Ask HN: Will IP agreement with holdover period prevent work at startup?

I am considering a job offer from a very large Internet company in Silicon Valley. Here are some excerpts from their Intellectual Property agreement.

"Invention means any invention or work of authorship, including without limitation any and all ideas, concepts, information, improvements, discoveries, developments, designs, formulae, materials, processes, procedures, techniques, mask works, know-how, artwork, data programs, software, source and object codes, and any other works of authorship or other copyrightable or patentable works. ...

During the period of my employment and for six months thereafter, I will promptly disclose to the Company fully and in writing all Inventions authored, conceived or reduced to practice by me, either alone or with others, including any that might be covered under Section 2870. In addition, during the period of my employment and for one year thereafter, I will promptly disclose to the Company fully and in writing all patent applications filed by me, on my behalf, or in which I am named as an inventor or co-inventor."

Will signing such an agreement make it difficult for me to work for a start-up or any other company for six months after leaving this company? It appears that for 6 months after I leave I would have to report to this company every line of code I write at my new company. Is this sort of request common in the Valley?

I would read that as a short lived slavery contract and never sign such a thing. My freedom to act on an idea I have at any time is much too important for me to give up.

Thanks. Based on your feedback, I plan to turn down the offer unless the agreement is changed.

Regarding the identity of the company: I am concerned about embarrassing the company publicly. I can email it to you directly. It is possible that this is not a typical agreement at the company. I would be working in a group where IP is of greater than usual concern.

EDIT: Mailed to you at ycombinator.com with my account name in the body.

For big companies sadly that's pretty normal from my experience, I've had to sign a similar agreement a couple times. That's how ebay is suing google for google wallet. What you can do (what I do) is give a very broad prior art base (they can't claim any work you have previously worked on). When I was younger since I already worked on a huge range of projects they can't claim I originated an idea while working with them. Sometimes they are even willing to narrow the agreement, depending on the level of your position.

Learned about it when I got screwed a few times during college for a couple inventions. At the time I thought the bonus was a fortune (5 figures), but looking back they screwed me royally.

PG is right that it's not common. The problem with this provision is that it would require you to divulge the confidential information/trade secrets of third parties (e.g., your new employer, your startup, etc.) after your employment with the Company ends. And in the software industry, 6 months is a long time. The year-long obligation to disclose patent applications is troubling as well, especially since patent applications are treated as non-public/confidential information by the US Patent & Trademark Office until they are either published (which is 18 months after filing), or issued (if they are not published by special request).

It seems to me that this Company has this unusual provision probably because it got burned by a former employee who left the Company, joined a competitor, and filed a patent application for an invention that was conceived while he was at the Company. In such situations, the Company should bring an action to contest the ownership of the patent application rather than asking its employees at the outset to execute an agreement to violate the confidentiality agreement of any future employer.