diff --git a/scripts/gen_agreement_corpus.py b/scripts/gen_agreement_corpus.py
new file mode 100644
index 0000000..d7abd0a
--- /dev/null
+++ b/scripts/gen_agreement_corpus.py
@@ -0,0 +1,193 @@
+#!/usr/bin/env python3
+"""Generate the agreement test set from this implementation.
+
+An *agreement* is a small Liminate program of facts and `forbid` / `require` /
+`permit` rules. It is how a product states a floor ("a phone number in a public
+note is not allowed") in one file that several runtimes read. The Python package
+is the only complete interpreter; `@liminate/ts-validator` and `liminate-swift`
+carry a port of just the agreement subset, so a product can evaluate the same
+file on a server and on a phone.
+
+Two ports of one subset drift unless something outside both of them says what
+the subset does. This is that something: each program in the corpus is run
+through the reference interpreter, and what it did is written down. A port
+passes only by reproducing those recorded outcomes, never by agreeing with
+expectations a person typed beside its own code.
+
+The subset is exactly: `about`, `--` comments, `remember a number|text|truth
+called <name> with <value>`, and `forbid|require|permit <condition> [unless
+<condition>] because "<text>"`. Conditions are the comparisons the analyzer
+accepts there, joined by `and` / `or`.
+
+What is recorded for each program:
+
+    exit      the reference CLI's exit code (`--quiet --test`)
+    stdout    its standard output, verbatim
+    outcome   "pass"    nothing was crossed and nothing went wrong
+              "crossed" at least one `forbid` was violated or `require` unmet,
+                        and nothing else went wrong
+              "error"   any line the interpreter rejected (a parse error, an
+                        unknown name, a type it will not compare): never a pass
+    crossed   for each violated rule, in program order: its verb, the rule's
+              condition in canonical form, and its `because` text. Empty for
+              "pass" and for "error"
+
+`because` does not appear in the interpreter's output, so it is read from the
+rule's own line; the line is found by running the program through `run()`,
+which reports a result per source line, and every violation `run()` reports
+must equal a line the CLI printed. If the two ever disagree this script stops
+rather than write a corpus that one of them would contradict.
+
+Usage:
+    python3 scripts/gen_agreement_corpus.py > tests/fixtures/agreement-<version>.json
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import re
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "src"))
+
+from liminate.result import ResultStatus  # noqa: E402
+from liminate.run import run  # noqa: E402
+
+CORPUS_PATH = ROOT / "tests" / "fixtures" / "agreement_corpus.txt"
+
+_BECAUSE = re.compile(r'\s+because\s+"((?:[^"\\]|\\.)*)"\s*$')
+_VIOLATION = "Error: Prohibition violated: "
+_UNMET = "Error: Requirement not met: "
+
+
+def language_version() -> str:
+    """The version of the source being read, not of whatever is installed."""
+    for line in (ROOT / "pyproject.toml").read_text(encoding="utf-8").splitlines():
+        if line.startswith("version"):
+            return line.split("=", 1)[1].strip().strip('"')
+    raise SystemExit("pyproject.toml states no version")
+
+
+def read_corpus() -> list[dict]:
+    """A case is a `# ` line naming it, then the program's lines.
+
+    Blank lines inside a case are kept: a comment or blank line is part of what
+    the interpreter reads. A program ends at the next `# ` header.
+    """
+    cases: list[dict] = []
+    name: str | None = None
+    lines: list[str] = []
+
+    def close() -> None:
+        if name is not None:
+            while lines and not lines[-1].strip():
+                lines.pop()
+            cases.append({"id": name, "program": "\n".join(lines) + "\n"})
+
+    for raw in CORPUS_PATH.read_text(encoding="utf-8").splitlines():
+        if raw.startswith("# "):
+            close()
+            name, lines = raw[2:].strip(), []
+        elif name is not None:
+            lines.append(raw)
+    close()
+    return cases
+
+
+def run_cli(program: str) -> tuple[int, str]:
+    """The reference CLI, `--quiet --test`, on this tree's source."""
