diff --git a/.github/scripts/check_dispatch_surface.sh b/.github/scripts/check_dispatch_surface.sh
new file mode 100755
index 000000000..f9d19a15f
--- /dev/null
+++ b/.github/scripts/check_dispatch_surface.sh
@@ -0,0 +1,111 @@
+#!/bin/bash
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Runs cmake/validate-dispatch-surface.cmake over the fixtures in
+# tests/cmake/dispatch-surface and checks each verdict.
+#
+#   valid-*.cmake    must be accepted.
+#   invalid-*.cmake  must be rejected, with a message containing the substring
+#                    given by that fixture's `# EXPECT-ERROR:` line.
+#
+# Needs nothing but cmake -- no compiler, no dependencies, no build directory.
+
+set -uo pipefail
+
+root=$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)
+fixtures="${root}/tests/cmake/dispatch-surface"
+validator="${root}/cmake/validate-dispatch-surface.cmake"
+x86_src_dir="${root}/include/svs/multi-arch/x86"
+
+if [[ ! -d ${fixtures} ]]; then
+    echo "no fixture directory: ${fixtures}" >&2
+    exit 1
+fi
+
+# The default declaration must itself be valid -- checked as its own case so that
+# a broken default is reported here rather than only at configure time.
+run_validator() {
+    cmake "-DSVS_DISPATCH_SURFACE_FILE=$1" "-DSVS_X86_SRC_DIR=${x86_src_dir}" \
+        -P "${validator}" 2>&1
+}
+
+# CMake indents and line-wraps error text, so compare against a whitespace-
+# collapsed copy of the output.
+flatten() { tr '\n' ' ' | tr -s '[:space:]' ' '; }
+
+failures=0
+checked=0
+
+check_accepted() {
+    local fixture=$1 name=$2 output status
+    output=$(run_validator "${fixture}")
+    status=$?
+    if ((status != 0)); then
+        echo "FAIL ${name}: expected to be accepted, but validation failed:" >&2
+        echo "${output}" | sed 's/^/    /' >&2
+        ((failures++))
+    else
+        echo "ok   ${name}: accepted"
+    fi
+    ((checked++))
+}
+
+check_rejected() {
+    local fixture=$1 name=$2 expected output status
+    expected=$(sed -n 's/^# EXPECT-ERROR: *//p' "${fixture}")
+    if [[ -z ${expected} ]]; then
+        echo "FAIL ${name}: fixture has no '# EXPECT-ERROR:' line" >&2
+        ((failures++))
+        ((checked++))
+        return
+    fi
+
+    output=$(run_validator "${fixture}")
+    status=$?
+    if ((status == 0)); then
+        echo "FAIL ${name}: expected rejection, but validation succeeded" >&2
+        ((failures++))
+    elif [[ $(printf '%s' "${output}" | flatten) != *"${expected}"* ]]; then
+        echo "FAIL ${name}: rejected, but not for the stated reason." >&2
+        echo "    expected: ${expected}" >&2
+        echo "${output}" | sed 's/^/    actual:   /' >&2
+        ((failures++))
+    else
+        echo "ok   ${name}: rejected (${expected})"
+    fi
+    ((checked++))
+}
+
+check_accepted "${root}/cmake/dispatch-surface.cmake" "dispatch-surface.cmake (default)"
+
+for fixture in "${fixtures}"/*.cmake; do
+    name=$(basename "${fixture}")
+    case ${name} in
+    valid-*) check_accepted "${fixture}" "${name}" ;;
+    invalid-*) check_rejected "${fixture}" "${name}" ;;
+    *)
+        echo "FAIL ${name}: fixture name must start with valid- or invalid-" >&2
+        ((failures++))
+        ((checked++))
+        ;;
+    esac
+done
+
+echo
+if ((failures != 0)); then
+    echo "${failures} of ${checked} dispatch-surface checks failed" >&2
+    exit 1
+fi
+echo "all ${checked} dispatch-surface checks passed"
diff --git a/.github/workflows/dispatch-surface.yml b/.github/workflows/dispatch-surface.yml
new file mode 100644
index 000000000..dbe878a36
--- /dev/null
+++ b/.github/workflows/dispatch-surface.yml
@@ -0,0 +1,106 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# The set of distance kernels compiled ahead of time is declared once, in
+# cmake/dispatch-surface.cmake, and generated from there. Two things have to stay
+# true for that to be worth anything: the declaration must be checked rather than
+# trusted, and it must be genuinely configurable -- a knob nobody turns is a knob
+# that quietly stops working.
+
+name: Dispatch Surface
+
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }} @ ${{ github.event.pull_request.head.label || github.head_ref || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  declaration:
+    name: declaration is checked, committed header is current
+    runs-on: ubuntu-22.04
+    steps:
+    - uses: actions/checkout@v6
+
+    # Every fixture in tests/cmake/dispatch-surface, plus the default
+    # declaration. Needs nothing but cmake.
+    - name: Accept and reject declarations
+      run: .github/scripts/check_dispatch_surface.sh
+
+    # include/svs/core/distance/dispatch_surface.h is generated but committed, so
+    # that a bare `-I include` compile works without cmake. A configure refreshes
+    # it; if that produces a diff, either the declaration changed without a
+    # reconfigure or the header was edited by hand.
