Gate recall on the margin over the runner-up, not just the score

The e5 embedder puts every cosine in one narrow band (0.79-0.89), so the
absolute query_min_score gate cannot tell a real hit from a made-up
question: any value under the band answers everything, any value above it
answers nothing. False recall was 5/5.

New gate asks whether one note is clearly the best instead: top1 - top2 >
delta. New query_min_margin config knob, default 0.008, read off the sweep
in the recall harness. The absolute floor stays as a second check.

On the recall fixture with e5: answered 72% -> 68%, false recall 5/5 -> 1/5.

Vikunja #359

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

cmd/mavend/recall.go

@@ -8,16 +8,13 @@ import "github.com/kami/maven/internal/memory"
 // that can answer "when did I last …?" from a captured fact). A note hit here
 // is redundant with the notes-RAG path — by design; the two indexes can diverge
 // once the backend is swapped for a persistent/external store. ok=false when
-// there's no hit above the threshold or the hit carries no text.
-func bestRecall(results []memory.Result, min float64) (string, bool) {
-	if len(results) == 0 {
+// the hit fails the confidence gate (see memory.Confident: an absolute floor
+// plus a margin over the runner-up) or carries no text.
+func bestRecall(results []memory.Result, minScore, minMargin float64) (string, bool) {
+	if !memory.Confident(results, minScore, minMargin) {
 		return "", false
 	}
-	top := results[0]
-	if top.Score < min {
-		return "", false
-	}
-	text := top.Meta["text"]
+	text := results[0].Meta["text"]
 	if text == "" {
 		return "", false
 	}

cmd/mavend/recall_test.go

@@ -8,23 +8,24 @@ import (
 
 func TestBestRecall(t *testing.T) {
 	const min = 0.55
+	const margin = 0.008
 
 	t.Run("empty results", func(t *testing.T) {
-		if _, ok := bestRecall(nil, min); ok {
+		if _, ok := bestRecall(nil, min, margin); ok {
 			t.Error("empty results returned ok")
 		}
 	})
 
 	t.Run("top below threshold", func(t *testing.T) {
 		res := []memory.Result{{Score: 0.4, Meta: map[string]string{"text": "выпил воды"}}}
-		if _, ok := bestRecall(res, min); ok {
+		if _, ok := bestRecall(res, min, margin); ok {
 			t.Error("below-threshold hit returned ok")
 		}
 	})
 
 	t.Run("hit without text meta", func(t *testing.T) {
 		res := []memory.Result{{Score: 0.9, Meta: map[string]string{"type": "fact"}}}
-		if _, ok := bestRecall(res, min); ok {
+		if _, ok := bestRecall(res, min, margin); ok {
 			t.Error("textless hit returned ok")
 		}
 	})
@@ -34,7 +35,7 @@ func TestBestRecall(t *testing.T) {
 			{Score: 0.82, Meta: map[string]string{"text": "выпил воды в три часа", "type": "fact"}},
 			{Score: 0.60, Meta: map[string]string{"text": "другое"}},
 		}
-		got, ok := bestRecall(res, min)
+		got, ok := bestRecall(res, min, margin)
 		if !ok {
 			t.Fatal("clearing hit not returned")
 		}
@@ -42,4 +43,16 @@ func TestBestRecall(t *testing.T) {
 			t.Errorf("wrong text: %q", got)
 		}
 	})
+
+	// The runner-up is almost as close, so the embedder cannot tell the two
+	// notes apart. Silence beats reading back a coin flip.
+	t.Run("runner-up too close", func(t *testing.T) {
+		res := []memory.Result{
+			{Score: 0.860, Meta: map[string]string{"text": "выпил воды в три часа"}},
+			{Score: 0.858, Meta: map[string]string{"text": "другое"}},
+		}
+		if _, ok := bestRecall(res, min, margin); ok {
+			t.Error("thin-margin hit returned ok")
+		}
+	})
 }

cmd/mavend/voice.go

@@ -257,6 +257,7 @@ func wireVoice(cfg *config.Config, coreAPI ipc.CoreAPI, phr phraser.Phraser, mem
 		clarifyStore:     clarifyStore,
 		extractor:        router.Extractor{Time: timeParser, Acts: matcher, Facts: router.DefaultFactParser{}},
 		queryMinScore:    cfg.Voice.QueryMinScore,
+		queryMinMargin:   cfg.Voice.QueryMinMargin,
 		timeParser:       timeParser,
 		ecosystem:        eco,
 	}
@@ -300,6 +301,9 @@ type reactiveHandler struct {
 	// load-bearing math (same posture as the presence thresholds). Set by
 	// wireVoice from VoiceConfig; default 0.55.
 	queryMinScore float64
+	// queryMinMargin — the second half of that gate: how far the top hit must
+	// beat the runner-up. 0 ⇒ margin off.
+	queryMinMargin float64
 
