Our team is trying to use flex consumption plan (Linux) for our Azure Functions. During this we realized that logging isn't showing other than warning and higher level logs. So information and debug level logs are missing when checking from function invocations. I tested the same app in consumption and app service plan (both Windows) and there logging via host.json works as intended.

After some searching and help from ChatGPT I found this claim:

What's Going On in Flex Consumption? Flex Consumption Plan (Linux) does not yet fully support fine-grained logging via Application Insights like traditional App Service Plans.

Logging is limited to Warning and above, regardless of your host.json, unless specific diagnostic settings are manually overridden — but even then, results vary.

This is because Flex uses a different hosting model, closer to container-based execution, and doesn't integrate the same built-in logger pipeline used by Windows/App Service Plan functions.

In short: Flex plan is currently stricter about what gets logged, possibly for cost/performance reasons, and it drops lower-level logs (Information, Debug, etc.) by design or current limitation.

Plan Type                   Info-Level Logs          Default Logging
App Service Plan (Win)      ✅ Yes                    Info + above
App Service Plan (Linux)    ✅ Yes                    Info + above
Flex Consumption (Linux)    ❌ Not yet fully      Only Warning + above (currently)

Now these are claims made by ChatGPT, so I don't trust this information fully. Are there any experts here who can say if the info above is actually valid or not? Also if this is valid is there any way to fix this logging issue? From how this is working right now using Flex consumption plan seems pretty pointless.