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424424This pairs Opus's reasoning for planning with Sonnet's efficiency for execution.
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426The plan-mode Opus phase uses the same context window as the `opus` model setting. On subscription tiers where Opus is [automatically upgraded to 1M context](#extended-context), `opusplan` receives the upgrade in plan mode as well. To force 1M context for both phases when you aren't on an auto-upgrade tier, [set the model](#setting-your-model) to `opusplan[1m]`, for example with `/model opusplan[1m]`. Setting it with `/model` requires Claude Code v2.1.265 or later; on earlier versions, use the `--model` flag or the `model` setting instead.
426The plan-mode Opus phase uses the same context window as the `opus` model setting, and the execution phase uses the same window as `sonnet`. When `opus` and `sonnet` resolve to models that run with the [1M context window](#extended-context) by default, as the current models do on the Anthropic API, both phases run with it. To request 1M context for both phases where they don't, [set the model](#setting-your-model) to `opusplan[1m]`, for example with `/model opusplan[1m]`. Setting it with `/model` requires Claude Code v2.1.265 or later; on earlier versions, use the `--model` flag or the `model` setting instead.
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428428When [`availableModels`](#restrict-model-selection) excludes the newest Opus but permits an older version, for example `["sonnet", "claude-opus-4-6"]`, `opusplan` uses the newest permitted Opus for planning and stays on Sonnet only when every Opus is excluded. A Haiku session that would normally upgrade to Sonnet in plan mode likewise uses the newest permitted Sonnet, and stays on Haiku only when every Sonnet is excluded. Before v2.1.205, plan mode stayed on the session's model whenever the newest version of the upgrade family was excluded, even when the allowlist permitted an older one.
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641641Fable 5.1, Fable 5, Sonnet 5, Opus 4.6 and later, and Sonnet 4.6 support a [1 million token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows#context-window-sizes-by-model) for long sessions with large codebases.
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643Availability varies by model and plan. On the Anthropic API, Fable 5.1, Fable 5, Sonnet 5, and Opus 4.7 and later run with the 1M window by default.
643On the Anthropic API, Fable 5.1, Fable 5, Sonnet 5, and Opus 4.7 and later run with the 1M window on every plan, including Pro. You don't select a `[1m]` variant or turn on usage credits for the 1M window on these models. Fable usage itself can bill to usage credits on some plans; see [Fable and usage credits](#fable-and-usage-credits).
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645On Max, Team, and Enterprise plans, including both Team Standard and Team Premium seats, Opus is automatically upgraded to 1M context with no additional configuration. Sonnet 4.6 with 1M context is not part of the automatic upgrade and requires [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) on every subscription plan, including Max.
645Opus 4.6 and Sonnet 4.6 reach 1M only through their `[1m]` variant, and access to that variant depends on your plan. On Max, Team, and Enterprise plans, including both Team Standard and Team Premium seats, Opus 4.6 with 1M context is included with your subscription. Sonnet 4.6 with 1M context requires [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) on every subscription plan, including Max.
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647| Plan | Opus with 1M context | Sonnet 4.6 with 1M context |
647| Plan | Opus 4.6 with 1M context | Sonnet 4.6 with 1M context |
648648| ------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------- |
649649| Max, Team, and Enterprise | Included with subscription | Requires [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) |
650650| Pro | Requires [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) | Requires [usage credits](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) |