feat(todo-cleanup): add --convert-subtasks dated-rewrite mode

Rewrites every level-3+ DONE/CANCELLED/FAILED heading into a dated event-log entry from its CLOSED cookie, enforcing the todo-format depth rule that interactive closes and --archive-done (level-2 only) leave unapplied. A new lint-org checker (subtask-done-not-dated) flags stragglers, and the clean-todo, wrap-up, open-tasks, and task-review workflows now run the converter before archiving.

Removing the CLOSED cookie keeps a DEADLINE or SCHEDULED cookie that shares its planning line, rather than dropping the whole line.

From the .emacs.d handoff (2026-07-01 convert-subtasks bundle).

17 files changed, 916 insertions, 22 deletions

diff --git a/.ai/scripts/lint-org.el b/.ai/scripts/lint-org.el
index 5447cb3..90b1b1d 100644
--- a/.ai/scripts/lint-org.el
+++ b/.ai/scripts/lint-org.el
@@ -35,6 +35,7 @@
 ;;   empty-heading                     bare stars with no title
 ;;   malformed-priority-cookie         [#x]-shaped token org rejected
 ;;   level2-done-without-closed        completed level-2 task with no CLOSED
+;;   subtask-done-not-dated            level-3+ done sub-task still a DONE keyword
 ;;   (anything else)                   surfaced as judgment with checker name
 ;;
 ;; Output format on stdout:
@@ -503,6 +504,32 @@ the live file on the next `task-sorted'."
                "level-2 DONE/CANCELLED has no CLOSED date — add CLOSED: [YYYY-MM-DD Day]; task-sorted's aging step archives an undated completed task immediately"))))))))
 
 ;;; ---------------------------------------------------------------------------
+;;; level-3+ dated-header check (claude-rules/todo-format.md)
+;;
+;; The inverse of the level-2 check above.  A completed sub-task — a heading at
+;; level 3 or deeper, under a parent task — becomes a dated event-log entry, not
+;; a DONE keyword, so the parent's subtree grows a chronological history instead
+;; of a long tail of nested DONE lines.  An interactive org close
+;; (`org-log-done' → DONE + CLOSED) leaves the keyword in place, and
+;; `--archive-done' only touches level 2, so these accumulate.  Flag them for
+;; conversion.  Judgment-only and regex-based (independent of which TODO keywords
+;; the batch Emacs recognizes); todo-cleanup.el --convert-subtasks does the fix.
+
+(defun lo--check-subtask-done-not-dated ()
+  "Flag level-3+ headings carrying a done keyword (DONE/CANCELLED/FAILED).
+Emits one judgment item per offending heading (checker
+`subtask-done-not-dated')."
+  (save-excursion
+    (goto-char (point-min))
+    ;; Case-sensitive: the keywords are uppercase, not the words in a title.
+    (let ((case-fold-search nil))
+      (while (re-search-forward
+              "^\\*\\{3,\\} \\(DONE\\|CANCELLED\\|FAILED\\) " nil t)
+        (lo--emit-judgment
+         'subtask-done-not-dated (line-number-at-pos)
+         "level-3+ done sub-task should be a dated event-log entry (todo-format.md): run todo-cleanup.el --convert-subtasks to rewrite it")))))
+
+;;; ---------------------------------------------------------------------------
 ;;; File processing
 
 (defun lo--backup (file)
@@ -543,6 +570,7 @@ left unmodified and mechanical entries are recorded with :preview t."
           (lo--check-empty-headings)
           (lo--check-malformed-priority-cookies)
           (lo--check-level2-done-without-closed)
+          (lo--check-subtask-done-not-dated)
           (when (and (not lo-check-only) (buffer-modified-p))
             (save-buffer)))
       (with-current-buffer buf (set-buffer-modified-p nil))
diff --git a/.ai/scripts/tests/test-lint-org.el b/.ai/scripts/tests/test-lint-org.el
index 3b8a9bb..d14879f 100644
--- a/.ai/scripts/tests/test-lint-org.el
+++ b/.ai/scripts/tests/test-lint-org.el
@@ -685,6 +685,37 @@ missing-rules violation."
          (judgments (lo-test--judgments (plist-get out :issues))))
     (should-not (member 'level-2-dated-header (lo-test--checkers judgments)))))
 
+;;; subtask-done-not-dated check (the inverse: level-3+ done keyword)
+
+(ert-deftest lo-subtask-done-not-dated-flags-level3 ()
+  "A level-3 DONE sub-task still carrying the keyword is flagged for conversion."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** TODO [#B] Parent\n*** DONE [#C] Sub-task done\nCLOSED: [2026-06-20 Sat 10:00]\nBody.\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should (= 0 (plist-get out :fixes)))       ; judgment-only, never auto-fixed
+    (should (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
+(ert-deftest lo-subtask-done-not-dated-flags-level4-cancelled ()
+  "A level-4 CANCELLED sub-task is flagged too."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** PROJECT [#B] Parent\n*** TODO Mid\n**** CANCELLED Deep abandoned\nCLOSED: [2026-06-20 Sat]\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
+(ert-deftest lo-subtask-done-not-dated-ignores-level2 ()
+  "A level-2 DONE task is a top-level task, not a sub-task — this checker skips it."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** DONE [#B] Top-level\nCLOSED: [2026-06-20 Sat]\nBody.\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should-not (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
+(ert-deftest lo-subtask-done-not-dated-ignores-dated-and-lowercase ()
+  "An already-dated level-3 entry, and the word done in a title, are not flagged."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** TODO [#B] Parent\n*** 2026-06-20 Sat @ 10:00:00 -0400 landed\n*** TODO wrap the done cleanup\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should-not (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
 ;;; ---------------------------------------------------------------------------
 ;;; structural heading checks (org-lint gaps)
 
diff --git a/.ai/scripts/tests/test-todo-cleanup.el b/.ai/scripts/tests/test-todo-cleanup.el
index e569d9a..ffbf2fb 100644
--- a/.ai/scripts/tests/test-todo-cleanup.el
+++ b/.ai/scripts/tests/test-todo-cleanup.el
@@ -768,5 +768,176 @@ in ISSUES, in document order."
     (should (= 2 (plist-get once :bumped)))
     (should (= 2 (plist-get twice :bumped)))))
 
