Published AI context windows, 2018–2026 (tokenusage.dev research note 003)

25 selected published context-window records, from GPT-1's 512 tokens in 2018 to models available in October 2026, with what each number counts (training sequence length, input limit, or input plus output), access level and sources. Windows are recorded as published, as text, so provider shorthand and separate input and output limits stay visible. This is the data behind tokenusage.dev research note 003, "AI context windows grew 4,096-fold, then stalled" (https://tokenusage.dev/publications/oct-26-context-windows).