 	// timeParser — used as a fallback for stage-0 reminder grammar matches
 	// (where the extractor didn't run). Shared with the router's extractor.
@@ -760,18 +764,23 @@ func (h *reactiveHandler) applyAction(ctx context.Context, dec router.Decision)
 			log.Printf("voice: query notes: %v", err)
 			return "не получилось найти ответ."
 		}
-		// Confidence gate: below threshold, say "I don't know" rather than read
-		// back the least-unrelated note — a confident wrong recall is worse than
-		// a gap (spec's "not a guesser-of-truth"). Same instinct as the loop's
-		// since(key)==null → don't fire. Tuned for the ONNX embedder; the Hash
-		// floor scores lexically and may rarely clear it.
-		if len(notes) == 0 || notes[0].Score < h.queryMinScore {
+		// Confidence gate: below it, say "I don't know" rather than read back
+		// the least-unrelated note — a confident wrong recall is worse than a
+		// gap (spec's "not a guesser-of-truth"). Same instinct as the loop's
+		// since(key)==null → don't fire. Two parts: an absolute cosine floor,
+		// and a margin over the runner-up, which is the part that works with
+		// the e5 embedder's narrow score band. See memory.Confident.
+		noteScores := make([]float64, len(notes))
+		for i, n := range notes {
+			noteScores[i] = n.Score
+		}
+		if !memory.ConfidentScores(noteScores, h.queryMinScore, h.queryMinMargin) {
 			// Long-term memory recall (notes + facts) before general knowledge:
 			// the notes table can't answer fact questions, but the memory store
 			// indexes both. Only runs when notes-RAG already gave up → additive.
 			if h.memStore != nil {
 				if hits, herr := h.memStore.Search(ctx, vec, 3); herr == nil {
-					if text, ok := bestRecall(hits, h.queryMinScore); ok {
+					if text, ok := bestRecall(hits, h.queryMinScore, h.queryMinMargin); ok {
 						return text
 					}
 				}

deploy/mavend.json

@@ -41,6 +41,8 @@
       "lib_path": "/opt/maven/lib/libonnxruntime.so"
     },
     "llm_router": false,
+    "query_min_score": 0.55,
+    "query_min_margin": 0.008,
     "tool_timeout": "30s",
     "tools": [
       { "name": "status",     "cmd": ["systemctl", "status"],         "scope": "homelab", "destructive": false },

internal/config/config.go

@@ -277,6 +277,14 @@ type VoiceConfig struct {
 	// default if unset.
 	QueryMinScore float64 `json:"query_min_score,omitempty"`
 
+	// QueryMinMargin — the second half of the recall gate: the top hit must
+	// beat the runner-up by more than this. The absolute score above cannot do
+	// the job on its own, because the e5 embedder puts every cosine in one
+	// narrow high band, so a made-up question scores as high as a real one.
+	// The margin asks whether one note is clearly the best instead.
+	// Negative ⇒ off. 0 ⇒ the default below.
+	QueryMinMargin float64 `json:"query_min_margin,omitempty"`
+
 	// Persona — optional prompt prefix that tunes maven's character. Prepended
 	// to every LLM system prompt (nudge phrasing, note queries, general
 	// knowledge). Empty string ⇒ current hardcoded persona (feminine-gendered
@@ -404,7 +412,12 @@ const (
 	DefaultAutotuneInterval = 10 * time.Minute
 	DefaultRouterThreshold  = 0.55
 	DefaultQueryMinScore    = 0.55
-	DefaultToolTimeout      = 30 * time.Second
+	// Read off the margin sweep in internal/memory/recalleval on the e5
+	// embedder: 0.008 answers 68% of real questions (down from 72%) and cuts
+	// false recall from 5/5 to 1/5. Every larger delta costs real recall
+	// without removing that last one until 0.020, which drops recall to 44%.
+	DefaultQueryMinMargin = 0.008
+	DefaultToolTimeout    = 30 * time.Second
 
