diff --git a/CMakeLists.txt b/CMakeLists.txt
index 23e560f4..c448cc69 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -132,6 +132,16 @@ pybind11_add_module(tesseract_decoder MODULE ${TESSERACT_SRC_DIR}/tesseract.pybi
 target_compile_options(tesseract_decoder PRIVATE ${OPT_COPTS})
 target_include_directories(tesseract_decoder PRIVATE ${TESSERACT_SRC_DIR})
 target_link_libraries(tesseract_decoder PRIVATE common utils simplex tesseract_lib)
+# Keep statically linked HiGHS symbols private to this extension on every
+# supported Unix platform. Mach-O uses an explicit export list because it has
+# no ELF-style --exclude-libs option; otherwise highspy can resolve symbols to
+# Tesseract's private HiGHS copy when both extensions share a process.
+if(APPLE)
+  target_link_options(tesseract_decoder PRIVATE
+    "-Wl,-exported_symbols_list,${TESSERACT_SRC_DIR}/tesseract_decoder.exports")
+elseif(UNIX)
+  target_link_options(tesseract_decoder PRIVATE "-Wl,--exclude-libs,ALL")
+endif()
 set_target_properties(tesseract_decoder PROPERTIES
     LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/src
     LIBRARY_OUTPUT_DIRECTORY_DEBUG ${PROJECT_SOURCE_DIR}/src
diff --git a/src/BUILD b/src/BUILD
index 1b1407bf..b40ca00c 100644
--- a/src/BUILD
+++ b/src/BUILD
@@ -105,6 +105,19 @@ pybind_extension(
         "tesseract.pybind.cc",
     ],
     copts = OPT_COPTS,
+    # Keep static-library symbols (notably HiGHS) private to this extension.
+    # Mach-O has no equivalent to ELF's --exclude-libs, so it needs an explicit
+    # export list; without it, highspy can see the linked HiGHS symbols.
+    additional_linker_inputs = ["tesseract_decoder.exports"],
+    linkopts = select({
+        "@platforms//os:osx": [
+            "-Wl,-exported_symbols_list,$(location :tesseract_decoder.exports)",
+        ],
+        # The ELF equivalent also hides symbols pulled from static archives.
+        "@platforms//os:linux": ["-Wl,--exclude-libs,ALL"],
+        # The default also covers Windows and non-ELF toolchains.
+        "//conditions:default": [],
+    }),
     deps = [
         ":tesseract_decoder_pybind",
     ],
diff --git a/src/common.cc b/src/common.cc
index 654c68ad..3a0cce01 100644
--- a/src/common.cc
+++ b/src/common.cc
@@ -20,6 +20,8 @@
 #include <string>
 #include <vector>
 
+namespace {
+
 std::string vector_to_string(const std::vector<int>& vec) {
   std::stringstream ss;
   ss << "[";
@@ -34,6 +36,10 @@ std::string vector_to_string(const std::vector<int>& vec) {
   return ss.str();
 }
 
+}  // namespace
+
+namespace tesseract_decoder {
+
 std::string common::Symptom::str() const {
   std::string s = "Symptom{detectors=";
   s += vector_to_string(detectors);
@@ -255,3 +261,5 @@ stim::DetectorErrorModel common::dem_from_counts(const stim::DetectorErrorModel&
   }
   return out_dem;
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/common.h b/src/common.h
index 560246a8..3524cb34 100644
--- a/src/common.h
+++ b/src/common.h
@@ -18,6 +18,7 @@
 
 #include "stim.h"
 
+namespace tesseract_decoder {
 namespace common {
 
 // Represents the effect of an error
@@ -113,5 +114,6 @@ stim::DetectorErrorModel dem_from_counts(const stim::DetectorErrorModel& orig_de
 double merge_weights(double a, double b);
 
 }  // namespace common
+}  // namespace tesseract_decoder
 
 #endif
diff --git a/src/common.pybind.h b/src/common.pybind.h
index 693aae83..d3d5fa9e 100644
--- a/src/common.pybind.h
+++ b/src/common.pybind.h
@@ -26,6 +26,8 @@
 
 namespace py = pybind11;
 