+;;; ---------------------------------------------------------------------------
+;;; --convert-subtasks harness + tests
+
+(defun tc-test--reset-convert (&optional check)
+  (setq tc-fixes 0 tc-archived 0 tc-bumped 0 tc-converted 0 tc-archived-to-file 0
+        tc-issues nil
+        tc-check-only (and check t)
+        tc-archive-done nil tc-sync-child-priority nil tc-convert-subtasks t
+        tc-current-file nil
+        tc-archive-retain-days nil tc-archive-reference-date nil tc-archive-file nil))
+
+(defun tc-test--convert (content &optional runs check)
+  "Write CONTENT to a temp .org file, run `--convert-subtasks' RUNS times (default 1).
+Return a plist: :result final file contents, :converted count from the last run,
+:issues from the last run.  CHECK non-nil ⇒ --check (preview, no writes)."
+  (let ((file (make-temp-file "tc-test-" nil ".org"))
+        last-converted last-issues)
+    (unwind-protect
+        (progn
+          (with-temp-file file (insert content))
+          (dotimes (_ (or runs 1))
+            (tc-test--reset-convert check)
+            (tc-process-file file)
+            (setq last-converted tc-converted last-issues tc-issues)
+            (tc-test--drop-buffer file))
+          (list :result (with-temp-buffer (insert-file-contents file)
+                                          (buffer-string))
+                :converted last-converted
+                :issues last-issues))
+      (tc-test--drop-buffer file)
+      (delete-file file))))
+
+;; The UTC offset in a converted header is the test machine's local offset for
+;; that date, so assertions match it as `[-+]NNNN' rather than a fixed value —
+;; the mode's job is to emit a well-formed offset, not to run in one timezone.
+
+(defconst tc-test--convert-timed
+  "* Project Open Work
+** TODO [#B] Parent task
+*** DONE [#C] F12 opens the terminal :feature:quick:
+CLOSED: [2026-06-27 Sat 12:50]
+Verified live: docks, toggles, colors clean.
+")
+
+(ert-deftest tc-convert-timed-subtask-normal ()
+  "Normal: a timed CLOSED close becomes a dated header, keyword/priority/tags/CLOSED gone."
+  (let* ((out (tc-test--convert tc-test--convert-timed))
+         (res (plist-get out :result)))
+    (should (= 1 (plist-get out :converted)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-27 Sat @ 12:50:00 [-+][0-9]\\{4\\} F12 opens the terminal$"
+             res))
+    (should-not (string-match-p "CLOSED:" res))
+    (should-not (string-match-p "DONE" res))
+    (should (string-match-p "Verified live: docks, toggles, colors clean\\." res))
+    (should (string-match-p "^\\*\\* TODO \\[#B\\] Parent task$" res))))
+
+(defconst tc-test--convert-dateonly
+  "* Project Open Work
+** PROJECT [#B] Parent
+**** DONE [#B] Write full spec :refactor:
+CLOSED: [2026-05-04 Mon]
+Body.
+")
+
+(ert-deftest tc-convert-dateonly-boundary-midnight ()
+  "Boundary: a date-only CLOSED (no time) yields 00:00:00, at level 4."
+  (let ((res (plist-get (tc-test--convert tc-test--convert-dateonly) :result)))
+    (should (string-match-p
+             "^\\*\\*\\*\\* 2026-05-04 Mon @ 00:00:00 [-+][0-9]\\{4\\} Write full spec$"
+             res))
+    (should-not (string-match-p "CLOSED:" res))))
+
+(defconst tc-test--convert-level2
+  "* Project Open Work
+** DONE [#B] Top-level task
+CLOSED: [2026-06-01 Mon 09:00]
+Body.
+")
+
+(ert-deftest tc-convert-leaves-level-2-alone-boundary ()
+  "Boundary: a level-2 DONE task is a top-level task, not a sub-task — untouched."
+  (let ((out (tc-test--convert tc-test--convert-level2)))
+    (should (= 0 (plist-get out :converted)))
+    (should (equal tc-test--convert-level2 (plist-get out :result)))))
+
+(ert-deftest tc-convert-idempotent-boundary ()
+  "Boundary: a second run over an already-dated entry converts nothing new."
+  (let ((once (tc-test--convert tc-test--convert-timed 1))
+        (twice (tc-test--convert tc-test--convert-timed 2)))
+    (should (equal (plist-get once :result) (plist-get twice :result)))
+    (should (= 0 (plist-get twice :converted)))))
+
+(defconst tc-test--convert-nested
+  "* Project Open Work
+** TODO [#B] Parent
+*** DONE Outer sub :feature:
+CLOSED: [2026-06-10 Wed 08:15]
+**** DONE Inner sub
+CLOSED: [2026-06-09 Tue 07:00]
+Inner body.
+")
+
+(ert-deftest tc-convert-nested-done-subtasks-boundary ()
+  "Boundary: a done sub-task nested under a done sub-task — both convert."
+  (let* ((out (tc-test--convert tc-test--convert-nested))
+         (res (plist-get out :result)))
+    (should (= 2 (plist-get out :converted)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-10 Wed @ 08:15:00 [-+][0-9]\\{4\\} Outer sub$" res))
+    (should (string-match-p
+             "^\\*\\*\\*\\* 2026-06-09 Tue @ 07:00:00 [-+][0-9]\\{4\\} Inner sub$" res))
+    (should-not (string-match-p "CLOSED:" res))))
+
+(defconst tc-test--convert-cancelled
+  "* Project Open Work
+** TODO [#B] Parent
+*** CANCELLED [#C] Abandoned idea :feature:
+CLOSED: [2026-06-15 Mon 10:00]
+")
+
+(ert-deftest tc-convert-cancelled-subtask-boundary ()
+  "Boundary: a CANCELLED sub-task converts too (terminal state)."
+  (let ((res (plist-get (tc-test--convert tc-test--convert-cancelled) :result)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-15 Mon @ 10:00:00 [-+][0-9]\\{4\\} Abandoned idea$" res))
+    (should-not (string-match-p "CANCELLED" res))))
+
+(defconst tc-test--convert-noclosed
+  "* Project Open Work
+** TODO [#B] Parent
+*** DONE Orphan with no closed date
+Body only.
+")
+
+(ert-deftest tc-convert-skips-subtask-without-closed-error ()
+  "Error: a done sub-task with no parseable CLOSED is flagged and left unchanged."
+  (let ((out (tc-test--convert tc-test--convert-noclosed)))
+    (should (= 0 (plist-get out :converted)))
+    (should (equal tc-test--convert-noclosed (plist-get out :result)))
+    (should (cl-some (lambda (i) (eq (plist-get i :kind) 'convert-skip))
+                     (plist-get out :issues)))))
+
+(ert-deftest tc-convert-check-mode-previews-without-writing ()
+  "Check mode reports the conversion but writes nothing."
+  (let ((out (tc-test--convert tc-test--convert-timed 1 t)))
+    (should (= 1 (plist-get out :converted)))
+    (should (equal tc-test--convert-timed (plist-get out :result)))
+    (should (cl-some (lambda (i) (eq (plist-get i :kind) 'convert-would))
+                     (plist-get out :issues)))))
+
+(defconst tc-test--convert-closed-with-deadline
+  "* Project Open Work
+** TODO [#B] Parent task
+*** DONE [#C] Ship the panel :feature:
+CLOSED: [2026-06-27 Sat 12:50] DEADLINE: <2026-06-30 Tue>
+Body line.
+")
+
+(ert-deftest tc-convert-preserves-deadline-on-shared-planning-line-boundary ()
+  "Boundary: removing the CLOSED cookie keeps a DEADLINE sharing its planning line."
+  (let* ((out (tc-test--convert tc-test--convert-closed-with-deadline))
+         (res (plist-get out :result)))
+    (should (= 1 (plist-get out :converted)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-27 Sat @ 12:50:00 [-+][0-9]\\{4\\} Ship the panel$"
+             res))
+    (should-not (string-match-p "CLOSED:" res))
+    (should (string-match-p "^DEADLINE: <2026-06-30 Tue>$" res))
+    (should (string-match-p "^Body line\\.$" res))))
+
 (provide 'test-todo-cleanup)
 ;;; test-todo-cleanup.el ends here
diff --git a/.ai/scripts/todo-cleanup.el b/.ai/scripts/todo-cleanup.el
index 541d106..bd8166d 100644
--- a/.ai/scripts/todo-cleanup.el
+++ b/.ai/scripts/todo-cleanup.el
@@ -5,10 +5,12 @@
 ;;   emacs --batch -q -l todo-cleanup.el --check todo.org                  # hygiene report only
 ;;   emacs --batch -q -l todo-cleanup.el --archive-done todo.org           # archive completed subtrees
 ;;   emacs --batch -q -l todo-cleanup.el --archive-done --check todo.org   # preview the archive
+;;   emacs --batch -q -l todo-cleanup.el --convert-subtasks todo.org       # dated-rewrite done level-3+ sub-tasks
+;;   emacs --batch -q -l todo-cleanup.el --convert-subtasks --check todo.org  # preview the conversion
 ;;   emacs --batch -q -l todo-cleanup.el --sync-child-priority todo.org    # bump children whose priority drifted below the parent's
 ;;   emacs --batch -q -l todo-cleanup.el --check-child-priority todo.org   # preview the sync (same as --sync-child-priority --check)
 ;;
-;; Three independent modes:
+;; Four independent modes:
 ;;
 ;; * Default (hygiene). Designed for the wrap-it-up workflow: cheap, idempotent,
 ;;   safe to run every session.
@@ -52,6 +54,20 @@
 ;;   Archiving is consequential, so it's never run by default; it does *not*
 ;;   also run the hygiene passes.
 ;;
+;; * --convert-subtasks (opt-in). Rewrites every level-3-and-deeper heading whose
+;;   TODO state is DONE/CANCELLED/FAILED into a dated event-log entry
+;;   (`<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>'), dropping the keyword,
+;;   priority cookie, and tags, and removing the now-redundant CLOSED line. The
+;;   date and time come from that entry's own CLOSED cookie; a date-only close
+;;   yields 00:00:00, and the UTC offset is computed DST-aware for that date.
+;;   This enforces the todo-format depth rule that interactive closes
+;;   (`org-log-done' → DONE + CLOSED) and `--archive-done' (level-2 only) leave
+;;   unapplied. The heading text is preserved verbatim — a batch tool can't
+;;   past-tense an imperative title reliably. Idempotent (an already-dated
+;;   heading has no done keyword); a done sub-task with no parseable CLOSED date
+;;   is flagged and left alone, never stamped with a fabricated date. Like
+;;   --archive-done it does not also run the hygiene passes.
+;;
 ;; * --sync-child-priority (opt-in). Walks every heading with a priority cookie
 ;;   ([#A]-[#D]) and, for each of its direct child headings whose own priority
 ;;   is lower (later in the alphabet — D is lower than A), bumps the child's
@@ -73,11 +89,16 @@
 (require 'calendar)
 
 (setq org-todo-keywords
-      '((sequence "TODO" "DOING" "WAITING" "NEXT" "|" "DONE" "CANCELLED")))
+      '((sequence "TODO" "DOING" "WAITING" "NEXT" "|" "DONE" "CANCELLED" "FAILED")))
 
 (defconst tc-done-states '("DONE" "CANCELLED")
   "TODO keywords that mark an entry as completed for `--archive-done'.")
 
+(defconst tc--convert-done-states '("DONE" "CANCELLED" "FAILED")
+  "TODO keywords whose level-3-and-deeper entries `--convert-subtasks' rewrites
+to dated event-log entries.  Broader than `tc-done-states' because a FAILED
+sub-task is terminal too and belongs in the parent's dated history.")
+
 (defconst tc--priority-cookie-regexp "\\[#\\([A-Z]\\)\\]"
   "Regexp matching an org priority cookie. Match group 1 is the letter.")
 
@@ -89,10 +110,12 @@ every heading below it.")
 (defvar tc-fixes 0)
 (defvar tc-archived 0)
 (defvar tc-bumped 0)
+(defvar tc-converted 0)
 (defvar tc-issues nil)
 (defvar tc-check-only nil)
 (defvar tc-archive-done nil)
 (defvar tc-sync-child-priority nil)
+(defvar tc-convert-subtasks nil)
 (defvar tc-current-file nil)
 (defvar tc-current-dir nil)
 (defvar tc-archived-to-file 0)
@@ -578,6 +601,138 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
   (org-map-entries #'tc-sync-child-priority-at-heading nil 'file))
 