+    with tempfile.TemporaryDirectory() as tmp:
+        path = Path(tmp) / "agreement.limn"
+        path.write_text(program, encoding="utf-8")
+        env = {**os.environ, "PYTHONPATH": str(ROOT / "src")}
+        done = subprocess.run(
+            [sys.executable, "-m", "liminate", "--quiet", "--test", str(path)],
+            capture_output=True,
+            text=True,
+            env=env,
+            timeout=60,
+            check=False,
+        )
+    return done.returncode, done.stdout
+
+
+def because_of(source: str | None) -> str:
+    match = _BECAUSE.search(source or "")
+    return match.group(1) if match else ""
+
+
+def classify(program: str, exit_code: int, stdout: str) -> tuple[str, list[dict]]:
+    lines = [ln for ln in stdout.splitlines() if ln.strip()]
+    printed = [ln for ln in lines if ln.startswith((_VIOLATION, _UNMET))]
+    other_errors = [
+        ln for ln in lines if ln.startswith("Error:") and ln not in printed
+    ]
+
+    structured = []
+    for result in run(program, auto_confirm_amber=True).results:
+        if result.status in (
+            ResultStatus.PROHIBITION_VIOLATED,
+            ResultStatus.REQUIREMENT_NOT_MET,
+        ):
+            meta = result.metadata or {}
+            structured.append(
+                {
+                    "verb": meta["verb"],
+                    "condition": meta["condition"],
+                    "because": because_of(result.source),
+                    "_line": "Error: " + (result.message or ""),
+                }
+            )
+    if [s["_line"] for s in structured] != printed:
+        raise SystemExit(
+            "run() and the CLI disagree about which rules were crossed:\n"
+            f"  run(): {[s['_line'] for s in structured]}\n"
+            f"  CLI:   {printed}\n"
+            f"  program:\n{program}"
+        )
+    if other_errors:
+        return "error", []
+    if printed:
+        return "crossed", [{k: v for k, v in s.items() if k != "_line"} for s in structured]
+    if exit_code != 0:
+        raise SystemExit(f"exit {exit_code} with no error line:\n{stdout}\n{program}")
+    return "pass", []
+
+
+def main() -> None:
+    cases = []
+    for case in read_corpus():
+        exit_code, stdout = run_cli(case["program"])
+        outcome, crossed = classify(case["program"], exit_code, stdout)
+        cases.append(
+            {
+                "id": case["id"],
+                "program": case["program"],
+                "exit": exit_code,
+                "outcome": outcome,
+                "crossed": crossed,
+                "stdout": stdout,
+            }
+        )
+    json.dump(
+        {
+            "language_version": language_version(),
+            "generator": "scripts/gen_agreement_corpus.py",
+            "surface": "about, comments, remember number|text|truth, forbid|require|permit [unless] because",
+            "cases": cases,
+        },
+        sys.stdout,
+        indent=2,
+        sort_keys=True,
+        ensure_ascii=False,
+    )
+    sys.stdout.write("\n")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tests/fixtures/agreement-0.18.4.json b/tests/fixtures/agreement-0.18.4.json
new file mode 100644
index 0000000..40f5244
--- /dev/null
+++ b/tests/fixtures/agreement-0.18.4.json
@@ -0,0 +1,895 @@
+{
+  "cases": [
+    {
+      "crossed": [
+        {
+          "because": "equals five",
+          "condition": "n is 5",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number is: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is 5 because \"equals five\"\n",
+      "stdout": "Error: Prohibition violated: n is 5. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number is: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is 4 because \"equals four\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "rule above",
+          "condition": "n is above 4",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number above: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 4 because \"rule above\"\n",
+      "stdout": "Error: Prohibition violated: n is above 4. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number above: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is above 5 because \"rule above\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "rule below",
+          "condition": "n is below 6",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number below: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is below 6 because \"rule below\"\n",
+      "stdout": "Error: Prohibition violated: n is below 6. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number below: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is below 5 because \"rule below\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "rule equal to",
+          "condition": "n is equal to 5",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number equal to: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is equal to 5 because \"rule equal to\"\n",
+      "stdout": "Error: Prohibition violated: n is equal to 5. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number equal to: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is equal to 4 because \"rule equal to\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "rule not above",
+          "condition": "n is not above 5",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number not above: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is not above 5 because \"rule not above\"\n",
+      "stdout": "Error: Prohibition violated: n is not above 5. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number not above: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is not above 4 because \"rule not above\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "rule not below",
+          "condition": "n is not below 5",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number not below: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is not below 5 because \"rule not below\"\n",
+      "stdout": "Error: Prohibition violated: n is not below 5. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number not below: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is not below 6 because \"rule not below\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "rule not equal to",
+          "condition": "n is not equal to 4",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "number not equal to: crosses",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is not equal to 4 because \"rule not equal to\"\n",
+      "stdout": "Error: Prohibition violated: n is not equal to 4. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "number not equal to: does not cross",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is not equal to 5 because \"rule not equal to\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "boundary: equal to the limit is not above it",
