diff --git a/opm/simulators/flow/rescoup/ReservoirCouplingMaster.cpp b/opm/simulators/flow/rescoup/ReservoirCouplingMaster.cpp
index 0809302ff3..3bfc4d448b 100644
--- a/opm/simulators/flow/rescoup/ReservoirCouplingMaster.cpp
+++ b/opm/simulators/flow/rescoup/ReservoirCouplingMaster.cpp
@@ -31,6 +31,8 @@
 #include <opm/input/eclipse/Schedule/ResCoup/Slaves.hpp>
 #include <opm/common/ErrorMacros.hpp>
 
+#include <opm/models/utils/parametersystem.hpp>
+#include <opm/simulators/timestepping/EclTimeSteppingParams.hpp>
 #include <opm/simulators/utils/ParallelCommunication.hpp>
 
 #include <opm/input/eclipse/Schedule/Schedule.hpp>
@@ -57,9 +59,18 @@ ReservoirCouplingMaster(
     schedule_{schedule},
     argc_{argc},
     argv_{argv},
-    logger_{comm}
+    logger_{comm},
+    sync_at_report_steps_{Parameters::Get<Parameters::RescoupSyncAtReportSteps>()}
 {
     this->activation_date_ = this->getMasterActivationDate_();
+    if (this->comm_.rank() == 0) {
+        OpmLog::info(fmt::format(
+            "Reservoir coupling: master synchronizes with slaves at {}.",
+            this->sync_at_report_steps_
+                ? "report-step boundaries (RSYNC) (--rescoup-sync-at-report-steps=true)"
+                : "every master time step (TSYNC) (--rescoup-sync-at-report-steps=false)"
+        ));
+    }
 }
 
 // ------------------
diff --git a/opm/simulators/flow/rescoup/ReservoirCouplingMaster.hpp b/opm/simulators/flow/rescoup/ReservoirCouplingMaster.hpp
index f3448ba4dc..23ff46a765 100644
--- a/opm/simulators/flow/rescoup/ReservoirCouplingMaster.hpp
+++ b/opm/simulators/flow/rescoup/ReservoirCouplingMaster.hpp
@@ -164,6 +164,11 @@ public:
     void setSlaveNextReportTimeOffset(int index, double offset);
     void setSlaveStartDate(int index, std::time_t date) { this->slave_start_dates_[index] = date; }
     bool slaveIsActivated(int index) const { return this->slave_activation_status_[index] != 0; }
+    /// @brief Whether the master syncs with slaves at slave report-step boundaries
+    ///        (true) or at every master actual time step (false, default CLI flag value).
+    /// @details Set from the --rescoup-sync-at-report-steps CLI flag in the
+    ///          constructor.  See `Parameters::RescoupSyncAtReportSteps`.
+    bool syncAtReportSteps() const { return this->sync_at_report_steps_; }
     void updateMasterGroupNameOrderMap(
         const std::string& slave_name, const std::map<std::string, std::size_t>& master_group_map);
 
@@ -232,6 +237,10 @@ private:
     std::unique_ptr<ReservoirCouplingMasterReportStep<Scalar>> report_step_data_{nullptr};
     // Handles time stepping for the master and slaves
     std::unique_ptr<ReservoirCouplingTimeStepper<Scalar>> time_stepper_{nullptr};
+    // CLI flag --rescoup-sync-at-report-steps.  When true, the master syncs with
+    // its slaves at report-step boundaries (RSYNC).  When false
+    // (default), it syncs at every master time step (TSYNC).
+    bool sync_at_report_steps_{false};
 };
 
 } // namespace Opm
diff --git a/opm/simulators/timestepping/EclTimeSteppingParams.cpp b/opm/simulators/timestepping/EclTimeSteppingParams.cpp
index 7a1e3c8dbe..349c247213 100644
--- a/opm/simulators/timestepping/EclTimeSteppingParams.cpp
+++ b/opm/simulators/timestepping/EclTimeSteppingParams.cpp
@@ -34,6 +34,11 @@ void registerEclTimeSteppingParameters()
 {
     Parameters::Register<Parameters::EnableTuning>
         ("Honor some aspects of the TUNING keyword.");
+    Parameters::Register<Parameters::RescoupSyncAtReportSteps>
+        ("Developer flag for reservoir coupling.  If true, the master "
+         "synchronizes with its slaves at slave report-step boundaries. "
+         "If false (default), the master synchronizes at every master actual time step. "
+         "Has no effect in non-rescoup runs.");
     Parameters::Register<Parameters::SolverGrowthFactor<Scalar>>
         ("The factor time steps are elongated after a successful substep");
     Parameters::Register<Parameters::SolverMaxGrowth<Scalar>>
diff --git a/opm/simulators/timestepping/EclTimeSteppingParams.hpp b/opm/simulators/timestepping/EclTimeSteppingParams.hpp
index 12ee327c30..dc663e7c19 100644
--- a/opm/simulators/timestepping/EclTimeSteppingParams.hpp
+++ b/opm/simulators/timestepping/EclTimeSteppingParams.hpp
@@ -26,6 +26,9 @@
 namespace Opm::Parameters {
 
 struct EnableTuning { static constexpr bool value = false; };
+
+struct RescoupSyncAtReportSteps { static constexpr bool value = false; };
+
 template<class Scalar>
 struct SolverGrowthFactor { static constexpr Scalar value = 2.0; };