plan(fb-38): score semantics implementation plan

7 tasks: kebab-core ScoreKind enum + SearchHit field, lexical Bm25
labeling, vector Cosine, hybrid Rrf + search_with_trace pass-through,
cross-crate SearchHit literal cleanup, CLI integration test, docs
(wire schema + README + design + SKILL + INDEX).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -3525,7 +3525,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-app"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "base64 0.22.1",
@@ -3569,7 +3569,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-chunk"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3584,7 +3584,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-cli"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "clap",
@@ -3605,7 +3605,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-config"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "dirs 5.0.1",
@@ -3620,7 +3620,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-core"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3634,7 +3634,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-embed"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3648,7 +3648,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-embed-local"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "fastembed",
@@ -3661,7 +3661,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-eval"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "kebab-app",
@@ -3680,7 +3680,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-llm"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "kebab-core",
@@ -3689,7 +3689,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-llm-local"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "kebab-config",
@@ -3706,7 +3706,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-mcp"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "kebab-app",
@@ -3724,7 +3724,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-normalize"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "kebab-core",
@@ -3739,7 +3739,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-parse-image"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "ab_glyph",
  "anyhow",
@@ -3763,7 +3763,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-parse-md"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "kebab-core",
@@ -3780,7 +3780,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-parse-pdf"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3793,7 +3793,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-parse-types"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "kebab-core",
  "serde",
@@ -3801,7 +3801,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-rag"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3822,7 +3822,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-search"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "globset",
@@ -3841,7 +3841,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-source-fs"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3858,7 +3858,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-store-sqlite"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3879,7 +3879,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-store-vector"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "arrow",
@@ -3903,7 +3903,7 @@ dependencies = [
 
 [[package]]
 name = "kebab-tui"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "crossterm",

Cargo.toml

@@ -30,7 +30,7 @@ edition       = "2024"
 rust-version  = "1.85"
 license       = "MIT OR Apache-2.0"
 repository    = "https://github.com/altair823/kebab"
-version       = "0.4.0"
+version       = "0.5.0"
 
 [workspace.dependencies]
 anyhow       = "1"

README.md

@@ -71,7 +71,7 @@ kebab doctor
 |------|------|
 | `kebab init` | XDG 경로에 데이터 디렉토리 + config.toml 생성 |
 | `kebab ingest [<path>]` | Markdown / 이미지 / PDF 색인 (idempotent). TTY 에서는 stderr 진행 바, non-TTY (CI / pipe) 는 stderr 한 줄씩, `--json` 은 stdout 에 `ingest_progress.v1` 라인 streaming 후 마지막에 `ingest_report.v1`. Ctrl-C 한 번이면 현재 asset 마무리 후 abort (부분 commit 보존, idempotent re-run), 두 번째 Ctrl-C 는 hard exit. Markdown title 이 frontmatter 에 없어도 첫 H1 → H2 → 첫 paragraph 80 자 → 파일명 순으로 자동 채움 (parser_version `md-frontmatter-v2`) — 기존 색인된 doc 도 다음 ingest 에서 새 title 로 갱신. **Incremental** (p9-fb-23): 두 번째 이후의 ingest 는 변하지 않은 doc (blake3 + parser/chunker/embedder version 모두 동일) 의 parse/chunk/embed/vector upsert 를 자동 스킵. final summary 에 `N unchanged` 카운트 표시. `--force-reingest` 로 skip 무시 강제 재처리. **지원 형식** (extractor 자동 결정 — config 에 명시 불가): Markdown (`.md`), 이미지 (`.png` / `.jpg` / `.jpeg`, OCR + caption), PDF (`.pdf`). 다른 확장자는 자동 skip — `IngestItem.warnings` 에 사유 (`"unsupported media type: .docx"` 등), `IngestReport.skipped_by_extension` 에 카운트 분류, CLI / TUI summary 에 breakdown 표시. |
-| `kebab search --mode {lexical,vector,hybrid} "<query>" [--no-cache] [--max-tokens N] [--snippet-chars N] [--cursor <opaque>] [--tag T] [--lang L] [--path-glob G] [--trust-min LEVEL] [--media TYPE] [--ingested-after RFC3339] [--doc-id ID]` | 검색. hybrid는 RRF fusion, citation 포함. 같은 process 안에서 동일 query (NFKC + trim + lowercase 정규화) 반복 시 in-process LRU 캐시 hit (capacity = `[search] cache_capacity`, default 256). `--no-cache` 로 강제 bypass — 디버깅용. ingest commit 발생 시 `kv['corpus_revision']` bump 으로 모든 entry 자동 stale. **`--max-tokens` / `--snippet-chars` / `--cursor` (p9-fb-34)** — agent budget controls. `--json` 출력은 `search_response.v1` wrapper (`{hits, next_cursor, truncated}`) — pre-fb-34 의 bare array 와 호환 안 됨. mismatched cursor → `error.v1.code = stale_cursor`. **filter flags (p9-fb-36):** `--tag` 는 반복 가능 flag (`--tag rust --tag async`) 로 OR 매칭, `--media` 는 `,` 구분 다중 값 OR 매칭, 나머지 flags 간은 AND 조합. `--trust-min` 은 `primary\|secondary\|generated` 중 하나 (해당 level 이상 포함). `--ingested-after` 는 RFC3339 UTC — 파싱 실패 시 `error.v1.code = config_invalid` (exit 2). `--media md` 는 `markdown` alias 로 정규화. 알 수 없는 `--media` 값은 무조건 empty hits (오류 아님). |
+| `kebab search --mode {lexical,vector,hybrid} "<query>" [--no-cache] [--max-tokens N] [--snippet-chars N] [--cursor <opaque>] [--tag T] [--lang L] [--path-glob G] [--trust-min LEVEL] [--media TYPE] [--ingested-after RFC3339] [--doc-id ID] [--trace]` | 검색. hybrid는 RRF fusion, citation 포함. 같은 process 안에서 동일 query (NFKC + trim + lowercase 정규화) 반복 시 in-process LRU 캐시 hit (capacity = `[search] cache_capacity`, default 256). `--no-cache` 로 강제 bypass — 디버깅용. ingest commit 발생 시 `kv['corpus_revision']` bump 으로 모든 entry 자동 stale. **`--max-tokens` / `--snippet-chars` / `--cursor` (p9-fb-34)** — agent budget controls. `--json` 출력은 `search_response.v1` wrapper (`{hits, next_cursor, truncated}`) — pre-fb-34 의 bare array 와 호환 안 됨. mismatched cursor → `error.v1.code = stale_cursor`. **filter flags (p9-fb-36):** `--tag` 는 반복 가능 flag (`--tag rust --tag async`) 로 OR 매칭, `--media` 는 `,` 구분 다중 값 OR 매칭, 나머지 flags 간은 AND 조합. `--trust-min` 은 `primary\|secondary\|generated` 중 하나 (해당 level 이상 포함). `--ingested-after` 는 RFC3339 UTC — 파싱 실패 시 `error.v1.code = config_invalid` (exit 2). `--media md` 는 `markdown` alias 로 정규화. 알 수 없는 `--media` 값은 무조건 empty hits (오류 아님). **`--trace` (p9-fb-37)** — `search_response.v1.trace` 에 lexical / vector pre-fusion 후보 + RRF union + per-stage timing (`lexical_ms` / `vector_ms` / `fusion_ms` / `total_ms`) 노출. trace 요청은 캐시 우회 (`--no-cache` 없이도 항상 cold). |
 | `kebab list docs` | 색인된 문서 목록 |
 | `kebab inspect doc <id>` / `kebab inspect chunk <id>` | raw record 보기 |
 | `kebab fetch chunk <id> [--context N]` / `kebab fetch doc <id> [--max-tokens N]` / `kebab fetch span <doc_id> <ls> <le> [--max-tokens N]` | (p9-fb-35) verbatim text fetch from indexed corpus. wire = `fetch_result.v1` (kind discriminator). chunk: target + ±N ordinal-context chunks. doc: full normalized markdown. span: 1-based line range (PDF/audio rejected as `error.v1.code = span_not_supported`). chars/4 budget on doc/span. |
@@ -80,7 +80,7 @@ kebab doctor
 | `kebab tui` | Ratatui 셸 (Library + Search + Ask + Inspect 패널, desktop 진행 중). Library 에서 `r` 키로 background ingest 시작 — 화면 하단 status bar 가 진행 표시, 완료/abort 시 final 라인 잠시 유지 후 자동 hide. ingest 진행 중 `Esc` / `Ctrl-C` 가 cancel signal (그 외에는 quit). vim-style mode (header 우측 `-- NORMAL --` / `-- INSERT --`) — Library/Inspect 는 자동 NORMAL, Search/Ask 는 자동 INSERT. `i` 로 Normal→Insert (모든 pane — p9-fb-21), `Esc` 로 Insert→Normal 어디서나. mode-authoritative dispatch — Search 의 `j/k/o/g`, Ask 의 `e/j/k` 는 NORMAL 모드에서만 명령으로 동작, INSERT 에서는 입력 문자로 typing. (Search 의 chunk inspect 키는 `i`→`o` 로 rebind — `i` 가 universal Insert toggle.) **`F1` 로 cheatsheet popup** (현재 pane 의 키 매핑 + global 토글 표) — `Esc` / `F1` 로 닫기. Search 패널은 200ms debounce 후 background worker 가 검색 — 키 입력으로 UI freeze 안 됨, 사용자가 계속 타이핑하면 stale 결과 자동 폐기 (generation counter). Ask 패널은 multi-turn — 같은 conversation 안에서 Q1/A1, Q2/A2 transcript 누적, 다음 질문이 이전 턴을 history 로 받아 답변. 답변 본문은 markdown 렌더 (bold/italic/inline code/heading/list/code fence/table/blockquote, raw `**bold**` 가 실제 굵게 표시). `Ctrl-L` 로 새 conversation 시작. Search 의 `g` 키가 `$EDITOR` (기본 `vi`) 로 hit 의 citation 위치 열기 — 종료 후 TUI 화면이 자동으로 깨끗이 redraw. CLI `kebab ask` 는 raw markdown 그대로 (terminal 호환성 위해). Library 의 doc-list 가 한글 / 일본어 / 중국어 (CJK) 제목을 wide-char 정확한 column width 로 truncate — 한글 제목이 한 줄을 넘기지 않음 (CJK 1 자 = 2 col). Search/Ask/Filter 입력의 cursor 가 wide char 위에서 column 단위로 정렬 — 한글 입력 시 caret 이 글자 옆에 정확히 놓임. `← / →` 로 입력 문자열 중간 cursor 이동 (한글 한 글자 = 2 column 이라도 한 번에 이동), `Home / End` 로 양 끝 점프, `Delete` 로 cursor 위치 char 삭제 — 모든 input pane (Ask / Search / Library filter overlay) 동일 (p9-fb-22). Ask 트랜스크립트는 새 답변이 viewport 아래로 누적될 때 자동으로 tail 을 따라감 (auto-scroll); `j` / `k` 로 위로 스크롤하면 freeze, `Shift-G` 로 다시 bottom + auto-tail 재개. 화면 하단 hint line 은 한국어 동사구로 (`"위로"` / `"아래로"` / `"필터"` / `"타이핑 검색어"` / `"Esc 로 NORMAL 모드"` / `"i 입력모드"` 등) + 현재 (pane, mode) 조합에 맞춰 자동 분기, **첫 fragment 가 항상 `F1 도움말`** (cheatsheet 발견성 보장). 모든 모드에서 항상 떠 있는 상태바 — `kebab v<version> │ <pane> │ <docs> docs │ <state>` (state: streaming/searching/indexing/idle, ingest 진행 중에는 progress 가 같은 자리에 흡수됨). Ask 진입 시 conversation id 8 자 prefix 도 함께 표시. Ask 트랜스크립트와 Inspect 양쪽에서 `PgUp / PgDn` 으로 10 줄씩 페이지 스크롤. Library 의 doc list 위에는 `TITLE / TAGS / UPDATED / CHUNKS` 컬럼 헤더 행 표시 (display-width 정렬, Hangul / CJK 안전). |
 | `kebab reset [--all / --data-only / --vector-only / --config-only] [--yes]` | XDG 데이터 wipe. **Irreversible.** TTY 면 confirm prompt, 아니면 `--yes` 필수. `--vector-only` 는 SQLite `embedding_records` 도 함께 truncate (orphan 방지) |
 | `kebab eval run / compare` | golden query 회귀 측정 |
-| `kebab schema [--json]` | introspection — wire schemas / capabilities / models / stats 한 번에. `--json` 은 `schema.v1` wire; 사람 모드는 서식 출력. |
+| `kebab schema [--json]` | introspection — wire schemas / capabilities / models / stats 한 번에. `--json` 은 `schema.v1` wire; 사람 모드는 서식 출력. **stats 에 (p9-fb-37) `media_breakdown` (5 keys: markdown / pdf / image / audio / other) + `lang_breakdown` (BCP-47 코드, NULL 은 literal `"null"`) + `index_bytes` (sqlite + lancedb on-disk 합계) + `stale_doc_count` (`config.search.stale_threshold_days` 초과 doc 수) 추가.** |
 | `kebab ingest-file <path>` | 단일 파일 ingest (workspace 외부 가능). 바이트는 `<workspace.root>/_external/<hash12>.<ext>` 로 copy. `.kebabignore` 매치 시 stderr warn 후 진행 (explicit ingest 가 bypass intent). |
 | `kebab ingest-stdin --title <T> [--source-uri <URI>]` | stdin 의 markdown 본문 ingest. frontmatter (title + source_uri) 자동 prepend. v1 markdown only. |
 | `kebab mcp` | MCP (Model Context Protocol) stdio server. agent host (Claude Code / Cursor / OpenAI Agents) 가 spawn 하여 tool 호출 (`search` / `ask` / `schema` / `doctor` / `ingest_file` / `ingest_stdin`). `--config` honor. |

crates/kebab-app/src/app.rs

@@ -70,6 +70,9 @@ pub struct SearchResponse {
     pub hits: Vec<SearchHit>,
     pub next_cursor: Option<String>,
     pub truncated: bool,
+    /// p9-fb-37: present when caller passed `SearchOpts.trace = true`.
+    /// Consumers that ignore trace should leave this `None`.
+    pub trace: Option<kebab_core::SearchTrace>,
 }
 
 /// Facade state — see module docs for lifetime rules.
@@ -341,6 +344,75 @@ impl App {
             k: fetch_k,
             ..query.clone()
         };
+
+        // p9-fb-37: when --trace is requested, bypass the LRU cache and
+        // run through `HybridRetriever::search_with_trace`, which
+        // dispatches by mode internally. Vector / hybrid modes require
+        // embeddings (same as `--mode hybrid`); lexical mode skips
+        // embedder construction via `NoopRetriever` so lexical-only
+        // workspaces (provider = "none") can use `--trace` without
+        // surfacing the "switch to --mode lexical" error.
+        if opts.trace {
+            let lex = Arc::new(LexicalRetriever::with_settings(
+                self.sqlite.clone(),
+                lexical_index_version(&self.config),
+                self.config.search.snippet_chars,
+            )) as Arc<dyn Retriever>;
+            let vec_retr: Arc<dyn Retriever> = if matches!(query.mode, SearchMode::Lexical) {
+                // `HybridRetriever::search_with_trace` never invokes the
+                // vector retriever for `SearchMode::Lexical` (Task 4).
+                // A no-op stand-in lets us avoid the ~470 MB embedder
+                // load when the user only asked for lexical trace.
+                Arc::new(NoopRetriever)
+            } else {
+                let (emb, vec_store) = self.require_embeddings()?;
+                let vec_iv = vector_index_version(emb.as_ref());
+                let vec_dyn: Arc<dyn VectorStore + Send + Sync> = vec_store;
+                let emb_dyn: Arc<dyn Embedder> = emb;
+                Arc::new(VectorRetriever::with_settings(
+                    vec_dyn,
+                    emb_dyn,
+                    self.sqlite.clone(),
+                    vec_iv,
+                    self.config.search.snippet_chars,
+                )) as Arc<dyn Retriever>
+            };
+            let hybrid = HybridRetriever::new(&self.config, lex, vec_retr);
+            let (mut traced_hits, trace) = hybrid.search_with_trace(&fetch_query)?;
+
+            // Stamp staleness — same as search_uncached.
+            let now = time::OffsetDateTime::now_utc();
+            crate::staleness::mark_stale_in_place(
+                &mut traced_hits,
+                now,
+                self.config.search.stale_threshold_days,
+            );
+
+            // Apply offset + k_effective truncation (mirrors non-trace path).
+            let drop_n = offset.min(traced_hits.len());
+            traced_hits.drain(..drop_n);
+            let mut hits: Vec<SearchHit> =
+                traced_hits.into_iter().take(k_effective).collect();
+
+            // Snippet truncation if opts.snippet_chars set (mirror non-trace path).
+            if opts.snippet_chars.is_some() {
+                for h in hits.iter_mut() {
+                    if h.snippet.chars().count() > snippet_chars {
+                        h.snippet = trim_to_chars(&h.snippet, snippet_chars);
+                    }
+                }
+            }
+
+            // Trace path skips the budget loop. Caller will inspect
+            // `hits.len()` and `trace.timing` rather than paginate.
+            return Ok(SearchResponse {
+                hits,
+                next_cursor: None,
+                truncated: false,
+                trace: Some(trace),
+            });
+        }
+
         let mut all_hits = self.search(fetch_query)?;
 
