Remove third party libraries

[bmehta001]

Remove third-party OpenAI libraries; replace with custom DTOs

Removes Betalgo.Ranul.OpenAI (C#) and async-openai (Rust) dependencies, replacing them with custom data transfer objects that map directly to the OpenAI JSON wire format. This gives us full control over serialization, AOT compatibility, and spec alignment without waiting on third-party release cycles.

Why remove Betalgo?

Betalgo is a community-maintained library that lags behind the official OpenAI spec:

• Missing fields: no refusal on ChatMessage (added mid-2024), no max_completion_tokens (used by VS Code / newer clients)
• Heavyweight: pulls in types/abstractions we don't use (images, embeddings, fine-tuning, assistants)
• AOT friction: not designed for System.Text.Json source generators — our SDK needs [JsonSerializable] registration for trimming/AOT
• Spec drift: when OpenAI adds fields, we're blocked until Betalgo ships an update

Similarly, async-openai for Rust used Cow<'a, str> patterns that caused clippy warnings after removal, and brought in unnecessary complexity.

What replaced them

Custom DTOs in each SDK that map 1:1 to the OpenAI chat completion wire format. Design principle: our types match the JSON field names exactly (not the official SDK's abstracted class hierarchy).

Enums introduced (C#)

We added typed enums with [JsonStringEnumConverter] and [JsonStringEnumMemberName] for AOT-safe serialization, matching the wire format string values:

Enum	Values	Why
ChatMessageRole	system, user, assistant, tool, developer	Type safety for role field; developer added for reasoning model support (o1/o3)
FinishReason	stop, length, tool_calls, content_filter, function_call	Wire-format-aligned name; function_call included for backward compat even though deprecated
ToolType	function	Wire-format-aligned name; single value today, forward-compatible

Rust uses a FinishReason enum with #[serde(rename_all = "snake_case")] and #[non_exhaustive].
Python and JS use plain strings — no enums needed (dynamic typing).

Fields added beyond Betalgo

These fields exist in the OpenAI spec and were missing from Betalgo:

Field	Where	Why
max_completion_tokens	Request settings (all 4 SDKs)	Newer OpenAI field used by VS Code and other clients
developer role	ChatMessageRole (C#, Rust)	Required for reasoning models; Core already supports it
function_call	FinishReason enum (C#)	Was in Rust but missing from C#; needed for backward compat

Fields intentionally omitted

These exist in the OpenAI spec but are either cloud-only or not yet emitted by Core's OpenAI layer:

• service_tier — cloud routing concept (auto/default/flex/scale/priority)
• annotations — web search URL citations
• audio on ChatCompletionMessage — audio output modality
• stream_options, parallel_tool_calls — cloud features not supported by local models
• completion_tokens_details, prompt_tokens_details — Core has these internally but doesn't emit them through the OpenAI layer yet; will add when Core supports them
• logprobs — same; Core has internal support but doesn't expose through OpenAI layer
• refusal — same; Core's OpenAI ChatMessage doesn't include refusal; will add when it does

Nullability fixes

Audited all value types across the C# SDK against the OpenAI spec and streaming behavior:

Field	Change	Reason
ChatMessage.Role	ChatMessageRole? (nullable)	Streaming deltas may omit role — matches official SDK's ChatMessageRole?
ToolCall.Index	int? (nullable)	Only present in streaming delta chunks, absent in non-streaming
AudioTranscriptionResponse.Duration	float? (nullable)	May be absent depending on response format

Rust SDK changes

• Removed async-openai dependency from Cargo.toml
• New chat_types.rs — all custom DTOs: request messages (System/User/Assistant/Tool/Developer), response types, streaming types, tool call types
• Simplified ChatClientSettings serialization — replaced 80-line manual JSON builder with #[derive(Serialize)] + #[serde(skip_serializing_if)] annotations
• Custom Serialize impls for ChatResponseFormat and ChatToolChoice in types.rs — these serialize as either plain strings or objects depending on variant
• Wire format alignment: ChatResponseFormat uses json_schema/lark_grammar (snake_case), ChatToolChoice serializes None/Auto/Required as plain strings ("none", "auto", "required") and Function as {"type":"function","function":{"name":"..."}}
• Deduplicated From impls — From<&str> delegates to From<String> instead of duplicating logic
• Fixed clippy errors — removed 6 useless .into() calls (were needed for Cow<'a, str> but not for String)
• pub(crate) mod detail — restored visibility restriction accidentally changed to pub
• .expect() over .unwrap() — better panic messages in serialize()

C# SDK — Official OpenAI .NET SDK alignment

Following the patterns from openai/openai-dotnet:

