The final vowel of viśva is lengthened before nara when the compound is a Name.,
Thus विश्वानरः, वैश्वानरिः (the son of Vishvanara). But विश्वनरः = विश्वे नरा यस्य when it is not a name.,
नरे सञ्ज्ञायाम्
Adhyāya 6 · Pāda 3 · Rule 129
Adhyāya 6 · Pāda 3 · Rule 129
The final vowel of viśva is lengthened before nara when the compound is a Name.,
Thus विश्वानरः, वैश्वानरिः (the son of Vishvanara). But विश्वनरः = विश्वे नरा यस्य when it is not a name.,