Add configurable pace-artifact filtering to replace the hardcoded cutoff

Two new Profile settings -- "minimum representative pace" and "minimum
representative time" -- replace the previous hardcoded 20:00/km cutoff. A
stretch of consecutive samples slower than the configured pace is now
dropped from the chart (and its Y-axis scale) only if it lasts no longer
than the configured time; a longer stretch is kept as a real stop or walk
break rather than noise. Defaults to 12:00/km and 3 seconds.

Caught a boundary bug while verifying against real data: a run lasting
exactly the threshold duration survived filtering because the comparison
used strict "<" instead of "<=", contradicting "not lasting more than N
seconds" (which should include exactly N).

backend/internal/store/migrations/0010_pace_artifact_filter.sql

@@ -0,0 +1,9 @@
+-- Filters brief pace "artifacts" (e.g. GPS/motion still settling right as
+-- recording starts, before the run itself begins) out of the Review
+-- Queue's pace chart: a stretch of samples slower than
+-- min_representative_pace_sec_per_km is dropped unless it persists for at
+-- least min_representative_time_seconds, in which case it's treated as a
+-- real stop or walk break, not noise. Defaults match the values used to
+-- design this feature (12:00/km, 3 seconds).
+ALTER TABLE profile ADD COLUMN min_representative_pace_sec_per_km REAL NOT NULL DEFAULT 720;
+ALTER TABLE profile ADD COLUMN min_representative_time_seconds REAL NOT NULL DEFAULT 3;

backend/internal/store/profile.go

@@ -32,6 +32,15 @@ type Profile struct {
 	// don't use these.
 	WarmupMinutes, CooldownMinutes float64
 
+	// MinRepresentativePaceSecPerKm/MinRepresentativeTimeSeconds drive the
+	// Review Queue pace chart's artifact filter: a stretch of samples slower
+	// than MinRepresentativePaceSecPerKm is dropped from the chart (and its
+	// Y-axis scale) unless it persists for at least
+	// MinRepresentativeTimeSeconds, in which case it's treated as a real
+	// stop or walk break rather than noise (e.g. GPS/motion still settling
+	// right as recording starts, before the run itself begins).
+	MinRepresentativePaceSecPerKm, MinRepresentativeTimeSeconds float64
+
 	CreatedAt, UpdatedAt string
 }
 
@@ -41,6 +50,7 @@ const profileColumns = `
 	hr_zone3_min_pct, hr_zone3_max_pct, hr_zone4_min_pct, hr_zone4_max_pct,
 	hr_zone5_min_pct, hr_zone5_max_pct,
 	warmup_minutes, cooldown_minutes,
+	min_representative_pace_sec_per_km, min_representative_time_seconds,
 	created_at, updated_at
 `
 
@@ -53,6 +63,7 @@ func (db *DB) GetProfile(ctx context.Context) (Profile, error) {
 		&p.HRZone3MinPct, &p.HRZone3MaxPct, &p.HRZone4MinPct, &p.HRZone4MaxPct,
 		&p.HRZone5MinPct, &p.HRZone5MaxPct,
 		&p.WarmupMinutes, &p.CooldownMinutes,
+		&p.MinRepresentativePaceSecPerKm, &p.MinRepresentativeTimeSeconds,
 		&p.CreatedAt, &p.UpdatedAt,
 	)
 	if err != nil {
@@ -72,6 +83,7 @@ func (db *DB) UpdateProfile(ctx context.Context, p Profile) error {
 			hr_zone3_min_pct=?, hr_zone3_max_pct=?, hr_zone4_min_pct=?, hr_zone4_max_pct=?,
 			hr_zone5_min_pct=?, hr_zone5_max_pct=?,
 			warmup_minutes=?, cooldown_minutes=?,
+			min_representative_pace_sec_per_km=?, min_representative_time_seconds=?,
 			updated_at=datetime('now')
 		WHERE id = 1`,
 		p.GarminEmail, p.GarminPassword, p.RollingWindowDays, p.BackfillHorizonDays, p.MaxHeartRate, p.RestingHeartRate,
@@ -79,6 +91,7 @@ func (db *DB) UpdateProfile(ctx context.Context, p Profile) error {
 		p.HRZone3MinPct, p.HRZone3MaxPct, p.HRZone4MinPct, p.HRZone4MaxPct,
 		p.HRZone5MinPct, p.HRZone5MaxPct,
 		p.WarmupMinutes, p.CooldownMinutes,
+		p.MinRepresentativePaceSecPerKm, p.MinRepresentativeTimeSeconds,
 	)
 	if err != nil {
 		return fmt.Errorf("update profile: %w", err)