• ToolChoice factory methods — CreateAutoChoice(), CreateNoneChoice(), CreateRequiredChoice(), CreateFunctionChoice(string) instead of static properties (matches ChatToolChoice in official SDK)
• ToolDefinition.Type — non-nullable with default ToolType.Function (matches official SDK's ChatTool.Kind)
• FunctionDefinition — Function and Name marked required (matches official SDK requiring function name at construction time)
• ToolChoiceConverter.Write() — null safety check added

File renames (C#)

Old	New	Reason
AudioTranscriptionRequestResponseTypes.cs	AudioTranscriptionExtensions.cs	Better describes contents (extension methods + internal request DTO)
ChatCompletionRequestResponseTypes.cs	ChatCompletionExtensions.cs	Same — internal plumbing, not public types

New file organization (C#)

Public types and internal plumbing are cleanly separated:

File	Visibility	Contents
ChatMessage.cs	Public	ChatMessageRole, ToolType, ChatMessage, ToolCall, FunctionCall
ChatCompletionResponse.cs	Public	ChatCompletionResponse, ChatChoice, FinishReason, CompletionUsage, token details
ToolCallingTypes.cs	Public	ToolDefinition, FunctionDefinition, PropertyDefinition, ResponseFormat, ToolChoice
AudioTypes.cs	Public	AudioTranscriptionResponse, AudioTranscriptionRequest (internal)
ChatCompletionExtensions.cs	Internal	ChatCompletionRequest, serialization/deserialization helpers
AudioTranscriptionExtensions.cs	Internal	Serialization/deserialization helpers

Core compatibility

• All fields emitted by Core's OpenAI layer (UsageResponse, ChatChoiceResponse, ChatCompletionCreateResponse) are covered by our SDK types
• developer role is already supported by Core's ResponseEnums.cs
• Fields not yet emitted by Core's OpenAI layer (completion_tokens_details, prompt_tokens_details, logprobs) are intentionally omitted — will add when Core exposes them

Cross-SDK field alignment

Field	C#	Rust	Python	JS
max_completion_tokens	✅	✅	✅	✅
function_call (deprecated)	✅	✅	N/A (dicts)	✅
FinishReason.FunctionCall	✅	✅	strings	strings
developer role	✅	✅	strings	strings

Python and JS use dynamic types (dicts/objects), so new fields are automatically captured without SDK changes.

Testing

• C# SDK: builds clean, 15/27 tests pass (12 failures are pre-existing model path issues unrelated to this PR)
• Rust SDK: cargo check/clippy pass in CI (can't test locally due to ORT-Nightly registry)
• JS/TS: npx tsc --noEmit compiles clean
• Python: serialization verified manually

Related issues

• Foundry local doesn't support array for "type" property in tools #576 — The max_completion_tokens field used in the issue's example payload is now supported by all SDKs. The root cause (array type in tool parameter schemas) requires a Core-side fix (separate PR in neutron-server).

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Project	Deployment	Actions	Updated (UTC)
foundry-local	Ready	Preview, Comment	Apr 6, 2026 0:26am

[Copilot]

Pull request overview

This PR removes external OpenAI SDK dependencies from the Rust and C# SDKs by introducing/using first-party OpenAI-compatible DTOs and updating tests, docs, and samples accordingly.

Changes:

• Rust: replace async-openai chat DTOs with in-repo openai::chat_types and update crate exports/dependencies.
• C#: remove Betalgo.Ranul.OpenAI usage by adding custom OpenAI-compatible request/response/tool DTOs and updating clients/tests/docs.
• Samples: remove Betalgo package references and update sample code to use the new DTOs.

