Why it matters
- GPT-4 branding on directories is stale — ChatGPT moved to the GPT-5.x line; GPT-4o was retired from ChatGPT in Feb 2026.
- GPT-5.6 splits into durable tiers (Sol / Terra / Luna) instead of a single "flagship = GPT-4" label.
- Developers still hit older
gpt-4oIDs on the API; treat those as legacy, not the consumer default.
Key capabilities
- GPT-5.6 Sol: Flagship reasoning / everyday paid ChatGPT experience.
- GPT-5.6 Terra: Balanced everyday work tier.
- GPT-5.6 Luna: Cost-efficient / Free–Go default.
- GPT-6 Pro: Higher-plan Pro option (where enabled).
- Multimodal chat, coding, and tool use via ChatGPT and API surfaces.
Technical notes
- ChatGPT product: /ai/chatgpt
- API: /ai/openai-api
- Retired in ChatGPT (2026): GPT-4o, GPT-4.1, o4-mini, early GPT-5 Instant/Thinking variants (see OpenAI Help Center)
- Evidence: GPT-5.6 announcement, Retiring GPT-4o in ChatGPT
Ideal for
- Tracking which OpenAI model generation a product or compare refers to.
- Migrating docs and prompts off GPT-4 / GPT-4o naming.
Not ideal for
- End-user product discovery — use ChatGPT.
- Billing / endpoint details — use OpenAI API.
See also
- ChatGPT — Consumer and Plus/Pro chat product.
- OpenAI API — Programmatic access.
- Claude — Anthropic assistant alternative.