Summary

Add a task orchestration layer to Zeph's sub-agent system that enables:

• Task decomposition: LLM breaks complex goals into structured TODO lists
• DAG dependency modeling: Tasks have explicit dependencies, forming a directed acyclic graph
• Parallel scheduling: Independent tasks execute concurrently across sub-agents
• Capability-based routing: Automatic agent selection based on task requirements
• Failure handling: Retry, fallback, skip, abort strategies
• Result aggregation: Collecting and synthesizing outputs from completed sub-tasks

Child issues

Phase dependency graph

Phase 1 (#1236) Types + DAG + Persistence
    |         \
    v          v
Phase 2       Phase 3
(#1237)       (#1238)
Planner       Scheduler + Router
    \         /
     v       v
    Phase 4 (#1239) CLI + Agent Loop
        |
        v
    Phase 5 (#1240) Aggregator + Resume/Retry
       / \
      v   v
Phase 6   Phase 7
(#1241)   (#1242)
TUI       Docs

Phases 2 and 3 can run in parallel. Phases 6 and 7 can run in parallel.

Cross-Epic Dependencies

With #1195 (Untrusted Content Isolation)

With #1222 (Graph Memory)

Recommended ordering

1. Migration numbering: Whichever of feat(memory): graph memory schema, core types, and CRUD operations #1224 or feat(orchestration): Phase 1 — TaskGraph core types, DAG operations, persistence #1236 lands first takes 021_. The other takes 022_. Track in PR review.
2. Quarantined summarizer pattern ([SEC-3.1] QuarantinedSummarizer for high-risk sources #1204): Should land before both feat(orchestration): Phase 5 — Aggregator + resume/retry #1240 (aggregator) and feat(memory): community detection with label propagation #1228 (community summaries) to define the shared isolated-LLM-call abstraction.
3. Memory write poisoning ([SEC-4.3] Memory write poisoning guard #1207): Should land before or alongside feat(memory): LLM-powered entity and relation extraction pipeline #1225 (graph extraction) AND feat(orchestration): Phase 1 — TaskGraph core types, DAG operations, persistence #1236 (task graph persistence) to cover both new write paths.
4. Cross-task sanitization: feat(orchestration): Phase 3 — DAG Scheduler + SubAgentManager integration #1238 should document that <completed-dependencies> injection is a new untrusted-content boundary; [SEC-4.2] Tool call argument validation guard #1206 should be updated to cover it.

Architecture

Feature-gated under orchestration (optional, not default).

Module: crates/zeph-core/src/orchestration/ — coordination layer over existing SubAgentManager
Persistence: GraphStore trait in zeph-core, SqliteGraphStore impl in zeph-memory (ADR-021)
Scheduler: Command pattern (SchedulerAction enum) — no long-lived &mut SubAgentManager borrow (ADR-026)
Events: Aggregated mpsc::Sender<TaskEvent> channel for agent completion notifications (ADR-027)

Core types

• TaskGraph, TaskNode, TaskId(u32), TaskStatus, GraphStatus, TaskResult
• FailureStrategy: Abort | Retry | Skip | Ask
• GraphId(Uuid): graph identifier

Traits

• Planner — LLM-based goal decomposition
• AgentRouter — capability-based agent selection (rule-based MVP, semantic future)
• Aggregator — result synthesis via LLM
• GraphStore — persistence (SQLite in zeph-memory)

Config: [orchestration]

• enabled (false), max_tasks (20), max_parallel (4)
• default_failure_strategy (abort), task_timeout_secs (600)
• planner_model, confirm_before_execute (true), dependency_context_budget (16384)

Design documents

• Research: .local/plan/subagent-task-orchestration-research.md
• Architecture (v2): .local/plan/task-orchestration-architecture.md
• Critique: .local/plan/task-orchestration-critique.md

Estimated tests: ~105 across all phases