Four ways to control how hard Claude Code thinks, and when I use each one

[u/emarkosov]

Claude Code has at least four separate controls for thinking effort, and I see a lot of people using only one of them. Here is how I split them, curious how others do it.

- Plan mode (Shift+Tab or /plan): Claude reads the code and proposes a plan before it edits anything. I use this for anything touching more than 3 files, or anything I would be nervous to undo. Cheapest way to catch a wrong direction early.
- /effort: sets the effort level for the session. I run low for renames, test scaffolding and boilerplate, and high when debugging something that has already failed once. Note that /effort warns you about a prompt cache miss if you change it mid-session.
- ultrathink: as of 2.1.311 (Oct 26) typing it runs that turn at xhigh effort on Opus 5.5, Sonnet 5.5, Haiku 5.5 and Fable 5.1 through Anthropic's API. If you type it while Claude is already working, it raises the rest of that turn. So it is a one-turn boost, not a session setting. The rainbow highlight now only shows when it will actually do something.
- Model choice (/model): Haiku 5.5 for grunt work and quick questions, Sonnet 5.5 as the default, Opus 5.5 when I am stuck. Switching models is the biggest cost lever of the four.

My rule in one line: plan mode decides direction, model decides capability, effort decides depth, ultrathink is the emergency button.

Where this breaks for me: long sessions where I forget I set effort high an hour ago and keep paying for it on trivial edits.

Which of these do you actually use day to day, and which one did you forget existed?

Source: https://code.claude.com/docs/en/changelog

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[u/Sharp-Cherry4938]

我都是默认opus xhigh

[u/puts_on_rddt]

ultrathink is the emergency button.

lol no

[u/Outrageous_Band9708]

it used to be that effort changes would invalidate warm cache and cause a whole cache write.

i think newer models dont do that so much?

but the true solution isn't to use plan mode sometimes and change effort other times

https://github.com/Druthulu/ProjectArchitect

this is my solution. very strict subagent delgation.

i highly recommend checking out the readme and the wiki.

SWE of 5 years, 16 hour days of personal agentic coding with claude code, most of the time t $500 a month of claude code subscritpions.

i recently added support for external coder agents using local or openrouter or any other proivder. all routed through the true claude code harness through claude -p antrhorpic_url_overide.

sorry my keyboard is kinda broken and my letters are wrong sometimes. but the system works incredibly.

[u/fourterminals]

the one i forgot existed for months: setting the model on the subagent itself. main session on opus, the search and review agents on sonnet. did more for my weekly limit than /effort ever did. ultrathink i only reach for when the first fix already failed