diff --git a/scripts/check-memory-rotation.py b/scripts/check-memory-rotation.py
index 7a1170a2..a2642023 100644
--- a/scripts/check-memory-rotation.py
+++ b/scripts/check-memory-rotation.py
@@ -48,6 +48,15 @@
 `.emrg/sessions/*/memory/**/*.md` - the two places the rotation's rule names - and
 keeps the newest file strictly newer than that project's stamp.
 
+**The rotation's third key has a carrier here too.** §1.5 orders the rotation by changed
+projects first and **least recently visited** after that, and the second key can only be
+ordered from a bookmark that records which cycle read which row. This tool therefore reads
+a row's cycle id wherever the row puts it and prints it beside the project, plus one line
+saying how many of the table's rows record one - so a bookmark that records none says so,
+instead of leaving every project looking equally recent (issue #2525). The field is read,
+never required: a row written before the column existed is not unreadable, it is a row that
+does not answer this question yet.
+
 **The bookmark is not memory content.** On this host it lives under the evolution
 project's own memory root, so counting it would make that project's newest file the clock
 itself: the row could never be current, and every run would report the project changed on
@@ -147,6 +156,14 @@ def now() -> datetime:
 #: visited.
 KEY_CELL = re.compile(r"^`(?P<key>[^`]+)`\s*(?:\((?P<hint>[^)]*)\))?$")
 
+#: A row's **reading cycle**: the cycle id §1.5 asks a row to carry beside the stamp it read,
+#: so that "least recently visited" - the rotation's third key - can be ordered from the
+#: bookmark instead of from recollection. Found, never required: this installation's 32 rows
+#: carried none when the field was added (issue #2525), and a reader that refused them would
+#: have called every live project unreadable. A row without one is reported as not recording
+#: it, which is a fact about that row rather than a fault in the reading.
+READ_BY_CELL = re.compile(r"\bcyc\d{8}-\d{6}\b")
+
 #: What a row's **value cell** carries: a stamp, or one of the two notes. A cell may append
 #: a parenthetical - this host writes `path missing (gone from disk)`, another writes the
 #: stamp followed by the memory file it was read from - so the note is read from the cell
@@ -257,6 +274,22 @@ def _value_of(cells: list[str]) -> str | None:
     return None
 
 
+def _read_by_of(cells: list[str]) -> str | None:
+    """The cycle id a row carries, from whichever cell holds it, or `None`.
+
+    Searched rather than counted, for the reason `_value_of` gives: the column's index
+    belongs to the installation writing the bookmark, and this host's table puts the cycle
+    nowhere at all. A cell is only read as a cycle when it *is* one - `cyc` and a stamp of
+    the right width - so a date, a path or a word that resembles an id is left alone
+    (issue #2525).
+    """
+    for cell in cells:
+        found = READ_BY_CELL.search(cell)
+        if found:
+            return found.group(0)
+    return None
+
+
 #: The heading that opens a bookmark's per-cycle narration section.
 #:
 #: The bookmark keeps **exactly one** such section, replaced in place each cycle. That is
@@ -324,7 +357,8 @@ def parse_bookmark(path: Path) -> list[dict]:
             continue
         key = key_cell.group("key")
         hint = key_cell.group("hint")
-        rows.append({"key": f"{key} ({hint})" if hint else key, "value": value})
+        rows.append({"key": f"{key} ({hint})" if hint else key, "value": value,
+                     "read_by": _read_by_of(cells[1:])})
     if not saw_table:
         sections = [line.strip() for line in lines if CYCLE_SECTION.match(line)]
         if sections:
@@ -567,7 +601,8 @@ def project_state(project: dict, row: dict | None, bookmark_path: Path | None =
     """
     name = project["name"]
     raw_path = project.get("path") or ""
-    state = {"name": name, "path": raw_path, "key": row["key"] if row else None}
+    state = {"name": name, "path": raw_path, "key": row["key"] if row else None,
+             "read_by": row.get("read_by") if row else None}
     if row is None:
         state.update(state="no bookmark row", bookmark=None, newest=None)
         return state
@@ -653,6 +688,7 @@ def read(projects_path: Path, bookmark_path: Path) -> dict:
         "bookmark_file": str(bookmark_path),
         "project_count": len(projects),
         "row_count": len(rows),
+        "rows_with_cycle": sum(1 for row in rows if row.get("read_by")),
         "states": states,
         "faults": faults,
         "cycle_sections": len(sections),
@@ -660,6 +696,15 @@ def read(projects_path: Path, bookmark_path: Path) -> dict:
     }
 
