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Runtime Modes and Patching

Summary

Runtime mode defines how Meridian rewrites the target config for execution. This is the heart of the product's deterministic review model.

Why it exists

A normal Collector config may send data to live backends or external services. That is often the wrong first feedback loop for pre-merge review. Meridian instead patches the config so it can inject and capture telemetry in a controlled way.

How patching works

The patch package:

  • injects a Meridian-managed OTLP receiver
  • injects a Meridian-managed OTLP capture exporter
  • selects pipelines by name or signal when requested
  • rewrites pipeline receivers and exporters according to the chosen mode
  • preserves connector exporters in safe mode
  • records the resulting plan and writes config.patched.yaml

Modes

safe

safe replaces normal exporters with the Meridian capture exporter while preserving connector exporters.

Use this when you want deterministic, low-risk evidence.

tee

tee preserves original exporters and appends Meridian capture.

Use it when you want to observe runtime output while keeping the original exporter path active.

live

live also preserves real exporters and appends Meridian capture.

Use it only when synthetic telemetry reaching real destinations is acceptable.

What it proves and does not prove

safe proves pipeline flow under the patched harness. It does not prove live vendor connectivity.

tee and live increase realism, but they also increase operational risk and reduce the purity of the deterministic test harness.