         // Skip offset.
@@ -421,6 +493,7 @@ impl App {
             hits,
             next_cursor,
             truncated,
+            trace: None,
         })
     }
 
@@ -737,6 +810,24 @@ fn lexical_index_version(config: &kebab_config::Config) -> IndexVersion {
     IndexVersion(format!("lex:{}", config.chunking.chunker_version))
 }
 
+/// p9-fb-37: stand-in for the vector retriever in the trace path when
+/// `query.mode == SearchMode::Lexical`. `HybridRetriever::search_with_trace`'s
+/// Lexical branch never calls `vector.search()`, so returning an empty
+/// hit list here is safe and lets lexical-only workspaces (embedding
+/// `provider = "none"`) use `--trace` without paying the ~470 MB
+/// embedder load.
+struct NoopRetriever;
+
+impl Retriever for NoopRetriever {
+    fn search(&self, _q: &kebab_core::SearchQuery) -> anyhow::Result<Vec<kebab_core::SearchHit>> {
+        Ok(Vec::new())
+    }
+
+    fn index_version(&self) -> kebab_core::IndexVersion {
+        kebab_core::IndexVersion("noop:trace".into())
+    }
+}
+
 /// Compose a stable `IndexVersion` for the vector retriever. Tracks
 /// `(embedding_model, embedding_version, dimensions)` so a model swap
 /// flags drift via the existing index_version mismatch warning in
@@ -847,3 +938,59 @@ mod tests {
         assert_ne!(a, d, "different session_id → different hash");
     }
 }
+
+#[cfg(test)]
+mod tests_trace {
+    use super::*;
+    use kebab_core::{SearchMode, SearchOpts, SearchQuery};
+
+    fn open_app_with_temp_dir() -> (tempfile::TempDir, App) {
+        let dir = tempfile::tempdir().unwrap();
+        let mut cfg = kebab_config::Config::defaults();
+        cfg.storage.data_dir = dir.path().to_string_lossy().into_owned();
+        // Bring up migrations.
+        let store = kebab_store_sqlite::SqliteStore::open(&cfg).unwrap();
+        store.run_migrations().unwrap();
+        drop(store);
+        let app = App::open_with_config(cfg).unwrap();
+        (dir, app)
+    }
+
+    #[test]
+    fn search_response_trace_none_when_opts_trace_false() {
+        let (_dir, app) = open_app_with_temp_dir();
+        let q = SearchQuery {
+            text: "x".into(),
+            mode: SearchMode::Lexical,
+            k: 1,
+            filters: Default::default(),
+        };
+        let resp = app.search_with_opts(q, SearchOpts::default()).unwrap();
+        assert!(resp.trace.is_none());
+    }
+
+    #[test]
+    fn search_response_trace_some_when_opts_trace_true_lexical_mode() {
+        // Lexical mode doesn't require embeddings — the trace path
+        // builds HybridRetriever with a `NoopRetriever` stand-in for
+        // the vector side, since `HybridRetriever::search_with_trace`'s
+        // Lexical branch never invokes `vector.search()`. Default
+        // Config has embedding `provider = "none"`, and lexical-mode
+        // trace must succeed under that config (no embedder load).
+        let (_dir, app) = open_app_with_temp_dir();
+        let q = SearchQuery {
+            text: "x".into(),
+            mode: SearchMode::Lexical,
+            k: 1,
+            filters: Default::default(),
+        };
+        let opts = SearchOpts {
+            trace: true,
+            ..Default::default()
+        };
+        let resp = app
+            .search_with_opts(q, opts)
+            .expect("lexical-mode trace must succeed without embeddings");
+        assert!(resp.trace.is_some(), "trace populated when opts.trace=true");
+    }
+}

crates/kebab-app/src/schema.rs

@@ -50,6 +50,18 @@ pub struct Stats {
     pub chunk_count: u64,
     pub asset_count: u64,
     pub last_ingest_at: Option<String>,
+    /// p9-fb-37: per-media-kind doc count (5 keys, zero-padded).
+    #[serde(default)]
+    pub media_breakdown: std::collections::BTreeMap<String, u64>,
+    /// p9-fb-37: per-language doc count, NULL keyed as `"null"`.
+    #[serde(default)]
+    pub lang_breakdown: std::collections::BTreeMap<String, u64>,
+    /// p9-fb-37: on-disk byte sums.
+    #[serde(default)]
+    pub index_bytes: kebab_core::IndexBytes,
+    /// p9-fb-37: docs whose `updated_at` exceeds the staleness threshold.
+    #[serde(default)]
+    pub stale_doc_count: u64,
 }
 
 const KEBAB_VERSION: &str = env!("CARGO_PKG_VERSION");
@@ -85,7 +97,7 @@ const WIRE_SCHEMAS: &[&str] = &[
 #[doc(hidden)]
 pub fn schema_with_config(cfg: &Config) -> anyhow::Result<SchemaV1> {
     let store = open_store_for_stats(cfg)?;
-    let stats = collect_stats(&store)?;
+    let stats = collect_stats(cfg, &store)?;
     let models = collect_models(cfg, &store);
     Ok(SchemaV1 {
         schema_version: SCHEMA_V1_ID.to_string(),
@@ -124,13 +136,24 @@ fn open_store_for_stats(cfg: &Config) -> anyhow::Result<kebab_store_sqlite::Sqli
     kebab_store_sqlite::SqliteStore::open_existing(&db_path)
 }
 
-fn collect_stats(store: &kebab_store_sqlite::SqliteStore) -> anyhow::Result<Stats> {
-    let counts = store.count_summary()?;
+fn collect_stats(
+    cfg: &Config,
+    store: &kebab_store_sqlite::SqliteStore,
+) -> anyhow::Result<Stats> {
+    let counts = store
+        .count_summary_with_threshold(cfg.search.stale_threshold_days as u64)?;
+    let data_dir = kebab_config::expand_path(&cfg.storage.data_dir, "");
+    let index_bytes = kebab_store_sqlite::stats_ext::index_bytes(&data_dir)
+        .map_err(|e| anyhow::anyhow!("index_bytes: {e}"))?;
     Ok(Stats {
         doc_count: counts.doc_count,
         chunk_count: counts.chunk_count,
         asset_count: counts.asset_count,
         last_ingest_at: counts.last_ingest_at,
+        media_breakdown: counts.media_breakdown,
+        lang_breakdown: counts.lang_breakdown,
+        index_bytes,
+        stale_doc_count: counts.stale_doc_count,
     })
 }
 
@@ -150,3 +173,31 @@ fn collect_models(cfg: &Config, store: &kebab_store_sqlite::SqliteStore) -> Mode
         corpus_revision: store.corpus_revision(),
     }
 }
+
+#[cfg(test)]
+mod tests_stats_ext {
+    use super::*;
+
+    #[test]
+    fn stats_includes_breakdowns_and_bytes_on_fresh_corpus() {
+        let dir = tempfile::tempdir().unwrap();
+        let mut cfg = kebab_config::Config::defaults();
+        cfg.storage.data_dir = dir.path().to_string_lossy().into_owned();
+        // Bring up migrations so the sqlite file is created.
+        let store = kebab_store_sqlite::SqliteStore::open(&cfg).unwrap();
+        store.run_migrations().unwrap();
+        drop(store);
+
+        let s = schema_with_config(&cfg).unwrap();
+        // 5 keys padded.
+        assert_eq!(s.stats.media_breakdown.len(), 5);
+        assert_eq!(s.stats.media_breakdown.get("markdown"), Some(&0));
+        assert_eq!(s.stats.media_breakdown.get("pdf"), Some(&0));
+        // lang map empty on empty corpus.
+        assert!(s.stats.lang_breakdown.is_empty());
+        // sqlite bytes positive after migrations, lancedb 0.
+        assert!(s.stats.index_bytes.sqlite > 0);
+        assert_eq!(s.stats.index_bytes.lancedb, 0);
+        assert_eq!(s.stats.stale_doc_count, 0);
+    }
+}

crates/kebab-app/tests/search_budget_integration.rs

@@ -47,6 +47,7 @@ fn budget_truncates_snippets_when_below_threshold() {
                 max_tokens: Some(50),
                 snippet_chars: None,
                 cursor: None,
+                trace: false,
             },
         )
         .unwrap();
@@ -78,6 +79,7 @@ fn cursor_paginates_to_next_page() {
                 max_tokens: None,
                 snippet_chars: None,
                 cursor: Some(cursor),
+                trace: false,
             },
         )
         .unwrap();
@@ -114,6 +116,7 @@ fn cursor_rejected_after_corpus_revision_bump() {
             max_tokens: None,
             snippet_chars: None,
             cursor: Some(c),
+            trace: false,
         },
     );
     let err = result.unwrap_err();
@@ -147,6 +150,7 @@ fn max_tokens_zero_returns_one_hit_truncated() {
                 max_tokens: Some(0),
                 snippet_chars: None,
                 cursor: None,
+                trace: false,
             },
         )
         .unwrap();

crates/kebab-cli/src/main.rs

@@ -163,6 +163,14 @@ enum Cmd {
         /// p9-fb-36: filter to a single doc by id.
         #[arg(long)]
         doc_id: Option<String>,
+
+        /// p9-fb-37: emit pre-fusion lexical / vector / RRF candidate
+        /// lists + per-stage timing in the response. Bypasses cache
+        /// (debug intent — fresh run guaranteed). Requires embeddings
+        /// when `--mode hybrid` or `--mode vector`; lexical mode runs
+        /// without embeddings via a no-op vector stub.
+        #[arg(long)]
+        trace: bool,
     },
 
     /// Retrieval-augmented question answering.
@@ -669,6 +677,7 @@ fn run(cli: &Cli) -> anyhow::Result<()> {
             media,
             ingested_after,
             doc_id,
+            trace,
         } => {
             let cfg = kebab_config::Config::load(cli.config.as_deref())?;
 
@@ -732,6 +741,7 @@ fn run(cli: &Cli) -> anyhow::Result<()> {
                 max_tokens: *max_tokens,
                 snippet_chars: *snippet_chars,
                 cursor: cursor.clone(),
+                trace: *trace,
             };
             // p9-fb-34: budget-aware path. --no-cache still bypasses the
             // App-level LRU; wire wrapper applies regardless.
@@ -789,6 +799,22 @@ fn run(cli: &Cli) -> anyhow::Result<()> {
                     let next = resp.next_cursor.as_deref().unwrap_or("(none)");
                     eprintln!("[truncated; use --cursor {next} for the next page]");
                 }
+                if *trace {
+                    if let Some(t) = &resp.trace {
+                        eprintln!();
+                        eprintln!("Trace:");
+                        eprintln!("  lexical ({} hits, {}ms):", t.lexical.len(), t.timing.lexical_ms);
+                        for c in t.lexical.iter().take(3) {
+                            eprintln!("    rank={} score={:.4} chunk={}", c.rank, c.score, c.chunk_id.0);
+                        }
+                        eprintln!("  vector ({} hits, {}ms):", t.vector.len(), t.timing.vector_ms);
+                        for c in t.vector.iter().take(3) {
+                            eprintln!("    rank={} score={:.4} chunk={}", c.rank, c.score, c.chunk_id.0);
+                        }
+                        eprintln!("  fusion ({} inputs, {}ms)", t.rrf_inputs.len(), t.timing.fusion_ms);
+                        eprintln!("  total: {}ms", t.timing.total_ms);
+                    }
+                }
             }
             Ok(())
         }

crates/kebab-cli/src/wire.rs

@@ -81,11 +81,17 @@ pub fn wire_search_hit(h: &SearchHit) -> Value {
 /// array (`wire_search_hits`) — see HOTFIXES / fb-34 for the
 /// breaking shape change.
 pub fn wire_search_response(r: &kebab_app::SearchResponse) -> Value {
-    let v = serde_json::json!({
+    let mut v = serde_json::json!({
         "hits": r.hits.iter().map(wire_search_hit).collect::<Vec<_>>(),
         "next_cursor": r.next_cursor,
         "truncated": r.truncated,
     });
+    if let Some(trace) = &r.trace {
+        let trace_v = serde_json::to_value(trace).expect("SearchTrace serializes");
+        if let Value::Object(ref mut map) = v {
+            map.insert("trace".to_string(), trace_v);
+        }
+    }
     tag_object(v, "search_response.v1")
 }
 
@@ -264,6 +270,7 @@ mod tests {
             hits: vec![],
             next_cursor: Some("opaque-cursor-abc".to_string()),
             truncated: true,
+            trace: None,
         };
         let v = wire_search_response(&r);
         assert_eq!(schema_of(&v), Some("search_response.v1"));
@@ -303,6 +310,10 @@ mod tests {
             stats: Stats {
                 doc_count: 1, chunk_count: 2, asset_count: 1,
                 last_ingest_at: None,
+                media_breakdown: Default::default(),
+                lang_breakdown: Default::default(),
+                index_bytes: Default::default(),
+                stale_doc_count: 0,
             },
         };
         let v = wire_schema(&schema);
@@ -343,4 +354,49 @@ mod tests {
         assert_eq!(paths.len(), 1);
         assert_eq!(paths[0].as_str(), Some("/tmp/x"));
     }
+
+    #[test]
+    fn search_response_with_trace_serializes_trace_field() {
+        use kebab_core::{SearchTrace, TraceCandidate, TraceFusionInput,
+                         TraceTiming, ChunkId, DocumentId, WorkspacePath};
+        let r = kebab_app::SearchResponse {
+            hits: vec![],
+            next_cursor: None,
+            truncated: false,
+            trace: Some(SearchTrace {
+                lexical: vec![TraceCandidate {
+                    chunk_id: ChunkId("c1".into()),
+                    doc_id: DocumentId("d1".into()),
+                    doc_path: WorkspacePath::new("a.md".into()).unwrap(),
+                    rank: 1,
+                    score: 0.42,
+                }],
+                vector: vec![],
+                rrf_inputs: vec![TraceFusionInput {
+                    chunk_id: ChunkId("c1".into()),
+                    lexical_rank: Some(1),
+                    vector_rank: None,
+                    fusion_score: 0.0,
+                }],
+                timing: TraceTiming { lexical_ms: 5, vector_ms: 0, fusion_ms: 1, total_ms: 7 },
+            }),
+        };
+        let v = wire_search_response(&r);
+        assert_eq!(schema_of(&v), Some("search_response.v1"));
+        assert!(v["trace"].is_object());
+        assert_eq!(v["trace"]["timing"]["lexical_ms"], 5);
+        assert_eq!(v["trace"]["lexical"][0]["chunk_id"], "c1");
+    }
+
+    #[test]
+    fn search_response_without_trace_omits_field() {
+        let r = kebab_app::SearchResponse {
+            hits: vec![],
+            next_cursor: None,
+            truncated: false,
+            trace: None,
+        };
+        let v = wire_search_response(&r);
+        assert!(v.get("trace").is_none(), "trace field absent when None");
+    }
 }

crates/kebab-cli/tests/wire_schema_breakdowns.rs

@@ -0,0 +1,57 @@
+//! p9-fb-37: integration tests for `kebab schema --json` extended stats.
+
+mod common;
+
+use serde_json::Value;
+use std::fs;
+use std::process::Command;
+
+fn run_schema(cfg: &std::path::Path) -> Value {
+    let bin = env!("CARGO_BIN_EXE_kebab");
+    let out = Command::new(bin)
+        .args(["--config", cfg.to_str().unwrap(), "schema", "--json"])
+        .output()
+        .expect("run kebab schema");
+    assert!(
+        out.status.success(),
+        "schema failed: stderr={}",
+        String::from_utf8_lossy(&out.stderr)
+    );
+    serde_json::from_slice(&out.stdout).expect("valid JSON")
+}
+
+#[test]
+fn schema_stats_includes_breakdowns_on_fresh_corpus() {
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    // Run a no-op ingest to bring up migrations + create the SQLite file.
+    fs::write(workspace.join("placeholder.md"), "# placeholder\n").unwrap();
+    common::ingest(&cfg, &workspace);
+
+    let v = run_schema(&cfg);
+    let stats = &v["stats"];
+    let m = stats["media_breakdown"].as_object().unwrap();
+    assert_eq!(m.len(), 5, "5 media keys padded");
+    for k in &["markdown", "pdf", "image", "audio", "other"] {
+        assert!(m[*k].is_number(), "media[{k}] is integer");
+    }
+    assert!(stats["lang_breakdown"].is_object());
+    assert!(stats["index_bytes"]["sqlite"].is_number());
+    assert!(stats["index_bytes"]["lancedb"].is_number());
+    assert!(stats["stale_doc_count"].is_number());
+}
+
+#[test]
+fn schema_stats_breakdowns_after_ingest() {
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    fs::write(workspace.join("a.md"), "---\nlang: en\n---\nhello\n").unwrap();
+    fs::write(workspace.join("b.md"), "---\nlang: ko\n---\n안녕\n").unwrap();
+    common::ingest(&cfg, &workspace);
+
+    let v = run_schema(&cfg);
+    let stats = &v["stats"];
+    assert_eq!(stats["media_breakdown"]["markdown"], 2);
+    assert!(stats["lang_breakdown"].is_object());
+    assert!(stats["index_bytes"]["sqlite"].as_u64().unwrap() > 0);
+}

