[oxyc]

Problem

Snellman reported intermittent "Sorry, your submission could not be verified" on forms 43/45 (cost set to Very high, 1M), with ALTCHA [name=altcha] verification failed Error: Failed to find solution. in the console. The GF log shows every rejection as reason: missing, in bursts of retries seconds apart.

• auto="onload" only starts the proof; submitting before it finishes posts an empty altcha field.
• A rejected AJAX submit re-renders the form, so the proof restarts from zero and quick retries fail the same way.
• A solve that hits the widget's 90s timeout leaves it in error and is never retried.
• Browser WebCrypto PBKDF2 measured ~1M iterations/s per core (Chromium, M-series Mac), so 1M cost averages ~25s on a fast 10-core desktop and exceeds 90s on an ordinary laptop. The old labels (~20s) were off by an order of magnitude on slower hardware.

Changes

• Hold GF submissions via the async gform/submission/pre_submission filter until the proof is solved or has failed for good. GF keeps its spinner up meanwhile.
• On error, fetch a fresh challenge and retry, capped at 3 retries.
• Corrected strength labels and README guidance.

Tested

Against snellmanrecipes locally (form 43, cost 1M), with this build swapped in:

• Submit immediately after load → waited for the proof, entry accepted (82s).
• Forced timeout on the first solve → retried with a fresh challenge, verified.
• Every attempt forced to time out → retries stopped at the cap and the submit finished with the server's "reload" message (no hang).
• composer test (67 tests) and composer lint pass.

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