Add additionalContext support to MLXLanguageModel

[noorbhatia]

Add CustomGenerationOptions struct to MLXLanguageModel with an additionalContext: [String: JSONValue]? property for injecting variables into Jinja2 chat templates

Usage

var options = GenerationOptions()
options[custom: MLXLanguageModel.self] = .init(
    additionalContext: ["enable_thinking": .bool(true)]
)
let response = try await session.respond(to: "Hello", options: options)

[noorbhatia]

Hi @mattt , can you take a look at this. Thanks!

[mattt]

Sorry for not reviewing sooner. #147 also introduces MLXLanguageModel.CustomGenerationOptions, so we'll have to do some traffic control here. Should have both of these merged today.

[Copilot]

Pull request overview

Adds support for passing an additionalContext dictionary through GenerationOptions into MLXLMCommon’s chat-template rendering context, enabling callers to inject custom variables for Jinja2-based templates.

Changes:

• Extends MLXLanguageModel.CustomGenerationOptions with additionalContext and threads it into MLXLMCommon.UserInput construction paths.
• Adds a basic MLX test that exercises setting additionalContext via GenerationOptions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
Sources/AnyLanguageModel/Models/MLXLanguageModel.swift	Introduces additionalContext custom option and forwards it into MLX user input creation for standard, streaming, and structured generation flows.
Tests/AnyLanguageModelTests/MLXLanguageModelTests.swift	Adds a regression test ensuring additionalContext can be set and a response is produced.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

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[mattt]

@noorbhatia Alright, I think this is in really good shape now! Thanks for your help on this and your patience 🙇

[noorbhatia]

Amazing, thanks @mattt !!