Power & Performance with asc

Download performance metrics and diagnostic logs to monitor app performance indicators — launch time, hang rate, disk writes, memory use, battery life, termination, and animation hitches.

Authentication

asc auth login --key-id <id> --issuer-id <id> --private-key-path ~/.asc/AuthKey.p8

How to Navigate (CAEOAS Affordances)

Every JSON response contains an "affordances" field with ready-to-run commands — IDs already filled in. Follow the affordances to drill down from metrics to diagnostics to logs.

App metrics → Diagnostics → Logs flow:

// 1. asc perf-metrics list --app-id app-1 → shows performance overview
{
  "id": "app-1-LAUNCH-launchTime",
  "category": "LAUNCH",
  "latestValue": 1.5,
  "affordances": {
    "listAppMetrics": "asc perf-metrics list --app-id app-1"
  }
}

// 2. asc diagnostics list --build-id build-1 → shows hotspots
{
  "id": "sig-1",
  "diagnosticType": "HANGS",
  "weight": 45.2,
  "affordances": {
    "listLogs": "asc diagnostic-logs list --signature-id sig-1",
    "listSignatures": "asc diagnostics list --build-id build-1"
  }
}

// 3. asc diagnostic-logs list --signature-id sig-1 → shows call stacks
{
  "id": "sig-1-0-0",
  "bundleId": "com.example.app",
  "callStackSummary": "main > UIKit > layoutSubviews",
  "affordances": {
    "listLogs": "asc diagnostic-logs list --signature-id sig-1"
  }
}

Typical Workflows

Check app performance at a glance

asc perf-metrics list --app-id 123456789 --pretty

Investigate a specific metric type

# Launch time only
asc perf-metrics list --app-id 123456789 --metric-type LAUNCH --pretty

# Hang rate only
asc perf-metrics list --app-id 123456789 --metric-type HANG --pretty

Compare build-specific metrics

asc builds list --app-id 123456789 --output table
asc perf-metrics list --build-id build-abc --pretty

Diagnose hangs in a build

# 1. List diagnostic signatures (hang hotspots)
asc diagnostics list --build-id build-abc --diagnostic-type HANGS --pretty

# 2. Drill into the top signature's call stacks
asc diagnostic-logs list --signature-id sig-1 --pretty

Full investigation pipeline

# Start from builds
BUILD_ID=$(asc builds list --app-id APP_ID | jq -r '.data[0].id')

# Check performance metrics
asc perf-metrics list --build-id "$BUILD_ID" --pretty

# Find hang hotspots
asc diagnostics list --build-id "$BUILD_ID" --diagnostic-type HANGS --pretty

# Get call stacks for the heaviest signature
SIG_ID=$(asc diagnostics list --build-id "$BUILD_ID" --diagnostic-type HANGS \
  | jq -r '.data | sort_by(-.weight) | .[0].id')
asc diagnostic-logs list --signature-id "$SIG_ID" --pretty

Performance Metric Categories

Category	--metric-type value	What it measures
Launch	LAUNCH	App launch time
Hang	HANG	Main thread hang rate
Memory	MEMORY	Peak and average memory use
Disk	DISK	Disk write volume
Battery	BATTERY	Energy impact
Termination	TERMINATION	Background/foreground terminations
Animation	ANIMATION	Animation hitch rate

Diagnostic Types

Type	--diagnostic-type value	What it captures
Hangs	HANGS	Main thread hang signatures
Disk Writes	DISK_WRITES	Excessive disk write signatures
Launches	LAUNCHES	Slow launch signatures

Reading Results

PerformanceMetric — one row per metric identifier (e.g. launchTime, peakMemory), flattened from the nested Xcode Metrics API. Key fields:

• category — which metric group (LAUNCH, HANG, etc.)
• latestValue + unit — most recent measurement
• goalValue — Apple's recommended target
• parentType — "app" or "build" (tells you whether this came from app-level or build-level metrics)

DiagnosticSignatureInfo — a recurring issue pattern ranked by weight (% of occurrences). Higher weight = more impactful. insightDirection of "UP" means the issue is getting worse.

DiagnosticLogEntry — individual log with device metadata and callStackSummary (top 5 frames joined with >).

Full Command Reference

See commands.md for all flags and examples.