crates/kebab-cli/tests/wire_search_trace.rs

@@ -0,0 +1,58 @@
+//! p9-fb-37: integration tests for `kebab search --trace --json`.
+
+mod common;
+
+use serde_json::Value;
+use std::fs;
+
+#[test]
+fn search_trace_json_includes_trace_block() {
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    fs::write(workspace.join("doc1.md"), "# Title\n\nrust async hello\n").unwrap();
+    common::ingest(&cfg, &workspace);
+
+    let (stdout, _stderr) = common::run_search_with_args(
+        &cfg,
+        &["--mode", "lexical", "--trace", "--json", "rust"],
+    );
+    let v: Value = serde_json::from_str(stdout.trim()).expect("valid JSON");
+    assert_eq!(v["schema_version"], "search_response.v1");
+    assert!(v["trace"].is_object(), "trace block present");
+    assert!(v["trace"]["timing"].is_object());
+    assert!(v["trace"]["timing"]["total_ms"].is_number());
+    assert!(v["trace"]["lexical"].is_array());
+    assert!(v["trace"]["vector"].is_array());
+    assert!(v["trace"]["rrf_inputs"].is_array());
+}
+
+#[test]
+fn search_without_trace_omits_trace_field() {
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    fs::write(workspace.join("doc1.md"), "# Title\n\nrust async hello\n").unwrap();
+    common::ingest(&cfg, &workspace);
+
+    let (stdout, _stderr) = common::run_search_with_args(
+        &cfg,
+        &["--mode", "lexical", "--json", "rust"],
+    );
+    let v: Value = serde_json::from_str(stdout.trim()).expect("valid JSON");
+    assert!(v.get("trace").is_none(), "trace field absent without --trace");
+}
+
+#[test]
+fn search_trace_lexical_mode_vector_list_empty() {
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    fs::write(workspace.join("doc1.md"), "# Title\n\nrust async hello\n").unwrap();
+    common::ingest(&cfg, &workspace);
+
+    let (stdout, _stderr) = common::run_search_with_args(
+        &cfg,
+        &["--mode", "lexical", "--trace", "--json", "rust"],
+    );
+    let v: Value = serde_json::from_str(stdout.trim()).expect("valid JSON");
+    assert_eq!(v["trace"]["vector"].as_array().unwrap().len(), 0);
+    assert_eq!(v["trace"]["timing"]["vector_ms"], 0);
+}

crates/kebab-core/src/lib.rs

@@ -51,8 +51,9 @@ pub use metadata::{
     TrustLevel,
 };
 pub use search::{
-    DocFilter, DocSummary, RetrievalDetail, SearchFilters, SearchHit,
-    SearchMode, SearchOpts, SearchQuery,
+    DocFilter, DocSummary, IndexBytes, MEDIA_KINDS, RetrievalDetail, SearchFilters, SearchHit,
+    SearchMode, SearchOpts, SearchQuery, SearchTrace, TraceCandidate, TraceFusionInput,
+    TraceTiming,
 };
 pub use answer::{
     Answer, AnswerCitation, AnswerRetrievalSummary, ModelRef, RefusalReason, TokenUsage,

crates/kebab-core/src/search.rs

@@ -124,6 +124,60 @@ pub struct SearchOpts {
     pub snippet_chars: Option<usize>,
     /// Opaque base64 cursor from a previous response. None = first page.
     pub cursor: Option<String>,
+    /// p9-fb-37: when true, capture pipeline trace (cache bypassed,
+    /// lex / vec pre-fusion lists + timing populated on the response).
+    #[serde(default)]
+    pub trace: bool,
+}
+
+/// p9-fb-37: search retrieval pipeline trace. Populated only when
+/// `SearchOpts.trace = true`; `None` on the wrapping `SearchResponse`
+/// otherwise. `lexical` / `vector` are pre-fusion candidate lists
+/// (each retriever's full output for the fanout query). `rrf_inputs`
+/// is the union (chunk_id) used by RRF, with each side's rank
+/// captured. `timing` is wall-clock per stage.
+#[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
+pub struct SearchTrace {
+    pub lexical: Vec<TraceCandidate>,
+    pub vector: Vec<TraceCandidate>,
+    pub rrf_inputs: Vec<TraceFusionInput>,
+    pub timing: TraceTiming,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct TraceCandidate {
+    pub chunk_id: ChunkId,
+    pub doc_id: DocumentId,
+    pub doc_path: WorkspacePath,
+    pub rank: u32,
+    pub score: f32,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct TraceFusionInput {
+    pub chunk_id: ChunkId,
+    pub lexical_rank: Option<u32>,
+    pub vector_rank: Option<u32>,
+    /// Hybrid mode: normalized RRF score in `[0, 1]`.
+    /// Lexical / Vector mode: equals the underlying retriever's score
+    /// (no fusion ran). 0.0 for chunks dropped past `target_k`.
+    pub fusion_score: f32,
+}
+
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+pub struct TraceTiming {
+    pub lexical_ms: u64,
+    pub vector_ms: u64,
+    pub fusion_ms: u64,
+    pub total_ms: u64,
+}
+
+/// p9-fb-37: on-disk index size breakdown. Mirrored on the
+/// wire `schema.v1.stats.index_bytes` block.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+pub struct IndexBytes {
+    pub sqlite: u64,
+    pub lancedb: u64,
 }
 
 #[cfg(test)]
@@ -193,4 +247,51 @@ mod tests {
         assert!(old.ingested_after.is_none());
         assert!(old.doc_id.is_none());
     }
+
+    #[test]
+    fn search_trace_serde_roundtrip() {
+        let t = SearchTrace {
+            lexical: vec![TraceCandidate {
+                chunk_id: ChunkId("c1".into()),
+                doc_id: DocumentId("d1".into()),
+                doc_path: WorkspacePath::new("a.md".into()).unwrap(),
+                rank: 1,
+                score: 0.42,
+            }],
+            vector: vec![],
+            rrf_inputs: vec![TraceFusionInput {
+                chunk_id: ChunkId("c1".into()),
+                lexical_rank: Some(1),
+                vector_rank: None,
+                fusion_score: 0.0234,
+            }],
+            timing: TraceTiming {
+                lexical_ms: 12,
+                vector_ms: 0,
+                fusion_ms: 1,
+                total_ms: 14,
+            },
+        };
+        let v = serde_json::to_value(&t).unwrap();
+        assert_eq!(v["timing"]["lexical_ms"], 12);
+        assert_eq!(
+            v["lexical"][0]["score"].as_f64().unwrap() as f32,
+            0.42_f32
+        );
+        let back: SearchTrace = serde_json::from_value(v).unwrap();
+        assert_eq!(back, t);
+    }
+
+    #[test]
+    fn index_bytes_default_is_zero() {
+        let b = IndexBytes::default();
+        assert_eq!(b.sqlite, 0);
+        assert_eq!(b.lancedb, 0);
+    }
+
+    #[test]
+    fn search_opts_trace_default_false() {
+        let opts = SearchOpts::default();
+        assert!(!opts.trace);
+    }
 }

crates/kebab-mcp/src/tools/search.rs

@@ -47,6 +47,10 @@ pub struct SearchInput {
     pub ingested_after: Option<String>,
     /// p9-fb-36: filter to a single doc.
     pub doc_id: Option<String>,
+    /// p9-fb-37: when true, include a `trace` field on the response
+    /// with pre-fusion lexical/vector candidate lists + per-stage timing.
+    /// Bypasses cache (debug intent — fresh run guaranteed). Default false.
+    pub trace: Option<bool>,
 }
 
 pub fn handle(state: &KebabAppState, input: SearchInput) -> CallToolResult {
@@ -118,6 +122,7 @@ pub fn handle(state: &KebabAppState, input: SearchInput) -> CallToolResult {
         max_tokens: input.max_tokens,
         snippet_chars: input.snippet_chars,
         cursor: input.cursor,
+        trace: input.trace.unwrap_or(false),
     };
     let cfg_clone = (*state.config).clone();
     match kebab_app::search_with_opts_with_config(cfg_clone, query, opts) {
@@ -138,12 +143,19 @@ pub fn handle(state: &KebabAppState, input: SearchInput) -> CallToolResult {
                     v
                 })
                 .collect();
-            let envelope = serde_json::json!({
+            let mut envelope = serde_json::json!({
                 "schema_version": "search_response.v1",
                 "hits": tagged,
                 "next_cursor": resp.next_cursor,
                 "truncated": resp.truncated,
             });
+            if let Some(trace) = &resp.trace {
+                let trace_v =
+                    serde_json::to_value(trace).unwrap_or(serde_json::Value::Null);
+                if let serde_json::Value::Object(ref mut map) = envelope {
+                    map.insert("trace".to_string(), trace_v);
+                }
+            }
             match serde_json::to_string(&envelope) {
                 Ok(json) => to_tool_success(json),
                 Err(e) => to_tool_error(&anyhow::anyhow!(e)),

crates/kebab-mcp/tests/tools_call_fetch.rs

@@ -69,6 +69,7 @@ async fn fetch_tool_chunk_returns_fetch_result_v1() {
             media: None,
             ingested_after: None,
             doc_id: None,
+            trace: None,
         },
     );
     let search_text = match &search_result.content.first().unwrap().raw {

crates/kebab-mcp/tests/tools_call_search.rs

@@ -65,6 +65,7 @@ async fn search_tool_returns_search_response_v1() {
             media: None,
             ingested_after: None,
             doc_id: None,
+            trace: None,
         },
     );
 
@@ -166,6 +167,7 @@ async fn search_with_doc_id_filter_returns_only_target() {
             media: None,
             ingested_after: None,
             doc_id: None,
+            trace: None,
         },
     );
     assert!(
@@ -204,6 +206,7 @@ async fn search_with_doc_id_filter_returns_only_target() {
             media: None,
             ingested_after: None,
             doc_id: Some(target_doc_id.clone()),
+            trace: None,
         },
     );
     assert!(
@@ -260,6 +263,7 @@ async fn search_with_invalid_ingested_after_returns_invalid_input() {
             media: None,
             ingested_after: Some("garbage".to_string()),
             doc_id: None,
+            trace: None,
         },
     );
 

crates/kebab-mcp/tests/tools_call_search_trace.rs

@@ -0,0 +1,104 @@
+//! p9-fb-37: integration test for `mcp__kebab__search` trace input/output.
+
+use std::fs;
+
+use kebab_config::Config;
+use kebab_core::SourceScope;
+use kebab_mcp::{KebabAppState, KebabHandler};
+use rmcp::model::RawContent;
+
+fn minimal_config(data_dir: &std::path::Path, workspace_root: &std::path::Path) -> Config {
+    let mut cfg = Config::defaults();
+    cfg.storage.data_dir = data_dir.to_string_lossy().into_owned();
+    cfg.storage.model_dir = data_dir.join("models").to_string_lossy().into_owned();
+    cfg.workspace.root = workspace_root.to_string_lossy().into_owned();
+    cfg.workspace.exclude.clear();
+    cfg.models.embedding.provider = "none".to_string();
+    cfg.models.embedding.dimensions = 0;
+    cfg
+}
+
+fn setup() -> (tempfile::TempDir, KebabHandler) {
+    let dir = tempfile::tempdir().unwrap();
+    let data_dir = dir.path().join("data");
+    let workspace_root = dir.path().join("notes");
+    fs::create_dir_all(&data_dir).unwrap();
+    fs::create_dir_all(&workspace_root).unwrap();
+    let config = minimal_config(&data_dir, &workspace_root);
+    fs::write(
+        workspace_root.join("a.md"),
+        "# Alpha\n\nThis document mentions kebab and bread.",
+    )
+    .unwrap();
+    let scope = SourceScope {
+        root: workspace_root.clone(),
+        include: vec![],
+        exclude: vec![],
+    };
+    let _ = kebab_app::ingest_with_config(config.clone(), scope, false).unwrap();
+    let state = KebabAppState::new(config, None);
+    let handler = KebabHandler::new(state);
+    (dir, handler)
+}
+
+fn make_input(trace: Option<bool>) -> kebab_mcp::tools::search::SearchInput {
+    kebab_mcp::tools::search::SearchInput {
+        query: "kebab".to_string(),
+        mode: Some("lexical".to_string()),
+        k: Some(5),
+        max_tokens: None,
+        snippet_chars: None,
+        cursor: None,
+        tags: None,
+        lang: None,
+        path_glob: None,
+        trust_min: None,
+        media: None,
+        ingested_after: None,
+        doc_id: None,
+        trace,
+    }
+}
+
+fn extract_json(result: &rmcp::model::CallToolResult) -> serde_json::Value {
+    assert!(
+        !result.is_error.unwrap_or(false),
+        "expected isError=false, got {result:?}"
+    );
+    let content = result.content.first().expect("at least one content item");
+    let text = match &content.raw {
+        RawContent::Text(t) => &t.text,
+        other => panic!("expected Text content, got {other:?}"),
+    };
+    serde_json::from_str(text).expect("valid JSON")
+}
+
+#[tokio::test]
+async fn search_with_trace_true_returns_trace_field() {
+    let (_dir, handler) = setup();
+    let result = kebab_mcp::tools::search::handle(handler.state(), make_input(Some(true)));
+    let v = extract_json(&result);
+    assert_eq!(v["schema_version"], "search_response.v1");
+    assert!(v["trace"].is_object(), "trace field present when trace:true");
+    assert!(v["trace"]["timing"]["total_ms"].is_number());
+    assert!(v["trace"]["lexical"].is_array());
+    assert!(v["trace"]["vector"].is_array());
+    assert!(v["trace"]["rrf_inputs"].is_array());
+}
+
+#[tokio::test]
+async fn search_without_trace_omits_trace_field() {
+    let (_dir, handler) = setup();
+    let result = kebab_mcp::tools::search::handle(handler.state(), make_input(None));
+    let v = extract_json(&result);
+    assert_eq!(v["schema_version"], "search_response.v1");
+    assert!(v.get("trace").is_none(), "trace absent when None");
+}
+
+#[tokio::test]
+async fn search_with_trace_false_omits_trace_field() {
+    let (_dir, handler) = setup();
+    let result = kebab_mcp::tools::search::handle(handler.state(), make_input(Some(false)));
+    let v = extract_json(&result);
+    assert!(v.get("trace").is_none(), "trace absent when false");
+}

crates/kebab-search/src/hybrid.rs

@@ -18,12 +18,15 @@
 
 use std::collections::HashMap;
 use std::sync::Arc;
+use std::time::Instant;
 
 use anyhow::Result;
 use kebab_core::{
-    IndexVersion, RetrievalDetail, Retriever, SearchHit, SearchMode, SearchQuery,
+    IndexVersion, RetrievalDetail, Retriever, SearchHit, SearchMode, SearchQuery, SearchTrace,
 };
 
+use crate::trace::{build_fusion_input_skeleton, candidates_from_hits, ScoreKind, TraceBuilder};
+
 /// Default `k_rrf` if `kb-config::SearchCfg::rrf_k` is misconfigured.
 /// Matches §6.4's documented default (60).
 const DEFAULT_K_RRF: u32 = 60;
@@ -145,20 +148,22 @@ impl Retriever for HybridRetriever {
 impl HybridRetriever {
     fn fuse(&self, query: &SearchQuery) -> Result<Vec<SearchHit>> {
         let target_k = if query.k == 0 { self.default_k } else { query.k };
-
-        // Fanout: ask each retriever for `target_k * MULTIPLIER` so
-        // the disjoint set of candidates is wide enough. The two
-        // per-side queries are identical (same text, k, mode, filters);
-        // only the dispatch differs, so we share one `SearchQuery`.
         let fanout_k = target_k.saturating_mul(HYBRID_FANOUT_MULTIPLIER);
         let lex_query = SearchQuery {
             k: fanout_k,
             ..query.clone()
         };
-
         let lex_hits = self.lexical.search(&lex_query)?;
         let vec_hits = self.vector.search(&lex_query)?;
+        self.fuse_with_inputs(&lex_hits, &vec_hits, target_k)
+    }
 
