This phase II trial compares the effect of GI-102 alone and in combination with pembrolizumab given before surgery in treating patients with IDH wildtype glioblastoma and IDH mutated grade 4 astrocytoma that has come back after a period of improvement (recurrent) or that is growing, spreading, or getting worse (progressive). Glioblastoma is the most common and the most aggressive primary brain tumor in adults. Current standard of care includes surgical resection, radiation and chemotherapy. Treatment is often given before surgery (neoadjuvant therapy) to shrink the tumor and make it easier to remove. Treatment with GI-102, a bispecific fusion protein, may induce changes in body's immune system and may interfere with the ability of tumor cells to grow and spread. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the tumor, and may interfere with the ability of tumor cells to grow and spread. Giving GI-102 alone and in combination with pembrolizumab between neoadjuvant therapy and surgery may be safe, tolerable, and effective in treating patients with recurrent or progressive IDH wildtype glioblastoma and IDH mutated grade 4 astrocytoma.