As I understand it, Redirect-Origin is something that security-conscious
RPs could implement if they want, but isn't required for functionality. So
existing form_post RPs would work out of the box.  Furthermore, I'd expect
a switch from query to post to be a fairly trivial one handled nearly
invisibly by most robust HTTP frameworks, whereas a switch to
Redirect-Query would require more custom impl. (Yes I assume if/when this
spec lands HTTP frameworks would gradually adopt support, but that's a slow
process and RPs will be even slower to pull new versions of HTTP
frameworks, as it can be a big change.)

On Mon, Jan 5, 2026 at 10:59 AM Dick Hardt <[email protected]> wrote:

> I reread your proposal and see my response did not address what you
> actually proposed, sorry!
>
> Your proposal would only work for the RPs that are using
> response_mode=form_post -- but for RPs that are expecting a query or
> fragment, they will fail if they get a POST.
>
> Also, if the RP is using response_mode=form_post, sending cookies with
> SameSite=Lax is not going to help as they are not expecting that to work
> and if they use cookies, they are using SameSite=none.
>
> The RP would also need to have updates for it to take advantage of the
> Redirect-Origin header.
>
> In short, I don't see how the RP is going to get the benefit unless the RP
> makes changes -- or am I missing something?
>
> On Mon, Jan 5, 2026 at 6:49 PM Nick Watson <[email protected]> wrote:
>
>> > The RP has to be updated if it is going to look for the response
>> parameters in the headers first before looking at the query string or form
>> body
>>
>> With my version of the proposal the RP doesn't need that. The browser
>> handles it entirely, and the RP receives a normal-looking form post.
>>
>> On Mon, Jan 5, 2026 at 8:56 AM Dick Hardt <[email protected]> wrote:
>>
>>> To close out this thread, I've posted
>>> https://datatracker.ietf.org/doc/draft-hardt-httpbis-redirect-headers/ to
>>> datatracker and hope the work is adopted by the httpbis WG.
>>>
>>> On Tue, Dec 23, 2025 at 7:58 PM Dick Hardt <[email protected]> wrote:
>>>
>>>>
>>>>
>>>> On Tue, Dec 23, 2025 at 6:25 PM Nick Watson <[email protected]> wrote:
>>>>
>>>>> For OAuth/OIDC specifically, I'm worried about the amount of churn on
>>>>> RPs' having to adopt Redirect-Query.
>>>>>
>>>>
>>>> The RP has to be updated if it is going to look for the response
>>>> parameters in the headers first before looking at the query string or form
>>>> body. Once the RP is making one change, doing the other one is simple. I
>>>> would expect that this would be added to libraries and be invisible to the
>>>> long tail of RPs.
>>>>
>>>>
>>>
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