diff --git a/.github/workflows/clang-format-fix.yaml b/.github/workflows/clang-format-fix.yaml
index e19d86bec..a9c045c9b 100644
--- a/.github/workflows/clang-format-fix.yaml
+++ b/.github/workflows/clang-format-fix.yaml
@@ -8,7 +8,9 @@ run-name: "${{ github.actor }} fixing C++ code format"
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
   workflow_call:
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
 
     steps:
       - name: Get PR Info
diff --git a/.github/workflows/clang-tidy-fix.yaml b/.github/workflows/clang-tidy-fix.yaml
index f7e850ba4..e7cf74302 100644
--- a/.github/workflows/clang-tidy-fix.yaml
+++ b/.github/workflows/clang-tidy-fix.yaml
@@ -8,7 +8,9 @@ name: Clang-Tidy Fix
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
       tidy-checks:
diff --git a/.github/workflows/cmake-format-fix.yaml b/.github/workflows/cmake-format-fix.yaml
index 2bb6f6398..6b6269f63 100644
--- a/.github/workflows/cmake-format-fix.yaml
+++ b/.github/workflows/cmake-format-fix.yaml
@@ -8,7 +8,9 @@ run-name: "${{ github.actor }} fixing CMake format"
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
   workflow_call:
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
 
     steps:
       - name: Get PR Info
diff --git a/.github/workflows/codeql-analysis.yaml b/.github/workflows/codeql-analysis.yaml
index f9bfad776..322cf978d 100644
--- a/.github/workflows/codeql-analysis.yaml
+++ b/.github/workflows/codeql-analysis.yaml
@@ -218,13 +218,7 @@ jobs:
           fi
 
   determine-languages:
-    needs:
-      [
-        pre-check,
-        detect-changes-cpp,
-        detect-changes-python,
-        detect-changes-actions,
-      ]
+    needs: [pre-check, detect-changes-cpp, detect-changes-python, detect-changes-actions]
     if: always() && needs.pre-check.result == 'success'
     runs-on: ubuntu-latest
     outputs:
diff --git a/.github/workflows/header-guards-fix.yaml b/.github/workflows/header-guards-fix.yaml
index 2c0f7fb6a..5abea8d3a 100644
--- a/.github/workflows/header-guards-fix.yaml
+++ b/.github/workflows/header-guards-fix.yaml
@@ -43,7 +43,9 @@ run-name: "${{ github.actor }} fixing header guards"
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
 
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
 
     steps:
       - name: Get PR Info
diff --git a/.github/workflows/jsonnet-format-fix.yaml b/.github/workflows/jsonnet-format-fix.yaml
index 5a02e4aaa..1f721e9be 100644
--- a/.github/workflows/jsonnet-format-fix.yaml
+++ b/.github/workflows/jsonnet-format-fix.yaml
@@ -8,7 +8,9 @@ run-name: "${{ github.actor }} fixing Jsonnet format"
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
   workflow_call:
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
 
     steps:
       - name: Get PR Info
diff --git a/.github/workflows/markdown-fix.yaml b/.github/workflows/markdown-fix.yaml
index bee7f76e6..e0150475c 100644
--- a/.github/workflows/markdown-fix.yaml
+++ b/.github/workflows/markdown-fix.yaml
@@ -43,7 +43,9 @@ run-name: "${{ github.actor }} fixing Markdown format"
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
 
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
 
     steps:
       - name: Get PR Info
diff --git a/.github/workflows/python-fix.yaml b/.github/workflows/python-fix.yaml
index 1f2bcc059..c9961213c 100644
--- a/.github/workflows/python-fix.yaml
+++ b/.github/workflows/python-fix.yaml
@@ -8,7 +8,9 @@ run-name: "${{ github.actor }} fixing Python code"
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
   workflow_call:
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
     steps:
       - name: Get PR Info
         if: github.event_name == 'issue_comment' && inputs.ref == ''
diff --git a/.github/workflows/yaml-fix.yaml b/.github/workflows/yaml-fix.yaml
index 36c9f5c51..cbb53491c 100644
--- a/.github/workflows/yaml-fix.yaml
+++ b/.github/workflows/yaml-fix.yaml
@@ -8,7 +8,9 @@ name: YAML Fix
   workflow_dispatch:
     inputs:
       ref:
-        description: "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the repository's default branch."
+        description:
+          "The branch name to checkout and push fixes to (must be a branch, not a commit SHA). Defaults to the
+          repository's default branch."
         required: false
         type: string
   workflow_call:
@@ -52,8 +54,7 @@ permissions:
   contents: write
 
 env:
-  local_checkout_path:
-    ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
+  local_checkout_path: ${{ inputs.checkout-path || format('{0}-src', github.event.repository.name) }}
 
 jobs:
   pre-check:
@@ -70,11 +71,11 @@ jobs:
     # This covers repo owners, invited collaborators, and all org members.
     outputs:
       ref:
-        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' &&
-        (github.event.inputs.ref || github.ref_name)) || steps.get_pr.outputs.ref }}
+        ${{ inputs.ref || (github.event_name == 'workflow_dispatch' && (github.event.inputs.ref || github.ref_name)) ||
+        steps.get_pr.outputs.ref }}
       repo:
-        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' &&
-        github.repository) || steps.get_pr.outputs.repo }}
+        ${{ inputs.repo || (github.event_name == 'workflow_dispatch' && github.repository) || steps.get_pr.outputs.repo
+        }}
 
     steps:
       - name: Get PR Info
diff --git a/CMakeLists.txt b/CMakeLists.txt
index dad564236..17454494d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,6 +39,21 @@ FetchContent_Declare(
   FIND_PACKAGE_ARGS
 )
 
+# ##############################################################################
+# Initial compilation flags for build types we care about
+if(NOT CMAKE_CXX_FLAGS_DEBUG)
+  set(CMAKE_CXX_FLAGS_DEBUG "-Og -g" CACHE STRING "" FORCE)
+endif()
+
+if(NOT CMAKE_CXX_FLAGS_RELEASE)
+  set(CMAKE_CXX_FLAGS_RELEASE "-O3 -g0 -DNDEBUG" CACHE STRING "" FORCE)
+endif()
+
+if(NOT CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+  set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O3 -fno-omit-frame-pointer -g -DNDEBUG" CACHE STRING "" FORCE)
+endif()
+# ##############################################################################
+
 # Make cetmodules available
 FetchContent_MakeAvailable(cetmodules)
 find_package(cetmodules 4.01.01 REQUIRED)
@@ -58,6 +73,8 @@ set(CTEST_TEST_TIMEOUT 90 CACHE STRING "Per-test timeout (s) for CTest")
 FetchContent_MakeAvailable(Catch2 GSL mimicpp)
 
 include(Modules/private/CreateCoverageTargets.cmake)
+include(Modules/private/PhlexSymbolVisibility.cmake)
+include(Modules/private/PhlexOptimization.cmake)
 
