diff --git a/.claude/rules/plugin-system.md b/.claude/rules/plugin-system.md
index ea3c0602ab..ea0d5c7242 100644
--- a/.claude/rules/plugin-system.md
+++ b/.claude/rules/plugin-system.md
@@ -28,8 +28,8 @@ TableProPluginKit is built with Library Evolution, so an already-built plugin ke
 - The build stamps that value into `TableProPluginKitVersion` of the app and of every plugin. A plugin's `Info.plist` holds `<integer>TABLEPRO_PLUGINKIT_VERSION</integer>` and is preprocessed, because every shipped app reads the key with `as? Int`; the source file therefore fails `plutil -lint`.
 - After an additive change, built plugins keep loading, and the bump makes an older app refuse a plugin rebuilt against the new API instead of failing its load.
 - A breaking change also raises `TABLEPRO_PLUGINKIT_MINIMUM_VERSION`. Every tag ships every registry plugin built against its own kit, so the release that carries the change carries plugins in its range.
-- `scripts/check-pluginkit-abi.sh [--frozen] [base]` (`verify.sh abi [base]`) builds PluginKit at the base, by default the newest `v*` tag reachable from HEAD, and at HEAD with Xcode's ABI checker (`RUN_SWIFT_ABI_CHECKER_TOOL`). macOS Tests runs it whenever it compiles the plugins, with `--frozen` on a PR into `release/*`.
-- A checker error is a breaking change: the kit and the minimum must both be one past the base's kit, so the host refuses every plugin built before it. A baseline that changed with no error needs the kit one past the base's; an identical one needs the base's kit. `--frozen` fails on any change.
+- `scripts/check-pluginkit-abi.sh [--frozen] [base]` (`verify.sh abi [base]`) builds PluginKit at the base, by default the newest `v*` tag reachable from HEAD, and at HEAD with Xcode's ABI checker (`RUN_SWIFT_ABI_CHECKER_TOOL`). When CI runs it: `.claude/rules/ci.md`, macOS Tests.
+- A checker error is a breaking change: the kit and the minimum must both be one past the base's kit, so the host refuses every plugin built before it. A baseline that changed with no error needs the kit one past the base's and the base's minimum; an identical one needs the base's kit and minimum. `--frozen` fails on any ABI change.
 - The checker reports breakage only; an additive change shows as a changed baseline. Its errors are in the log `verify.sh abi` prints.
 - Mark a public enum `@frozen` only when its case set is closed. `PluginCapability` and the transfer structs stay non-frozen so they can grow.
 - PluginKit code with no callers stays: removing it is an ABI change.
diff --git a/.claude/skills/fix-issue/references/platform-apple.md b/.claude/skills/fix-issue/references/platform-apple.md
index 40ab83906b..d384e9155f 100644
--- a/.claude/skills/fix-issue/references/platform-apple.md
+++ b/.claude/skills/fix-issue/references/platform-apple.md
@@ -38,7 +38,7 @@ The macOS app and the iOS app, with everything they build from. Every profile ha
 | `package` | `<Package> [regex]` | `Packages/` changed and you want the whole package; `test <Suite>` already routes a package suite |
 | `ios` | `<Suite> [Suite...]`, at least one | `TableProMobile/` or a file it compiles changed |
 | `plugins` | none | anything under `Plugins/` changed. Builds `AllPlugins`, building the HANA helper first when it is missing and Go is installed |
-| `abi` | `<merge-base>` | PluginKit changed: after the commit, before the push (`.claude/rules/plugin-system.md`, ABI) |
+| `abi` | `[base]`, default the newest `v*` tag | PluginKit changed (`.claude/rules/plugin-system.md`, ABI) |
 | `lint` | AGENTS | every changed Swift file |
 | `l10n` | none | strings, or plugin or package messages, changed. Passes only when every plugin and package string is in both the macOS and iOS catalogs, and prints the `--add` command for each target that failed |
 | `docs` | `[docs-checkout]`, default `tablepro-docs` beside the main checkout | AGENTS Every change 4 applies, or a menu, shortcut, driver list or docs.tablepro.app link changed |
diff --git a/scripts/check-pluginkit-abi.sh b/scripts/check-pluginkit-abi.sh
index 70c472110d..41602eeef7 100755
--- a/scripts/check-pluginkit-abi.sh
+++ b/scripts/check-pluginkit-abi.sh
@@ -22,21 +22,20 @@ fail() {
 }
 
 kits() {
-    awk -F' *= *' -v origin="$1" '
+    awk -F' *= *' '
         $1 == "TABLEPRO_PLUGINKIT_VERSION" { kit = $2 }
         $1 == "TABLEPRO_PLUGINKIT_MINIMUM_VERSION" { minimum = $2 }
         END {
-            if (kit !~ /^[0-9]+$/ || minimum !~ /^[0-9]+$/) {
-                print "::error::no PluginKit versions in " origin
-                exit 1
-            }
+            if (kit !~ /^[0-9]+$/ || minimum !~ /^[0-9]+$/) exit 1
             print kit, minimum
         }'
 }
 
-base_kits="$(git -C "$root" show "$base:Configs/PluginKit.xcconfig" | kits "$base")"
-head_kits="$(kits HEAD < "$root/Configs/PluginKit.xcconfig")"
-read -r base_kit _ <<< "$base_kits"
+config="Configs/PluginKit.xcconfig"
+settings="TABLEPRO_PLUGINKIT_VERSION and TABLEPRO_PLUGINKIT_MINIMUM_VERSION"
+base_kits="$(git -C "$root" show "$base:$config" | kits)" || fail "$config at $base does not set $settings to integers."
+head_kits="$(kits < "$root/$config")" || fail "$config does not set $settings to integers."
+read -r base_kit base_minimum <<< "$base_kits"
 read -r head_kit head_minimum <<< "$head_kits"
 
 work="$(mktemp -d)"
@@ -86,26 +85,16 @@ else
     esac
 fi
 
-next=$((base_kit + 1))
-config="Configs/PluginKit.xcconfig"
 if [ "$frozen" -eq 1 ] && [ "$change" != unchanged ]; then
     fail "PluginKit's ABI differs from $base, and a release line never changes it."
 fi
+next=$((base_kit + 1))
 case "$change" in
-    breaking)
-        if [ "$head_kit" -ne "$next" ] || [ "$head_minimum" -ne "$next" ]; then
-            fail "Breaking change since $base: set TABLEPRO_PLUGINKIT_VERSION and TABLEPRO_PLUGINKIT_MINIMUM_VERSION to $next in $config."
-        fi
-        ;;
-    changed)
-        if [ "$head_kit" -ne "$next" ]; then
-            fail "PluginKit's ABI changed since $base: set TABLEPRO_PLUGINKIT_VERSION to $next in $config."
-        fi
-        ;;
-    unchanged)
-        if [ "$head_kit" -ne "$base_kit" ]; then
-            fail "PluginKit's ABI matches $base: TABLEPRO_PLUGINKIT_VERSION stays $base_kit in $config."
-        fi
-        ;;
+    breaking) want_kit=$next want_minimum=$next ;;
+    changed) want_kit=$next want_minimum=$base_minimum ;;
+    unchanged) want_kit=$base_kit want_minimum=$base_minimum ;;
 esac
+if [ "$head_kit" -ne "$want_kit" ] || [ "$head_minimum" -ne "$want_minimum" ]; then
+    fail "PluginKit's ABI against $base: $change. Set TABLEPRO_PLUGINKIT_VERSION to $want_kit and TABLEPRO_PLUGINKIT_MINIMUM_VERSION to $want_minimum in $config."
+fi
 echo "PluginKit ABI against $base: $change; kit $head_kit, minimum $head_minimum."
diff --git a/scripts/ci/test_check_pluginkit_abi.py b/scripts/ci/test_check_pluginkit_abi.py
new file mode 100644
index 0000000000..dc48b52600
--- /dev/null
+++ b/scripts/ci/test_check_pluginkit_abi.py
@@ -0,0 +1,192 @@
+#!/usr/bin/env python3
+
+import os
+import shutil
+import subprocess
+import tempfile
+import unittest
+from pathlib import Path
+
+SCRIPT = Path(__file__).resolve().parent.parent / "check-pluginkit-abi.sh"
+API = ["query", "fetchRows"]
+
+# Stands in for Xcode: a build writes the tree's api.txt as its ABI baseline, and the checker
+# reports each baseline line missing from api.txt as a breakage.