 	DefaultFactEnrichmentInterval = 30 * time.Second
 )
@@ -486,6 +499,14 @@ func (c *Config) applyDefaults() {
 		if c.Voice.QueryMinScore <= 0 {
 			c.Voice.QueryMinScore = DefaultQueryMinScore
 		}
+		// Unset ⇒ default. Negative is how you turn the margin off on purpose,
+		// so it is clamped to 0 rather than replaced by the default.
+		switch {
+		case c.Voice.QueryMinMargin == 0:
+			c.Voice.QueryMinMargin = DefaultQueryMinMargin
+		case c.Voice.QueryMinMargin < 0:
+			c.Voice.QueryMinMargin = 0
+		}
 		if c.Voice.ToolTimeout <= 0 {
 			c.Voice.ToolTimeout = Duration(DefaultToolTimeout)
 		}

internal/memory/gate.go

@@ -0,0 +1,38 @@
+package memory
+
+// Confidence gate for a recall. Two checks, both must pass before Maven says a
+// note back:
+//
+//   - minScore — an absolute cosine floor.
+//   - minMargin — the top hit must beat the runner-up by more than this.
+//
+// The margin is the one that carries the weight. The e5 embedder packs every
+// score into a narrow high band (0.79-0.89 on the recall fixture), so an
+// absolute floor cannot tell a real hit from a confident-looking miss: every
+// value under the band admits everything, every value above it answers nothing.
+// A margin asks a different question — "is this note clearly the best one, or
+// is the whole shelf equally close?" — and a made-up question has no clear best.
+//
+// With one hit and no runner-up there is nothing to compare, so only the floor
+// applies.
+
+// ConfidentScores reports whether the top score clears both gates. scores must
+// be sorted highest first. minMargin <= 0 turns the margin check off.
+func ConfidentScores(scores []float64, minScore, minMargin float64) bool {
+	if len(scores) == 0 || scores[0] < minScore {
+		return false
+	}
+	if minMargin > 0 && len(scores) > 1 && scores[0]-scores[1] <= minMargin {
+		return false
+	}
+	return true
+}
+
+// Confident is ConfidentScores for search results.
+func Confident(results []Result, minScore, minMargin float64) bool {
+	scores := make([]float64, len(results))
+	for i, r := range results {
+		scores[i] = r.Score
+	}
+	return ConfidentScores(scores, minScore, minMargin)
+}

internal/memory/gate_test.go

@@ -0,0 +1,45 @@
+package memory
+
+import "testing"
+
+func TestConfidentScores(t *testing.T) {
+	cases := []struct {
+		name      string
+		scores    []float64
+		minScore  float64
+		minMargin float64
+		want      bool
+	}{
+		{"no hits", nil, 0.55, 0.008, false},
+		{"below the floor", []float64{0.40, 0.10}, 0.55, 0.008, false},
+		{"clear winner", []float64{0.86, 0.70}, 0.55, 0.008, true},
+		{"runner-up too close", []float64{0.860, 0.858}, 0.55, 0.008, false},
+		// The rule is "beats the runner-up by MORE than delta". Not testing an
+		// exactly-equal margin: no pair of these decimals subtracts to exactly
+		// 0.008 in binary float, so such a test would pin rounding, not the rule.
+		{"margin just under delta", []float64{0.8079, 0.8}, 0.55, 0.008, false},
+		{"margin just over delta", []float64{0.8081, 0.8}, 0.55, 0.008, true},
+		// One hit: nothing to compare against, so only the floor applies.
+		{"single hit clears", []float64{0.86}, 0.55, 0.008, true},
+		{"single hit below floor", []float64{0.10}, 0.55, 0.008, false},
+		// Margin off — the old absolute-only behaviour.
+		{"margin off admits a tie", []float64{0.86, 0.86}, 0.55, 0, true},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := ConfidentScores(c.scores, c.minScore, c.minMargin); got != c.want {
+				t.Errorf("got %v, want %v", got, c.want)
+			}
+		})
+	}
+}
+
+func TestConfidentReadsResultScores(t *testing.T) {
+	res := []Result{{ID: "a", Score: 0.86}, {ID: "b", Score: 0.858}}
+	if Confident(res, 0.55, 0.008) {
+		t.Error("thin margin passed the gate")
+	}
+	if !Confident(res, 0.55, 0) {
+		t.Error("margin off should fall back to the floor alone")
+	}
+}

internal/memory/recalleval/recalleval.go

@@ -177,6 +177,8 @@ type Outcome struct {
 	Tied    bool
 	TopID   string
 	TopScor float64
+	// Margin — top1 − top2. 0 when fewer than two hits came back.
+	Margin  float64
 	Reasons []string
 }
 