 option(ENABLE_TSAN "Enable Thread Sanitizer" OFF)
 option(ENABLE_ASAN "Enable Address Sanitizer" OFF)
diff --git a/Modules/private/PhlexOptimization.cmake b/Modules/private/PhlexOptimization.cmake
new file mode 100644
index 000000000..a0528d7d2
--- /dev/null
+++ b/Modules/private/PhlexOptimization.cmake
@@ -0,0 +1,175 @@
+# Provides phlex_apply_optimizations(target), which applies safe,
+# performance-oriented compiler flags to a Phlex shared library target.
+# Also defines the PHLEX_HIDE_SYMBOLS and PHLEX_ENABLE_IPO options and
+# documents how they interact.
+#
+# Two flags are applied (subject to compiler support and platform):
+#
+#   -fno-semantic-interposition (GCC >= 9, Clang >= 8)
+#     The compiler may assume that exported symbols in this shared library are
+#     not overridden at runtime by LD_PRELOAD or another DSO.  This is the
+#     natural complement of -fvisibility=hidden: once the exported-symbol
+#     surface is bounded by explicit export macros, treating those symbols as
+#     non-interposable allows the compiler to inline, devirtualise, and
+#     generate direct (non-PLT) calls for same-DSO accesses to exported
+#     functions.
+#
+#     External plugins continue to call Phlex symbols through the standard
+#     PLT/GOT mechanism; only code compiled as part of a Phlex shared library
+#     itself benefits.
+#
+#     Applied only when PHLEX_HIDE_SYMBOLS=ON (export macros are present and
+#     the exported-symbol set is well-defined).
+#
+#   -fno-plt (GCC >= 7.3, Clang >= 4, ELF platforms)
+#     Calls FROM a Phlex library TO symbols in other shared libraries (TBB,
+#     Boost, spdlog, ...) bypass the PLT stub and load the target address
+#     directly from the GOT.  This replaces one level of indirection on every
+#     cross-DSO call after first resolution.  Semantics are unchanged; only
+#     the dispatch mechanism differs.
+#
+#     Not applied on Apple platforms: Mach-O uses two-level namespaces and the
+#     PLT abstraction does not map directly to ELF semantics.
+#
+# Intentionally excluded:
+#   -ffast-math / -funsafe-math-optimizations
+#     Physics and numerical code relies on well-defined floating-point
+#     semantics (NaN propagation, exact rounding, signed-zero behaviour).
+#     These flags may silently produce incorrect numerical results and are
+#     therefore not enabled.
+#
+# Options and their interaction with CMAKE_BUILD_TYPE
+#
+#   Both PHLEX_HIDE_SYMBOLS and PHLEX_ENABLE_IPO are defined here so that their
+#   defaults can be derived together.  The effective defaults are:
+#
+#     CMAKE_BUILD_TYPE    PHLEX_ENABLE_IPO  PHLEX_HIDE_SYMBOLS
+#     ─────────────────   ───────────────   ─────────────────
+#     Release             ON                ON
+#     RelWithDebInfo      ON                ON
+#     Debug / sanitizer   OFF               OFF
+#     not set             OFF               OFF
+#
+#   Both options can be overridden independently on the command line:
+#
+#     -DPHLEX_HIDE_SYMBOLS=ON  -DPHLEX_ENABLE_IPO=ON  → LTO + -fno-semantic-interposition
+#                                                         (maximum optimization)
+#     -DPHLEX_HIDE_SYMBOLS=OFF -DPHLEX_ENABLE_IPO=ON  → LTO only; -fno-semantic-interposition
+#                                                         is NOT applied (valid, useful for
+#                                                         benchmarking against the ON case)
+#     -DPHLEX_HIDE_SYMBOLS=ON  -DPHLEX_ENABLE_IPO=OFF → -fno-semantic-interposition only
+#     -DPHLEX_HIDE_SYMBOLS=OFF -DPHLEX_ENABLE_IPO=OFF → no special optimization flags
+#
+#   The per-target flags in phlex_apply_optimizations() self-adjust automatically
+#   to reflect whichever combination is in effect.
+#
+# PHLEX_ENABLE_IPO (default ON for Release/RelWithDebInfo, OFF otherwise)
+#   When ON, enables interprocedural optimization (LTO) for Release and
+#   RelWithDebInfo configurations.  LTO is safe with or without symbol hiding
+#   because export attributes preserve the complete exported-symbol set.
+#   External plugins compiled without LTO link against the normal
+#   exported-symbol table and are unaffected.
+#
+# PHLEX_HIDE_SYMBOLS (default ON for Release/RelWithDebInfo, OFF otherwise)
+#   When ON: hidden-by-default visibility; export macros mark the public API.
+#   When OFF: all symbols visible; _internal targets become thin INTERFACE
+#   aliases of their public counterparts.
+
+
+include_guard()
+
+include(CheckCXXCompilerFlag)
+
+# Probe flag availability once at module-load time (results are cached in the
+# CMake cache and reused across reconfigures).
+check_cxx_compiler_flag(
+  "-fno-semantic-interposition"
+  PHLEX_CXX_HAVE_NO_SEMANTIC_INTERPOSITION
+)
+
+if(NOT APPLE)
+  check_cxx_compiler_flag("-fno-plt" PHLEX_CXX_HAVE_NO_PLT)
+endif()
+
+# ---------------------------------------------------------------------------
+# Interprocedural optimization (LTO) — defined first so its value can inform
+# the PHLEX_HIDE_SYMBOLS default below.
+# ---------------------------------------------------------------------------
+cmake_policy(SET CMP0069 NEW)
+include(CheckIPOSupported)
+
+if(CMAKE_BUILD_TYPE MATCHES "^(Release|RelWithDebInfo)$")
+  set(_phlex_ipo_default ON)
+else()
+  set(_phlex_ipo_default OFF)
+endif()
+
+option(
+  PHLEX_ENABLE_IPO
+  [=[Enable interprocedural optimization (LTO) for Release and RelWithDebInfo
+builds.  Defaults to ON when CMAKE_BUILD_TYPE is Release or RelWithDebInfo.
+Can be combined with PHLEX_HIDE_SYMBOLS=ON for maximum optimization, or with
+PHLEX_HIDE_SYMBOLS=OFF to benchmark LTO benefit without symbol hiding.]=]
+  "${_phlex_ipo_default}"
+)
+
+# ---------------------------------------------------------------------------
+# Symbol hiding — default follows CMAKE_BUILD_TYPE independently of IPO.
+# The two options are orthogonal: both ON/OFF combinations are valid and
+# produce different optimization profiles for benchmarking.
+# ---------------------------------------------------------------------------
+if(CMAKE_BUILD_TYPE MATCHES "^(Release|RelWithDebInfo)$")
+  set(_phlex_hide_default ON)
+else()
+  set(_phlex_hide_default OFF)
+endif()
+
+option(
+  PHLEX_HIDE_SYMBOLS
+  [=[Hide non-exported symbols in shared libraries (ON = curated API with
+hidden-by-default visibility; OFF = all symbols visible).  Defaults to ON for
+Release/RelWithDebInfo builds.
+Combined with PHLEX_ENABLE_IPO=ON: -fno-semantic-interposition is also applied
+for maximum optimization.  Setting OFF while PHLEX_ENABLE_IPO=ON is valid and
+useful for comparing LTO performance with and without symbol hiding.]=]
+  "${_phlex_hide_default}"
+)
+
+# ---------------------------------------------------------------------------
+# Activate LTO (if enabled and supported)
+# ---------------------------------------------------------------------------
+if(PHLEX_ENABLE_IPO)
+  check_ipo_supported(
+    RESULT _phlex_ipo_supported
+    OUTPUT _phlex_ipo_output
+    LANGUAGES CXX
+  )
+  if(_phlex_ipo_supported)
+    # Set defaults for all targets created in this scope and below.  The
+    # *_RELEASE and *_RELWITHDEBINFO variants leave Debug/Coverage/sanitizer
+    # builds unaffected (those configs override optimization independently).
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE ON)
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELWITHDEBINFO ON)
+    message(STATUS "Phlex: LTO enabled for Release and RelWithDebInfo builds")
+  else()
+    message(
+      WARNING
+      "Phlex: PHLEX_ENABLE_IPO=ON but LTO is not supported: ${_phlex_ipo_output}"
+    )
+  endif()
+endif()
+
+# ---------------------------------------------------------------------------
+function(phlex_apply_optimizations target)
+  # -fno-semantic-interposition pairs with PHLEX_HIDE_SYMBOLS: the compiler
+  # may only treat exported symbols as non-interposable once the exported-
+  # symbol surface has been explicitly bounded by export macros.
+  if(PHLEX_HIDE_SYMBOLS AND PHLEX_CXX_HAVE_NO_SEMANTIC_INTERPOSITION)
+    target_compile_options("${target}" PRIVATE "-fno-semantic-interposition")
+  endif()
+
+  # -fno-plt reduces cross-DSO call overhead on ELF (Linux) platforms.
+  if(PHLEX_CXX_HAVE_NO_PLT)
+    target_compile_options("${target}" PRIVATE "-fno-plt")
+  endif()
+endfunction()
diff --git a/Modules/private/PhlexSymbolVisibility.cmake b/Modules/private/PhlexSymbolVisibility.cmake
new file mode 100644
index 000000000..69590f457
--- /dev/null
+++ b/Modules/private/PhlexSymbolVisibility.cmake
@@ -0,0 +1,112 @@
+include(GenerateExportHeader)
+
+function(phlex_apply_symbol_visibility target)
+  set(EXPORT_HEADER "${PROJECT_BINARY_DIR}/include/phlex/${target}_export.hpp")
+  set(EXPORT_MACRO_NAME "${target}_EXPORT")
+
+  generate_export_header(
+    ${target}
+    BASE_NAME ${target}
+    EXPORT_FILE_NAME ${EXPORT_HEADER}
+    EXPORT_MACRO_NAME ${EXPORT_MACRO_NAME}
+    STATIC_DEFINE "${target}_STATIC_DEFINE"
+  )
+
+  if(PHLEX_HIDE_SYMBOLS)
+    set_target_properties(
+      ${target}
+      PROPERTIES CXX_VISIBILITY_PRESET hidden VISIBILITY_INLINES_HIDDEN ON
+    )
+  endif()
+
+  target_include_directories(${target} PUBLIC $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>)
+
+  install(FILES "${EXPORT_HEADER}" DESTINATION include/phlex)
+endfunction()
+
+# Create a companion library <target>_internal:
+#
+# When PHLEX_HIDE_SYMBOLS is ON (default): a non-installed shared library with
+# default (visible) symbol visibility, compiled from the same sources as
+# <target>. This allows tests to access non-exported implementation details
+# without requiring every internal symbol to carry an EXPORT macro, and enables
+# before/after comparison of library/executable sizes and link/load times.
+#
+# When PHLEX_HIDE_SYMBOLS is OFF: an INTERFACE target that simply links to
+# <target>. Since all public library symbols are already visible in this mode,
+# no separate compilation is needed and _internal targets are effectively
+# identical to their public counterparts.
+#
+# Usage (in the same CMakeLists.txt that defines <target>):
+#   phlex_make_internal_library(<target> LIBRARIES [PUBLIC ...] [PRIVATE ...])
+#
+# The LIBRARIES arguments mirror those of the original cet_make_library call but
+# may substitute other _internal targets for the corresponding public ones so
+# that the full transitive symbol set is visible (PHLEX_HIDE_SYMBOLS=ON only).
+function(phlex_make_internal_library target)
+  cmake_parse_arguments(ARG "" "" "LIBRARIES" ${ARGN})
+
+  set(internal "${target}_internal")
+
+  if(NOT PHLEX_HIDE_SYMBOLS)
+    # All public symbols already visible — _internal is a thin INTERFACE wrapper.
+    add_library(${internal} INTERFACE)
+    target_link_libraries(${internal} INTERFACE ${target})
+    return()
+  endif()
+
+  # Retrieve sources and source directory from the public target so we don't
+  # have to maintain a separate source list.
+  get_target_property(srcs ${target} SOURCES)
+  if(NOT srcs)
+    message(FATAL_ERROR "phlex_make_internal_library: ${target} has no SOURCES property")
+  endif()
+  get_target_property(src_dir ${target} SOURCE_DIR)
+  get_target_property(bin_dir ${target} BINARY_DIR)
+
+  # Convert relative paths to absolute. Generated sources (e.g. configure_file
+  # output) live in the binary directory rather than the source directory.
+  set(abs_srcs "")
+  foreach(s IN LISTS srcs)
+    if(IS_ABSOLUTE "${s}")
+      list(APPEND abs_srcs "${s}")
+    elseif(EXISTS "${src_dir}/${s}")
+      list(APPEND abs_srcs "${src_dir}/${s}")
+    else()
+      list(APPEND abs_srcs "${bin_dir}/${s}")
+    endif()
+  endforeach()
+
+  # Use add_library directly (not cet_make_library) so that cetmodules does not
+  # register this target for installation or package export.
+  add_library(${internal} SHARED ${abs_srcs})
+
+  if(ARG_LIBRARIES)
+    target_link_libraries(${internal} ${ARG_LIBRARIES})
+  endif()
+
+  # Cetmodules automatically adds $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}> for
+  # libraries it manages; replicate that here so consumers (e.g. layer_generator_internal)
+  # can resolve project headers such as #include "phlex/core/...".
+  # The _export.hpp headers live in PROJECT_BINARY_DIR/include/phlex.
+  # Without CXX_VISIBILITY_PRESET hidden the export macros expand to the default
+  # visibility attribute, making every symbol visible — exactly what we want here.
+  target_include_directories(
+    ${internal}
+    PUBLIC
+      "$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>"
+      "$<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>"
+  )
+
+  # Propagate compile definitions and options that the public target carries
+  # (e.g. BOOST_DLL_USE_STD_FS for run_phlex) so the internal build is equivalent.
+  get_target_property(defs ${target} COMPILE_DEFINITIONS)
+  if(defs)
+    target_compile_definitions(${internal} PRIVATE ${defs})
+  endif()
+
+  get_target_property(opts ${target} COMPILE_OPTIONS)
+  if(opts)
+    target_compile_options(${internal} PRIVATE ${opts})
+  endif()
+endfunction()
diff --git a/phlex/CMakeLists.txt b/phlex/CMakeLists.txt
index f208a812a..76e54ae2e 100644
--- a/phlex/CMakeLists.txt
+++ b/phlex/CMakeLists.txt
@@ -33,6 +33,8 @@ cet_make_library(
   Boost::json
   phlex::core
 )
+phlex_apply_symbol_visibility(phlex_configuration_internal)
+phlex_apply_optimizations(phlex_configuration_internal)
 