backend/internal/store/profile_test.go

@@ -25,6 +25,9 @@ func TestProfile_DefaultsThenUpdate(t *testing.T) {
 	if p.BackfillHorizonDays != 1095 {
 		t.Errorf("BackfillHorizonDays = %d, want 1095 (migration default)", p.BackfillHorizonDays)
 	}
+	if p.MinRepresentativePaceSecPerKm != 720 || p.MinRepresentativeTimeSeconds != 3 {
+		t.Errorf("pace artifact filter defaults = %+v, want pace=720, time=3", p)
+	}
 
 	maxHR, restingHR := 190.0, 50.0
 	p.GarminEmail = "runner@example.com"
@@ -34,6 +37,8 @@ func TestProfile_DefaultsThenUpdate(t *testing.T) {
 	p.RestingHeartRate = &restingHR
 	p.WarmupMinutes = 8
 	p.BackfillHorizonDays = 14
+	p.MinRepresentativePaceSecPerKm = 600
+	p.MinRepresentativeTimeSeconds = 5
 
 	if err := db.UpdateProfile(ctx, p); err != nil {
 		t.Fatalf("UpdateProfile: %v", err)
@@ -55,4 +60,7 @@ func TestProfile_DefaultsThenUpdate(t *testing.T) {
 	if got.BackfillHorizonDays != 14 {
 		t.Errorf("BackfillHorizonDays = %v, want 14", got.BackfillHorizonDays)
 	}
+	if got.MinRepresentativePaceSecPerKm != 600 || got.MinRepresentativeTimeSeconds != 5 {
+		t.Errorf("pace artifact filter after update = %+v, want pace=600, time=5", got)
+	}
 }

frontend/src/components/charts/ExpectedVsActualChart.tsx

@@ -1,17 +1,46 @@
 import { Area, AreaChart, Line, ReferenceArea, ReferenceLine, ResponsiveContainer, Tooltip, XAxis, YAxis } from "recharts";
 import type { Lap, Sample } from "../../types/api";
 
-// Speeds below this read as an implausibly slow "pace" (20:00/km is well
-// past even a very slow walk) -- in practice these come from GPS/motion
-// still settling right as recording starts, before the run itself begins,
-// not a real pace. Treating them as unknown keeps that artifact out of both
-// the trace and the axis scale it would otherwise blow out.
-const MAX_PLAUSIBLE_PACE_SEC_PER_KM = 1200;
-
 function paceSecPerKm(mps: number | null): number | null {
   if (mps == null || mps <= 0) return null;
-  const pace = 1000 / mps;
-  return pace <= MAX_PLAUSIBLE_PACE_SEC_PER_KM ? pace : null;
+  return 1000 / mps;
+}
+
+// Drops brief pace "artifacts" -- e.g. GPS/motion still settling right as
+// recording starts, before the run itself begins -- without hiding a real
+// stop or walk break. A stretch of consecutive points slower than
+// minRepresentativePaceSecPerKm (including points with no pace at all,
+// i.e. truly stationary) is nulled out unless it lasts at least
+// minRepresentativeTimeSeconds, in which case it's kept as-is: long enough
+// to be a real part of the run, not noise. A pace threshold of 0 (or below)
+// disables filtering entirely.
+function filterPaceArtifacts(
+  points: Array<{ t: number; pace: number | null }>,
+  minRepresentativePaceSecPerKm: number,
+  minRepresentativeTimeSeconds: number,
+): Array<number | null> {
+  const result: Array<number | null> = points.map((p) => p.pace);
+  if (minRepresentativePaceSecPerKm <= 0) return result;
+
+  const isSlowOrStopped = (pace: number | null) => pace == null || pace > minRepresentativePaceSecPerKm;
+
+  let i = 0;
+  while (i < points.length) {
+    if (!isSlowOrStopped(points[i].pace)) {
+      i++;
+      continue;
+    }
+    let j = i;
+    while (j < points.length && isSlowOrStopped(points[j].pace)) j++;
+    // "Not lasting more than" the threshold means a run exactly at the
+    // threshold still counts as an artifact, hence <= rather than <.
+    const durationSeconds = (points[j - 1].t - points[i].t) * 60;
+    if (durationSeconds <= minRepresentativeTimeSeconds) {
+      for (let k = i; k < j; k++) result[k] = null;
+    }
+    i = j;
+  }
+  return result;
 }
 
