feat(gamut): second-profile compare and click-inspect (#147)

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Packages/ICCeryCore/Sources/ICCeryCore/Argyll/ArgyllRunner.swift

@@ -742,6 +742,148 @@ public struct ArgyllRunner: Sendable {
         }
     }
 
+    // MARK: - spotread (spot-read console, issue #148)
+
+    /// Runs `spotread` and returns an `AsyncStream` of typed events.
+    ///
+    /// Same subscribe-before-spawn shape as `runChartread`, but there is
+    /// no artefact: the stream ends with `.exit(code)`. The single-lease
+    /// process id is `ProcessID.spotread` — never `chartread_{basename}`.
+    /// Missing sidecar surfaces as `.failed`; there is no `$PATH` or
+    /// `chartread` fallback (#116, R14/R21).
+    public func runSpotread(config: SpotReadConfig) -> AsyncStream<SpotReadEvent> {
+        let cwd = PathSecurity.resolveSafeCwd(config.workingDirectory)
+        let args = SpotReadArgs.build(config: config)
+        let binaryURL = binaryResolver.resolve("spotread")
+        let processId = ProcessID.spotread
+        let processManager = self.processManager
+        let isXY = config.isXY
+        let instrumentName = config.instrumentName
+        let instrumentPort = config.instrumentPort
+
+        return AsyncStream { continuation in
+            let task = Task {
+                await ensureNotRunning(id: processId)
+                let events = processManager.events()
+
+                // XY parking hook before any kill, same as chartread.
+                await processManager.setPreKillHook(id: processId) { [processManager] in
+                    if isXY {
+                        try? await processManager.sendStdin(id: processId, bytes: ChartreadInput.quit.bytes)
+                        try? await Task.sleep(nanoseconds: Self.testAwareDelay(500_000_000))
+                    }
+                }
+
+                guard binaryResolver.exists(binaryURL) else {
+                    continuation.yield(.failed(ArgyllRunnerError.toolFailed(
+                        tool: "spotread", code: -1,
+                        logs: ["spotread sidecar missing — run fetch-argyll"])))
+                    continuation.finish()
+                    return
+                }
+
+                do {
+                    try await processManager.runStreaming(
+                        id: processId,
+                        binary: binaryURL,
+                        arguments: args,
+                        workingDirectory: cwd
+                    )
+                } catch {
+                    continuation.yield(.failed(ArgyllRunnerError.toolFailed(
+                        tool: "spotread", code: -1, logs: [error.localizedDescription])))
+                    continuation.finish()
+                    return
+                }
+
+                var state: ChartreadState = .idle
+                var pendingLogs: [String] = []
+                var lastFlush = Date()
+                var exitCode: Int32?
+
+                func flushLogs() {
+                    guard !pendingLogs.isEmpty else { return }
+                    let batch = pendingLogs
+                    pendingLogs.removeAll(keepingCapacity: true)
+                    continuation.yield(.log(batch))
+                }
+
+                for await event in events {
+                    guard event.id == processId else { continue }
+
+                    switch event {
+                    case .stdout(_, let line):
+                        if let parsed = SpotReadParser.parse(line: line) {
+                            continuation.yield(.sample(SpotReadSample(
+                                lab: parsed.lab,
+                                xyz: parsed.xyz,
+                                instrumentName: instrumentName,
+                                port: instrumentPort,
+                                rawLine: line
+                            )))
+                        }
+                        let classified = SpotReadClassifier.classify(
+                            line: line, previousState: state)
+                        if classified.state != state
+                            || classified.requestedWarningKey != nil {
+                            state = classified.state
+                            continuation.yield(.prompt(classified))
+                        }
+                        pendingLogs.append(line)
+
+                    case .stderr(_, let line):
+                        pendingLogs.append(line)
+
+                    case .jsonRow:
+                        // spotread is never run with `-u`.
+                        break
+
+                    case .error(_, let message):
+                        pendingLogs.append("Error: \(message)")
+
+                    case .exit(_, let code):
+                        exitCode = code
+                    }
+
+                    if exitCode == nil,
+                       pendingLogs.count >= 20 || Date().timeIntervalSince(lastFlush) >= 0.1 {
+                        flushLogs()
+                        lastFlush = Date()
+                    }
+
+                    if exitCode != nil {
+                        flushLogs()
+                        break
+                    }
+                }
+
+                continuation.yield(.exit(exitCode ?? -1))
+                continuation.finish()
+            }
+
+            continuation.onTermination = { _ in
+                task.cancel()
+                Task {
+                    await processManager.kill(id: processId)
+                }
+            }
+        }
+    }
+
+    /// Send input bytes to the running `spotread` child. Reuses
+    /// `ChartreadInput` — the stdin protocol is identical.
+    public func sendSpotreadInput(_ input: ChartreadInput) async throws {
+        try await processManager.sendStdin(id: ProcessID.spotread, bytes: input.bytes)
+    }
+
+    /// Terminate a running `spotread` child. The XY park (`q\n` +
+    /// ~500 ms) runs in the pre-kill hook registered by `runSpotread`.
+    public func cancelSpotread() {
+        Task {
+            await processManager.kill(id: ProcessID.spotread)
+        }
+    }
+
     // MARK: - Stage 0 calibration
 
     /// Generates a calibration wedge `.ti1`.
@@ -828,6 +970,20 @@ public enum ChartreadEvent: Sendable {
     case failed(ArgyllRunnerError)
 }
 
+/// Events emitted by a running `spotread` session (issue #148).
+public enum SpotReadEvent: Sendable {
+    /// Classified prompt / state update (reuses `ChartreadState`).
+    case prompt(ChartreadClassifyResult)
+    /// A parsed `Result is …` sample line.
+    case sample(SpotReadSample)
+    /// A batched log chunk (stdout + stderr lines).
+    case log([String])
+    /// Process exited with the given code.
+    case exit(Int32)
+    /// Failure (missing sidecar, spawn error).
+    case failed(ArgyllRunnerError)
+}
+
 /// Exact bytes sent to `chartread` stdin.
 public enum ChartreadInput: Sendable {
     case trigger    // " \n"

Packages/ICCeryCore/Sources/ICCeryCore/Argyll/SpotReadArgs.swift

@@ -0,0 +1,28 @@
+import Foundation
+
+/// Pure argv builder for Argyll's `spotread` tool (issue #148).
+public enum SpotReadArgs {
+
+    /// Builds `spotread` argv per the Gronod fork protocol.
+    ///
+    /// - Always `-v -e` (paper / reflective; never display `-d`).
+    /// - `-c N` is emitted only for `selectedPort != nil` and `N > 1`
+    ///   (Auto and port 1 omit it, #111).
+    /// - `-Y l` (letter L) is emitted only when `enableLEDs` is `true` (#204).
+    /// - Never `-u`: the v2.0 `-u` policy covers printtarg + chartread +
+    ///   profcheck only.
+    /// - No basename — `spotread` writes no artefact.
+    public static func build(config: SpotReadConfig) -> [String] {
+        var args: [String] = ["-v", "-e"]
+
+        if let port = config.selectedPort, port > 1 {
+            args.append(contentsOf: ["-c", "\(port)"])
+        }
+
+        if config.enableLEDs {
+            args.append(contentsOf: ["-Y", "l"])
+        }
+
+        return args
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Argyll/SpotReadConfig.swift

@@ -0,0 +1,37 @@
+import Foundation
+
+/// Configuration for a `spotread` invocation (issue #148).
+///
+/// `spotread` writes no artefact; `workingDirectory` is still required
+/// for the spawn (#59 — empty cwd is illegal).
+public struct SpotReadConfig: Codable, Equatable, Sendable {
+    public var workingDirectory: URL?
+    /// Communication port for `spotread -c`.
+    /// `nil` means omit `-c` (Auto or port 1, #111). Never an array index.
+    public var selectedPort: Int?
+    /// Enable i1Pro 2 visual LEDs (`-Y l`, #204).
+    public var enableLEDs: Bool
+    /// Whether the selected instrument is an XY table — controls the
+    /// `q\n` + ~500 ms park before kill on cancel.
+    public var isXY: Bool
+    /// Display name stamped onto each `SpotReadSample`.
+    public var instrumentName: String
+    /// Instrument port stamped onto each sample (nil for Auto).
+    public var instrumentPort: Int?
+
+    public init(
+        workingDirectory: URL? = nil,
+        selectedPort: Int? = nil,
+        enableLEDs: Bool = false,
+        isXY: Bool = false,
+        instrumentName: String = "",
+        instrumentPort: Int? = nil
+    ) {
+        self.workingDirectory = workingDirectory
+        self.selectedPort = selectedPort
+        self.enableLEDs = enableLEDs
+        self.isXY = isXY
+        self.instrumentName = instrumentName
+        self.instrumentPort = instrumentPort
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Gamut/ApproximateLab.swift

@@ -0,0 +1,64 @@
+import Foundation
+
+/// Approximate sRGB → CIELab D50 conversion for the gamut inspect panel
+/// (issue #147).
+///
+/// This is a fixed-matrix helper, **not** a colour-management module: it
+/// never touches ICC profiles, ColorSync, or lcms. The UI labels its
+/// output "approx. Lab, not ColorSync".
+public enum ApproximateLab {
+
+    /// linear-sRGB → XYZ (D65) matrix, IEC 61966-2-1.
+    private static let srgbToXYZ: [[Double]] = [
+        [0.4124, 0.3576, 0.1805],
+        [0.2126, 0.7152, 0.0722],
+        [0.0193, 0.1192, 0.9505],
+    ]
+
+    /// 8-bit sRGB triple → Lab D50 (approximate).
+    public static func srgb8ToLab(r: Int, g: Int, b: Int) -> LabColor {
+        srgbToLab(DisplayRGB(
+            r: Double(r) / 255.0,
+            g: Double(g) / 255.0,
+            b: Double(b) / 255.0))
+    }
+
+    /// 0–1 sRGB triple → Lab D50 (approximate).
+    public static func srgbToLab(_ rgb: DisplayRGB) -> LabColor {
+        func linear(_ c: Double) -> Double {
+            c <= 0.04045 ? c / 12.92 : pow((c + 0.055) / 1.055, 2.4)
+        }
+        let v = [linear(rgb.r), linear(rgb.g), linear(rgb.b)]
+        // 0–1 XYZ D65 → the 0–100 scale `LabColorMath` works in.
+        let xyz65 = XYZColor(
+            x: (srgbToXYZ[0][0] * v[0] + srgbToXYZ[0][1] * v[1] + srgbToXYZ[0][2] * v[2]) * 100,
+            y: (srgbToXYZ[1][0] * v[0] + srgbToXYZ[1][1] * v[1] + srgbToXYZ[1][2] * v[2]) * 100,
+            z: (srgbToXYZ[2][0] * v[0] + srgbToXYZ[2][1] * v[1] + srgbToXYZ[2][2] * v[2]) * 100)
+        return LabColorMath.xyzToLab(adaptD65ToD50(xyz65))
+    }
+
+    /// Bradford D65 → D50 chromatic adaptation — the mirror of
+    /// `LabColorMath.adaptD50ToD65`.
+    private static func adaptD65ToD50(_ xyz: XYZColor) -> XYZColor {
+        let m = LabColorMath.bradford
+        let inv = LabColorMath.bradfordInv
+        let d65 = LabColorMath.d65White
+        let d50 = LabColorMath.d50White
+        let source = multiply(m, [xyz.x, xyz.y, xyz.z])
+        let srcWhite = multiply(m, [d65.X, d65.Y, d65.Z])
+        let dstWhite = multiply(m, [d50.X, d50.Y, d50.Z])
+        let scaled = [
+            source[0] * (dstWhite[0] / srcWhite[0]),
+            source[1] * (dstWhite[1] / srcWhite[1]),
+            source[2] * (dstWhite[2] / srcWhite[2]),
+        ]
+        return XYZColor(
+            x: inv[0][0] * scaled[0] + inv[0][1] * scaled[1] + inv[0][2] * scaled[2],
+            y: inv[1][0] * scaled[0] + inv[1][1] * scaled[1] + inv[1][2] * scaled[2],
+            z: inv[2][0] * scaled[0] + inv[2][1] * scaled[1] + inv[2][2] * scaled[2])
+    }
+
+    private static func multiply(_ m: [[Double]], _ v: [Double]) -> [Double] {
+        m.map { row in zip(row, v).reduce(0) { $0 + $1.0 * $1.1 } }
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Gamut/GamutContainment.swift

@@ -0,0 +1,115 @@
+import Foundation
+import simd
+
+/// Result of a point-in-gamut test (issue #147).
+public enum GamutContainment: String, Sendable, Equatable {
+    /// The point lies inside the mesh volume.
+    case inside
+    /// The point lies outside the mesh volume.
+    case outside
+    /// The mesh has no faces to test against.
+    case unknown
+}
+
+/// Point-in-mesh containment and volume estimation for ``GamutMesh``.
+///
+/// Both tests run on the scene-space positions stored on
+/// ``GamutVertex/position`` (`x = a*`, `y = L*`, `z = b*`), the same
+/// mapping the SceneKit viewer uses. No colour management is involved.
+public enum GamutGeometry {
+
+    /// Whether `lab` is inside `mesh`.
+    ///
+    /// Ray-casts through the face list: an odd crossing count means the
+    /// point is inside a closed surface. A ray that grazes a vertex or
+    /// edge gives an ambiguous count, so the test retries with off-axis
+    /// directions before answering. Meshes without faces report
+    /// ``GamutContainment/unknown``.
+    public static func containment(of lab: LabColor, in mesh: GamutMesh) -> GamutContainment {
+        guard !mesh.faces.isEmpty else { return .unknown }
+        let origin = SIMD3<Double>(lab.a, lab.l, lab.b)
+        for direction in rayDirections {
+            if let inside = castRay(from: origin, direction: direction, mesh: mesh) {
+                return inside ? .inside : .outside
+            }
+        }
+        return .unknown
+    }
+
+    /// Approximate mesh volume in Lab-cubic units.
+    ///
+    /// Sums signed tetrahedra from the vertex centroid to each face; for
+    /// a closed surface the magnitude equals the enclosed volume
+    /// regardless of face winding. Returns 0 for empty or face-less
+    /// meshes.
+    public static func volume(of mesh: GamutMesh) -> Double {
+        guard !mesh.faces.isEmpty, !mesh.vertices.isEmpty else { return 0 }
+        var centroid = SIMD3<Double>.zero
+        for vertex in mesh.vertices {
+            centroid += SIMD3<Double>(vertex.position)
+        }
+        centroid /= Double(mesh.vertices.count)
+
+        var sum = 0.0
+        let count = mesh.vertices.count
+        for face in mesh.faces {
+            guard Int(face.a) < count, Int(face.b) < count, Int(face.c) < count else {
+                continue
+            }
+            let a = SIMD3<Double>(mesh.vertices[Int(face.a)].position) - centroid
+            let b = SIMD3<Double>(mesh.vertices[Int(face.b)].position) - centroid
+            let c = SIMD3<Double>(mesh.vertices[Int(face.c)].position) - centroid
+            sum += simd_dot(a, simd_cross(b, c)) / 6.0
+        }
+        return abs(sum)
+    }
+
+    // MARK: - Ray casting
+
+    /// Primary +X ray, then off-axis retries for degenerate edge hits.
+    private static let rayDirections: [SIMD3<Double>] = [
+        SIMD3(1, 0, 0),
+        simd_normalize(SIMD3<Double>(0.71, 1.0, 0.53)),
+        simd_normalize(SIMD3<Double>(0.53, 0.71, 1.0)),
+    ]
+
+    /// Möller–Trumbore crossing count. Returns `nil` when a crossing
+    /// lands on a triangle edge or vertex (ambiguous parity) so the
+    /// caller can retry with a different direction.
+    private static func castRay(
+        from origin: SIMD3<Double>,
+        direction dir: SIMD3<Double>,
+        mesh: GamutMesh
+    ) -> Bool? {
+        let epsilon = 1e-9
+        var crossings = 0
+        let count = mesh.vertices.count
+        for face in mesh.faces {
+            guard Int(face.a) < count, Int(face.b) < count, Int(face.c) < count else {
+                continue
+            }
+            let va = SIMD3<Double>(mesh.vertices[Int(face.a)].position)
+            let vb = SIMD3<Double>(mesh.vertices[Int(face.b)].position)
+            let vc = SIMD3<Double>(mesh.vertices[Int(face.c)].position)
+
+            let e1 = vb - va
+            let e2 = vc - va
+            let p = simd_cross(dir, e2)
+            let det = simd_dot(e1, p)
+            if abs(det) < 1e-12 { continue }  // ray parallel to face
+            let inv = 1.0 / det
+            let tvec = origin - va
+            let u = simd_dot(tvec, p) * inv
+            let q = simd_cross(tvec, e1)
+            let v = simd_dot(dir, q) * inv
+            let t = simd_dot(e2, q) * inv
+
+            guard t > epsilon else { continue }
+            if u < -epsilon || v < -epsilon || u + v > 1 + epsilon { continue }
+            // Crossing on an edge or vertex — parity is ambiguous.
+            if u < epsilon || v < epsilon || u + v > 1 - epsilon { return nil }
+            crossings += 1
+        }
+        return crossings % 2 == 1
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Gamut/NamedGamut.swift

@@ -0,0 +1,39 @@
+import Foundation
+
+/// A parsed gamut mesh plus the display metadata the compare viewer
+/// needs (issue #147).
+///
+/// `displayName` is user-derived (a file name); views must render it
+/// through `Text` only (#114).
+public struct NamedGamut: Sendable, Equatable, Identifiable {
+
+    /// What the layer is used for in the compare UI.
+    public enum Role: String, Sendable, Equatable {
+        /// Bundled reference space (sRGB). Cannot be removed, only hidden.
+        case reference
+        /// The workflow's own profile gamut.
+        case profileA
+        /// The user-added compare gamut. Replaced, never stacked.
+        case profileB
+    }
+
+    public var id: String
+    public var displayName: String
+    public var role: Role
+    public var mesh: GamutMesh
+    public var sourceURL: URL
+
+    public init(
+        id: String,
+        displayName: String,
+        role: Role,
+        mesh: GamutMesh,
+        sourceURL: URL
+    ) {
+        self.id = id
+        self.displayName = displayName
+        self.role = role
+        self.mesh = mesh
+        self.sourceURL = sourceURL
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Measurement/SpotReadClassifier.swift

