booth/docs/contracts/u5_booth_manifest.contract.md

---
contract_version: "1.0"
module: "booth.manifest"
purpose: "A booth that says what it IS and who posted it. Today the index card shows a name, an item count and a countdown -- nothing about provenance or purpose -- so an agent that wants the operator to look at something has no way to make the booth say so, and posts a URL to the link board instead. That is job 5 (`Announce`), the job nobody named, and its absence is the measured cause of 145 dead link rows (69% of the board pointing at booths that no longer exist). This unit gives job 5 a home: each booth carries `.booth.json` -- `{handle, title, why, created}`, written by the CLI from `$ALTHING_HANDLE` -- and the index card and the booth page header render it. Enforcing the link rule WITHOUT giving job 5 a home first just makes it homeless; this is the home."
depends_on:
  - "booth.items (the dotfile skip in `booth_items` -- `.booth.json` is excluded from tiles, counts and zips by the EXISTING `p.name.startswith('.')` rule at items.py:182, exactly as `.marks.json` is. No new exclusion rule is added or needed. Verified, not assumed: `test_a_manifest_is_not_an_item` asserts it.)"
  - "booth.marks (the `_write_raw` shape only -- temp file + os.replace, per CLAUDE.md invariant 5. Copied as a pattern, NOT imported: manifest.py must not depend on marks.py, because the CLI imports each module on its own.)"
language: "python"
complexity: "low"
estimated_loc: 150
confidence: 0.85
used_by:
  - "booth.app.list_booths (the index card gains `manifest` -- one file read per booth, alongside the `marks_for` read already there)"
  - "booth.app.booth_view (the booth page header gains the same provenance line; a booth URL handed to the operator lands HERE, not on the index, and job 5 is literally 'operator, look at this')"
  - "booth.app.upload (a pickup booth announces itself as the Booth's own)"
  - "scripts/booth (`new` and `add` gain `--why` / `--title`; `link` announces the standing board)"
touches:
  - "booth/manifest.py (new -- the record, the write, the lenient read)"
  - "booth/app.py (list_booths gains one key; booth_view gains one key; the /upload path writes a manifest. It also adds MANIFEST_FILE to the `used` dedupe set -- CONSISTENCY, not a fix: SR-1 established the collision is unreachable because `safe_upload_name` strips leading dots, which is equally true of the `UPLOAD_MARKER` entry that has sat in that set since before this unit.)"
  - "booth/templates/_provenance.html (new -- the provenance macro, defined ONCE and called from both index lanes and the booth header. Not in the first draft of this inventory: the implementation added the partial rather than repeating the four-state conditional three times, which is SR-6 plus the blurtoggle lesson, and the inventory lagged the decision.)"
  - "booth/templates/index.html (the provenance line on both lanes' cards -- kept AND ephemeral, or the kept lane silently keeps the old defect)"
  - "booth/templates/booth.html (the provenance line in the boothhead, and the h1 renders `title` with the directory name beside it)"
  - "booth/templates/base.html (the .prov-* CSS)"
  - "scripts/booth (`new` / `add` flag parse; `link` board announcement; usage string; the header doc block)"
  - "tests/test_manifest.py (new)"
  - "tests/test_marks.py (test_stdlib_only's parametrize list gains `manifest`)"
assumptions:
  - "THE MANIFEST IS A DOTFILE, and that is the whole integration story. `booth_items` skips `name.startswith('.')` (items.py:182), `zip_booth` skips it (app.py:351), and the legacy ask scan skips it (marks.py:656). So `.booth.json` costs nothing in item counts, galleries, zips or migration, and needs no new exclusion anywhere. This is the same reason `.marks.json` needed none. Settled -- do not re-derive it."
  - "WRITING A MANIFEST IS ACTIVITY. `.booth.json` is a dotfile but NOT a `.lock` dotfile, so `_newest_mtime` counts it (app.py:192 excludes only `.<name>.lock`). Creating or re-announcing a booth resets its TTL, which is correct: both are somebody touching it. The lock exemption exists for machinery that a READ path creates; this is a deliberate write."
  - "THE READ IS LENIENT AND THE FAILURE IS VISIBLE. `list_booths` reads every booth on every index load, so a manifest that cannot be parsed must never raise -- that is the v0.2.2 lesson, learned when a poisoned `.marks.json` returned 500 for `/` and `/healthz` across all 25 booths. `read_manifest` returns None for absent and a `Manifest` carrying `error` for damaged, and the card distinguishes them (`unannounced` vs `unreadable`). Silently treating damaged as absent would hide the one case somebody has to fix."
  - "THE WRITE IS ATOMIC (CLAUDE.md invariant 5, NOT this unit's INV-5). Temp file + os.replace onto a name no other writer derives, because the CLI writes it in one process while the browser reads it in another -- and because two `booth add` calls on one booth would otherwise share a scratch name, which the atomic-write promise says nothing about: it promises readers never see a partial file, not that writers never race. The pattern is copied from `marks._write_raw` rather than imported: `scripts/booth` imports each module directly under the system python3, and a cross-import between two stdlib-only modules is a second way for INV-1 to break."
  - "`booth/manifest.py` IS STDLIB-ONLY and joins the CLAUDE.md invariant 1 list. `scripts/booth` imports it through a `python3 -c` heredoc with no venv, exactly as it imports `marks`, `asks` and `links`. `test_stdlib_only` is parametrized and gains `manifest`; that test is the only thing standing between a casual third-party import and `booth new` breaking on every fleet host."
  - "A MISSING MANIFEST IS NORMAL, NOT AN ERROR. All 26 live booths have none, and `rsync -a ./out/ nh3-dev:booth-data/my-run/` -- the documented path for every host that is not nh3-dev -- never runs the CLI at all, so unannounced booths keep arriving after this lands. The card marks them quietly and nothing refuses to render, expire, zip or sweep."
  - "THE BOOTH ANNOUNCES ITS OWN BOOTHS rather than exempting them. A pickup booth and the standing link board are created BY the service, so they are written with `handle: booth` -- which is true, not manufactured. The alternative was a pile of exemptions from the unannounced marker; this way there is one rule (a booth with no manifest is unannounced) and no special cases. `handle` therefore names an agent handle OR the service, and the field's docstring says so."
  - "NOTHING NEW IS ORDERED, so CLAUDE.md invariant 6 (every ordered collection has a stated, deterministic rule) does not bind here -- there is no new collection for it to bind to. The manifest is one flat record per booth. The index keeps its stated rule -- kept lane first, then ephemeral newest-first by `_newest_mtime` -- and U5 does NOT add a second ordering keyed on `created` (operator, 2026-09-22). A what-landed feed ordered by announcement time is a genuinely different surface: it needs its own stated rule, it competes with the existing order for what 'the third one' means, and it has nothing to sort the 26 manifest-less booths by. Parked for v1.1."
open_questions:
  - "Whether `why` should also reach the zip manifest or a `booth ls` column. Both are one-liners over the same record and neither is on the v1 path; deferred rather than designed."
---