@@ -184,8 +186,10 @@ type Outcome struct {
 // ranks first but is silenced by query_min_score is a threshold problem, and a
 // note that never ranks first is an embedder problem. Those are different fixes.
 type Report struct {
-	Name       string
-	MinScore   float64
+	Name     string
+	MinScore float64
+	// MinMargin — how far the top hit must beat the runner-up. 0 ⇒ off.
+	MinMargin  float64
 	Total      int
 	Answerable int
 	Rank1      int
@@ -212,9 +216,14 @@ type Report struct {
 	// where the right note ranked first, and for the no-answer cases. The gap
 	// between these two distributions is what a defensible query_min_score
 	// would have to sit inside; if they overlap, no threshold separates them.
-	CorrectTop    []float64
-	NoAnswerTop   []float64
-	P50, P95, Max time.Duration
+	CorrectTop  []float64
+	NoAnswerTop []float64
+	// CorrectMargin / NoAnswerMargin — the same two groups, but top1 − top2
+	// instead of top1. This is the pair the margin gate has to separate, and
+	// unlike the absolute scores it is what the sweep reads.
+	CorrectMargin  []float64
+	NoAnswerMargin []float64
+	P50, P95, Max  time.Duration
 }
 
 // TagStat — passed/total for one slice of the fixture.
@@ -245,13 +254,14 @@ func ratio(n, d int) float64 {
 // the run on an embed or search error: an erroring case scores as a miss and is
 // counted in Errors, because "the embedder was down" and "the embedder was
 // wrong" are different numbers.
-func Score(ctx context.Context, name string, emb router.Embedder, newStore NewStore, minScore float64, f Fixture) (Report, error) {
+func Score(ctx context.Context, name string, emb router.Embedder, newStore NewStore, minScore, minMargin float64, f Fixture) (Report, error) {
 	rep := Report{
-		Name:     name,
-		MinScore: minScore,
-		Total:    len(f.Cases),
-		ByTag:    map[string]TagStat{},
-		ByLang:   map[string]TagStat{},
+		Name:      name,
+		MinScore:  minScore,
+		MinMargin: minMargin,
+		Total:     len(f.Cases),
+		ByTag:     map[string]TagStat{},
+		ByLang:    map[string]TagStat{},
 	}
 	lat := make([]time.Duration, 0, len(f.Cases))
 
@@ -261,7 +271,7 @@ func Score(ctx context.Context, name string, emb router.Embedder, newStore NewSt
 		} else {
 			rep.NoAnswer++
 		}
-		o, err := scoreCase(ctx, emb, newStore, minScore, c, f.Filler)
+		o, err := scoreCase(ctx, emb, newStore, minScore, minMargin, c, f.Filler)
 		if err != nil {
 			return Report{}, err
 		}
@@ -285,6 +295,11 @@ func Score(ctx context.Context, name string, emb router.Embedder, newStore NewSt
 			} else if !o.Rank1 {
 				rep.WrongTop++
 			}
+			if o.Rank1 {
+				// Margins are collected on rank, not on the gate, so the
+				// distribution does not move as the sweep changes the gate.
+				rep.CorrectMargin = append(rep.CorrectMargin, o.Margin)
+			}
 			if o.Rank1 && o.Recalled != "" {
 				rep.CorrectTop = append(rep.CorrectTop, o.TopScor)
 			}
@@ -293,6 +308,7 @@ func Score(ctx context.Context, name string, emb router.Embedder, newStore NewSt
 				rep.FalseRecall++
 			}
 			rep.NoAnswerTop = append(rep.NoAnswerTop, o.TopScor)
+			rep.NoAnswerMargin = append(rep.NoAnswerMargin, o.Margin)
 		}
 
 		if o.Pass {
@@ -307,6 +323,8 @@ func Score(ctx context.Context, name string, emb router.Embedder, newStore NewSt
 
