diff --git a/src/cli/llm.py b/src/cli/llm.py
index 6585fe6..3125428 100644
--- a/src/cli/llm.py
+++ b/src/cli/llm.py
@@ -26,7 +26,7 @@ def _refs_for(
     zotero = ZoteroPdfIndex.lazy(
         path("db.zotero"), path("storage.zotero"), ROOT / ".state" / "llm"
     )
-    return iter_corpus_refs(store, zotero=zotero)
+    return iter_corpus_refs(store, keys=keys, zotero=zotero)
 
 
 @app.command()
@@ -35,7 +35,9 @@ def index(
         "comments", help="Which collection: comments | rules | corpus | all."
     ),
     docket: str = typer.Option("", help="Limit comments to one docket id."),
-    key: list[str] = typer.Option([], "--key", help="Limit rules to these item keys."),
+    key: list[str] = typer.Option(
+        [], "--key", help="Limit rules/corpus to these item keys."
+    ),
     force: bool = typer.Option(False, help="Re-embed even when unchanged."),
     limit: int = typer.Option(0, help="Stop after N docs per collection (0 = all)."),
 ) -> None:
diff --git a/src/llm/source.py b/src/llm/source.py
index e5a96f1..532c397 100644
--- a/src/llm/source.py
+++ b/src/llm/source.py
@@ -493,7 +493,11 @@ def _attachment_sections(
 
 
 def iter_corpus_refs(
-    store: Store, *, tag: str = "", zotero: "ZoteroPdfIndex | None" = None
+    store: Store,
+    *,
+    tag: str = "",
+    keys: tuple[str, ...] = (),
+    zotero: "ZoteroPdfIndex | None" = None,
 ) -> Iterator[DocRef]:
     """One DocRef per non-comment, non-skipped item. Fingerprint =
     updated_at + the bib attachment file stats; the Zotero fallback is
@@ -502,7 +506,12 @@ def iter_corpus_refs(
     Items tagged ``llm:skip`` are excluded — a generic opt-out for
     material that should not be embedded (e.g. a scratch export, or a
     duplicate scan of something already in the corpus). It's never
-    applied automatically; a caller opts an item in by tagging it."""
+    applied automatically; a caller opts an item in by tagging it.
+
+    *keys*, when given, limits the yield to those item keys (same
+    Python-side post-filter ``iter_rule_refs`` uses for its own
+    ``keys`` — the corpus scan is cheap enough that this doesn't need
+    to be pushed into the SQL)."""
     sql = (
         "SELECT i.key, COALESCE(i.updated_at,'') AS updated_at FROM items i "
         "WHERE i.id NOT IN (SELECT item_id FROM item_tags WHERE tag_id IN "
@@ -517,6 +526,8 @@ def iter_corpus_refs(
     )
     for row in store._con().execute(sql, (tag,) if tag else ()).fetchall():
         key = row["key"]
+        if keys and key not in keys:
+            continue
         fp = row["updated_at"] + "|" + fingerprint_files(_attachment_paths(store, key))
 
         def _load(key=key) -> Doc | None:
diff --git a/tests/cli/test_llm_exercise.py b/tests/cli/test_llm_exercise.py
index 50b48f6..a0e5c9e 100644
--- a/tests/cli/test_llm_exercise.py
+++ b/tests/cli/test_llm_exercise.py
@@ -96,11 +96,58 @@ class TestIndexCorpus:
         result = runner.invoke(app, ["index", "--collection", "corpus"])
 
         assert result.exit_code == 0, result.output
-        mock_iter.assert_called_once_with(store, zotero=zot)
+        mock_iter.assert_called_once_with(store, keys=(), zotero=zot)
         kwargs = mock_index_refs.call_args.kwargs
         assert kwargs["collection"] == "corpus"
         assert "corpus: indexed=3 skipped=1 chunks=7" in result.output
 
+    @patch("llm.index.docket_complete", return_value={})
+    @patch("llm.index._engine")
+    @patch("llm.source.ZoteroPdfIndex.lazy")
+    @patch("llm.source.iter_corpus_refs")
+    @patch("llm.pool.HostPool.from_config")
+    @patch("llm.index.index_refs")
+    @patch("conf.connect.bib")
+    @patch("llm.config.load")
+    def test_key_option_limits_corpus_to_those_items(
+        self,
+        mock_load,
+        mock_bib,
+        mock_index_refs,
+        mock_from_config,
+        mock_iter,
+        mock_lazy,
+        _engine,
+        _complete,
+    ):
+        mock_load.return_value = MagicMock()
+        store = MagicMock()
+        store.sealed_dockets.return_value = {}
+        mock_bib.return_value = store
+        mock_iter.return_value = iter(["doc1"])
+        mock_from_config.return_value = MagicMock()
+        mock_index_refs.return_value = _STATS
+        zot = MagicMock()
+        mock_lazy.return_value = zot
+
+        result = runner.invoke(
+            app,
+            [
+                "index",
+                "--collection",
+                "corpus",
+                "--key",
+                "GQGTPGYV",
+                "--key",
+                "T6H4ZPEQ",
+            ],
+        )
+
+        assert result.exit_code == 0, result.output
+        mock_iter.assert_called_once_with(
+            store, keys=("GQGTPGYV", "T6H4ZPEQ"), zotero=zot
+        )
+
 
 class TestIndexAll:
     @patch("llm.index.docket_complete", return_value={})
diff --git a/tests/llm/test_source_refs.py b/tests/llm/test_source_refs.py
index 4c14982..1ac4d68 100644
--- a/tests/llm/test_source_refs.py
+++ b/tests/llm/test_source_refs.py
@@ -188,6 +188,17 @@ class TestCorpusRefs:
         store.create(Item(item_type="report", title="U", abstract="Body."))
         assert [r.key for r in iter_corpus_refs(store, tag="project:pfs")] == [tagged]
 
+    def test_keys_filter_selects_only_named_items(self, store):
+        wanted = store.create(Item(item_type="source", title="CPT 2024", abstract="."))
+        store.create(Item(item_type="source", title="Other book", abstract="."))
+        refs = list(iter_corpus_refs(store, keys=(wanted,)))
+        assert [r.key for r in refs] == [wanted]
+
+    def test_keys_empty_tuple_yields_every_item(self, store):
+        a = store.create(Item(item_type="source", title="A", abstract="."))
+        b = store.create(Item(item_type="source", title="B", abstract="."))
+        assert {r.key for r in iter_corpus_refs(store, keys=())} == {a, b}
+
 
 class TestLazyZotero:
     def test_no_copy_until_first_lookup(self, tmp_path):