tx block

Add blocking dependencies between tasks

Purpose

tx block creates a dependency between two tasks. The blocked task cannot be ready until the blocker is marked done.

tx enforces two rules to maintain consistency:

No self-blocking: A task cannot block itself
No cycles: A→B→C→A chains are not allowed

Usage

tx block <task-id> <blocker-id> [options]

Arguments

Argument	Required	Description
`<task-id>`	Yes	The task that will be blocked
`<blocker-id>`	Yes	The task that blocks it

Options

Option	Description
`--json`	Output as JSON
`--help`	Show help

Examples

Basic Usage

# tx-def456 blocks tx-abc123
tx block tx-abc123 tx-def456

This means: "tx-abc123 cannot start until tx-def456 is done."

Multiple Blockers

# Add multiple blockers to a single task
tx block tx-feature tx-design
tx block tx-feature tx-api
tx block tx-feature tx-tests

Output

Text Output

Dependency added: tx-def456 now blocks tx-abc123

Task tx-abc123:
  Status: blocked
  Blocked by: tx-def456

JSON Output

{
  "task": {
    "id": "tx-abc123",
    "title": "Implement login page",
    "status": "blocked",
    "blockedBy": ["tx-def456"],
    "blocks": [],
    "children": [],
    "isReady": false
  }
}

Cycle Detection

tx uses BFS (Breadth-First Search) to detect cycles at insert time:

# This would create a cycle and will be rejected
tx block tx-a tx-b
tx block tx-b tx-c
tx block tx-c tx-a  # Error: Would create cycle A→B→C→A

Error output:

Error: Cannot add dependency - would create cycle: tx-a → tx-b → tx-c → tx-a

Removing Dependencies

Use tx unblock to remove a dependency:

# Remove the blocker
tx unblock tx-abc123 tx-def456

Dependency Visualization

Use tx tree to visualize task dependencies:

tx tree tx-feature

tx-feature (blocked)
├── tx-design (done) ✓
├── tx-api (active)
└── tx-tests (blocked)
    └── tx-unit (ready)

Agent Workflow

#!/bin/bash
# Decompose a task into subtasks with dependencies

# Create main task
MAIN=$(tx add "Build user profile page" --json | jq -r '.id')

# Create subtasks
API=$(tx add "Create profile API endpoint" --parent "$MAIN" --json | jq -r '.id')
UI=$(tx add "Build profile UI component" --parent "$MAIN" --json | jq -r '.id')
TEST=$(tx add "Write integration tests" --parent "$MAIN" --json | jq -r '.id')

# Set dependencies: UI depends on API, tests depend on both
tx block "$UI" "$API"
tx block "$TEST" "$API"
tx block "$TEST" "$UI"

tx unblock - Remove a blocking dependency
tx ready - List tasks with no blockers
tx done - Complete a task and unblock dependents

tx block

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