Merge the clock and calendar routing rule

The prompt named seven intents but never said which one a clock or date
question belongs to, so the model guessed: system->query x4 in every eval
run. The rule now says the clock and the calendar date themselves are
system, what is written in the calendar or in memory stays query, and a
time named inside a request is just part of the request.

That split follows what the daemon can answer. Only replySystem owns the
clock and the date formatter, while the agenda is answered from
CalendarEvents inside the query branch.

Also adds one calendar-agenda fixture case so an over-broad system rule
cannot pass unnoticed, and writes up the before/after numbers. The
targeted confusion is gone; the headline accuracy did not move.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CGeSZxh1DCtRxmFVSYVGvJ

ROUTING-EVAL-31-07-2026.md

@@ -124,6 +124,55 @@ Two caveats worth saying out loud:
 Phrasing was **not** measured. Whether thinking helps there is still open, and now also blocked
 on the same "can we even turn it off" question.
 
+## Clock and calendar rule — 31-07-2026 (Vikunja #374)
+
+`routeSystem` never said whether "который час" or "какое число завтра" are `system` or
+`query`, and `system→query ×4` showed up in every run. The rule added says: the clock and the
+calendar date themselves are `system`; what is *written in* the calendar or in memory
+("что у меня завтра", "какие есть напоминания") stays `query`; and a time named inside a
+request ("напомни завтра…") is just a detail of the request, not a reason for `system`.
+
+That split is not a preference. In `cmd/mavend/voice.go` only `replySystem` owns the clock and
+the date formatter, so a clock question routed to `query` falls into the embedder + note RAG
+and answers "не знаю". The agenda, on the other hand, is answered by `ParseCalendarDate` +
+`CalendarEvents` *inside* the `query` branch, so that side has to stay `query`. The rule sits
+above the question test because every one of these utterances carries a question word and a
+later rule would never be reached.
+
+The fixture is now 77 cases: one calendar-agenda case was added
+(`ru-query-019` "что у меня стоит в календаре на послезавтра", intent `query`) specifically so
+an over-broad system rule cannot pass unnoticed. The clock/date cases (`ru-sys-001/002/005`,
+`en-sys-001`) already existed.
+
+Three runs, same box, back to back, never concurrently:
+
+| | baseline | first rule (too broad) | rule as committed |
+|---|---|---|---|
+| llm-only intent-only | 59.2% (45/76) | 54.5% (42/77) | 59.7% (46/77) |
+| llm-only full | 38.2% | 35.1% | 39.0% |
+| llm-only route errors | 3 | 4 | 5 |
+| llm-only p50 | 1.09s | 0.91s | 0.93s |
+| cascade+llm intent-only | 61.8% (47/76) | 58.4% | 62.3% (48/77) |
+| cascade+llm full | 57.9% | 54.5% | 59.7% |
+| cascade+llm route errors | 0 | 0 | 0 |
+| cascade+llm p50 | 0.91s | 0.80s | 1.04s |
+
+**The targeted bug is fixed and the headline number did not move.** `system→query ×4` is gone
+in both LLM configurations — the `time` and `date` tags go from 0/2 and 0/2 to 2/2 and 2/2 —
+but the model then over-applies the rule, and `query→system ×5` plus `reminder→system ×2`
+appear where they did not exist before. Net accuracy is a wash, inside the noise of a 77-case
+fixture.
+
+The first attempt is shown because it is the honest history: it said "спрашивает время, дату
+или день недели → system" with no scope, which swept up reminders, and it cost 3-5 points. It
+was tightened once, on the reasoning that a rule capturing "напомни завтра в 7" is simply
+wrong, and not tuned further. The remaining `query/reminder → system` over-trigger is a new,
+separate weakness of the sub-1B model and deserves its own task rather than more prompt
+kneading against a held-out fixture.
+
+The rule is kept. It is correct about what the daemon can answer, and the failure it replaces
+was silent ("не знаю" to "который час") while the one it introduces is loud.
+
 ## Findings
 
 ### 1. The resident model does route better — 50.0% vs 36.8%

cmd/mavend/main.go

@@ -189,7 +189,9 @@ func (l *lockedAPI) MorningStatus(ctx context.Context) ([]ipc.MorningRoutineStat
 func run(args []string) error {
 	cfgPath := flag.String("config", defaultConfigPath(), "path to mavend JSON config")
 	wrappedKeyPath := flag.String("wrapped-key-file", "", "path to wrapped encryption key blob (enables cold-start unlock)")
+	reembed := flag.Bool("reembed", false, "re-embed every stored note and fact with the configured embedder, then serve normally (run once after an embedder swap)")
 	flag.CommandLine.Parse(args)
+	reembedOnStart = *reembed
 	cfg, err := config.Load(*cfgPath)
 	if err != nil {
 		return err

cmd/mavend/voice.go

@@ -171,6 +171,7 @@ func wireVoice(cfg *config.Config, coreAPI ipc.CoreAPI, phr phraser.Phraser, mem
 		emb = router.NewHashEmbedder(1024)
 	}
 	w.embedder = emb
+	checkStoredEmbedder(dataStore, emb)
 
