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Sweep 27 Oct 2026 · 19:04Z Build v2.1.312 531 read Stable v2.1.308 Latest v2.1.312 Next v2.1.312 Feeds RSS JSON llms.txt llms-full.txt Unofficial
HomeDocsClaude Code CLI 27 Oct 2026
One change · claude-code

Claude Code on Google Cloud's Agent Platform changedgoogle-vertex-ai

Nearest release: v2.1.312, published under an hour before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

Upstream edited this page at 27 Oct 2026 19:25 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 27 Oct 2026 19:37 UTC.

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First seen 14 Aug 2026 this site's first read of the page
Recorded edits21to this page, all time

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162162| Primary model | `claude-opus-5-5` |
163163| Small/fast model | `claude-sonnet-4-5@20250929` |
164164 
165Before v2.1.280, the primary model on Google Cloud's Agent Platform defaulted to Opus 5 and the `opus` alias resolved to Opus 5 from v2.1.219.
166 
165167Background tasks such as session title generation use the small/fast model, normally a Haiku-class model. On Google Cloud's Agent Platform, Claude Code uses the default Sonnet model for background tasks because Haiku may not be enabled in every project or region. Two selections change which model carries them:
166168 
167169* When you select a primary model with `--model`, `ANTHROPIC_MODEL`, or the `model` setting, background tasks use that model. When Claude Code starts the session on the model you set with [`ANTHROPIC_DEFAULT_MODEL`](https://code.claude.com/docs/en/model-config#set-a-default-model-for-new-sessions), background tasks use that model too. Setting `ANTHROPIC_DEFAULT_OPUS_MODEL` without `ANTHROPIC_DEFAULT_SONNET_MODEL` also counts as a selection, because the built-in Sonnet model may not be enabled in a project that steers its own Opus.
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170172> [!WARNING]
171173>
172174> Opus models have a higher per-token price than Sonnet models, so if you don't pin a primary model, you're billed at the Opus rate. To use Sonnet 4.5 as the primary model, set `ANTHROPIC_MODEL` to its full model ID. A deployment that steers the default with `ANTHROPIC_DEFAULT_SONNET_MODEL` and doesn't set `ANTHROPIC_DEFAULT_OPUS_MODEL` keeps its steered Sonnet model as the default.
173 
174Before v2.1.280, the primary model on Google Cloud's Agent Platform defaulted to Opus 5 and the `opus` alias resolved to Opus 5 from v2.1.219. On v2.1.207 through v2.1.218, the primary model on Google Cloud's Agent Platform defaulted to Opus 4.8 and the `opus` alias resolved to Opus 4.8.
175175 
176176To customize models further:
177177 
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