gistfile1.txt

Reasoning Effort in Claude Code v2.1.37

  Feature gate

  Effort is gated behind:
  1. Feature flag: tengu_workout2 must be enabled server-side
  2. Model support: only Opus 4.6 (opus-4-6 in model name) via Dg1()

  Valid values

  ["low", "medium", "high", "max"]

  It also accepts integer values (parsed via parseInt).

  How to set it

  Priority order (first defined wins):

  X1 = y6q()           // 1. env var CLAUDE_CODE_EFFORT_LEVEL
    ?? w.effortValue    // 2. UI/settings value (from /model menu or persisted)
    ?? dt8(w.model);    // 3. model default (currently returns undefined for all models)

  1. Environment variable

  CLAUDE_CODE_EFFORT_LEVEL=low claude
  CLAUDE_CODE_EFFORT_LEVEL=medium claude
  CLAUDE_CODE_EFFORT_LEVEL=high claude   # same as default
  CLAUDE_CODE_EFFORT_LEVEL=max claude

  2. In-session via /model menu

  When you run /model, if effort is supported (Opus 4.6 + feature flag), the menu shows effort
  level options. The selection is persisted to user settings as effortLevel and saved via
  w7("userSettings", {effortLevel: ...}).

  3. User settings (persisted)

  The R6q() function reads effortLevel from user settings (jq() which loads the settings file). So
  it persists across sessions.

  How it's applied (BKz function)

  function BKz(effortValue, outputConfig, params, betas, model) {
      // Must have feature flag AND model must support effort
      if (!It() || !Dg1(model) || "effort" in outputConfig) return;

      if (effortValue === undefined)
          betas.push("effort-2025-11-24");  // just adds beta, no explicit effort
      else if (typeof effortValue === "string")
          outputConfig.effort = effortValue;  // sets effort in output_config
          betas.push("effort-2025-11-24");
  }

  The effort value is sent as part of output_config in the API request, using the effort-2025-11-24
   beta header.

  No CLI flag

  There is no --effort CLI argument. The only ways to set it are:

  1. CLAUDE_CODE_EFFORT_LEVEL env var (takes highest priority)
  2. /model menu in the TUI (persisted to settings)
  3. User settings file (effortLevel key)

  Default behavior

  When effort is "high" (selected via menu), it's stored as undefined internally (meaning: don't
  send an explicit effort value). The default behavior when undefined is to just add the beta
  header without setting an explicit effort level, letting the API use its default.