 cet_make_library(
   LIBRARY_NAME
diff --git a/phlex/app/CMakeLists.txt b/phlex/app/CMakeLists.txt
index 3c0a57af0..66c537496 100644
--- a/phlex/app/CMakeLists.txt
+++ b/phlex/app/CMakeLists.txt
@@ -18,10 +18,20 @@ cet_make_library(
 )
 
 install(FILES load_module.hpp run.hpp version.hpp DESTINATION include/phlex/app)
+phlex_apply_symbol_visibility(run_phlex)
+phlex_apply_optimizations(run_phlex)
 
 # We'll use C++17's filesystem instead of Boost's
 target_compile_definitions(run_phlex PRIVATE BOOST_DLL_USE_STD_FS)
 
+phlex_make_internal_library(
+  run_phlex
+  LIBRARIES
+  PUBLIC phlex_core_internal Boost::json Boost::boost
+)
+# BOOST_DLL_USE_STD_FS is propagated from run_phlex's COMPILE_DEFINITIONS by
+# phlex_make_internal_library, so no explicit repeat is needed here.
+
 cet_make_exec(
   NAME phlex
   SOURCE phlex.cpp
diff --git a/phlex/app/load_module.hpp b/phlex/app/load_module.hpp
index 14d3ba1f4..20fbcc3b8 100644
--- a/phlex/app/load_module.hpp
+++ b/phlex/app/load_module.hpp
@@ -1,23 +1,31 @@
 #ifndef PHLEX_APP_LOAD_MODULE_HPP
 #define PHLEX_APP_LOAD_MODULE_HPP
 
+#include "phlex/run_phlex_export.hpp"
+
 #include "phlex/core/fwd.hpp"
 #include "phlex/driver.hpp"
 
 #include "boost/json.hpp"
 
 #include <functional>
+#include <string>
 
 namespace phlex::experimental {
   namespace detail {
     // Adjust_config adds the module_label as a parameter, and it checks if the 'py'
     // parameter exists, inserting the 'cpp: "pymodule"' configuration if necessary.
-    boost::json::object adjust_config(std::string const& label, boost::json::object raw_config);
+    run_phlex_EXPORT boost::json::object adjust_config(std::string const& label,
+                                                       boost::json::object raw_config);
   }
 
-  void load_module(framework_graph& g, std::string const& label, boost::json::object config);
-  void load_source(framework_graph& g, std::string const& label, boost::json::object config);
-  detail::next_index_t load_driver(boost::json::object const& config);
+  run_phlex_EXPORT void load_module(framework_graph& g,
+                                    std::string const& label,
+                                    boost::json::object config);
+  run_phlex_EXPORT void load_source(framework_graph& g,
+                                    std::string const& label,
+                                    boost::json::object config);
+  run_phlex_EXPORT detail::next_index_t load_driver(boost::json::object const& config);
 }
 
 #endif // PHLEX_APP_LOAD_MODULE_HPP
diff --git a/phlex/app/run.hpp b/phlex/app/run.hpp
index 96161b773..af4ab113f 100644
--- a/phlex/app/run.hpp
+++ b/phlex/app/run.hpp
@@ -1,12 +1,14 @@
 #ifndef PHLEX_APP_RUN_HPP
 #define PHLEX_APP_RUN_HPP
 
+#include "phlex/run_phlex_export.hpp"
+
 #include "boost/json.hpp"
 
 #include <optional>
 
 namespace phlex::experimental {
-  void run(boost::json::object const& configurations, int max_parallelism);
+  run_phlex_EXPORT void run(boost::json::object const& configurations, int max_parallelism);
 }
 
 #endif // PHLEX_APP_RUN_HPP
diff --git a/phlex/app/version.hpp b/phlex/app/version.hpp
index ec1dbe940..dfb9b93cc 100644
--- a/phlex/app/version.hpp
+++ b/phlex/app/version.hpp
@@ -1,7 +1,9 @@
 #ifndef PHLEX_APP_VERSION_HPP
 #define PHLEX_APP_VERSION_HPP
 
+#include "phlex/run_phlex_export.hpp"
+
 namespace phlex::experimental {
-  char const* version();
+  run_phlex_EXPORT char const* version();
 }
 #endif // PHLEX_APP_VERSION_HPP
diff --git a/phlex/concurrency.hpp b/phlex/concurrency.hpp
index b456b9137..cb98595fb 100644
--- a/phlex/concurrency.hpp
+++ b/phlex/concurrency.hpp
@@ -1,10 +1,12 @@
 #ifndef PHLEX_CONCURRENCY_HPP
 #define PHLEX_CONCURRENCY_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include <cstddef>
 
 namespace phlex {
-  struct concurrency {
+  struct phlex_core_EXPORT concurrency {
     static concurrency const unlimited;
     static concurrency const serial;
 
diff --git a/phlex/configuration.hpp b/phlex/configuration.hpp
index 7dcf3945d..1a5ec1ef0 100644
--- a/phlex/configuration.hpp
+++ b/phlex/configuration.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CONFIGURATION_HPP
 #define PHLEX_CONFIGURATION_HPP
 
+#include "phlex/phlex_configuration_internal_export.hpp"
+
 #include "boost/json.hpp"
 #include "phlex/core/product_query.hpp"
 #include "phlex/model/identifier.hpp"
@@ -22,8 +24,8 @@ namespace phlex {
     }
 
     // Used later for product_query
-    std::optional<phlex::experimental::identifier> value_if_exists(boost::json::object const& obj,
-                                                                   std::string_view parameter);
+    phlex_configuration_internal_EXPORT std::optional<phlex::experimental::identifier>
+    value_if_exists(boost::json::object const& obj, std::string_view parameter);
 
     // helper for unpacking json array
     template <typename T, std::size_t... I>
@@ -34,7 +36,7 @@ namespace phlex {
     }
   }
 
-  class configuration {
+  class phlex_configuration_internal_EXPORT configuration {
   public:
     configuration() = default;
     explicit configuration(boost::json::object const& config) : config_{config} {}
@@ -89,15 +91,15 @@ namespace phlex {
   // To enable direct conversions from Boost JSON types to our own types, we implement
   // tag_invoke(...) function overloads, which are the customization points Boost JSON
   // provides.
-  configuration tag_invoke(boost::json::value_to_tag<configuration> const&,
-                           boost::json::value const& jv);
+  phlex_configuration_internal_EXPORT configuration
+  tag_invoke(boost::json::value_to_tag<configuration> const&, boost::json::value const& jv);
 
-  product_query tag_invoke(boost::json::value_to_tag<product_query> const&,
-                           boost::json::value const& jv);
+  phlex_configuration_internal_EXPORT product_query
+  tag_invoke(boost::json::value_to_tag<product_query> const&, boost::json::value const& jv);
 
   namespace experimental {
-    identifier tag_invoke(boost::json::value_to_tag<identifier> const&,
-                          boost::json::value const& jv);
+    phlex_configuration_internal_EXPORT identifier
+    tag_invoke(boost::json::value_to_tag<identifier> const&, boost::json::value const& jv);
   }
 
   template <std::size_t N>
diff --git a/phlex/core/CMakeLists.txt b/phlex/core/CMakeLists.txt
index 36fd293a3..fce6340f3 100644
--- a/phlex/core/CMakeLists.txt
+++ b/phlex/core/CMakeLists.txt
@@ -81,6 +81,8 @@ install(
   DESTINATION include/phlex/core/detail
 )
 target_include_directories(phlex_core PRIVATE ${PROJECT_SOURCE_DIR})
+phlex_apply_symbol_visibility(phlex_core)
+phlex_apply_optimizations(phlex_core)
 
 # AppleClang 15.0 still treats std::views::join as experimental
 if(
@@ -90,6 +92,14 @@ if(
   target_compile_options(phlex_core PRIVATE "-fexperimental-library")
 endif()
 
+phlex_make_internal_library(
+  phlex_core
+  LIBRARIES
+  PUBLIC TBB::tbb phlex::metaprogramming phlex_model_internal phlex_utilities_internal
+  PRIVATE Boost::json spdlog::spdlog
+)
+add_library(phlex::core_internal ALIAS phlex_core_internal)
+
 # Interface library
 cet_make_library(
   LIBRARY_NAME
diff --git a/phlex/core/consumer.hpp b/phlex/core/consumer.hpp
index fbd38b055..bc4c70a00 100644
--- a/phlex/core/consumer.hpp
+++ b/phlex/core/consumer.hpp
@@ -1,13 +1,15 @@
 #ifndef PHLEX_CORE_CONSUMER_HPP
 #define PHLEX_CORE_CONSUMER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/model/algorithm_name.hpp"
 
