diff --git a/include/amici/model.h b/include/amici/model.h
index de0abe4eb9..4e41f94778 100644
--- a/include/amici/model.h
+++ b/include/amici/model.h
@@ -11,6 +11,8 @@
 #include "amici/sundials_matrix_wrapper.h"
 
 #include <map>
+#include <span>
+#include <string_view>
 #include <vector>
 
 namespace amici {
@@ -618,7 +620,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return The parameter names
      */
-    virtual std::vector<std::string> get_free_parameter_names() const;
+    virtual std::span<std::string_view const> get_free_parameter_names() const;
 
     /**
      * @brief Report whether the model has state names set.
@@ -633,14 +635,14 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return State names
      */
-    virtual std::vector<std::string> get_state_names() const;
+    virtual std::span<std::string_view const> get_state_names() const;
 
     /**
      * @brief Get names of the solver states.
      *
      * @return State names
      */
-    virtual std::vector<std::string> get_state_names_solver() const;
+    virtual std::span<std::string_view const> get_state_names_solver() const;
 
     /**
      * @brief Report whether the model has fixed parameter names set.
@@ -655,7 +657,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Fixed parameter names
      */
-    virtual std::vector<std::string> get_fixed_parameter_names() const;
+    virtual std::span<std::string_view const> get_fixed_parameter_names() const;
 
     /**
      * @brief Report whether the model has observable names set.
@@ -670,7 +672,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Observable names
      */
-    virtual std::vector<std::string> get_observable_names() const;
+    virtual std::span<std::string_view const> get_observable_names() const;
 
     /**
      * @brief Report whether the model has expression names set.
@@ -685,7 +687,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Expression names
      */
-    virtual std::vector<std::string> get_expression_names() const;
+    virtual std::span<std::string_view const> get_expression_names() const;
 
     /**
      * @brief Report whether the model has parameter IDs set.
@@ -700,7 +702,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Parameter IDs
      */
-    virtual std::vector<std::string> get_free_parameter_ids() const;
+    virtual std::span<std::string_view const> get_free_parameter_ids() const;
 
     /**
      * @brief Report whether the model has state IDs set.
@@ -715,14 +717,14 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return State IDs
      */
-    virtual std::vector<std::string> get_state_ids() const;
+    virtual std::span<std::string_view const> get_state_ids() const;
 
     /**
      * @brief Get IDs of the solver states.
      *
      * @return State IDs
      */
-    virtual std::vector<std::string> get_state_ids_solver() const;
+    virtual std::span<std::string_view const> get_state_ids_solver() const;
 
     /**
      * @brief Report whether the model has fixed parameter IDs set.
@@ -737,7 +739,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Fixed parameter IDs
      */
-    virtual std::vector<std::string> get_fixed_parameter_ids() const;
+    virtual std::span<std::string_view const> get_fixed_parameter_ids() const;
 
     /**
      * @brief Report whether the model has observable IDs set.
@@ -752,7 +754,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Observable IDs
      */
-    virtual std::vector<std::string> get_observable_ids() const;
+    virtual std::span<std::string_view const> get_observable_ids() const;
 
     /**
      * @brief Report whether the model has expression IDs set.
@@ -767,7 +769,7 @@ class Model : public AbstractModel, public ModelDimensions {
      *
      * @return Expression IDs
      */
-    virtual std::vector<std::string> get_expression_ids() const;
+    virtual std::span<std::string_view const> get_expression_ids() const;
 
     /**
      * @brief Checks whether the defined noise model is Gaussian, i.e., the nllh
diff --git a/models/model_calvetti_py/CMakeLists.txt b/models/model_calvetti_py/CMakeLists.txt
index d7ad2f5ada..c60c49c92c 100644
--- a/models/model_calvetti_py/CMakeLists.txt
+++ b/models/model_calvetti_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_calvetti_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_calvetti_py/model_calvetti_py.cpp b/models/model_calvetti_py/model_calvetti_py.cpp
index 7ddbedab18..b3a69ae302 100644
--- a/models/model_calvetti_py/model_calvetti_py.cpp
+++ b/models/model_calvetti_py/model_calvetti_py.cpp
@@ -1,15 +1,16 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_calvetti_py {
 
 // clang-format off
 
-std::array<const char*, 0> free_parameter_names = {
+extern const std::array<std::string_view const, 0> free_parameter_names = {
     
 };
 
-std::array<const char*, 6> fixed_parameter_names = {
+extern const std::array<std::string_view const, 6> fixed_parameter_names = {
     "V1ss", // k[0]
 "R1ss", // k[1]
 "V2ss", // k[2]
@@ -18,7 +19,7 @@ std::array<const char*, 6> fixed_parameter_names = {
 "R3ss", // k[5]
 };
 
-std::array<const char*, 6> state_names = {
+extern const std::array<std::string_view const, 6> state_names = {
     "V1", // x_rdata[0]
 "V2", // x_rdata[1]
 "V3", // x_rdata[2]
@@ -27,7 +28,16 @@ std::array<const char*, 6> state_names = {
 "f3", // x_rdata[5]
 };
 
-std::array<const char*, 6> observable_names = {
+extern const std::array<std::string_view const, 6> state_names_solver = {
+    "V1", // x_solver[0]
+"V2", // x_solver[1]
+"V3", // x_solver[2]
+"f1", // x_solver[3]
+"f2", // x_solver[4]
+"f3", // x_solver[5]
+};
+
+extern const std::array<std::string_view const, 6> observable_names = {
     "y0", // y[0]
 "y1", // y[1]
 "y2", // y[2]
@@ -45,7 +55,7 @@ ObservableScaling::lin, // y[4]
 ObservableScaling::lin, // y[5]
 };
 
-std::array<const char*, 16> expression_names = {
+extern const std::array<std::string_view const, 16> expression_names = {
     "C1ss", // w[0]
 "C2ss", // w[1]
 "C3ss", // w[2]
@@ -64,11 +74,11 @@ std::array<const char*, 16> expression_names = {
 "rate_of_V3", // w[15]
 };
 
-std::array<const char*, 0> free_parameter_ids = {
+extern const std::array<std::string_view const, 0> free_parameter_ids = {
     
 };
 
-std::array<const char*, 6> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 6> fixed_parameter_ids = {
     "V1ss", // k[0]
 "R1ss", // k[1]
 "V2ss", // k[2]
@@ -77,7 +87,7 @@ std::array<const char*, 6> fixed_parameter_ids = {
 "R3ss", // k[5]
 };
 
-std::array<const char*, 6> state_ids = {
+extern const std::array<std::string_view const, 6> state_ids = {
     "V1", // x_rdata[0]
 "V2", // x_rdata[1]
 "V3", // x_rdata[2]
@@ -86,7 +96,16 @@ std::array<const char*, 6> state_ids = {
 "f3", // x_rdata[5]
 };
 
-std::array<const char*, 6> observable_ids = {
+extern const std::array<std::string_view const, 6> state_ids_solver = {
+    "V1", // x_solver[0]
+"V2", // x_solver[1]
+"V3", // x_solver[2]
+"f1", // x_solver[3]
+"f2", // x_solver[4]
+"f3", // x_solver[5]
+};
+
+extern const std::array<std::string_view const, 6> observable_ids = {
     "obs_V1", // y[0]
 "obs_V2", // y[1]
 "obs_V3", // y[2]
@@ -95,7 +114,7 @@ std::array<const char*, 6> observable_ids = {
 "obs_f2", // y[5]
 };
 
-std::array<const char*, 16> expression_ids = {
+extern const std::array<std::string_view const, 16> expression_ids = {
     "C1ss", // w[0]
 "C2ss", // w[1]
 "C3ss", // w[2]
diff --git a/models/model_calvetti_py/model_calvetti_py.h b/models/model_calvetti_py/model_calvetti_py.h
index a683b6010e..641b17963a 100644
--- a/models/model_calvetti_py/model_calvetti_py.h
+++ b/models/model_calvetti_py/model_calvetti_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_calvetti_py {
 
-extern std::array<const char*, 0> free_parameter_names;
-extern std::array<const char*, 6> fixed_parameter_names;
-extern std::array<const char*, 6> state_names;
-extern std::array<const char*, 6> observable_names;
+extern const std::array<std::string_view const, 0> free_parameter_names;
+extern const std::array<std::string_view const, 6> fixed_parameter_names;
+extern const std::array<std::string_view const, 6> state_names;
+extern const std::array<std::string_view const, 6> state_names_solver;
+extern const std::array<std::string_view const, 6> observable_names;
 extern std::array<const ObservableScaling, 6> observable_scalings;
-extern std::array<const char*, 16> expression_names;
-extern std::array<const char*, 0> free_parameter_ids;
-extern std::array<const char*, 6> fixed_parameter_ids;
-extern std::array<const char*, 6> state_ids;
-extern std::array<const char*, 6> observable_ids;
-extern std::array<const char*, 16> expression_ids;
+extern const std::array<std::string_view const, 16> expression_names;
+extern const std::array<std::string_view const, 0> free_parameter_ids;
+extern const std::array<std::string_view const, 6> fixed_parameter_ids;
+extern const std::array<std::string_view const, 6> state_ids;
+extern const std::array<std::string_view const, 6> state_ids_solver;
+extern const std::array<std::string_view const, 6> observable_ids;
+extern const std::array<std::string_view const, 16> expression_ids;
 extern std::array<int, 6> state_idxs_solver;
 
 extern void Jy_model_calvetti_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -424,114 +426,96 @@ class Model_model_calvetti_py : public amici::Model_DAE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -557,7 +541,7 @@ class Model_model_calvetti_py : public amici::Model_DAE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_dirac_py/CMakeLists.txt b/models/model_dirac_py/CMakeLists.txt
index e5b80c5342..015fbe4cc4 100644
--- a/models/model_dirac_py/CMakeLists.txt
+++ b/models/model_dirac_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_dirac_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_dirac_py/model_dirac_py.cpp b/models/model_dirac_py/model_dirac_py.cpp
index e52ab31800..073c842703 100644
--- a/models/model_dirac_py/model_dirac_py.cpp
+++ b/models/model_dirac_py/model_dirac_py.cpp
@@ -1,27 +1,33 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_dirac_py {
 
