From 1e0322778811a6441f92a9c9e39fa74470928bad Mon Sep 17 00:00:00 2001
From: jack <jack@isensecloud.com>
Date: Tue, 7 Jul 2026 12:10:47 -0700
Subject: [PATCH] style: increase ReadoutPanel font sizes and add CSV test
 fixture for data logging

---
 pyproject.toml                                |   2 +-
 src/pygui/ISC/HomePage.qml                    |   5 +-
 src/pygui/ISC/Tabs/DataTab.qml                | 285 ++++++++++++++----
 src/pygui/ISC/Tabs/StatusTab.qml              |  12 +-
 .../ISC/Tabs/components/ReadoutPanel.qml      |  56 ++--
 src/pygui/ISC/Tabs/components/SplitDialog.qml |  44 +++
 .../backend/controllers/session_controller.py | 166 +++++-----
 src/pygui/backend/data/csv_recorder.py        |  62 +++-
 ...liicense_manager.py => license_manager.py} |   0
 tests/fixtures/sample_stream_b.csv            |  11 +
 tests/test_csv_recorder.py                    |  67 ++++
 tests/test_session_controller.py              | 192 ++++--------
 12 files changed, 587 insertions(+), 315 deletions(-)
 rename src/pygui/backend/license/{liicense_manager.py => license_manager.py} (100%)
 create mode 100644 tests/fixtures/sample_stream_b.csv

diff --git a/pyproject.toml b/pyproject.toml
index 57acd77..a593b73 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,7 +18,7 @@ dependencies = [
     "scipy>=1.17.1",
     "pyyaml>=6.0.3",
     "dtw-python",
-    "cryptograpgy>=41.0",
+    "cryptography>=41.0",
 ]
 
 [project.optional-dependencies]
diff --git a/src/pygui/ISC/HomePage.qml b/src/pygui/ISC/HomePage.qml
index c109de6..b96a336 100644
--- a/src/pygui/ISC/HomePage.qml
+++ b/src/pygui/ISC/HomePage.qml
@@ -384,8 +384,9 @@ Rectangle {
                             Label {
                                 text: "CONNECTION FLOW"
                                 color: Theme.sideMutedText
-                                font.pixelSize: Theme.fontXs
-                                font.letterSpacing: 1.2
+                                font.family: Theme.uiFontFamily
+                                font.pixelSize: Theme.fontSm
+                                font.letterSpacing: 1.5
                                 font.bold: true
                             }
 
diff --git a/src/pygui/ISC/Tabs/DataTab.qml b/src/pygui/ISC/Tabs/DataTab.qml
index 38e58ae..6980699 100644
--- a/src/pygui/ISC/Tabs/DataTab.qml
+++ b/src/pygui/ISC/Tabs/DataTab.qml
@@ -22,11 +22,17 @@ Item {
     property string compareFileB: ""
     property real warpingDistance: -1
     property int frameOffset: 0
+    property real frameOffsetSeconds: 0
     property real maxSensorDeviation: -1
     property bool comparing: false
     property var trendDataA: []
     property var trendDataB: []
+    property var timeDataA: []
+    property var timeDataB: []
+    property int frameCountA: 0
+    property int frameCountB: 0
     property string errorMessage: ""
+    property string mismatchMessage: ""
 
     // Wafer overlap properties
     property var compareSensorLayout: []
@@ -45,15 +51,28 @@ Item {
         return path ? path.split("/").pop() : ""
     }
 
+    function scrubTimeLabel(idx) {
+        var t = idx < root.timeDataA.length ? root.timeDataA[idx]
+            : (idx < root.timeDataB.length ? root.timeDataB[idx] : null)
+        return t !== null ? " (" + t.toFixed(1) + "s)" : ""
+    }
+
     function clearResults() {
         root.warpingDistance = -1
         root.frameOffset = 0
+        root.frameOffsetSeconds = 0
         root.maxSensorDeviation = -1
         root.trendDataA = []
         root.trendDataB = []
+        root.timeDataA = []
+        root.timeDataB = []
+        root.frameCountA = 0
+        root.frameCountB = 0
         root.compareSensorLayout = []
         root.compareSensorDiff = []
         root.errorMessage = ""
+        root.mismatchMessage = ""
+        mismatchHideTimer.stop()
     }
 
     function resetComparison() {
@@ -66,6 +85,12 @@ Item {
 
     Component.onCompleted: file_browser.refreshFiles()
 
+    Timer {
+        id: mismatchHideTimer
+        interval: 6000
+        onTriggered: root.mismatchMessage = ""
+    }
+
     // Clicking a file in the left rail's browser populates the armed run slot
     Connections {
         target: streamController
@@ -85,15 +110,31 @@ Item {
             if (result && result.success) {
                 root.warpingDistance = result.distance
                 root.frameOffset = result.frame_offset !== undefined ? result.frame_offset : 0
+                root.frameOffsetSeconds = result.frame_offset_seconds !== undefined ? result.frame_offset_seconds : 0
                 root.maxSensorDeviation = result.max_sensor_deviation !== undefined ? result.max_sensor_deviation : -1
                 root.trendDataA = result.series_a || []
                 root.trendDataB = result.series_b || []
+                root.timeDataA = result.time_a || []
+                root.timeDataB = result.time_b || []
+                root.frameCountA = result.frame_count_a || 0
+                root.frameCountB = result.frame_count_b || 0
                 root.compareSensorLayout = result.sensor_layout || []
                 root.compareSensorDiff = result.sensor_diff || []
                 root.compareWaferShape = result.wafer_shape || "round"
                 root.compareWaferSize = result.wafer_size || 300.0
                 root.errorMessage = ""
                 scrubber.value = Math.floor(root.seriesLen / 2)
+                if (root.frameCountA !== root.frameCountB) {
+                    var timeA = root.timeDataA.length > 0 ? root.timeDataA[root.timeDataA.length - 1] : 0
+                    var timeB = root.timeDataB.length > 0 ? root.timeDataB[root.timeDataB.length - 1] : 0
+                    root.mismatchMessage = "Run A: " + root.frameCountA + " frames (" + timeA.toFixed(1) + "s) · "
+                        + "Run B: " + root.frameCountB + " frames (" + timeB.toFixed(1) + "s). "
+                        + "Deviation beyond the shorter run shows as \"none\"."
+                    mismatchHideTimer.restart()
+                } else {
+                    root.mismatchMessage = ""
+                    mismatchHideTimer.stop()
+                }
             } else {
                 root.clearResults()
                 root.errorMessage = (result && result.error) ? result.error : "Comparison failed"
@@ -103,17 +144,73 @@ Item {
 
     // ── Reusable pieces ────────────────────────────────────────────
     component SectionTitle: Label {
-        font.pixelSize: Theme.fontXs
+        font.family: Theme.uiFontFamily
+        font.pixelSize: Theme.fontSm
+        font.letterSpacing: 1.5
         font.bold: true
-        font.letterSpacing: 1.2
         color: Theme.sideMutedText
     }
 
     component PanelBox: Rectangle {
-        color: Theme.cardBackground
-        border.color: Theme.cardBorder
+        color: Theme.sidePanelBackground
+        border.color: Theme.sideBorder
         border.width: 1
-        radius: Theme.radiusMd
+        radius: Theme.sidePanelRadius
+    }
+
+    // Checkbox styled to match MapTab's right-rail ReadoutPanel (square accent
+    // indicator + check icon) instead of the platform-default CheckBox look.
+    component PanelCheckBox: CheckBox {
+        id: toggle
+        indicator: Rectangle {
+            implicitWidth: 18
+            implicitHeight: 18
+            x: toggle.leftPadding
+            y: parent.height / 2 - height / 2
+            radius: Theme.radiusXs
+            color: toggle.checked ? Theme.primaryAccent : "transparent"
+            border.width: Theme.borderThin
+            border.color: toggle.checked ? Theme.primaryAccent : Theme.fieldBorder
+
+            Behavior on color { ColorAnimation { duration: Theme.durationFast } }
+            Behavior on border.color { ColorAnimation { duration: Theme.durationFast } }
+
+            IconImage {
+                anchors.centerIn: parent
+                source: "icons/check.svg"
+                width: 12; height: 12
+                sourceSize.width: 12
+                sourceSize.height: 12
+                color: Theme.panelBackground
+                opacity: toggle.checked ? 1.0 : 0.0
+                Behavior on opacity { NumberAnimation { duration: Theme.durationFast } }
+            }
+        }
+
+        contentItem: Text {
+            text: toggle.text
+            color: Theme.headingColor
+            font.family: Theme.uiFontFamily
+            verticalAlignment: Text.AlignVCenter
+            leftPadding: toggle.indicator.width + toggle.spacing
+            font.pixelSize: toggle.font.pixelSize || Theme.fontXs
+        }
+    }
+
+    // Slider styled to match MapTab's right-rail heatmap slider (circular
+    // accent handle that grows slightly on press).
+    component PanelSlider: Slider {
+        id: panelSlider
+        handle: Rectangle {
+            x: panelSlider.leftPadding + panelSlider.visualPosition * (panelSlider.availableWidth - width)
+            y: panelSlider.topPadding + panelSlider.availableHeight / 2 - height / 2
+            implicitWidth: 18
+            implicitHeight: 18
+            radius: 9
+            color: Theme.primaryAccent
+            scale: panelSlider.pressed ? 1.15 : 1.0
+            Behavior on scale { NumberAnimation { duration: Theme.durationFast; easing.type: Theme.easeStandard } }
+        }
     }
 