+XCODEBUILD = """#!/usr/bin/env bash
+set -euo pipefail
+project="" out="" baseline="" previous=""
+for arg in "$@"; do
+    [ "$previous" = -project ] && project="${arg%/TablePro.xcodeproj}"
+    case "$arg" in
+        SWIFT_ABI_GENERATION_TOOL_OUTPUT_DIR=*) out="${arg#*=}" ;;
+        SWIFT_ABI_CHECKER_BASELINE_DIR=*) baseline="${arg#*=}" ;;
+    esac
+    previous="$arg"
+done
+if [ -e "$project/build-fails" ]; then
+    echo "$project/Kit.swift:1:1: error: cannot find type 'Row' in scope"
+    exit 65
+fi
+mkdir -p "$out"
+cp "$project/api.txt" "$out/arm64-apple-macos.json"
+[ -n "$baseline" ] || exit 0
+removed="$(grep -vxFf "$project/api.txt" "$baseline/ABI/arm64-apple-macos.json" || true)"
+[ -n "$removed" ] || exit 0
+while IFS= read -r symbol; do
+    echo "$project/Kit.swift:1:1: error: ABI breakage: func $symbol has been removed"
+done <<< "$removed"
+exit 65
+"""
+
+
+class CheckPluginKitABITests(unittest.TestCase):
+    def setUp(self):
+        self.temp = tempfile.TemporaryDirectory()
+        scratch = Path(self.temp.name)
+        stubs = scratch / "bin"
+        stubs.mkdir()
+        (stubs / "xcodebuild").write_text(XCODEBUILD, encoding="utf-8")
+        (stubs / "xcodegen").write_text("#!/bin/sh\nexit 0\n", encoding="utf-8")
+        for stub in stubs.iterdir():
+            stub.chmod(0o755)
+        self.env = {key: value for key, value in os.environ.items() if not key.startswith("GIT_")}
+        self.env["PATH"] = f"{stubs}{os.pathsep}{self.env['PATH']}"
+        self.repo = scratch / "repo"
+        (self.repo / "scripts").mkdir(parents=True)
+        shutil.copy(SCRIPT, self.repo / "scripts/check-pluginkit-abi.sh")
+        self.git("-c", "init.defaultBranch=main", "init", "-q")
+        self.commit(API, 39, 19, tag="v1.0.0")
+
+    def tearDown(self):
+        self.temp.cleanup()
+
+    def git(self, *args):
+        result = subprocess.run(
+            ["git", "-c", "user.name=test", "-c", "user.email=test@example.com", "-c", "commit.gpgsign=false",
+             "-c", "tag.gpgsign=false", *args],
+            cwd=self.repo, env=self.env, check=True, capture_output=True, text=True, stdin=subprocess.DEVNULL,
+        )
+        return result.stdout.strip()
+
+    def commit(self, api, kit, minimum, tag=None, config=None):
+        (self.repo / "api.txt").write_text("".join(f"{symbol}\n" for symbol in api), encoding="utf-8")
+        if config is None:
+            config = f"TABLEPRO_PLUGINKIT_VERSION = {kit}\nTABLEPRO_PLUGINKIT_MINIMUM_VERSION = {minimum}\n"
+        (self.repo / "Configs").mkdir(exist_ok=True)
+        (self.repo / "Configs/PluginKit.xcconfig").write_text(
+            "// When to raise each: .claude/rules/plugin-system.md, ABI.\n" + config, encoding="utf-8")
+        self.git("add", "-A")
+        self.git("commit", "-q", "--allow-empty", "-m", "change")
+        if tag:
+            self.git("tag", tag)
+
+    def check(self, *args):
+        result = subprocess.run(
+            ["bash", "scripts/check-pluginkit-abi.sh", *args],
+            cwd=self.repo, env=self.env, capture_output=True, text=True, stdin=subprocess.DEVNULL,
+        )
+        return result.returncode, result.stdout + result.stderr
+
+    def assertPasses(self, expected, *args):
+        code, out = self.check(*args)
+        self.assertEqual(code, 0, out)
+        self.assertIn(expected, out)
+
+    def assertFails(self, expected, *args):
+        code, out = self.check(*args)
+        self.assertEqual(code, 1, out)
+        errors = [line for line in out.splitlines() if line.startswith("::error::")]
+        self.assertEqual(len(errors), 1, out)
+        self.assertIn(expected, errors[0])
+
+    def test_same_api_and_versions_pass(self):
+        self.commit(API, 39, 19)
+        self.assertPasses("against v1.0.0: unchanged; kit 39, minimum 19.")
+
+    def test_same_api_with_a_kit_bump_fails(self):
+        self.commit(API, 40, 19)
+        self.assertFails("against v1.0.0: unchanged. Set TABLEPRO_PLUGINKIT_VERSION to 39 and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to 19 in Configs/PluginKit.xcconfig.")
