diff --git a/plugins/memory/openviking/__init__.py b/plugins/memory/openviking/__init__.py
index 92c04ba6c7..b88114def1 100644
--- a/plugins/memory/openviking/__init__.py
+++ b/plugins/memory/openviking/__init__.py
@@ -594,16 +594,28 @@ class OpenVikingMemoryProvider(MemoryProvider):
 
         level = args.get("level", "overview")
 
-        # OpenViking v0.3.3 expects directory URIs for abstract/overview.
-        resolved_uri = self._normalize_summary_uri(uri) if level in ("abstract", "overview") else uri
+        summary_level = level in ("abstract", "overview")
+        # OpenViking expects directory URIs for pseudo summary files
+        # (e.g. viking://user/hermes/.overview.md).
+        resolved_uri = self._normalize_summary_uri(uri) if summary_level else uri
+        used_fallback = False
 
-        # Map our level names to OpenViking GET endpoints
+        # Map our level names to OpenViking GET endpoints.
+        endpoint = "/api/v1/content/read"
         if level == "abstract":
-            resp = self._client.get("/api/v1/content/abstract", params={"uri": resolved_uri})
-        elif level == "full":
-            resp = self._client.get("/api/v1/content/read", params={"uri": resolved_uri})
-        else:  # overview
-            resp = self._client.get("/api/v1/content/overview", params={"uri": resolved_uri})
+            endpoint = "/api/v1/content/abstract"
+        elif level == "overview":
+            endpoint = "/api/v1/content/overview"
+
+        try:
+            resp = self._client.get(endpoint, params={"uri": resolved_uri})
+        except Exception:
+            # OpenViking may return HTTP 500 for abstract/overview reads on normal
+            # file URIs (mem_*.md). For those, gracefully fallback to full read.
+            if not summary_level or resolved_uri != uri:
+                raise
+            resp = self._client.get("/api/v1/content/read", params={"uri": uri})
+            used_fallback = True
 
         result = self._unwrap_result(resp)
         # Content endpoints may return either plain strings or objects.
@@ -614,16 +626,26 @@ class OpenVikingMemoryProvider(MemoryProvider):
         else:
             content = ""
 
-        # Truncate very long content to avoid flooding the context
-        if len(content) > 8000:
-            content = content[:8000] + "\n\n[... truncated, use a more specific URI or abstract level]"
+        # Truncate long content to avoid flooding context.
+        max_len = 8000
+        if level == "overview":
+            max_len = 4000
+        elif level == "abstract":
+            max_len = 1200
 
-        return json.dumps({
+        if len(content) > max_len:
+            content = content[:max_len] + "\n\n[... truncated, use a more specific URI or full level]"
+
+        payload = {
             "uri": uri,
             "resolved_uri": resolved_uri,
             "level": level,
             "content": content,
-        }, ensure_ascii=False)
+        }
+        if used_fallback:
+            payload["fallback"] = "content/read"
+
+        return json.dumps(payload, ensure_ascii=False)
 
     def _tool_browse(self, args: dict) -> str:
         action = args.get("action", "list")
diff --git a/tests/openviking_plugin/test_openviking.py b/tests/openviking_plugin/test_openviking.py
index 5248cde1d0..81dcfb0cf1 100644
--- a/tests/openviking_plugin/test_openviking.py
+++ b/tests/openviking_plugin/test_openviking.py
@@ -12,7 +12,10 @@ class FakeVikingClient:
 
     def get(self, path, params=None, **kwargs):
         self.calls.append((path, params or {}))
-        return self.responses[(path, tuple(sorted((params or {}).items())))]
+        response = self.responses[(path, tuple(sorted((params or {}).items())))]
+        if isinstance(response, Exception):
+            raise response
+        return response
 
 
 class TestOpenVikingSummaryUriNormalization:
@@ -68,6 +71,55 @@ class TestOpenVikingRead:
             {"uri": "viking://user/hermes/memories/profile.md"},
         )]
 
+    def test_overview_file_uri_falls_back_to_content_read_on_summary_error(self):
+        provider = OpenVikingMemoryProvider()
+        file_uri = "viking://user/hermes/memories/entities/mem_abc.md"
+        provider._client = FakeVikingClient(
+            {
+                (
+                    "/api/v1/content/overview",
+                    (("uri", file_uri),),
+                ): RuntimeError("500 Internal Server Error"),
+                (
+                    "/api/v1/content/read",
+                    (("uri", file_uri),),
+                ): {"result": {"content": "fallback full content"}},
+            }
+        )
+
+        result = json.loads(provider._tool_read({"uri": file_uri, "level": "overview"}))
+
+        assert result["uri"] == file_uri
+        assert result["resolved_uri"] == file_uri
+        assert result["level"] == "overview"
+        assert result["fallback"] == "content/read"
+        assert result["content"] == "fallback full content"
+        assert provider._client.calls == [
+            ("/api/v1/content/overview", {"uri": file_uri}),
+            ("/api/v1/content/read", {"uri": file_uri}),
+        ]
+
+    def test_summary_uri_error_does_not_fallback_and_raises(self):
+        provider = OpenVikingMemoryProvider()
+        provider._client = FakeVikingClient(
+            {
+                (
+                    "/api/v1/content/overview",
+                    (("uri", "viking://user/hermes"),),
+                ): RuntimeError("500 Internal Server Error"),
+            }
+        )
+
+        try:
+            provider._tool_read({"uri": "viking://user/hermes/.overview.md", "level": "overview"})
+            assert False, "Expected summary endpoint error to be raised"
+        except RuntimeError:
+            pass
+
+        assert provider._client.calls == [
+            ("/api/v1/content/overview", {"uri": "viking://user/hermes"}),
+        ]
+
 
 class TestOpenVikingBrowse:
     def test_list_browse_unwraps_and_normalizes_entry_shapes(self):