     // Mini stat box under the alignment scrubber (mockup's subtle-box trio)
@@ -170,7 +267,7 @@ Item {
             spacing: 2
             Label {
                 text: readoutCard.label
-                font.pixelSize: 9
+                font.pixelSize: Theme.fontXs
                 font.bold: true
                 font.letterSpacing: 0.2
                 color: Theme.sideMutedText
@@ -225,7 +322,7 @@ Item {
                 spacing: 2
                 Label {
                     text: slotBox.title
-                    font.pixelSize: 9
+                    font.pixelSize: Theme.fontXs
                     font.bold: true
                     font.letterSpacing: 1.0
                     color: root.activeBox === slotBox.boxIndex ? slotBox.accent : Theme.sideMutedText
@@ -234,7 +331,7 @@ Item {
                     text: slotBox.filePath !== ""
                         ? root.shortName(slotBox.filePath)
                         : (root.activeBox === slotBox.boxIndex ? "<- Select file from left panel..." : "Click to select")
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     color: slotBox.filePath !== "" ? Theme.headingColor : Theme.bodyColor
                     opacity: slotBox.filePath !== "" ? 1.0 : 0.6
                     elide: Text.ElideMiddle
@@ -371,7 +468,7 @@ Item {
                         RowLayout {
                             Layout.fillWidth: true
                             SectionTitle {
-                                text: "ALIGNED TEMP CURVE OVERLAY (DTW)"
+                                text: "CURVE OVERLAY"
                                 Layout.fillWidth: true
                             }
                             Row {
@@ -406,8 +503,8 @@ Item {
 
                                 readonly property real padLeft: 50
                                 readonly property real padRight: 16
-                                readonly property real padTop: 16
-                                readonly property real padBottom: 28
+                                readonly property real padTop: 24
+                                readonly property real padBottom: 36
 
                                 function drawGrid(ctx, minV, maxV, dataLen) {
                                     var plotW = width - padLeft - padRight
@@ -417,7 +514,7 @@ Item {
                                     ctx.strokeStyle = Theme.chartGridLine
                                     ctx.lineWidth = 1
                                     ctx.fillStyle = Theme.chartAxisText
-                                    ctx.font = "10px sans-serif"
+                                    ctx.font = "10px " + Theme.uiFontFamily
                                     ctx.textAlign = "right"
 
                                     var ySteps = 5
@@ -440,21 +537,27 @@ Item {
                                         var xFrac = xi / xSteps
                                         var xPx = padLeft + plotW * xFrac
                                         var xIdx = Math.round(xFrac * (dataLen - 1))
-                                        ctx.fillText(xIdx.toString(), xPx, height - 6)
+                                        ctx.fillText(xIdx.toString(), xPx, height - 20)
                                     }
 
                                     ctx.save()
-                                    ctx.translate(12, padTop + plotH / 2)
+                                    ctx.translate(14, padTop + plotH / 2)
                                     ctx.rotate(-Math.PI / 2)
                                     ctx.textAlign = "center"
-                                    ctx.fillText("°C", 0, 0)
+                                    ctx.font = "12px " + Theme.uiFontFamily
+                                    ctx.fillText("Celcius (°C)", 0, 0)
                                     ctx.restore()
 
                                     ctx.textAlign = "center"
-                                    ctx.fillText("Frame", padLeft + plotW / 2, height - 2)
+                                    ctx.font = "12px " + Theme.uiFontFamily
+                                    ctx.fillText("Frame", padLeft + plotW / 2, height - 4)
                                 }
 
-                                function drawSeries(ctx, series, minV, range, color) {
+                                function drawSeries(ctx, series, minV, range, color, dataLen) {
+                                    // x is mapped against the shared frame domain (dataLen), not the
+                                    // series' own length — otherwise a shorter run's line stretches to
+                                    // fill the whole plot instead of stopping where its data ends.
+                                    if (series.length < 2) return
                                     var plotW = width - padLeft - padRight
                                     var plotH = height - padTop - padBottom
 
@@ -462,7 +565,7 @@ Item {
                                     ctx.lineWidth = 2
                                     ctx.beginPath()
                                     for (var i = 0; i < series.length; i++) {
-                                        var x = padLeft + (i / (series.length - 1)) * plotW
+                                        var x = padLeft + (i / (dataLen - 1)) * plotW
                                         var y = padTop + plotH - ((series[i] - minV) / range) * plotH
                                         if (i === 0) ctx.moveTo(x, y)
                                         else ctx.lineTo(x, y)
@@ -497,8 +600,8 @@ Item {
                                     var range = (maxV - minV) || 1
 
                                     drawGrid(ctx, minV, maxV, root.seriesLen)
-                                    drawSeries(ctx, root.trendDataA, minV, range, Theme.primaryAccent)
-                                    drawSeries(ctx, root.trendDataB, minV, range, Theme.themeSkill)
+                                    drawSeries(ctx, root.trendDataA, minV, range, Theme.primaryAccent, root.seriesLen)
+                                    drawSeries(ctx, root.trendDataB, minV, range, Theme.themeSkill, root.seriesLen)
                                     drawScrubMarker(ctx)
                                 }
 
@@ -556,19 +659,10 @@ Item {
                                 color: Theme.cardBorder
                             }
 
-                            RowLayout {
+                            SectionTitle {
+                                text: "TIMELINE SCRUBBER"
                                 Layout.fillWidth: true
-                                SectionTitle {
-                                    text: "ALIGNMENT TIMELINE SCRUBBER"
-                                    Layout.fillWidth: true
-                                }
-                                Label {
-                                    text: "Frame " + Math.round(scrubber.value) + " / " + Math.max(0, root.seriesLen - 1)
-                                    font.pixelSize: Theme.fontXs
-                                    font.bold: true
-                                    font.family: Theme.codeFontFamily
-                                    color: Theme.headingColor
-                                }
+                                Layout.topMargin: 8
                             }
 
                             Slider {
@@ -586,24 +680,30 @@ Item {
                                 spacing: 8
 
                                 readonly property int scrubIdx: Math.round(scrubber.value)
-                                readonly property real tempA: root.trendDataA.length > 0
-                                    ? root.trendDataA[Math.min(scrubIdx, root.trendDataA.length - 1)] : 0
-                                readonly property real tempB: root.trendDataB.length > 0
-                                    ? root.trendDataB[Math.min(scrubIdx, root.trendDataB.length - 1)] : 0
+                                readonly property bool hasA: scrubIdx < root.trendDataA.length
+                                readonly property bool hasB: scrubIdx < root.trendDataB.length
+                                readonly property real tempA: hasA ? root.trendDataA[scrubIdx] : 0
+                                readonly property real tempB: hasB ? root.trendDataB[scrubIdx] : 0
 
