In the US, there are at least two USPTO proceedings that can be filed by third parties against invalid or unduly broad patents (e.g., in light of prior art not considered during prosecution):

1. Ex Parte Re-Examination
2. Post-grant review (up to 9 mo after grant) / Inter-partes review (starting 9 mo after grant)

However, the EPO appears to have limited options for post-grant challenges. Based on a wikipedia article, "limitation" proceedings (analogous to US re-exam) can only be initiated by the patentee. Additionally, in comparison with US AIA proceedings (PGR, CBM, IPR), I am only aware of "opposition" at the EPO, which has a 9 month window after grant, similar to the US PGR. I am not aware of the upcoming UPC changes affecting these options.

So is this the extent of options for patent challenges at the EPO -- i.e. no options after 9 months? I have some very strong (102/novelty) prior art that was not considered during examination, and I will miss the 9 month window. However, bringing this up in litigation requires legal standing (which seems to essentially require infringement for savvy patentees who avoid triggering standing), which could push the patentee to counterclaim infringement, which could result in an even longer/pricier process, esp. if the court is DE (mandatory bifurcation) or UPC (discretionary bifurcation). Though such strong prior art may make the patentee hesitant to litigate due to "loser pays".

In the US, there are at least two USPTO proceedings that can be filed by third parties against invalid or unduly broad patents (e.g., in light of prior art not considered during prosecution):

1. Ex Parte Re-Examination
2. Post-grant review (up to 9 mo after grant) / Inter-partes review (starting 9 mo after grant)

However, the EPO appears to have limited options for post-grant challenges (see wikipedia article):

1. "Limitation" proceedings (analogous to US re-exam), which can only be initiated by the patentee.
2. "Opposition" proceedings, which are only available up to 9 months after grant (analogous to US PGR).

I am not aware of the upcoming UPC changes affecting these options. So is this the extent of options for patent challenges at the EPO -- i.e. no options after 9 months?

I have some very strong (102/novelty) prior art that was not considered during examination, and I will miss the 9 month window. However, bringing this up in litigation requires legal standing (which seems to essentially require infringement for savvy patentees who avoid triggering standing), which could push the patentee to counterclaim infringement, which could result in an even longer/pricier process, esp. if the court is DE (mandatory bifurcation) or UPC (discretionary bifurcation). The only other out is if the patentee decides not to litigate due to the EPO "loser pays" fee shifting in light of the strength of the prior art.