Declarative Pipeline `environment` block compatibility across Jenkins LTS releases

Direct Answers

1. Parity with Scripted Pipeline: No. Declarative environment variables are immutable for the build run and cannot be reassigned mid-pipeline like env.VAR = 'new' in Scripted Pipeline. They are available in when, options, tools, and stage-level environment blocks, but dynamic recomputation requires a script { env.VAR = ... } block inside a stage.
2. Version boundaries: No documented removal or semantic change to the environment directive between 2.401 and 2.452. The feature has been stable since Declarative Pipeline 1.0 (~Jenkins 2.60). Only bug fixes (e.g., credential variable expansion in when conditions) may alter edge-case behavior.
3. Trigger interaction: pollSCM and upstream triggers start a new build execution. The environment block is re-evaluated for that new build. Variables from the triggering build are not automatically inherited unless explicitly passed via build job: ..., parameters: [...] or similar parameter-passing mechanisms.

Why Inconsistencies Appear

Reported "variable inheritance" problems usually stem from confusing build-level parameters (which can be passed between jobs) with environment variables (which are re-initialized per build). The environment directive does not propagate across builds; it only scopes variables within a single build's stages.

Verification Steps (Run on Both LTS Versions)

1. Create a minimal Declarative Pipeline:

   pipeline {
     agent any
     environment { FOO = 'bar' }
     triggers { pollSCM('H/5 * * * *') }
     stages {
       stage('One') { steps { echo "FOO=$FOO" } }
       stage('Two') { steps { echo "FOO=$FOO" } }
     }
   }

2. Trigger a build manually and via pollSCM; confirm FOO=bar prints in both stages on every run.
3. Add an upstream job that passes PARAM=value via build job: 'downstream', parameters: [string(name: 'PARAM', value: 'value')]. In the downstream job, use environment { FROM_UPSTREAM = "${params.PARAM}" } and verify the variable appears in stages.

One Diagnostic Detail Needed

If you observe a specific variable missing in a stage on one LTS but not the other, provide the exact environment snippet and the stage where it fails. That determines whether it's a credential-binding expansion bug (fixed post-2.300) or a scoping misunderstanding.