+    - name: Configure with the default surface
+      run: |
+        cmake -B "${{ runner.temp }}/build" -S "${GITHUB_WORKSPACE}" \
+              -DCMAKE_BUILD_TYPE=Release \
+              -DSVS_BUILD_TESTS=NO \
+              -DSVS_BUILD_BINARIES=NO
+
+    - name: Committed header matches the declaration
+      run: |
+        if ! git diff --exit-code -- include/svs/core/distance/dispatch_surface.h; then
+            echo "::error::include/svs/core/distance/dispatch_surface.h is stale." \
+                 "It is generated from cmake/dispatch-surface.cmake -- re-run cmake" \
+                 "and commit the result. Do not edit it by hand."
+            exit 1
+        fi
+
+  non-default-surface:
+    name: builds and tests with a non-default surface
+    runs-on: ubuntu-22.04
+    steps:
+    - uses: actions/checkout@v6
+
+    # valid-reduced.cmake shares no extent with the default declaration, so a
+    # build that silently fell back to the committed header would fail to
+    # compile rather than pass by accident.
+    - name: Configure
+      run: |
+        cmake -B "${{ runner.temp }}/build" -S "${GITHUB_WORKSPACE}" \
+              -DCMAKE_BUILD_TYPE=Release \
+              -DSVS_BUILD_TESTS=YES \
+              -DSVS_BUILD_BINARIES=NO \
+              -DSVS_DISPATCH_SURFACE_FILE="${GITHUB_WORKSPACE}/tests/cmake/dispatch-surface/valid-reduced.cmake"
+
+    - name: Build
+      working-directory: ${{ runner.temp }}/build
+      run: make -j$(nproc)
+
+    # Correctness must not depend on which extents have a fixed-extent kernel:
+    # an extent without one is served by the svs::Dynamic kernel instead. The
+    # long-running tests are covered by the default-surface build.
+    - name: Run tests
+      env:
+        CTEST_OUTPUT_ON_FAILURE: 1
+      working-directory: ${{ runner.temp }}/build/tests
+      run: ctest -C Release -LE long
+
+    # Overriding the surface for one build must not rewrite the committed header.
+    - name: Committed header was left alone
+      run: |
+        if ! git diff --exit-code -- include/svs/core/distance/dispatch_surface.h; then
+            echo "::error::A build with an overridden dispatch surface rewrote the" \
+                 "committed header. Only the default declaration may refresh it."
+            exit 1
+        fi
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index baf697990..f2772dc6f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -34,3 +34,14 @@ repos:
         args: [--markdown-linebreak-ext=md]
         exclude: .*\.svg$
       - id: mixed-line-ending
+
+  - repo: local
+    hooks:
+      # Cheap enough to run on every touch of the declaration, and it needs
+      # nothing but cmake -- no compiler, no build directory.
+      - id: dispatch-surface
+        name: dispatch surface declaration
+        entry: .github/scripts/check_dispatch_surface.sh
+        language: script
+        pass_filenames: false
+        files: ^(cmake/(dispatch-surface|validate-dispatch-surface)\.cmake|tests/cmake/dispatch-surface/.*\.cmake|\.github/scripts/check_dispatch_surface\.sh)$
diff --git a/cmake/check-dispatch-linkage.cmake b/cmake/check-dispatch-linkage.cmake
new file mode 100644
index 000000000..3eecaf7e8
--- /dev/null
+++ b/cmake/check-dispatch-linkage.cmake
@@ -0,0 +1,163 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#####
+##### Checks the dispatch surface against the symbols that were actually built.
+#####
+##### Run in script mode:
+#####
+#####   cmake -DSVS_PROBE_OBJECT=<link_probe.cpp.o> \
+#####         -DSVS_ARCHIVE=<libsvs_x86_objects.a> \
+#####         -DSVS_NM=<nm> \
+#####         -P cmake/check-dispatch-linkage.cmake
+#####
+##### The probe object names every kernel the surface declares and nothing else
+##### (see tests/multi-arch/x86/link_probe.cpp), so the kernels it *references*
+##### are exactly the kernels the archive must *define* -- and it must define no
+##### others. Both directions are checked, plus that the probe defines none of
+##### its own.
+#####
+
+foreach(required SVS_PROBE_OBJECT SVS_ARCHIVE SVS_NM)
+    if(NOT ${required})
+        message(FATAL_ERROR "${required} is not set.")
+    endif()
+endforeach()
+foreach(required SVS_PROBE_OBJECT SVS_ARCHIVE)
+    if(NOT EXISTS "${${required}}")
+        message(FATAL_ERROR "${required} does not exist: ${${required}}")
+    endif()
+endforeach()
+
+# Distance kernels, and nothing else in the archive. Mangled names are used
+# throughout: demangled ones carry `[clone .isra.0]` suffixes that differ between
+# a local instantiation and an explicit one.
+set(svs_kernel_regex "_ZN3svs8distance.*Impl")
+
+# Returns the mangled names of the matching symbols, one per list element.
+function(svs_symbols out_var)
+    cmake_parse_arguments(arg "" "FILE" "NM_ARGS" ${ARGN})
+    execute_process(
+        COMMAND "${SVS_NM}" ${arg_NM_ARGS} "${arg_FILE}"
+        OUTPUT_VARIABLE raw
+        ERROR_VARIABLE err
+        RESULT_VARIABLE status
+    )
+    if(NOT status EQUAL 0)
+        message(FATAL_ERROR "${SVS_NM} failed on ${arg_FILE}: ${err}")
+    endif()
+
+    set(symbols)
+    string(REPLACE "\n" ";" lines "${raw}")
+    foreach(line IN LISTS lines)
+        if(line MATCHES "${svs_kernel_regex}")
+            # The mangled name is the last whitespace-separated field.
