Lambda Managed Instances don't support --log-type Tail — use CloudWatch platform.report instead

Tried invoking a Lambda Managed Instances function with --log-type Tail and got an immediate error.

Output

Tail logs are not supported for functions configured with capacity provider.

With standard Lambda, --log-type Tail is the go-to for getting REPORT lines (Duration, Billed Duration, Init Duration). Not an option with MI.

Instead, platform.report events in CloudWatch Logs contain the Duration metrics.

Terminal

aws logs filter-log-events \
  --log-group-name /aws/lambda/YOUR_FUNCTION_NAME \
  --filter-pattern "platform.report" \
  --start-time $(( $(date +%s) - 300 ))000 \
  --region ap-northeast-1 \
  --query 'events[*].message' --output text

The platform.report JSON includes metrics.durationMs and spans (responseLatency, responseDuration) — actually more detailed than the REPORT line from Tail logs.