 ;;; ---------------------------------------------------------------------------
+;;; --convert-subtasks mode
+;;
+;; A sub-task (a heading at level 3 or deeper, i.e. under a parent task) that is
+;; marked DONE/CANCELLED/FAILED should become a dated event-log entry per the
+;; todo-format depth rule: drop the keyword, priority cookie, and tags, and
+;; rewrite the heading to `<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>' so the
+;; parent's subtree grows a chronological history instead of a long tail of
+;; nested DONE lines.  Nothing enforced this before: `org-log-done' just flips an
+;; interactive close to DONE + CLOSED, and `--archive-done' only touches level 2.
+;; So level-3+ closes piled up as DONE keywords.  This mode converts them
+;; mechanically, pulling the timestamp from each entry's own CLOSED cookie.  The
+;; heading text is kept verbatim (a batch tool can't reliably past-tense an
+;; imperative title, and guessing prose in the task file is worse than leaving it
+;; as written).  Idempotent: an already-dated heading has no done keyword, so it
+;; is skipped.  A done sub-task with no parseable CLOSED cookie can't be dated, so
+;; it is flagged and left alone rather than stamped with a fabricated date.
+
+(defun tc--closed-parts-in-entry ()
+  "Return a plist (:year :month :day :dow :hour :minute) from the CLOSED cookie
+of the entry at point, or nil when the entry has no parseable CLOSED line.
+:hour and :minute are nil when the cookie carries only a date.  The CLOSED line
+sits in canonical position directly under the heading, so the first match within
+the entry is the task's own close."
+  (save-excursion
+    (org-back-to-heading t)
+    (let ((end (save-excursion
+                 (or (outline-next-heading) (goto-char (point-max)))
+                 (point))))
+      (when (re-search-forward
+             (concat "CLOSED:[ \t]*\\[\\([0-9]\\{4\\}\\)-\\([0-9]\\{2\\}\\)-\\([0-9]\\{2\\}\\)"
+                     "[ \t]+\\([A-Za-z]+\\)"
+                     "\\(?:[ \t]+\\([0-9]\\{2\\}\\):\\([0-9]\\{2\\}\\)\\)?\\]")
+             end t)
+        (list :year (match-string 1) :month (match-string 2) :day (match-string 3)
+              :dow (match-string 4)
+              :hour (match-string 5) :minute (match-string 6))))))
+
+(defun tc--tz-offset-string (year month day hour minute)
+  "Return the local UTC offset (e.g. \"-0500\") for the given wall-clock instant.
+DST-aware: `encode-time' with an unknown-DST field lets the system pick the
+correct offset for that date, so a summer close reads -0400 and a winter one
+-0500 without hardcoding either."
+  (format-time-string
+   "%z" (encode-time (list 0 minute hour day month year nil -1 nil))))
+
+(defun tc--dated-header-line (level parts title)
+  "Build the dated event-log heading string from LEVEL, CLOSED PARTS, and TITLE.
+Missing time in PARTS defaults to 00:00:00 (the close logged only a date)."
+  (let* ((year (plist-get parts :year))
+         (month (plist-get parts :month))
+         (day (plist-get parts :day))
+         (dow (plist-get parts :dow))
+         (hh (or (plist-get parts :hour) "00"))
+         (mm (or (plist-get parts :minute) "00"))
+         (tz (tc--tz-offset-string (string-to-number year)
+                                   (string-to-number month)
+                                   (string-to-number day)
+                                   (string-to-number hh)
+                                   (string-to-number mm))))
+    (format "%s %s-%s-%s %s @ %s:%s:00 %s %s"
+            (make-string level ?*) year month day dow hh mm tz title)))
+
+(defun tc--convert-collect-targets ()
+  "Markers at every heading at level >= 3 whose TODO state is a done state.
+Collected up front so the rewrite loop can edit the buffer without disturbing an
+in-progress `org-map-entries' walk; markers track their headings across edits."
+  (let (targets)
+    (org-map-entries
+     (lambda ()
+       (when (and (>= (org-current-level) 3)
+                  (member (org-get-todo-state) tc--convert-done-states))
+         (push (copy-marker (point)) targets)))
+     nil 'file)
+    (nreverse targets)))
+
+(defun tc--convert-one-subtask (marker)
+  "Convert the done sub-task heading at MARKER to a dated event-log entry.
+Under `tc-check-only' the conversion is reported but not performed."
+  (goto-char marker)
+  (org-back-to-heading t)
+  (let* ((level (org-current-level))
+         (title (org-get-heading t t t t))
+         (line (line-number-at-pos))
+         (parts (tc--closed-parts-in-entry)))
+    (cond
+     ((null parts)
+      (push (list :kind 'convert-skip :file tc-current-file
+                  :line line :heading title
+                  :detail "no CLOSED date to derive the timestamp")
+            tc-issues))
+     (t
+      (let ((new (tc--dated-header-line level parts title)))
+        (cl-incf tc-converted)
+        (if tc-check-only
+            (push (list :kind 'convert-would :file tc-current-file
+                        :line line :heading title :new new)
+                  tc-issues)
+          ;; Replace the heading line, then drop the now-redundant CLOSED
+          ;; cookie from the entry (its date now lives in the header).  Only
+          ;; the cookie goes: a planning line can also carry DEADLINE: or
+          ;; SCHEDULED: beside it, and those survive on their line.  A line
+          ;; left blank by the removal is deleted whole.
+          (delete-region (line-beginning-position) (line-end-position))
+          (insert new)
+          (let ((end (save-excursion
+                       (or (outline-next-heading) (goto-char (point-max)))
+                       (point))))
+            (save-excursion
+              (when (re-search-forward "CLOSED:[ \t]*\\[[^]]*\\][ \t]*" end t)
+                (replace-match "")
+                (let ((bol (line-beginning-position))
+                      (eol (line-end-position)))
+                  (if (string-match-p "\\`[ \t]*\\'"
+                                      (buffer-substring bol eol))
+                      (delete-region bol (min (1+ eol) (point-max)))
+                    (goto-char bol)
+                    (when (looking-at "[ \t]+")
+                      (replace-match "")))))))
+          (push (list :kind 'convert-done :file tc-current-file
+                      :line line :heading title :new new)
+                tc-issues)))))))
+
+(defun tc-convert-subtasks-in-file ()
+  "Rewrite every level-3-and-deeper DONE/CANCELLED/FAILED heading to a dated
+event-log entry, pulling the timestamp from its CLOSED cookie.  Honors
+`tc-check-only'."
+  (let ((targets (tc--convert-collect-targets)))
+    (dolist (m targets)
+      (tc--convert-one-subtask m)
+      (set-marker m nil))))
+
+;;; ---------------------------------------------------------------------------
 ;;; Driver + reporting
 
 (defun tc-process-file (file)
@@ -590,6 +745,8 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
       (tc-archive-done-in-file))
      (tc-sync-child-priority
       (tc-sync-child-priority-in-file))
+     (tc-convert-subtasks
+      (tc-convert-subtasks-in-file))
      (t
       ;; Pass 1: auto-fix bogus state logs (or report under --check).
       (org-map-entries #'tc-fix-bogus-state-log-in-entry nil 'file)
@@ -684,9 +841,34 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
                       (plist-get i :child-heading)
                       (plist-get i :parent-heading)))))))
 
+(defun tc--emit-convert-report ()
+  ;; Silent on a real-mode no-op (nothing to convert and nothing skipped), for
+  ;; the same reason as the archive report: the wrap runs cleanup passes more
+  ;; than once, and a vocal \"0 converted\" reads as noise. Check mode always
+  ;; reports (the preview is what the caller asked for), and a skip always
+  ;; reports (a done sub-task with no CLOSED date is a real condition to see).
+  (let ((has-skip (cl-some (lambda (i) (eq (plist-get i :kind) 'convert-skip))
+                           tc-issues)))
+    (when (or tc-check-only (> tc-converted 0) has-skip)
+      (princ (format "todo-cleanup --convert-subtasks: %d sub-task(s) %s%s\n"
+                     tc-converted
+                     (if tc-check-only "would convert" "converted")
+                     (if tc-check-only " — CHECK MODE (no writes)" "")))
+      (dolist (i (reverse tc-issues))
+        (pcase (plist-get i :kind)
+          ((or 'convert-done 'convert-would)
+           (princ (format "    %s:%d: %s\n      → %s\n"
+                          (plist-get i :file) (plist-get i :line)
+                          (plist-get i :heading) (plist-get i :new))))
+          ('convert-skip
+           (princ (format "  skipped %s:%d: %s — %s\n"
+                          (plist-get i :file) (plist-get i :line)
+                          (plist-get i :heading) (plist-get i :detail)))))))))
+
 (defun tc-emit-report ()
   (cond (tc-archive-done (tc--emit-archive-report))
         (tc-sync-child-priority (tc--emit-sync-report))
+        (tc-convert-subtasks (tc--emit-convert-report))
         (t (tc--emit-hygiene-report))))
 
 (defun tc-main ()
@@ -701,6 +883,9 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
   (when (member "--sync-child-priority" command-line-args-left)
     (setq tc-sync-child-priority t)
     (setq command-line-args-left (delete "--sync-child-priority" command-line-args-left)))
+  (when (member "--convert-subtasks" command-line-args-left)
+    (setq tc-convert-subtasks t)
+    (setq command-line-args-left (delete "--convert-subtasks" command-line-args-left)))
   ;; --check-child-priority is the report-only alias for
   ;; `--sync-child-priority --check'.
   (when (member "--check-child-priority" command-line-args-left)
@@ -708,7 +893,7 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
     (setq command-line-args-left (delete "--check-child-priority" command-line-args-left)))
   (if (null command-line-args-left)
       (progn
-        (princ "Usage: emacs --batch -q -l todo-cleanup.el [--check] [--archive-done | --sync-child-priority | --check-child-priority] FILE...\n")
+        (princ "Usage: emacs --batch -q -l todo-cleanup.el [--check] [--archive-done | --convert-subtasks | --sync-child-priority | --check-child-priority] FILE...\n")
         (kill-emacs 1))
     (let ((files command-line-args-left))
       (setq command-line-args-left nil)
@@ -727,6 +912,7 @@ ert-run-tests-batch-and-exit'."
        (cl-every (lambda (a)
                    (cond ((member a '("--check"
                                       "--archive-done"
+                                      "--convert-subtasks"
                                       "--sync-child-priority"
                                       "--check-child-priority"))
                           t)
diff --git a/.ai/workflows/clean-todo.org b/.ai/workflows/clean-todo.org
index dd33056..a1b2af5 100644
--- a/.ai/workflows/clean-todo.org
+++ b/.ai/workflows/clean-todo.org
@@ -27,7 +27,17 @@ Deletes bogus =- State "X" from "X" [date]= log lines (state didn't actually cha
 
 To preview without writing, run =--check= first: =emacs --batch -q -l .ai/scripts/todo-cleanup.el --check todo.org=.
 
