Context

PR #1514 added 2 unit tests for the concurrency-limit deferral path in DagScheduler::record_spawn_failure(). The tester identified 3 missing edge cases worth covering:

Missing tests

1. Multi-task graph: 2 tasks, one Running, one hits concurrency limit — verify the Running task is unaffected and the deferred task reverts to Ready
2. max_concurrent=0: every spawn is rejected — verify the scheduler does not enter a Spawn → failure → Spawn infinite loop across ticks
3. All tasks deferred: empty running set + all tasks deferred to Ready — verify no premature Done(Failed) is emitted and the graph stays Running

Location

crates/zeph-core/src/orchestration/scheduler.rs, mod tests

Related

• DagScheduler: concurrency limit hit marks task as Failed instead of deferring #1513
• PR fix(orchestration): defer task to Ready on concurrency-limit spawn failure #1514
• orchestration: replace concurrency-limit string matching with typed SubAgentError variant #1515 (typed error variant)