+
+    def test_same_api_with_a_lowered_minimum_fails(self):
+        self.commit(API, 39, 18)
+        self.assertFails("against v1.0.0: unchanged. Set TABLEPRO_PLUGINKIT_VERSION to 39 and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to 19")
+
+    def test_reverted_break_that_keeps_its_minimum_fails(self):
+        self.commit(["query"], 40, 40)
+        self.commit(API, 39, 40)
+        self.assertFails("against v1.0.0: unchanged. Set TABLEPRO_PLUGINKIT_VERSION to 39 and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to 19")
+
+    def test_added_api_without_a_kit_bump_fails(self):
+        self.commit(API + ["prepare"], 39, 19)
+        self.assertFails("against v1.0.0: changed. Set TABLEPRO_PLUGINKIT_VERSION to 40 and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to 19")
+
+    def test_added_api_with_a_kit_bump_passes(self):
+        self.commit(API + ["prepare"], 40, 19)
+        self.assertPasses("against v1.0.0: changed; kit 40, minimum 19.")
+
+    def test_added_api_with_a_raised_minimum_fails(self):
+        self.commit(API + ["prepare"], 40, 40)
+        self.assertFails("against v1.0.0: changed. Set TABLEPRO_PLUGINKIT_VERSION to 40 and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to 19")
+
+    def test_removed_api_with_only_a_kit_bump_fails(self):
+        self.commit(["query"], 40, 19)
+        self.assertFails("against v1.0.0: breaking. Set TABLEPRO_PLUGINKIT_VERSION to 40 and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to 40")
+        self.assertIn("error: ABI breakage: func fetchRows has been removed", self.check()[1])
+
+    def test_removed_api_with_kit_and_minimum_bumps_passes(self):
+        self.commit(["query"], 40, 40)
+        self.assertPasses("against v1.0.0: breaking; kit 40, minimum 40.")
+
+    def test_frozen_passes_with_no_change(self):
+        self.commit(API, 39, 19)
+        self.assertPasses("against v1.0.0: unchanged; kit 39, minimum 19.", "--frozen")
+
+    def test_frozen_fails_on_added_api_even_with_a_kit_bump(self):
+        self.commit(API + ["prepare"], 40, 19)
+        self.assertFails("PluginKit's ABI differs from v1.0.0, and a release line never changes it.", "--frozen")
+
+    def test_frozen_fails_on_a_minimum_change(self):
+        self.commit(API, 39, 18)
+        self.assertFails("against v1.0.0: unchanged.", "--frozen")
+
+    def test_default_base_is_the_nearest_v_tag_reachable_from_head(self):
+        self.commit(API + ["prepare"], 40, 19, tag="v1.1.0")
+        self.git("checkout", "-q", "-b", "side", "v1.0.0")
+        self.commit(API, 39, 19, tag="v9.0.0")
+        self.git("checkout", "-q", "main")
+        self.commit(API + ["prepare", "explain"], 41, 19, tag="libs-1")
+        self.assertPasses("against v1.1.0: changed; kit 41, minimum 19.")
+
+    def test_an_explicit_base_replaces_the_tag(self):
+        self.commit(API + ["prepare"], 40, 19, tag="v1.1.0")
+        self.assertPasses("against v1.1.0: unchanged; kit 40, minimum 19.")
+        self.assertPasses("against v1.0.0: changed; kit 40, minimum 19.", "v1.0.0")
+
+    def test_versions_that_are_not_integers_fail_with_a_message(self):
+        self.commit(API, 40, 19, config="TABLEPRO_PLUGINKIT_VERSION = 40 // bumped\n"
+                                        "TABLEPRO_PLUGINKIT_MINIMUM_VERSION = 19\n")
+        self.assertFails("Configs/PluginKit.xcconfig does not set TABLEPRO_PLUGINKIT_VERSION and "
+                         "TABLEPRO_PLUGINKIT_MINIMUM_VERSION to integers.")
+
+    def test_a_missing_base_version_fails_with_a_message(self):
+        self.commit(API, 39, 19, config="TABLEPRO_PLUGINKIT_VERSION = 39\n", tag="v1.1.0")
+        self.commit(API, 39, 19)
+        self.assertFails("Configs/PluginKit.xcconfig at v1.1.0 does not set")
+
+    def test_a_head_that_does_not_build_fails(self):
+        (self.repo / "build-fails").touch()
+        self.commit(API, 39, 19)
+        self.assertFails("TableProPluginKit does not build at HEAD")
+
+    def test_two_bases_are_a_usage_error(self):
+        self.assertEqual(self.check("v1.0.0", "v1.0.0")[0], 2)
+
+
+if __name__ == "__main__":
+    unittest.main()