 	sort.Float64s(rep.CorrectTop)
 	sort.Float64s(rep.NoAnswerTop)
+	sort.Float64s(rep.CorrectMargin)
+	sort.Float64s(rep.NoAnswerMargin)
 	sort.Slice(lat, func(i, j int) bool { return lat[i] < lat[j] })
 	rep.P50, rep.P95 = percentile(lat, 0.50), percentile(lat, 0.95)
 	if len(lat) > 0 {
@@ -318,7 +336,7 @@ func Score(ctx context.Context, name string, emb router.Embedder, newStore NewSt
 // scoreCase inserts the case's notes into a fresh store, then runs the read
 // path the daemon runs. The returned error is fatal (the harness is broken);
 // an embedder or store failure on the query lands in Outcome.Err instead.
-func scoreCase(ctx context.Context, emb router.Embedder, newStore NewStore, minScore float64, c Case, filler []StoredNote) (Outcome, error) {
+func scoreCase(ctx context.Context, emb router.Embedder, newStore NewStore, minScore, minMargin float64, c Case, filler []StoredNote) (Outcome, error) {
 	st, release, err := newStore()
 	if err != nil {
 		return Outcome{}, fmt.Errorf("%s: new store: %w", c.ID, err)
@@ -357,7 +375,10 @@ func scoreCase(ctx context.Context, emb router.Embedder, newStore NewStore, minS
 
 	if len(hits) > 0 {
 		o.TopID, o.TopScor = hits[0].ID, hits[0].Score
-		o.Recalled = bestRecall(hits, minScore)
+		if len(hits) > 1 {
+			o.Margin = hits[0].Score - hits[1].Score
+		}
+		o.Recalled = bestRecall(hits, minScore, minMargin)
 	}
 	for i, h := range hits {
 		if h.ID != c.Want {
@@ -378,14 +399,14 @@ func scoreCase(ctx context.Context, emb router.Embedder, newStore NewStore, minS
 	switch {
 	case !c.Answerable():
 		if o.Recalled != "" {
-			o.Reasons = append(o.Reasons, fmt.Sprintf("false recall: %q at %.3f, want silence", o.TopID, o.TopScor))
+			o.Reasons = append(o.Reasons, fmt.Sprintf("false recall: %q at %.3f (margin %.3f), want silence", o.TopID, o.TopScor, o.Margin))
 		}
 	case o.Tied:
 		o.Reasons = append(o.Reasons, fmt.Sprintf("tie at %.3f — the right note is on top only by sort order", o.TopScor))
 	case !o.Rank1:
 		o.Reasons = append(o.Reasons, fmt.Sprintf("top hit %q (%.3f), want %q%s", o.TopID, o.TopScor, c.Want, rankNote(o.Rank3)))
 	case o.Recalled == "":
-		o.Reasons = append(o.Reasons, fmt.Sprintf("right note ranked first but scored %.3f < gate %.2f — daemon says \"не знаю\"", o.TopScor, minScore))
+		o.Reasons = append(o.Reasons, fmt.Sprintf("right note ranked first at %.3f (margin %.3f) but the gate silenced it — daemon says \"не знаю\"", o.TopScor, o.Margin))
 	}
 	o.Pass = len(o.Reasons) == 0
 	return o, nil
@@ -401,8 +422,8 @@ func rankNote(inTop3 bool) string {
 // bestRecall mirrors cmd/mavend/recall.go — the gate the daemon actually
 // applies to a memory hit. Duplicated rather than imported because package main
 // is not importable; recalleval_test.go asserts the two agree in behaviour.
-func bestRecall(results []memory.Result, min float64) string {
-	if len(results) == 0 || results[0].Score < min {
+func bestRecall(results []memory.Result, minScore, minMargin float64) string {
+	if !memory.Confident(results, minScore, minMargin) {
 		return ""
 	}
 	return results[0].Meta["text"]
@@ -437,7 +458,7 @@ func percentile(sorted []time.Duration, p float64) time.Duration {
 // the slices that name where the path is weak.
 func (r Report) String() string {
 	var b strings.Builder
-	fmt.Fprintf(&b, "%s: %d/%d cases pass (gate %.2f)\n", r.Name, r.Passed, r.Total, r.MinScore)
+	fmt.Fprintf(&b, "%s: %d/%d cases pass (gate %.2f, margin %.3f)\n", r.Name, r.Passed, r.Total, r.MinScore, r.MinMargin)
 	fmt.Fprintf(&b, "  recall@1 %.1f%% (%d/%d)  recall@3 %.1f%% (%d/%d)  answered after gate %.1f%% (%d/%d)\n",
 		100*r.Recall1(), r.Rank1, r.Answerable,
 		100*r.Recall3(), r.Rank3, r.Answerable,
@@ -448,6 +469,8 @@ func (r Report) String() string {
 		100*r.FalseRecallRate(), r.FalseRecall, r.NoAnswer)
 	fmt.Fprintf(&b, "  top-1 score, right note first: %s\n", spread(r.CorrectTop))
 	fmt.Fprintf(&b, "  top-1 score, must be silent:   %s\n", spread(r.NoAnswerTop))
+	fmt.Fprintf(&b, "  margin top1-top2, right note first: %s\n", spread(r.CorrectMargin))
+	fmt.Fprintf(&b, "  margin top1-top2, must be silent:  %s\n", spread(r.NoAnswerMargin))
 	fmt.Fprintf(&b, "  latency: p50 %s  p95 %s  max %s\n", r.P50, r.P95, r.Max)
 	fmt.Fprintf(&b, "  by lang: %s\n", renderStats(r.ByLang))
 	fmt.Fprintf(&b, "  by tag:  %s\n", renderStats(r.ByTag))

