diff --git a/Packages/StrandAnalytics/Sources/StrandAnalytics/SkinTempDisplay.swift b/Packages/StrandAnalytics/Sources/StrandAnalytics/SkinTempDisplay.swift
index 3f71229e92..5b8f2aa018 100644
--- a/Packages/StrandAnalytics/Sources/StrandAnalytics/SkinTempDisplay.swift
+++ b/Packages/StrandAnalytics/Sources/StrandAnalytics/SkinTempDisplay.swift
@@ -22,6 +22,26 @@ public enum SkinTempDisplay {
         VitalBands.isAbsoluteSkinTemp(value) ? .absolute : .deviation
     }
 
+    /// The one kind a MIXED series must be reduced to before any aggregate is taken (#1705).
+    ///
+    /// A CSV import writes absolute °C and the computed pipeline writes a deviation, both into this
+    /// same field, so one window can hold both. Formatting stays honest per value — `kind(of:)` is
+    /// re-derived for each — but a min, max, mean or window-over-window delta drawn across both is
+    /// arithmetic on two different scales, and it looks plausible: a handful of ~34 °C readings lift a
+    /// should-be-near-zero deviation average past a full degree, and the mean is then itself below 20
+    /// so it gets labelled Δ°C.
+    ///
+    /// The newest entry decides, matching what `VitalSignsSummary` already does for its sparkline —
+    /// the reading the user is actually looking at sets the scale, and older entries of the other kind
+    /// drop out rather than being converted, because converting needs a baseline that a fresh
+    /// import-only install does not have.
+    ///
+    /// - Parameter values: the window's values, ascending by day.
+    /// - Returns: the kind to keep, or nil for an empty window.
+    public static func dominantKind(valuesAscendingByDay values: [Double]) -> Kind? {
+        values.last.map(kind(of:))
+    }
+
     /// Trailing unit chip: `"°C"` / `"°F"` for absolute, `"Δ°C"` / `"Δ°F"` for deviation.
     public static func unitSymbol(kind: Kind, fahrenheit: Bool) -> String {
         let base = fahrenheit ? "°F" : "°C"
diff --git a/Packages/StrandAnalytics/Tests/StrandAnalyticsTests/SkinTempDisplayTests.swift b/Packages/StrandAnalytics/Tests/StrandAnalyticsTests/SkinTempDisplayTests.swift
index a42d607409..2793cd2859 100644
--- a/Packages/StrandAnalytics/Tests/StrandAnalyticsTests/SkinTempDisplayTests.swift
+++ b/Packages/StrandAnalytics/Tests/StrandAnalyticsTests/SkinTempDisplayTests.swift
@@ -66,4 +66,37 @@ final class SkinTempDisplayTests: XCTestCase {
             XCTAssertEqual(SkinTempDisplay.kind(of: v) == .absolute, abs, "v=\(v)")
         }
     }
+
+    // MARK: - dominantKind (#1705)
+
+    func testDominantKindIsTheNewestEntrys() {
+        XCTAssertEqual(SkinTempDisplay.dominantKind(valuesAscendingByDay: [34.6, 35.1, -0.2]), .deviation)
+        XCTAssertEqual(SkinTempDisplay.dominantKind(valuesAscendingByDay: [-0.2, 0.1, 34.6]), .absolute)
+        XCTAssertNil(SkinTempDisplay.dominantKind(valuesAscendingByDay: []))
+    }
+
+    func testDominantKindOfASingleKindWindowIsThatKind() {
+        XCTAssertEqual(SkinTempDisplay.dominantKind(valuesAscendingByDay: [-0.24, 0.21, 0.01]), .deviation)
+        XCTAssertEqual(SkinTempDisplay.dominantKind(valuesAscendingByDay: [32.39, 34.60, 36.64]), .absolute)
+    }
+
+    /// The regression guard the issue asked for: filtering by `dominantKind` must leave a window that
+    /// no aggregate can straddle. Values are the reported ones — a 313-row absolute import
+    /// (32.39…36.64, mean 34.60) coexisting with computed deviations inside ±0.3.
+    func testFilteringByDominantKindLeavesOneScale() {
+        let mixed: [Double] = [34.60, 35.12, 32.39, 36.64, -0.24, 0.21, 0.01, 0.11, 0.0]
+        guard let keep = SkinTempDisplay.dominantKind(valuesAscendingByDay: mixed) else {
+            return XCTFail("a non-empty window must have a kind")
+        }
+        let kept = mixed.filter { SkinTempDisplay.kind(of: $0) == keep }
+        XCTAssertEqual(kept, [-0.24, 0.21, 0.01, 0.11, 0.0])
+        XCTAssertTrue(kept.allSatisfy { SkinTempDisplay.kind(of: $0) == keep })
+        // The defect: unfiltered, the mean of a should-be-near-zero deviation window clears a degree
+        // and then reads BELOW 20, so it gets labelled Δ°C — plausible-looking and wrong.
+        let unfilteredMean = mixed.reduce(0, +) / Double(mixed.count)
+        XCTAssertGreaterThan(unfilteredMean, 1.0)
+        XCTAssertEqual(SkinTempDisplay.kind(of: unfilteredMean), .deviation)
+        let filteredMean = kept.reduce(0, +) / Double(kept.count)
+        XCTAssertLessThan(abs(filteredMean), 0.3)
+    }
 }
diff --git a/Strand/Data/Repository.swift b/Strand/Data/Repository.swift
index eeff3df288..5bd913a6b3 100644
--- a/Strand/Data/Repository.swift
+++ b/Strand/Data/Repository.swift
@@ -2160,7 +2160,9 @@ final class Repository: ObservableObject {
     /// byte-identical. The flag is forwarded to the non-strap `series(...)` delegation below so every source
     /// path honours it.
     func exploreSeries(key: String, source: String, days: Int = 4000, fullHistory: Bool = false) async -> [(day: String, value: Double)] {
-        guard source == "my-whoop" else { return await series(key: key, source: source, days: days, fullHistory: fullHistory) }
+        guard source == "my-whoop" else {
+            return Self.oneSkinTempScale(key: key, await series(key: key, source: source, days: days, fullHistory: fullHistory))
+        }
         guard let store = await ensureStore() else { return [] }
         let now = Date()
         let from = fullHistory ? "0000-01-01" : Self.dayString(now.addingTimeInterval(-Double(days) * 86_400))
@@ -2187,7 +2189,29 @@ final class Repository: ObservableObject {
             for p in (try? await store.metricSeries(deviceId: id, key: key, from: from, to: to)) ?? [] { byDay[p.day] = p.value }
         }
 