@@ -0,0 +1,48 @@
+import Foundation
+
+/// Line classifier for `spotread` stdout (issue #148).
+///
+/// `spotread` shares `chartread`'s white-tile calibration phrasing, so
+/// this wraps `ChartreadClassifier` and only intercepts the lines that
+/// would otherwise misclassify:
+///
+/// - `… and then hit any key to continue,` / `or hit Esc or Q to abort:`
+///   continuation lines that trail the calibration and spot prompts —
+///   sticky to the current prompt state instead of `PROMPT_CONTINUE`.
+/// - `Place instrument on a spot to be measured,` /
+///   `and hit a key to take a reading,` → `AWAITING_STRIP` (the Read
+///   prompt; the generic chartread matcher does not know "take a
+///   reading").
+///
+/// Sample lines (`Result is XYZ: …, D50 Lab: …`) are parsed by
+/// `SpotReadParser`, not classified here.
+public enum SpotReadClassifier {
+
+    public static func classify(
+        line: String,
+        previousState: ChartreadState
+    ) -> ChartreadClassifyResult {
+        let text = line.lowercased()
+
+        // Spot-read prompt continuations keep the current prompt state.
+        if previousState == .calibrating || previousState == .awaitingStrip {
+            if text.contains("hit any key")
+                || text.contains("hit space")
+                || text.contains("esc or")
+                || text.contains("abort")
+                || text.contains("to abort") {
+                return ChartreadClassifyResult(state: previousState)
+            }
+        }
+
+        // "Place instrument on a spot to be measured," /
+        // " and hit a key to take a reading," — the Read trigger prompt.
+        if text.contains("spot to be measured")
+            || text.contains("take a reading")
+            || text.contains("measure the spot") {
+            return ChartreadClassifyResult(state: .awaitingStrip)
+        }
+
+        return ChartreadClassifier.classify(line: line, previousState: previousState)
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Measurement/SpotReadSample.swift

@@ -0,0 +1,80 @@
+import Foundation
+
+/// One patch measurement emitted by a running `spotread` child (#148).
+public struct SpotReadSample: Codable, Sendable, Equatable, Identifiable {
+    public var id: UUID
+    public var timestamp: Date
+    /// D50 Lab (always present — derived from XYZ when needed).
+    public var lab: LabColor
+    /// XYZ on the 0–100 scale used by the fork, when the line carried it.
+    public var xyz: XYZColor?
+    public var instrumentName: String
+    public var port: Int?
+    /// Diagnostics only — never rendered as HTML or shown in the table.
+    public var rawLine: String
+
+    public init(
+        id: UUID = UUID(),
+        timestamp: Date = Date(),
+        lab: LabColor,
+        xyz: XYZColor? = nil,
+        instrumentName: String = "",
+        port: Int? = nil,
+        rawLine: String = ""
+    ) {
+        self.id = id
+        self.timestamp = timestamp
+        self.lab = lab
+        self.xyz = xyz
+        self.instrumentName = instrumentName
+        self.port = port
+        self.rawLine = rawLine
+    }
+}
+
+/// Parses `spotread` result lines into Lab / XYZ triples.
+///
+/// The fork's line shape is the upstream
+/// `Result is XYZ: <x> <y> <z>, D50 Lab: <L> <a> <b>`; a Lab-only line
+/// also parses, and an XYZ-only line derives Lab via
+/// `LabColorMath.xyzToLab` (D50).
+public enum SpotReadParser {
+
+    public static func parse(line: String) -> (xyz: XYZColor?, lab: LabColor)? {
+        guard line.range(of: "result is", options: .caseInsensitive) != nil
+            || line.range(of: #"\bLab\b"#, options: .regularExpression) != nil
+            || line.range(of: #"\bXYZ\b"#, options: .regularExpression) != nil
+        else { return nil }
+
+        var xyz: XYZColor?
+        var lab: LabColor?
+
+        if let m = triple(#"\bXYZ\b[:\s]"#, in: line) {
+            xyz = XYZColor(x: m.0, y: m.1, z: m.2)
+        }
+        if let m = triple(#"\bLab\b[:\s]"#, in: line) {
+            lab = LabColor(l: m.0, a: m.1, b: m.2)
+        }
+        if lab == nil, let xyz {
+            lab = LabColorMath.xyzToLab(xyz)
+        }
+        guard let lab else { return nil }
+        return (xyz, lab)
+    }
+
+    private static func triple(_ marker: String, in line: String) -> (Double, Double, Double)? {
+        let pattern = marker + #"\s*(-?\d+(?:\.\d+)?)\s+(-?\d+(?:\.\d+)?)\s+(-?\d+(?:\.\d+)?)"#
+        guard let regex = try? NSRegularExpression(pattern: pattern, options: .caseInsensitive),
+              let match = regex.firstMatch(
+                in: line, options: [], range: NSRange(line.startIndex..., in: line)),
+              match.numberOfRanges == 4,
+              let r1 = Range(match.range(at: 1), in: line),
+              let r2 = Range(match.range(at: 2), in: line),
+              let r3 = Range(match.range(at: 3), in: line),
+              let a = Double(line[r1]),
+              let b = Double(line[r2]),
+              let c = Double(line[r3])
+        else { return nil }
+        return (a, b, c)
+    }
+}

Packages/ICCeryCore/Sources/ICCeryCore/Process/ProcessID.swift

@@ -4,6 +4,8 @@ import Foundation
 /// filter events on `id` — historical bug #56 was an id mismatch.
 public enum ProcessID {
     public static let instlist = "instlist"
+    /// Spot-read console (issue #148) — single lease, like `instlist`.
+    public static let spotread = "spotread"
 
     public static func targen(_ basename: String) -> String { "targen_\(basename)" }
     public static func printtarg(_ basename: String) -> String { "printtarg_\(basename)" }

Sources/ICCery/AppEnvironment.swift

@@ -21,11 +21,15 @@ struct AppEnvironment: Sendable {
         let settingsStore = SettingsStore()
         var overrideDir = settingsStore.load().argyllBinaryDir
             .map { URL(fileURLWithPath: $0) }
+        var bundledRoot = AppPaths.bundledArgyllDir
         var cupsDir = URL(fileURLWithPath: "/usr/bin")
         #if DEBUG
         if let dir = environment["ICCERY_ARGYLL_BINARY_DIR"], !dir.isEmpty {
             overrideDir = URL(fileURLWithPath: dir)
         }
+        if let dir = environment["ICCERY_ARGYLL_BUNDLED_ROOT"], !dir.isEmpty {
+            bundledRoot = URL(fileURLWithPath: dir)
+        }
         if let dir = environment["ICCERY_CUPS_BIN_DIR"], !dir.isEmpty {
             cupsDir = URL(fileURLWithPath: dir)
         }
@@ -36,7 +40,8 @@ struct AppEnvironment: Sendable {
             presetStore: PresetStore(settingsStore: settingsStore),
             runner: ArgyllRunner(
                 processManager: .shared,
-                binaryResolver: BinaryResolver(overrideDir: overrideDir)
+                binaryResolver: BinaryResolver(
+                    bundledRoot: bundledRoot, overrideDir: overrideDir)
             ),
             cupsService: CupsService(
                 processManager: .shared,
@@ -76,6 +81,14 @@ enum UITestHooks {
     static var presetImportURL: URL? { url("ICCERY_TEST_PRESET_IMPORT") }
     /// Preset export destination.
     static var presetExportURL: URL? { url("ICCERY_TEST_PRESET_EXPORT") }
+    /// Spot-read CSV export destination (`selectCsvSavePath`, #148).
+    static var csvExportURL: URL? { url("ICCERY_TEST_CSV_EXPORT") }
+    /// `.gam` compare picker result (gamut sheet, #147). Unset → cancel.
+    static var gamutFileURL: URL? { url("ICCERY_TEST_GAMUT_FILE") }
+    /// `.icc/.icm` compare picker result (gamut sheet, #147). Unset → cancel.
+    static var gamutProfileURL: URL? { url("ICCERY_TEST_GAMUT_PROFILE") }
+    /// TIFF sample picker result (gamut sheet, #147). Unset → cancel.
+    static var gamutTiffURL: URL? { url("ICCERY_TEST_GAMUT_TIFF") }
 
     // MARK: - Print panel / CUPS stubs (issue 13/17)
 

Sources/ICCery/FileDialogService.swift

@@ -70,6 +70,19 @@ final class FileDialogService {
              message: "Choose a calibration file (.cal)")
     }
 
+    /// `selectGamutFile` — `.gam` surface mesh for the compare slot (#147).
+    func selectGamutFile(startingAt start: URL? = nil) -> URL? {
+        open(extensions: ["gam"], startingAt: start,
+             message: "Choose a .gam surface mesh",
+             allowsOtherFileTypes: false)
+    }
+
+    /// `selectTiffFile` — `.tif`/`.tiff` target page for gamut sampling (#147).
+    func selectTiffFile(startingAt start: URL? = nil) -> URL? {
+        open(extensions: ["tif", "tiff"], startingAt: start,
+             message: "Choose a target TIFF page")
+    }
+
     /// `btnImportPreset` — open a `.json` preset file.
     func selectPresetFile(startingAt start: URL? = nil) -> URL? {
         open(extensions: ["json"], startingAt: start,
@@ -102,14 +115,15 @@ final class FileDialogService {
     private func open(
         extensions: [String],
         startingAt start: URL?,
-        message: String?
+        message: String?,
+        allowsOtherFileTypes: Bool = true
     ) -> URL? {
         let panel = NSOpenPanel()
         panel.canChooseDirectories = false
         panel.canChooseFiles = true
         panel.allowsMultipleSelection = false
         panel.allowedContentTypes = utTypes(extensions)
-        panel.allowsOtherFileTypes = true
+        panel.allowsOtherFileTypes = allowsOtherFileTypes
         panel.directoryURL = start
         if let message { panel.message = message }
         return run(panel)

Sources/ICCery/GamutView.swift

@@ -1,5 +1,6 @@
 import SwiftUI
 import SceneKit
+import Metal
 import ICCeryCore
 import simd
 
@@ -62,72 +63,300 @@ internal struct GamutSceneGeometryBuilder {
     }
 }
 
-/// Native SceneKit 3D gamut viewer.
+/// Native SceneKit 3D gamut viewer (issues #28, #147).
 ///
-/// Displays a profile gamut mesh and the bundled `sRGB.gam` reference.  Uses
+/// Displays the bundled `sRGB.gam` reference plus up to two profile
-/// the CIELAB coordinate convention `x = a*`, `y = L*`, `z = b*` so that the
+/// meshes with independent visibility toggles, a status line, and an
-/// a* (green-red) axis is horizontal, L* (lightness) is vertical, and b*
+/// inspect panel (click a mesh, type a Lab value, or sample a TIFF
-/// (blue-yellow) is depth.
+/// pixel). Uses the CIELAB coordinate convention `x = a*`, `y = L*`,
+/// `z = b*`.
 struct GamutView: View {
     @StateObject private var viewModel: GamutViewModel
     @State private var pause: () -> Void = {}
     @FocusState private var isFocused: Bool
+    @Binding var showingAllHelp: Bool
 
-    init(profileGamURL: URL? = nil) {
+    init(
-        _viewModel = StateObject(wrappedValue: GamutViewModel(profileGamURL: profileGamURL))
+        environment: AppEnvironment,
+        profileGamURL: URL? = nil,
+        showingAllHelp: Binding<Bool>
+    ) {
+        _viewModel = StateObject(wrappedValue: GamutViewModel(
+            environment: environment, profileGamURL: profileGamURL))
+        _showingAllHelp = showingAllHelp
     }
 
     var body: some View {
-        ZStack {
+        VStack(spacing: 0) {
+            toolbar
+            Divider().overlay(Theme.border)
+            sceneArea
+            Divider().overlay(Theme.border)
+            statusLine
+            inspectPanel
+        }
+        .frame(minWidth: 720, minHeight: 520)
+        .background(Theme.background)
+        .onDisappear { pause() }
+        .accessibilityElement(children: .contain)
+        .accessibilityIdentifier("gamutView")
+        .sheet(isPresented: $viewModel.showingTiffPreview) {
+            tiffPreviewSheet
+        }
+    }
+
+    // MARK: - Toolbar
+
+    private var toolbar: some View {
+        HStack(spacing: 12) {
+            layerToggle(id: GamutViewModel.srgbLayerID, fallback: "sRGB")
+            layerToggle(id: GamutViewModel.profileLayerID, fallback: "Profile")
+            layerToggle(id: GamutViewModel.compareLayerID, fallback: "Compare")
+            Spacer()
+            addCompareMenu
+            Button("Remove compare") { viewModel.removeCompare() }
+                .disabled(viewModel.layer(id: GamutViewModel.compareLayerID) == nil)
+                .accessibilityIdentifier("btnGamutRemoveCompare")
+            Button("Sample TIFF…") { viewModel.openTiffSample() }
+                .accessibilityIdentifier("btnGamutSampleTiff")
+                .helpOverlay(
+                    "Sample a colour from a target TIFF page.",
+                    showing: $showingAllHelp)
+        }
+        .padding(.horizontal, 12)
+        .padding(.vertical, 8)
+    }
+
+    private func layerToggle(id: String, fallback: String) -> some View {
+        let layer = viewModel.layer(id: id)
+        return Toggle(isOn: Binding(
+            get: { layer != nil && viewModel.visibleIDs.contains(id) },
+            set: { on in
+                if on {
+                    viewModel.visibleIDs.insert(id)
+                } else {
+                    viewModel.visibleIDs.remove(id)
+                }
+            }
+        )) {
+            Text(layer?.displayName ?? fallback)
+        }
+        .toggleStyle(.checkbox)
+        .disabled(layer == nil || viewModel.viewerUnavailable)
+        .help(layer.map { $0.sourceURL.lastPathComponent } ?? "No profile .gam loaded")
+        .accessibilityIdentifier("gamutLayer-\(id)")
+    }
+
+    private var addCompareMenu: some View {
+        Menu("Add compare…") {
+            Button("Open .gam…") { viewModel.openCompareGam() }
+                .accessibilityIdentifier("btnGamutOpenGam")
+            Button("Open profile…") { viewModel.openCompareProfile() }
+                .accessibilityIdentifier("btnGamutOpenProfile")
+        }
+        .accessibilityIdentifier("btnGamutAddCompare")
+        .helpOverlay(
+            "Add a second profile or .gam mesh to compare against.",
+            showing: $showingAllHelp)
+    }
+
+    // MARK: - Scene
+
+    private var sceneArea: some View {
+        ZStack(alignment: .topTrailing) {
+            if viewModel.viewerUnavailable {
+                Text("3D gamut viewer is unavailable on this Mac; the rest of ICCery still works.")
+                    .font(.callout)
+                    .foregroundStyle(.secondary)
+                    .frame(maxWidth: .infinity, maxHeight: .infinity)
+                    .accessibilityIdentifier("gamutViewerUnavailable")
+            } else {
                 GamutSceneView(
-                profileMesh: viewModel.profileMesh,
+                    layers: viewModel.layers,
-                referenceMesh: viewModel.sRGBMesh,
+                    visibleIDs: viewModel.visibleIDs,
                     onReset: $viewModel.resetCamera,
-                onPause: $pause
+                    onPause: $pause,
+                    onUnavailable: { viewModel.viewerUnavailable = true },
+                    onInspect: { point, layerID in
+                        if let layerID {
+                            viewModel.inspectSceneHit(world: point, layerID: layerID)
+                        } else {
+                            viewModel.clearInspect()
+                        }
+                    }
                 )
                 .focusable()
                 .focused($isFocused)
                 .onAppear { isFocused = true }
-
+            }
-            VStack {
-                HStack {
-                    Spacer()
             Button(action: { viewModel.resetCamera() }) {
                 Text("Reset view")
             }
             .accessibilityIdentifier("btnResetGamutCamera")
             .padding(8)
         }
-                Spacer()
+        .frame(maxWidth: .infinity, maxHeight: .infinity)
-                HStack {
+    }
+
+    // MARK: - Status
+
+    private var statusLine: some View {
+        HStack(spacing: 10) {
             Text(viewModel.status)
                 .font(.caption)
-                        .padding(8)
+                .foregroundStyle(Theme.text)
-                        .background(.thinMaterial)
-                        .cornerRadius(6)
                 .accessibilityIdentifier("gamutStatusText")
+            if let notice = viewModel.noticeText {
+                Text(notice)
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                    .accessibilityIdentifier("gamutNoticeText")
+            }
             Spacer()
         }
-                .padding(8)
+        .padding(.horizontal, 12)
+        .padding(.vertical, 6)
     }
+
+    // MARK: - Inspect panel
+
+    private var inspectPanel: some View {
+        HStack(spacing: 12) {
+            if let lab = viewModel.inspectLab {
+                inspectSwatch
+                labReadout(lab)
+                containmentColumn
+                if viewModel.inspectIsApproximate {
+                    Text("approx. Lab, not ColorSync")
+                        .font(.caption2)
+                        .foregroundStyle(.secondary)
+                        .accessibilityIdentifier("gamutInspectApprox")
                 }
-        .frame(minWidth: 500, minHeight: 400)
+            } else {
-        .onDisappear { pause() }
+                Text("Click the mesh, or enter Lab, to inspect.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                    .accessibilityIdentifier("gamutInspectIdle")
+            }
+            Spacer()
+            labEntryFields
+        }
+        .padding(.horizontal, 12)
+        .padding(.vertical, 8)
+        .frame(minHeight: 56)
+        .background(Theme.panel)
         .accessibilityElement(children: .contain)
-        .accessibilityIdentifier("gamutView")
+        .accessibilityIdentifier("gamutInspectPanel")
+        .helpOverlay(
+            "Inspect a Lab point against each loaded gamut.",
+            showing: $showingAllHelp)
+    }
+
+    @ViewBuilder
+    private var inspectSwatch: some View {
+        if let swatch = viewModel.inspectSwatch {
+            Color(red: swatch.r, green: swatch.g, blue: swatch.b)
+                .frame(width: 16, height: 16)
+                .clipShape(RoundedRectangle(cornerRadius: 2))
+                .overlay(RoundedRectangle(cornerRadius: 2).stroke(Theme.border))
+                .accessibilityIdentifier("gamutInspectSwatch")
+        }
+    }
+
+    private func labReadout(_ lab: LabColor) -> some View {
+        HStack(spacing: 10) {
+            Text(String(format: "L %.1f", lab.l))
+                .accessibilityIdentifier("gamutInspectL")
+            Text(String(format: "a %.1f", lab.a))
+                .accessibilityIdentifier("gamutInspectA")
+            Text(String(format: "b %.1f", lab.b))
+                .accessibilityIdentifier("gamutInspectB")
+        }
+        .font(.caption.monospacedDigit())
+        .foregroundStyle(Theme.text)
+    }
+
+    private var containmentColumn: some View {
+        HStack(spacing: 10) {
+            ForEach(viewModel.inspectResults, id: \.id) { result in
+                Text("\(result.name) \(containmentWord(result.containment))")
+                    .font(.caption)
+                    .foregroundStyle(Theme.text)
+                    .accessibilityIdentifier("gamutInspect-\(result.id)")
+            }
+        }
+    }
+
+    private func containmentWord(_ containment: GamutContainment) -> String {
+        switch containment {
+        case .inside: return "in"
+        case .outside: return "out"
+        case .unknown: return "?"
+        }
+    }
+
+    private var labEntryFields: some View {
+        HStack(spacing: 6) {
+            Text("Lab 0–100 · ±128")
+                .font(.caption2)
+                .foregroundStyle(.secondary)
+            TextField("L", text: $viewModel.labEntryL)
+                .textFieldStyle(.roundedBorder)
+                .frame(width: 56)
+                .accessibilityIdentifier("gamutLabEntryL")
+            TextField("a", text: $viewModel.labEntryA)
+                .textFieldStyle(.roundedBorder)
+                .frame(width: 56)
+                .accessibilityIdentifier("gamutLabEntryA")
+            TextField("b", text: $viewModel.labEntryB)
+                .textFieldStyle(.roundedBorder)
+                .frame(width: 56)
+                .accessibilityIdentifier("gamutLabEntryB")
+            Button("Inspect") { viewModel.inspectEnteredLab() }
+                .disabled(!viewModel.canInspectLab)
+                .accessibilityIdentifier("btnGamutInspectLab")
+        }
+    }
+
+    // MARK: - TIFF sample sheet
+
+    private var tiffPreviewSheet: some View {
+        VStack(spacing: 12) {
+            Text("Click a pixel to sample its colour.")
+                .font(.headline)
+                .foregroundStyle(Theme.text)
+            if let png = viewModel.tiffPreviewPNG {
+                TiffSampleImageView(pngData: png) { r, g, b in
+                    viewModel.sampleTiffPixel(r: r, g: g, b: b)
+                }
+                .frame(minWidth: 320, minHeight: 240)
+            }
+            HStack {
+                Spacer()
+                Button("Cancel") { viewModel.showingTiffPreview = false }
+                    .accessibilityIdentifier("btnCloseGamutTiffPreview")
+            }
+        }
+        .padding(16)
+        .background(Theme.background)
+        .accessibilityElement(children: .contain)
+        .accessibilityIdentifier("gamutTiffPreview")
     }
 }
 