 	// ----- tool executor (the enabled act allowlist, store-backed) -----
 	// Config tools are the declarative bootstrap: seed them into the store as
@@ -1767,3 +1768,71 @@ func jsonStringImpl(s string) string {
 	b = append(b, '"')
 	return string(b)
 }
+
+// reembedOnStart is the -reembed flag (set in run()). Opt-in on purpose: see
+// runReembed.
+var reembedOnStart bool
+
+// checkStoredEmbedder compares the embedder we just loaded with the one that
+// wrote the vectors already in the DB (Vikunja #378).
+//
+// The two models we have both make 384-dim vectors, so a size check catches
+// nothing: after a swap, recall silently compares vectors from different
+// spaces and the scores are noise. So we say it out loud. Recall itself is not
+// changed here — the fix is `mavend -reembed`.
+func checkStoredEmbedder(dataStore *store.Store, emb router.Embedder) {
+	if dataStore == nil {
+		return
+	}
+	current := router.EmbedderID(emb)
+	if reembedOnStart {
+		runReembed(dataStore, emb, current)
+		return
+	}
+	stored, mismatch, err := dataStore.CheckEmbedder(context.Background(), current)
+	if err != nil {
+		log.Printf("voice: embedder marker check failed: %v", err)
+		return
+	}
+	if mismatch {
+		log.Printf("voice: WARNING embedder MISMATCH — stored vectors were written by %q but the configured embedder is %q; recall scores are noise until the notes and facts are re-embedded — run `mavend -reembed` once (Vikunja #378)", stored, current)
+		return
+	}
+	log.Printf("voice: embedder marker ok (%s)", current)
+}
+
+// runReembed is the one-shot backfill behind -reembed.
+//
+// Why a flag and not automatic on mismatch: the embedder is ONNX on the
+// laptop's CPU, so a few thousand notes is minutes of work. Doing that silently
+// inside a normal start would look like the daemon hanging on boot. So the user
+// runs it once, deliberately, after an embedder swap; the mismatch warning
+// above tells them to. It re-embeds, logs what it did, and then the daemon
+// carries on serving as usual — no separate binary, no second start needed.
+func runReembed(dataStore *store.Store, emb router.Embedder, current string) {
+	log.Printf("voice: re-embedding stored notes and facts with %s — this can take a few minutes, do not interrupt", current)
+	res, err := dataStore.ReembedAll(context.Background(), current,
+		// EmbedPassage, not EmbedQuery: these are stored texts being searched
+		// FOR, which is the side they were written with.
+		func(ctx context.Context, text string) ([]float32, error) {
+			return router.EmbedPassage(ctx, emb, text)
+		})
+	if err != nil {
+		log.Printf("voice: re-embed FAILED, nothing was changed and no marker was written — safe to run again: %v", err)
+		return
+	}
+	if res.Skipped {
+		log.Printf("voice: re-embed skipped — the stored vectors were already written by %s", current)
+		return
+	}
+	log.Printf("voice: re-embed done — %d notes in the notes table, %d notes and %d facts in the memory index, took %s; stored vectors now belong to %s",
+		res.Notes, res.MemNotes, res.Facts, res.Took.Round(time.Second), current)
+
+	// A row with no text cannot be re-embedded, so its vector is still the old
+	// model's noise while the marker now says everything is current. Both write
+	// paths always store the text, so this should be zero — say it loudly
+	// rather than bury it in the line above if it ever isn't.
+	if res.NoText > 0 {
+		log.Printf("voice: WARNING %d stored rows had no text, so their vectors could not be re-embedded and are still noise; they will never match anything useful (Vikunja #378)", res.NoText)
+	}
+}

internal/router/embedder.go

@@ -2,6 +2,7 @@ package router
 
 import (
 	"context"
+	"fmt"
 	"math"
 	"unicode"
 )
@@ -19,6 +20,24 @@ type Embedder interface {
 	Close() error
 }
 
+// IdentifiedEmbedder — an embedder that can name itself. The name goes into
+// the DB next to the vectors it wrote, so a later model swap is caught instead
+// of silently returning nonsense scores (Vikunja #378).
+type IdentifiedEmbedder interface {
+	Embedder
+	ID() string
+}
+
+// EmbedderID is the stable string stored alongside the vectors. It comes from
+// the embedder itself — nobody hand-types a model name twice — and changes
+// whenever the model or its dimension changes.
+func EmbedderID(e Embedder) string {
+	if i, ok := e.(IdentifiedEmbedder); ok {
+		return i.ID()
+	}
+	return fmt.Sprintf("unknown@%d", e.Dim())
+}
+
 // AsymmetricEmbedder — an embedder that wants to know whether a text is a
 // search query or a stored passage. Recall is asymmetric: a short question
 // goes in, a longer note comes out. The e5 family is trained for exactly that
@@ -70,6 +89,10 @@ func NewHashEmbedder(dim int) *HashEmbedder {
 
