Agent tool ignores `effort:` frontmatter in subagent .md files — inherits global effortLevel instead

Summary

When spawning subagents via the Agent tool, the effort: field declared in the subagent's .md frontmatter is ignored. All subagents inherit the global effortLevel from .claude/settings.json regardless of their individual frontmatter declaration.

Environment

• Claude Code version: latest
• Project settings: .claude/settings.json with "effortLevel": "xhigh"
• Subagent files in .claude/agents/ with varying effort: frontmatter values

Steps to Reproduce

1. Create .claude/settings.json with "effortLevel": "high"
2. Create a subagent file .claude/agents/agent-a.md with frontmatter effort: low
3. Create a subagent file .claude/agents/agent-b.md with frontmatter effort: xhigh
4. Spawn both subagents via the Agent tool in the same session
5. Observe: both subagents run at high (the global setting), not at their declared effort: level

Expected Behavior

Each subagent spawned via the Agent tool should use the effort: value declared in its own frontmatter, allowing per-agent effort configuration.

Actual Behavior

All subagents inherit effortLevel from the parent session's .claude/settings.json, ignoring the frontmatter effort: field entirely.

Impact

This makes it impossible to build multi-agent pipelines with differentiated effort levels per role. A natural pattern is having some agents that perform simple, mechanical tasks (effort: low) alongside others that require deep reasoning (effort: xhigh). With the current behavior, the global effortLevel must be set to the highest required value, causing all agents — including lightweight ones — to run at maximum effort unnecessarily.

Workaround

Set effortLevel globally to the highest required value and accept the token overhead for lower-effort agents.

Request

Respect the effort: frontmatter field when spawning subagents via the Agent tool, using it to override the global effortLevel for that specific subagent invocation.