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The keyset table's column is headed "Counter (hex)" with the placeholder 0000000001, and cardsAdd refuses a save whose counter is not 1-10 hex digits (empty included; whitespace stripped) - the same rule the store enforces. The store keeps its import-compatible empty -> 1 default for API/import callers. Docs: repo AGENTS (v3.13.4 note). sw cache simple-v374. Tests: 667 Python + 797 frontend green.