# Focused diff — D2 field driver, preserved 81dc4fe8 -> current f7b7773f.
# sha256(history/fp-driver-d2-81dc4fe8.sh) = 81dc4fe8288105ed65998f2b152896f1cd4e068e29f1d3b1defe3ae5ed1c315d
# sha256(fp-driver-d2.sh)                  = f7b7773f6988768421fb4a4f19eeb6a6e12faec6136e7c1cad3032f0c1e2fde0
# One hunk, 9 added / 5 removed, entirely inside ts_readable(). Arm R10 is rig-side.
# Runtime dependency recorded per doyle 2026-09-13: date -u -d is GNU coreutils (8.32 measured
# here); acceptable for this Windows/MSYS-specific diagnostic, no BSD/macOS support requested.
--- history/fp-driver-d2-81dc4fe8.sh	2026-09-12 19:36:20.063144100 -0700
+++ fp-driver-d2.sh	2026-09-12 19:36:20.983438300 -0700
@@ -718,11 +718,15 @@
 #   every row carries a numeric pid, a READABLE creation timestamp, a non-empty executable and a
 #     non-empty command line.
 # Anything else is UNREADABLE -- INCLUDING the case where every recorded pid is now absent.
-ts_readable() { # a timestamp we can compare, not merely a string that is not the word UNREADABLE
-  case "$1" in
-    [0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]T[0-9][0-9]:[0-9][0-9]:[0-9][0-9]*Z) return 0 ;;
-    *) return 1 ;;
-  esac
+ts_readable() { # a timestamp we can COMPARE -- parsed, not merely shaped
+  # SHAPE IS NOT VALIDITY (doyle, 2026-09-13). "2026-02-30T00:00:00.000Z" matches every character
+  # class an ISO-8601 pattern asks for and names a day that does not exist, so a pattern test would
+  # let an impossible date establish pid reuse. This PARSES the value with the calendar and treats
+  # a parse failure as unreadable. The empty string is rejected first, because `date -d ""` is
+  # accepted as "now" and would otherwise pass.
+  [ -n "$1" ] || return 1
+  case "$1" in [0-9][0-9][0-9][0-9]-*) ;; *) return 1 ;; esac
+  date -u -d "$1" +%s >/dev/null 2>&1
 }
 capture_is_complete() { # -> 0 when the recorded set may support a CLEAR verdict
   local f="$R/run-identities.txt"