feat(llm): lineage evidence — timeline events, element diffs and guidance as a lineage SSE event + cited prompt block (refs #691)

src/llm/config.py

@@ -49,6 +49,8 @@ class LlmConfig:
     code_cited_per_code: int = 3
     code_cited_collections: tuple[str, ...] = ("rules", "comments", "corpus")
     code_cited_max: int = 12
+    lineage_max_rows: int = 25
+    lineage_on_demand_max: int = 3
 
 
 def parse_hosts(spec: str) -> tuple[tuple[str, float], ...]:
@@ -120,6 +122,8 @@ def load() -> LlmConfig:
             _opt(section, "code_cited_collections", ["rules", "comments", "corpus"])
         ),
         code_cited_max=int(_opt(section, "code_cited_max", 12)),
+        lineage_max_rows=int(_opt(section, "lineage_max_rows", 25)),
+        lineage_on_demand_max=int(_opt(section, "lineage_on_demand_max", 3)),
         embed_dim=int(section.embed_dim),
         build_ann_index=build_ann_index,
         pg_host=os.environ.get("LLM_PG_HOST", str(section.pg_host)),

src/llm/evidence.py

@@ -393,3 +393,10 @@ def code_cited_sources(
 def merge_sources(retrieved: list[dict], extra: list[dict]) -> list[dict]:
     labels = {s["label"] for s in retrieved}
     return retrieved + [s for s in extra if s["label"] not in labels]
+
+
+# Re-exported so rag.py imports both evidence functions from one place,
+# like valuation_evidence — llm.lineage lazily imports this module's
+# _connect/_replica_path/_mtime/warm inside lineage_evidence() rather
+# than at module scope, so this import carries no circularity risk.
+from llm.lineage import lineage_evidence  # noqa: E402,F401

src/llm/lineage.py

@@ -0,0 +1,510 @@
+"""Structured lineage evidence for the chat: a dated timeline, cross-code
+element differences, and CFR/IOM/MLN guidance references, beside the
+excerpts and the valuation table.
+
+``lineage_evidence`` detects HCPCS/CPT codes (and registered families)
+in the question, then reads the precomputed ``pfs.code_event`` rows
+(``pfs.codetables.read_events`` — every A/R/T code, Task 2's
+``stack pfs lineage --all-payable --write``) from the cached DuckDB
+read replica. A code with no precomputed rows falls back on demand to
+``pfs.lineage.lineage`` (bounded by ``cfg.lineage_on_demand_max`` codes
+per turn — that path re-derives events from the RVU files and a live
+scan of ``fr_anchors``, too slow to run for every code on every turn).
+Events for the same ``(code, year, kind, from_codes, to_codes)`` are
+collapsed to one representative row, preferring an anchored FR
+paragraph. ``pfs.code_element`` supplies element differences across the
+detected codes' newest year, and ``pfs.code_guidance`` supplies CFR/IOM/
+MLN references for the detected families. Like ``llm.evidence``, this
+degrades to "no evidence" on any failure — the chat never fails because
+of it.
+"""
+
+from __future__ import annotations
+
+import logging
+import threading
+from dataclasses import asdict, dataclass
+from typing import Any, Sequence
+
+from llm.config import LlmConfig
+from pfs.codetables import (
+    ElementRow,
+    EventRow,
+    GuidanceRow,
+    is_missing_table_error,
+    read_elements,
+    read_events,
+    read_guidance,
+)
+from pfs.descriptors import rule_year_of
+from pfs.families import detect_codes
+
+log = logging.getLogger(__name__)
+
+_HEADER = (
+    "Lineage (dated events with anchors; cite the bracketed label for any dated claim):"
+)
+
+#: Event kinds a prompt block never drops for the row cap (ruling 17) —
+#: these are the "what happened and what replaced it" facts a dated
+#: claim usually hinges on; revaluation/descriptor noise can be trimmed
+#: first.
+_PRIORITY_KINDS = frozenset(
+    {"created", "adopted_cpt", "replaces", "replaced_by", "deleted", "disappeared"}
+)
+
+#: Sort order for collapsed events sharing a year and code: FR event
+#: kinds (their own internal order), then RVU-file kinds, then the two
+#: CPT-codebook kinds. Anything unrecognized sorts last.
+_KIND_ORDER = (
+    "created",
+    "adopted_cpt",
+    "replaces",
+    "replaced_by",
+    "deleted",
+    "crosswalk",
+    "bundled",
+    "telehealth_list",
+    "appeared",
+    "disappeared",
+    "status_change",
+    "descriptor_change",
+    "revalued",
+    "cpt_changed",
+    "cpt_deleted",
+)
+
+#: Guidance rows kept in the prompt/payload per question — a code's
+#: CFR/IOM/MLN references rarely run past a handful, and a long tail
+#: would crowd the lineage block out of the prompt budget.
+_GUIDANCE_CAP = 8
+
+#: Element diffs kept, most-shared value first (ruling 18).
+_ELEMENT_DIFF_CAP = 12
+
+
+def _kind_rank(kind: str) -> int:
+    try:
+        return _KIND_ORDER.index(kind)
+    except ValueError:
+        return len(_KIND_ORDER)
+
+
+@dataclass(frozen=True)
+class LineageEvent:
+    code: str
+    year: int
+    kind: str
+    from_codes: tuple[str, ...]
+    to_codes: tuple[str, ...]
+    label: str
+    item_key: str
+    p_id: int
+    page: int
+    url: str
+    source: str  # "fr" | "rvu" | "cpt"
+    anchored: bool
+    note: str
+
+
+@dataclass(frozen=True)
+class ElementDiff:
+    type: str
+    value: str
+    in_codes: tuple[str, ...]
+    not_in_codes: tuple[str, ...]
+    label: str
+    item_key: str
+    p_id: int
+
+
+@dataclass(frozen=True)
+class GuidanceRef:
+    kind: str  # "cfr" | "iom" | "mln"
+    locator: str
+    url: str
+    label: str
+    item_key_src: str
+    p_id_src: int
+
+
+def _event_line(e: LineageEvent) -> str:
+    line = f"[{e.label}] {e.year} {e.kind} {e.code}"
+    if e.from_codes or e.to_codes:
+        line += f" ({', '.join(e.from_codes)} → {', '.join(e.to_codes)})"
+    if e.note:
+        line += f" — {e.note}"
+    return line
+
+
+def _diff_line(d: ElementDiff) -> str:
+    return (
+        f"[{d.label}] {d.type}={d.value}: "
+        f"in {', '.join(d.in_codes)}; not in {', '.join(d.not_in_codes)}"
+    )
+
+
+def _guidance_line(g: GuidanceRef) -> str:
+    return f"[{g.label}] {g.locator} — {g.kind.upper()}"
+
+
+@dataclass(frozen=True)
+class LineageEvidence:
+    codes: tuple[str, ...]
+    families: tuple[str, ...]
+    #: Every collapsed event row, sorted (year, code, kind order) — the
+    #: SSE payload carries all of these; ``prompt_block`` trims them.
+    events: tuple[LineageEvent, ...]
+    element_diffs: tuple[ElementDiff, ...]
+    guidance: tuple[GuidanceRef, ...]
+    #: "elements extracted for N of M codes" when only one detected code
+    #: has any ``pfs.code_element`` rows (ruling 18) — "" otherwise.
+    elements_note: str = ""
+    #: ``cfg.lineage_max_rows`` at construction time — ``prompt_block``
+    #: is self-contained (no cfg argument), like ``ValuationEvidence``.
+    max_prompt_rows: int = 25
+
+    def _prompt_events(self) -> list[LineageEvent]:
+        priority = [e for e in self.events if e.kind in _PRIORITY_KINDS]
+        rest = [e for e in self.events if e.kind not in _PRIORITY_KINDS]
+        budget = max(self.max_prompt_rows - len(priority), 0)
+        keep = set(priority) | set(rest[:budget])
+        return [e for e in self.events if e in keep]
+
+    def prompt_block(self) -> str:
+        lines = [_HEADER]
+        lines.extend(_event_line(e) for e in self._prompt_events())
+        if self.element_diffs:
+            lines.append("Element differences:")
+            lines.extend(_diff_line(d) for d in self.element_diffs)
+        if self.guidance:
+            lines.append("Guidance:")
+            lines.extend(_guidance_line(g) for g in self.guidance)
+        return "\n".join(lines)
+
+    def payload(self) -> dict[str, Any]:
+        out: dict[str, Any] = {
+            "type": "lineage",
+            "codes": list(self.codes),
+            "families": list(self.families),
+            "events": [asdict(e) for e in self.events],
+            "element_diffs": [asdict(d) for d in self.element_diffs],
+            "guidance": [asdict(g) for g in self.guidance],
+        }
+        if self.elements_note:
+            out["elements_note"] = self.elements_note
+        return out
+
+
+def rule_label(title: str, date_published: str, p_id: int) -> str:
+    """``"CY2021 PFS final ¶1578"`` / ``"CY2027 PFS proposed ¶394"`` —
+    ``proposed`` when *title* contains "Proposed" (case-insensitive),
+    else ``final``; the year from ``rule_year_of``."""
+    year = rule_year_of(title, date_published)
+    kind = "proposed" if "proposed" in (title or "").lower() else "final"
+    return f"CY{year} PFS {kind} ¶{p_id}"
+
+
+# ── The bib Store, opened lazily once per process (sqlite, cheap) ──────
+
+_STORE: Any | None = None
+_STORE_LOCK = threading.Lock()
+
+
+def _store() -> Any:
+    global _STORE
+    with _STORE_LOCK:
+        if _STORE is None:
+            from conf.connect import bib
+
+            _STORE = bib()
+        return _STORE
+
+
+def _source_label(store: Any, item_key: str, p_id: int) -> str:
+    """``rule_label`` for the FR rule at *item_key* — falls back to the
+    bare item key when the item can't be fetched (unresolvable/missing
+    item must never break the chat over a label)."""
+    try:
+        item = store.get(item_key)
+    except Exception as e:  # noqa: BLE001
+        log.warning("lineage label unresolved (%s): %s", item_key, e)
+        return item_key or "?"
+    return rule_label(item.title, item.date_published, p_id)
+
+
+# ── FR jump links, cached per (item_key, p_id) ──────────────────────────
+
+_URL_CACHE: dict[tuple[str, int], str] = {}
+_URL_LOCK = threading.Lock()
+
+
+def _fr_url(store: Any, item_key: str, p_id: int) -> str:
+    if not item_key or not p_id:
+        return ""
+    key = (item_key, p_id)
+    with _URL_LOCK:
+        cached = _URL_CACHE.get(key)
+    if cached is not None:
+        return cached
+    url = ""
+    try:
+        from bib import frlink
+
+        url = frlink.resolve(f"p-{p_id}", store=store, item_key=item_key).url
+    except Exception as e:  # noqa: BLE001 — a bad anchor must not break the chat
+        log.warning("lineage FR url unresolved (%s p-%s): %s", item_key, p_id, e)
+    with _URL_LOCK:
+        _URL_CACHE[key] = url
+    return url
+
+
+def _to_lineage_event(store: Any, r: EventRow) -> LineageEvent:
+    from_codes = tuple(r.from_codes.split()) if r.from_codes else ()
+    to_codes = tuple(r.to_codes.split()) if r.to_codes else ()
+    if r.source == "fr":
+        label = _source_label(store, r.item_key, r.p_id)
+        url = _fr_url(store, r.item_key, r.p_id)
+    elif r.source == "cpt":
+        label = r.note or f"CPT Changes {r.year}"
+        url = ""
+    else:  # "rvu"
+        label = f"PFS CY{r.year} RVU file"
+        url = ""
+    return LineageEvent(
+        code=r.code,
+        year=r.year,
+        kind=r.kind,
+        from_codes=from_codes,
+        to_codes=to_codes,
+        label=label,
+        item_key=r.item_key,
+        p_id=r.p_id,
+        page=r.page,
+        url=url,
+        source=r.source,
+        anchored=r.anchored,
+        note=r.note,
+    )
+
+
+def _collapse(rows: Sequence[EventRow]) -> list[EventRow]:
+    """One representative row per ``(code, year, kind, from_codes,
+    to_codes)`` — prefer an anchored FR row, then the lowest ``p_id`` —
+    sorted by ``(year, code, kind order)``."""
+    groups: dict[tuple[str, int, str, str, str], list[EventRow]] = {}
+    for r in rows:
+        key = (r.code, r.year, r.kind, r.from_codes, r.to_codes)
+        groups.setdefault(key, []).append(r)
+    reps = [
+        min(
+            grp,
+            key=lambda r: (0 if (r.source == "fr" and r.anchored) else 1, r.p_id),
+        )
+        for grp in groups.values()
+    ]
+    return sorted(reps, key=lambda r: (r.year, r.code, _kind_rank(r.kind)))
+
+
+# ── On-demand fallback for codes with no precomputed rows, cached by
+# (replica mtime, code) — see the module docstring. ─────────────────────
+
+_ON_DEMAND_CACHE: dict[str, list[EventRow]] = {}
+_ON_DEMAND_MTIME: int | None = None
+_ON_DEMAND_LOCK = threading.Lock()
+
+
+def _on_demand_events(cur: Any, store: Any, mtime: int, code: str) -> list[EventRow]:
+    global _ON_DEMAND_MTIME
+    with _ON_DEMAND_LOCK:
+        if _ON_DEMAND_MTIME != mtime:
+            _ON_DEMAND_CACHE.clear()
+            _ON_DEMAND_MTIME = mtime
+        cached = _ON_DEMAND_CACHE.get(code)
+    if cached is not None:
+        return cached
+    try:
+        import pfs.lineage as pfs_lineage
+
+        rows = pfs_lineage.lineage(cur, store, code)
+    except Exception as e:  # noqa: BLE001 — on-demand fallback must not break the chat
+        log.warning("on-demand lineage skipped for %s: %s", code, e)
+        rows = []
+    with _ON_DEMAND_LOCK:
+        if _ON_DEMAND_MTIME == mtime:
+            _ON_DEMAND_CACHE[code] = rows
+    return rows
+
+
+def _collect_events(
+    cur: Any, store: Any, mtime: int, codes: Sequence[str], on_demand_max: int
+) -> list[EventRow]:
+    out: list[EventRow] = []
+    used = 0
+    for code in codes:
+        try:
+            rows = read_events(cur, code)
+        except Exception as e:  # noqa: BLE001
+            if not is_missing_table_error(e):
+                raise
+            rows = []
+        if not rows and used < on_demand_max:
+            rows = _on_demand_events(cur, store, mtime, code)
+            used += 1
+        out.extend(rows)
+    return out
+
+
+def _element_label(store: Any, row: ElementRow) -> str:
+    if row.item_key and row.p_id:
+        return _source_label(store, row.item_key, row.p_id)
+    if row.source == "cpt":
+        return f"CPT Changes {row.year}"
+    return f"PFS CY{row.year} RVU file"
+
+
+def _element_diffs(
+    cur: Any, codes: Sequence[str], store: Any
+) -> tuple[tuple[ElementDiff, ...], str]:
+    """Element values present for some detected codes and absent for
+    others, from each code's newest ``pfs.code_element`` year. Needs
+    >= 2 detected codes with any element rows at all — a single code's
+    elements have nothing to diff against (ruling 18)."""
+    by_code: dict[str, list[ElementRow]] = {}
+    for code in codes:
+        try:
+            rows = read_elements(cur, code)
+        except Exception as e:  # noqa: BLE001
+            if not is_missing_table_error(e):
+                raise
+            rows = []
+        if not rows:
+            continue
+        newest = max(r.year for r in rows)
+        by_code[code] = [r for r in rows if r.year == newest]
+    n, m = len(by_code), len(codes)
+    if n < 2:
+        note = f"elements extracted for {n} of {m} codes" if n == 1 else ""
+        return (), note
+
+    groups: dict[tuple[str, str], list[tuple[str, ElementRow]]] = {}
+    for code, rows in by_code.items():
+        seen: set[tuple[str, str]] = set()
+        for r in rows:
+            pair = (r.type, r.value)
+            if pair in seen:
+                continue
+            seen.add(pair)
+            groups.setdefault(pair, []).append((code, r))
+
+    all_with_elements = set(by_code)
+    diffs: list[ElementDiff] = []
+    for (type_, value_), entries in groups.items():
+        in_codes = tuple(sorted({code for code, _ in entries}))
+        not_in_codes = tuple(sorted(all_with_elements - set(in_codes)))
+        if not not_in_codes:
+            continue  # present for every code that has elements at all
+        best = min(
+            (row for _, row in entries),
+            key=lambda r: (0 if (r.item_key and r.p_id) else 1, r.year),
+        )
+        diffs.append(
+            ElementDiff(
+                type=type_,
+                value=value_,
+                in_codes=in_codes,
+                not_in_codes=not_in_codes,
+                label=_element_label(store, best),
+                item_key=best.item_key,
+                p_id=best.p_id,
+            )
+        )
+    diffs.sort(key=lambda d: (-len(d.in_codes), d.type, d.value))
+    return tuple(diffs[:_ELEMENT_DIFF_CAP]), ""
+
+
+def _collect_guidance(
+    cur: Any, store: Any, families: Sequence[str], wide: Sequence[str]
+) -> tuple[GuidanceRef, ...]:
+    wide_set = set(wide)
+    rows: list[GuidanceRow] = []
+    for family in families:
+        if family in wide_set:
+            continue
+        try:
+            rows.extend(read_guidance(cur, family))
+        except Exception as e:  # noqa: BLE001
+            if not is_missing_table_error(e):
+                raise
+    rows.sort(key=lambda r: (0 if r.kind == "cfr" else 1, r.kind, r.locator))
+
+    out: list[GuidanceRef] = []
+    seen: set[str] = set()
+    for r in rows:
+        if r.locator in seen:
+            continue
+        seen.add(r.locator)
+        url = ""
+        if r.kind == "cfr":
+            try:
+                from bib import cfrlink
+
+                url = cfrlink.url(cfrlink.parse_cite(r.locator))
+            except Exception as e:  # noqa: BLE001
+                log.warning("lineage CFR url unresolved (%s): %s", r.locator, e)
+        out.append(
+            GuidanceRef(
+                kind=r.kind,
+                locator=r.locator,
+                url=url,
+                label=_source_label(store, r.item_key_src, r.p_id_src),
+                item_key_src=r.item_key_src,
+                p_id_src=r.p_id_src,
+            )
+        )
+        if len(out) >= _GUIDANCE_CAP:
+            break
+    return tuple(out)
+
+
+def lineage_evidence(question: str, cfg: LlmConfig) -> LineageEvidence | None:
+    """Timeline events, element differences and guidance for the codes
+    detected in *question* — ``None`` when no codes are detected. Never
+    raises: any failure opening the replica or querying it is logged and
+    degrades to ``None``, the same contract as ``valuation_evidence``."""
+    import llm.evidence as evidence
+
+    evidence.warm(cfg)
+    det = detect_codes(question)
+    if not det.codes:
+        return None
+    path = evidence._replica_path(cfg)
+    try:
+        con = evidence._connect(path)
+    except Exception as e:  # noqa: BLE001 — duckdb raises several types
+        log.warning("lineage evidence skipped (%s): %s", path, e)
+        return None
+    cur = con.cursor()
+    try:
+        store = _store()
+        mtime = evidence._mtime(path)
+        raw_events = _collect_events(
+            cur, store, mtime, det.codes, cfg.lineage_on_demand_max
+        )
+        events = tuple(_to_lineage_event(store, r) for r in _collapse(raw_events))
+        element_diffs, elements_note = _element_diffs(cur, det.codes, store)
+        guidance = _collect_guidance(cur, store, det.families, det.wide)
+    except Exception as e:  # noqa: BLE001
+        log.warning("lineage evidence skipped (query): %s", e)
+        return None
+    finally:
+        cur.close()  # the cached parent connection stays open
+    return LineageEvidence(
+        codes=det.codes,
+        families=det.families,
+        events=events,
+        element_diffs=element_diffs,
+        guidance=guidance,
+        elements_note=elements_note,
+        max_prompt_rows=cfg.lineage_max_rows,
+    )

