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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

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Claude Code v2.1.59 25 Feb 2026

Opus 4.6 Model Routing [Gradual Rollout]

What

Infrastructure for routing requests to the Opus 4.6 model when a coral_reef_opus feature flag is enabled server-side.

Status

Feature-flagged via coral_reef_opus

Details

When coral_reef_opus is "true" and the model string contains "opus-4-6", a special token limit of 1,000,000 is applied
Extended output is enabled for matching Opus 4.6 models via the HbA() function
Gated behind multiple checks: not in test mode, not using custom provider

Evidence

Model routing (search for "coral_reef_opus", "opus-4-6")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.59 →