+            string(REGEX MATCH "[^ \t]+$" symbol "${line}")
+            list(APPEND symbols "${symbol}")
+        endif()
+    endforeach()
+    list(REMOVE_DUPLICATES symbols)
+    list(SORT symbols)
+    set(${out_var} "${symbols}" PARENT_SCOPE)
+endfunction()
+
+# Shows up to `limit` entries of a list. The names stay mangled -- pipe them
+# through c++filt to read them.
+function(svs_report_symbols symbols limit)
+    list(LENGTH symbols count)
+    set(shown ${symbols})
+    if(count GREATER limit)
+        list(SUBLIST shown 0 ${limit} shown)
+    endif()
+    foreach(symbol IN LISTS shown)
+        message("      ${symbol}")
+    endforeach()
+    if(count GREATER limit)
+        math(EXPR rest "${count} - ${limit}")
+        message("      ... and ${rest} more")
+    endif()
+endfunction()
+
+svs_symbols(probe_defines FILE "${SVS_PROBE_OBJECT}" NM_ARGS --defined-only)
+svs_symbols(probe_references FILE "${SVS_PROBE_OBJECT}" NM_ARGS --undefined-only)
+svs_symbols(archive_defines FILE "${SVS_ARCHIVE}" NM_ARGS --defined-only)
+
+list(LENGTH probe_defines n_probe_defines)
+list(LENGTH probe_references n_probe_references)
+list(LENGTH archive_defines n_archive_defines)
+
+set(errors 0)
+
+# A probe that names nothing is not a passing probe. This is what an LTO build
+# looks like here, since the object holds IR rather than symbols.
+if(n_probe_references EQUAL 0 AND n_probe_defines EQUAL 0)
+    message("${SVS_PROBE_OBJECT} names no distance kernels at all.")
+    message("Nothing can be concluded from it. If this is a link-time-optimized")
+    message("build, nm cannot see the symbols and this check does not apply.")
+    message(FATAL_ERROR "dispatch linkage check found no symbols to check")
+endif()
+
+# The probe compiles at -march=x86-64 and guarantees nothing about the host, so a
+# kernel it defines itself is a kernel some other consumer would also define
+# itself -- at whatever -march that consumer happens to use.
+if(NOT n_probe_defines EQUAL 0)
+    message("${n_probe_defines} kernels are instantiated by the probe itself.")
+    message("Each is missing its `extern template` declaration, so every consumer")
+    message("of the headers instantiates it locally, from the generic primary")
+    message("template, at the consumer's own -march. Declare them: the extern")
+    message("blocks in the distance headers must cover the whole surface.")
+    message("    Instantiated locally:")
+    svs_report_symbols("${probe_defines}" 10)
+    math(EXPR errors "${errors} + 1")
+endif()
+
+# Declared but never instantiated. The link should already have failed, so this
+# only fires when the object is inspected without being linked.
+set(missing ${probe_references})
+if(archive_defines)
+    list(REMOVE_ITEM missing ${archive_defines})
+endif()
+list(LENGTH missing n_missing)
+if(NOT n_missing EQUAL 0)
+    message("${n_missing} kernels are declared but never instantiated.")
+    message("They are declared `extern template` in the distance headers but no")
+    message("translation unit defines them, so linking against the library fails.")
+    message("    Undefined:")
+    svs_report_symbols("${missing}" 10)
+    math(EXPR errors "${errors} + 1")
+endif()
+
+# Instantiated but unreachable through the surface: dead weight in the archive.
+set(unreachable ${archive_defines})
+if(probe_references)
+    list(REMOVE_ITEM unreachable ${probe_references})
+endif()
+list(LENGTH unreachable n_unreachable)
+if(NOT n_unreachable EQUAL 0)
+    message("${n_unreachable} kernels are instantiated but are not part of the")
+    message("dispatch surface. Nothing declares them, so no consumer reaches")
+    message("them; they only add to the size of the library.")
+    message("    Unreachable:")
+    svs_report_symbols("${unreachable}" 10)
+    math(EXPR errors "${errors} + 1")
+endif()
+
+if(NOT errors EQUAL 0)
+    message(FATAL_ERROR "dispatch linkage check failed")
+endif()
+
+message(
+    "dispatch linkage: ${n_archive_defines} kernels declared, instantiated and "
+    "reachable; none instantiated by the consumer"
+)
diff --git a/cmake/generate-dispatch-surface.cmake b/cmake/generate-dispatch-surface.cmake
index 4aed2467e..9186639ef 100644
--- a/cmake/generate-dispatch-surface.cmake
+++ b/cmake/generate-dispatch-surface.cmake
@@ -27,12 +27,11 @@ set(SVS_DISPATCH_SURFACE_FILE "${SVS_DEFAULT_DISPATCH_SURFACE_FILE}"
     CACHE FILEPATH
     "Declaration of the ahead-of-time distance-kernel dispatch surface"
 )
-if(NOT EXISTS "${SVS_DISPATCH_SURFACE_FILE}")
-    message(FATAL_ERROR
-        "SVS_DISPATCH_SURFACE_FILE does not exist: ${SVS_DISPATCH_SURFACE_FILE}"
-    )
-endif()
-include("${SVS_DISPATCH_SURFACE_FILE}")
+
+# Reads the declaration and rejects it if it is malformed. Also runnable on its
+# own -- see .github/scripts/check_dispatch_surface.sh.
