diff --git a/grub/cli.py b/grub/cli.py
index c39affd..a951a83 100644
--- a/grub/cli.py
+++ b/grub/cli.py
@@ -13,7 +13,7 @@
 
 import sys
 
-import argh
+import cw
 
 from grub.searcher import Searcher
 
@@ -88,9 +88,13 @@ def _repl(searcher: Searcher, *, snippets: bool) -> None:
 
 
 def main(argv=None) -> int:
-    """Entry point for the ``grub`` console script."""
-    argh.dispatch_command(run, argv=argv)
-    return 0
+    """Entry point for the ``grub`` console script; returns its exit code.
+
+    ``argv`` defaults to ``sys.argv[1:]``. :func:`cw.dispatch` takes it positionally and
+    reproduces the grammar this CLI has always had -- pinned by ``misc/cli_golden_py*.json``
+    and asserted by ``tests/test_cli_parity.py``.
+    """
+    return cw.dispatch(run, argv)
 
 
 if __name__ == "__main__":  # pragma: no cover
diff --git a/misc/README.md b/misc/README.md
new file mode 100644
index 0000000..b37247e
--- /dev/null
+++ b/misc/README.md
@@ -0,0 +1,51 @@
+# `misc/` — the CLI parity harness
+
+`grub`'s command line is **pinned**. `cli_cases.txt` is a corpus of argv vectors;
+`cli_golden_py<major><minor>.json` records what each one does — exit code, stdout,
+stderr, the normalised `usage:` line, and the full `--help` body. `tests/test_cli_parity.py`
+replays the golden matching the running interpreter on every test run.
+
+The goldens were recorded from the **argh-based** CLI, before the migration to
+[`cw`](https://pypi.org/project/cw/) and before any source edit. That is what makes them
+evidence rather than decoration: they describe a command line nobody had yet had the
+chance to change.
+
+## When the parity test goes red
+
+**Read the diff before touching anything.** It tells you which of three things happened.
+
+1. **You changed the CLI on purpose** — added a command, renamed a flag, reworded a
+   message. Re-record (below) and put the diff in the pull request.
+2. **A dependency moved.** The only byte in the golden that a dependency can
+   legitimately move is a `[0.437]` similarity score, which comes from scikit-learn's
+   `TfidfVectorizer`. A diff confined to the bracketed numbers is a scikit-learn change;
+   re-record. A diff anywhere else is not.
+3. **You changed the CLI by accident.** This is what the test is for. Fix the code, not
+   the golden.
+
+## Re-recording
+
+One golden per Python version in `[tool.wads.ci.testing]`, each recorded on its own
+interpreter, from the repo root:
+
+```bash
+python3.12 -m cw.testing characterize grub --cases misc/cli_cases.txt \
+    -o misc/cli_golden_py312.json
+```
+
+`argparse` is part of the standard library and rewrites its own text between CPython
+versions, which is why one golden cannot cover the matrix. Adding a version to CI means
+recording a golden for it; the test fails loudly, with instructions, rather than skipping
+when one is missing.
+
+## Adding a case
+
+Anything a user can type belongs here. Four rules, all learned the hard way:
+
+- **No case may print an absolute path.** The golden is committed and has to replay on
+  someone else's machine. In particular, no case whose failure escapes as an uncaught
+  traceback — the traceback names every frame's file.
+- **No case may write to the filesystem or reach the network.**
+- **No case may need an optional extra**, so the corpus replays on a bare install.
+- **Prefer output that a dependency upgrade cannot move.** `-n 1` on a search keeps the
+  assertion to a single score rather than four.
diff --git a/misc/cli_cases.txt b/misc/cli_cases.txt
new file mode 100644
index 0000000..761e22c
--- /dev/null
+++ b/misc/cli_cases.txt
@@ -0,0 +1,59 @@
+# grub CLI characterization corpus. Replayed by tests/test_cli_parity.py;
+# re-recording procedure is in misc/README.md.
+#
+# Recorded from the argh-based CLI *before* the migration to cw, and replayed after, so a
+# dispatcher swap that changes anything a shell can see fails loudly.
