Tell the summarizer who the characters are

`_create_due_memories` sent six actions of second-person prose and
nothing else — no protagonist, no cast, no setting, and no instruction
about what person to write in. So for `You push the door open. She grabs
your arm.` the only honest memory was "You entered a room and she
stopped you", which names nobody when it is retrieved forty turns later.
The framing wandered too: with no rule, the model picked a person per
call, and one bank ended up holding "You entered the crypt", "The player
entered the crypt" and "He entered the crypt" for the same kind of
event.

Both prompts now carry a cast brief and a framing rule: third person,
the protagonist by name, other characters named rather than left as bare
pronouns. The rule states its reason, because a memory really is read in
isolation much later and a model told why complies far more
consistently than one handed a bare instruction.

The cast comes from the story cards, not from `stat_schema`. Every
schema NPC is already turned into a card at adventure creation,
deduplicated against the hand-written ones by name, so the cards cover
schema NPCs, an author's own cards, and an adventure with no RPG layer
at all through one path instead of three.

Keyword matching alone was not enough, and finding that out changed the
design. Built that way first, the brief for "She grabs your arm" listed
the protagonist and nobody else: the block that most needs a cast is
exactly the one written in bare pronouns, and Gwen's trigger keys
include "her" but the text says "she". So matched cards come first and
the remaining slots are filled with the other character cards. Places
and items are not topped up — an unmentioned tavern is not who "she"
was — though a place that is mentioned still matches normally. The
asymmetry with the turn prompt is deliberate: an untriggered card is
wrong as lore and right in a roster, because the roster answers "who
could these pronouns be" rather than "what is on stage".

Fixed descriptions only, never live values. `Gwen: trust 40 (wary)` in
the brief would make the same event summarized at two different times
come out framed differently, which is the fault this removes.

An adventure with no persona still gets the cast and the setting, and
the model is told to write "the player". One with nothing to say sends
byte for byte the prompt it sent before.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NPyQN926gkZTAYfgugcaok

backend/app/context/builder.py

@@ -209,11 +209,15 @@ def _visible_npcs(actions: list[models.Action], stat_schema: dict) -> dict[str,
     return visible
 
 
-def _match_cards(cards: list[models.StoryCard], window_text: str) -> list[dict]:
+def match_cards(cards: list[models.StoryCard], window_text: str) -> list[dict]:
     """Returns one record per matched story card, naming the keyword that matched.
 
     Matching follows AI Dungeon's rules. It ignores case, respects spaces, and
     matches partial words, so "boat" matches "boats".
+
+    Public since Phase 18b: `memorybank.cast_brief` runs the same rule over the
+    block it is about to summarize, so that the summarizer is told who the
+    characters in that stretch of story are. One rule, one implementation.
     """
     haystack = window_text.lower()
     matched = []
@@ -352,7 +356,7 @@ def build_context(
 
     # ----- Story cards: triggered by recent story text (the window history could fill) -----
     trigger_window = truncate_to_last_tokens(SEPARATOR.join(a.text for a in actions), available)
-    triggered = _match_cards(adventure.story_cards, trigger_window)
+    triggered = match_cards(adventure.story_cards, trigger_window)
 
     card_budget = int(available * CARD_BUDGET_SHARE)
     card_records = []