 // clang-format off
 
-std::array<const char*, 4> free_parameter_names = {
+extern const std::array<std::string_view const, 4> free_parameter_names = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
 "p4", // p[3]
 };
 
-std::array<const char*, 0> fixed_parameter_names = {
+extern const std::array<std::string_view const, 0> fixed_parameter_names = {
     
 };
 
-std::array<const char*, 2> state_names = {
+extern const std::array<std::string_view const, 2> state_names = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 };
 
-std::array<const char*, 1> observable_names = {
+extern const std::array<std::string_view const, 2> state_names_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+};
+
+extern const std::array<std::string_view const, 1> observable_names = {
     "y0", // y[0]
 };
 
@@ -29,31 +35,36 @@ std::array<const ObservableScaling, 1> observable_scalings = {
     ObservableScaling::lin, // y[0]
 };
 
-std::array<const char*, 0> expression_names = {
+extern const std::array<std::string_view const, 0> expression_names = {
     
 };
 
-std::array<const char*, 4> free_parameter_ids = {
+extern const std::array<std::string_view const, 4> free_parameter_ids = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
 "p4", // p[3]
 };
 
-std::array<const char*, 0> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 0> fixed_parameter_ids = {
     
 };
 
-std::array<const char*, 2> state_ids = {
+extern const std::array<std::string_view const, 2> state_ids = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 };
 
-std::array<const char*, 1> observable_ids = {
+extern const std::array<std::string_view const, 2> state_ids_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+};
+
+extern const std::array<std::string_view const, 1> observable_ids = {
     "obs_x2", // y[0]
 };
 
-std::array<const char*, 0> expression_ids = {
+extern const std::array<std::string_view const, 0> expression_ids = {
     
 };
 
diff --git a/models/model_dirac_py/model_dirac_py.h b/models/model_dirac_py/model_dirac_py.h
index 1d4e41430d..4952a901d1 100644
--- a/models/model_dirac_py/model_dirac_py.h
+++ b/models/model_dirac_py/model_dirac_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_dirac_py {
 
-extern std::array<const char*, 4> free_parameter_names;
-extern std::array<const char*, 0> fixed_parameter_names;
-extern std::array<const char*, 2> state_names;
-extern std::array<const char*, 1> observable_names;
+extern const std::array<std::string_view const, 4> free_parameter_names;
+extern const std::array<std::string_view const, 0> fixed_parameter_names;
+extern const std::array<std::string_view const, 2> state_names;
+extern const std::array<std::string_view const, 2> state_names_solver;
+extern const std::array<std::string_view const, 1> observable_names;
 extern std::array<const ObservableScaling, 1> observable_scalings;
-extern std::array<const char*, 0> expression_names;
-extern std::array<const char*, 4> free_parameter_ids;
-extern std::array<const char*, 0> fixed_parameter_ids;
-extern std::array<const char*, 2> state_ids;
-extern std::array<const char*, 1> observable_ids;
-extern std::array<const char*, 0> expression_ids;
+extern const std::array<std::string_view const, 0> expression_names;
+extern const std::array<std::string_view const, 4> free_parameter_ids;
+extern const std::array<std::string_view const, 0> fixed_parameter_ids;
+extern const std::array<std::string_view const, 2> state_ids;
+extern const std::array<std::string_view const, 2> state_ids_solver;
+extern const std::array<std::string_view const, 1> observable_ids;
+extern const std::array<std::string_view const, 0> expression_ids;
 extern std::array<int, 2> state_idxs_solver;
 
 extern void Jy_model_dirac_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -411,114 +413,96 @@ class Model_model_dirac_py : public amici::Model_ODE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -544,7 +528,7 @@ class Model_model_dirac_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_events_py/CMakeLists.txt b/models/model_events_py/CMakeLists.txt
index 5b4c57907c..2d628c888e 100644
--- a/models/model_events_py/CMakeLists.txt
+++ b/models/model_events_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_events_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_events_py/model_events_py.cpp b/models/model_events_py/model_events_py.cpp
index 2f5da7d8a7..89c13088b5 100644
--- a/models/model_events_py/model_events_py.cpp
+++ b/models/model_events_py/model_events_py.cpp
@@ -1,31 +1,38 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_events_py {
 
 // clang-format off
 
-std::array<const char*, 4> free_parameter_names = {
+extern const std::array<std::string_view const, 4> free_parameter_names = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
 "p4", // p[3]
 };
 
-std::array<const char*, 4> fixed_parameter_names = {
+extern const std::array<std::string_view const, 4> fixed_parameter_names = {
     "k1", // k[0]
 "k2", // k[1]
 "k3", // k[2]
 "k4", // k[3]
 };
 
-std::array<const char*, 3> state_names = {
+extern const std::array<std::string_view const, 3> state_names = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 "x3", // x_rdata[2]
 };
 
-std::array<const char*, 1> observable_names = {
+extern const std::array<std::string_view const, 3> state_names_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+"x3", // x_solver[2]
+};
+
+extern const std::array<std::string_view const, 1> observable_names = {
     "y1", // y[0]
 };
 
@@ -33,35 +40,41 @@ std::array<const ObservableScaling, 1> observable_scalings = {
     ObservableScaling::lin, // y[0]
 };
 
-std::array<const char*, 0> expression_names = {
+extern const std::array<std::string_view const, 0> expression_names = {
     
 };
 
-std::array<const char*, 4> free_parameter_ids = {
+extern const std::array<std::string_view const, 4> free_parameter_ids = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
 "p4", // p[3]
 };
 
-std::array<const char*, 4> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 4> fixed_parameter_ids = {
     "k1", // k[0]
 "k2", // k[1]
 "k3", // k[2]
 "k4", // k[3]
 };
 
-std::array<const char*, 3> state_ids = {
+extern const std::array<std::string_view const, 3> state_ids = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 "x3", // x_rdata[2]
 };
 
-std::array<const char*, 1> observable_ids = {
+extern const std::array<std::string_view const, 3> state_ids_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+"x3", // x_solver[2]
+};
+
+extern const std::array<std::string_view const, 1> observable_ids = {
     "y1", // y[0]
 };
 
-std::array<const char*, 0> expression_ids = {
+extern const std::array<std::string_view const, 0> expression_ids = {
     
 };
 
diff --git a/models/model_events_py/model_events_py.h b/models/model_events_py/model_events_py.h
index 5c2d058a6a..ffa1da8fc7 100644
--- a/models/model_events_py/model_events_py.h
+++ b/models/model_events_py/model_events_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_events_py {
 
-extern std::array<const char*, 4> free_parameter_names;
-extern std::array<const char*, 4> fixed_parameter_names;
-extern std::array<const char*, 3> state_names;
-extern std::array<const char*, 1> observable_names;
+extern const std::array<std::string_view const, 4> free_parameter_names;
+extern const std::array<std::string_view const, 4> fixed_parameter_names;
+extern const std::array<std::string_view const, 3> state_names;
+extern const std::array<std::string_view const, 3> state_names_solver;
+extern const std::array<std::string_view const, 1> observable_names;
 extern std::array<const ObservableScaling, 1> observable_scalings;
-extern std::array<const char*, 0> expression_names;
-extern std::array<const char*, 4> free_parameter_ids;
-extern std::array<const char*, 4> fixed_parameter_ids;
-extern std::array<const char*, 3> state_ids;
-extern std::array<const char*, 1> observable_ids;
-extern std::array<const char*, 0> expression_ids;
+extern const std::array<std::string_view const, 0> expression_names;
+extern const std::array<std::string_view const, 4> free_parameter_ids;
+extern const std::array<std::string_view const, 4> fixed_parameter_ids;
+extern const std::array<std::string_view const, 3> state_ids;
+extern const std::array<std::string_view const, 3> state_ids_solver;
+extern const std::array<std::string_view const, 1> observable_ids;
+extern const std::array<std::string_view const, 0> expression_ids;
 extern std::array<int, 3> state_idxs_solver;
 
 extern void Jy_model_events_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -446,114 +448,96 @@ class Model_model_events_py : public amici::Model_ODE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -579,7 +563,7 @@ class Model_model_events_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_jakstat_adjoint_py/CMakeLists.txt b/models/model_jakstat_adjoint_py/CMakeLists.txt
index d3a16024cb..ba0095a279 100644
--- a/models/model_jakstat_adjoint_py/CMakeLists.txt
+++ b/models/model_jakstat_adjoint_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_jakstat_adjoint_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.cpp b/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.cpp
index 85d326e72d..0409a90c61 100644
--- a/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.cpp
+++ b/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.cpp
@@ -1,11 +1,12 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_jakstat_adjoint_py {
 