src/llm/rag.py

@@ -8,10 +8,11 @@ merged and re-ranked by similarity × recency (``llm.rerank``), then each
 source gets a deep link (``llm.links``). Generation streams from the
 largest live Ollama host (``HostPool.acquire_generation``) with the
 model tier that host can hold (``pick_model``). When the question
-cites HCPCS/CPT codes, ``llm.evidence`` supplies authoritative
-valuation rows and code- or family-cited chunks from rules, comments and
-the reference corpus; the SSE event order is ``valuation`` (only when
-evidence is found) → ``token``* → ``sources`` → ``done``.
+cites HCPCS/CPT codes, ``llm.evidence``/``llm.lineage`` supply
+authoritative valuation rows, a dated lineage timeline, and code- or
+family-cited chunks from rules, comments and the reference corpus; the
+SSE event order is ``lineage`` (only when detected) → ``valuation``
+(only when found) → ``token``* → ``sources`` → ``done``.
 """
 
 from __future__ import annotations
@@ -26,10 +27,12 @@ from llm.config import LlmConfig
 from llm.evidence import (
     ValuationEvidence,
     code_cited_sources,
+    lineage_evidence,
     merge_sources,
     valuation_evidence,
 )
 from llm.index import _engine
+from llm.lineage import LineageEvidence
 from llm.links import as_source
 from llm.pool import HostPool, PoolEmbeddings, pick_model
 from llm.rerank import Hit, blend, filter_since
@@ -57,6 +60,11 @@ _SYSTEM = (
     "e.g. [PFS CY2026 Addendum B]. Do not compute, extrapolate or convert "
     "numbers beyond what the rows show; if a code is listed as not priced, "
     "say so."
+    " A Lineage section may also follow. It is authoritative for when a "
+    "code was created, adopted, replaced or deleted and what replaced it; "
+    "cite its bracketed label for every dated claim. If the Lineage "
+    "section does not give a date for something, say so rather than "
+    "inventing one."
 )
 
 
@@ -109,11 +117,14 @@ def retrieve(
 
 
 def build_messages(
-    question: str, sources: list[dict], evidence: ValuationEvidence | None = None
+    question: str,
+    sources: list[dict],
+    evidence: ValuationEvidence | None = None,
+    lineage: LineageEvidence | None = None,
 ) -> list[dict]:
     """Grounded chat messages: system rules + question with excerpts and,
-    when available, a Valuation block between the excerpts and the
-    question."""
+    when available, a Lineage block and a Valuation block — in that
+    order — between the excerpts and the question."""
     if sources:
         context = "\n\n".join(
             f"[{s['label']}] ({s.get('kind', '')}, {s.get('date', '') or 'undated'}) "
@@ -123,6 +134,8 @@ def build_messages(
     else:
         context = "(no relevant excerpts found)"
     parts = [f"Excerpts:\n\n{context}"]
+    if lineage is not None:
+        parts.append(lineage.prompt_block())
     if evidence is not None:
         parts.append(evidence.prompt_block())
     parts.append(f"Question: {question}")
@@ -138,30 +151,39 @@ def stream_answer(
 ) -> Iterator[dict]:
     """Retrieve, then stream a grounded answer from the largest live host.
 
-    When the question cites HCPCS/CPT codes, yields a ``valuation`` event
-    first (evidence's ``payload()``) and merges chunks from rules,
-    comments and the corpus that cite those codes — or, for a detected
-    family, its family key — into ``sources``. Then yields
-    ``{"type":"token","text":…}``
-    events as the model generates, then one
-    ``{"type":"sources", "sources": […], "model": …, "host": …}`` and a
-    final ``{"type":"done"}``.
+    When the question cites HCPCS/CPT codes, yields a ``lineage`` event
+    (evidence's ``payload()``, the dated timeline) then a ``valuation``
+    event (RVUs and payment) — both before any tokens — and merges
+    chunks from rules, comments and the corpus that cite those codes —
+    or, for a detected family, its family key — into ``sources``. Then
+    yields ``{"type":"token","text":…}`` events as the model generates,
+    then one ``{"type":"sources", "sources": […], "model": …, "host":
+    …}`` and a final ``{"type":"done"}``.
     """
     sources = retrieve(question, cfg=cfg, pool=pool, since=since)
+    lineage = lineage_evidence(question, cfg)
     evidence = valuation_evidence(question, cfg)
-    if evidence is not None:
+    codes: tuple[str, ...] = evidence.codes if evidence is not None else ()
+    families: tuple[str, ...] = evidence.families if evidence is not None else ()
+    if lineage is not None:
+        codes = tuple(sorted(set(codes) | set(lineage.codes)))
+        families = tuple(sorted(set(families) | set(lineage.families)))
+    if evidence is not None or lineage is not None:
         cited = code_cited_sources(
             _engine(cfg),
-            evidence.codes,
+            codes,
             per_code=cfg.code_cited_per_code,
             collections=tuple(cfg.code_cited_collections),
-            families=evidence.families,
+            families=families,
             max_total=cfg.code_cited_max,
         )
         sources = merge_sources(sources, cited)
+    if lineage is not None:
+        yield lineage.payload()
+    if evidence is not None:
         yield evidence.payload()
     pool.check(cfg.instruct_model)
-    messages = build_messages(question, sources, evidence)
+    messages = build_messages(question, sources, evidence, lineage)
     with pool.acquire_generation() as host, httpx.Client(timeout=_TIMEOUT) as client:
         model = pick_model(cfg, pool, host)
         with client.stream(

stack.toml

@@ -129,6 +129,8 @@ valuation_years = 4                      # final-rule vintages shown per code (p
 code_cited_per_code = 3                  # excerpts literally citing each detected code (or family)
 code_cited_collections = ["rules", "comments", "corpus"]  # searched in this order
 code_cited_max = 12                      # cited excerpts kept after round-robin interleave across collections; <= 0 = unlimited
+lineage_max_rows = 25                    # collapsed lineage events kept in the prompt block (the SSE payload always carries every collapsed row)
+lineage_on_demand_max = 3                # detected codes per turn allowed to fall back to pfs.lineage.lineage() when pfs.code_event has no rows for them
 
 [llm.k_per_kind]                       # over-fetched ×3 per kind, then re-ranked
 comment = 8

tests/llm/test_config.py

@@ -96,6 +96,8 @@ class TestNewKnobs:
         assert cfg.code_cited_per_code == 3
         assert cfg.code_cited_collections == ("rules", "comments", "corpus")
         assert cfg.code_cited_max == 12
+        assert cfg.lineage_max_rows == 25
+        assert cfg.lineage_on_demand_max == 3
 
     def test_duckdb_replica_env_override(self, monkeypatch):
         monkeypatch.setenv("LLM_DUCKDB_REPLICA", "/app/data/replica/aco.ro.duckdb")

tests/llm/test_lineage.py

@@ -0,0 +1,775 @@
+"""llm.lineage — dated timeline, element diffs and guidance as a
+lineage SSE event + cited prompt block."""
+
+from __future__ import annotations
+
+import json
+import sqlite3
+import time
+from dataclasses import replace
+from types import SimpleNamespace
+from unittest.mock import patch
+
+import duckdb
+import pytest
+
+import llm.lineage as lineage
+from llm.config import LlmConfig
+from llm.lineage import (
+    ElementDiff,
+    GuidanceRef,
+    LineageEvent,
+    LineageEvidence,
+    lineage_evidence,
+    rule_label,
+)
+from pfs.codetables import (
+    ElementRow,
+    EventRow,
+    GuidanceRow,
+    ensure_tables,
+    write_elements,
+    write_events,
+    write_guidance,
+)
+from pfs.families import Detection
+
+CFG = LlmConfig(
+    ollama_hosts=("http://h1:11434",),
+    embed_model="e",
+    instruct_model="c",
+    embed_dim=768,
+    build_ann_index=False,
+    pg_host="x",
+    pg_port=5432,
+    pg_db="llm",
+    pg_user="llm",
+    duckdb_replica="/nonexistent/aco.ro.duckdb",
+    lineage_max_rows=25,
+    lineage_on_demand_max=3,
+)
+
+
+@pytest.fixture(autouse=True)
+def _clear_caches():
+    """Every process-global cache lineage.py keeps is shared across
+    tests (and with llm.evidence's replica cache) — no test may inherit
+    another's handle, store, or on-demand memo."""
+    import llm.evidence as evidence
+
+    def _reset():
+        evidence._REPLICA = None
+        lineage._STORE = None
+        lineage._URL_CACHE.clear()
+        lineage._ON_DEMAND_CACHE.clear()
+        lineage._ON_DEMAND_MTIME = None
+
+    _reset()
+    yield
+    _reset()
+
+
+class _FakeStore:
+    """A bib.Store stand-in: ``items``/``fr_anchors``/``fr_anchor_docs``
+    tables the way bib.frlink.resolve and Store.get expect, seeded with
+    the real CY2015/CY2021 CCM history (99490 adopted in 2015, G2058
+    replaced by the new CPT code 99439 in 2021) already used as a fixture
+    in tests/pfs/test_lineage.py."""
+
+    def __init__(self):
+        self.con = sqlite3.connect(":memory:")
+        self.con.row_factory = sqlite3.Row
+        self.con.executescript(
+            "CREATE TABLE items (key TEXT PRIMARY KEY, title TEXT, "
+            "date_published TEXT);"
+            "CREATE TABLE fr_anchors (item_key TEXT, p_id INTEGER, "
+            "page INTEGER, ordinal INTEGER, text TEXT);"
+            "CREATE TABLE fr_anchor_docs (item_key TEXT, html_url TEXT, "
+            "start_page INTEGER, end_page INTEGER, fr_volume INTEGER);"
+        )
+        self.con.executemany(
+            "INSERT INTO items VALUES (?,?,?)",
+            [
+                (
+                    "DE2VH9PD",
+                    "Medicare Program; CY 2015 PFS Final Rule",
+                    "2014-11-13",
+                ),
+                (
+                    "YBM4IZUS",
+                    "Medicare Program; CY 2021 Payment Policies Under the PFS",
+                    "2020-12-28",
+                ),
+                (
+                    "ZPROP2027",
+                    "Medicare Program; CY 2027 Proposed Payment Policies",
+                    "2026-07-16",
+                ),
+            ],
+        )
+        self.con.executemany(
+            "INSERT INTO fr_anchor_docs VALUES (?,?,?,?,?)",
+            [
+                ("DE2VH9PD", "https://fr.test/2015-doc", 67000, 68000, 79),
+                ("YBM4IZUS", "https://fr.test/2021-doc", 84000, 85000, 85),
+            ],
+        )
+        self.con.executemany(
+            "INSERT INTO fr_anchors VALUES (?,?,?,?,?)",
+            [
+                (
+                    "DE2VH9PD",
+                    1251,
+                    67716,
+                    1,
+                    "Accordingly, we will adopt CPT code 99490 for Medicare "
+                    "CCM services.",
+                ),
+                (
+                    "YBM4IZUS",
+                    686,
+                    84547,
+                    1,
+                    "We are finalizing HCPCS code G2058 as new CPT code 99439.",
+                ),
+                (
+                    "YBM4IZUS",
+                    1578,
+                    84639,
+                    2,
+                    "A temporary crosswalk between G2058 and new CPT code "
+                    "99439 (with a descriptor identical to G2058).",
+                ),
+            ],
+        )
+
+    def _con(self):
+        return self.con
+
+    def get(self, key: str) -> SimpleNamespace:
+        row = self.con.execute(
+            "SELECT title, date_published FROM items WHERE key = ?", (key,)
+        ).fetchone()
+        if row is None:
+            raise KeyError(key)
+        return SimpleNamespace(title=row["title"], date_published=row["date_published"])
+
+    def close(self):
+        self.con.close()
+
+
+@pytest.fixture
+def store():
+    s = _FakeStore()
+    yield s
+    s.close()
+
+
+@pytest.fixture
+def con(tmp_path):
+    """A real temp DuckDB replica (not :memory:) so lineage_evidence's
+    real _connect/_replica_path path is exercised end to end, the same
+    way TestConcurrentChats in test_evidence.py does."""
+    db = tmp_path / "aco.ro.duckdb"
+    c = duckdb.connect(str(db))
+    ensure_tables(c)
+    yield c, db
+    c.close()
+
+
+def _ev(
+    code,
+    year,
+    kind,
+    frm="",
+    to="",
+    item_key="",
+    p_id=0,
+    page=0,
+    source="fr",
+    anchored=True,
+    note="",
+) -> EventRow:
+    return EventRow(
+        code, year, kind, frm, to, item_key, p_id, page, source, anchored, note
+    )
+
+
+def _el(code, year, type_, value, item_key="", p_id=0, source="fr") -> ElementRow:
+    return ElementRow(code, year, type_, value, "", "", item_key, p_id, 0, source)
+
+
+def _gd(
+    family, code, kind, locator, item_key_src, p_id_src, item_key=""
+) -> GuidanceRow:
+    return GuidanceRow(family, code, kind, locator, item_key, item_key_src, p_id_src, 0)
+
+
+class TestRuleLabel:
+    def test_final(self):
+        assert (
+            rule_label(
+                "Medicare Program; CY 2021 Payment Policies Under the PFS",
+                "2020-12-28",
+                1578,
+            )
+            == "CY2021 PFS final ¶1578"
+        )
+
+    def test_proposed(self):
+        assert (
+            rule_label(
+                "Medicare Program; CY 2027 Proposed Payment Policies",
+                "2026-07-16",
+                394,
+            )
+            == "CY2027 PFS proposed ¶394"
+        )
+
+
+class TestCollapse:
+    def test_prefers_anchored_fr_over_rvu_for_the_same_group(self):
+        rows = [
+            _ev("99439", 2021, "created", item_key="YBM4IZUS", p_id=686, source="fr"),
+            _ev("99439", 2021, "created", source="rvu", anchored=True, note="dupe"),
+        ]
+        collapsed = lineage._collapse(rows)
+        assert len(collapsed) == 1
+        assert collapsed[0].source == "fr" and collapsed[0].p_id == 686
+
+    def test_tiebreaks_on_lowest_p_id(self):
+        rows = [
+            _ev(
+                "99439",
+                2021,
+                "replaces",
+                to="",
+                frm="G2058",
+                item_key="YBM4IZUS",
+                p_id=2999,
+                source="fr",
+            ),
+            _ev(
+                "99439",
+                2021,
+                "replaces",
+                frm="G2058",
+                item_key="YBM4IZUS",
+                p_id=1578,
+                source="fr",
+            ),
+        ]
+        collapsed = lineage._collapse(rows)
+        assert len(collapsed) == 1 and collapsed[0].p_id == 1578
+
+    def test_sorted_by_year_code_then_kind_order(self):
+        rows = [
+            _ev("99439", 2021, "replaces", frm="G2058", p_id=1),
+            _ev("G2058", 2021, "replaced_by", to="99439", p_id=1),
+            _ev("99439", 2015, "created", p_id=2),
+        ]
+        collapsed = lineage._collapse(rows)
+        assert [(e.year, e.code, e.kind) for e in collapsed] == [
+            (2015, "99439", "created"),
+            (2021, "99439", "replaces"),
+            (2021, "G2058", "replaced_by"),
+        ]
+
+    def test_distinct_groups_are_not_merged(self):
+        rows = [
+            _ev("99439", 2021, "created", p_id=1),
+            _ev("99439", 2021, "replaces", frm="G2058", p_id=1),
+        ]
+        assert len(lineage._collapse(rows)) == 2
+
+
+class TestElementDiffs:
+    def test_no_diffs_when_fewer_than_two_codes_have_elements(self, con):
+        c, _ = con
+        assert lineage._element_diffs(c, ["99490"], None) == ((), "")
+
+    def test_notes_when_exactly_one_code_has_elements(self, con):
+        c, _ = con
+        write_elements(c, "99490", [_el("99490", 2026, "consent", "required")], [])
+        diffs, note = lineage._element_diffs(c, ["99490", "99491", "G0556"], None)
+        assert diffs == ()
+        assert note == "elements extracted for 1 of 3 codes"
+
+    def test_shared_value_diffs_from_the_one_missing_code(self, con, store):
+        c, _ = con
+        write_elements(
+            c,
+            "99490",
+            [_el("99490", 2026, "consent", "required", "YBM4IZUS", 1578)],
+            [],
+        )
+        write_elements(c, "99491", [_el("99491", 2026, "consent", "required")], [])
+        write_elements(c, "G0556", [_el("G0556", 2026, "telehealth", "yes")], [])
+        diffs, note = lineage._element_diffs(c, ["99490", "99491", "G0556"], store)
+        assert note == ""
+        by_pair = {(d.type, d.value): d for d in diffs}
+        assert set(by_pair) == {("consent", "required"), ("telehealth", "yes")}
+        consent = by_pair[("consent", "required")]
+        assert consent.in_codes == ("99490", "99491")
+        assert consent.not_in_codes == ("G0556",)
+        assert consent.label == "CY2021 PFS final ¶1578"  # from the anchored 99490 row
+        telehealth = by_pair[("telehealth", "yes")]
+        assert telehealth.in_codes == ("G0556",)
+        assert telehealth.not_in_codes == ("99490", "99491")
+
+    def test_no_diff_when_every_code_with_elements_shares_the_value(self, con):
+        c, _ = con
+        write_elements(c, "99490", [_el("99490", 2026, "consent", "required")], [])
+        write_elements(c, "99491", [_el("99491", 2026, "consent", "required")], [])
+        diffs, _ = lineage._element_diffs(c, ["99490", "99491"], None)
+        assert diffs == ()
+
+    def test_only_the_newest_year_per_code_is_compared(self, con):
+        c, _ = con
+        write_elements(
+            c,
+            "99490",
+            [
+                _el("99490", 2020, "consent", "verbal"),
+                _el("99490", 2026, "consent", "required"),
+            ],
+            [],
+        )
+        write_elements(c, "99491", [_el("99491", 2026, "consent", "verbal")], [])
+        diffs, _ = lineage._element_diffs(c, ["99490", "99491"], None)
+        # 2020's "verbal" for 99490 must not be compared — only 2026's
+        # "required" — so the diff is required (99490) vs verbal (99491).
+        values = {d.value: d for d in diffs}
+        assert "verbal" not in {d.value for d in diffs if "99490" in d.in_codes}
+        assert values["required"].in_codes == ("99490",)
+
+    def test_capped_at_twelve_most_shared_first(self, con):
+        c, _ = con
+        codes = ["A0001", "A0002", "A0003"]
+        for code in codes:
+            rows = [_el(code, 2026, f"t{i}", f"v{i}") for i in range(20)]
+            # one shared value across all three codes, sorts first
+            rows.append(_el(code, 2026, "shared", "yes"))
+            write_elements(c, code, rows, [])
+        # a fourth code with none of the "t*" values, so every t* pair
+        # differs (present in the three, absent in the fourth)
+        write_elements(c, "A0004", [_el("A0004", 2026, "shared", "no")], [])
+        diffs, _ = lineage._element_diffs(c, codes + ["A0004"], None)
+        assert len(diffs) == 12
+        assert diffs[0].in_codes == ("A0001", "A0002", "A0003")
+
+
+class TestGuidance:
+    def test_cfr_first_deduped_and_capped(self, con, store):
+        c, _ = con
+        rows = [
+            _gd("CCM", "99490", "cfr", f"42 CFR 410.{i}", "YBM4IZUS", 686)
+            for i in range(6)
+        ]
+        rows += [
+            _gd("CCM", "99490", "iom", f"100-04 ch.{i}", "YBM4IZUS", 686)
+            for i in range(6)
+        ]
+        write_guidance(c, "CCM", rows)
+        out = lineage._collect_guidance(c, store, ["CCM"], [])
+        assert len(out) == 8
+        assert [g.kind for g in out[:6]] == ["cfr"] * 6
+        assert out[0].url == "https://www.ecfr.gov/current/title-42/section-410.0"
+
+    def test_dedupes_by_locator(self, con, store):
+        c, _ = con
+        write_guidance(
+            c,
+            "CCM",
+            [
+                _gd("CCM", "99490", "cfr", "42 CFR 410.78(a)(3)", "YBM4IZUS", 1578),
+                _gd("CCM", "99491", "cfr", "42 CFR 410.78(a)(3)", "YBM4IZUS", 686),
+            ],
+        )
+        out = lineage._collect_guidance(c, store, ["CCM"], [])
+        assert len(out) == 1
+
+    def test_wide_families_are_skipped(self, con, store):
+        c, _ = con
+        write_guidance(
+            c, "APCM", [_gd("APCM", "G0556", "mln", "MLN 907166", "YBM4IZUS", 686)]
+        )
+        out = lineage._collect_guidance(c, store, ["APCM"], ["APCM"])
+        assert out == ()
+
+    def test_iom_mln_have_no_url(self, con, store):
+        c, _ = con
+        write_guidance(
+            c,
+            "CCM",
+            [_gd("CCM", "99490", "iom", "100-04 ch.12 §30.6.4", "YBM4IZUS", 686)],