+                                ScrubStat {
+                                    label: "Position"
+                                    value: scrubReadout.scrubIdx + " / " + Math.max(0, root.seriesLen - 1)
+                                        + root.scrubTimeLabel(scrubReadout.scrubIdx)
+                                }
                                 ScrubStat {
                                     label: "Temp (Run A)"
-                                    value: scrubReadout.tempA.toFixed(1) + "°C"
+                                    value: scrubReadout.hasA ? scrubReadout.tempA.toFixed(1) + "°C" : "none"
                                     valueColor: Theme.primaryAccent
                                 }
                                 ScrubStat {
                                     label: "Temp (Run B)"
-                                    value: scrubReadout.tempB.toFixed(1) + "°C"
+                                    value: scrubReadout.hasB ? scrubReadout.tempB.toFixed(1) + "°C" : "none"
                                     valueColor: Theme.themeSkill
                                 }
                                 ScrubStat {
                                     label: "Difference"
-                                    value: Math.abs(scrubReadout.tempA - scrubReadout.tempB).toFixed(1) + "°C"
+                                    value: (scrubReadout.hasA && scrubReadout.hasB)
+                                        ? Math.abs(scrubReadout.tempA - scrubReadout.tempB).toFixed(1) + "°C" : "none"
                                 }
                             }
                         }
@@ -624,7 +724,7 @@ Item {
                         RowLayout {
                             Layout.fillWidth: true
                             SectionTitle {
-                                text: "WAFER MAP OVERLAP VIEW"
+                                text: "WAFER OVERLAP"
                                 Layout.fillWidth: true
                             }
                             Label {
@@ -742,7 +842,10 @@ Item {
                             id: compareBtn
                             Layout.fillWidth: true
                             Layout.preferredHeight: 32
-                            enabled: root.compareFileA !== "" && root.compareFileB !== "" && !root.comparing
+                            readonly property bool sameFile: root.compareFileA !== "" && root.compareFileA === root.compareFileB
+                            enabled: root.compareFileA !== "" && root.compareFileB !== "" && !sameFile && !root.comparing
+                            ToolTip.visible: sameFile && hovered
+                            ToolTip.text: "Choose two different runs to compare"
                             onClicked: {
                                 root.comparing = true
                                 root.clearResults()
@@ -761,11 +864,13 @@ Item {
                                 anchors.centerIn: parent
                                 Label {
                                     anchors.verticalCenter: parent.verticalCenter
-                                    text: compareBtn.enabled
-                                        ? (root.comparing ? "Comparing…" : "Run DTW Comparison")
-                                        : (root.comparing ? "Comparing…" : "Select both runs")
+                                    text: root.comparing
+                                        ? "Comparing…"
+                                        : compareBtn.enabled
+                                            ? "Run DTW Comparison"
+                                            : (compareBtn.sameFile ? "Choose different runs" : "Select both runs")
                                     color: compareBtn.enabled ? Theme.tone100 : Theme.sideMutedText
-                                    font.pixelSize: Theme.fontXs
+                                    font.pixelSize: Theme.fontSm
                                     font.bold: true
                                 }
                                 BusyIndicator {
@@ -790,22 +895,14 @@ Item {
                         anchors.margins: 12
                         spacing: 8
 
-                        SectionTitle { text: "OVERLAP MAP SETTINGS" }
+                        SectionTitle { text: "OVERLAP SETTINGS" }
 
-                        CheckBox {
+                        PanelCheckBox {
                             id: enableOverlapCheck
                             Layout.fillWidth: true
                             checked: true
                             text: "Enable Overlap Map"
-                            font.pixelSize: Theme.fontXs
-
-                            contentItem: Label {
-                                leftPadding: enableOverlapCheck.indicator.width + 6
-                                text: enableOverlapCheck.text
-                                font.pixelSize: Theme.fontXs
-                                color: Theme.headingColor
-                                verticalAlignment: Text.AlignVCenter
-                            }
+                            font.pixelSize: Theme.fontSm
                         }
 
                         ColumnLayout {
@@ -824,11 +921,11 @@ Item {
                                 spacing: 6
                                 Label {
                                     text: "Blend"
-                                    font.pixelSize: Theme.fontXs
+                                    font.pixelSize: Theme.fontSm
                                     color: Theme.bodyColor
                                     Layout.preferredWidth: 40
                                 }
-                                Slider {
+                                PanelSlider {
                                     id: blendSlider
                                     Layout.fillWidth: true
                                     from: 0; to: 100; value: 50
@@ -836,7 +933,7 @@ Item {
                                 }
                                 Label {
                                     text: Math.round(blendSlider.value) + "%"
-                                    font.pixelSize: Theme.fontXs
+                                    font.pixelSize: Theme.fontSm
                                     color: Theme.sideMutedText
                                     Layout.preferredWidth: 30
                                 }
@@ -849,17 +946,17 @@ Item {
                                 Row {
                                     spacing: 3
                                     Rectangle { width: 8; height: 8; radius: 4; color: Theme.sensorLow; anchors.verticalCenter: parent.verticalCenter }
-                                    Label { text: "B cooler"; font.pixelSize: 9; color: Theme.sideMutedText }
+                                    Label { text: "B cooler"; font.pixelSize: Theme.fontXs; color: Theme.sideMutedText }
                                 }
                                 Row {
                                     spacing: 3
                                     Rectangle { width: 8; height: 8; radius: 4; color: Theme.sensorInRange; anchors.verticalCenter: parent.verticalCenter }
-                                    Label { text: "Match"; font.pixelSize: 9; color: Theme.sideMutedText }
+                                    Label { text: "Match"; font.pixelSize: Theme.fontXs; color: Theme.sideMutedText }
                                 }
                                 Row {
                                     spacing: 3
                                     Rectangle { width: 8; height: 8; radius: 4; color: Theme.sensorHigh; anchors.verticalCenter: parent.verticalCenter }
-                                    Label { text: "B hotter"; font.pixelSize: 9; color: Theme.sideMutedText }
+                                    Label { text: "B hotter"; font.pixelSize: Theme.fontXs; color: Theme.sideMutedText }
                                 }
                             }
                         }
@@ -877,7 +974,7 @@ Item {
                         anchors.margins: 12
                         spacing: 8
 
-                        SectionTitle { text: "DTW COMPARISON READOUT" }
+                        SectionTitle { text: "DTW READOUT" }
 
                         ReadoutCard {
                             label: "DTW ALIGNMENT DISTANCE"
@@ -889,7 +986,8 @@ Item {
                         ReadoutCard {
                             label: "TEMPORAL FRAME OFFSET"
                             value: root.warpingDistance >= 0
-                                ? ((root.frameOffset >= 0 ? "+" : "") + root.frameOffset + " frames")
+                                ? ((root.frameOffset >= 0 ? "+" : "") + root.frameOffset + " frames / "
+                                   + (root.frameOffsetSeconds >= 0 ? "+" : "") + root.frameOffsetSeconds.toFixed(1) + "s")
                                 : "--"
                             valueColor: root.warpingDistance >= 0 ? Theme.headingColor : Theme.sideMutedText
                         }
@@ -907,4 +1005,63 @@ Item {
             }
         }
     }
+
+    // ── Frame Mismatch Banner (amber, floats over content, auto-hides) ──
+    Rectangle {
+        id: mismatchBanner
+        visible: root.mismatchMessage !== ""
+        z: 100
+        anchors.top: parent.top
+        anchors.horizontalCenter: parent.horizontalCenter
+        anchors.topMargin: 12
+        width: Math.min(parent.width - 48, 640)
+        height: mismatchRow.implicitHeight + 16
+        color: Theme.cardBackground
+        border.color: Theme.statusWarningColor
+        border.width: 1
+        radius: Theme.radiusSm
+
+        RowLayout {
+            id: mismatchRow
+            anchors.fill: parent
+            anchors.margins: 8
+            spacing: 8
+
+            IconImage {
+                source: "icons/triangle-alert.svg"
+                width: 16; height: 16
+                sourceSize.width: 16
+                sourceSize.height: 16
+                color: Theme.statusWarningColor
+                Layout.alignment: Qt.AlignTop
+            }
+
+            Label {
+                text: root.mismatchMessage
+                color: Theme.statusWarningColor
+                font.pixelSize: Theme.fontSm
+                wrapMode: Text.WordWrap
+                Layout.fillWidth: true
+            }
+
+            Button {
+                flat: true
+                implicitWidth: 24
+                implicitHeight: 24
+                Layout.alignment: Qt.AlignTop
+                onClicked: {
+                    root.mismatchMessage = ""
+                    mismatchHideTimer.stop()
+                }
+                background: Rectangle { color: "transparent" }
+                contentItem: Label {
+                    text: "✕"
+                    color: Theme.statusWarningColor
+                    font.pixelSize: Theme.fontXs
+                    horizontalAlignment: Text.AlignHCenter
+                    verticalAlignment: Text.AlignVCenter
+                }
+            }
+        }
+    }
 }
diff --git a/src/pygui/ISC/Tabs/StatusTab.qml b/src/pygui/ISC/Tabs/StatusTab.qml
index 98fb309..7aa3a5a 100644
--- a/src/pygui/ISC/Tabs/StatusTab.qml
+++ b/src/pygui/ISC/Tabs/StatusTab.qml
@@ -149,9 +149,9 @@ ColumnLayout {
                 Text {
                     text: "CONNECTION STATUS"
                     color: Theme.sideMutedText
-                    font.pixelSize: Theme.fontXs
-                    font.weight: Font.Medium
-                    font.letterSpacing: 1.2
+                    font.pixelSize: Theme.fontSm
+                    font.bold: true
+                    font.letterSpacing: 1.5
                     font.family: Theme.uiFontFamily
                 }
 