-/// `NSViewRepresentable` wrapper around an `SCNView` that builds the scene from
+/// `NSViewRepresentable` wrapper around an `SCNView` rendering one node
-/// one or two ``GamutMesh`` values.
+/// per ``NamedGamut`` layer.
 ///
-/// Scene construction and camera reset are coordinated through a typed callback
+/// Layer toggles hide/show `SCNNode`s — the scene is built once and the
-/// binding owned by the view model.
+/// camera is only reset through the explicit reset path, never on a
+/// mesh or visibility update.
 private struct GamutSceneView: NSViewRepresentable {
-    var profileMesh: GamutMesh?
+    var layers: [NamedGamut]
-    var referenceMesh: GamutMesh?
+    var visibleIDs: Set<String>
     var onReset: Binding<() -> Void>
     var onPause: Binding<() -> Void>
+    var onUnavailable: () -> Void
+    var onInspect: (SIMD3<Float>, String?) -> Void
 
     func makeNSView(context: Context) -> SCNView {
         let scnView = SCNView()
@@ -142,14 +371,23 @@ private struct GamutSceneView: NSViewRepresentable {
 
         context.coordinator.scnView = scnView
         context.coordinator.scene = scene
-        context.coordinator.buildScene(profile: profileMesh, reference: referenceMesh)
+        context.coordinator.onInspect = onInspect
+        context.coordinator.buildSceneOnce()
+        context.coordinator.syncLayers(layers, visibleIDs: visibleIDs)
         context.coordinator.installKeyMonitor()
+        context.coordinator.installClickGesture()
+
+        // No GPU → the docs/18 fallback; never respawn the view in a loop.
+        if MTLCreateSystemDefaultDevice() == nil {
+            DispatchQueue.main.async { onUnavailable() }
+        }
 
         return scnView
     }
 
     func updateNSView(_ nsView: SCNView, context: Context) {
-        context.coordinator.buildScene(profile: profileMesh, reference: referenceMesh)
+        context.coordinator.onInspect = onInspect
+        context.coordinator.syncLayers(layers, visibleIDs: visibleIDs)
     }
 
     func makeCoordinator() -> Coordinator {
@@ -165,6 +403,9 @@ private struct GamutSceneView: NSViewRepresentable {
 
     static func dismantleNSView(_ nsView: SCNView, coordinator: Coordinator) {
         coordinator.removeKeyMonitor()
+        if let click = coordinator.clickGesture {
+            nsView.removeGestureRecognizer(click)
+        }
         nsView.isPlaying = false
     }
 
@@ -172,11 +413,14 @@ private struct GamutSceneView: NSViewRepresentable {
     final class Coordinator: NSObject {
         weak var scnView: SCNView?
         weak var scene: SCNScene?
+        var onInspect: (SIMD3<Float>, String?) -> Void = { _, _ in }
+        private(set) var clickGesture: NSClickGestureRecognizer?
         private var keyMonitor: Any?
 
-        private let profileNode = SCNNode()
+        /// One `SCNNode` per loaded layer, keyed by `NamedGamut.id`.
-        private let referenceGroup = SCNNode()
+        private var layerNodes: [String: SCNNode] = [:]
         private let axisNode = SCNNode()
+        private let layerGroup = SCNNode()
         private let cameraNode: SCNNode = {
             let node = SCNNode()
             node.camera = SCNCamera()
@@ -184,33 +428,97 @@ private struct GamutSceneView: NSViewRepresentable {
             return node
         }()
 
-        func buildScene(profile: GamutMesh?, reference: GamutMesh?) {
+        /// Builds the static scene furniture exactly once — axis
-            guard let scene else { return }
+        /// scaffold, lights, camera home. Layer content lives under
+        /// `layerGroup` and is managed by `syncLayers`.
+        func buildSceneOnce() {
+            guard let scene, scene.rootNode.childNodes.isEmpty else { return }
 
-            // Rebuild from scratch on every mesh change to avoid stale geometry.
-            scene.rootNode.childNodes.forEach { $0.removeFromParentNode() }
             scene.rootNode.addChildNode(axisNode)
-            scene.rootNode.addChildNode(profileNode)
+            scene.rootNode.addChildNode(layerGroup)
-            scene.rootNode.addChildNode(referenceGroup)
             scene.rootNode.addChildNode(cameraNode)
 
             buildAxisScaffold()
-
-            if let profile {
-                profileNode.addChildNode(profileMeshNode(profile, name: "profile"))
-            } else {
-                profileNode.childNodes.forEach { $0.removeFromParentNode() }
-            }
-
-            if let reference {
-                referenceGroup.childNodes.forEach { $0.removeFromParentNode() }
-                referenceGroup.addChildNode(referenceMeshNode(reference))
-            }
-
             addLights(to: scene)
             resetCamera()
         }
 
+        /// Reconciles the node set with `layers` and `visibleIDs`.
+        ///
+        /// New layers get a node; removed layers lose theirs; hidden
+        /// layers keep their mesh (`isHidden` only). Never rebuilds the
+        /// scene, so the camera is untouched by a checkbox toggle.
+        func syncLayers(_ layers: [NamedGamut], visibleIDs: Set<String>) {
+            guard scene != nil else { return }
+            let wanted = Set(layers.map { $0.id })
+            for (id, node) in layerNodes where !wanted.contains(id) {
+                node.removeFromParentNode()
+                layerNodes.removeValue(forKey: id)
+            }
+            for layer in layers {
+                if layerNodes[layer.id] == nil {
+                    let node = makeLayerNode(for: layer)
+                    layerNodes[layer.id] = node
+                    layerGroup.addChildNode(node)
+                }
+                layerNodes[layer.id]?.isHidden = !visibleIDs.contains(layer.id)
+            }
+        }
+
+        private func makeLayerNode(for layer: NamedGamut) -> SCNNode {
+            let node: SCNNode
+            switch layer.role {
+            case .reference:
+                node = referenceMeshNode(layer.mesh)
+            case .profileA:
+                node = profileMeshNode(layer.mesh)
+            case .profileB:
+                node = compareMeshNode(layer.mesh)
+            }
+            node.name = layer.id
+            return node
+        }
+
+        // MARK: - Click inspect (#147)
+
+        /// Click (not drag) hit-tests the scene. `NSClickGestureRecognizer`
+        /// only fires on a press+release in place, so orbit drags are
+        /// untouched.
+        func installClickGesture() {
+            guard let scnView, clickGesture == nil else { return }
+            let gesture = NSClickGestureRecognizer(target: self, action: #selector(handleClick(_:)))
+            scnView.addGestureRecognizer(gesture)
+            clickGesture = gesture
+        }
+
+        @objc private func handleClick(_ gesture: NSClickGestureRecognizer) {
+            guard let scnView else { return }
+            let point = gesture.location(in: scnView)
+            for hit in scnView.hitTest(point, options: nil) {
+                if let layerID = layerID(for: hit.node) {
+                    let world = hit.worldCoordinates
+                    onInspect(
+                        SIMD3<Float>(Float(world.x), Float(world.y), Float(world.z)),
+                        layerID)
+                    return
+                }
+            }
+            // Axis scaffold / empty background → back to idle.
+            onInspect(.zero, nil)
+        }
+
+        /// Walks the hit node's ancestor chain looking for a layer node.
+        private func layerID(for node: SCNNode) -> String? {
+            var current: SCNNode? = node
+            while let node = current {
+                if let name = node.name, layerNodes[name] != nil { return name }
+                current = node.parent
+            }
+            return nil
+        }
+
+        // MARK: - Scene furniture (unchanged from #28)
+
         private func addLights(to scene: SCNScene) {
             let ambient = SCNNode()
             ambient.light = SCNLight()
@@ -351,7 +659,8 @@ private struct GamutSceneView: NSViewRepresentable {
             return SCNNode(geometry: geometry)
         }
 
-        private func profileMeshNode(_ mesh: GamutMesh, name: String) -> SCNNode {
+        /// Profile A: solid vertex-coloured surface.
+        private func profileMeshNode(_ mesh: GamutMesh) -> SCNNode {
             let (geometry, _) = scnGeometry(for: mesh)
 
             let material = SCNMaterial()
@@ -361,11 +670,26 @@ private struct GamutSceneView: NSViewRepresentable {
             material.isDoubleSided = true
             geometry.materials = [material]
 
-            let node = SCNNode(geometry: geometry)
+            return SCNNode(geometry: geometry)
-            node.name = name
-            return node
         }
 
+        /// Compare profile B: same vertex colours at ~30 % opacity so
+        /// overlaps with A and the sRGB reference stay readable.
+        private func compareMeshNode(_ mesh: GamutMesh) -> SCNNode {
+            let (geometry, _) = scnGeometry(for: mesh)
+
+            let material = SCNMaterial()
+            material.lightingModel = .lambert
+            material.diffuse.contents = NSColor.white
+            material.transparency = 0.30
+            material.isDoubleSided = true
+            material.writesToDepthBuffer = false
+            geometry.materials = [material]
+
+            return SCNNode(geometry: geometry)
+        }
+
+        /// Bundled sRGB reference: faint fill + structural edge lines.
         private func referenceMeshNode(_ mesh: GamutMesh) -> SCNNode {
             let (geometry, _) = scnGeometry(for: mesh)
 
@@ -488,3 +812,81 @@ private struct GamutSceneView: NSViewRepresentable {
         }
     }
 }
+
+/// Click-to-sample image view for the TIFF preview sheet (#147).
+///
+/// The TIFF is already decoded to PNG on the host side (#58); the view
+/// reports 8-bit sRGB pixel values at the clicked point — the Lab
+/// conversion is the documented approximate matrix helper, not a CMM.
+private struct TiffSampleImageView: NSViewRepresentable {
+    let pngData: Data
+    var onSample: (Int, Int, Int) -> Void
+
+    func makeNSView(context: Context) -> TiffSampleNSView {
+        let view = TiffSampleNSView()
+        view.image = NSImage(data: pngData)
+        view.onSample = onSample
+        return view
+    }
+
+    func updateNSView(_ nsView: TiffSampleNSView, context: Context) {
+        nsView.onSample = onSample
+    }
+}
+
+private final class TiffSampleNSView: NSView {
+    var image: NSImage? {
+        didSet {
+            bitmapRep = image?.cgImage(forProposedRect: nil, context: nil, hints: nil)
+                .flatMap { NSBitmapImageRep(cgImage: $0) }
+            invalidateIntrinsicContentSize()
+            needsDisplay = true
+        }
+    }
+    var onSample: ((Int, Int, Int) -> Void)?
+    private var bitmapRep: NSBitmapImageRep?
+
+    override var intrinsicContentSize: NSSize {
+        image?.size ?? NSSize(width: 320, height: 240)
+    }
+
+    override var acceptsFirstResponder: Bool { true }
+
+    override func draw(_ dirtyRect: NSRect) {
+        NSColor(red: 0.055, green: 0.055, blue: 0.078, alpha: 1).setFill()
+        dirtyRect.fill()
+        guard let image else { return }
+        image.draw(in: imageRect())
+    }
+
+    override func mouseUp(with event: NSEvent) {
+        guard let rep = bitmapRep else { return }
+        let rect = imageRect()
+        let location = convert(event.locationInWindow, from: nil)
+        guard rect.contains(location), rect.width > 0, rect.height > 0 else { return }
+
+        let x = Int((location.x - rect.minX) / rect.width * CGFloat(rep.pixelsWide))
+        // This view is not flipped: y grows up, bitmap rows grow down.
+        let y = rep.pixelsHigh - 1
+            - Int((location.y - rect.minY) / rect.height * CGFloat(rep.pixelsHigh))
+        guard x >= 0, x < rep.pixelsWide, y >= 0, y < rep.pixelsHigh else { return }
+
+        guard let color = rep.colorAt(x: x, y: y)?.usingColorSpace(.sRGB) else { return }
+        onSample?(
+            Int((color.redComponent * 255).rounded()),
+            Int((color.greenComponent * 255).rounded()),
+            Int((color.blueComponent * 255).rounded()))
+    }
+
+    /// Aspect-fit rect of the image inside `bounds`.
+    private func imageRect() -> NSRect {
+        guard let image, image.size.width > 0, image.size.height > 0 else { return .zero }
+        let scale = min(bounds.width / image.size.width, bounds.height / image.size.height)
+        let size = NSSize(width: image.size.width * scale, height: image.size.height * scale)
+        return NSRect(
+            x: (bounds.width - size.width) / 2,
+            y: (bounds.height - size.height) / 2,
+            width: size.width,
+            height: size.height)
+    }
+}

Sources/ICCery/GamutViewModel.swift

@@ -1,53 +1,303 @@
 import Combine
 import Foundation
 import ICCeryCore
+import simd
 
-/// View model for the native SceneKit gamut viewer.
+/// View model for the native SceneKit gamut viewer (issues #28, #147).
 ///
-/// Loads the bundled `sRGB.gam` reference immediately and, optionally, a
+/// Loads the bundled `sRGB.gam` reference immediately, the workflow's own
-/// printer/profile `.gam` from the current working directory.
+/// profile `.gam` when one exists, and an optional compare mesh the user
+/// adds from the sheet toolbar. `iccgamut` failure is an in-sheet info
+/// notice, never fatal (#24).
 @MainActor
 final class GamutViewModel: ObservableObject {
 
-    /// Parsed reference sRGB gamut mesh.
+    /// Stable layer ids — also the `gamutLayer-<id>` a11y suffixes.
-    @Published var sRGBMesh: GamutMesh?
+    static let srgbLayerID = "sRGB"
+    static let profileLayerID = "profile"
+    static let compareLayerID = "compare"
 
-    /// Parsed printer/profile gamut mesh.
+    /// Loaded meshes: bundled sRGB plus up to two profiles.
-    @Published var profileMesh: GamutMesh?
+    @Published var layers: [NamedGamut] = []
 
-    /// User-facing status line.
+    /// Layer ids currently shown in the scene. Toggling never unloads
+    /// the mesh — the `SCNNode` is hidden only.
+    @Published var visibleIDs: Set<String> = [srgbLayerID]
+
+    /// User-facing status line (`gamutStatusText`). Always non-empty
+    /// once set — `Milestone6GamutUITests` asserts it.
     @Published var status = "Loading gamut…"
 
+    /// In-sheet info line (`gamutNoticeText`). The main `NoticeBanner`
+    /// sits behind the sheet, so notices surface here instead.
+    @Published var noticeText: String?
+
+    /// Set when `SCNView` cannot create a render context; the scene is
+    /// replaced by the docs/18 fallback text (`gamutViewerUnavailable`).
+    @Published var viewerUnavailable = false
+
     /// Closure injected into the SceneKit view to request a camera reset.
     @Published var resetCamera: () -> Void = {}
 
-    private let profileGamURL: URL?
+    // MARK: - Inspect panel
 
-    init(profileGamURL: URL? = nil) {
+    /// Lab point currently inspected, or `nil` for the idle state.
+    @Published var inspectLab: LabColor?
+
+    /// Swatch colour: the hit vertex's `rgb`, or the approximate sRGB of
+    /// the inspected Lab.
+    @Published var inspectSwatch: DisplayRGB?
+
+    /// `true` when the swatch/Lab came from the approximate helper or a
+    /// typed value — drives the "approx. Lab, not ColorSync" caption.
+    @Published var inspectIsApproximate = false
+
+    /// Per-layer containment for `inspectLab`, in layer order.
+    @Published var inspectResults: [(id: String, name: String, containment: GamutContainment)] = []
+
+    /// Manual Lab entry fields (`gamutLabEntry*`).
+    @Published var labEntryL = ""
+    @Published var labEntryA = ""
+    @Published var labEntryB = ""
+
+    // MARK: - TIFF sampling
+
+    /// PNG bytes for the preview sheet (`gamutTiffPreview`).
+    @Published var tiffPreviewPNG: Data?
+    @Published var showingTiffPreview = false
+
+    private let environment: AppEnvironment
+    private let profileGamURL: URL?
+    private let fileDialogs = FileDialogService.shared
+
+    init(environment: AppEnvironment, profileGamURL: URL? = nil) {
+        self.environment = environment
         self.profileGamURL = profileGamURL
-        Task { await load() }
+        loadTask = Task { await load() }
     }
 
