diff --git a/.abicheck.yml b/.abicheck.yml
new file mode 100644
index 000000000..b790f090c
--- /dev/null
+++ b/.abicheck.yml
@@ -0,0 +1,35 @@
+# Copyright 2026 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.
+
+# abicheck configuration, picked up from the repo root by `abicheck compare`.
+# Validated against the abicheck 0.5.0 config schema.
+#
+# Kept identical to .abicheck.yml in the innersource repo: the two repos build
+# the same runtime library and must not disagree on how it is parsed.
+
+# castxml's default cc-gnu detection parses SVS's C++20 headers at the wrong
+# standard (std::span / constexpr dtor fail). The clang AST frontend handles
+# C++20 cleanly; layout-only checks fall back to the .so's DWARF.
+compile:
+  frontend: clang
+  std: c++20
+
+# Scope the compared surface to what we publish, and collapse the std/gnu_cxx
+# template-instantiation noise that leaks past --exclude-libs,ALL.
+scope:
+  public: true
+  collapse_versioned_symbols: true
+
+suppression:
+  require_justification: true
diff --git a/.github/abi-baseline-tag b/.github/abi-baseline-tag
new file mode 100644
index 000000000..8eb83dd30
--- /dev/null
+++ b/.github/abi-baseline-tag
@@ -0,0 +1,27 @@
+# Copyright 2026 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 released tag that runtime-bindings ABI compatibility is measured against.
+# Assets are pulled from this repo's GitHub releases at check time.
+#
+# Bumped deliberately as part of cutting a release, so that resetting the ABI
+# baseline is a reviewable act rather than a side effect of tagging. Pinning also
+# keeps a new release from silently moving the target under already-open PRs.
+#
+# `latest` is accepted and resolves dynamically, but is not the default: patch
+# tags can land out of order (v0.3.1 and v0.3.2 were both tagged after v0.4.0),
+# so "newest tag" is not always "current release line".
+#
+# Keep in sync with .github/abi-baseline-tag in the innersource repo.
+v0.4.0
diff --git a/.github/abi-suppressions.yml b/.github/abi-suppressions.yml
new file mode 100644
index 000000000..cf2819f78
--- /dev/null
+++ b/.github/abi-suppressions.yml
@@ -0,0 +1,82 @@
+# Copyright 2026 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.
+
+# ABI check suppression rules for the SVS C++ runtime bindings, used by
+# napetrov/abicheck. Owned here rather than in the innersource repo so that both
+# repos measure libsvs_runtime.so against the same rules -- a suppression present
+# on one side only would make the innersource-vs-public equivalence check report
+# a difference that is really just an asymmetric filter.
+#
+# Scope is the runtime bindings alone. The innersource repo keeps its own file
+# for libsvs_shared_library.so, which leaks a far larger third-party surface.
+#
+# Measured on libsvs_runtime.so v0.4.0: 253 exported symbols, of which 55 are the
+# declared svs::runtime::v0 API. Nearly everything suppressed below is a
+# libstdc++ template instantiation that reached the export table because the
+# bindings are built without -fvisibility=hidden.
+
+version: 1
+suppressions:
+  # --- C++ standard library / runtime (never part of the SVS API) ---
+  - symbol_pattern: "^_ZNSt.*"
+    reason: "C++ standard library symbols (leaked template instantiations)"
+    label: "stdlib"
+
+  - symbol_pattern: "^_ZSt.*"
+    reason: "C++ standard library functions"
+    label: "stdlib"
+
+  - symbol_pattern: "^_ZN9__gnu_cxx.*"
+    reason: "libstdc++ __gnu_cxx internals (numeric_traits etc.), leaked"
+    label: "stdlib"
+
+  # RTTI/vtable/VTT for std types mangle as _ZTI/_ZTS/_ZTV/_ZTT, not _ZNSt.