 // Rounds the total seconds first, then splits into minutes/seconds -- doing
@@ -263,7 +292,17 @@ function weightedMean(pairs: Array<[number | null, number]>): number | null {
 // would hide real within-lap variation (a single-lap hill repeat, for
 // example, would otherwise render as a dead-flat line despite the pace/HR
 // swinging throughout it).
-export function ExpectedVsActualChart({ laps, samples }: { laps: Lap[]; samples: Sample[] }) {
+export function ExpectedVsActualChart({
+  laps,
+  samples,
+  minRepresentativePaceSecPerKm,
+  minRepresentativeTimeSeconds,
+}: {
+  laps: Lap[];
+  samples: Sample[];
+  minRepresentativePaceSecPerKm: number;
+  minRepresentativeTimeSeconds: number;
+}) {
   if (laps.length === 0) return null;
 
   const hasPaceTarget = laps.some((l) => l.TargetPaceLowMps != null && l.TargetPaceHighMps != null);
@@ -313,6 +352,13 @@ export function ExpectedVsActualChart({ laps, samples }: { laps: Lap[]; samples:
     elapsedMin = lapTotalMin;
   }
 
+  const filteredActualPace = filterPaceArtifacts(
+    points.map((p) => ({ t: p.t, pace: p.actualPace })),
+    minRepresentativePaceSecPerKm,
+    minRepresentativeTimeSeconds,
+  );
+  points = points.map((p, i) => ({ ...p, actualPace: filteredActualPace[i] }));
+
   if (singleEffortType) {
     // The whole workout is one undifferentiated effort -- draw one flat
     // average line across the entire span instead of per-lap segments.

frontend/src/pages/Profile.tsx

@@ -26,6 +26,56 @@ function NumberField({
   );
 }
 
+// Pace is entered/displayed as "m:ss" but stored as whole seconds.
+function parsePace(text: string): number | null {
+  const trimmed = text.trim();
+  if (trimmed === "") return null;
+  const match = /^(\d+):([0-5]?\d)$/.exec(trimmed);
+  if (!match) return null;
+  return Number(match[1]) * 60 + Number(match[2]);
+}
+
+function formatPace(seconds: number): string {
+  const m = Math.floor(seconds / 60);
+  const s = Math.round(seconds % 60);
+  return `${m}:${s.toString().padStart(2, "0")}`;
+}
+
+function PaceField({
+  label,
+  value,
+  onChange,
+}: {
+  label: string;
+  value: number;
+  onChange: (v: number) => void;
+}) {
+  const [text, setText] = useState(formatPace(value));
+  useEffect(() => setText(formatPace(value)), [value]);
+
+  function commit(raw: string) {
+    const parsed = parsePace(raw);
+    if (parsed != null) {
+      onChange(parsed);
+    } else {
+      setText(formatPace(value)); // invalid input -- revert to the last valid value
+    }
+  }
+
+  return (
+    <label>
+      {label}
+      <input
+        type="text"
+        value={text}
+        onChange={(e) => setText(e.target.value)}
+        onBlur={(e) => commit(e.target.value)}
+        placeholder="12:00"
+      />
+    </label>
+  );
+}
+
 function NullableNumberField({
   label,
   value,
@@ -178,6 +228,27 @@ export function Profile() {
         </p>
       </fieldset>
 
