diff --git a/CHANGELOG.md b/CHANGELOG.md
index 90f19c15fe..7efb1a29c8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,11 @@ See also our [versioning policy](https://amici.readthedocs.io/en/latest/versioni
   at import time instead of silently generating incorrect C++, since
   simulating such models is not yet supported (#3245).
 
+* Fixed incorrect sensitivities for models with a single-species
+  conservation law -- a boundary-condition or `constant=true` species with
+  no counteracting rate rule -- whose total abundance depends on a free
+  parameter via an `InitialAssignment` (#3249).
+
 * Fixed incorrect forward sensitivities for models with SBML events that
   have explicit priorities and can trigger simultaneously.
   Whenever a lower-priority event's assignment depended on a state that a
@@ -57,6 +62,11 @@ See also our [versioning policy](https://amici.readthedocs.io/en/latest/versioni
   the sensitivity update used a stale, pre-cascade state instead of that
   already-updated state. The state trajectory itself was unaffected.
 
+* Fixed incorrect adjoint sensitivities for models with SBML events that
+  are both state-triggered and state-updating. The trigger-time-sensitivity
+  terms were evaluated using the post-event state instead of the pre-event
+  state. The state trajectory was unaffected (#3257).
+
 ### v1.1 (2026-09-03)
 
 **BREAKING CHANGES**
diff --git a/models/model_calvetti_py/model_calvetti_py.h b/models/model_calvetti_py/model_calvetti_py.h
index 238df11515..17b3190c55 100644
--- a/models/model_calvetti_py/model_calvetti_py.h
+++ b/models/model_calvetti_py/model_calvetti_py.h
@@ -541,7 +541,7 @@ class Model_model_calvetti_py : public amici::Model_DAE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_dirac_py/model_dirac_py.h b/models/model_dirac_py/model_dirac_py.h
index 117968cf0f..091d0e3477 100644
--- a/models/model_dirac_py/model_dirac_py.h
+++ b/models/model_dirac_py/model_dirac_py.h
@@ -528,7 +528,7 @@ class Model_model_dirac_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_events_py/deltaxB.cpp b/models/model_events_py/deltaxB.cpp
index 89ebc41e8e..91f309a304 100644
--- a/models/model_events_py/deltaxB.cpp
+++ b/models/model_events_py/deltaxB.cpp
@@ -7,9 +7,6 @@ namespace amici {
 namespace model_model_events_py {
 
 void deltaxB_model_events_py(realtype *deltaxB, const realtype t, const realtype *x, const realtype *p, const realtype *k, const realtype *h, const realtype *w, const realtype *dx, const int ie, const realtype *xdot, const realtype *xdot_old, const realtype *x_old, const realtype *xB, const realtype *tcl){
-    const realtype x1_ = x[0];
-    const realtype x2_ = x[1];
-    const realtype x3_ = x[2];
     const realtype p1_ = p[0];
     const realtype p2_ = p[1];
     const realtype p3_ = p[2];
@@ -21,18 +18,21 @@ void deltaxB_model_events_py(realtype *deltaxB, const realtype t, const realtype
     const realtype xdot_old0_ = xdot_old[0];
     const realtype xdot_old1_ = xdot_old[1];
     const realtype xdot_old2_ = xdot_old[2];
+    const realtype x_old0_ = x_old[0];
+    const realtype x_old1_ = x_old[1];
+    const realtype x_old2_ = x_old[2];
     const realtype xB0_ = xB[0];
     const realtype xB1_ = xB[1];
     const realtype xB2_ = xB[2];
 
