2026-10-13-claude-code-defaults-moved-to-opus-5-5-sonnet-5-5-and-haiku-5-5-new-managed-keys-pin-exact-model-versi

Defaults moved to Opus 5.5, Sonnet 5.5 and Haiku 5.5; new managed keys pin exact model versions and providers. Three model families changed default in 15 days: Opus 5.5 on 2026-09-22, when Opus also replaced Sonnet as the default model on Pro and Team Standard; Sonnet 5.5 on 2026-09-28; Haiku 5.5 on 2026-10-07. Opus 4.7+ and Fable moved to a 1M context by default on Bedrock, Vertex, Foundry and gateways. An availableModels allowlist naming claude-opus-5 admits Opus 5.5 automatically; 2.1.283 adds availableModelsMatch: "exact" and deniedModels to stop that, and 2.1.285 adds allowedProviders to fence which API providers a machine may use. The setup page now warns that a new model can need a build newer than stable; Haiku 5.5 needs 2.1.293, which stable lacks.

Channel: tagged-release (all but 2.1.293 on stable); docs-only for the setup-page channel warning. Half: both. Date: 2026-09-22 (2.1.280), 2026-09-25 (2.1.283), 2026-09-28 (2.1.284), 2026-09-29 (2.1.285), 2026-10-01 (2.1.287), 2026-10-07 (2.1.293).

Operator consequence: Pro and Team Standard seats default to Opus and spend usage faster; set model if Sonnet was the plan. Evals keyed on opus, sonnet or haiku aliases changed model three times this window; pin full model IDs for alias drift, but record the model actually served because safety-related switches can override a pinned Opus model (section 17). Fleets with prefix allowlists should decide whether point releases enter automatically; availableModelsMatch: "exact" makes each one a deliberate change. Gateways that stop at 200K need CLAUDE_CODE_DISABLE_1M_CONTEXT=1 or /autocompact 200k.

Receipt

• https://github.com/anthropics/claude-code/blob/2301018b1f61/CHANGELOG.md?plain=1#L1597
• https://github.com/anthropics/claude-code/releases/tag/v2.1.283
• https://code.claude.com/docs/en/settings-reference#availablemodelsmatch