Summary

Adds per-provider max_tokens support to custom_providers, mirroring the existing context_length pattern. This allows users to set a provider-scoped output-token cap without affecting fallback providers.

Problem

model.max_tokens in config.yaml is global — it applies to all providers including fallbacks. There is no way to scope max_tokens to a specific provider, unlike context_length which already supports per-provider overrides.

Changes

hermes_cli/config.py

• Adds get_custom_provider_max_tokens() — mirrors get_custom_provider_context_length() exactly. Matches by base_url + model name, returns models.<model>.max_tokens if present and valid.
• Adds "max_tokens" to _KNOWN_KEYS in _normalize_custom_provider_entry so the top-level key is not flagged as unknown (defensive, for users who had it at top level).

agent/agent_init.py

• After the global model.max_tokens fallback (and before context_length resolution), adds a second fallback that checks custom_providers for a per-provider max_tokens when agent.max_tokens is still None.

Usage

custom_providers:
  - name: My Provider
    base_url: https://example.com/v1
    api_key: ...
    model: my-model
    api_mode: chat_completions
    models:
      my-model:
        context_length: 1000000
        max_tokens: 131072       # ← new per-provider field

Related

Closes #28782