diff --git a/sdk/wren-langchain/src/wren_langchain/_format.py b/sdk/wren-langchain/src/wren_langchain/_format.py
index 82d3085197..7398a0ccbc 100644
--- a/sdk/wren-langchain/src/wren_langchain/_format.py
+++ b/sdk/wren-langchain/src/wren_langchain/_format.py
@@ -75,17 +75,25 @@ def format_fetch_context_content(result: dict[str, Any]) -> str:
         return _cap_to_bytes(text, suffix="\n\n...[truncated]")
 
     items = result.get("results", []) or []
-    if not items:
+    if not isinstance(items, list) or not items:
         return "_No relevant context items found._"
 
     lines = []
-    for i, item in enumerate(items, start=1):
+    n = 0
+    for item in items:
+        if not isinstance(item, dict):
+            continue
+        n += 1
         item_type = item.get("item_type", "item")
         name = item.get("name", "")
         summary = item.get("summary") or item.get("text") or ""
+        if not isinstance(summary, str):
+            summary = str(summary) if summary is not None else ""
         if len(summary) > 120:
             summary = summary[:117] + "..."
-        lines.append(f"{i}. [{item_type}] {name} — {summary}")
+        lines.append(f"{n}. [{item_type}] {name} — {summary}")
+    if not lines:
+        return "_No relevant context items found._"
     return _cap_to_bytes("\n".join(lines), suffix="\n...[truncated]")
 
 
@@ -106,14 +114,20 @@ def _cap_to_bytes(text: str, *, suffix: str) -> str:
 
 def format_recall_content(rows: list[dict[str, Any]]) -> str:
     """Render recalled NL→SQL pairs as a numbered list with code fences."""
-    if not rows:
+    if not isinstance(rows, list) or not rows:
         return "_No similar past queries found._"
 
     chunks = []
-    for i, row in enumerate(rows, start=1):
+    n = 0
+    for row in rows:
+        if not isinstance(row, dict):
+            continue
+        n += 1
         nl = row.get("nl_query") or row.get("nl") or ""
         sql = row.get("sql_query") or row.get("sql") or ""
-        chunks.append(f'{i}. "{nl}"\n   ```sql\n   {sql}\n   ```')
+        chunks.append(f'{n}. "{nl}"\n   ```sql\n   {sql}\n   ```')
+    if not chunks:
+        return "_No similar past queries found._"
     return "\n".join(chunks)
 
 
@@ -132,18 +146,28 @@ def format_list_models_content(manifest: dict[str, Any]) -> str:
     Columns: model | cols | description.
     """
     models = manifest.get("models", []) or []
-    if not models:
+    if not isinstance(models, list) or not models:
         return "_No models defined in this Wren project._"
 