-** Step 2: Archive completed work
+** Step 2: Convert done sub-tasks to dated entries
+
+#+begin_src bash
+emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks todo.org
+#+end_src
+
+Rewrites every heading at level 3 or deeper whose TODO state is DONE/CANCELLED/FAILED into a dated event-log entry (=<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>=), dropping the keyword, priority cookie, and tags, and removing the =CLOSED:= line. Enforces the depth rule that a completed sub-task becomes dated history — a shape interactive org closes and =--archive-done= (level-2 only) leave unapplied. Timestamp comes from each entry's =CLOSED= cookie; heading text kept verbatim; idempotent; a done sub-task with no parseable =CLOSED= is flagged and left alone. Run before archiving so a parent's sub-tasks are already dated when it moves. Capture the output.
+
+To preview without writing: =emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks --check todo.org=.
+
+** Step 3: Archive completed work
 
 #+begin_src bash
 emacs --batch -q -l .ai/scripts/todo-cleanup.el --archive-done todo.org
@@ -37,10 +47,11 @@ Moves every level-2 subtree whose TODO state is DONE or CANCELLED out of the "Op
 
 To preview the moves without writing: =emacs --batch -q -l .ai/scripts/todo-cleanup.el --archive-done --check todo.org=.
 
-** Step 3: Summarize
+** Step 4: Summarize
 
-Report to Craig from the two captured outputs:
+Report to Craig from the three captured outputs:
 - Hygiene: how many bogus state-log lines were deleted; any orphan-planning warnings (file:line + heading), or "none".
+- Convert: how many done sub-tasks were rewritten to dated entries (heading + line), any flagged for no =CLOSED= date, or "nothing to convert".
 - Archive: how many subtrees moved and which (heading + line), or "nothing to move" / the skip reason if a section was missing or ambiguous.
 - If the file changed, note that =todo.org= now has an uncommitted edit — review =git diff -- todo.org= and commit it (in this repo's commit style) if it looks right. If nothing changed, say so and stop.
 
@@ -49,7 +60,7 @@ Don't auto-commit. The summary is the review point; Craig decides whether the di
 * Principles
 
 - *Both passes apply, not just preview.* The workflow is invoked because cleanup is wanted. Use the =--check= variants only when Craig asks for a dry run.
-- *Two passes, two invocations.* =--archive-done= is its own mode and does not run the hygiene pass; run both.
+- *Separate modes, separate invocations.* =--convert-subtasks=, =--archive-done=, and the hygiene pass are each their own mode and don't run the others; run all three.
 - *Never auto-commit todo.org.* Surface the diff and let Craig commit it. The cleanup is a working-tree change, fully reversible until committed.
 - *Trust the script.* It's fast and idempotent; if there's nothing to do, it reports zero and exits clean. No pre-checks.
 
diff --git a/.ai/workflows/open-tasks.org b/.ai/workflows/open-tasks.org
index 4ba29dd..02a0847 100644
--- a/.ai/workflows/open-tasks.org
+++ b/.ai/workflows/open-tasks.org
@@ -23,15 +23,16 @@ Don't route "task review" / "review tasks" here — those trigger the hygiene ha
 
 * Phase A: Data Gathering (both modes)
 
-** Phase A pre-step — archive any freshly-DONE tasks
+** Phase A pre-step — normalize freshly-closed tasks
 
-Before reading =todo.org=, run the cleanup script's archive-done sweep so completed level-2 subtrees move from =* $Project Open Work= to =* $Project Resolved=:
+Before reading =todo.org=, run two cleanup sweeps so the read reflects current state. First convert any done sub-tasks to dated entries, then archive completed level-2 subtrees from =* $Project Open Work= to =* $Project Resolved=:
 
 #+begin_src bash
+emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks todo.org
 emacs --batch -q -l .ai/scripts/todo-cleanup.el --archive-done todo.org
 #+end_src
 
-Costs a few hundred milliseconds. Without it, a task that completed earlier in the session sits as =** DONE= under Open Work until the next =clean-todo= or wrap-up pass, and Next Mode would surface it as a "what's next" candidate. The sweep makes Phase A's read of =todo.org= reflect current state.
+Costs a few hundred milliseconds. Without the archive sweep, a task that completed earlier in the session sits as =** DONE= under Open Work until the next =clean-todo= or wrap-up pass, and Next Mode would surface it as a "what's next" candidate. The convert sweep runs first so a completed parent's sub-tasks are already dated when it archives; it also keeps interactive level-3 closes from lingering as DONE keywords. Together they make Phase A's read of =todo.org= reflect current state.
 
 Skip the sweep if the workflow is invoked in an explicit read-only or dry-run context. Default is to run it.
 
diff --git a/.ai/workflows/task-review.org b/.ai/workflows/task-review.org
index 69e172d..7b6327b 100644
--- a/.ai/workflows/task-review.org
+++ b/.ai/workflows/task-review.org
@@ -96,6 +96,8 @@ The exact date string matters: =task-review-staleness.sh= and the wrap-up health
 
 Follow the completion rules in [[file:../../claude-rules/todo-format.md][todo-format.md]]. A killed top-level =**= task stays task-shaped: change the keyword to =CANCELLED=, add a =CLOSED: [YYYY-MM-DD Day]= line under the heading (generate with =date "+%Y-%m-%d %a"=), and leave the priority and tags intact. It's then a candidate for =--archive-done= at the next cleanup. Don't stamp =:LAST_REVIEWED:= on a kill — it's leaving the review pool anyway.
 
+A killed *sub-task* (=***= or deeper, under a parent task) instead becomes a dated event-log entry per the depth rule — but you don't have to hand-format it here. =todo-cleanup.el --convert-subtasks= (run in the =clean-todo= and wrap-up cleanup passes) rewrites any level-3+ DONE/CANCELLED/FAILED heading into its dated form mechanically from the =CLOSED= cookie, so a keyword-plus-=CLOSED= close at depth gets normalized on the next cleanup rather than lingering. =lint-org.el= flags any that slip through (checker =subtask-done-not-dated=).
+
 * Phase D: Close out
 
 When the batch is done (or Craig calls it early):
diff --git a/.ai/workflows/wrap-it-up.org b/.ai/workflows/wrap-it-up.org
index 5d2cdd2..4fa5a3a 100644
--- a/.ai/workflows/wrap-it-up.org
+++ b/.ai/workflows/wrap-it-up.org
@@ -137,6 +137,22 @@ Run the report-only variant first if you want to see what would change without w
 emacs --batch -q -l .ai/scripts/todo-cleanup.el --check todo.org
 #+end_src
 
+*** Convert done sub-tasks to dated entries
+
+#+begin_src bash
+[ -f todo.org ] && emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks todo.org
+#+end_src
+
+=--convert-subtasks= rewrites every heading at level 3 or deeper whose TODO state is DONE/CANCELLED/FAILED into a dated event-log entry (=<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>=), dropping the keyword, priority cookie, and tags, and removing the now-redundant =CLOSED:= line. This enforces the =todo-format.md= depth rule that a completed *sub-task* (a heading under a parent task) becomes dated history, not a lingering DONE keyword — a shape an interactive org close (=org-log-done= → DONE + CLOSED) never applies and =--archive-done= (level-2 only) never reaches. The timestamp comes from each entry's own =CLOSED= cookie; a date-only close yields =00:00:00=. Heading text is kept verbatim. Idempotent (an already-dated heading has no keyword to match), and a done sub-task with no parseable =CLOSED= is flagged and left alone rather than stamped with a fabricated date.
+
+Run this *before* =--archive-done= so that when a completed level-2 parent is archived, its sub-tasks already carry their dated form. Any rewrites show up in the wrap-up commit's diff for review before push.
+
+Preview without writing:
+
+#+begin_src bash
+emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks --check todo.org
+#+end_src
+
 *** Archive completed work
 
 #+begin_src bash
@@ -536,7 +552,7 @@ Before considering wrap-up complete:
 - [ ] The Summary ends with the =KB: promoted N / consulted yes-no= line (promotion check ran)
 - [ ] File renamed to =.ai/sessions/YYYY-MM-DD-HH-MM-description.org=
 - [ ] =.ai/session-context.org= no longer exists
-- [ ] =todo-cleanup.el= ran — hygiene pass + =--archive-done= + =--sync-child-priority= (if =todo.org= exists at project root)
+- [ ] =todo-cleanup.el= ran — hygiene pass + =--convert-subtasks= + =--archive-done= + =--sync-child-priority= (if =todo.org= exists at project root)
 - [ ] =lint-org.el= ran on =todo.org= — mechanical fixes applied, judgments appended to follow-ups file (if =todo.org= exists)
 - [ ] Any orphan-planning-line warnings reviewed (fix or accept)
 - [ ] Inbox carries nothing but expected pipeline artifacts (=.gitkeep=, =lint-followups.org=, =PROCESSED-*= prefixes), OR each remaining handoff has an explicit deferral logged in the valediction
diff --git a/claude-rules/todo-format.md b/claude-rules/todo-format.md
index 55530de..90d801f 100644
--- a/claude-rules/todo-format.md
+++ b/claude-rules/todo-format.md
@@ -172,6 +172,8 @@ becomes
 
     *** 2026-05-15 Fri @ 12:58:08 -0500 Wired yasnippet for universal availability
 
+**Enforcement.** This is applied at close time by whoever closes the task, but an interactive org close (`org-log-done` flips the keyword to `DONE` and stamps `CLOSED:`) never applies the dated rewrite, so level-3+ closes accumulate as `DONE` keywords. `todo-cleanup.el --convert-subtasks` (run in the `clean-todo` and wrap-up cleanup passes) normalizes them mechanically: it rewrites any level-3+ `DONE`/`CANCELLED`/`FAILED` heading into the dated form above, pulling the timestamp from the `CLOSED` cookie and keeping the heading text verbatim (a batch tool can't reliably past-tense a title — polish wording by hand where it matters). `lint-org.el` flags any that slip through (checker `subtask-done-not-dated`). So the depth rule holds even when tasks are closed interactively rather than by an agent applying this section.
+
 ### Why depth-based
 