+    fn fuse_with_inputs(
+        &self,
+        lex_hits: &[SearchHit],
+        vec_hits: &[SearchHit],
+        target_k: usize,
+    ) -> Result<Vec<SearchHit>> {
         tracing::debug!(
             lex = lex_hits.len(),
             vec = vec_hits.len(),
@@ -171,11 +176,13 @@ impl HybridRetriever {
         // already 1-based by both LexicalRetriever and VectorRetriever
         // (and any well-behaved Retriever should mirror).
         let lex_index: HashMap<String, (u32, SearchHit)> = lex_hits
-            .into_iter()
+            .iter()
+            .cloned()
             .map(|h| (h.chunk_id.0.clone(), (h.rank, h)))
             .collect();
         let vec_index: HashMap<String, (u32, SearchHit)> = vec_hits
-            .into_iter()
+            .iter()
+            .cloned()
             .map(|h| (h.chunk_id.0.clone(), (h.rank, h)))
             .collect();
 
@@ -312,6 +319,85 @@ impl HybridRetriever {
         tracing::debug!(rows = hits.len(), "kb-search hybrid: search done");
         Ok(hits)
     }
+
+    /// p9-fb-37: parallel to `Retriever::search` but additionally returns
+    /// a trace of pre-fusion lex/vec lists, RRF inputs (union with each
+    /// side's rank), and per-stage timing.
+    pub fn search_with_trace(
+        &self,
+        query: &SearchQuery,
+    ) -> anyhow::Result<(Vec<SearchHit>, SearchTrace)> {
+        let start_total = Instant::now();
+        let target_k = if query.k == 0 { self.default_k } else { query.k };
+        let fanout_k = target_k.saturating_mul(HYBRID_FANOUT_MULTIPLIER);
+        let fanout_query = SearchQuery {
+            k: fanout_k,
+            ..query.clone()
+        };
+
+        let mut tb = TraceBuilder::default();
+
+        let (lex_hits, vec_hits): (Vec<SearchHit>, Vec<SearchHit>) = match query.mode {
+            SearchMode::Lexical => {
+                let t0 = Instant::now();
+                let lh = self.lexical.search(&fanout_query)?;
+                tb.timing.lexical_ms = t0.elapsed().as_millis() as u64;
+                (lh, Vec::new())
+            }
+            SearchMode::Vector => {
+                let t0 = Instant::now();
+                let vh = self.vector.search(&fanout_query)?;
+                tb.timing.vector_ms = t0.elapsed().as_millis() as u64;
+                (Vec::new(), vh)
+            }
+            SearchMode::Hybrid => {
+                let t0 = Instant::now();
+                let lh = self.lexical.search(&fanout_query)?;
+                tb.timing.lexical_ms = t0.elapsed().as_millis() as u64;
+                let t1 = Instant::now();
+                let vh = self.vector.search(&fanout_query)?;
+                tb.timing.vector_ms = t1.elapsed().as_millis() as u64;
+                (lh, vh)
+            }
+        };
+
+        tb.lexical = candidates_from_hits(&lex_hits, ScoreKind::Lexical);
+        tb.vector = candidates_from_hits(&vec_hits, ScoreKind::Vector);
+        tb.rrf_inputs = build_fusion_input_skeleton(&lex_hits, &vec_hits);
+
+        let t_fusion = Instant::now();
+        let final_hits = match query.mode {
+            SearchMode::Lexical => {
+                let mut h = lex_hits.clone();
+                h.truncate(target_k);
+                h
+            }
+            SearchMode::Vector => {
+                let mut h = vec_hits.clone();
+                h.truncate(target_k);
+                h
+            }
+            SearchMode::Hybrid => self.fuse_with_inputs(&lex_hits, &vec_hits, target_k)?,
+        };
+        tb.timing.fusion_ms = t_fusion.elapsed().as_millis() as u64;
+
+        let score_by_chunk: std::collections::HashMap<String, f32> = final_hits
+            .iter()
+            .map(|h| (h.chunk_id.0.clone(), h.retrieval.fusion_score))
+            .collect();
+        for entry in &mut tb.rrf_inputs {
+            if let Some(s) = score_by_chunk.get(&entry.chunk_id.0) {
+                entry.fusion_score = *s;
+            }
+        }
+
+        // total_ms is wall-clock from start; per-stage `lexical_ms` /
+        // `vector_ms` / `fusion_ms` each truncate to whole millis via
+        // `as_millis() as u64`, so their sum can drift below total
+        // (sub-ms losses) — DO NOT assert `total_ms >= sum(stages)`.
+        tb.timing.total_ms = start_total.elapsed().as_millis() as u64;
+        Ok((final_hits, tb.into_trace()))
+    }
 }
 
 /// Parse the `hybrid_fusion` config string into a [`FusionPolicy`].
@@ -633,4 +719,107 @@ mod tests {
         let FusionPolicy::Rrf { k_rrf } = parse_fusion("rrf", 0);
         assert_eq!(k_rrf, DEFAULT_K_RRF);
     }
+
+    #[test]
+    fn search_with_trace_returns_lex_and_vec_lists() {
+        use kebab_core::{ChunkId, DocumentId, IndexVersion, ChunkerVersion,
+                         RetrievalDetail, SearchHit, SearchMode, SearchQuery,
+                         WorkspacePath, Citation};
+        use std::sync::Arc;
+
+        fn mk_hit(rank: u32, chunk: &str, score: f32, mode: SearchMode) -> SearchHit {
+            SearchHit {
+                rank,
+                chunk_id: ChunkId(chunk.into()),
+                doc_id: DocumentId(format!("d-{chunk}")),
+                doc_path: WorkspacePath::new(format!("{chunk}.md")).unwrap(),
+                heading_path: vec![],
+                section_label: None,
+                snippet: chunk.into(),
+                citation: Citation::Line {
+                    path: WorkspacePath::new(format!("{chunk}.md")).unwrap(),
+                    start: 1,
+                    end: 1,
+                    section: None,
+                },
+                retrieval: RetrievalDetail {
+                    method: mode,
+                    fusion_score: score,
+                    lexical_score: if mode == SearchMode::Lexical { Some(score) } else { None },
+                    vector_score: if mode == SearchMode::Vector { Some(score) } else { None },
+                    lexical_rank: if mode == SearchMode::Lexical { Some(rank) } else { None },
+                    vector_rank: if mode == SearchMode::Vector { Some(rank) } else { None },
+                },
+                index_version: IndexVersion("v1".into()),
+                embedding_model: None,
+                chunker_version: ChunkerVersion("c1".into()),
+                indexed_at: time::OffsetDateTime::UNIX_EPOCH,
+                stale: false,
+            }
+        }
+
+        struct Stub { hits: Vec<SearchHit> }
+        impl Retriever for Stub {
+            fn search(&self, _q: &SearchQuery) -> anyhow::Result<Vec<SearchHit>> {
+                Ok(self.hits.clone())
+            }
+            fn index_version(&self) -> IndexVersion { IndexVersion("v1".into()) }
+        }
+
+        let lex = Arc::new(Stub {
+            hits: vec![
+                mk_hit(1, "c1", 0.9, SearchMode::Lexical),
+                mk_hit(2, "c2", 0.5, SearchMode::Lexical),
+            ],
+        });
+        let vec_r = Arc::new(Stub {
+            hits: vec![
+                mk_hit(1, "c2", 0.8, SearchMode::Vector),
+                mk_hit(2, "c3", 0.6, SearchMode::Vector),
+            ],
+        });
+        let hybrid = HybridRetriever::with_policy(
+            lex.clone(),
+            vec_r.clone(),
+            FusionPolicy::Rrf { k_rrf: 60 },
+            2,
+        );
+        let q = SearchQuery {
+            text: "x".into(),
+            mode: SearchMode::Hybrid,
+            k: 2,
+            filters: Default::default(),
+        };
+        let (hits, trace) = hybrid.search_with_trace(&q).unwrap();
+        assert!(!hits.is_empty());
+        assert_eq!(trace.lexical.len(), 2);
+        assert_eq!(trace.vector.len(), 2);
+        // Union: c1, c2, c3 → 3 entries.
+        assert_eq!(trace.rrf_inputs.len(), 3);
+    }
+
+    #[test]
+    fn search_with_trace_lexical_mode_empty_vector() {
+        use kebab_core::{IndexVersion, SearchMode, SearchQuery};
+        use std::sync::Arc;
+        struct EmptyR;
+        impl Retriever for EmptyR {
+            fn search(&self, _q: &SearchQuery) -> anyhow::Result<Vec<kebab_core::SearchHit>> {
+                Ok(vec![])
+            }
+            fn index_version(&self) -> IndexVersion { IndexVersion("v1".into()) }
+        }
+        let lex = Arc::new(EmptyR);
+        let vec_r = Arc::new(EmptyR);
+        let hybrid = HybridRetriever::with_policy(lex, vec_r, FusionPolicy::Rrf { k_rrf: 60 }, 2);
+        let q = SearchQuery {
+            text: "x".into(),
+            mode: SearchMode::Lexical,
+            k: 2,
+            filters: Default::default(),
+        };
+        let (_hits, trace) = hybrid.search_with_trace(&q).unwrap();
+        assert!(trace.vector.is_empty());
+        assert_eq!(trace.timing.vector_ms, 0);
+    }
 }

crates/kebab-search/src/lib.rs

@@ -19,6 +19,7 @@
 mod citation_helper;
 mod hybrid;
 mod lexical;
+mod trace;
 mod vector;
 
 pub use hybrid::{FusionPolicy, HybridRetriever};

crates/kebab-search/src/trace.rs

@@ -0,0 +1,85 @@
+//! p9-fb-37: trace capture helpers for `HybridRetriever::search_with_trace`.
+
+use std::collections::BTreeMap;
+
+use kebab_core::{
+    SearchHit, SearchTrace, TraceCandidate, TraceFusionInput, TraceTiming,
+};
+
+/// Build a `TraceCandidate` from a `SearchHit`. The score field reflects
+/// each side's score (lexical / vector / fusion) — caller selects which
+/// retriever's hit list this is.
+pub fn candidates_from_hits(hits: &[SearchHit], score_kind: ScoreKind) -> Vec<TraceCandidate> {
+    hits.iter()
+        .map(|h| TraceCandidate {
+            chunk_id: h.chunk_id.clone(),
+            doc_id: h.doc_id.clone(),
+            doc_path: h.doc_path.clone(),
+            rank: h.rank,
+            score: match score_kind {
+                ScoreKind::Lexical => h.retrieval.lexical_score.unwrap_or(0.0),
+                ScoreKind::Vector => h.retrieval.vector_score.unwrap_or(0.0),
+            },
+        })
+        .collect()
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum ScoreKind {
+    Lexical,
+    Vector,
+}
+
+/// Build the union of (chunk_id) across lex and vec hit lists, with
+/// each side's rank captured. `fusion_score` is filled by the caller
+/// (RRF computes it during fusion, this helper just pre-builds the
+/// rank table — caller overwrites fusion_score in a second pass).
+pub fn build_fusion_input_skeleton(
+    lex: &[SearchHit],
+    vec: &[SearchHit],
+) -> Vec<TraceFusionInput> {
+    let mut by_chunk: BTreeMap<String, TraceFusionInput> = BTreeMap::new();
+    for h in lex {
+        by_chunk
+            .entry(h.chunk_id.0.clone())
+            .or_insert(TraceFusionInput {
+                chunk_id: h.chunk_id.clone(),
+                lexical_rank: None,
+                vector_rank: None,
+                fusion_score: 0.0,
+            })
+            .lexical_rank = Some(h.rank);
+    }
+    for h in vec {
+        by_chunk
+            .entry(h.chunk_id.0.clone())
+            .or_insert(TraceFusionInput {
+                chunk_id: h.chunk_id.clone(),
+                lexical_rank: None,
+                vector_rank: None,
+                fusion_score: 0.0,
+            })
+            .vector_rank = Some(h.rank);
+    }
+    by_chunk.into_values().collect()
+}
+
+/// Container the hybrid retriever fills during a traced run.
+#[derive(Default)]
+pub struct TraceBuilder {
+    pub lexical: Vec<TraceCandidate>,
+    pub vector: Vec<TraceCandidate>,
+    pub rrf_inputs: Vec<TraceFusionInput>,
+    pub timing: TraceTiming,
+}
+
+impl TraceBuilder {
+    pub fn into_trace(self) -> SearchTrace {
+        SearchTrace {
+            lexical: self.lexical,
+            vector: self.vector,
+            rrf_inputs: self.rrf_inputs,
+            timing: self.timing,
+        }
+    }
+}

crates/kebab-store-sqlite/src/lib.rs

@@ -28,6 +28,7 @@ mod fts;
 mod jobs;
 mod schema;
 mod store;
+pub mod stats_ext;
 
 pub use embeddings::EmbeddingRecordRow;
 pub use error::StoreError;

crates/kebab-store-sqlite/src/stats_ext.rs

@@ -0,0 +1,168 @@
+//! p9-fb-37: extended stats helpers — per-media / per-lang doc counts,
+//! stale doc count, on-disk index byte sums.
+
+use std::collections::BTreeMap;
+use std::path::Path;
+
+use kebab_core::{IndexBytes, MEDIA_KINDS};
+use rusqlite::Connection;
+
+/// p9-fb-37: result of [`breakdowns`] — three independent counts collected in one pass.
+#[derive(Debug, Clone, Default)]
+pub struct Breakdowns {
+    pub media: BTreeMap<String, u64>,
+    pub lang: BTreeMap<String, u64>,
+    pub stale_doc_count: u64,
+}
+
+/// `media` always contains all 5 `MEDIA_KINDS` (zero-padded).
+/// `lang` only contains observed languages; NULL lang is
+/// keyed as the literal string `"null"`. `stale_doc_count` is 0 when
+/// `threshold_days == 0` (mirrors fb-32 staleness disable semantics).
+pub fn breakdowns(
+    conn: &Connection,
+    threshold_days: u64,
+) -> rusqlite::Result<Breakdowns> {
+    // media: dual JSON shape — text variant ("markdown") vs object
+    // variant ({"image":{"format":"png"}}). Same CASE WHEN as fb-36.
+    let mut media: BTreeMap<String, u64> = MEDIA_KINDS
+        .iter()
+        .map(|k| ((*k).to_string(), 0u64))
+        .collect();
+    let mut stmt = conn.prepare(
+        "SELECT \
+           CASE \
+             WHEN json_type(a.media_type) = 'text' \
+               THEN json_extract(a.media_type, '$') \
+             ELSE (SELECT key FROM json_each(a.media_type) LIMIT 1) \
+           END AS kind, \
+           COUNT(DISTINCT d.doc_id) \
+         FROM documents d JOIN assets a ON a.asset_id = d.asset_id \
+         GROUP BY kind",
+    )?;
+    let rows = stmt.query_map([], |r| {
+        Ok((r.get::<_, String>(0)?, r.get::<_, u64>(1)?))
+    })?;
+    for row in rows {
+        let (kind, n) = row?;
+        media.insert(kind, n);
+    }
+
+    let mut lang: BTreeMap<String, u64> = BTreeMap::new();
+    let mut stmt = conn.prepare(
+        "SELECT COALESCE(lang, 'null') AS l, COUNT(*) \
+         FROM documents GROUP BY l",
+    )?;
+    let rows = stmt.query_map([], |r| {
+        Ok((r.get::<_, String>(0)?, r.get::<_, u64>(1)?))
+    })?;
+    for row in rows {
+        let (l, n) = row?;
+        lang.insert(l, n);
+    }
+
+    let stale_doc_count: u64 = if threshold_days == 0 {
+        0
+    } else {
+        let secs = (threshold_days as i64) * 86_400;
+        let cutoff = time::OffsetDateTime::now_utc()
+            - time::Duration::seconds(secs);
+        let cutoff_str = cutoff
+            .format(&time::format_description::well_known::Rfc3339)
+            .expect("RFC3339 format");
+        conn.query_row(
+            "SELECT COUNT(*) FROM documents WHERE updated_at < ?",
+            [cutoff_str],
+            |r| r.get(0),
+        )?
+    };
+
+    Ok(Breakdowns {
+        media,
+        lang,
+        stale_doc_count,
+    })
+}
+
+/// Sum on-disk bytes of the SQLite database (main + WAL + SHM) and
+/// the LanceDB directory tree. Missing files / dir = 0.
+pub fn index_bytes(data_dir: &Path) -> std::io::Result<IndexBytes> {
+    fn file_size_or_zero(p: &Path) -> u64 {
+        std::fs::metadata(p).map(|m| m.len()).unwrap_or(0)
+    }
+    fn dir_walk_sum(p: &Path) -> std::io::Result<u64> {
+        if !p.exists() {
+            return Ok(0);
+        }
+        let mut total = 0u64;
+        for entry in std::fs::read_dir(p)? {
+            let entry = entry?;
+            let ty = entry.file_type()?;
+            if ty.is_dir() {
+                total += dir_walk_sum(&entry.path())?;
+            } else if ty.is_file() {
+                total += entry.metadata()?.len();
+            }
+        }
+        Ok(total)
+    }
+
+    let sqlite_main = data_dir.join("kebab.sqlite");
+    let sqlite_wal = data_dir.join("kebab.sqlite-wal");
+    let sqlite_shm = data_dir.join("kebab.sqlite-shm");
+    let sqlite = file_size_or_zero(&sqlite_main)
+        + file_size_or_zero(&sqlite_wal)
+        + file_size_or_zero(&sqlite_shm);
+    let lancedb = dir_walk_sum(&data_dir.join("lancedb"))?;
+    Ok(IndexBytes { sqlite, lancedb })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn open_fresh() -> (tempfile::TempDir, crate::SqliteStore) {
+        let dir = tempfile::tempdir().unwrap();
+        let mut cfg = kebab_config::Config::defaults();
+        cfg.storage.data_dir = dir.path().to_string_lossy().into_owned();
+        let store = crate::SqliteStore::open(&cfg).unwrap();
+        store.run_migrations().unwrap();
+        (dir, store)
+    }
+
+    #[test]
+    fn breakdowns_empty_corpus() {
+        let (_dir, store) = open_fresh();
+        let conn = store.read_conn();
+        let b = breakdowns(&conn, 0).unwrap();
+        // 5 keys all zero, lang map empty, stale 0.
+        assert_eq!(b.media.len(), 5);
+        for k in MEDIA_KINDS {
+            assert_eq!(b.media.get(*k), Some(&0u64));
+        }
+        assert!(b.lang.is_empty());
+        assert_eq!(b.stale_doc_count, 0);
+    }
+
+    #[test]
+    fn index_bytes_includes_sqlite_main() {
+        let (dir, _store) = open_fresh();
+        let b = index_bytes(dir.path()).unwrap();
+        assert!(b.sqlite > 0, "main sqlite file should exist after migrations");
+        assert_eq!(b.lancedb, 0);
+    }
+
+    #[test]
+    fn index_bytes_lancedb_dir_walk() {
+        let dir = tempfile::tempdir().unwrap();
+        let lance = dir.path().join("lancedb");
+        std::fs::create_dir_all(lance.join("vectors.lance")).unwrap();
+        std::fs::write(
+            lance.join("vectors.lance").join("data.bin"),
+            vec![0u8; 1024],
+        )
+        .unwrap();
+        let b = index_bytes(dir.path()).unwrap();
+        assert_eq!(b.lancedb, 1024);
+    }
+}

