diff --git a/mempalace/cli.py b/mempalace/cli.py
index 1181120..714c64c 100644
--- a/mempalace/cli.py
+++ b/mempalace/cli.py
@@ -120,12 +120,19 @@ def cmd_init(args):
     total = len(detected["people"]) + len(detected["projects"]) + len(detected["uncertain"])
     if total > 0:
         confirmed = confirm_entities(detected, yes=getattr(args, "yes", False))
-        # Save confirmed entities to <project>/entities.json for the miner
+        # Save confirmed entities to <project>/entities.json (per-project
+        # audit trail — user can inspect or hand-edit) AND merge into the
+        # global registry the miner reads at mine time.
         if confirmed["people"] or confirmed["projects"]:
             entities_path = Path(args.dir).expanduser().resolve() / "entities.json"
-            with open(entities_path, "w") as f:
-                json.dump(confirmed, f, indent=2)
+            with open(entities_path, "w", encoding="utf-8") as f:
+                json.dump(confirmed, f, indent=2, ensure_ascii=False)
             print(f"  Entities saved: {entities_path}")
+
+            from .miner import add_to_known_entities
+
+            registry_path = add_to_known_entities(confirmed)
+            print(f"  Registry updated: {registry_path}")
     else:
         print("  No entities detected — proceeding with directory-based rooms.")
 
diff --git a/mempalace/miner.py b/mempalace/miner.py
index c837d4d..9e8ff5e 100644
--- a/mempalace/miner.py
+++ b/mempalace/miner.py
@@ -472,6 +472,97 @@ def _load_known_entities_raw() -> dict:
     return dict(_ENTITY_REGISTRY_CACHE["raw"])
 
 
+def add_to_known_entities(entities_by_category: dict) -> str:
+    """Union ``entities_by_category`` into ``~/.mempalace/known_entities.json``.
+
+    Accepts ``{category: [names]}`` shape as produced by ``mempalace init``
+    and merges into the registry the miner reads at mine time. Existing
+    categories are preserved untouched unless also present in the input;
+    for categories present in both, entries are unioned case-insensitively
+    without changing the on-disk ordering of pre-existing names.
+
+    If a category is stored on-disk as ``{name: code}`` (the alternate
+    miner-supported shape, used by dialect-style configs), new names are
+    added as keys with ``None`` values so existing code mappings aren't
+    overwritten. A later compress pass can assign codes.
+
+    The in-process cache is invalidated on write so same-process callers
+    (notably ``cmd_init`` → ``cmd_mine`` in sequence) see the update
+    immediately instead of waiting for a mtime re-check.
+
+    Returns the registry path as a string for logging.
+    """
+    import json as _json
+    from pathlib import Path as _Path
+
+    registry_path = _Path(_ENTITY_REGISTRY_PATH)
+    registry_path.parent.mkdir(parents=True, exist_ok=True)
+
+    existing: dict = {}
+    if registry_path.exists():
+        try:
+            loaded = _json.loads(registry_path.read_text(encoding="utf-8"))
+            if isinstance(loaded, dict):
+                existing = loaded
+        except (_json.JSONDecodeError, OSError):
+            existing = {}
+
+    def _coerce_name(value):
+        if not value:
+            return None
+        name = str(value)
+        return name if name else None
+
+    for category, names in entities_by_category.items():
+        if not isinstance(names, list) or not names:
+            continue
+        current = existing.get(category)
+        if isinstance(current, list):
+            seen_lower = {str(n).lower() for n in current}
+            for n in names:
+                name = _coerce_name(n)
+                if not name:
+                    continue
+                if name.lower() not in seen_lower:
+                    current.append(name)
+                    seen_lower.add(name.lower())
+        elif isinstance(current, dict):
+            seen_lower = {str(name).lower() for name in current}
+            for n in names:
+                name = _coerce_name(n)
+                if not name or name.lower() in seen_lower:
+                    continue
+                current[name] = None
+                seen_lower.add(name.lower())
+        else:
+            # Missing or unrecognized shape — seed as a fresh list, deduped
+            seen: set = set()
+            ordered: list = []
+            for n in names:
+                name = _coerce_name(n)
+                if not name:
+                    continue
+                key = name.lower()
+                if key in seen:
+                    continue
+                seen.add(key)
+                ordered.append(name)
+            existing[category] = ordered
+
+    registry_path.write_text(_json.dumps(existing, indent=2, ensure_ascii=False), encoding="utf-8")
+    try:
+        registry_path.chmod(0o600)
+    except (OSError, NotImplementedError):
+        pass
+
+    # Invalidate in-process cache so later calls in the same run see the write.
