diff --git a/src/mir/method/MethodWeighted.cc b/src/mir/method/MethodWeighted.cc
index 51be149a9..7e1574e16 100644
--- a/src/mir/method/MethodWeighted.cc
+++ b/src/mir/method/MethodWeighted.cc
@@ -174,6 +174,18 @@ void MethodWeighted::createMatrix(context::Context& ctx, const repres::Represent
         applyMasks(W, masks);
         W.validate("applyMasks", checks);
     }
+
+    bool bitmask;
+    parametrisation_.get("imm", bitmask);
+    if (bitmask){
+        std::vector<bool> vec_bitmask;
+        parametrisation_.get("imm-mask", vec_bitmask);
+        applyIMM(W,vec_bitmask);
+        if (matrixValidate_) {
+            W.validate("applyMasks");
+        }
+    }
+
 }
 
 
@@ -208,6 +220,14 @@ MethodWeighted::CacheKeys MethodWeighted::getDiskAndMemoryCacheKeys(const repres
         }
     }
 
+    bool bitmask;
+    parametrisation_.get("imm", bitmask);
+    if (bitmask){
+        std::string missing_mask_key;
+        parametrisation_.get("imm-name", missing_mask_key);
+        memory_key += "_" + missing_mask_key;
+        disk_key += "_" + missing_mask_key;
+     }
     return {disk_key, memory_key};
 }
 
@@ -450,12 +470,16 @@ void MethodWeighted::execute(context::Context& ctx, const repres::Representation
     const double missingValue = field.missingValue();
 
     // matrix copy: run-time modifiable matrix is not cacheable
-    const bool matrixCopy = std::any_of(nonLinear_.begin(), nonLinear_.end(),
+    bool imm_active;
+    parametrisation_.get("imm", imm_active);
+    bool matrixCopy = false;
+    if (!imm_active) {
+    matrixCopy = std::any_of(nonLinear_.begin(), nonLinear_.end(),
                                         [&field](const std::unique_ptr<const nonlinear::NonLinear>& n) {
                                             return n->modifiesMatrix(field.hasMissing());
                                         });
-
-
+    }
+    
     for (size_t i = 0; i < field.dimensions(); i++) {
 
         std::ostringstream os;
@@ -621,6 +645,73 @@ void MethodWeighted::applyMasks(WeightMatrix& W, const lsm::LandSeaMasks& masks)
         << Log::Pretty(W.rows(), {"output point"}) << std::endl;
 }
 
+void MethodWeighted::applyIMM(WeightMatrix& W, const std::vector<bool>& imask) const {
+   trace::Timer timer("MethodWeighted::applyIMM");
+auto& log = Log::debug();
+
+log << "MethodWeighted::applyIMM" << std::endl;
+log << "mask size=" << imask.size() << " == #cols=" << W.cols() << std::endl;
+
+// Ensure that the mask size matches the number of columns in W
+ASSERT(imask.size() == W.cols());
+
+auto* data = const_cast<WeightMatrix::Scalar*>(W.data());
+auto* outer = W.outer();
+auto* inner = W.inner();
+size_t fix = 0;
+
+// Iterate over each row
+for (WeightMatrix::Size r = 0; r < W.rows(); ++r) {
+    WeightMatrix::Size row_start = outer[r];
+    WeightMatrix::Size row_end = outer[r + 1];
+
+    size_t i_missing = row_start;
+    size_t N_missing = 0;
+    size_t N_entries = row_end - row_start;
+    double sum = 0.0;
+    double heaviest = -1.0;
+    bool heaviest_is_missing = false;
+
+    // Iterate over the entries in the current row
+    for (WeightMatrix::Size i = row_start; i < row_end; ++i) {
+        const bool miss = !imask[inner[i]];
+
+        if (miss) {
+            ++N_missing;
+            i_missing = i;
+        } else {
+            sum += data[i];
+        }
+
+        if (heaviest < data[i]) {
+            heaviest = data[i];
+            heaviest_is_missing = miss;
+        }
+    }
+
+    // Weights redistribution: zero-weight all missing values, linear re-weighting for the others
+    if (N_missing > 0) {
+        ++fix;
+        if (N_missing == N_entries || heaviest_is_missing || eckit::types::is_approximately_equal(sum, 0.0)) {
+            // All values are missing or the heaviest is missing; set only i_missing to 1
+            for (WeightMatrix::Size i = row_start; i < row_end; ++i) {
+                data[i] = (i == i_missing) ? 1.0 : 0.0;
+            }
+        } else {
+            // Scale non-missing entries so they sum to 1
+            const double factor = 1.0 / sum;
+            for (WeightMatrix::Size i = row_start; i < row_end; ++i) {
+                const bool miss = !imask[inner[i]];
+                data[i] = miss ? 0.0 : (factor * data[i]);
+            }
+        }
+    }
+}
+
+// Log the number of corrections made
+log << "MethodWeighted: applyIMM corrected " << Log::Pretty(fix) << " out of "
+    << Log::Pretty(W.rows(), {"Weight matrix rows"}) << std::endl;
+}     
 