+set(SVS_X86_SRC_DIR "${PROJECT_SOURCE_DIR}/include/svs/multi-arch/x86")
+include("${CMAKE_CURRENT_LIST_DIR}/validate-dispatch-surface.cmake")
 
 file(REAL_PATH "${SVS_DISPATCH_SURFACE_FILE}" svs_surface_real)
 file(REAL_PATH "${SVS_DEFAULT_DISPATCH_SURFACE_FILE}" svs_default_surface_real)
@@ -54,121 +53,38 @@ set_property(
 )
 
 #####
-##### Validate the extent list
-#####
-
-if(NOT SVS_SUPPORTED_DIMS)
-    message(FATAL_ERROR
-        "SVS_SUPPORTED_DIMS is empty in ${SVS_DISPATCH_SURFACE_FILE}. At least "
-        "one fixed extent is required."
-    )
-endif()
-
-foreach(dim IN LISTS SVS_SUPPORTED_DIMS)
-    if(NOT dim MATCHES "^[1-9][0-9]*$")
-        message(FATAL_ERROR
-            "SVS_SUPPORTED_DIMS contains '${dim}', which is not a positive "
-            "integer. svs::Dynamic is required and is appended automatically, "
-            "so it must not be listed."
-        )
-    endif()
-endforeach()
-
-set(svs_dims_sorted ${SVS_SUPPORTED_DIMS})
-list(REMOVE_DUPLICATES svs_dims_sorted)
-list(LENGTH SVS_SUPPORTED_DIMS svs_dims_given)
-list(LENGTH svs_dims_sorted svs_dims_unique)
-if(NOT svs_dims_given EQUAL svs_dims_unique)
-    message(FATAL_ERROR
-        "SVS_SUPPORTED_DIMS contains duplicate extents. Every extent must "
-        "appear exactly once."
-    )
-endif()
-
-# svs::Dynamic is mandatory: it is what serves every dimensionality without a
-# fixed-extent kernel, and the library is incorrect without it.
-set(svs_dim_list ${SVS_SUPPORTED_DIMS} "svs::Dynamic")
-list(LENGTH svs_dim_list SVS_GEN_DIM_COUNT)
-
-#####
-##### Validate the ISA levels
-#####
-
-if(NOT SVS_ISA_LEVELS)
-    message(FATAL_ERROR "SVS_ISA_LEVELS is empty in ${SVS_DISPATCH_SURFACE_FILE}.")
-endif()
-
-set(svs_seen_levels)
-set(svs_seen_infixes)
-foreach(level_spec IN LISTS SVS_ISA_LEVELS)
-    string(REPLACE "|" ";" level_fields "${level_spec}")
-    list(LENGTH level_fields nfields)
-    if(NOT nfields EQUAL 3)
-        message(FATAL_ERROR
-            "Malformed SVS_ISA_LEVELS entry '${level_spec}': expected exactly "
-            "three '|'-separated fields <enumerator>|<instruction budget>|<TU infix>."
-        )
-    endif()
-    list(GET level_fields 0 level)
-    list(GET level_fields 1 arch)
-    list(GET level_fields 2 infix)
-    foreach(field level arch infix)
-        if(NOT ${field})
-            message(FATAL_ERROR
-                "Malformed SVS_ISA_LEVELS entry '${level_spec}': ${field} is empty."
-            )
-        endif()
-    endforeach()
-    if(level IN_LIST svs_seen_levels)
-        message(FATAL_ERROR "Duplicate ISA level '${level}' in SVS_ISA_LEVELS.")
-    endif()
-    if(infix IN_LIST svs_seen_infixes)
-        message(FATAL_ERROR
-            "Duplicate TU infix '${infix}' in SVS_ISA_LEVELS; infixes name "
-            "generated files and must be unique."
-        )
-    endif()
-    list(APPEND svs_seen_levels ${level})
-    list(APPEND svs_seen_infixes ${infix})
-endforeach()
-
-#####
-##### Generate the header
+##### Build the macro bodies
 #####
 
 # Line continuations are emitted with a trailing backslash; the generated macros
 # are one logical line each.
+set(SVS_GEN_DIM_COUNT ${SVS_DIM_COUNT})
+
 set(SVS_GEN_DIM_LOOP "\\\n")
-foreach(dim IN LISTS svs_dim_list)
+foreach(dim IN LISTS SVS_DIM_LIST)
     string(APPEND SVS_GEN_DIM_LOOP "    M(${dim}) \\\n")
 endforeach()
 string(APPEND SVS_GEN_DIM_LOOP "    /* end */")
 
 set(SVS_GEN_TARGET_LOOP "\\\n")
 set(SVS_DISPATCH_TU_SPECS)
-set(svs_x86_src_dir "${PROJECT_SOURCE_DIR}/include/svs/multi-arch/x86")
 foreach(level_spec IN LISTS SVS_ISA_LEVELS)
     string(REPLACE "|" ";" level_fields "${level_spec}")
     list(GET level_fields 0 level)
     list(GET level_fields 1 arch)
     list(GET level_fields 2 infix)
 
-    foreach(dim IN LISTS svs_dim_list)
+    foreach(dim IN LISTS SVS_DIM_LIST)
         string(APPEND SVS_GEN_TARGET_LOOP "    M(${dim}, ${level}) \\\n")
     endforeach()
 
     # One translation unit per level, named after the level's infix. The file
     # itself is short -- it loops over the generated extent list -- but it is
-    # committed rather than generated, because the private repository compiles
-    # these sources by path.
-    set(tu_src "${svs_x86_src_dir}/${infix}.cpp")
-    if(NOT EXISTS "${tu_src}")
-        message(FATAL_ERROR
-            "ISA level '${level}' has no translation unit: expected ${tu_src}. "
-            "Adding a level to SVS_ISA_LEVELS requires creating that file."