+#
+# Rules for adding a case:
+#   * paths are relative to the repo root (characterize/replay run with cwd=repo root);
+#   * no case may print an absolute path -- the golden is committed and must replay on
+#     someone else's machine. That rules out any case whose failure escapes as an
+#     uncaught traceback: `grub SRC Q --extensions .md` over a .txt-only corpus raises
+#     `ValueError: empty vocabulary` out of scikit-learn, and the traceback names every
+#     frame's file. (It also names the dispatcher's own frames, so it could never have
+#     replayed across this migration anyway.)
+#   * no case may write to the filesystem or reach the network;
+#   * no case may need the optional `semantic` extra (sentence-transformers).
+
+# -- tier 3: the whole surface. grub is one command, so this is all of its grammar --
+--help
+
+# -- tier 1: the headline behaviour. With no query, grub drops into an interactive
+#    prompt; recorded with stdin closed, so it prints the banner and one prompt and
+#    exits 0 on EOF. This case is why cw.testing had to pin stdin (i2mint/cw#34):
+#    inheriting the recorder's made it record a timeout at a terminal and an EOF in CI.
+tests/fixtures/corpus
+
+# -- tier 1: a search. `-n 1` keeps the output to a single result line, so exactly one
+#    similarity score is asserted.
+#
+#    NOTE: that score comes from scikit-learn's TfidfVectorizer, and is the only byte in
+#    this golden a dependency upgrade could legitimately move. A diff confined to the
+#    bracketed number is a scikit-learn change -- re-record. A diff anywhere else is a
+#    CLI change; read it before you re-record anything.
+tests/fixtures/corpus "musical instrument" -n 1
+tests/fixtures/corpus "musical instrument" --snippets -n 1
+tests/fixtures/corpus "hot drink" --method tfidf -n 1
+tests/fixtures/corpus "hot drink" -m tfidf -n 1
+
+# -- tier 1: a multi-word query as separate argv items, which is what *query catches --
+tests/fixtures/corpus python programming language -n 1
+
+# -- tier 1: flags that reach the Searcher's constructor rather than its search --
+tests/fixtures/corpus "musical instrument" --extensions .txt -n 1
+tests/fixtures/corpus "musical instrument" -e .txt -n 1
+tests/fixtures/corpus "musical instrument" --chunk 40 -n 2
+tests/fixtures/corpus "musical instrument" -c 40 -n 2
+
+# -- tier 1: --n is the long spelling argh derives for a one-character parameter --
+tests/fixtures/corpus "musical instrument" --n 1
+
+# -- tier 1: the error path grub handles itself. Exits 1, not argparse's 2 --
+./no/such/place query
+
+# -- tier 1: usage errors. These must keep argparse's exit code 2 --
+[]
+--nosuchflag
+-n notanint
+--n notanint
+--method
diff --git a/misc/cli_golden_py310.json b/misc/cli_golden_py310.json
new file mode 100644
index 0000000..f566530
--- /dev/null
+++ b/misc/cli_golden_py310.json
@@ -0,0 +1,249 @@
+{
+  "cases": [
+    {
+      "argv": [
+        "--help"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\n\nSearch ``source``; with no query, drop into an interactive prompt.\n\n:param source: folder, glob, ``dir/{}.ext`` format, module path, or URL.\n:param query: the search query (omit for an interactive session).\n:param method: ``tfidf``, ``semantic``, or ``hybrid``.\n:param n: number of results to show.\n:param snippets: also show the matching snippet for each result.\n:param semantic: shortcut for ``--method semantic``.\n:param hybrid: shortcut for ``--method hybrid``.\n:param chunk: split documents into windows of this many characters.\n:param extensions: comma-separated file extensions to restrict to,\n    e.g. ``.py,.md``.\n\npositional arguments:\n  source                -\n  query                 -\n\noptions:\n  -h, --help            show this help message and exit\n  -m METHOD, --method METHOD\n                        'tfidf'\n  -n N, --n N           10\n  --snippets            False\n  --semantic            False\n  --hybrid              False\n  -c CHUNK, --chunk CHUNK\n                        0\n  -e EXTENSIONS, --extensions EXTENSIONS\n                        ''\n",
+      "tier": 3,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...]"