+      "outcome": "pass",
+      "program": "remember a number called n with 3.0\nforbid n is above 3 because \"limit\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "limit",
+          "condition": "n is above 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "boundary: just past the limit is above it",
+      "outcome": "crossed",
+      "program": "remember a number called n with 3.1\nforbid n is above 3 because \"limit\"\n",
+      "stdout": "Error: Prohibition violated: n is above 3. n is 3.1.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "boundary: zero against above zero",
+      "outcome": "pass",
+      "program": "remember a number called n with 0\nforbid n is above 0 because \"any\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "negative",
+          "condition": "n is below 0",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "negative numbers",
+      "outcome": "crossed",
+      "program": "remember a number called n with -5\nforbid n is below 0 because \"negative\"\n",
+      "stdout": "Error: Prohibition violated: n is below 0. n is -5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "at or past",
+          "condition": "n is not below 2.5",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "decimals compare as numbers",
+      "outcome": "crossed",
+      "program": "remember a number called n with 2.5\nforbid n is above 2.5 because \"not past\"\nforbid n is not below 2.5 because \"at or past\"\n",
+      "stdout": "Error: Prohibition violated: n is not below 2.5. n is 2.5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "same number",
+          "condition": "n is equal to 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "integer and decimal are equal",
+      "outcome": "crossed",
+      "program": "remember a number called n with 3\nforbid n is equal to 3.0 because \"same number\"\n",
+      "stdout": "Error: Prohibition violated: n is equal to 3. n is 3.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "large",
+          "condition": "n is above 999999",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "a large number",
+      "outcome": "crossed",
+      "program": "remember a number called n with 1000000\nforbid n is above 999999 because \"large\"\n",
+      "stdout": "Error: Prohibition violated: n is above 999999. n is 1000000.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "near four",
+          "condition": "n is within 1 of 4",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "within: inside the tolerance",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is within 1 of 4 because \"near four\"\n",
+      "stdout": "Error: Prohibition violated: n is within 1 of 4. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "within: outside the tolerance",
+      "outcome": "pass",
+      "program": "remember a number called n with 9\nforbid n is within 1 of 4 because \"near four\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "calm is forbidden",
+          "condition": "mood is calm",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "text equality: crosses",
+      "outcome": "crossed",
+      "program": "remember a text called mood with \"calm\"\nforbid mood is \"calm\" because \"calm is forbidden\"\n",
+      "stdout": "Error: Prohibition violated: mood is calm. mood is calm.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "text equality: does not cross",
+      "outcome": "pass",
+      "program": "remember a text called mood with \"calm\"\nforbid mood is \"angry\" because \"angry is forbidden\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "anything but angry",
+          "condition": "mood is not equal to angry",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "text not equal to",
+      "outcome": "crossed",
+      "program": "remember a text called mood with \"calm\"\nforbid mood is not equal to \"angry\" because \"anything but angry\"\n",
+      "stdout": "Error: Prohibition violated: mood is not equal to angry. mood is calm.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "bareword compares as text",
+          "condition": "mood is calm",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "text against a bareword",
+      "outcome": "crossed",
+      "program": "remember a text called mood with \"calm\"\nforbid mood is calm because \"bareword compares as text\"\n",
+      "stdout": "Error: Prohibition violated: mood is calm. mood is calm.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "a space inside the value",
+          "condition": "city is \"new york\"",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "text with a space",
+      "outcome": "crossed",
+      "program": "remember a text called city with \"new york\"\nforbid city is \"new york\" because \"a space inside the value\"\n",
+      "stdout": "Error: Prohibition violated: city is \"new york\". city is new york.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "text is case sensitive",
+      "outcome": "pass",
+      "program": "remember a text called mood with \"Calm\"\nforbid mood is \"calm\" because \"case\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "flag set",
+          "condition": "flag is true",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "truth is true: crosses",
+      "outcome": "crossed",
+      "program": "remember a truth called flag with true\nforbid flag is true because \"flag set\"\n",
+      "stdout": "Error: Prohibition violated: flag is true. flag is true.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "truth is true: does not cross",
+      "outcome": "pass",
+      "program": "remember a truth called flag with false\nforbid flag is true because \"flag set\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "must be ready",
+          "condition": "ready is true",
+          "verb": "require"
+        }
+      ],
+      "exit": 1,
+      "id": "require a truth",
+      "outcome": "crossed",
+      "program": "remember a truth called ready with false\nrequire ready is true because \"must be ready\"\n",
+      "stdout": "Error: Requirement not met: ready is true. ready is false.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "require: met",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nrequire n is above 1 because \"at least two\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "under two",
+          "condition": "n is below 2",
+          "verb": "require"
+        }
+      ],
+      "exit": 1,
+      "id": "require: unmet",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nrequire n is below 2 because \"under two\"\n",
