Claude Code defaults to Sonnet 4.6, dispatch Opus subagents when needed

One-sentence takeaway

Keep Claude Code's main session on Sonnet 4.6 and only dispatch Opus subagents for research or security testing; the author reports four parallel sessions running 14+ hours still consumed only about 20% of the weekly quota.

Use cases

• Suitable tasks: Multi-session day-to-day development, implementation/fix work that needs to stretch across a week of quota; upgrade only for planning or security review.

• Unsuitable tasks: Whole-repository architecture decisions, high-risk refactors, audits that require the strongest model end to end.

• Applicable model versions: Claude Sonnet 4.6 as the default executor; Opus only for subagents. A commenter also pairs with /model opusplan.

• Applicable clients, agents, or APIs: Claude Code (including parallel sessions and subagents).

• Recommended reasoning tier and parameters: The post gives no effort level; the core idea is model tiering rather than running the main session on Opus.

Ready-to-use content

Main session constraints (can go in project CLAUDE.md or at the start of each session):

Default model: Claude Sonnet 4.6 for implementation, edits, tests, and routine refactors.

Do not switch the main session to Opus.

If the task is architecture research, threat modeling, or security testing,
launch a subagent on Opus, then return a short plan and evidence to this session.
Execute the plan here with Sonnet 4.6.

Keep four or fewer parallel sessions unless the token budget is explicitly raised.

When you need the official plan/execute switch, add:

/model opusplan

Quota-tight checklist:

1. Is the main session still on claude-sonnet-4-6?
2. Are Opus subagents dispatched only for research/security testing?
3. Was the 1M window accidentally enabled and triggering extra-usage?

Test/workflow steps

1. Within the same week, run two configurations: A all Opus; B main session Sonnet 4.6 + Opus subagents when needed.

2. Fix parallel session count (author used 4), repository, and task types.

3. Record weekly quota percentage, completed PRs/tasks, rework count, and security-related gaps.

4. If using opusplan, also verify execution-stage model ID and whether the context window is 200k or 1M.

Original evidence and data

• Author's original post: defaulting to Sonnet 4.6 is to avoid "blowing through the token budget in an hour"; four parallel sessions ran 14+ hours using only about 20% of the weekly quota.

• Author's upgrade condition: for research or security testing, have it launch a subagent with opus.

• Comment robbyatcuprbotlabs: after /model opusplan (Max 20x) no longer burns through 25% of quota in a day.

• Comment asenna987: forcing 1M window on Max 5x reports Extra usage is required for 1M context.

• This is quota and routing experience; no public repository, prompt, or quality score.

Scope and limitations

• The 20% weekly quota depends on the author's task density, plan, and parallel setup; it cannot be treated as a universal consumption formula.

• "Use Sonnet 4.6 for most work" aligns with official guidance but does not prove Sonnet 4.6 equals Opus on high-risk tasks.

• Subagents isolate context; the main session only sees summaries; security-test conclusions must be brought back with verifiable evidence.

• No complete prompt sample; the CLAUDE.md fragment is a copyable constraint organized from the original workflow, not a verbatim export from the author.

Source excerpt or observation (short compliant paraphrase only)

The author's opening line is "Use Sonnet 4.6 for most of your work." (short compliant paraphrase).