diff --git a/akashic.plugin.toml b/akashic.plugin.toml
index 44a3e17..4a64931 100644
--- a/akashic.plugin.toml
+++ b/akashic.plugin.toml
@@ -1,6 +1,6 @@
 schema_version = 1
 name = "feed"
-version = "3.1.1"
+version = "3.1.2"
 api_version = 3
 entrypoint = "plugin.py"
 
diff --git a/content_source.py b/content_source.py
index 171796b..e829c7e 100644
--- a/content_source.py
+++ b/content_source.py
@@ -174,7 +174,7 @@ async def _settle_delivered(self) -> int:
                     row["settlement_ref"], "Feed settlement_ref"
                 )
                 receipt = self._content.ack(settlement_ref)
-                if receipt.get("changed") is not True:
+                if receipt.get("settled") is not True:
                     raise RuntimeError(f"Feed Content ACK 未提交: {receipt!r}")
                 settled += 1
         return settled
diff --git a/mcp/tests/test_runtime_paths.py b/mcp/tests/test_runtime_paths.py
index 7be0ad5..5c5613a 100644
--- a/mcp/tests/test_runtime_paths.py
+++ b/mcp/tests/test_runtime_paths.py
@@ -27,7 +27,7 @@ def test_runtime_entrypoints_reject_missing_data_dir(
 def test_v3_module_keeps_skill_root_and_identity_exports() -> None:
     assert plugin.api_version == 3
     assert plugin.name == "feed"
-    assert plugin.version == "3.1.1"
+    assert plugin.version == "3.1.2"
     assert plugin.skill_roots == ("skills",)
     assert _config_path() == Path(__file__).resolve().parents[1] / "feed_mcp.json"
 
diff --git a/plugin.py b/plugin.py
index 18073d9..30d9a32 100644
--- a/plugin.py
+++ b/plugin.py
@@ -23,7 +23,7 @@ class FeedConfig(BaseModel):
 
 api_version = 3
 name = "feed"
-version = "3.1.1"
+version = "3.1.2"
 desc = "由 Timer 驱动的 Feed Content source 与用户 MCP"
 Config = FeedConfig
 inject = (MCP_SERVERS, TIMERS, CONTENT_SOURCE)
diff --git a/tests/test_content_source.py b/tests/test_content_source.py
index 2d36283..6c0cdfc 100644
--- a/tests/test_content_source.py
+++ b/tests/test_content_source.py
@@ -58,6 +58,10 @@ def __init__(self) -> None:
         self.submissions: list[tuple[str, tuple[dict[str, object], ...]]] = []
         self.rows: list[dict[str, object]] = []
         self.fail_ack_once = False
+        self.ack_receipt: dict[str, object] = {
+            "settled": True,
+            "duplicate": False,
+        }
 
     def submit(self, batch_id, items):
         frozen = tuple(dict(item) for item in items)
@@ -71,10 +75,13 @@ def ack(self, settlement_ref):
         if self.fail_ack_once:
             self.fail_ack_once = False
             raise RuntimeError("crash after provider ACK")
-        self.rows = [
-            row for row in self.rows if row["settlement_ref"] != settlement_ref
-        ]
-        return {"changed": True}
+        if self.ack_receipt.get("settled") is True:
+            self.rows = [
+                row
+                for row in self.rows
+                if row["settlement_ref"] != settlement_ref
+            ]
+        return dict(self.ack_receipt)
 
 
 def _seed_item(data_root: Path, now: datetime) -> None:
@@ -177,3 +184,50 @@ async def test_provider_ack_retries_after_crash_before_content_ack(
         assert connection.execute(
             "SELECT event_id FROM acked_items"
         ).fetchall() == [("event-1",)]
+
+
+@pytest.mark.asyncio
+async def test_duplicate_content_ack_is_already_settled(tmp_path: Path) -> None:
+    now = datetime(2026, 8, 23, 10, tzinfo=UTC)
+    _seed_item(tmp_path, now)
+    content = _Content()
+    content.rows = [
+        {
+            "ref": {"item_id": "event-1", "revision": "revision-1"},
+            "settlement_ref": "delivery:1",
+        }
+    ]
+    content.ack_receipt = {"settled": True, "duplicate": True}
+    runtime = FeedContentRuntime(
+        tmp_path,
+        PluginTimers(_Timer(now)),
+        content,
+        now=lambda: now,
+    )
+
+    assert await runtime._settle_delivered() == 1  # pyright: ignore[reportPrivateUsage]
+    assert content.rows == []
+
+
+@pytest.mark.asyncio
+async def test_unsettled_content_ack_fails_loud(tmp_path: Path) -> None:
+    now = datetime(2026, 8, 23, 10, tzinfo=UTC)
+    _seed_item(tmp_path, now)
+    content = _Content()
+    content.rows = [
+        {
+            "ref": {"item_id": "event-1", "revision": "revision-1"},
+            "settlement_ref": "delivery:1",
+        }
+    ]
+    content.ack_receipt = {"settled": False, "reason": "state_mismatch"}
+    runtime = FeedContentRuntime(
+        tmp_path,
+        PluginTimers(_Timer(now)),
+        content,
+        now=lambda: now,
+    )
+
+    with pytest.raises(RuntimeError, match="Feed Content ACK 未提交"):
+        await runtime._settle_delivered()  # pyright: ignore[reportPrivateUsage]
+    assert content.rows
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index 36e7be6..41ca83e 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -51,7 +51,7 @@ def bind(self, source_id: str) -> BoundContentSource:
 def test_pure_v3_exports_and_exact_apply() -> None:
     assert plugin.api_version == 3
     assert plugin.name == "feed"
-    assert plugin.version == "3.1.1"
+    assert plugin.version == "3.1.2"
     assert plugin.skill_roots == ("skills",)
     assert tuple(inspect.signature(plugin.apply).parameters) == ("ctx", "config")
     assert ComposablePlugin.from_module(plugin).skill_roots == ("skills",)
@@ -102,7 +102,7 @@ def test_static_manifest_freezes_tools_and_data_exclusions() -> None:
     manifest = load_static_plugin_manifest(ROOT)
 
     assert manifest.name == "feed"
-    assert manifest.version == "3.1.1"
+    assert manifest.version == "3.1.2"
     assert manifest.api_version == 3
     assert manifest.requirements == ("mcp/requirements.txt",)
     assert "feed_mcp.sqlite3" in manifest.exclude_data_paths