[vhladiienko]

Summary

The capture response to the popup carried every output PNG as full-size base64 data URLs. Chromium caps extension messages at ~64MiB (serialized length, so base64 costs 4 bytes per 3 raw bytes), and a long page's capture crossed it — so the response died after the capture had already succeeded. The popup showed Error: Message exceeded maximum allowed size of 64MiB. and a blank preview over a healthy capture: the bytes were already in blob-store, which is why Save PNG, PDF export, history and the editor (all blob-store readers) kept working.

The response now carries a small thumbnail instead — the first output image re-encoded at 320px wide through shot-core's existing cropAndEncode, a few KB that cannot reach the cap. Full-size bytes stay in blob-store, exactly where everything that needs them already reads them.

 background handleRequest (captureFullPage / captureVisible / captureSelectedArea)
   response to the popup over chrome.runtime.sendMessage
-    pngDataUrls: every output PNG, base64        ← ~64MiB+ on a long page
+    previewDataUrl: first image at 320px wide    ← a few KB

The popup uses the response image in exactly one place — the preview <img> — so the thumbnail covers all of its consumption. Split captures change nothing semantically: the preview always showed the first image only; before, it also shipped every part's bytes, which is precisely what overflowed.

Evidence

• Before: full-page capture of a page whose output PNG encoded ≥ ~48MiB raw (a detailed 30,000px segment does) → popup showed the browser's error text and an empty #preview, while savePngs from the same state saved every file fine.
• After: the response is a few KB, immune to the cap; the popup reports the capture normally with a preview thumbnail.

Full runs on this branch: npm run typecheck ✓, npm test ✓ (13 files, 110 tests). The e2e suite was not run for this change; no spec asserts on the popup response shape (pngDataUrls appeared only in the three response sites, types.ts, and the popup preview).

Merge Danger

Door: two-way — reverting the single commit restores the old response shape exactly.

Blast Radius: small — the popup response and the popup's preview read; blob-store, history, editor handoff and PDF paths untouched. Merges cleanly with #66 (both touch popup.ts; verified with merge-tree, regions are disjoint).