+      "stdout": "Error: Requirement not met: n is below 2. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "permit: never crosses",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\npermit n is above 1 because \"allowed\"\n",
+      "stdout": "Permitted: n is above 1. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "permit: true condition",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\npermit n is above 4 because \"allowed\"\npermit n is below 1 because \"not applicable\"\n",
+      "stdout": "Permitted: n is above 4. n is 5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "in the band",
+          "condition": "n is above 1 and n is below 9",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "and: both true",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 1 and n is below 9 because \"in the band\"\n",
+      "stdout": "Error: Prohibition violated: n is above 1 and n is below 9. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "and: one false",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is above 1 and n is below 3 because \"in the band\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "either side",
+          "condition": "n is above 9 or n is below 6",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "or: one true",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 9 or n is below 6 because \"either side\"\n",
+      "stdout": "Error: Prohibition violated: n is above 9 or n is below 6. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "or: both false",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is above 9 or n is below 1 because \"either side\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "both counts high",
+          "condition": "a-count is above 1 and b-count is above 6",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "and across two facts",
+      "outcome": "crossed",
+      "program": "remember a number called a-count with 2\nremember a number called b-count with 7\nforbid a-count is above 1 and b-count is above 6 because \"both counts high\"\n",
+      "stdout": "Error: Prohibition violated: a-count is above 1 and b-count is above 6. b-count is 7.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "unless: excuses the rule",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is above 3 unless n is above 4 because \"excused\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "not excused",
+          "condition": "n is above 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "unless: does not excuse",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 3 unless n is above 9 because \"not excused\"\n",
+      "stdout": "Error: Prohibition violated: n is above 3. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "require with unless",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nrequire n is below 2 unless n is above 4 because \"excused\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "over the allowance",
+          "condition": "used is above allowed",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "a rule that compares two facts",
+      "outcome": "crossed",
+      "program": "remember a number called used with 8\nremember a number called allowed with 5\nforbid used is above allowed because \"over the allowance\"\n",
+      "stdout": "Error: Prohibition violated: used is above allowed. used is 8.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "last value wins",
+          "condition": "n is above 5",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "a fact remembered twice keeps the last value",
+      "outcome": "crossed",
+      "program": "remember a number called n with 1\nremember a number called n with 9\nforbid n is above 5 because \"last value wins\"\n",
+      "stdout": "Error: Prohibition violated: n is above 5. n is 9.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "a fact remembered after the rule is not seen by it",
+      "outcome": "pass",
+      "program": "remember a number called n with 1\nforbid n is above 5 because \"uses what is known at this point\"\nremember a number called n with 9\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "first",
+          "condition": "n is above 1",
+          "verb": "forbid"
+        },
+        {
+          "because": "third",
+          "condition": "n is above 2",
+          "verb": "forbid"
+        },
+        {
+          "because": "fourth",
+          "condition": "n is below 3",
+          "verb": "require"
+        }
+      ],
+      "exit": 1,
+      "id": "several rules crossing are reported in program order",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 1 because \"first\"\nforbid n is below 1 because \"second, does not cross\"\nforbid n is above 2 because \"third\"\nrequire n is below 3 because \"fourth\"\n",
+      "stdout": "Error: Prohibition violated: n is above 1. n is 5.\nError: Prohibition violated: n is above 2. n is 5.\nError: Requirement not met: n is below 3. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "no rule crossing",
+      "outcome": "pass",
+      "program": "remember a number called n with 5\nforbid n is above 9 because \"one\"\nforbid n is below 1 because \"two\"\nrequire n is above 0 because \"three\"\npermit n is above 0 because \"four\"\n",
+      "stdout": "Permitted: n is above 0. n is 5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "unmet",
+          "condition": "n is below 2",
+          "verb": "require"
+        }
+      ],
+      "exit": 1,
+      "id": "only a required rule is unmet",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 9 because \"fine\"\nrequire n is below 2 because \"unmet\"\n",
+      "stdout": "Error: Requirement not met: n is below 2. n is 5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "first reason",
+          "condition": "n is above 1",
+          "verb": "forbid"
+        },
+        {
+          "because": "second reason",
+          "condition": "n is above 1",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "the same condition twice reports twice, each with its own because",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 1 because \"first reason\"\nforbid n is above 1 because \"second reason\"\n",
+      "stdout": "Error: Prohibition violated: n is above 1. n is 5.\nError: Prohibition violated: n is above 1. n is 5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "comments do not matter",
+          "condition": "n is above 1",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "comments and blank lines are not statements",
+      "outcome": "crossed",
+      "program": "-- A header comment.\nabout \"comment-case\"\n\n-- another comment\nremember a number called n with 5\n\nforbid n is above 1 because \"comments do not matter\"\n-- a trailing comment\n",
+      "stdout": "\n\n\n\nError: Prohibition violated: n is above 1. n is 5.\n\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "about alone",