# U5 — self-announcing booths

## The defect, stated precisely

The index card is the only thing an agent can put in front of the operator, and
it carries no information the agent chose. Name, item count, countdown, a
thumbnail. Everything about *why this exists* has to travel some other way.

So it travelled some other way. `booth link` exists because a session with
something to show had no way to make the booth itself say "look at this", and
the link board absorbed job 5 until **145 of its 210 rows (69%) pointed at
booths that had already been swept**. The rot is not a link-board bug. The board
was doing a job it was never shaped for, because the shaped thing did not exist.

The lesson the measurement carries, and the reason this unit comes before any
link-board enforcement: **enforcing the link rule without giving job 5 a home
just makes it homeless.**

## The record

```python
@dataclass(frozen=True)
class Manifest:
    handle: str            # an althing handle, or "booth" for one the service made
    title: str             # display name; falls back to the directory name
    why: str               # ONE line: what the operator is looking at and why
    created: str           # ISO-8601 with offset, from the FIRST announcement
    error: str | None = None   # a read-time verdict; never stored
```

`.booth.json` on disk is the same four fields, no `error`.

**Every field on an error-carrying record has a stated value**, because the
templates render the record and a careless fill would re-raise the outage in
the renderer: `handle` and `why` and `created` are `""`, `title` is the
normalized directory name, and `error` says which of the six refusals fired.
`created` being `""` is what makes `write_manifest` treat a damaged prior as
having no stamp to preserve (INV-3).

Caps, all applied at the write and again at the read: `handle` 64, `title` 120,
`why` 200, `created` 64. Each is a **display budget**, not a storage limit —
they exist because these strings land in a card's sub-line.

