OpenTelemetry Migration for Existing Applications

Guide for retrofitting OpenTelemetry into an existing, uninstrumented application. This covers the phased migration approach, context propagation refactoring, logging and metrics bridges, and verification. This is distinct from greenfield OTel setup (see otel-instrumentation skill) and Beeline-specific migration (see beeline-migration skill).

When to Use This Skill

Use this skill when the user has an existing application that:

• Has no OpenTelemetry instrumentation and needs to add it
• Has existing logging, metrics, or context patterns that must coexist with OTel
• Needs to refactor function signatures to thread trace context through the call stack
• Uses a framework with OTel middleware gotchas (e.g., Fiber, Gin, Express)

For greenfield OTel setup, use the otel-instrumentation skill instead. For Beeline-to-OTel migration, use the beeline-migration skill instead. For understanding why to instrument, see the observability-fundamentals skill.