Here is just a small list of things™ that I’m aware will break, some quite badly, others in minor ways:

1. Link rot & migrations: domain changes, path reshuffles, CDN/mirror use, or moving from txt → jsonfeed will orphan replies unless every reader implements perfect 301/410 history, which they won’t.
   
2. Duplication & forks: mirrors/relays produce multiple valid locations for the same post; readers see several “parents” and split the thread.
   
3. Verification & spam-resistance: content addressing lets you dedupe and verify you’re pointing at exactly the post you meant (hash matches bytes). Location anchors can be replayed or spoofed more easily unless you add signing and canonicalization.
   
4. Offline/cached reading: without the original URL being reachable, readers can’t resolve anchors; with hashes they can match against local caches/archives.
   
5. Ecosystem churn: all existing clients, archives, and tools that assume content-derived IDs need migrations, mapping layers, and fallback logic. Expect long-lived threads to fracture across implementations.

@prologic@twtxt.net I know we won’t ever convince each other of the other’s favorite addressing scheme. :-D But I wanna address (haha) your concerns:

1. I don’t see any difference between the two schemes regarding link rot and migration. If the URL changes, both approaches are equally terrible as the feed URL is part of the hashed value and reference of some sort in the location-based scheme. It doesn’t matter.

2. The same is true for duplication and forks. Even today, the “cannonical URL” has to be chosen to build the hash. That’s exactly the same with location-based addressing. Why would a mirror only duplicate stuff with location- but not content-based addressing? I really fail to see that. Also, who is using mirrors or relays anyway? I don’t know of any such software to be honest.

3. If there is a spam feed, I just unfollow it. Done. Not a concern for me at all. Not the slightest bit. And the byte verification is THE source of all broken threads when the conversation start is edited. Yes, this can be viewed as a feature, but how many times was it actually a feature and not more behaving as an anti-feature in terms of user experience?

4. I don’t get your argument. If the feed in question is offline, one can simply look in local caches and see if there is a message at that particular time, just like looking up a hash. Where’s the difference? Except that the lookup key is longer or compound or whatever depending on the cache format.

5. Even a new hashing algorithm requires work on clients etc. It’s not that you get some backwards-compatibility for free. It just cannot be backwards-compatible in my opinion, no matter which approach we take. That’s why I believe some magic time for the switch causes the least amount of trouble. You leave the old world untouched and working.

If these are general concerns, I’m completely with you. But I don’t think that they only apply to location-based addressing. That’s how I interpreted your message. I could be wrong. Happy to read your explanations. :-)

@lyse@lyse.isobeef.org 🍿🍿🍿😅

@lyse@lyse.isobeef.org I don’t think there’s any point in continuing the discussion of Location vs. Content based addressing.

I want us to preserve Content based addressing.

Let’s improve the user experience and fix the hash commission problems.

@lyse@lyse.isobeef.org @prologic@twtxt.net Can’t we find a middle ground and support both?

The thread is defined by two parts:

1. The hash
   
2. The subject
   

The client/pod generate the hash and index it in it’s database/cache, then it simply query the subject of other posts to find the related posts, right?

In my own client current implementation (using hashes), the only calculation is in the hash generation, the rest is a verbatim copy of the subject (minus the # character), if this is the common implemented approach then adding the location based one is somewhat simple.

function setPostIndex(post) {
    // Current hash approach
    const hash = createHash(post.url, post.timestamp, post.content);

    // New location approach
    const location = post.url + '#' + post.timestamp;

    // Unchanged (probably)
    const subject = post.subject;

    // Index them all
    addToIndex(hash, post);
    addToIndex(location, post);
    addToIndex(subject, post);
}

// Both should work if the index contains both versions
getThreadBySubject('#abcdef') => [post1, post2, post3]; // Hash
getThreadBySubject('https://example.com#2025-01-01T12:00:00') => [post1, post2, post3]; // Location

As I said before, the mention is already location based @<example https://example.com/twtxt.txt>, so I think we should keep that in consideration.

Of course this will lead to a bit of fragmentation (without merging the two) but I think this can make everyone happy.

Otherwise, the only other solution I can think of is a different approach where the value doesn’t matter, allowing to use anything as a reference (hash, location, git commit) for greater flexibility and freedom of implementation (this probably need the use of a fixed “header” for each post, but it can be seen as a separate extension).

@alexonit@twtxt.alessandrocutolo.it Yhays kind of love you!! Stance and position on this. If we are going to make chicken changes in the threading model, let’s keep content based addressing, but also improve the use of experience. So in fact, in order to answer your question, I think yes, we can do some kind of combination of both.

@prologic@twtxt.net That is really great to hear!

If there are opposing opinions we either build a bridge or provide a new parallel road.

Also, I wouldn’t call my opinion a “stance”, I just wish for a better twtxt thanks to everyone’s effort.

The last thing we need to do is decide a proper format for the location-based version.

My proposal is to keep the “Subject extension” unchanged and include the reference to the mention like this:

// Current hash format: starts with a '#'
(#hash) here's text
(#hash) @<nick url> here's text

// New location format: valid URL-like + '#' + TIMESTAMP (verbatim format of feed source)
(url#timestamp) here's text
(url#timestamp) @<nick url> here's text

I think the timestamp should be referenced verbatim to prevent broken references with multiple variations (especially with the many timezones out there) which would also make it even easier to implement for everyone.

I’m sure we can get @zvava@twtxt.net, @lyse@lyse.isobeef.org and everyone else to help on this one.

I personally think we should also consider allowing a generic format to build on custom references, this would allow for creating threads using any custom source (manual, computed or external generated), maybe using a new “Topic extension”, here’s some examples.

// New format for custom references: starts with a '!' maybe?
(!custom) here's text
(!custom) @<nick url> here's text

// A possible "Topic" parse as a thread root:
[!custom] start here
[custom] simpler format

This one is just an idea of mine, but I feel it can unleash new ways of using twtxt.

@alexonit@twtxt.alessandrocutolo.it Holy fuck! 🤣 I just realized how bad my typing was in my reply before 🤣 🤦‍♂️ So sorry about that haha 😆 I blame the stupid iPhone on-screen keyboard ⌨️

I was trying to say (badly):

That’s kind of my position on this. If we are going to make significant changes in the threading model, let’s keep content based addressing, but also improve the user experience. Answering your question, yes I think we can do some combination of both.

I would personally rather see something like this:

2025-09-25T22:41:19+10:00	Hello World
2025-09-25T22:41:19+10:00	(#kexv5vq https://example.com/twtxt.html#:~:text=2025-09-25T22:41:19%2B10:00) Hey!

Preserving both content-based addressing as well as location-based addressing and text fragment linking.

Of course we still have to fix the hashing algorithm and length.