diff --git a/arborist/qa/_text_norm.py b/arborist/qa/_text_norm.py
index 9ec56a2..829648f 100644
--- a/arborist/qa/_text_norm.py
+++ b/arborist/qa/_text_norm.py
@@ -82,3 +82,23 @@ def tokenize_text(text: str) -> list[str]:
             continue
         out.append(t)
     return out
+
+
+def stem_for_match(t: str) -> str:
+    """Light suffix-strip for query-token vs title/body matching.
+
+    Two normalizations rolled into one trailing-s strip:
+      - possessive  "superman's" → "supermans" → "superman"
+                    (apostrophe stripped first; ASCII and curly quotes
+                    handled — fold safely on tokens that pre-strippers
+                    don't reach, e.g. raw title text)
+      - plural      "powers" → "power", "girlfriends" → "girlfriend"
+
+    Conservative: only fires on tokens > 4 chars (preserves "is", "as",
+    "us") and skips ``ss``-enders ("class", "moss"). Idempotent —
+    stemming an already-stemmed token is a no-op.
+    """
+    t = t.replace("'", "").replace("’", "")
+    if len(t) > 4 and t.endswith("s") and not t.endswith("ss"):
+        return t[:-1]
+    return t
diff --git a/arborist/qa/corpus.py b/arborist/qa/corpus.py
index 26e3d61..f60ab13 100644
--- a/arborist/qa/corpus.py
+++ b/arborist/qa/corpus.py
@@ -89,15 +89,9 @@ def apply_title_boost(
         return hits
     from arborist.qa._text_norm import (
         _WORD_RE, STOPWORDS,
-        fold_accents, numeral_expand, tokenize_text,
+        fold_accents, numeral_expand, stem_for_match as _stem, tokenize_text,
     )
 
-    def _stem(t: str) -> str:
-        t = t.replace("'", "").replace("’", "")
-        if len(t) > 4 and t.endswith("s") and not t.endswith("ss"):
-            return t[:-1]
-        return t
-
     query_stems = numeral_expand({_stem(t) for t in tokenize_text(query)})
     if not query_stems:
         return hits
diff --git a/arborist/qa/query.py b/arborist/qa/query.py
index d4d16da..4f88c0b 100644
--- a/arborist/qa/query.py
+++ b/arborist/qa/query.py
@@ -1048,23 +1048,10 @@ def _docs_with_core_keyword_match(
     return rows
 
 
-def _stem_token_for_match(t: str) -> str:
-    """Light suffix-strip for query-token vs body matching.
-
-    Two normalizations:
-        possessive  ``"superman's" -> "supermans" -> "superman"`` (the apostrophe
-                    is already gone via _TITLE_TOKEN_RE; we drop the trailing
-                    ``s`` here so the lookup matches plain ``superman`` in body).
-        plural      ``"powers" -> "power"``, ``"girlfriends" -> "girlfriend"``
-                    so plural questions match singular source mentions.
-
-    Both are the same operation: strip trailing ``s`` for tokens > 4 chars.
-    Conservative on short tokens (``"is"``, ``"as"``, ``"us"`` would lose
-    meaning) and on tokens that don't end in ``s`` (no-op).
-    """
-    if len(t) > 4 and t.endswith("s") and not t.endswith("ss"):
-        return t[:-1]
-    return t
+# Canonical stemmer lives in _text_norm.py so query.py + corpus.py +
+# source_roles.py share one implementation. Re-exported under the old
+# name so existing call sites (and tests) keep working.
+from arborist.qa._text_norm import stem_for_match as _stem_token_for_match  # noqa: E402
 
 
 def _body_count_with_stem(body: str, t: str) -> int:
diff --git a/arborist/qa/source_roles.py b/arborist/qa/source_roles.py
index 568b8c4..aac5ce8 100644
--- a/arborist/qa/source_roles.py
+++ b/arborist/qa/source_roles.py
@@ -100,12 +100,13 @@ def classify_source_role(
         return "sequel_background_source"
     if any(k in t for k in _SECONDARY_TITLE_MARKERS):
         return "secondary_context_source"
-    # Lazy import — `_title_query_tokens` + `_stem_token_for_match`
-    # live in query.py today; they move to _text_norm.py in a later
-    # Phase 1 step. Import-cycle-safe by deferring to call time.
-    from arborist.qa.query import _title_query_tokens, _stem_token_for_match
+    # _title_query_tokens still lives in query.py (full fold stack is
+    # not lifted yet); the stemmer is now canonical in _text_norm.
+    # Lazy import keeps the import path acyclic.
+    from arborist.qa.query import _title_query_tokens
+    from arborist.qa._text_norm import stem_for_match
     title_tokens = _title_query_tokens(t.replace("_", " "))
-    title_stems = {_stem_token_for_match(tok) for tok in title_tokens}
+    title_stems = {stem_for_match(tok) for tok in title_tokens}
     if qtokens_stem and len(title_stems & qtokens_stem) >= max(
         1, len(qtokens_stem) - 1
     ):