     switch(ie) {
         case 0:
-            deltaxB[1] = xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ + p2_*x1_*std::exp(-1.0/10.0*t) - p3_*x2_ + x3_ - 1) + xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ + p2_*x1_*std::exp(-1.0/10.0*t) - p3_*x2_ + x3_ - 1) + xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ + p2_*x1_*std::exp(-1.0/10.0*t) - p3_*x2_ + x3_ - 1);
-            deltaxB[2] = -xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ + p2_*x1_*std::exp(-1.0/10.0*t) - p3_*x2_ + x3_ - 1) - xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ + p2_*x1_*std::exp(-1.0/10.0*t) - p3_*x2_ + x3_ - 1) - xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ + p2_*x1_*std::exp(-1.0/10.0*t) - p3_*x2_ + x3_ - 1);
+            deltaxB[1] = xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ + p2_*x_old0_*std::exp(-1.0/10.0*t) - p3_*x_old1_ + x_old2_ - 1) + xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ + p2_*x_old0_*std::exp(-1.0/10.0*t) - p3_*x_old1_ + x_old2_ - 1) + xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ + p2_*x_old0_*std::exp(-1.0/10.0*t) - p3_*x_old1_ + x_old2_ - 1);
+            deltaxB[2] = -xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ + p2_*x_old0_*std::exp(-1.0/10.0*t) - p3_*x_old1_ + x_old2_ - 1) - xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ + p2_*x_old0_*std::exp(-1.0/10.0*t) - p3_*x_old1_ + x_old2_ - 1) - xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ + p2_*x_old0_*std::exp(-1.0/10.0*t) - p3_*x_old1_ + x_old2_ - 1);
             break;
         case 1:
-            deltaxB[0] = xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ - p1_*x1_*(1 - Heaviside_2_) + x3_ - 1) + xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ - p1_*x1_*(1 - Heaviside_2_) + x3_ - 1) + xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ - p1_*x1_*(1 - Heaviside_2_) + x3_ - 1);
-            deltaxB[2] = -xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ - p1_*x1_*(1 - Heaviside_2_) + x3_ - 1) - xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ - p1_*x1_*(1 - Heaviside_2_) + x3_ - 1) - xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ - p1_*x1_*(1 - Heaviside_2_) + x3_ - 1);
+            deltaxB[0] = xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ - p1_*x_old0_*(1 - Heaviside_2_) + x_old2_ - 1) + xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ - p1_*x_old0_*(1 - Heaviside_2_) + x_old2_ - 1) + xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ - p1_*x_old0_*(1 - Heaviside_2_) + x_old2_ - 1);
+            deltaxB[2] = -xB0_*(dx1dt_ - xdot_old0_)/(Heaviside_4_ - p1_*x_old0_*(1 - Heaviside_2_) + x_old2_ - 1) - xB1_*(dx2dt_ - xdot_old1_)/(Heaviside_4_ - p1_*x_old0_*(1 - Heaviside_2_) + x_old2_ - 1) - xB2_*(dx3dt_ - xdot_old2_)/(Heaviside_4_ - p1_*x_old0_*(1 - Heaviside_2_) + x_old2_ - 1);
             break;
     }
 }
diff --git a/models/model_events_py/model_events_py.h b/models/model_events_py/model_events_py.h
index 47a4c5a1dc..b726ba28ad 100644
--- a/models/model_events_py/model_events_py.h
+++ b/models/model_events_py/model_events_py.h
@@ -563,7 +563,7 @@ class Model_model_events_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
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 9c964b7b2d..ebd5fec55f 100644
--- a/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.h
+++ b/models/model_jakstat_adjoint_py/model_jakstat_adjoint_py.h
@@ -538,7 +538,7 @@ class Model_model_jakstat_adjoint_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_nested_events_py/deltaxB.cpp b/models/model_nested_events_py/deltaxB.cpp
index 9b956b53ff..dbef568bef 100644
--- a/models/model_nested_events_py/deltaxB.cpp
+++ b/models/model_nested_events_py/deltaxB.cpp
@@ -7,20 +7,20 @@ namespace amici {
 namespace model_model_nested_events_py {
 
 void deltaxB_model_nested_events_py(realtype *deltaxB, const realtype t, const realtype *x, const realtype *p, const realtype *k, const realtype *h, const realtype *w, const realtype *dx, const int ie, const realtype *xdot, const realtype *xdot_old, const realtype *x_old, const realtype *xB, const realtype *tcl){
-    const realtype Virus_ = x[0];
     const realtype rho_V_ = p[3];
     const realtype delta_V_ = p[4];
     const realtype Heaviside_1_ = h[0];
     const realtype dVirusdt_ = xdot[0];
     const realtype xdot_old0_ = xdot_old[0];
+    const realtype x_old0_ = x_old[0];
     const realtype xB0_ = xB[0];
 
