diff --git a/cpp/ql/lib/change-notes/2026-09-14-bdlcc-models.md b/cpp/ql/lib/change-notes/2026-09-14-bdlcc-models.md
new file mode 100644
index 000000000000..2994cfd242e0
--- /dev/null
+++ b/cpp/ql/lib/change-notes/2026-09-14-bdlcc-models.md
@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Added data-flow models for single-element operations on BDE `bdlcc::Deque` and `bdlcc::BoundedQueue`.
diff --git a/cpp/ql/lib/ext/bdlcc.model.yml b/cpp/ql/lib/ext/bdlcc.model.yml
new file mode 100644
index 000000000000..f081c1276876
--- /dev/null
+++ b/cpp/ql/lib/ext/bdlcc.model.yml
@@ -0,0 +1,31 @@
+# BDE single-element concurrent queue operations (C++11 reference overloads).
+# https://github.com/bloomberg/bde/tree/ec310b87e008199ecbdbc00a0b0264a53d806a0a/groups/bdl/bdlcc
+extensions:
+  - addsTo:
+      pack: codeql/cpp-all
+      extensible: summaryModel
+    data:
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "pushBack", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "pushBack", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "pushFront", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "pushFront", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "forcePushBack", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "forcePushBack", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "forcePushFront", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "forcePushFront", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "tryPushBack", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "tryPushBack", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "popBack", "(T *)", "", "Argument[-1].Element[@]", "Argument[*@0]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "popFront", "(T *)", "", "Argument[-1].Element[@]", "Argument[*@0]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "tryPopBack", "(T *)", "", "Argument[-1].Element[@]", "Argument[*@0]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque<T>", False, "tryPopFront", "(T *)", "", "Argument[-1].Element[@]", "Argument[*@0]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "BoundedQueue<T>", False, "pushBack", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "BoundedQueue<T>", False, "pushBack", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "BoundedQueue<T>", False, "tryPushBack", "(const T &)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "BoundedQueue<T>", False, "tryPushBack", "(T &&)", "", "Argument[*@0]", "Argument[-1].Element[@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "BoundedQueue<T>", False, "popFront", "(T *)", "", "Argument[-1].Element[@]", "Argument[*@0]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "BoundedQueue<T>", False, "tryPopFront", "(T *)", "", "Argument[-1].Element[@]", "Argument[*@0]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque", False, "popBack", "", "", "Argument[-1].Element[]", "ReturnValue", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque", False, "popFront", "", "", "Argument[-1].Element[]", "ReturnValue", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque", False, "popBack", "", "", "Argument[-1].Element[*@]", "ReturnValue[*@]", "value", "manual"]
+      - ["BloombergLP::bdlcc", "Deque", False, "popFront", "", "", "Argument[-1].Element[*@]", "ReturnValue[*@]", "value", "manual"]
diff --git a/cpp/ql/test/library-tests/dataflow/bdlcc/flow.expected b/cpp/ql/test/library-tests/dataflow/bdlcc/flow.expected
new file mode 100644
index 000000000000..8b137891791f
--- /dev/null
+++ b/cpp/ql/test/library-tests/dataflow/bdlcc/flow.expected
@@ -0,0 +1 @@
+
diff --git a/cpp/ql/test/library-tests/dataflow/bdlcc/flow.ql b/cpp/ql/test/library-tests/dataflow/bdlcc/flow.ql
new file mode 100644
index 000000000000..6bdf085e721b
--- /dev/null
+++ b/cpp/ql/test/library-tests/dataflow/bdlcc/flow.ql
@@ -0,0 +1,19 @@
+import cpp
+import utils.test.dataflow.FlowTestCommon
+import semmle.code.cpp.ir.dataflow.TaintTracking
+
+module Config implements DataFlow::ConfigSig {
+  predicate isSource(DataFlow::Node node) {
+    node.asExpr().(FunctionCall).getTarget().hasName("source")
+  }
+
+  predicate isSink(DataFlow::Node node) {
+    exists(FunctionCall call |
+      call.getTarget().hasName("sink") and node.asExpr() = call.getArgument(0)
+    )
+  }
+}
+
+module Flow = TaintTracking::Global<Config>;
+
+import MakeTest<IRFlowTest<Flow>>
diff --git a/cpp/ql/test/library-tests/dataflow/bdlcc/queues.h b/cpp/ql/test/library-tests/dataflow/bdlcc/queues.h
new file mode 100644
index 000000000000..ccf22fe89b1b
--- /dev/null
+++ b/cpp/ql/test/library-tests/dataflow/bdlcc/queues.h
@@ -0,0 +1,34 @@
+// Public single-element overloads from bloomberg/bde groups/bdl/bdlcc.