-        )
-    endif()
-    list(APPEND SVS_DISPATCH_TU_SPECS "${tu_src}|${level}|${arch}|${infix}")
+    # committed rather than generated, because the downstream repository compiles
+    # these sources by path. Its existence was checked during validation.
+    list(APPEND SVS_DISPATCH_TU_SPECS
+        "${SVS_X86_SRC_DIR}/${infix}.cpp|${level}|${arch}|${infix}"
+    )
 endforeach()
 string(APPEND SVS_GEN_TARGET_LOOP "    /* end */")
 
@@ -206,6 +122,6 @@ endif()
 
 list(LENGTH SVS_ISA_LEVELS svs_level_count)
 message(STATUS
-    "Dispatch surface: ${SVS_GEN_DIM_COUNT} extents (${svs_dims_unique} fixed + "
+    "Dispatch surface: ${SVS_DIM_COUNT} extents (${SVS_FIXED_DIM_COUNT} fixed + "
     "svs::Dynamic) x ${svs_level_count} ISA levels"
 )
diff --git a/cmake/validate-dispatch-surface.cmake b/cmake/validate-dispatch-surface.cmake
new file mode 100644
index 000000000..fe9a06af5
--- /dev/null
+++ b/cmake/validate-dispatch-surface.cmake
@@ -0,0 +1,148 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#####
+##### Reads and checks a dispatch-surface declaration.
+#####
+##### This is deliberately free of build-system state so that it runs in script
+##### mode as well as during configure:
+#####
+#####   cmake -DSVS_DISPATCH_SURFACE_FILE=<file> \
+#####         -DSVS_X86_SRC_DIR=<dir> \
+#####         -P cmake/validate-dispatch-surface.cmake
+#####
+##### Inputs:
+#####   SVS_DISPATCH_SURFACE_FILE -- the declaration to read
+#####   SVS_X86_SRC_DIR           -- where per-level translation units live
+#####
+##### Outputs:
+#####   SVS_SUPPORTED_DIMS, SVS_ISA_LEVELS -- verbatim from the declaration
+#####   SVS_DIM_LIST                       -- extents, with svs::Dynamic appended
+#####   SVS_DIM_COUNT                      -- length of SVS_DIM_LIST
+#####   SVS_FIXED_DIM_COUNT                -- length of SVS_SUPPORTED_DIMS
+#####
+
+## In script mode there is no cmake_minimum_required, so policies default to OLD.
+## Both of these are load-bearing here: CMP0007 keeps an empty `|`-field from
+## vanishing when the entry is split, and CMP0057 enables `IN_LIST`.
+cmake_policy(PUSH)
+cmake_policy(SET CMP0007 NEW)
+cmake_policy(SET CMP0057 NEW)
+
+if(NOT SVS_DISPATCH_SURFACE_FILE)
+    message(FATAL_ERROR "SVS_DISPATCH_SURFACE_FILE is not set.")
+endif()
+if(NOT EXISTS "${SVS_DISPATCH_SURFACE_FILE}")
+    message(FATAL_ERROR
+        "SVS_DISPATCH_SURFACE_FILE does not exist: ${SVS_DISPATCH_SURFACE_FILE}"
+    )
+endif()
+if(NOT SVS_X86_SRC_DIR)
+    message(FATAL_ERROR "SVS_X86_SRC_DIR is not set.")
+endif()
+
+# The declaration is plain CMake: it sets SVS_SUPPORTED_DIMS and SVS_ISA_LEVELS
+# and does nothing else. Clear them first so that a declaration which forgets one
+# is reported as empty rather than inheriting a value from the caller.
+set(SVS_SUPPORTED_DIMS)
+set(SVS_ISA_LEVELS)
+include("${SVS_DISPATCH_SURFACE_FILE}")
+
+#####
+##### The extent list
+#####
+
+if(NOT SVS_SUPPORTED_DIMS)
+    message(FATAL_ERROR
+        "SVS_SUPPORTED_DIMS is empty in ${SVS_DISPATCH_SURFACE_FILE}. At least "
+        "one fixed extent is required."
+    )
+endif()
+
+foreach(dim IN LISTS SVS_SUPPORTED_DIMS)
+    if(NOT dim MATCHES "^[1-9][0-9]*$")
+        message(FATAL_ERROR
+            "SVS_SUPPORTED_DIMS contains '${dim}', which is not a positive "
+            "integer. svs::Dynamic is required and is appended automatically, "
+            "so it must not be listed."
+        )
+    endif()
+endforeach()
+
+set(svs_dims_deduped ${SVS_SUPPORTED_DIMS})
+list(REMOVE_DUPLICATES svs_dims_deduped)
+list(LENGTH SVS_SUPPORTED_DIMS SVS_FIXED_DIM_COUNT)
+list(LENGTH svs_dims_deduped svs_dims_unique)
+if(NOT SVS_FIXED_DIM_COUNT EQUAL svs_dims_unique)
+    message(FATAL_ERROR
+        "SVS_SUPPORTED_DIMS contains duplicate extents. Every extent must "
+        "appear exactly once."
+    )
+endif()
+
+# svs::Dynamic is mandatory: it is what serves every dimensionality without a
+# fixed-extent kernel, and the library is incorrect without it.
+set(SVS_DIM_LIST ${SVS_SUPPORTED_DIMS} "svs::Dynamic")
+list(LENGTH SVS_DIM_LIST SVS_DIM_COUNT)
+
+#####
+##### The ISA levels
+#####
+
+if(NOT SVS_ISA_LEVELS)
+    message(FATAL_ERROR "SVS_ISA_LEVELS is empty in ${SVS_DISPATCH_SURFACE_FILE}.")
