diff --git a/mempalace/mcp_server.py b/mempalace/mcp_server.py
index 1f3cef2..99ae542 100644
--- a/mempalace/mcp_server.py
+++ b/mempalace/mcp_server.py
@@ -9,7 +9,7 @@ Tools (read):
   mempalace_list_wings      — all wings with drawer counts
   mempalace_list_rooms      — rooms within a wing
   mempalace_get_taxonomy    — full wing → room → count tree
-  mempalace_search          — semantic search, optional wing/room filter
+  mempalace_search          — semantic search, optional wing/room/source_file filter
   mempalace_check_duplicate — check if content already exists before filing
 
 Tools (write):
@@ -1152,6 +1152,41 @@ def _sanitize_optional_name(value: str = None, field_name: str = "name") -> str:
     return sanitize_name(value, field_name)
 
 
+# Bounds the whole stored source_file string (often an absolute path), so it is
+# Linux PATH_MAX rather than the 128-char wing/room NAME limit.
+_MAX_SOURCE_FILE_LENGTH = 4096
+
+
+def _sanitize_optional_source_file(value: str = None) -> str:
+    """Validate an optional source_file search filter (#1815).
+
+    Unlike wing/room, a source_file is a path: ``/``, ``\\`` and ``.`` are
+    legal, so it is NOT run through ``sanitize_name`` (which rejects path
+    characters as traversal attempts). The value is matched verbatim as a
+    ChromaDB metadata-equality / parameterized-SQL value — never used as a
+    filesystem path — so there is no traversal risk to guard against. A null
+    byte or a pathological length can still upset the backend (chromadb
+    add/upsert chokes on null bytes / lone surrogates, #1235), so guard those
+    for parity with ``sanitize_name``. Blank / whitespace-only is "no filter".
+    """
+    if value is None:
+        return None
+    if not isinstance(value, str):
+        raise ValueError("source_file must be a string")
+    value = value.strip()
+    if not value:
+        return None
+    if "\x00" in value:
+        raise ValueError("source_file contains null bytes")
+    if value != strip_lone_surrogates(value):
+        raise ValueError("source_file contains invalid surrogate characters")
+    if len(value) > _MAX_SOURCE_FILE_LENGTH:
+        raise ValueError(
+            f"source_file exceeds maximum length of {_MAX_SOURCE_FILE_LENGTH} characters"
+        )
+    return value
+
+
 # ==================== READ TOOLS ====================
 
 
@@ -1590,6 +1625,7 @@ def tool_search(
     limit: int = 5,
     wing: str = None,
     room: str = None,
+    source_file: str = None,
     max_distance: float = 1.5,
     min_similarity: float = None,
     context: str = None,
@@ -1598,6 +1634,7 @@ def tool_search(
     try:
         wing = _sanitize_optional_name(wing, "wing")
         room = _sanitize_optional_name(room, "room")
+        source_file = _sanitize_optional_source_file(source_file)
     except ValueError as e:
         return {"error": str(e)}
     # Backwards compat: accept old name
@@ -1616,6 +1653,7 @@ def tool_search(
         palace_path=_config.palace_path,
         wing=wing,
         room=room,
+        source_file=source_file,
         n_results=limit,
         max_distance=dist,
         vector_disabled=_vector_disabled,
@@ -1633,6 +1671,7 @@ def tool_search(
             palace_path=_config.palace_path,
             wing=wing,
             room=room,
+            source_file=source_file,
             n_results=limit,
             max_distance=dist,
             vector_disabled=_vector_disabled,
@@ -3483,6 +3522,15 @@ TOOLS = {
                 },
                 "wing": {"type": "string", "description": "Filter by wing (optional)"},
                 "room": {"type": "string", "description": "Filter by room (optional)"},
+                "source_file": {
+                    "type": "string",
+                    "description": (
+                        "Filter to one exact source_file (optional). Matches the full "
+                        "stored path exactly (leading/trailing whitespace trimmed); no "
+                        "glob or basename matching. Pass the value from a result's "
+                        "'source_path' field; the displayed 'source_file' is only a basename."
+                    ),
+                },
                 "max_distance": {
                     "type": "number",
                     "description": "Max cosine distance threshold (0=identical, 2=opposite). Results further than this are dropped. Lower = stricter. Default 1.5. Set to 0 to disable.",
diff --git a/mempalace/searcher.py b/mempalace/searcher.py
index 239367b..eac488f 100644
--- a/mempalace/searcher.py
+++ b/mempalace/searcher.py
@@ -226,15 +226,24 @@ def _hybrid_rank(
     return results
 