+      <fieldset className="kind-editor">
+        <legend>Pace chart artifacts</legend>
+        <div className="controls">
+          <PaceField
+            label="Minimum representative pace (m:ss/km)"
+            value={profile.MinRepresentativePaceSecPerKm}
+            onChange={(v) => set("MinRepresentativePaceSecPerKm", v)}
+          />
+          <NumberField
+            label="Minimum representative time (seconds)"
+            value={profile.MinRepresentativeTimeSeconds}
+            onChange={(v) => set("MinRepresentativeTimeSeconds", v)}
+          />
+        </div>
+        <p className="empty-state">
+          A stretch of samples slower than this pace is hidden from the Review Queue's pace chart (and doesn't stretch
+          its scale) unless it lasts at least this long -- e.g. a brief GPS blip right as recording starts gets
+          dropped, but a real walk break or stop is kept.
+        </p>
+      </fieldset>
+
       <button onClick={save}>Save</button>
     </div>
   );

frontend/src/pages/ReviewQueue.tsx

@@ -2,7 +2,7 @@ import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { api } from "../api/client";
 import { ExpectedVsActualChart } from "../components/charts/ExpectedVsActualChart";
 import { RawDataModal } from "../components/RawDataModal";
-import type { ReviewQueueItem, ScoredKind, WorkoutKind } from "../types/api";
+import type { Profile, ReviewQueueItem, ScoredKind, WorkoutKind } from "../types/api";
 
 const UNSORTED = "__unsorted__";
 const PAGE_SIZE = 10;
@@ -30,6 +30,7 @@ export function ReviewQueue() {
   const [initialLoading, setInitialLoading] = useState(true);
   const [loadingMore, setLoadingMore] = useState(false);
   const [kinds, setKinds] = useState<WorkoutKind[]>([]);
+  const [profile, setProfile] = useState<Profile | null>(null);
   const [filterKindId, setFilterKindId] = useState<string>("");
   const [error, setError] = useState<string | null>(null);
   const [resolvingId, setResolvingId] = useState<number | null>(null);
@@ -89,13 +90,14 @@ export function ReviewQueue() {
   function reload() {
     setItems([]);
     setInitialLoading(true);
-    Promise.all([api.reviewQueue({ limit: PAGE_SIZE }), api.listWorkoutKinds()])
-      .then(([page, workoutKinds]) => {
+    Promise.all([api.reviewQueue({ limit: PAGE_SIZE }), api.listWorkoutKinds(), api.getProfile()])
+      .then(([page, workoutKinds, userProfile]) => {
         nextCursorRef.current = page.next_cursor;
         setItems(page.items);
         setNextCursor(page.next_cursor);
         setTotal(page.total);
         setKinds(workoutKinds);
+        setProfile(userProfile);
       })
       .catch((e) => setError(String(e)))
       .finally(() => setInitialLoading(false));
@@ -217,7 +219,12 @@ export function ReviewQueue() {
                   </p>
                 )}
 
-                <ExpectedVsActualChart laps={item.laps} samples={item.samples} />
+                <ExpectedVsActualChart
+                  laps={item.laps}
+                  samples={item.samples}
+                  minRepresentativePaceSecPerKm={profile?.MinRepresentativePaceSecPerKm ?? 0}
+                  minRepresentativeTimeSeconds={profile?.MinRepresentativeTimeSeconds ?? 0}
+                />
 
                 <div className="review-item-actions">
                   {manuallyAssignableKinds.map((k) => (

frontend/src/types/api.ts

@@ -113,6 +113,8 @@ export interface Profile {
   HRZone5MaxPct: number;
   WarmupMinutes: number;
   CooldownMinutes: number;
+  MinRepresentativePaceSecPerKm: number;
+  MinRepresentativeTimeSeconds: number;
   CreatedAt: string;
   UpdatedAt: string;
 }