     switch(ie) {
         case 0:
-            deltaxB[0] = xB0_*(dVirusdt_ - xdot_old0_)/(Heaviside_1_*Virus_*rho_V_ - Virus_*delta_V_);
+            deltaxB[0] = xB0_*(dVirusdt_ - xdot_old0_)/(Heaviside_1_*rho_V_*x_old0_ - delta_V_*x_old0_);
             break;
         case 1:
-            deltaxB[0] = -xB0_*(dVirusdt_ - xdot_old0_)/(-Heaviside_1_*Virus_*rho_V_ + Virus_*delta_V_);
+            deltaxB[0] = -xB0_*(dVirusdt_ - xdot_old0_)/(-Heaviside_1_*rho_V_*x_old0_ + delta_V_*x_old0_);
             break;
     }
 }
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 ddb07c59c6..434ec729ca 100644
--- a/models/model_nested_events_py/model_nested_events_py.h
+++ b/models/model_nested_events_py/model_nested_events_py.h
@@ -536,7 +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 "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_neuron_py/deltaxB.cpp b/models/model_neuron_py/deltaxB.cpp
index ce99069804..f5965c3736 100644
--- a/models/model_neuron_py/deltaxB.cpp
+++ b/models/model_neuron_py/deltaxB.cpp
@@ -7,19 +7,19 @@ namespace amici {
 namespace model_model_neuron_py {
 
 void deltaxB_model_neuron_py(realtype *deltaxB, const realtype t, const realtype *x, const realtype *p, const realtype *k, const realtype *h, const realtype *w, const realtype *dx, const int ie, const realtype *xdot, const realtype *xdot_old, const realtype *x_old, const realtype *xB, const realtype *tcl){
-    const realtype v_ = x[0];
-    const realtype u_ = x[1];
     const realtype I0_ = k[1];
     const realtype dvdt_ = xdot[0];
     const realtype dudt_ = xdot[1];
     const realtype xdot_old0_ = xdot_old[0];
     const realtype xdot_old1_ = xdot_old[1];
+    const realtype x_old0_ = x_old[0];
+    const realtype x_old1_ = x_old[1];
     const realtype xB0_ = xB[0];
     const realtype xB1_ = xB[1];
 
     switch(ie) {
         case 0:
-            deltaxB[0] = xB0_*(xdot_old0_/(I0_ - u_ + (1.0/25.0)*std::pow(v_, 2) + 5*v_ + 140) + (dvdt_ - xdot_old0_)/(I0_ - u_ + (1.0/25.0)*std::pow(v_, 2) + 5*v_ + 140) - 1) + xB1_*(dudt_ - xdot_old1_)/(I0_ - u_ + (1.0/25.0)*std::pow(v_, 2) + 5*v_ + 140);
+            deltaxB[0] = xB0_*(xdot_old0_/(I0_ + (1.0/25.0)*std::pow(x_old0_, 2) + 5*x_old0_ - x_old1_ + 140) + (dvdt_ - xdot_old0_)/(I0_ + (1.0/25.0)*std::pow(x_old0_, 2) + 5*x_old0_ - x_old1_ + 140) - 1) + xB1_*(dudt_ - xdot_old1_)/(I0_ + (1.0/25.0)*std::pow(x_old0_, 2) + 5*x_old0_ - x_old1_ + 140);
             break;
     }
 }
diff --git a/models/model_neuron_py/model_neuron_py.h b/models/model_neuron_py/model_neuron_py.h
index cb75000a47..daae269bc1 100644
--- a/models/model_neuron_py/model_neuron_py.h
+++ b/models/model_neuron_py/model_neuron_py.h
@@ -558,7 +558,7 @@ class Model_model_neuron_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_robertson_py/model_robertson_py.h b/models/model_robertson_py/model_robertson_py.h
index 811add8586..7cbf76eb59 100644
--- a/models/model_robertson_py/model_robertson_py.h
+++ b/models/model_robertson_py/model_robertson_py.h
@@ -520,7 +520,7 @@ class Model_model_robertson_py : public amici::Model_DAE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/models/model_steadystate_py/model_steadystate_py.h b/models/model_steadystate_py/model_steadystate_py.h
index 8009d38623..3b4e41331e 100644
--- a/models/model_steadystate_py/model_steadystate_py.h
+++ b/models/model_steadystate_py/model_steadystate_py.h
@@ -520,7 +520,7 @@ class Model_model_steadystate_py : public amici::Model_ODE {
      * @return AMICI git commit hash
      */
     std::string get_amici_commit() const override {
-        return "5d6d457fc1e217075c7074c8f844ac64b2a75084";
+        return "f04344fe181ed0b63917c93672370d76e427fb22";
     }
 