+  - symbol_pattern: "^_ZT[VIST]N?St.*"
+    reason: "RTTI/vtable/VTT for std:: types (e.g. thread::_State_impl, future)"
+    label: "stdlib"
+
+  - symbol_pattern: "^_ZT[VIST].*__gnu_cxx.*"
+    reason: "RTTI/vtable for __gnu_cxx types, leaked"
+    label: "stdlib"
+
+  - symbol_pattern: "^__cxa_.*"
+    reason: "C++ ABI runtime symbols"
+    label: "cxx-abi"
+
+  - symbol_pattern: "^__gxx_.*"
+    reason: "GCC C++ runtime symbols"
+    label: "cxx-abi"
+
+  # --- Header-only third-party deps that leak via template instantiation ---
+  - symbol_pattern: "^_ZN[0-9]+toml.*"
+    reason: "toml++ header-only symbols leaked via instantiation"
+    label: "third-party"
+
+  - symbol_pattern: "^_ZN3fmt.*"
+    reason: "fmt header-only symbols leaked via instantiation"
+    label: "third-party"
+
+  - symbol_pattern: "^_ZN3tsl.*"
+    reason: "tsl::robin_map header-only symbols leaked via instantiation"
+    label: "third-party"
+
+  - symbol_pattern: "^_ZN6spdlog.*"
+    reason: "spdlog header-only symbols leaked via instantiation"
+    label: "third-party"
+
+  # --- svs::runtime::v0 and svs::...detail...: deliberately NOT suppressed ---
+  # The 55 declared v0 functions are the whole point of the check. `detail`
+  # symbols are not suppressed either: users reach them transitively through
+  # template instantiation, so a vtable or layout change there is a real break.
+  # See the same note in the innersource suppression file.
diff --git a/.github/scripts/abi-check.sh b/.github/scripts/abi-check.sh
new file mode 100755
index 000000000..6cfd23073
--- /dev/null
+++ b/.github/scripts/abi-check.sh
@@ -0,0 +1,126 @@
+#!/bin/bash
+# Copyright 2026 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.
+
+# Compare the ABI of two SVS build tarballs with napetrov/abicheck.
+#
+# One primitive serves both questions asked of it:
+#   temporal    old = a release tarball, new = this build -- did we break users?
+#   equivalence old and new are the same source revision built two ways -- did
+#               the build paths diverge?
+# The distinction is in what the caller passes, not in the logic, so this lives
+# in one place. It is called from this repo's build-cpp-runtime-bindings.yml and
+# from build-share-lib.yml in the innersource repo via the submodule path.
+#
+# Usage: abi-check.sh <old-label> <old-tarball> <new-label> <new-tarball>
+#
+# Overridable via environment:
+#   LIBRARY        library basename to compare (default libsvs_runtime.so)
+#   HEADER_SUBDIR  header root inside the tarball (default include/svs/runtime)
+#   SUPPRESSIONS   suppression file (default .github/abi-suppressions.yml)
+#   POLICY         abicheck policy (default strict_abi)
+#   REPORT         markdown report path (default abi-report.md)
+#   WORKDIR        scratch directory (default abi-work)
+#
+# Exit status is abicheck's: 0 compatible, 2 source-level API break, 4 binary
+# ABI break, 64 invalid invocation. 77 is added to mean "an input was missing",
+# which is not a finding and must never be reported as one.
+
+set -euo pipefail
+
+OLD_LABEL="${1:?Usage: abi-check.sh <old-label> <old-tarball> <new-label> <new-tarball>}"
+OLD_TARBALL="${2:?missing old tarball}"
+NEW_LABEL="${3:?missing new label}"
+NEW_TARBALL="${4:?missing new tarball}"
+
+LIBRARY="${LIBRARY:-libsvs_runtime.so}"
+HEADER_SUBDIR="${HEADER_SUBDIR:-include/svs/runtime}"
+SUPPRESSIONS="${SUPPRESSIONS:-.github/abi-suppressions.yml}"
+POLICY="${POLICY:-strict_abi}"
+REPORT="${REPORT:-abi-report.md}"
+WORKDIR="${WORKDIR:-abi-work}"
+
+# Prints the resolved library path on success. Release tarballs and CI artifacts
+# have differed on whether the unversioned symlink is included, so accept the
+# versioned real file too.
