hermes - 💡(How to fix) Fix [Feature]: OpenCode Free provider plugin

Problem or Use Case

OpenCode offers a free tier of models (big-pickle, deepseek-v4-flash-free, mimo-v2.5-free, nemotron-3-super-free) that requires no API key, but Hermes currently has no dedicated provider for it (and the Zen or Go one does not work). Users must either use a paid provider or work around the missing integration.

Proposed Solution

A new opencode-free provider plugin (alongside existing opencode-zen and opencode-go) that:

• Auto-detects via OPENCODE_FREE_API_KEY env var (value unused — for detection only)
• Lists free models using the same filter logic as the opencode CLI: cost.input == 0 AND status != "deprecated" from models.dev
• Strips Authorization headers at the transport level (the free tier rejects them)
• Integrates with both hermes model (CLI) and /model (TUI)

Alternatives Considered

Using opencode-zen with an empty/missing key, but the Zen provider's model listing requires a valid API key and the free tier models aren't isolated.

Feature Type

Other

Scope

Medium (few files, < 300 lines)

Contribution

• I'd like to implement this myself and submit a PR

Debug Report (optional)