 
-def build_where_filter(wing: str = None, room: str = None) -> dict:
-    """Build ChromaDB where filter for wing/room filtering."""
-    if wing and room:
-        return {"$and": [{"wing": wing}, {"room": room}]}
-    elif wing:
-        return {"wing": wing}
-    elif room:
-        return {"room": room}
-    return {}
+def build_where_filter(wing: str = None, room: str = None, source_file: str = None) -> dict:
+    """Build a ChromaDB where filter from optional wing/room/source_file.
+
+    ChromaDB needs a ``$and`` only when ≥2 clauses are present; a single
+    clause is returned bare and zero clauses yield an empty filter (#1815).
+    """
+    clauses = []
+    if wing:
+        clauses.append({"wing": wing})
+    if room:
+        clauses.append({"room": room})
+    if source_file:
+        clauses.append({"source_file": source_file})
+    if not clauses:
+        return {}
+    if len(clauses) == 1:
+        return clauses[0]
+    return {"$and": clauses}
 
 
 def _extract_drawer_ids_from_closet(closet_doc: str) -> list:
@@ -476,6 +485,7 @@ def _bm25_only_via_sqlite(
     palace_path: str,
     wing: str = None,
     room: str = None,
+    source_file: str = None,
     n_results: int = 5,
     max_candidates: int = 500,
     _include_internal: bool = False,
@@ -511,7 +521,7 @@ def _bm25_only_via_sqlite(
     def _metadata_filter_sql(row_id_expr: str) -> tuple[str, list[str]]:
         clauses = []
         params = []
-        for key, value in (("wing", wing), ("room", room)):
+        for key, value in (("wing", wing), ("room", room), ("source_file", source_file)):
             if not value:
                 continue
             clauses.append(
@@ -624,7 +634,7 @@ def _bm25_only_via_sqlite(
         if not candidate_ids:
             return {
                 "query": query,
-                "filters": {"wing": wing, "room": room},
+                "filters": {"wing": wing, "room": room, "source_file": source_file},
                 "total_before_filter": 0,
                 "results": [],
                 "fallback": "bm25_only_via_sqlite",
@@ -660,6 +670,8 @@ def _bm25_only_via_sqlite(
             continue
         if room and meta.get("room") != room:
             continue
+        if source_file and meta.get("source_file") != source_file:
+            continue
         full_source = meta.get("source_file", "") or ""
         candidates.append(
             {
@@ -667,6 +679,7 @@ def _bm25_only_via_sqlite(
                 "wing": meta.get("wing", "unknown"),
                 "room": meta.get("room", "unknown"),
                 "source_file": Path(full_source).name if full_source else "?",
+                "source_path": full_source,
                 "created_at": meta.get("filed_at", "unknown"),
                 # No vector distance available in BM25-only mode.
                 "similarity": None,
@@ -702,7 +715,7 @@ def _bm25_only_via_sqlite(
 
     return {
         "query": query,
-        "filters": {"wing": wing, "room": room},
+        "filters": {"wing": wing, "room": room, "source_file": source_file},
         "total_before_filter": len(candidates),
         "results": hits,
         "fallback": "bm25_only_via_sqlite",
@@ -718,6 +731,7 @@ def _merge_bm25_union_candidates(
     room: str,
     n_results: int,
     max_distance: float = 0.0,
+    source_file: str = None,
 ) -> None:
     """Append top-K backend lexical candidates into ``hits`` in place.
 
@@ -744,7 +758,7 @@ def _merge_bm25_union_candidates(
     if max_distance > 0.0:
         return
 
-    where = build_where_filter(wing, room)
+    where = build_where_filter(wing, room, source_file)
     try:
         lexical = drawers_col.lexical_search(
             query=query,
@@ -767,6 +781,7 @@ def _merge_bm25_union_candidates(
                 "wing": meta.get("wing", "unknown"),
                 "room": meta.get("room", "unknown"),
                 "source_file": Path(full_source).name if full_source else "?",
+                "source_path": full_source,
                 "created_at": meta.get("filed_at", "unknown"),
                 "similarity": None,
                 "distance": None,
@@ -832,6 +847,7 @@ def _apply_candidate_strategy(
     room: str,
     n_results: int,
     max_distance: float = 0.0,
+    source_file: str = None,
 ) -> None:
     """Dispatch to the registered merger for ``strategy``.
 