+unpack() {
+    local tarball="$1" dest="$2" label="$3" lib
+
+    if [ ! -f "$tarball" ]; then
+        echo "::warning::$label: tarball not found at $tarball" >&2
+        return 1
+    fi
+
+    rm -rf "$dest"
+    mkdir -p "$dest"
+    tar -xzf "$tarball" -C "$dest"
+
+    lib=$(find "$dest" -name "$LIBRARY" -o -name "$LIBRARY.*" | sort | head -1)
+    if [ -z "$lib" ]; then
+        echo "::error::$label: $LIBRARY not found in $tarball" >&2
+        return 1
+    fi
+    if [ ! -d "$dest/$HEADER_SUBDIR" ]; then
+        echo "::error::$label: headers missing from $tarball ($HEADER_SUBDIR)" >&2
+        return 1
+    fi
+    echo "$lib"
+}
+
+OLD_DIR="$WORKDIR/old"
+NEW_DIR="$WORKDIR/new"
+
+OLD_LIB=$(unpack "$OLD_TARBALL" "$OLD_DIR" "$OLD_LABEL") || exit 77
+NEW_LIB=$(unpack "$NEW_TARBALL" "$NEW_DIR" "$NEW_LABEL") || exit 77
+
+echo "Comparing $LIBRARY: [$OLD_LABEL] -> [$NEW_LABEL]"
+
+suppress_args=()
+[ -f "$SUPPRESSIONS" ] && suppress_args=(--suppress "$SUPPRESSIONS")
+
+rc=0
+# Without pipefail the pipe into tee masks abicheck's exit status.
+set -o pipefail
+# castxml is not installed on the runners; clang is. `auto` does not fall back to
+# clang on its own. If header parsing degrades, abicheck still reports from the
+# ELF tier -- which is where vtable-size findings come from anyway.
+abicheck compare \
+    "$OLD_LIB" \
+    "$NEW_LIB" \
+    --header old="$OLD_DIR/$HEADER_SUBDIR" \
+    --header new="$NEW_DIR/$HEADER_SUBDIR" \
+    --include old="$OLD_DIR/include" \
+    --include new="$NEW_DIR/include" \
+    --version old="$OLD_LABEL" \
+    --version new="$NEW_LABEL" \
+    --ast-frontend clang \
+    --gcc-options "-std=c++20 -include cstddef" \
+    --policy "$POLICY" \
+    "${suppress_args[@]}" \
+    --format markdown | tee "$REPORT" || rc=$?
+
+case "$rc" in
+    0)
+        echo "ABI compatible: $OLD_LABEL -> $NEW_LABEL"
+        ;;
+    64)
+        echo "::error::abicheck rejected the invocation (exit 64) comparing" \
+             "$OLD_LABEL -> $NEW_LABEL. This is a harness bug, not an ABI finding."
+        ;;
+    *)
+        echo "::warning::ABI incompatibility: $NEW_LABEL differs from $OLD_LABEL (rc=$rc)"
+        ;;
+esac
+
+exit "$rc"
diff --git a/.github/workflows/build-cpp-runtime-bindings.yml b/.github/workflows/build-cpp-runtime-bindings.yml
index b87cd0ab5..330abd19f 100644
--- a/.github/workflows/build-cpp-runtime-bindings.yml
+++ b/.github/workflows/build-cpp-runtime-bindings.yml
@@ -133,3 +133,102 @@ jobs:
             -e ENABLE_LVQ_LEANVEC=${{ matrix.enable_lvq_leanvec }} \
             svs-manylinux228:latest \
             /bin/bash .github/scripts/test-faiss.sh
+
+  # Check the built runtime bindings against the last published release.
+  #
+  # Only the default variant is checked: releases publish
+  # svs-cpp-runtime-bindings.tar.gz but no -public-only asset, so that variant has
+  # nothing to compare against. It is covered indirectly -- both variants build
+  # from the same headers.