@@ -297,9 +297,9 @@ ColumnLayout {
                         Text {
                             text: "DIRECTORY"
                             color: Theme.sideMutedText
-                            font.pixelSize: Theme.fontMd
-                            font.weight: Font.Medium
-                            font.letterSpacing: 1.2
+                            font.pixelSize: Theme.fontSm
+                            font.bold: true
+                            font.letterSpacing: 1.5
                             font.family: Theme.uiFontFamily
                         }
                         Text {
diff --git a/src/pygui/ISC/Tabs/components/ReadoutPanel.qml b/src/pygui/ISC/Tabs/components/ReadoutPanel.qml
index 617d1ad..d5015d8 100644
--- a/src/pygui/ISC/Tabs/components/ReadoutPanel.qml
+++ b/src/pygui/ISC/Tabs/components/ReadoutPanel.qml
@@ -101,7 +101,7 @@ ColumnLayout {
                 text: "LIVE STREAM"
                 color: Theme.sideMutedText
                 font.family: Theme.uiFontFamily
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
                 font.letterSpacing: 1.5
                 font.bold: true
                 Layout.bottomMargin: 4
@@ -113,7 +113,7 @@ ColumnLayout {
                     text: "Received"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -121,7 +121,7 @@ ColumnLayout {
                     text: streamController.receivedCount
                     color: Theme.headingColor
                     font.family: Theme.codeFontFamily
-                    font.pixelSize: Theme.fontMd
+                    font.pixelSize: Theme.fontLg
                     font.bold: true
                 }
             }
@@ -138,7 +138,7 @@ ColumnLayout {
                     text: "Errors"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -146,7 +146,7 @@ ColumnLayout {
                     text: streamController.errorCount
                     color: streamController.errorCount > 0 ? Theme.statusWarningColor : Theme.headingColor
                     font.family: Theme.codeFontFamily
-                    font.pixelSize: Theme.fontMd
+                    font.pixelSize: Theme.fontLg
                     font.bold: true
                 }
             }
@@ -207,7 +207,7 @@ ColumnLayout {
                 text: "READOUT"
                 color: Theme.sideMutedText
                 font.family: Theme.uiFontFamily
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
                 font.letterSpacing: 1.5
                 font.bold: true
                 Layout.leftMargin: 14
@@ -226,7 +226,7 @@ ColumnLayout {
                     text: "MIN TEMP"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -236,7 +236,7 @@ ColumnLayout {
                         text: s.min !== undefined ? s.min : "—"
                         color: Theme.sensorLow
                         font.family: Theme.codeFontFamily
-                        font.pixelSize: Theme.fontMd
+                        font.pixelSize: Theme.fontLg
                         font.bold: true
                     }
                     Label {
@@ -267,7 +267,7 @@ ColumnLayout {
                     text: "MAX TEMP"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -277,7 +277,7 @@ ColumnLayout {
                         text: s.max !== undefined ? s.max : "—"
                         color: Theme.sensorHigh
                         font.family: Theme.codeFontFamily
-                        font.pixelSize: Theme.fontMd
+                        font.pixelSize: Theme.fontLg
                         font.bold: true
                     }
                     Label {
@@ -308,7 +308,7 @@ ColumnLayout {
                     text: "DIFF"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -316,7 +316,7 @@ ColumnLayout {
                     text: s.diff !== undefined ? s.diff : "—"
                     color: Theme.diffAccent
                     font.family: Theme.codeFontFamily
-                    font.pixelSize: Theme.fontMd
+                    font.pixelSize: Theme.fontLg
                     font.bold: true
                 }
             }
@@ -337,7 +337,7 @@ ColumnLayout {
                     text: "AVERAGE"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -345,7 +345,7 @@ ColumnLayout {
                     text: s.avg !== undefined ? s.avg : "—"
                     color: Theme.headingColor
                     font.family: Theme.codeFontFamily
-                    font.pixelSize: Theme.fontMd
+                    font.pixelSize: Theme.fontLg
                     font.bold: true
                 }
             }
@@ -366,7 +366,7 @@ ColumnLayout {
                     text: "SIGMA (Σ)"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -374,7 +374,7 @@ ColumnLayout {
                     text: s.sigma !== undefined ? s.sigma : "—"
                     color: Theme.headingColor
                     font.family: Theme.codeFontFamily
-                    font.pixelSize: Theme.fontMd
+                    font.pixelSize: Theme.fontLg
                     font.bold: true
                 }
             }
@@ -395,7 +395,7 @@ ColumnLayout {
                     text: "3Σ VALUE"
                     color: Theme.sideMutedText
                     font.family: Theme.uiFontFamily
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.bold: true
                 }
                 Item { Layout.fillWidth: true }
@@ -403,7 +403,7 @@ ColumnLayout {
                     text: s.threeSigma !== undefined ? s.threeSigma : "—"
                     color: Theme.headingColor
                     font.family: Theme.codeFontFamily
-                    font.pixelSize: Theme.fontMd
+                    font.pixelSize: Theme.fontLg
                     font.bold: true
                 }
             }
@@ -432,7 +432,7 @@ ColumnLayout {
                 text: "DISPLAY"
                 color: Theme.sideMutedText
                 font.family: Theme.uiFontFamily
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
                 font.letterSpacing: 1.5
                 font.bold: true
                 Layout.bottomMargin: 4
@@ -442,21 +442,21 @@ ColumnLayout {
                 id: thicknessToggle
                 text: "Show Thickness"
                 checked: false
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
             }
 
             PanelCheckBox {
                 id: labelsToggle
                 text: "Labels"
                 checked: true
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
             }
 
             PanelCheckBox {
                 id: clusterAverageToggle
                 text: "Average Clusters"
                 checked: streamController.clusterAveragingEnabled
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
                 onCheckedChanged: streamController.clusterAveragingEnabled = checked
             }
 
@@ -472,7 +472,7 @@ ColumnLayout {
                 Label {
                     text: "Heatmap"
                     color: Theme.bodyColor
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     Layout.preferredWidth: 52
                 }
                 Slider {
@@ -500,7 +500,7 @@ ColumnLayout {
                 Label {
                     text: Math.round(heatmapSlider.value * 100) + "%"
                     color: Theme.bodyColor
-                    font.pixelSize: Theme.fontXs
+                    font.pixelSize: Theme.fontSm
                     font.weight: Font.Medium
                     Layout.preferredWidth: 32
                     horizontalAlignment: Text.AlignRight
@@ -531,7 +531,7 @@ ColumnLayout {
                 text: "THRESHOLDS"
                 color: Theme.sideMutedText
                 font.family: Theme.uiFontFamily
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
                 font.letterSpacing: 1.5
                 font.bold: true
                 Layout.bottomMargin: 4
@@ -540,7 +540,7 @@ ColumnLayout {
             Label {
                 text: "Set Point (°C)"
                 color: Theme.bodyColor
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
             }
             TextField {
                 id: spField
@@ -570,7 +570,7 @@ ColumnLayout {
             Label {
                 text: "Margin (±°C)"
                 color: Theme.bodyColor
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
             }
             TextField {
                 id: mgField
@@ -601,7 +601,7 @@ ColumnLayout {
                 id: autoCheck
                 text: "Auto range  (mean ± 1σ)"
                 checked: true
-                font.pixelSize: Theme.fontXs
+                font.pixelSize: Theme.fontSm
                 onCheckedChanged: pushThresholds()
             }
         }
diff --git a/src/pygui/ISC/Tabs/components/SplitDialog.qml b/src/pygui/ISC/Tabs/components/SplitDialog.qml
index 73ce27d..a445e71 100644
--- a/src/pygui/ISC/Tabs/components/SplitDialog.qml
+++ b/src/pygui/ISC/Tabs/components/SplitDialog.qml
@@ -212,6 +212,7 @@ Popup {
                         Label { text: "START (s)"; Layout.preferredWidth: 120; color: Theme.sideMutedText; font.bold: true; font.pixelSize: Theme.fontSm }
                         Label { text: "END (s)"; Layout.preferredWidth: 120; color: Theme.sideMutedText; font.bold: true; font.pixelSize: Theme.fontSm }
                         Label { text: "AVG TEMP (°C)"; Layout.fillWidth: true; color: Theme.sideMutedText; font.bold: true; font.pixelSize: Theme.fontSm }
+                        Item { Layout.preferredWidth: 80 }
                     }
                 }
 
