Add batch/bulk task operations for efficient agent workflows

[aadhar-agarwal]

Problem

When AI agents work on multi-step tasks, they often need to create or update multiple related tasks at once. Currently, this requires N separate bn task create or bn task update calls, which:

1. Increases latency - Each command opens storage, parses JSONL, updates cache
2. Fragments audit logs - Related operations appear as separate log entries instead of a single atomic batch
3. Loses atomicity - If agent crashes mid-batch, partial state may be left behind
4. Verbose for agents - MCP tool calls multiply, increasing context window usage

Proposed Solution

Add batch operation commands:

bn task create-batch

# Create multiple tasks from JSON array (stdin or file)
echo '[{"title": "Task A"}, {"title": "Task B", "priority": 1}]' | bn task create-batch

# Or from file
bn task create-batch --file tasks.json

# With common defaults
bn task create-batch --priority 2 --tag sprint-1 --file tasks.json

Output (JSON):

{
  "created": ["bn-a1b2", "bn-c3d4"],
  "count": 2,
  "errors": []
}

bn task update-batch

# Update multiple tasks at once
echo '[{"id": "bn-a1b2", "status": "done"}, {"id": "bn-c3d4", "status": "in_progress"}]' | bn task update-batch

bn link add-batch

# Create multiple edges at once (common when creating a task tree)
echo '[{"source": "bn-a1b2", "target": "bn-c3d4", "type": "depends_on"}]' | bn link add-batch

Benefits

1. Performance: Single storage open/close cycle for all operations
2. Atomicity: Either all succeed or transaction can be rolled back
3. Audit clarity: Single log entry shows "batch created 5 tasks"
4. Agent efficiency: One MCP tool call instead of N
5. Enables workflows: "Create PRD → spawn 10 subtasks → link all" becomes practical

Acceptance Criteria

• bn task create-batch accepts JSON array from stdin or --file
• bn task update-batch accepts JSON array with id + fields to update
• bn link add-batch accepts JSON array of edge definitions
• Batch operations produce single audit log entry
• On error, partial results are returned with error details
• MCP manifest includes batch tool definitions
• Human-readable output shows summary (e.g., "Created 5 tasks")

Related

• This would complement Tools to help organize tasks #2 (tools to organize tasks)
• Enables workflows like "import folder structure as task tree" from prds/PRD_FOLDER_IMPORT.md