+endif()
+
+set(svs_seen_levels)
+set(svs_seen_infixes)
+foreach(level_spec IN LISTS SVS_ISA_LEVELS)
+    string(REPLACE "|" ";" level_fields "${level_spec}")
+    list(LENGTH level_fields nfields)
+    if(NOT nfields EQUAL 3)
+        message(FATAL_ERROR
+            "Malformed SVS_ISA_LEVELS entry '${level_spec}': expected exactly "
+            "three '|'-separated fields <enumerator>|<instruction budget>|<TU infix>."
+        )
+    endif()
+    list(GET level_fields 0 level)
+    list(GET level_fields 1 arch)
+    list(GET level_fields 2 infix)
+    foreach(field level arch infix)
+        if(NOT ${field})
+            message(FATAL_ERROR
+                "Malformed SVS_ISA_LEVELS entry '${level_spec}': ${field} is empty."
+            )
+        endif()
+    endforeach()
+    if(level IN_LIST svs_seen_levels)
+        message(FATAL_ERROR "Duplicate ISA level '${level}' in SVS_ISA_LEVELS.")
+    endif()
+    if(infix IN_LIST svs_seen_infixes)
+        message(FATAL_ERROR
+            "Duplicate TU infix '${infix}' in SVS_ISA_LEVELS; infixes name "
+            "generated files and must be unique."
+        )
+    endif()
+    if(NOT EXISTS "${SVS_X86_SRC_DIR}/${infix}.cpp")
+        message(FATAL_ERROR
+            "ISA level '${level}' has no translation unit: expected "
+            "${SVS_X86_SRC_DIR}/${infix}.cpp. Adding a level to SVS_ISA_LEVELS "
+            "requires creating that file."
+        )
+    endif()
+    list(APPEND svs_seen_levels ${level})
+    list(APPEND svs_seen_infixes ${infix})
+endforeach()
+
+cmake_policy(POP)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 8c812d35a..bb6d2a7d8 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -237,3 +237,9 @@ list(APPEND CMAKE_MODULE_PATH ${catch2_SOURCE_DIR}/extras)
 include(CTest)
 include(Catch)
 catch_discover_tests(tests ADD_TAGS_AS_LABELS SKIP_IS_FAILURE)
+
+# Checks the x86 dispatch surface. The target only exists where the multi-arch
+# build ran, which is the same condition that makes the surface meaningful.
+if(TARGET svs_x86_objects)
+    add_subdirectory(multi-arch)
+endif()
diff --git a/tests/cmake/dispatch-surface/invalid-duplicate-extent.cmake b/tests/cmake/dispatch-surface/invalid-duplicate-extent.cmake
new file mode 100644
index 000000000..0d2efd2db
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-duplicate-extent.cmake
@@ -0,0 +1,17 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# EXPECT-ERROR: SVS_SUPPORTED_DIMS contains duplicate extents
+set(SVS_SUPPORTED_DIMS 128 256 128)
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/invalid-duplicate-infix.cmake b/tests/cmake/dispatch-surface/invalid-duplicate-infix.cmake
new file mode 100644
index 000000000..e7b76fb3e
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-duplicate-infix.cmake
@@ -0,0 +1,22 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Two levels cannot share one translation unit: it is compiled once, at one
+# instruction budget.
+# EXPECT-ERROR: Duplicate TU infix 'avx2'
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS
+    "AVX2|haswell|avx2"
+    "AVX512|cascadelake|avx2"
+)
diff --git a/tests/cmake/dispatch-surface/invalid-duplicate-level.cmake b/tests/cmake/dispatch-surface/invalid-duplicate-level.cmake
new file mode 100644
index 000000000..0cd32fc8f
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-duplicate-level.cmake
@@ -0,0 +1,21 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# One enumerator cannot have two instruction budgets.
+# EXPECT-ERROR: Duplicate ISA level 'AVX2'
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS
+    "AVX2|haswell|avx2"
+    "AVX2|cascadelake|avx512"
+)
diff --git a/tests/cmake/dispatch-surface/invalid-dynamic-listed.cmake b/tests/cmake/dispatch-surface/invalid-dynamic-listed.cmake
new file mode 100644
index 000000000..ffe7d6d6d
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-dynamic-listed.cmake
@@ -0,0 +1,18 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# svs::Dynamic is appended automatically and must not be spelled out.
+# EXPECT-ERROR: svs::Dynamic is required and is appended automatically
+set(SVS_SUPPORTED_DIMS 128 svs::Dynamic)
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/invalid-level-empty-field.cmake b/tests/cmake/dispatch-surface/invalid-level-empty-field.cmake
new file mode 100644
index 000000000..2e6b83972
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-level-empty-field.cmake
@@ -0,0 +1,17 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# EXPECT-ERROR: arch is empty
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS "AVX2||avx2")
diff --git a/tests/cmake/dispatch-surface/invalid-level-missing-field.cmake b/tests/cmake/dispatch-surface/invalid-level-missing-field.cmake
new file mode 100644
index 000000000..899632d9f
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-level-missing-field.cmake
@@ -0,0 +1,18 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# The TU infix is absent.
+# EXPECT-ERROR: expected exactly three '|'-separated fields
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS "AVX2|haswell")
diff --git a/tests/cmake/dispatch-surface/invalid-level-without-tu.cmake b/tests/cmake/dispatch-surface/invalid-level-without-tu.cmake
new file mode 100644
index 000000000..341258c99
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-level-without-tu.cmake
@@ -0,0 +1,22 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Adding a level means adding the translation unit that defines its kernels.
