feat(scarfmon): chat + transport + sqlite measure points (Phase 2)

Wires ScarfMon measure points into the chat hot path on both targets,
plus the underlying SSH transport and remote-SQLite backend. All
callsites are surgical adds — no behavior change. Cost when ScarfMon
is in `.signpostOnly` (default) is one os_signpost emit per call,
elided by the runtime outside an Instruments session. In `.full` mode
the same callsites also push samples into the in-memory ring buffer.

Render counters (event):
- mac.ChatView.body / ios.ChatView.body — full transcript pane re-evals
- mac.RichMessageBubble.body / ios.MessageBubble.body — per-bubble re-evals

Stream + session (event + interval):
- mac.sendViaACP, mac.sendPrompt — user tap → first-byte
- mac.acpEvent, mac.handleACPEvent — per-event delivery + handle cost
- mac.startACPSession — session boot
- ios.send, ios.startResuming — same shape on iOS
- ios.acpEvent, ios.handleACPEvent — same per-event split on iOS

Transport + SQLite (interval, with byte counts on rows):
- ssh.streamScript (Citadel iOS) — SSH round-trip
- ssh.run (SSHScriptRunner Mac) — SSH round-trip
- sqlite.query, sqlite.queryBatch — Remote SQLite per-call
- sqlite.query.rows — row count + stdout bytes per query

Disk I/O (interval):
- diskIO.loadConfig — config.yaml read + parse
- diskIO.loadCronJobs — cron jobs.json decode

Body counters use the `let _: Void = ScarfMon.event(...)` pattern at
the top of `body` — works inside `@ViewBuilder` and fires on every
re-eval, which is exactly the signal we want.

To use:
  Mac: Settings → Advanced → Performance Diagnostics → Full
  iOS: Settings → Diagnostics → Performance → Full
Both panels auto-aggregate by (category, name), surface top 20 by
p95, and offer Copy as JSON for sharing in feedback threads.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scarf/Packages/ScarfCore/Sources/ScarfCore/Services/Backends/RemoteSQLiteBackend.swift

@@ -149,27 +149,37 @@ public actor RemoteSQLiteBackend: HermesQueryBackend {
     // MARK: - Queries
 
     public func query(_ sql: String, params: [SQLValue]) async throws -> [Row] {
-        guard isOpen else { throw BackendError.notOpen }
-        let inlined = SQLValueInliner.inline(sql, params: params)
-        let dbPath = context.paths.stateDB
-        let script = """
-        sqlite3 -readonly -json \(quoteForRemoteShell(dbPath)) <<'__SCARF_SQL__'
-        \(inlined)
-        __SCARF_SQL__
-        """
-        let result: ProcessResult
-        do {
-            result = try await transport.streamScript(script, timeout: queryTimeout)
-        } catch {
-            throw BackendError.transport(error.localizedDescription)
+        try await ScarfMon.measureAsync(.sqlite, "query") {
+            guard isOpen else { throw BackendError.notOpen }
+            let inlined = SQLValueInliner.inline(sql, params: params)
+            let dbPath = context.paths.stateDB
+            let script = """
+            sqlite3 -readonly -json \(quoteForRemoteShell(dbPath)) <<'__SCARF_SQL__'
+            \(inlined)
+            __SCARF_SQL__
+            """
+            let result: ProcessResult
+            do {
+                result = try await transport.streamScript(script, timeout: queryTimeout)
+            } catch {
+                throw BackendError.transport(error.localizedDescription)
+            }
+            if result.exitCode != 0 {
+                throw BackendError.sqlite(exitCode: result.exitCode, stderr: result.stderrString)
+            }
+            let rows = try parseSingleResultSet(result.stdoutString)
+            ScarfMon.event(.sqlite, "query.rows", count: rows.count, bytes: result.stdout.count)
+            return rows
         }
-        if result.exitCode != 0 {
-            throw BackendError.sqlite(exitCode: result.exitCode, stderr: result.stderrString)
-        }
-        return try parseSingleResultSet(result.stdoutString)
     }
 
     public func queryBatch(_ statements: [(sql: String, params: [SQLValue])]) async throws -> [[Row]] {
+        try await ScarfMon.measureAsync(.sqlite, "queryBatch") {
+            try await _queryBatchImpl(statements)
+        }
+    }
+
+    private func _queryBatchImpl(_ statements: [(sql: String, params: [SQLValue])]) async throws -> [[Row]] {
         guard isOpen else { throw BackendError.notOpen }
         if statements.isEmpty { return [] }
         // Build one sqlite3 invocation with marker SELECTs separating

