The Congress Assembly Party was an unofficial forum consisting on Constituent Assembly's Congress Party Members ( and some special invitees) where provisions of the Constitution and related issues were discussed and debated before they came up in the Constituent Assembly. All members elected on a Congress party ticket were free to attend and contribute to these meetings. There is no historical record of the proceedings of these meerting which makes it difficult to discern the exact extent of the Constituent Assembly Party’s impact on the processes and outcomes of Indian constitution making. However, proceedings of the Constituent Assembly indicate that the Congress Assembly Party did wield influence, especially through the Party whip.
We do not have a historical record of the Congress Assembly Party's meetings. Granville Austin's 'The Indian Constitution: Cornerstone of a Nation ' contains some anecdotal accounts.