[BUG] Sonnet subagents fail from 1M context sessions with “Extra usage is required for 1M context” on Max 20x

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug report

Claude Code appears to be incorrectly propagating the 1M context flag into Sonnet subagents/background agents, causing them to fail with:

API Error: Extra usage is required for 1M context · run /extra-usage to enable, or /model to switch to standard context

This is happening on a Max 20x plan.

Expected behavior

When I am in a 1M context parent session, I should still be able to launch normal Sonnet subagents using the standard 200K context window.

I am not trying to launch Sonnet 1M subagents. I just want the regular Sonnet subagent behavior that used to work.

Actual behavior

When Claude Code launches a Sonnet subagent/skill/background agent from a 1M context parent session, it appears to inherit the 1M context setting. Then Sonnet hits the extra-usage gate and fails with:

API Error: Extra usage is required for 1M context · run /extra-usage to enable, or /model to switch to standard context
````

This breaks workflows that previously worked fine with Sonnet subagents.

## Why this seems like a bug

The parent session may be allowed to use 1M context, but the subagent should not automatically become a Sonnet 1M session.

If Sonnet 1M requires separate extra usage, then Claude Code should either:

1. Launch the Sonnet subagent with standard 200K context by default, or
2. Provide a setting to force subagents to use standard context, or
3. Clearly expose the routing behavior and allow users to choose.

Right now, the subagent seems to inherit the 1M tier unintentionally, which causes a billing-gate failure even though the user only wanted a normal Sonnet worker.


## Impact

This is a serious regression for agentic workflows. I used to be able to use Sonnet subagents just fine, but now they fail unless I disable 1M context or avoid workflows that spawn Sonnet agents.

This effectively makes 1M context incompatible with Sonnet subagents unless extra usage is enabled, even when the desired behavior is only standard 200K Sonnet.

## Suggested fix

Please make subagents default to standard context unless explicitly configured otherwise.

For example:

* Parent session: Opus/Sonnet 1M if selected
* Subagent: Sonnet 200K by default
* Optional setting: allow users to explicitly enable 1M subagents if they want to pay extra usage

A config flag like this would also solve it:

```json
{
  "subagents": {
    "context": "standard"
  }
}

or:

CLAUDE_CODE_SUBAGENTS_DISABLE_1M_CONTEXT=1

Environment

• Plan: Max 20x
• Product: Claude Code, on both Mac and Windows
• Error: Extra usage is required for 1M context
• Affected workflow: Sonnet subagents / skills / background agents launched from a 1M parent session

What Should Happen?

Claude Code should launch Sonnet subagents, skills, and background agents with the standard 200K context window by default, even when the parent session is using 1M context.

A Sonnet subagent should not automatically inherit the parent session’s 1M context setting unless I explicitly request Sonnet 1M or enable extra usage.

Expected behavior:

• Parent session can use 1M context.
• Sonnet subagents should launch normally with standard context.
• No extra-usage error should appear unless I explicitly choose a 1M Sonnet subagent.
• Existing Sonnet subagent workflows should continue working as they did before.

Error Messages/Logs

API Error: Extra usage is required for 1M context · run /extra-usage to enable, or /model to switch to standard context

Steps to Reproduce

Reproduction steps

1. Use Claude Code on a Max 20x plan.
2. Start a session using a 1M context model.
3. Launch a task, skill, or subagent that uses Sonnet.
4. Observe that the subagent fails with:

API Error: Extra usage is required for 1M context · run /extra-usage to enable, or /model to switch to standard context

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.178

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_