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Since May 2026: what Claude Opus 5 cannot know

Claude Opus 5 was trained on data up to May 2026. Since then, 301 models, APIs and runtimes have reached their end date and packages have shipped 168,391 breaking changes. Code it writes from memory can still use any of them.

Knowledge cutoff May 2026

On this page

The model ID is claude-opus-5, from Anthropic, released July 24, 2026. The endings and the package changes below came after its training data ends, so they are not in what the model learned.

Ended since May 2026

301 models, APIs and runtimes have reached their end date since the cutoff. The newest of each:

AI models

And 271 more on the calendar.

Still ahead

450 end dates are still ahead. Some were announced after the cutoff, so the model may write what they end. The soonest of each:

AI models

APIs

And 420 more on the calendar.

Packages that changed most

Since the cutoff, package versions shipped 168,391 breaking changes, and 30,106 security advisories were published. The packages with the most breaking changes in versions released since:

  • happy-dom npm, 2,562 breaking changes, newest in 21.0.4 (October 20, 2026)
  • skit.flurlhttpclient.wechat.api NuGet, 2,398 breaking changes, newest in 4.0.0 (November 13, 2026)
  • @types/three npm, 1,884 breaking changes, newest in 0.187.0 (October 30, 2026)
  • three npm, 1,884 breaking changes, newest in 0.187.0 (October 30, 2026)
  • qcodes PyPI, 1,602 breaking changes, newest in 0.63.0 (November 12, 2026)
  • typescript npm, 1,539 breaking changes, newest in 7.0.2 (July 8, 2026)
  • equadrat.framework.core.interfaces NuGet, 1,506 breaking changes, newest in 9.0.0 (November 12, 2026)
  • skit.flurlhttpclient.wechat.tenpayv3 NuGet, 1,351 breaking changes, newest in 4.0.0 (November 13, 2026)
  • typegpu npm, 1,331 breaking changes, newest in 0.12.10 (November 12, 2026)
  • particle PyPI, 1,298 breaking changes, newest in 1.0.0 (June 25, 2026)

Check before it writes

Run npx since-dev init in a repository and your coding agent checks a version or a model ID before it writes one, whatever model it runs on. To see what a repository already uses that has ended, scan it, or run npx since-dev inside it.

Knowledge cutoffs are from models.dev (MIT License). A cutoff given as a month is read as that month’s last day.

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Put your code on continuous maintenance.

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See how out of date your code is.

Any public GitHub repository. No sign-in.

Tell your agent what changed since it was trained.

claude mcp add --transport http since https://api.since.dev/mcp
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