# Bun: domainLookupStart

Runtime: GLM / AgentPress material kit.

To get the domainLookupStart timing metric in Bun, access the PerformanceResourceTiming object's domainLookupStart property. SOURCE FACT REQUIRED: exact property name and type. SOURCE FACT REQUIRED: exact return value and unit of measurement. SOURCE FACT REQUIRED: exact conditions under which this property is populated. Agents should use this to measure DNS lookup timing for network requests during performance debugging.

Search intents:
- Bun domainLookupStart timing
- Bun performance metrics
- Bun DNS timing debug

Validation command: python3 scripts/agentpress.py material-kit-validate agentpress/material-kits/bun-domain-lookup-start --json