+    private var loadTask: Task<Void, Never>?
+
+    /// Awaits the initial sRGB/profile load — used by tests.
+    func awaitInitialLoad() async {
+        await loadTask?.value
+    }
+
+    func layer(id: String) -> NamedGamut? {
+        layers.first { $0.id == id }
+    }
+
+    // MARK: - Initial load
+
     private func load() async {
         do {
-            let referenceURL = BinaryResolver().referenceGamut("sRGB")
+            let referenceURL = environment.runner.binaryResolver.referenceGamut("sRGB")
             let reference = try await parse(url: referenceURL)
-            sRGBMesh = reference
+            layers.append(NamedGamut(
-
+                id: Self.srgbLayerID,
-            if let profileGamURL {
+                displayName: "sRGB",
-                let profile = try await parse(url: profileGamURL)
+                role: .reference,
-                profileMesh = profile
+                mesh: reference,
-                status = "Profile gamut (\(profile.faces.count) faces) vs sRGB reference"
+                sourceURL: referenceURL))
-            } else {
+            visibleIDs.insert(Self.srgbLayerID)
-                status = "sRGB reference gamut (\(reference.faces.count) faces)"
-            }
         } catch {
             status = "Could not load gamut: \(error.localizedDescription)"
+            return
+        }
+
+        if let profileGamURL {
+            do {
+                let profile = try await parse(url: profileGamURL)
+                layers.append(NamedGamut(
+                    id: Self.profileLayerID,
+                    displayName: profileGamURL.deletingPathExtension().lastPathComponent,
+                    role: .profileA,
+                    mesh: profile,
+                    sourceURL: profileGamURL))
+                visibleIDs.insert(Self.profileLayerID)
+            } catch {
+                // #24 — a missing/unparseable profile mesh is info, not fatal.
+                noticeText = "Profile gamut could not be loaded: \(error.localizedDescription)"
+            }
+        }
+        refreshStatus()
+    }
+
+    // MARK: - Compare slot (profile B)
+
+    /// `btnGamutOpenGam` — pick an existing `.gam` for the compare slot.
+    func openCompareGam() {
+        let url = UITestHooks.isEnabled
+            ? UITestHooks.gamutFileURL
+            : fileDialogs.selectGamutFile()
+        guard let url else { return }
+        Task { await loadCompareGam(url: url) }
+    }
+
+    /// `btnGamutOpenProfile` — pick `.icc/.icm`; uses a sibling `.gam`
+    /// when present, otherwise runs bundled `iccgamut -v -d 10` (#24).
+    func openCompareProfile() {
+        let url = UITestHooks.isEnabled
+            ? UITestHooks.gamutProfileURL
+            : fileDialogs.selectProfileFile()
+        guard let url else { return }
+        Task { await loadCompareProfile(url: url) }
+    }
+
+    /// `btnGamutRemoveCompare` — drops layer B, leaves sRGB + A.
+    func removeCompare() {
+        layers.removeAll { $0.id == Self.compareLayerID }
+        visibleIDs.remove(Self.compareLayerID)
+        refreshStatus()
+    }
+
+    /// Parses `url` into the compare slot. Internal for tests — the UI
+    /// reaches it through `openCompareGam` / `openCompareProfile`.
+    func loadCompareGam(url: URL) async {
+        do {
+            let mesh = try await parse(url: url)
+            installCompare(NamedGamut(
+                id: Self.compareLayerID,
+                displayName: url.deletingPathExtension().lastPathComponent,
+                role: .profileB,
+                mesh: mesh,
+                sourceURL: url))
+        } catch {
+            noticeText = "Could not load compare gamut: \(error.localizedDescription)"
         }
     }
 
-    /// Parses a `.gam` file off the main actor so large meshes do not stall
+    /// `.icc/.icm` → sibling `.gam` or `iccgamut` → compare slot.
-    /// the UI.
+    /// Internal for tests.
+    func loadCompareProfile(url: URL) async {
+        let gamURL = url.deletingPathExtension().appendingPathExtension("gam")
+        do {
+            if !FileManager.default.fileExists(atPath: gamURL.path) {
+                _ = try await environment.runner.runIccgamut(
+                    config: IccgamutConfig(profileURL: url))
+            }
+            await loadCompareGam(url: gamURL)
+        } catch {
+            noticeText = "Gamut extraction failed: \(error.localizedDescription)"
+        }
+    }
+
+    /// A third profile replaces B — the compare slot never stacks and
+    /// sRGB is never touched.
+    private func installCompare(_ gamut: NamedGamut) {
+        if layers.contains(where: { $0.id == gamut.id }) {
+            noticeText = "Compare slot holds one profile. The previous compare mesh was replaced."
+        }
+        layers.removeAll { $0.id == gamut.id }
+        layers.append(gamut)
+        visibleIDs.insert(gamut.id)
+        refreshStatus()
+    }
+
+    // MARK: - Status line
+
+    /// `sRGB 448v / 892 faces · Profile 1024v / 2048 faces · vol 62% of sRGB`.
+    /// Unloaded layers are omitted; the volume clause appears only when
+    /// both volumes are finite and positive.
+    private func refreshStatus() {
+        var clauses = layers.map {
+            "\($0.displayName) \($0.mesh.vertices.count)v / \($0.mesh.faces.count) faces"
+        }
+        if let srgb = layer(id: Self.srgbLayerID),
+           let profile = layer(id: Self.profileLayerID) {
+            let srgbVolume = GamutGeometry.volume(of: srgb.mesh)
+            let profileVolume = GamutGeometry.volume(of: profile.mesh)
+            if srgbVolume.isFinite, srgbVolume > 0,
+               profileVolume.isFinite, profileVolume > 0 {
+                clauses.append("vol \(Int((profileVolume / srgbVolume * 100).rounded()))% of sRGB")
+            }
+        }
+        status = clauses.isEmpty ? "No gamut loaded" : clauses.joined(separator: " · ")
+    }
+
+    // MARK: - Inspect
+
+    /// Whether every manual Lab field parses as a number; the Inspect
+    /// button is disabled while this is false.
+    var canInspectLab: Bool {
+        [labEntryL, labEntryA, labEntryB].allSatisfy { Double($0) != nil }
+    }
+
+    /// Runs containment for a Lab point and publishes the inspect row.
+    func inspect(lab: LabColor, swatch: DisplayRGB?, isApproximate: Bool) {
+        inspectLab = lab
+        inspectSwatch = swatch ?? LabColorMath.labToSRGB(lab)
+        inspectIsApproximate = isApproximate
+        inspectResults = layers.map {
+            ($0.id, $0.displayName, GamutGeometry.containment(of: lab, in: $0.mesh))
+        }
+    }
+
+    /// Click on the axis scaffold or empty background returns the panel
+    /// to idle.
+    func clearInspect() {
+        inspectLab = nil
+        inspectSwatch = nil
+        inspectIsApproximate = false
+        inspectResults = []
+    }
+
+    /// SceneKit hit callback: world `(x, y, z)` → Lab `(x→a*, y→L*, z→b*)`.
+    /// The swatch is the nearest vertex colour of the hit layer's mesh.
+    func inspectSceneHit(world: SIMD3<Float>, layerID: String) {
+        let lab = LabColor(l: Double(world.y), a: Double(world.x), b: Double(world.z))
+        var swatch: DisplayRGB?
+        var approximate = true
+        if let mesh = layer(id: layerID)?.mesh,
+           let nearest = mesh.vertices.min(by: {
+               simd_distance($0.position, world) < simd_distance($1.position, world)
+           }) {
+            swatch = nearest.rgb
+            approximate = false
+        }
+        inspect(lab: lab, swatch: swatch, isApproximate: approximate)
+    }
+
+    /// `btnGamutInspectLab` — typed L*a*b* path. No clamping; out-of-axis
+    /// values still run containment and report `?` outside every hull.
+    func inspectEnteredLab() {
+        guard let l = Double(labEntryL),
+              let a = Double(labEntryA),
+              let b = Double(labEntryB) else { return }
+        inspect(lab: LabColor(l: l, a: a, b: b), swatch: nil, isApproximate: true)
+    }
+
+    // MARK: - TIFF sampling
+
+    /// `btnGamutSampleTiff` — pick a target TIFF, decode a host-side PNG
+    /// preview (#58), and open the click-to-sample sheet.
+    func openTiffSample() {
+        let url = UITestHooks.isEnabled
+            ? UITestHooks.gamutTiffURL
+            : fileDialogs.selectTiffFile()
+        guard let url else { return }
+        guard let png = TiffPreview.previewPNG(tiff: url) else {
+            noticeText = "Could not decode TIFF preview."
+            return
+        }
+        tiffPreviewPNG = png
+        showingTiffPreview = true
+    }
+
+    /// Pixel tap inside the preview sheet: sRGB8 → approximate Lab D50.
+    func sampleTiffPixel(r: Int, g: Int, b: Int) {
+        inspect(
+            lab: ApproximateLab.srgb8ToLab(r: r, g: g, b: b),
+            swatch: DisplayRGB(
+                r: Double(r) / 255.0,
+                g: Double(g) / 255.0,
+                b: Double(b) / 255.0),
+            isApproximate: true)
+        showingTiffPreview = false
+    }
+
+    /// Parses a `.gam` file off the main actor so large meshes do not
+    /// stall the UI.
     private func parse(url: URL) async throws -> GamutMesh {
         try await Task.detached {
             try GamutMeshParser.parse(url: url)

Sources/ICCery/RootView.swift

@@ -67,6 +67,14 @@ struct RootView: View {
         ) {
             ManageMediaDialog(workflow: workflow)
         }
+        // Spot-read console sheet (issue #148). Dismiss runs the same
+        // `q\n` + ~500 ms + kill path as the sheet's Stop button.
+        .sheet(
+            isPresented: $workflow.showingSpotRead,
+            onDismiss: { workflow.spotRead.sheetClosed() }
+        ) {
+            SpotReadView(model: workflow.spotRead)
+        }
         .sheet(isPresented: $showingAbout) {
             AboutView { showingAbout = false }
         }
@@ -74,7 +82,10 @@ struct RootView: View {
             get: { workflow.wizard.showingGamutViewer },
             set: { workflow.wizard.showingGamutViewer = $0 }
         )) {
-            GamutView(profileGamURL: workflow.wizard.gamutProfileURL)
+            GamutView(
+                environment: workflow.environment,
+                profileGamURL: workflow.wizard.gamutProfileURL,
+                showingAllHelp: $showingAllHelp)
         }
     }
 

Sources/ICCery/SettingsView.swift

@@ -58,7 +58,7 @@ struct SettingsView: View {
                             Text($0.label).tag($0.code)
                         }
                     }
-                    Text("Display-only — Stage 2's instrument select is used for actual runs.")
+                    Text("Seeds Spot Read and Stage 3 when the instrument is plugged in. printtarg -i is still chosen on Stage 2.")
                         .font(.caption)
                         .foregroundStyle(.secondary)
 

Sources/ICCery/SidebarView.swift

@@ -11,6 +11,7 @@ struct SidebarView: View {
     @ObservedObject private var profile: ProfileWorkflowViewModel
     @ObservedObject private var media: MediaLibraryViewModel
     @ObservedObject private var printSession: PrintSessionViewModel
+    @ObservedObject private var measurement: MeasurementWorkflowViewModel
     var onOpenSettings: () -> Void
     var onOpenAbout: () -> Void
     @Binding var showingAllHelp: Bool
@@ -26,6 +27,7 @@ struct SidebarView: View {
         self._profile = ObservedObject(wrappedValue: workflow.profile)
         self._media = ObservedObject(wrappedValue: workflow.media)
         self._printSession = ObservedObject(wrappedValue: workflow.print)
+        self._measurement = ObservedObject(wrappedValue: workflow.measurement)
         self.onOpenSettings = onOpenSettings
         self.onOpenAbout = onOpenAbout
         self._showingAllHelp = showingAllHelp
@@ -158,9 +160,32 @@ struct SidebarView: View {
                     .frame(maxWidth: .infinity)
             }
             .controlSize(.large)
+            .helpOverlay(
+                "View the profile gamut in 3D against sRGB.",
+                showing: $showingAllHelp)
             .accessibilityIdentifier("btnViewGamut")
             .padding(.horizontal, 12)
 
+            // Spot Read sheet (`#btnSpotRead`) — issue #148. Enabled
+            // only with a working folder (#59) and while no Stage 3
+            // chartread child is live; opening never kills
+            // `chartread_{basename}`.
+            Button(action: { workflow.showingSpotRead = true }) {
+                Label("Spot Read", systemImage: "eyedropper")
+                    .frame(maxWidth: .infinity)
+            }
+            .controlSize(.large)
+            .disabled(model.workingDirectory == nil || measurement.isChartreadRunning)
+            .helpOverlay(
+                model.workingDirectory == nil
+                    ? "Set a working folder in Stage 1 first."
+                    : (measurement.isChartreadRunning
+                        ? "Stop the Stage 3 chart read first."
+                        : "Read a single patch as Lab/XYZ from the instrument."),
+                showing: $showingAllHelp)
+            .accessibilityIdentifier("btnSpotRead")
+            .padding(.horizontal, 12)
+
             Divider().overlay(Theme.border)
                 .padding(.vertical, 8)
 

Sources/ICCery/SpotReadView.swift

@@ -0,0 +1,360 @@
+import SwiftUI
+import ICCeryCore
+
+/// Spot Read sheet (issue #148) — one patch Lab/XYZ from the live
+/// instrument. A `RootView` sheet, not a wizard stage and not a Stage 3
+/// tab; all identifiers are `spot*` — Stage 3 `chartread` ids are never
+/// reused here.
+struct SpotReadView: View {
+    @ObservedObject var model: SpotReadViewModel
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 12) {
+            header
+            if !model.sidecarAvailable {
+                missingSidecar
+            } else {
+                ScrollView {
+                    VStack(alignment: .leading, spacing: 12) {
+                        instrumentCard
+                        promptLine
+                        transport
+                        lastSampleCard
+                        historySection
+                    }
+                }
+            }
+            footer
+        }
+        .padding(16)
+        .frame(width: 560, height: 640)
+        .background(Theme.background)
+        .accessibilityElement(children: .contain)
+        .accessibilityIdentifier("spotReadView")
+        .onAppear { model.sheetOpened() }
+        .onDisappear { model.sheetClosed() }
+    }
+
+    // MARK: - Header / missing sidecar
+
+    private var header: some View {
+        HStack(alignment: .firstTextBaseline) {
+            Text("Spot Read")
+                .font(.title3)
+                .foregroundStyle(Theme.text)
+            Spacer()
+            if model.isRunning {
+                ProgressView()
+                    .scaleEffect(0.8)
+            }
+        }
+    }
+
+    private var missingSidecar: some View {
+        VStack(alignment: .leading, spacing: 12) {
+            Text("spotread sidecar missing — run fetch-argyll")
+                .foregroundStyle(Theme.text)
+                .accessibilityIdentifier("spotSidecarMissing")
+            Spacer()
+        }
+    }
+
+    // MARK: - Instrument card (clones Stage 3 look, own ids)
+
+    private var instrumentCard: some View {
+        VStack(alignment: .leading, spacing: 10) {
+            HStack {
+                Text("Instrument")
+                    .font(.headline)
+                    .foregroundStyle(Theme.text)
+                Spacer()
+                Button(action: { model.detectInstruments() }) {
+                    Image(systemName: "arrow.clockwise")
+                }
+                .disabled(!model.canDetect)
+                .accessibilityIdentifier("btnSpotDetectInstruments")
+            }
+
+            if let error = model.detectionError {
+                Text(error)
+                    .font(.caption)
+                    .foregroundStyle(.red)
+                    .accessibilityIdentifier("spotDetectError")
+            }
+
+            Picker("Instrument", selection: Binding(
+                get: { instrumentTag },
+                set: { newTag in
+                    if newTag.isEmpty {
+                        model.selectedInstrument = .auto
+                    } else if let device = model.instruments.first(where: { "\($0.port)" == newTag }) {
+                        model.selectedInstrument = .device(device)
+                    }
+                }
+            )) {
+                Text("Auto (first available port)").tag("")
+                ForEach(model.instruments) { device in
+                    Text(device.displayName).tag("\(device.port)")
+                }
+            }
+            .pickerStyle(.menu)
+            .disabled(model.isRunning)
+            .accessibilityIdentifier("spotInstrumentSelect")
+
+            if model.defaultMissing {
+                Text("Saved default instrument not present")
+                    .font(.caption)
+                    .foregroundStyle(.orange)
+                    .accessibilityIdentifier("spotDefaultMissing")
+            }
+
+            Toggle("Also set as default instrument", isOn: Binding(
+                get: { model.setAsDefault },
+                set: { model.applyDefaultToggle($0) }
+            ))
+            .accessibilityIdentifier("spotSetDefault")
+
+            if model.selectedInstrument.isXY {
+                Text("XY tables use Stage 3. Spot Read is a handheld / reflective probe.")
+                    .font(.caption)
+                    .foregroundStyle(Theme.accent)
+                    .accessibilityIdentifier("spotXYHint")
+            }
+        }
+        .padding(16)
+        .background(Theme.panel)
+    }
+
+    private var instrumentTag: String {
+        switch model.selectedInstrument {
+        case .auto:
+            return ""
+        case .device(let device):
+            return "\(device.port)"
+        }
+    }
+
+    // MARK: - Prompt line
+
+    private var promptLine: some View {
+        VStack(alignment: .leading, spacing: 6) {
+            HStack {
+                Text("Status")
+                    .font(.headline)
+                    .foregroundStyle(Theme.text)
+                Spacer()
+                Text(model.prompt)
+                    .font(.callout)
+                    .foregroundStyle(Theme.text)
+                    .accessibilityIdentifier("spotPrompt")
+            }
+            if let error = model.lastError {
+                Text(error)
+                    .font(.caption)
+                    .foregroundStyle(.red)
+                    .accessibilityIdentifier("spotLastError")
+                    .accessibilityValue(error)
+            }
+            if !model.log.isEmpty {
+                ProcessLogView(
+                    lines: model.log,
+                    minHeight: 60,
+                    maxHeight: 100,
+                    containerId: "spotLogContainer",
+                    logId: "spotLog"
+                )
+            }
+        }
+        .padding(16)
+        .background(Theme.panel)
+    }
+
+    // MARK: - Transport
+
+    private var transport: some View {
+        HStack(spacing: 12) {
+            if !model.isRunning {
+                Button("Start") { model.start() }
+                    .disabled(!model.canStart)
+                    .accessibilityIdentifier("btnSpotStart")
+            } else {
+                switch model.state {
+                case .calibrating:
+                    Button("Calibrate") { model.calibrate() }
+                        .accessibilityIdentifier("btnSpotCalibrate")
+                case .awaitingStrip:
+                    Button("Read") { model.trigger() }
+                        .accessibilityIdentifier("btnSpotTrigger")
+                default:
+                    EmptyView()
+                }
+                Button("Stop") { model.stopIfNeeded() }
+                    .accessibilityIdentifier("btnSpotStop")
+            }
+            Spacer()
+        }
+        .padding(.horizontal, 4)
+    }
+
+    // MARK: - Last sample
+
+    @ViewBuilder
+    private var lastSampleCard: some View {
+        VStack(alignment: .leading, spacing: 8) {
+            Text("Last sample")
+                .font(.headline)
+                .foregroundStyle(Theme.text)
+
+            if let sample = model.displayedSample {
+                HStack(spacing: 16) {
+                    let rgb = LabColorMath.labToSRGB(sample.lab)
+                    RoundedRectangle(cornerRadius: 4)
+                        .fill(Color(red: rgb.r, green: rgb.g, blue: rgb.b))
+                        .frame(width: 32, height: 32)
+                        .overlay(RoundedRectangle(cornerRadius: 4).stroke(Theme.border))
+                        .accessibilityIdentifier("spotSwatch")
+
+                    VStack(alignment: .leading, spacing: 2) {
+                        HStack(spacing: 12) {
+                            Text(String(format: "L* %.1f", sample.lab.l))
+                                .accessibilityIdentifier("spotLabL")
+                            Text(String(format: "a* %.1f", sample.lab.a))
+                                .accessibilityIdentifier("spotLabA")
+                            Text(String(format: "b* %.1f", sample.lab.b))
+                                .accessibilityIdentifier("spotLabB")
+                        }
+                        .font(.callout)
+                        .foregroundStyle(Theme.text)
+
+                        if let xyz = sample.xyz {
+                            Text(String(format: "XYZ %.2f %.2f %.2f", xyz.x, xyz.y, xyz.z))
+                                .font(.caption)
+                                .foregroundStyle(.secondary)
+                                .accessibilityIdentifier("spotXYZ")
+                        }
+
+                        HStack(spacing: 8) {
+                            Text(sample.port.map { "\(sample.instrumentName) · port \($0)" }
+                                 ?? sample.instrumentName)
+                                .font(.caption)
+                                .foregroundStyle(.secondary)
+                                .accessibilityIdentifier("spotLastInstrument")
+
+                            if let de = model.displayedDeltaE {
+                                HStack(spacing: 6) {
+                                    Circle()
+                                        .fill(deltaEColor)
+                                        .frame(width: 8, height: 8)
+                                    Text(String(format: "ΔE %.2f", de))
+                                        .font(.caption)
+                                        .foregroundStyle(.secondary)
+                                }
+                                .accessibilityElement(children: .contain)
+                                .accessibilityIdentifier("spotDeltaE")
+                            }
+                        }
+
+                        if model.isDisplayedLabImplausible {
+                            Text("Implausible L*")
+                                .font(.caption)
+                                .foregroundStyle(.orange)
+                                .accessibilityIdentifier("spotLabImplausible")
+                        }
+                    }
+                    Spacer()
+                }
+                .accessibilityElement(children: .contain)
+                .accessibilityIdentifier("spotLastSample")
+            } else {
+                Text("No readings yet.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                    .accessibilityIdentifier("spotLastEmpty")
+            }
+        }
+        .padding(16)
+        .background(Theme.panel)
+    }
+
+    private var deltaEColor: Color {
+        switch model.deltaEClassification {
+        case .good, nil: return .green
+        case .warning: return .orange
+        case .bad: return .red
+        }
+    }
+
+    // MARK: - History
+
+    @ViewBuilder
+    private var historySection: some View {
+        VStack(alignment: .leading, spacing: 8) {
+            Text("History")
+                .font(.headline)
+                .foregroundStyle(Theme.text)
+
+            if model.samples.isEmpty {
+                Text("No history.")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                    .accessibilityIdentifier("spotHistoryEmpty")
+            } else {
+                List {
+                    ForEach(Array(model.samples.enumerated()), id: \.element.id) { index, sample in
+                        historyRow(index: index, sample: sample)
+                    }
+                }
+                .frame(minHeight: 120)
+                .accessibilityIdentifier("spotHistoryTable")
+            }
+        }
+        .padding(16)
+        .background(Theme.panel)
+    }
+
+    private func historyRow(index: Int, sample: SpotReadSample) -> some View {
+        let previous = index + 1 < model.samples.count ? model.samples[index + 1] : nil
+        let deltaE = previous.map { ColorDifference.deltaE00($0.lab, sample.lab) }
+        return Button(action: { model.selectFromHistory(sample) }) {
+            HStack(spacing: 10) {
+                Text(sample.timestamp, style: .time)
+                    .frame(width: 70, alignment: .leading)
+                Text(String(format: "%.1f", sample.lab.l))
+                    .frame(width: 44, alignment: .trailing)
+                Text(String(format: "%.1f", sample.lab.a))
+                    .frame(width: 44, alignment: .trailing)
+                Text(String(format: "%.1f", sample.lab.b))
+                    .frame(width: 44, alignment: .trailing)
+                Text(deltaE.map { String(format: "%.2f", $0) } ?? "")
+                    .frame(width: 44, alignment: .trailing)
+                Text(sample.instrumentName)
+                    .lineLimit(1)
+                Spacer()
+            }
+            .font(.caption)
+            .foregroundStyle(Theme.text)
+            .contentShape(Rectangle())
+        }
+        .buttonStyle(.plain)
+        .accessibilityIdentifier("spotHistoryRow-\(sample.id.uuidString)")
+    }
+
+    // MARK: - Footer
+
+    private var footer: some View {
+        HStack(spacing: 12) {
+            Button("Copy Lab") { model.copyLab() }
+                .disabled(model.displayedSample == nil)
+                .accessibilityIdentifier("btnSpotCopyLab")
+            Button("Export CSV…") { model.exportCsv() }
+                .disabled(model.samples.isEmpty)
+                .accessibilityIdentifier("btnSpotExportCsv")
+            Spacer()
+            Button("Close") { dismiss() }
+                .keyboardShortcut(.cancelAction)
+                .accessibilityIdentifier("btnCloseSpotRead")
+        }
+        .padding(.top, 4)
+    }
+}

