Junta leader General Deby appointed the 104 "additional members of the CNT", including former opposition party figures who have joined the regime, rebels who signed a peace deal in August and civil society representatives.
A national forum for reconciliation last month recommended boosting the number of members of the National Transition Council (CNT), which operates as a de facto parliament, from 93 to 197.
Much of the opposition and the most powerful armed rebel groups however boycotted the forum, protesting the "dynastic succession."
The CNT is tasked with drawing up a new constitution and preparing the election.
The 38-year-old five-star General Deby took control in April 2021 after his father, Chad's iron-fisted ruler for three decades, was killed during an operation against jihadist rebels.
The junta had declared it would restore civilian rule after 18 months in power, and Deby had at first promised he would not take part in the future elections.
But as the 18-month deadline neared, the nationwide forum staged by Deby reset the clock, approving a new 24-month timeframe for holding elections, naming him "transitional president" and declaring he could be a candidate in the poll.
On October 20, the authorities put down opposition protests officially leaving 50 people dead, 300 wounded and hundreds detained.
The European Union strongly condemned an "excessive use of force" and violation of the right to freedom of speech and assembly.
Chad has been chronically unstable since it gained independence from France in 1960.