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fix(macOS): replace @State caches with NSCache and remove nested ScrollViews in StepDetailRow #24336

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Merged
siddseethepalli merged 1 commit into from
Apr 8, 2026
Merged

fix(macOS): replace @State caches with NSCache and remove nested ScrollViews in StepDetailRow #24336

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126 changes: 52 additions & 74 deletions clients/macos/vellum-assistant/Features/Chat/AssistantProgressView.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -792,6 +792,14 @@ struct AssistantProgressView: View {

// MARK: - Step Detail Row

private final class StepDetailAttributedStringCacheEntry: NSObject {
let value: AttributedString

init(_ value: AttributedString) {
self.value = value
}
}

/// Unified row for tool call steps — handles completed, running, and blocked states.
/// Completed rows are expandable to show technical details, screenshots, and output.
private struct StepDetailRow: View {
Expand All @@ -803,22 +811,34 @@ private struct StepDetailRow: View {
/// Human-friendly label for skill_execute rows (e.g. "Using my frontend design skill").
var skillLabel: String?
var onRehydrate: (() -> Void)?
/// Cached colored AttributedString for the tool call result — computed once
/// on first expand / result change to avoid rebuilding on every render.
@State private var cachedColoredResult: AttributedString?
/// Cached line count + isLong flag for resolvedInputFull — avoids O(n)
/// byte scan in the view body on every render.
@State private var cachedInputIsLong: Bool?
@Environment(\.displayScale) private var displayScale
@Environment(\.suppressAutoScroll) private var suppressAutoScroll

private static let coloredOutputCache: NSCache<NSString, StepDetailAttributedStringCacheEntry> = {
let cache = NSCache<NSString, StepDetailAttributedStringCacheEntry>()
cache.countLimit = 128
return cache
}()

/// Lazily resolved full input text.
private var resolvedInputFull: String {
if !toolCall.inputFull.isEmpty { return toolCall.inputFull }
if let dict = toolCall.inputRawDict { return ToolCallData.formatAllToolInput(dict) }
return ""
}

/// Render-time memoization that stays off SwiftUI-owned state.
private var cachedColoredResult: AttributedString? {
guard let result = toolCall.result, !result.isEmpty else { return nil }
let key = Self.coloredOutputCacheKey(for: result, isError: toolCall.isError)
if let cached = Self.coloredOutputCache.object(forKey: key) {
return cached.value
}

let colored = coloredOutput(result, isError: toolCall.isError)
Self.coloredOutputCache.setObject(StepDetailAttributedStringCacheEntry(colored), forKey: key)
return colored
}

/// Whether this tool has detail content to show (running or completed).
private var hasDetails: Bool {
return !toolCall.inputFull.isEmpty || toolCall.inputRawDict != nil
Expand Down Expand Up @@ -929,20 +949,9 @@ private struct StepDetailRow: View {
}
.animation(VAnimation.fast, value: isDetailExpanded)
.onChange(of: isDetailExpanded) { _, newValue in
if newValue {
// Eagerly populate caches before the expanded body evaluates
// so the first render has colored output and correct input sizing.
if cachedColoredResult == nil,
let result = toolCall.result, !result.isEmpty {
cachedColoredResult = coloredOutput(result, isError: toolCall.isError)
}
if cachedInputIsLong == nil && !resolvedInputFull.isEmpty {
let lines = resolvedInputFull.utf8.reduce(1) { c, b in b == 0x0A ? c + 1 : c }
cachedInputIsLong = lines > 30 || (lines == 1 && resolvedInputFull.utf8.count > 50_000)
}
Task { @MainActor in
onRehydrate?()
}
guard newValue else { return }
DispatchQueue.main.async {
onRehydrate?()
}
}
}
Expand Down Expand Up @@ -971,22 +980,12 @@ private struct StepDetailRow: View {
.font(VFont.labelDefault)
.foregroundStyle(VColor.contentSecondary)
if !resolvedInputFull.isEmpty {
let inputIsLong = cachedInputIsLong ?? false

if inputIsLong {
ScrollView {
Text(resolvedInputFull)
.font(VFont.bodySmallDefault)
.foregroundStyle(VColor.contentSecondary)
.frame(maxWidth: .infinity, alignment: .leading)
}
.frame(height: 300)
.clipShape(RoundedRectangle(cornerRadius: VRadius.sm))
} else {
Text(resolvedInputFull)
.font(VFont.bodySmallDefault)
.foregroundStyle(VColor.contentSecondary)
}
outputBlock(
text: resolvedInputFull,
attributedText: nil,
copyText: resolvedInputFull,
copyLabel: "Copy input"
)
}
}
}
Expand Down Expand Up @@ -1022,8 +1021,8 @@ private struct StepDetailRow: View {
.foregroundStyle(VColor.contentTertiary)
.textCase(.uppercase)

