diff --git a/src/pkgcheck/checks/prohibited_stable.py b/src/pkgcheck/checks/prohibited_stable.py
new file mode 100644
index 000000000..27e97a414
--- /dev/null
+++ b/src/pkgcheck/checks/prohibited_stable.py
@@ -0,0 +1,41 @@
+import typing
+
+from pkgcore.ebuild.misc import sort_keywords
+from snakeoil.strings import pluralism
+
+from .. import results
+from . import OptionalCheck
+
+
+class ProhibitedStableKeywords(results.VersionResult, results.Error):
+    """Package uses stable keywords prohibited by the repository."""
+
+    def __init__(self, arches, **kwargs):
+        super().__init__(**kwargs)
+        self.arches = tuple(sort_keywords(arches))
+
+    @property
+    def desc(self):
+        s = pluralism(self.arches)
+        arches = ", ".join(self.arches)
+        return f"prohibited stable keyword{s}: [ {arches} ]"
+
+
+class ProhibitedStableKeywordsCheck(OptionalCheck):
+    """Scan for packages using stable keywords prohibited by the repository."""
+
+    known_results: typing.ClassVar[frozenset] = frozenset({ProhibitedStableKeywords})
+
+    # acct-group and acct-user eclasses define KEYWORDS
+    # See https://bugs.gentoo.org/342185
+    ignored_categories: typing.ClassVar[frozenset] = frozenset({"acct-group", "acct-user"})
+
+    def feed(self, pkg):
+        if pkg.category in self.ignored_categories:
+            return
+
+        arches = {k for k in pkg.keywords if not k.startswith(("~", "-"))}
+        if not arches:
+            return
+
+        yield ProhibitedStableKeywords(arches, pkg=pkg)
diff --git a/testdata/data/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/expected.json b/testdata/data/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/expected.json
new file mode 100644
index 000000000..6b1ef9ee1
--- /dev/null
+++ b/testdata/data/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/expected.json
@@ -0,0 +1,2 @@
+{"__class__": "ProhibitedStableKeywords", "category": "ProhibitedStableKeywordsCheck", "package": "ProhibitedStableKeywords", "version": "0", "arches": ["amd64"]}
+{"__class__": "ProhibitedStableKeywords", "category": "ProhibitedStableKeywordsCheck", "package": "ProhibitedStableKeywords", "version": "1", "arches": ["x86"]}
diff --git a/testdata/data/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/fix.patch b/testdata/data/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/fix.patch
new file mode 100644
index 000000000..3e564d4cf
--- /dev/null
+++ b/testdata/data/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/fix.patch
@@ -0,0 +1,20 @@
+diff --git prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild fixed/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild
+index fc606dee..52f19ba0 100644
+--- prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild
++++ fixed/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild
+@@ -9,4 +9,4 @@ SRC_URI="https://example.com/"
+ 
+ LICENSE="MIT"
+ SLOT="0"
+-KEYWORDS="amd64"
++KEYWORDS="~amd64"
+diff --git prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild fixed/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild
+index e8774608..12e0329a 100644
+--- prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild
++++ fixed/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild
+@@ -9,4 +9,4 @@ SRC_URI="https://example.com/"
+ 
+ LICENSE="MIT"
+ SLOT="0"
+-KEYWORDS="~amd64 x86"
++KEYWORDS="~amd64 ~x86"
diff --git a/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild
new file mode 100644
index 000000000..f1afc7a96
--- /dev/null
+++ b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-0.ebuild
@@ -0,0 +1,12 @@
+# Copyright 2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+DESCRIPTION="ProhibitedStableKeywords"
