diff --git a/devel/qt6-tools/Makefile b/devel/qt6-tools/Makefile
index f698e7729c97..63b3deb3d8df 100644
--- a/devel/qt6-tools/Makefile
+++ b/devel/qt6-tools/Makefile
@@ -1,30 +1,38 @@
 PORTNAME=	tools
 DISTVERSION=	${QT6_VERSION}
 CATEGORIES=	devel
 PKGNAMEPREFIX=	qt6-
 
 MAINTAINER=	kde@FreeBSD.org
 COMMENT=	Qt declarative framework for dynamic user interfaces
 
 BUILD_DEPENDS=	${LOCALBASE}/include/vulkan/vulkan.h:graphics/vulkan-headers
 LIB_DEPENDS=	libxkbcommon.so:x11/libxkbcommon \
 		libzstd.so:archivers/zstd
 
-USES=		cmake compiler:c++17-lang gl llvm:min=17,lib,noexport python:build \
-		qt-dist:6
+USES=		cmake compiler:c++17-lang gl llvm:min=17,max=20,lib,noexport \
+		python:build qt-dist:6
 USE_GL=		opengl
 USE_LDCONFIG=	${PREFIX}/${QT_LIBDIR_REL}
 USE_QT=		base declarative sqldriver-sqlite:run
 
-CMAKE_ARGS+=	-DClang_DIR:PATH="${LLVM_PREFIX}/lib/cmake/clang" \
-		-DLLVM_DIR:PATH="${LLVM_PREFIX}/lib/cmake/llvm"
+# QDOC_USER_CLANG_VERSION is an unofficial CMake variable intended to override
+# the list of supported LLVM versions, i.e., QDOC_SUPPORTED_CLANG_VERSIONS in
+# .cmake.conf with the chosen version of LLVM. We must be careful here and adjust
+# llvm min/max in USES to align with the versions of LLVM that future releases
+# support. LLVM_VERSION only provides the major version, but at least the minor
+# version must also be passed, hence the use of "black magic" to determine this
+# value, which does not respect relative paths.
+CMAKE_ARGS=	-DClang_DIR:PATH="${LLVM_PREFIX}/lib/cmake/clang" \
+		-DLLVM_DIR:PATH="${LLVM_PREFIX}/lib/cmake/llvm" \
+		-DQDOC_USER_CLANG_VERSION:STRING="`${MAKE} -C ${PORTSDIR}/devel/llvm${LLVM_VERSION} -VDISTVERSION:R`"
 
 post-install:
 # Install symlinks for user-facing tools
 	while read line; do \
 		source="$$(${ECHO_CMD} $${line} | ${AWK} '{print $$1}')"; \
 		target="${STAGEDIR}${PREFIX}/$$(${ECHO_CMD} $${line} | ${AWK} '{print $$2}')"; \
 		${RLN} $${source} $${target}; \
 	done <${BUILD_WRKSRC}/user_facing_tool_links.txt
 
 .include <bsd.port.mk>
diff --git a/devel/qt6-tools/files/patch-.cmake.conf b/devel/qt6-tools/files/patch-.cmake.conf
new file mode 100644
index 000000000000..ec629a036b7e
--- /dev/null
+++ b/devel/qt6-tools/files/patch-.cmake.conf
@@ -0,0 +1,19 @@
+Supply the version of LLVM we are intending to use via QDOC_USER_CLANG_VERSION,
+a made-up CMake varible derived from LLVM_VERSION in the port Makefile, instead
+of iterating through potential candidates. This avoids mismatches during the
+configure stage when a user has a version of LLVM installed greater than what is
+set in DEFAULT_VERSIONS.
+
+PR: 287430
+
+--- .cmake.conf.orig	2025-05-29 00:19:42 UTC
++++ .cmake.conf
+@@ -3,7 +3,7 @@ set(QDOC_SUPPORTED_CLANG_VERSIONS
+ set(QT_EXTRA_INTERNAL_TARGET_DEFINES "QT_NO_AS_CONST=1")
+ set(QDOC_MINIMUM_CLANG_VERSION "17")
+ set(QDOC_SUPPORTED_CLANG_VERSIONS
+-    "20.1" "19.1" "18.1" "17.0"
++    ${QDOC_USER_CLANG_VERSION}
+ )
+ list(APPEND QT_EXTRA_INTERNAL_TARGET_DEFINES "QT_NO_FOREACH=1")
+ list(APPEND QT_EXTRA_INTERNAL_TARGET_DEFINES "QT_NO_CONTEXTLESS_CONNECT=1")