diff --git a/litellm/proxy/spend_tracking/baseline_accounting.py b/litellm/proxy/spend_tracking/baseline_accounting.py
index 17ed248459a..e99473c8b61 100644
--- a/litellm/proxy/spend_tracking/baseline_accounting.py
+++ b/litellm/proxy/spend_tracking/baseline_accounting.py
@@ -384,7 +384,14 @@ def advance_baseline_history(
     )
     legacy_lifetime: Final = (
         MAX_ESTIMATED_CACHE_TTL
-        if history.version == 1 and (history.uncertain_before > 0 or any(entry.uncertain for entry in history.entries))
+        if history.version == 1
+        and (
+            history.uncertain_before > (history.first_at or 0)
+            or history.uncertain_before > 0
+            and not history.entries
+            or history.blocked_until > 0
+            or any(entry.uncertain for entry in history.entries)
+        )
         else 0
     )
     legacy_until: Final = (
diff --git a/tests/unit/proxy/spend_tracking/test_baseline_accounting.py b/tests/unit/proxy/spend_tracking/test_baseline_accounting.py
index a71b0dfda19..2cf1d57a091 100644
--- a/tests/unit/proxy/spend_tracking/test_baseline_accounting.py
+++ b/tests/unit/proxy/spend_tracking/test_baseline_accounting.py
@@ -119,11 +119,13 @@ def test_skipped_long_cache_lifetime_survives_shorter_followups(ttl: int | None,
     assert warm[0].usage is not None and warm[0].usage.prompt_tokens_details.cached_tokens == 6000
 
 
-@pytest.mark.parametrize("ambiguous_entry", (False, True))
-def test_legacy_checkpoint_accounts_for_refreshes_after_a_skipped_request(ambiguous_entry: bool) -> None:
+@pytest.mark.parametrize("uncertain_before,ambiguous_entry", ((1000.0, False), (0.0, True), (1.0, False)))
+def test_legacy_checkpoint_accounts_for_refreshes_after_a_skipped_request(
+    uncertain_before: float, ambiguous_entry: bool,
+) -> None:
     restored: Final = TypeAdapter(BaselineHistory).validate_python({
         "first_at": 1.0, "last_at": 80000.0, "equivalent": False,
-        "uncertain_before": 0.0 if ambiguous_entry else 1000.0,
+        "uncertain_before": uncertain_before,
         "entries": (CacheEntry("p:300", "p", 6000, 300, 80000.0, 83600.0, uncertain=True),)
         if ambiguous_entry else (),
     })
@@ -134,6 +136,21 @@ def test_legacy_checkpoint_accounts_for_refreshes_after_a_skipped_request(ambigu
     assert expired[0].usage is not None and expired[0].usage.prompt_tokens_details.cached_tokens == 0
 
 
+@pytest.mark.parametrize("policy", ("anthropic", "estimated"))
+def test_healthy_legacy_checkpoint_preserves_known_cache_hits(policy: str) -> None:
+    history, _ = advance_baseline_history(BaselineHistory(), (_observation("first"),))
+    adapter: Final = TypeAdapter(BaselineHistory)
+    restored: Final = adapter.validate_python(adapter.dump_python(
+        history, exclude={"version", "uncertain_until", "uncertain_ttl_seconds"},
+    ))
+    updated, estimates = advance_baseline_history(
+        restored, (_observation("after_upgrade", 10002.0, cache_policy=policy),),
+    )
+    assert estimates[0].reason == "cache_prefix_available"
+    assert estimates[0].usage is not None and estimates[0].usage.prompt_tokens_details.cached_tokens == 6000
+    assert updated.uncertain_until == 0 and updated.uncertain_ttl_seconds == 0
+
+
 def test_skipped_turn_preserves_lifetime_of_an_earlier_ambiguous_write() -> None:
     first: Final = _observation("long", 1.0, cache_policy="estimated", cache_ttl_seconds=3600)
     short: Final = _observation(