+# Without this check the level would silently contribute nothing.
+# EXPECT-ERROR: has no translation unit
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS
+    "AVX2|haswell|avx2"
+    "AVX512VNNI|sapphirerapids|avx512vnni"
+)
diff --git a/tests/cmake/dispatch-surface/invalid-missing-extents.cmake b/tests/cmake/dispatch-surface/invalid-missing-extents.cmake
new file mode 100644
index 000000000..eb35b6d3f
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-missing-extents.cmake
@@ -0,0 +1,17 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# The variable is never set at all.
+# EXPECT-ERROR: SVS_SUPPORTED_DIMS is empty
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/invalid-no-extents.cmake b/tests/cmake/dispatch-surface/invalid-no-extents.cmake
new file mode 100644
index 000000000..df6b538ba
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-no-extents.cmake
@@ -0,0 +1,17 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# EXPECT-ERROR: SVS_SUPPORTED_DIMS is empty
+set(SVS_SUPPORTED_DIMS)
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/invalid-no-levels.cmake b/tests/cmake/dispatch-surface/invalid-no-levels.cmake
new file mode 100644
index 000000000..f3297e809
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-no-levels.cmake
@@ -0,0 +1,17 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# EXPECT-ERROR: SVS_ISA_LEVELS is empty
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS)
diff --git a/tests/cmake/dispatch-surface/invalid-non-numeric-extent.cmake b/tests/cmake/dispatch-surface/invalid-non-numeric-extent.cmake
new file mode 100644
index 000000000..21e2f98f4
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-non-numeric-extent.cmake
@@ -0,0 +1,17 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# EXPECT-ERROR: SVS_SUPPORTED_DIMS contains '12a'
+set(SVS_SUPPORTED_DIMS 128 12a)
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/invalid-zero-extent.cmake b/tests/cmake/dispatch-surface/invalid-zero-extent.cmake
new file mode 100644
index 000000000..d68ae0b0b
--- /dev/null
+++ b/tests/cmake/dispatch-surface/invalid-zero-extent.cmake
@@ -0,0 +1,18 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# A zero-length vector has no kernel to compile.
+# EXPECT-ERROR: SVS_SUPPORTED_DIMS contains '0'
+set(SVS_SUPPORTED_DIMS 0 128)
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/valid-minimal.cmake b/tests/cmake/dispatch-surface/valid-minimal.cmake
new file mode 100644
index 000000000..f1ca55f8b
--- /dev/null
+++ b/tests/cmake/dispatch-surface/valid-minimal.cmake
@@ -0,0 +1,19 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# The smallest declaration that is still a library: one fixed extent, one ISA
+# level. Every other dimensionality is served by the svs::Dynamic kernel.
+
+set(SVS_SUPPORTED_DIMS 128)
+set(SVS_ISA_LEVELS "AVX2|haswell|avx2")
diff --git a/tests/cmake/dispatch-surface/valid-reduced.cmake b/tests/cmake/dispatch-surface/valid-reduced.cmake
new file mode 100644
index 000000000..e2410222f
--- /dev/null
+++ b/tests/cmake/dispatch-surface/valid-reduced.cmake
@@ -0,0 +1,25 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# A surface that shares no extent with the default declaration, so a build using
+# it cannot accidentally pass by reusing a committed header. Both ISA levels are
+# kept so that runtime dispatch is still exercised on an AVX-512 host.
+#
+# Built and tested by the `non-default surface` CI job.
+
+set(SVS_SUPPORTED_DIMS 32 384)
+set(SVS_ISA_LEVELS
+    "AVX2|haswell|avx2"
+    "AVX512|cascadelake|avx512"
+)
diff --git a/tests/multi-arch/CMakeLists.txt b/tests/multi-arch/CMakeLists.txt
new file mode 100644
index 000000000..20380b7f7
--- /dev/null
+++ b/tests/multi-arch/CMakeLists.txt
@@ -0,0 +1,69 @@
+# Copyright 2025 Intel Corporation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#####
+##### The dispatch surface link probe.
+#####
+##### Not a Catch2 test: what is being checked is a property of the object file,
+##### so the probe has to be its own translation unit, compiled at a known
+##### instruction budget and inspected from outside.
+#####
+
+# The object library exists so that the probe's single object file can be named
+# with $<TARGET_OBJECTS:>, which is what the linkage check reads.
+add_library(dispatch_surface_probe_objects OBJECT x86/link_probe.cpp)
+target_link_libraries(
+    dispatch_surface_probe_objects
+    PRIVATE svs::svs svs::compile_options svs::x86_options_base
+)
+
+# svs::x86_options_base is -march=x86-64 -mtune=generic: the probe must know no
+# more about the host than an arbitrary consumer of the headers does.
+add_executable(dispatch_surface_probe)
+target_link_libraries(
+    dispatch_surface_probe
+    PRIVATE
+    dispatch_surface_probe_objects
+    svs::svs
+    svs::compile_options
+    svs::x86_options_base
+)
+
+# Calls every kernel whose ISA level this host satisfies. Which kernels those are
+# depends on the host, so this covers the whole surface only across the CI matrix.
+add_test(NAME dispatch_surface_probe COMMAND dispatch_surface_probe)
+
+if(DEFINED CMAKE_NM AND CMAKE_NM)
+    set(svs_nm "${CMAKE_NM}")
+else()
+    find_program(svs_nm NAMES nm llvm-nm)
+endif()
+
+if(svs_nm)
+    # Host-independent, unlike the run above: it reads the symbol table rather
+    # than executing anything, so it sees every kernel in the surface everywhere.