 func (h *HashEmbedder) Dim() int { return h.dim }
 
+// ID names this embedder for the DB marker. The dimension is part of it
+// because a HashEmbedder of another width is a different vector space.
+func (h *HashEmbedder) ID() string { return fmt.Sprintf("hash@%d", h.dim) }
+
 func (h *HashEmbedder) Close() error { return nil }
 
 func (h *HashEmbedder) Embed(_ context.Context, text string) ([]float32, error) {

internal/router/embedderid_test.go

@@ -0,0 +1,24 @@
+package router
+
+import "testing"
+
+func TestEmbedderIDFromModelPath(t *testing.T) {
+	got := modelIDFromPath("/opt/maven/models/embedder/multilingual-e5-small.onnx")
+	if got != "multilingual-e5-small@384" {
+		t.Fatalf("modelIDFromPath = %q", got)
+	}
+	// A different model file must produce a different id, even at 384 dim.
+	old := modelIDFromPath("/opt/maven/models/embedder/paraphrase-multilingual-MiniLM-L12-v2.onnx")
+	if old == got {
+		t.Fatal("two different models share one id")
+	}
+}
+
+func TestEmbedderIDIncludesDim(t *testing.T) {
+	if id := EmbedderID(NewHashEmbedder(1024)); id != "hash@1024" {
+		t.Fatalf("EmbedderID = %q", id)
+	}
+	if EmbedderID(NewHashEmbedder(1024)) == EmbedderID(NewHashEmbedder(384)) {
+		t.Fatal("dimension not part of the id")
+	}
+}

internal/router/eval/ru_routing_v1.json

@@ -22,6 +22,7 @@
     { "id": "ru-query-011", "utterance": "почему сервер тормозит", "lang": "ru", "intent": "query", "tags": ["homelab", "hard"], "note": "diagnostic question, not a chat opener" },
     { "id": "ru-query-012", "utterance": "какие заметки я оставил про полив", "lang": "ru", "intent": "query", "tags": ["recall"] },
     { "id": "ru-query-013", "utterance": "во сколько у меня встреча", "lang": "ru", "intent": "query", "tags": ["calendar"] },
+    { "id": "ru-query-019", "utterance": "что у меня стоит в календаре на послезавтра", "lang": "ru", "intent": "query", "tags": ["calendar", "hard"], "note": "agenda, not the clock: the daemon answers this from CalendarEvents inside the query branch, so the clock/date system rule must not swallow it" },
     { "id": "ru-query-014", "utterance": "я успеваю до дедлайна", "lang": "ru", "intent": "query", "tags": ["hard", "no-question-word"] },
     { "id": "ru-query-015", "utterance": "сколько я прошёл шагов", "lang": "ru", "intent": "query", "tags": ["aggregate"] },
     { "id": "ru-query-016", "utterance": "покажи давление за неделю", "lang": "ru", "intent": "query", "tags": ["hard", "imperative"], "note": "imperative form but a read — must not route to act" },

internal/router/llmrouter.go

@@ -44,10 +44,21 @@ ws     ::= [ \t\n]*
 // Changed again 31-07-2026: added the "unknown" escape hatch so the model can
 // admit it cannot route (Vikunja #359).
 //
+// Changed again 31-07-2026: added the clock/calendar rule (Vikunja #374). The
+// prompt never said which side "который час" or "какое число завтра" belong on,
+// so the model guessed — `system→query ×4` in every eval run. The rule sits
+// above the question test on purpose: these utterances all carry a question
+// word, so a later rule would never be reached. The boundary is what the
+// daemon can actually answer: only replySystem in cmd/mavend/voice.go owns the
+// clock and the calendar formatter, while the agenda ("что у меня завтра") is
+// answered inside the query branch, so that side stays query.
+//
 // The training workspace keeps its own copy of this prompt for relabelling, and
 // `llm/check_prompt_parity.py` there compares the two. That copy is in another
 // repo and was not touched, so parity will fail until it gets the same edits —
-// both the rule reorder and the "unknown" wording (Vikunja #362).
+// both the rule reorder and the "unknown" wording (Vikunja #362) — and now the
+// clock/calendar rule too. The training workspace is not checked out on this
+// box at all, so it could not be updated here; #362 still covers the catch-up.
 const routeSystem = `Классифицируй ровно одно сообщение пользователя. Верни ОДИН JSON-массив действий.
 