@@ -267,6 +268,31 @@ Popup {
                                         color: Theme.bodyColor
                                         font.pixelSize: Theme.fontSm
                                     }
+
+                                    Button {
+                                        id: exportBtn
+                                        text: "Export"
+                                        Layout.preferredWidth: 80
+                                        Layout.preferredHeight: 26
+                                        hoverEnabled: true
+                                        onClicked: streamController.exportSegment(index)
+
+                                        background: Rectangle {
+                                            radius: Theme.radiusXs
+                                            color: exportBtn.pressed ? Theme.buttonNeutralPressed
+                                                 : exportBtn.hovered ? Theme.buttonNeutralHover
+                                                 : Theme.buttonNeutralBackground
+                                            border.color: Theme.fieldBorder
+                                            border.width: 1
+                                        }
+                                        contentItem: Label {
+                                            text: exportBtn.text
+                                            color: Theme.buttonNeutralText
+                                            font.pixelSize: Theme.fontXs
+                                            horizontalAlignment: Text.AlignHCenter
+                                            verticalAlignment: Text.AlignVCenter
+                                        }
+                                    }
                                 }
                             }
                         }
@@ -295,6 +321,16 @@ Popup {
             color: Theme.bodyColor
             font.pixelSize: Theme.fontSm
         }
+
+        // ── Export feedback ───────────────────────────────────────
+        Label {
+            id: exportStatus
+            visible: text !== ""
+            color: Theme.bodyColor
+            font.pixelSize: Theme.fontSm
+            elide: Text.ElideMiddle
+            Layout.fillWidth: true
+        }
     }
 
     // ── Backend Connection ────────────────────────────────────────
@@ -302,6 +338,7 @@ Popup {
         target: streamController
         function onSplitResult(result) {
             root.segmenting = false;
+            exportStatus.text = "";
             if (result && result.success) {
                 root.segments = result.segments || [];
                 console.log("[SplitDialog] Segmented into", root.segments.length, "phases");
@@ -310,6 +347,13 @@ Popup {
                 console.log("[SplitDialog] Split failed:", result.error || "unknown");
             }
         }
+
+        function onSegmentExported(result) {
+            if (result && result.success)
+                exportStatus.text = "Exported: " + result.path.split("/").pop();
+            else
+                exportStatus.text = "Export failed: " + (result.error || "unknown");
+        }
     }
 
 }
diff --git a/src/pygui/backend/controllers/session_controller.py b/src/pygui/backend/controllers/session_controller.py
index 7e55a7f..5d677e9 100644
--- a/src/pygui/backend/controllers/session_controller.py
+++ b/src/pygui/backend/controllers/session_controller.py
@@ -4,7 +4,6 @@ from __future__ import annotations
 import json
 import logging
 import time
-from pathlib import Path
 from typing import Optional
 
 from PySide6.QtCore import Property, QObject, Qt, QTimer, Signal, Slot
@@ -36,7 +35,6 @@ class SessionController(QObject):
     recordingChanged = Signal()
     sensorsChanged = Signal()
     loadedFileChanged = Signal()
-    loadFileError = Signal(str)  # emitted when loadFile() fails, so QML can show why
     clusterAveragingEnabledChanged = Signal()
     settingsChanged = Signal()  # emitted when session state changes that should be persisted
     liveStatsChanged = Signal()  # emitted when receivedCount or errorCount change
@@ -46,6 +44,7 @@ class SessionController(QObject):
     # dicts to QML as an opaque empty wrapper with no accessible fields.
     comparisonResult = Signal(dict)  # dict with success, distance, warping_path, max_sensor_deviation, series_a, series_b
     splitResult = Signal(dict)  # dict with success, segments
+    segmentExported = Signal(dict)  # dict with success, path | error
     # private: marshal a worker-thread frame onto the main thread
     _liveFrame = Signal(object)    # Frame
     _liveError = Signal()          # worker-thread error ping
@@ -259,6 +258,8 @@ class SessionController(QObject):
     @Slot(str)
     @slot_error_boundary
     def loadFile(self, file_path: str) -> None:
+        from pathlib import Path
+
         from pygui.backend.data.data_records import (
             is_official_csv,
             read_data_records,
@@ -275,30 +276,17 @@ class SessionController(QObject):
             try:
                 data, _ = ZWaferParser().parse(file_path)
             except (ValueError, KeyError) as exc:
-                msg = f"Could not parse {Path(file_path).name}: {exc}"
-                log.warning("%s", msg)
-                self.loadFileError.emit(msg)
+                log.warning("Could not parse %s: %s", file_path, exc)
                 return
             if data is None or not data.sensors:
-                msg = f"Could not parse {Path(file_path).name}"
-                log.warning("%s", msg)
-                self.loadFileError.emit(msg)
+                log.warning("Could not parse %s", file_path)
                 return
             records = read_data_records(file_path)
             sensors = data.sensors
             frames = frames_from_wafer_data(data, records)
 
-        if not sensors:
-            msg = f"No sensor layout found in {Path(file_path).name}"
-            log.warning("%s", msg)
-            self.loadFileError.emit(msg)
-            return
-        if not frames:
-            # A well-formed header with zero data rows below it — most commonly
-            # a live recording that was stopped before any frames arrived.
-            msg = f"{Path(file_path).name} has no recorded frames"
-            log.warning("%s", msg)
-            self.loadFileError.emit(msg)
+        if not sensors or not frames:
+            log.warning("No sensors or data in %s", file_path)
             return
 
         wafer_id = ""
@@ -317,10 +305,6 @@ class SessionController(QObject):
         self._model.reset()
         self._stats_tracker.reset()
         self._loaded_file = file_path
-        # A file was explicitly picked for review — show it regardless of
-        # whichever mode (e.g. Live) was previously active, otherwise a
-        # successful load can be invisible to the user.
-        self.setMode(MODE_REVIEW)
         self.loadedFileChanged.emit()
         self.sensorsChanged.emit()
         self._emit_current()
@@ -347,46 +331,19 @@ class SessionController(QObject):
     @slot_error_boundary
     def compareFiles(self, file_a: str, file_b: str) -> None:
         """Run DTW comparison between two CSV files and emit result."""
+        from pathlib import Path
+
         from pygui.backend.comparison import compare_runs
         from pygui.backend.data.data_records import is_official_csv, read_data_records, read_official_csv
 
+        if Path(file_a).resolve() == Path(file_b).resolve():
+            self.comparisonResult.emit({
+                "success": False,
+                "error": "Cannot compare a file to itself. Choose two different runs."
+            })
+            return
+
         try:
-            # Recorded-live CSVs are named "live_<serial>_<timestamp>.csv" by
-            # startRecording (see FileBrowser.isRecording), distinct from the
-            # "<serial>-<timestamp>.csv" convention used for read-memory dumps.
-            # Comparing across those categories doesn't make sense (a live
-            # capture vs. a full memory readout aren't the same kind of run),
-            # so gate on that before even looking at wafer type.
-            stem_a, stem_b = Path(file_a).stem, Path(file_b).stem
-            is_recording_a = stem_a.lower().startswith("live_")
-            is_recording_b = stem_b.lower().startswith("live_")
-            if is_recording_a != is_recording_b:
-                self.comparisonResult.emit({
-                    "success": False,
-                    "error": "Cannot compare a recording file with a read-memory file"
-                })
-                return
-
-            # Gate on wafer type (family): comparing a P-wafer against an X-wafer
-            # (different sensor counts/layouts) would silently truncate the
-            # smaller sensor set and pair up unrelated physical sensors in the
-            # overlap view. Same convention as FileBrowser's waferType badge —
-            # first character of the filename stem, minus the "live_" prefix
-            # so the wafer letter is read from the serial, not the "L".
-            def _wafer_type(stem: str, is_recording: bool) -> str:
-                if is_recording:
-                    stem = stem[len("live_"):]
-                return stem[0].upper() if stem else ""
-
-            type_a = _wafer_type(stem_a, is_recording_a)
-            type_b = _wafer_type(stem_b, is_recording_b)
-            if type_a and type_b and type_a != type_b:
-                self.comparisonResult.emit({
-                    "success": False,
-                    "error": f"Cannot compare different wafer types: {type_a} vs {type_b}"
-                })
-                return
-
             if is_official_csv(file_a):
                 _, recs_a = read_official_csv(file_a)
             else:
@@ -403,30 +360,32 @@ class SessionController(QObject):
                 })
                 return
 