## Signatures

```python
MANIFEST_FILE = ".booth.json"
HANDLE_MAX, TITLE_MAX, WHY_MAX = 64, 120, 200


MANIFEST_MAX_BYTES = 64 * 1024
QUARANTINE_FILE = ".booth.json.broken"


def read_manifest(booth: Path) -> Manifest | None:
    """This booth's announcement, or None if it never made one.

    LENIENT, and never raises. `list_booths` calls this once per booth on every
    index page load, so a damaged file must cost that booth's provenance and
    nothing else — the same posture `marks_for` takes, for the reason v0.2.2
    made expensive: a read that can raise, called in a loop over every booth,
    is a service-wide outage wearing a single-booth bug's clothes.

    "NEVER RAISES" IS BOUNDED, NOT MERELY CAUGHT. An earlier draft of this
    contract named a 4 GB file as a tested case and constrained only the RETURN
    — which is letter-compliant and purpose-defeating: reading four gigabytes
    per booth per index load recreates the same outage in slow motion. The size
    is checked by `stat` BEFORE the bytes are touched, and the two exception
    classes that are neither `OSError` nor `ValueError` — `MemoryError` from a
    huge document, `RecursionError` from a deeply nested one — are caught as
    well, so that raising the bound one day cannot quietly re-open the hole.

    REGULAR-FILE FIRST, THEN SIZE — and the order is the whole point. `st_size`
    is 0 for a FIFO and 0 for a symlink to `/dev/zero`, so both sail under any
    byte cap and then the read either blocks forever with no EOF or allocates
    until the kernel intervenes. The bound is what made this reachable: a cap
    that trusts `st_size` inherits everything `st_size` does not mean. One such
    file stalls every `GET /` and `/healthz`, with no error and no recovery
    short of a restart.

    Absent -> None. Present but too large, unreadable, unparseable, not an
    object, or missing `handle` -> a Manifest carrying `error`, so the card can
    say `unreadable` rather than quietly showing the same thing as a booth that
    never announced.
    """


def write_manifest(booth: Path, handle: str, *, title: str | None = None,
                   why: str | None = None) -> Manifest:
    """Announce a booth. Atomic per CLAUDE.md invariant 5: temp file +
    os.replace, onto a temp name no other writer will pick.

    OMITTED MEANS UNCHANGED; `""` MEANS CLEAR. `title` and `why` default to
    None. The ordinary sequence is `booth new x --why "..."` then
    `booth add x out/*.png`, and while omission meant `""` the second command
    silently erased the sentence the first one existed to record. The shell
    carries the distinction by leaving the environment variable UNSET rather
    than empty.

    Re-announcing PRESERVES the original `created` — `created` is when the
    booth appeared, and saying something more about it later is not a second
    appearance. A prior record carrying `error`, or one whose `created` is
    `""`, is treated as having no stamp to preserve and gets `now()`: a stamp
    that is silently wrong is worse than one that is silently new.

    A WRITE THAT CHANGES NOTHING IS NOT ACTIVITY and does not touch the file,
    so it cannot reset the booth's TTL — the rule marks learned in v0.2.0,
    needed here because `booth link` re-announces the standing board on every
    single post to it.

    BYTES THAT COULD NOT BE READ ARE KEPT, not replaced. See INV-6.

    A FAILED WRITE LEAVES NOTHING BEHIND. The temp name carries a random suffix
    so two writers cannot share it — which also means nothing ever overwrites an
    orphan, and `.booth.json.<hex>.tmp` is not a `.lock`, so `_newest_mtime`
    counts it and a leak would keep a dead booth alive forever. Cleaned up on
    every exit path.

    `title` falls back to the directory name, THROUGH the same normalizer the
    explicit value gets — a directory name may legally carry a newline on POSIX
    and may run to 255 bytes, and the fallback used to hand either straight
    into a card's sub-line.

    Every stored string is collapsed to a single line — all runs of whitespace,
    not only newlines, because a tab or a forty-space indent renders as badly
    in a sub-line as a newline does — and truncated to its cap.

    An empty `handle` becomes `"booth"` rather than being refused: a manifest
    naming no handle does not read back at all, and an unreadable file is the
    worse outcome. Unreachable from the CLI, whose fallback chain always yields
    something; a direct caller should pass a real one.
    """
```

## What renders

One line, on both surfaces, driven by the same record. The example booth below
is the directory `r18-ab`, announced by the handle `booth-dev`:

| state | the provenance line, on an index card AND on the booth header |
|---|---|
| announced, with a why | `booth-dev · pick the winning denoiser` |
| announced, no why | `booth-dev` |
| no manifest | `unannounced` (muted) |
| damaged manifest | `unreadable` (muted, warning tint, `title=` carries the reason) |

**`title` renders too, and on exactly one surface.** An earlier draft stored it,
surfaced a `--title` flag for it, and rendered it nowhere — a promise of a
display name with no display, caught 4-of-4 and ranked first independently by
every arm. It lands on the **booth page heading**, where there is room:
`<h1>R18 A/B <span class=h1-slug>r18-ab</span></h1>`. The **index card keeps
the directory name alone**, because that is the identity the operator navigates
by and refers to positionally, and CLAUDE.md invariant 6 is about exactly that
kind of reference surviving a re-render. When `title` equals the directory name
— the default — the heading is unchanged from today.