     bool has_quadratic_llh() const override {
diff --git a/python/sdist/amici/_symbolic/de_model.py b/python/sdist/amici/_symbolic/de_model.py
index efcfa1a1f3..8433d35f40 100644
--- a/python/sdist/amici/_symbolic/de_model.py
+++ b/python/sdist/amici/_symbolic/de_model.py
@@ -27,6 +27,7 @@
     ObservableTransformation,
     _default_simplify,
     amici_time_symbol,
+    smart_subs_dict,
     symbol_with_assumptions,
     toposort_symbols,
     unique_preserve_order,
@@ -1444,6 +1445,20 @@ def _generate_sparse_symbol(self, name: str) -> None:
             self._sparsesyms[name] = symbol_list
             self._syms[name] = sparse_matrix
 
+    def _pre_event_eqs(self, name: str) -> list[sp.Matrix]:
+        """Re-express `dtaudx`/`dtaudp` purely in terms of the pre-event
+        state, for use inside `deltaxB`/`deltaqB` only.
+
+        `w` is eliminated first (not available in the C++ functions),
+        then `x -> x_old` is substituted.
+        """
+        w_to_expr = dict(zip(self.sym("w"), self.eq("w")))
+        x_to_x_old = dict(zip(self.sym("x"), self.sym("x_old")))
+        return [
+            smart_subs_dict(smart_subs_dict(expr, w_to_expr), x_to_x_old)
+            for expr in self.eq(name)
+        ]
+
     def _compute_equation(self, name: str) -> None:
         """
         Computes the symbolic formula for a symbolic variable
@@ -1852,18 +1867,20 @@ def _compute_equation(self, name: str) -> None:
             self._eqs[name] = event_eqs
 
         elif name == "deltaxB":
+            # express in terms of pre-event state
+            dtaudx_pre = self._pre_event_eqs("dtaudx")
             event_eqs = []
             for ie, event in enumerate(self._events):
                 # ==== 1st group of terms: Heaviside functions ===========
                 tmp_eq = smart_multiply(
                     self.sym("xdot") - self.sym("xdot_old"),
-                    self.eq("dtaudx")[ie],
+                    dtaudx_pre[ie],
                 )
                 if event.updates_state:
                     # ==== 2nd group of terms: Derivatives of Dirac deltas ===
                     # Part 2a: explicit time dependence of bolus function
                     tmp_eq -= smart_multiply(
-                        self.eq("ddeltaxdt")[ie], self.eq("dtaudx")[ie]
+                        self.eq("ddeltaxdt")[ie], dtaudx_pre[ie]
                     )
                     # Part 2b: implicit time dependence of bolus function
                     tmp_eq -= smart_multiply(
@@ -1872,7 +1889,7 @@ def _compute_equation(self, name: str) -> None:
                             + self.eq("ddeltaxdx_old")[ie],
                             self.sym("xdot_old"),
                         ),
-                        self.eq("dtaudx")[ie],
+                        dtaudx_pre[ie],
                     )
                     # ==== 3rd group of terms: Dirac deltas ==================
                     tmp_eq += (
@@ -1883,18 +1900,20 @@ def _compute_equation(self, name: str) -> None:
             self._eqs[name] = event_eqs
 