+        )
+        out = lineage._collect_guidance(c, store, ["CCM"], [])
+        assert out[0].url == ""
+        assert out[0].label == "CY2021 PFS final ¶686"
+
+
+class TestPromptBlock:
+    def test_exact_text(self):
+        events = (
+            LineageEvent(
+                code="G2058",
+                year=2021,
+                kind="replaced_by",
+                from_codes=(),
+                to_codes=("99439",),
+                label="CY2021 PFS final ¶686",
+                item_key="YBM4IZUS",
+                p_id=686,
+                page=84547,
+                url="https://fr.test/2021-doc#p-686",
+                source="fr",
+                anchored=True,
+                note="",
+            ),
+            LineageEvent(
+                code="99439",
+                year=2021,
+                kind="created",
+                from_codes=(),
+                to_codes=(),
+                label="CY2021 PFS final ¶686",
+                item_key="YBM4IZUS",
+                p_id=686,
+                page=84547,
+                url="https://fr.test/2021-doc#p-686",
+                source="fr",
+                anchored=True,
+                note="from CPT Editorial Panel",
+            ),
+        )
+        diffs = (
+            ElementDiff(
+                type="consent",
+                value="required",
+                in_codes=("99490", "99491"),
+                not_in_codes=("G0556",),
+                label="CY2021 PFS final ¶1578",
+                item_key="YBM4IZUS",
+                p_id=1578,
+            ),
+        )
+        guidance = (
+            GuidanceRef(
+                kind="cfr",
+                locator="42 CFR 410.78(a)(3)",
+                url="https://www.ecfr.gov/current/title-42/section-410.78",
+                label="CY2021 PFS final ¶1578",
+                item_key_src="YBM4IZUS",
+                p_id_src=1578,
+            ),
+        )
+        ev = LineageEvidence(
+            codes=("99439", "99490", "99491", "G0556", "G2058"),
+            families=("CCM", "APCM"),
+            events=events,
+            element_diffs=diffs,
+            guidance=guidance,
+        )
+        assert ev.prompt_block() == (
+            "Lineage (dated events with anchors; cite the bracketed label "
+            "for any dated claim):\n"
+            "[CY2021 PFS final ¶686] 2021 replaced_by G2058 ( → 99439)\n"
+            "[CY2021 PFS final ¶686] 2021 created 99439 — "
+            "from CPT Editorial Panel\n"
+            "Element differences:\n"
+            "[CY2021 PFS final ¶1578] consent=required: "
+            "in 99490, 99491; not in G0556\n"
+            "Guidance:\n"
+            "[CY2021 PFS final ¶1578] 42 CFR 410.78(a)(3) — CFR"
+        )
+
+    def test_header_only_with_no_events(self):
+        ev = LineageEvidence(
+            codes=("99490",), families=(), events=(), element_diffs=(), guidance=()
+        )
+        assert ev.prompt_block() == (
+            "Lineage (dated events with anchors; cite the bracketed label "
+            "for any dated claim):"
+        )
+
+    def test_priority_kinds_always_kept_non_priority_trimmed(self):
+        priority = LineageEvent(
+            "99490", 2021, "created", (), (), "[L]", "K", 1, 0, "", "fr", True, ""
+        )
+        noisy = [
+            LineageEvent(
+                "99490",
+                2022 + i,
+                "revalued",
+                (),
+                (),
+                f"[L{i}]",
+                "K",
+                1,
+                0,
+                "",
+                "rvu",
+                True,
+                "",
+            )
+            for i in range(5)
+        ]
+        ev = LineageEvidence(
+            codes=("99490",),
+            families=(),
+            events=(priority, *noisy),
+            element_diffs=(),
+            guidance=(),
+            max_prompt_rows=3,
+        )
+        rendered = ev.prompt_block()
+        assert "created" in rendered
+        assert rendered.count("revalued") == 2  # budget: 3 - 1 priority = 2 kept
+
+    def test_priority_kinds_exceed_cap_but_are_never_dropped(self):
+        priorities = [
+            LineageEvent(
+                "99490", 2020 + i, k, (), (), f"[L{i}]", "K", 1, 0, "", "fr", True, ""
+            )
+            for i, k in enumerate(["created", "replaces", "replaced_by", "deleted"])
+        ]
+        ev = LineageEvidence(
+            codes=("99490",),
+            families=(),
+            events=tuple(priorities),
+            element_diffs=(),
+            guidance=(),
+            max_prompt_rows=2,
+        )
+        rendered = ev.prompt_block()
+        for kind in ("created", "replaces", "replaced_by", "deleted"):
+            assert kind in rendered
+
+
+class TestPayload:
+    def test_json_serializable_and_shaped(self):
+        events = (
+            LineageEvent(
+                "99439",
+                2021,
+                "created",
+                (),
+                (),
+                "[L]",
+                "YBM4IZUS",
+                686,
+                84547,
+                "u",
+                "fr",
+                True,
+                "",
+            ),
+        )
+        ev = LineageEvidence(
+            codes=("99439",),
+            families=("CCM",),
+            events=events,
+            element_diffs=(),
+            guidance=(),
+            elements_note="elements extracted for 1 of 3 codes",
+        )
+        payload = ev.payload()
+        raw = json.dumps(payload)
+        back = json.loads(raw)
+        assert back["type"] == "lineage"
+        assert back["codes"] == ["99439"]
+        assert back["families"] == ["CCM"]
+        assert back["events"][0]["kind"] == "created"
+        assert back["elements_note"] == "elements extracted for 1 of 3 codes"
+
+    def test_no_elements_note_key_when_empty(self):
+        ev = LineageEvidence(("99439",), (), (), (), ())
+        assert "elements_note" not in ev.payload()
+
+
+class TestLineageEvidence:
+    def test_none_when_no_codes_detected(self):
+        assert (
+            lineage_evidence("what did commenters say about telehealth?", CFG) is None
+        )
+
+    def test_collapsed_events_and_labels_for_the_ccm_fixture(self, con, store):
+        c, path = con
+        write_events(
+            c,
+            "99490",
+            [
+                _ev(
+                    "99490",
+                    2015,
+                    "adopted_cpt",
+                    item_key="DE2VH9PD",
+                    p_id=1251,
+                    page=67716,
+                )
+            ],
+        )
+        write_events(
+            c,
+            "G2058",
+            [
+                _ev(
+                    "G2058",
+                    2021,
+                    "replaced_by",
+                    to="99439",
+                    item_key="YBM4IZUS",
+                    p_id=686,
+                    page=84547,
+                ),
+                _ev("G2058", 2022, "disappeared", source="rvu", item_key="", p_id=0),
+            ],
+        )
+        write_events(
+            c,
+            "99439",
+            [
+                _ev(
+                    "99439", 2021, "created", item_key="YBM4IZUS", p_id=686, page=84547
+                ),
+                _ev(
+                    "99439",
+                    2021,
+                    "replaces",
+                    frm="G2058",
+                    item_key="YBM4IZUS",
+                    p_id=1578,
+                    page=84639,
+                ),
+                # same group as the fr "created" row above — collapse must
+                # drop this rvu duplicate.
+                _ev(
+                    "99439",
+                    2021,
+                    "created",
+                    source="rvu",
+                    item_key="",
+                    p_id=0,
+                    note="dupe",
+                ),
+            ],
+        )
+        c.close()  # release the write handle before lineage_evidence opens read-only
+        cfg = replace(CFG, duckdb_replica=str(path))
+        det = Detection(
+            codes=("99439", "99490", "G2058"), families=(), explicit=(), wide=()
+        )
+        with patch("llm.lineage._store", return_value=store):
+            with patch("llm.lineage.detect_codes", return_value=det):
+                ev = lineage_evidence("irrelevant text", cfg)
+        assert ev is not None
+        assert [(e.year, e.code, e.kind, e.source) for e in ev.events] == [
+            (2015, "99490", "adopted_cpt", "fr"),
+            (2021, "99439", "created", "fr"),
+            (2021, "99439", "replaces", "fr"),
+            (2021, "G2058", "replaced_by", "fr"),
+            (2022, "G2058", "disappeared", "rvu"),
+        ]
+        adopted, created, replaces, replaced_by, disappeared = ev.events
+        assert adopted.label == "CY2015 PFS final ¶1251"
+        assert created.label == "CY2021 PFS final ¶686"
+        assert replaces.label == "CY2021 PFS final ¶1578"
+        assert replaces.from_codes == ("G2058",)
+        assert replaced_by.to_codes == ("99439",)
+        assert disappeared.label == "PFS CY2022 RVU file"
+        assert created.url == "https://fr.test/2021-doc#p-686"
+
+    def test_on_demand_fallback_only_for_codes_without_rows_and_capped(
+        self, con, store
+    ):
+        c, path = con
+        rvu_cols = (
+            "hcpcs VARCHAR, mod VARCHAR, description VARCHAR, status_code VARCHAR, "
+            "non_fac_total DOUBLE, year INTEGER"
+        )
+        c.execute(f"CREATE TABLE pfs.rvu ({rvu_cols})")
+        c.executemany(
+            "INSERT INTO pfs.rvu VALUES (?,?,?,?,?,?)",
+            [
+                *[("00000", None, "filler", "A", 1.0, y) for y in range(2015, 2027)],
+                ("99441", None, "d", "A", 1.0, 2020),
+                ("99441", None, "d", "A", 1.0, 2021),
+                ("99442", None, "d", "A", 1.0, 2020),
+                ("99442", None, "d", "A", 1.0, 2021),
+            ],
+        )
+        # 99490 has precomputed rows — must not trigger the fallback.
+        write_events(
+            c,
+            "99490",
+            [_ev("99490", 2015, "adopted_cpt", item_key="DE2VH9PD", p_id=1251)],
+        )
+        c.close()  # release the write handle before lineage_evidence opens read-only
+        cfg = replace(CFG, duckdb_replica=str(path), lineage_on_demand_max=1)
+        det = Detection(
+            codes=("99441", "99442", "99490"), families=(), explicit=(), wide=()
+        )
+        with patch("llm.lineage._store", return_value=store):
+            with patch("llm.lineage.detect_codes", return_value=det):
+                with patch(
+                    "llm.lineage._on_demand_events", wraps=lineage._on_demand_events
+                ) as spy:
+                    ev = lineage_evidence("irrelevant text", cfg)
+        assert ev is not None
+        # budget is 1: only the first no-rows code (99441, sorted first)
+        # gets the fallback; 99442 and the precomputed 99490 do not.
+        assert spy.call_count == 1
+        assert spy.call_args.args[-1] == "99441"
+        codes_with_events = {e.code for e in ev.events}
+        assert "99441" in codes_with_events
+        assert "99442" not in codes_with_events
+
+    def test_never_raises_on_a_broken_replica(self, tmp_path):
+        bad = tmp_path / "not-a-duckdb-file"
+        bad.write_text("not a database")
+        cfg = replace(CFG, duckdb_replica=str(bad))
+        det = Detection(codes=("99490",), families=(), explicit=(), wide=())
+        with patch("llm.lineage.detect_codes", return_value=det):
+            assert lineage_evidence("irrelevant", cfg) is None
+
+    def test_elements_note_and_guidance_flow_through(self, con, store):
+        c, path = con
+        write_elements(c, "99490", [_el("99490", 2026, "consent", "required")], [])
+        write_guidance(
+            c,
+            "CCM",
+            [_gd("CCM", "99490", "cfr", "42 CFR 410.78(a)(3)", "YBM4IZUS", 1578)],
+        )
+        c.close()  # release the write handle before lineage_evidence opens read-only
+        cfg = replace(CFG, duckdb_replica=str(path))
+        det = Detection(codes=("99490",), families=("CCM",), explicit=(), wide=())
+        with patch("llm.lineage._store", return_value=store):
+            with patch("llm.lineage.detect_codes", return_value=det):
+                ev = lineage_evidence("irrelevant", cfg)
+        assert ev is not None
+        assert ev.elements_note == "elements extracted for 1 of 1 codes"
+        assert ev.element_diffs == ()
+        assert len(ev.guidance) == 1
+        assert ev.guidance[0].locator == "42 CFR 410.78(a)(3)"
+
+
+class TestLineageEvidenceLive:
+    @pytest.mark.live
+    def test_median_under_300ms_on_live_replica(self):
+        from conf import ROOT
+
+        replica = ROOT / "data" / "replica" / "aco.ro.duckdb"
+        if not replica.exists():
+            pytest.skip(f"no live replica at {replica}")
+        cfg = replace(CFG, duckdb_replica=str(replica))
+        lineage_evidence("history of CCM coding and payment", cfg)  # warm
+        times_ms = []
+        for _ in range(5):
+            start = time.perf_counter()
+            lineage_evidence("history of CCM coding and payment", cfg)
+            times_ms.append((time.perf_counter() - start) * 1000)
+        times_ms.sort()
+        median = times_ms[len(times_ms) // 2]
+        print(f"lineage_evidence median: {median:.2f} ms (all: {times_ms})")
+        assert median < 300, f"{median:.2f} ms over {times_ms}"