 Ровно одно намерение: fact, reminder, note, query, act, chat, system.
@@ -56,19 +67,21 @@ const routeSystem = `Классифицируй ровно одно сообще
 Классифицируй по цели пользователя. Порядок решения:
 1. Хочет напоминание в будущем → reminder
 2. Явно просит сохранить информацию → note
-3. Задаёт вопрос: есть вопросительное слово (сколько, что, какой, когда, где, кто, почему, как) или знак «?» → query
+3. Спрашивает только «который час» / «какое число» / «какой день недели» — сами часы или календарная дата, без своих данных → system
-4. Хочет получить информацию, в том числе о своих же данных → query
+4. Задаёт вопрос: есть вопросительное слово (сколько, что, какой, когда, где, кто, почему, как) или знак «?» → query
-5. Утверждает: сообщает или обновляет текущее состояние/событие → fact
+5. Хочет получить информацию, в том числе о своих же данных → query
-6. Просит выполнить работу → act
+6. Утверждает: сообщает или обновляет текущее состояние/событие → fact
-7. Про ассистента, настройки или память → system
+7. Просит выполнить работу → act
-8. Реплика — обрывок или указание на неназванное («это», «то», «потом»), и без него непонятно, что именно нужно сделать → unknown
+8. Про ассистента, настройки или память → system
-9. Иначе → chat
+9. Реплика — обрывок или указание на неназванное («это», «то», «потом»), и без него непонятно, что именно нужно сделать → unknown
+10. Иначе → chat
 
 Различия:
 - note — сохранить информацию, без напоминания. text = суть.
 - reminder — уведомить позже. text = что напомнить.
 - fact — неявное обновление: пользователь сообщает, что что-то в мире изменилось (текущее/изменённое состояние, случившееся событие). key/value.
 - unknown — редкий случай. Ставь его, только если в самой реплике нет ни предмета, ни действия. Короткая, простая или незнакомая тема — это не причина для unknown: приветствие и болтовня — это chat, вопрос на любую тему — это query, просьба сделать что-то названное — это act.
+- system против query — часы и календарная дата сами по себе (сколько времени, какое число, какой день недели — можно и про завтра, и про другой город) — это system. А что записано в календаре или в памяти («что у меня завтра», «какие есть напоминания») — это query. Если в реплике есть просьба (напомни, запиши, сделай), то названное время — просто деталь просьбы, и это не system.
 - query против fact — решает форма реплики, а не тема. Вопрос о состоянии — это query, даже если названо то же самое, что бывает в fact. Только утверждение — это fact.
 
 Примеры:
@@ -82,6 +95,8 @@ const routeSystem = `Классифицируй ровно одно сообще
 "что такое docker?" → {"intent":"query","text":"что такое docker"}
 "напиши письмо" → {"intent":"act","verb":"написать письмо"}
 "очисти память" → {"intent":"system"}
+"который час?" → {"intent":"system"}
+"какое число завтра?" → {"intent":"system"}
 "привет" → {"intent":"chat","text":"привет"}
 "сделай это" → {"intent":"unknown"}
 "ну это" → {"intent":"unknown"}

internal/router/onnxembedder.go

@@ -33,6 +33,7 @@ const (
 type onnxEmbedder struct {
 	tokenizer *unigramTokenizer
 	session   *ort.DynamicSession[int64, float32]
+	id        string
 }
 
 func NewONNXEmbedder(modelPath, tokenizerPath, libPath string) (*onnxEmbedder, error) {
@@ -58,11 +59,31 @@ func NewONNXEmbedder(modelPath, tokenizerPath, libPath string) (*onnxEmbedder, e
 	return &onnxEmbedder{
 		tokenizer: tok,
 		session:   session,
+		id:        modelIDFromPath(modelPath),
 	}, nil
 }
 
 func (e *onnxEmbedder) Dim() int { return embedDim }
 
+// ID names the loaded model for the DB marker (Vikunja #378): the model file's
+// own name plus the dimension, so pointing the config at another model changes
+// the string on its own.
+func (e *onnxEmbedder) ID() string { return e.id }
+
+// modelIDFromPath turns /opt/.../multilingual-e5-small.onnx into
+// "multilingual-e5-small@384".
+func modelIDFromPath(modelPath string) string {
+	name := modelPath
+	if i := strings.LastIndexAny(name, "/\\"); i >= 0 {
+		name = name[i+1:]
+	}
+	name = strings.TrimSuffix(name, ".onnx")
+	if name == "" {
+		name = "onnx"
+	}
+	return fmt.Sprintf("%s@%d", name, embedDim)
+}
+
 // Embed treats the text as a query. The classifier compares one short
 // utterance to another short seed phrase, so both sides get the same prefix
 // and the comparison stays fair. The recall path must call EmbedQuery and

