CFM-18: lower attachment threshold so large saves succeed (backport of #428) - #429
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Large interactive states near 480 KiB produced ~1.06 MB Firestore answer documents that exceeded the 1 MB limit and failed to save. Activity Player stores the state twice as escaped JSON strings inside a report wrapper, expanding it to ~2.2 bytes of document per character of state. Lower kDynamicAttachmentSizeThreshold from 480 KiB to 400 KiB so oversized states are offloaded to an S3 attachment before the document grows too large. (cherry picked from commit 41cd3cd)
- Clarify that state at or above the threshold is offloaded, matching the inclusive >= check in shouldSaveAsAttachment. - Use consistent KiB/MiB units in the size math. (cherry picked from commit de0d63a)
shouldSaveAsAttachment() measured String.prototype.length (UTF-16 code units), which undercounts non-ASCII content relative to Firestore's byte-based 1 MiB document limit. Switch to UTF-8 byte counting via TextEncoder so the size check matches the byte-based threshold. Adds a jsdom test-environment shim for TextEncoder and a regression test covering multi-byte content. (spec R6) (cherry picked from commit ddc46e9)
This was referenced May 21, 2026
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This was referenced Aug 27, 2026
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Backports the bug fix from #428 onto the
v2.2.xrelease branch.Summary
Large interactive states near 480 KiB produced ~1.06 MB Firestore answer documents that exceeded the 1 MB limit and failed to save. Activity Player stores the state twice as escaped JSON strings inside a report wrapper, expanding it to ~2.2 bytes of document per character of state. This lowers
kDynamicAttachmentSizeThresholdfrom 480 KiB to 400 KiB so oversized states are offloaded to an S3 attachment before the document grows too large.Additionally,
shouldSaveAsAttachment()now measures the serialized state's UTF-8 byte length (viaTextEncoder) instead ofJSON.stringify(content).length, which counts UTF-16 code units. The previous check undercounted non-ASCII content relative to Firestore's byte-based 1 MB limit, so multi-byte states could exceed the limit even while reported as "below" the threshold. A regression test covers this case, and a jsdom test-environment shim providesTextEncoderfor tests.Details
This is a clean cherry-pick (
git cherry-pick -x) of the three commits from #428. The resulting diff is byte-identical to the original PR's diff. Theinteractive-api-providertest suite passes (17/17).See the original investigation: https://gist.github.com/dougmartin/54bafa93a9dc5185a609da8b5b63b4ac
Relates to CFM-18.
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