+namespace tesseract_decoder {
+
 void add_common_module(py::module& root) {
   auto m = root.def_submodule("common", "classes commonly used by the decoder");
 
@@ -217,4 +219,6 @@ void add_common_module(py::module& root) {
       )pbdoc");
 }
 
+}  // namespace tesseract_decoder
+
 #endif
diff --git a/src/common.test.cc b/src/common.test.cc
index 350853c8..70eebd97 100644
--- a/src/common.test.cc
+++ b/src/common.test.cc
@@ -17,6 +17,9 @@
 #include "gtest/gtest.h"
 #include "stim.h"
 
+namespace tesseract_decoder {
+namespace {
+
 TEST(common, ErrorsStructFromDemInstruction) {
   // Test a pathological DEM error instruction
   stim::DetectorErrorModel dem("error(0.1) D0 ^  D0 D1  L0 L1 L1");
@@ -194,3 +197,6 @@ TEST(CommonTest, merge_indistinguishable_errors_two_errors) {
   auto merged_dem4 = common::merge_indistinguishable_errors(dem4, error_index_map);
   ASSERT_NEAR(get_merged_probability(merged_dem4), expected_merged_p, 1e-9);
 }
+
+}  // namespace
+}  // namespace tesseract_decoder
diff --git a/src/simplex.cc b/src/simplex.cc
index ec98dad2..9d746e8e 100644
--- a/src/simplex.cc
+++ b/src/simplex.cc
@@ -20,6 +20,8 @@
 #include "io/HMPSIO.h"
 #include "utils.h"
 
+namespace tesseract_decoder {
+
 constexpr size_t T_COORD = 2;
 
 std::string SimplexConfig::str() {
@@ -401,3 +403,5 @@ void SimplexDecoder::decode_shots(std::vector<stim::SparseShot>& shots,
 }
 
 SimplexDecoder::~SimplexDecoder() {}
+
+}  // namespace tesseract_decoder
diff --git a/src/simplex.h b/src/simplex.h
index 4288f8ec..5929feb4 100644
--- a/src/simplex.h
+++ b/src/simplex.h
@@ -24,6 +24,8 @@ struct HighsModel;
 struct Highs;
 enum class HighsStatus;
 
+namespace tesseract_decoder {
+
 struct SimplexConfig {
   stim::DetectorErrorModel dem;
   bool parallelize = false;
@@ -81,4 +83,6 @@ struct SimplexDecoder {
   void init_ilp();
 };
 
+}  // namespace tesseract_decoder
+
 #endif  // SIMPLEX_HPP
diff --git a/src/simplex.pybind.h b/src/simplex.pybind.h
index 27439b25..8648cbf2 100644
--- a/src/simplex.pybind.h
+++ b/src/simplex.pybind.h
@@ -27,7 +27,9 @@
 
 namespace py = pybind11;
 
+namespace tesseract_decoder {
 namespace {
+
 // Helper function to compile the decoder.
 std::unique_ptr<SimplexDecoder> _compile_simplex_decoder_helper(const SimplexConfig& self) {
   return std::make_unique<SimplexDecoder>(self);
@@ -41,19 +43,27 @@ SimplexConfig simplex_config_maker(py::object dem, bool parallelize = false,
       {input_dem, parallelize, window_length, window_slide_length, verbose, merge_errors});
 }
 
-};  // namespace
+}  // namespace
 
 void add_simplex_module(py::module& root) {
   auto m =
       root.def_submodule("simplex", "Module containing the SimplexDecoder and related methods");
 
-  py::class_<SimplexConfig>(m, "SimplexConfig", R"pbdoc(
+  auto py_simplex_config = py::class_<SimplexConfig>(m, "SimplexConfig", R"pbdoc(
         Configuration object for the `SimplexDecoder`.
 
