GPT-5.5 after GPT-5.6: ChatGPT legacy status, API availability, context, pricing, and migration
Updated: Sep 17
GPT-5.5 is no longer the newest ChatGPT generation, but it has not vanished from OpenAI's ecosystem. The base GPT-5.5 API model remains documented, while ChatGPT has moved toward GPT-5.6 Luna, Sol, and Sol Pro.
The safe current description is therefore 'earlier or legacy where supported' for ChatGPT and 'available' for the base API model, unless a specific picker or workspace explicitly shows otherwise.
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GPT-5.5 BECAME THE CHATGPT DEFAULT ON JUNE 12
GPT-5.5 Instant replaced GPT-5.3 Instant as ChatGPT's everyday default and also became the migration target for conversations using retired GPT-5.2 models.
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Area | GPT-5.5 current status |
|---|---|
ChatGPT default | Replaced by GPT-5.6 generation |
Legacy ChatGPT access | May remain where supported; picker/workspace is source of truth |
OpenAI API | Available |
Context / max output | 1.05M / 128K |
API price | $5 input / $0.50 cached / $30 output per 1M tokens |
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GPT-5.6 IS NOW THE CURRENT CHATGPT GENERATION
GPT-5.6 Luna now powers the default experience for Free and Go, while GPT-5.6 Sol powers eligible paid ChatGPT reasoning levels and Sol Pro serves the higher GPT-5.6 Pro path.
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OPENAI DOES NOT PRESENT A UNIVERSAL GPT-5.5 CHATGPT RETIREMENT DATE IN THE CURRENT HELP PAGE
The current GPT-5.6 documentation says earlier models may remain available where supported. For managed workspaces, legacy-model availability depends on workspace settings and the live model picker.
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THE BASE GPT-5.5 API MODEL IS STILL AVAILABLE
OpenAI's developer catalog lists GPT-5.5 as a flagship model for complex professional work with 1.05M context, 128K maximum output, and reasoning effort from none through xhigh.
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GPT-5.5 IS EXPENSIVE RELATIVE TO EARLIER GPT-5 MODELS
Current API pricing is $5 per million input tokens, $0.50 cached input, and $30 output. Prompts above 272K input tokens use 2× input and 1.5× output pricing for the full session.
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DS CALCULATION: 10M INPUT + 2M OUTPUT
At standard list price, 10 million uncached input tokens plus 2 million output tokens cost about $110 on GPT-5.5: $50 input plus $60 output, before tool fees or long-context uplifts.
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MIGRATION SHOULD START FROM A FRESH BASELINE
OpenAI's model guidance recommends treating GPT-5.5 as its own family rather than blindly carrying forward older prompt stacks. The same principle applies when moving onward to GPT-5.6 or GPT-6: re-test prompts, tools, reasoning effort, latency, and cost.
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