJsonOptions.OPTIONS),
                 });
             
             case TYPE_TOOL_USE:

app/MindWork AI Studio/Provider/OpenAI/ChatCompletionToolCallAccumulator.cs

@@ -117,7 +117,7 @@ public sealed class ChatCompletionToolCallAccumulator(Func<ServerSentEvent, ILis
             // No text means no content field, the way a round which only calls a tool arrives
             // when it is not streamed. Some providers reject an empty string in its place.
             //
-            RawContent = answer.Length is 0 ? null : JsonSerializer.SerializeToElement(answer),
+            RawContent = answer.Length is 0 ? null : JsonSerializer.SerializeToElement(answer, ProviderJsonOptions.OPTIONS),
             ReasoningContent = this.reasoning.Length is 0 ? null : this.reasoning.ToString(),
             ToolCalls = this.toolCalls.Count is 0
                 ? null

app/MindWork AI Studio/Provider/OpenAI/OpenAIStrictToolSchema.cs

@@ -59,7 +59,7 @@ public static class OpenAIStrictToolSchema
         // schema stays stable across requests, which prompt caching depends on.
         //
         schema["required"] = new JsonArray([..properties.Select(property => JsonValue.Create(property.Key))]);
-        return JsonSerializer.Deserialize<JsonElement>(schema.ToJsonString());
+        return JsonSerializer.Deserialize<JsonElement>(schema.ToJsonString(), ProviderJsonOptions.OPTIONS);
     }
 
     private static void AllowNullType(JsonObject property)