Sources/ICCery/SpotReadViewModel.swift

@@ -0,0 +1,420 @@
+import AppKit
+import Combine
+import Foundation
+import ICCeryCore
+
+/// Spot-read console state and interaction (issue #148).
+///
+/// Runs the bundled `spotread` sidecar under the single-lease process id
+/// `spotread`; Stage 3 `chartread` is untouched. `defaultInstrument`
+/// seeds the instrument picker on sheet open — it is never written into
+/// `printtarg -i` or `targen` argv (R15).
+@MainActor
+final class SpotReadViewModel: ObservableObject {
+
+    let workflow: TargetWorkflowViewModel
+    let environment: AppEnvironment
+    private let fileDialogs = FileDialogService.shared
+
+    // MARK: - Instrument card
+
+    @Published var instruments: [InstrumentDevice] = []
+    @Published var selectedInstrument: InstrumentSelection = .auto
+    @Published var isDetecting = false
+    @Published var detectionError: String?
+    /// `spotDefaultMissing` — set when `defaultInstrument` is saved but
+    /// no detected device matches it.
+    @Published var defaultMissing = false
+    /// `spotSetDefault` toggle state.
+    @Published var setAsDefault = false
+
+    // MARK: - Session
+
+    @Published var isRunning = false
+    @Published var state: ChartreadState = .idle
+    @Published var prompt = "Press Start to open the instrument."
+    @Published var lastError: String?
+    @Published var log: [String] = []
+
+    // MARK: - Samples / history (in-memory, cap 50, newest first)
+
+    @Published private(set) var samples: [SpotReadSample] = []
+    @Published private(set) var displayedSample: SpotReadSample?
+    @Published private(set) var displayedDeltaE: Double?
+
+    private let historyLimit = 50
+    private var streamTask: Task<Void, Never>?
+
+    init(workflow: TargetWorkflowViewModel, environment: AppEnvironment) {
+        self.workflow = workflow
+        self.environment = environment
+    }
+
+    // MARK: - Derived state
+
+    /// Whether the bundled `spotread` sidecar resolves to an executable.
+    /// `BinaryResolver` only — never `$PATH`, never `chartread`.
+    var sidecarAvailable: Bool {
+        let url = environment.runner.binaryResolver.resolve("spotread")
+        return environment.runner.binaryResolver.exists(url)
+    }
+
+    var isChartreadRunning: Bool { workflow.measurement.isChartreadRunning }
+
+    var canStart: Bool {
+        sidecarAvailable && !isDetecting && !isRunning && !isChartreadRunning
+            && workflow.wizard.effectiveWorkingDirectory != nil
+    }
+
+    var canDetect: Bool { !isDetecting && !isRunning }
+
+    var deltaEClassification: SwatchClassification? {
+        guard let de = displayedDeltaE else { return nil }
+        let settings = environment.settingsStore.load()
+        return ColorDifference.classify(
+            deltaE: de,
+            goodMax: settings.deltaEGoodMax,
+            warningMax: settings.deltaEWarningMax)
+    }
+
+    /// `spotLabImplausible` — L* outside 0…100 still displays, unclamped.
+    var isDisplayedLabImplausible: Bool {
+        guard let l = displayedSample?.lab.l else { return false }
+        return l < 0 || l > 100
+    }
+
+    // MARK: - Sheet lifecycle
+
+    /// Called from `SpotReadView.onAppear`. Resets the in-memory session
+    /// and runs detection once; a missing sidecar gets a wizard notice.
+    func sheetOpened() {
+        samples = []
+        displayedSample = nil
+        displayedDeltaE = nil
+        log = []
+        lastError = nil
+        state = .idle
+        prompt = "Press Start to open the instrument."
+
+        guard sidecarAvailable else {
+            workflow.wizard.showNotice(
+                "spotread sidecar missing — run fetch-argyll", kind: .error)
+            return
+        }
+        detectInstruments()
+    }
+
+    /// Called from `onDisappear` *and* the sheet's `onDismiss` — clearing
+    /// the flag alone is not enough; a live child must be quit and
+    /// killed (R14).
+    func sheetClosed() {
+        stopIfNeeded()
+        samples = []
+        displayedSample = nil
+        displayedDeltaE = nil
+        log = []
+        defaultMissing = false
+    }
+
+    // MARK: - Detection
+
+    func detectInstruments() {
+        guard canDetect else { return }
+        isDetecting = true
+        detectionError = nil
+
+        Task { @MainActor [weak self] in
+            guard let self else { return }
+            // `instlist` is an exclusive lease (#116) — never spawn a
+            // second one; surface the busy state instead.
+            if await self.environment.runner.processManager.isRunning(ProcessID.instlist) {
+                self.detectionError = "Instrument detection is already running."
+                self.isDetecting = false
+                return
+            }
+            do {
+                let devices = try await self.environment.runner.detectInstruments()
+                self.instruments = devices
+                self.seedDefault(from: devices)
+                if case .device(let selected) = self.selectedInstrument,
+                   !devices.contains(where: { $0.port == selected.port }) {
+                    self.selectedInstrument = .auto
+                }
+            } catch {
+                self.detectionError = error.localizedDescription
+            }
+            self.isDetecting = false
+        }
+    }
+
+    /// Seed the picker from `AppSettings.defaultInstrument`; no match →
+    /// `.auto` + `spotDefaultMissing`.
+    private func seedDefault(from devices: [InstrumentDevice]) {
+        guard let code = environment.settingsStore.load().defaultInstrument,
+              !code.isEmpty else {
+            defaultMissing = false
+            return
+        }
+        if let match = devices.first(where: { Self.matches(code: code, device: $0) }) {
+            selectedInstrument = .device(match)
+            defaultMissing = false
+        } else {
+            selectedInstrument = .auto
+            defaultMissing = true
+        }
+    }
+
+    /// Whether an `instlist` device corresponds to a `printtarg -i` /
+    /// settings instrument code (`i1`, `CM`, `p3`, `SS`, `20`/`22`/`41`/`51`).
+    static func matches(code: String, device: InstrumentDevice) -> Bool {
+        let haystack = "\(device.name) \(device.type)".lowercased()
+        switch code {
+        case "i1": return haystack.contains("i1pro") && !haystack.contains("i1pro 3") && !haystack.contains("i1pro3")
+        case "p3": return haystack.contains("i1pro 3") || haystack.contains("i1pro3")
+        case "CM": return haystack.contains("colormunki")
+        case "SS": return haystack.contains("specbos") || haystack.contains("spectraval") || haystack.contains("spectroscan") || haystack.contains("spectro scan")
+        case "20": return haystack.contains("display 2")
+        case "22": return haystack.contains("display")
+        case "41": return haystack.contains("spyder 4") || haystack.contains("spyder 5") || haystack.contains("spyder4") || haystack.contains("spyder5")
+        case "51": return haystack.contains("spyder x")
+        default: return false
+        }
+    }
+
+    /// Reverse of `matches` — most specific codes first.
+    static func code(for device: InstrumentDevice) -> String? {
+        for code in ["p3", "51", "41", "22", "20", "CM", "SS", "i1"]
+        where matches(code: code, device: device) {
+            return code
+        }
+        return nil
+    }
+
+    /// `spotSetDefault` — writes `AppSettings.defaultInstrument` only.
+    /// Never touches `printtarg -i` or `targen`.
+    func applyDefaultToggle(_ on: Bool) {
+        setAsDefault = on
+        var settings = environment.settingsStore.load()
+        if on, case .device(let device) = selectedInstrument {
+            settings.defaultInstrument = Self.code(for: device)
+        } else if !on {
+            settings.defaultInstrument = nil
+        }
+        try? environment.settingsStore.save(settings)
+    }
+
+    // MARK: - Session control
+
+    func start() {
+        guard sidecarAvailable else {
+            lastError = "spotread sidecar missing — run fetch-argyll"
+            return
+        }
+        guard !isChartreadRunning else {
+            lastError = "Stop the Stage 3 chart read first."
+            return
+        }
+        guard let cwd = workflow.wizard.effectiveWorkingDirectory else {
+            lastError = "Set a working folder in Stage 1 first."
+            return
+        }
+        Task { @MainActor [weak self] in
+            guard let self else { return }
+            // `spotread` is an exclusive lease — a second Start while a
+            // child is live is an error, not a kill + respawn (#116).
+            if await self.environment.runner.processManager.isRunning(ProcessID.spotread) {
+                self.lastError = "A spotread session is already running."
+                return
+            }
+            self.begin(config: self.buildConfig(cwd: cwd))
+        }
+    }
+
+    private func buildConfig(cwd: URL) -> SpotReadConfig {
+        let port: Int?
+        let name: String
+        switch selectedInstrument {
+        case .auto:
+            port = nil
+            name = "Auto"
+        case .device(let device):
+            port = device.port
+            name = device.name
+        }
+        return SpotReadConfig(
+            workingDirectory: cwd,
+            selectedPort: selectedInstrument.chartreadPort,
+            enableLEDs: environment.settingsStore.load().enableI1Pro2Leds,
+            isXY: selectedInstrument.isXY,
+            instrumentName: name,
+            instrumentPort: port
+        )
+    }
+
+    private func begin(config: SpotReadConfig) {
+        isRunning = true
+        state = .idle
+        lastError = nil
+        prompt = "Waiting for a reading…"
+
+        let stream = environment.runner.runSpotread(config: config)
+        streamTask = Task { @MainActor [weak self] in
+            guard let self else { return }
+            for await event in stream {
+                self.handle(event: event)
+            }
+            self.isRunning = false
+            self.state = .idle
+            if self.lastError == nil {
+                self.prompt = "Press Start to open the instrument."
+            }
+        }
+    }
+
+    private func handle(event: SpotReadEvent) {
+        switch event {
+        case .prompt(let result):
+            state = result.state
+            prompt = promptText(for: result.state)
+
+        case .sample(let sample):
+            let previous = samples.first
+            samples.insert(sample, at: 0)
+            if samples.count > historyLimit {
+                samples.removeLast()
+            }
+            displayedSample = sample
+            displayedDeltaE = previous.map {
+                ColorDifference.deltaE00($0.lab, sample.lab)
+            }
+
+        case .log(let batch):
+            log.append(contentsOf: batch)
+
+        case .exit(let code):
+            if code != 0 {
+                lastError = "spotread exited with code \(code)"
+            }
+
+        case .failed(let error):
+            lastError = error.localizedDescription
+        }
+    }
+
+    private func promptText(for state: ChartreadState) -> String {
+        switch state {
+        case .calibrating:
+            return "Place the instrument on the calibration tile, then Calibrate."
+        case .awaitingStrip:
+            return "Place on the patch, then Read."
+        case .reading, .promptContinue:
+            return "Waiting for a reading…"
+        case .warning:
+            return "Instrument warning — stop and restart if it persists."
+        case .error:
+            return "Read error — Stop, then Start again."
+        default:
+            return "Waiting for a reading…"
+        }
+    }
+
+    // MARK: - Transport
+
+    /// `btnSpotCalibrate` — same bytes Stage 3 sends for calibrate.
+    func calibrate() {
+        send(.trigger)
+    }
+
+    /// `btnSpotTrigger` — the Read key (`" \n"`).
+    func trigger() {
+        send(.trigger)
+    }
+
+    private func send(_ input: ChartreadInput) {
+        Task { @MainActor [weak self] in
+            guard let self, self.isRunning else { return }
+            try? await self.environment.runner.sendSpotreadInput(input)
+        }
+    }
+
+    /// `btnSpotStop` / sheet dismiss: `q\n`, ~500 ms, then kill if the
+    /// child is still live.
+    func stopIfNeeded() {
+        guard isRunning else { return }
+        streamTask?.cancel()
+        streamTask = nil
+        let processManager = environment.runner.processManager
+        Task { @MainActor in
+            try? await processManager.sendStdin(
+                id: ProcessID.spotread, bytes: ChartreadInput.quit.bytes)
+            try? await Task.sleep(nanoseconds: 500_000_000)
+            await processManager.kill(id: ProcessID.spotread)
+        }
+        isRunning = false
+        state = .idle
+        prompt = "Press Start to open the instrument."
+    }
+
+    // MARK: - History / export
+
+    /// Click a history row: copies that sample into the last-sample card.
+    /// Never re-triggers the instrument.
+    func selectFromHistory(_ sample: SpotReadSample) {
+        displayedSample = sample
+        if let index = samples.firstIndex(of: sample), index + 1 < samples.count {
+            displayedDeltaE = ColorDifference.deltaE00(samples[index + 1].lab, sample.lab)
+        } else {
+            displayedDeltaE = nil
+        }
+    }
+
+    /// `btnSpotCopyLab` — `L* a* b*` of the displayed sample as plain
+    /// text (`50.0 1.2 -3.4`).
+    func copyLab() {
+        guard let sample = displayedSample else { return }
+        let text = String(format: "%.1f %.1f %.1f", sample.lab.l, sample.lab.a, sample.lab.b)
+        NSPasteboard.general.clearContents()
+        NSPasteboard.general.setString(text, forType: .string)
+    }
+
+    /// `btnSpotExportCsv` — RFC-4180 via `selectCsvSavePath`. Cancel is
+    /// a no-op. Rows are newest-first, matching the history list.
+    func exportCsv() {
+        guard !samples.isEmpty else { return }
+        let url = UITestHooks.isEnabled
+            ? UITestHooks.csvExportURL
+            : fileDialogs.selectCsvSavePath()
+        guard let url else { return }
+
+        var out = "timestamp,L,a,b,dE00,instrument,port\r\n"
+        for (index, sample) in samples.enumerated() {
+            let deltaE = index + 1 < samples.count
+                ? String(format: "%.2f", ColorDifference.deltaE00(samples[index + 1].lab, sample.lab))
+                : ""
+            out += "\(csvField(iso8601(sample.timestamp))),\(f1(sample.lab.l)),\(f1(sample.lab.a)),\(f1(sample.lab.b)),\(deltaE),\(csvField(sample.instrumentName)),\(sample.port.map(String.init) ?? "")\r\n"
+        }
+
+        do {
+            try out.write(to: url, atomically: true, encoding: .utf8)
+            workflow.wizard.showNotice("Spot readings exported: \(url.lastPathComponent)")
+        } catch {
+            workflow.wizard.showNotice(
+                "Export failed: \(error.localizedDescription)", kind: .error)
+        }
+    }
+
+    private func f1(_ value: Double) -> String {
+        String(format: "%.1f", value)
+    }
+
+    private func iso8601(_ date: Date) -> String {
+        ISO8601DateFormatter().string(from: date)
+    }
+
+    private func csvField(_ text: String) -> String {
+        guard text.contains(",") || text.contains("\"") || text.contains("\n") else {
+            return text
+        }
+        return "\"\(text.replacingOccurrences(of: "\"", with: "\"\""))\""
+    }
+}