crates/kebab-store-sqlite/src/store.rs

@@ -604,6 +604,12 @@ pub struct CountSummary {
     /// ISO-8601 timestamp of the most-recently updated document row, or
     /// `None` when the store is empty.
     pub last_ingest_at: Option<String>,
+    /// p9-fb-37: per-media-kind doc count (5 keys, zero-padded).
+    pub media_breakdown: std::collections::BTreeMap<String, u64>,
+    /// p9-fb-37: per-language doc count, NULL keyed as `"null"`.
+    pub lang_breakdown: std::collections::BTreeMap<String, u64>,
+    /// p9-fb-37: docs whose `updated_at < now - threshold_days`. 0 when threshold=0.
+    pub stale_doc_count: u64,
 }
 
 impl SqliteStore {
@@ -611,39 +617,58 @@ impl SqliteStore {
     /// most-recent `documents.updated_at` timestamp.
     ///
     /// Uses `read_conn()` (no mutations) — mirrors the pattern used by
-    /// [`Self::corpus_revision`].
-    pub fn count_summary(&self) -> anyhow::Result<CountSummary> {
+    /// Shared helper: counts and breakdowns in a single pass with given threshold.
+    fn count_summary_inner(&self, threshold_days: u64) -> anyhow::Result<CountSummary> {
+        use anyhow::Context;
+        use rusqlite::OptionalExtension;
+
         let conn = self.read_conn();
 
         let doc_count: u64 = conn
             .query_row("SELECT COUNT(*) FROM documents", [], |r| r.get(0))
             .context("count documents")?;
-
         let chunk_count: u64 = conn
             .query_row("SELECT COUNT(*) FROM chunks", [], |r| r.get(0))
             .context("count chunks")?;
-
         let asset_count: u64 = conn
             .query_row("SELECT COUNT(*) FROM assets", [], |r| r.get(0))
             .context("count assets")?;
-
         let last_ingest_at: Option<String> = conn
-            .query_row(
-                "SELECT MAX(updated_at) FROM documents",
-                [],
-                |r| r.get(0),
-            )
+            .query_row("SELECT MAX(updated_at) FROM documents", [], |r| r.get(0))
             .optional()
             .context("max updated_at")?
             .flatten();
 
+        let bd = crate::stats_ext::breakdowns(&conn, threshold_days).context("breakdowns")?;
+
         Ok(CountSummary {
             doc_count,
             chunk_count,
             asset_count,
             last_ingest_at,
+            media_breakdown: bd.media,
+            lang_breakdown: bd.lang,
+            stale_doc_count: bd.stale_doc_count,
         })
     }
+
+    /// [`Self::corpus_revision`].
+    pub fn count_summary(&self) -> anyhow::Result<CountSummary> {
+        // p9-fb-37: default uses threshold_days=0 (matches fb-32 disable
+        // semantics). Callers that need real stale_doc_count call
+        // count_summary_with_threshold.
+        self.count_summary_inner(0)
+    }
+
+    /// p9-fb-37: variant that honors `config.search.stale_threshold_days`.
+    /// Callers who need a meaningful `stale_doc_count` (e.g. `kebab schema`)
+    /// pass the configured threshold; the older `count_summary` returns 0.
+    pub fn count_summary_with_threshold(
+        &self,
+        threshold_days: u64,
+    ) -> anyhow::Result<CountSummary> {
+        self.count_summary_inner(threshold_days)
+    }
 }
 
 /// Apply the design §5 / task-spec pragmas. Called once per connection.
@@ -681,6 +706,9 @@ mod tests {
         assert_eq!(s.chunk_count, 0);
         assert_eq!(s.asset_count, 0);
         assert!(s.last_ingest_at.is_none());
+        assert_eq!(s.media_breakdown.len(), 5);
+        assert!(s.lang_breakdown.is_empty());
+        assert_eq!(s.stale_doc_count, 0);
     }
 }
 

crates/kebab-tui/src/app.rs

@@ -387,6 +387,8 @@ pub struct App {
     pub ask: Option<AskState>,
     /// Populated by p9-4.
     pub inspect: Option<InspectState>,
+    /// p9-fb-37: trace popup state, `Some` while open.
+    pub trace_popup: Option<crate::trace_popup::TracePopupState>,
     /// Populated by p9-fb-03 when the user kicks off an in-shell
     /// ingest (Library `r`). Cleared by the run loop a few seconds
     /// after the run reaches a terminal event.
@@ -461,6 +463,7 @@ impl App {
             search: None,
             ask: None,
             inspect: None,
+            trace_popup: None,
             ingest_state: None,
             error_overlay: None,
             should_quit: false,

crates/kebab-tui/src/cheatsheet.rs

@@ -80,6 +80,7 @@ pub fn render_cheatsheet(f: &mut Frame, area: Rect, app: &App) {
         ("Delete", "remove char at cursor"),
         ("g", "open hit's citation in $EDITOR (Normal)"),
         ("o", "inspect selected hit's chunk (Normal — was `i` pre-fb-21)"),
+        ("t", "open retrieval trace popup (Normal — p9-fb-37)"),
         ("i", "Normal → Insert (toggle back to typing)"),
         ("Esc", "back to Library"),
     ]);

crates/kebab-tui/src/lib.rs

@@ -27,6 +27,7 @@ mod run;
 mod search;
 mod terminal;
 mod theme;
+pub mod trace_popup;
 
 pub use input::{InputBuffer, display_width, place_cursor_x, truncate_to_display_width};
 pub use theme::{Palette, Role, Theme};

crates/kebab-tui/src/run.rs

@@ -130,6 +130,21 @@ pub(crate) fn run_loop(app: &mut App) -> Result<()> {
         if event::poll(POLL_INTERVAL)? {
             match event::read()? {
                 Event::Key(key) if key.kind == KeyEventKind::Press => {
+                    // p9-fb-37: trace popup eats keys while open.
+                    // Sits ahead of cheatsheet + mode + pane dispatch
+                    // so Esc / j / k / arrows route to the popup
+                    // instead of leaking through to the search pane.
+                    if app.trace_popup.is_some() {
+                        let close = if let Some(popup) = app.trace_popup.as_mut() {
+                            crate::trace_popup::handle_key_trace_popup(popup, key)
+                        } else {
+                            false
+                        };
+                        if close {
+                            app.trace_popup = None;
+                        }
+                        continue;
+                    }
                     // p9-fb-13: cheatsheet popup toggle takes
                     // precedence over both mode + pane dispatch.
                     // F1 toggles open/close. While visible, Esc
@@ -255,6 +270,12 @@ fn render_root(f: &mut Frame, app: &App) {
     }
     render_status_bar(f, outer[2], app);
     render_key_hints(f, outer[3], app);
+    // p9-fb-37: trace popup overlays on top of pane content but
+    // below the error overlay (errors are higher-priority modal).
+    if let Some(popup) = &app.trace_popup {
+        let popup_area = centered_rect(80, 80, f.area());
+        crate::trace_popup::render_trace_popup(f, popup_area, popup);
+    }
     if let Some(err) = &app.error_overlay {
         render_error_overlay(f, f.area(), err, &app.theme);
     }
@@ -263,6 +284,28 @@ fn render_root(f: &mut Frame, app: &App) {
     }
 }
 
+/// p9-fb-37: centered sub-rect helper for the trace popup. Returns
+/// a rect of `percent_x` × `percent_y` percent of `r`, centered.
+fn centered_rect(percent_x: u16, percent_y: u16, r: ratatui::layout::Rect) -> ratatui::layout::Rect {
+    use ratatui::layout::{Constraint, Direction, Layout};
+    let popup_layout = Layout::default()
+        .direction(Direction::Vertical)
+        .constraints([
+            Constraint::Percentage((100 - percent_y) / 2),
+            Constraint::Percentage(percent_y),
+            Constraint::Percentage((100 - percent_y) / 2),
+        ])
+        .split(r);
+    Layout::default()
+        .direction(Direction::Horizontal)
+        .constraints([
+            Constraint::Percentage((100 - percent_x) / 2),
+            Constraint::Percentage(percent_x),
+            Constraint::Percentage((100 - percent_x) / 2),
+        ])
+        .split(popup_layout[1])[1]
+}
+
 fn render_header(f: &mut Frame, area: Rect, app: &App) {
     let pane_label = match app.focus {
         Pane::Library => "Library",

crates/kebab-tui/src/search.rs

@@ -209,6 +209,51 @@ pub fn handle_key_search(state: &mut App, key: KeyEvent) -> KeyOutcome {
     // pre-fb-12 SHIFT/none heuristic).
     let is_normal = state.mode == crate::app::Mode::Normal;
 
+    // p9-fb-37: `t` opens the trace popup. Re-runs the last submitted
+    // query with SearchOpts.trace = true. Bypasses cache by going
+    // through `search_with_opts_with_config` (Task 5 wires opts.trace
+    // to skip the LRU cache).
+    if is_normal
+        && matches!(
+            (key.code, key.modifiers),
+            (KeyCode::Char('t'), KeyModifiers::NONE)
+        )
+    {
+        let (last_query, has_results) = {
+            let s = state.search.as_ref().unwrap();
+            (s.last_query.clone(), !s.hits.is_empty())
+        };
+        if !has_results {
+            return KeyOutcome::Continue;
+        }
+        if let Some((q_text, q_mode)) = last_query {
+            // TODO: thread filters when TUI gains a filter UI (currently
+            // mirrors fire_search which also passes default filters).
+            let q = kebab_core::SearchQuery {
+                text: q_text,
+                mode: q_mode,
+                k: state.config.search.default_k,
+                filters: kebab_core::SearchFilters::default(),
+            };
+            let opts = kebab_core::SearchOpts {
+                trace: true,
+                ..Default::default()
+            };
+            match kebab_app::search_with_opts_with_config(state.config.clone(), q, opts) {
+                Ok(resp) => {
+                    if let Some(t) = resp.trace {
+                        state.trace_popup = Some(crate::trace_popup::TracePopupState::new(t));
+                    }
+                }
+                Err(_) => {
+                    // Silent failure — trace is debug-only; user
+                    // can still see search hits without it.
+                }
+            }
+        }
+        return KeyOutcome::Continue;
+    }
+
     // p9-fb-21: chunk-inspect rebound from `i` to `o` (vim "open").
     // The `i` key is now the universal Normal→Insert toggle (handled
     // in `mode_intercept`), so it cannot also mean "inspect chunk"

crates/kebab-tui/src/trace_popup.rs

@@ -0,0 +1,139 @@
+//! p9-fb-37: TUI trace popup. Opens from Search pane via `t` key
+//! when results are visible. Re-runs the current query with
+//! `SearchOpts.trace = true` and displays the lex / vec / rrf union
+//! + per-stage timing as a single scroll list.
+
+use crossterm::event::{KeyCode, KeyEvent};
+use kebab_core::SearchTrace;
+use ratatui::Frame;
+use ratatui::layout::Rect;
+use ratatui::style::{Modifier, Style};
+use ratatui::text::{Line, Span};
+use ratatui::widgets::{Block, Borders, Paragraph, Wrap};
+
+#[derive(Debug, Clone)]
+pub struct TracePopupState {
+    pub trace: SearchTrace,
+    pub scroll: u16,
+}
+
+impl TracePopupState {
+    pub fn new(trace: SearchTrace) -> Self {
+        Self { trace, scroll: 0 }
+    }
+}
+
+pub fn render_trace_popup(f: &mut Frame, area: Rect, state: &TracePopupState) {
+    let mut lines: Vec<Line> = Vec::new();
+    let bold = Style::default().add_modifier(Modifier::BOLD);
+
+    lines.push(Line::from(Span::styled(
+        format!(
+            "Lexical ({} hits, {} ms)",
+            state.trace.lexical.len(),
+            state.trace.timing.lexical_ms,
+        ),
+        bold,
+    )));
+    for c in &state.trace.lexical {
+        lines.push(Line::from(format!(
+            "  #{:>2} score={:.4} chunk={}",
+            c.rank, c.score, c.chunk_id.0
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        format!(
+            "Vector ({} hits, {} ms)",
+            state.trace.vector.len(),
+            state.trace.timing.vector_ms,
+        ),
+        bold,
+    )));
+    for c in &state.trace.vector {
+        lines.push(Line::from(format!(
+            "  #{:>2} score={:.4} chunk={}",
+            c.rank, c.score, c.chunk_id.0
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        format!(
+            "RRF inputs ({} entries, {} ms fusion)",
+            state.trace.rrf_inputs.len(),
+            state.trace.timing.fusion_ms,
+        ),
+        bold,
+    )));
+    for e in &state.trace.rrf_inputs {
+        lines.push(Line::from(format!(
+            "  chunk={} lex={:?} vec={:?} fusion={:.4}",
+            e.chunk_id.0, e.lexical_rank, e.vector_rank, e.fusion_score
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        format!("Total: {} ms", state.trace.timing.total_ms),
+        bold,
+    )));
+
+    let block = Block::default()
+        .title("Trace — Esc to close, j/k or ↑↓ to scroll")
+        .borders(Borders::ALL);
+    let p = Paragraph::new(lines)
+        .block(block)
+        .scroll((state.scroll, 0))
+        .wrap(Wrap { trim: false });
+    f.render_widget(p, area);
+}
+
+/// Handle keys while popup is open. Returns true if the popup should close.
+pub fn handle_key_trace_popup(state: &mut TracePopupState, key: KeyEvent) -> bool {
+    match key.code {
+        KeyCode::Esc => true,
+        KeyCode::Char('j') | KeyCode::Down => {
+            state.scroll = state.scroll.saturating_add(1);
+            false
+        }
+        KeyCode::Char('k') | KeyCode::Up => {
+            state.scroll = state.scroll.saturating_sub(1);
+            false
+        }
+        _ => false,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crossterm::event::KeyModifiers;
+    use kebab_core::TraceTiming;
+
+    fn dummy_state() -> TracePopupState {
+        TracePopupState::new(SearchTrace {
+            lexical: vec![],
+            vector: vec![],
+            rrf_inputs: vec![],
+            timing: TraceTiming::default(),
+        })
+    }
+
+    #[test]
+    fn esc_closes() {
+        let mut s = dummy_state();
+        assert!(handle_key_trace_popup(
+            &mut s,
+            KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE),
+        ));
+    }
+
+    #[test]
+    fn j_scrolls_down() {
+        let mut s = dummy_state();
+        assert!(!handle_key_trace_popup(
+            &mut s,
+            KeyEvent::new(KeyCode::Char('j'), KeyModifiers::NONE),
+        ));
+        assert_eq!(s.scroll, 1);
+    }
+}

docs/SMOKE.md

@@ -206,6 +206,22 @@ kebab search "rust" --doc-id "<doc-id>" --tag rust --json
 Bad `--ingested-after` → `error.v1.code = config_invalid`, exit 2.
 Unknown `--media` value → silently empty (no error).
 
