How to fix "No such DSL method 'agent' found among steps"? - jenkins-pipeline

Question

I am trying to execute a portion of my script in a docker container.
...
stage ("run test") {
agent {
docker {
label "docker"
image "dyalog/dyalog"
}
}
steps {
....
However, Jenkins gives an error message that is not helpful (at least for me):
java.lang.NoSuchMethodError: No such DSL method 'agent' found among steps [acceptGitLabMR, addEmbeddableBadgeConfiguration, addGitLabMRComment, archive, bat, build, catchError, checkout, compareVersions, deleteDir, dir, dockerFingerprintFrom, dockerFingerprintRun, dockerNode, echo, emailext, emailextrecipients, envVarsForTool, error, exws, exwsAllocate, fileExists, findFiles, getContext, getHighestSemanticVersion, getNextSemanticVersion, git, gitChangelog, gitlabBuilds, gitlabCommitStatus, influxDbPublisher, input, isUnix, junit, library, libraryResource, load, lock, mail, milestone, node, nodesByLabel, parallel, powershell, prependToFile, properties, publishChecks, publishHTML, pwd, pwsh, readCSV, readFile, readJSON, readManifest, readMavenPom, readProperties, readTrusted, readYaml, resolveScm, retry, script, setGitHubPullRequestStatus, sh, sha1, sha256, sleep, sshagent, stage, stash, step, svn, tar, tee, timeout, timestamps, tm, tool, touch, unarchive, unstable, unstash, untar, unzip, updateGitlabCommitStatus, validateDeclarativePipeline, verifySha1, verifySha256, waitUntil, warnError, withChecks, withContext, withCredentials, withDockerContainer, withDockerRegistry, withDockerServer, withEnv, wrap, writeCSV, writeFile, writeJSON, writeMavenPom, writeYaml, ws, zip] or symbols [GitUsernamePassword, Number, Open, all, allBranchesSame, allOf, allowRunOnStatus, always, ant, antFromApache, antOutcome, antTarget, any, anyOf, apiToken, architecture, archiveArtifacts, artifactManager, asIsGITScm, attach, authorizationMatrix, batchFile, bitbucketServer, booleanParam, branch, branchCreated, branches, brokenBuildSuspects, brokenTestsSuspects, buildButton, buildDiscarder, buildDiscarders, buildParameter, buildRetention, buildSelector, buildUser, buildingTag, builtInNode, caseInsensitive, caseSensitive, certificate, changeRequest, changelog, changeset, checkoutToSubdirectory, choice, choiceParam, cleanWs, clock, close, command, commentPattern, commit, commitChanged, commitMessagePattern, configFile, configFileProvider, contributor, copyArtifactPermission, copyArtifacts, copyartifact, created, credentials, cron, crumb, culprits, default, defaultFolderConfiguration, defaultView, deleted, demand, description, developers, disableConcurrentBuilds, disableResume, docker, dockerCert, dockerServer, dockerTool, dockerfile, downstream, dumb, durabilityHint, email-ext, envInject, envVars, envVarsFilter, environment, equals, executor, expression, extendedEmailPublisher, exwsGlobalConfigurationDiskPools, exwsGlobalConfigurationTemplates, exwsNodeConfigurationDiskPools, fastestReadSpeed, fastestWriteSpeed, file, fileParam, filePath, fingerprint, fingerprints, frameOptions, freeStyle, freeStyleJob, fromDocker, fromScm, fromSource, ftpPublisher, git, gitBranchDiscovery, gitHub, gitHubBranchDiscovery, gitHubBranchHeadAuthority, gitHubEvents, gitHubExcludeArchivedRepositories, gitHubExcludeForkedRepositories, gitHubExcludePublicRepositories, gitHubForkDiscovery, gitHubIgnoreDraftPullRequestFilter, gitHubPRStatus, gitHubPlugin, gitHubPullRequestDiscovery, gitHubSshCheckout, gitHubTagDiscovery, gitHubTopicsFilter, gitHubTrustContributors, gitHubTrustEveryone, gitHubTrustNobody, gitHubTrustPermissions, gitLabConnection, gitParameter, gitTagDiscovery, gitUsernamePassword, github, githubBranches, githubPRAddLabels, githubPRClosePublisher, githubPRComment, githubPRMessage, githubPRRemoveLabels, githubPRStatusPublisher, githubPlugin, githubProjectProperty, githubPullRequests, githubPush, gitlab, globalConfigFiles, hashChanged, headRegexFilter, headWildcardFilter, hyperlink, hyperlinkToModels, inheriting, inheritingGlobal, installSource, isRestartedRun, javadoc, jdk, jdkInstaller, jgit, jgitapache, jnlp, jobBuildDiscarder, jobName, junitTestResultStorage, label, labels, labelsAdded, labelsExist, labelsNotExist, labelsPatternExists, labelsRemoved, lastCompleted, lastDuration, lastFailure, lastGrantedAuthorities, lastStable, lastSuccess, lastSuccessful, lastWithArtifacts, latestSavedBuild, legacy, legacySCM, list, local, location