Reasoning Models Architecture & Controls — OpenAI Frontier Architecture
Reasoning Models Architecture & Controls
OpenAI Frontier Reasoning: GPT-6 Family & Codex
OpenAI's unified GPT-6 reasoning family (GPT-6 Astra, GPT-6.1 Sol, GPT-6.1 Terra, and GPT-6 Luna) succeeds the retired o1, o3-mini, and o4-mini models (shut down October 23, 2026) and deprecated o3/o3-pro models (sunset December 11, 2026). Trained with reinforcement learning to generate internal chains of thought across a 1.05M-token context window (128K max output), these models power STEM proofs, multi-file software engineering, and autonomous coding via Codex CLI (@openai/codex) and Codex Cloud.
Calibrating Reasoning Effort
In the Responses API, calibrate thinking depth via reasoning: { effort: ... } (or reasoning_effort in Chat Completions):
| Effort Level | Latency | Best For |
|---|---|---|
none (Luna only) | Ultra-Fast | Sub-second classification, extraction, high-volume chat routing |
low | Fast | Straightforward code fixes, light edits, fast decision routing |
medium (default) | Balanced | General software engineering, data analysis, standard multi-step reasoning |
high / xhigh / max | Thorough | Complex mathematical proofs, multi-repo refactoring, long-horizon agentic execution |
const response = await openai.responses.create({
model: "gpt-6.1-sol",
reasoning: { effort: "high" },
input: [
{ role: "developer", content: "You are a senior algorithmic engineer." },
{ role: "user", content: "Optimize this dynamic programming solution for memory bounds." }
]
});
Developer Messages & Codex Harnesses
Reasoning models replace the legacy system role with the developer role to preserve strict instruction hierarchy. For repository-scale automation, pair GPT-6 Astra or Sol with Codex CLI (npm install -g @openai/codex, configured via ~/.codex/config.toml and repo AGENTS.md files) or asynchronous Codex Cloud virtual machines.
strict: true), remote MCP servers, and parallel Function Calling inside their reasoning loops.OpenAI reasoning models replace the legacy system role with developer messages for strict behavioral hierarchy. Submit a developer-scoped instruction to gpt-6.1-sol.