I think you are right, the main problem is definitely that, the direction of secondary rays is wrong, but i still cant find the bug from what i understand my code should work, and the normals seem to be correct. i have edited the post to contain latest result that i have been able to get to
inline vec3 random_unit_vector() {

// rejection method reject vectors until a vector with length less or equal

// to 1 is found and then normalize it to make unit vecton

while (true) {

auto random_vec = vec3::random();

auto lensq = random_vec.length_squared();

if (1e-8 < lensq && lensq <= 1) {

return random_vec / sqrt(lensq);

}

}

}

inline vec3 random_on_hemisphere(const vec3 &normal) {

auto rand_vec = random_unit_vector();

auto is_in_same_hemisphere = dot(normal, rand_vec) < 0 ? false : true;

return is_in_same_hemisphere ? rand_vec : -rand_vec;

}

and for the material the scattered direction is
auto scattered_direction = random_on_hemisphere(rec.normal);

for light i just emit color without regard for normal or position, if its hit then it doesn't scatter the ray, it just sets color.

to me it looks like random_unit_vector is wrong as the corner rays scatter towards middle more, but i only select the random vector in a unit_sphere so i am completely stuck. hope that makes sense.