CC[100]'s command audit (AUDIT-COMMANDS-08-21-26.md) found HISTORY.php?system=10 returns a real, well-formed history -- of the wrong system (Travel instead of Master). Root cause: two separate hand-rolled maps in the file ($decade_map for locating the system DB directory, $decade_codes for the transfers query) both keyed by OLD, RETIRED single-digit codes rather than the real decade codes every current caller actually passes -- and both contained the exact '10 trap' SOP-COMMAND-BUILD.md warns about: retired code 10 was Travel, so $decade_map['10'] resolved to 95-travel and $decade_codes['10'] resolved to '95', even though the caller meant decade 10 (Master). Systems 20/30/50/60/70/80/90/95 (everything except 00 and 40, which happened to have matching old/new single digits in different ways) were also silently wrong, just less noticeably than the Master/Travel collision. FIX: replaced $decade_map with roster_lib.php's build_roster() (same pattern as PLATFORM_CHECK.php's F1 fix, same session) for the directory lookup; replaced $decade_codes entirely -- no conversion is needed at all since $system IS the real decade code already for every current caller, so $dc = $system directly.