         This class holds all the parameters needed to initialize and configure a
         Simplex decoder instance, including the detector error model and
         decoding options.
-    )pbdoc")
+    )pbdoc");
+  auto py_simplex_decoder = py::class_<SimplexDecoder>(m, "SimplexDecoder", R"pbdoc(
+        A class that implements the Simplex decoding algorithm.
+
+        It can decode syndromes from a `stim.DetectorErrorModel` to predict
+        which observables have been flipped.
+    )pbdoc");
+
+  py_simplex_config
       .def(py::init(&simplex_config_maker), py::arg("dem"), py::arg("parallelize") = false,
            py::arg("window_length") = 0, py::arg("window_slide_length") = 0,
            py::arg("verbose") = false, py::arg("merge_errors") = true, R"pbdoc(
@@ -101,12 +111,7 @@ void add_simplex_module(py::module& root) {
                 settings.
            )pbdoc");
 
-  py::class_<SimplexDecoder>(m, "SimplexDecoder", R"pbdoc(
-        A class that implements the Simplex decoding algorithm.
-
-        It can decode syndromes from a `stim.DetectorErrorModel` to predict
-        which observables have been flipped.
-    )pbdoc")
+  py_simplex_decoder
       .def(py::init<SimplexConfig>(), py::arg("config"), R"pbdoc(
         The constructor for the `SimplexDecoder` class.
 
@@ -351,4 +356,7 @@ void add_simplex_module(py::module& root) {
             (num_shots, num_observables).
     )pbdoc");
 }
+
+}  // namespace tesseract_decoder
+
 #endif
diff --git a/src/simplex_main.cc b/src/simplex_main.cc
index 7c8542a8..560284a5 100644
--- a/src/simplex_main.cc
+++ b/src/simplex_main.cc
@@ -24,6 +24,8 @@
 #include "stim.h"
 #include "utils.h"
 
+using namespace tesseract_decoder;
+
 struct Args {
   std::string circuit_path;
   std::string dem_path;
diff --git a/src/stim_utils.pybind.h b/src/stim_utils.pybind.h
index ff638a79..a8a7ae4f 100644
--- a/src/stim_utils.pybind.h
+++ b/src/stim_utils.pybind.h
@@ -7,6 +7,8 @@
 
 #include "stim.h"
 
+namespace tesseract_decoder {
+
 namespace {
 namespace py = pybind11;
 }
@@ -66,4 +68,6 @@ void dem_setter(T& config, py::object dem) {
   config.dem = parse_py_object<stim::DetectorErrorModel>(dem);
 }
 
+}  // namespace tesseract_decoder
+
 #endif
diff --git a/src/tesseract.cc b/src/tesseract.cc
index 0a180754..9ed11507 100644
--- a/src/tesseract.cc
+++ b/src/tesseract.cc
@@ -81,6 +81,8 @@ struct hash<boost::dynamic_bitset<>> {
 };
 }  // namespace std
 
+namespace tesseract_decoder {
+
 std::string TesseractConfig::str() {
   auto& config = *this;
   std::stringstream ss;
@@ -733,3 +735,5 @@ void TesseractDecoder::build_sparse_d2e(const std::vector<uint64_t>& detections)
     }
   }
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/tesseract.h b/src/tesseract.h
index 97b88eb4..d06e47e1 100644
--- a/src/tesseract.h
+++ b/src/tesseract.h
@@ -28,6 +28,8 @@
 #include "utils.h"
 #include "visualization.h"
 
+namespace tesseract_decoder {
+
 constexpr size_t INF_DET_BEAM = std::numeric_limits<uint16_t>::max();
 constexpr int DEFAULT_DET_BEAM = 5;
 constexpr size_t DEFAULT_PQLIMIT = 200000;
@@ -144,4 +146,6 @@ struct TesseractDecoder {
                                    const std::vector<std::vector<int>>& active_d2e);
 };
 
+}  // namespace tesseract_decoder
+
 #endif  // TESSERACT_DECODER_H
diff --git a/src/tesseract.perf.cc b/src/tesseract.perf.cc
index a92dbe66..2de6928d 100644
--- a/src/tesseract.perf.cc
+++ b/src/tesseract.perf.cc
@@ -20,6 +20,8 @@
 #include "stim.h"
 #include "utils.h"
 
+using namespace tesseract_decoder;
+
 constexpr uint64_t test_data_seed = 752024;
 
 template <typename Decoder>
diff --git a/src/tesseract.pybind.cc b/src/tesseract.pybind.cc
index 9f2808f4..f81486d0 100644
--- a/src/tesseract.pybind.cc
+++ b/src/tesseract.pybind.cc
@@ -25,6 +25,7 @@
 #include "visualization.pybind.h"
 