 // clang-format off
 
-std::array<const char*, 17> free_parameter_names = {
+extern const std::array<std::string_view const, 17> free_parameter_names = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
@@ -25,12 +26,12 @@ std::array<const char*, 17> free_parameter_names = {
 "sigma_pEpoR", // p[16]
 };
 
-std::array<const char*, 2> fixed_parameter_names = {
+extern const std::array<std::string_view const, 2> fixed_parameter_names = {
     "Omega_cyt", // k[0]
 "Omega_nuc", // k[1]
 };
 
-std::array<const char*, 9> state_names = {
+extern const std::array<std::string_view const, 9> state_names = {
     "STAT", // x_rdata[0]
 "pSTAT", // x_rdata[1]
 "pSTAT_pSTAT", // x_rdata[2]
@@ -42,7 +43,19 @@ std::array<const char*, 9> state_names = {
 "nSTAT5", // x_rdata[8]
 };
 
-std::array<const char*, 3> observable_names = {
+extern const std::array<std::string_view const, 9> state_names_solver = {
+    "STAT", // x_solver[0]
+"pSTAT", // x_solver[1]
+"pSTAT_pSTAT", // x_solver[2]
+"npSTAT_npSTAT", // x_solver[3]
+"nSTAT1", // x_solver[4]
+"nSTAT2", // x_solver[5]
+"nSTAT3", // x_solver[6]
+"nSTAT4", // x_solver[7]
+"nSTAT5", // x_solver[8]
+};
+
+extern const std::array<std::string_view const, 3> observable_names = {
     "y0", // y[0]
 "y1", // y[1]
 "y2", // y[2]
@@ -54,11 +67,11 @@ ObservableScaling::lin, // y[1]
 ObservableScaling::lin, // y[2]
 };
 
-std::array<const char*, 1> expression_names = {
+extern const std::array<std::string_view const, 1> expression_names = {
     "u", // w[0]
 };
 
-std::array<const char*, 17> free_parameter_ids = {
+extern const std::array<std::string_view const, 17> free_parameter_ids = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
@@ -78,12 +91,12 @@ std::array<const char*, 17> free_parameter_ids = {
 "sigma_pEpoR", // p[16]
 };
 
-std::array<const char*, 2> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 2> fixed_parameter_ids = {
     "Omega_cyt", // k[0]
 "Omega_nuc", // k[1]
 };
 
-std::array<const char*, 9> state_ids = {
+extern const std::array<std::string_view const, 9> state_ids = {
     "STAT", // x_rdata[0]
 "pSTAT", // x_rdata[1]
 "pSTAT_pSTAT", // x_rdata[2]
@@ -95,13 +108,25 @@ std::array<const char*, 9> state_ids = {
 "nSTAT5", // x_rdata[8]
 };
 
-std::array<const char*, 3> observable_ids = {
+extern const std::array<std::string_view const, 9> state_ids_solver = {
+    "STAT", // x_solver[0]
+"pSTAT", // x_solver[1]
+"pSTAT_pSTAT", // x_solver[2]
+"npSTAT_npSTAT", // x_solver[3]
+"nSTAT1", // x_solver[4]
+"nSTAT2", // x_solver[5]
+"nSTAT3", // x_solver[6]
+"nSTAT4", // x_solver[7]
+"nSTAT5", // x_solver[8]
+};
+
+extern const std::array<std::string_view const, 3> observable_ids = {
     "obs_pSTAT", // y[0]
 "obs_tSTAT", // y[1]
 "obs_spline", // y[2]
 };
 
-std::array<const char*, 1> expression_ids = {
+extern const std::array<std::string_view const, 1> expression_ids = {
     "u", // w[0]
 };
 
diff --git a/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.h b/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.h
index 076cd143f0..5cc9be9063 100644
--- a/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.h
+++ b/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_jakstat_adjoint_py {
 
-extern std::array<const char*, 17> free_parameter_names;
-extern std::array<const char*, 2> fixed_parameter_names;
-extern std::array<const char*, 9> state_names;
-extern std::array<const char*, 3> observable_names;
+extern const std::array<std::string_view const, 17> free_parameter_names;
+extern const std::array<std::string_view const, 2> fixed_parameter_names;
+extern const std::array<std::string_view const, 9> state_names;
+extern const std::array<std::string_view const, 9> state_names_solver;
+extern const std::array<std::string_view const, 3> observable_names;
 extern std::array<const ObservableScaling, 3> observable_scalings;
-extern std::array<const char*, 1> expression_names;
-extern std::array<const char*, 17> free_parameter_ids;
-extern std::array<const char*, 2> fixed_parameter_ids;
-extern std::array<const char*, 9> state_ids;
-extern std::array<const char*, 3> observable_ids;
-extern std::array<const char*, 1> expression_ids;
+extern const std::array<std::string_view const, 1> expression_names;
+extern const std::array<std::string_view const, 17> free_parameter_ids;
+extern const std::array<std::string_view const, 2> fixed_parameter_ids;
+extern const std::array<std::string_view const, 9> state_ids;
+extern const std::array<std::string_view const, 9> state_ids_solver;
+extern const std::array<std::string_view const, 3> observable_ids;
+extern const std::array<std::string_view const, 1> expression_ids;
 extern std::array<int, 9> state_idxs_solver;
 
 extern void Jy_model_jakstat_adjoint_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -419,114 +421,96 @@ class Model_model_jakstat_adjoint_py : public amici::Model_ODE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -552,7 +536,7 @@ class Model_model_jakstat_adjoint_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_nested_events_py/CMakeLists.txt b/models/model_nested_events_py/CMakeLists.txt
index faf49f9b21..f1edd47182 100644
--- a/models/model_nested_events_py/CMakeLists.txt
+++ b/models/model_nested_events_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_nested_events_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_nested_events_py/model_nested_events_py.cpp b/models/model_nested_events_py/model_nested_events_py.cpp
index 15df7aa91a..fbada254fb 100644
--- a/models/model_nested_events_py/model_nested_events_py.cpp
+++ b/models/model_nested_events_py/model_nested_events_py.cpp
@@ -1,11 +1,12 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_nested_events_py {
 
 // clang-format off
 
-std::array<const char*, 5> free_parameter_names = {
+extern const std::array<std::string_view const, 5> free_parameter_names = {
     "V_0", // p[0]
 "V_0_inject", // p[1]
 "t_0", // p[2]
@@ -13,15 +14,19 @@ std::array<const char*, 5> free_parameter_names = {
 "delta_V", // p[4]
 };
 
-std::array<const char*, 0> fixed_parameter_names = {
+extern const std::array<std::string_view const, 0> fixed_parameter_names = {
     
 };
 
-std::array<const char*, 1> state_names = {
+extern const std::array<std::string_view const, 1> state_names = {
     "Virus", // x_rdata[0]
 };
 
-std::array<const char*, 1> observable_names = {
+extern const std::array<std::string_view const, 1> state_names_solver = {
+    "Virus", // x_solver[0]
+};
+
+extern const std::array<std::string_view const, 1> observable_names = {
     "y0", // y[0]
 };
 
@@ -29,11 +34,11 @@ std::array<const ObservableScaling, 1> observable_scalings = {
     ObservableScaling::lin, // y[0]
 };
 
-std::array<const char*, 0> expression_names = {
+extern const std::array<std::string_view const, 0> expression_names = {
     
 };
 
-std::array<const char*, 5> free_parameter_ids = {
+extern const std::array<std::string_view const, 5> free_parameter_ids = {
     "V_0", // p[0]
 "V_0_inject", // p[1]
 "t_0", // p[2]
@@ -41,19 +46,23 @@ std::array<const char*, 5> free_parameter_ids = {
 "delta_V", // p[4]
 };
 
-std::array<const char*, 0> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 0> fixed_parameter_ids = {
     
 };
 
-std::array<const char*, 1> state_ids = {
+extern const std::array<std::string_view const, 1> state_ids = {
     "Virus", // x_rdata[0]
 };
 
-std::array<const char*, 1> observable_ids = {
+extern const std::array<std::string_view const, 1> state_ids_solver = {
+    "Virus", // x_solver[0]
+};
+
+extern const std::array<std::string_view const, 1> observable_ids = {
     "obs_Virus", // y[0]
 };
 
-std::array<const char*, 0> expression_ids = {
+extern const std::array<std::string_view const, 0> expression_ids = {
     
 };
 
diff --git a/models/model_nested_events_py/model_nested_events_py.h b/models/model_nested_events_py/model_nested_events_py.h
index 18a8727846..ae97183ea4 100644
--- a/models/model_nested_events_py/model_nested_events_py.h
+++ b/models/model_nested_events_py/model_nested_events_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_nested_events_py {
 