+namespace BloombergLP { namespace bslma { class Allocator; } namespace bdlcc {
+template<class TYPE> class Deque {
+public:
+  void pushBack(const TYPE& value);
+  void pushBack(TYPE&& value);
+  void pushFront(const TYPE& value);
+  void pushFront(TYPE&& value);
+  void forcePushBack(const TYPE& value);
+  void forcePushBack(TYPE&& value);
+  void forcePushFront(const TYPE& value);
+  void forcePushFront(TYPE&& value);
+  int tryPushBack(const TYPE& value);
+  int tryPushBack(TYPE&& value);
+  void popBack(TYPE *value);
+  void popFront(TYPE *value);
+  int tryPopBack(TYPE *value);
+  int tryPopFront(TYPE *value);
+  TYPE popBack();
+  TYPE popFront();
+  template<class ITER> void forcePushBack(ITER begin, ITER end);
+  void tryPopFront(unsigned long count);
+};
+template<class TYPE> class BoundedQueue {
+public:
+  BoundedQueue(unsigned long capacity, bslma::Allocator *allocator = 0);
+  int pushBack(const TYPE& value);
+  int pushBack(TYPE&& value);
+  int tryPushBack(const TYPE& value);
+  int tryPushBack(TYPE&& value);
+  int popFront(TYPE *value);
+  int tryPopFront(TYPE *value);
+};
+} }
diff --git a/cpp/ql/test/library-tests/dataflow/bdlcc/ranges.cpp b/cpp/ql/test/library-tests/dataflow/bdlcc/ranges.cpp
new file mode 100644
index 000000000000..f5b2cd1f2642
--- /dev/null
+++ b/cpp/ql/test/library-tests/dataflow/bdlcc/ranges.cpp
@@ -0,0 +1,24 @@
+#include "queues.h"
+int source();
+void sink(int);
+
+struct InputIterator {
+  int value;
+  const int &operator*() const { return value; }
+};
+
+// Reduced range overload body. The single-element models must not replace it.
+namespace BloombergLP { namespace bdlcc {
+template<class TYPE>
+template<class ITER>
+void Deque<TYPE>::forcePushBack(ITER begin, ITER end) {
+  pushBack(*begin);
+}
+} }
+
+void rangeOverloadKeepsItsBody() {
+  BloombergLP::bdlcc::Deque<int> q;
+  InputIterator begin = {source()}, end = {0};
+  q.forcePushBack(begin, end);
+  sink(q.popFront()); // $ ir
+}
diff --git a/cpp/ql/test/library-tests/dataflow/bdlcc/test.cpp b/cpp/ql/test/library-tests/dataflow/bdlcc/test.cpp
new file mode 100644
index 000000000000..52c75e502627
--- /dev/null
+++ b/cpp/ql/test/library-tests/dataflow/bdlcc/test.cpp
@@ -0,0 +1,107 @@
+#include "queues.h"
+int source();
+void sink(int);
+using namespace BloombergLP::bdlcc;
+
+void DequepushBack() {
+  Deque<int> q;
+  int input = source(), output = 0;
+  q.pushBack(input);
+  q.popBack(&output);
+  sink(output); // $ ir
+}
+void DequepushFront() {
+  Deque<int> q;
+  int input = source(), output = 0;
+  q.pushFront(input);
+  q.popFront(&output);
+  sink(output); // $ ir
+}
+void DequeforcePushBack() {
+  Deque<int> q;
+  int input = source(), output = 0;
+  q.forcePushBack(input);
+  q.tryPopBack(&output);
+  sink(output); // $ ir
+}
+void DequeforcePushFront() {
+  Deque<int> q;
+  int input = source(), output = 0;
+  q.forcePushFront(input);
+  q.tryPopFront(&output);
+  sink(output); // $ ir
+}
+void DequetryPushBack() {
+  Deque<int> q;
+  int input = source(), output = 0;
+  q.tryPushBack(input);
+  q.popBack(&output);
+  sink(output); // $ ir
+}
+void BoundedQueuepushBack() {
+  BoundedQueue<int> q(8);
+  int input = source(), output = 0;
+  q.pushBack(input);
+  q.popFront(&output);
+  sink(output); // $ ir
+}
+void BoundedQueuetryPushBack() {
+  BoundedQueue<int> q(8);
+  int input = source(), output = 0;
+  q.tryPushBack(input);
+  q.tryPopFront(&output);
+  sink(output); // $ ir
+}
+
+void returnAndMove() {
+  Deque<int> q;
+  int input = source();
+  q.pushBack(static_cast<int&&>(input));
+  int output = 0;
+  q.popBack(&output);
+  sink(output); // $ ir
+  sink(q.popFront()); // $ ir
+  sink(q.popBack()); // $ ir
+}
+void returnAfterCopy() {
+  Deque<int> q;
+  int input = source();
+  q.pushBack(input);
+  sink(q.popFront()); // $ ir
+}
+void pointerPayload() {
+  int input = source();
+  int *p = &input, *output = 0;
+  BoundedQueue<int*> q(8);
+  q.pushBack(p);
+  q.popFront(&output);
+  sink(*output); // $ ir
+}
+void pointerReturn() {
+  int input = source();
+  int *p = &input;
+  Deque<int*> q;
+  q.pushBack(p);
+  sink(*q.popFront()); // $ ir
+}
+struct Payload { int value; };
+void objectPayload() {
+  Payload input = {source()}, output = {0};
+  Deque<Payload> q;
+  q.pushFront(input);
+  q.popBack(&output);
+  sink(output.value); // $ ir
+}
+void statusesAreNotPayload() {
+  BoundedQueue<int> q(8);
+  int input = source(), output = 0;
+  sink(q.tryPushBack(input));
+  sink(q.tryPopFront(&output));
+  sink(output); // $ ir
+}
+void failureCanPreserveOutput() {
+  Deque<int> q;
+  int output = source();
+  if (q.tryPopFront(&output) != 0)
+    sink(output); // $ ir
+}
diff --git a/cpp/ql/test/library-tests/dataflow/external-models/validatemodels.expected b/cpp/ql/test/library-tests/dataflow/external-models/validatemodels.expected
index d5b0b0cc0213..4ac97908c7ad 100644
--- a/cpp/ql/test/library-tests/dataflow/external-models/validatemodels.expected
+++ b/cpp/ql/test/library-tests/dataflow/external-models/validatemodels.expected
@@ -2437,6 +2437,7 @@
 | Dubious signature "(Strent *)" in summary model. |
 | Dubious signature "(Strtab *,const char *,size_t)" in summary model. |
 | Dubious signature "(Strtab *,size_t *)" in summary model. |
+| Dubious signature "(T &&)" in summary model. |
 | Dubious signature "(T *)" in summary model. |
 | Dubious signature "(T **)" in summary model. |
 | Dubious signature "(TLS_FEATURE *)" in summary model. |
@@ -3691,6 +3692,7 @@
 | Dubious signature "(const SSL_SESSION *,unsigned int *)" in summary model. |
 | Dubious signature "(const SXNET *,unsigned char **)" in summary model. |
 | Dubious signature "(const SXNETID *,unsigned char **)" in summary model. |
+| Dubious signature "(const T &)" in summary model. |
 | Dubious signature "(const T &,BOOL)" in summary model. |
 | Dubious signature "(const TS_ACCURACY *)" in summary model. |
 | Dubious signature "(const TS_ACCURACY *,unsigned char **)" in summary model. |