The KOSPI rose 0.7 percent, or 44.9 points, to 6,735.5, led by SK hynix and Samsung Electronics after their AI partnerships with Nvidia and Broadcom.
The tech-heavy KOSDAQ outperformed, climbing 3.2 percent to 772.0, as investors also welcomed Lee's meeting with Silicon Valley's leading venture capital firms aimed at attracting investment into Korean startups.
The rebound, however, lacked conviction as foreign investors remained sellers.
Investors viewed the summit announcements — highlighted by an SK hynix partnership with Nvidia valued at more than $500 billion and a Samsung Electronics memorandum with Broadcom worth up to $200 billion — as fresh confirmation that Korean memory makers remain central to the global AI infrastructure buildout.
The gains in the two chipmakers were relatively modest given the scale of the announcements.
Samsung Electronics rose 1.3 percent to 252,750 won ($172.9), while SK hynix edged up 0.3 percent to 1,764,000 won ($1,206.8).
Foreign investors were not buying the rally. They sold a net 785 billion won worth of shares on the main board through mid-morning, while institutions also remained net sellers, limiting the market's rebound.
Not all heavyweight stocks participated. SK Square fell 2.5 percent to 1,081,000 won ($739.5), while Hanwha Aerospace lost 4.3 percent to 937,000 won ($641.0) as investors locked in profits from recent gains in defense shares.
Elsewhere in Asia, Japan's Nikkei 225 was little changed, slipping less than 0.1 percent.
The Korean won traded at 1,461.70 per dollar, marginally firmer than the previous session.
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