Microsoft.Extensions.AI bridge

RecursiveAI.OneLlm.Extensions.AI connects OneLLM to the Microsoft.Extensions.AI abstractions (version 10.11 of Microsoft.Extensions.AI.Abstractions) in both directions. It references the OneLLM core package and that one package.

The speech, text-to-speech and image abstractions are marked experimental by Microsoft.Extensions.AI (MEAI001). The bridge opts in inside one source file; code that uses OneLlmSpeechToTextClient, OneLlmTextToSpeechClient or OneLlmImageGenerator sees the same diagnostic on the Microsoft.Extensions.AI types it touches.

A OneLLM model as a client

var rt = new Runtime();
IChatClient client = rt.AsChatClient("claude-sonnet");
ChatResponse r = await client.GetResponseAsync("Summarize this", new ChatOptions { MaxOutputTokens = 500 });
decimal dollars = (decimal)r.AdditionalProperties![OneLlmProperties.CostTotal]!;

The model resolves through the runtime's catalog, so requests are adjusted to what the model accepts (a parameter it rejects is dropped and reported in OneLlmProperties.Warnings) and every call is priced. ChatOptions.ModelId names another catalog model for one request. The client does not run functions: wrap it with Microsoft.Extensions.AI's function-invoking middleware, or use a OneLLM agent.

Over a bare provider the client sends the model name as given and prices nothing: new OneLlmChatClient(provider, "model-name", timeProvider); pass a ResolvedModel instead of the name to adjust and price.

Options

What comes back

Text, tool calls and reasoning arrive as TextContent, FunctionCallContent and TextReasoningContent in the order the model produced them, so the order of parts inside a turn is the order of the Contents list. Streaming sends text and reasoning as deltas; a tool call arrives complete, once its arguments have finished streaming. A stream ends with one update that carries FinishReason and one UsageContent, so Microsoft.Extensions.AI's ToChatResponse() counts usage once.

Keys in AdditionalProperties

On the ChatResponse (and on the final UsageContent of a stream), and on an embedding result:

Cost is present only when the model is priced in the catalog. Money is always decimal.

The lossy edges, carried so they survive a round trip through Microsoft.Extensions.AI and back:

The speech, text-to-speech and image types carry usage on their Usage property; speech-to-text and text-to-speech responses also carry the cost keys. ImageGenerationResponse has no property dictionary, so an image call's cost is not on it: use the runtime's result.

A client as a provider

var rt = new Runtime { Catalog = ModelCatalog.Create([CatalogLayer.FromFile(CatalogLayer.User, "my-models.yaml")]) };
rt.Providers.AddChatClient("acme", someChatClient, someEmbeddingGenerator);   // someEmbeddingGenerator is optional
AskResult a = await rt.AskAsync(new AskRequest { Model = "acme-large", Prompt = "hi" });   // priced from my-models.yaml

The catalog entry supplies what the client cannot: the model's name patterns, context window, capabilities and prices. Its name must be the provider name passed to AddChatClient. The client's usage becomes OneLLM Usage: InputTokenCount is the whole input and CachedInputTokenCount the part read from a cache, so the cached tokens are priced at the cache-read rate and not twice. Tool definitions go out as declarations, results come back as function-result content, and a streamed update list becomes OneLLM stream events that build the same Message a non-streaming call builds.

Tools

tool.AsAIFunction(time) passes the tool's name, description, input schema and output schema through unchanged, so function.JsonSchema equals tool.Definition.InputSchema. The function runs the tool in a context with no capabilities; pass a Func<string, ToolContext> to grant the files, shell or network the tool needs. A tool that reports an error makes the function throw InvalidOperationException with the tool's message, which Microsoft.Extensions.AI's function-invoking client reports to the model. function.AsTool() does the reverse: the schema is read from JsonSchema, an ApprovalRequiredAIFunction becomes a tool with RequiresApproval, and a result becomes text (a string), a JSON part (a JSON value) or parts (a content list). The name must be a valid tool name (letters, digits, _, -, at most 64): a function named has.dot is refused with ArgumentException.

Tools made with AIFunctionFactory.Create use reflection and are not trim or AOT safe; that is a property of Microsoft.Extensions.AI, not of the bridge. Declarations, AsAIFunction and AsTool over a hand-written or generated ITool are.

Reads like

A table for readers who know the Microsoft.Extensions.AI calls. It maps calls in the public documentation to OneLLM calls and makes no comparison.