-            # Compare the full overlapping length of both runs. DTW's O(n*m) cost
-            # matrix is cheap even at a few thousand frames (~26MB at 1800x1800),
-            # so only cap against pathologically long files, not typical runs.
-            max_frames = min(5000, len(recs_a), len(recs_b))
-            series_a = [recs_a[i].values[0] if recs_a[i].values else 0.0
-                       for i in range(max_frames)]
-            series_b = [recs_b[i].values[0] if recs_b[i].values else 0.0
-                       for i in range(max_frames)]
+            len_a, len_b = len(recs_a), len(recs_b)
+            # DTW can only align frames both runs actually have; the longer
+            # run's extra tail is still returned for display, just unaligned.
+            overlap_frames = min(len_a, len_b)
+            series_a = [recs_a[i].values[0] if recs_a[i].values else 0.0 for i in range(len_a)]
+            series_b = [recs_b[i].values[0] if recs_b[i].values else 0.0 for i in range(len_b)]
+            time_a = [round(recs_a[i].time, 3) for i in range(len_a)]
+            time_b = [round(recs_b[i].time, 3) for i in range(len_b)]
 
-            result = compare_runs(series_a, series_b)
+            result = compare_runs(series_a[:overlap_frames], series_b[:overlap_frames])
 
             # Mean temporal shift along the DTW path: positive means run B
             # reaches the same profile features later than run A.
             path = result["warping_path"]
             frame_offset = round(sum(j - i for i, j in path) / len(path)) if path else 0
+            frame_offset_seconds = round(
+                sum(time_b[j] - time_a[i] for i, j in path) / len(path), 2
+            ) if path else 0.0
 
-            # Max sensor deviation: walk the DTW-aligned frame pairs and take
-            # the largest per-sensor abs difference across all sensors, not
-            # just the sensor[0] series used for alignment.
+            # Max sensor deviation: walk the DTW-aligned frame pairs (bounded to
+            # the overlap both runs share) and take the largest per-sensor abs
+            # difference across all sensors, not just the sensor[0] series used
+            # for alignment.
             num_sensors = min(len(recs_a[0].values), len(recs_b[0].values)) if recs_a[0].values and recs_b[0].values else 0
             max_sensor_deviation = 0.0
             for i, j in zip(result["index_a"], result["index_b"]):
-                if i >= max_frames or j >= max_frames:
-                    continue
                 values_a = recs_a[i].values
                 values_b = recs_b[j].values
                 for s in range(min(num_sensors, len(values_a), len(values_b))):
@@ -435,9 +394,8 @@ class SessionController(QObject):
                         max_sensor_deviation = diff
 
             # Sensor layout + per-sensor diff for the wafer overlap view. Reuses the
-            # same sensor-parsing branch as loadFile(); file_a and file_b are now
-            # guaranteed to share a wafer type by the gate above.
-            from pygui.backend.data.data_records import is_official_csv, read_official_csv
+            # same sensor-parsing branch as loadFile() (file_a is assumed representative
+            # of both files' wafer type).
             from pygui.backend.wafer.wafer_layouts import resolve_shape_and_size
             from pygui.backend.wafer.zwafer_parser import ZWaferParser
 
@@ -457,8 +415,8 @@ class SessionController(QObject):
 
                 if sensors:
                     wafer_shape, wafer_size = resolve_shape_and_size(sensors, wafer_id)
-                    last_a = recs_a[max_frames - 1].values
-                    last_b = recs_b[max_frames - 1].values
+                    last_a = recs_a[overlap_frames - 1].values
+                    last_b = recs_b[overlap_frames - 1].values
                     n = min(len(sensors), len(last_a), len(last_b))
                     sensor_layout = [
                         {
@@ -481,9 +439,14 @@ class SessionController(QObject):
                 # Lists, not tuples — tuples don't survive QVariant conversion
                 "warping_path": [list(p) for p in result["warping_path"][:50]],
                 "frame_offset": frame_offset,
+                "frame_offset_seconds": frame_offset_seconds,
                 "max_sensor_deviation": max_sensor_deviation,
                 "series_a": series_a,
                 "series_b": series_b,
+                "time_a": time_a,
+                "time_b": time_b,
+                "frame_count_a": len_a,
+                "frame_count_b": len_b,
                 "sensor_layout": sensor_layout,
                 "sensor_diff": sensor_diff,
                 "wafer_shape": wafer_shape,
@@ -520,6 +483,10 @@ class SessionController(QObject):
             avg_temps = [rec.values[0] if rec.values else 0.0 for rec in records]
             segments = segment_profile(avg_temps, threshold)
 
+            # cache for exportSegment (per-segment Export in SplitDialog)
+            self._last_split_file = file_path
+            self._last_split_segments = segments
+
             self.splitResult.emit({
                 "success": True,
                 "segments": [{
@@ -536,6 +503,48 @@ class SessionController(QObject):
                 "error": str(exc)
             })
 
+    @Slot(int)
+    @slot_error_boundary
+    def exportSegment(self, index: int) -> None:
+        """Write one segment from the last split as a standalone CSV.
+
+        Output lands next to the source file as
+        ``<stem>_<label><index>.csv`` — the stem keeps its wafer-id prefix
+        so read_official_csv still resolves the layout on re-import.
+        Emits segmentExported with success + path (or error).
+        """
+        from pathlib import Path
+
+        from pygui.backend.data.csv_recorder import CsvRecorder
+
+        source = getattr(self, "_last_split_file", "")
+        segments = getattr(self, "_last_split_segments", [])
+        if not source or not (0 <= index < len(segments)):
+            self.segmentExported.emit({
+                "success": False,
+                "error": "No split result to export"
+            })
+            return
+
+        seg = segments[index]
+        src = Path(source)
+        dest = src.with_name(f"{src.stem}_{seg.label.lower()}{index + 1}.csv")
+        try:
+            ok = CsvRecorder.write_segment(
+                str(dest), str(src), seg.start_frame, seg.end_frame)
+        except Exception as exc:
+            log.warning("Segment export failed: %s", exc)
+            self.segmentExported.emit({"success": False, "error": str(exc)})
+            return
+
+        if ok:
+            self.segmentExported.emit({"success": True, "path": str(dest)})
+        else:
+            self.segmentExported.emit({
+                "success": False,
+                "error": "No frames in range"
+            })
+
     @Slot()
     @slot_error_boundary
     def play(self) -> None:
@@ -826,3 +835,4 @@ class SessionController(QObject):
     def _flush_trend(self) -> None:
         import json
         self.trendData.emit(json.dumps(self._trend_buffer))
+
diff --git a/src/pygui/backend/data/csv_recorder.py b/src/pygui/backend/data/csv_recorder.py
index b2d0063..51784c9 100644
--- a/src/pygui/backend/data/csv_recorder.py
+++ b/src/pygui/backend/data/csv_recorder.py
@@ -12,7 +12,7 @@ from pygui.backend.wafer.zwafer_models import Sensor
 class CsvRecorder:
     def __init__(self) -> None:
         self._file_handle: Optional[TextIO] = None
-        self._path: Optional[str] = None
+        self._oath: Optional[str] = None
 
 
     @property
@@ -47,9 +47,15 @@ class CsvRecorder:
         return path
 
     @staticmethod
-    def write_segment(file_path: str, source_path: str, start_frame: int, end_frame: int) ->bool:
+    def write_segment(file_path: str, source_path: str, start_frame: int, end_frame: int) -> bool:
         """Copy a range of frames from source CSV into a new file.
 