+    _ENTITY_REGISTRY_CACHE["mtime"] = None
+    _ENTITY_REGISTRY_CACHE["names"] = frozenset()
+    _ENTITY_REGISTRY_CACHE["raw"] = {}
+
+    return str(registry_path)
+
+
 _HALL_KEYWORDS_CACHE = None
 
 
diff --git a/tests/test_known_entities_registry.py b/tests/test_known_entities_registry.py
new file mode 100644
index 0000000..300cfb6
--- /dev/null
+++ b/tests/test_known_entities_registry.py
@@ -0,0 +1,208 @@
+"""Tests for mempalace.miner.add_to_known_entities.
+
+Covers the init → miner wire-up: init's confirmed entities merged into
+``~/.mempalace/known_entities.json`` so the miner's drawer-tagging path
+recognizes them at mine time.
+
+Every test redirects the registry path to a tmp_path to avoid touching
+the real ~/.mempalace/ on the developer's machine.
+"""
+
+import json
+
+import pytest
+
+from mempalace import miner
+
+
+@pytest.fixture
+def temp_registry(tmp_path, monkeypatch):
+    """Redirect the module-level registry path to a tmp file and reset cache."""
+    registry = tmp_path / "known_entities.json"
+    monkeypatch.setattr(miner, "_ENTITY_REGISTRY_PATH", str(registry))
+    miner._ENTITY_REGISTRY_CACHE.update({"mtime": None, "names": frozenset(), "raw": {}})
+    return registry
+
+
+# ── fresh-file cases ────────────────────────────────────────────────────
+
+
+def test_creates_registry_when_absent(temp_registry):
+    assert not temp_registry.exists()
+    miner.add_to_known_entities({"people": ["Alice", "Bob"], "projects": ["foo"]})
+    assert temp_registry.exists()
+    data = json.loads(temp_registry.read_text())
+    assert sorted(data["people"]) == ["Alice", "Bob"]
+    assert data["projects"] == ["foo"]
+
+
+def test_returns_registry_path(temp_registry):
+    result = miner.add_to_known_entities({"people": ["Alice"]})
+    assert result == str(temp_registry)
+
+
+def test_empty_input_still_creates_file(temp_registry):
+    """A no-op merge still touches the file (idempotent), but no entries added."""
+    miner.add_to_known_entities({})
+    # File may or may not be written for a truly empty call — tolerate either.
+    if temp_registry.exists():
+        data = json.loads(temp_registry.read_text())
+        assert data == {} or all(not v for v in data.values())
+
+
+def test_skips_empty_name_strings(temp_registry):
+    miner.add_to_known_entities({"people": ["Alice", "", None]})
+    data = json.loads(temp_registry.read_text())
+    assert data["people"] == ["Alice"]
+
+
+# ── union / dedup cases ────────────────────────────────────────────────
+
+
+def test_unions_with_existing_list_category(temp_registry):
+    temp_registry.write_text(json.dumps({"people": ["Alice", "Bob"]}))
+    miner.add_to_known_entities({"people": ["Bob", "Carol"]})
+    data = json.loads(temp_registry.read_text())
+    # Bob not duplicated, Carol appended, original order preserved
+    assert data["people"] == ["Alice", "Bob", "Carol"]
+
+
+def test_case_insensitive_dedup_preserves_first_seen_variant(temp_registry):
+    temp_registry.write_text(json.dumps({"people": ["Alice"]}))
+    miner.add_to_known_entities({"people": ["alice", "ALICE", "Bob"]})
+    data = json.loads(temp_registry.read_text())
+    # Alice stays as-is; lowercase/uppercase variants don't create new entries
+    assert data["people"] == ["Alice", "Bob"]
+
+
+def test_preserves_untouched_categories(temp_registry):
+    """A category the caller didn't mention must be left alone."""
+    temp_registry.write_text(json.dumps({"people": ["Alice"], "places": ["Paris", "Tokyo"]}))
+    miner.add_to_known_entities({"people": ["Bob"]})
+    data = json.loads(temp_registry.read_text())
+    assert data["places"] == ["Paris", "Tokyo"]
+    assert data["people"] == ["Alice", "Bob"]
+
+
+def test_adds_new_categories(temp_registry):
+    temp_registry.write_text(json.dumps({"people": ["Alice"]}))
+    miner.add_to_known_entities({"projects": ["foo", "bar"]})
+    data = json.loads(temp_registry.read_text())
+    assert data["people"] == ["Alice"]
+    assert data["projects"] == ["foo", "bar"]
+
+
+def test_dedupes_within_input(temp_registry):
+    miner.add_to_known_entities({"people": ["Alice", "alice", "Alice"]})
+    data = json.loads(temp_registry.read_text())
+    assert data["people"] == ["Alice"]
+
+
+# ── dict-format existing registry ──────────────────────────────────────
+
+
+def test_dict_format_existing_category_gets_new_keys(temp_registry):
+    """Miner supports {name: code} dict categories (alternate registry shape).