tests/llm/test_rag.py

@@ -1,5 +1,6 @@
 """llm.rag — multi-collection retrieval + grounded streaming answer."""
 
+import json
 from datetime import date
 from unittest.mock import MagicMock, patch
 
@@ -7,6 +8,7 @@ import pytest
 from langchain_core.documents import Document
 
 from llm.config import LlmConfig
+from llm.lineage import LineageEvent, LineageEvidence
 from llm.rag import build_messages, retrieve, stream_answer
 
 CFG = LlmConfig(
@@ -287,6 +289,57 @@ class TestBuildMessages:
         assert build_messages("q", []) == build_messages("q", [], evidence=None)
         assert "Valuation" not in build_messages("q", [])[1]["content"]
 
+    def test_lineage_block_between_excerpts_and_valuation(self):
+        from llm.evidence import ValuationEvidence
+
+        le = LineageEvidence(
+            codes=("G2058",),
+            families=("CCM",),
+            events=(
+                LineageEvent(
+                    "G2058",
+                    2021,
+                    "replaced_by",
+                    (),
+                    ("99439",),
+                    "CY2021 PFS final ¶686",
+                    "YBM4IZUS",
+                    686,
+                    0,
+                    "u",
+                    "fr",
+                    True,
+                    "",
+                ),
+            ),
+            element_diffs=(),
+            guidance=(),
+        )
+        ev = ValuationEvidence(("G2058",), ("CCM",), (), ())
+        msgs = build_messages("history?", [], evidence=ev, lineage=le)
+        user = msgs[1]["content"]
+        assert (
+            user.index("Excerpts:")
+            < user.index("Lineage (dated events")
+            < user.index("Valuation (authoritative")
+            < user.index("Question: history?")
+        )
+        assert "[CY2021 PFS final ¶686] 2021 replaced_by G2058" in user
+        assert "lineage" in msgs[0]["content"].lower()
+        assert "cite its bracketed label for every dated claim" in msgs[0]["content"]
+
+    def test_lineage_only_no_valuation_block(self):
+        le = LineageEvidence(
+            codes=("G2058",), families=(), events=(), element_diffs=(), guidance=()
+        )
+        msgs = build_messages("q", [], lineage=le)
+        user = msgs[1]["content"]
+        assert "Lineage (dated events" in user
+        assert "Valuation (authoritative" not in user
+
+    def test_no_lineage_prompt_unchanged(self):
+        assert build_messages("q", []) == build_messages("q", [], lineage=None)
+
 
 class TestStreamAnswer:
     def _pool(self, vram=24.0, serves_big=True):
@@ -298,10 +351,11 @@ class TestStreamAnswer:
 
     @patch("llm.rag._engine")
     @patch("llm.rag.valuation_evidence", return_value=None)
+    @patch("llm.rag.lineage_evidence", return_value=None)
     @patch("llm.rag.httpx.Client")
     @patch("llm.rag.retrieve")
     def test_yields_tokens_then_sources_then_done(
-        self, mock_retrieve, MockClient, _ev, mock_engine
+        self, mock_retrieve, MockClient, _lin, _ev, mock_engine
     ):
         src = {
             "id": "C1",
@@ -343,9 +397,10 @@ class TestStreamAnswer:
         assert client.stream.call_args.args[1] == "http://h1:11434/api/chat"
 
     @patch("llm.rag.valuation_evidence", return_value=None)
+    @patch("llm.rag.lineage_evidence", return_value=None)
     @patch("llm.rag.httpx.Client")
     @patch("llm.rag.retrieve")
-    def test_small_host_uses_baseline_model(self, mock_retrieve, MockClient, _ev):
+    def test_small_host_uses_baseline_model(self, mock_retrieve, MockClient, _lin, _ev):
         mock_retrieve.return_value = []
         client = MockClient.return_value.__enter__.return_value
         resp = client.stream.return_value.__enter__.return_value
@@ -355,9 +410,10 @@ class TestStreamAnswer:
         assert events[-2]["model"] == "chat"
 
