docs: chat retrieval authority map and cut (extends prose-knowledge-target §4)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/chat-retrieval-map.md

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+# Chat retrieval: authority map and cut
+
+Serves `gamecult-chat:follow_up:chat-s732-733` (Meta, #swarm, 2026-11-01).
+Extends `prose-knowledge-target.md` §4. Written by Imagination (Self, run
+`mind-20261101T073859496Z`) against Huginn `55484c0`. Nothing here is built.
+
+## What changed since §4
+
+§4 rejected "a second prose index in Huginn" because VoidBot owned prose
+retrieval. Ruling `eureka-body:ruling:huginn-owns-prose-retrieval` moved it, and
+Huginn now has the index: `huginn-daemon/src/sources` (collection
+`huginn_sources`, one writer `refresh` run by the `huginn-sources` oneshot, the
+daemon only reads through `sources::search`). The rejection stands in a new
+form: **chat joins that organ; there is no second collection, embedder, writer
+or search path.**
+
+## Current mechanism (read, not guessed)
+
+- `sources::search` (sources/mod.rs:433) embeds ONE text, `Instruct:`-prefixed,
+  and asks `SourceIndex::search_sources` for the nearest chunks. `SourceQuery`
+  (huginn-mind wire.rs:103) is `{text: Line, top_k, repo}`; `Line` is 1,000
+  bytes, so a long brief cannot even be sent whole, and a clipped brief is one
+  vector that averages its topics. That is the "long briefs retrieve poorly".
+- `Embedder::embed(&[String])` already takes a batch (index/mod.rs:208).
+- `SourcesMeta.corpus` is the constant `forge:GameCult`; cursors are
+  `BTreeMap<repo, commit>` written whole by the job alone, advanced only after
+  acknowledged upserts, dropped before a repo's first delete (sources/mod.rs:9-18).
+- A Persona turn's recall (`mind-body/src/recall.rs`) reads only her own mind
+  and "reads no chat"; ruling `persona-memory-written-not-transcript` says what
+  she must keep is written as memory, not recovered from a transcript. The
+  Persona call is tool-less (persona.rs:13), so retrieval has to arrive in her
+  input; she has no shell.
+- Matrix: Synapse is the truth of events. Only the Bifrost mouth holds Matrix
+  tokens; no Persona unit holds a credential. Rooms are plain (F2 recommends
+  encrypted DMs only), DMs exist, and the Discord bridge is a later campaign.
+  Rulings `no-discord-ingestion` and `discord-taints-training` are in force.
+
+## Authority map
+
+| Decision | Owner | Forbidden writers |
+| --- | --- | --- |
+| Which events exist, who sent them, redactions | Synapse | Huginn, Bifrost mouth |
+| Which rooms are in the corpus | Huginn `sources` config: an **allowlist** of public community room ids | any Persona, any query |
+| Chunks, vectors, cursors for rooms | `sources::refresh`, the one writer | the daemon's `search`, Persona units |
+| Query embedding and rank fusion | `sources::search` | the caller (Persona, CLI) |
+| What a turn shows from chat | Persona `recall` lane, within a byte budget | the model, the retrieval hit text itself |
+| Discord exclusion | the allowlist plus an ingest refusal (below), both in `refresh` | nothing downstream may be relied on to filter |
+
+One cursor map, keyed by source id (`repo name` or `room id`); a room cursor is
+the last event the collection holds, advanced only after acknowledged upserts,
+exactly as a repo's commit is. Payload gains `corpus` (`forge` or `chat`) so a
+query can filter; `SourcesMeta.corpus` becomes the set both write under, which
+is a collection rebuild once (the meta already forces rebuild on mismatch).
+
+## Citations
+
+A chat chunk is a window of consecutive messages in one room (bounded by bytes
+and a time gap), so a hit cites: room id and alias, the first and last event id
+in the window, each message's sender mxid and timestamp inside the chunk text.
+A hit renders as quoted data with the organ's own provenance tag; the organ,
+never the text, decides what looks like a framed message (the existing
+`message_line` rule in persona.rs). Edits replace by event id; a redaction
+deletes the chunk window's points and re-chunks the window without it.
+
+## Cuts, smallest first
+
+1. **multi-text-query** (no chat needed). `SourceQuery` gains `texts` (1..8
+   Lines) beside, then replacing, `text`; `search` embeds all in one
+   `embed` batch, asks `search_sources` per vector, fuses by reciprocal rank
+   `score = Σ 1/(k + rank_i)`, k=60 (Cormack, Clarke, Büttcher, SIGIR 2009; k=60
+   is their value, and the one place to calibrate), de-duplicates by chunk id,
+   returns `top_k`. Negative checks: one text gives exactly today's order and
+   hits; a chunk first in two lists outranks one first in a single list;
+   duplicated text does not double-count; more than 8 texts or an empty one is
+   refused naming the field.
+2. **chat-ingest**. Port `RoomHistory` (rooms, events after a token); chunker
+   for message windows; room cursors; redaction; allowlist. Negative checks,
+   each a test that fails when the rule breaks: a room not on the allowlist is
+   never read; a room carrying a bridge state event (`m.bridge` /
+   `uk.half-shot.bridge`) or a sender in a bridge's puppet namespace is refused
+   whole and named in the journal; an encrypted event is skipped, never stored
+   as ciphertext; a DM room is refused even if listed; a redacted event's text
+   is absent from every point after the next refresh; a failed upsert leaves
+   the cursor where it was. A grep over the collection payload for the Discord
+   puppet pattern returns nothing.
+3. **persona-chat-recall**. A recall lane built from the batch's messages as
+   the `texts` of cut 1, `corpus=chat`, own byte budget, not shown for text
+   already in the batch, shown as conversation (not memory). Negative checks: a
+   hit from a room the sender could not read is never shown (DM rule, persona.rs
+   `next_batch`); a hit whose text imitates a `message` line or `role=operator`
+   is rendered quoted and carries no role; the lane failing leaves the turn
+   going without it (as `Search::Unavailable`).
+
+Cut 1 ships alone and improves every `huginn sources` caller. Cut 2 waits on
+questions 1 and 2. Cut 3 waits on 2 and 3.
+
+## Questions (put to the operator; admitted as questions)
+
+1. Credential: who reads Synapse? Recommend a read-only service user, joined
+   only to allowlisted public rooms, its token a systemd credential on the
+   refresh job only. Alternatives: Bifrost exports history over typed CultNet
+   (one more server in the path), or Synapse admin API (broader than needed).
+2. Scope: public community rooms only (recommended) or also Persona-visible
+   private rooms. DMs stay out either way.
+3. Recall tension: does transcript search in a Persona turn contradict
+   `persona-memory-written-not-transcript`? Recommend no: it is lookup, labelled
+   conversation, not memory; what she must keep is still written.
+
+Confidence: cut 1 and the owner decision, high. The window chunker size and
+k=60 are calibration, not design; RRF over a handful of lists is the
+established baseline and I did not survey learned fusion (it needs training
+data we lack).