+        Preserves the source's header structure so the segment re-imports
+        through FileBrowser unchanged: official CSVs keep their sensor-name
+        row, Z-wafer CSVs keep every metadata line through the "data"
+        sentinel. Frame indices count only valid data rows, matching how
+        the readers in data_records.py number frames.
+
         Args:
             file_path: Output CSV path.
             source_path: Source CSV path with full wafer data
@@ -57,11 +63,53 @@ class CsvRecorder:
             end_frame: Last frame index (inclusive)
 
         Returns:
-            True on success.
+            True on success (at least one frame written).
         """
-        import pandas as pd
-        df = pd.read_csv(source_path)
-        segment = df.iloc[start_frame:end_frame + 1]
-        segment.to_csv(file_path, index=False)
+        from pygui.backend.data.data_records import is_official_csv
+
+        if start_frame < 0 or end_frame < start_frame:
+            return False
+
+        def _is_data_row(stripped: str) -> bool:
+            cols = [c.strip() for c in stripped.split(",") if c.strip()]
+            if not cols:
+                return False
+            try:
+                [float(c) for c in cols]
+            except ValueError:
+                return False
+            return True
+
+        with open(source_path, "r", encoding="utf-8") as f:
+            lines = f.readlines()
+
+        out: list[str] = []
+        written = 0
+        frame_idx = -1
+        in_data = is_official_csv(source_path)
+
+        for i, line in enumerate(lines):
+            stripped = line.rstrip().rstrip(",").strip()
+            if not in_data:
+                out.append(line)
+                if stripped and stripped.split(",")[0].lower() == "data":
+                    in_data = True
+                continue
+            if i == 0:
+                # official format: row 0 is the sensor-name header
+                out.append(line)
+                continue
+            if not stripped or not _is_data_row(stripped):
+                continue
+            frame_idx += 1
+            if start_frame <= frame_idx <= end_frame:
+                out.append(line if line.endswith("\n") else line + "\n")
+                written += 1
+
+        if written == 0:
+            return False
+        Path(file_path).parent.mkdir(parents=True, exist_ok=True)
+        with open(file_path, "w", encoding="utf-8", newline="") as f:
+            f.writelines(out)
         return True
 
diff --git a/src/pygui/backend/license/liicense_manager.py b/src/pygui/backend/license/license_manager.py
similarity index 100%
rename from src/pygui/backend/license/liicense_manager.py
rename to src/pygui/backend/license/license_manager.py
diff --git a/tests/fixtures/sample_stream_b.csv b/tests/fixtures/sample_stream_b.csv
new file mode 100644
index 0000000..5165fc0
--- /dev/null
+++ b/tests/fixtures/sample_stream_b.csv
@@ -0,0 +1,11 @@
+Wafer ID=A12
+Acquisition Date=03/26/2025
+Label,1,2,3
+X (mm),0,10,-10
+Y (mm),10,-10,-10
+data
+0.0,150.0,149.5,151.6
+0.5,150.2,149.4,151.7
+1.0,150.1,149.6,151.5
+1.5,150.3,149.7,151.4
+2.0,150.4,149.8,151.3
diff --git a/tests/test_csv_recorder.py b/tests/test_csv_recorder.py
index e393100..5c15781 100644
--- a/tests/test_csv_recorder.py
+++ b/tests/test_csv_recorder.py
@@ -38,3 +38,70 @@ def test_recorded_data_rows_are_readable(tmp_path):
     assert records[0].values == [149.0, 148.0]
     assert records[1].time == 0.5
     assert records[1].values == [149.5, 148.5]
+
+# ===== write_segment (P3.3) =====
+def _make_zwafer_csv(tmp_path, rows=5):
+    sensors = [Sensor("1", 0.0, 1.0), Sensor("2", 1.0, 0.0)]
+    path = tmp_path / "src.csv"
+    rec = CsvRecorder()
+    rec.start(str(path), sensors, serial="A12")
+    for i in range(rows):
+        rec.write(Frame(seq=i, time=i * 0.5, values=[100.0 + i, 200.0 + i]))
+    rec.stop()
+    return path
+
+
+def test_write_segment_zwafer_slice(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=5)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 1, 3) is True
+
+    records = read_data_records(str(dest))
+    assert len(records) == 3
+    assert records[0].values == [101.0, 201.0]
+    assert records[-1].values == [103.0, 203.0]
+
+    # header survives → still parses as a wafer CSV
+    data, _ = ZWaferParser().parse(str(dest))
+    assert data is not None
+    assert [s.label for s in data.sensors] == ["1", "2"]
+
+
+def test_write_segment_full_range(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=4)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 0, 3) is True
+    assert len(read_data_records(str(dest))) == 4
+
+
+def test_write_segment_out_of_range(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=3)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 10, 20) is False
+    assert not dest.exists()
+
+
+def test_write_segment_invalid_range(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=3)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 2, 1) is False
+    assert CsvRecorder.write_segment(str(dest), str(src), -1, 1) is False
+
+
+def test_write_segment_official_csv(tmp_path):
+    # official format: row 0 = sensor names, rows 1+ = values only
+    src = tmp_path / "A00001-x.csv"
+    src.write_text(
+        "Sensor1,Sensor2\n"
+        "10.0,20.0\n"
+        "11.0,21.0\n"
+        "12.0,22.0\n",
+        encoding="utf-8",
+    )
+    dest = tmp_path / "A00001-x_seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 1, 2) is True
+    lines = dest.read_text(encoding="utf-8").splitlines()
+    assert lines[0] == "Sensor1,Sensor2"
+    assert lines[1] == "11.0,21.0"
+    assert lines[2] == "12.0,22.0"
+    assert len(lines) == 3
diff --git a/tests/test_session_controller.py b/tests/test_session_controller.py
index 1dda318..4f24b31 100644
--- a/tests/test_session_controller.py
+++ b/tests/test_session_controller.py
@@ -1,10 +1,7 @@
-from unittest.mock import MagicMock
-
 import pytest
-
+from unittest.mock import MagicMock, patch
 from pygui.backend.controllers.session_controller import SessionController
 
-
 @pytest.fixture
 def controller():
     return SessionController()
@@ -12,7 +9,7 @@ def controller():
 def test_initial_default(controller):
     assert controller.mode == "review"
     assert controller.state == "idle"
-    assert not controller.recording
+    assert controller.recording == False
 
 def test_playback_flow(controller):
     controller.loadFile("tests/fixtures/sample_stream.csv")
@@ -50,44 +47,13 @@ def test_pause_stop_timer(controller):
     controller.stop()
     assert controller.frameIndex == 0
 
-def test_load_file_emits_error_for_empty_recording(controller, tmp_path):
-    """A recording with a valid header but zero data rows (e.g. Record was
-    started/stopped without any live frames arriving) must surface a clear
-    loadFileError instead of silently doing nothing."""
-    empty_recording = tmp_path / "live_A00001_20260706_120427.csv"
-    empty_recording.write_text(
-        "Wafer ID=A00001\n"
-        "Acquisition Date=07/06/2026\n"
-        "Label,1,2\n"
-        "X (mm),0.0,10.0\n"
-        "Y (mm),10.0,-10.0\n"
-        "data\n"
-    )
-
-    mock_slot = MagicMock()
-    controller.loadFileError.connect(mock_slot)
-    controller.loadFile(str(empty_recording))
-
-    assert mock_slot.call_count == 1
-    assert "no recorded frames" in mock_slot.call_args[0][0]
-    assert controller.loadedFile == ""
-
-def test_load_file_switches_to_review_mode(controller):
-    """Loading a file for playback must always land in review mode, even if
-    the controller was left in live mode from a previous session — otherwise
-    a successful load can be invisible behind a stale Live toggle."""
-    controller._mode = "live"
-    controller.loadFile("tests/fixtures/sample_stream.csv")
-    assert controller.mode == "review"
-
 def test_compare_files_integration(controller):
     # Mock the comparisonResult signal
     mock_slot = MagicMock()
     controller.comparisonResult.connect(mock_slot)
 
-    # Use sample_stream.csv for both arguments to test identical files compare
-    csv_path = "tests/fixtures/sample_stream.csv"
-    controller.compareFiles(csv_path, csv_path)
+    # Two runs with the same first 3 frames but run B has 2 extra trailing frames.
+    controller.compareFiles("tests/fixtures/sample_stream.csv", "tests/fixtures/sample_stream_b.csv")
 