-extern std::array<const char*, 5> free_parameter_names;
-extern std::array<const char*, 0> fixed_parameter_names;
-extern std::array<const char*, 1> state_names;
-extern std::array<const char*, 1> observable_names;
+extern const std::array<std::string_view const, 5> free_parameter_names;
+extern const std::array<std::string_view const, 0> fixed_parameter_names;
+extern const std::array<std::string_view const, 1> state_names;
+extern const std::array<std::string_view const, 1> state_names_solver;
+extern const std::array<std::string_view const, 1> observable_names;
 extern std::array<const ObservableScaling, 1> observable_scalings;
-extern std::array<const char*, 0> expression_names;
-extern std::array<const char*, 5> free_parameter_ids;
-extern std::array<const char*, 0> fixed_parameter_ids;
-extern std::array<const char*, 1> state_ids;
-extern std::array<const char*, 1> observable_ids;
-extern std::array<const char*, 0> expression_ids;
+extern const std::array<std::string_view const, 0> expression_names;
+extern const std::array<std::string_view const, 5> free_parameter_ids;
+extern const std::array<std::string_view const, 0> fixed_parameter_ids;
+extern const std::array<std::string_view const, 1> state_ids;
+extern const std::array<std::string_view const, 1> state_ids_solver;
+extern const std::array<std::string_view const, 1> observable_ids;
+extern const std::array<std::string_view const, 0> expression_ids;
 extern std::array<int, 1> state_idxs_solver;
 
 extern void Jy_model_nested_events_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -419,114 +421,96 @@ class Model_model_nested_events_py : public amici::Model_ODE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -552,7 +536,7 @@ class Model_model_nested_events_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_neuron_py/CMakeLists.txt b/models/model_neuron_py/CMakeLists.txt
index 440bc4fdd4..5792978baa 100644
--- a/models/model_neuron_py/CMakeLists.txt
+++ b/models/model_neuron_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_neuron_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_neuron_py/model_neuron_py.cpp b/models/model_neuron_py/model_neuron_py.cpp
index c9ba737562..9afa8a4d5c 100644
--- a/models/model_neuron_py/model_neuron_py.cpp
+++ b/models/model_neuron_py/model_neuron_py.cpp
@@ -1,28 +1,34 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_neuron_py {
 
 // clang-format off
 
-std::array<const char*, 4> free_parameter_names = {
+extern const std::array<std::string_view const, 4> free_parameter_names = {
     "a", // p[0]
 "b", // p[1]
 "c", // p[2]
 "d", // p[3]
 };
 
-std::array<const char*, 2> fixed_parameter_names = {
+extern const std::array<std::string_view const, 2> fixed_parameter_names = {
     "v0", // k[0]
 "I0", // k[1]
 };
 
-std::array<const char*, 2> state_names = {
+extern const std::array<std::string_view const, 2> state_names = {
     "v", // x_rdata[0]
 "u", // x_rdata[1]
 };
 
-std::array<const char*, 1> observable_names = {
+extern const std::array<std::string_view const, 2> state_names_solver = {
+    "v", // x_solver[0]
+"u", // x_solver[1]
+};
+
+extern const std::array<std::string_view const, 1> observable_names = {
     "v", // y[0]
 };
 
@@ -30,32 +36,37 @@ std::array<const ObservableScaling, 1> observable_scalings = {
     ObservableScaling::lin, // y[0]
 };
 
-std::array<const char*, 0> expression_names = {
+extern const std::array<std::string_view const, 0> expression_names = {
     
 };
 
-std::array<const char*, 4> free_parameter_ids = {
+extern const std::array<std::string_view const, 4> free_parameter_ids = {
     "a", // p[0]
 "b", // p[1]
 "c", // p[2]
 "d", // p[3]
 };
 
-std::array<const char*, 2> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 2> fixed_parameter_ids = {
     "v0", // k[0]
 "I0", // k[1]
 };
 
-std::array<const char*, 2> state_ids = {
+extern const std::array<std::string_view const, 2> state_ids = {
     "v", // x_rdata[0]
 "u", // x_rdata[1]
 };
 
-std::array<const char*, 1> observable_ids = {
+extern const std::array<std::string_view const, 2> state_ids_solver = {
+    "v", // x_solver[0]
+"u", // x_solver[1]
+};
+
+extern const std::array<std::string_view const, 1> observable_ids = {
     "y1", // y[0]
 };
 
-std::array<const char*, 0> expression_ids = {
+extern const std::array<std::string_view const, 0> expression_ids = {
     
 };
 
diff --git a/models/model_neuron_py/model_neuron_py.h b/models/model_neuron_py/model_neuron_py.h
index c56016dc5e..84c40c6758 100644
--- a/models/model_neuron_py/model_neuron_py.h
+++ b/models/model_neuron_py/model_neuron_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_neuron_py {
 
-extern std::array<const char*, 4> free_parameter_names;
-extern std::array<const char*, 2> fixed_parameter_names;
-extern std::array<const char*, 2> state_names;
-extern std::array<const char*, 1> observable_names;
+extern const std::array<std::string_view const, 4> free_parameter_names;
+extern const std::array<std::string_view const, 2> fixed_parameter_names;
+extern const std::array<std::string_view const, 2> state_names;
+extern const std::array<std::string_view const, 2> state_names_solver;
+extern const std::array<std::string_view const, 1> observable_names;
 extern std::array<const ObservableScaling, 1> observable_scalings;
-extern std::array<const char*, 0> expression_names;
-extern std::array<const char*, 4> free_parameter_ids;
-extern std::array<const char*, 2> fixed_parameter_ids;
-extern std::array<const char*, 2> state_ids;
-extern std::array<const char*, 1> observable_ids;
-extern std::array<const char*, 0> expression_ids;
+extern const std::array<std::string_view const, 0> expression_names;
+extern const std::array<std::string_view const, 4> free_parameter_ids;
+extern const std::array<std::string_view const, 2> fixed_parameter_ids;
+extern const std::array<std::string_view const, 2> state_ids;
+extern const std::array<std::string_view const, 2> state_ids_solver;
+extern const std::array<std::string_view const, 1> observable_ids;
+extern const std::array<std::string_view const, 0> expression_ids;
 extern std::array<int, 2> state_idxs_solver;
 
 extern void Jy_model_neuron_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -441,114 +443,96 @@ class Model_model_neuron_py : public amici::Model_ODE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -574,7 +558,7 @@ class Model_model_neuron_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_robertson_py/CMakeLists.txt b/models/model_robertson_py/CMakeLists.txt
index 6442492172..e0b561a15b 100644
--- a/models/model_robertson_py/CMakeLists.txt
+++ b/models/model_robertson_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_robertson_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_robertson_py/model_robertson_py.cpp b/models/model_robertson_py/model_robertson_py.cpp
index fa7e441dfb..6f31088c96 100644
--- a/models/model_robertson_py/model_robertson_py.cpp
+++ b/models/model_robertson_py/model_robertson_py.cpp
@@ -1,27 +1,34 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_robertson_py {
 
 // clang-format off
 
-std::array<const char*, 3> free_parameter_names = {
+extern const std::array<std::string_view const, 3> free_parameter_names = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
 };
 
-std::array<const char*, 1> fixed_parameter_names = {
+extern const std::array<std::string_view const, 1> fixed_parameter_names = {
     "k1", // k[0]
 };
 
-std::array<const char*, 3> state_names = {
+extern const std::array<std::string_view const, 3> state_names = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 "x3", // x_rdata[2]
 };
 
-std::array<const char*, 3> observable_names = {
+extern const std::array<std::string_view const, 3> state_names_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+"x3", // x_solver[2]
+};
+
+extern const std::array<std::string_view const, 3> observable_names = {
     "y0", // y[0]
 "y1", // y[1]
 "y2", // y[2]
@@ -33,33 +40,39 @@ ObservableScaling::lin, // y[1]
 ObservableScaling::lin, // y[2]
 };
 
-std::array<const char*, 0> expression_names = {
+extern const std::array<std::string_view const, 0> expression_names = {
     
 };
 
-std::array<const char*, 3> free_parameter_ids = {
+extern const std::array<std::string_view const, 3> free_parameter_ids = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
 };
 
-std::array<const char*, 1> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 1> fixed_parameter_ids = {
     "k1", // k[0]
 };
 
-std::array<const char*, 3> state_ids = {
+extern const std::array<std::string_view const, 3> state_ids = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 "x3", // x_rdata[2]
 };
 
-std::array<const char*, 3> observable_ids = {
+extern const std::array<std::string_view const, 3> state_ids_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+"x3", // x_solver[2]
+};
+
+extern const std::array<std::string_view const, 3> observable_ids = {
     "obs_x1", // y[0]
 "obs_x2", // y[1]
 "obs_x3", // y[2]
 };
 
-std::array<const char*, 0> expression_ids = {
+extern const std::array<std::string_view const, 0> expression_ids = {
     
 };
 
diff --git a/models/model_robertson_py/model_robertson_py.h b/models/model_robertson_py/model_robertson_py.h
index 84cbfa524b..aabaabf30f 100644
--- a/models/model_robertson_py/model_robertson_py.h
+++ b/models/model_robertson_py/model_robertson_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_robertson_py {
 