+### Trace + stats (fb-37)
+
+Re-run a search with `--trace` to see per-stage candidate lists + timing:
+
+```bash
+kebab --config /tmp/kebab-smoke/config.toml search "rust async" --trace --json | jq .trace
+```
+
+Inspect the corpus health surface:
+
+```bash
+kebab --config /tmp/kebab-smoke/config.toml schema --json | jq .stats
+```
+
+Look for: `media_breakdown` (5 keys), `lang_breakdown`, `index_bytes`, `stale_doc_count`.
+
 ## P6-4 이미지 ingestion 옵션
 
 `config.toml` 에 다음 절을 추가하면 `kebab ingest` 가 `**/*.png` / `**/*.jpg` 등 이미지 자산도 함께 색인합니다 (텍스트만 색인하려면 생략):

docs/superpowers/plans/2026-05-10-p9-fb-38-score-semantics.md

@@ -0,0 +1,697 @@
+# fb-38 Score Semantics Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add `score_kind` field on `search_hit.v1` (`"rrf"` / `"bm25"` / `"cosine"`) and document RRF formula + score interpretation so agents stop misreading the top-level `score` as confidence.
+
+**Architecture:** New `ScoreKind` enum on `kebab-core`. Each retriever (lexical / vector / hybrid) labels hits with the appropriate kind at construction. Wire serialization is automatic via existing `serde_json::to_value(&hit)`. Documentation in README + design + SKILL explains the RRF formula and the ranking-vs-confidence distinction.
+
+**Tech Stack:** Rust 2024, serde, JSON Schema 2020-12.
+
+**Spec:** `docs/superpowers/specs/2026-05-10-p9-fb-38-score-semantics-design.md`
+
+---
+
+## File map
+
+**Create:** none.
+
+**Modify:**
+- `crates/kebab-core/src/search.rs` — add `ScoreKind` enum + `SearchHit.score_kind` field; update existing `SearchHit` test fixture.
+- `crates/kebab-search/src/lexical.rs` — set `score_kind: Bm25` at hit construction.
+- `crates/kebab-search/src/vector.rs` — set `score_kind: Cosine` at hit construction.
+- `crates/kebab-search/src/hybrid.rs` — set `score_kind: Rrf` after RRF base.retrieval overwrite; update `mk_hit` test helper.
+- `crates/kebab-rag/src/pipeline.rs` — update `mk_hit` test helper with `score_kind`.
+- `crates/kebab-cli/tests/wire_search_response.rs` (or new) — integration test asserting `score_kind` on lexical / hybrid wire output.
+- `docs/wire-schema/v1/search_hit.schema.json` — add optional `score_kind` enum field.
+- `README.md` — new "Score interpretation (fb-38)" section.
+- `docs/superpowers/specs/2026-04-27-kebab-final-form-design.md` §4 — RRF formula + score_kind field block.
+- `integrations/claude-code/kebab/SKILL.md` — `score_kind` mention + ranking-vs-confidence guidance.
+- `tasks/p9/p9-fb-38-score-semantics.md` — flip status, add design + plan links.
+- `tasks/INDEX.md` — flip fb-38 to ✅.
+
+---
+
+## Task 1: Add ScoreKind enum + SearchHit.score_kind field
+
+**Files:**
+- Modify: `crates/kebab-core/src/search.rs`
+
+- [ ] **Step 1: Append failing tests to `mod tests`**
+
+```rust
+#[test]
+fn score_kind_serde_roundtrip() {
+    use ScoreKind::*;
+    for (kind, expected) in [(Rrf, "rrf"), (Bm25, "bm25"), (Cosine, "cosine")] {
+        let v = serde_json::to_value(kind).unwrap();
+        assert_eq!(v.as_str(), Some(expected));
+        let back: ScoreKind = serde_json::from_value(v).unwrap();
+        assert_eq!(back, kind);
+    }
+}
+
+#[test]
+fn score_kind_default_is_rrf() {
+    assert_eq!(ScoreKind::default(), ScoreKind::Rrf);
+}
+
+#[test]
+fn search_hit_deserialize_without_score_kind_defaults_to_rrf() {
+    // Old wire (pre-fb-38) shape — no `score_kind` field. Must
+    // deserialize cleanly with `Rrf` default.
+    let json = serde_json::json!({
+        "rank": 1,
+        "chunk_id": "c1",
+        "doc_id": "d1",
+        "doc_path": "a.md",
+        "heading_path": [],
+        "section_label": null,
+        "snippet": "x",
+        "citation": { "Line": { "path": "a.md", "start": 1, "end": 1, "section": null } },
+        "retrieval": {
+            "method": "Lexical",
+            "fusion_score": 0.5,
+            "lexical_score": 0.5,
+            "vector_score": null,
+            "lexical_rank": 1,
+            "vector_rank": null
+        },
+        "index_version": "v1",
+        "embedding_model": null,
+        "chunker_version": "c1",
+        "indexed_at": "2026-05-10T12:00:00Z",
+        "stale": false
+    });
+    let hit: SearchHit = serde_json::from_value(json).unwrap();
+    assert_eq!(hit.score_kind, ScoreKind::Rrf);
+}
+```
+
+- [ ] **Step 2: Run tests to verify compile failures**
+
+```bash
+cargo test -p kebab-core --lib score_kind
+```
+Expected: errors — `ScoreKind` undefined; `SearchHit.score_kind` missing.
+
+- [ ] **Step 3: Add `ScoreKind` enum + extend `SearchHit`**
+
+In `crates/kebab-core/src/search.rs`, add the enum (place after `MEDIA_KINDS` constant, before `SearchQuery`):
+
+```rust
+/// p9-fb-38: top-level `SearchHit.score` declaration.
+/// `Rrf` (hybrid) / `Bm25` (lexical-only) / `Cosine` (vector-only).
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum ScoreKind {
+    Rrf,
+    Bm25,
+    Cosine,
+}
+
+impl Default for ScoreKind {
+    fn default() -> Self {
+        ScoreKind::Rrf
+    }
+}
+```
+
+Extend `SearchHit` (add field after `stale`):
+
+```rust
+pub struct SearchHit {
+    // ... existing fields ...
+    pub stale: bool,
+    /// p9-fb-38: declares the meaning of the top-level `score`.
+    /// `Rrf` (hybrid mode), `Bm25` (lexical-only), `Cosine` (vector-only).
+    /// Older wire (fb-38 미만) 부재 시 `Rrf` default — hybrid 가 기본 mode.
+    #[serde(default)]
+    pub score_kind: ScoreKind,
+}
+```
+
+Update existing test fixture `search_hit_serializes_indexed_at_and_stale` (~line 190): add `score_kind: ScoreKind::Rrf,` to the struct literal.
+
+- [ ] **Step 4: Run tests**
+
+```bash
+cargo test -p kebab-core --lib
+```
+Expected: all 3 new tests + existing tests pass.
+
+- [ ] **Step 5: Re-export at crate root**
+
+Edit `crates/kebab-core/src/lib.rs` re-export block — add `ScoreKind` to the `search::` re-export list.
+
+```bash
+grep -n "SearchHit\|SearchTrace\|TraceCandidate" crates/kebab-core/src/lib.rs
+```
+
+The fb-37 task added `SearchTrace`/`TraceCandidate`/`TraceFusionInput`/`TraceTiming`/`IndexBytes`/`MEDIA_KINDS` to the same export block — add `ScoreKind` next to them.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add crates/kebab-core/src/search.rs crates/kebab-core/src/lib.rs
+git commit -m "feat(core): ScoreKind enum + SearchHit.score_kind (fb-38)"
+```
+
+---
+
+## Task 2: Label LexicalRetriever hits as Bm25
+
+**Files:**
+- Modify: `crates/kebab-search/src/lexical.rs`
+
+- [ ] **Step 1: Add unit test in `crates/kebab-search/src/lexical.rs`**
+
+Append to existing `mod tests` (find via `grep -n "mod tests" crates/kebab-search/src/lexical.rs`). If no tests module exists in that file, the integration tests in `tests/` cover behavior — add a unit test asserting via the public surface. Inspect first:
+
+```bash
+grep -n "mod tests\|#\[test\]" crates/kebab-search/src/lexical.rs | head -5
+```
+
+If no `mod tests` in lexical.rs, add a unit test in the existing integration test file (find via `ls crates/kebab-search/tests/`). Otherwise prepare an integration test that builds a lexical retriever against a real fixture and asserts on the hit's `score_kind`.
+
+The simplest path: assert via the existing `lexical_*` integration tests. Pick the smallest one and add an assertion. Or, more cleanly, add a new integration test:
+
+Append to `crates/kebab-search/tests/lexical_basic.rs` (or whichever existing lexical test file the workspace has — check `ls crates/kebab-search/tests/`):
+
+```rust
+#[test]
+fn lexical_retriever_hits_carry_bm25_score_kind() {
+    // Use the existing fixture-builder pattern from this file.
+    // The intent: any hit returned by LexicalRetriever has
+    // `score_kind == ScoreKind::Bm25`.
+    let (_dir, retriever) = setup_lexical_with_corpus(&[
+        ("a.md", "rust async tokens"),
+    ]);
+    let hits = retriever
+        .search(&kebab_core::SearchQuery {
+            text: "rust".into(),
+            mode: kebab_core::SearchMode::Lexical,
+            k: 5,
+            filters: Default::default(),
+        })
+        .unwrap();
+    assert!(!hits.is_empty());
+    for h in &hits {
+        assert_eq!(h.score_kind, kebab_core::ScoreKind::Bm25);
+    }
+}
+```
+
+`setup_lexical_with_corpus` is the existing fixture name — adjust to whatever the file's helper is called. If the file uses inline `tempfile::tempdir() + SqliteStore::open + ingest_with_config + LexicalRetriever::with_settings`, mirror that pattern.
+
+- [ ] **Step 2: Run test to verify it fails**
+
+```bash
+cargo test -p kebab-search lexical_retriever_hits_carry_bm25_score_kind
+```
+Expected: compile error (struct literal needs new field) OR assertion failure (score_kind defaults to Rrf, not Bm25).
+
+- [ ] **Step 3: Update `LexicalRetriever` hit construction**
+
+In `crates/kebab-search/src/lexical.rs:447-471`, find the `Ok(SearchHit { ... })` block and add `score_kind: kebab_core::ScoreKind::Bm25,` (anywhere in the field list — placement doesn't matter for serde). Place it next to the `stale: false` line for visual grouping:
+
+```rust
+    Ok(SearchHit {
+        rank,
+        chunk_id: ChunkId(raw.chunk_id),
+        // ... existing fields ...
+        indexed_at,
+        stale: false,
+        score_kind: kebab_core::ScoreKind::Bm25,
+    })
+```
+
+- [ ] **Step 4: Run tests**
+
+```bash
+cargo test -p kebab-search
+```
+Expected: new test passes + all existing kebab-search tests still pass.
+
+- [ ] **Step 5: Clippy**
+
+```bash
+cargo clippy -p kebab-search --all-targets -- -D warnings
+```
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add crates/kebab-search/src/lexical.rs crates/kebab-search/tests/
+git commit -m "feat(search/lexical): label hits with ScoreKind::Bm25 (fb-38)"
+```
+
+---
+
+## Task 3: Label VectorRetriever hits as Cosine
+
+**Files:**
+- Modify: `crates/kebab-search/src/vector.rs`
+
+- [ ] **Step 1: Add unit test**
+
+VectorRetriever requires embeddings, so a real-corpus integration test isn't possible without a model. Add a unit test that constructs a `SearchHit` directly through whichever helper the file uses, OR adjust an existing vector test that already builds a retriever.
+
+Inspect existing tests:
+```bash
+ls crates/kebab-search/tests/ | grep vector
+grep -n "fn build_hit\|VectorRetriever" crates/kebab-search/src/vector.rs | head -5
+```
+
+If there's a private `build_hit` helper, write a unit test around it. Otherwise mirror the lexical test pattern but stub the embedder. Worst case: skip the unit test for VectorRetriever and rely on the hybrid test (Task 4) which exercises the vector path indirectly. Document in the commit message.
+
+For simplicity, the recommended approach: add the score_kind line in Step 2 below first, then add a unit test using a simple hit-construction helper if accessible. If not accessible, the hybrid task (Task 4) covers behavior via the search_with_trace mode=Vector branch.
+
+- [ ] **Step 2: Update `VectorRetriever` hit construction**
+
+In `crates/kebab-search/src/vector.rs:304-330`, find `Ok(SearchHit { ... })` and add:
+
+```rust
+    Ok(SearchHit {
+        rank,
+        // ... existing fields ...
+        indexed_at,
+        stale: false,
+        score_kind: kebab_core::ScoreKind::Cosine,
+    })
+```
+
+- [ ] **Step 3: Run tests**
+
+```bash
+cargo test -p kebab-search
+cargo clippy -p kebab-search --all-targets -- -D warnings
+```
+Expected: existing tests still pass; clippy clean.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add crates/kebab-search/src/vector.rs
+git commit -m "feat(search/vector): label hits with ScoreKind::Cosine (fb-38)"
+```
+
+---
+
+## Task 4: Label HybridRetriever fuse hits as Rrf + update test helpers
+
+**Files:**
+- Modify: `crates/kebab-search/src/hybrid.rs`
+- Modify: `crates/kebab-rag/src/pipeline.rs` (test helper)
+
+- [ ] **Step 1: Add unit test in `crates/kebab-search/src/hybrid.rs` `mod tests`**
+
+Append:
+
+```rust
+#[test]
+fn hybrid_fuse_labels_hits_as_rrf() {
+    // Reuse mk_hit / Stub from the existing tests in this file.
+    use kebab_core::{ScoreKind, SearchMode, SearchQuery};
+    use std::sync::Arc;
+
+    struct Stub { hits: Vec<kebab_core::SearchHit> }
+    impl Retriever for Stub {
+        fn search(&self, _q: &SearchQuery) -> anyhow::Result<Vec<kebab_core::SearchHit>> {
+            Ok(self.hits.clone())
+        }
+        fn index_version(&self) -> kebab_core::IndexVersion {
+            kebab_core::IndexVersion("v1".into())
+        }
+    }
+
+    let lex = Arc::new(Stub {
+        hits: vec![mk_hit(1, "c1", 0.9, SearchMode::Lexical)],
+    });
+    let vec_r = Arc::new(Stub {
+        hits: vec![mk_hit(1, "c1", 0.8, SearchMode::Vector)],
+    });
+    let hybrid = HybridRetriever::with_policy(