app/MindWork AI Studio/Provider/ProviderJsonContext.cs

@@ -0,0 +1,129 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+using AIStudio.Provider.Anthropic;
+using AIStudio.Provider.Google;
+using AIStudio.Provider.Groq;
+using AIStudio.Provider.HuggingFace;
+using AIStudio.Provider.OpenAI;
+using AIStudio.Provider.OpenRouter;
+using AIStudio.Provider.Requesty;
+
+using AnthropicDelta = AIStudio.Provider.Anthropic.Delta;
+using AnthropicImageUrl = AIStudio.Provider.Anthropic.SubContentImageUrl;
+using AnthropicResponseStreamLine = AIStudio.Provider.Anthropic.ResponseStreamLine;
+using FireworksChoice = AIStudio.Provider.Fireworks.Choice;
+using FireworksDelta = AIStudio.Provider.Fireworks.Delta;
+using FireworksResponseStreamLine = AIStudio.Provider.Fireworks.ResponseStreamLine;
+using HuggingFaceModelsResponse = AIStudio.Provider.HuggingFace.ModelsResponse;
+using MistralModel = AIStudio.Provider.Mistral.Model;
+using MistralModelsResponse = AIStudio.Provider.Mistral.ModelsResponse;
+using OpenAIImageUrl = AIStudio.Provider.OpenAI.SubContentImageUrl;
+using OpenAIModelsResponse = AIStudio.Provider.OpenAI.ModelsResponse;
+using PerplexityChoice = AIStudio.Provider.Perplexity.Choice;
+using PerplexityDelta = AIStudio.Provider.Perplexity.Delta;
+using PerplexityResponseStreamLine = AIStudio.Provider.Perplexity.ResponseStreamLine;
+using SelfHostedModel = AIStudio.Provider.SelfHosted.Model;
+using SelfHostedModelsResponse = AIStudio.Provider.SelfHosted.ModelsResponse;
+
+namespace AIStudio.Provider;
+
+/// <summary>
+/// The contracts with which System.Text.Json reads and writes the requests and answers of LLM providers, built
+/// at compile time.
+/// </summary>
+/// <remarks>
+/// Some types System.Text.Json meets only while it runs, since no property names them: the messages and their
+/// parts, which converters write as the type they are of; the annotations, which a converter reads as the type
+/// their JSON tells; and whatever a request holds as an object, i.e., the values of the additional API
+/// parameters, the tools, and the items of an earlier answer. A test fails for such a type which is missing
+/// here.<br/><br/>
+///
+/// Two types with the same name need a name of their own for their contract, else the generator builds only
+/// the first of them and warns with SYSLIB1031.
+/// </remarks>
+[JsonSourceGenerationOptions(GenerationMode = JsonSourceGenerationMode.Metadata)]
+
+// The requests:
+[JsonSerializable(typeof(ChatCompletionAPIRequest))]
+[JsonSerializable(typeof(ResponsesAPIRequest))]
+[JsonSerializable(typeof(ChatRequest))]
+[JsonSerializable(typeof(EmbeddingRequest))]
+[JsonSerializable(typeof(GoogleEmbeddingRequest))]
+
+// The messages and their parts:
+[JsonSerializable(typeof(TextMessage))]
+[JsonSerializable(typeof(MultimodalMessage))]
+[JsonSerializable(typeof(AssistantToolCallMessage))]
+[JsonSerializable(typeof(ToolResultMessage))]
+[JsonSerializable(typeof(AnthropicMessage))]
+[JsonSerializable(typeof(AnthropicToolResultMessage))]
+[JsonSerializable(typeof(SubContentText))]
+[JsonSerializable(typeof(OpenAIImageUrl), TypeInfoPropertyName = "OpenAISubContentImageUrl")]
+[JsonSerializable(typeof(SubContentImageUrlNested))]
+[JsonSerializable(typeof(SubContentImageUrlData))]
+[JsonSerializable(typeof(SubContentInputText))]
+[JsonSerializable(typeof(SubContentInputImage))]
+[JsonSerializable(typeof(SubContentImage))]
+[JsonSerializable(typeof(SubContentBase64Image))]
+[JsonSerializable(typeof(AnthropicImageUrl), TypeInfoPropertyName = "AnthropicSubContentImageUrl")]
+
+// What a request holds as an object:
+[JsonSerializable(typeof(string))]
+[JsonSerializable(typeof(int))]
+[JsonSerializable(typeof(long))]
+[JsonSerializable(typeof(double))]
+[JsonSerializable(typeof(decimal))]
+[JsonSerializable(typeof(bool))]
+[JsonSerializable(typeof(Dictionary<string, object>))]
+[JsonSerializable(typeof(List<object>))]
+[JsonSerializable(typeof(JsonElement))]
+[JsonSerializable(typeof(ChatCompletionFunctionTool))]
+[JsonSerializable(typeof(ResponsesFunctionTool))]
+[JsonSerializable(typeof(ResponsesFunctionCallOutputItem))]
+
+// The lists of models:
+[JsonSerializable(typeof(OpenAIModelsResponse), TypeInfoPropertyName = "OpenAIModelsResponse")]
+[JsonSerializable(typeof(MistralModelsResponse), TypeInfoPropertyName = "MistralModelsResponse")]
+[JsonSerializable(typeof(SelfHostedModelsResponse), TypeInfoPropertyName = "SelfHostedModelsResponse")]
+[JsonSerializable(typeof(HuggingFaceModelsResponse), TypeInfoPropertyName = "HuggingFaceModelsResponse")]
+[JsonSerializable(typeof(IList<HubModel>))]
+[JsonSerializable(typeof(RequestyModelsResponse))]
+[JsonSerializable(typeof(OpenRouterModelsResponse))]
+[JsonSerializable(typeof(GroqModelsResponse))]
+
+// The lines of streamed answers, with the annotations:
+[JsonSerializable(typeof(ChatCompletionDeltaStreamLine))]
+[JsonSerializable(typeof(ChatCompletionAnnotationStreamLine))]
+[JsonSerializable(typeof(ChatCompletionToolStreamLine))]
+[JsonSerializable(typeof(ResponsesDeltaStreamLine))]
+[JsonSerializable(typeof(ResponsesAnnotationStreamLine))]
+[JsonSerializable(typeof(ResponsesCompletedStreamLine))]
+[JsonSerializable(typeof(AnthropicResponseStreamLine), TypeInfoPropertyName = "AnthropicResponseStreamLine")]
+[JsonSerializable(typeof(AnthropicStreamLine))]
+[JsonSerializable(typeof(FireworksResponseStreamLine), TypeInfoPropertyName = "FireworksResponseStreamLine")]
+[JsonSerializable(typeof(PerplexityResponseStreamLine), TypeInfoPropertyName = "PerplexityResponseStreamLine")]
+[JsonSerializable(typeof(AnnotatingUnknown))]
+[JsonSerializable(typeof(ChatCompletionAnnotatingURL))]
+[JsonSerializable(typeof(ResponsesAnnotatingUrlCitationData))]
+
+// Transcriptions and embeddings:
+[JsonSerializable(typeof(TranscriptionResponse))]
+[JsonSerializable(typeof(EmbeddingResponse))]
+[JsonSerializable(typeof(GoogleEmbeddingResponse))]
+[JsonSerializable(typeof(GoogleEmbedding))]
+[JsonSerializable(typeof(List<GoogleEmbedding>))]
+
+// The types inside the answers which share their names with others:
+[JsonSerializable(typeof(MistralModel), TypeInfoPropertyName = "MistralModel")]
+[JsonSerializable(typeof(MistralModel[]), TypeInfoPropertyName = "MistralModelArray")]
+[JsonSerializable(typeof(SelfHostedModel), TypeInfoPropertyName = "SelfHostedModel")]
+[JsonSerializable(typeof(SelfHostedModel[]), TypeInfoPropertyName = "SelfHostedModelArray")]
+[JsonSerializable(typeof(FireworksChoice), TypeInfoPropertyName = "FireworksChoice")]
+[JsonSerializable(typeof(IList<FireworksChoice>), TypeInfoPropertyName = "IListFireworksChoice")]
+[JsonSerializable(typeof(PerplexityChoice), TypeInfoPropertyName = "PerplexityChoice")]
+[JsonSerializable(typeof(IList<PerplexityChoice>), TypeInfoPropertyName = "IListPerplexityChoice")]
+[JsonSerializable(typeof(AnthropicDelta), TypeInfoPropertyName = "AnthropicDelta")]
+[JsonSerializable(typeof(FireworksDelta), TypeInfoPropertyName = "FireworksDelta")]
+[JsonSerializable(typeof(PerplexityDelta), TypeInfoPropertyName = "PerplexityDelta")]
+internal sealed partial class ProviderJsonContext : JsonSerializerContext;