 #include <string>
 #include <vector>
 
 namespace phlex::experimental {
-  class consumer {
+  class phlex_core_EXPORT consumer {
   public:
     consumer(algorithm_name name, std::vector<std::string> predicates);
 
diff --git a/phlex/core/declared_fold.hpp b/phlex/core/declared_fold.hpp
index 4a6415324..429a252d3 100644
--- a/phlex/core/declared_fold.hpp
+++ b/phlex/core/declared_fold.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_FOLD_HPP
 #define PHLEX_CORE_DECLARED_FOLD_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/concurrency.hpp"
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/fold/send.hpp"
@@ -34,7 +36,7 @@
 #include <utility>
 
 namespace phlex::experimental {
-  class declared_fold : public products_consumer {
+  class phlex_core_EXPORT declared_fold : public products_consumer {
   public:
     declared_fold(algorithm_name name,
                   std::vector<std::string> predicates,
diff --git a/phlex/core/declared_observer.hpp b/phlex/core/declared_observer.hpp
index d1bea85e8..fc3e6d0eb 100644
--- a/phlex/core/declared_observer.hpp
+++ b/phlex/core/declared_observer.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_OBSERVER_HPP
 #define PHLEX_CORE_DECLARED_OBSERVER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/input_arguments.hpp"
@@ -30,7 +32,7 @@
 
 namespace phlex::experimental {
 
-  class declared_observer : public products_consumer {
+  class phlex_core_EXPORT declared_observer : public products_consumer {
   public:
     declared_observer(algorithm_name name,
                       std::vector<std::string> predicates,
diff --git a/phlex/core/declared_output.hpp b/phlex/core/declared_output.hpp
index 7ca82f4f2..4e2643583 100644
--- a/phlex/core/declared_output.hpp
+++ b/phlex/core/declared_output.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_OUTPUT_HPP
 #define PHLEX_CORE_DECLARED_OUTPUT_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/consumer.hpp"
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/message.hpp"
@@ -20,7 +22,7 @@ namespace phlex::experimental {
   namespace detail {
     using output_function_t = std::function<void(product_store const&)>;
   }
-  class declared_output : public consumer {
+  class phlex_core_EXPORT declared_output : public consumer {
   public:
     declared_output(algorithm_name name,
                     std::size_t concurrency,
diff --git a/phlex/core/declared_predicate.hpp b/phlex/core/declared_predicate.hpp
index 72643c7da..755d8b295 100644
--- a/phlex/core/declared_predicate.hpp
+++ b/phlex/core/declared_predicate.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_PREDICATE_HPP
 #define PHLEX_CORE_DECLARED_PREDICATE_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/detail/filter_impl.hpp"
 #include "phlex/core/fwd.hpp"
@@ -32,7 +34,7 @@
 
 namespace phlex::experimental {
 
-  class declared_predicate : public products_consumer {
+  class phlex_core_EXPORT declared_predicate : public products_consumer {
   public:
     declared_predicate(algorithm_name name,
                        std::vector<std::string> predicates,
diff --git a/phlex/core/declared_provider.hpp b/phlex/core/declared_provider.hpp
index 33576de6e..9ade62ef1 100644
--- a/phlex/core/declared_provider.hpp
+++ b/phlex/core/declared_provider.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_PROVIDER_HPP
 #define PHLEX_CORE_DECLARED_PROVIDER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/message.hpp"
@@ -22,7 +24,7 @@
 
 namespace phlex::experimental {
 
-  class declared_provider {
+  class phlex_core_EXPORT declared_provider {
   public:
     declared_provider(algorithm_name name, product_query output_product);
     virtual ~declared_provider();
diff --git a/phlex/core/declared_transform.hpp b/phlex/core/declared_transform.hpp
index 34358cd8d..8e9586c2b 100644
--- a/phlex/core/declared_transform.hpp
+++ b/phlex/core/declared_transform.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_TRANSFORM_HPP
 #define PHLEX_CORE_DECLARED_TRANSFORM_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 // FIXME: Add comments explaining the process.  For each implementation, explain what part
 //        of the process a given section of code is addressing.
 
@@ -36,7 +38,7 @@
 
 namespace phlex::experimental {
 
-  class declared_transform : public products_consumer {
+  class phlex_core_EXPORT declared_transform : public products_consumer {
   public:
     declared_transform(algorithm_name name,
                        std::vector<std::string> predicates,
diff --git a/phlex/core/declared_unfold.hpp b/phlex/core/declared_unfold.hpp
index 8d5010cf5..8952f6f36 100644
--- a/phlex/core/declared_unfold.hpp
+++ b/phlex/core/declared_unfold.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DECLARED_UNFOLD_HPP
 #define PHLEX_CORE_DECLARED_UNFOLD_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/input_arguments.hpp"
@@ -32,7 +34,7 @@
 
 namespace phlex::experimental {
 
-  class generator {
+  class phlex_core_EXPORT generator {
   public:
     explicit generator(product_store_const_ptr const& parent,
                        algorithm_name node_name,
@@ -53,7 +55,7 @@ namespace phlex::experimental {
     std::map<data_cell_index::hash_type, std::size_t> child_counts_;
   };
 
-  class declared_unfold : public products_consumer {
+  class phlex_core_EXPORT declared_unfold : public products_consumer {
   public:
     declared_unfold(algorithm_name name,
                     std::vector<std::string> predicates,
diff --git a/phlex/core/detail/filter_impl.hpp b/phlex/core/detail/filter_impl.hpp
index 4d6dcd2de..0277ee876 100644
--- a/phlex/core/detail/filter_impl.hpp
+++ b/phlex/core/detail/filter_impl.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DETAIL_FILTER_IMPL_HPP
 #define PHLEX_CORE_DETAIL_FILTER_IMPL_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/product_query.hpp"
 #include "phlex/model/product_store.hpp"
@@ -29,7 +31,7 @@ namespace phlex::experimental {
     return value == true_value;
   }
 
-  class decision_map {
+  class phlex_core_EXPORT decision_map {
     using decisions_t = oneapi::tbb::concurrent_hash_map<std::size_t, unsigned int>;
 
   public:
@@ -47,7 +49,7 @@ namespace phlex::experimental {
     decisions_t results_;
   };
 
-  class data_map {
+  class phlex_core_EXPORT data_map {
     using stores_t =
       oneapi::tbb::concurrent_hash_map<std::size_t, std::vector<product_store_const_ptr>>;
 
diff --git a/phlex/core/detail/make_algorithm_name.hpp b/phlex/core/detail/make_algorithm_name.hpp
index 2edde613d..b554e1b9f 100644
--- a/phlex/core/detail/make_algorithm_name.hpp
+++ b/phlex/core/detail/make_algorithm_name.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DETAIL_MAKE_ALGORITHM_NAME_HPP
 #define PHLEX_CORE_DETAIL_MAKE_ALGORITHM_NAME_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 // This simple utility is placed in an implementation file to avoid including the
 // phlex/configuration.hpp in framework code.
 
@@ -14,7 +16,8 @@ namespace phlex::experimental {
   class algorithm_name;
 
   namespace detail {
-    algorithm_name make_algorithm_name(configuration const* config, std::string_view name);
+    phlex_core_EXPORT algorithm_name make_algorithm_name(configuration const* config,
+                                                         std::string_view name);
   }
 }
 
diff --git a/phlex/core/detail/maybe_predicates.hpp b/phlex/core/detail/maybe_predicates.hpp
index 196915d7f..f48c33a87 100644
--- a/phlex/core/detail/maybe_predicates.hpp
+++ b/phlex/core/detail/maybe_predicates.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DETAIL_MAYBE_PREDICATES_HPP
 #define PHLEX_CORE_DETAIL_MAYBE_PREDICATES_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 // This simple utility is placed in an implementation file to avoid including the
 // phlex/configuration.hpp in framework code.
 
@@ -13,7 +15,8 @@ namespace phlex {
 }
 
 namespace phlex::experimental::detail {
-  std::optional<std::vector<std::string>> maybe_predicates(configuration const* config);
+  phlex_core_EXPORT std::optional<std::vector<std::string>> maybe_predicates(
+    configuration const* config);
 }
 
 #endif // PHLEX_CORE_DETAIL_MAYBE_PREDICATES_HPP
diff --git a/phlex/core/detail/repeater_node.hpp b/phlex/core/detail/repeater_node.hpp
index eb9ba978f..1b48fec9c 100644
--- a/phlex/core/detail/repeater_node.hpp
+++ b/phlex/core/detail/repeater_node.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_DETAIL_REPEATER_NODE_HPP
 #define PHLEX_CORE_DETAIL_REPEATER_NODE_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/message.hpp"
 
 #include "oneapi/tbb/concurrent_hash_map.h"
@@ -15,7 +17,8 @@ namespace phlex::experimental::detail {
 
   using repeater_node_input = std::tuple<message, indexed_end_token, index_message>;
 
-  class repeater_node : public tbb::flow::composite_node<repeater_node_input, message_tuple<1>> {
+  class phlex_core_EXPORT repeater_node :
+    public tbb::flow::composite_node<repeater_node_input, message_tuple<1>> {
   public:
     repeater_node(tbb::flow::graph& g, std::string node_name, identifier layer_name);
 
diff --git a/phlex/core/edge_creation_policy.hpp b/phlex/core/edge_creation_policy.hpp
index b6f0783e7..caede8b78 100644
--- a/phlex/core/edge_creation_policy.hpp
+++ b/phlex/core/edge_creation_policy.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_EDGE_CREATION_POLICY_HPP
 #define PHLEX_CORE_EDGE_CREATION_POLICY_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/message.hpp"
 #include "phlex/model/identifier.hpp"
 #include "phlex/model/product_specification.hpp"
@@ -15,7 +17,7 @@
 namespace phlex::experimental {
   using product_name_t = identifier;
 
-  class edge_creation_policy {
+  class phlex_core_EXPORT edge_creation_policy {
   public:
     template <typename... Args>
     edge_creation_policy(Args&... producers);
diff --git a/phlex/core/edge_maker.hpp b/phlex/core/edge_maker.hpp
index fb4bf3289..a40a46028 100644
--- a/phlex/core/edge_maker.hpp
+++ b/phlex/core/edge_maker.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_EDGE_MAKER_HPP
 #define PHLEX_CORE_EDGE_MAKER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/declared_fold.hpp"
 #include "phlex/core/declared_output.hpp"
 #include "phlex/core/declared_provider.hpp"
@@ -28,7 +30,7 @@ namespace phlex::experimental {
   index_router::provider_input_ports_t make_provider_edges(index_router::head_ports_t head_ports,
                                                            declared_providers& providers);
 