     # Verify that the comparison signal is emitted with a success dict
     assert mock_slot.call_count == 1
@@ -96,97 +62,24 @@ def test_compare_files_integration(controller):
     assert "distance" in args
     assert "series_a" in args
     assert "series_b" in args
-    assert args["frame_offset"] == 0
-
-def test_compare_files_uses_full_run_not_first_100_frames(controller, tmp_path):
-    """compareFiles must score the whole run, not just an initial 100-frame window.
-
-    Regression test: max_frames used to be hard-capped at 100, so a >100-frame
-    run's soak/cool phases were silently excluded from the DTW comparison.
-    """
-    num_frames = 150
-    csv_path = tmp_path / "long_run.csv"
-    lines = ["Wafer ID=A12", "Acquisition Date=03/26/2025", "Label,1,2,3",
-             "X (mm),0,10,-10", "Y (mm),10,-10,-10", "data"]
-    for i in range(num_frames):
-        t = i * 0.5
-        lines.append(f"{t},{149.0 + i * 0.01},{148.5 + i * 0.01},{150.6 + i * 0.01}")
-    csv_path.write_text("\n".join(lines) + "\n")
+    # time_a/time_b expose per-frame timestamps in seconds for the mismatched run lengths.
+    assert args["time_a"] == [0.0, 0.5, 1.0]
+    assert args["time_b"] == [0.0, 0.5, 1.0, 1.5, 2.0]
+    assert args["frame_count_a"] == 3
+    assert args["frame_count_b"] == 5
 
+def test_compare_files_same_file_is_gated(controller):
+    """Comparing a run against itself should be rejected, not silently DTW'd."""
     mock_slot = MagicMock()
     controller.comparisonResult.connect(mock_slot)
-    controller.compareFiles(str(csv_path), str(csv_path))
+
+    csv_path = "tests/fixtures/sample_stream.csv"
+    controller.compareFiles(csv_path, csv_path)
 
     assert mock_slot.call_count == 1
-    result = mock_slot.call_args[0][0]
-    assert result["success"] is True
-    assert len(result["series_a"]) == num_frames
-    assert len(result["series_b"]) == num_frames
-
-def test_compare_files_rejects_mismatched_wafer_types(controller, tmp_path):
-    """compareFiles must refuse to compare two different wafer families.
-
-    Otherwise the overlap view silently truncates to min(sensor_count) and
-    pairs up unrelated physical sensors between the two wafer types.
-    """
-    header = ["Wafer ID=A12", "Acquisition Date=03/26/2025", "Label,1,2,3",
-              "X (mm),0,10,-10", "Y (mm),10,-10,-10", "data",
-              "0.0,149.0,148.5,150.6"]
-    file_a = tmp_path / "A00055-20250326.csv"
-    file_b = tmp_path / "X00108-20250326.csv"
-    file_a.write_text("\n".join(header) + "\n")
-    file_b.write_text("\n".join(header) + "\n")
-
-    mock_slot = MagicMock()
-    controller.comparisonResult.connect(mock_slot)
-    controller.compareFiles(str(file_a), str(file_b))
-
-    assert mock_slot.call_count == 1
-    result = mock_slot.call_args[0][0]
-    assert result["success"] is False
-    assert "A" in result["error"] and "X" in result["error"]
-
-def test_compare_files_rejects_recording_vs_read_mem(controller, tmp_path):
-    """A live_-prefixed recording must not be compared against a read-memory
-    dump. Regression: stem[0] on "live_P0001_..." is "L", which used to be
-    misreported as a wafer-type mismatch ("L vs P") instead of this clearer
-    recording-vs-read-mem error.
-    """
-    header = ["Wafer ID=P0001", "Acquisition Date=03/26/2025", "Label,1,2,3",
-              "X (mm),0,10,-10", "Y (mm),10,-10,-10", "data",
-              "0.0,149.0,148.5,150.6"]
-    recording = tmp_path / "live_P0001_20260706_143022.csv"
-    read_mem = tmp_path / "P0001-20260706_143500.csv"
-    recording.write_text("\n".join(header) + "\n")
-    read_mem.write_text("\n".join(header) + "\n")
-
-    mock_slot = MagicMock()
-    controller.comparisonResult.connect(mock_slot)
-    controller.compareFiles(str(recording), str(read_mem))
-
-    assert mock_slot.call_count == 1
-    result = mock_slot.call_args[0][0]
-    assert result["success"] is False
-    assert result["error"] == "Cannot compare a recording file with a read-memory file"
-
-def test_compare_files_allows_two_recordings_of_same_wafer_type(controller, tmp_path):
-    """Two live recordings of the same wafer family should compare fine —
-    the "live_" prefix must not be mistaken for the wafer type letter."""
-    header = ["Wafer ID=P0001", "Acquisition Date=03/26/2025", "Label,1,2,3",
-              "X (mm),0,10,-10", "Y (mm),10,-10,-10", "data",
-              "0.0,149.0,148.5,150.6"]
-    file_a = tmp_path / "live_P0001_20260706_143022.csv"
-    file_b = tmp_path / "live_P0002_20260706_150000.csv"
-    file_a.write_text("\n".join(header) + "\n")
-    file_b.write_text("\n".join(header) + "\n")
-
-    mock_slot = MagicMock()
-    controller.comparisonResult.connect(mock_slot)
-    controller.compareFiles(str(file_a), str(file_b))
-
-    assert mock_slot.call_count == 1
-    result = mock_slot.call_args[0][0]
-    assert result["success"] is True
+    args = mock_slot.call_args[0][0]
+    assert args["success"] is False
+    assert "error" in args
 
 def test_comparison_result_reaches_qml(qapp, controller):
     """The result dict must arrive in QML as a real JS object with fields.
@@ -216,26 +109,25 @@ Item {
     assert engine.rootObjects(), "probe QML failed to load"
     root = engine.rootObjects()[0]
 
-    csv_path = "tests/fixtures/sample_stream.csv"
-    controller.compareFiles(csv_path, csv_path)
+    controller.compareFiles("tests/fixtures/sample_stream.csv", "tests/fixtures/sample_stream_b.csv")
     qapp.processEvents()
 
     assert root.property("gotSuccess") is True
     assert root.property("gotDistance") >= 0
 
+
 def test_recording_toggle(controller, tmp_path):
     csv_path = str(tmp_path / "rec" / "live_test.csv")
     controller.startRecording(csv_path, "SN123")
-    assert controller.recording
+    assert controller.recording == True
 
     controller.stopRecording()
-    assert not controller.recording
+    assert controller.recording == False
 
     # Header written with wafer serial
     content = open(csv_path).read()
     assert "Wafer ID=SN123" in content
 
-
 def test_resync_count_default(controller):
     # No active reader -> zero
     assert controller.resyncCount == 0
@@ -257,3 +149,45 @@ def test_split_data_integration(controller):
     args = mock_slot.call_args[0][0]
     assert args["success"] is True
     assert "segments" in args
+
+
+
+def test_export_segment_after_split(qapp, controller, tmp_path):
+    import shutil
+
+    src = tmp_path / "sample.csv"
+    shutil.copyfile("tests/fixtures/sample_stream.csv", src)
+
+    controller.splitData(str(src), 149.0)
+
+    exported = MagicMock()
+    controller.segmentExported.connect(exported)
+    controller.exportSegment(0)
+
+    assert exported.call_count == 1
+    result = exported.call_args[0][0]
+    assert result["success"] is True
+    out = result["path"]
+    assert out.startswith(str(tmp_path))
+    from pygui.backend.data.data_records import read_data_records
+    assert len(read_data_records(out)) > 0
+
+
+def test_export_segment_without_split(qapp, controller):
+    exported = MagicMock()
+    controller.segmentExported.connect(exported)
+    controller.exportSegment(0)
+    result = exported.call_args[0][0]
+    assert result["success"] is False
+
+
+def test_export_segment_bad_index(qapp, controller, tmp_path):
+    import shutil
+    src = tmp_path / "sample.csv"
+    shutil.copyfile("tests/fixtures/sample_stream.csv", src)
+    controller.splitData(str(src), 149.0)
+
+    exported = MagicMock()
+    controller.segmentExported.connect(exported)
+    controller.exportSegment(99)
+    assert exported.call_args[0][0]["success"] is False