+  #
+  # The comparison primitive is .github/scripts/abi-check.sh, which the
+  # innersource repo also calls through its submodule path so the two repos cannot
+  # drift on how the same library is measured.
+  abi-check:
+    name: ABI check against the last release
+    needs: build-cpp-runtime-bindings
+    runs-on: ubuntu-22.04
+    # An intentionally-breaking PR still gets a full report: the label downgrades
+    # this job from blocking to informational rather than skipping it, so the
+    # break is recorded on the PR instead of going unmeasured.
+    continue-on-error: ${{ contains(toJson(github.event.pull_request.labels.*.name), '"API/ABI breaking change"') }}
+
+    steps:
+      - uses: actions/checkout@v6
+
+      # The hosted ubuntu-22.04 image ships only clang-13/14, which degrades
+      # abicheck's clang AST frontend to ELF-tier and drops constrained-template
+      # diffs. innersource gets a c++20-capable clang from its self-hosted
+      # toolchain; this keeps the two repos measuring at the same fidelity.
+      - name: Install clang for the AST frontend
+        run: |
+          wget -qO /tmp/llvm.sh https://apt.llvm.org/llvm.sh
+          chmod +x /tmp/llvm.sh
+          sudo /tmp/llvm.sh 18
+          sudo apt-get install -y --no-install-recommends libclang-18-dev llvm-18-dev
+          sudo update-alternatives --install /usr/bin/clang   clang   /usr/bin/clang-18   100
+          sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-18 100
+
+      - name: Install abicheck
+        run: pip install 'abicheck==0.5.*'
+
+      - name: Resolve baseline release tag
+        id: baseline
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          tag=$(grep -v '^#' .github/abi-baseline-tag | tr -d '[:space:]')
+          if [ "$tag" = 'latest' ]; then
+            tag=$(gh release view --json tagName --jq '.tagName')
+          fi
+          echo "tag=$tag" >> "$GITHUB_OUTPUT"
+
+      # A missing baseline is a hard failure: a green check that silently skipped
+      # the comparison is worse than a red one.
+      - name: Download release baseline
+        env:
+          GH_TOKEN: ${{ github.token }}
+          TAG: ${{ steps.baseline.outputs.tag }}
+        run: |
+          mkdir -p baseline
+          if ! gh release download "$TAG" --pattern svs-cpp-runtime-bindings.tar.gz \
+                 --dir baseline; then
+            echo "::error::Release $TAG has no svs-cpp-runtime-bindings.tar.gz asset." \
+                 "Fix the pin in .github/abi-baseline-tag."
+            exit 1
+          fi
+
+      - name: Download this build
+        uses: actions/download-artifact@v8
+        with:
+          name: svs-cpp-runtime-bindings
+          path: current
+
+      - name: Compare
+        env:
+          LIBRARY: libsvs_runtime.so
+          HEADER_SUBDIR: include/svs/runtime
+          SUPPRESSIONS: .github/abi-suppressions.yml
+          POLICY: strict_abi
+        run: |
+          chmod +x .github/scripts/abi-check.sh
+          label='${{ github.event.pull_request.number && format('PR {0}', github.event.pull_request.number) || github.ref_name }}'
+          rc=0
+          .github/scripts/abi-check.sh \
+            '${{ steps.baseline.outputs.tag }}' baseline/svs-cpp-runtime-bindings.tar.gz \
+            "$label" current/svs-cpp-runtime-bindings.tar.gz || rc=$?
+
+          if [ -s abi-report.md ]; then
+            {
+              echo "## ABI vs ${{ steps.baseline.outputs.tag }}"
+              cat abi-report.md
+            } >> "$GITHUB_STEP_SUMMARY"
+          fi
+
+          # 77 means an input tarball was missing; that is a harness/plumbing
+          # problem and must fail loudly rather than pass as "no findings".
+          if [ "$rc" -eq 77 ] || [ "$rc" -eq 64 ]; then
+            echo "::error::ABI check could not run (rc=$rc)."
+            exit 1
+          fi
+          exit "$rc"