Epic: Composite triggers — AND/OR combinators for multi-condition workflows

[geoffjay]

Summary

Implement a composite trigger system that combines multiple trigger strategies with boolean logic (AND/OR). This enables powerful multi-condition workflows — e.g., "fire when a PR has label ready AND review is approved" or "fire on cron schedule OR manual trigger."

Goals

• Design a combinator architecture wrapping existing TriggerStrategy implementations
• Implement CompositeStrategy supporting AND (all conditions) and OR (any condition) semantics
• Add Composite variant to TriggerConfig with nested trigger configurations
• Handle task merging/correlation for AND conditions across sub-strategies
• Adapt the runner loop to evaluate composite conditions correctly
• Wire into the strategy factory, API validation, and CLI

Design Notes

• OR combinator: Fires when ANY sub-strategy produces tasks. Straightforward — tokio::select! across sub-strategies.
• AND combinator: Fires when ALL sub-strategies have produced at least one task within a configurable time window. Requires a correlation window and state tracking.
• AND semantics are significantly more complex — consider a phased approach: OR first, AND later
• Nested composites should be supported (AND of ORs, etc.) but may be deferred
• Task merging: when AND fires, the produced task should include context from all sub-conditions
• This likely requires changes to how WorkflowRunner interacts with strategies, particularly for AND conditions that need to accumulate state

Architectural Considerations

• The current TriggerStrategy::next_tasks() interface returns when tasks are ready — AND combinators need to buffer partial results
• Consider a CompositeStrategy that internally manages sub-strategy tasks and only yields when the composite condition is met
• Template variables should provide access to all sub-trigger contexts (e.g., {{triggers[0].source_id}})
• Config validation must detect circular references in nested composites

Acceptance Criteria

• CompositeStrategy implements TriggerStrategy trait
• OR combinator: fires when any sub-strategy produces tasks
• AND combinator: fires when all sub-strategies have produced tasks within a time window
• Composite variant added to TriggerConfig with nested configs
• Configurable correlation window for AND conditions
• Strategy factory recursively creates sub-strategies
• API and CLI support for creating composite workflows
• Config validation prevents circular references
• Unit and integration tests for all combinator types
• Documentation with usage examples

Blocked By

• Phase 1-5 (Epic: Phase 1 — Introduce TriggerStrategy abstraction #326, Epic: Phase 2 — Cron and Delay triggers #327, Epic: Phase 4 — Webhook trigger #329, Epic: Phase 5 — Manual trigger and API dispatch #330) — all closed
• AgentIdle and FileWatch epics should ideally land first so they can be composed

Stack Base

Stack on: feature/autonomous-pipeline — this epic depends on other Phase 6 epics being available for composition but can begin implementation in parallel since it wraps the existing strategy trait.

Key Files

• crates/orchestrator/src/scheduler/strategy.rs — add CompositeStrategy
• crates/orchestrator/src/scheduler/types.rs — add Composite variant with nested TriggerConfig
• crates/orchestrator/src/scheduler/runner.rs — recursive strategy creation
• crates/orchestrator/src/scheduler/api.rs — validation for nested configs

[geoffjay]

All sub-issues implemented and PRs submitted as a stacked branch chain.

Stack root: epic-805 → PR #880 to main

Sub-issue PRs submitted with review-agent label:

• Implement OR combinator CompositeStrategy wrapping multiple sub-strategies #814 OR combinator CompositeStrategy → PR feat(scheduler): implement OR combinator CompositeStrategy #881
• Implement AND combinator with correlation window for CompositeStrategy #815 AND combinator with correlation window → PR feat(scheduler): implement AND combinator with correlation window #882
• Add Composite variant to TriggerConfig with nested config support #816 Composite variant to TriggerConfig + factory wiring → PR feat(scheduler): add Composite variant to TriggerConfig with nested config support #883
• Add tests and documentation for composite triggers #817 Tests and documentation → PR feat(scheduler): add tests and documentation for composite triggers #884

Implementation highlights:

• OR mode: each sub-strategy runs in a background tokio task; first to produce tasks wins
• AND mode: all sub-strategies tracked per-slot with correlation window timer; merged task produced when all fire
• create_strategy() refactored to recursive create_trigger_strategy() supporting up to 3 nesting levels
• Full serde support for nested TriggerConfig::Composite
• API validation: mode, minimum 2 sub-triggers, depth limit
• 384 tests passing total (77 strategy unit + 8 composite integration + 11 scheduler integration)

[geoffjay]

All sub-issues implemented and PRs submitted as a stacked branch chain.

Stack Summary

• epic-805 → PR epic: Composite triggers — AND/OR combinators for multi-condition workflows (#805) #880 (rollup)
  • issue-814 → PR feat(scheduler): implement OR combinator CompositeStrategy #881: OR combinator CompositeStrategy
    • issue-815 → PR feat(scheduler): implement AND combinator with correlation window #882: AND combinator with correlation window
      • issue-816 → PR feat(scheduler): add Composite variant to TriggerConfig with nested config support #883: Composite variant in TriggerConfig + recursive strategy factory
        • issue-817 → PR feat(scheduler): add tests and documentation for composite triggers #884: tests and documentation

Implementation Notes

The implementation was already complete across all sub-issues. Two clippy errors were fixed on the issue-817 branch:

1. api.rs: replaced format!() with .to_string() in the composite nesting depth validator
2. strategy.rs: changed merge_and_tasks() parameter from &mut Vec<Option<Vec<Task>>> to &mut [Option<Vec<Task>>]

All 365 unit tests pass, cargo fmt and cargo clippy clean.

All PRs submitted with review-agent label.