diff --git a/polylogue/storage/sqlite/archive_tiers/archive.py b/polylogue/storage/sqlite/archive_tiers/archive.py
index 1b85253d2b..d1eec6d14d 100644
--- a/polylogue/storage/sqlite/archive_tiers/archive.py
+++ b/polylogue/storage/sqlite/archive_tiers/archive.py
@@ -8711,6 +8711,8 @@ def _learning_correction_from_archive_row(row: sqlite3.Row | tuple[object, ...])
 def _origin_value(origin: str | None) -> str | None:
     if origin is None:
         return None
+    if origin == "":
+        return Origin.UNKNOWN_EXPORT.value
     return Origin(origin).value
 
 
diff --git a/polylogue/storage/sqlite/queries/filter_builder.py b/polylogue/storage/sqlite/queries/filter_builder.py
index 4afe487338..0d829815bf 100644
--- a/polylogue/storage/sqlite/queries/filter_builder.py
+++ b/polylogue/storage/sqlite/queries/filter_builder.py
@@ -30,6 +30,8 @@ def _iso_to_epoch(iso_str: str) -> float:
 
 
 def _origin_value(value: str) -> str:
+    if value == "":
+        return Origin.UNKNOWN_EXPORT.value
     return Origin(value).value
 
 
diff --git a/tests/unit/insights/test_tool_usage.py b/tests/unit/insights/test_tool_usage.py
index 2221a0b1bd..3d190bce0f 100644
--- a/tests/unit/insights/test_tool_usage.py
+++ b/tests/unit/insights/test_tool_usage.py
@@ -24,6 +24,7 @@
 import pytest
 
 from polylogue import Polylogue
+from polylogue.insights.archive import ArchiveCoverageInsightQuery
 from polylogue.insights.tool_usage import (
     TOOL_USAGE_INSIGHT_VERSION,
     ToolUsageInsight,
@@ -309,6 +310,41 @@ async def test_aggregates_per_origin_and_tool(self, tmp_path: Path) -> None:
         origins = {entry.source_name for entry in insight.origin_coverage}
         assert origins == {"claude-code-session", "codex-session"}
 
+    async def test_empty_origin_selects_unknown_export_in_tool_and_coverage_routes(self, tmp_path: Path) -> None:
+        """An empty public filter is the explicit unknown-origin scope, not an error or unfiltered read."""
+        archive = _archive(tmp_path)
+        db_path = archive.archive_root / "index.db"
+        (
+            SessionBuilder(db_path, "unknown-1")
+            .provider("unknown")
+            .add_message(
+                "unknown-msg",
+                role="assistant",
+                text="Unknown provenance tool call",
+                blocks=[{"type": "tool_use", "name": "Inspect", "id": "unknown-tool"}],
+            )
+            .save()
+        )
+        (
+            SessionBuilder(db_path, "codex-1")
+            .provider("codex")
+            .add_message(
+                "codex-msg",
+                role="assistant",
+                text="Codex tool call",
+                blocks=[{"type": "tool_use", "name": "ApplyPatch", "id": "codex-tool"}],
+            )
+            .save()
+        )
+
+        [tool_usage] = await archive.list_tool_usage_insights(ToolUsageInsightQuery(origin=""))
+        coverage = await archive.list_archive_coverage_insights(ArchiveCoverageInsightQuery(origin=""))
+
+        assert [(entry.source_name, entry.normalized_tool_name) for entry in tool_usage.entries] == [
+            ("unknown-export", "inspect")
+        ]
+        assert [(entry.bucket, entry.session_count) for entry in coverage] == [("unknown-export", 1)]
+
     async def test_coverage_reports_origin_without_actions(self, tmp_path: Path) -> None:
         archive = _archive(tmp_path)
         db_path = archive.archive_root / "index.db"
diff --git a/tests/unit/storage/test_schema_safety.py b/tests/unit/storage/test_schema_safety.py
index d589bac2d5..162a801398 100644
--- a/tests/unit/storage/test_schema_safety.py
+++ b/tests/unit/storage/test_schema_safety.py
@@ -384,6 +384,8 @@ def test_build_filters_with_empty_origin(self) -> None:
         where_clause, params = _build_session_filters(origin="")
         assert isinstance(where_clause, str)
         assert isinstance(params, list)
+        assert "origin = ?" in where_clause
+        assert params == ["unknown-export"]
 
     def test_build_filters_with_no_args(self) -> None:
         """No filters should produce empty/trivial WHERE clause."""