task-dependency-patterns

What this skill does

# Task Dependency Patterns

## Overview

Claude Code 2.1.16 introduces a native Task Management System with four tools:
- **TaskCreate**: Create new tasks with subject, description, and activeForm
- **TaskUpdate**: Update status (pending → in_progress → completed), set dependencies
- **TaskGet**: Retrieve full task details including blockers
- **TaskList**: View all tasks with status and dependency summary

Tasks enable structured work tracking, parallel coordination, and clear progress visibility.

## When to Use

- Breaking down complex multi-step implementations
- Coordinating parallel work across multiple files
- Tracking progress on large features
- Managing dependencies between related changes
- Providing visibility into work status

## Key Patterns

### 1. Task Decomposition

Break complex work into atomic, trackable units:

```
Feature: Add user authentication

Tasks:
#1. [pending] Create User model
#2. [pending] Add auth endpoints (blockedBy: #1)
#3. [pending] Implement JWT tokens (blockedBy: #2)
#4. [pending] Add auth middleware (blockedBy: #3)
#5. [pending] Write integration tests (blockedBy: #4)
```

### 2. Dependency Chains

Use `addBlockedBy` to create execution order:

```json
// Task #3 cannot start until #1 and #2 complete
{"taskId": "3", "addBlockedBy": ["1", "2"]}
```

### 3. Status Workflow

```
pending → in_progress → completed
   ↓           ↓
(unblocked)  (active)

pending/in_progress → deleted
```

- **pending**: Task created but not started
- **in_progress**: Actively being worked on
- **completed**: Work finished and verified
- **deleted**: Task removed — permanently removes the task

### Task Deletion

Use `status: "deleted"` to permanently remove tasks:

```json
// Delete a task
{"taskId": "3", "status": "deleted"}
```

**When to delete:**
- Orphaned tasks whose blockers have all failed
- Tasks superseded by a different approach
- Duplicate tasks created in error
- Tasks from a cancelled pipeline

**When NOT to delete:**
- Tasks that might be retried later (keep as pending)
- Tasks with useful history (mark completed instead)
- Tasks blocked by in_progress work (wait for resolution)

### 4. activeForm Pattern

Provide present-continuous form for spinner display:

| subject (imperative) | activeForm (continuous) |
|---------------------|------------------------|
| Run tests | Running tests |
| Update schema | Updating schema |
| Fix authentication | Fixing authentication |

## Agent Teams

Agent Teams provides multi-agent coordination with shared task lists and peer-to-peer messaging.

> **CC 2.1.161 — independent parallel-tool failure:** A failed tool call in a parallel batch no longer cancels siblings; each returns its own result. Teammates must check task status independently and handle failures explicitly rather than assuming a batch-wide abort.

### Team Workflow

```
1. TeamCreate("my-feature")           → Creates team + shared task list
2. TaskCreate(subject, description)    → Add tasks to shared list
3. Agent(prompt, team_name, name)       → Spawn teammates
4. TaskUpdate(owner: "teammate-name")  → Assign tasks
5. SendMessage(to, message, summary)   → Direct teammate communication
6. TeamDelete()                          → Graceful team shutdown
```

### When to Use Teams vs Task Tool

| Criteria | Task Tool (subagents) | Agent Teams |
|----------|----------------------|-------------|
| Independent tasks | Yes | Overkill |
| Cross-cutting changes | Limited | Yes |
| Agents need to talk | No (star topology) | Yes (mesh) |
| Cost sensitivity | Lower (~1x) | Higher (~2.5x) |
| Complexity < 3.0 | Yes | No |
| Complexity > 3.5 | Possible | Recommended |

### Team Task Patterns

```
# Spawn teammate into shared task list
Agent(
  prompt="You are the backend architect...",
  team_name="my-feature",
  name="backend-architect",
  subagent_type="backend-system-architect"
)

# Teammate claims and works tasks
TaskList → find unblocked, unowned tasks
TaskUpdate(taskId, owner: "backend-architect", status: "in_progress")
# ... do work ...
TaskUpdate(taskId, status: "completed")
TaskList → find next task
```

### Peer Messaging

```
# Direct message between teammates (params: to, message, summary)
SendMessage(to: "frontend-dev",
  message: "API contract ready: GET /users/:id returns {...}",
  summary: "API contract shared")

# No broadcast primitive — send to each teammate, or post to the shared
# task list (TaskCreate/TaskUpdate) so every teammate sees it
SendMessage(to: "backend-dev",
  message: "Breaking change: auth header format changed",
  summary: "Breaking auth change")
```

## Context Exhaustion Handling

When using Agent Teams, if context limit is reached mid-workflow:
- Collect partial results from completed teammates via `TaskList`
- Synthesize available outputs — prefer partial results over silent failure
- Log skipped tasks with `TaskUpdate(taskId: task_id, status: "completed", metadata: {"skipped": "context limit"})`

## Anti-Patterns

- Creating tasks for trivial single-step work
- Circular dependencies (A blocks B, B blocks A)
- Leaving tasks in_progress when blocked
- Not marking tasks completed after finishing
- Using broadcast for messages that only concern one teammate
- Spawning teams for simple sequential work (use Task tool instead)

## Related Skills

- `ork:implement` - Implementation workflow with task tracking and progress updates
- `ork:verify` - Verification tasks and completion checklists
- `ork:fix-issue` - Issue resolution with hypothesis-based RCA tracking
- `ork:brainstorm` - Design exploration with parallel agent tasks

## References

Load on demand with `Read("${CLAUDE_SKILL_DIR}/references/<file>")`:

| File | Content |
|------|---------|
| `dependency-tracking.md` | Dependency tracking patterns |
| `status-workflow.md` | Status workflow details |
| `multi-agent-coordination.md` | Multi-agent coordination |