 
+def _cycle_of(state: dict) -> str:
+    """The cycle that read this project's row, or a phrase saying the row recorded none.
+
+    A phrase rather than a blank, because the two are different readings: a project read by
+    `cyc…` and one whose row predates the column must not print alike.
+    """
+    return state.get("read_by") or "no cycle recorded"
+
+
 def render(reading: dict, show_all: bool) -> str:
     """The report, with both subjects named before any verdict."""
     out = [
@@ -674,7 +719,7 @@ def render(reading: dict, show_all: bool) -> str:
         out.append(f"changed since their bookmark: {len(changed)}")
         for state in changed:
             out.append(f"  {state['name']}  {state['bookmark']} -> {state['newest']['mtime']}  "
-                       f"{state['newest']['path']}")
+                       f"{state['newest']['path']}  read by {_cycle_of(state)}")
     else:
         out.append("changed since their bookmark: 0 - every project is at or before its stamp")
     if show_all:
@@ -682,9 +727,18 @@ def render(reading: dict, show_all: bool) -> str:
         if others:
             out.append("every other project:")
             for state in others:
-                out.append(f"  {state['state']:<16} {state['name']}  {state['path']}")
+                out.append(f"  {state['state']:<16} {state['name']}  {state['path']}  "
+                           f"read by {_cycle_of(state)}")
     summary = ", ".join(f"{name} {count}" for name, count in sorted(counts.items()))
     out.append(f"states: {summary}" if summary else "states: none recorded")
+    recorded = reading["rows_with_cycle"]
+    out.append(
+        f"reading cycles: {recorded} of {reading['row_count']} row(s) record the cycle that read "
+        f"them"
+        + ("" if recorded else
+           ' - none does, so "least recently visited" cannot be ordered from this bookmark '
+           'until the rows that are read carry one (§1.5)')
+    )
     if reading["faults"]:
         out.append(f"coverage faults: {len(reading['faults'])}")
         out.extend(f"  {fault}" for fault in reading["faults"])
diff --git a/tests/test_check_memory_rotation.py b/tests/test_check_memory_rotation.py
index 7c74a6fd..ea135d73 100644
--- a/tests/test_check_memory_rotation.py
+++ b/tests/test_check_memory_rotation.py
@@ -21,6 +21,11 @@
   stamp that does not parse, and a row that matches two projects all answer exit **2**
   or exit **1** with the reason named, and `0` is reserved for a reading that covered
   every project and every row;
+* **the rotation's third key has a carrier or it is not a key** - a row's reading cycle is
+  found wherever the table puts it and printed beside its project, and a row that records
+  none is reported as recording none rather than left looking recently read: §1.5 orders the
+  rotation by "least recently visited", which no bookmark without that field can answer
+  (issue #2525);
 * **a note from an earlier day is re-measured, not repeated** - `no memory root` and
   `path missing` are readings, so a row carrying one the disk now contradicts is a fault
   rather than a verdict that hides a project for ever.
@@ -728,6 +733,71 @@ def test_a_bookmark_truncated_at_its_section_is_diagnosed_as_truncation(mod, tmp
     assert "another shape" in str(excinfo.value)
 