@@ -840,7 +856,16 @@ def _apply_candidate_strategy(
     """
     merger = _CANDIDATE_MERGERS[strategy]
     if merger is not None:
-        merger(hits, drawers_col, query, wing, room, n_results, max_distance=max_distance)
+        merger(
+            hits,
+            drawers_col,
+            query,
+            wing,
+            room,
+            n_results,
+            max_distance=max_distance,
+            source_file=source_file,
+        )
 
 
 def _finalize_candidate_hits(
@@ -853,6 +878,7 @@ def _finalize_candidate_hits(
     room: str,
     n_results: int,
     max_distance: float,
+    source_file: str = None,
 ) -> tuple:
     try:
         _apply_candidate_strategy(
@@ -864,6 +890,7 @@ def _finalize_candidate_hits(
             room,
             n_results,
             max_distance=max_distance,
+            source_file=source_file,
         )
     except UnsupportedCapabilityError:
         return [], {
@@ -905,6 +932,7 @@ def _vector_disabled_search(
     room: str,
     n_results: int,
     collection_name: str,
+    source_file: str = None,
 ) -> dict:
     try:
         backend_name = resolve_backend_name(palace_path)
@@ -924,6 +952,7 @@ def _vector_disabled_search(
         palace_path,
         wing=wing,
         room=room,
+        source_file=source_file,
         n_results=n_results,
         collection_name=collection_name,
     )
@@ -957,7 +986,9 @@ def _open_search_collection(palace_path: str, collection_name: str):
         }
 
 
-def _query_drawers_with_filter_fallback(drawers_col, dkwargs, query, n_results, wing, room):
+def _query_drawers_with_filter_fallback(
+    drawers_col, dkwargs, query, n_results, wing, room, source_file=None
+):
     """Run the filtered drawer query, falling back to an unfiltered query plus a
     Python-side post-filter when ChromaDB raises on the filtered query.
 
@@ -965,7 +996,7 @@ def _query_drawers_with_filter_fallback(drawers_col, dkwargs, query, n_results,
     "Error finding id" even when unfiltered search works fine — it happens when
     drawers are ingested via two different paths (e.g. bulk import vs MCP tool
     calls), leaving the vector index inconsistent with the metadata store. We
-    retry unfiltered (over-fetching) and re-apply the wing/room filter in Python.
+    retry unfiltered (over-fetching) and re-apply the wing/room/source_file filter in Python.
     See #1245 / #1035.
     """
     where = dkwargs.get("where")
@@ -994,6 +1025,8 @@ def _query_drawers_with_filter_fallback(drawers_col, dkwargs, query, n_results,
                 continue
             if room and meta.get("room") != room:
                 continue
+            if source_file and meta.get("source_file") != source_file:
+                continue
             fdocs.append(doc)
             fmetas.append(meta)
             fdists.append(dist)
@@ -1005,6 +1038,7 @@ def search_memories(
     palace_path: str,
     wing: str = None,
     room: str = None,
+    source_file: str = None,
     n_results: int = 5,
     max_distance: float = 0.0,
     vector_disabled: bool = False,
@@ -1020,6 +1054,8 @@ def search_memories(
         palace_path: Path to the ChromaDB palace directory.
         wing: Optional wing filter.
         room: Optional room filter.
+        source_file: Optional exact source_file filter. Matches the full
+            stored source_file value verbatim (#1815).
         n_results: Max results to return.
         max_distance: Max cosine distance threshold. The palace collection uses
             cosine distance (hnsw:space=cosine) — 0 = identical, 2 = opposite.
@@ -1059,6 +1095,7 @@ def search_memories(
             room=room,
             n_results=n_results,
             collection_name=collection_name,
+            source_file=source_file,
         )
 
     drawers_col, open_error = _open_search_collection(palace_path, collection_name)
@@ -1066,7 +1103,7 @@ def search_memories(
         return open_error
 
     metric = _metric_for_collection(drawers_col)
-    where = build_where_filter(wing, room)
+    where = build_where_filter(wing, room, source_file)
 