 The agenda view (`org-agenda`) shows entries at the section + top-task level. Letting `**` tasks stay task-shaped preserves their visibility as "things that recently shipped." Letting `***+` sub-tasks flip to dated entries keeps the agenda from being clogged with a long list of completed sub-tasks at every depth — those become history within their parent instead.
diff --git a/claude-templates/.ai/scripts/lint-org.el b/claude-templates/.ai/scripts/lint-org.el
index 5447cb3..90b1b1d 100644
--- a/claude-templates/.ai/scripts/lint-org.el
+++ b/claude-templates/.ai/scripts/lint-org.el
@@ -35,6 +35,7 @@
 ;;   empty-heading                     bare stars with no title
 ;;   malformed-priority-cookie         [#x]-shaped token org rejected
 ;;   level2-done-without-closed        completed level-2 task with no CLOSED
+;;   subtask-done-not-dated            level-3+ done sub-task still a DONE keyword
 ;;   (anything else)                   surfaced as judgment with checker name
 ;;
 ;; Output format on stdout:
@@ -503,6 +504,32 @@ the live file on the next `task-sorted'."
                "level-2 DONE/CANCELLED has no CLOSED date — add CLOSED: [YYYY-MM-DD Day]; task-sorted's aging step archives an undated completed task immediately"))))))))
 
 ;;; ---------------------------------------------------------------------------
+;;; level-3+ dated-header check (claude-rules/todo-format.md)
+;;
+;; The inverse of the level-2 check above.  A completed sub-task — a heading at
+;; level 3 or deeper, under a parent task — becomes a dated event-log entry, not
+;; a DONE keyword, so the parent's subtree grows a chronological history instead
+;; of a long tail of nested DONE lines.  An interactive org close
+;; (`org-log-done' → DONE + CLOSED) leaves the keyword in place, and
+;; `--archive-done' only touches level 2, so these accumulate.  Flag them for
+;; conversion.  Judgment-only and regex-based (independent of which TODO keywords
+;; the batch Emacs recognizes); todo-cleanup.el --convert-subtasks does the fix.
+
+(defun lo--check-subtask-done-not-dated ()
+  "Flag level-3+ headings carrying a done keyword (DONE/CANCELLED/FAILED).
+Emits one judgment item per offending heading (checker
+`subtask-done-not-dated')."
+  (save-excursion
+    (goto-char (point-min))
+    ;; Case-sensitive: the keywords are uppercase, not the words in a title.
+    (let ((case-fold-search nil))
+      (while (re-search-forward
+              "^\\*\\{3,\\} \\(DONE\\|CANCELLED\\|FAILED\\) " nil t)
+        (lo--emit-judgment
+         'subtask-done-not-dated (line-number-at-pos)
+         "level-3+ done sub-task should be a dated event-log entry (todo-format.md): run todo-cleanup.el --convert-subtasks to rewrite it")))))
+
+;;; ---------------------------------------------------------------------------
 ;;; File processing
 
 (defun lo--backup (file)
@@ -543,6 +570,7 @@ left unmodified and mechanical entries are recorded with :preview t."
           (lo--check-empty-headings)
           (lo--check-malformed-priority-cookies)
           (lo--check-level2-done-without-closed)
+          (lo--check-subtask-done-not-dated)
           (when (and (not lo-check-only) (buffer-modified-p))
             (save-buffer)))
       (with-current-buffer buf (set-buffer-modified-p nil))
diff --git a/claude-templates/.ai/scripts/tests/test-lint-org.el b/claude-templates/.ai/scripts/tests/test-lint-org.el
index 3b8a9bb..d14879f 100644
--- a/claude-templates/.ai/scripts/tests/test-lint-org.el
+++ b/claude-templates/.ai/scripts/tests/test-lint-org.el
@@ -685,6 +685,37 @@ missing-rules violation."
          (judgments (lo-test--judgments (plist-get out :issues))))
     (should-not (member 'level-2-dated-header (lo-test--checkers judgments)))))
 
+;;; subtask-done-not-dated check (the inverse: level-3+ done keyword)
+
+(ert-deftest lo-subtask-done-not-dated-flags-level3 ()
+  "A level-3 DONE sub-task still carrying the keyword is flagged for conversion."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** TODO [#B] Parent\n*** DONE [#C] Sub-task done\nCLOSED: [2026-06-20 Sat 10:00]\nBody.\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should (= 0 (plist-get out :fixes)))       ; judgment-only, never auto-fixed
+    (should (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
+(ert-deftest lo-subtask-done-not-dated-flags-level4-cancelled ()
+  "A level-4 CANCELLED sub-task is flagged too."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** PROJECT [#B] Parent\n*** TODO Mid\n**** CANCELLED Deep abandoned\nCLOSED: [2026-06-20 Sat]\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
+(ert-deftest lo-subtask-done-not-dated-ignores-level2 ()
+  "A level-2 DONE task is a top-level task, not a sub-task — this checker skips it."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** DONE [#B] Top-level\nCLOSED: [2026-06-20 Sat]\nBody.\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should-not (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
+(ert-deftest lo-subtask-done-not-dated-ignores-dated-and-lowercase ()
+  "An already-dated level-3 entry, and the word done in a title, are not flagged."
+  (let* ((out (lo-test--run
+               "* Open Work\n\n** TODO [#B] Parent\n*** 2026-06-20 Sat @ 10:00:00 -0400 landed\n*** TODO wrap the done cleanup\n"))
+         (judgments (lo-test--judgments (plist-get out :issues))))
+    (should-not (member 'subtask-done-not-dated (lo-test--checkers judgments)))))
+
 ;;; ---------------------------------------------------------------------------
 ;;; structural heading checks (org-lint gaps)
 
diff --git a/claude-templates/.ai/scripts/tests/test-todo-cleanup.el b/claude-templates/.ai/scripts/tests/test-todo-cleanup.el
index e569d9a..ffbf2fb 100644
--- a/claude-templates/.ai/scripts/tests/test-todo-cleanup.el
+++ b/claude-templates/.ai/scripts/tests/test-todo-cleanup.el
@@ -768,5 +768,176 @@ in ISSUES, in document order."
     (should (= 2 (plist-get once :bumped)))
     (should (= 2 (plist-get twice :bumped)))))
 
