diff --git a/src/tsim/circuit.py b/src/tsim/circuit.py
index 3dd8c5d8..1381cbee 100644
--- a/src/tsim/circuit.py
+++ b/src/tsim/circuit.py
@@ -555,7 +555,11 @@ def strip(circuit: stim.Circuit) -> stim.Circuit:
             for instr in circuit:
                 if isinstance(instr, stim.CircuitRepeatBlock):
                     stripped = strip(instr.body_copy())
-                    result.append(stim.CircuitRepeatBlock(instr.repeat_count, stripped))
+                    result.append(
+                        stim.CircuitRepeatBlock(
+                            instr.repeat_count, stripped, tag=instr.tag
+                        )
+                    )
                     continue
                 if instr.name in ["OBSERVABLE_INCLUDE", "DETECTOR"]:
                     continue
@@ -881,7 +885,11 @@ def fix_tags(circuit: stim.Circuit) -> stim.Circuit:
             for instr in circuit:
                 if isinstance(instr, stim.CircuitRepeatBlock):
                     fixed = fix_tags(instr.body_copy())
-                    result.append(stim.CircuitRepeatBlock(instr.repeat_count, fixed))
+                    result.append(
+                        stim.CircuitRepeatBlock(
+                            instr.repeat_count, fixed, tag=instr.tag
+                        )
+                    )
                     continue
 
                 name = instr.name
diff --git a/src/tsim/utils/clifford.py b/src/tsim/utils/clifford.py
index 6d5fc02e..cb283754 100644
--- a/src/tsim/utils/clifford.py
+++ b/src/tsim/utils/clifford.py
@@ -157,7 +157,9 @@ def expand_clifford_rotations(source: stim.Circuit) -> stim.Circuit:
         if isinstance(instr, stim.CircuitRepeatBlock):
             out.append(
                 stim.CircuitRepeatBlock(
-                    instr.repeat_count, expand_clifford_rotations(instr.body_copy())
+                    instr.repeat_count,
+                    expand_clifford_rotations(instr.body_copy()),
+                    tag=instr.tag,
                 )
             )
             continue
diff --git a/src/tsim/utils/diagram.py b/src/tsim/utils/diagram.py
index 166c7bba..0e3240ba 100644
--- a/src/tsim/utils/diagram.py
+++ b/src/tsim/utils/diagram.py
@@ -383,7 +383,9 @@ def _replace_tagged_gates(
         if isinstance(instr, stim.CircuitRepeatBlock):
             modified_body = _replace_tagged_gates(instr.body_copy(), replace_dict)
             modified_circ.append(
-                stim.CircuitRepeatBlock(instr.repeat_count, modified_body)
+                stim.CircuitRepeatBlock(
+                    instr.repeat_count, modified_body, tag=instr.tag
+                )
             )
             continue
 
diff --git a/test/unit/test_circuit.py b/test/unit/test_circuit.py
index 46644c7d..43dacf3b 100644
--- a/test/unit/test_circuit.py
+++ b/test/unit/test_circuit.py
@@ -754,6 +754,20 @@ def test_stim_circuit_repeat_block_preserves_non_clifford():
     assert block.repeat_count == 2
 
 
+def test_stim_circuit_preserves_repeat_block_tags():
+    """Tags on REPEAT blocks survive the round-trip through stim_circuit."""
+    c = Circuit(
+        "REPEAT[outer] 3 {\n    H 0\n    REPEAT[inner] 2 {\n        CX 0 1\n    }\n}"
+    )
+    stim_c = c.stim_circuit
+    outer = stim_c[0]
+    assert isinstance(outer, stim.CircuitRepeatBlock)
+    assert outer.tag == "outer"
+    inner = outer.body_copy()[-1]
+    assert isinstance(inner, stim.CircuitRepeatBlock)
+    assert inner.tag == "inner"
+
+
 def test_get_graph():
     """Test get_graph returns a ZX graph."""
     c = Circuit("H 0\nCNOT 0 1")