[ENHANCEMENT] Add Harmony AI Provider Support for GPT-OSS Models

[ajgreyling]

Problem (one or two sentences)

Add Harmony AI Provider Support for GPT-OSS Models

Description

Overview

Add first-class support for Harmony, OpenAI's response format specification for open-weight GPT-OSS models (gpt-oss-20b and gpt-oss-120b).

Problem

Currently, users wanting to use Harmony-compatible endpoints must use the generic "OpenAI Compatible" provider, which:

• Requires manual base URL configuration each time
• Lacks visibility as a dedicated provider option in the UI
• Doesn't clearly indicate Harmony-specific features like reasoning effort levels
• Provides no optimized configuration for Harmony's unique capabilities

Solution

Implement Harmony as a first-class API provider in Roo Code, similar to how Groq, SambaNova, and other providers are implemented.

Benefits

• Better User Experience: Harmony appears as a dedicated provider option in settings
• Clear Configuration: Pre-configured defaults for Harmony endpoints with customizable base URL
• Feature Visibility: Reasoning effort levels (low/medium/high) become discoverable and configurable
• Reliability: Extends proven BaseOpenAiCompatibleProvider pattern for consistency
• Open-Weight Support: Enables developers to use open-source models with Roo Code

What Will Be Implemented

Models:

• gpt-oss-20b - 20B parameter model, optimized for speed (default)
• gpt-oss-120b - 120B parameter model, optimized for quality

Features:

• 128,000 token context window for comprehensive codebase analysis
• Reasoning effort levels: low, medium, high
• Streaming support for real-time responses
• Function/tool calling capabilities
• Configurable API key and base URL
• Full i18n support (17 languages)

Code Quality:

• Complete test coverage (12 test cases)
• Comprehensive JSDoc documentation
• TypeScript strict mode compliance
• Follows Roo Code contribution guidelines

References

• OpenAI Harmony Specification
• Harmony GitHub Repository
• Roo Code Contributing Guidelines

Alignment with Project Goals

• ✅ Reliability First: Extends proven provider pattern for consistency
• ✅ Enhanced UX: First-class provider option with clear feature visibility
• ✅ Agent Performance: Support for reasoning effort levels enables better model configuration

Context (who is affected and when)

Roo Code users when using a GPT-OSS Harmony compatible endpoint with OpenAI Compatible provider

Desired behavior (conceptual, not technical)

• Harmony provider is available as a selectable option in API provider settings
• Both gpt-oss-20b and gpt-oss-120b models are selectable
• Configurable API key and base URL with sensible defaults
• Reasoning effort selector (low/medium/high) is visible in settings

Constraints / preferences (optional)

• ✅ Reliability First: Extends proven provider pattern for consistency

• ✅ Enhanced UX: First-class provider option with clear feature visibility

• ✅ Agent Performance: Support for reasoning effort levels enables better model configuration

• Full i18n support (17 languages)

Code Quality:

• Complete test coverage (12 test cases)
• Comprehensive JSDoc documentation
• TypeScript strict mode compliance
• Follows Roo Code contribution guidelines

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

Acceptance Criteria

• Harmony provider is available as a selectable option in API provider settings
• Both gpt-oss-20b and gpt-oss-120b models are selectable
• Configurable API key and base URL with sensible defaults
• Reasoning effort selector (low/medium/high) is visible in settings
• All tests pass (npm test)
• TypeScript compilation succeeds with no errors
• README documents Harmony as a supported provider
• JSDoc documentation is comprehensive

Proposed approach (optional)

Add as Provider:
modified: README.md
modified: packages/types/src/provider-settings.ts
new file: packages/types/src/providers/harmony.ts
modified: packages/types/src/providers/index.ts
modified: src/api/index.ts
new file: src/api/providers/tests/harmony.spec.ts
new file: src/api/providers/harmony.ts
modified: src/api/providers/index.ts
new file: test-harmony-api.ts
modified: webview-ui/src/components/settings/ApiOptions.tsx
new file: webview-ui/src/components/settings/providers/Harmony.tsx
modified: webview-ui/src/components/settings/providers/index.ts
modified: webview-ui/src/components/ui/hooks/useSelectedModel.ts
modified: webview-ui/src/i18n/locales/en/settings.json

Trade-offs / risks (optional)

None

[ajgreyling]

Claiming

[roomote]

Hi @ajgreyling! I see you have already claimed this issue - that is great!

Your proposed implementation plan looks comprehensive and well-structured. The file list you provided covers all the necessary components:

• Provider types in packages/types/
• API provider implementation in src/api/providers/
• UI components in webview-ui/
• i18n support

If you would like any assistance with the implementation or would like me to take over, please feel free to mention @roomote in a comment. Otherwise, best of luck with your implementation!