+;;; ---------------------------------------------------------------------------
+;;; --convert-subtasks harness + tests
+
+(defun tc-test--reset-convert (&optional check)
+  (setq tc-fixes 0 tc-archived 0 tc-bumped 0 tc-converted 0 tc-archived-to-file 0
+        tc-issues nil
+        tc-check-only (and check t)
+        tc-archive-done nil tc-sync-child-priority nil tc-convert-subtasks t
+        tc-current-file nil
+        tc-archive-retain-days nil tc-archive-reference-date nil tc-archive-file nil))
+
+(defun tc-test--convert (content &optional runs check)
+  "Write CONTENT to a temp .org file, run `--convert-subtasks' RUNS times (default 1).
+Return a plist: :result final file contents, :converted count from the last run,
+:issues from the last run.  CHECK non-nil ⇒ --check (preview, no writes)."
+  (let ((file (make-temp-file "tc-test-" nil ".org"))
+        last-converted last-issues)
+    (unwind-protect
+        (progn
+          (with-temp-file file (insert content))
+          (dotimes (_ (or runs 1))
+            (tc-test--reset-convert check)
+            (tc-process-file file)
+            (setq last-converted tc-converted last-issues tc-issues)
+            (tc-test--drop-buffer file))
+          (list :result (with-temp-buffer (insert-file-contents file)
+                                          (buffer-string))
+                :converted last-converted
+                :issues last-issues))
+      (tc-test--drop-buffer file)
+      (delete-file file))))
+
+;; The UTC offset in a converted header is the test machine's local offset for
+;; that date, so assertions match it as `[-+]NNNN' rather than a fixed value —
+;; the mode's job is to emit a well-formed offset, not to run in one timezone.
+
+(defconst tc-test--convert-timed
+  "* Project Open Work
+** TODO [#B] Parent task
+*** DONE [#C] F12 opens the terminal :feature:quick:
+CLOSED: [2026-06-27 Sat 12:50]
+Verified live: docks, toggles, colors clean.
+")
+
+(ert-deftest tc-convert-timed-subtask-normal ()
+  "Normal: a timed CLOSED close becomes a dated header, keyword/priority/tags/CLOSED gone."
+  (let* ((out (tc-test--convert tc-test--convert-timed))
+         (res (plist-get out :result)))
+    (should (= 1 (plist-get out :converted)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-27 Sat @ 12:50:00 [-+][0-9]\\{4\\} F12 opens the terminal$"
+             res))
+    (should-not (string-match-p "CLOSED:" res))
+    (should-not (string-match-p "DONE" res))
+    (should (string-match-p "Verified live: docks, toggles, colors clean\\." res))
+    (should (string-match-p "^\\*\\* TODO \\[#B\\] Parent task$" res))))
+
+(defconst tc-test--convert-dateonly
+  "* Project Open Work
+** PROJECT [#B] Parent
+**** DONE [#B] Write full spec :refactor:
+CLOSED: [2026-05-04 Mon]
+Body.
+")
+
+(ert-deftest tc-convert-dateonly-boundary-midnight ()
+  "Boundary: a date-only CLOSED (no time) yields 00:00:00, at level 4."
+  (let ((res (plist-get (tc-test--convert tc-test--convert-dateonly) :result)))
+    (should (string-match-p
+             "^\\*\\*\\*\\* 2026-05-04 Mon @ 00:00:00 [-+][0-9]\\{4\\} Write full spec$"
+             res))
+    (should-not (string-match-p "CLOSED:" res))))
+
+(defconst tc-test--convert-level2
+  "* Project Open Work
+** DONE [#B] Top-level task
+CLOSED: [2026-06-01 Mon 09:00]
+Body.
+")
+
+(ert-deftest tc-convert-leaves-level-2-alone-boundary ()
+  "Boundary: a level-2 DONE task is a top-level task, not a sub-task — untouched."
+  (let ((out (tc-test--convert tc-test--convert-level2)))
+    (should (= 0 (plist-get out :converted)))
+    (should (equal tc-test--convert-level2 (plist-get out :result)))))
+
+(ert-deftest tc-convert-idempotent-boundary ()
+  "Boundary: a second run over an already-dated entry converts nothing new."
+  (let ((once (tc-test--convert tc-test--convert-timed 1))
+        (twice (tc-test--convert tc-test--convert-timed 2)))
+    (should (equal (plist-get once :result) (plist-get twice :result)))
+    (should (= 0 (plist-get twice :converted)))))
+
+(defconst tc-test--convert-nested
+  "* Project Open Work
+** TODO [#B] Parent
+*** DONE Outer sub :feature:
+CLOSED: [2026-06-10 Wed 08:15]
+**** DONE Inner sub
+CLOSED: [2026-06-09 Tue 07:00]
+Inner body.
+")
+
+(ert-deftest tc-convert-nested-done-subtasks-boundary ()
+  "Boundary: a done sub-task nested under a done sub-task — both convert."
+  (let* ((out (tc-test--convert tc-test--convert-nested))
+         (res (plist-get out :result)))
+    (should (= 2 (plist-get out :converted)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-10 Wed @ 08:15:00 [-+][0-9]\\{4\\} Outer sub$" res))
+    (should (string-match-p
+             "^\\*\\*\\*\\* 2026-06-09 Tue @ 07:00:00 [-+][0-9]\\{4\\} Inner sub$" res))
+    (should-not (string-match-p "CLOSED:" res))))
+
+(defconst tc-test--convert-cancelled
+  "* Project Open Work
+** TODO [#B] Parent
+*** CANCELLED [#C] Abandoned idea :feature:
+CLOSED: [2026-06-15 Mon 10:00]
+")
+
+(ert-deftest tc-convert-cancelled-subtask-boundary ()
+  "Boundary: a CANCELLED sub-task converts too (terminal state)."
+  (let ((res (plist-get (tc-test--convert tc-test--convert-cancelled) :result)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-15 Mon @ 10:00:00 [-+][0-9]\\{4\\} Abandoned idea$" res))
+    (should-not (string-match-p "CANCELLED" res))))
+
+(defconst tc-test--convert-noclosed
+  "* Project Open Work
+** TODO [#B] Parent
+*** DONE Orphan with no closed date
+Body only.
+")
+
+(ert-deftest tc-convert-skips-subtask-without-closed-error ()
+  "Error: a done sub-task with no parseable CLOSED is flagged and left unchanged."
+  (let ((out (tc-test--convert tc-test--convert-noclosed)))
+    (should (= 0 (plist-get out :converted)))
+    (should (equal tc-test--convert-noclosed (plist-get out :result)))
+    (should (cl-some (lambda (i) (eq (plist-get i :kind) 'convert-skip))
+                     (plist-get out :issues)))))
+
+(ert-deftest tc-convert-check-mode-previews-without-writing ()
+  "Check mode reports the conversion but writes nothing."
+  (let ((out (tc-test--convert tc-test--convert-timed 1 t)))
+    (should (= 1 (plist-get out :converted)))
+    (should (equal tc-test--convert-timed (plist-get out :result)))
+    (should (cl-some (lambda (i) (eq (plist-get i :kind) 'convert-would))
+                     (plist-get out :issues)))))
+
+(defconst tc-test--convert-closed-with-deadline
+  "* Project Open Work
+** TODO [#B] Parent task
+*** DONE [#C] Ship the panel :feature:
+CLOSED: [2026-06-27 Sat 12:50] DEADLINE: <2026-06-30 Tue>
+Body line.
+")
+
+(ert-deftest tc-convert-preserves-deadline-on-shared-planning-line-boundary ()
+  "Boundary: removing the CLOSED cookie keeps a DEADLINE sharing its planning line."
+  (let* ((out (tc-test--convert tc-test--convert-closed-with-deadline))
+         (res (plist-get out :result)))
+    (should (= 1 (plist-get out :converted)))
+    (should (string-match-p
+             "^\\*\\*\\* 2026-06-27 Sat @ 12:50:00 [-+][0-9]\\{4\\} Ship the panel$"
+             res))
+    (should-not (string-match-p "CLOSED:" res))
+    (should (string-match-p "^DEADLINE: <2026-06-30 Tue>$" res))
+    (should (string-match-p "^Body line\\.$" res))))
+
 (provide 'test-todo-cleanup)
 ;;; test-todo-cleanup.el ends here
diff --git a/claude-templates/.ai/scripts/todo-cleanup.el b/claude-templates/.ai/scripts/todo-cleanup.el
index 541d106..bd8166d 100644
--- a/claude-templates/.ai/scripts/todo-cleanup.el
+++ b/claude-templates/.ai/scripts/todo-cleanup.el
@@ -5,10 +5,12 @@
 ;;   emacs --batch -q -l todo-cleanup.el --check todo.org                  # hygiene report only
 ;;   emacs --batch -q -l todo-cleanup.el --archive-done todo.org           # archive completed subtrees
 ;;   emacs --batch -q -l todo-cleanup.el --archive-done --check todo.org   # preview the archive
+;;   emacs --batch -q -l todo-cleanup.el --convert-subtasks todo.org       # dated-rewrite done level-3+ sub-tasks
+;;   emacs --batch -q -l todo-cleanup.el --convert-subtasks --check todo.org  # preview the conversion
 ;;   emacs --batch -q -l todo-cleanup.el --sync-child-priority todo.org    # bump children whose priority drifted below the parent's
 ;;   emacs --batch -q -l todo-cleanup.el --check-child-priority todo.org   # preview the sync (same as --sync-child-priority --check)
 ;;
-;; Three independent modes:
+;; Four independent modes:
 ;;
 ;; * Default (hygiene). Designed for the wrap-it-up workflow: cheap, idempotent,
 ;;   safe to run every session.
@@ -52,6 +54,20 @@
 ;;   Archiving is consequential, so it's never run by default; it does *not*
 ;;   also run the hygiene passes.
 ;;
+;; * --convert-subtasks (opt-in). Rewrites every level-3-and-deeper heading whose
+;;   TODO state is DONE/CANCELLED/FAILED into a dated event-log entry
+;;   (`<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>'), dropping the keyword,
+;;   priority cookie, and tags, and removing the now-redundant CLOSED line. The
+;;   date and time come from that entry's own CLOSED cookie; a date-only close
+;;   yields 00:00:00, and the UTC offset is computed DST-aware for that date.
+;;   This enforces the todo-format depth rule that interactive closes
+;;   (`org-log-done' → DONE + CLOSED) and `--archive-done' (level-2 only) leave
+;;   unapplied. The heading text is preserved verbatim — a batch tool can't
+;;   past-tense an imperative title reliably. Idempotent (an already-dated
+;;   heading has no done keyword); a done sub-task with no parseable CLOSED date
+;;   is flagged and left alone, never stamped with a fabricated date. Like
+;;   --archive-done it does not also run the hygiene passes.
+;;
 ;; * --sync-child-priority (opt-in). Walks every heading with a priority cookie
 ;;   ([#A]-[#D]) and, for each of its direct child headings whose own priority
 ;;   is lower (later in the alphabet — D is lower than A), bumps the child's
@@ -73,11 +89,16 @@
 (require 'calendar)
 
 (setq org-todo-keywords
-      '((sequence "TODO" "DOING" "WAITING" "NEXT" "|" "DONE" "CANCELLED")))
+      '((sequence "TODO" "DOING" "WAITING" "NEXT" "|" "DONE" "CANCELLED" "FAILED")))
 
 (defconst tc-done-states '("DONE" "CANCELLED")
   "TODO keywords that mark an entry as completed for `--archive-done'.")
 
+(defconst tc--convert-done-states '("DONE" "CANCELLED" "FAILED")
+  "TODO keywords whose level-3-and-deeper entries `--convert-subtasks' rewrites
+to dated event-log entries.  Broader than `tc-done-states' because a FAILED
+sub-task is terminal too and belongs in the parent's dated history.")
+
 (defconst tc--priority-cookie-regexp "\\[#\\([A-Z]\\)\\]"
   "Regexp matching an org priority cookie. Match group 1 is the letter.")
 
