Feature: first-class GPT-5.1 models and reasoningEffort="none" support

[riatzukiza]

Summary

Add native GPT-5.1 model awareness and reasoningEffort: "none" support to opencode core so providers like the Codex OAuth plugin can match the latest Codex CLI behavior without fighting the framework.

Background

In openai/codex (the official Codex CLI), GPT-5.1 is now the primary family, with:

• gpt-5.1 general models supporting a new reasoningEffort: "none" mode.
• gpt-5.1-codex and gpt-5.1-codex-mini for code-heavy workloads.
• Model presets wired into model_presets.rs with specific reasoning defaults.

In opencode today (based on gh search code):

• There are no direct references to GPT-5.1 model IDs or reasoningEffort: "none".
• Providers can approximate GPT-5.1 behavior via their own config, but the core schema and model picker aren’t aware of these new variants.

In the Codex OAuth plugin (@promethean-os/opencode-openai-codex-auth):

• We’ve already added GPT-5.1 presets (e.g. gpt-5.1-codex-low, gpt-5.1-none) and adjusted plugin-side normalization + reasoning heuristics to match Codex CLI.
• However, these show up as “just more models” from opencode’s perspective; the core doesn’t know they are the new default family.

Proposed Changes

1. Extend model configuration schema

   • Allow reasoningEffort to include "none" in addition to "minimal" | "low" | "medium" | "high".
   • Ensure this is reflected consistently in:
     • TypeScript/JSON schema used by opencode config.
     • Any validation logic around model options in core.

2. Add GPT-5.1 model awareness to core

   • Introduce GPT-5.1 model IDs at the provider level (for provider.openai):
     • gpt-5.1, gpt-5.1-codex, gpt-5.1-codex-mini.
   • Mark GPT-5.1 as the preferred family for new configs, while keeping GPT-5 as a legacy/compatibility option.
   • Ensure the model picker / TUI shows GPT-5.1 variants with friendly names and correct reasoning defaults.

3. Reasoning defaults aligned with Codex CLI

   • For GPT-5.1 general models:
     • Default reasoningEffort: "none" (new no-reasoning mode) when not overridden.
   • For GPT-5.1 Codex / Codex Mini:
     • Keep effort defaults aligned with Codex CLI presets (e.g. low/medium/high only, no none where unsupported).
   • For legacy GPT-5:
     • Maintain current opencode defaults to avoid breaking existing configs, or provide a migration path.

4. Configuration helpers and docs

   • Update any core docs/config generators that currently mention GPT-5-only presets to include GPT-5.1 examples.
   • Add guidance for plugin authors on when to use GPT-5.1 vs GPT-5, and how reasoningEffort: "none" should behave.

Why This Belongs in Core (not just plugins)

• Plugins can normalize model names and clamp reasoning values, but:
  • The opencode model picker, config wizards, and validation logic remain unaware of GPT-5.1.
  • Users configuring GPT-5.1 manually get no guidance or type safety from opencode itself.
• Making GPT-5.1 first-class in core ensures:
  • Consistent UX across all OpenAI-based providers (not just the Codex plugin).
  • Easier future migration if OpenAI deprecates parts of the GPT-5 family.

Acceptance Criteria

• Core config/schema supports reasoningEffort: "none" for appropriate models.
• GPT-5.1 models appear in the opencode model picker with correct names and defaults.
• Providers like the Codex OAuth plugin can reference GPT-5.1 model IDs without triggering validation errors or confusing UX.
• Existing GPT-5-only configurations continue to work unchanged.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Support for reasoning_effort parameter in UI #450: Support for reasoning_effort parameter in UI - This issue is already tracking the need for reasoning_effort parameter support in the UI, which overlaps with your request for reasoningEffort="none" support

Feel free to ignore if none of these address your specific case.

[rekram1-node]

"none" is currently supported