diff --git a/tests/test_closets.py b/tests/test_closets.py
new file mode 100644
index 0000000..b365102
--- /dev/null
+++ b/tests/test_closets.py
@@ -0,0 +1,201 @@
+"""Tests for the closet layer, mine_lock, entity metadata, BM25 hybrid search,
+and diary ingest.
+
+Content derived from Milla's omnibus test file; trimmed to only the features
+present in this PR stack (#784 lock, #788 closets, this PR's entity/BM25/diary).
+Strip-noise tests live with #785; tunnel tests live with the tunnels PR.
+"""
+
+import os
+import tempfile
+import threading
+import time
+
+from mempalace.palace import (
+    CLOSET_CHAR_LIMIT,
+    build_closet_lines,
+    get_closets_collection,
+    get_collection,
+    mine_lock,
+    upsert_closet_lines,
+)
+from mempalace.miner import _extract_entities_for_metadata
+from mempalace.searcher import _bm25_score, _hybrid_rank
+
+
+# ── mine_lock ────────────────────────────────────────────────────────────
+
+
+class TestMineLock:
+    def test_lock_acquires_and_releases(self):
+        with mine_lock("/tmp/test_lock_file.txt"):
+            lock_dir = os.path.expanduser("~/.mempalace/locks")
+            assert os.path.isdir(lock_dir)
+
+    def test_lock_blocks_concurrent_access(self):
+        results = []
+
+        def worker(name):
+            start = time.time()
+            with mine_lock("/tmp/same_file_lock_test.txt"):
+                results.append((name, time.time() - start))
+                time.sleep(0.2)
+
+        t1 = threading.Thread(target=worker, args=("a",))
+        t2 = threading.Thread(target=worker, args=("b",))
+        t1.start()
+        time.sleep(0.05)
+        t2.start()
+        t1.join()
+        t2.join()
+
+        # Second thread should have waited
+        wait_times = sorted(results, key=lambda x: x[1])
+        assert wait_times[1][1] > 0.1, "Second thread should block"
+
+
+# ── closet lines ─────────────────────────────────────────────────────────
+
+
+class TestBuildClosetLines:
+    def test_returns_list_of_lines(self):
+        lines = build_closet_lines(
+            "/tmp/test.py", ["drawer_001"], "We built the auth system", "code", "general"
+        )
+        assert isinstance(lines, list)
+        assert len(lines) >= 1
+
+    def test_each_line_has_pointer(self):
+        lines = build_closet_lines(
+            "/tmp/test.py",
+            ["drawer_001", "drawer_002"],
+            "We built the auth system and tested the login flow",
+            "code",
+            "general",
+        )
+        for line in lines:
+            assert "→" in line, f"Line missing pointer: {line}"
+
+    def test_fallback_when_no_topics(self):
+        lines = build_closet_lines(
+            "/tmp/test.py", ["drawer_001"], "short text", "wing", "room"
+        )
+        assert len(lines) >= 1
+        assert "→" in lines[0]
+
+
+# ── upsert_closet_lines ─────────────────────────────────────────────────
+
+
+class TestUpsertClosetLines:
+    def test_writes_closets(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            col = get_closets_collection(tmpdir)
+            lines = [
+                "topic one|Entity1|→drawer_001",
+                "topic two|Entity2|→drawer_002",
+            ]
+            n = upsert_closet_lines(col, "test_closet", lines, {"wing": "test"})
+            assert n >= 1
+            assert col.count() >= 1
+
+    def test_never_splits_mid_topic(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            col = get_closets_collection(tmpdir)
+            # Create lines that together exceed CLOSET_CHAR_LIMIT
+            lines = [f"topic_{i}|{'x' * 200}|→drawer_{i}" for i in range(20)]
+            n = upsert_closet_lines(col, "test_closet", lines, {"wing": "test"})
+            assert n >= 2, "Should create multiple closets"
+
+            # Verify each closet has complete lines
+            all_data = col.get(include=["documents"])
+            for doc in all_data["documents"]:
+                for line in doc.strip().split("\n"):
+                    assert "→" in line, f"Split topic found: {line}"
+
+    def test_respects_char_limit(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            col = get_closets_collection(tmpdir)
+            lines = [f"topic_{i}|entities|→drawer_{i}" for i in range(50)]
+            upsert_closet_lines(col, "test_closet", lines, {"wing": "test"})
+
+            all_data = col.get(include=["documents"])
+            for doc in all_data["documents"]:
+                assert len(doc) <= CLOSET_CHAR_LIMIT + 100  # small buffer for existing content
+
+
+# ── entity metadata ──────────────────────────────────────────────────────
+
+
+class TestEntityMetadata:
+    def test_extracts_capitalized_names(self):
+        text = "Ben reviewed the code. Ben approved it. Igor flagged two issues. Igor fixed them."
+        entities = _extract_entities_for_metadata(text)
+        assert "Ben" in entities
+        assert "Igor" in entities
+
+    def test_empty_for_no_entities(self):
+        text = "this is all lowercase with no proper nouns at all"
+        entities = _extract_entities_for_metadata(text)
+        assert entities == ""
+
+    def test_semicolon_separated(self):
+        text = "Alice and Bob met Charlie. Alice said hello. Bob agreed. Charlie laughed."
+        entities = _extract_entities_for_metadata(text)
+        assert ";" in entities
+
+
+# ── BM25 hybrid search ──────────────────────────────────────────────────
+
+
+class TestBM25:
+    def test_bm25_score_positive_for_match(self):
+        score = _bm25_score("database migration", "We migrated the database to Postgres")
+        assert score > 0
+
+    def test_bm25_score_zero_for_no_match(self):
+        score = _bm25_score("quantum physics", "We built a web application in React")
+        assert score == 0.0
+
+    def test_hybrid_rank_reorders(self):
+        results = [
+            {"text": "database schema design for Postgres", "distance": 0.5},
+            {"text": "unrelated topic about cooking", "distance": 0.3},
+        ]
+        ranked = _hybrid_rank(results, "database Postgres schema")
+        # The database result should rank higher despite worse vector distance
+        assert "database" in ranked[0]["text"]
+
+
+# ── diary ingest ─────────────────────────────────────────────────────────
+
+
+class TestDiaryIngest:
+    def test_ingest_creates_drawers_and_closets(self):
+        with tempfile.TemporaryDirectory() as palace_dir:
+            diary_dir = tempfile.mkdtemp()
+            # Write a test diary
+            with open(os.path.join(diary_dir, "2026-04-13.md"), "w") as f:
+                f.write("# 2026-04-13\n\n## 10:00 PDT — Test\n\nBuilt the auth system.\n")
+
+            from mempalace.diary_ingest import ingest_diaries
+
+            result = ingest_diaries(diary_dir, palace_dir, force=True)
+            assert result["days_updated"] >= 1
+
+            # Check drawer exists
+            drawers = get_collection(palace_dir)
+            count = drawers.count()
+            assert count >= 1
+
+    def test_ingest_skips_unchanged(self):
+        with tempfile.TemporaryDirectory() as palace_dir:
+            diary_dir = tempfile.mkdtemp()
+            with open(os.path.join(diary_dir, "2026-04-13.md"), "w") as f:
+                f.write("# 2026-04-13\n\n## 10:00 — Test\n\nContent.\n")
+
+            from mempalace.diary_ingest import ingest_diaries
+
+            ingest_diaries(diary_dir, palace_dir, force=True)
+            result = ingest_diaries(diary_dir, palace_dir)  # second run, no force
+            assert result["days_updated"] == 0