diff --git a/shelfmark/core/author_match.py b/shelfmark/core/author_match.py
index d8e82153..ceac8796 100644
--- a/shelfmark/core/author_match.py
+++ b/shelfmark/core/author_match.py
@@ -15,8 +15,9 @@ _AUTHOR_NOISE_TOKENS = frozenset(
 # Ordering tiers for author agreement between the requested book and what an
 # indexer reported. Lower sorts first.
 AUTHOR_MATCH = 0
-AUTHOR_UNKNOWN = 1
-AUTHOR_MISMATCH = 2
+AUTHOR_PARTIAL = 1
+AUTHOR_UNKNOWN = 2
+AUTHOR_MISMATCH = 3
 
 # A mononym ("Homer") can only ever agree on one token; a longer name needs a
 # given name and a surname to agree before it counts as the same person.
@@ -45,9 +46,15 @@ def author_affinity(wanted: object, offered: object) -> int:
     agree, while a transliteration ("Dostoevsky"/"Dostoyevsky") is merely sorted
     last instead of being hidden.
 
-    Three-way on purpose: an indexer that reports no author at all must not sort
-    below one that reports a wrong author, so "no metadata" ranks between
-    agreement and disagreement rather than counting as either.
+    Graded, not binary, because the ways of falling short are not equally bad.
+    An indexer that reports no author at all must not sort below one that reports
+    a wrong author, so "no metadata" ranks between agreement and disagreement. And
+    a name that merely says *less* than the one asked for is not evidence of a
+    different person: "Petrie" contradicts nothing about "David Petrie", while
+    "Gordon Petrie" does. That gap matters most where a source is searched by
+    surname alone (#1331) - the filenames such a search is meant to reach are
+    exactly the ones filed under a bare surname, and ranking them as wrong put
+    them below every result that named someone else entirely.
     """
     wanted_tokens = _author_tokens(wanted)
     offered_tokens = _author_tokens(offered)
@@ -63,7 +70,22 @@ def author_affinity(wanted: object, offered: object) -> int:
         )
     )
     required = min(_AUTHOR_TOKENS_REQUIRED, len(wanted_tokens))
-    return AUTHOR_MATCH if matched >= required else AUTHOR_MISMATCH
+    if matched >= required:
+        return AUTHOR_MATCH
+
+    # Too little agreement to call it the same person, so the question is whether
+    # what was offered *disagrees*. A name every token of which fits the wanted
+    # name is an abbreviation of it; one carrying a token that fits nothing is a
+    # different name that happens to share a surname.
+    if all(
+        any(
+            _author_tokens_compatible(wanted_token, offered_token) for wanted_token in wanted_tokens
+        )
+        for offered_token in offered_tokens
+    ):
+        return AUTHOR_PARTIAL
+
+    return AUTHOR_MISMATCH
 
 
 def search_surname(author: object) -> str:
diff --git a/shelfmark/release_sources/irc/source.py b/shelfmark/release_sources/irc/source.py
index 3820eee3..571b7354 100644
--- a/shelfmark/release_sources/irc/source.py
+++ b/shelfmark/release_sources/irc/source.py
@@ -419,9 +419,16 @@ class IRCReleaseSource(ReleaseSource):
         carries `author=""` on purpose (search_plan.py:246), and so does a manual
         query, so reading `plan.author` here would append a surname to searches
         that deliberately have none.
+
+        Returns "" without a title, so the caller reports "no query" rather than
+        posting one. A surname on its own is not a search: `@search Petrie` asks
+        the bot for every Petrie on the channel, and a bare over-broad line is the
+        kind of post `is_available` refuses queries to avoid being banned for.
         """
         variant = plan.title_variants[0] if plan.title_variants else None
         title = variant.title if variant else (book.search_title or book.title)
+        if not title:
+            return ""
         author = variant.author if variant else plan.author
         parts = [part for part in (title, search_surname(author)) if part]
         return " ".join(parts)
diff --git a/tests/irc/test_search_query.py b/tests/irc/test_search_query.py
index 8021a371..4a1458f8 100644
--- a/tests/irc/test_search_query.py
+++ b/tests/irc/test_search_query.py
@@ -89,6 +89,17 @@ class TestQueryPostedToChannel:
 
         assert IRCReleaseSource()._build_query(book, build_release_search_plan(book)) == "Beowulf"
 