-extern std::array<const char*, 3> free_parameter_names;
-extern std::array<const char*, 1> fixed_parameter_names;
-extern std::array<const char*, 3> state_names;
-extern std::array<const char*, 3> observable_names;
+extern const std::array<std::string_view const, 3> free_parameter_names;
+extern const std::array<std::string_view const, 1> fixed_parameter_names;
+extern const std::array<std::string_view const, 3> state_names;
+extern const std::array<std::string_view const, 3> state_names_solver;
+extern const std::array<std::string_view const, 3> observable_names;
 extern std::array<const ObservableScaling, 3> observable_scalings;
-extern std::array<const char*, 0> expression_names;
-extern std::array<const char*, 3> free_parameter_ids;
-extern std::array<const char*, 1> fixed_parameter_ids;
-extern std::array<const char*, 3> state_ids;
-extern std::array<const char*, 3> observable_ids;
-extern std::array<const char*, 0> expression_ids;
+extern const std::array<std::string_view const, 0> expression_names;
+extern const std::array<std::string_view const, 3> free_parameter_ids;
+extern const std::array<std::string_view const, 1> fixed_parameter_ids;
+extern const std::array<std::string_view const, 3> state_ids;
+extern const std::array<std::string_view const, 3> state_ids_solver;
+extern const std::array<std::string_view const, 3> observable_ids;
+extern const std::array<std::string_view const, 0> expression_ids;
 extern std::array<int, 3> state_idxs_solver;
 
 extern void Jy_model_robertson_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -403,114 +405,96 @@ class Model_model_robertson_py : public amici::Model_DAE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -536,7 +520,7 @@ class Model_model_robertson_py : public amici::Model_DAE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_steadystate_py/CMakeLists.txt b/models/model_steadystate_py/CMakeLists.txt
index 69cb4d4bf4..4d2a75c76d 100644
--- a/models/model_steadystate_py/CMakeLists.txt
+++ b/models/model_steadystate_py/CMakeLists.txt
@@ -2,6 +2,11 @@
 cmake_minimum_required(VERSION 3.22)
 cmake_policy(VERSION 3.22...3.31)
 
+# We aren't using C++20 modules, so disable scanning for them to avoid
+# clang-scan-deps-notfound errors.
+# See also https://discourse.cmake.org/t/cmake-3-28-cmake-cxx-compiler-clang-scan-deps-notfound-not-found/9244/3
+set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
+
 project(model_steadystate_py)
 
 message(STATUS "CMAKE_CURRENT_SOURCE_DIR: ${CMAKE_CURRENT_SOURCE_DIR}")
diff --git a/models/model_steadystate_py/model_steadystate_py.cpp b/models/model_steadystate_py/model_steadystate_py.cpp
index 65de9fee33..51717fba30 100644
--- a/models/model_steadystate_py/model_steadystate_py.cpp
+++ b/models/model_steadystate_py/model_steadystate_py.cpp
@@ -1,11 +1,12 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_model_steadystate_py {
 
 // clang-format off
 
-std::array<const char*, 5> free_parameter_names = {
+extern const std::array<std::string_view const, 5> free_parameter_names = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
@@ -13,20 +14,26 @@ std::array<const char*, 5> free_parameter_names = {
 "p5", // p[4]
 };
 
-std::array<const char*, 4> fixed_parameter_names = {
+extern const std::array<std::string_view const, 4> fixed_parameter_names = {
     "k1", // k[0]
 "k2", // k[1]
 "k3", // k[2]
 "k4", // k[3]
 };
 
-std::array<const char*, 3> state_names = {
+extern const std::array<std::string_view const, 3> state_names = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 "x3", // x_rdata[2]
 };
 
-std::array<const char*, 3> observable_names = {
+extern const std::array<std::string_view const, 3> state_names_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+"x3", // x_solver[2]
+};
+
+extern const std::array<std::string_view const, 3> observable_names = {
     "y0", // y[0]
 "y1", // y[1]
 "y2", // y[2]
@@ -38,11 +45,11 @@ ObservableScaling::lin, // y[1]
 ObservableScaling::lin, // y[2]
 };
 
-std::array<const char*, 0> expression_names = {
+extern const std::array<std::string_view const, 0> expression_names = {
     
 };
 
-std::array<const char*, 5> free_parameter_ids = {
+extern const std::array<std::string_view const, 5> free_parameter_ids = {
     "p1", // p[0]
 "p2", // p[1]
 "p3", // p[2]
@@ -50,26 +57,32 @@ std::array<const char*, 5> free_parameter_ids = {
 "p5", // p[4]
 };
 
-std::array<const char*, 4> fixed_parameter_ids = {
+extern const std::array<std::string_view const, 4> fixed_parameter_ids = {
     "k1", // k[0]
 "k2", // k[1]
 "k3", // k[2]
 "k4", // k[3]
 };
 
-std::array<const char*, 3> state_ids = {
+extern const std::array<std::string_view const, 3> state_ids = {
     "x1", // x_rdata[0]
 "x2", // x_rdata[1]
 "x3", // x_rdata[2]
 };
 
-std::array<const char*, 3> observable_ids = {
+extern const std::array<std::string_view const, 3> state_ids_solver = {
+    "x1", // x_solver[0]
+"x2", // x_solver[1]
+"x3", // x_solver[2]
+};
+
+extern const std::array<std::string_view const, 3> observable_ids = {
     "obs_x1", // y[0]
 "obs_x2", // y[1]
 "obs_x3", // y[2]
 };
 
-std::array<const char*, 0> expression_ids = {
+extern const std::array<std::string_view const, 0> expression_ids = {
     
 };
 
diff --git a/models/model_steadystate_py/model_steadystate_py.h b/models/model_steadystate_py/model_steadystate_py.h
index cbe88ddd70..1548d01f9f 100644
--- a/models/model_steadystate_py/model_steadystate_py.h
+++ b/models/model_steadystate_py/model_steadystate_py.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_model_steadystate_py {
 
-extern std::array<const char*, 5> free_parameter_names;
-extern std::array<const char*, 4> fixed_parameter_names;
-extern std::array<const char*, 3> state_names;
-extern std::array<const char*, 3> observable_names;
+extern const std::array<std::string_view const, 5> free_parameter_names;
+extern const std::array<std::string_view const, 4> fixed_parameter_names;
+extern const std::array<std::string_view const, 3> state_names;
+extern const std::array<std::string_view const, 3> state_names_solver;
+extern const std::array<std::string_view const, 3> observable_names;
 extern std::array<const ObservableScaling, 3> observable_scalings;
-extern std::array<const char*, 0> expression_names;
-extern std::array<const char*, 5> free_parameter_ids;
-extern std::array<const char*, 4> fixed_parameter_ids;
-extern std::array<const char*, 3> state_ids;
-extern std::array<const char*, 3> observable_ids;
-extern std::array<const char*, 0> expression_ids;
+extern const std::array<std::string_view const, 0> expression_names;
+extern const std::array<std::string_view const, 5> free_parameter_ids;
+extern const std::array<std::string_view const, 4> fixed_parameter_ids;
+extern const std::array<std::string_view const, 3> state_ids;
+extern const std::array<std::string_view const, 3> state_ids_solver;
+extern const std::array<std::string_view const, 3> observable_ids;
+extern const std::array<std::string_view const, 0> expression_ids;
 extern std::array<int, 3> state_idxs_solver;
 
 extern void Jy_model_steadystate_py(realtype *Jy, const int iy, const realtype *p, const realtype *k, const realtype *y, const realtype *sigmay, const realtype *my);
@@ -403,114 +405,96 @@ class Model_model_steadystate_py : public amici::Model_ODE {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
@@ -536,7 +520,7 @@ class Model_model_steadystate_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "a8dfd6e0963f32c1ce4647a652e93a271b14a053";
+        return "2b036e909775bc4645c617839fb23d3ed5f07421";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/python/sdist/amici/_installation/swig.py b/python/sdist/amici/_installation/swig.py
index 90fde75265..70bff6b7a6 100644
--- a/python/sdist/amici/_installation/swig.py
+++ b/python/sdist/amici/_installation/swig.py
@@ -54,6 +54,7 @@ class TypeHintFixer(ast.NodeTransformer):
         "std::allocator< amici::ParameterScaling > > const &": ast.Name(
             "ParameterScalingVector"
         ),
+        "std::span< std::string_view const >": ast.Name("Sequence[str]"),
     }
 
     def __init__(self):
diff --git a/python/sdist/amici/exporters/sundials/de_export.py b/python/sdist/amici/exporters/sundials/de_export.py
index c4a1e5807b..38042ae72d 100644
--- a/python/sdist/amici/exporters/sundials/de_export.py
+++ b/python/sdist/amici/exporters/sundials/de_export.py
@@ -1040,6 +1040,9 @@ def event_initializer_list() -> str:
             "STATE_NAMES_INITIALIZER_LIST": self._get_symbol_name_initializer_list(
                 "x_rdata"
             ),
+            "STATE_NAMES_SOLVER_INITIALIZER_LIST": self._get_symbol_name_initializer_list(
+                "x_solver"
+            ),
             "FIXED_PARAMETER_NAMES_INITIALIZER_LIST": self._get_symbol_name_initializer_list(
                 "k"
             ),
@@ -1061,6 +1064,9 @@ def event_initializer_list() -> str:
             "STATE_IDS_INITIALIZER_LIST": self._get_symbol_id_initializer_list(
                 "x_rdata"
             ),
+            "STATE_IDS_SOLVER_INITIALIZER_LIST": self._get_symbol_id_initializer_list(
+                "x_solver"
+            ),
             "FIXED_PARAMETER_IDS_INITIALIZER_LIST": self._get_symbol_id_initializer_list(
                 "k"
             ),
@@ -1198,9 +1204,19 @@ def _get_symbol_name_initializer_list(self, name: str) -> str:
         :return:
             Template initializer list of names
         """
+        if name == "x_solver":
+            # The current x_solver symbols are different from the names we
+            #  want here
+            names = [
+                state.get_name()
+                for state in self.model.states()
+                if not state.has_conservation_law()
+            ]
+        else:
+            names = self.model.name(name)
+
         return "\n".join(
-            f'"{symbol}", // {name}[{idx}]'
-            for idx, symbol in enumerate(self.model.name(name))
+            f'"{symbol}", // {name}[{idx}]' for idx, symbol in enumerate(names)
         )
 