-        return byDay.sorted { $0.key < $1.key }.map { (day: $0.key, value: $0.value) }
+        return Self.oneSkinTempScale(key: key, byDay.sorted { $0.key < $1.key }.map { (day: $0.key, value: $0.value) })
+    }
+
+    /// #1705: reduce a `skin_temp` window to a single scale; every other key passes through untouched.
+    ///
+    /// The key is bimodal — a CSV import writes ABSOLUTE °C where the computed layers write a baseline
+    /// DEVIATION, so one window can hold both. Every consumer of an Explore series aggregates it
+    /// (min/max/mean, the window-over-window delta, the correlation scan), and those are arithmetic
+    /// across two scales: on the reported account a few ~34 °C readings lifted a should-be-near-zero
+    /// average past a full degree, and the mean then read below 20 so it was labelled Δ°C.
+    ///
+    /// Applied on BOTH of `exploreSeries`' return paths, deliberately. Today the only `skin_temp`
+    /// descriptor is `my-whoop`, so the delegating path is unreachable for it — but a guard that is
+    /// correct only because of a fact in another file is how this bug happened in the first place.
+    /// `series(day:value:)` is ordered ascending by day, which `dominantKind` relies on.
+    private static func oneSkinTempScale(
+        key: String,
+        _ series: [(day: String, value: Double)]
+    ) -> [(day: String, value: Double)] {
+        guard key == "skin_temp",
+              let keep = SkinTempDisplay.dominantKind(valuesAscendingByDay: series.map(\.value))
+        else { return series }
+        return series.filter { SkinTempDisplay.kind(of: $0.value) == keep }
     }
 
     /// Every catalog metric's Explore series at once, memoized — the cross-catalog scan behind the
diff --git a/android/app/src/main/java/com/noop/analytics/SkinTempDisplay.kt b/android/app/src/main/java/com/noop/analytics/SkinTempDisplay.kt
index d6564aff5d..8d222d02de 100644
--- a/android/app/src/main/java/com/noop/analytics/SkinTempDisplay.kt
+++ b/android/app/src/main/java/com/noop/analytics/SkinTempDisplay.kt
@@ -19,6 +19,27 @@ object SkinTempDisplay {
         DEVIATION,
     }
 
+    /**
+     * The one kind a MIXED series must be reduced to before any aggregate is taken (#1705).
+     *
+     * A CSV import writes absolute °C and the computed pipeline writes a deviation, both into this
+     * same field, so one window can hold both. Formatting stays honest per value — [kind] is
+     * re-derived for each — but a min, max, mean or window-over-window delta drawn across both is
+     * arithmetic on two different scales, and it looks plausible: a handful of ~34 °C readings lift a
+     * should-be-near-zero deviation average past a full degree, and the mean is then itself below 20
+     * so it gets labelled Δ°C.
+     *
+     * The newest entry decides, matching what `HealthVitalsLogic` already does for its sparkline — the
+     * reading the user is actually looking at sets the scale, and older entries of the other kind drop
+     * out rather than being converted, because converting needs a baseline that a fresh import-only
+     * install does not have.
+     *
+     * @param valuesAscendingByDay the window's values, ascending by day.
+     * @return the kind to keep, or null for an empty window.
+     */
+    fun dominantKind(valuesAscendingByDay: List<Double>): Kind? =
+        valuesAscendingByDay.lastOrNull()?.let { kind(it) }
+
     fun kind(value: Double): Kind =
         if (VitalBands.isAbsoluteSkinTemp(value)) Kind.ABSOLUTE else Kind.DEVIATION
 