+    add_test(
+        NAME dispatch_surface_linkage
+        COMMAND
+        "${CMAKE_COMMAND}"
+        "-DSVS_PROBE_OBJECT=$<TARGET_OBJECTS:dispatch_surface_probe_objects>"
+        "-DSVS_ARCHIVE=$<TARGET_FILE:svs_x86_objects>"
+        "-DSVS_NM=${svs_nm}"
+        # Not PROJECT_SOURCE_DIR: the downstream repository adds this directory
+        # to its own project, where that points somewhere else entirely.
+        -P "${CMAKE_CURRENT_LIST_DIR}/../../cmake/check-dispatch-linkage.cmake"
+    )
+else()
+    message(STATUS "nm not found; skipping the dispatch surface linkage test")
+endif()
diff --git a/tests/multi-arch/x86/link_probe.cpp b/tests/multi-arch/x86/link_probe.cpp
new file mode 100644
index 000000000..f3c3d8a63
--- /dev/null
+++ b/tests/multi-arch/x86/link_probe.cpp
@@ -0,0 +1,120 @@
+/*
+ * Copyright 2025 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// A consumer that names every kernel the dispatch surface declares and nothing
+// else, so a declared-but-uninstantiated kernel is an undefined symbol here.
+
+#include "svs/core/distance/cosine.h"
+#include "svs/core/distance/euclidean.h"
+#include "svs/core/distance/inner_product.h"
+#include "svs/lib/avx_detection.h"
+#include "svs/lib/static.h"
+#include "svs/multi-arch/x86/preprocessor.h"
+
+#include <algorithm>
+#include <array>
+#include <cstddef>
+#include <cstdio>
+
+namespace {
+
+using svs::distance::AVX_AVAILABILITY;
+
+// A level added to the surface without a specialization here is an undefined
+// symbol, deliberately: there is no way to guess the right predicate.
+template <AVX_AVAILABILITY Level> bool host_satisfies();
+
+template <> bool host_satisfies<AVX_AVAILABILITY::AVX2>() {
+    return svs::detail::avx_runtime_flags.is_avx2_supported();
+}
+
+template <> bool host_satisfies<AVX_AVAILABILITY::AVX512>() {
+    return svs::detail::avx_runtime_flags.is_avx512f_supported();
+}
+
+// The longest fixed extent in the surface.
+constexpr size_t probe_max_dim = []() {
+    size_t longest = 1;
+    for (auto dim : svs::distance::supported_dim_list) {
+        if (dim != svs::Dynamic && dim > longest) {
+            longest = dim;
+        }
+    }
+    return longest;
+}();
+
+// A length for the svs::Dynamic kernels. Deliberately not a multiple of any
+// vector width, so the epilogue is exercised too.
+constexpr size_t probe_dynamic_dim = 97;
+
+// One buffer serves every call, whichever extents the surface happens to declare.
+constexpr size_t probe_buffer_dim = std::max(probe_max_dim, probe_dynamic_dim);
+
+template <typename E> const E* buffer() {
+    static const std::array<E, probe_buffer_dim> values = []() {
+        std::array<E, probe_buffer_dim> filled{};
+        filled.fill(static_cast<E>(1.0F));
+        return filled;
+    }();
+    return values.data();
+}
+
+// svs::lib::MaybeStatic<svs::Dynamic> has no default constructor: a dynamic
+// extent must be told its length.
+template <size_t N> svs::lib::MaybeStatic<N> probe_length() {
+    if constexpr (N == svs::Dynamic) {
+        return svs::lib::MaybeStatic<N>(probe_dynamic_dim);
+    } else {
+        return svs::lib::MaybeStatic<N>();
+    }
+}
+
+// Named directly rather than through L2::compute, which also reaches
+// AVX_AVAILABILITY::NONE -- not in the surface, so every consumer instantiates it.
+#define SVS_PROBE_ONE(Ea, Eb, N, LEVEL)                                                   \
+    total += svs::distance::L2Impl<N, Ea, Eb, AVX_AVAILABILITY::LEVEL>::compute(          \
+        buffer<Ea>(), buffer<Eb>(), probe_length<N>()                                     \
+    );                                                                                    \
+    total += svs::distance::IPImpl<N, Ea, Eb, AVX_AVAILABILITY::LEVEL>::compute(          \
+        buffer<Ea>(), buffer<Eb>(), probe_length<N>()                                     \
+    );                                                                                    \
+    total +=                                                                              \
+        svs::distance::CosineSimilarityImpl<N, Ea, Eb, AVX_AVAILABILITY::LEVEL>::compute( \
+            buffer<Ea>(), buffer<Eb>(), 1.0F, probe_length<N>()                           \
+        );
+
+#define SVS_PROBE_TARGET(N, LEVEL)                      \
+    if (host_satisfies<AVX_AVAILABILITY::LEVEL>()) {    \
+        SVS_FOR_EACH_TYPE_PAIR(SVS_PROBE_ONE, N, LEVEL) \
+    }
+
+float probe_all() {
+    float total = 0;
+    SVS_FOR_EACH_DISPATCH_TARGET(SVS_PROBE_TARGET)
+    return total;
+}
+
+#undef SVS_PROBE_TARGET
+#undef SVS_PROBE_ONE
+
+} // namespace
+
+int main() {
+    // Printing keeps the calls above from being optimized away, and makes the run
+    // a smoke test of every kernel this host can reach.
+    std::printf("dispatch surface probe: %f\n", static_cast<double>(probe_all()));
+    return 0;
+}