@@ -89,10 +110,12 @@ every heading below it.")
 (defvar tc-fixes 0)
 (defvar tc-archived 0)
 (defvar tc-bumped 0)
+(defvar tc-converted 0)
 (defvar tc-issues nil)
 (defvar tc-check-only nil)
 (defvar tc-archive-done nil)
 (defvar tc-sync-child-priority nil)
+(defvar tc-convert-subtasks nil)
 (defvar tc-current-file nil)
 (defvar tc-current-dir nil)
 (defvar tc-archived-to-file 0)
@@ -578,6 +601,138 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
   (org-map-entries #'tc-sync-child-priority-at-heading nil 'file))
 
 ;;; ---------------------------------------------------------------------------
+;;; --convert-subtasks mode
+;;
+;; A sub-task (a heading at level 3 or deeper, i.e. under a parent task) that is
+;; marked DONE/CANCELLED/FAILED should become a dated event-log entry per the
+;; todo-format depth rule: drop the keyword, priority cookie, and tags, and
+;; rewrite the heading to `<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>' so the
+;; parent's subtree grows a chronological history instead of a long tail of
+;; nested DONE lines.  Nothing enforced this before: `org-log-done' just flips an
+;; interactive close to DONE + CLOSED, and `--archive-done' only touches level 2.
+;; So level-3+ closes piled up as DONE keywords.  This mode converts them
+;; mechanically, pulling the timestamp from each entry's own CLOSED cookie.  The
+;; heading text is kept verbatim (a batch tool can't reliably past-tense an
+;; imperative title, and guessing prose in the task file is worse than leaving it
+;; as written).  Idempotent: an already-dated heading has no done keyword, so it
+;; is skipped.  A done sub-task with no parseable CLOSED cookie can't be dated, so
+;; it is flagged and left alone rather than stamped with a fabricated date.
+
+(defun tc--closed-parts-in-entry ()
+  "Return a plist (:year :month :day :dow :hour :minute) from the CLOSED cookie
+of the entry at point, or nil when the entry has no parseable CLOSED line.
+:hour and :minute are nil when the cookie carries only a date.  The CLOSED line
+sits in canonical position directly under the heading, so the first match within
+the entry is the task's own close."
+  (save-excursion
+    (org-back-to-heading t)
+    (let ((end (save-excursion
+                 (or (outline-next-heading) (goto-char (point-max)))
+                 (point))))
+      (when (re-search-forward
+             (concat "CLOSED:[ \t]*\\[\\([0-9]\\{4\\}\\)-\\([0-9]\\{2\\}\\)-\\([0-9]\\{2\\}\\)"
+                     "[ \t]+\\([A-Za-z]+\\)"
+                     "\\(?:[ \t]+\\([0-9]\\{2\\}\\):\\([0-9]\\{2\\}\\)\\)?\\]")
+             end t)
+        (list :year (match-string 1) :month (match-string 2) :day (match-string 3)
+              :dow (match-string 4)
+              :hour (match-string 5) :minute (match-string 6))))))
+
+(defun tc--tz-offset-string (year month day hour minute)
+  "Return the local UTC offset (e.g. \"-0500\") for the given wall-clock instant.
+DST-aware: `encode-time' with an unknown-DST field lets the system pick the
+correct offset for that date, so a summer close reads -0400 and a winter one
+-0500 without hardcoding either."
+  (format-time-string
+   "%z" (encode-time (list 0 minute hour day month year nil -1 nil))))
+
+(defun tc--dated-header-line (level parts title)
+  "Build the dated event-log heading string from LEVEL, CLOSED PARTS, and TITLE.
+Missing time in PARTS defaults to 00:00:00 (the close logged only a date)."
+  (let* ((year (plist-get parts :year))
+         (month (plist-get parts :month))
+         (day (plist-get parts :day))
+         (dow (plist-get parts :dow))
+         (hh (or (plist-get parts :hour) "00"))
+         (mm (or (plist-get parts :minute) "00"))
+         (tz (tc--tz-offset-string (string-to-number year)
+                                   (string-to-number month)
+                                   (string-to-number day)
+                                   (string-to-number hh)
+                                   (string-to-number mm))))
+    (format "%s %s-%s-%s %s @ %s:%s:00 %s %s"
+            (make-string level ?*) year month day dow hh mm tz title)))
+
+(defun tc--convert-collect-targets ()
+  "Markers at every heading at level >= 3 whose TODO state is a done state.
+Collected up front so the rewrite loop can edit the buffer without disturbing an
+in-progress `org-map-entries' walk; markers track their headings across edits."
+  (let (targets)
+    (org-map-entries
+     (lambda ()
+       (when (and (>= (org-current-level) 3)
+                  (member (org-get-todo-state) tc--convert-done-states))
+         (push (copy-marker (point)) targets)))
+     nil 'file)
+    (nreverse targets)))
+
+(defun tc--convert-one-subtask (marker)
+  "Convert the done sub-task heading at MARKER to a dated event-log entry.
+Under `tc-check-only' the conversion is reported but not performed."
+  (goto-char marker)
+  (org-back-to-heading t)
+  (let* ((level (org-current-level))
+         (title (org-get-heading t t t t))
+         (line (line-number-at-pos))
+         (parts (tc--closed-parts-in-entry)))
+    (cond
+     ((null parts)
+      (push (list :kind 'convert-skip :file tc-current-file
+                  :line line :heading title
+                  :detail "no CLOSED date to derive the timestamp")
+            tc-issues))
+     (t
+      (let ((new (tc--dated-header-line level parts title)))
+        (cl-incf tc-converted)
+        (if tc-check-only
+            (push (list :kind 'convert-would :file tc-current-file
+                        :line line :heading title :new new)
+                  tc-issues)
+          ;; Replace the heading line, then drop the now-redundant CLOSED
+          ;; cookie from the entry (its date now lives in the header).  Only
+          ;; the cookie goes: a planning line can also carry DEADLINE: or
+          ;; SCHEDULED: beside it, and those survive on their line.  A line
+          ;; left blank by the removal is deleted whole.
+          (delete-region (line-beginning-position) (line-end-position))
+          (insert new)
+          (let ((end (save-excursion
+                       (or (outline-next-heading) (goto-char (point-max)))
+                       (point))))
+            (save-excursion
+              (when (re-search-forward "CLOSED:[ \t]*\\[[^]]*\\][ \t]*" end t)
+                (replace-match "")
+                (let ((bol (line-beginning-position))
+                      (eol (line-end-position)))
+                  (if (string-match-p "\\`[ \t]*\\'"
+                                      (buffer-substring bol eol))
+                      (delete-region bol (min (1+ eol) (point-max)))
+                    (goto-char bol)
+                    (when (looking-at "[ \t]+")
+                      (replace-match "")))))))
+          (push (list :kind 'convert-done :file tc-current-file
+                      :line line :heading title :new new)
+                tc-issues)))))))
+
+(defun tc-convert-subtasks-in-file ()
+  "Rewrite every level-3-and-deeper DONE/CANCELLED/FAILED heading to a dated
+event-log entry, pulling the timestamp from its CLOSED cookie.  Honors
+`tc-check-only'."
+  (let ((targets (tc--convert-collect-targets)))
+    (dolist (m targets)
+      (tc--convert-one-subtask m)
+      (set-marker m nil))))
+
+;;; ---------------------------------------------------------------------------
 ;;; Driver + reporting
 
 (defun tc-process-file (file)
@@ -590,6 +745,8 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
       (tc-archive-done-in-file))
      (tc-sync-child-priority
       (tc-sync-child-priority-in-file))
+     (tc-convert-subtasks
+      (tc-convert-subtasks-in-file))
      (t
       ;; Pass 1: auto-fix bogus state logs (or report under --check).
       (org-map-entries #'tc-fix-bogus-state-log-in-entry nil 'file)
@@ -684,9 +841,34 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
                       (plist-get i :child-heading)
                       (plist-get i :parent-heading)))))))
 
+(defun tc--emit-convert-report ()
+  ;; Silent on a real-mode no-op (nothing to convert and nothing skipped), for
+  ;; the same reason as the archive report: the wrap runs cleanup passes more
+  ;; than once, and a vocal \"0 converted\" reads as noise. Check mode always
+  ;; reports (the preview is what the caller asked for), and a skip always
+  ;; reports (a done sub-task with no CLOSED date is a real condition to see).
+  (let ((has-skip (cl-some (lambda (i) (eq (plist-get i :kind) 'convert-skip))
+                           tc-issues)))
+    (when (or tc-check-only (> tc-converted 0) has-skip)
+      (princ (format "todo-cleanup --convert-subtasks: %d sub-task(s) %s%s\n"
+                     tc-converted
+                     (if tc-check-only "would convert" "converted")
+                     (if tc-check-only " — CHECK MODE (no writes)" "")))
+      (dolist (i (reverse tc-issues))
+        (pcase (plist-get i :kind)
+          ((or 'convert-done 'convert-would)
+           (princ (format "    %s:%d: %s\n      → %s\n"
+                          (plist-get i :file) (plist-get i :line)
+                          (plist-get i :heading) (plist-get i :new))))
+          ('convert-skip
+           (princ (format "  skipped %s:%d: %s — %s\n"
+                          (plist-get i :file) (plist-get i :line)
+                          (plist-get i :heading) (plist-get i :detail)))))))))
+
 (defun tc-emit-report ()
   (cond (tc-archive-done (tc--emit-archive-report))
         (tc-sync-child-priority (tc--emit-sync-report))
+        (tc-convert-subtasks (tc--emit-convert-report))
         (t (tc--emit-hygiene-report))))
 
 (defun tc-main ()
@@ -701,6 +883,9 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
   (when (member "--sync-child-priority" command-line-args-left)
     (setq tc-sync-child-priority t)
     (setq command-line-args-left (delete "--sync-child-priority" command-line-args-left)))
+  (when (member "--convert-subtasks" command-line-args-left)
+    (setq tc-convert-subtasks t)
+    (setq command-line-args-left (delete "--convert-subtasks" command-line-args-left)))
   ;; --check-child-priority is the report-only alias for
   ;; `--sync-child-priority --check'.
   (when (member "--check-child-priority" command-line-args-left)
@@ -708,7 +893,7 @@ before their descendants — a [#A] → [#B] → [#D] chain collapses in one pas
     (setq command-line-args-left (delete "--check-child-priority" command-line-args-left)))
   (if (null command-line-args-left)
       (progn
-        (princ "Usage: emacs --batch -q -l todo-cleanup.el [--check] [--archive-done | --sync-child-priority | --check-child-priority] FILE...\n")
+        (princ "Usage: emacs --batch -q -l todo-cleanup.el [--check] [--archive-done | --convert-subtasks | --sync-child-priority | --check-child-priority] FILE...\n")
         (kill-emacs 1))
     (let ((files command-line-args-left))
       (setq command-line-args-left nil)
@@ -727,6 +912,7 @@ ert-run-tests-batch-and-exit'."
        (cl-every (lambda (a)
                    (cond ((member a '("--check"
                                       "--archive-done"
+                                      "--convert-subtasks"
                                       "--sync-child-priority"
                                       "--check-child-priority"))
                           t)
diff --git a/claude-templates/.ai/workflows/clean-todo.org b/claude-templates/.ai/workflows/clean-todo.org
index dd33056..a1b2af5 100644
--- a/claude-templates/.ai/workflows/clean-todo.org
+++ b/claude-templates/.ai/workflows/clean-todo.org
@@ -27,7 +27,17 @@ Deletes bogus =- State "X" from "X" [date]= log lines (state didn't actually cha
 
 To preview without writing, run =--check= first: =emacs --batch -q -l .ai/scripts/todo-cleanup.el --check todo.org=.
 