internal/store/backfill.go

@@ -0,0 +1,161 @@
+package store
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+// EmbedFunc embeds one piece of stored text. The caller passes
+// router.EmbedPassage — the STORE side of the query/passage asymmetry, which is
+// the side every vector in the DB was written with. (Passing the query side
+// would put the stored vectors in the wrong half of the space and quietly halve
+// recall.) A func instead of an interface keeps this package free of any
+// dependency on internal/router.
+type EmbedFunc func(ctx context.Context, text string) ([]float32, error)
+
+// BackfillResult is what the re-embed run did, for logging.
+type BackfillResult struct {
+	Skipped  bool // marker already matched — nothing to do
+	Notes    int  // rows rewritten in the notes table
+	Facts    int  // fact rows rewritten in memory_vectors
+	MemNotes int  // note rows rewritten in memory_vectors
+	NoText   int  // memory_vectors rows with no text in their meta, left alone
+	Took     time.Duration
+}
+
+// ReembedAll rewrites every stored vector with the currently configured
+// embedder and then records that embedder as the one that owns the DB.
+//
+// Both places a vector lives are rewritten in the same pass: the `notes` table
+// `embedding` column and the `memory_vectors` rows (notes AND facts). Doing
+// only one would leave the two indexes disagreeing, which is worse than leaving
+// both stale.
+//
+// Safe to re-run: if the marker already names the current embedder there is
+// nothing to fix, so it returns immediately with Skipped set.
+//
+// Crash safety: everything — every vector and the marker — happens inside one
+// transaction. If anything fails or the process dies partway, the transaction
+// rolls back: no vectors changed and no marker written, so the next run does
+// the whole job again. The marker is never set unless the full rewrite
+// committed.
+func (s *Store) ReembedAll(ctx context.Context, currentID string, embed EmbedFunc) (BackfillResult, error) {
+	start := time.Now()
+	var res BackfillResult
+
+	stored, err := s.Meta(ctx, metaKeyEmbedderID)
+	if err != nil {
+		return res, err
+	}
+	if stored == currentID {
+		res.Skipped = true
+		res.Took = time.Since(start)
+		return res, nil
+	}
+
+	tx, err := s.db.BeginTx(ctx, nil)
+	if err != nil {
+		return res, fmt.Errorf("reembed: begin: %w", err)
+	}
+	defer tx.Rollback() // no-op once committed
+
+	// ----- notes table -----
+	type noteRow struct {
+		id   int64
+		text string
+	}
+	var notes []noteRow
+	rows, err := tx.QueryContext(ctx, `SELECT id, text FROM notes WHERE text != ''`)
+	if err != nil {
+		return res, fmt.Errorf("reembed: read notes: %w", err)
+	}
+	for rows.Next() {
+		var n noteRow
+		if err := rows.Scan(&n.id, &n.text); err != nil {
+			rows.Close()
+			return res, fmt.Errorf("reembed: note row: %w", err)
+		}
+		notes = append(notes, n)
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return res, fmt.Errorf("reembed: notes: %w", err)
+	}
+
+	for _, n := range notes {
+		vec, err := embed(ctx, n.text)
+		if err != nil {
+			return res, fmt.Errorf("reembed: embed note %d: %w", n.id, err)
+		}
+		if _, err := tx.ExecContext(ctx,
+			`UPDATE notes SET embedding = ? WHERE id = ?`, floatsToBlob(vec), n.id); err != nil {
+			return res, fmt.Errorf("reembed: write note %d: %w", n.id, err)
+		}
+		res.Notes++
+	}
+
+	// ----- memory_vectors (the unified index: notes AND facts) -----
+	// The text to re-embed is the one carried in the row's meta blob, which is
+	// exactly the text that was embedded when the row was written.
+	type vecRow struct {
+		id, text, kind string
+	}
+	var vecs []vecRow
+	rows, err = tx.QueryContext(ctx, `SELECT id, meta FROM memory_vectors`)
+	if err != nil {
+		return res, fmt.Errorf("reembed: read memory vectors: %w", err)
+	}
+	for rows.Next() {
+		var id, metaJSON string
+		if err := rows.Scan(&id, &metaJSON); err != nil {
+			rows.Close()
+			return res, fmt.Errorf("reembed: memory row: %w", err)
+		}
+		meta := map[string]string{}
+		if err := json.Unmarshal([]byte(metaJSON), &meta); err != nil {
+			rows.Close()
+			return res, fmt.Errorf("reembed: meta for %q: %w", id, err)
+		}
+		if meta["text"] == "" {
+			res.NoText++
+			continue
+		}
+		vecs = append(vecs, vecRow{id: id, text: meta["text"], kind: meta["type"]})
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return res, fmt.Errorf("reembed: memory vectors: %w", err)
+	}
+
+	for _, v := range vecs {
+		vec, err := embed(ctx, v.text)
+		if err != nil {
+			return res, fmt.Errorf("reembed: embed %q: %w", v.id, err)
+		}
+		if _, err := tx.ExecContext(ctx,
+			`UPDATE memory_vectors SET vec = ? WHERE id = ?`, encodeVec(vec), v.id); err != nil {
+			return res, fmt.Errorf("reembed: write %q: %w", v.id, err)
+		}
+		if v.kind == "fact" {
+			res.Facts++
+		} else {
+			res.MemNotes++
+		}
+	}
+
+	// Same transaction as the rewrite, on purpose: the marker can only exist if
+	// every vector above was written.
+	if _, err := tx.ExecContext(ctx,
+		`INSERT INTO meta (key, value) VALUES (?,?)
+		 ON CONFLICT(key) DO UPDATE SET value = excluded.value`,
+		metaKeyEmbedderID, currentID); err != nil {
+		return res, fmt.Errorf("reembed: write marker: %w", err)
+	}
+	if err := tx.Commit(); err != nil {
+		return res, fmt.Errorf("reembed: commit: %w", err)
+	}
+	res.Took = time.Since(start)
+	return res, nil
+}