     def _get_symbol_id_initializer_list(self, name: str) -> str:
@@ -1214,9 +1230,20 @@ def _get_symbol_id_initializer_list(self, name: str) -> str:
         :return:
             Template initializer list of ids
         """
+        if name == "x_solver":
+            # The current x_solver symbols are different from the ones we
+            #  want here
+            syms = [
+                state.get_sym()
+                for state in self.model.states()
+                if not state.has_conservation_law()
+            ]
+        else:
+            syms = self.model.sym(name)
+
         return "\n".join(
             f'"{self._code_printer.doprint(symbol)}", // {name}[{idx}]'
-            for idx, symbol in enumerate(self.model.sym(name))
+            for idx, symbol in enumerate(syms)
         )
 
     def _write_c_make_file(self):
diff --git a/python/sdist/amici/exporters/sundials/templates/model.template.cpp b/python/sdist/amici/exporters/sundials/templates/model.template.cpp
index 5bee191c3d..3104ed1f03 100644
--- a/python/sdist/amici/exporters/sundials/templates/model.template.cpp
+++ b/python/sdist/amici/exporters/sundials/templates/model.template.cpp
@@ -1,23 +1,28 @@
 #include <amici/defines.h>
 #include <array>
+#include <string_view>
 
 namespace amici::model_TPL_MODELNAME {
 
 // clang-format off
 
-std::array<const char*, TPL_NP> free_parameter_names = {
+extern const std::array<std::string_view const, TPL_NP> free_parameter_names = {
     TPL_FREE_PARAMETER_NAMES_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NK> fixed_parameter_names = {
+extern const std::array<std::string_view const, TPL_NK> fixed_parameter_names = {
     TPL_FIXED_PARAMETER_NAMES_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NX_RDATA> state_names = {
+extern const std::array<std::string_view const, TPL_NX_RDATA> state_names = {
     TPL_STATE_NAMES_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NY> observable_names = {
+extern const std::array<std::string_view const, TPL_NX_SOLVER> state_names_solver = {
+    TPL_STATE_NAMES_SOLVER_INITIALIZER_LIST
+};
+
+extern const std::array<std::string_view const, TPL_NY> observable_names = {
     TPL_OBSERVABLE_NAMES_INITIALIZER_LIST
 };
 
@@ -25,27 +30,31 @@ std::array<const ObservableScaling, TPL_NY> observable_scalings = {
     TPL_OBSERVABLE_TRAFO_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NW> expression_names = {
+extern const std::array<std::string_view const, TPL_NW> expression_names = {
     TPL_EXPRESSION_NAMES_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NP> free_parameter_ids = {
+extern const std::array<std::string_view const, TPL_NP> free_parameter_ids = {
     TPL_FREE_PARAMETER_IDS_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NK> fixed_parameter_ids = {
+extern const std::array<std::string_view const, TPL_NK> fixed_parameter_ids = {
     TPL_FIXED_PARAMETER_IDS_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NX_RDATA> state_ids = {
+extern const std::array<std::string_view const, TPL_NX_RDATA> state_ids = {
     TPL_STATE_IDS_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NY> observable_ids = {
+extern const std::array<std::string_view const, TPL_NX_SOLVER> state_ids_solver = {
+    TPL_STATE_IDS_SOLVER_INITIALIZER_LIST
+};
+
+extern const std::array<std::string_view const, TPL_NY> observable_ids = {
     TPL_OBSERVABLE_IDS_INITIALIZER_LIST
 };
 
-std::array<const char*, TPL_NW> expression_ids = {
+extern const std::array<std::string_view const, TPL_NW> expression_ids = {
     TPL_EXPRESSION_IDS_INITIALIZER_LIST
 };
 
diff --git a/python/sdist/amici/exporters/sundials/templates/model_header.template.h b/python/sdist/amici/exporters/sundials/templates/model_header.template.h
index e71b556f36..115bc878ea 100644
--- a/python/sdist/amici/exporters/sundials/templates/model_header.template.h
+++ b/python/sdist/amici/exporters/sundials/templates/model_header.template.h
@@ -14,17 +14,19 @@ class Solver;
 
 namespace model_TPL_MODELNAME {
 
-extern std::array<const char*, TPL_NP> free_parameter_names;
-extern std::array<const char*, TPL_NK> fixed_parameter_names;
-extern std::array<const char*, TPL_NX_RDATA> state_names;
-extern std::array<const char*, TPL_NY> observable_names;
+extern const std::array<std::string_view const, TPL_NP> free_parameter_names;
+extern const std::array<std::string_view const, TPL_NK> fixed_parameter_names;
+extern const std::array<std::string_view const, TPL_NX_RDATA> state_names;
+extern const std::array<std::string_view const, TPL_NX_SOLVER> state_names_solver;
+extern const std::array<std::string_view const, TPL_NY> observable_names;
 extern std::array<const ObservableScaling, TPL_NY> observable_scalings;
-extern std::array<const char*, TPL_NW> expression_names;
-extern std::array<const char*, TPL_NP> free_parameter_ids;
-extern std::array<const char*, TPL_NK> fixed_parameter_ids;
-extern std::array<const char*, TPL_NX_RDATA> state_ids;
-extern std::array<const char*, TPL_NY> observable_ids;
-extern std::array<const char*, TPL_NW> expression_ids;
+extern const std::array<std::string_view const, TPL_NW> expression_names;
+extern const std::array<std::string_view const, TPL_NP> free_parameter_ids;
+extern const std::array<std::string_view const, TPL_NK> fixed_parameter_ids;
+extern const std::array<std::string_view const, TPL_NX_RDATA> state_ids;
+extern const std::array<std::string_view const, TPL_NX_SOLVER> state_ids_solver;
+extern const std::array<std::string_view const, TPL_NY> observable_ids;
+extern const std::array<std::string_view const, TPL_NW> expression_ids;
 extern std::array<int, TPL_NX_SOLVER> state_idxs_solver;
 
 TPL_JY_DEF
@@ -291,114 +293,96 @@ class Model_TPL_MODELNAME : public amici::Model_TPL_MODEL_TYPE_UPPER {
      * @brief Get names of the free model parameters
      * @return the names
      */
-    std::vector<std::string> get_free_parameter_names() const override {
-        return std::vector<std::string>(free_parameter_names.begin(),
-                                        free_parameter_names.end());
+    std::span<std::string_view const> get_free_parameter_names() const override {
+        return free_parameter_names;
     }
 
     /**
      * @brief Get names of the model states
      * @return the names
      */
-    std::vector<std::string> get_state_names() const override {
-        return std::vector<std::string>(state_names.begin(), state_names.end());
+    std::span<std::string_view const> get_state_names() const override {
+        return state_names;
     }
 
     /**
      * @brief Get names of the solver states
      * @return the names
      */
-    std::vector<std::string> get_state_names_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto const idx: state_idxs_solver) {
-            result.push_back(state_names[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_names_solver() const override {
+        return state_names_solver;
     }
 
     /**
      * @brief Get names of the fixed model parameters
      * @return the names
      */
-    std::vector<std::string> get_fixed_parameter_names() const override {
-        return std::vector<std::string>(fixed_parameter_names.begin(),
-                                        fixed_parameter_names.end());
+    std::span<std::string_view const> get_fixed_parameter_names() const override {
+        return fixed_parameter_names;
     }
 
     /**
      * @brief Get names of the observables
      * @return the names
      */
-    std::vector<std::string> get_observable_names() const override {
-        return std::vector<std::string>(observable_names.begin(),
-                                        observable_names.end());
+    std::span<std::string_view const> get_observable_names() const override {
+        return observable_names;
     }
 
     /**
      * @brief Get names of model expressions
      * @return Expression names
      */
-    std::vector<std::string> get_expression_names() const override {
-        return std::vector<std::string>(expression_names.begin(),
-                                        expression_names.end());
+    std::span<std::string_view const> get_expression_names() const override {
+        return expression_names;
     }
 
     /**
      * @brief Get ids of the free model parameters
      * @return the ids
      */
-    std::vector<std::string> get_free_parameter_ids() const override {
-        return std::vector<std::string>(free_parameter_ids.begin(),
-                                        free_parameter_ids.end());
+    std::span<std::string_view const> get_free_parameter_ids() const override {
+        return free_parameter_ids;
     }
 
     /**
      * @brief Get ids of the model states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids() const override {
-        return std::vector<std::string>(state_ids.begin(), state_ids.end());
+    std::span<std::string_view const> get_state_ids() const override {
+        return state_ids;
     }
 
     /**
      * @brief Get ids of the solver states
      * @return the ids
      */
-    std::vector<std::string> get_state_ids_solver() const override {
-        std::vector<std::string> result;
-        result.reserve(state_idxs_solver.size());
-        for(auto idx: state_idxs_solver) {
-            result.push_back(state_ids[idx]);
-        }
-        return result;
+    std::span<std::string_view const> get_state_ids_solver() const override {
+        return state_ids_solver;
     }
 
