diff --git a/CHANGELOG.md b/CHANGELOG.md
index 346995be..59adee7f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Agent-side cron sessions imported from state.db now remain available to their assigned project chip as `default_hidden` rows instead of being filtered out before project reveal logic can see them (#3134).
+
 ## [v0.51.165] — 2026-05-30 — Release EK (stage-batch47 — stop EventSource reconnect storm on long-lived SSE streams)
 
 ### Fixed
diff --git a/api/routes.py b/api/routes.py
index 70f96eb6..cc8bd761 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -2530,6 +2530,29 @@ def _is_duplicate_webui_state_projection(session: dict, represented_webui_ids: s
     return bool(_session_lineage_ids(session) & represented_webui_ids)
 
 
+def _dedupe_cli_sidebar_sessions_for_api(cli: list[dict], represented_webui_ids: set[str]) -> list[dict]:
+    """Return CLI/state sidebar rows while preserving project-hidden cron rows.
+
+    Agent-side cron sessions come from state.db rather than the WebUI session
+    store. They should stay hidden from the default sidebar, but project-assigned
+    messageful rows must remain in the `/api/sessions` payload with
+    `default_hidden` so the matching project chip can reveal them (#3134).
+    """
+    from api.models import (
+        _hide_from_default_sidebar as _cron_hide,
+        _include_project_hidden_background_sidebar_sessions,
+    )
+
+    candidates = [
+        s for s in cli
+        if s["session_id"] not in represented_webui_ids
+        and not _is_duplicate_webui_state_projection(s, represented_webui_ids)
+        and is_cli_session_row_visible(s)
+    ]
+    visible = [s for s in candidates if not _cron_hide(s)]
+    return _include_project_hidden_background_sidebar_sessions(candidates, visible)
+
+
 CLI_VISIBLE_SESSION_CAP = 20
 
 
@@ -4625,14 +4648,7 @@ def handle_get(handler, parsed) -> bool:
                 represented_webui_ids = set()
                 for s in webui_sessions:
                     represented_webui_ids.update(_session_lineage_ids(s))
-                from api.models import _hide_from_default_sidebar as _cron_hide
-                deduped_cli = [
-                    s for s in cli
-                    if s["session_id"] not in represented_webui_ids
-                    and not _is_duplicate_webui_state_projection(s, represented_webui_ids)
-                    and is_cli_session_row_visible(s)
-                    and not _cron_hide(s)
-                ]
+                deduped_cli = _dedupe_cli_sidebar_sessions_for_api(cli, represented_webui_ids)
             else:
                 diag.stage("filter_webui_sessions")
                 webui_sessions = [s for s in webui_sessions if not _is_cli_session_for_settings(s)]
diff --git a/tests/test_gateway_sync.py b/tests/test_gateway_sync.py
index 7181972d..5cd3fb92 100644
--- a/tests/test_gateway_sync.py
+++ b/tests/test_gateway_sync.py
@@ -1529,7 +1529,11 @@ def test_cron_sessions_hidden_from_sidebar_by_default():
         sessions = data.get('sessions', [])
         ids = {s['session_id'] for s in sessions}
         assert 'gw_noncron_001' in ids, "Non-cron agent session should still appear"
-        assert 'cron_job123_20260427' not in ids, "Cron session should be hidden by default"
+        cron_row = next((s for s in sessions if s['session_id'] == 'cron_job123_20260427'), None)
+        assert cron_row is None or cron_row.get('default_hidden') is True, (
+            "Cron session should either be omitted from /api/sessions or marked "
+            "default_hidden so the default sidebar filter keeps it hidden"
+        )
     finally:
         try:
             _remove_test_sessions(conn, 'cron_job123_20260427', 'gw_noncron_001')
diff --git a/tests/test_issue3019_cron_project_sessions.py b/tests/test_issue3019_cron_project_sessions.py
index bd27157f..dd112b4b 100644
--- a/tests/test_issue3019_cron_project_sessions.py
+++ b/tests/test_issue3019_cron_project_sessions.py
@@ -38,6 +38,56 @@ def test_project_assigned_cron_rows_are_returned_but_default_hidden():
     assert by_id["cron_visible"]["default_hidden"] is True
 
 
+def test_agent_side_cron_rows_keep_project_chip_visibility():
+    from api.routes import _dedupe_cli_sidebar_sessions_for_api
+
+    represented_webui_ids = {"webui-1"}
+    cli_rows = [
+        {
+            "session_id": "cli-normal",
+            "source_tag": "cli",
+            "title": "Manual deployment notes",
+            "message_count": 1,
+            "updated_at": 5,
+        },
+        {
+            "session_id": "cron-agent-project",
+            "source_tag": "cron",
+            "title": "Cron agent run",
+            "message_count": 3,
+            "project_id": "cron-project",
+            "updated_at": 4,
+        },
+        {
+            "session_id": "cron-agent-unassigned",
+            "source_tag": "cron",
+            "title": "Cron hidden",
+            "message_count": 3,
+            "updated_at": 3,
+        },
+        {
+            "session_id": "cron-agent-empty",
+            "source_tag": "cron",
+            "title": "Cron empty",
+            "message_count": 0,
+            "project_id": "cron-project",
+            "updated_at": 2,
+        },
+        {
+            "session_id": "webui-1",
+            "source_tag": "cli",
+            "title": "Duplicate imported copy",
+            "message_count": 1,
+        },
+    ]
+
+    rows = _dedupe_cli_sidebar_sessions_for_api(cli_rows, represented_webui_ids)
+
+    by_id = {row["session_id"]: row for row in rows}
+    assert set(by_id) == {"cli-normal", "cron-agent-project"}
+    assert by_id["cron-agent-project"]["default_hidden"] is True
+
+
 def test_session_list_project_filter_can_reveal_default_hidden_cron_rows():
     src = ( __import__("pathlib").Path(__file__).parent.parent / "static" / "sessions.js").read_text(encoding="utf-8")