Azure DevOps CI pipeline for master being triggered by changes in branch and vice versa

I have a CI build trigger setup for a repo as follows:

trigger:
- master

I have a branch of the same repo that I would like to have it's own pipeline.

In the pipeline.yml for the branch I have:

trigger:
- ops-workshop/ms-lab01

However, if I commit changes to my branch, builds are triggered for both the master and branch pipelines.

Committing to master also triggers the pipeline for the branch (which it shouldn't).

I have tried using the branches node to exclude master but it doesn't seem to have any effect. See:

trigger:
  branches:
    include:
    - ops-workshop/ms-lab01
    exclude:
    - master

The only thing that seems to stop builds from being triggered against the master pipeline is if I use the wildcard operator to exclude everything - no builds are then triggered.

I am making these changes in the Azure DevOps portal if that makes a difference.

This seems to be something very trivial, but I don't understand why I'm getting two pipelines triggered for the same commit, even with exclusions set.

My full YAML file looks like this:

# ASP.NET Core
# Build and test ASP.NET Core projects targeting .NET Core.
# Add steps that run tests, create a NuGet package, deploy, and more:
# https://learn.microsoft.com/azure/devops/pipelines/languages/dotnet-core

trigger:
- ops-workshop/ms-lab01

pool:
  vmImage: 'ubuntu-latest'

variables:
  buildConfiguration: 'Release'

steps:
- script: dotnet build --configuration $(buildConfiguration)
  displayName: 'dotnet build $(buildConfiguration)'

Any suggestions would be appreciated.

I see 2 suggestions/things you can check.

First check which branch is set by default in build pipeline definition, YAML -> GetSources -> (image)

Second is to try set triggered branches in build pipeline definition, choose option "Triggers", override yaml, and set branches there (look at image)