Strider is a lightweight, embedded workflow engine for Scala 3 on the JVM.

Define workflows as a list of typed steps — jobs, triggers, conditions, approvals, parallel forks, loops, and sub-workflows — and let Strider handle scheduling, retries, persistence, and crash recovery. No external server required; Strider runs in-process and persists state through LightDB.

• Step-based programming model — express workflows as first-class Scala types (case class/trait), not XML or a DSL
• Triggers — pause workflows and resume on external events. Triggers can either Continue (resume the same workflow) or Branch (clone the workflow at its current state on every firing — ideal for recurring schedules)
• Conditions — branch execution based on workflow state
• Approvals — pause for human decisions with timeouts
• Parallel — fork into multiple branches and join on all or any
• Loops — iterate body steps over a variable list with scoped iteration variables
• Sub-workflows — execute child workflows inline
• Recycle — reset a completed workflow to run again (useful for "once-at-a-time" recurring jobs)
• Retries with backoff — configurable per-step with Fixed/Exponential/Linear strategies
• Continue on error — let specific steps fail without failing the whole workflow
• Workflow-level timeouts — bound total execution time
• Step-level timeouts — bound individual step execution via cooperative cancellation
• Lifecycle hooks — onWorkflowCompleted, onWorkflowFailed, onStepCompleted for observability
• Tags & listing — tag workflows for categorization; query by name/tag/status
• Deduplication — prevent duplicate scheduling with scheduleIfNotActive
• Bulk operations — cancelAll by name/tag
• Configurable concurrency — maxConcurrentWorkflows controls parallel execution
• Crash recovery — running and waiting workflows are safely marked failed on restart
• REST services — optional status/list/resume/cancel endpoints built on spice

• Scala 3.8+
• Java 21+ (uses virtual threads)

libraryDependencies += "com.outr" %% "strider" % "1.0.3"

import strider._
import strider.step.{Job, Step}
import fabric.rw.given
import rapid.Task
import lightdb.id.Id
import lightdb.progress.ProgressManager

// Define a job step
case class ReverseTextJob(text: String, id: Id[Step] = Step.id()) extends Job[String] {
  def execute(workflow: Workflow, pm: ProgressManager): Task[String] =
    Task(text.reverse)
}

Then wire up the model and manager, schedule a workflow, and await its completion.

Strider is extracted from a production workflow system and tested with 66+ scenarios. Version 0.x indicates the API may evolve as it's put through broader use.

MIT License — see LICENSE.