+    def test_a_book_with_no_title_is_not_searched_by_surname_alone(self):
+        # "@search Petrie" asks the bot for every Petrie it holds. It is not a
+        # search for anything, and a bare over-broad line posted to a public
+        # channel is what gets the nick banned - so no query is built at all.
+        book = BookMetadata(provider="hardcover", provider_id="1", title="", authors=["D. Petrie"])
+        plan = build_release_search_plan(book)
+
+        assert plan.title_variants == []
+        assert plan.author == "D. Petrie"
+        assert IRCReleaseSource()._build_query(book, plan) == ""
+
 
 class TestAuthorOrdersTheAnswer:
     def test_requested_author_leads_and_the_rest_stay_visible(self):
@@ -99,6 +110,10 @@ class TestAuthorOrdersTheAnswer:
             # What the parser writes when a filename has no " - " separator; it
             # must not sort below a result that named a different author.
             _release("Unknown"),
+            # The shape the surname query exists to reach: the channel filed this
+            # under the surname alone, so it agrees with everything known about
+            # "David Petrie" and contradicts none of it.
+            _release("Petrie"),
             _release("D Petrie"),
         ]
 
@@ -106,6 +121,7 @@ class TestAuthorOrdersTheAnswer:
 
         assert [release.extra["author"] for release in ranked] == [
             "D Petrie",
+            "Petrie",
             "Unknown",
             "Gordon Petrie",
         ]
diff --git a/tests/prowlarr/test_author_matching.py b/tests/prowlarr/test_author_matching.py
index d782a4e9..adb6523b 100644
--- a/tests/prowlarr/test_author_matching.py
+++ b/tests/prowlarr/test_author_matching.py
@@ -11,6 +11,7 @@ import pytest
 from shelfmark.core.author_match import (
     AUTHOR_MATCH,
     AUTHOR_MISMATCH,
+    AUTHOR_PARTIAL,
     AUTHOR_UNKNOWN,
     author_affinity,
 )
@@ -62,12 +63,33 @@ class TestAuthorAffinity:
         # An indexer that reports no author must not sort below one that reports
         # the wrong author, so this tier sits between the two.
         assert author_affinity(wanted, offered) == AUTHOR_UNKNOWN
-        assert AUTHOR_MATCH < AUTHOR_UNKNOWN < AUTHOR_MISMATCH
+        assert AUTHOR_MATCH < AUTHOR_PARTIAL < AUTHOR_UNKNOWN < AUTHOR_MISMATCH
 
-    def test_a_surname_alone_is_not_enough_for_a_full_name(self):
-        # "Ferriss" appearing under some other given name is a different person.
+    def test_another_given_name_under_the_same_surname_is_a_different_person(self):
         assert author_affinity("Timothy Ferriss", "Bruce Ferriss") == AUTHOR_MISMATCH
 
+    @pytest.mark.parametrize(
+        ("wanted", "offered"),
+        [
+            ("Timothy Ferriss", "Ferriss"),
+            ("David Petrie", "Petrie"),
+            ("Ursula K. Le Guin", "Guin"),
+            ("Timothy Ferriss", "T."),
+        ],
+    )
+    def test_a_name_that_says_less_is_not_a_name_that_disagrees(self, wanted, offered):
+        # Every token offered fits the name asked for; there is just not enough of
+        # it to confirm the person. Weaker evidence than full agreement, stronger
+        # than none - and far from the wrong-author tier these used to land in,
+        # which is where a surname-only search put most of its own answer (#1331).
+        assert author_affinity(wanted, offered) == AUTHOR_PARTIAL
+        assert AUTHOR_MATCH < AUTHOR_PARTIAL < AUTHOR_UNKNOWN < AUTHOR_MISMATCH
+
+    def test_a_mononym_still_agrees_with_a_longer_name_that_contains_it(self):
+        # The one-token requirement for a mononym is unchanged: the extra token
+        # must not turn an agreement into a partial.
+        assert author_affinity("Homer", "Homer Simpson") == AUTHOR_MATCH
+
 
 class _EnrichedIndexerClient:
     """Stands in for a Prowlarr with MyAnonamouse enabled."""