diff --git a/integrations/agent-plugin-core/python/telemetry.py b/integrations/agent-plugin-core/python/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/agent-plugin-core/python/telemetry.py
+++ b/integrations/agent-plugin-core/python/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try:
diff --git a/integrations/agent-plugin-core/tests/test_spool_delivery.py b/integrations/agent-plugin-core/tests/test_spool_delivery.py
index a7646cc31..ac0bf6b22 100644
--- a/integrations/agent-plugin-core/tests/test_spool_delivery.py
+++ b/integrations/agent-plugin-core/tests/test_spool_delivery.py
@@ -266,13 +266,102 @@ def test_an_undeliverable_batch_is_eventually_given_up_on(telemetry):
     telemetry.record("doomed")
     telemetry._post = lambda payload, url: False
 
+    directory = telemetry.memory_core.data_dir()
     for _ in range(telemetry.MAX_CLAIM_ATTEMPTS + 3):
         telemetry.flush()
+        # Attempts now carry a cooldown, so a released claim is not instantly
+        # reclaimable. Age it to stand in for the wall time a real retry waits;
+        # without this the loop spins inside one cooldown and proves nothing.
+        for parked in directory.glob("telemetry-*.sending"):
+            stale = time.time() - (telemetry.CLAIM_STALE_SECONDS + 60)
+            os.utime(parked, (stale, stale))
 
-    leftover = list(telemetry.memory_core.data_dir().glob("telemetry-*.sending"))
+    leftover = list(directory.glob("telemetry-*.sending"))
     assert leftover == [], f"batch never given up on: {[p.name for p in leftover]}"
 
 
+def test_a_batch_that_cannot_be_read_is_not_counted_as_delivered(telemetry):
+    """Review finding: a read failure reported 'everything delivered'.
+
+    Nothing was posted, so calling it delivered lets flush() carry on to other
+    claims as though this batch had arrived, and hides the failure from the one
+    signal that says the run went badly. It also must not quarantine: a briefly
+    unreadable file is retryable, and moving it to .corrupt discards the events
+    over a transient filesystem error, because nothing ever re-globs .corrupt.
+    """
+    telemetry.record("search")
+    spool = telemetry._spool_path()
+    stale = time.time() - (telemetry.CLAIM_STALE_SECONDS + 60)
+    os.utime(spool, (stale, stale))
+    claim = telemetry._claim_spool()
+    assert claim is not None
+
+    original = Path.read_text
+
+    def unreadable(self, *args, **kwargs):
+        if self == claim:
+            raise OSError(5, "I/O error")
+        return original(self, *args, **kwargs)
+
+    Path.read_text = unreadable
+    try:
+        sent, delivered = telemetry._drain(claim)
+    finally:
+        Path.read_text = original
+
+    assert sent == 0
+    assert delivered is False, "an unread batch was reported as delivered"
+    assert claim.exists(), "a transient read error discarded the batch"
+    assert not list(claim.parent.glob("*.corrupt")), "quarantined over a transient error"
+
+
+def test_undecodable_content_is_still_quarantined_and_the_run_continues(telemetry):
+    """The other half: genuinely unrecoverable content must not block the run.
+
+    Guards the over-correction. If every read problem returned undelivered, one
+    torn file would stop every later claim on every flush, forever.
+    """
+    telemetry.record("search")
+    spool = telemetry._spool_path()
+    stale = time.time() - (telemetry.CLAIM_STALE_SECONDS + 60)
+    os.utime(spool, (stale, stale))
+    claim = telemetry._claim_spool()
+    assert claim is not None
+    claim.write_bytes(b"\xff\xfe torn \x00 write")
+
+    sent, delivered = telemetry._drain(claim)
+
+    assert (sent, delivered) == (0, True)
+    assert not claim.exists()
+    assert list(claim.parent.glob("*.corrupt")), "unrecoverable content was not quarantined"
+
+
+def test_retries_are_spread_over_real_time_not_burned_at_once(telemetry):
+    """Review finding: releasing straight to reclaimable spent the budget instantly.
+
+    Two senders hitting one momentary failure could walk a batch from attempt 0
+    to the limit within seconds and discard it, when a retry a minute later would
+    have delivered. Each release now has to age past a cooldown that grows with
+    the attempts already spent.
+    """
+    telemetry.record("doomed")
+    telemetry._post = lambda payload, url: False
+
+    directory = telemetry.memory_core.data_dir()
+    telemetry.flush()
+
+    parked = list(directory.glob("telemetry-*.sending"))
+    assert parked, "the batch was discarded on its first failure"
+    assert telemetry._claim_attempt(parked[0]) == 0
+
+    # Second sender, immediately: the cooldown has not elapsed, so it must not
+    # be able to spend another attempt.
+    telemetry.flush()
+    still = list(directory.glob("telemetry-*.sending"))
+    assert len(still) == 1
+    assert telemetry._claim_attempt(still[0]) <= 1, "burned attempts without waiting"
+
+
 def test_a_legacy_claim_filename_is_not_mistaken_for_a_huge_attempt_count(telemetry):
     """The old shape is telemetry-<pid>-<hex>.sending, and hex can start with 'a'."""
     assert telemetry._claim_attempt(Path("telemetry-999-deadbeef.sending")) == 0
diff --git a/integrations/antigravity-plugin/core/telemetry.py b/integrations/antigravity-plugin/core/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/antigravity-plugin/core/telemetry.py
+++ b/integrations/antigravity-plugin/core/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try:
diff --git a/integrations/claude-code-plugin/core/telemetry.py b/integrations/claude-code-plugin/core/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/claude-code-plugin/core/telemetry.py
+++ b/integrations/claude-code-plugin/core/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try:
diff --git a/integrations/codex-plugin/core/telemetry.py b/integrations/codex-plugin/core/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/codex-plugin/core/telemetry.py
+++ b/integrations/codex-plugin/core/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try:
diff --git a/integrations/cursor-plugin/core/telemetry.py b/integrations/cursor-plugin/core/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/cursor-plugin/core/telemetry.py
+++ b/integrations/cursor-plugin/core/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try:
diff --git a/integrations/kimi-plugin/core/telemetry.py b/integrations/kimi-plugin/core/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/kimi-plugin/core/telemetry.py
+++ b/integrations/kimi-plugin/core/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try:
diff --git a/integrations/mem0-agent-plugin/core/telemetry.py b/integrations/mem0-agent-plugin/core/telemetry.py
index aa5cb0dce..b7e52d24f 100644
--- a/integrations/mem0-agent-plugin/core/telemetry.py
+++ b/integrations/mem0-agent-plugin/core/telemetry.py
@@ -105,6 +105,11 @@ MAX_CLAIM_ATTEMPTS = 3
 # Parked claims drained per run, after the live spool. Bounded so a long backlog
 # cannot turn one flush into an unbounded send loop.
 MAX_PARKED_PER_RUN = 3
+# Added to the wait before a released claim becomes reclaimable, per attempt
+# already spent. Releasing straight to "reclaimable now" let two senders burn the
+# whole budget within seconds of one another on a single momentary failure, and
+# discard a batch a retry a minute later would have delivered.
+RETRY_COOLDOWN_SECONDS = 60
 