     @patch("llm.rag.valuation_evidence", return_value=None)
+    @patch("llm.rag.lineage_evidence", return_value=None)
     @patch("llm.rag.httpx.Client")
     @patch("llm.rag.retrieve")
-    def test_since_forwarded(self, mock_retrieve, MockClient, _ev):
+    def test_since_forwarded(self, mock_retrieve, MockClient, _lin, _ev):
         mock_retrieve.return_value = []
         client = MockClient.return_value.__enter__.return_value
         resp = client.stream.return_value.__enter__.return_value
@@ -366,9 +422,10 @@ class TestStreamAnswer:
         assert mock_retrieve.call_args.kwargs["since"] == "2025-09-01"
 
     @patch("llm.rag.valuation_evidence", return_value=None)
+    @patch("llm.rag.lineage_evidence", return_value=None)
     @patch("llm.rag.httpx.Client")
     @patch("llm.rag.retrieve")
-    def test_http_error_propagates(self, mock_retrieve, MockClient, _ev):
+    def test_http_error_propagates(self, mock_retrieve, MockClient, _lin, _ev):
         mock_retrieve.return_value = []
         client = MockClient.return_value.__enter__.return_value
         resp = client.stream.return_value.__enter__.return_value
@@ -379,10 +436,11 @@ class TestStreamAnswer:
     @patch("llm.rag._engine")
     @patch("llm.rag.code_cited_sources")
     @patch("llm.rag.valuation_evidence")
+    @patch("llm.rag.lineage_evidence", return_value=None)
     @patch("llm.rag.httpx.Client")
     @patch("llm.rag.retrieve")
     def test_valuation_event_first_and_sources_merged(
-        self, mock_retrieve, MockClient, mock_ev, mock_cited, mock_engine
+        self, mock_retrieve, MockClient, _lin, mock_ev, mock_cited, mock_engine
     ):
         from llm.evidence import ValuationEvidence
 
@@ -422,3 +480,161 @@ class TestStreamAnswer:
         )
         body = client.stream.call_args.kwargs["json"]
         assert "Valuation (authoritative" in body["messages"][1]["content"]
+
+    @patch("llm.rag._engine")
+    @patch("llm.rag.code_cited_sources")
+    @patch("llm.rag.valuation_evidence")
+    @patch("llm.rag.lineage_evidence")
+    @patch("llm.rag.httpx.Client")
+    @patch("llm.rag.retrieve")
+    def test_lineage_event_before_valuation_and_tokens(
+        self, mock_retrieve, MockClient, mock_lin, mock_ev, mock_cited, mock_engine
+    ):
+        from llm.evidence import ValuationEvidence
+
+        mock_retrieve.return_value = []
+        mock_cited.return_value = []
+        mock_lin.return_value = LineageEvidence(
+            codes=("G2058",),
+            families=("CCM",),
+            events=(
+                LineageEvent(
+                    "G2058",
+                    2021,
+                    "replaced_by",
+                    (),
+                    ("99439",),
+                    "CY2021 PFS final ¶686",
+                    "YBM4IZUS",
+                    686,
+                    0,
+                    "u",
+                    "fr",
+                    True,
+                    "",
+                ),
+            ),
+            element_diffs=(),
+            guidance=(),
+        )
+        mock_ev.return_value = ValuationEvidence(("G2058",), ("CCM",), (), ())
+        client = MockClient.return_value.__enter__.return_value
+        resp = client.stream.return_value.__enter__.return_value
+        resp.iter_lines.return_value = iter(['{"message":{"content":"x"},"done":true}'])
+
+        events = list(stream_answer("history of G2058?", cfg=CFG, pool=self._pool()))
+
+        assert [e["type"] for e in events] == [
+            "lineage",
+            "valuation",
+            "token",
+            "sources",
+            "done",
+        ]
+        assert events[0]["codes"] == ["G2058"]
+        body = client.stream.call_args.kwargs["json"]
+        content = body["messages"][1]["content"]
+        assert content.index("Lineage (dated events") < content.index(
+            "Valuation (authoritative"
+        )
+
+    @patch("llm.rag._engine")
+    @patch("llm.rag.code_cited_sources")
+    @patch("llm.rag.valuation_evidence", return_value=None)
+    @patch("llm.rag.lineage_evidence")
+    @patch("llm.rag.httpx.Client")
+    @patch("llm.rag.retrieve")
+    def test_lineage_only_calls_cited_sources_with_lineage_codes(
+        self, mock_retrieve, MockClient, mock_lin, _ev, mock_cited, mock_engine
+    ):
+        mock_retrieve.return_value = []
+        mock_cited.return_value = []
+        mock_lin.return_value = LineageEvidence(
+            codes=("99490", "99491"),
+            families=("CCM",),
+            events=(),
+            element_diffs=(),
+            guidance=(),
+        )
+        client = MockClient.return_value.__enter__.return_value
+        resp = client.stream.return_value.__enter__.return_value
+        resp.iter_lines.return_value = iter(['{"message":{"content":"x"},"done":true}'])
+
+        events = list(stream_answer("CCM history?", cfg=CFG, pool=self._pool()))
+
+        assert events[0]["type"] == "lineage"
+        mock_cited.assert_called_once_with(
+            mock_engine.return_value,
+            ("99490", "99491"),
+            per_code=CFG.code_cited_per_code,
+            collections=CFG.code_cited_collections,
+            families=("CCM",),
+            max_total=CFG.code_cited_max,
+        )
+
+    @patch("llm.rag._engine")
+    @patch("llm.rag.code_cited_sources")
+    @patch("llm.rag.valuation_evidence")
+    @patch("llm.rag.lineage_evidence")
+    @patch("llm.rag.httpx.Client")
+    @patch("llm.rag.retrieve")
+    def test_codes_and_families_unioned_when_both_present(
+        self, mock_retrieve, MockClient, mock_lin, mock_ev, mock_cited, mock_engine
+    ):
+        from llm.evidence import ValuationEvidence
+
+        mock_retrieve.return_value = []
+        mock_cited.return_value = []
+        # lineage reaches a code (G2058) with no RVU rows valuation never sees.
+        mock_lin.return_value = LineageEvidence(
+            codes=("99490", "G2058"),
+            families=("CCM",),
+            events=(),
+            element_diffs=(),
+            guidance=(),
+        )
+        mock_ev.return_value = ValuationEvidence(("99490",), ("CCM",), (), ())
+        client = MockClient.return_value.__enter__.return_value
+        resp = client.stream.return_value.__enter__.return_value
+        resp.iter_lines.return_value = iter(['{"message":{"content":"x"},"done":true}'])
+
+        list(stream_answer("CCM and G2058?", cfg=CFG, pool=self._pool()))
+
+        mock_cited.assert_called_once_with(
+            mock_engine.return_value,
+            ("99490", "G2058"),
+            per_code=CFG.code_cited_per_code,
+            collections=CFG.code_cited_collections,
+            families=("CCM",),
+            max_total=CFG.code_cited_max,
+        )
+
+    @patch("llm.rag.valuation_evidence", return_value=None)
+    @patch("llm.rag.httpx.Client")
+    @patch("llm.rag.retrieve")
+    def test_control_question_events_match_the_no_lineage_baseline(
+        self, mock_retrieve, MockClient, _ev
+    ):
+        """No codes in the question — the real lineage_evidence short-
+        circuits on an empty Detection without touching the replica, so
+        its event stream must be byte-identical to one where the feature
+        is switched off outright (``lineage_evidence`` patched to
+        ``None``)."""
+        mock_retrieve.return_value = []
+        client = MockClient.return_value.__enter__.return_value
+        resp = client.stream.return_value.__enter__.return_value
+
+        def _run():
+            resp.iter_lines.return_value = iter(
+                ['{"message":{"content":"x"},"done":true}']
+            )
+            return list(
+                stream_answer(
+                    "why did CMS finalize this policy?", cfg=CFG, pool=self._pool()
+                )
+            )
+
+        with_real_lineage = json.dumps(_run())
+        with patch("llm.rag.lineage_evidence", return_value=None):
+            with_lineage_off = json.dumps(_run())
+        assert with_real_lineage == with_lineage_off