+    New names are added as keys without overwriting existing codes."""
+    temp_registry.write_text(json.dumps({"people": {"Alice": "ALC", "Bob": "BOB"}}))
+    miner.add_to_known_entities({"people": ["Alice", "Carol"]})
+    data = json.loads(temp_registry.read_text())
+    # Alice's code survives; Carol added with None; Bob untouched
+    assert data["people"]["Alice"] == "ALC"
+    assert data["people"]["Bob"] == "BOB"
+    assert "Carol" in data["people"]
+    assert data["people"]["Carol"] is None
+
+
+def test_dict_format_dedupes_case_insensitively_and_stringifies_new_names(temp_registry):
+    temp_registry.write_text(json.dumps({"people": {"Alice": "ALC"}}))
+    miner.add_to_known_entities({"people": ["alice", 123]})
+    data = json.loads(temp_registry.read_text())
+    assert data["people"] == {"Alice": "ALC", "123": None}
+
+
+# ── error tolerance ───────────────────────────────────────────────────
+
+
+def test_malformed_existing_registry_starts_fresh(temp_registry):
+    temp_registry.write_text("{ not valid json")
+    miner.add_to_known_entities({"people": ["Alice"]})
+    data = json.loads(temp_registry.read_text())
+    assert data == {"people": ["Alice"]}
+
+
+def test_non_dict_existing_registry_starts_fresh(temp_registry):
+    temp_registry.write_text(json.dumps(["unexpected", "array"]))
+    miner.add_to_known_entities({"people": ["Alice"]})
+    data = json.loads(temp_registry.read_text())
+    assert data == {"people": ["Alice"]}
+
+
+def test_non_list_input_category_ignored(temp_registry):
+    miner.add_to_known_entities({"people": ["Alice"], "weird": "not a list"})
+    data = json.loads(temp_registry.read_text())
+    assert "weird" not in data or data.get("weird") == "not a list"
+    assert data["people"] == ["Alice"]
+
+
+# ── cache invalidation ───────────────────────────────────────────────
+
+
+def test_cache_invalidated_so_subsequent_load_sees_write(temp_registry):
+    """cmd_init → cmd_mine runs in the same process; the load path must
+    see what init just wrote without a process restart."""
+    # Prime the cache with an empty state
+    miner._load_known_entities()
+    assert miner._load_known_entities() == frozenset()
+
+    miner.add_to_known_entities({"people": ["Alice", "Bob"], "projects": ["foo"]})
+
+    loaded = miner._load_known_entities()
+    assert "Alice" in loaded
+    assert "Bob" in loaded
+    assert "foo" in loaded
+
+
+def test_raw_view_reflects_write(temp_registry):
+    miner.add_to_known_entities({"people": ["Alice"]})
+    raw = miner._load_known_entities_raw()
+    assert raw.get("people") == ["Alice"]
+
+
+# ── Unicode round-trip ────────────────────────────────────────────────
+
+
+def test_unicode_names_written_literally_not_escaped(temp_registry):
+    """`ensure_ascii=False` so non-ASCII names stay readable on disk."""
+    miner.add_to_known_entities({"people": ["Gergő Móricz", "Arturo Domínguez"]})
+    raw_text = temp_registry.read_text(encoding="utf-8")
+    assert "Gergő" in raw_text
+    assert "Móricz" in raw_text
+    # Round-trips through JSON
+    data = json.loads(raw_text)
+    assert "Gergő Móricz" in data["people"]
+
+
+# ── end-to-end: does the write actually help _extract_entities_for_metadata? ──
+
+
+def test_populated_registry_improves_miner_recall(temp_registry):
+    """The whole point of the wire-up: names written via add_to_known_entities
+    must be recognized by the miner's entity-extraction metadata pass."""
+    miner.add_to_known_entities(
+        {
+            "people": ["Julia Grib", "Kevin Heifner"],
+            "projects": ["hyperion-history", "mempalace"],
+        }
+    )
+
+    sample = (
+        "Met with Julia Grib yesterday about the mempalace release. "
+        "Kevin Heifner pushed the hyperion-history fix."
+    )
+    result = miner._extract_entities_for_metadata(sample)
+    tagged = set(result.split(";")) if result else set()
+
+    # All four registered entities should land in the metadata string
+    for expected in ("Julia Grib", "Kevin Heifner", "hyperion-history", "mempalace"):
+        assert expected in tagged, f"expected '{expected}' in metadata {tagged!r}"