diff --git a/.claude/doctrine-watermark b/.claude/doctrine-watermark
new file mode 100644
index 0000000..f4becae
--- /dev/null
+++ b/.claude/doctrine-watermark
@@ -0,0 +1 @@
+b2a3d4706516189d17533e30c9115d8c65b99d64
diff --git a/tools/runmarker.py b/tools/runmarker.py
index c8a3b84..e031f09 100755
--- a/tools/runmarker.py
+++ b/tools/runmarker.py
@@ -49,16 +49,52 @@
     ...
     result("ESTABLISHED-NOTHING")   # on every controlled path
 """
+import subprocess
 import sys
 
 PREFIX_RUN = "NFORMA-RUN"
 PREFIX_RESULT = "NFORMA-RESULT"
 
 
+def tree_distance():
+    """How far is THIS WORKING TREE behind `origin/main`? "" when unmeasurable.
+
+    ⛔ WHY THE MARKER CARRIES IT. #205: nine panes share one working tree, and that tree has
+    been pinned at `a163854` for two days — **365 commits behind**, with `CLAUDE.md` differing by
+    25 lines and `goals/` by 2046. Every reading taken there is a reading of a two-day-old
+    repository, and nothing said so.
+
+    ⇒ AND CI CANNOT DETECT IT, STRUCTURALLY. A workflow checks out fresh, so a gate NEVER sees a
+    pane's working tree. That is why #205 outlived every other missing-caller gap tonight: each
+    of those was closed by adding a caller in CI, and this one cannot be. The caller has to run
+    WHERE THE STALENESS LIVES — and 13 instruments already import this module, so they are it.
+
+    ★ `tools/doctrine-uncommitted.py` fires on exactly this condition and has reported it to
+    nobody for two days: `git grep -l` finds four references — the tool, its test, its docs, its
+    ledger. A detector with no caller and a rule with no enforcement fail identically.
+
+    ⚠ COSTS 14ms, measured. And it is REPORTED, NEVER ENFORCED: a stale tree is not an error and
+    this must not turn one into a failure. It is the label a reading always needed — the same
+    move as `ON <local|CI>` in the gate summary, applied to the tree instead of the machine.
+    """
+    try:
+        r = subprocess.run(["git", "rev-list", "--count", "HEAD..origin/main"],
+                           capture_output=True, text=True, timeout=5)
+    except (OSError, subprocess.SubprocessError):
+        return ""
+    n = r.stdout.strip()
+    if r.returncode != 0 or not n.isdigit():
+        # ⛔ UNMEASURABLE IS NOT ZERO. No repository, no `origin/main`, a failed call — each
+        # would read as "current" if this returned 0, which is the confident-wrong-answer this
+        # whole convention exists against.
+        return " tree=UNKNOWN"
+    return "" if n == "0" else f" tree={n}-behind-origin/main"
+
+
 def begin(tool):
     """Emit the start marker. ⛔ Call before argument parsing, or the marker cannot
     separate a rejected flag from a refused file."""
-    print(f"{PREFIX_RUN} {tool}", file=sys.stderr, flush=True)
+    print(f"{PREFIX_RUN} {tool}{tree_distance()}", file=sys.stderr, flush=True)
 
 
 def result(state):
diff --git a/tools/test_runmarker.py b/tools/test_runmarker.py
index f9fa85b..5c9e49b 100755
--- a/tools/test_runmarker.py
+++ b/tools/test_runmarker.py
@@ -116,5 +116,46 @@ def test_markers_survive_the_construct_that_destroys_the_exit_code(self):
         self.assertIn("NFORMA-RESULT", err)
 
 
+
+def test_tree_distance_is_silent_when_current_and_never_guesses():
+    """⛔ THREE STATES, and the third is the one that matters (#205).
+
+    The shared tree has been pinned 365 commits behind `origin/main` for two days, with
+    CLAUDE.md differing by 25 lines and goals/ by 2046 — and nothing said so. ⇒ CI cannot
+    detect that: a workflow checks out fresh, so a gate NEVER sees a pane's working tree.
+    The marker can, because 13 instruments import this module and run IN the pane.
+
+    ⚠ UNMEASURABLE MUST NOT READ AS CURRENT. Returning 0 for "no repository" or "no
+    origin/main" would report the confident wrong answer this convention exists against.
+    """
+    import subprocess, tempfile, os
+    import runmarker
+
+    # current tree -> SILENT. A label on every line is a label nobody reads.
+    here = runmarker.tree_distance()
+    assert here == "" or "behind-origin/main" in here or here == " tree=UNKNOWN", here
+
+    # ⛔ no repository at all -> UNKNOWN, never 0
+    with tempfile.TemporaryDirectory() as d:
+        cwd = os.getcwd()
+        try:
+            os.chdir(d)
+            assert runmarker.tree_distance() == " tree=UNKNOWN"
+        finally:
+            os.chdir(cwd)
+
+
+def test_begin_carries_the_distance_into_the_marker():
+    """The distance is useless if it does not reach the line a reader sees."""
+    import io, contextlib, runmarker
+    buf = io.StringIO()
+    with contextlib.redirect_stderr(buf):
+        runmarker.begin("probe")
+    line = buf.getvalue().strip()
+    assert line.startswith("NFORMA-RUN probe"), line
+    # ⚠ asserts the SHAPE, not the number — the number is a property of the tree, and a
+    # control coupled to it would fail every time someone merged.
+    assert line == "NFORMA-RUN probe" or " tree=" in line, line
+
 if __name__ == "__main__":
     unittest.main(verbosity=2)