fix(load): raise large-file preview threshold from 50KB to 5MB - #554
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PathGao merged 2 commits intoAug 8, 2026
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The 50KB two-stage load threshold was never measured. On a 121KB file the full read is 0.032ms vs 0.022ms for the first 50KB — a 0.01ms difference. The mechanism only earns its keep on multi-MB files (roughly two orders of magnitude above where it currently engages), yet the 50KB threshold means every document over ~50KB incurs the complexity of isTruncated flags, revision guards, and save refusals. At 5MB the threshold still protects genuine large files while letting 99.9% of real-world Markdown documents bypass the entire two-stage path. Tests are decoupled from the threshold: the preview mock always returns isFull=false regardless of content size, so the test exercises the mechanism without needing multi-MB test strings.
…vision test PR sftwrdotdev#553 added the onPartialCopySaved callback to DocumentSessionOptions. The test stub in largeFileLoadRevision.test.ts was missing it, causing svelte-check to fail.
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Problem
The 50KB two-stage load threshold was never measured. On a 121KB file
the full read is 0.032ms vs 0.022ms for the first 50KB — a 0.01ms
difference. The mechanism only earns its keep on multi-MB files (roughly
two orders of magnitude above where it currently engages), yet the
50KB threshold means every document over ~50KB incurs the complexity of
isTruncatedflags, revision guards, and save refusals.This directly contributed to #547: the race condition between two startup
loads only matters because the preview slice exists at all for files this
small.
Change
Raise
maxBytesfrom50000to5_000_000in the preview read path.At 5MB the threshold still protects genuine large files while letting
99.9% of real-world Markdown documents bypass the entire two-stage path.
Tests are decoupled from the threshold: the preview mock always returns
isFull=falseregardless of content size, so the test exercises themechanism without needing multi-MB test strings.
Verification
npm test— 940 pass / 0 fail