+HOMEPAGE="https://example.com/"
+SRC_URI="https://example.com/"
+
+LICENSE="MIT"
+SLOT="0"
+KEYWORDS="amd64"
diff --git a/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild
new file mode 100644
index 000000000..a681ea6d0
--- /dev/null
+++ b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-1.ebuild
@@ -0,0 +1,12 @@
+# Copyright 2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+DESCRIPTION="ProhibitedStableKeywords"
+HOMEPAGE="https://example.com/"
+SRC_URI="https://example.com/"
+
+LICENSE="MIT"
+SLOT="0"
+KEYWORDS="~amd64 x86"
diff --git a/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-2.ebuild b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-2.ebuild
new file mode 100644
index 000000000..64df5d383
--- /dev/null
+++ b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-2.ebuild
@@ -0,0 +1,12 @@
+# Copyright 2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+DESCRIPTION="ProhibitedStableKeywords"
+HOMEPAGE="https://example.com/"
+SRC_URI="https://example.com/"
+
+LICENSE="MIT"
+SLOT="0"
+KEYWORDS="~amd64"
diff --git a/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-9999.ebuild b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-9999.ebuild
new file mode 100644
index 000000000..a3e5afb01
--- /dev/null
+++ b/testdata/repos/prohibited_stable/ProhibitedStableKeywordsCheck/ProhibitedStableKeywords/ProhibitedStableKeywords-9999.ebuild
@@ -0,0 +1,11 @@
+# Copyright 2026 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+DESCRIPTION="ProhibitedStableKeywords"
+HOMEPAGE="https://example.com/"
+SRC_URI="https://example.com/"
+
+LICENSE="MIT"
+SLOT="0"
diff --git a/testdata/repos/prohibited_stable/metadata/layout.conf b/testdata/repos/prohibited_stable/metadata/layout.conf
new file mode 100644
index 000000000..5ea183486
--- /dev/null
+++ b/testdata/repos/prohibited_stable/metadata/layout.conf
@@ -0,0 +1,2 @@
+masters =
+cache-formats =
diff --git a/testdata/repos/prohibited_stable/profiles/arch.list b/testdata/repos/prohibited_stable/profiles/arch.list
new file mode 100644
index 000000000..1677fa6f4
--- /dev/null
+++ b/testdata/repos/prohibited_stable/profiles/arch.list
@@ -0,0 +1,2 @@
+amd64
+x86
diff --git a/testdata/repos/prohibited_stable/profiles/categories b/testdata/repos/prohibited_stable/profiles/categories
new file mode 100644
index 000000000..515b4979c
--- /dev/null
+++ b/testdata/repos/prohibited_stable/profiles/categories
@@ -0,0 +1 @@
+ProhibitedStableKeywordsCheck
diff --git a/testdata/repos/prohibited_stable/profiles/default/amd64/make.defaults b/testdata/repos/prohibited_stable/profiles/default/amd64/make.defaults
new file mode 100644
index 000000000..b3e0df883
--- /dev/null
+++ b/testdata/repos/prohibited_stable/profiles/default/amd64/make.defaults
@@ -0,0 +1 @@
+ARCH="amd64"
diff --git a/testdata/repos/prohibited_stable/profiles/default/x86/make.defaults b/testdata/repos/prohibited_stable/profiles/default/x86/make.defaults
new file mode 100644
index 000000000..e8f156818
--- /dev/null
+++ b/testdata/repos/prohibited_stable/profiles/default/x86/make.defaults
@@ -0,0 +1 @@
+ARCH="x86"
diff --git a/testdata/repos/prohibited_stable/profiles/profiles.desc b/testdata/repos/prohibited_stable/profiles/profiles.desc
new file mode 100644
index 000000000..0f7102bcb
--- /dev/null
+++ b/testdata/repos/prohibited_stable/profiles/profiles.desc
@@ -0,0 +1,2 @@
+amd64 default/amd64 stable
+x86 default/x86 stable
diff --git a/testdata/repos/prohibited_stable/profiles/repo_name b/testdata/repos/prohibited_stable/profiles/repo_name
new file mode 100644
index 000000000..fee27daba
--- /dev/null
+++ b/testdata/repos/prohibited_stable/profiles/repo_name
@@ -0,0 +1 @@
+prohibited_stable