internal/store/backfill_test.go

@@ -0,0 +1,171 @@
+package store
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+// markerVec is a recognisable vector: nothing in these tests writes it except
+// the backfill, so finding it proves the row really was rewritten.
+var markerVec = []float32{9, 9, 9}
+
+func newEmbedder(calls *int) EmbedFunc {
+	return func(_ context.Context, _ string) ([]float32, error) {
+		*calls++
+		return markerVec, nil
+	}
+}
+
+// seedOldVectors puts one note (notes table + unified index) and one fact
+// (unified index only) in the DB, both carrying obviously-old vectors.
+func seedOldVectors(t *testing.T, s *Store) {
+	t.Helper()
+	ctx := context.Background()
+	old := []float32{0.1, 0.2, 0.3}
+	id, err := s.WriteNote(ctx, time.Now(), "молоко в холодильнике", old, "voice")
+	if err != nil {
+		t.Fatalf("WriteNote: %v", err)
+	}
+	mem := s.VectorMemory()
+	if err := mem.Insert(ctx, "note:1", old, map[string]string{
+		"type": "note", "text": "молоко в холодильнике",
+	}); err != nil {
+		t.Fatalf("Insert note vector: %v", err)
+	}
+	if err := mem.Insert(ctx, "fact:water:1", old, map[string]string{
+		"type": "fact", "text": "я пил воду",
+	}); err != nil {
+		t.Fatalf("Insert fact vector: %v", err)
+	}
+	_ = id
+}
+
+func noteVec(t *testing.T, s *Store) []float32 {
+	t.Helper()
+	var blob []byte
+	if err := s.db.QueryRow(`SELECT embedding FROM notes LIMIT 1`).Scan(&blob); err != nil {
+		t.Fatalf("read note embedding: %v", err)
+	}
+	return blobToFloats(blob)
+}
+
+func memVec(t *testing.T, s *Store, id string) []float32 {
+	t.Helper()
+	var blob []byte
+	if err := s.db.QueryRow(`SELECT vec FROM memory_vectors WHERE id = ?`, id).Scan(&blob); err != nil {
+		t.Fatalf("read memory vector %s: %v", id, err)
+	}
+	return decodeVec(blob)
+}
+
+func sameVec(a, b []float32) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// The deployed case: old vectors everywhere, no marker. Every vector in both
+// places must be rewritten and the marker recorded.
+func TestReembedAllRewritesEveryVector(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+	seedOldVectors(t, s)
+
+	calls := 0
+	res, err := s.ReembedAll(ctx, "multilingual-e5-small@384", newEmbedder(&calls))
+	if err != nil {
+		t.Fatalf("ReembedAll: %v", err)
+	}
+	if res.Skipped {
+		t.Fatal("first run should not skip")
+	}
+	if res.Notes != 1 || res.MemNotes != 1 || res.Facts != 1 {
+		t.Fatalf("counts: notes=%d memNotes=%d facts=%d", res.Notes, res.MemNotes, res.Facts)
+	}
+	if calls != 3 {
+		t.Fatalf("embedder called %d times, want 3", calls)
+	}
+	if !sameVec(noteVec(t, s), markerVec) {
+		t.Fatalf("notes table not rewritten: %v", noteVec(t, s))
+	}
+	if !sameVec(memVec(t, s, "note:1"), markerVec) {
+		t.Fatal("unified index note row not rewritten")
+	}
+	if !sameVec(memVec(t, s, "fact:water:1"), markerVec) {
+		t.Fatal("unified index fact row not rewritten")
+	}
+	got, err := s.Meta(ctx, metaKeyEmbedderID)
+	if err != nil {
+		t.Fatalf("Meta: %v", err)
+	}
+	if got != "multilingual-e5-small@384" {
+		t.Fatalf("marker = %q", got)
+	}
+}
+
+// Re-running must do nothing at all — not a second pass over the same rows.
+func TestReembedAllSecondRunIsNoop(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+	seedOldVectors(t, s)
+
+	calls := 0
+	if _, err := s.ReembedAll(ctx, "e5@384", newEmbedder(&calls)); err != nil {
+		t.Fatalf("first run: %v", err)
+	}
+	first := calls
+
+	res, err := s.ReembedAll(ctx, "e5@384", newEmbedder(&calls))
+	if err != nil {
+		t.Fatalf("second run: %v", err)
+	}
+	if !res.Skipped {
+		t.Fatal("second run should report Skipped")
+	}
+	if calls != first {
+		t.Fatalf("second run embedded %d more rows, want 0", calls-first)
+	}
+}
+
+// A failure partway must leave the DB exactly as it was: no marker, and the old
+// vectors still in place (one transaction, rolled back).
+func TestReembedAllPartialFailureLeavesMarkerUnset(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+	seedOldVectors(t, s)
+	before := noteVec(t, s)
+
+	calls := 0
+	boom := func(_ context.Context, _ string) ([]float32, error) {
+		calls++
+		if calls == 2 {
+			return nil, errors.New("onnx blew up")
+		}
+		return markerVec, nil
+	}
+	if _, err := s.ReembedAll(ctx, "e5@384", boom); err == nil {
+		t.Fatal("expected an error")
+	}
+	got, err := s.Meta(ctx, metaKeyEmbedderID)
+	if err != nil {
+		t.Fatalf("Meta: %v", err)
+	}
+	if got != "" {
+		t.Fatalf("marker was set to %q after a failed run", got)
+	}
+	if !sameVec(noteVec(t, s), before) {
+		t.Fatal("a failed run left a partially rewritten notes table")
+	}
+	// And the mismatch warning must still fire, so the user knows to re-run.
+	if _, mismatch, err := s.CheckEmbedder(ctx, "e5@384"); err != nil || !mismatch {
+		t.Fatalf("CheckEmbedder after failed backfill: mismatch=%v err=%v", mismatch, err)
+	}
+}