app/MindWork AI Studio/Provider/ProviderJsonOptions.cs

@@ -21,7 +21,7 @@ public static class ProviderJsonOptions
     /// <summary>
     /// The shared options.
     /// </summary>
-    public static readonly JsonSerializerOptions OPTIONS = new()
+    public static readonly JsonSerializerOptions OPTIONS = new JsonSerializerOptions
     {
         PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
         Converters =
@@ -33,6 +33,7 @@ public static class ProviderJsonOptions
             new SubContentImageSourceConverter(),
             new SubContentImageUrlConverter(),
         },
-        AllowTrailingCommas = false
-    };
+        AllowTrailingCommas = false,
+        TypeInfoResolver = ProviderJsonContext.Default,
+    }.AsReadOnly();
 }

app/Tests/Provider/ToolCalling/ChatCompletionToolCallingAdapterTests.cs

@@ -1,5 +1,6 @@
 using System.Runtime.CompilerServices;
 using System.Text.Json;
+using System.Text.Json.Nodes;
 
 using AIStudio.Provider;
 using AIStudio.Provider.OpenAI;
@@ -198,10 +199,27 @@ public sealed class ChatCompletionToolCallingAdapterTests
     /// <returns>The call as the loop sees it, and the request of the next round as it goes over the wire.</returns>
     private static async Task<(ToolCallingRequestedCall Call, string NextRequest)> AnswerOneCall(string functionName, string arguments, string result)
     {
-        var toolCallLine = JsonSerializer.Serialize(new
+        //
+        // Built as nodes, since the options of the providers know no anonymous types. The nodes escape the name and the
+        // arguments the way a provider would:
+        //
+        var toolCallLine = new JsonObject
         {
-            Choices = new[] { new { Index = 0, Delta = new { ToolCalls = new[] { new { Index = 0, Id = "call_1", Type = "function", Function = new { Name = functionName, Arguments = arguments } } } } } },
-        }, ProviderJsonOptions.OPTIONS);
+            ["choices"] = new JsonArray(new JsonObject
+            {
+                ["index"] = 0,
+                ["delta"] = new JsonObject
+                {
+                    ["tool_calls"] = new JsonArray(new JsonObject
+                    {
+                        ["index"] = 0,
+                        ["id"] = "call_1",
+                        ["type"] = "function",
+                        ["function"] = new JsonObject { ["name"] = functionName, ["arguments"] = arguments },
+                    }),
+                },
+            }),
+        }.ToJsonString();
 
         var sent = new List<ChatCompletionAPIRequest>();
         var adapter = Adapter(true, sent.Add,

app/Tests/Serialization/JsonCoverageTests.cs

@@ -14,6 +14,8 @@ namespace AIStudio.Tests.Serialization;
 public sealed class JsonCoverageTests
 {
     [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.Stored))]
+    [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.ProviderRequests))]
+    [TestCaseSource(typeof(JsonTestRoots), nameof(JsonTestRoots.ProviderAnswers))]
     public void EveryContractComesFromSourceGeneration(JsonTestRoot root)
     {
         var typesWithoutGeneratedContract = JsonTypeGraph.Collect(root.Type, root.Options)