Sources/ICCery/TargetWorkflowViewModel.swift

@@ -102,6 +102,11 @@ final class TargetWorkflowViewModel: ObservableObject {
     @Published var showingSaveMedia = false
     @Published var showingManageMedia = false
 
+    // MARK: - Spot read (issue #148)
+
+    /// `RootView` sheet binding for the spot-read console.
+    @Published var showingSpotRead = false
+
     /// Stage 3 measurement workflow, owned at the app level so it persists
     /// across stage switches and can observe settings changes.
     @Published var measurement: MeasurementWorkflowViewModel
@@ -112,8 +117,10 @@ final class TargetWorkflowViewModel: ObservableObject {
     @Published var calibration: CalibrationViewModel!
     /// Stage 2 unmanaged print session.
     @Published var print: PrintSessionViewModel!
-    /// Media recipe library, created last — it needs a complete `self`.
+    /// Media recipe library — needs a complete `self`.
     @Published var media: MediaLibraryViewModel!
+    /// Spot-read console, created last — needs `wizard` / `measurement`.
+    @Published var spotRead: SpotReadViewModel!
 
     init(environment: AppEnvironment = .live()) {
         self.environment = environment
@@ -137,6 +144,10 @@ final class TargetWorkflowViewModel: ObservableObject {
             workflow: self,
             environment: environment
         )
+        self.spotRead = SpotReadViewModel(
+            workflow: self,
+            environment: environment
+        )
         reloadPresets()
     }
 

Tests/ICCeryCoreTests/ApproximateLabTests.swift

@@ -0,0 +1,39 @@
+import Foundation
+import XCTest
+@testable import ICCeryCore
+
+/// ``ApproximateLab`` sanity tests (issue #147).
+///
+/// These are loose sanity checks on a fixed-matrix approximation — not
+/// ColorSync goldens.
+final class ApproximateLabTests: XCTestCase {
+
+    func testWhiteMapsToHighLStar() {
+        let lab = ApproximateLab.srgb8ToLab(r: 255, g: 255, b: 255)
+        XCTAssertGreaterThan(lab.l, 95)
+        XCTAssertEqual(lab.a, 0, accuracy: 2)
+        XCTAssertEqual(lab.b, 0, accuracy: 2)
+    }
+
+    func testBlackMapsToZeroLStar() {
+        let lab = ApproximateLab.srgb8ToLab(r: 0, g: 0, b: 0)
+        XCTAssertEqual(lab.l, 0, accuracy: 1)
+    }
+
+    func testPureRedIsChromatic() {
+        let lab = ApproximateLab.srgb8ToLab(r: 255, g: 0, b: 0)
+        // sRGB red ≈ Lab D50 (54, 81, 70) — loose bounds only.
+        XCTAssertGreaterThan(lab.l, 40)
+        XCTAssertLessThan(lab.l, 65)
+        XCTAssertGreaterThan(lab.a, 60)
+        XCTAssertGreaterThan(lab.b, 40)
+    }
+
+    func testMidGreyIsNeutral() {
+        let lab = ApproximateLab.srgb8ToLab(r: 128, g: 128, b: 128)
+        XCTAssertGreaterThan(lab.l, 45)
+        XCTAssertLessThan(lab.l, 65)
+        XCTAssertEqual(lab.a, 0, accuracy: 1)
+        XCTAssertEqual(lab.b, 0, accuracy: 1)
+    }
+}

Tests/ICCeryCoreTests/GamutContainmentTests.swift

@@ -0,0 +1,85 @@
+import Foundation
+import XCTest
+@testable import ICCeryCore
+
+/// ``GamutGeometry`` containment and volume goldens on the bundled
+/// `sRGB.gam` reference mesh (issue #147). No GPU involved.
+final class GamutContainmentTests: XCTestCase {
+
+    /// Returns the bundled real `sRGB.gam` in `Resources/Argyll/reference_gamuts`.
+    private var bundledSRGBGamURL: URL {
+        let bundle = Bundle.main
+        let resource = bundle.resourceURL ?? bundle.bundleURL
+        return resource.appendingPathComponent("Argyll/reference_gamuts/sRGB.gam")
+    }
+
+    private func loadSRGB() throws -> GamutMesh {
+        try GamutMeshParser.parse(url: bundledSRGBGamURL)
+    }
+
+    func testNeutralMidGreyIsInsideSRGB() throws {
+        let mesh = try loadSRGB()
+        XCTAssertEqual(
+            GamutGeometry.containment(of: LabColor(l: 50, a: 0, b: 0), in: mesh),
+            .inside)
+    }
+
+    func testSaturatedColourIsOutsideSRGB() throws {
+        let mesh = try loadSRGB()
+        XCTAssertEqual(
+            GamutGeometry.containment(of: LabColor(l: 50, a: 80, b: 80), in: mesh),
+            .outside)
+    }
+
+    func testVolumeIsFiniteAndPositiveOnBundledSRGB() throws {
+        let mesh = try loadSRGB()
+        let volume = GamutGeometry.volume(of: mesh)
+        XCTAssertTrue(volume.isFinite)
+        XCTAssertGreaterThan(volume, 0)
+    }
+
+    func testVertexOnlyMeshReportsUnknown() {
+        let mesh = GamutMesh(
+            vertices: [
+                GamutVertex(lab: LabColor(l: 50, a: 0, b: 0), rgb: DisplayRGB(r: 0.5, g: 0.5, b: 0.5)),
+            ],
+            faces: [])
+        XCTAssertEqual(
+            GamutGeometry.containment(of: LabColor(l: 50, a: 0, b: 0), in: mesh),
+            .unknown)
+        XCTAssertEqual(GamutGeometry.volume(of: mesh), 0)
+    }
+
+    func testKnownCubeFixture() throws {
+        // Unit cube centred at Lab (50, 0, 0): a*,b* ∈ ±10, L* ∈ 40...60.
+        // Two triangles per face, outward winding.
+        let lab = { (l: Double, a: Double, b: Double) in
+            GamutVertex(lab: LabColor(l: l, a: a, b: b), rgb: DisplayRGB(r: 0, g: 0, b: 0))
+        }
+        // Corners in (a, L, b) space.
+        let c = [
+            lab(40, -10, -10), lab(40, 10, -10), lab(40, 10, 10), lab(40, -10, 10),  // bottom
+            lab(60, -10, -10), lab(60, 10, -10), lab(60, 10, 10), lab(60, -10, 10),  // top
+        ]
+        let quad = { (a: UInt32, b: UInt32, c: UInt32, d: UInt32) in
+            [GamutTriangle(a: a, b: b, c: c), GamutTriangle(a: a, b: c, c: d)]
+        }
+        var faces: [GamutTriangle] = []
+        faces += quad(0, 3, 2, 1)  // bottom (y=40)
+        faces += quad(4, 5, 6, 7)  // top (y=60)
+        faces += quad(0, 1, 5, 4)  // z=-10
+        faces += quad(3, 7, 6, 2)  // z=+10
+        faces += quad(1, 2, 6, 5)  // x=+10
+        faces += quad(0, 4, 7, 3)  // x=-10
+        let mesh = GamutMesh(vertices: c, faces: faces)
+
+        XCTAssertEqual(
+            GamutGeometry.containment(of: LabColor(l: 50, a: 0, b: 0), in: mesh),
+            .inside)
+        XCTAssertEqual(
+            GamutGeometry.containment(of: LabColor(l: 50, a: 20, b: 0), in: mesh),
+            .outside)
+        // 20 × 20 × 20 Lab-cube.
+        XCTAssertEqual(GamutGeometry.volume(of: mesh), 8000, accuracy: 1)
+    }
+}

Tests/ICCeryCoreTests/GamutViewModelTests.swift

@@ -0,0 +1,127 @@
+import Foundation
+import XCTest
+@testable import ICCeryCore
+@testable import ICCery
+
+/// Issue #147 — `GamutViewModel` compare-slot behaviour: failed or
+/// missing compare meshes are info, never fatal (#24); sRGB always stays.
+@MainActor
+final class GamutViewModelTests: XCTestCase {
+
+    /// Bundled root that has `reference_gamuts/sRGB.gam` but **no** tool
+    /// binaries, so `iccgamut` spawns deterministically fail.
+    private func bundledRootWithoutTools() throws -> URL {
+        let root = FileManager.default.temporaryDirectory
+            .appendingPathComponent("iccery-gamut-vm-\(UUID().uuidString)")
+        let gamutDir = root.appendingPathComponent("reference_gamuts")
+        try FileManager.default.createDirectory(
+            at: gamutDir, withIntermediateDirectories: true)
+        let bundle = Bundle.main.resourceURL ?? Bundle.main.bundleURL
+        try FileManager.default.copyItem(
+            at: bundle.appendingPathComponent("Argyll/reference_gamuts/sRGB.gam"),
+            to: gamutDir.appendingPathComponent("sRGB.gam"))
+        return root
+    }
+
+    private func makeViewModel(root: URL? = nil) throws -> GamutViewModel {
+        let env = try TestAppEnvironment.make(bundledArgyllRoot: root)
+        return GamutViewModel(environment: env.environment)
+    }
+
+    func testInitialLoadHasSRGBAndFacesStatus() async throws {
+        let vm = try makeViewModel()
+        await vm.awaitInitialLoad()
+
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.srgbLayerID))
+        XCTAssertTrue(vm.status.contains("faces"), "status: \(vm.status)")
+    }
+
+    func testMissingCompareGamLeavesSRGBAndSetsNotice() async throws {
+        let vm = try makeViewModel()
+        await vm.awaitInitialLoad()
+
+        await vm.loadCompareGam(
+            url: URL(fileURLWithPath: "/nonexistent/compare.gam"))
+
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.srgbLayerID))
+        XCTAssertNil(vm.layer(id: GamutViewModel.compareLayerID))
+        XCTAssertNotNil(vm.noticeText)
+    }
+
+    func testFailedIccgamutLeavesSRGBAndSetsNotice() async throws {
+        // bundledRootWithoutTools has no macos-universal/iccgamut.
+        let vm = try makeViewModel(root: bundledRootWithoutTools())
+        await vm.awaitInitialLoad()
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.srgbLayerID))
+
+        let profile = FileManager.default.temporaryDirectory
+            .appendingPathComponent("iccery-gamut-icc-\(UUID().uuidString).icc")
+        try Data("MOCK_ICC".utf8).write(to: profile)
+        defer { try? FileManager.default.removeItem(at: profile) }
+
+        await vm.loadCompareProfile(url: profile)
+
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.srgbLayerID))
+        XCTAssertNil(vm.layer(id: GamutViewModel.compareLayerID))
+        XCTAssertNotNil(vm.noticeText)
+    }
+
+    func testThirdProfileReplacesCompareSlot() async throws {
+        let vm = try makeViewModel()
+        await vm.awaitInitialLoad()
+
+        let bundle = Bundle.main.resourceURL ?? Bundle.main.bundleURL
+        let srgb = bundle.appendingPathComponent("Argyll/reference_gamuts/sRGB.gam")
+        let dir = FileManager.default.temporaryDirectory
+            .appendingPathComponent("iccery-gamut-cmp-\(UUID().uuidString)")
+        try FileManager.default.createDirectory(
+            at: dir, withIntermediateDirectories: true)
+        let first = dir.appendingPathComponent("first.gam")
+        let second = dir.appendingPathComponent("second.gam")
+        try FileManager.default.copyItem(at: srgb, to: first)
+        try FileManager.default.copyItem(at: srgb, to: second)
+        defer { try? FileManager.default.removeItem(at: dir) }
+
+        await vm.loadCompareGam(url: first)
+        XCTAssertNil(vm.noticeText)
+        XCTAssertEqual(vm.layer(id: GamutViewModel.compareLayerID)?.displayName, "first")
+
+        await vm.loadCompareGam(url: second)
+        XCTAssertEqual(vm.layer(id: GamutViewModel.compareLayerID)?.displayName, "second")
+        XCTAssertEqual(
+            vm.layers.filter { $0.role == .profileB }.count, 1,
+            "compare slot holds one profile")
+        XCTAssertNotNil(vm.noticeText)
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.srgbLayerID))
+    }
+
+    func testRemoveCompareLeavesSRGB() async throws {
+        let vm = try makeViewModel()
+        await vm.awaitInitialLoad()
+
+        let bundle = Bundle.main.resourceURL ?? Bundle.main.bundleURL
+        await vm.loadCompareGam(
+            url: bundle.appendingPathComponent("Argyll/reference_gamuts/sRGB.gam"))
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.compareLayerID))
+
+        vm.removeCompare()
+        XCTAssertNil(vm.layer(id: GamutViewModel.compareLayerID))
+        XCTAssertNotNil(vm.layer(id: GamutViewModel.srgbLayerID))
+    }
+
+    func testInspectLabRunsContainmentPerLayer() async throws {
+        let vm = try makeViewModel()
+        await vm.awaitInitialLoad()
+
+        vm.labEntryL = "50"
+        vm.labEntryA = "0"
+        vm.labEntryB = "0"
+        XCTAssertTrue(vm.canInspectLab)
+        vm.inspectEnteredLab()
+
+        let srgb = vm.inspectResults.first { $0.id == GamutViewModel.srgbLayerID }
+        XCTAssertEqual(srgb?.containment, .inside)
+        XCTAssertTrue(vm.inspectIsApproximate)
+        XCTAssertNotNil(vm.inspectSwatch)
+    }
+}

Tests/ICCeryCoreTests/SpotReadArgsTests.swift

@@ -0,0 +1,46 @@
+import XCTest
+@testable import ICCeryCore
+
+/// `SpotReadArgs` goldens (issue #148):
+/// `spotread -v -e [-c port] [-Y l]` — never `-u`, never a basename,
+/// `-c` only for ports > 1, `-Y l` only when the LED setting is on.
+final class SpotReadArgsTests: XCTestCase {
+
+    func testAutoOmitsPort() {
+        let args = SpotReadArgs.build(config: SpotReadConfig())
+        XCTAssertEqual(args, ["-v", "-e"])
+    }
+
+    func testPort1OmitsC() {
+        let args = SpotReadArgs.build(config: SpotReadConfig(selectedPort: 1))
+        XCTAssertEqual(args, ["-v", "-e"])
+    }
+
+    func testPort2IncludesC() {
+        let args = SpotReadArgs.build(config: SpotReadConfig(selectedPort: 2))
+        XCTAssertEqual(args, ["-v", "-e", "-c", "2"])
+    }
+
+    func testLedFlag() {
+        let args = SpotReadArgs.build(config: SpotReadConfig(enableLEDs: true))
+        XCTAssertEqual(args, ["-v", "-e", "-Y", "l"])
+    }
+
+    func testPortAndLeds() {
+        let args = SpotReadArgs.build(
+            config: SpotReadConfig(selectedPort: 2, enableLEDs: true))
+        XCTAssertEqual(args, ["-v", "-e", "-c", "2", "-Y", "l"])
+    }
+
+    func testNeverU() {
+        for config in [
+            SpotReadConfig(),
+            SpotReadConfig(selectedPort: 2),
+            SpotReadConfig(enableLEDs: true),
+            SpotReadConfig(selectedPort: 3, enableLEDs: true),
+        ] {
+            XCTAssertFalse(SpotReadArgs.build(config: config).contains("-u"))
+            XCTAssertFalse(SpotReadArgs.build(config: config).contains("-d"))
+        }
+    }
+}

Tests/ICCeryCoreTests/SpotReadClassifierTests.swift

@@ -0,0 +1,91 @@
+import XCTest
+@testable import ICCeryCore
+
+/// `SpotReadClassifier` / `SpotReadParser` against real `spotread`
+/// phrasing (issue #148). The calibration-tile line classifies through
+/// `ChartreadClassifier`; the spot prompt and its continuation lines
+/// need the spot-specific matchers.
+final class SpotReadClassifierTests: XCTestCase {
+
+    // Real `spotread` stdout (calibration then spot prompt).
+    private let calibrateLines = [
+        "Spot read needs a calibration before continuing",
+        "Place instrument on spot reading white calibration tile,",
+        " and then hit any key to continue,",
+        "or hit Esc or Q to abort:",
+    ]
+    private let spotPromptLines = [
+        "Place instrument on a spot to be measured,",
+        " and hit a key to take a reading,",
+        "or hit Esc or Q to abort:",
+    ]
+
+    func testCalibrationPrompt() {
+        var state = ChartreadState.idle
+        for line in calibrateLines {
+            state = SpotReadClassifier.classify(line: line, previousState: state).state
+        }
+        XCTAssertEqual(state, .calibrating)
+    }
+
+    func testSpotPromptIsAwaitingTrigger() {
+        var state = ChartreadState.calibrating
+        for line in spotPromptLines {
+            state = SpotReadClassifier.classify(line: line, previousState: state).state
+        }
+        XCTAssertEqual(state, .awaitingStrip)
+    }
+
+    func testAbortLineDoesNotBecomeWarning() {
+        // "or hit Esc or Q to abort:" contains no '?' but does contain
+        // "abort" — it must stay on the current prompt, never flip to
+        // a warning.
+        let r = SpotReadClassifier.classify(
+            line: "or hit Esc or Q to abort:", previousState: .awaitingStrip)
+        XCTAssertEqual(r.state, .awaitingStrip)
+    }
+
+    func testParseResultLine() throws {
+        let parsed = SpotReadParser.parse(
+            line: "Result is XYZ: 18.51 20.05 15.71, D50 Lab: 51.9 -8.3 12.2")
+        let lab = try XCTUnwrap(parsed?.lab)
+        XCTAssertEqual(lab.l, 51.9, accuracy: 0.001)
+        XCTAssertEqual(lab.a, -8.3, accuracy: 0.001)
+        XCTAssertEqual(lab.b, 12.2, accuracy: 0.001)
+        let xyz = try XCTUnwrap(parsed?.xyz)
+        XCTAssertEqual(xyz.x, 18.51, accuracy: 0.001)
+        XCTAssertEqual(xyz.y, 20.05, accuracy: 0.001)
+        XCTAssertEqual(xyz.z, 15.71, accuracy: 0.001)
+    }
+
+    func testParseLabOnlyLine() throws {
+        let parsed = SpotReadParser.parse(line: "Result is Lab: 40.0 1.2 -3.4")
+        let lab = try XCTUnwrap(parsed?.lab)
+        XCTAssertEqual(lab.l, 40.0, accuracy: 0.001)
+        XCTAssertNil(parsed?.xyz)
+    }
+
+    func testNonSampleLineParsesNil() {
+        XCTAssertNil(SpotReadParser.parse(line: "Place instrument on a spot to be measured,"))
+        XCTAssertNil(SpotReadParser.parse(line: "Calibration successful."))
+        XCTAssertNil(SpotReadParser.parse(line: ""))
+    }
+
+    func testDeltaEBetweenFixtures() {
+        let a = SpotReadParser.parse(
+            line: "Result is XYZ: 18.51 20.05 15.71, D50 Lab: 51.9 -8.3 12.2")!.lab
+        let b = SpotReadParser.parse(
+            line: "Result is XYZ: 19.00 20.50 16.00, D50 Lab: 52.3 -8.0 12.6")!.lab
+        XCTAssertEqual(ColorDifference.deltaE00(a, a), 0, accuracy: 0.0001)
+        XCTAssertGreaterThan(ColorDifference.deltaE00(a, b), 0)
+        XCTAssertEqual(
+            ColorDifference.classify(deltaE: 1.0, goodMax: 2.0, warningMax: 5.0),
+            .good)
+        XCTAssertEqual(
+            ColorDifference.classify(deltaE: 3.0, goodMax: 2.0, warningMax: 5.0),
+            .warning)
+        XCTAssertEqual(
+            ColorDifference.classify(deltaE: 6.0, goodMax: 2.0, warningMax: 5.0),
+            .bad)
+    }
+}