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "<Searcher: tfidf index over 4 documents>  --  type a query (blank line or Ctrl-D to quit)\ngrub> \n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--snippets",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n      A guitar is a musical instrument with six strings played by hand.\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "hot drink",
+        "--method",
+        "tfidf",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'hot drink':\n   1. [0.414] coffee.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "hot drink",
+        "-m",
+        "tfidf",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'hot drink':\n   1. [0.414] coffee.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "python",
+        "programming",
+        "language",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'python programming language':\n   1. [0.557] python.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--extensions",
+        ".txt",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "-e",
+        ".txt",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--chunk",
+        "40",
+        "-n",
+        "2"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "2 results for 'musical instrument':\n   1. [0.530] guitar.txt#0\n   2. [0.000] coffee.txt#0\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "-c",
+        "40",
+        "-n",
+        "2"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "2 results for 'musical instrument':\n   1. [0.530] guitar.txt#0\n   2. [0.000] coffee.txt#0\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "./no/such/place",
+        "query"
+      ],
+      "returncode": 1,
+      "stderr": "grub: No such file, folder, or glob: './no/such/place'. Pass an existing path, a glob like 'docs/*.md', a 'dir/{}.py' format, a module, or a dict.\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: the following arguments are required: source, query\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: the following arguments are required: source, query"
+    },
+    {
+      "argv": [
+        "--nosuchflag"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: the following arguments are required: source, query\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: the following arguments are required: source, query"
+    },
+    {
+      "argv": [
+        "-n",
+        "notanint"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: argument -n/--n: invalid int value: 'notanint'\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: argument -n/--n: invalid int value: 'notanint'"
+    },
+    {
+      "argv": [
+        "--n",
+        "notanint"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: argument -n/--n: invalid int value: 'notanint'\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: argument -n/--n: invalid int value: 'notanint'"
+    },
+    {
+      "argv": [
+        "--method"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: argument -m/--method: expected one argument\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: argument -m/--method: expected one argument"
+    }
+  ],
+  "cw_golden": 1,
+  "env": {
+    "COLUMNS": "100",
+    "NO_COLOR": "1",
+    "PYTHONHASHSEED": "0",
+    "PYTHONIOENCODING": "utf-8",
+    "PYTHONUTF8": "1",
+    "TERM": "dumb"
+  },
+  "newlines": "lf",
+  "note": "argh 0.31.3, grub 6956353, pre-cw-migration, CPython 3.10",
+  "prog": [
+    "grub"
+  ],
+  "recorded_with": {
+    "implementation": "CPython",
+    "platform": "Darwin",
+    "python": "3.10.13"
+  }
+}
diff --git a/misc/cli_golden_py312.json b/misc/cli_golden_py312.json
new file mode 100644
index 0000000..466b2cb
--- /dev/null
+++ b/misc/cli_golden_py312.json
@@ -0,0 +1,249 @@
+{
+  "cases": [
+    {
+      "argv": [
+        "--help"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\n\nSearch ``source``; with no query, drop into an interactive prompt.\n\n:param source: folder, glob, ``dir/{}.ext`` format, module path, or URL.\n:param query: the search query (omit for an interactive session).\n:param method: ``tfidf``, ``semantic``, or ``hybrid``.\n:param n: number of results to show.\n:param snippets: also show the matching snippet for each result.\n:param semantic: shortcut for ``--method semantic``.\n:param hybrid: shortcut for ``--method hybrid``.\n:param chunk: split documents into windows of this many characters.\n:param extensions: comma-separated file extensions to restrict to,\n    e.g. ``.py,.md``.\n\npositional arguments:\n  source                -\n  query                 -\n\noptions:\n  -h, --help            show this help message and exit\n  -m METHOD, --method METHOD\n                        'tfidf'\n  -n N, --n N           10\n  --snippets            False\n  --semantic            False\n  --hybrid              False\n  -c CHUNK, --chunk CHUNK\n                        0\n  -e EXTENSIONS, --extensions EXTENSIONS\n                        ''\n",
+      "tier": 3,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...]"