     # Hybrid retrieval: always query drawers directly (the floor), then use
     # closet hits to boost rankings. Closets are a ranking SIGNAL, never a
@@ -1084,7 +1121,7 @@ def search_memories(
         if where:
             dkwargs["where"] = where
         drawer_results = _query_drawers_with_filter_fallback(
-            drawers_col, dkwargs, query, n_results, wing, room
+            drawers_col, dkwargs, query, n_results, wing, room, source_file
         )
     except Exception as e:
         return {"error": f"Search error: {e}"}
@@ -1156,7 +1193,10 @@ def search_memories(
             "text": doc,
             "wing": meta.get("wing", "unknown"),
             "room": meta.get("room", "unknown"),
+            # source_file is the basename (display); source_path is the full
+            # stored value, the round-trippable key for the source_file filter.
             "source_file": Path(source).name if source else "?",
+            "source_path": source,
             "created_at": meta.get("filed_at", "unknown"),
             "similarity": round(_distance_to_similarity(effective_dist, metric), 3),
             "distance": round(dist, 4),
@@ -1254,13 +1294,14 @@ def search_memories(
         room=room,
         n_results=n_results,
         max_distance=max_distance,
+        source_file=source_file,
     )
     if strategy_error:
         return strategy_error
 
     return {
         "query": query,
-        "filters": {"wing": wing, "room": room},
+        "filters": {"wing": wing, "room": room, "source_file": source_file},
         "total_before_filter": len(_first_or_empty(drawer_results, "documents")),
         "results": hits,
     }
diff --git a/tests/test_hybrid_candidate_union.py b/tests/test_hybrid_candidate_union.py
index 0771001..7c1a129 100644
--- a/tests/test_hybrid_candidate_union.py
+++ b/tests/test_hybrid_candidate_union.py
@@ -213,6 +213,26 @@ class TestCandidateUnion:
             f"(basename collision would drop one); got sources={sources}"
         )
 
+    def test_union_respects_source_file_filter(self, tmp_path):
+        """Union pulls BM25 candidates from sqlite FTS5 directly; the
+        source_file filter must constrain that pool too, not just the vector
+        path — otherwise union silently re-injects other sources (#1815)."""
+        palace = str(tmp_path / "palace")
+        _seed_drawers(palace)
+        result = search_memories(
+            _NARRATIVE_QUERY,
+            palace,
+            n_results=5,
+            candidate_strategy="union",
+            source_file="ticket_D2.md",
+        )
+        sources = {h["source_file"] for h in result["results"]}
+        assert sources <= {"ticket_D2.md"}, (
+            f"union must honor source_file on the BM25 pool; got {sources}"
+        )
+        # The BM25-strong brand-voice doc must NOT leak past the filter.
+        assert "brand_voice_D4.md" not in sources
+
 
 class TestHybridRankTolerantOfMissingDistance:
     """``_hybrid_rank`` accepts ``distance=None`` — required for BM25-only
diff --git a/tests/test_hybrid_search.py b/tests/test_hybrid_search.py
index a2672de..35aa579 100644
--- a/tests/test_hybrid_search.py
+++ b/tests/test_hybrid_search.py
@@ -133,3 +133,43 @@ class TestClosetMetadata:
             assert h["matched_via"] == "drawer"
             assert "closet_preview" not in h
             assert h["closet_boost"] == 0.0
+
+
+# ── source_file filter scopes both drawer and closet queries (#1815) ──────
+
+
+class TestSourceFileFilter:
+    def test_source_file_filter_excludes_other_sources(self, tmp_path):
+        palace = str(tmp_path / "palace")
+        _seed_drawers(palace)
+        result = search_memories(
+            "Kafka consumer rebalance timeout",
+            palace,
+            n_results=5,
+            source_file="fixture_D4.md",
+        )
+        ids = [h["source_file"] for h in result["results"]]
+        assert ids, "the matching source_file drawer should be returned"
+        assert set(ids) == {"fixture_D4.md"}
+
+    def test_source_file_filter_overrides_closet_boost_for_other_source(self, tmp_path):
+        # A strong closet pointing at D1 must NOT leak D1 in when the search
+        # is scoped to a different source_file — the where clause is applied
+        # to the closet query too, not just the drawer query.
+        palace = str(tmp_path / "palace")
+        _seed_drawers(palace)
+        _seed_strong_closet_for(
+            palace,
+            drawer_id="D1",
+            source_file="fixture_D1.md",
+            topics=["Kafka queue tuning", "consumer rebalance config"],
+        )
+        result = search_memories(
+            "Kafka consumer rebalance",
+            palace,
+            n_results=5,
+            source_file="fixture_D4.md",
+        )
+        ids = [h["source_file"] for h in result["results"]]
+        assert "fixture_D1.md" not in ids
+        assert set(ids) <= {"fixture_D4.md"}
diff --git a/tests/test_mcp_server.py b/tests/test_mcp_server.py
index 7e745a4..f232c88 100644
--- a/tests/test_mcp_server.py
+++ b/tests/test_mcp_server.py
@@ -1105,6 +1105,91 @@ class TestSearchTool:
         result = tool_search(query="database", room="backend")
         assert all(r["room"] == "backend" for r in result["results"])
 