-** Step 2: Archive completed work
+** Step 2: Convert done sub-tasks to dated entries
+
+#+begin_src bash
+emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks todo.org
+#+end_src
+
+Rewrites every heading at level 3 or deeper whose TODO state is DONE/CANCELLED/FAILED into a dated event-log entry (=<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>=), dropping the keyword, priority cookie, and tags, and removing the =CLOSED:= line. Enforces the depth rule that a completed sub-task becomes dated history — a shape interactive org closes and =--archive-done= (level-2 only) leave unapplied. Timestamp comes from each entry's =CLOSED= cookie; heading text kept verbatim; idempotent; a done sub-task with no parseable =CLOSED= is flagged and left alone. Run before archiving so a parent's sub-tasks are already dated when it moves. Capture the output.
+
+To preview without writing: =emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks --check todo.org=.
+
+** Step 3: Archive completed work
 
 #+begin_src bash
 emacs --batch -q -l .ai/scripts/todo-cleanup.el --archive-done todo.org
@@ -37,10 +47,11 @@ Moves every level-2 subtree whose TODO state is DONE or CANCELLED out of the "Op
 
 To preview the moves without writing: =emacs --batch -q -l .ai/scripts/todo-cleanup.el --archive-done --check todo.org=.
 
-** Step 3: Summarize
+** Step 4: Summarize
 
-Report to Craig from the two captured outputs:
+Report to Craig from the three captured outputs:
 - Hygiene: how many bogus state-log lines were deleted; any orphan-planning warnings (file:line + heading), or "none".
+- Convert: how many done sub-tasks were rewritten to dated entries (heading + line), any flagged for no =CLOSED= date, or "nothing to convert".
 - Archive: how many subtrees moved and which (heading + line), or "nothing to move" / the skip reason if a section was missing or ambiguous.
 - If the file changed, note that =todo.org= now has an uncommitted edit — review =git diff -- todo.org= and commit it (in this repo's commit style) if it looks right. If nothing changed, say so and stop.
 
@@ -49,7 +60,7 @@ Don't auto-commit. The summary is the review point; Craig decides whether the di
 * Principles
 
 - *Both passes apply, not just preview.* The workflow is invoked because cleanup is wanted. Use the =--check= variants only when Craig asks for a dry run.
-- *Two passes, two invocations.* =--archive-done= is its own mode and does not run the hygiene pass; run both.
+- *Separate modes, separate invocations.* =--convert-subtasks=, =--archive-done=, and the hygiene pass are each their own mode and don't run the others; run all three.
 - *Never auto-commit todo.org.* Surface the diff and let Craig commit it. The cleanup is a working-tree change, fully reversible until committed.
 - *Trust the script.* It's fast and idempotent; if there's nothing to do, it reports zero and exits clean. No pre-checks.
 
diff --git a/claude-templates/.ai/workflows/open-tasks.org b/claude-templates/.ai/workflows/open-tasks.org
index 4ba29dd..02a0847 100644
--- a/claude-templates/.ai/workflows/open-tasks.org
+++ b/claude-templates/.ai/workflows/open-tasks.org
@@ -23,15 +23,16 @@ Don't route "task review" / "review tasks" here — those trigger the hygiene ha
 
 * Phase A: Data Gathering (both modes)
 
-** Phase A pre-step — archive any freshly-DONE tasks
+** Phase A pre-step — normalize freshly-closed tasks
 
-Before reading =todo.org=, run the cleanup script's archive-done sweep so completed level-2 subtrees move from =* $Project Open Work= to =* $Project Resolved=:
+Before reading =todo.org=, run two cleanup sweeps so the read reflects current state. First convert any done sub-tasks to dated entries, then archive completed level-2 subtrees from =* $Project Open Work= to =* $Project Resolved=:
 
 #+begin_src bash
+emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks todo.org
 emacs --batch -q -l .ai/scripts/todo-cleanup.el --archive-done todo.org
 #+end_src
 
-Costs a few hundred milliseconds. Without it, a task that completed earlier in the session sits as =** DONE= under Open Work until the next =clean-todo= or wrap-up pass, and Next Mode would surface it as a "what's next" candidate. The sweep makes Phase A's read of =todo.org= reflect current state.
+Costs a few hundred milliseconds. Without the archive sweep, a task that completed earlier in the session sits as =** DONE= under Open Work until the next =clean-todo= or wrap-up pass, and Next Mode would surface it as a "what's next" candidate. The convert sweep runs first so a completed parent's sub-tasks are already dated when it archives; it also keeps interactive level-3 closes from lingering as DONE keywords. Together they make Phase A's read of =todo.org= reflect current state.
 
 Skip the sweep if the workflow is invoked in an explicit read-only or dry-run context. Default is to run it.
 
diff --git a/claude-templates/.ai/workflows/task-review.org b/claude-templates/.ai/workflows/task-review.org
index 69e172d..7b6327b 100644
--- a/claude-templates/.ai/workflows/task-review.org
+++ b/claude-templates/.ai/workflows/task-review.org
@@ -96,6 +96,8 @@ The exact date string matters: =task-review-staleness.sh= and the wrap-up health
 
 Follow the completion rules in [[file:../../claude-rules/todo-format.md][todo-format.md]]. A killed top-level =**= task stays task-shaped: change the keyword to =CANCELLED=, add a =CLOSED: [YYYY-MM-DD Day]= line under the heading (generate with =date "+%Y-%m-%d %a"=), and leave the priority and tags intact. It's then a candidate for =--archive-done= at the next cleanup. Don't stamp =:LAST_REVIEWED:= on a kill — it's leaving the review pool anyway.
 
+A killed *sub-task* (=***= or deeper, under a parent task) instead becomes a dated event-log entry per the depth rule — but you don't have to hand-format it here. =todo-cleanup.el --convert-subtasks= (run in the =clean-todo= and wrap-up cleanup passes) rewrites any level-3+ DONE/CANCELLED/FAILED heading into its dated form mechanically from the =CLOSED= cookie, so a keyword-plus-=CLOSED= close at depth gets normalized on the next cleanup rather than lingering. =lint-org.el= flags any that slip through (checker =subtask-done-not-dated=).
+
 * Phase D: Close out
 
 When the batch is done (or Craig calls it early):
diff --git a/claude-templates/.ai/workflows/wrap-it-up.org b/claude-templates/.ai/workflows/wrap-it-up.org
index 5d2cdd2..4fa5a3a 100644
--- a/claude-templates/.ai/workflows/wrap-it-up.org
+++ b/claude-templates/.ai/workflows/wrap-it-up.org
@@ -137,6 +137,22 @@ Run the report-only variant first if you want to see what would change without w
 emacs --batch -q -l .ai/scripts/todo-cleanup.el --check todo.org
 #+end_src
 
+*** Convert done sub-tasks to dated entries
+
+#+begin_src bash
+[ -f todo.org ] && emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks todo.org
+#+end_src
+
+=--convert-subtasks= rewrites every heading at level 3 or deeper whose TODO state is DONE/CANCELLED/FAILED into a dated event-log entry (=<stars> YYYY-MM-DD Day @ HH:MM:SS -ZZZZ <text>=), dropping the keyword, priority cookie, and tags, and removing the now-redundant =CLOSED:= line. This enforces the =todo-format.md= depth rule that a completed *sub-task* (a heading under a parent task) becomes dated history, not a lingering DONE keyword — a shape an interactive org close (=org-log-done= → DONE + CLOSED) never applies and =--archive-done= (level-2 only) never reaches. The timestamp comes from each entry's own =CLOSED= cookie; a date-only close yields =00:00:00=. Heading text is kept verbatim. Idempotent (an already-dated heading has no keyword to match), and a done sub-task with no parseable =CLOSED= is flagged and left alone rather than stamped with a fabricated date.
+
+Run this *before* =--archive-done= so that when a completed level-2 parent is archived, its sub-tasks already carry their dated form. Any rewrites show up in the wrap-up commit's diff for review before push.
+
+Preview without writing:
+
+#+begin_src bash
+emacs --batch -q -l .ai/scripts/todo-cleanup.el --convert-subtasks --check todo.org
+#+end_src
+
 *** Archive completed work
 
 #+begin_src bash
@@ -536,7 +552,7 @@ Before considering wrap-up complete:
 - [ ] The Summary ends with the =KB: promoted N / consulted yes-no= line (promotion check ran)
 - [ ] File renamed to =.ai/sessions/YYYY-MM-DD-HH-MM-description.org=
 - [ ] =.ai/session-context.org= no longer exists
-- [ ] =todo-cleanup.el= ran — hygiene pass + =--archive-done= + =--sync-child-priority= (if =todo.org= exists at project root)
+- [ ] =todo-cleanup.el= ran — hygiene pass + =--convert-subtasks= + =--archive-done= + =--sync-child-priority= (if =todo.org= exists at project root)
 - [ ] =lint-org.el= ran on =todo.org= — mechanical fixes applied, judgments appended to follow-ups file (if =todo.org= exists)
 - [ ] Any orphan-planning-line warnings reviewed (fix or accept)
 - [ ] Inbox carries nothing but expected pipeline artifacts (=.gitkeep=, =lint-followups.org=, =PROCESSED-*= prefixes), OR each remaining handoff has an explicit deferral logged in the valediction