Tests/ICCeryCoreTests/SpotReadViewModelTests.swift

@@ -0,0 +1,250 @@
+import Foundation
+import XCTest
+@testable import ICCeryCore
+@testable import ICCery
+
+/// Issue #148 — `SpotReadViewModel` under an isolated
+/// `TestAppEnvironment` with per-test mock `spotread`/`instlist`
+/// sidecars in a temp bin dir.
+@MainActor
+final class SpotReadViewModelTests: XCTestCase {
+
+    private var env: TestAppEnvironment!
+    private var workflow: TargetWorkflowViewModel!
+    private var spot: SpotReadViewModel!
+    private var binDir: URL!
+
+    override func setUp() async throws {
+        binDir = FileManager.default.temporaryDirectory
+            .appendingPathComponent("spot-bin-\(UUID().uuidString)")
+        try FileManager.default.createDirectory(
+            at: binDir, withIntermediateDirectories: true)
+        // `bundledArgyllRoot` also points at the temp bin dir so the
+        // real sidecars copied into the host app by the build phase do
+        // not mask a missing `spotread` in the override dir.
+        env = try TestAppEnvironment.make(
+            argyllBinDir: binDir, bundledArgyllRoot: binDir)
+        workflow = TargetWorkflowViewModel(environment: env.environment)
+        spot = workflow.spotRead
+        workflow.wizard.setTarget(basename: "spot", workingDirectory: env.root)
+    }
+
+    override func tearDown() async throws {
+        spot?.stopIfNeeded()
+        try? await Task.sleep(nanoseconds: 700_000_000)
+        env?.cleanup()
+        try? FileManager.default.removeItem(at: binDir)
+        env = nil
+        workflow = nil
+        spot = nil
+        binDir = nil
+    }
+
+    // MARK: - Helpers
+
+    private func writeMock(_ name: String, _ body: String) throws {
+        let url = binDir.appendingPathComponent(name)
+        try body.write(to: url, atomically: true, encoding: .utf8)
+        try FileManager.default.setAttributes(
+            [.posixPermissions: 0o755], ofItemAtPath: url.path)
+    }
+
+    private func installInstlist(_ devicesJson: String) throws {
+        try writeMock("instlist", """
+            #!/bin/sh
+            printf '%s' '\(devicesJson)'
+            exit 0
+            """)
+    }
+
+    private func installSpotread(lab: String = "51.9 -8.3 12.2") throws {
+        try writeMock("spotread", """
+            #!/bin/sh
+            echo "Spot read needs a calibration before continuing"
+            echo "Place instrument on spot reading white calibration tile,"
+            echo " and then hit any key to continue,"
+            echo "or hit Esc or Q to abort:"
+            IFS= read -r line || exit 0
+            echo "Calibration successful."
+            while true; do
+              echo "Place instrument on a spot to be measured,"
+              echo " and hit a key to take a reading,"
+              echo "or hit Esc or Q to abort:"
+              IFS= read -r line || exit 0
+              case "$line" in
+                q*|Q*) exit 0 ;;
+              esac
+              echo "Result is XYZ: 18.51 20.05 15.71, D50 Lab: \(lab)"
+            done
+            """)
+    }
+
+    private func waitFor(
+        _ predicate: @escaping () async -> Bool,
+        timeout: TimeInterval = 10
+    ) async -> Bool {
+        let deadline = Date().addingTimeInterval(timeout)
+        while Date() < deadline {
+            if await predicate() { return true }
+            try? await Task.sleep(nanoseconds: 50_000_000)
+        }
+        return await predicate()
+    }
+
+    private func waitForSync(
+        _ predicate: @escaping () -> Bool,
+        timeout: TimeInterval = 10
+    ) async -> Bool {
+        let deadline = Date().addingTimeInterval(timeout)
+        while Date() < deadline {
+            if predicate() { return true }
+            try? await Task.sleep(nanoseconds: 50_000_000)
+        }
+        return predicate()
+    }
+
+    // MARK: - Missing sidecar
+
+    func testMissingSidecarNoSpawn() async throws {
+        // bin dir has no spotread → resolver override misses and the
+        // bundled path does not exist either.
+        XCTAssertFalse(spot.sidecarAvailable)
+        spot.sheetOpened()
+        XCTAssertEqual(workflow.wizard.notice?.kind, .error)
+
+        spot.start()
+        XCTAssertEqual(spot.lastError, "spotread sidecar missing — run fetch-argyll")
+        XCTAssertFalse(spot.isRunning)
+        let running = await env.environment.runner.processManager.isRunning(ProcessID.spotread)
+        XCTAssertFalse(running)
+    }
+
+    // MARK: - defaultInstrument seeding
+
+    func testDefaultInstrumentSeedsPicker() async throws {
+        try installSpotread()
+        try installInstlist("""
+            {"event":"instruments","devices":[
+              {"port":1,"name":"X-Rite i1Pro","type":"i1"},
+              {"port":2,"name":"ColorMunki Photo","type":"CM"}]}
+            """)
+        var settings = env.environment.settingsStore.load()
+        settings.defaultInstrument = "CM"
+        try env.environment.settingsStore.save(settings)
+
+        spot.sheetOpened()
+        let ok1 = await waitFor { !self.spot.isDetecting && !self.spot.instruments.isEmpty }
+        XCTAssertTrue(ok1)
+        guard case .device(let device) = spot.selectedInstrument else {
+            XCTFail("Expected device selection, got .auto")
+            return
+        }
+        XCTAssertEqual(device.port, 2)
+        XCTAssertFalse(spot.defaultMissing)
+    }
+
+    func testDefaultInstrumentNotPresent() async throws {
+        try installSpotread()
+        try installInstlist("""
+            {"event":"instruments","devices":[
+              {"port":1,"name":"X-Rite i1Pro","type":"i1"}]}
+            """)
+        var settings = env.environment.settingsStore.load()
+        settings.defaultInstrument = "51"   // Spyder X — absent
+        try env.environment.settingsStore.save(settings)
+
+        spot.sheetOpened()
+        let ok2 = await waitFor { !self.spot.isDetecting }
+        XCTAssertTrue(ok2)
+        XCTAssertEqual(spot.selectedInstrument, .auto)
+        XCTAssertTrue(spot.defaultMissing)
+    }
+
+    func testSetDefaultToggleWritesSettingsOnly() async throws {
+        try installSpotread()
+        try installInstlist("""
+            {"event":"instruments","devices":[
+              {"port":2,"name":"ColorMunki Photo","type":"CM"}]}
+            """)
+        spot.sheetOpened()
+        let ok3 = await waitFor { !self.spot.instruments.isEmpty }
+        XCTAssertTrue(ok3)
+        spot.selectedInstrument = .device(spot.instruments[0])
+        spot.applyDefaultToggle(true)
+        XCTAssertEqual(env.environment.settingsStore.load().defaultInstrument, "CM")
+        // printtarg instrument is untouched (R15).
+        XCTAssertEqual(workflow.instrument, .i1)
+        spot.applyDefaultToggle(false)
+        XCTAssertNil(env.environment.settingsStore.load().defaultInstrument)
+    }
+
+    // MARK: - Exclusive lease
+
+    func testDuplicateSpotreadIdRejected() async throws {
+        try writeMock("spotread", "#!/bin/sh\nsleep 30\n")
+        let pm = env.environment.runner.processManager
+        let bin = env.environment.runner.binaryResolver.resolve("spotread")
+        try await pm.runStreaming(id: ProcessID.spotread, binary: bin, arguments: [])
+        let ok4 = await pm.isRunning(ProcessID.spotread)
+        XCTAssertTrue(ok4)
+        do {
+            try await pm.runStreaming(id: ProcessID.spotread, binary: bin, arguments: [])
+            XCTFail("Expected duplicateID")
+        } catch let error as ProcessError {
+            guard case .duplicateID(let id) = error else {
+                XCTFail("Expected duplicateID, got \(error)")
+                return
+            }
+            XCTAssertEqual(id, "spotread")
+        }
+        await pm.kill(id: ProcessID.spotread)
+    }
+
+    // MARK: - Session
+
+    func testMockSpotreadProducesSample() async throws {
+        try installSpotread()
+        spot.sheetOpened()
+        spot.start()
+        let ok5 = await waitFor { self.spot.state == .calibrating }
+        XCTAssertTrue(ok5, "expected calibrating prompt")
+
+        spot.calibrate()
+        let ok6 = await waitFor { self.spot.state == .awaitingStrip }
+        XCTAssertTrue(ok6, "expected read prompt")
+
+        spot.trigger()
+        let ok7 = await waitFor { !self.spot.samples.isEmpty }
+        XCTAssertTrue(ok7, "expected a sample")
+        let sample = try XCTUnwrap(spot.samples.first)
+        XCTAssertEqual(sample.lab.l, 51.9, accuracy: 0.001)
+        XCTAssertNotNil(sample.xyz)
+        XCTAssertNil(spot.displayedDeltaE)   // first sample hides ΔE
+
+        spot.trigger()
+        let ok8 = await waitFor { self.spot.samples.count >= 2 }
+        XCTAssertTrue(ok8, "expected a second sample")
+        XCTAssertNotNil(spot.displayedDeltaE)
+        XCTAssertEqual(spot.displayedDeltaE ?? -1, 0, accuracy: 0.0001)  // identical Lab
+
+        spot.stopIfNeeded()
+        XCTAssertFalse(spot.isRunning)
+        let deadline = Date().addingTimeInterval(5)
+        var alive = await env.environment.runner.processManager.isRunning(ProcessID.spotread)
+        while alive && Date() < deadline {
+            try await Task.sleep(nanoseconds: 100_000_000)
+            alive = await env.environment.runner.processManager.isRunning(ProcessID.spotread)
+        }
+        XCTAssertFalse(alive, "spotread child must not outlive Stop")
+    }
+
+    func testStartBlockedWhileChartreadRunning() async throws {
+        try installSpotread()
+        // Simulate a live Stage 3 chartread child.
+        workflow.measurement.isChartreadRunning = true
+        spot.sheetOpened()
+        spot.start()
+        XCTAssertEqual(spot.lastError, "Stop the Stage 3 chart read first.")
+        XCTAssertFalse(spot.isRunning)
+    }
+}

Tests/ICCeryCoreTests/TestAppEnvironment.swift

@@ -25,7 +25,15 @@ struct TestAppEnvironment {
 
     /// Creates an isolated environment under `NSTemporaryDirectory()`.
     /// Call `cleanup()` when finished.
-    static func make() throws -> TestAppEnvironment {
+    /// `argyllBinDir` overrides the `BinaryResolver` tool directory so
+    /// tests can point at mock sidecar scripts (#148).
+    /// `bundledArgyllRoot` replaces the real app-bundle sidecar root so
+    /// tests can simulate a missing sidecar even when the build phase
+    /// copied real binaries into the host app.
+    static func make(
+        argyllBinDir: URL? = nil,
+        bundledArgyllRoot: URL? = nil
+    ) throws -> TestAppEnvironment {
         let root = FileManager.default.temporaryDirectory
             .appendingPathComponent("iccery-test-env-\(UUID().uuidString)")
         try FileManager.default.createDirectory(
@@ -44,7 +52,9 @@ struct TestAppEnvironment {
             presetStore: PresetStore(settingsStore: settingsStore),
             runner: ArgyllRunner(
                 processManager: processManager,
-                binaryResolver: BinaryResolver(overrideDir: nil)
+                binaryResolver: BinaryResolver(
+                    bundledRoot: bundledArgyllRoot ?? AppPaths.bundledArgyllDir,
+                    overrideDir: argyllBinDir)
             ),
             cupsService: CupsService(
                 processManager: processManager,

Tests/ICCeryUITests/Fixtures/bin/spotread

@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+"""Mock spotread for Milestone10SpotReadUITests.
+
+Emits the real spotread prompt phrasing; each trigger line produces one
+"Result is XYZ: …, D50 Lab: …" sample. Override the emitted colour with
+MOCK_SPOTREAD_LAB / MOCK_SPOTREAD_XYZ. 'q' quits with exit 0.
+Usage: spotread -v -e [-c port] [-Y l]
+"""
+import os
+import sys
+
+LAB = os.environ.get("MOCK_SPOTREAD_LAB", "51.9 -8.3 12.2")
+XYZ = os.environ.get("MOCK_SPOTREAD_XYZ", "18.51 20.05 15.71")
+
+
+def read_line():
+    try:
+        return sys.stdin.readline()
+    except Exception:
+        return ""
+
+
+def main():
+    print("Spot read needs a calibration before continuing")
+    print("Place instrument on spot reading white calibration tile,")
+    print(" and then hit any key to continue,")
+    print("or hit Esc or Q to abort:")
+    sys.stdout.flush()
+    if not read_line():
+        return 0
+    print("Calibration successful.")
+
+    while True:
+        print("Place instrument on a spot to be measured,")
+        print(" and hit a key to take a reading,")
+        print("or hit Esc or Q to abort:")
+        sys.stdout.flush()
+        line = read_line()
+        if not line:
+            return 0
+        if line.strip().lower().startswith("q"):
+            return 0
+        print("Result is XYZ: %s, D50 Lab: %s" % (XYZ, LAB))
+        sys.stdout.flush()
+
+
+if __name__ == "__main__":
+    sys.exit(main())

Tests/ICCeryUITests/Milestone10GamutCompareUITests.swift

@@ -0,0 +1,186 @@
+import Foundation
+import XCTest
+
+/// Milestone 10 — Issue #147 gamut compare chrome tests.
+///
+/// Sheet-opened only: no GPU hit-test assertions (no reliable SceneKit
+/// click on the runner). Containment itself is covered by
+/// `GamutContainmentTests`.
+@MainActor
+final class Milestone10GamutCompareUITests: XCTestCase {
+
+    private var app: XCUIApplication!
+    private var testRoot: URL!
+    private var binDir: URL!
+    private var workDir: URL!
+    private var appDataDir: URL!
+    private var referenceGamutURL: URL!
+
+    override func setUp() async throws {
+        continueAfterFailure = false
+        testRoot = FileManager.default.temporaryDirectory
+            .appendingPathComponent("iccery-ui-m10-gamut-\(UUID().uuidString)")
+        binDir = URL(fileURLWithPath: #filePath)
+            .deletingLastPathComponent()
+            .appendingPathComponent("Fixtures/bin")
+        workDir = testRoot.appendingPathComponent("work")
+        appDataDir = testRoot.appendingPathComponent("AppData")
+        referenceGamutURL = URL(fileURLWithPath: #filePath)
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+            .appendingPathComponent("Resources/Argyll/reference_gamuts/sRGB.gam")
+
+        try FileManager.default.createDirectory(
+            at: workDir, withIntermediateDirectories: true)
+        try FileManager.default.createDirectory(
+            at: appDataDir, withIntermediateDirectories: true)
+
+        app = XCUIApplication()
+        app.launchEnvironment = [
+            "ICCERY_UI_TESTING": "1",
+            "ICCERY_TEST_ROOT": testRoot.path,
+            "ICCERY_ARGYLL_BINARY_DIR": binDir.path,
+            "ICCERY_TEST_WORKDIR": workDir.path,
+        ]
+    }
+
+    override func tearDown() async throws {
+        app?.terminate()
+        app = nil
+        if let testRoot {
+            try? FileManager.default.removeItem(at: testRoot)
+        }
+        testRoot = nil
+    }
+
+    private func element(_ id: String) -> XCUIElement {
+        let inApp = app.descendants(matching: .any)[id].firstMatch
+        if inApp.exists { return inApp }
+        let inSheet = app.sheets.firstMatch.descendants(matching: .any)[id].firstMatch
+        if inSheet.exists { return inSheet }
+        // Menu popup items live outside the window hierarchy.
+        return app.menuItems[id].firstMatch
+    }
+
+    private func waitFor(_ id: String, timeout: TimeInterval = 15) -> XCUIElement {
+        let deadline = Date().addingTimeInterval(timeout)
+        while Date() < deadline {
+            let el = element(id)
+            if el.exists { return el }
+            RunLoop.current.run(until: Date().addingTimeInterval(0.1))
+        }
+        let el = element(id)
+        XCTAssertTrue(el.exists, "Expected element \(id)")
+        return el
+    }
+
+    private func launchApp() {
+        app.launch()
+        if !app.wait(for: .runningForeground, timeout: 10) {
+            app.activate()
+        }
+    }
+
+    private func openGamutSheet() {
+        launchApp()
+        waitFor("btnViewGamut").click()
+        _ = waitFor("gamutView")
+    }
+
+    func testLayerTogglesExistWithSRGB() throws {
+        openGamutSheet()
+
+        let srgb = waitFor("gamutLayer-sRGB")
+        XCTAssertTrue(srgb.exists)
+        XCTAssertTrue(srgb.isEnabled)
+        // NSButton checkbox value is 1 when checked.
+        XCTAssertEqual(srgb.value as? Int, 1, "sRGB layer should be on")
+
+        let compare = waitFor("gamutLayer-compare")
+        XCTAssertTrue(compare.exists)
+        XCTAssertFalse(compare.isEnabled, "Compare toggle must be disabled before a load")
+    }
+
+    func testAddCompareButtonExists() throws {
+        openGamutSheet()
+
+        waitFor("btnGamutAddCompare").click()
+        // No ICCERY_TEST_GAMUT_FILE set → the stubbed picker cancels;
+        // the sRGB status must stay non-empty.
+        waitFor("btnGamutOpenGam").click()
+
+        let status = waitFor("gamutStatusText")
+        let value = status.value as? String ?? ""
+        XCTAssertTrue(value.contains("sRGB"), "Status should keep the sRGB clause, got: \(value)")
+    }
+
+    func testCompareGamLoadEnablesToggle() throws {
+        let compareURL = workDir.appendingPathComponent("compare.gam")
+        try FileManager.default.copyItem(at: referenceGamutURL, to: compareURL)
+        app.launchEnvironment["ICCERY_TEST_GAMUT_FILE"] = compareURL.path
+
+        openGamutSheet()
+        waitFor("btnGamutAddCompare").click()
+        waitFor("btnGamutOpenGam").click()
+
+        let compare = waitFor("gamutLayer-compare")
+        XCTAssertTrue(compare.isEnabled, "Compare toggle should enable after load")
+
+        let status = waitFor("gamutStatusText")
+        let value = status.value as? String ?? ""
+        XCTAssertTrue(value.contains("compare"), "Status should list the compare layer, got: \(value)")
+
+        let remove = waitFor("btnGamutRemoveCompare")
+        XCTAssertTrue(remove.isEnabled)
+    }
+
+    func testOpenProfileRunsIccgamutForCompare() throws {
+        // A profile with no sibling .gam → the mock iccgamut writes one.
+        let profileURL = workDir.appendingPathComponent("myprinter.icc")
+        try Data("MOCK_ICC".utf8).write(to: profileURL)
+        app.launchEnvironment["ICCERY_TEST_GAMUT_PROFILE"] = profileURL.path
+        app.launchEnvironment["ICCERY_MOCK_GAMUT_SOURCE"] = referenceGamutURL.path
+
+        openGamutSheet()
+        waitFor("btnGamutAddCompare").click()
+        waitFor("btnGamutOpenProfile").click()
+
+        let compare = waitFor("gamutLayer-compare")
+        XCTAssertTrue(compare.isEnabled, "Compare toggle should enable after iccgamut")
+    }
+
+    func testInspectPanelIdleStableHeight() throws {
+        openGamutSheet()
+
+        let panel = waitFor("gamutInspectPanel")
+        XCTAssertTrue(panel.exists)
+        XCTAssertTrue(element("gamutInspectIdle").exists)
+        XCTAssertTrue(element("gamutStatusText").exists)
+    }
+
+    func testManualLabInspectShowsContainment() throws {
+        openGamutSheet()
+
+        waitFor("gamutLabEntryL").click()
+        element("gamutLabEntryL").typeText("50")
+        element("gamutLabEntryA").click()
+        element("gamutLabEntryA").typeText("0")
+        element("gamutLabEntryB").click()
+        element("gamutLabEntryB").typeText("0")
+
+        waitFor("btnGamutInspectLab").click()
+
+        let inside = waitFor("gamutInspect-sRGB")
+        let value = inside.value as? String ?? inside.label
+        XCTAssertTrue(value.contains("in"), "Lab(50,0,0) should be inside sRGB, got: \(value)")
+        XCTAssertTrue(element("gamutInspectL").exists)
+        XCTAssertTrue(element("gamutInspectSwatch").exists)
+    }
+
+    func testResetIdentifierUnchanged() throws {
+        openGamutSheet()
+        let reset = waitFor("btnResetGamutCamera")
+        XCTAssertTrue(reset.isEnabled)
+    }
+}