 PYBIND11_MODULE(tesseract_decoder, tesseract) {
+  using namespace tesseract_decoder;
   py::module::import("stim");
 
   add_common_module(tesseract);
diff --git a/src/tesseract.pybind.h b/src/tesseract.pybind.h
index 19a79fd9..2ebf892a 100644
--- a/src/tesseract.pybind.h
+++ b/src/tesseract.pybind.h
@@ -27,7 +27,9 @@
 
 namespace py = pybind11;
 
+namespace tesseract_decoder {
 namespace {
+
 // Helper function to compile the decoder.
 std::unique_ptr<TesseractDecoder> _compile_tesseract_decoder_helper(const TesseractConfig& self) {
   return std::make_unique<TesseractDecoder>(self);
@@ -79,12 +81,20 @@ void add_tesseract_module(py::module& root) {
         py::arg("num_detectors"), py::arg("sparsify_base_degree"),
         "Returns the suggested number of optional high-degree errors to reactivate per shot.");
 
-  py::class_<TesseractConfig>(m, "TesseractConfig", R"pbdoc(
+  auto py_tesseract_config = py::class_<TesseractConfig>(m, "TesseractConfig", R"pbdoc(
         Configuration object for the `TesseractDecoder`.
 
         This class holds all the parameters needed to initialize and configure a
         Tesseract decoder instance.
-    )pbdoc")
+    )pbdoc");
+  auto py_tesseract_decoder = py::class_<TesseractDecoder>(m, "TesseractDecoder", R"pbdoc(
+        A class that implements the Tesseract decoding algorithm.
+
+        It can decode syndromes from a `stim.DetectorErrorModel` to predict
+        which observables have been flipped.
+    )pbdoc");
+
+  py_tesseract_config
       .def(py::init<>(), R"pbdoc(
         Default constructor for TesseractConfig.
         Creates a new instance with default parameter values.
@@ -239,12 +249,7 @@ void add_tesseract_module(py::module& root) {
                 `TesseractConfig` object.
             )pbdoc");
 
-  py::class_<TesseractDecoder>(m, "TesseractDecoder", R"pbdoc(
-        A class that implements the Tesseract decoding algorithm.
-
-        It can decode syndromes from a `stim.DetectorErrorModel` to predict
-        which observables have been flipped.
-    )pbdoc")
+  py_tesseract_decoder
       .def(py::init<TesseractConfig>(), py::arg("config"), R"pbdoc(
         The constructor for the `TesseractDecoder` class.
 
@@ -522,4 +527,6 @@ void add_tesseract_module(py::module& root) {
                     "visualization of the algorithm");
 }
 
+}  // namespace tesseract_decoder
+
 #endif
diff --git a/src/tesseract.test.cc b/src/tesseract.test.cc
index fd0d471e..4bda92d9 100644
--- a/src/tesseract.test.cc
+++ b/src/tesseract.test.cc
@@ -23,6 +23,9 @@
 #include "stim.h"
 #include "utils.h"
 
+namespace tesseract_decoder {
+namespace {
+
 constexpr uint64_t test_data_seed = 752024;
 
 bool simplex_test_compare(stim::DetectorErrorModel& dem, std::vector<stim::SparseShot>& shots) {
@@ -559,3 +562,6 @@ TEST(tesseract, MoreThan64Observables) {
     ASSERT_EQ(flipped[i], i);
   }
 }
+
+}  // namespace
+}  // namespace tesseract_decoder
diff --git a/src/tesseract_decoder.exports b/src/tesseract_decoder.exports
new file mode 100644
index 00000000..896702d0
--- /dev/null
+++ b/src/tesseract_decoder.exports
@@ -0,0 +1 @@
+_PyInit_tesseract_decoder
diff --git a/src/tesseract_main.cc b/src/tesseract_main.cc
index 4b3975fc..bbffc1b8 100644
--- a/src/tesseract_main.cc
+++ b/src/tesseract_main.cc
@@ -29,6 +29,8 @@
 #include "tesseract.h"
 #include "utils.h"
 