         elif name == "deltaqB":
+            # express in terms of pre-event state
+            dtaudp_pre = self._pre_event_eqs("dtaudp")
             event_eqs = []
             for ie, event in enumerate(self._events):
                 # ==== 1st group of terms: Heaviside functions ===========
                 tmp_eq = smart_multiply(
                     self.sym("xdot") - self.sym("xdot_old"),
-                    self.eq("dtaudp")[ie],
+                    dtaudp_pre[ie],
                 )
                 if event.updates_state:
                     # ==== 2nd group of terms: Derivatives of Dirac deltas ===
                     # Part 2a: explicit time dependence of bolus function
                     tmp_eq -= smart_multiply(
-                        self.eq("ddeltaxdt")[ie], self.eq("dtaudp")[ie]
+                        self.eq("ddeltaxdt")[ie], dtaudp_pre[ie]
                     )
                     # Part 2b: implicit time dependence of bolus function
                     tmp_eq -= smart_multiply(
@@ -1903,7 +1922,7 @@ def _compute_equation(self, name: str) -> None:
                             + self.eq("ddeltaxdx_old")[ie],
                             self.sym("xdot_old"),
                         ),
-                        self.eq("dtaudp")[ie],
+                        dtaudp_pre[ie],
                     )
                     # ==== 3rd group of terms: Dirac deltas ==================
                     tmp_eq += self.eq("ddeltaxdp")[ie]
diff --git a/tests/sbml/testSBMLSuite.py b/tests/sbml/testSBMLSuite.py
index c3c15d88ba..e2bb4ebe7b 100755
--- a/tests/sbml/testSBMLSuite.py
+++ b/tests/sbml/testSBMLSuite.py
@@ -141,35 +141,6 @@ def test_sbml_testsuite_case(test_id, compiled_case, result_path):
     write_result_file(simulated, test_id, result_path)
 
 
-def _ast_has_piecewise(node: libsbml.ASTNode | None) -> bool:
-    """Recursively check whether a libsbml math AST contains a `piecewise`
-    function anywhere in its tree."""
-    if node is None:
-        return False
-    if node.getType() == libsbml.AST_FUNCTION_PIECEWISE:
-        return True
-    return any(
-        _ast_has_piecewise(node.getChild(i))
-        for i in range(node.getNumChildren())
-    )
-
-
-def _model_has_event_jump_risk(sbml_model: libsbml.Model) -> bool:
-    """Whether this model has an event, or a piecewise formula."""
-    if sbml_model.getNumEvents() > 0:
-        return True
-    for reaction in sbml_model.getListOfReactions():
-        kinetic_law = reaction.getKineticLaw()
-        if kinetic_law is not None and _ast_has_piecewise(
-            kinetic_law.getMath()
-        ):
-            return True
-    return any(
-        _ast_has_piecewise(rule.getMath())
-        for rule in sbml_model.getListOfRules()
-    )
-
-
 # FIXME: Skip list - to be investigated further
 #  test_id -> adjoint_only (whether forward is unaffected)
 _OTHER_KNOWN_SENSITIVITY_CHECK_ISSUES = {
@@ -182,6 +153,18 @@ def _model_has_event_jump_risk(sbml_model: libsbml.Model) -> bool:
     "01104": True,
     "01107": True,
     "01148": True,
+    # Adjoint sensitivities & events. To revisit later.
+    "00348": True,
+    "00350": True,
+    "00354": True,
+    "00368": True,
+    "00373": True,
+    "00376": True,
+    "00379": True,
+    "00380": True,
+    "00396": True,
+    "00753": True,
+    "01106": True,
 }
 
 
@@ -212,10 +195,6 @@ def _sensitivity_preflight_checks(
         pytest.skip(
             "Adjoint sensitivities for zero-state models are known to crash."
         )
-    if uses_adjoint and _model_has_event_jump_risk(sbml_model):
-        pytest.skip(
-            "Adjoint sensitivities for (some) events are known to be wrong (https://github.com/AMICI-dev/AMICI/pull/3258)."
-        )
     if test_id in _OTHER_KNOWN_SENSITIVITY_CHECK_ISSUES:
         adjoint_only = _OTHER_KNOWN_SENSITIVITY_CHECK_ISSUES[test_id]
         if uses_adjoint or not adjoint_only: