diff --git a/headroom/cache/prefix_tracker.py b/headroom/cache/prefix_tracker.py
index d7e62f436..d54950191 100644
--- a/headroom/cache/prefix_tracker.py
+++ b/headroom/cache/prefix_tracker.py
@@ -379,16 +379,29 @@ def normalize_message_cache_control(
     ``messages`` and are left untouched (they still count toward the 4 limit, so
     holding messages to one breakpoint leaves room for them).
 
+    Headroom owns WHERE the breakpoint goes; the client still owns WHAT it says:
+    the re-placed marker reuses the newest client marker verbatim, so an explicit
+    ``ttl`` (e.g. ``"1h"``) survives consolidation instead of silently
+    downgrading to the 5-minute default (#2375).
+
     Only block-style (list) content can carry cache_control; string content is
     left as-is. Returns the input unchanged when there is nothing to normalize.
     """
     changed = False
     out: list[dict[str, Any]] = []
     last_block_idx = -1
+    last_marker: dict[str, Any] | None = None
     for i, msg in enumerate(messages):
         content = msg.get("content") if isinstance(msg, dict) else None
         if isinstance(content, list):
-            had = any(isinstance(b, dict) and "cache_control" in b for b in content)
+            had = False
+            for b in content:
+                if isinstance(b, dict) and "cache_control" in b:
+                    had = True
+                    # The newest marker in message order is the client's current
+                    # intent (older ones are replay leftovers) — keep it.
+                    if isinstance(b["cache_control"], dict):
+                        last_marker = b["cache_control"]
             stripped = [
                 {k: v for k, v in b.items() if k != "cache_control"} if isinstance(b, dict) else b
                 for b in content
@@ -403,7 +416,8 @@ def normalize_message_cache_control(
     if last_block_idx >= 0:
         msg = out[last_block_idx]
         content = list(msg["content"])
-        content[-1] = {**content[-1], "cache_control": {"type": "ephemeral"}}
+        marker = dict(last_marker) if last_marker else {"type": "ephemeral"}
+        content[-1] = {**content[-1], "cache_control": marker}
         out[last_block_idx] = {**msg, "content": content}
         changed = True
     return out if changed else messages
diff --git a/tests/test_cache_control_move_bust.py b/tests/test_cache_control_move_bust.py
index 087cd38eb..0b74ff92d 100644
--- a/tests/test_cache_control_move_bust.py
+++ b/tests/test_cache_control_move_bust.py
@@ -188,3 +188,39 @@ def test_normalize_is_noop_when_no_block_markers():
     # places exactly one breakpoint (so the prefix gets cached), content stable
     assert _markers(out) == 1
     assert _strip_cache_control(out) == _strip_cache_control(plain)
+
+
+# ── fix-3 (#2375): consolidation must not silently drop the client's ttl ─────
+
+
+def B_ttl(role, text, ttl):
+    """Block-style message whose marker carries an explicit ttl (1h caching)."""
+    blk = {"type": "text", "text": text, "cache_control": {"type": "ephemeral", "ttl": ttl}}
+    return {"role": role, "content": [blk]}
+
+
+def test_normalize_preserves_ttl_of_newest_marker():
+    """A 1h-ttl client must not be silently downgraded to the 5m default."""
+    msgs = [B("user", "a", cc=True), B_ttl("user", "b", "1h")]
+    out = normalize_message_cache_control(msgs)
+    assert _markers(out) == 1
+    assert out[-1]["content"][-1]["cache_control"] == {"type": "ephemeral", "ttl": "1h"}
+
+
+def test_normalize_newest_marker_wins_over_stale_ttl():
+    # Older replayed markers still carry 1h, but the client's NEWEST marker has
+    # no ttl — the client switched back to the default; don't resurrect 1h.
+    msgs = [B_ttl("user", "a", "1h"), B_ttl("assistant", "b", "1h"), B("user", "c", cc=True)]
+    out = normalize_message_cache_control(msgs)
+    assert _markers(out) == 1
+    assert out[-1]["content"][-1]["cache_control"] == {"type": "ephemeral"}
+
+
+def test_normalize_ttl_survives_many_turns():
+    """The #2375 scenario: ttl held for one turn, gone on every later turn."""
+    conv = []
+    for t in range(1, 8):
+        conv = conv + [B_ttl("user", f"turn-{t}", "1h")]  # client always asks 1h
+        conv = normalize_message_cache_control(conv)
+        assert _markers(conv) == 1
+        assert conv[-1]["content"][-1]["cache_control"] == {"type": "ephemeral", "ttl": "1h"}