+using namespace tesseract_decoder;
+
 struct Args {
   std::string circuit_path;
   std::string dem_path;
diff --git a/src/tesseract_sinter_compat.pybind.h b/src/tesseract_sinter_compat.pybind.h
index aecaa6b8..f118750b 100644
--- a/src/tesseract_sinter_compat.pybind.h
+++ b/src/tesseract_sinter_compat.pybind.h
@@ -25,6 +25,8 @@
 
 namespace py = pybind11;
 
+namespace tesseract_decoder {
+
 // These are the classes that will be exposed to Python.
 struct TesseractSinterCompiledDecoder;
 struct TesseractSinterDecoder;
@@ -495,3 +497,5 @@ void pybind_sinter_compat(py::module& root) {
   root.attr("TesseractSinterDecoder") = m.attr("TesseractSinterDecoder");
   root.attr("make_tesseract_sinter_decoders_dict") = m.attr("make_tesseract_sinter_decoders_dict");
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/tesseract_trellis.cc b/src/tesseract_trellis.cc
index afc91faa..034191b4 100644
--- a/src/tesseract_trellis.cc
+++ b/src/tesseract_trellis.cc
@@ -33,6 +33,8 @@
 
 #include "utils.h"
 
+namespace tesseract_decoder {
+
 struct TesseractTrellisWideKernelBase {
   virtual ~TesseractTrellisWideKernelBase() = default;
   virtual void decode_shot(TesseractTrellisDecoder* decoder,
@@ -1288,3 +1290,5 @@ void TesseractTrellisDecoder::decode_shots(std::vector<stim::SparseShot>& shots,
     obs_predicted[i] = decode(shots[i].hits);
   }
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/tesseract_trellis.h b/src/tesseract_trellis.h
index fec0a5ec..cea404a5 100644
--- a/src/tesseract_trellis.h
+++ b/src/tesseract_trellis.h
@@ -22,6 +22,8 @@
 #include "common.h"
 #include "stim.h"
 
+namespace tesseract_decoder {
+
 struct TesseractTrellisWideKernelBase;
 
 enum class TesseractTrellisRankingMode {
@@ -102,4 +104,6 @@ struct TesseractTrellisDecoder {
   std::vector<uint32_t> kept_state_histogram_scratch;
 };
 
+}  // namespace tesseract_decoder
+
 #endif  // TESSERACT_TRELLIS_DECODER_H
diff --git a/src/tesseract_trellis.test.cc b/src/tesseract_trellis.test.cc
index e375212b..e25f234a 100644
--- a/src/tesseract_trellis.test.cc
+++ b/src/tesseract_trellis.test.cc
@@ -22,6 +22,8 @@
 
 #include "stim.h"
 
+namespace tesseract_decoder {
+
 TEST(TesseractTrellisDecoderTest, ComputesObservableProbabilityForAmbiguousSyndrome) {
   stim::DetectorErrorModel dem(R"DEM(
     error(0.1) D0
@@ -221,3 +223,5 @@ TEST(TesseractTrellisDecoderTest, RejectsMoreThanOneObservable) {
     EXPECT_NE(std::string(err.what()).find("supports at most one observable"), std::string::npos);
   }
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/tesseract_trellis_main.cc b/src/tesseract_trellis_main.cc
index e131f70d..11c89dc7 100644
--- a/src/tesseract_trellis_main.cc
+++ b/src/tesseract_trellis_main.cc
@@ -26,6 +26,8 @@
 #include "tesseract_trellis.h"
 #include "utils.h"
 
+using namespace tesseract_decoder;
+
 namespace {
 
 TesseractTrellisRankingMode parse_ranking_mode(const std::string& value) {
diff --git a/src/test_data.h b/src/test_data.h
index 137f57e9..afe22bb7 100644
--- a/src/test_data.h
+++ b/src/test_data.h
@@ -19,6 +19,8 @@
 
 #include "stim.h"
 
+namespace tesseract_decoder {
+
 std::vector<std::string> get_small_test_circuits() {
   return {};
 }
@@ -27,4 +29,6 @@ std::vector<std::string> get_large_test_circuits() {
   return {};
 }
 