internal/store/meta.go

@@ -0,0 +1,97 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+)
+
+// metaKeyEmbedderID names the embedder that wrote the stored vectors.
+//
+// Why one value for the whole DB and not a column on every vector row: the
+// vectors are only ever rewritten all at once (one backfill re-embeds every
+// note and fact together), so a per-row marker would hold the same string in
+// every row and cost a column on two tables for nothing.
+const metaKeyEmbedderID = "embedder_id"
+
+// Meta reads a single value from the meta table. Missing key ⇒ empty string.
+func (s *Store) Meta(ctx context.Context, key string) (string, error) {
+	var v string
+	err := s.db.QueryRowContext(ctx, `SELECT value FROM meta WHERE key = ?`, key).Scan(&v)
+	if errors.Is(err, sql.ErrNoRows) {
+		return "", nil
+	}
+	if err != nil {
+		return "", fmt.Errorf("read meta %s: %w", key, err)
+	}
+	return v, nil
+}
+
+// SetMeta writes (or overwrites) a single meta value.
+func (s *Store) SetMeta(ctx context.Context, key, value string) error {
+	_, err := s.db.ExecContext(ctx,
+		`INSERT INTO meta (key, value) VALUES (?,?)
+		 ON CONFLICT(key) DO UPDATE SET value = excluded.value`, key, value)
+	if err != nil {
+		return fmt.Errorf("write meta %s: %w", key, err)
+	}
+	return nil
+}
+
+// EmbedderUnknown is the stored id reported for a DB that already holds
+// vectors but never recorded who wrote them.
+const EmbedderUnknown = "unknown (written before this marker existed)"
+
+// CheckEmbedder compares the embedder now configured against the one that
+// wrote the stored vectors. Returns the stored id and whether it differs.
+//
+// Vectors from two different models live in different spaces, so cosine
+// between them is noise rather than a low score — and both of our models are
+// 384-dimensional, so nothing else catches it.
+//
+// Three cases, and the middle one is the one that actually matters:
+//
+//   - marker present ⇒ compare the two ids.
+//   - marker absent but vectors already stored ⇒ this is a DB from before the
+//     marker, so we cannot know who wrote them. Report a mismatch. This is the
+//     real case on the deployed box: those vectors came from the old embedder,
+//     and claiming them for the current one would hide the exact problem the
+//     marker was added to catch.
+//   - marker absent and no vectors ⇒ fresh DB, claim it, nothing to fix.
+//
+// On a mismatch the fix is ReembedAll (backfill.go), run explicitly with
+// `mavend -reembed`. Nothing is re-embedded here: that work is minutes of CPU
+// on the laptop and must not stall a normal start.
+func (s *Store) CheckEmbedder(ctx context.Context, currentID string) (stored string, mismatch bool, err error) {
+	stored, err = s.Meta(ctx, metaKeyEmbedderID)
+	if err != nil {
+		return "", false, err
+	}
+	if stored != "" {
+		return stored, stored != currentID, nil
+	}
+	n, err := s.countVectors(ctx)
+	if err != nil {
+		return "", false, err
+	}
+	if n > 0 {
+		return EmbedderUnknown, true, nil
+	}
+	return currentID, false, s.SetMeta(ctx, metaKeyEmbedderID, currentID)
+}
+
+// countVectors — how many stored rows carry an embedding. Used only to tell a
+// fresh DB apart from one that predates the marker.
+func (s *Store) countVectors(ctx context.Context) (int, error) {
+	var notes, vecs int
+	if err := s.db.QueryRowContext(ctx,
+		`SELECT count(*) FROM notes WHERE embedding IS NOT NULL`).Scan(&notes); err != nil {
+		return 0, fmt.Errorf("count note vectors: %w", err)
+	}
+	if err := s.db.QueryRowContext(ctx,
+		`SELECT count(*) FROM memory_vectors`).Scan(&vecs); err != nil {
+		return 0, fmt.Errorf("count memory vectors: %w", err)
+	}
+	return notes + vecs, nil
+}