+    def test_search_with_source_file_filter(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="authentication module", source_file="auth.py")
+        assert result["results"]
+        assert all(r["source_file"] == "auth.py" for r in result["results"])
+        assert result["filters"]["source_file"] == "auth.py"
+
+    def test_search_source_file_allows_path_separators(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        # Unlike wing/room, a source_file is a path — '/' must NOT be rejected
+        # as a path-traversal attempt the way sanitize_name() would.
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="authentication", source_file="/abs/path/to/auth.py")
+        assert "error" not in result
+
+    def test_search_blank_source_file_ignored(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="JWT authentication", source_file="   ")
+        assert "results" in result
+        assert result["filters"]["source_file"] is None
+
+    def test_search_rejects_null_byte_source_file(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        # A null byte in a metadata where-value can crash chromadb add/upsert
+        # (#1235 lineage); reject it cleanly the way sanitize_name does.
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="JWT", source_file="bad\x00null")
+        assert "error" in result
+
+    def test_search_rejects_overlong_source_file(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="JWT", source_file="x" * 5000)
+        assert "error" in result
+
+    def test_search_rejects_non_string_source_file(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        # A non-string source_file (e.g. a JSON number, which the schema's
+        # string type does not coerce) must yield a clean validation error,
+        # not an unhandled AttributeError from .strip().
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="JWT", source_file=42)
+        assert "error" in result
+
+    def test_search_rejects_lone_surrogate_source_file(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        # A lone UTF-16 surrogate can crash chromadb (#1235); reject it for
+        # parity with sanitize_name rather than letting it reach the backend.
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import tool_search
+
+        result = tool_search(query="JWT", source_file="bad\udc80surrogate")
+        assert "error" in result
+
+    def test_search_accepts_source_file_at_length_boundary(
+        self, monkeypatch, config, palace_path, seeded_collection, kg
+    ):
+        # Exactly _MAX_SOURCE_FILE_LENGTH is allowed (the cap is a strict '>').
+        _patch_mcp_server(monkeypatch, config, kg)
+        from mempalace.mcp_server import _MAX_SOURCE_FILE_LENGTH, tool_search
+
+        result = tool_search(query="JWT", source_file="x" * _MAX_SOURCE_FILE_LENGTH)
+        assert "error" not in result
+
     def test_search_min_similarity_backwards_compat(
         self, monkeypatch, config, palace_path, seeded_collection, kg
     ):
diff --git a/tests/test_searcher.py b/tests/test_searcher.py
index 236d5b9..c99ae65 100644
--- a/tests/test_searcher.py
+++ b/tests/test_searcher.py
@@ -9,7 +9,49 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
-from mempalace.searcher import SearchError, search, search_memories
+from mempalace.searcher import SearchError, build_where_filter, search, search_memories
+
+
+# ── build_where_filter (unit) ──────────────────────────────────────────
+
+
+class TestBuildWhereFilter:
+    """build_where_filter composes a ChromaDB where clause from optional
+    wing / room / source_file constraints (#1815). ChromaDB needs a ``$and``
+    only when ≥2 clauses are present; a single clause is returned bare and
+    zero clauses yield an empty filter."""
+
+    def test_no_filters_returns_empty(self):
+        assert build_where_filter() == {}
+
+    def test_wing_only(self):
+        assert build_where_filter(wing="backend") == {"wing": "backend"}
+
+    def test_room_only(self):
+        assert build_where_filter(room="auth") == {"room": "auth"}
+
+    def test_wing_and_room(self):
+        assert build_where_filter(wing="backend", room="auth") == {
+            "$and": [{"wing": "backend"}, {"room": "auth"}]
+        }
+
+    def test_source_file_only(self):
+        assert build_where_filter(source_file="auth.py") == {"source_file": "auth.py"}
+
+    def test_wing_and_source_file(self):
+        assert build_where_filter(wing="backend", source_file="auth.py") == {
+            "$and": [{"wing": "backend"}, {"source_file": "auth.py"}]
+        }
+
+    def test_room_and_source_file(self):
+        assert build_where_filter(room="auth", source_file="auth.py") == {
+            "$and": [{"room": "auth"}, {"source_file": "auth.py"}]
+        }
+
+    def test_wing_room_and_source_file(self):
+        assert build_where_filter(wing="backend", room="auth", source_file="auth.py") == {
+            "$and": [{"wing": "backend"}, {"room": "auth"}, {"source_file": "auth.py"}]
+        }
 
