# claude-substrate — cart `osprey`

**Opened before you arrived**, so that the first thing here is a round rather
than a briefing.

---

## What is in this repository already

**Four externals, fetched and locked**, under `.loom/externals/`. *`bedrock` is
the primitives, `externals` is the convention you are implementing, `cart` and
`annotating` are how we will work together.* **They are copies. Do not edit
them** — a facet goes beside a file, never into it.

**One specimen: [`proposed-spec.md`](specimens/proposed-spec.md).** *It is the
tool as we imagined it, and **a specimen is discard-by-default** — it belongs to
this repository and you may throw it away without asking us.* **That is not
politeness; it is what a specimen is.**

> **`bedrock` and `externals` are not discardable.** *Accommodating them is what
> makes this a loom tool rather than some other thing.* **Read them as given.
> Argue with the specimen.**

## What we think this is

**A fetcher and a comparator, and it should stay one.** *Every act in the model is
a file in somebody's repository — publishing is writing one, adopting is fetching
a URL, reporting a gap is writing one.* **Nothing sends a service a request.**

**The idea that makes it small:** *on gitea, a raw file's `ETag` **is** the git
blob hash of that file.* **So there is nothing to record** — hash the local copy,
compare to the remote's `ETag`, done. *Verified on both a public and a private
repository.*

## Where we expect to be wrong

**Where the conventions chafed.** *A thing you had to do twice. A rule you worked
around to make a command sane.* **Friction is data about us, not a failure of
yours**, and most of it never gets reported because it reads the other way.

**Whether `check` can say anything useful about a `404`.** *Over HTTP, "gone" and
"you lost access" are the same response.* **We decided to report the ambiguity
rather than guess** — *if that is annoying in practice, it is worth knowing.*

**Whether the hash-as-lock survives contact.** *It assumes the local copy is
byte-identical to the remote. **A fetch that normalises anything breaks it**, and
we have not tested a proxy, a CDN, or a host that is not gitea.*

## What we would ask you not to do

**Do not build `init` as a scaffolder.** *Four empty directories assert four
things nobody has decided, and **a file that carries no delta should not
exist.*** *If `init` earns its place, it creates one file and asks one question.*

---

## Answered before you arrived: the `ETag` is **not** universally a blob hash

**We asked ourselves to verify this first and then did, an hour later, against
GitHub. It does not hold.**

```
gitea    etag "530c5bef…"   40 hex   ==  git blob sha
github   etag "d01c4a8b…"   64 hex   !=  git blob sha  (sha-256 of something else)
         api  d848552d…              ==  git blob sha
```

**What survives:** *conditional requests work on both.* `If-None-Match` returns
`304` from GitHub exactly as from gitea. **The mechanism is fine.**

**What does not:** *"hash the local copy and compare to the remote's `ETag`"* is a
**gitea coincidence.** **So there is something to record after all: the `ETag`
itself**, opaque, per document.

*Where it lives is yours. **We would not make it a `.md` facet** — it is machine
state, not prose, and the sibling-facet pattern is for things people write.*

> **And the check we thought we were getting for free is already free from
> somewhere else.** *"Did somebody edit our copy of their document?" needs no hash
> — **the copy is committed, so `git status` says so.***

*The specimen still describes the old idea. **It is wrong and it is left as
written**, because a specimen is a snapshot of what we proposed and correcting it
in place would hide that we were wrong within a day of proposing it.*

## Question: what isolates your work while a round is open?

*The one role we left uncast — see
[`cart.usages.md`](../../externals/git.hypertheory-labs.dev/loom/cart/cart.usages.md).*

## ~~Affirm: is the `ETag`-as-blob-hash assumption load-bearing enough to verify first?~~

**Withdrawn — we verified it, and it failed.** *See above. **Less of the specimen
collapsed than we feared**: the mechanism holds and only the storage-free
optimisation goes.*