diff --git a/android/app/src/main/java/com/noop/data/WhoopRepository.kt b/android/app/src/main/java/com/noop/data/WhoopRepository.kt
index 80b7b2dea4..b4b92d35a5 100644
--- a/android/app/src/main/java/com/noop/data/WhoopRepository.kt
+++ b/android/app/src/main/java/com/noop/data/WhoopRepository.kt
@@ -1823,7 +1823,24 @@ class WhoopRepository(
         // Book / any resolver read agrees with the mergeDaily dashboards instead of re-surfacing the
         // schedule target the merge already rejects.
         val perCandidate = candidates.map { it to resolvedRows(it, from, to) }
-        return MetricSeriesResolution(preferredSource, candidates, resolveFirstWins(perCandidate))
+        val points = resolveFirstWins(perCandidate)
+        // #1705: skin_temp is bimodal — a CSV import writes ABSOLUTE °C into skinTempDevC while the
+        // computed pipeline writes a baseline DEVIATION, and the candidate list unions the imported and
+        // computed identities, so first-wins can resolve older days to one kind and recent days to the
+        // other. Every consumer aggregates these points (Compare's min/max and its min-max chart
+        // normalisation, Lab Book), and that is arithmetic across two scales. Reduce to the newest
+        // entry's kind HERE, at the one place the candidates are resolved, rather than at each screen.
+        if (key == "skin_temp") {
+            val keep = com.noop.analytics.SkinTempDisplay.dominantKind(points.map { it.value })
+            if (keep != null) {
+                return MetricSeriesResolution(
+                    preferredSource,
+                    candidates,
+                    points.filter { com.noop.analytics.SkinTempDisplay.kind(it.value) == keep },
+                )
+            }
+        }
+        return MetricSeriesResolution(preferredSource, candidates, points)
     }
 
     /**
diff --git a/android/app/src/test/java/com/noop/analytics/SkinTempDisplayTest.kt b/android/app/src/test/java/com/noop/analytics/SkinTempDisplayTest.kt
index 53d97ca1af..450ec4e40a 100644
--- a/android/app/src/test/java/com/noop/analytics/SkinTempDisplayTest.kt
+++ b/android/app/src/test/java/com/noop/analytics/SkinTempDisplayTest.kt
@@ -1,6 +1,7 @@
 package com.noop.analytics
 
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
 import org.junit.Assert.assertTrue
 import org.junit.Test
 
@@ -73,4 +74,36 @@ class SkinTempDisplayTest {
             )
         }
     }
-}
+
+    // ---- dominantKind (#1705) ----
+
+    @Test fun dominantKindIsTheNewestEntrys() {
+        assertEquals(SkinTempDisplay.Kind.DEVIATION, SkinTempDisplay.dominantKind(listOf(34.6, 35.1, -0.2)))
+        assertEquals(SkinTempDisplay.Kind.ABSOLUTE, SkinTempDisplay.dominantKind(listOf(-0.2, 0.1, 34.6)))
+        assertNull(SkinTempDisplay.dominantKind(emptyList()))
+    }
+
+    @Test fun dominantKindOfASingleKindWindowIsThatKind() {
+        assertEquals(SkinTempDisplay.Kind.DEVIATION, SkinTempDisplay.dominantKind(listOf(-0.24, 0.21, 0.01)))
+        assertEquals(SkinTempDisplay.Kind.ABSOLUTE, SkinTempDisplay.dominantKind(listOf(32.39, 34.60, 36.64)))
+    }
+
+    /**
+     * The regression guard the issue asked for: filtering by [SkinTempDisplay.dominantKind] must leave a
+     * window that no aggregate can straddle. Values are the reported ones — a 313-row absolute import
+     * (32.39..36.64, mean 34.60) coexisting with computed deviations inside +/-0.3.
+     */
+    @Test fun filteringByDominantKindLeavesOneScale() {
+        val mixed = listOf(34.60, 35.12, 32.39, 36.64, -0.24, 0.21, 0.01, 0.11, 0.0)
+        val keep = SkinTempDisplay.dominantKind(mixed)!!
+        val kept = mixed.filter { SkinTempDisplay.kind(it) == keep }
+        assertEquals(listOf(-0.24, 0.21, 0.01, 0.11, 0.0), kept)
+        assertTrue(kept.all { SkinTempDisplay.kind(it) == keep })
+        // The defect: unfiltered, the mean of a should-be-near-zero deviation window clears a degree and
+        // then reads BELOW 20, so it gets labelled deviation — plausible-looking and wrong.
+        val unfilteredMean = mixed.average()
+        assertTrue(unfilteredMean > 1.0)
+        assertEquals(SkinTempDisplay.Kind.DEVIATION, SkinTempDisplay.kind(unfilteredMean))
+        assertTrue(kotlin.math.abs(kept.average()) < 0.3)
+    }
+}
\ No newline at end of file