scarf/Packages/ScarfCore/Sources/ScarfCore/Transport/SSHScriptRunner.swift

@@ -46,16 +46,18 @@ public enum SSHScriptRunner {
     /// cross-platform we return a connect failure on non-macOS so
     /// the file compiles everywhere.
     public static func run(script: String, context: ServerContext, timeout: TimeInterval = 30) async -> Outcome {
-        #if os(macOS)
-        switch context.kind {
-        case .local:
-            return await runLocally(script: script, timeout: timeout)
-        case .ssh(let config):
-            return await runOverSSH(script: script, config: config, timeout: timeout)
+        await ScarfMon.measureAsync(.transport, "ssh.run") {
+            #if os(macOS)
+            switch context.kind {
+            case .local:
+                return await runLocally(script: script, timeout: timeout)
+            case .ssh(let config):
+                return await runOverSSH(script: script, config: config, timeout: timeout)
+            }
+            #else
+            return .connectFailure("SSHScriptRunner is only available on macOS")
+            #endif
         }
-        #else
-        return .connectFailure("SSHScriptRunner is only available on macOS")
-        #endif
     }
 
     // MARK: - SSH path

scarf/Packages/ScarfIOS/Sources/ScarfIOS/CitadelServerTransport.swift

@@ -179,6 +179,12 @@ public final class CitadelServerTransport: ServerTransport, @unchecked Sendable
     /// untouched — same correctness guarantee as `SSHScriptRunner`'s
     /// stdin-pipe approach.
     public func streamScript(_ script: String, timeout: TimeInterval) async throws -> ProcessResult {
+        try await ScarfMon.measureAsync(.transport, "ssh.streamScript") {
+            try await _streamScriptImpl(script, timeout: timeout)
+        }
+    }
+
+    private func _streamScriptImpl(_ script: String, timeout: TimeInterval) async throws -> ProcessResult {
         let scriptBytes = Data(script.utf8)
         let b64 = scriptBytes.base64EncodedString()
         // Prepend the same PATH guard that `asyncRunProcess` uses so

scarf/Scarf iOS/Chat/ChatView.swift

@@ -66,7 +66,12 @@ struct ChatView: View {
     )!
 
     var body: some View {
-        VStack(spacing: 0) {
+        // ScarfMon body-evaluation counter. Re-render churn during
+        // streaming is one of the load-bearing perf signals; rendering
+        // here costs ~one signpost emit + ring-buffer append (off the
+        // hot path otherwise).
+        let _: Void = ScarfMon.event(.chatRender, "ios.ChatView.body")
+        return VStack(spacing: 0) {
             connectionBanner
             errorBanner
             projectContextBar
@@ -1254,6 +1259,12 @@ final class ChatController {
     /// assistant reply streams back as ACP notifications handled by
     /// the event task.
     func send() async {
+        await ScarfMon.measureAsync(.chatStream, "ios.send") {
+            await _sendImpl()
+        }
+    }
+
+    private func _sendImpl() async {
         guard state == .ready, let client else { return }
         let text = draft.trimmingCharacters(in: .whitespacesAndNewlines)
         // v0.12+ allows image-only sends — vision models accept "describe
@@ -1358,7 +1369,10 @@ final class ChatController {
             let stream = await client.events
             for await event in stream {
                 guard !Task.isCancelled else { break }
-                self?.vm.handleACPEvent(event)
+                ScarfMon.event(.chatStream, "ios.acpEvent", count: 1)
+                ScarfMon.measure(.chatStream, "ios.handleACPEvent") {
+                    self?.vm.handleACPEvent(event)
+                }
             }
             // Stream ended — if we weren't explicitly cancelled the
             // channel died (EOF on stdin/out, write to dead pipe,
@@ -1788,6 +1802,12 @@ final class ChatController {
     /// to `session/load` if the remote doesn't support `session/resume`
     /// (Hermes < 0.9.x).
     func startResuming(sessionID: String) async {
+        await ScarfMon.measureAsync(.sessionLoad, "ios.startResuming") {
+            await _startResumingImpl(sessionID: sessionID)
+        }
+    }
+
+    private func _startResumingImpl(sessionID: String) async {
         guard await passModelPreflight(intent: .resume(sessionID: sessionID)) else { return }
         await stop()
         vm.reset()
@@ -1952,6 +1972,11 @@ private struct MessageBubble: View, Equatable {
     }
 
     var body: some View {
+        // Per-bubble render counter. The streaming bubble
+        // (`message.id == 0`) re-renders on every chunk; tracking the
+        // count here is what tells us if a slow chat is bottlenecked
+        // on body re-eval vs. event-loop delivery.
+        let _: Void = ScarfMon.event(.chatRender, "ios.MessageBubble.body")
         if message.isToolResult {
             ToolResultRow(message: message)
         } else {

scarf/scarf/Core/Services/HermesFileService.swift

@@ -17,8 +17,10 @@ struct HermesFileService: Sendable {
     // MARK: - Config
 
     nonisolated func loadConfig() -> HermesConfig {
-        guard let content = readFile(context.paths.configYAML) else { return .empty }
-        return parseConfig(content)
+        ScarfMon.measure(.diskIO, "loadConfig") {
+            guard let content = readFile(context.paths.configYAML) else { return .empty }
+            return parseConfig(content)
+        }
     }
 
     /// Error-surfacing config load. Used by Dashboard to show the user a
@@ -480,13 +482,15 @@ struct HermesFileService: Sendable {
     // MARK: - Cron
 
     nonisolated func loadCronJobs() -> [HermesCronJob] {
-        guard let data = readFileData(context.paths.cronJobsJSON) else { return [] }
-        do {
-            let file = try JSONDecoder().decode(CronJobsFile.self, from: data)
-            return file.jobs
-        } catch {
-            print("[Scarf] Failed to decode cron jobs: \(error.localizedDescription)")
-            return []
+        ScarfMon.measure(.diskIO, "loadCronJobs") {
+            guard let data = readFileData(context.paths.cronJobsJSON) else { return [] }
+            do {
+                let file = try JSONDecoder().decode(CronJobsFile.self, from: data)
+                return file.jobs
+            } catch {
+                print("[Scarf] Failed to decode cron jobs: \(error.localizedDescription)")
+                return []
+            }
         }
     }
 

scarf/scarf/Features/Chat/ViewModels/ChatViewModel.swift

@@ -395,6 +395,7 @@ final class ChatViewModel {
     }
 
     private func sendViaACP(client: ACPClient, text: String, images: [ChatImageAttachment] = []) {
+        ScarfMon.event(.chatStream, "mac.sendViaACP", count: 1, bytes: text.utf8.count)
         guard let sessionId = richChatViewModel.sessionId else {
             clearACPErrorState()
             acpError = "No session ID — cannot send"
@@ -434,7 +435,9 @@ final class ChatViewModel {
         }
         acpPromptTask = Task { @MainActor in
             do {
-                let result = try await client.sendPrompt(sessionId: sessionId, text: wireText, images: images)
+                let result = try await ScarfMon.measureAsync(.chatStream, "mac.sendPrompt") {
+                    try await client.sendPrompt(sessionId: sessionId, text: wireText, images: images)
+                }
                 acpStatus = "Ready"
                 richChatViewModel.handleACPEvent(
                     .promptComplete(sessionId: sessionId, response: result)
@@ -475,6 +478,7 @@ final class ChatViewModel {
     // MARK: - ACP Session Management
 
     private func startACPSession(resume sessionId: String?, projectPath: String? = nil) {
+        ScarfMon.event(.sessionLoad, "mac.startACPSession", count: 1)
         stopACP()
         clearACPErrorState()
 
@@ -655,7 +659,10 @@ final class ChatViewModel {
             let eventStream = await client.events
             for await event in eventStream {
                 guard !Task.isCancelled else { break }
-                self?.richChatViewModel.handleACPEvent(event)
+                ScarfMon.event(.chatStream, "mac.acpEvent", count: 1)
+                ScarfMon.measure(.chatStream, "mac.handleACPEvent") {
+                    self?.richChatViewModel.handleACPEvent(event)
+                }
                 self?.acpStatus = await client.statusMessage
             }
             // Stream ended — if we weren't cancelled, the connection died

scarf/scarf/Features/Chat/Views/ChatView.swift

@@ -17,6 +17,12 @@ struct ChatView: View {
     private var showInspector: Bool = true
 
     var body: some View {
+        // ScarfMon body-evaluation counter — tracks how many times
+        // SwiftUI re-evaluates this view per second during streaming.
+        // High counts here usually mean state is fanning out further
+        // than necessary; pair with `mac.RichMessageBubble.body` to
+        // see whether the churn lives in the parent or the bubbles.
+        let _: Void = ScarfMon.event(.chatRender, "mac.ChatView.body")
         @Bindable var vm = viewModel
         @Bindable var coord = coordinator
         VStack(spacing: 0) {

scarf/scarf/Features/Chat/Views/RichMessageBubble.swift

@@ -58,6 +58,11 @@ struct RichMessageBubble: View, Equatable {
     }
 
     var body: some View {
+        // Per-bubble render counter. The streaming bubble re-renders
+        // per token; cross-reference with `mac.ChatView.body` and
+        // `chatStream.handleACPEvent` to see whether streaming churn
+        // lives in the parent, the bubble, or the event handler.
+        let _: Void = ScarfMon.event(.chatRender, "mac.RichMessageBubble.body")
         if message.isUser {
             userBubble
         } else if message.isAssistant {