Function getContextWindowForModel

src/utils/context.ts:54–112

(
  model: string,
  betas?: string[],
)

}

export function getContextWindowForModel(
  model: string,
  betas?: string[],
): number {
  // Allow override via environment variable (ant-only)
  // This takes precedence over all other context window resolution, including 1M detection,
  // so users can cap the effective context window for local decisions (auto-compact, etc.)
  // while still using a 1M-capable endpoint.
  if (
    isInternalBuild() &&
    process.env.CLAUDE_CODE_MAX_CONTEXT_TOKENS
  ) {
    const override = parseInt(process.env.CLAUDE_CODE_MAX_CONTEXT_TOKENS, 10)
    if (!isNaN(override) && override > 0) {
      return override
    }
  }

  // Managed model profile is authoritative. This runs BEFORE the [1m] regex
  // so that attaching [1m] to an alias that resolves to a managed model
  // (e.g. `sonnet[1m]` -> Kimi K2.7, which has a 200K usable budget) cannot
  // silently inflate the context window past what the model can actually
  // serve. The [1m] tag still works as expected for unmanaged Anthropic-style
  // models below.
  const ncodeModel = resolveNCodeManagedModel(model)
  if (ncodeModel) {
    return ncodeModel.contextWindow
  }

  // [1m] suffix — explicit client-side opt-in for unmanaged Anthropic models.
  if (has1mContext(model)) {
    return 1_000_000
  }

  const cap = getModelCapability(model)
  if (cap?.max_input_tokens && cap.max_input_tokens >= 100_000) {
    if (
      cap.max_input_tokens > MODEL_CONTEXT_WINDOW_DEFAULT &&
      is1mContextDisabled()
    ) {
      return MODEL_CONTEXT_WINDOW_DEFAULT
    }
    return cap.max_input_tokens
  }

  if (betas?.includes(CONTEXT_1M_BETA_HEADER) && modelSupports1M(model)) {
    return 1_000_000
  }
  if (getSonnet1mExpTreatmentEnabled(model)) {
    return 1_000_000
  }
  if (isInternalBuild()) {
    const antModel = resolveAntModel(model)
    if (antModel?.contextWindow) {
      return antModel.contextWindow
    }
  }
  return MODEL_CONTEXT_WINDOW_DEFAULT