 void MethodWeighted::hash(eckit::MD5& md5) const {
     md5.add(name());
diff --git a/src/mir/method/MethodWeighted.h b/src/mir/method/MethodWeighted.h
index 0c81775fe..1a6f4238a 100644
--- a/src/mir/method/MethodWeighted.h
+++ b/src/mir/method/MethodWeighted.h
@@ -125,6 +125,7 @@ class MethodWeighted : public Method {
                                                 const lsm::LandSeaMasks&) const;
 
     virtual void applyMasks(WeightMatrix&, const lsm::LandSeaMasks&) const;
+    virtual void applyIMM(WeightMatrix&, const std::vector<bool>&) const;
     virtual lsm::LandSeaMasks getMasks(const repres::Representation& in, const repres::Representation& out) const;
     virtual WeightMatrix::Check validateMatrixWeights() const;
 
diff --git a/src/mir/param/CombinedParametrisation.cc b/src/mir/param/CombinedParametrisation.cc
index 4635e5a9f..653e27681 100644
--- a/src/mir/param/CombinedParametrisation.cc
+++ b/src/mir/param/CombinedParametrisation.cc
@@ -108,6 +108,10 @@ bool CombinedParametrisation::get(const std::string& name, std::vector<double>&
     return _get(name, value);
 }
 
+bool CombinedParametrisation::get(const std::string& name, std::vector<bool>& value) const {
+    return _get(name, value);
+}
+
 bool CombinedParametrisation::get(const std::string& name, std::vector<std::string>& value) const {
     return _get(name, value);
 }
diff --git a/src/mir/param/CombinedParametrisation.h b/src/mir/param/CombinedParametrisation.h
index 884ec8fc6..13960181e 100644
--- a/src/mir/param/CombinedParametrisation.h
+++ b/src/mir/param/CombinedParametrisation.h
@@ -100,6 +100,7 @@ class CombinedParametrisation : public MIRParametrisation {
     bool get(const std::string& name, std::vector<long>& value) const override;
     bool get(const std::string& name, std::vector<float>& value) const override;
     bool get(const std::string& name, std::vector<double>& value) const override;
+    bool get(const std::string& name, std::vector<bool>& value) const override;
     bool get(const std::string& name, std::vector<std::string>& value) const override;
 
     // -- Class members
diff --git a/src/mir/param/DefaultParametrisation.cc b/src/mir/param/DefaultParametrisation.cc
index 8d76e4693..bc0d414eb 100644
--- a/src/mir/param/DefaultParametrisation.cc
+++ b/src/mir/param/DefaultParametrisation.cc
@@ -37,6 +37,10 @@ DefaultParametrisation::DefaultParametrisation() {
     set("lsm-weight-adjustment", 0.2);
     set("lsm-value-threshold", 0.5);
 
+    set("imm", false);
+    set("imm-name", "bitmasked");
+    set("imm-mask", std::vector<bool>{});
+
     set("spectral-order", "linear");
 
     set("compare", "scalar");
diff --git a/src/mir/param/MIRParametrisation.cc b/src/mir/param/MIRParametrisation.cc
index 882088a72..566ec8efc 100644
--- a/src/mir/param/MIRParametrisation.cc
+++ b/src/mir/param/MIRParametrisation.cc
@@ -89,4 +89,9 @@ bool MIRParametrisation::get(const std::string& name, std::vector<long long>& va
     return false;
 }
 
+bool MIRParametrisation::get(const std::string& name, std::vector<bool>& value) const {
+	 std::ostringstream os;
+	 os << "MIRParametrisation::get(const std::string& name, std::vector<bool>& value) not implemented for " << *this;
+	 throw exception::SeriousBug(os.str());
+ }
 }  // namespace mir::param
diff --git a/src/mir/param/MIRParametrisation.h b/src/mir/param/MIRParametrisation.h
index ad8efc61d..b2d52efea 100644
--- a/src/mir/param/MIRParametrisation.h
+++ b/src/mir/param/MIRParametrisation.h
@@ -63,6 +63,7 @@ class MIRParametrisation : public eckit::Parametrisation {
     bool get(const std::string& name, std::vector<float>& value) const override       = 0;
     bool get(const std::string& name, std::vector<double>& value) const override      = 0;
     bool get(const std::string& name, std::vector<std::string>& value) const override = 0;
+    virtual bool get(const std::string& name, std::vector<bool>& value) const ;
 
     bool get(const std::string& name, size_t& value) const override;
     bool get(const std::string& name, std::vector<size_t>& value) const override;
diff --git a/src/mir/param/SimpleParametrisation.cc b/src/mir/param/SimpleParametrisation.cc
index 57177b3da..839f03171 100644
--- a/src/mir/param/SimpleParametrisation.cc
+++ b/src/mir/param/SimpleParametrisation.cc
@@ -54,6 +54,7 @@ class Setting {
     virtual void get(const std::string& name, std::vector<float>& value) const       = 0;
     virtual void get(const std::string& name, std::vector<double>& value) const      = 0;
     virtual void get(const std::string& name, std::vector<std::string>& value) const = 0;
+    virtual void get(const std::string& name, std::vector<bool>& value) const = 0;
 
     virtual bool matchAll(const std::string& name, const MIRParametrisation&) const = 0;
     virtual bool matchAny(const std::string& name, const MIRParametrisation&) const = 0;
@@ -158,6 +159,12 @@ const char* TNamed<std::vector<std::string>>() {
     return "vector<string>";
 }
 