     lines = ["| model | cols | description |", "|---|---|---|"]
+    any_model = False
     for m in models:
+        if not isinstance(m, dict):
+            continue
+        any_model = True
         name = m.get("name", "")
-        col_count = len(m.get("columns", []) or [])
-        desc = (
-            (m.get("properties") or {}).get("description") or m.get("description") or ""
-        )
+        cols = m.get("columns", []) or []
+        col_count = len(cols) if isinstance(cols, list) else 0
+        props = m.get("properties") or {}
+        if not isinstance(props, dict):
+            props = {}
+        desc = props.get("description") or m.get("description") or ""
+        if not isinstance(desc, str):
+            desc = str(desc) if desc is not None else ""
         # Trim long descriptions to keep table compact.
         if len(desc) > 80:
             desc = desc[:77] + "..."
         lines.append(f"| {name} | {col_count} | {desc} |")
+    if not any_model:
+        return "_No models defined in this Wren project._"
     return "\n".join(lines)
diff --git a/sdk/wren-langchain/tests/unit/test_format_malformed.py b/sdk/wren-langchain/tests/unit/test_format_malformed.py
new file mode 100644
index 0000000000..b5b88c32b9
--- /dev/null
+++ b/sdk/wren-langchain/tests/unit/test_format_malformed.py
@@ -0,0 +1,123 @@
+"""format_* helpers must tolerate non-dict list rows from memory/search APIs."""
+
+from __future__ import annotations
+
+from wren_langchain._format import (
+    format_fetch_context_content,
+    format_list_models_content,
+    format_recall_content,
+)
+
+_FETCH_FALLBACK = "_No relevant context items found._"
+_RECALL_FALLBACK = "_No similar past queries found._"
+_MODELS_FALLBACK = "_No models defined in this Wren project._"
+
+
+def test_format_fetch_context_skips_non_dict_items() -> None:
+    out = format_fetch_context_content(
+        {
+            "strategy": "search",
+            "results": [
+                "not-a-dict",
+                None,
+                {
+                    "item_type": "model",
+                    "name": "orders",
+                    "summary": "Orders table",
+                },
+            ],
+        }
+    )
+    # Skipped rows must not shift the numbering — the first valid row is `1.`.
+    assert "1. [model] orders" in out
+    assert "not-a-dict" not in out
+
+
+def test_format_fetch_context_non_list_container_falls_back() -> None:
+    out = format_fetch_context_content({"strategy": "search", "results": "oops"})
+    assert out == _FETCH_FALLBACK
+
+
+def test_format_fetch_context_all_invalid_falls_back() -> None:
+    out = format_fetch_context_content(
+        {"strategy": "search", "results": ["x", None, 3]}
+    )
+    assert out == _FETCH_FALLBACK
+
+
+def test_format_fetch_context_normalizes_non_str_summary() -> None:
+    out = format_fetch_context_content(
+        {
+            "strategy": "search",
+            "results": [{"item_type": "model", "name": "orders", "summary": 42}],
+        }
+    )
+    assert "1. [model] orders — 42" in out
+
+
+def test_format_recall_skips_non_dict_rows() -> None:
+    out = format_recall_content(
+        [
+            "x",
+            {"nl": "List orders", "sql": "SELECT 1"},
+        ]
+    )
+    # Renumbering: the valid row is `1.` even though a bad row preceded it.
+    assert '1. "List orders"' in out
+    assert "SELECT 1" in out
+
+
+def test_format_recall_non_list_falls_back() -> None:
+    assert format_recall_content("nope") == _RECALL_FALLBACK  # type: ignore[arg-type]
+
+
+def test_format_recall_all_invalid_falls_back() -> None:
+    assert format_recall_content(["x", None, 3]) == _RECALL_FALLBACK
+
+
+def test_format_list_models_skips_non_dict_models() -> None:
+    out = format_list_models_content(
+        {
+            "models": [
+                "bad",
+                None,
+                {
+                    "name": "customers",
+                    "columns": [{}, {}],
+                    "description": "desc",
+                },
+            ]
+        }
+    )
+    assert "| customers | 2 | desc |" in out
+
+
+def test_format_list_models_non_list_falls_back() -> None:
+    assert format_list_models_content({"models": "oops"}) == _MODELS_FALLBACK
+
+
+def test_format_list_models_all_invalid_falls_back() -> None:
+    assert format_list_models_content({"models": ["x", None]}) == _MODELS_FALLBACK
+
+
+def test_format_list_models_normalizes_non_list_columns() -> None:
+    out = format_list_models_content(
+        {"models": [{"name": "customers", "columns": "nope", "description": "d"}]}
+    )
+    assert "| customers | 0 | d |" in out
+
+
+def test_format_list_models_normalizes_non_dict_properties() -> None:
+    out = format_list_models_content(
+        {
+            "models": [
+                {
+                    "name": "customers",
+                    "columns": [{}],
+                    "properties": "oops",
+                    "description": "fallback desc",
+                }
+            ]
+        }
+    )
+    assert "| customers | 1 | fallback desc |" in out