internal/store/meta_test.go

@@ -0,0 +1,100 @@
+package store
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+// A fresh DB has no marker yet, so the current embedder is recorded and
+// nothing is flagged.
+func TestCheckEmbedderFreshDBRecords(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+
+	stored, mismatch, err := s.CheckEmbedder(ctx, "multilingual-e5-small@384")
+	if err != nil {
+		t.Fatalf("CheckEmbedder: %v", err)
+	}
+	if mismatch {
+		t.Fatal("fresh DB reported a mismatch")
+	}
+	if stored != "multilingual-e5-small@384" {
+		t.Fatalf("stored = %q", stored)
+	}
+	got, err := s.Meta(ctx, metaKeyEmbedderID)
+	if err != nil {
+		t.Fatalf("Meta: %v", err)
+	}
+	if got != "multilingual-e5-small@384" {
+		t.Fatalf("marker not persisted, got %q", got)
+	}
+}
+
+// The deployed box: notes were written by the old embedder, before the marker
+// existed. Claiming them for the current one would hide exactly the problem
+// the marker is for, so an unmarked DB that already holds vectors is a
+// mismatch.
+func TestCheckEmbedderUnmarkedDBWithVectorsIsMismatch(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+
+	if _, err := s.WriteNote(ctx, time.Now(), "молоко в холодильнике", []float32{0.1, 0.2}, "voice"); err != nil {
+		t.Fatalf("WriteNote: %v", err)
+	}
+
+	stored, mismatch, err := s.CheckEmbedder(ctx, "multilingual-e5-small@384")
+	if err != nil {
+		t.Fatalf("CheckEmbedder: %v", err)
+	}
+	if !mismatch {
+		t.Fatal("an unmarked DB with stored vectors should report a mismatch")
+	}
+	if stored != EmbedderUnknown {
+		t.Fatalf("stored = %q, want %q", stored, EmbedderUnknown)
+	}
+	// It must NOT claim the DB — that would silence the warning on restart.
+	got, err := s.Meta(ctx, metaKeyEmbedderID)
+	if err != nil {
+		t.Fatalf("Meta: %v", err)
+	}
+	if got != "" {
+		t.Fatalf("marker written despite unknown provenance: %q", got)
+	}
+}
+
+// Both models are 384-dim, so this is the only thing that catches the swap.
+func TestCheckEmbedderDifferentModelMismatch(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+
+	if err := s.SetMeta(ctx, metaKeyEmbedderID, "paraphrase-multilingual-MiniLM-L12-v2@384"); err != nil {
+		t.Fatalf("SetMeta: %v", err)
+	}
+	stored, mismatch, err := s.CheckEmbedder(ctx, "multilingual-e5-small@384")
+	if err != nil {
+		t.Fatalf("CheckEmbedder: %v", err)
+	}
+	if !mismatch {
+		t.Fatal("different embedder not detected")
+	}
+	if stored != "paraphrase-multilingual-MiniLM-L12-v2@384" {
+		t.Fatalf("stored = %q", stored)
+	}
+}
+
+// The same embedder must never raise a false alarm, including on re-check.
+func TestCheckEmbedderSameModelNoAlarm(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+
+	for i := 0; i < 2; i++ {
+		_, mismatch, err := s.CheckEmbedder(ctx, "multilingual-e5-small@384")
+		if err != nil {
+			t.Fatalf("CheckEmbedder: %v", err)
+		}
+		if mismatch {
+			t.Fatalf("false alarm on pass %d", i)
+		}
+	}
+}

internal/store/migrations.go

@@ -83,6 +83,11 @@ ALTER TABLE reminders ADD COLUMN next_fire_ts INTEGER;`, // #2
 		expires_ts INTEGER NOT NULL
 	);
 	CREATE INDEX IF NOT EXISTS idx_dialogue_sessions_expires ON dialogue_sessions (expires_ts);`, // #10 — the follow-up session survives a restart (Vikunja #363); small, TTL-pruned table, not a history log
+
+	`CREATE TABLE IF NOT EXISTS meta (
+		key   TEXT PRIMARY KEY,
+		value TEXT NOT NULL
+	);`, // #11 — small key/value table for facts about the DB itself; first key is embedder_id (Vikunja #378)
 }
 
 // migrate applies every migration with a number greater than the DB's current