Reference — CodexHow
The data-led layer underneath the tools and guides: every priced model's specs, capped and curated model-to-model comparisons, migration tables for the version changes that actually matter, and singleton pages covering the batch API, prompt caching, service tiers, rate-limit tiers, sandbox and approval modes, and the long-context repricing rule in full. These pages are short and dense on purpose — a lookup answer padded into paragraphs is slower to use, not more valuable.
Every table on every page here is generated directly from this site's own facts module, never retyped by hand — the same numbers the tools and calculators use, just presented as a direct lookup instead of run through arithmetic.
GPT-5.6 Sol — Specs, Pricing & Limits
GPT-5.6 Terra — Specs, Pricing & Limits
GPT-5.6 Luna — Specs, Pricing & Limits
GPT-5.5 — Specs, Pricing & Limits
GPT-5.5 Pro — Specs, Pricing & Limits
GPT-5.4 — Specs, Pricing & Limits
GPT-5.4 Mini — Specs, Pricing & Limits
GPT-5.4 Nano — Specs, Pricing & Limits
GPT-5.4 Pro — Specs, Pricing & Limits
GPT-5.3 Codex — Specs, Pricing & Limits
GPT-5.4 Cyber — Specs, Pricing & Limits
GPT-5.5 Cyber — Specs, Pricing & Limits
GPT-5.6 Sol vs GPT-5.3 Codex
GPT-5.6 Sol vs GPT-5.6 Terra
GPT-5.6 Terra vs GPT-5.6 Luna
GPT-5.5 vs GPT-5.6 Sol
GPT-5.4 vs GPT-5.6 Terra
GPT-5.5 Pro vs GPT-5.4 Pro
GPT-5.4 Mini vs GPT-5.4 Nano
GPT-5.3 Codex vs GPT-5.4
GPT-5.6 Luna vs GPT-5.4 Nano
GPT-5.4 vs GPT-5.4 Cyber
Migrating: GPT-5.4 to GPT-5.6 Sol
Migrating: GPT-5.4 to GPT-5.6 Terra
Migrating: GPT-5.5 to GPT-5.6 Sol
Migrating: GPT-5.4 Mini to GPT-5.6 Luna
Migrating: GPT-5.4 Pro to GPT-5.5 Pro
Migrating: GPT-5.6 Sol to GPT-5.3 Codex
The Batch API, Fully Specified
Prompt Caching, Fully Specified
Service Tiers: Standard, Batch, Flex & Fast
Usage Tiers, Rate Limits & Response Headers
Sandbox & Approval Modes, Fully Specified
Why This Site Publishes No Subscription Price
Where Each Model Is Actually Available
The 272K Long-Context Cliff, Fully Specified
Data Residency & Regional Pricing
Priority Became Fast Mode — What Changed
Reasoning Effort, and Why It's Codex-Only For Now
Codex CLI: Defaults, Versions & Commands