-  class edge_maker {
+  class phlex_core_EXPORT edge_maker {
   public:
     template <typename... Args>
     edge_maker(Args&... args);
diff --git a/phlex/core/filter.hpp b/phlex/core/filter.hpp
index 36ccac003..b96b116a3 100644
--- a/phlex/core/filter.hpp
+++ b/phlex/core/filter.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_FILTER_HPP
 #define PHLEX_CORE_FILTER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/detail/filter_impl.hpp"
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/message.hpp"
@@ -12,7 +14,7 @@ namespace phlex::experimental {
     oneapi::tbb::flow::composite_node<std::tuple<message, predicate_result>,
                                       std::tuple<oneapi::tbb::flow::continue_msg>>;
 
-  class filter : public filter_base {
+  class phlex_core_EXPORT filter : public filter_base {
     using indexer_t = oneapi::tbb::flow::indexer_node<message, predicate_result>;
     using tag_t = indexer_t::output_type;
 
diff --git a/phlex/core/framework_graph.hpp b/phlex/core/framework_graph.hpp
index 49a1a6c04..c45f426ff 100644
--- a/phlex/core/framework_graph.hpp
+++ b/phlex/core/framework_graph.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_FRAMEWORK_GRAPH_HPP
 #define PHLEX_CORE_FRAMEWORK_GRAPH_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/declared_fold.hpp"
 #include "phlex/core/declared_unfold.hpp"
 #include "phlex/core/filter.hpp"
@@ -31,7 +33,7 @@ namespace phlex {
 }
 
 namespace phlex::experimental {
-  class framework_graph {
+  class phlex_core_EXPORT framework_graph {
   public:
     explicit framework_graph(data_cell_index_ptr index,
                              int max_parallelism = oneapi::tbb::info::default_concurrency());
diff --git a/phlex/core/glue.hpp b/phlex/core/glue.hpp
index 86d47e12d..1b8c008b2 100644
--- a/phlex/core/glue.hpp
+++ b/phlex/core/glue.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_GLUE_HPP
 #define PHLEX_CORE_GLUE_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/concurrency.hpp"
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/registrar.hpp"
@@ -23,7 +25,7 @@ namespace phlex::experimental {
   struct node_catalog;
 
   namespace detail {
-    void verify_name(std::string const& name, configuration const* config);
+    phlex_core_EXPORT void verify_name(std::string const& name, configuration const* config);
   }
 
   // ==============================================================================
@@ -39,7 +41,7 @@ namespace phlex::experimental {
  *           This object is stored as a shared pointer and its methods are bound to the created nodes.
  */
   template <typename T>
-  class glue {
+  class phlex_core_EXPORT glue {
   public:
     glue(tbb::flow::graph& g,
          node_catalog& nodes,
diff --git a/phlex/core/index_router.hpp b/phlex/core/index_router.hpp
index b15065eb4..0fbfdfd2b 100644
--- a/phlex/core/index_router.hpp
+++ b/phlex/core/index_router.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_INDEX_ROUTER_HPP
 #define PHLEX_CORE_INDEX_ROUTER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/message.hpp"
 #include "phlex/model/data_cell_counter.hpp"
@@ -30,7 +32,7 @@ namespace phlex::experimental {
     // join operation.  It:
     //   (a) routes index messages to either the matching layer or its data-layer parent, and
     //   (b) emits flush tokens to the repeater to evict a cached data product from memory.
-    class multilayer_slot {
+    class phlex_core_EXPORT multilayer_slot {
     public:
       multilayer_slot(tbb::flow::graph& g,
                       identifier layer,
@@ -55,7 +57,7 @@ namespace phlex::experimental {
     // A layer_scope object is an RAII object that manages layer-scoped operations during
     // data-cell-index routing. It updates flush counters on construction and ensures cleanup
     // (flushing end tokens and releasing fold results) on destruction.
-    class layer_scope {
+    class phlex_core_EXPORT layer_scope {
     public:
       layer_scope(flush_counters& counters,
                   flusher_t& flusher,
@@ -74,7 +76,7 @@ namespace phlex::experimental {
     };
   }
 
-  class index_router {
+  class phlex_core_EXPORT index_router {
   public:
     struct named_input_port {
       product_query product_label;
diff --git a/phlex/core/input_arguments.hpp b/phlex/core/input_arguments.hpp
index c22867878..6ed74aedf 100644
--- a/phlex/core/input_arguments.hpp
+++ b/phlex/core/input_arguments.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_INPUT_ARGUMENTS_HPP
 #define PHLEX_CORE_INPUT_ARGUMENTS_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/message.hpp"
 #include "phlex/core/product_query.hpp"
 #include "phlex/model/handle.hpp"
@@ -56,8 +58,8 @@ namespace phlex::experimental {
   }
 
   namespace detail {
-    void verify_no_duplicate_input_products(std::string const& algorithm_name,
-                                            product_queries to_sort);
+    phlex_core_EXPORT void verify_no_duplicate_input_products(std::string const& algorithm_name,
+                                                              product_queries to_sort);
   }
 
   template <typename InputTypes>
diff --git a/phlex/core/message.hpp b/phlex/core/message.hpp
index bea2af04a..62f423220 100644
--- a/phlex/core/message.hpp
+++ b/phlex/core/message.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_MESSAGE_HPP
 #define PHLEX_CORE_MESSAGE_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/product_query.hpp"
 #include "phlex/model/fwd.hpp"
@@ -44,7 +46,7 @@ namespace phlex::experimental {
     std::size_t id;
   };
 
-  struct message_matcher {
+  struct phlex_core_EXPORT message_matcher {
     std::size_t operator()(message const& msg) const noexcept;
   };
 
@@ -62,13 +64,13 @@ namespace phlex::experimental {
   using named_index_ports = std::vector<named_index_port>;
 
   // Overload for use with most_derived
-  message const& more_derived(message const& a, message const& b);
+  phlex_core_EXPORT message const& more_derived(message const& a, message const& b);
 
   // Non-template overload for single message case
   inline message const& most_derived(message const& msg) { return msg; }
 
-  std::size_t port_index_for(product_queries const& product_labels,
-                             product_query const& product_label);
+  phlex_core_EXPORT std::size_t port_index_for(product_queries const& product_labels,
+                                               product_query const& product_label);
 }
 
 #endif // PHLEX_CORE_MESSAGE_HPP
diff --git a/phlex/core/node_catalog.hpp b/phlex/core/node_catalog.hpp
index 447f11d40..68051aaa5 100644
--- a/phlex/core/node_catalog.hpp
+++ b/phlex/core/node_catalog.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_NODE_CATALOG_HPP
 #define PHLEX_CORE_NODE_CATALOG_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/declared_fold.hpp"
 #include "phlex/core/declared_observer.hpp"
 #include "phlex/core/declared_output.hpp"
@@ -17,7 +19,7 @@
 #include <vector>
 
 namespace phlex::experimental {
-  struct node_catalog {
+  struct phlex_core_EXPORT node_catalog {
     template <typename Ptr>
     auto registrar_for(std::vector<std::string>& errors)
     {
diff --git a/phlex/core/product_query.hpp b/phlex/core/product_query.hpp
index dfd73bb6f..dd0f4859f 100644
--- a/phlex/core/product_query.hpp
+++ b/phlex/core/product_query.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_PRODUCT_QUERY_HPP
 #define PHLEX_CORE_PRODUCT_QUERY_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/model/identifier.hpp"
 #include "phlex/model/product_specification.hpp"
 #include "phlex/model/type_id.hpp"
@@ -63,7 +65,7 @@ namespace phlex {
     };
   }
 
-  struct product_query {
+  struct phlex_core_EXPORT product_query {
     detail::required_creator_name<experimental::identifier> creator;
     detail::required_layer_name<experimental::identifier> layer;
     std::optional<experimental::identifier> suffix;
diff --git a/phlex/core/products_consumer.hpp b/phlex/core/products_consumer.hpp
index c6ae79c04..180b6b7db 100644
--- a/phlex/core/products_consumer.hpp
+++ b/phlex/core/products_consumer.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_PRODUCTS_CONSUMER_HPP
 #define PHLEX_CORE_PRODUCTS_CONSUMER_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/consumer.hpp"
 #include "phlex/core/fwd.hpp"
 #include "phlex/core/input_arguments.hpp"
@@ -15,7 +17,7 @@
 #include <vector>
 
 namespace phlex::experimental {
-  class products_consumer : public consumer {
+  class phlex_core_EXPORT products_consumer : public consumer {
   public:
     products_consumer(algorithm_name name,
                       std::vector<std::string> predicates,
diff --git a/phlex/core/registrar.hpp b/phlex/core/registrar.hpp
index d51fa32e6..82ae79d55 100644
--- a/phlex/core/registrar.hpp
+++ b/phlex/core/registrar.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_REGISTRAR_HPP
 #define PHLEX_CORE_REGISTRAR_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 // =======================================================================================
 //
 // The registrar class completes the registration of a node at the end of a registration
@@ -58,7 +60,8 @@
 namespace phlex::experimental {
 
   namespace detail {
-    void add_to_error_messages(std::vector<std::string>& errors, std::string const& name);
+    phlex_core_EXPORT void add_to_error_messages(std::vector<std::string>& errors,
+                                                 std::string const& name);
   }
 
   template <typename Ptr>
diff --git a/phlex/core/registration_api.hpp b/phlex/core/registration_api.hpp
index ce4d8e5b4..93a7532aa 100644
--- a/phlex/core/registration_api.hpp
+++ b/phlex/core/registration_api.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_REGISTRATION_API_HPP
 #define PHLEX_CORE_REGISTRATION_API_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/concurrency.hpp"
 #include "phlex/core/concepts.hpp"
 #include "phlex/core/declared_fold.hpp"
@@ -304,7 +306,7 @@ namespace phlex::experimental {
   // ====================================================================================
   // Output API
 
-  class output_api {
+  class phlex_core_EXPORT output_api {
   public:
     output_api(registrar<declared_output_ptr> reg,
                configuration const* config,
diff --git a/phlex/core/store_counters.hpp b/phlex/core/store_counters.hpp
index 8363a93d8..0e97b9f56 100644
--- a/phlex/core/store_counters.hpp
+++ b/phlex/core/store_counters.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_CORE_STORE_COUNTERS_HPP
 #define PHLEX_CORE_STORE_COUNTERS_HPP
 
+#include "phlex/phlex_core_export.hpp"
+
 #include "phlex/core/fwd.hpp"
 #include "phlex/model/data_cell_counter.hpp"
 #include "phlex/model/data_cell_index.hpp"
@@ -14,7 +16,7 @@
 #include <version>
 
 namespace phlex::experimental {
-  class store_counter {
+  class phlex_core_EXPORT store_counter {
   public:
     void set_flush_value(flush_counts_ptr counts, std::size_t original_message_id);
     void increment(data_cell_index::hash_type layer_hash);
@@ -35,7 +37,7 @@ namespace phlex::experimental {
     std::atomic<bool> ready_to_flush_{true};
   };
 
-  class count_stores {
+  class phlex_core_EXPORT count_stores {
   protected:
     store_counter& counter_for(data_cell_index::hash_type hash);
     std::unique_ptr<store_counter> done_with(data_cell_index::hash_type hash);
diff --git a/phlex/model/CMakeLists.txt b/phlex/model/CMakeLists.txt
index 6b5eabf27..f75e21f7f 100644
--- a/phlex/model/CMakeLists.txt
+++ b/phlex/model/CMakeLists.txt
@@ -40,6 +40,16 @@ install(
 )
 
 target_include_directories(phlex_model PRIVATE ${PROJECT_SOURCE_DIR})
+phlex_apply_symbol_visibility(phlex_model)
+phlex_apply_optimizations(phlex_model)
+
+phlex_make_internal_library(
+  phlex_model
+  LIBRARIES
+  PUBLIC Boost::boost spdlog::spdlog fmt::fmt
+  PRIVATE phlex_utilities_internal TBB::tbb
+)
+add_library(phlex::model_internal ALIAS phlex_model_internal)
 
 # Interface library
 cet_make_library(
diff --git a/phlex/model/algorithm_name.hpp b/phlex/model/algorithm_name.hpp
index 139704408..778f10803 100644
--- a/phlex/model/algorithm_name.hpp
+++ b/phlex/model/algorithm_name.hpp
@@ -1,10 +1,12 @@
 #ifndef PHLEX_MODEL_ALGORITHM_NAME_HPP
 #define PHLEX_MODEL_ALGORITHM_NAME_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/identifier.hpp"
 
 namespace phlex::experimental {
-  class algorithm_name {
+  class phlex_model_EXPORT algorithm_name {
     enum class specified_fields { neither, either, both };
 
   public:
diff --git a/phlex/model/data_cell_counter.hpp b/phlex/model/data_cell_counter.hpp
index 6cbd615c1..888a7da22 100644
--- a/phlex/model/data_cell_counter.hpp
+++ b/phlex/model/data_cell_counter.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_MODEL_DATA_CELL_COUNTER_HPP
 #define PHLEX_MODEL_DATA_CELL_COUNTER_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/data_cell_index.hpp"
 #include "phlex/model/fwd.hpp"
 #include "phlex/model/identifier.hpp"
@@ -12,7 +14,7 @@
 #include <optional>
 
 namespace phlex::experimental {
-  class flush_counts {
+  class phlex_model_EXPORT flush_counts {
   public:
     flush_counts();
     explicit flush_counts(std::map<data_cell_index::hash_type, std::size_t> child_counts);
@@ -34,7 +36,7 @@ namespace phlex::experimental {
     std::map<data_cell_index::hash_type, std::size_t> child_counts_{};
   };
 
-  class data_cell_counter {
+  class phlex_model_EXPORT data_cell_counter {
   public:
     data_cell_counter();
     data_cell_counter(data_cell_counter* parent, identifier const& layer_name);
@@ -57,7 +59,7 @@ namespace phlex::experimental {
     std::map<data_cell_index::hash_type, std::size_t> child_counts_{};
   };
 
-  class flush_counters {
+  class phlex_model_EXPORT flush_counters {
   public:
     void update(data_cell_index_ptr const id);
     flush_counts extract(data_cell_index_ptr const id);
diff --git a/phlex/model/data_cell_index.hpp b/phlex/model/data_cell_index.hpp
index d4bdc83ff..18c64325f 100644
--- a/phlex/model/data_cell_index.hpp
+++ b/phlex/model/data_cell_index.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_MODEL_DATA_CELL_INDEX_HPP
 #define PHLEX_MODEL_DATA_CELL_INDEX_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/fwd.hpp"
 #include "phlex/model/identifier.hpp"
 
@@ -14,7 +16,7 @@
 #include <vector>
 
 namespace phlex {
-  class data_cell_index : public std::enable_shared_from_this<data_cell_index> {
+  class phlex_model_EXPORT data_cell_index : public std::enable_shared_from_this<data_cell_index> {
   public:
     static data_cell_index const& base();
     static data_cell_index_ptr base_ptr();
@@ -51,7 +53,7 @@ namespace phlex {
     hash_type hash_{0};
   };
 
-  std::ostream& operator<<(std::ostream& os, data_cell_index const& id);
+  phlex_model_EXPORT std::ostream& operator<<(std::ostream& os, data_cell_index const& id);
 }
 
 namespace std {
diff --git a/phlex/model/data_layer_hierarchy.hpp b/phlex/model/data_layer_hierarchy.hpp
index 8e03819ae..426aefd37 100644
--- a/phlex/model/data_layer_hierarchy.hpp
+++ b/phlex/model/data_layer_hierarchy.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_MODEL_DATA_LAYER_HIERARCHY_HPP
 #define PHLEX_MODEL_DATA_LAYER_HIERARCHY_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/data_cell_index.hpp"
 #include "phlex/model/fwd.hpp"
 
@@ -13,7 +15,7 @@
 
 namespace phlex::experimental {
 
-  class data_layer_hierarchy {
+  class phlex_model_EXPORT data_layer_hierarchy {
   public:
     ~data_layer_hierarchy();
     void increment_count(data_cell_index_ptr const& id);
diff --git a/phlex/model/identifier.hpp b/phlex/model/identifier.hpp
index 89769117f..cc002bcb0 100644
--- a/phlex/model/identifier.hpp
+++ b/phlex/model/identifier.hpp
@@ -1,10 +1,14 @@
 #ifndef PHLEX_MODEL_IDENTIFIER_HPP
 #define PHLEX_MODEL_IDENTIFIER_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include <boost/json/fwd.hpp>
 
 #include <fmt/format.h>
 
+#include <compare>
+#include <cstddef>
 #include <cstdint>
 #include <string>
 #include <string_view>
@@ -18,7 +22,7 @@ namespace phlex::experimental {
 
   /// Carries around the string itself (as a shared_ptr to string to make copies lighter)
   /// along with a precomputed hash used for all comparisons
-  class identifier {
+  class phlex_model_EXPORT identifier {
   public:
     static std::uint64_t hash_string(std::string_view str);
     // The default constructor is necessary so other classes containing identifiers
@@ -56,8 +60,9 @@ namespace phlex::experimental {
     std::string const& trans_get_string() const noexcept { return content_; }
 
     // Comparison operators with _id queries
-    friend bool operator==(identifier const& lhs, identifier_query rhs);
-    friend std::strong_ordering operator<=>(identifier const& lhs, identifier_query rhs);
+    friend phlex_model_EXPORT bool operator==(identifier const& lhs, identifier_query rhs);
+    friend phlex_model_EXPORT std::strong_ordering operator<=>(identifier const& lhs,
+                                                               identifier_query rhs);
     friend std::hash<identifier>;
 
   private:
@@ -67,8 +72,8 @@ namespace phlex::experimental {
 
   // Identifier UDL
   namespace literals {
-    identifier operator""_id(char const* lit, std::size_t len);
-    identifier_query operator""_idq(char const* lit, std::size_t len);
+    phlex_model_EXPORT identifier operator""_id(char const* lit, std::size_t len);
+    phlex_model_EXPORT identifier_query operator""_idq(char const* lit, std::size_t len);
   }
 
   // Really trying to avoid the extra function call here
diff --git a/phlex/model/product_matcher.hpp b/phlex/model/product_matcher.hpp
index 632273f06..e6f13bdef 100644
--- a/phlex/model/product_matcher.hpp
+++ b/phlex/model/product_matcher.hpp
@@ -9,13 +9,15 @@
 //
 // =======================================================================================
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/fwd.hpp"
 
 #include <array>
 #include <string>
 
 namespace phlex::experimental {
-  class product_matcher {
+  class phlex_model_EXPORT product_matcher {
   public:
     explicit product_matcher(std::string matcher_spec);
     bool matches(product_store_const_ptr const& store) const;
diff --git a/phlex/model/product_specification.hpp b/phlex/model/product_specification.hpp
index 5167f4741..35de9f0d6 100644
--- a/phlex/model/product_specification.hpp
+++ b/phlex/model/product_specification.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_MODEL_PRODUCT_SPECIFICATION_HPP
 #define PHLEX_MODEL_PRODUCT_SPECIFICATION_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/algorithm_name.hpp"
 #include "phlex/model/identifier.hpp"
 #include "phlex/model/type_id.hpp"
@@ -12,7 +14,7 @@
 #include <vector>
 
 namespace phlex::experimental {
-  class product_specification {
+  class phlex_model_EXPORT product_specification {
   public:
     product_specification();
     product_specification(char const* name);
@@ -44,9 +46,10 @@ namespace phlex::experimental {
 
   using product_specifications = std::vector<product_specification>;
 