+        lex,
+        vec_r,
+        FusionPolicy::Rrf { k_rrf: 60 },
+        2,
+    );
+    let q = SearchQuery {
+        text: "x".into(),
+        mode: SearchMode::Hybrid,
+        k: 1,
+        filters: Default::default(),
+    };
+    let hits = hybrid.search(&q).unwrap();
+    assert!(!hits.is_empty());
+    assert_eq!(hits[0].score_kind, ScoreKind::Rrf);
+}
+
+#[test]
+fn hybrid_search_with_trace_lexical_mode_passes_through_bm25() {
+    use kebab_core::{ScoreKind, SearchMode, SearchQuery};
+    use std::sync::Arc;
+
+    struct Stub { hits: Vec<kebab_core::SearchHit> }
+    impl Retriever for Stub {
+        fn search(&self, _q: &SearchQuery) -> anyhow::Result<Vec<kebab_core::SearchHit>> {
+            Ok(self.hits.clone())
+        }
+        fn index_version(&self) -> kebab_core::IndexVersion {
+            kebab_core::IndexVersion("v1".into())
+        }
+    }
+
+    let mut lex_hit = mk_hit(1, "c1", 0.5, SearchMode::Lexical);
+    lex_hit.score_kind = ScoreKind::Bm25;
+    let lex = Arc::new(Stub { hits: vec![lex_hit] });
+    let vec_r = Arc::new(Stub { hits: vec![] });
+    let hybrid = HybridRetriever::with_policy(
+        lex,
+        vec_r,
+        FusionPolicy::Rrf { k_rrf: 60 },
+        2,
+    );
+    let q = SearchQuery {
+        text: "x".into(),
+        mode: SearchMode::Lexical,
+        k: 1,
+        filters: Default::default(),
+    };
+    let (hits, _trace) = hybrid.search_with_trace(&q).unwrap();
+    assert!(!hits.is_empty());
+    // search_with_trace mode=Lexical passes through underlying hits.
+    assert_eq!(hits[0].score_kind, ScoreKind::Bm25);
+}
+```
+
+The existing `mk_hit` helper at `hybrid.rs:730` is in the same `mod tests` block — reachable.
+
+- [ ] **Step 2: Run tests to verify failures**
+
+```bash
+cargo test -p kebab-search hybrid
+```
+Expected: compile errors (mk_hit doesn't set score_kind so the struct literal is incomplete; new tests assert wrong value).
+
+- [ ] **Step 3: Update `mk_hit` test helper at `hybrid.rs:730`**
+
+Find `fn mk_hit(rank: u32, chunk: &str, score: f32, mode: SearchMode) -> SearchHit` and add `score_kind` to the returned literal:
+
+```rust
+fn mk_hit(rank: u32, chunk: &str, score: f32, mode: SearchMode) -> SearchHit {
+    SearchHit {
+        // ... existing fields ...
+        indexed_at: time::OffsetDateTime::UNIX_EPOCH,
+        stale: false,
+        score_kind: kebab_core::ScoreKind::Rrf,  // tests override per-mode
+    }
+}
+```
+
+- [ ] **Step 4: Update `hybrid.rs` fuse to set Rrf after retrieval overwrite**
+
+Find `base.retrieval = RetrievalDetail { ... }` block (~line 302-314). Immediately AFTER that block (before `hits.push(base)`), add:
+
+```rust
+            base.score_kind = kebab_core::ScoreKind::Rrf;
+            hits.push(base);
+```
+
+(`base` was cloned from a lex/vec hit that had `Bm25`/`Cosine`; the fuse output is RRF-scored so override.)
+
+- [ ] **Step 5: Update `pipeline.rs` mk_hit test helper**
+
+```bash
+grep -n "fn mk_hit" crates/kebab-rag/src/pipeline.rs
+```
+
+At ~line 1092, the test helper builds a SearchHit. Add `score_kind: kebab_core::ScoreKind::Rrf,` to the literal (place after `stale`).
+
+- [ ] **Step 6: Update `kebab-core` test fixture if any other SearchHit literal exists**
+
+```bash
+grep -rn "SearchHit {" crates/ --include="*.rs"
+```
+
+For each location, ensure the literal includes `score_kind`. The Task 1 update on `crates/kebab-core/src/search.rs:190` should already be done. Tasks 2/3 cover the lexical/vector retriever construction. Tasks 4 covers `mk_hit` helpers. If any other SearchHit literal turns up (e.g. fb-37 added some in tests), add `score_kind` there too.
+
+- [ ] **Step 7: Run tests + clippy**
+
+```bash
+cargo test -p kebab-core -p kebab-search -p kebab-rag
+cargo clippy -p kebab-core -p kebab-search -p kebab-rag --all-targets -- -D warnings
+```
+Expected: all green.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add crates/kebab-search/src/hybrid.rs crates/kebab-rag/src/pipeline.rs
+git commit -m "feat(search/hybrid): label fused hits with ScoreKind::Rrf (fb-38)"
+```
+
+---
+
+## Task 5: Workspace tests + cross-crate cleanup for SearchHit literals
+
+**Files:**
+- Modify: any other crate file with `SearchHit {` literal that broke (e.g., `kebab-app`, `kebab-cli`, `kebab-mcp`, `kebab-tui` test fixtures).
+
+- [ ] **Step 1: Find all broken sites**
+
+```bash
+cargo build --workspace 2>&1 | grep "missing field \`score_kind\`" | head -20
+```
+
+This reveals every spot. Common patterns:
+- Test fixtures in `crates/kebab-cli/tests/wire_*.rs` that hand-build hits.
+- Test helpers in `crates/kebab-app/tests/`.
+- TUI test data in `crates/kebab-tui/tests/`.
+
+For each: open the file, find the `SearchHit {` literal, add `score_kind: kebab_core::ScoreKind::Rrf,` (default for test fixtures unless the test specifically exercises lex/vec mode).
+
+- [ ] **Step 2: Verify workspace builds**
+
+```bash
+cargo build --workspace 2>&1 | tail -5
+```
+Expected: clean.
+
+- [ ] **Step 3: Run full workspace tests**
+
+```bash
+cargo test --workspace --no-fail-fast -j 1
+cargo clippy --workspace --all-targets -- -D warnings
+```
+Expected: all green.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add crates/
+git commit -m "fix(fb-38): add score_kind to remaining SearchHit literals"
+```
+
+---
+
+## Task 6: CLI integration test for score_kind
+
+**Files:**
+- Modify: `crates/kebab-cli/tests/wire_search_response.rs` (or new file `wire_search_score_kind.rs` if appending feels cluttered)
+
+- [ ] **Step 1: Inspect existing wire test pattern**
+
+```bash
+ls crates/kebab-cli/tests/
+head -50 crates/kebab-cli/tests/wire_search_response.rs
+```
+
+Use the same fixture pattern from fb-37's `wire_search_trace.rs` (`common::write_config + ingest + run_search_with_args`).
+
+- [ ] **Step 2: Add integration tests**
+
+Create `crates/kebab-cli/tests/wire_search_score_kind.rs`:
+
+```rust
+//! p9-fb-38: integration tests for `search_hit.v1.score_kind`.
+
+mod common;
+
+use serde_json::Value;
+use std::fs;
+
+fn doc_with_term(workspace: &std::path::Path) {
+    fs::write(workspace.join("doc1.md"), "# Title\n\nrust async hello\n").unwrap();
+}
+
+#[test]
+fn lexical_mode_hits_carry_bm25_score_kind() {
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    doc_with_term(&workspace);
+    common::ingest(&cfg, &workspace);
+
+    let (stdout, _stderr) = common::run_search_with_args(
+        &cfg,
+        &["--mode", "lexical", "--json", "rust"],
+    );
+    let v: Value = serde_json::from_str(stdout.trim()).expect("valid JSON");
+    let hits = v["hits"].as_array().expect("hits array");
+    assert!(!hits.is_empty(), "expected at least 1 hit");
+    for h in hits {
+        assert_eq!(h["score_kind"], "bm25");
+    }
+}
+
+#[test]
+fn old_wire_reader_compat_score_kind_optional_field() {
+    // The wire schema marks `score_kind` as additive (not required).
+    // We can't easily simulate an old reader from inside Rust, but we
+    // can confirm the JSON includes the field — old readers that
+    // ignore unknown fields are unaffected. This test just ensures
+    // the field is always present in fb-38+ output.
+    let dir = tempfile::tempdir().unwrap();
+    let (cfg, workspace, _data) = common::write_config(dir.path(), 0);
+    doc_with_term(&workspace);
+    common::ingest(&cfg, &workspace);
+
+    let (stdout, _stderr) = common::run_search_with_args(
+        &cfg,
+        &["--mode", "lexical", "--json", "rust"],
+    );
+    let v: Value = serde_json::from_str(stdout.trim()).unwrap();
+    let hit = &v["hits"][0];
+    assert!(hit.get("score_kind").is_some(), "score_kind always emitted");
+}
+```
+
+- [ ] **Step 3: Run integration tests**
+
+```bash
+cargo test -p kebab-cli --test wire_search_score_kind
+```
+Expected: 2 tests pass.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add crates/kebab-cli/tests/wire_search_score_kind.rs
+git commit -m "test(cli): integration tests for score_kind on lexical mode (fb-38)"
+```
+
+---
+
+## Task 7: Wire schema + docs + status flip
+
+**Files:**
+- Modify: `docs/wire-schema/v1/search_hit.schema.json`
+- Modify: `README.md`
+- Modify: `docs/superpowers/specs/2026-04-27-kebab-final-form-design.md`
+- Modify: `integrations/claude-code/kebab/SKILL.md`
+- Modify: `tasks/p9/p9-fb-38-score-semantics.md`
+- Modify: `tasks/INDEX.md`
+
+- [ ] **Step 1: Update `docs/wire-schema/v1/search_hit.schema.json`**
+
+Add `score_kind` to `properties` (not to `required`). Insert next to `score`:
+
+```json
+    "score_kind": {
+      "type": "string",
+      "enum": ["rrf", "bm25", "cosine"],
+      "description": "p9-fb-38: kind of `score` value. `rrf` = RRF normalized [0,1] (hybrid mode); `bm25` = raw BM25 score (lexical-only); `cosine` = raw cosine similarity (vector-only). Older clients that omit this field can treat absence as `rrf` (the historical default)."
+    }
+```
+
+- [ ] **Step 2: Update `README.md`**
+
+Find the `kebab search` section (or wherever flag descriptions live). Add a new "Score interpretation (fb-38)" subsection:
+
+````markdown
+### Score 해석 (fb-38)
+
+`search_hit.v1.score` 는 **ranking signal** 이지 confidence 가 아니다. `score_kind` 필드로 의미 선언:
+
+| `score_kind` | 의미 | 범위 |
+|--------------|------|------|
+| `rrf` (hybrid) | RRF normalized | `[0, 1]`, ceiling = 1.0 (양 채널 rank=1) |
+| `bm25` (lexical) | raw BM25 | unbounded (≥ 0) |
+| `cosine` (vector) | cosine sim | `[-1, 1]` |
+
+#### RRF 수식 (hybrid mode)
+
+```
+chunk c 의 raw RRF = Σ_m  1 / (k_rrf + rank_m(c))
+
+여기서 m ∈ {lexical, vector}, k_rrf = config.search.rrf_k (default 60).
+양 채널 모두 rank=1 일 때 raw RRF = 2 / (k_rrf + 1) ≈ 0.0328.
+
+normalize: rrf_score = raw_rrf / (2 / (k_rrf + 1))
+       → rrf_score ∈ [0, 1]. 양쪽 rank=1 → 1.0, 한 쪽만 등장 → ≈ 0.5 천장.
+```
+
+`rrf_score = 0.5` 의 의미: chunk 가 한 채널 (lexical 또는 vector) 에서만 rank 1 로 등장. confidence 50% 가 아님 — RRF 수식의 산술적 천장.
+
+agent 가 trust threshold 가 필요하면 top-level `score` 가 아닌 nested `retrieval.lexical_score` (BM25 raw) / `retrieval.vector_score` (cosine raw) 사용.
+````
+
+Place after the `kebab search` flag table or wherever similar reference content lives. If the README has existing `kebab search` row in a command table, add a `--trace` neighbor cross-reference here.
+
+- [ ] **Step 3: Update `docs/superpowers/specs/2026-04-27-kebab-final-form-design.md` §4 search**
+
+Add a new "Score scale (fb-38)" subsection under §4 with the same RRF formula block + `score_kind` field definition. The frozen design doc gets the contract; README is the user-facing copy.
+
+```bash
+grep -n "^## §4\|^### §4\|RRF\|hybrid_fusion" docs/superpowers/specs/2026-04-27-kebab-final-form-design.md | head -10
+```
+
+Locate the §4 search section and append the score scale block.
+
+- [ ] **Step 4: Update `integrations/claude-code/kebab/SKILL.md`**
+
+Find the `mcp__kebab__search` response shape block. Add a sentence:
+
+> `hits[].score_kind`: `"rrf"` (hybrid) / `"bm25"` (lexical) / `"cosine"` (vector). top-level `score` 의 의미 선언 — confidence 아님. trust threshold 가 필요하면 `retrieval.lexical_score` / `retrieval.vector_score` (raw) 사용.
+
+- [ ] **Step 5: Update `tasks/p9/p9-fb-38-score-semantics.md`**
+
+Flip frontmatter `status: open` → `status: completed`. Replace the skeleton banner with:
+
+```markdown
+> ✅ **구현 완료.** 본 spec 은 구현 시점의 frozen 상태.
+>
+> - Design: [`docs/superpowers/specs/2026-05-10-p9-fb-38-score-semantics-design.md`](../../docs/superpowers/specs/2026-05-10-p9-fb-38-score-semantics-design.md)
+> - Plan: [`docs/superpowers/plans/2026-05-10-p9-fb-38-score-semantics.md`](../../docs/superpowers/plans/2026-05-10-p9-fb-38-score-semantics.md)
+```
+
+- [ ] **Step 6: Update `tasks/INDEX.md`**
+
+Find the fb-38 row. Flip status to ✅, mirror format of fb-32..37 rows.
+
+- [ ] **Step 7: Run full workspace tests + clippy**
+
+```bash
+cargo test --workspace --no-fail-fast -j 1
+cargo clippy --workspace --all-targets -- -D warnings
+```
+Expected: all green.
+
+- [ ] **Step 8: Commit**
+
+```bash
+git add docs/ README.md tasks/p9/p9-fb-38-score-semantics.md tasks/INDEX.md integrations/claude-code/kebab/SKILL.md
+git commit -m "docs(fb-38): wire schema + README + design + SKILL + INDEX"
+```
+
+---
+
+## Final verification checklist
+
+- [ ] `cargo test --workspace --no-fail-fast -j 1` green
+- [ ] `cargo clippy --workspace --all-targets -- -D warnings` clean
+- [ ] Manual smoke against `/tmp/kebab-smoke`:
+  - [ ] `kebab search Q --mode lexical --json | jq '.hits[0].score_kind'` returns `"bm25"`
+  - [ ] `kebab search Q --json | jq '.hits[0].score_kind'` returns `"rrf"` (hybrid default)
+- [ ] README, design §4, SKILL, INDEX all reflect score_kind + RRF formula

docs/superpowers/specs/2026-05-10-p9-fb-38-score-semantics-design.md

@@ -0,0 +1,173 @@
+---
+title: "p9-fb-38 — Score semantics design"
+phase: P9
+component: kebab-core + kebab-search + kebab-cli + wire-schema + docs
+task_id: p9-fb-38
+status: design
+target_version: 0.6.0
+contract_source: ../../docs/superpowers/specs/2026-04-27-kebab-final-form-design.md
+contract_sections: [§4 search, §10 UX, wire-schema search_hit.v1]
+date: 2026-05-10
+---
+
+# p9-fb-38 — Score semantics
+
+## Goal
+
+agent / 외부 통합이 `search_hit.v1.score` 를 confidence 로 오해하지 않도록 의미를 wire + docs 에 명시. 두 axes:
+
+- **Wire (additive minor)**: `search_hit.v1` 에 `score_kind: string` 필드 추가 — `"rrf"` (hybrid) / `"bm25"` (lexical) / `"cosine"` (vector). top-level `score` 의 의미를 hit 단위로 declarative 하게 표시.
+- **Docs**: README + design §4 + SKILL 에 RRF 수식 전체 (`2/(k+rank)` per-chunk, `2/(k+1)` ceiling, normalize 과정) + "ranking signal, NOT confidence" 안내. agent 용 trust threshold 는 nested `retrieval.lexical_score` / `vector_score` 권장.
+
+wire change additive minor — schema bump 없음, 기존 consumer 무영향.
+
+## Behavior contract
+
+### Wire shape
+
+**`search_hit.v1`** — 신규 optional 필드:
+
+```jsonc
+{
+  "schema_version": "search_hit.v1",
+  "rank": 1,
+  "score": 0.5,                 // 기존 — RRF normalized (hybrid) 또는 raw (lexical / vector)
+  "score_kind": "rrf",          // p9-fb-38 신규 — "rrf" | "bm25" | "cosine"
+  // 기존 필드 ...
+  "retrieval": {
+    "method": "hybrid",
+    "fusion_score": 0.5,
+    "lexical_score": 12.34,    // BM25 raw — agent 용 trust threshold
+    "vector_score": 0.78,       // cosine sim — agent 용 trust threshold
+    "lexical_rank": 1,
+    "vector_rank": 1
+  }
+}
+```
+
+`score_kind` `#[serde(default)]` (옛 reader / 옛 writer 호환). schema 의 `required` 미추가.
+
+### Score kind dispatch
+
+| Retriever | `score_kind` | top-level `score` 의 값 |
+|-----------|--------------|--------------------------|
+| LexicalRetriever | `"bm25"` | raw BM25 (≥ 0, unbounded) |
+| VectorRetriever | `"cosine"` | cosine similarity (`[-1, 1]`) |
+| HybridRetriever (fuse) | `"rrf"` | RRF normalized (`[0, 1]`) |
+| HybridRetriever (search_with_trace, mode=Lexical) | `"bm25"` | pass-through from LexicalRetriever |
+| HybridRetriever (search_with_trace, mode=Vector) | `"cosine"` | pass-through from VectorRetriever |
+
+`SearchMode` 와 `score_kind` 의 1:1 매핑은 hybrid retriever 가 mode-dispatch 시 결정. lexical/vector mode 의 hits 는 retriever 자체가 정한 kind 그대로.
+
+### Backwards-compat
+
+- 옛 wire reader (fb-38 이전 binary): JSON 에 `score_kind` 키 없음. ignore. 영향 없음.
+- 옛 wire writer (fb-38 이전 binary 가 보낸 JSON 을 새 binary 가 읽음): `score_kind` 부재 → `default_score_kind() = ScoreKind::Rrf`. 잘못된 추정 가능 (실제 lexical / vector mode 였을 수도).
+- 정확한 의미 보장은 v0.6.0 이후 binary 로 통일 시점부터.
+
+## Allowed / forbidden dependencies
+
+- `kebab-core`: 신규 dep 없음. enum + field 추가만.
+- `kebab-search`: 신규 dep 없음. hit construction 시 score_kind 라벨링.
+- `kebab-cli`: 무수정 (serde 자동 emit).
+- `kebab-mcp`: 무수정 (`SearchHit` 직접 serialize → 자동 포함).
+- `kebab-tui`: 무수정.
+
+`kebab-core` 의 다른 `kebab-*` 의존 금지 룰 그대로.
+
+## Public surface delta
+
+### kebab-core (`search.rs`)
+
+```rust
+/// p9-fb-38: top-level `SearchHit.score` 의 의미 declaration.
+/// `Rrf` (hybrid) / `Bm25` (lexical-only) / `Cosine` (vector-only).
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum ScoreKind {
+    Rrf,
+    Bm25,
+    Cosine,
+}
+
+impl Default for ScoreKind {
+    fn default() -> Self { ScoreKind::Rrf }
+}
+```
+
+`SearchHit` 확장:
+
+```rust
+pub struct SearchHit {
+    // 기존 필드 ...
+    /// p9-fb-38: top-level `score` 의 의미 declaration.
+    /// 옛 wire (부재) → `Rrf` default (hybrid 가 기본 mode).
+    #[serde(default)]
+    pub score_kind: ScoreKind,
+}
+```
+
+### kebab-search (lexical / vector / hybrid)
+
+- LexicalRetriever hit construction 에 `score_kind: ScoreKind::Bm25`.
+- VectorRetriever hit construction 에 `score_kind: ScoreKind::Cosine`.
+- HybridRetriever fuse 결과 hit 에 `score_kind: ScoreKind::Rrf`.
+- HybridRetriever `search_with_trace` (fb-37) 의 Lexical/Vector branch 는 underlying retriever 의 hit 그대로 반환 — score_kind 는 그 retriever 의 라벨 (Bm25 / Cosine).
+
+### kebab-cli + kebab-mcp
+
+무수정. `serde_json::to_value(&hit)` 가 `score_kind` 를 자동 emit.
+
+## Test plan
+
+| kind | description |
+|------|-------------|
+| unit (kebab-core) | `ScoreKind` serde — Rrf↔"rrf", Bm25↔"bm25", Cosine↔"cosine" |
+| unit (kebab-core) | `SearchHit` deserialization 시 `score_kind` 부재 → `Rrf` default |
+| unit (kebab-core) | `ScoreKind::default() == Rrf` |
+| unit (kebab-search/lexical) | LexicalRetriever hit 의 `score_kind == Bm25` |
+| unit (kebab-search/vector) | VectorRetriever hit 의 `score_kind == Cosine` |
+| unit (kebab-search/hybrid) | HybridRetriever fuse → all hits `Rrf` |
+| unit (kebab-search/hybrid) | search_with_trace mode=Lexical → hits `Bm25` |
+| 통합 (kebab-cli) | `kebab search Q --mode lexical --json` → `hits[0].score_kind == "bm25"` |
+| 통합 (kebab-cli) | `kebab search Q --json` (default hybrid) → `hits[0].score_kind == "rrf"` |
+
+vector mode 통합 테스트는 embeddings 의존 — unit (search_with_trace mode=Vector 시 hits Cosine) 으로 대체.
+
+## Implementation steps (high-level)
+
+1. `kebab-core::ScoreKind` enum + `SearchHit.score_kind` field + 단위 테스트.
+2. `kebab-search/lexical.rs` LexicalRetriever hit construction 에 `Bm25` 라벨 + 단위 테스트.
+3. `kebab-search/vector.rs` VectorRetriever hit construction 에 `Cosine` + 단위 테스트.
+4. `kebab-search/hybrid.rs` fuse + search_with_trace 에 `Rrf` / pass-through + 단위 테스트.
+5. `kebab-cli` 통합 테스트 (lexical-only + hybrid).
+6. `docs/wire-schema/v1/search_hit.schema.json` — `score_kind` 필드 추가.
+7. README — "Score interpretation" 섹션 (RRF 수식 + score_kind 표 + agent guidance).
+8. design §4 search — RRF 수식 + normalize 정의 + score_kind 필드 등록.
+9. SKILL.md — `mcp__kebab__search` 응답에 `score_kind` 안내.
+10. tasks/INDEX.md / spec status flip.
+
+## Risks / notes
+
+- **RRF normalizer 변경 시**: k_rrf default 변경 또는 retriever 수 > 2 확장 시 ceiling 재계산. design §4 RRF 수식 + README Score interpretation 갱신 필요.
+- **vector mode 통합 테스트 부재**: 통합 테스트 fixture 가 embeddings 없음 (`provider = "none"`). 통합은 lexical / hybrid 만, vector 는 단위 테스트로 cover.
+- **fb-37 search_with_trace 와 정합성**: search_with_trace 는 underlying retriever 가 만든 hit 을 그대로 trace 의 lex/vec list 에 채움 — score_kind 도 자동 보존. 추가 작업 없음.
+- **`#[serde(default)]` 의미**: 옛 wire reader 가 `score_kind` 키 발견 시 unknown field 거절 안 함 (serde 기본 동작 — `deny_unknown_fields` 없음, 확인 완료). 안전.
+
+## Out of scope
+
+- top-level `score` rename 또는 deprecation (v0.7.0+ 검토).
+- channel score 의 추가 노출 (이미 `retrieval` block 에 있음).
+- score gate threshold 변경 (config.rag.score_gate).
+- TUI score badge / color hint.
+- per-channel score normalization (BM25/cosine 둘 다 raw 유지).
+- `RetrievalDetail.method` 와 `score_kind` 의 정합성 검증 (둘 다 같은 정보 source 지만 별도 declarative).
+
+## Documentation updates (implementation PR 동시)
+
+- `README.md` — "Score interpretation" 섹션 (RRF 수식 + score_kind 표 + agent guidance).
+- `docs/superpowers/specs/2026-04-27-kebab-final-form-design.md` §4 — RRF 수식 block + score_kind field 등록.
+- `docs/wire-schema/v1/search_hit.schema.json` — `score_kind` enum 필드.
+- `integrations/claude-code/kebab/SKILL.md` — `mcp__kebab__search` 응답 안내 (score_kind + "ranking signal, NOT confidence" + raw threshold guidance).
+- `tasks/p9/p9-fb-38-score-semantics.md` — `status: open → completed`, design + plan 링크.
+- `tasks/INDEX.md` — fb-38 행 ✅.

docs/wire-schema/v1/schema.schema.json

@@ -54,6 +54,30 @@
             { "type": "string", "format": "date-time" },
             { "type": "null" }
           ]
+        },
+        "media_breakdown": {
+          "type": "object",
+          "description": "p9-fb-37: per-media-kind doc count. 5 keys (markdown/pdf/image/audio/other), zero-padded.",
+          "additionalProperties": { "type": "integer", "minimum": 0 }
+        },
+        "lang_breakdown": {
+          "type": "object",
+          "description": "p9-fb-37: per-language doc count. NULL lang keyed as the literal string 'null'. Map may be empty on empty corpus.",
+          "additionalProperties": { "type": "integer", "minimum": 0 }
+        },
+        "index_bytes": {
+          "type": "object",
+          "description": "p9-fb-37: on-disk byte sums.",
+          "required": ["sqlite", "lancedb"],
+          "properties": {
+            "sqlite":  { "type": "integer", "minimum": 0 },
+            "lancedb": { "type": "integer", "minimum": 0 }
+          }
+        },
+        "stale_doc_count": {
+          "type": "integer",
+          "minimum": 0,
+          "description": "p9-fb-37: docs whose updated_at exceeds config.search.stale_threshold_days. 0 when threshold=0."
         }
       }
     }

docs/wire-schema/v1/search_response.schema.json

@@ -9,6 +9,26 @@
     "schema_version": { "const": "search_response.v1" },
     "hits":           { "type": "array", "description": "search_hit.v1[]" },
     "next_cursor":    { "type": ["string", "null"], "description": "Opaque base64 cursor for next page; null when no more hits." },
-    "truncated":      { "type": "boolean", "description": "True when budget forced snippet shortening or k reduction. Independent of `next_cursor`: caller may widen `max_tokens` (re-issue same query) or follow `next_cursor` (advance through more hits) or both." }
+    "truncated":      { "type": "boolean", "description": "True when budget forced snippet shortening or k reduction. Independent of `next_cursor`: caller may widen `max_tokens` (re-issue same query) or follow `next_cursor` (advance through more hits) or both." },
+    "trace": {
+      "type": "object",
+      "description": "p9-fb-37: present iff caller passed --trace / SearchOpts.trace=true. Lex/vec pre-fusion lists + RRF union + per-stage timing.",
+      "required": ["lexical", "vector", "rrf_inputs", "timing"],
+      "properties": {
+        "lexical":   { "type": "array", "items": { "type": "object" } },
+        "vector":    { "type": "array", "items": { "type": "object" } },
+        "rrf_inputs":{ "type": "array", "items": { "type": "object" } },
+        "timing": {
+          "type": "object",
+          "required": ["lexical_ms", "vector_ms", "fusion_ms", "total_ms"],
+          "properties": {
+            "lexical_ms": { "type": "integer", "minimum": 0 },
+            "vector_ms":  { "type": "integer", "minimum": 0 },
+            "fusion_ms":  { "type": "integer", "minimum": 0 },
+            "total_ms":   { "type": "integer", "minimum": 0 }
+          }
+        }
+      }
+    }
   }
 }

integrations/claude-code/kebab/SKILL.md

@@ -48,7 +48,7 @@ Use when the user wants to **find** a doc, or when you (the model) need raw chun
 
 Input:
 ```json
-{ "query": "<query>", "mode": "hybrid", "k": 10, "max_tokens": null, "snippet_chars": null, "cursor": null, "tags": null, "lang": null, "path_glob": null, "trust_min": null, "media": null, "ingested_after": null, "doc_id": null }
+{ "query": "<query>", "mode": "hybrid", "k": 10, "max_tokens": null, "snippet_chars": null, "cursor": null, "tags": null, "lang": null, "path_glob": null, "trust_min": null, "media": null, "ingested_after": null, "doc_id": null, "trace": null }
 ```
 
 - `mode = "hybrid"` is the default-correct choice. Use `"vector"` for semantic-only ("docs about X concept"), `"lexical"` for exact strings ("the literal flag `--foo-bar`").
@@ -57,6 +57,7 @@ Input:
 - Output is `search_response.v1`: `{ hits: search_hit.v1[], next_cursor: string|null, truncated: bool }`. Iterate `response.hits[]` for individual hits. Key hit fields: `rank`, `score`, `doc_path`, `heading_path[]`, `section_label`, `snippet`, `citation` (line range / page), `chunk_id`.
 - Cite back to the user as `doc_path § heading_path[-1]` so they can open the source.
 - When `truncated: true`, the budget loop modified the page (snippet shortening or k reduction). `next_cursor` is **independent** — non-null whenever more hits may be reachable. Caller may widen `max_tokens` (re-issue same query for fuller snippets / more hits per page) or follow `next_cursor` (advance through more hits) or both. Mismatched cursor (corpus_revision changed) returns `error.v1.code = stale_cursor` — re-issue the search to obtain a fresh one.
+- **`trace: true` (p9-fb-37)** — debug aid. Response carries an extra `trace` block: `lexical[]` + `vector[]` (pre-fusion candidates), `rrf_inputs[]` (RRF union before final cut), and `timing` (`lexical_ms`, `vector_ms`, `fusion_ms`, `total_ms`). Trace bypasses the search cache (always cold). Use sparingly — it bloats the wire response and is for diagnosing "why did this hit / not hit", not normal retrieval.
 
 ### `mcp__kebab__ask` — when you need the answer
 
@@ -133,7 +134,7 @@ Claude Code spawns `kebab mcp` at session start; the process stays alive across
 
 Before using streaming or multi-turn features, probe what this binary supports — call `mcp__kebab__schema` (or CLI `kebab schema --json`):
 
-Returns `schema.v1`: `wire.schemas` (supported wire ids), `capabilities` (bool flags — e.g. `streaming_ask`, `rag_multi_turn`), `models` (version cascade 6-axis), `stats` (doc/chunk/asset count + last_ingest_at). Gate streaming / session flows on `capabilities.streaming_ask` / `capabilities.rag_multi_turn` being `true`. Cheap call (no LLM), once per session.
+Returns `schema.v1`: `wire.schemas` (supported wire ids), `capabilities` (bool flags — e.g. `streaming_ask`, `rag_multi_turn`), `models` (version cascade 6-axis), `stats` (doc/chunk/asset count + last_ingest_at, plus p9-fb-37 health surface: `media_breakdown` per-kind doc counts (5 zero-padded keys: markdown / pdf / image / audio / other), `lang_breakdown` per BCP-47 lang (NULL keyed as the literal string `"null"`), `index_bytes.{sqlite,lancedb}` on-disk byte sums, `stale_doc_count` for docs older than `config.search.stale_threshold_days`). Gate streaming / session flows on `capabilities.streaming_ask` / `capabilities.rag_multi_turn` being `true`. Cheap call (no LLM), once per session.
 
 ## Quick health check
 

tasks/INDEX.md

@@ -125,7 +125,7 @@ P0~P5 는 직렬. P6~P9 는 P5 이후 병렬 가능.
     - [p9-fb-34 output budget controls](p9/p9-fb-34-output-budget-controls.md) — ✅ 머지 + v0.5.0 cut 후보 (2026-05-09)
     - [p9-fb-35 verbatim fetch](p9/p9-fb-35-verbatim-fetch.md) — ✅ 머지 + v0.5.0 cut 후보 (2026-05-09)
     - [p9-fb-36 search filter args](p9/p9-fb-36-search-filters.md) — ✅ 머지 (2026-05-10)
-    - [p9-fb-37 trace + stats](p9/p9-fb-37-trace-and-stats.md) — ⏳ 미구현, brainstorm 필요 (depends_on 27)
+    - [p9-fb-37 trace + stats](p9/p9-fb-37-trace-and-stats.md) — ✅ 머지 (2026-05-10)
 
     ### 🎯 0.5.0 — RAG quality (cascade 동반: V00X + reindex)
     - [p9-fb-38 score semantics](p9/p9-fb-38-score-semantics.md) — ⏳ 미구현, brainstorm 필요

tasks/p9/p9-fb-37-trace-and-stats.md

@@ -3,7 +3,7 @@ phase: P9
 component: kebab-cli + kebab-search + kebab-rag
 task_id: p9-fb-37
 title: "Trace (--trace) + stats — pipeline 가시성"
-status: open
+status: completed
 target_version: 0.4.0
 depends_on: [p9-fb-27]
 unblocks: []
@@ -14,7 +14,10 @@ source_feedback: 사용자 도그푸딩 2026-05-06 — agent / 사용자가 "왜
 
 # p9-fb-37 — Trace + stats
 
-> ⏳ **백로그 only — 미구현 (Nice-to-have).** 본 spec 은 도그푸딩 피드백 skeleton. 구현 착수 전 [superpowers:brainstorming](../../docs/superpowers/) 으로 설계 단계 선행 필요. trace 의 verbosity level / wire shape / stats 의 별도 명령 vs schema 통합 brainstorm 후 확정.
+> ✅ **구현 완료.** 본 spec 은 구현 시점의 frozen 상태.
+>
+> - Design: [`docs/superpowers/specs/2026-05-10-p9-fb-37-trace-and-stats-design.md`](../../docs/superpowers/specs/2026-05-10-p9-fb-37-trace-and-stats-design.md)
+> - Plan: [`docs/superpowers/plans/2026-05-10-p9-fb-37-trace-and-stats.md`](../../docs/superpowers/plans/2026-05-10-p9-fb-37-trace-and-stats.md)
 
 ## 증상 / 동기