internal/memory/recalleval/recalleval_test.go

@@ -142,21 +142,40 @@ func words(s string) []string {
 // cmd/mavend/recall.go (package main is not importable). This pins the copy to
 // the original's three rules: no hits, below the gate, or no text ⇒ silence.
 func TestBestRecallMatchesDaemon(t *testing.T) {
-	if got := bestRecall(nil, 0.55); got != "" {
+	if got := bestRecall(nil, 0.55, 0); got != "" {
 		t.Errorf("no hits: got %q, want silence", got)
 	}
 	low := []memory.Result{{ID: "a", Score: 0.4, Meta: map[string]string{"text": "чай"}}}
-	if got := bestRecall(low, 0.55); got != "" {
+	if got := bestRecall(low, 0.55, 0); got != "" {
 		t.Errorf("below gate: got %q, want silence", got)
 	}
 	noText := []memory.Result{{ID: "a", Score: 0.9, Meta: map[string]string{}}}
-	if got := bestRecall(noText, 0.55); got != "" {
+	if got := bestRecall(noText, 0.55, 0); got != "" {
 		t.Errorf("no text: got %q, want silence", got)
 	}
 	ok := []memory.Result{{ID: "a", Score: 0.9, Meta: map[string]string{"text": "чай"}}}
-	if got := bestRecall(ok, 0.55); got != "чай" {
+	if got := bestRecall(ok, 0.55, 0); got != "чай" {
 		t.Errorf("above gate: got %q, want %q", got, "чай")
 	}
+	// Margin: a close runner-up means the embedder cannot tell the two apart,
+	// so Maven stays silent even though both clear the absolute floor.
+	close := []memory.Result{
+		{ID: "a", Score: 0.86, Meta: map[string]string{"text": "чай"}},
+		{ID: "b", Score: 0.85, Meta: map[string]string{"text": "кофе"}},
+	}
+	if got := bestRecall(close, 0.55, 0.03); got != "" {
+		t.Errorf("thin margin: got %q, want silence", got)
+	}
+	if got := bestRecall(close, 0.55, 0); got != "чай" {
+		t.Errorf("margin off: got %q, want %q", got, "чай")
+	}
+	clear := []memory.Result{
+		{ID: "a", Score: 0.86, Meta: map[string]string{"text": "чай"}},
+		{ID: "b", Score: 0.70, Meta: map[string]string{"text": "кофе"}},
+	}
+	if got := bestRecall(clear, 0.55, 0.03); got != "чай" {
+		t.Errorf("wide margin: got %q, want %q", got, "чай")
+	}
 }
 