     /**
      * @brief Get ids of the fixed model parameters
      * @return the ids
      */
-    std::vector<std::string> get_fixed_parameter_ids() const override {
-        return std::vector<std::string>(fixed_parameter_ids.begin(),
-                                        fixed_parameter_ids.end());
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
+        return fixed_parameter_ids;
     }
 
     /**
      * @brief Get ids of the observables
      * @return the ids
      */
-    std::vector<std::string> get_observable_ids() const override {
-        return std::vector<std::string>(observable_ids.begin(),
-                                        observable_ids.end());
+    std::span<std::string_view const> get_observable_ids() const override {
+        return observable_ids;
     }
 
     /**
      * @brief Get IDs of model expressions
      * @return Expression IDs
      */
-    std::vector<std::string> get_expression_ids() const override {
-        return std::vector<std::string>(expression_ids.begin(),
-                                        expression_ids.end());
+    std::span<std::string_view const> get_expression_ids() const override {
+        return expression_ids;
     }
 
     /**
diff --git a/python/sdist/amici/testing/models.py b/python/sdist/amici/testing/models.py
index 6aca290947..adf48f2176 100644
--- a/python/sdist/amici/testing/models.py
+++ b/python/sdist/amici/testing/models.py
@@ -165,7 +165,7 @@ def import_model_calvetti(output_dir: Path = None) -> Model:
         "R2ss",
         "V3ss",
         "R3ss",
-    )
+    ), model.get_fixed_parameter_ids()
 
     return model
 
diff --git a/src/model.cpp b/src/model.cpp
index bf56f966dc..375556fec8 100644
--- a/src/model.cpp
+++ b/src/model.cpp
@@ -86,7 +86,7 @@ static void set_nan_to_zero(std::vector<realtype>& vec) {
 
 /**
  * @brief local helper function to get parameters
- * @param ids vector of name/ids of (fixed)Parameters
+ * @param ids span of name/ids of (fixed)Parameters
  * @param values values of the (fixed)Parameters
  * @param id name/id to look for in the vector
  * @param variable_name string indicating what variable we are looking at
@@ -94,8 +94,9 @@ static void set_nan_to_zero(std::vector<realtype>& vec) {
  * @return value of the selected parameter
  */
 static realtype get_value_by_id(
-    std::vector<std::string> const& ids, std::vector<realtype> const& values,
-    std::string const& id, char const* variable_name, char const* id_name
+    std::span<std::string_view const> const& ids,
+    std::vector<realtype> const& values, std::string const& id,
+    char const* variable_name, char const* id_name
 ) {
     auto it = std::ranges::find(ids, id);
     if (it != ids.end())
@@ -108,7 +109,7 @@ static realtype get_value_by_id(
 
 /**
  * @brief local helper function to set parameters
- * @param ids vector of names/ids of (fixed)Parameters
+ * @param ids span of names/ids of (fixed)Parameters
  * @param values values of the (fixed)Parameters
  * @param value for the selected parameter
  * @param id name/id to look for in the vector
@@ -116,7 +117,7 @@ static realtype get_value_by_id(
  * @param id_name string indicating whether name or id was specified
  */
 static void set_value_by_id(
-    std::vector<std::string> const& ids, std::vector<realtype>& values,
+    std::span<std::string_view const> const& ids, std::vector<realtype>& values,
     realtype const value, std::string const& id, char const* variable_name,
     char const* id_name
 ) {
@@ -131,7 +132,7 @@ static void set_value_by_id(
 
 /**
  * @brief local helper function to set parameters via regex
- * @param ids vector of names/ids of (fixed)Parameters
+ * @param ids span of names/ids of (fixed)Parameters
  * @param values values of the (fixed)Parameters
  * @param value for the selected parameter
  * @param regex string according to which names/ids are to be matched
@@ -141,15 +142,16 @@ static void set_value_by_id(
  */
 
 static int set_value_by_id_regex(
-    std::vector<std::string> const& ids, std::vector<realtype>& values,
+    std::span<std::string_view const> const& ids, std::vector<realtype>& values,
     realtype value, std::string const& regex, char const* variable_name,
     char const* id_name
 ) {
     try {
         std::regex pattern(regex);
         int n_found = 0;
+        std::match_results<std::string_view::const_iterator> m;
         for (auto const& id : ids) {
-            if (std::regex_match(id, pattern)) {
+            if (std::regex_match(id.begin(), id.end(), m, pattern)) {
                 values.at(&id - &ids[0]) = value;
                 ++n_found;
             }
@@ -769,65 +771,85 @@ bool Model::has_free_parameter_names() const {
     return np() == 0 || !get_free_parameter_names().empty();
 }
 
-std::vector<std::string> Model::get_free_parameter_names() const { return {}; }
+std::span<std::string_view const> Model::get_free_parameter_names() const {
+    return {};
+}
 
 bool Model::has_state_names() const {
     return nx_rdata == 0 || !get_state_names().empty();
 }
 
-std::vector<std::string> Model::get_state_names() const { return {}; }
+std::span<std::string_view const> Model::get_state_names() const { return {}; }
 
-std::vector<std::string> Model::get_state_names_solver() const { return {}; }
+std::span<std::string_view const> Model::get_state_names_solver() const {
+    return {};
+}
 
 bool Model::has_fixed_parameter_names() const {
     return nk() == 0 || !get_fixed_parameter_names().empty();
 }
 
-std::vector<std::string> Model::get_fixed_parameter_names() const { return {}; }
+std::span<std::string_view const> Model::get_fixed_parameter_names() const {
+    return {};
+}
 
 bool Model::has_observable_names() const {
     return ny == 0 || !get_observable_names().empty();
 }
 
-std::vector<std::string> Model::get_observable_names() const { return {}; }
+std::span<std::string_view const> Model::get_observable_names() const {
+    return {};
+}
 
 bool Model::has_expression_names() const {
     return ny == 0 || !get_expression_names().empty();
 }
 
-std::vector<std::string> Model::get_expression_names() const { return {}; }
+std::span<std::string_view const> Model::get_expression_names() const {
+    return {};
+}
 
 bool Model::has_free_parameter_ids() const {
     return np() == 0 || !get_free_parameter_ids().empty();
 }
 
-std::vector<std::string> Model::get_free_parameter_ids() const { return {}; }
+std::span<std::string_view const> Model::get_free_parameter_ids() const {
+    return {};
+}
 
 bool Model::has_state_ids() const {
     return nx_rdata == 0 || !get_state_ids().empty();
 }
 
-std::vector<std::string> Model::get_state_ids() const { return {}; }
+std::span<std::string_view const> Model::get_state_ids() const { return {}; }
 
-std::vector<std::string> Model::get_state_ids_solver() const { return {}; }
+std::span<std::string_view const> Model::get_state_ids_solver() const {
+    return {};
+}
 
 bool Model::has_fixed_parameter_ids() const {
     return nk() == 0 || !get_fixed_parameter_ids().empty();
 }
 
-std::vector<std::string> Model::get_fixed_parameter_ids() const { return {}; }
+std::span<std::string_view const> Model::get_fixed_parameter_ids() const {
+    return {};
+}
 
 bool Model::has_observable_ids() const {
     return ny == 0 || !get_observable_ids().empty();
 }
 
-std::vector<std::string> Model::get_observable_ids() const { return {}; }
+std::span<std::string_view const> Model::get_observable_ids() const {
+    return {};
+}
 
 bool Model::has_expression_ids() const {
     return ny == 0 || !get_expression_ids().empty();
 }
 
-std::vector<std::string> Model::get_expression_ids() const { return {}; }
+std::span<std::string_view const> Model::get_expression_ids() const {
+    return {};
+}
 