, logRotator, loggedInUsersCanDoAnything, mailer, masterBuild, maven, maven3Mojos, mavenErrors, mavenGlobalConfig, mavenMojos, mavenWarnings, message, modernSCM, mostUsableSpace, msbuild, msbuildError, msbuildWarning, myView, namedBranchesDifferent, newContainerPerStage, noGITScm, node, nodeProperties, nodejs, nodejsci, nonInheriting, nonMergeable, none, not, organizationFolder, overrideIndexTriggers, paneStatus, parallelsAlwaysFailFast, parameters, password, pattern, permalink, permanent, pipeline, pipeline-model, pipeline-model-docker, pipelineTriggers, plainText, plugin, pollSCM, preserveStashes, projectNamingStrategy, proxy, pruneTags, pullRequest, pullRequests, queueItemAuthenticator, quietPeriod, rateLimit, rateLimitBuilds, recipients, requestor, resourceRoot, restriction, restrictions, retainOnlyVariables, run, runParam, sSHLauncher, schedule, scmRetryCount, scriptApproval, scriptApprovalLink, search, security, shell, simpleBuildDiscarder, skipDefaultCheckout, skipStagesAfterUnstable, slave, sourceRegexFilter, sourceWildcardFilter, specific, ssh, sshPublicKey, sshUserPrivateKey, standard, status, statusOnPublisherError, string, stringParam, suppressAutomaticTriggering, suppressFolderAutomaticTriggering, swapSpace, tag, tags, teamSlugFilter, text, textParam, timestamper, timestamperConfig, timezone, tmpSpace, toolLocation, triggeredBy, unsecured, untrusted, upstream, upstreamDevelopers, userSeed, usernameColonPassword, usernamePassword, viewsTabBar, weather, withAnt, workspace, x509ClientCert, zip] or globals [currentBuild, docker, env, params, pipeline, scm]
at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:219)
at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:124)
at jdk.internal.reflect.GeneratedMethodAccessor666.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:98)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1225)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1034)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:41)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:163)
at org.kohsuke.groovy.sandbox.GroovyInterceptor.onMethodCall(GroovyInterceptor.java:23)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:158)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:161)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:165)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:135)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:135)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:135)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:135)
at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:17)
at WorkflowScript.run(WorkflowScript:48)
at ___cps.transform___(Native Method)
at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:86)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:113)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:83)
at jdk.internal.reflect.GeneratedMethodAccessor596.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.ClosureBlock.eval(ClosureBlock.java:46)
at com.cloudbees.groovy.cps.Next.step(Next.java:83)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:136)
at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:275)
at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:18)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:51)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:187)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:420)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$400(CpsThreadGroup.java:95)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:330)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:294)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:67)
at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:139)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:68)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.base/java.lang.Thread.run(Unknown Source)
Finished: FAILURE
To the (admittedly, my) uneducated brain this seems to indicate that agent is not accepted following stage - but I have applied similar constructs w/o issues before, so I do not understand what the issue is here.

Answer 1

I was able to solve this by restructuring the script a bit (removing earlier steps).
I'm still puzzled this helped and am still worried about an environment that leaves its user as much in the dark as $#% Jenkins does with its useless error message, but hey, it's working! ;)