Re: Why do HTTP/2 CONTINUATION frames not have an END_STREAM flag?

On Mon, Mar 2, 2026, at 21:44, Sean McArthur wrote:
> It reads like you can send the END_STREAM flag on the HEADERS frame, without END_HEADERS, and then send CONTINUATION frames, and when they end, the stream ends.
> 
> https://httpwg.org/specs/rfc9113.html#HEADERS
> 
> > A HEADERS frame with the END_STREAM flag set signals the end of a stream. However, a HEADERS frame with the END_STREAM flag set can be followed by CONTINUATION frames on the same stream. Logically, the CONTINUATION frames are part of the HEADERS frame.
Thanks Sean, I missed that! Also seems reinforced by https://www.rfc-editor.org/rfc/rfc9113.html#section-8.1-5

> The last frame in the sequence bears an END_STREAM flag, noting that a HEADERS <https://www.rfc-editor.org/rfc/rfc9113.html#HEADERS> frame with the END_STREAM flag set can be followed by CONTINUATION <https://www.rfc-editor.org/rfc/rfc9113.html#CONTINUATION> frames that carry any remaining fragments of the field block.

Cheers,
Lucas

> 
> On Mon, Mar 2, 2026, 4:39 PM Lucas Pardue <lucas@lucaspardue.com> wrote:
>> __
>> Hi folks,
>> 
>> I was looking again at HTTP/2 frames and realized that CONTINUATION frames don't have an END_STREAM flag. Knowing why this is the case is not critical to anything but it got me curious.
>> 
>> Its possible to send HEADERS with END_STREAM=1, to send a request or response with no DATA frames at all. However, it seems any stream that uses CONTINUATION but has no HTTP content to send would have to use a sequence like:
>> 
>> 1. HEADERS (END_HEADERS=0, END_STREAM=0),
>> 2. CONTINUATION (END_HEADERS=1),
>> 3. DATA (LENGTH=0, END_STREAM=1).
>> 
>> Empty DATA frames to signal stream close are not themselves a problem. The deployments I'm familiar with regularly send them. 
>> 
>> However, this raises an issue for anyone that might try to use CONTINUATION in trailers. You can't can't clean close the stream:
>> 
>> 1. HEADERS (END_HEADERS=1, END_STREAM=0),
>> 2. DATA (END_STREAM=0),
>> 3. HEADERS (END_HEADERS=0, END_STREAM=0), CONTINUATION (END_HEADERS=1)
>> 4. Not valid to send DATA again, oops
>> 
>> Cheers,
>> Lucas