# Feature Specification: OpenRouter Provider Support

**Feature Branch**: `002-openrouter-provider-in`
**Created**: 2025-09-19
**Status**: Draft
**Input**: User description: "openrouter: provider in addition to openai: and cerebras: etc. read api key from OPENROUTER_API_KEY env var"

## Execution Flow (main)
```
1. Parse user description from Input
   → OpenRouter provider support requested for remote model access
2. Extract key concepts from description
   → Actors: developers using SteadyText API/CLI
   → Actions: generate text, embed text using OpenRouter models
   → Data: API keys, model responses, error handling
   → Constraints: must follow existing provider pattern
3. For each unclear aspect:
   → ✓ Clear requirements identified
4. Fill User Scenarios & Testing section
   → ✓ User flows for API and CLI usage defined
5. Generate Functional Requirements
   → ✓ Each requirement is testable
6. Identify Key Entities (if data involved)
   → ✓ Provider configuration and model access patterns
7. Run Review Checklist
   → ✓ No implementation details included
   → ✓ Focus on user value and behavior
8. Return: SUCCESS (spec ready for planning)
```

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## ⚡ Quick Guidelines
- ✅ Focus on WHAT users need and WHY
- ❌ Avoid HOW to implement (no tech stack, APIs, code structure)
- 👥 Written for business stakeholders, not developers

---

## User Scenarios & Testing

### Primary User Story
Developers want to use OpenRouter's unified API to access multiple AI models through SteadyText's consistent interface, allowing them to leverage OpenRouter's model routing and competitive pricing while maintaining the same deterministic fallback behavior and API patterns they're familiar with.

### Acceptance Scenarios
1. **Given** a developer has an OpenRouter API key, **When** they specify a model like "openrouter:anthropic/claude-3.5-sonnet", **Then** the system generates text using OpenRouter's API
2. **Given** unsafe mode is enabled and OPENROUTER_API_KEY is set, **When** a user runs CLI command with openrouter: prefix, **Then** the system successfully connects to OpenRouter and returns model output
3. **Given** OpenRouter API key is missing, **When** user attempts to use openrouter: model, **Then** system provides clear error message about missing API key
4. **Given** OpenRouter service is unavailable, **When** user requests generation, **Then** system falls back to deterministic behavior with appropriate warning

### Edge Cases
- What happens when OpenRouter API returns rate limit errors?
- How does system handle invalid OpenRouter model names?
- What occurs if OpenRouter API key is invalid or expired?
- How does the system behave when OpenRouter returns unexpected response formats?

## Requirements

### Functional Requirements
- **FR-001**: System MUST support "openrouter:" prefix for model specification in both Python API and CLI
- **FR-002**: System MUST read OpenRouter API key from OPENROUTER_API_KEY environment variable
- **FR-003**: System MUST provide clear error messages when OPENROUTER_API_KEY is missing or invalid
- **FR-004**: System MUST follow the same unsafe mode requirement as other remote providers
- **FR-005**: System MUST maintain deterministic fallback behavior when OpenRouter is unavailable
- **FR-006**: System MUST support both text generation and embedding operations through OpenRouter
- **FR-007**: System MUST validate OpenRouter model names and provide helpful error messages for invalid models
- **FR-008**: System MUST handle OpenRouter-specific error responses and rate limiting gracefully
- **FR-009**: System MUST integrate with existing provider registry pattern without breaking other providers
- **FR-010**: System MUST support the same parameter passing (temperature, max_tokens, etc.) as other providers

### Key Entities
- **OpenRouter Provider**: Manages authentication, model routing, and API communication with OpenRouter service
- **Model Specification**: String format "openrouter:model-name" that identifies OpenRouter models within the system
- **API Configuration**: Environment-based settings including OPENROUTER_API_KEY and unsafe mode flags

---

## Review & Acceptance Checklist

### Content Quality
- [x] No implementation details (languages, frameworks, APIs)
- [x] Focused on user value and business needs
- [x] Written for non-technical stakeholders
- [x] All mandatory sections completed

### Requirement Completeness
- [x] No [NEEDS CLARIFICATION] markers remain
- [x] Requirements are testable and unambiguous
- [x] Success criteria are measurable
- [x] Scope is clearly bounded
- [x] Dependencies and assumptions identified

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## Execution Status

- [x] User description parsed
- [x] Key concepts extracted
- [x] Ambiguities marked
- [x] User scenarios defined
- [x] Requirements generated
- [x] Entities identified
- [x] Review checklist passed

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