Can I also bring a claim against the real estate agent, not just the seller?

Sometimes, yes, depending on the agent's own actual knowledge and conduct during the transaction. A seller's real estate agent carries an independent legal duty under Civil Code section 2079 to personally conduct a reasonably competent visual inspection of reasonably accessible areas of the property and to disclose to buyers whatever that inspection reveals, a duty that exists separately from whatever the seller personally discloses or fails to disclose.

Real estate agents also typically carry errors and omissions insurance, a specific form of professional liability coverage, which in practice can make them a considerably more realistic and collectible source of financial recovery compared to a seller who may have already relocated out of state or otherwise become difficult to pursue. Naming both the seller and their agent, where the facts support agent involvement or awareness, is a reasonable and common strategy in these cases.