Tests/ICCeryUITests/Milestone10SpotReadUITests.swift

@@ -0,0 +1,235 @@
+import XCTest
+
+/// Milestone 10 UI tests — issue #148 spot-read console. Mock Argyll
+/// sidecars (`ICCERY_ARGYLL_BINARY_DIR` → `Fixtures/bin`) provide
+/// `instlist`, `chartread`, and `spotread`; no real USB Detect is ever
+/// clicked. All queries are by identifier only.
+@MainActor
+final class Milestone10SpotReadUITests: XCTestCase {
+
+    private var app: XCUIApplication!
+    private var testRoot: URL!
+    private var binDir: URL!
+    private var workDir: URL!
+
+    override func setUp() async throws {
+        continueAfterFailure = false
+        testRoot = FileManager.default.temporaryDirectory
+            .appendingPathComponent("iccery-ui10spot-\(UUID().uuidString)")
+        binDir = URL(fileURLWithPath: #filePath)
+            .deletingLastPathComponent()
+            .appendingPathComponent("Fixtures/bin")
+        workDir = testRoot.appendingPathComponent("work")
+        try FileManager.default.createDirectory(
+            at: workDir, withIntermediateDirectories: true)
+
+        app = XCUIApplication()
+        app.launchEnvironment = [
+            "ICCERY_UI_TESTING": "1",
+            "ICCERY_TEST_ROOT": testRoot.path,
+            "ICCERY_ARGYLL_BINARY_DIR": binDir.path,
+            // Redirect the bundled root too so the real sidecars copied
+            // into the product by the build phase cannot mask a missing
+            // override binary (`testMissingSidecarShowsMessage`).
+            "ICCERY_ARGYLL_BUNDLED_ROOT": binDir.path,
+            "ICCERY_CUPS_BIN_DIR": binDir.path,
+            "ICCERY_TEST_SAVE_TARGET":
+                workDir.appendingPathComponent("mytarget.ti1").path,
+            "ICCERY_TEST_WORKDIR": workDir.path,
+            "ICCERY_TEST_CSV_EXPORT":
+                workDir.appendingPathComponent("spot-history.csv").path,
+        ]
+    }
+
+    override func tearDown() async throws {
+        app?.terminate()
+        app = nil
+        if let testRoot {
+            try? FileManager.default.removeItem(at: testRoot)
+        }
+        testRoot = nil
+    }
+
+    private func launchApp() {
+        app.launch()
+        if !app.wait(for: .runningForeground, timeout: 10) {
+            app.activate()
+        }
+    }
+
+    /// Seed `wizard_state.json` with a working directory so `btnSpotRead`
+    /// is enabled without driving the whole Stage 1/2 flow.
+    private func seedWorkingDirectory() throws {
+        let appData = testRoot.appendingPathComponent("AppData", isDirectory: true)
+        try FileManager.default.createDirectory(
+            at: appData, withIntermediateDirectories: true)
+        let state = """
+        {
+          "currentStage": 0,
+          "basename": "spotui",
+          "cwd": "\(workDir.path)",
+          "sessionMode": "profile"
+        }
+        """
+        try state.write(
+            to: appData.appendingPathComponent("wizard_state.json"),
+            atomically: true, encoding: .utf8)
+    }
+
+    private func element(_ id: String) -> XCUIElement {
+        let inApp = app.descendants(matching: .any)[id].firstMatch
+        if inApp.exists { return inApp }
+        return app.sheets.firstMatch.descendants(matching: .any)[id].firstMatch
+    }
+
+    private func waitFor(_ id: String, timeout: TimeInterval = 10) -> XCUIElement {
+        let deadline = Date().addingTimeInterval(timeout)
+        while Date() < deadline {
+            let el = element(id)
+            if el.exists { return el }
+            RunLoop.current.run(until: Date().addingTimeInterval(0.1))
+        }
+        let el = element(id)
+        XCTAssertTrue(el.exists, "Expected element \(id)")
+        return el
+    }
+
+    // MARK: - Sidebar gating
+
+    func testSpotReadButtonDisabledWithoutCwd() throws {
+        launchApp()
+        let button = app.buttons["btnSpotRead"]
+        XCTAssertTrue(button.waitForExistence(timeout: 10))
+        XCTAssertFalse(button.isEnabled)
+    }
+
+    func testSpotReadButtonDisabledDuringChartread() throws {
+        launchApp()
+        // Drive to Stage 3 with the mock targen/printtarg fixtures.
+        app.buttons["btnBrowse"].click()
+        app.buttons["btnGenerate"].click()
+        _ = waitFor("btnCreateLayout", timeout: 20)
+        app.buttons["btnCreateLayout"].click()
+        _ = waitFor("galleryPage-0", timeout: 20)
+        _ = waitFor("btnAdvanceToStage3", timeout: 10)
+        app.buttons["btnAdvanceToStage3"].click()
+        _ = waitFor("stage3TargetBasename", timeout: 10)
+
+        // Start the mock chartread — it blocks on the calibrate prompt.
+        app.buttons["btnStartRead"].click()
+        _ = waitFor("btnCalibrate", timeout: 25)
+
+        let button = app.buttons["btnSpotRead"]
+        XCTAssertTrue(button.exists)
+        XCTAssertFalse(button.isEnabled)
+
+        // Clean up the live chartread child before teardown.
+        if app.buttons["btnCancel"].exists {
+            app.buttons["btnCancel"].click()
+        }
+    }
+
+    // MARK: - Sheet contract
+
+    func testSheetHasOwnInstrumentIds() throws {
+        try seedWorkingDirectory()
+        launchApp()
+
+        let button = app.buttons["btnSpotRead"]
+        XCTAssertTrue(button.waitForExistence(timeout: 10))
+        let deadline = Date().addingTimeInterval(10)
+        while !button.isEnabled, Date() < deadline {
+            RunLoop.current.run(until: Date().addingTimeInterval(0.1))
+        }
+        XCTAssertTrue(button.isEnabled)
+        button.click()
+
+        _ = waitFor("spotReadView", timeout: 10)
+        XCTAssertTrue(element("spotInstrumentSelect").waitForExistence(timeout: 10))
+        // Stage 3 ids must not appear inside the sheet.
+        XCTAssertFalse(
+            app.sheets.firstMatch.descendants(matching: .any)["chartreadInstrumentSelect"].exists)
+        XCTAssertFalse(
+            app.sheets.firstMatch.descendants(matching: .any)["btnDetectInstruments"].exists)
+        XCTAssertTrue(element("btnCloseSpotRead").exists)
+    }
+
+    func testMissingSidecarShowsMessage() throws {
+        // Point the override at an empty dir; the bundled root has no
+        // real sidecars in this checkout, so resolve() misses both.
+        let emptyBin = testRoot.appendingPathComponent("empty-bin")
+        try FileManager.default.createDirectory(
+            at: emptyBin, withIntermediateDirectories: true)
+        app.launchEnvironment["ICCERY_ARGYLL_BINARY_DIR"] = emptyBin.path
+        try seedWorkingDirectory()
+        launchApp()
+
+        let button = app.buttons["btnSpotRead"]
+        XCTAssertTrue(button.waitForExistence(timeout: 10))
+        let deadline = Date().addingTimeInterval(10)
+        while !button.isEnabled, Date() < deadline {
+            RunLoop.current.run(until: Date().addingTimeInterval(0.1))
+        }
+        button.click()
+
+        _ = waitFor("spotReadView", timeout: 10)
+        XCTAssertTrue(element("spotSidecarMissing").waitForExistence(timeout: 10))
+        XCTAssertFalse(element("btnSpotStart").exists)
+        XCTAssertFalse(element("btnSpotDetectInstruments").exists)
+        XCTAssertTrue(element("btnCloseSpotRead").exists)
+    }
+
+    func testHistoryCopyDisabledWhenEmpty() throws {
+        try seedWorkingDirectory()
+        launchApp()
+
+        let button = app.buttons["btnSpotRead"]
+        XCTAssertTrue(button.waitForExistence(timeout: 10))
+        let deadline = Date().addingTimeInterval(10)
+        while !button.isEnabled, Date() < deadline {
+            RunLoop.current.run(until: Date().addingTimeInterval(0.1))
+        }
+        button.click()
+
+        _ = waitFor("spotReadView", timeout: 10)
+        XCTAssertTrue(element("spotHistoryEmpty").waitForExistence(timeout: 10))
+        XCTAssertTrue(element("spotLastEmpty").exists)
+        XCTAssertFalse(element("btnSpotCopyLab").isEnabled)
+        XCTAssertFalse(element("btnSpotExportCsv").isEnabled)
+    }
+
+    /// Full mock session: Start → Calibrate → Read produces one Lab
+    /// sample and enables Copy/Export.
+    func testMockSessionProducesSample() throws {
+        try seedWorkingDirectory()
+        launchApp()
+
+        let button = app.buttons["btnSpotRead"]
+        XCTAssertTrue(button.waitForExistence(timeout: 10))
+        let deadline = Date().addingTimeInterval(10)
+        while !button.isEnabled, Date() < deadline {
+            RunLoop.current.run(until: Date().addingTimeInterval(0.1))
+        }
+        button.click()
+
+        _ = waitFor("spotReadView", timeout: 10)
+        let start = element("btnSpotStart")
+        XCTAssertTrue(start.waitForExistence(timeout: 10))
+        start.click()
+
+        XCTAssertTrue(element("btnSpotCalibrate").waitForExistence(timeout: 15))
+        element("btnSpotCalibrate").click()
+
+        XCTAssertTrue(element("btnSpotTrigger").waitForExistence(timeout: 15))
+        element("btnSpotTrigger").click()
+
+        XCTAssertTrue(element("spotLastSample").waitForExistence(timeout: 15))
+        XCTAssertTrue(element("spotLabL").exists)
+        XCTAssertTrue(element("spotSwatch").exists)
+        XCTAssertTrue(element("btnSpotCopyLab").isEnabled)
+        XCTAssertTrue(element("btnSpotExportCsv").isEnabled)
+
+        element("btnSpotStop").click()
+        element("btnCloseSpotRead").click()
+    }
+}

docs/04-argyll-binaries.md

@@ -695,7 +695,7 @@ Consumes ICC/ICM. Produces `{stem}.gam` next to the profile (Argyll default). Bu
 |---|---|
 | `dispwin` | Never spawned. ICCery#90 “Emissive display calibration (dispwin & dispread)” = Won't Fix |
 | `dispread` | Same |
-| `spotread`, `dispcal`, `collink`, `cctiff`, `spec2cie`, `illumread`, `synthacc` | Not referenced |
+| `dispcal`, `collink`, `cctiff`, `spec2cie`, `illumread`, `synthacc` | Not referenced |
 | Generic `spawn_process` | **Registered** (`lib.rs:55`, `commands.rs:6–14`) but **no JS caller**. Always `cwd=None`. Exists as an escape hatch |
 
 ---
@@ -725,6 +725,7 @@ The `Child` itself lives only in the wait task (not in a map) so `wait()` cannot
 | `profcheck_{ti3_path}` | profcheck (full path) |
 | `iccgamut_{stem}` | iccgamut |
 | `instlist` | instlist (literal) |
+| `spotread` | spotread (literal, issue #148) |
 | caller-supplied | unused `spawn_process` |
 
 ### 12.3 Duplicate rejection (ICCery#116, `07d28eb`)
@@ -830,6 +831,7 @@ From `lib.rs:54–119` plus the command bodies:
 | `run_profcheck` | profcheck | `profcheck_{ti3_path}` |
 | `extract_gamut` | iccgamut | `iccgamut_{stem}` |
 | `detect_instruments` | instlist | `instlist` |
+| `run_spotread` | spotread (`-v -e [-c port] [-Y l]`, no `-u`) | `spotread` |
 | `generate_calibration_target` | targen | `targen_{CAL_basename}` |
 
 ### Argyll runners (captured, no events)

docs/15-stage3-chartread.md

@@ -80,3 +80,14 @@ If an unpatched binary rejects `-Y l`, capture last stderr line and expand Proce
 ## Interactive buttons vs real keys
 
 See [05](05-argyll-fork.md) §12. Real strip-mode keys are `f/b/n/d/q`, Space, Return, `y/n`. UI labels "Skip" / "Undo" send `s\n` / `u\n` which the **mock** understands; upstream strip mode treats unknown letters as trigger. Preserve current UI behaviour or document a protocol change — do not silently change what bytes are sent without updating tests.
+
+## Spot Read (issue #148)
+
+The Spot Read sheet (`btnSpotRead` in the sidebar) runs the bundled
+`spotread` sidecar under the single-lease process id `spotread` — it is
+**not** Stage 3 and shares no identifiers or process ids with
+`chartread`. Stage 3 is unchanged: `chartread_{basename}` remains the
+only chart path. `spotread` argv is `-v -e [-c port] [-Y l]` — never
+`-u` (the v2.0 `-u` policy covers printtarg + chartread + profcheck
+only). Stdin reuses the `chartread` byte table (`" \n"` trigger,
+`"q\n"` quit + ~500 ms + kill).

docs/18-gamut-viewer.md

@@ -827,3 +827,35 @@ HTML ids that `_wireToggles` hard-codes: `chkProfileGamut`, `chkSrgbReference`,
 | #185 axes / EdgesGeometry / vertex colour / legend | All present (GridHelper kept; CSS2D parent-visibility bug). |
 | #212 Node test crash | Polyfill + dynamic import + `typeof window` guard. |
 | #225 Monterey WebGL | Lazy ensure, feature-detect, pause rAF, context-lost, low-power flags. |
+| #147 compare + inspect | macOS native: layer toggles (`gamutLayer-*`), compare slot (one extra profile or `.gam`), click/typed-Lab containment, TIFF pixel sample. |
+
+---
+
+## 13. macOS rewrite notes (#28, #147)
+
+The native viewer (`Sources/ICCery/GamutView.swift` + `GamutViewModel`) keeps
+the v1 contract points that matter — `(a*, L*, b*)` axes, camera home
+(180,120,180) lookAt (0,50,0), R resets via a local `NSEvent` monitor, native
+faces only — and adds the compare/inspect layer model:
+
+- **Layers.** `NamedGamut` (reference / profileA / profileB). sRGB cannot be
+  removed, only hidden. The compare slot holds exactly one profile; picking a
+  third replaces it and posts `gamutNoticeText`.
+- **Toggles hide, not unload.** `visibleIDs` maps to `SCNNode.isHidden`; the
+  scene is built once and a checkbox never resets the camera.
+- **Containment.** `GamutGeometry.containment` ray-casts the face table
+  (`GamutVertex.position` space) with off-axis retries on edge hits; no faces
+  → `.unknown`. `GamutGeometry.volume` sums signed tetrahedra from the vertex
+  centroid (Lab-cubic); the `vol % of sRGB` clause only prints when both
+  volumes are finite and > 0.
+- **Inspect.** Click a mesh (hit-test in the `SCNView` coordinator on
+  mouse-up, never a ZStack tap gesture), type Lab, or sample a TIFF pixel.
+  Per-layer in/out/? + swatch; `gamutInspectApprox` marks samples that went
+  through `ApproximateLab` (fixed-matrix sRGB→Lab D50, **not** ColorSync, no
+  CMM).
+- **Fallback.** No GPU → `gamutViewerUnavailable` text replaces the scene;
+  layer toggles stay visible but disabled; the representable is never
+  respawned in a loop.
+- **iccgamut** still runs only as the bundled sidecar, `-v -d {density}`
+  (density 10 = surface density, not a directory). Failure is an in-sheet
+  info notice — sRGB + profile A stay loaded (#24).