-  product_specifications to_product_specifications(std::string_view name,
-                                                   std::vector<std::string> output_labels,
-                                                   std::vector<type_id> output_types);
+  phlex_model_EXPORT product_specifications
+  to_product_specifications(std::string_view name,
+                            std::vector<std::string> output_labels,
+                            std::vector<type_id> output_types);
 }
 
 template <>
diff --git a/phlex/model/product_store.hpp b/phlex/model/product_store.hpp
index 23199001e..bbe29bc85 100644
--- a/phlex/model/product_store.hpp
+++ b/phlex/model/product_store.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_MODEL_PRODUCT_STORE_HPP
 #define PHLEX_MODEL_PRODUCT_STORE_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/algorithm_name.hpp"
 #include "phlex/model/data_cell_index.hpp"
 #include "phlex/model/fwd.hpp"
@@ -15,7 +17,7 @@
 #include <type_traits>
 
 namespace phlex::experimental {
-  class product_store {
+  class phlex_model_EXPORT product_store {
   public:
     explicit product_store(data_cell_index_ptr id,
                            algorithm_name source = default_source(),
@@ -58,7 +60,8 @@ namespace phlex::experimental {
       source_; // FIXME: Should not have to copy (the source should outlive the product store)
   };
 
-  product_store_ptr const& more_derived(product_store_ptr const& a, product_store_ptr const& b);
+  phlex_model_EXPORT product_store_ptr const& more_derived(product_store_ptr const& a,
+                                                           product_store_ptr const& b);
 
   // Non-template overload for single product_store_ptr case
   inline product_store_ptr const& most_derived(product_store_ptr const& store) { return store; }
diff --git a/phlex/model/products.hpp b/phlex/model/products.hpp
index d4ca44d93..60601423c 100644
--- a/phlex/model/products.hpp
+++ b/phlex/model/products.hpp
@@ -1,6 +1,8 @@
 #ifndef PHLEX_MODEL_PRODUCTS_HPP
 #define PHLEX_MODEL_PRODUCTS_HPP
 
+#include "phlex/phlex_model_export.hpp"
+
 #include "phlex/model/product_specification.hpp"
 
 #include <cassert>
@@ -12,7 +14,7 @@
 
 namespace phlex::experimental {
 
-  struct product_base {
+  struct phlex_model_EXPORT product_base {
     virtual ~product_base() = default;
     virtual void const* address() const = 0;
     virtual std::type_info const& type() const = 0;
@@ -32,7 +34,7 @@ namespace phlex::experimental {
     std::remove_cvref_t<T> obj;
   };
 
-  class products {
+  class phlex_model_EXPORT products {
     using collection_t = std::unordered_map<product_specification, std::unique_ptr<product_base>>;
 
   public:
diff --git a/phlex/utilities/CMakeLists.txt b/phlex/utilities/CMakeLists.txt
index cc6c0228d..5edf24c7b 100644
--- a/phlex/utilities/CMakeLists.txt
+++ b/phlex/utilities/CMakeLists.txt
@@ -27,6 +27,16 @@ install(
 )
 
 target_include_directories(phlex_utilities PRIVATE ${PROJECT_SOURCE_DIR})
+phlex_apply_symbol_visibility(phlex_utilities)
+phlex_apply_optimizations(phlex_utilities)
+
+phlex_make_internal_library(
+  phlex_utilities
+  LIBRARIES
+  PRIVATE Boost::boost
+  PUBLIC spdlog::spdlog
+)
+add_library(phlex::utilities_internal ALIAS phlex_utilities_internal)
 
 # Interface library
 cet_make_library(
diff --git a/phlex/utilities/hashing.hpp b/phlex/utilities/hashing.hpp
index 04b6c0455..f521654ae 100644
--- a/phlex/utilities/hashing.hpp
+++ b/phlex/utilities/hashing.hpp
@@ -1,14 +1,17 @@
 #ifndef PHLEX_UTILITIES_HASHING_HPP
 #define PHLEX_UTILITIES_HASHING_HPP
 
+#include "phlex/phlex_utilities_export.hpp"
+
+#include <cstddef>
 #include <cstdint>
 #include <string>
 
 namespace phlex::experimental {
-  std::size_t hash(std::string const& str);
-  std::size_t hash(std::size_t i) noexcept;
-  std::size_t hash(std::size_t i, std::size_t j);
-  std::size_t hash(std::size_t i, std::string const& str);
+  phlex_utilities_EXPORT std::size_t hash(std::string const& str);
+  phlex_utilities_EXPORT std::size_t hash(std::size_t i) noexcept;
+  phlex_utilities_EXPORT std::size_t hash(std::size_t i, std::size_t j);
+  phlex_utilities_EXPORT std::size_t hash(std::size_t i, std::string const& str);
   template <typename... Ts>
   std::size_t hash(std::size_t i, std::size_t j, Ts... ks)
   {
diff --git a/phlex/utilities/resource_usage.hpp b/phlex/utilities/resource_usage.hpp
index f79f4b4c6..d7b4e5b71 100644
--- a/phlex/utilities/resource_usage.hpp
+++ b/phlex/utilities/resource_usage.hpp
@@ -6,10 +6,12 @@
 // resource_usage object.  The destructor will also report the maximum RSS of the process.
 // =======================================================================================
 
+#include "phlex/phlex_utilities_export.hpp"
+
 #include <chrono>
 
 namespace phlex::experimental {
-  class resource_usage {
+  class phlex_utilities_EXPORT resource_usage {
   public:
     resource_usage() noexcept;
     ~resource_usage();
diff --git a/plugins/CMakeLists.txt b/plugins/CMakeLists.txt
index 63a32a9e5..8f14921e9 100644
--- a/plugins/CMakeLists.txt
+++ b/plugins/CMakeLists.txt
@@ -8,6 +8,20 @@ target_link_libraries(layer_generator PRIVATE phlex::core)
 
 install(TARGETS layer_generator LIBRARY)
 
+# Companion library for tests.
+# PHLEX_HIDE_SYMBOLS=ON: separate compile against phlex_core_internal so that
+#   tests linking it do not mix the visibility-hidden and all-visible variants
+#   of phlex_core in the same process.
+# PHLEX_HIDE_SYMBOLS=OFF: thin INTERFACE alias — layer_generator already
+#   exports all symbols, so no separate .so is needed.
+if(PHLEX_HIDE_SYMBOLS)
+  add_library(layer_generator_internal layer_generator.cpp)
+  target_link_libraries(layer_generator_internal PRIVATE phlex_core_internal)
+else()
+  add_library(layer_generator_internal INTERFACE)
+  target_link_libraries(layer_generator_internal INTERFACE layer_generator)
+endif()
+
 add_library(generate_layers MODULE generate_layers.cpp)
 target_link_libraries(generate_layers PRIVATE phlex::module layer_generator)
 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index b1a29f020..10e308867 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -5,24 +5,24 @@ include(CetTest)
 
 cet_test_env(SPDLOG_LEVEL=debug)
 
-cet_test(concepts SOURCE concepts.cpp LIBRARIES phlex::core)
+cet_test(concepts SOURCE concepts.cpp LIBRARIES phlex::core_internal)
 cet_test(
   adjust_config
   USE_CATCH2_MAIN
   SOURCE
   adjust_config.cpp
   LIBRARIES
-  run_phlex
+  run_phlex_internal
   Boost::json
 )
 cet_test(config_test USE_CATCH2_MAIN SOURCE configuration.cpp LIBRARIES
          phlex::configuration
 )
-cet_test(string_literal SOURCE string_literal.cpp LIBRARIES phlex::utilities)
+cet_test(string_literal SOURCE string_literal.cpp LIBRARIES phlex::utilities_internal)
 cet_test(type_deduction SOURCE type_deduction.cpp LIBRARIES
          phlex::metaprogramming
 )
-cet_test(type_id USE_CATCH2_MAIN SOURCE type_id.cpp LIBRARIES phlex::model fmt::fmt)
+cet_test(type_id USE_CATCH2_MAIN SOURCE type_id.cpp LIBRARIES phlex::model_internal fmt::fmt)
 cet_test(identifier USE_CATCH2_MAIN SOURCE identifier.cpp LIBRARIES phlex::model phlex::configuration Boost::json)
 cet_test(
   yielding_driver
@@ -30,7 +30,7 @@ cet_test(
   SOURCE
   yielding_driver.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   TBB::tbb
 )
 
@@ -40,9 +40,9 @@ cet_test(
   SOURCE
   allowed_families.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   Boost::json
-  layer_generator
+  layer_generator_internal
 )
 cet_test(
   vector_of_abstract_types
@@ -50,8 +50,8 @@ cet_test(
   SOURCE
   vector_of_abstract_types.cpp
   LIBRARIES
-  phlex::core
-  layer_generator
+  phlex::core_internal
+  layer_generator_internal
 )
 cet_test(
   cached_execution
@@ -59,9 +59,9 @@ cet_test(
   SOURCE
   cached_execution.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   Boost::json
-  layer_generator
+  layer_generator_internal
 )
 cet_test(
   class_registration
@@ -69,7 +69,7 @@ cet_test(
   SOURCE
   class_registration.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   Boost::json
 )
 cet_test(
@@ -78,12 +78,12 @@ cet_test(
   SOURCE
   different_hierarchies.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   spdlog::spdlog
-  layer_generator
+  layer_generator_internal
 )
 cet_test(filter_impl USE_CATCH2_MAIN SOURCE filter_impl.cpp LIBRARIES
-         phlex::core
+         phlex::core_internal
 )
 cet_test(
   filter
@@ -91,7 +91,7 @@ cet_test(
   SOURCE
   filter.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   Boost::json
 )
 cet_test(
@@ -100,9 +100,9 @@ cet_test(
   SOURCE
   framework_graph.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   Boost::json
-  layer_generator
+  layer_generator_internal
 )
 cet_test(
   function_registration
@@ -110,7 +110,7 @@ cet_test(
   SOURCE
   function_registration.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   Boost::json
 )
 cet_test(
@@ -121,9 +121,9 @@ cet_test(
   LIBRARIES
   Boost::json
   TBB::tbb
-  phlex::core
+  phlex::core_internal
   spdlog::spdlog
-  layer_generator
+  layer_generator_internal
 )
 cet_test(
   layer_generator_test
@@ -131,8 +131,8 @@ cet_test(
   SOURCE
   layer_generator.cpp
   LIBRARIES
-  phlex::core
-  layer_generator
+  phlex::core_internal
+  layer_generator_internal
 )
 cet_test(
   multiple_function_registration
@@ -141,13 +141,13 @@ cet_test(
   multiple_function_registration.cpp
   LIBRARIES
   Boost::json
-  phlex::core
+  phlex::core_internal
 )
 cet_test(
   output_products
   USE_CATCH2_MAIN
   SOURCE output_products.cpp
-  LIBRARIES layer_generator phlex::core spdlog::spdlog
+  LIBRARIES layer_generator_internal phlex::core_internal spdlog::spdlog
 )
 cet_test(
   data_cell_counting
@@ -155,20 +155,20 @@ cet_test(
   SOURCE
   data_cell_counting.cpp
   LIBRARIES
-  phlex::model
-  phlex::utilities
+  phlex::model_internal
+  phlex::utilities_internal
 )
 cet_test(data_cell_index USE_CATCH2_MAIN SOURCE data_cell_index.cpp LIBRARIES
-         phlex::model
+         phlex::model_internal
 )
 cet_test(product_handle USE_CATCH2_MAIN SOURCE product_handle.cpp LIBRARIES
-         phlex::core
+         phlex::core_internal
 )
 cet_test(product_matcher USE_CATCH2_MAIN SOURCE product_matcher.cpp LIBRARIES
-         phlex::model
+         phlex::model_internal
 )
 cet_test(product_store USE_CATCH2_MAIN SOURCE product_store.cpp LIBRARIES
-         phlex::core
+         phlex::core_internal
 )
 cet_test(
   fold
@@ -176,9 +176,9 @@ cet_test(
   SOURCE
   fold.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
   spdlog::spdlog
-  layer_generator
+  layer_generator_internal
 )
 cet_test(
   repeater_node
@@ -186,7 +186,7 @@ cet_test(
   SOURCE
   repeater_node_test.cpp
   LIBRARIES
-  phlex::core
+  phlex::core_internal
 )
 cet_test(
   replicated
@@ -195,15 +195,15 @@ cet_test(
   replicated.cpp
   LIBRARIES
   TBB::tbb
-  phlex::utilities
+  phlex::utilities_internal
   spdlog::spdlog
 )
 
 cet_test(product_query USE_CATCH2_MAIN SOURCE product_query.cpp LIBRARIES
-         phlex::core
+         phlex::core_internal
 )
 cet_test(core_misc_test USE_CATCH2_MAIN SOURCE core_misc_test.cpp LIBRARIES
-         phlex::core
+         phlex::core_internal
          Boost::json
 )
 cet_test(
@@ -212,8 +212,8 @@ cet_test(
   SOURCE
   provider_test.cpp
   LIBRARIES
-  phlex::core
-  layer_generator
+  phlex::core_internal
+  layer_generator_internal
 )
 cet_test(
   type_distinction
@@ -222,7 +222,7 @@ cet_test(
   type_distinction.cpp
   LIBRARIES
   spdlog::spdlog
-  phlex::core
+  phlex::core_internal
 )
 cet_test(
   unfold
@@ -231,10 +231,10 @@ cet_test(
   unfold.cpp
   LIBRARIES
   Boost::json
-  phlex::core
+  phlex::core_internal
   TBB::tbb
   spdlog::spdlog
-  layer_generator
+  layer_generator_internal
 )
 
 add_subdirectory(benchmarks)
diff --git a/test/python/all_config.py b/test/python/all_config.py
index aeee3b373..0a4c16310 100644
--- a/test/python/all_config.py
+++ b/test/python/all_config.py
@@ -49,9 +49,9 @@ def __init__(self, config):
 
         assert len(config["some_objects"]) == 3
         expected = [
-            {'a': 'b', 'c': 'd', 'e': 'f'},
-            {'g': 'h', 'i': 'j', 'k': 'l'},
-            {'m': 'n', 'o': 'p', 'q': 'r'},
+            {"a": "b", "c": "d", "e": "f"},
+            {"g": "h", "i": "j", "k": "l"},
+            {"m": "n", "o": "p", "q": "r"},
         ]
         for i in range(3):
             assert config["some_objects"][i] == expected[i]
@@ -60,10 +60,10 @@ def __init__(self, config):
         assert config["empty"] == ()
 
         try:
-            config[42]   # should raise
+            config[42]  # should raise
             assert not "did not raise TypeError"
         except TypeError:
-            pass         # all good as exception was raised
+            pass  # all good as exception was raised
 
     def __call__(self, i: int, j: int) -> None:
         """Dummy routine to do something.
diff --git a/test/python/reducer.py b/test/python/reducer.py
index b32fe0395..75b283e6d 100644
--- a/test/python/reducer.py
+++ b/test/python/reducer.py
@@ -74,17 +74,13 @@ def PHLEX_REGISTER_ALGORITHMS(m, config):
         {"creator": "reduce0", "layer": "event", "suffix": "sum0"},
         {"creator": "reduce1", "layer": "event", "suffix": "sum1"},
     ]
-    m.transform(
-        add_sum01, name="reduce01", input_family=input_family01, output_products=["sum01"]
-    )
+    m.transform(add_sum01, name="reduce01", input_family=input_family01, output_products=["sum01"])
 
     input_family01 = [
         {"creator": "reduce2", "layer": "event", "suffix": "sum2"},
         {"creator": "reduce3", "layer": "event", "suffix": "sum3"},
     ]
-    m.transform(
-        add_sum23, name="reduce23", input_family=input_family01, output_products=["sum23"]
-    )
+    m.transform(add_sum23, name="reduce23", input_family=input_family01, output_products=["sum23"])
 
     # once more (and the configuration will add a verifier)
     input_family_final = [
diff --git a/test/python/sumit.py b/test/python/sumit.py
index 17eaef93c..ae43e5ffc 100644
--- a/test/python/sumit.py
+++ b/test/python/sumit.py
@@ -63,8 +63,8 @@ def PHLEX_REGISTER_ALGORITHMS(m, config):
         None
     """
     m.transform(collectify, input_family=config["input"], output_products=["my_pyarray"])
-    m.transform(sum_array,
-                input_family=[
-                    {"creator" : "collectify", "layer" : "event", "suffix" : "my_pyarray"}
-                ],
-                output_products=config["output"])
+    m.transform(
+        sum_array,
+        input_family=[{"creator": "collectify", "layer": "event", "suffix": "my_pyarray"}],
+        output_products=config["output"],
+    )
diff --git a/test/python/test_coverage.py b/test/python/test_coverage.py
index 33f82d33b..52c844d89 100644
--- a/test/python/test_coverage.py
+++ b/test/python/test_coverage.py
@@ -42,13 +42,14 @@ def PHLEX_REGISTER_ALGORITHMS(m, config):
     """Register algorithms."""
     # We need to transform scalar inputs to lists first
     # i, f1, d1 come from cppsource4py
-    tfs = ((collect_int, "input", "i", "l_int"),
-           (collect_float, "input", "f1", "l_float"),
-           (collect_double, "input", "d1", "l_double"),
-           (list_int_func, collect_int.__name__, "l_int", "sum_int"),
-           (list_float_func, collect_float.__name__, "l_float", "sum_float"),
-           (list_double_func, collect_double.__name__, "l_double", "sum_double")
-          )
+    tfs = (
+        (collect_int, "input", "i", "l_int"),
+        (collect_float, "input", "f1", "l_float"),
+        (collect_double, "input", "d1", "l_double"),
+        (list_int_func, collect_int.__name__, "l_int", "sum_int"),
+        (list_float_func, collect_float.__name__, "l_float", "sum_float"),
+        (list_double_func, collect_double.__name__, "l_double", "sum_double"),
+    )
 
     for func, creator, suffix, output in tfs:
         input_family = [{"creator": creator, "layer": "event", "suffix": suffix}]
diff --git a/test/python/test_mismatch.py b/test/python/test_mismatch.py
index 2d188496c..55eca0e7c 100644
--- a/test/python/test_mismatch.py
+++ b/test/python/test_mismatch.py
@@ -10,6 +10,8 @@ def PHLEX_REGISTER_ALGORITHMS(m, config):
     """Register algorithms."""
     # input_family has 1 element, but function takes 2 arguments
     # This should trigger the error in modulewrap.cpp
-    m.transform(mismatch_func,
-                input_family=[{"creator": "input", "layer": "event", "suffix": "a"}],
-                output_products=["sum"])
+    m.transform(
+        mismatch_func,
+        input_family=[{"creator": "input", "layer": "event", "suffix": "a"}],
+        output_products=["sum"],
+    )
diff --git a/test/python/vectypes.py b/test/python/vectypes.py
index de182aabb..5cd464920 100644
--- a/test/python/vectypes.py
+++ b/test/python/vectypes.py
@@ -259,11 +259,13 @@ def PHLEX_REGISTER_ALGORITHMS(m, config):
         )
 
         sum_kwargs = {
-            "input_family": [{
-                "creator": list_collect.__name__ if use_lists else arr_collect.__name__,
-                "layer": "event",
-                "suffix": arr_name
-            }],
+            "input_family": [
+                {
+                    "creator": list_collect.__name__ if use_lists else arr_collect.__name__,
+                    "layer": "event",
+                    "suffix": arr_name,
+                }
+            ],
             "output_products": config[out_key],
         }
         if sum_name:
diff --git a/test/utilities/CMakeLists.txt b/test/utilities/CMakeLists.txt
index 9cfd780a0..9ace0e04e 100644
--- a/test/utilities/CMakeLists.txt
+++ b/test/utilities/CMakeLists.txt
@@ -1,7 +1,7 @@
-cet_test(sized_tuple SOURCE sized_tuple.cpp LIBRARIES phlex::utilities)
+cet_test(sized_tuple SOURCE sized_tuple.cpp LIBRARIES phlex::utilities_internal)
 
 cet_test(sleep_for USE_CATCH2_MAIN SOURCE sleep_for.cpp LIBRARIES
-         phlex::utilities
+         phlex::utilities_internal
 )
 cet_test(
   thread_counter
@@ -9,6 +9,6 @@ cet_test(
   SOURCE
   thread_counter.cpp
   LIBRARIES
-  phlex::utilities
+  phlex::utilities_internal
   TBB::tbb
 )