 
+# ------------------------------------------------------ the third key: who read this row
+
+
+def _bookmark_with_read_by(path: Path, rows: list[tuple[str, str, str]]) -> Path:
+    """A bookmark in the four-cell shape another installation writes.
+
+    Kept apart from `_bookmark` on purpose: that fixture is this host's three-cell table and
+    every other test in this file is written against it, so a second shape needs its own
+    writer rather than a changed one.
+    """
+    lines = ["# Bookmark", "",
+             "| project | newest read | files | read by |",
+             "| --- | --- | --- | --- |"]
+    lines += [f"| {key} | {value} | 0 | {cycle} |" for key, value, cycle in rows]
+    path.write_text("\n".join(lines) + "\n", encoding="utf-8")
+    return path
+
+
+def test_a_row_that_records_its_reading_cycle_is_reported_with_it(mod, tmp_path):
+    """A bookmark that records the cycle and a report that drops it is the same as neither.
+
+    §1.5 orders the rotation by "least recently visited" once the changed projects are
+    taken, so the field is the only carrier that key has (issue #2525).
+    """
+    root = _root(tmp_path, "cycled")
+    _write_memory(Path(root), ".emrg/memory/MEMORY.md", _stamp(mod))
+    register = _projects(tmp_path / "projects.yml", [{"name": "cycled", "path": root}])
+    book = _bookmark_with_read_by(tmp_path / "book.md", [("`cycled`", BASE, "cyc20261020-141450")])
+    reading = mod.read(register, book)
+    assert [s["read_by"] for s in reading["states"]] == ["cyc20261020-141450"]
+    assert reading["rows_with_cycle"] == 1
+    report = mod.render(reading, True)
+    assert "read by cyc20261020-141450" in report, report
+    assert "reading cycles: 1 of 1 row(s) record the cycle that read them" in report, report
+
+
+def test_a_row_without_a_cycle_says_so_instead_of_looking_recent(mod, tmp_path):
+    """This host's shape: three cells, no cycle. The absence is a reading, not a fault."""
+    root = _root(tmp_path, "uncycled")
+    _write_memory(Path(root), ".emrg/memory/MEMORY.md", _stamp(mod))
+    reading = _reading(mod, tmp_path, [{"name": "uncycled", "path": root}],
+                       [("`uncycled`", BASE)])
+    assert reading["rows_with_cycle"] == 0
+    report = mod.render(reading, True)
+    assert "read by no cycle recorded" in report, report
+    assert "reading cycles: 0 of 1 row(s) record the cycle that read them" in report, report
+    assert "cannot be ordered from this bookmark" in report, report
+    # The row answers every question it was asked, so it is not a coverage fault: a fault
+    # here would send a cycle to rewrite a row that is already correct for its own shape.
+    assert reading["faults"] == []
+
+
+def test_a_cell_that_only_resembles_a_cycle_is_not_read_as_one(mod, tmp_path):
+    """Shape decides, as `_value_of` already decides for the stamp: `cyc` and a stamp of the
+    right width, or nothing. A near miss must not become an ordering key."""
+    root = _root(tmp_path, "almost")
+    _write_memory(Path(root), ".emrg/memory/MEMORY.md", _stamp(mod))
+    register = _projects(tmp_path / "projects.yml", [{"name": "almost", "path": root}])
+    for near_miss in ("cyc2026102-14145", "cyc20261020-1414", "cyc20261020-1414500",
+                      "cycle 20261020-141450", "2026-10-20 14:14:50"):
+        book = _bookmark_with_read_by(tmp_path / "book.md", [("`almost`", BASE, near_miss)])
+        reading = mod.read(register, book)
+        assert [s["read_by"] for s in reading["states"]] == [None], near_miss
+        assert reading["rows_with_cycle"] == 0, near_miss
+        assert "read by no cycle recorded" in mod.render(reading, True), near_miss
 # ------------------------------------------------- the register's name, mid-move