The phase stays stored, beside the fetch

Status: accepted, 2026-10-05. Supersedes the derived phase of A handle keeps its fetch and derives its phase, by that record's own reopening line: its bench failed. Serves The store is the UI's state. Reopen if the verdict is made to cost less than a walk of every record the operation's own selection reaches, under the 50 µs a read that record set. Superseded in part on 2026-10-07 by The verdict is the root's, and the phase is derived from it, on the stored phase and the chain that settles it; the fetch as a value stands.

Context#

The record this one supersedes decided two things: the fetch as a value beside the phase, and the phase derived in its getter from what the store holds. It set a gate on the second before it was built: a read of the phase under 50 µs on the largest @throwOnFieldError operation the fixtures under spec/ answer. If the gate failed, the fetch's value was to ship alone and the phase to stay stored.

Decision#

• The fetch is a value of the handle, as decided: Fetch, read as fetch, is .idle, .inFlight or .failed(Failure, at:), with the failure and the instant it failed. A fetch that fails behind data, whoever started it, is read there by every view of the handle while the phase stays ready; the next response replaces it. isRefreshing is data present and a fetch in flight, and retry() with data behind it does not pass through loading.
• The phase stays stored on the handle and settled after each commit, as before the record this one supersedes. Phase keeps its three cases and its meaning.
• The chain that settles it, from the store's notice of a changed null, link or field error to each retained handle's walk, stays until the reopening line below is met.

Evidence#

• BENCHMARKS.md, "The re-evaluation a commit runs, for the handle step", 2026-10-05, on an Apple M1 Pro: the fixture under @throwOnFieldError, 899 records. The verdict, the field errors of the operation's own selection with none present, costs 567 µs untracked; with 20 present, 785 µs; in a body's tracking scope, where every slot the walk reads registers, 4.56 ms. The gate allowed 50 µs. The commit that settles a stored phase costs 939 µs with the handle retained, against 136 µs without it.
• 61c3ac4 built the fetch as a value and left the phase stored.

Not chosen#

• Shipping the derived phase over the gate: a body reading the phase would pay a walk of the selection on every evaluation, and register every slot it read.
• Caching the verdict in the handle to make the read cheap: a stored phase under another name.