Ultracode
A prompt keyword circulating in Claude Code usage that is functionally equivalent to the xHigh effort level combined with additional workflow instructions. It triggers the spawning of sub-agents to collaboratively complete tasks and is not an independent effort-level tier.
Timeline (last 90 days)
In Claude Code's Ultracode mode, Simon Willison entered a prompt containing a phone keyboard typo, asking for a SQLite extension written in Rust that embeds SPARQL and hits the delete row.
Simon Willison stated: reviewing the code produced by Ultracode mode is fundamentally infeasible, and even following the documentation is a significant time investment.
Claude Code for web ran continuously for more than 12 hours in Ultracode mode, generated a large number of Rust crates, and automatically coordinated a network of sub-agents to decompose the complex problem.
The developer assigned different effort levels across different sessions, with the more difficult shader session using the highest-tier Ultracode.
Ultracode has been separated into a standalone toggle within /effort (Tab key or /effort ultracode [on|off]), no longer forcing the xhigh effort level, and can remain enabled at any effort level.
Ultracode is not a genuine effort level; it is essentially xHigh plus an additional instruction to use workflows (spawning sub-agents for collaboration).
Writing Ultracode directly in the prompt is equivalent to telling the model to use workflows to launch sub-agents, rather than actually changing the effort level; the recommendation is to write 'use workflows' directly.
All Facts (7)
Simon Willison stated: reviewing the code produced by Ultracode mode is fundamentally infeasible, and even following the documentation is a significant time investment.
50%UnverifiedThe developer assigned different effort levels across different sessions, with the more difficult shader session using the highest-tier Ultracode.
50%UnverifiedUltracode is not a genuine effort level; it is essentially xHigh plus an additional instruction to use workflows (spawning sub-agents for collaboration).
50%UnverifiedWriting Ultracode directly in the prompt is equivalent to telling the model to use workflows to launch sub-agents, rather than actually changing the effort level; the recommendation is to write 'use workflows' directly.
50%UnverifiedIn Claude Code's Ultracode mode, Simon Willison entered a prompt containing a phone keyboard typo, asking for a SQLite extension written in Rust that embeds SPARQL and hits the delete row.
50%UnverifiedClaude Code for web ran continuously for more than 12 hours in Ultracode mode, generated a large number of Rust crates, and automatically coordinated a network of sub-agents to decompose the complex problem.
50%UnverifiedUltracode has been separated into a standalone toggle within /effort (Tab key or /effort ultracode [on|off]), no longer forcing the xhigh effort level, and can remain enabled at any effort level.
50%