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "<Searcher: tfidf index over 4 documents>  --  type a query (blank line or Ctrl-D to quit)\ngrub> \n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--snippets",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n      A guitar is a musical instrument with six strings played by hand.\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "hot drink",
+        "--method",
+        "tfidf",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'hot drink':\n   1. [0.414] coffee.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "hot drink",
+        "-m",
+        "tfidf",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'hot drink':\n   1. [0.414] coffee.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "python",
+        "programming",
+        "language",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'python programming language':\n   1. [0.557] python.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--extensions",
+        ".txt",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "-e",
+        ".txt",
+        "-n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--chunk",
+        "40",
+        "-n",
+        "2"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "2 results for 'musical instrument':\n   1. [0.530] guitar.txt#0\n   2. [0.000] coffee.txt#0\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "-c",
+        "40",
+        "-n",
+        "2"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "2 results for 'musical instrument':\n   1. [0.530] guitar.txt#0\n   2. [0.000] coffee.txt#0\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "tests/fixtures/corpus",
+        "musical instrument",
+        "--n",
+        "1"
+      ],
+      "returncode": 0,
+      "stderr": "",
+      "stdout": "1 results for 'musical instrument':\n   1. [0.437] guitar.txt\n",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [
+        "./no/such/place",
+        "query"
+      ],
+      "returncode": 1,
+      "stderr": "grub: No such file, folder, or glob: './no/such/place'. Pass an existing path, a glob like 'docs/*.md', a 'dir/{}.py' format, a module, or a dict.\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": ""
+    },
+    {
+      "argv": [],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: the following arguments are required: source\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: the following arguments are required: source"
+    },
+    {
+      "argv": [
+        "--nosuchflag"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: the following arguments are required: source\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: the following arguments are required: source"
+    },
+    {
+      "argv": [
+        "-n",
+        "notanint"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: argument -n/--n: invalid int value: 'notanint'\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: argument -n/--n: invalid int value: 'notanint'"
+    },
+    {
+      "argv": [
+        "--n",
+        "notanint"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: argument -n/--n: invalid int value: 'notanint'\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: argument -n/--n: invalid int value: 'notanint'"
+    },
+    {
+      "argv": [
+        "--method"
+      ],
+      "returncode": 2,
+      "stderr": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK]\n            [-e EXTENSIONS]\n            source [query ...]\ngrub: error: argument -m/--method: expected one argument\n",
+      "stdout": "",
+      "tier": 1,
+      "usage": "usage: grub [-h] [-m METHOD] [-n N] [--snippets] [--semantic] [--hybrid] [-c CHUNK] [-e EXTENSIONS] source [query ...] grub: error: argument -m/--method: expected one argument"
+    }
+  ],
+  "cw_golden": 1,
+  "env": {
+    "COLUMNS": "100",
+    "NO_COLOR": "1",
+    "PYTHONHASHSEED": "0",
+    "PYTHONIOENCODING": "utf-8",
+    "PYTHONUTF8": "1",
+    "TERM": "dumb"
+  },
+  "newlines": "lf",
+  "note": "argh 0.31.3, grub b69fd73, pre-cw-migration, CPython 3.12",
+  "prog": [
+    "grub"
+  ],
+  "recorded_with": {
+    "implementation": "CPython",
+    "platform": "Darwin",
+    "python": "3.12.12"
+  }
+}
diff --git a/pyproject.toml b/pyproject.toml
index fab42e5..b8061ea 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,7 +23,7 @@ dependencies = [
     "py2store",
     "scikit-learn",
     "numpy",
-    "argh",
+    "cw>=0.1.1,<0.2",
 ]
 
 [project.license]
diff --git a/tests/fixtures/corpus/coffee.txt b/tests/fixtures/corpus/coffee.txt
new file mode 100644
index 0000000..b9a5f83
--- /dev/null
+++ b/tests/fixtures/corpus/coffee.txt
@@ -0,0 +1 @@
+Coffee is a hot drink brewed from roasted ground coffee beans.