+}  // namespace tesseract_decoder
+
 #endif  // TESSERACT_TEST_DATA_H
diff --git a/src/utils.cc b/src/utils.cc
index a72a8ced..58659e02 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -27,6 +27,8 @@
 #include "common.h"
 #include "stim.h"
 
+namespace tesseract_decoder {
+
 std::vector<std::vector<double>> get_detector_coords(const stim::DetectorErrorModel& dem) {
   std::vector<std::vector<double>> detector_coords;
   for (const stim::DemInstruction& instruction : common::flatten(dem).instructions) {
@@ -279,3 +281,5 @@ uint64_t vector_to_u64_mask(const std::vector<int>& v) {
   }
   return mask;
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/utils.h b/src/utils.h
index 3c5d6569..ad6932fb 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -29,6 +29,8 @@
 #include "common.h"
 #include "stim.h"
 
+namespace tesseract_decoder {
+
 constexpr const double EPSILON = 1e-7;
 
 std::vector<std::vector<double>> get_detector_coords(const stim::DetectorErrorModel& dem);
@@ -112,4 +114,6 @@ size_t parallel_for_shots_in_order(size_t num_shots, size_t num_threads, Process
   return shot;
 }
 
+}  // namespace tesseract_decoder
+
 #endif  // __TESSERACT_UTILS_H__
diff --git a/src/utils.pybind.h b/src/utils.pybind.h
index 118b87e5..8ea9564e 100644
--- a/src/utils.pybind.h
+++ b/src/utils.pybind.h
@@ -23,6 +23,8 @@
 
 namespace py = pybind11;
 
+namespace tesseract_decoder {
+
 void add_utils_module(py::module& root) {
   auto m = root.def_submodule("utils", "utility methods");
 
@@ -137,4 +139,7 @@ void add_utils_module(py::module& root) {
   // Not exposing sampling_from_dem and sample_shots because they depend on
   // stim::SparseShot which stim doesn't expose to python.
 }
+
+}  // namespace tesseract_decoder
+
 #endif
diff --git a/src/visualization.cc b/src/visualization.cc
index ecd78faa..c9c6f9bb 100644
--- a/src/visualization.cc
+++ b/src/visualization.cc
@@ -1,6 +1,8 @@
 
 #include "visualization.h"
 
+namespace tesseract_decoder {
+
 void Visualizer::add_errors(const std::vector<common::Error>& errors) {
   for (auto& error : errors) {
     lines.push_back(error.str());
@@ -55,3 +57,5 @@ void Visualizer::write(const char* fpath) {
 
   fclose(fout);
 }
+
+}  // namespace tesseract_decoder
diff --git a/src/visualization.h b/src/visualization.h
index 64d9ad5c..d3af2e9b 100644
--- a/src/visualization.h
+++ b/src/visualization.h
@@ -7,6 +7,8 @@
 
 #include "common.h"
 
+namespace tesseract_decoder {
+
 struct Visualizer {
   void add_detector_coords(const std::vector<std::vector<double>>&);
   void add_errors(const std::vector<common::Error>&);
@@ -19,4 +21,6 @@ struct Visualizer {
   std::list<std::string> lines;
 };
 
+}  // namespace tesseract_decoder
+
 #endif
diff --git a/src/visualization.pybind.h b/src/visualization.pybind.h
index 820bf864..cdf1b671 100644
--- a/src/visualization.pybind.h
+++ b/src/visualization.pybind.h
@@ -8,9 +8,13 @@
 
 namespace py = pybind11;
 
+namespace tesseract_decoder {
+
 void add_visualization_module(py::module& root) {
   auto m = root.def_submodule("viz", "Module containing the visualization tools");
-  py::class_<Visualizer>(m, "Visualizer")
+  py::class_<tesseract_decoder::Visualizer>(m, "Visualizer")
       .def(py::init<>())
-      .def("write", &Visualizer::write, py::arg("fpath"));
+      .def("write", &tesseract_decoder::Visualizer::write, py::arg("fpath"));
 }
+
+}  // namespace tesseract_decoder