 // TestHashRecallBaseline — the CI ratchet. HashEmbedder, so it needs no model
@@ -171,7 +190,7 @@ func TestHashRecallBaseline(t *testing.T) {
 		t.Fatalf("Load: %v", err)
 	}
 	rep, err := Score(context.Background(), "recall+hash", router.NewHashEmbedder(hashDim), InMemory,
-		config.DefaultQueryMinScore, f)
+		config.DefaultQueryMinScore, config.DefaultQueryMinMargin, f)
 	if err != nil {
 		t.Fatalf("Score: %v", err)
 	}
@@ -201,11 +220,11 @@ func TestPersistentStoreScoresTheSame(t *testing.T) {
 		t.Fatalf("Load: %v", err)
 	}
 	emb := router.NewHashEmbedder(hashDim)
-	inMem, err := Score(context.Background(), "recall+hash+memory", emb, InMemory, config.DefaultQueryMinScore, f)
+	inMem, err := Score(context.Background(), "recall+hash+memory", emb, InMemory, config.DefaultQueryMinScore, config.DefaultQueryMinMargin, f)
 	if err != nil {
 		t.Fatalf("Score in-memory: %v", err)
 	}
-	persistent, err := Score(context.Background(), "recall+hash+sqlite", emb, sqliteStores(t), config.DefaultQueryMinScore, f)
+	persistent, err := Score(context.Background(), "recall+hash+sqlite", emb, sqliteStores(t), config.DefaultQueryMinScore, config.DefaultQueryMinMargin, f)
 	if err != nil {
 		t.Fatalf("Score sqlite: %v", err)
 	}
@@ -263,14 +282,16 @@ func TestONNXRecall(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Load: %v", err)
 	}
-	rep, err := Score(context.Background(), "recall+onnx", emb, InMemory, config.DefaultQueryMinScore, f)
+	rep, err := Score(context.Background(), "recall+onnx", emb, InMemory, config.DefaultQueryMinScore, config.DefaultQueryMinMargin, f)
 	if err != nil {
 		t.Fatalf("Score: %v", err)
 	}
 	t.Log("\n" + rep.String() + rep.Failures())
-	// Cached for the sweep only: the headline run above must pay the real
+	// Cached for the sweeps only: the headline run above must pay the real
 	// embedder cost so its latency numbers mean something.
-	t.Log("\ngate sweep:\n" + sweep(t, Cache(emb), f))
+	cached := Cache(emb)
+	t.Log("\ngate sweep (margin off):\n" + sweep(t, cached, f))
+	t.Log("\nmargin sweep (gate 0.55):\n" + marginSweep(t, cached, f))
 }
 
 // sweep scores the fixture at a range of gates and renders one line each. Two
@@ -281,7 +302,7 @@ func sweep(t *testing.T, emb router.Embedder, f Fixture) string {
 	t.Helper()
 	var b strings.Builder
 	for _, gate := range []float64{0.0, 0.30, 0.40, 0.50, 0.55, 0.60, 0.70, 0.80, 0.90} {
-		rep, err := Score(context.Background(), "sweep", emb, InMemory, gate, f)
+		rep, err := Score(context.Background(), "sweep", emb, InMemory, gate, 0, f)
 		if err != nil {
 			t.Fatalf("sweep at %.2f: %v", gate, err)
 		}
@@ -290,3 +311,21 @@ func sweep(t *testing.T, emb router.Embedder, f Fixture) string {
 	}
 	return b.String()
 }
+
+// marginSweep is the same idea for the margin gate (top1 − top2 > delta), with
+// the absolute gate held at its default. The absolute score cannot separate a
+// real hit from a made-up question under e5 — every score lands in one narrow
+// band — so this sweep is the one that picks a number.
+func marginSweep(t *testing.T, emb router.Embedder, f Fixture) string {
+	t.Helper()
+	var b strings.Builder
+	for _, d := range []float64{0, 0.002, 0.005, 0.008, 0.01, 0.012, 0.015, 0.02, 0.025, 0.03, 0.04, 0.05, 0.06} {
+		rep, err := Score(context.Background(), "margin sweep", emb, InMemory, config.DefaultQueryMinScore, d, f)
+		if err != nil {
+			t.Fatalf("margin sweep at %.3f: %v", d, err)
+		}
+		fmt.Fprintf(&b, "  delta %.3f: answered %d/%d (%.0f%%)  false recall %d/%d\n",
+			d, rep.Rank1-rep.Gated, rep.Answerable, 100*rep.Answered(), rep.FalseRecall, rep.NoAnswer)
+	}
+	return b.String()
+}