Feature Request: Configurable concurrent subagent limit in workflows

Problem

The workflow engine caps concurrent agent() calls at min(16, cpu_cores - 2). On a 10-core machine this means only 8 agents run in parallel. For large-scale workflows (research sweeps, exhaustive reviews, multi-perspective verification), this is a significant bottleneck.

Current Behavior

• Hard limit: min(16, cpu cores - 2)
• No configuration option to override
• Excess agents queue and wait

Proposed Solution

Add a configurable option (e.g., in .claude/settings.json or as a workflow script parameter) to override the concurrent limit:

{
  "workflow": {
    "maxConcurrentAgents": 32
  }
}

Or in workflow scripts:

const results = await parallel(tasks, { maxConcurrency: 32 })

Use Cases

• Large-scale code reviews across 50+ files
• Exhaustive bug finding with multiple independent finders
• Multi-perspective verification panels (5+ independent verifiers per finding)
• Research sweeps with diverse search strategies

Environment

• Claude Code version: 2.1.158
• Platform: macOS (Darwin 25.5.0), 10 cores
• Actual concurrent limit: 8

Notes

The current cpu_cores - 2 safeguard is sensible as a default, but power users with sufficient resources (cloud instances, dedicated machines) should be able to opt into higher concurrency. The 16 hard cap could also be raised or made configurable.