diff --git a/lumen/ai/agents/sql.py b/lumen/ai/agents/sql.py
index 931fa8eea..dfd92ff7d 100644
--- a/lumen/ai/agents/sql.py
+++ b/lumen/ai/agents/sql.py
@@ -377,6 +377,18 @@ async def _validate_sql(
                 feedback = f"{type(e).__name__}: {e!s}"
                 if "KeyError" in feedback:
                     feedback += " The data does not exist; select from available data sources."
+                elif "not found" in str(e).lower():
+                    # A referenced table does not exist (e.g. the model used the
+                    # source name instead of one of its tables, common for
+                    # multi-table sources like XArraySQLSource). Surface the
+                    # actual table names so the retry stops guessing.
+                    available = source.get_tables()
+                    if available:
+                        names = ", ".join(repr(t) for t in available[:50])
+                        feedback += (
+                            f" Use one of these exact table names, not the "
+                            f"source name: {names}."
+                        )
 
                 retry_result = await self.revise(
                     feedback, messages, context, spec=sql_query, language=f"sql.{source.dialect}",
diff --git a/lumen/tests/ai/test_sql_validation.py b/lumen/tests/ai/test_sql_validation.py
new file mode 100644
index 000000000..1f88226b8
--- /dev/null
+++ b/lumen/tests/ai/test_sql_validation.py
@@ -0,0 +1,87 @@
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+try:
+    import lumen.ai  # noqa
+except ModuleNotFoundError:
+    pytest.skip(
+        "lumen.ai could not be imported, skipping tests.",
+        allow_module_level=True,
+    )
+
+from lumen.ai.agents.sql import SQLAgent
+
+
+@pytest.mark.asyncio
+async def test_validate_sql_surfaces_table_names_on_not_found():
+    """On a 'table not found' error the retry feedback should list the
+    source's real table names so the model stops using the source name
+    (the failure mode for multi-table sources like XArraySQLSource)."""
+    agent = SQLAgent()
+
+    source = MagicMock()
+    source.dialect = "duckdb"
+    source.get_tables.return_value = ["CMI_C01", "DQF_C01"]
+
+    attempts = {"n": 0}
+
+    def execute(sql, *a, **k):
+        attempts["n"] += 1
+        if attempts["n"] == 1:
+            # First attempt: model referenced the source name as a table.
+            raise ValueError("Error during planning: table 'MySource' not found")
+        return None  # Corrected query validates.
+
+    source.execute.side_effect = execute
+
+    captured = {}
+
+    async def fake_revise(feedback, *a, **k):
+        captured["feedback"] = feedback
+        return "SELECT * FROM CMI_C01"
+
+    agent.revise = fake_revise
+
+    result = await agent._validate_sql(
+        context={},
+        sql_query='SELECT * FROM "MySource"',
+        expr_slug="x",
+        source=source,
+        messages=[],
+        step=MagicMock(),
+        max_retries=2,
+    )
+
+    # Recovered using the corrected SQL.
+    assert "CMI_C01" in result
+    # The retry feedback surfaced the real table names + the hint.
+    assert "CMI_C01" in captured["feedback"]
+    assert "DQF_C01" in captured["feedback"]
+    assert "not the source name" in captured["feedback"]
+
+
+@pytest.mark.asyncio
+async def test_validate_sql_valid_query_no_retry():
+    """A valid query validates on the first try with no retry/feedback."""
+    agent = SQLAgent()
+
+    source = MagicMock()
+    source.dialect = "duckdb"
+    source.execute.return_value = None  # valid
+
+    agent.revise = AsyncMock(
+        side_effect=AssertionError("revise should not be called")
+    )
+
+    result = await agent._validate_sql(
+        context={},
+        sql_query="SELECT * FROM CMI_C01",
+        expr_slug="x",
+        source=source,
+        messages=[],
+        step=MagicMock(),
+        max_retries=2,
+    )
+    assert "CMI_C01" in result
+    source.get_tables.assert_not_called()