Iterion

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Ultracode ​

reasoning_effort: ultracode is the highest setting on the effort dial. It is not an additional API effort value — Anthropic's Messages API only accepts up to xhigh/max on the wire. Ultracode is a mode, mirroring Claude Code's "Ultracode" level:

xhigh reasoning + a standing prerogative to orchestrate multi-agent workflows.

It is delivered through prompt engineering (a standing-consent system instruction) rather than a new wire parameter, and it is reliable only on claude-opus-4-8 — the orchestration half is backed by Anthropic's mid-conversation system messages, which ship on Opus 4.8 only. On any other model ultracode degrades gracefully to plain xhigh.

See Anthropic's reference: Effort and Build an orchestration mode.

What the runtime does ​

When a node declares reasoning_effort: ultracode, iterion:

  1. Sends xhigh on the wire. The value is remapped via model.wireEffort before it reaches the provider, then coerced to what the model accepts (xhigh on Opus 4.8/4.7, high on OpenAI, etc.). The literal ultracode never reaches an LLM API.
  2. Grants the orchestration prerogative. A ## Workflow Orchestration section is appended to the system prompt giving standing consent to decompose substantial work across parallel subagents (via the agent tool) and to verify findings adversarially — without asking first.
  3. Makes the subagent tool available. On the claw backend, the agent subagent tool is added to the node's allowlist when the node restricts its tools (an unrestricted set already exposes the claw builtins). The claude_code backend orchestrates through its native subagent mechanism.
  4. Warns off Opus 4.8. Compiling ultracode on a model that isn't claude-opus-4-8 emits diagnostic C089 (a warning, not an error): the orchestration half won't be reliable and the node runs as plain xhigh.

Adaptive thinking is enabled automatically for Opus 4.8 by the claw backend (thinking: {type: "adaptive"}), so ultracode gets extended thinking without extra configuration.

Usage ​

iter
agent implementer:
  backend: "claude_code"
  model: "anthropic/claude-opus-4-8"
  reasoning_effort: ultracode
  system: build_system
  user: build_task

Ultracode fits implementer/agent nodes that benefit from spawning helpers for independent sub-parts. It is wasteful on judges, routers, and simple read-only nodes — use high or xhigh there, and keep cheap LLM routers on a small model such as anthropic/claude-sonnet-4-6.

The value is also settable dynamically from an upstream node:

iter
router -> implementer with {_reasoning_effort: "ultracode"}

and via env substitution, which is resolved (and re-validated) at runtime:

iter
  reasoning_effort: "${ITERION_EFFORT:-ultracode}"

Relationship to other dials ​

  • Effort vs. cursors. Effort (including ultracode) controls compute and the orchestration prerogative. Cursors are qualitative framing dials (ambition/depth/rigor/autonomy) appended under ## Calibration. They are orthogonal and compose freely.
  • Ultracode vs. routers. Routers (fan_out_all, llm) orchestrate at the workflow graph level — the author wires the branches. Ultracode lets a single agent node orchestrate dynamically at run time by spawning subagents it decides it needs. Use both together for deep fan-out.

Studio ​

The effort selector offers ultracode only when the node's model is claude-opus-4-8 (the /api/effort-capabilities endpoint gates it server-side, complementing the C089 compile warning). The EffortBar renders it full-bar in a distinct accent tone, reading as "beyond max".