+      "outcome": "pass",
+      "program": "about \"nothing-else\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "an empty-looking program of comments",
+      "outcome": "pass",
+      "program": "-- only a comment\n",
+      "stdout": "\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "more than one (WCAG 2.3.1), see: the rule; it's firm",
+          "condition": "n is above 1",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "because text with punctuation",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 1 because \"more than one (WCAG 2.3.1), see: the rule; it's firm\"\n",
+      "stdout": "Error: Prohibition violated: n is above 1. n is 5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "",
+          "condition": "n is above 1",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "a rule without a because",
+      "outcome": "crossed",
+      "program": "remember a number called n with 5\nforbid n is above 1\n",
+      "stdout": "Error: Prohibition violated: n is above 1. n is 5.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "hyphens are fine",
+          "condition": "flashes-in-worst-second is above 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "a hyphenated and digit-bearing name",
+      "outcome": "crossed",
+      "program": "remember a number called flashes-in-worst-second with 4\nremember a number called count2 with 1\nforbid flashes-in-worst-second is above 3 because \"hyphens are fine\"\nforbid count2 is above 3 because \"digits are fine\"\n",
+      "stdout": "Error: Prohibition violated: flashes-in-worst-second is above 3. flashes-in-worst-second is 4.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a fact that was never remembered",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nforbid missing is above 1 because \"no such fact\"\n",
+      "stdout": "Error: I can't find 'missing'. You might need to 'remember' it first.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a missing fact does not hide a crossing elsewhere",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nforbid n is above 1 because \"crosses\"\nforbid missing is above 1 because \"no such fact\"\n",
+      "stdout": "Error: Prohibition violated: n is above 1. n is 5.\nError: I can't find 'missing'. You might need to 'remember' it first.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a range comparison over text",
+      "outcome": "error",
+      "program": "remember a text called mood with \"calm\"\nforbid mood is above 3 because \"text has no order\"\n",
+      "stdout": "Error: 'above' requires numbers or dates, but 'mood' is text.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: with and no value",
+      "outcome": "error",
+      "program": "remember a number called n with\nforbid n is above 1 because \"the fact never existed\"\n",
+      "stdout": "Error: I expected a value after 'with'.\nError: I can't find 'n'. You might need to 'remember' it first.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a reserved word as a name",
+      "outcome": "error",
+      "program": "remember a number called and with 5\nforbid and is above 1 because \"reserved\"\n",
+      "stdout": "Error: The word 'and' is reserved in Liminate — it's used as a connective. Please choose a different name.\nError: The word 'and' is reserved in Liminate — it's used as a connective and can't be used as a field name.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a rule with no condition",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nforbid because \"nothing to test\"\n",
+      "stdout": "Error: The word 'because' is reserved in Liminate — it's used as a connective and can't be used as a field name.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: an unterminated because",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nforbid n is above 1 because \"never closed\n",
+      "stdout": "Error: I see an opening quote mark but no closing one on this line. Each quoted phrase needs both opening and closing marks.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a sentence that is not a statement",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nthe quick brown fox\nforbid n is above 1 because \"after the noise\"\n",
+      "stdout": "Error: I didn't expect 'the' at the start of an operation.\nError: Prohibition violated: n is above 1. n is 5.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: an unknown comparison word",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nforbid n is around 5 because \"not a comparison\"\n",
+      "stdout": "Error: I didn't expect '5' here.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 1,
+      "id": "error: a number written as text compared by order",
+      "outcome": "error",
+      "program": "remember a number called n with 5\nforbid n is above \"3\" because \"quoted number\"\n",
+      "stdout": "Error: 'above' requires numbers or dates, but '3' is text.\n"
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "cuecue: nothing crossed",
+      "outcome": "pass",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 0.0\nremember a number called flashes-in-worst-second with 0\nremember a number called dead-picture-seconds with 0.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [],
+      "exit": 0,
+      "id": "cuecue: boundaries exactly at the limits pass",
+      "outcome": "pass",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 3.0\nremember a number called flashes-in-worst-second with 3\nremember a number called dead-picture-seconds with 10.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": ""
+    },
+    {
+      "crossed": [
+        {
+          "because": "a phone number spoken in a public cue",
+          "condition": "phone-numbers is above 0",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: a phone number",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 1\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 0.0\nremember a number called flashes-in-worst-second with 0\nremember a number called dead-picture-seconds with 0.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: phone-numbers is above 0. phone-numbers is 1.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "an email address spoken in a public cue",
+          "condition": "email-addresses is above 0",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: an email address",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 1\nremember a number called loud-seconds with 0.0\nremember a number called flashes-in-worst-second with 0\nremember a number called dead-picture-seconds with 0.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: email-addresses is above 0. email-addresses is 1.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "sustained volume past the floor",