Reviewed changes

Copilot reviewed 36 out of 36 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
sdk/rust/src/openai/mod.rs	Exposes new internal chat_types module and keeps OpenAI client module exports.
sdk/rust/src/openai/chat_types.rs	Adds first-party Rust DTOs for OpenAI-compatible chat request/response + streaming types.
sdk/rust/src/openai/chat_client.rs	Switches chat client to use local DTOs instead of async-openai.
sdk/rust/src/lib.rs	Adjusts module visibility and re-exports to point to local chat DTOs.
sdk/rust/Cargo.toml	Drops async-openai; moves tokio-stream to dev-dependencies.
sdk/cs/test/FoundryLocal.Tests/Microsoft.AI.Foundry.Local.Tests.csproj	Removes RichardSzalay.MockHttp test dependency.
sdk/cs/test/FoundryLocal.Tests/LiveAudioTranscriptionTests.cs	Removes an unused System.Text.Json import.
sdk/cs/test/FoundryLocal.Tests/ChatCompletionsTests.cs	Updates tests to use in-SDK OpenAI-compatible types.
sdk/cs/src/OpenAI/ToolCallingTypes.cs	Adds custom DTOs for tools/tool-choice/response-format + JSON converter.
sdk/cs/src/OpenAI/ToolCallingExtensions.cs	Updates extended response format type docs and removes Betalgo dependency.
sdk/cs/src/OpenAI/LiveAudioTranscriptionTypes.cs	Replaces Betalgo realtime inheritance with local DTOs for streaming transcription results.
sdk/cs/src/OpenAI/ChatMessage.cs	Adds custom chat message + tool call DTOs.
sdk/cs/src/OpenAI/ChatCompletionResponse.cs	Adds custom chat completion response DTOs (incl. error shape).
sdk/cs/src/OpenAI/ChatCompletionRequestResponseTypes.cs	Replaces Betalgo request/response types with local request/response DTOs and serialization.
sdk/cs/src/OpenAI/ChatClient.cs	Updates client to use new request/response DTOs and adds settings fields.
sdk/cs/src/OpenAI/AudioTypes.cs	Adds custom audio transcription request/response DTOs.
sdk/cs/src/OpenAI/AudioTranscriptionRequestResponseTypes.cs	Replaces Betalgo transcription types with local request/response types and serialization.
sdk/cs/src/OpenAI/AudioClient.cs	Updates audio client to use new audio request/response DTOs.
sdk/cs/src/Microsoft.AI.Foundry.Local.csproj	Removes Betalgo.Ranul.OpenAI package reference from the SDK.
sdk/cs/src/Detail/JsonSerializationContext.cs	Updates source-gen JSON registrations to the new DTOs.
sdk/cs/README.md	Updates documentation samples to use Microsoft.AI.Foundry.Local.OpenAI types.
sdk/cs/docs/api/microsoft.ai.foundry.local.openaichatclient.md	Updates docs to reflect custom OpenAI-compatible types.
sdk/cs/docs/api/microsoft.ai.foundry.local.openaiaudioclient.md	Updates docs to reflect custom OpenAI-compatible types.
samples/cs/tutorial-voice-to-text/TutorialVoiceToText.csproj	Removes Betalgo package dependency from sample.
samples/cs/tutorial-voice-to-text/Program.cs	Updates imports to use SDK OpenAI-compatible types.
samples/cs/tutorial-tool-calling/TutorialToolCalling.csproj	Removes Betalgo package dependency from sample.
samples/cs/tutorial-tool-calling/Program.cs	Updates imports to use SDK OpenAI-compatible types.
samples/cs/tutorial-document-summarizer/TutorialDocumentSummarizer.csproj	Removes Betalgo package dependency from sample.
samples/cs/tutorial-document-summarizer/Program.cs	Updates imports to use SDK OpenAI-compatible types.
samples/cs/tutorial-chat-assistant/TutorialChatAssistant.csproj	Removes Betalgo package dependency from sample.
samples/cs/tutorial-chat-assistant/Program.cs	Updates imports to use SDK OpenAI-compatible types.
samples/cs/tool-calling-foundry-local-web-server/Program.cs	Updates header; contains a modified finish-reason check in tool-calling loop.
samples/cs/tool-calling-foundry-local-sdk/Program.cs	Updates imports and response type names for tool-calling sample.
samples/cs/native-chat-completions/Program.cs	Updates imports to use SDK OpenAI-compatible types.
samples/cs/model-management-example/Program.cs	Updates imports to use SDK OpenAI-compatible types.
samples/cs/Directory.Packages.props	Removes Betalgo package version pin from samples.

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Pull request overview

Copilot reviewed 53 out of 53 changed files in this pull request and generated 3 comments.

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Pull request overview

Copilot reviewed 61 out of 61 changed files in this pull request and generated 5 comments.

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Pull request overview

Copilot reviewed 61 out of 61 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

sdk/js/src/openai/chatClient.ts:42

• response_format and tool_choice are being serialized by passing the objects through as-is. With the current JS types (ResponseFormat uses jsonSchema/larkGrammar and ToolChoice uses name), this produces JSON that doesn’t match the OpenAI wire format used by the other SDKs in this PR (e.g., json_schema/lark_grammar, and tool choice { type: "function", function: { name } } or plain strings for none|auto|required). Consider normalizing these objects in _serialize() so the emitted JSON matches the OpenAI field names/shapes.

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[Copilot]

ToolDefinition.Type is nullable, but OpenAI tool definitions require type. Because the source-gen context ignores nulls (JsonIgnoreCondition.WhenWritingNull), a missing Type will silently omit the field and produce an invalid request. Consider making Type non-nullable (and similarly requiring Function) or adding validation before sending the request.

[bmehta001]

I am following OpenAI SDK's convention - can revert if it seems too onerous

[Copilot]

FunctionDefinition.Name is required by the OpenAI tool spec, but it’s nullable here; when null it will be omitted during serialization (due to WhenWritingNull) and the request will fail at runtime. Consider making it non-nullable (or validating in ChatCompletionRequest.FromUserInput / before executing the command).

[bmehta001]

I am following OpenAI SDK's convention - can revert if it seems too onerous