 
 def is_enabled() -> bool:
@@ -715,7 +720,11 @@ def _release_claim(claim: Path, remaining: list[dict[str, Any]]) -> None:
     if not _rewrite_claim(claim, remaining):
         return
     try:
-        released = time.time() - CLAIM_STALE_SECONDS - 1
+        # Backdate past the stale threshold so the next flush can pick it up,
+        # minus a cooldown that grows with the attempts already spent. Clamped so
+        # the mtime never lands in the future, which would read as a live lease.
+        cooldown = min(_claim_attempt(claim) * RETRY_COOLDOWN_SECONDS, CLAIM_STALE_SECONDS)
+        released = time.time() - CLAIM_STALE_SECONDS - 1 + cooldown
         os.utime(claim, (released, released))
     except OSError:
         pass
@@ -852,11 +861,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
         return 0, True
     try:
         lines = claim.read_text(encoding="utf-8").splitlines()
-    except (OSError, ValueError):
-        # ValueError covers UnicodeDecodeError from a torn write. Quarantine
-        # rather than retry: flush() runs from a bare `finally:` in
+    except ValueError:
+        # UnicodeDecodeError from a torn write: the content is unrecoverable, so
+        # quarantine rather than retry. flush() runs from a bare `finally:` in
         # flush_worker, so raising here also skips the handoff cleanup, and an
         # undecodable file would otherwise be re-read on every flush forever.
+        # Reported as delivered because there is nothing left to deliver and the
+        # rest of the run should continue.
         try:
             claim.replace(claim.with_suffix(".corrupt"))
         except OSError:
@@ -865,6 +876,13 @@ def _drain(claim: Path | None) -> tuple[int, bool]:
             except OSError:
                 pass
         return 0, True
+    except OSError:
+        # Could not read it, which is not the same as having nothing to send.
+        # The file is left exactly where it is: a vanished or briefly unreadable
+        # claim is retryable, and quarantining it here would discard events over
+        # a transient filesystem error. Reported as undelivered so the run stops
+        # instead of counting a batch nothing was posted from as delivered.
+        return 0, False
     events = []
     for line in lines:
         try: