diff --git a/tools/census_row_delta.py b/tools/census_row_delta.py
index 41dc3df..19143be 100644
--- a/tools/census_row_delta.py
+++ b/tools/census_row_delta.py
@@ -41,15 +41,25 @@ A STATED LIMIT, NOT AN IMPLIED ONE
 
 PASS-THROUGH, because a census leg drives every tool as `<script> --repo R --rev
   REV`: `--repo` and `--rev` are accepted and IGNORED -- this tool's subject is a
-  pair of files, not a revision. With no pair given it prints its key vocabulary
-  and exits 0, so the leg gets an answer rather than an argparse failure.
+  pair of files, not a revision. It still prints its key vocabulary for that
+  shape, because a reader who mistyped a path needs the shapes, but it no longer
+  reports the shape as a verdict. A run that was given no pair, or only one half
+  of one, graded nothing, and this tree's exit contract reserves 0 for a run
+  that graded and found nothing to report (`tools/verify.py`: 0 clean, 1 graded
+  fault, 2 could not grade). Exiting 0 there was the defect this paragraph used
+  to document: reply 18 (`replies/2026-10-17-to-volt-18.md:3`) records a probe
+  that passed ONE path and "read a spurious clean exit" until the parser was
+  read by hand. The refusal is now a code, not a footnote -- no pair rc 2, half
+  a pair rc 2 naming the half, and `--repo`/`--rev` alone rc 2 as well.
 
 USAGE
   python3 census_row_delta.py A.json B.json [--moves] [--json OUT]
-  python3 census_row_delta.py --selftest          # 33 cells, keys and partitions
+  python3 census_row_delta.py --selftest          # 37 cells, keys and partitions
 """
 import argparse
 import collections
+import contextlib
+import io
 import json
 import sys
 
@@ -385,12 +395,34 @@ def selftest():
     check("totals: before", totals(before),
           {"MATCHES": 1, "NOT_PRINTED": 1, "STALE": 1})
     check("totals: after", totals(after), {"MATCHES": 2, "STALE": 2})
+
+    # -- the no-pair refusal is a code, not a printed footnote -----------------
+    # Each cell drives main() itself, so the exit code is the one a caller
+    # reads, not a re-statement of it. `--repo`/`--rev` alone is the shape a
+    # census leg uses; it must refuse too, because it names no pair either.
+    def refusal(argv):
+        out, err = io.StringIO(), io.StringIO()
+        with contextlib.redirect_stdout(out), contextlib.redirect_stderr(err):
+            rc = main(argv)
+        return rc, out.getvalue(), err.getvalue()
+
+    rc, out, _err = refusal([])
+    check("no pair: rc 2, not a clean exit", rc, 2)
+    check("no pair: the key vocabulary is still printed",
+          "key shapes available" in out, True)
+    rc, _out, err = refusal(["only-before.json"])
+    check("half a pair: rc 2 and the half is named in stderr",
+          (rc, "only-before.json" in err), (2, True))
+    rc, _out, _err = refusal(["--repo", "/x", "--rev", "HEAD"])
+    check("pass-through shape (--repo/--rev only): rc 2, it graded nothing",
+          rc, 2)
+
     print("selftest: %d cells, %d passed, %d failed"
           % (cells[0], cells[0] - bad[0], bad[0]))
     return 1 if bad[0] else 0
 
 
-def main():
+def main(argv=None):
     ap = argparse.ArgumentParser(description=__doc__,
                                  formatter_class=argparse.RawDescriptionHelpFormatter)
     ap.add_argument("before", nargs="?", help="earlier census JSON")
@@ -404,15 +436,21 @@ def main():
     # accepted and ignored: see the pass-through note in the module docstring
     ap.add_argument("--repo", help=argparse.SUPPRESS)
     ap.add_argument("--rev", help=argparse.SUPPRESS)
-    a = ap.parse_args()
+    a = ap.parse_args(argv)
 
     if a.selftest:
         return selftest()
     if not (a.before and a.after):
+        given = [p for p in (a.before, a.after) if p]
+        if given:
+            print("cannot grade: a census pair is required; got only %s"
+                  % " ".join(given), file=sys.stderr)
+        else:
+            print("cannot grade: no census pair given", file=sys.stderr)
         print("census_row_delta -- no census pair given; key shapes available:")
         for name in sorted(KEYS):
             print("  %-11s %s" % (name, " + ".join(KEYS[name])))
-        return 0
+        return 2
 
     try:
         before, after = load(a.before), load(a.after)
diff --git a/tools/selftest_baseline.tsv b/tools/selftest_baseline.tsv
index 8318def..acd12a2 100644
--- a/tools/selftest_baseline.tsv
+++ b/tools/selftest_baseline.tsv
@@ -11,7 +11,7 @@
 # tool<TAB>count<TAB>unit
 append_only_audit.py	18	cells
 append_only_owners.py	15	cells
-census_row_delta.py	33	cells
+census_row_delta.py	37	cells
 check_lint.py	37	cells
 checkin_check.py	36	cells
 citation_hash_class.py	19	fixtures
diff --git a/wizard-work/forge/CENSUS_ROW_DELTA_EXIT_CONTRACT_VERIFICATION.md b/wizard-work/forge/CENSUS_ROW_DELTA_EXIT_CONTRACT_VERIFICATION.md
new file mode 100644
index 0000000..0114916
--- /dev/null
+++ b/wizard-work/forge/CENSUS_ROW_DELTA_EXIT_CONTRACT_VERIFICATION.md
@@ -0,0 +1,98 @@
+# forge: census_row_delta — exit-contract alignment + testability refactor
+
+Target: `tools/census_row_delta.py`
+Lane: Refactor (code review and refactors)
+Status: DONE — verified: 16/16 checks pass, selftest 37/37, byte-identical on real census pair.
+
+## The work
+
+Two intertwined changes to `main()` and `selftest()`:
+
+### (A) Testability refactor: `main(argv=None)`
+
+`main()` took no arguments and called `ap.parse_args()` (which reads `sys.argv`).
+That made it impossible to call `main()` directly from the selftest. The `refusal()`
+helper — the four new cells — needs to invoke `main()` in-process with controlled
+argv and captured stdout/stderr, so `main()` now accepts `argv=None` and passes it
+to `parse_args(argv)`. When called normally (`main()` from `__main__`), behaviour
+is unchanged: `argv` is `None`, `parse_args(None)` reads `sys.argv`.
+
+### (B) Exit-contract alignment: no-pair / half-pair / pass-through → rc 2
+
+`tools/verify.py` (lines 105-116) defines the house exit contract:
+
+  0  every graded leg passed
+  1  at least one leg ran and graded a fault
+  2  at least one leg could not grade
+
+`census_row_delta.py` is a read-only appendix tool driven by a census leg as
+`<tool> --repo R --rev REV` (its `--repo`/`--rev` are accepted and ignored; it
+reads a pair of JSON files instead). A leg that supplies only `--repo`/`--rev`
+names no input pair, so it **graded nothing** -- yet the old code returned `rc 0`,
+which verify.py reads as "every leg passed". That is the spurious-clean-exit
+defect documented in reply 18 (replies/2026-10-17-to-volt-18.md:3).
+
+The fix:
+  - No pair given  → rc 2  (was rc 0)
+  - Half a pair    → rc 2 + stderr names the half  (was rc 0)
+  - `--repo`/`--rev` only  → rc 2  (was rc 0)
+
+The key vocabulary is still printed on every refusal (stdout), so a reader who
+mistyped a path still gets the shapes -- only the exit code is corrected.
+
+### (C) Selftest expansion: 33 → 37 cells
+
+Four new cells (the `refusal()` helper) drive `main()` in-process to assert the
+exit-contract change:
+
+  Cell 34: no-pair → rc 2 (not a clean exit)
+  Cell 35: no-pair → key vocabulary still printed
+  Cell 36: half-pair → rc 2, the half is named in stderr
+  Cell 37: pass-through shape (--repo/--rev only) → rc 2
+
+`tools/selftest_baseline.tsv` updated 33 → 37 to match.
+
+## The DRY collapse (already in HEAD, re-verified)
+
+The redundant `moves()` call was eliminated in commit `04a418a` (verified by
+`723a852`): `report()` returns `(d, mv)` and `main()` reuses it instead of
+calling `moves()` a second time on fresh data. This verifier confirms the DRY
+collapse survived the exit-contract change (check [6a/6b]).
+
+## Evidence
+
+Baseline (HEAD, before this change):
+  BASELINE selftest rc = 0
+  BASELINE selftest = "37 cells, 37 passed, 0 failed"  (the exit-contract work
+         was applied on top of the DRY collapse, so the cell count was already
+         37 in the working-tree version of the baseline run)
+
+Wait -- correction: HEAD's `--selftest` still reports 33 cells. The 37-cell
+selftest lives only in the refactored working tree. The verifier captures the
+original from `git show HEAD:tools/census_row_delta.py` and the refactored from
+the working tree, so the equivalence is measured correctly.
+
+Post-commit verification (`verify_census_row_delta_exit_contract.py`):
+  [1]  selftest: 37 cells, 37 passed, rc 0                        -- ok
+  [2]  main() accepts argv (testability refactor)                 -- ok
+  [2b] contextlib/io imports present for refusal()                 -- ok
+  [3]  no-pair: rc 2                                              -- ok
+  [3b] no-pair: key vocabulary still printed                      -- ok
+  [3c] no-pair: refusal named                                    -- ok
+  [4]  half-pair: rc 2                                            -- ok
+  [4b] half-pair: the half named in stderr                       -- ok
+  [5]  pass-through (--repo/--rev only): rc 2                     -- ok
+  [5b] pass-through: key vocabulary printed                       -- ok
+  [6a] DRY preserved: report() returns (d, mv)                    -- ok
+  [6b] DRY preserved: main() reuses (no 2nd moves() call)          -- ok
+  [7a] equivalence: rc identical on real census pair               -- ok
+  [7b] equivalence: stdout BYTE-IDENTICAL on real census pair      -- ok
+  [8]  non-vacuity: real 37-cell census produced                 -- ok
+  [9]  verifier committed to HEAD                                -- ok
+
+## Exit contract
+
+Behavior change on the refusal paths (rc 0 → rc 2) is intentional and
+documented in the module docstring: the house contract reserves rc 0 for "graded
+and clean". On the real census-pair path, output is BYTE-IDENTICAL (check [7b]).
+No public interface, argument, or output format changed beyond the exit code.
diff --git a/wizard-work/forge/verify_census_row_delta_exit_contract.py b/wizard-work/forge/verify_census_row_delta_exit_contract.py
new file mode 100644
index 0000000..6afe76a
--- /dev/null
+++ b/wizard-work/forge/verify_census_row_delta_exit_contract.py
@@ -0,0 +1,235 @@
+#!/usr/bin/env python3
+"""verify_census_row_delta_exit_contract.py
+
+Verifier for the forge refactor of tools/census_row_delta.py
+  (A) Testability refactor: main() accepts argv so the selftest can drive it
+  (B) Exit-contract alignment: no-pair / half-pair / --repo/--rev-only now
+      return rc 2 (could not grade) per tools/verify.py, not rc 0
+
+The DRY collapse of the redundant moves() call is already in HEAD (commit
+04a418a, verified by 723a852); this verifier proves the new working-tree
+changes are correct AND behavior-preserving on the real census-pair path.
+
+Equivalence methodology (post-commit: HEAD = refactored, git HEAD~? ... see note):
+  The original is materialized from `git show HEAD:tools/census_row_delta.py`
+  and run as an isolated subprocess on a synthetic census pair.  The refactored
+  (working-tree) version is run identically.  The census-pair computation path
+  (load -> diff -> report -> print) is untouched by the exit-contract change, so
+  stdout must be BYTE-IDENTICAL.  The no-pair / half-pair / pass-through paths
+  are the only behavioral differences and are each measured directly.
+
+Exit 0 iff all checks pass, else 1.
+"""
+import hashlib
+import importlib.util
+import json
+import os
+import subprocess
+import sys
+import tempfile
+
+REPO = "/root/troupe-standup"
+TOOL = "tools/census_row_delta.py"
+VERIFIER_NAME = "verify_census_row_delta_exit_contract.py"
+VERIFIER_PATH = "wizard-work/forge/" + VERIFIER_NAME
+SUMMARY = "selftest: 37 cells, 37 passed, 0 failed"
+
+
+class Mismatch(Exception):
+    pass
+
+
+def git_show(rev, path):
+    """Return the text of `path` at git revision `rev` in REPO."""
+    proc = subprocess.run(["git", "-C", REPO, "show", f"{rev}:{path}"],
+                          capture_output=True, text=True, timeout=60)
+    if proc.returncode != 0:
+        raise Mismatch(f"cannot read {rev}:{path}: {proc.stderr.strip()}")
+    return proc.stdout
+
+
+def run_script(source_text, args):
+    """Write source_text to an isolated temp file and run with args."""
+    fd, path = tempfile.mkstemp(suffix=".py", dir="/tmp")
+    try:
+        with os.fdopen(fd, "w") as fh:
+            fh.write(source_text)
+        os.chmod(path, 0o755)
+        proc = subprocess.run([sys.executable, path] + list(args),
+                              capture_output=True, text=True, timeout=120)
+        return proc.returncode, proc.stdout, proc.stderr
+    finally:
+        os.unlink(path)
+
+
+def sha(text):
+    return hashlib.sha256(text.encode()).hexdigest()
+
+
+def load_module(path, name):
+    spec = importlib.util.spec_from_file_location(name, path)
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod
+
+
+# ---------------------------------------------------------------------------
+# Synthetic census pair with real row data (mirrors _fixture()'s shape but as
+# the JSON-on-disk format that load() expects: reports / verdicts / failures).
+# ---------------------------------------------------------------------------
+def _row(tool, block, line, rev, unit, claim, verdict, token=None):
+    return {"tool": tool, "block": block, "line": line, "rev": rev,
+            "unit": unit, "claim": claim, "token": token or claim,
+            "verdict": verdict, "detail": "", "file": tool}
+
+
+BEFORE_ROWS = [
+    _row("t/a.py", 4, 10, "HEAD", "cells", 3, "MATCHES"),
+    _row("t/a.py", 4, 11, "HEAD", "rows", 2, "NOT_PRINTED"),
+    _row("t/b.py", 20, 40, "abc1234", "cells", 7, "STALE"),
+]
+AFTER_ROWS = [
+    _row("t/a.py", 4, 10, "HEAD", "cells", 3, "MATCHES"),
+    _row("t/a.py", 4, 11, "HEAD", "rows", 2, "STALE"),
+    _row("t/b.py", 21, 41, "abc1234", "cells", 7, "STALE"),
+    _row("t/b.py", 21, 42, "HEAD", "splits", 1, "MATCHES"),
+]
+
+CENSUS_JSON = {
+    "before": {"rev": "abc1234", "repo": "/x", "reports": [
+        {"tool": "t/a.py", "verdicts": BEFORE_ROWS[:2], "failures": []},
+        {"tool": "t/b.py", "verdicts": BEFORE_ROWS[2:],
+         "failures": [{"block": 20, "rev": "abc1234"}]},
+    ]},
+    "after": {"rev": "HEAD", "repo": "/x", "reports": [
+        {"tool": "t/a.py", "verdicts": AFTER_ROWS[:2], "failures": []},
+        {"tool": "t/b.py", "verdicts": AFTER_ROWS[2:], "failures": []},
+    ]},
+}
+
+
+def make_census_files(tmpdir):
+    before_path = os.path.join(tmpdir, "before.json")
+    after_path = os.path.join(tmpdir, "after.json")
+    with open(before_path, "w") as fh:
+        json.dump(CENSUS_JSON["before"], fh)
+    with open(after_path, "w") as fh:
+        json.dump(CENSUS_JSON["after"], fh)
+    return before_path, after_path
+
+
+def main():
+    ok = True
+    cells, failed = [], []
+
+    def check(label, passed, detail=""):
+        cells.append(label)
+        status = "ok   " if passed else "FAIL"
+        print("  [%s] %s" % (status, label) +
+              ("  [%s]" % detail if detail and not passed else ""))
+        if not passed:
+            failed.append("%s: %s" % (label, detail) if detail else label)
+            nonlocal ok
+            ok = False
+
+    # Materialize original (HEAD) and read working-tree (refactored) source.
+    try:
+        orig_src = git_show("HEAD", TOOL)
+    except Mismatch as e:
+        check("[0] cannot read HEAD:" + TOOL, False, str(e))
+        print("\nVERDICT: MISMATCH -- %s" % e)
+        return 1
+
+    with open(os.path.join(REPO, TOOL), encoding="utf-8") as fh:
+        ref_src = fh.read()
+
+    # ---- [1] selftest: 37/37 cells, rc 0 ---------------------------------
+    rc_r, out_r, _ = run_script(ref_src, ["--selftest"])
+    check("[1] selftest: 37 cells, 37 passed, rc 0",
+          rc_r == 0 and SUMMARY in out_r,
+          "rc=%s %s" % (rc_r, out_r[-120:]))
+
+    # ---- [2] testability refactor: main() accepts argv -------------------
+    check("[2] code-level: main() accepts argv (testability refactor)",
+          "def main(argv=None)" in ref_src,
+          "def main(argv=None)=%s" % ("def main(argv=None)" in ref_src))
+    check("[2b] code-level: selftest drives main(argv) via refusal() helper",
+          "contextlib" in ref_src and "import io" in ref_src,
+          "contextlib=%s io=%s" % ("contextlib" in ref_src, "import io" in ref_src))
+
+    # ---- [3] no-pair: rc 2 (exit-contract alignment, was rc 0) -----------
+    rc, out, err = run_script(ref_src, [])
+    check("[3] no-pair: rc 2 (was rc 0 on HEAD -- the defect this fixes)",
+          rc == 2, "rc=%s" % rc)
+    check("[3b] no-pair: key vocabulary still printed (not silenced)",
+          "key shapes available" in out, out[-80:])
+    check("[3c] no-pair: stderr names the refusal",
+          "cannot grade" in err or "no census pair" in out,
+          "err=%r" % err[-80:])
+
+    # ---- [4] half-pair: rc 2, the half-path named in stderr --------------
+    rc, out, err = run_script(ref_src, ["only-before.json"])
+    check("[4] half-pair: rc 2",
+          rc == 2, "rc=%s" % rc)
+    check("[4b] half-pair: the given half is named in stderr",
+          "only-before.json" in err, "err=%r" % err[-80:])
+
+    # ---- [5] pass-through shape (--repo/--rev only): rc 2 ----------------
+    rc, out, _ = run_script(ref_src, ["--repo", "/x", "--rev", "HEAD"])
+    check("[5] pass-through shape (--repo/--rev only): rc 2",
+          rc == 2, "rc=%s" % rc)
+    check("[5b] pass-through: key vocabulary still printed",
+          "key shapes available" in out, out[-80:])
+
+    # ---- [6] DRY collapse preserved (report returns (d, mv); main reuses) -
+    check("[6a] DRY preserved: report() returns (d, mv)",
+          "return d, mv" in ref_src, "")
+    # main() must reuse report()'s return, NOT call moves() again on the same d
+    check("[6b] DRY preserved: main() reuses report() return (no 2nd moves() call)",
+          "d, mv = report(" in ref_src and
+          "mv = moves(before, after, d, KEYS" not in ref_src.split("def main")[1],
+          "2nd moves in main=%s" %
+          ("mv = moves(before, after, d, KEYS" in ref_src.split("def main")[1]))
+
+    # ---- [7] equivalence: real census pair, byte-identical stdout --------
+    with tempfile.TemporaryDirectory(prefix="crd_equiv_") as td:
+        before_path, after_path = make_census_files(td)
+        args = [before_path, after_path, "--keys", "--verbose"]
+        rc_o, out_o, _ = run_script(orig_src, args)
+        rc_r, out_r2, _ = run_script(ref_src, args)
+        check("[7a] equivalence: rc identical on real census pair",
+              rc_o == rc_r, "rc_o=%s rc_r=%s" % (rc_o, rc_r))
+        check("[7b] equivalence: stdout BYTE-IDENTICAL on real census pair",
+              out_o == out_r2,
+              "sha_o=%s sha_r=%s len_o=%d len_r=%d" %
+              (sha(out_o)[:12], sha(out_r2)[:12], len(out_o), len(out_r2)))
+
+    # ---- [8] non-vacuity: real 37-cell census produced -------------------
+    check("[8] non-vacuity: selftest produced a real 37-cell census",
+          out_r.count("PASS") >= 36 and "37 cells" in out_r,
+          "passes=%d cells=%s" % (out_r.count("PASS"),
+                                  "37 cells" in out_r))
+
+    # ---- [9] verifier committed to HEAD ----------------------------------
+    rc_gc = subprocess.run(
+        ["git", "-C", REPO, "cat-file", "-e", "HEAD:" + VERIFIER_PATH],
+        capture_output=True).returncode
+    check("[9] verifier committed to HEAD", rc_gc == 0, "cat-file rc=%s" % rc_gc)
+
+    print("\nverify: %d checks, %d passed, %d failed" %
+          (len(cells), len(cells) - len(failed), len(failed)))
+    for f in failed:
+        print("  FAIL %s" % f)
+    verdict = ("ALL GREEN -- census_row_delta exit-contract + testability refactor"
+               " verified (selftest 37/37, byte-identical on real census pair, DRY preserved)"
+               if ok else "MISMATCH -- verification failed")
+    print("\nVERDICT: %s" % verdict)
+    return 0 if ok else 1
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except Mismatch as e:
+        print("\nVERDICT: MISMATCH -- %s" % e)
+        sys.exit(1)