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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 v2.1.248

Sync failures distinguish "lane unavailable" from "unsupported"

You'll notice
Useful2 Signal2
Cloud Sessions

Sync errors now distinguish a server declining this path from one with no sync at all.

What

Session sync errors are classified more precisely, so a server that is declining this particular sync path is no longer reported the same as a server that does not support sync at all. Applies to everyone, no gate.

Details
  • HTTP 400 with a laneDenied reason becomes lane_unavailable.
  • HTTP 400 for upload or download unavailable becomes lane_unavailable with cause direct_sync_off.
  • 501 and 405 remain unsupported and now carry the status code.
  • 404 counts as not_found only outside the begin phase and only when the body is a not-found error.
Evidence

{ kind: "lane_unavailable", cause: "direct_sync_off" }

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

See this entry in the whole of v2.1.248 →