// Cached colored output — populated eagerly in
// .onChange(of: isDetailExpanded) or .onAppear.
// Cached diff coloring now lives in a non-observable
// cache so expansion no longer mutates SwiftUI state.
outputBlock(
text: cachedColoredResult == nil ? result : nil,
attributedText: cachedColoredResult,
Expand All @@ -1036,31 +1035,13 @@ private struct StepDetailRow: View {
}
}
.padding(.bottom, VSpacing.sm)
.textSelection(.enabled)
.onAppear {
if cachedColoredResult == nil,
let result = toolCall.result, !result.isEmpty {
cachedColoredResult = coloredOutput(result, isError: toolCall.isError)
}
if cachedInputIsLong == nil && !resolvedInputFull.isEmpty {
let lines = resolvedInputFull.utf8.reduce(1) { c, b in b == 0x0A ? c + 1 : c }
cachedInputIsLong = lines > 30 || (lines == 1 && resolvedInputFull.utf8.count > 50_000)
}
}
.onChange(of: toolCall.result) { _, newResult in
if let result = newResult, !result.isEmpty {
cachedColoredResult = coloredOutput(result, isError: toolCall.isError)
} else {
cachedColoredResult = nil
}
}
}

// MARK: - Output Block

/// Reusable output block with copy button.
/// Long content (>30 lines) gets a definite-height ScrollView so LazyVStack
/// skips content measurement. Short content renders directly with no ScrollView.
/// The outer transcript owns vertical scrolling to avoid nested scroll-view
/// hit-testing and responder churn inside expanded tool rows.
@ViewBuilder
private func outputBlock(
text: String?,
Expand All @@ -1069,21 +1050,8 @@ private struct StepDetailRow: View {
copyLabel: String,
isError: Bool = false
) -> some View {
let lines = copyText.utf8.reduce(1) { count, byte in byte == 0x0A ? count + 1 : count }
let isLong = lines > 30 || (lines == 1 && copyText.utf8.count > 50_000)

ZStack(alignment: .topTrailing) {
VStack(alignment: .leading, spacing: VSpacing.xs) {
if isLong {
// Definite height — LazyVStack never measures content inside.
ScrollView {
outputTextView(text: text, attributedText: attributedText, isError: isError)
}
.frame(height: 400)
} else {
outputTextView(text: text, attributedText: attributedText, isError: isError)
}
}
outputTextView(text: text, attributedText: attributedText, isError: isError)
.padding(EdgeInsets(top: VSpacing.sm, leading: VSpacing.sm, bottom: VSpacing.sm, trailing: VSpacing.sm + VSpacing.xl))
.frame(maxWidth: .infinity, alignment: .leading)
.background(VColor.surfaceOverlay.opacity(0.6))
Expand Down Expand Up @@ -1114,7 +1082,7 @@ private struct StepDetailRow: View {
}
}

/// Text view for output content, used by both the ScrollView (long) and direct (short) paths.
/// Shared text view used by the detail blocks.
@ViewBuilder
private func outputTextView(
text: String?,
Expand All @@ -1125,16 +1093,26 @@ private struct StepDetailRow: View {
Text(attrText)
.font(VFont.bodySmallDefault)
.frame(maxWidth: .infinity, alignment: .leading)
.fixedSize(horizontal: false, vertical: true)
} else if let plainText = text {
Text(plainText)
.font(VFont.bodySmallDefault)
.foregroundStyle(isError ? VColor.systemNegativeStrong : VColor.contentSecondary)
.frame(maxWidth: .infinity, alignment: .leading)
.fixedSize(horizontal: false, vertical: true)
}
}

// MARK: - Helpers

private static func coloredOutputCacheKey(for result: String, isError: Bool) -> NSString {
var hasher = Hasher()
hasher.combine(result)
hasher.combine(result.utf8.count)
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hasher.combine(isError)
return "output:\(result.utf8.count):\(hasher.finalize())" as NSString
}

private func coloredOutput(_ result: String, isError: Bool) -> AttributedString {
let lines = result.components(separatedBy: "\n")
let isDiff = result.contains("@@") && result.contains("---") && result.contains("+++")
Expand Down