 
 # ── search_memories (API) ──────────────────────────────────────────────
@@ -34,6 +76,68 @@ class TestSearchMemories:
         result = search_memories("code", palace_path, wing="project", room="frontend")
         assert all(r["wing"] == "project" and r["room"] == "frontend" for r in result["results"])
 
+    def test_source_file_filter(self, palace_path, seeded_collection):
+        result = search_memories("authentication module", palace_path, source_file="auth.py")
+        assert result["results"], "exact source_file match should return its drawer"
+        assert all(r["source_file"] == "auth.py" for r in result["results"])
+
+    def test_source_file_with_wing_filter(self, palace_path, seeded_collection):
+        result = search_memories("database", palace_path, wing="project", source_file="db.py")
+        assert result["results"]
+        assert all(
+            r["source_file"] == "db.py" and r["wing"] == "project" for r in result["results"]
+        )
+
+    def test_nonmatching_source_file_returns_empty_not_error(self, palace_path, seeded_collection):
+        result = search_memories("authentication", palace_path, source_file="nope.md")
+        assert "error" not in result
+        assert result["results"] == []
+
+    def test_filters_envelope_includes_source_file(self, palace_path, seeded_collection):
+        result = search_memories("authentication", palace_path, source_file="auth.py")
+        assert result["filters"]["source_file"] == "auth.py"
+
+    def test_result_exposes_full_source_path(self, palace_path, seeded_collection):
+        # The displayed source_file is a basename; source_path carries the full
+        # stored value so a caller can round-trip it back into a source_file filter.
+        result = search_memories("authentication module", palace_path)
+        hit = result["results"][0]
+        assert hit["source_file"] == "auth.py"
+        assert hit["source_path"] == "auth.py"
+
+    def test_source_file_filter_matches_full_path_not_basename(self, palace_path):
+        from mempalace.palace import get_collection
+
+        col = get_collection(palace_path, create=True)
+        col.upsert(
+            ids=["fp1"],
+            documents=["The deploy script restarts the gunicorn workers nightly."],
+            metadatas=[{"wing": "ops", "room": "deploy", "source_file": "/srv/app/deploy.sh"}],
+        )
+        # The full stored path matches and round-trips via source_path.
+        hit = search_memories(
+            "deploy gunicorn workers", palace_path, source_file="/srv/app/deploy.sh"
+        )
+        assert [h["source_path"] for h in hit["results"]] == ["/srv/app/deploy.sh"]
+        assert [h["source_file"] for h in hit["results"]] == ["deploy.sh"]
+        # The basename does NOT match — exact full-path semantics only (issue v1).
+        miss = search_memories("deploy gunicorn workers", palace_path, source_file="deploy.sh")
+        assert miss["results"] == []
+
+    def test_source_file_filter_honored_in_bm25_fallback(self, palace_path, seeded_collection):
+        # vector_disabled routes through _bm25_only_via_sqlite (#1222); the
+        # source_file filter must hold there too, not silently no-op.
+        result = search_memories(
+            "authentication module",
+            palace_path,
+            source_file="auth.py",
+            vector_disabled=True,
+            collection_name="mempalace_drawers",
+        )
+        assert "error" not in result
+        assert result["results"], "BM25 fallback should still find the auth drawer"
+        assert all(r["source_file"] == "auth.py" for r in result["results"])
+
     def test_n_results_limit(self, palace_path, seeded_collection):
         result = search_memories("code", palace_path, n_results=2)
         assert len(result["results"]) <= 2