 bool Model::has_quadratic_llh() const { return true; }
 
@@ -1700,28 +1722,30 @@ int Model::check_finite(
     case ModelQuantity::dydp:
     case ModelQuantity::dsigmaydp:
         if (has_observable_ids())
-            row_id += " " + get_observable_ids()[row];
+            row_id.append(" ").append(get_observable_ids()[row]);
         if (has_free_parameter_ids())
-            col_id
-                += " " + get_free_parameter_ids()[plist(gsl::narrow<int>(col))];
+            col_id.append(" ").append(
+                get_free_parameter_ids()[plist(gsl::narrow<int>(col))]
+            );
         break;
     case ModelQuantity::dydx:
         if (has_observable_ids())
-            row_id += " " + get_observable_ids()[row];
+            row_id.append(" ").append(get_observable_ids()[row]);
         if (has_state_ids())
-            col_id += " " + get_state_ids_solver()[col];
+            col_id.append(" ").append(get_state_ids_solver()[col]);
         break;
     case ModelQuantity::deltasx:
         if (has_state_ids())
-            row_id += " " + get_state_ids_solver()[row];
+            row_id.append(" ").append(get_state_ids_solver()[row]);
         if (has_free_parameter_ids())
-            col_id
-                += " " + get_free_parameter_ids()[plist(gsl::narrow<int>(col))];
+            col_id.append(" ").append(
+                get_free_parameter_ids()[plist(gsl::narrow<int>(col))]
+            );
         break;
     case ModelQuantity::dJydy:
     case ModelQuantity::dJydsigma:
         if (has_observable_ids())
-            col_id += " " + get_observable_ids()[col];
+            col_id.append(" ").append(get_observable_ids()[col]);
         break;
     case ModelQuantity::dJydx:
     case ModelQuantity::dJzdx:
@@ -1729,7 +1753,7 @@ int Model::check_finite(
     case ModelQuantity::dzdx:
     case ModelQuantity::drzdx:
         if (has_state_ids())
-            col_id += " " + get_state_ids_solver()[col];
+            col_id.append(" ").append(get_state_ids_solver()[col]);
         break;
     case ModelQuantity::deltaqB:
     case ModelQuantity::sz:
@@ -1737,14 +1761,15 @@ int Model::check_finite(
     case ModelQuantity::drzdp:
     case ModelQuantity::dsigmazdp:
         if (has_free_parameter_ids())
-            col_id
-                += " " + get_free_parameter_ids()[plist(gsl::narrow<int>(col))];
+            col_id.append(" ").append(
+                get_free_parameter_ids()[plist(gsl::narrow<int>(col))]
+            );
         break;
     case ModelQuantity::dsigmaydy:
         if (has_observable_ids()) {
             auto obs_ids = get_observable_ids();
-            row_id += " " + obs_ids[row];
-            col_id += " " + obs_ids[col];
+            row_id.append(" ").append(obs_ids[row]);
+            col_id.append(" ").append(obs_ids[col]);
         }
         break;
     default:
@@ -1820,28 +1845,28 @@ int Model::check_finite(
     case ModelQuantity::JB:
         if (has_state_ids()) {
             auto state_ids = get_state_ids_solver();
-            row_id += " " + state_ids[row];
-            col_id += " " + state_ids[col];
+            row_id.append(" ").append(state_ids[row]);
+            col_id.append(" ").append(state_ids[col]);
         }
         break;
     case ModelQuantity::dwdx:
         if (has_expression_ids())
-            row_id += " " + get_expression_ids()[row];
+            row_id.append(" ").append(get_expression_ids()[row]);
         if (has_state_ids())
-            col_id += " " + get_state_ids_solver()[col];
+            col_id.append(" ").append(get_state_ids_solver()[col]);
         break;
     case ModelQuantity::dwdw:
         if (has_expression_ids()) {
             auto expr_ids = get_expression_ids();
-            row_id += " " + expr_ids[row];
-            col_id += " " + expr_ids[col];
+            row_id.append(" ").append(expr_ids[row]);
+            col_id.append(" ").append(expr_ids[col]);
         }
         break;
     case ModelQuantity::dwdp:
         if (has_expression_ids())
-            row_id += " " + get_expression_ids()[row];
+            row_id.append(" ").append(get_expression_ids()[row]);
         if (has_free_parameter_ids())
-            col_id += " " + get_free_parameter_ids()[col];
+            col_id.append(" ").append(get_free_parameter_ids()[col]);
         break;
     default:
         break;
@@ -2142,9 +2167,10 @@ void Model::fsigmay(int const it, ExpData const* edata) {
                 derived_state_.sigmay_.at(iytrue + iJ * nytrue) = 0;
 
             if (edata->is_set_measurement(it, iytrue)) {
-                std::string obs_id = has_observable_ids()
-                                         ? get_observable_ids().at(iytrue)
-                                         : std::to_string(iytrue);
+                std::string obs_id
+                    = has_observable_ids()
+                          ? std::string(get_observable_ids()[iytrue])
+                          : std::to_string(iytrue);
                 std::stringstream ss;
                 ss << "sigmay (" << obs_id << ", ExpData::id=" << edata->id
                    << ", t=" << get_timepoint(it) << ")";
diff --git a/swig/amici.i b/swig/amici.i
index cadd5efa44..0e36b51607 100644
--- a/swig/amici.i
+++ b/swig/amici.i
@@ -53,6 +53,32 @@ nonstandard type conversions.
 %typemap(doctype) size_t "int";
 
 
+// Typemap to support returning std::span<const std::string_view>
+// as Python tuple
+// Currently, the strings are copied; if performance becomes an issue,
+// we can see if we can return views into existing memory.
+// At least for the model entity IDs/names, there is no risk of dangling
+// pointers as long as the shared object is not unloaded.
+%include <std_string.i>
+
+%typemap(out) std::span<const std::string_view> {
+    PyObject *tuple = PyTuple_New((Py_ssize_t)$1.size());
+    if (!tuple) {
+        SWIG_exception_fail(SWIG_RuntimeError, "could not allocate tuple");
+    }
+    for (size_t i = 0; i < $1.size(); ++i) {
+        const std::string_view &sv = $1.data()[i];
+        PyObject *sobj = PyUnicode_DecodeUTF8(sv.data(), (Py_ssize_t)sv.size(), "strict");
+        if (!sobj) {
+            Py_DECREF(tuple);
+            SWIG_exception_fail(SWIG_RuntimeError, "failed to decode string_view as UTF-8");
+        }
+        PyTuple_SET_ITEM(tuple, (Py_ssize_t)i, sobj); // takes ownership of sobj
+    }
+    $result = tuple;
+}
+
+
 %include <exception.i>
 %exception {
     try {
diff --git a/tests/cpp/testfunctions.cpp b/tests/cpp/testfunctions.cpp
index 86a41aedc5..f683f2b6a5 100644
--- a/tests/cpp/testfunctions.cpp
+++ b/tests/cpp/testfunctions.cpp
@@ -9,7 +9,10 @@
 #include <unistd.h>
 #include <iostream>
 #include <format>
-
+#include <span>
+#include <string_view>
+#include <map>
+#include <vector>
 #include "gtest/gtest.h"
 
 namespace amici {
@@ -20,13 +23,30 @@ extern std::unique_ptr<amici::Model> get_model();
 
 } // namespace generic_model
 
-std::vector<std::string> getVariableNames(std::string const& name, int length) {
-    std::vector<std::string> names;
-    names.reserve(length);
-    for (int i = 0; i < length; ++i) {
-        names.push_back(name + std::to_string(i));
+std::map<std::string, std::vector<std::string_view>> var_names {
+    {"p", {"p0", "p1", "p2", "p3", "p4"}},
+    {"k", {"k0", "k1", "k2"}},
+    {"x", {"x0", "x1", "x2", "x3", "x4", "x5"}},
+    {"y", {"y0", "y1", "y2"}}
+};
+
+std::span<std::string_view const> getVariableNames(std::string const& name, int length) {
+    auto it = var_names.find(name);
+    if(it != var_names.end()) {
+        if((int)it->second.size() >= length) {
+            return std::span<std::string_view const>(it->second.data(), length);
+        } else {
+            // need to add more names to var_names above.
+            // this is a bit ugly, but we can't generate this dynamically, as
+            // we are only passing around references.
+            throw std::runtime_error(
+                "Variable names for " + name + " with length "
+                + std::to_string(length)
+                + " not available. Update tests/cpp/testfunctions.cpp:var_names."
+            );
+        }
     }
-    return names;
+    throw std::runtime_error("Variable names for " + name + " with length " + std::to_string(length) + " not found.");
 }
 
 void simulateVerifyWrite(const std::string& path)
diff --git a/tests/cpp/testfunctions.h b/tests/cpp/testfunctions.h
index a1557a0877..83699a7433 100644
--- a/tests/cpp/testfunctions.h
+++ b/tests/cpp/testfunctions.h
@@ -6,8 +6,10 @@
 
 #include <H5Cpp.h>
 
+#include <span>
 #include <string>
 #include <string_view>
+#include <vector>
 
 namespace amici {
 
@@ -27,7 +29,8 @@ class ExpData;
  * @param length number of variables
  * @return default names/ids
  */
-std::vector<std::string> getVariableNames(std::string const& name, int length);
+std::span<std::string_view const>
+getVariableNames(std::string const& name, int length);
 
 /**
  * @brief The Model_Test class is a model-unspecific implementation
@@ -147,35 +150,37 @@ class Model_Test : public Model {
         throw AmiException("not implemented");
     }
 
-    std::vector<std::string> get_free_parameter_names() const override {
+    std::span<std::string_view const>
+    get_free_parameter_names() const override {
         return getVariableNames("p", np());
     }
 
-    std::vector<std::string> get_state_names() const override {
+    std::span<std::string_view const> get_state_names() const override {
         return getVariableNames("x", nx_rdata);
     }
 
-    std::vector<std::string> get_fixed_parameter_names() const override {
+    std::span<std::string_view const>
+    get_fixed_parameter_names() const override {
         return getVariableNames("k", nk());
     }
 
-    std::vector<std::string> get_observable_names() const override {
+    std::span<std::string_view const> get_observable_names() const override {
         return getVariableNames("y", ny);
     }
 
-    std::vector<std::string> get_free_parameter_ids() const override {
+    std::span<std::string_view const> get_free_parameter_ids() const override {
         return getVariableNames("p", np());
     }
 
-    std::vector<std::string> get_state_ids() const override {
+    std::span<std::string_view const> get_state_ids() const override {
         return getVariableNames("x", nx_rdata);
     }
 
-    std::vector<std::string> get_fixed_parameter_ids() const override {
+    std::span<std::string_view const> get_fixed_parameter_ids() const override {
         return getVariableNames("k", nk());
     }
 
-    std::vector<std::string> get_observable_ids() const override {
+    std::span<std::string_view const> get_observable_ids() const override {
         return getVariableNames("y", ny);
     }
 };