diff --git a/tests/fixtures/corpus/garden.txt b/tests/fixtures/corpus/garden.txt
new file mode 100644
index 0000000..9df9557
--- /dev/null
+++ b/tests/fixtures/corpus/garden.txt
@@ -0,0 +1 @@
+A garden grows vegetables flowers and herbs in rich healthy soil.
diff --git a/tests/fixtures/corpus/guitar.txt b/tests/fixtures/corpus/guitar.txt
new file mode 100644
index 0000000..dcbab83
--- /dev/null
+++ b/tests/fixtures/corpus/guitar.txt
@@ -0,0 +1 @@
+A guitar is a musical instrument with six strings played by hand.
diff --git a/tests/fixtures/corpus/python.txt b/tests/fixtures/corpus/python.txt
new file mode 100644
index 0000000..a84feae
--- /dev/null
+++ b/tests/fixtures/corpus/python.txt
@@ -0,0 +1 @@
+Python is a popular high level programming language for general use.
diff --git a/tests/test_cli_parity.py b/tests/test_cli_parity.py
new file mode 100644
index 0000000..6acb840
--- /dev/null
+++ b/tests/test_cli_parity.py
@@ -0,0 +1,68 @@
+"""Assert grub's command line has not moved since it was recorded.
+
+``misc/cli_golden_py3XX.json`` were recorded from the **argh-based** CLI, before the
+migration to ``cw`` and before any source edit; ``misc/cli_cases.txt`` is the corpus they
+were recorded from, and ``misc/README.md`` explains how to read a red result and how to
+re-record. This test replays them against whatever dispatcher is installed now, so neither
+a refactor here nor a new ``cw`` release can change what a shell sees without a test going
+red.
+
+Every case's exit code, stdout, stderr and normalised ``usage:`` line is asserted, and so is
+the full ``--help`` body (``strict_help``). Nothing is advisory.
+
+One golden per CPython minor version, because ``argparse`` is stdlib and rewrites its own
+text between versions: 3.12 stopped listing ``nargs='*'`` positionals among "the following
+arguments are required", which is the only difference between the 3.10 and 3.12 recordings
+and predates this repo's migration. An unrecorded version fails loudly rather than skipping
+-- a parity test that quietly does nothing is worse than no parity test.
+"""
+
+import shutil
+import sys
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+GOLDEN_DIR = REPO_ROOT / "misc"
+
+
+def _golden_for_this_python() -> Path:
+    """The golden recorded by the CPython running this test."""
+    major, minor = sys.version_info[:2]
+    path = GOLDEN_DIR / f"cli_golden_py{major}{minor}.json"
+    if path.exists():
+        return path
+    recorded = sorted(p.name for p in GOLDEN_DIR.glob("cli_golden_py*.json"))
+    pytest.fail(
+        f"no CLI golden recorded for Python {major}.{minor} (have: {', '.join(recorded)}). "
+        f"argparse's own wording differs between CPython versions, so each version in CI "
+        f"needs its own recording. See misc/README.md."
+    )
+
+
+def _console_script() -> str:
+    """The installed ``grub`` executable, however this environment lays it out."""
+    found = shutil.which("grub")
+    if found:
+        return found
+    # A venv whose bin/ is not on PATH -- common under `uv run` and tox.
+    for name in ("grub", "grub.exe"):
+        candidate = Path(sys.executable).parent / name
+        if candidate.exists():
+            return str(candidate)
+    pytest.fail(
+        "the `grub` console script is not installed, so the CLI cannot be checked. "
+        "Install the package (`pip install -e .`) before running this test."
+    )
+
+
+def test_cli_surface_is_unchanged():
+    """Every recorded argv still produces the same exit code, stdout and stderr."""
+    cw_testing = pytest.importorskip("cw.testing")
+    cw_testing.assert_replay(
+        _golden_for_this_python(),
+        prog=[_console_script()],
+        cwd=str(REPO_ROOT),
+        strict_help=True,
+    )