+template <>
+const char* TNamed<std::vector<bool>>() {
+    return "vector<bool>";
+}
+
+
 
 template <class T>
 static void conversion_warning(const char* /*from*/, const char* /*to*/, const std::string& /*name*/,
@@ -226,6 +233,10 @@ class TSettings : public Setting {
         throw exception::CannotConvert(TNamed<T>(), "vector<string>", name, value_);
     }
 
+    void get(const std::string& name, std::vector<bool>& /*value*/) const  {
+        throw exception::CannotConvert(TNamed<T>(), "vector<bool>", name, value_);
+    }
+
     bool matchAll(const std::string& name, const MIRParametrisation& other) const override {
         T value;
         return other.get(name, value) && value_ == value;
@@ -269,6 +280,11 @@ void TSettings<std::vector<double>>::print(std::ostream& out) const {
     _put(out, value_);
 }
 
+template <>
+void TSettings<std::vector<bool>>::print(std::ostream& out) const {
+    _put(out, value_);  // Uses the `_put` helper function for formatting
+}
+
 
 template <>
 bool TSettings<std::vector<long>>::matchAll(const std::string& name, const MIRParametrisation& other) const {
@@ -443,6 +459,10 @@ void TSettings<std::vector<double>>::get(const std::string& /*name*/, std::vecto
     value = value_;
 }
 
+template <>
+void TSettings<std::vector<bool>>::get(const std::string& /*name*/, std::vector<bool>& value) const {
+    value = value_;
+}
 
 template <>
 void TSettings<int>::get(const std::string& name, std::string& value) const {
@@ -555,6 +575,18 @@ void TSettings<std::vector<std::string>>::get(const std::string& name, std::stri
     }
 }
 
+template <>
+void TSettings<std::vector<bool>>::get(const std::string& name, std::string& value) const {
+    conversion_warning("vector<bool>", "string", name, value_);
+    value.clear();
+
+    const char* sep = "";
+    for (const auto& entry : value_) {
+        value += sep + std::to_string(entry);
+        sep = "/";
+    }
+}
+
 
 SimpleParametrisation::SimpleParametrisation() = default;
 
@@ -642,6 +674,9 @@ bool SimpleParametrisation::get(const std::string& name, std::vector<double>& va
     return _get(name, value);
 }
 
+bool SimpleParametrisation::get(const std::string& name, std::vector<bool>& value) const {
+    return _get(name, value);
+}
 
 bool SimpleParametrisation::get(const std::string& /*name*/, std::vector<std::string>& /*value*/) const {
     NOTIMP;
@@ -779,6 +814,10 @@ SimpleParametrisation& SimpleParametrisation::set(const std::string& name, const
     _set(name, value);
     return *this;
 }
+SimpleParametrisation& SimpleParametrisation::set(const std::string& name, const std::vector<bool>& value) {
+    _set(name, value);
+    return *this;
+}
 
 
 void SimpleParametrisation::print(std::ostream& out) const {
diff --git a/src/mir/param/SimpleParametrisation.h b/src/mir/param/SimpleParametrisation.h
index a4548a6a7..98d509a0b 100644
--- a/src/mir/param/SimpleParametrisation.h
+++ b/src/mir/param/SimpleParametrisation.h
@@ -66,6 +66,7 @@ class SimpleParametrisation : public MIRParametrisation {
     SimpleParametrisation& set(const std::string& name, const std::vector<int>& value);
     SimpleParametrisation& set(const std::string& name, const std::vector<long>& value);
     SimpleParametrisation& set(const std::string& name, const std::vector<long long>& value);
+    SimpleParametrisation& set(const std::string& name, const std::vector<bool>& value);
     SimpleParametrisation& set(const std::string& name, const std::vector<size_t>& value);
     SimpleParametrisation& set(const std::string& name, const std::vector<float>& value);
     SimpleParametrisation& set(const std::string& name, const std::vector<double>& value);
@@ -95,6 +96,7 @@ class SimpleParametrisation : public MIRParametrisation {
 
     bool get(const std::string& name, std::vector<int>& value) const override;
     bool get(const std::string& name, std::vector<long>& value) const override;
+    bool get(const std::string& name, std::vector<bool>& value) const override;
     bool get(const std::string& name, std::vector<float>& value) const override;
     bool get(const std::string& name, std::vector<double>& value) const override;
     bool get(const std::string& name, std::vector<std::string>& value) const override;