+          "condition": "loud-seconds is above 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: sustained volume",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 3.1\nremember a number called flashes-in-worst-second with 0\nremember a number called dead-picture-seconds with 0.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: loud-seconds is above 3. loud-seconds is 3.1.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "more than three flashes in one second (WCAG 2.3.1)",
+          "condition": "flashes-in-worst-second is above 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: four flashes in a second",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 0.0\nremember a number called flashes-in-worst-second with 4\nremember a number called dead-picture-seconds with 0.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: flashes-in-worst-second is above 3. flashes-in-worst-second is 4.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "more than ten seconds of black or frozen picture",
+          "condition": "dead-picture-seconds is above 10",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: dead picture past ten seconds",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 0.0\nremember a number called flashes-in-worst-second with 0\nremember a number called dead-picture-seconds with 10.1\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: dead-picture-seconds is above 10. dead-picture-seconds is 10.1.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "sustained volume past the floor",
+          "condition": "loud-seconds is above 3",
+          "verb": "forbid"
+        },
+        {
+          "because": "more than three flashes in one second (WCAG 2.3.1)",
+          "condition": "flashes-in-worst-second is above 3",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: three and four crossed together",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 0\nremember a number called email-addresses with 0\nremember a number called loud-seconds with 3.1\nremember a number called flashes-in-worst-second with 4\nremember a number called dead-picture-seconds with 0.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: loud-seconds is above 3. loud-seconds is 3.1.\nError: Prohibition violated: flashes-in-worst-second is above 3. flashes-in-worst-second is 4.\n"
+    },
+    {
+      "crossed": [
+        {
+          "because": "a phone number spoken in a public cue",
+          "condition": "phone-numbers is above 0",
+          "verb": "forbid"
+        },
+        {
+          "because": "an email address spoken in a public cue",
+          "condition": "email-addresses is above 0",
+          "verb": "forbid"
+        },
+        {
+          "because": "sustained volume past the floor",
+          "condition": "loud-seconds is above 3",
+          "verb": "forbid"
+        },
+        {
+          "because": "more than three flashes in one second (WCAG 2.3.1)",
+          "condition": "flashes-in-worst-second is above 3",
+          "verb": "forbid"
+        },
+        {
+          "because": "more than ten seconds of black or frozen picture",
+          "condition": "dead-picture-seconds is above 10",
+          "verb": "forbid"
+        }
+      ],
+      "exit": 1,
+      "id": "cuecue: every rule crossed",
+      "outcome": "crossed",
+      "program": "about \"cuecue-floor-v1\"\nremember a number called phone-numbers with 2\nremember a number called email-addresses with 1\nremember a number called loud-seconds with 9.5\nremember a number called flashes-in-worst-second with 7\nremember a number called dead-picture-seconds with 30.0\nforbid phone-numbers is above 0 because \"a phone number spoken in a public cue\"\nforbid email-addresses is above 0 because \"an email address spoken in a public cue\"\nforbid loud-seconds is above 3 because \"sustained volume past the floor\"\nforbid flashes-in-worst-second is above 3 because \"more than three flashes in one second (WCAG 2.3.1)\"\nforbid dead-picture-seconds is above 10 because \"more than ten seconds of black or frozen picture\"\n",
+      "stdout": "Error: Prohibition violated: phone-numbers is above 0. phone-numbers is 2.\nError: Prohibition violated: email-addresses is above 0. email-addresses is 1.\nError: Prohibition violated: loud-seconds is above 3. loud-seconds is 9.5.\nError: Prohibition violated: flashes-in-worst-second is above 3. flashes-in-worst-second is 7.\nError: Prohibition violated: dead-picture-seconds is above 10. dead-picture-seconds is 30.\n"
+    }
+  ],
+  "generator": "scripts/gen_agreement_corpus.py",
+  "language_version": "0.18.4",
+  "surface": "about, comments, remember number|text|truth, forbid|require|permit [unless] because"
+}
diff --git a/tests/fixtures/agreement_corpus.txt b/tests/fixtures/agreement_corpus.txt
new file mode 100644
index 0000000..607c573
--- /dev/null
+++ b/tests/fixtures/agreement_corpus.txt
@@ -0,0 +1,421 @@
+## Liminate agreement corpus.
+##
+## The subset: `about`, `--` comments, `remember a number|text|truth called ...`,
+## and `forbid|require|permit <condition> [unless <condition>] because "..."`.
+## Every program here is run through the reference interpreter by
+## scripts/gen_agreement_corpus.py; what it did is written to
+## tests/fixtures/agreement-<version>.json, and the TypeScript and Swift
+## evaluators must reproduce it exactly. Nothing outside the subset belongs here:
+## a port rejects those on purpose, and the reference would accept them.
+##
+## Mixed `and` / `or` in one condition is out of the subset for the same reason:
+## the reference stops to ask which way to read it (an amber outcome), and an
+## agreement that depends on that reading is not one a floor should rest on.
+##
+
+# number is: crosses
+remember a number called n with 5
+forbid n is 5 because "equals five"
+
+# number is: does not cross
+remember a number called n with 5
+forbid n is 4 because "equals four"
+
+# number above: crosses
+remember a number called n with 5
+forbid n is above 4 because "rule above"
+
+# number above: does not cross
+remember a number called n with 5
+forbid n is above 5 because "rule above"
+
+# number below: crosses
+remember a number called n with 5
+forbid n is below 6 because "rule below"
+
+# number below: does not cross
+remember a number called n with 5
+forbid n is below 5 because "rule below"
+
+# number equal to: crosses
+remember a number called n with 5
+forbid n is equal to 5 because "rule equal to"
+
+# number equal to: does not cross
+remember a number called n with 5
+forbid n is equal to 4 because "rule equal to"
+
+# number not above: crosses
+remember a number called n with 5
+forbid n is not above 5 because "rule not above"
+
+# number not above: does not cross
+remember a number called n with 5
+forbid n is not above 4 because "rule not above"
+
+# number not below: crosses
+remember a number called n with 5
+forbid n is not below 5 because "rule not below"
+
+# number not below: does not cross
+remember a number called n with 5
+forbid n is not below 6 because "rule not below"
+
+# number not equal to: crosses
+remember a number called n with 5
+forbid n is not equal to 4 because "rule not equal to"
+
+# number not equal to: does not cross
+remember a number called n with 5
+forbid n is not equal to 5 because "rule not equal to"
+
+# boundary: equal to the limit is not above it
+remember a number called n with 3.0
+forbid n is above 3 because "limit"
+
+# boundary: just past the limit is above it
+remember a number called n with 3.1
+forbid n is above 3 because "limit"
+
+# boundary: zero against above zero
+remember a number called n with 0
+forbid n is above 0 because "any"
+
+# negative numbers
+remember a number called n with -5
+forbid n is below 0 because "negative"
+
+# decimals compare as numbers
+remember a number called n with 2.5
+forbid n is above 2.5 because "not past"
+forbid n is not below 2.5 because "at or past"
+
+# integer and decimal are equal
+remember a number called n with 3
+forbid n is equal to 3.0 because "same number"
+
+# a large number
+remember a number called n with 1000000
+forbid n is above 999999 because "large"
+
+# within: inside the tolerance
+remember a number called n with 5
+forbid n is within 1 of 4 because "near four"
+
+# within: outside the tolerance
+remember a number called n with 9
+forbid n is within 1 of 4 because "near four"
+
+# text equality: crosses
+remember a text called mood with "calm"
+forbid mood is "calm" because "calm is forbidden"
+
+# text equality: does not cross
+remember a text called mood with "calm"
+forbid mood is "angry" because "angry is forbidden"
+
+# text not equal to
+remember a text called mood with "calm"
+forbid mood is not equal to "angry" because "anything but angry"
+
+# text against a bareword
+remember a text called mood with "calm"
+forbid mood is calm because "bareword compares as text"
+
+# text with a space
+remember a text called city with "new york"
+forbid city is "new york" because "a space inside the value"
+
+# text is case sensitive
+remember a text called mood with "Calm"
+forbid mood is "calm" because "case"
+
+# truth is true: crosses
+remember a truth called flag with true
+forbid flag is true because "flag set"
+
+# truth is true: does not cross
+remember a truth called flag with false
+forbid flag is true because "flag set"
+
+# require a truth
+remember a truth called ready with false
+require ready is true because "must be ready"
+
+# require: met
+remember a number called n with 5
+require n is above 1 because "at least two"
+
+# require: unmet
+remember a number called n with 5
+require n is below 2 because "under two"
+
+# permit: never crosses
+remember a number called n with 5
+permit n is above 1 because "allowed"
+
+# permit: true condition
+remember a number called n with 5
+permit n is above 4 because "allowed"
+permit n is below 1 because "not applicable"
+
+# and: both true
+remember a number called n with 5
+forbid n is above 1 and n is below 9 because "in the band"
+
+# and: one false
+remember a number called n with 5
+forbid n is above 1 and n is below 3 because "in the band"
+
+# or: one true
+remember a number called n with 5
+forbid n is above 9 or n is below 6 because "either side"
+
+# or: both false
+remember a number called n with 5
+forbid n is above 9 or n is below 1 because "either side"
+
+# and across two facts
+remember a number called a-count with 2
+remember a number called b-count with 7
+forbid a-count is above 1 and b-count is above 6 because "both counts high"
+
+# unless: excuses the rule
+remember a number called n with 5
+forbid n is above 3 unless n is above 4 because "excused"
+
+# unless: does not excuse
+remember a number called n with 5
+forbid n is above 3 unless n is above 9 because "not excused"
+
+# require with unless
+remember a number called n with 5
+require n is below 2 unless n is above 4 because "excused"
+
+# a rule that compares two facts
+remember a number called used with 8
+remember a number called allowed with 5
+forbid used is above allowed because "over the allowance"
+
+# a fact remembered twice keeps the last value
+remember a number called n with 1
+remember a number called n with 9
+forbid n is above 5 because "last value wins"
+
+# a fact remembered after the rule is not seen by it
+remember a number called n with 1
+forbid n is above 5 because "uses what is known at this point"
+remember a number called n with 9
+
+# several rules crossing are reported in program order
+remember a number called n with 5
+forbid n is above 1 because "first"
+forbid n is below 1 because "second, does not cross"
+forbid n is above 2 because "third"
+require n is below 3 because "fourth"
+
+# no rule crossing
+remember a number called n with 5
+forbid n is above 9 because "one"
+forbid n is below 1 because "two"
+require n is above 0 because "three"
+permit n is above 0 because "four"
+
+# only a required rule is unmet
+remember a number called n with 5
+forbid n is above 9 because "fine"
+require n is below 2 because "unmet"
+
+# the same condition twice reports twice, each with its own because
+remember a number called n with 5
+forbid n is above 1 because "first reason"
+forbid n is above 1 because "second reason"
+
+# comments and blank lines are not statements
+-- A header comment.
+about "comment-case"
+
+-- another comment
+remember a number called n with 5
+
+forbid n is above 1 because "comments do not matter"
+-- a trailing comment
+
+# about alone
+about "nothing-else"
+
+# an empty-looking program of comments
+-- only a comment
+
+# because text with punctuation
+remember a number called n with 5
+forbid n is above 1 because "more than one (WCAG 2.3.1), see: the rule; it's firm"
+
+# a rule without a because
+remember a number called n with 5
+forbid n is above 1
+
+# a hyphenated and digit-bearing name
+remember a number called flashes-in-worst-second with 4
+remember a number called count2 with 1
+forbid flashes-in-worst-second is above 3 because "hyphens are fine"
+forbid count2 is above 3 because "digits are fine"
+
+# error: a fact that was never remembered
+remember a number called n with 5
+forbid missing is above 1 because "no such fact"
+
+# error: a missing fact does not hide a crossing elsewhere
+remember a number called n with 5
+forbid n is above 1 because "crosses"
+forbid missing is above 1 because "no such fact"
+
+# error: a range comparison over text
+remember a text called mood with "calm"
+forbid mood is above 3 because "text has no order"
+
+# error: with and no value
+remember a number called n with
+forbid n is above 1 because "the fact never existed"
+
+# error: a reserved word as a name
+remember a number called and with 5
+forbid and is above 1 because "reserved"
+
+# error: a rule with no condition
+remember a number called n with 5
+forbid because "nothing to test"
+
+# error: an unterminated because
+remember a number called n with 5
+forbid n is above 1 because "never closed
+
+# error: a sentence that is not a statement
+remember a number called n with 5
+the quick brown fox
+forbid n is above 1 because "after the noise"
+
+# error: an unknown comparison word
+remember a number called n with 5
+forbid n is around 5 because "not a comparison"
+
+# error: a number written as text compared by order
+remember a number called n with 5
+forbid n is above "3" because "quoted number"
+
+# cuecue: nothing crossed
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 0.0
+remember a number called flashes-in-worst-second with 0
+remember a number called dead-picture-seconds with 0.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: boundaries exactly at the limits pass
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 3.0
+remember a number called flashes-in-worst-second with 3
+remember a number called dead-picture-seconds with 10.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: a phone number
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 1
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 0.0
+remember a number called flashes-in-worst-second with 0
+remember a number called dead-picture-seconds with 0.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: an email address
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 1
+remember a number called loud-seconds with 0.0
+remember a number called flashes-in-worst-second with 0
+remember a number called dead-picture-seconds with 0.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: sustained volume
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 3.1
+remember a number called flashes-in-worst-second with 0
+remember a number called dead-picture-seconds with 0.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: four flashes in a second
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 0.0
+remember a number called flashes-in-worst-second with 4
+remember a number called dead-picture-seconds with 0.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: dead picture past ten seconds
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 0.0
+remember a number called flashes-in-worst-second with 0
+remember a number called dead-picture-seconds with 10.1
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: three and four crossed together
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 0
+remember a number called email-addresses with 0
+remember a number called loud-seconds with 3.1
+remember a number called flashes-in-worst-second with 4
+remember a number called dead-picture-seconds with 0.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
+
+# cuecue: every rule crossed
+about "cuecue-floor-v1"
+remember a number called phone-numbers with 2
+remember a number called email-addresses with 1
+remember a number called loud-seconds with 9.5
+remember a number called flashes-in-worst-second with 7
+remember a number called dead-picture-seconds with 30.0
+forbid phone-numbers is above 0 because "a phone number spoken in a public cue"
+forbid email-addresses is above 0 because "an email address spoken in a public cue"
+forbid loud-seconds is above 3 because "sustained volume past the floor"
+forbid flashes-in-worst-second is above 3 because "more than three flashes in one second (WCAG 2.3.1)"
+forbid dead-picture-seconds is above 10 because "more than ten seconds of black or frozen picture"
diff --git a/tests/test_agreement_corpus.py b/tests/test_agreement_corpus.py
new file mode 100644
index 0000000..387ebdf
--- /dev/null
+++ b/tests/test_agreement_corpus.py
@@ -0,0 +1,79 @@
+"""The agreement test set is generated, never typed.
+
+`tests/fixtures/agreement-<version>.json` is what the reference interpreter did
+with each program in `agreement_corpus.txt`. The TypeScript and Swift
+evaluators are held to that file, so a stale or hand-edited copy would let them
+agree with something the reference never said. These tests regenerate it and
+diff.
+"""
+
+from __future__ import annotations
+
+import json
+import subprocess
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+GENERATOR = ROOT / "scripts" / "gen_agreement_corpus.py"
+CORPUS = ROOT / "tests" / "fixtures" / "agreement_corpus.txt"
+
+
+def _version() -> str:
+    for line in (ROOT / "pyproject.toml").read_text(encoding="utf-8").splitlines():
+        if line.startswith("version"):
+            return line.split("=", 1)[1].strip().strip('"')
+    raise AssertionError("pyproject.toml states no version")
+
+
+def _committed() -> dict:
+    path = ROOT / "tests" / "fixtures" / f"agreement-{_version()}.json"
+    assert path.exists(), f"{path.name} is missing: run {GENERATOR.name} > {path}"
+    return json.loads(path.read_text(encoding="utf-8"))
+
+
+def _regenerated() -> dict:
+    done = subprocess.run(
+        [sys.executable, str(GENERATOR)], capture_output=True, text=True, check=True
+    )
+    return json.loads(done.stdout)
+
+
+def test_the_committed_file_is_what_the_reference_produces_now():
+    assert _regenerated() == _committed()
+
+
+def test_the_corpus_is_large_enough_to_mean_something():
+    assert len(_committed()["cases"]) >= 60
+
+
+def test_it_covers_every_outcome_and_every_verb():
+    cases = _committed()["cases"]
+    assert {c["outcome"] for c in cases} == {"pass", "crossed", "error"}
+    verbs = {x["verb"] for c in cases for x in c["crossed"]}
+    assert verbs == {"forbid", "require"}
+    programs = "\n".join(c["program"] for c in cases)
+    for word in ("permit", "unless", "within", " and ", " or ", "about"):
+        assert word in programs, f"no case exercises {word.strip()!r}"
+
+
+def test_an_error_never_carries_crossed_rules():
+    for case in _committed()["cases"]:
+        if case["outcome"] == "error":
+            assert case["crossed"] == [], case["id"]
+        if case["outcome"] == "pass":
+            assert case["exit"] == 0, case["id"]
+
+
+def test_case_ids_are_unique():
+    ids = [c["id"] for c in _committed()["cases"]]
+    assert len(ids) == len(set(ids))
+
+
+def test_every_case_is_in_the_corpus_file():
+    names = {
+        ln[2:].strip()
+        for ln in CORPUS.read_text(encoding="utf-8").splitlines()
+        if ln.startswith("# ")
+    }
+    assert {c["id"] for c in _committed()["cases"]} == names