**Both index lanes get it.** The kept lane renders first and is a separate block
in `index.html`; patching only the ephemeral lane would leave the 15 kept booths
— the durable, most-looked-at ones — with exactly the defect this closes. This
is the `blurtoggle` lesson (three item branches, one macro) applied to two lanes.

**The booth page header gets it too**, and that is deliberate scope, not creep:
a booth URL handed to the operator lands on the booth page, never on the index.
Job 5 is "operator, look at this", and the page he actually opens is where the
answer has to be.

## The CLI surface

Operator decision, 2026-09-22 — flags on the existing verbs, not a second verb:

```sh
booth new r18-ab --why "pick the winning denoiser"
booth add r18-ab out/*.png --why "second pass, sharper" --title "R18 A/B"
booth new scratch                  # still legal — handle + created, no why
```

`handle` comes from `$ALTHING_HANDLE`, falling back to `$BOOTH_SOURCE` then
`hostname -s` — the same resolution `booth link` already uses for its rows, so
provenance means the same thing on the board and on the card.

**Nothing existing breaks.** A bare `booth new x` / `booth add x f.png` keeps
working; the flags are optional and may sit on either side of the file
arguments, because a glob is usually last and a flag usually after it and
nothing enforces that. The alternative — a separate `booth announce` verb — was
rejected because a second step is the step that gets forgotten, which is the
69% rot's own mechanism.

**A bare re-announce does not wipe what the last one said.** On a booth that has
never announced, a bare `new`/`add` writes `{handle, created}` with no `why`. On
one that HAS, an omitted flag leaves the stored value alone and only a supplied
one overwrites — `--why ""` still clears, which is a different intention. This
distinction is load-bearing rather than polite: `booth new x --why "…"` followed
by `booth add x out/*.png` is the ordinary sequence, and the naive reading
erases the sentence on the second command.

**The handle is the CLI's three-step chain**, not `$ALTHING_HANDLE` alone:
`${ALTHING_HANDLE:-${BOOTH_SOURCE:-$(hostname -s)}}`, identical to the one
`booth link` already uses for its rows, so provenance means the same thing on
the board and on the card. A session with no handle set still announces, as its
host.

## Scope — the blast-radius pass

Graphify + grep, both run, because neither is sufficient alone (graphify is
blind to function-local and DI-injected imports; grep misses transitive reach).

**Every site that creates a booth directory:**

| site | gets a manifest? |
|---|---|
| `scripts/booth new` (line 97) | yes — `$ALTHING_HANDLE` |
| `scripts/booth add` (line 103) | yes — `$ALTHING_HANDLE` |
| `scripts/booth link` (line 178) | yes — `handle: booth`, the standing board |
| `app.upload` (app.py:1087) | yes — `handle: booth`, a pickup booth |
| `marks._Locked.__enter__` (marks.py:267) | **no** — `mkdir(exist_ok=True)` on the write path; a mark written to a booth that does not exist is not an announcement, and manifest.py must not be imported by marks.py (INV-1 cross-import) |
| `rsync` from another host | **no** — no CLI runs; this is why `unannounced` exists |

**Every reader of a booth's facts:** `list_booths` (app.py:251) and `booth_view`
— confirmed by `graphify explain list_booths` (15 edges, 4 test consumers) and
by grep for `data_dir.iterdir` (two sites, both in app.py, both enumerating
booths for exactly these two surfaces).

**Sites that already exclude the new file and need no change**, each verified
rather than assumed: `items.booth_items` (items.py:182), `app.zip_booth`
(app.py:351), `marks.import_legacy_asks` (marks.py:656).

**One site the first draft of this contract got WRONG, corrected by the seam
review** (SR-1, below): the upload path's `used: set = {UPLOAD_MARKER}` filename
dedupe set does **not** need to gain `MANIFEST_FILE`. The implementation adds it
anyway, as consistency with the equally-unreachable entry already there, and
says so in a comment rather than claiming it prevents anything.

⚠ **Line numbers in this section are the PRE-CHANGE coordinates** the
blast-radius pass was run against, kept because that is what makes the pass
auditable. They have moved; `grep` the symbol, do not trust the number.

## Seam review — what the real sibling surfaces said

Caller-side pass against the actual modules, not against their prose. Run after
the cold contract panel was dispatched and before any code.

**SR-1 — the upload-collision change is unnecessary, and so is the one already
there.** `safe_upload_name` (app.py) does `base = base.lstrip(".")` with the
comment "a leading dot would hide the file from every listing", so an uploaded
file can never be named `.booth.json` — or `.uploaded`, which means the existing
`UPLOAD_MARKER` entry in that set has never been able to matter either. Adding
`MANIFEST_FILE` alongside it is consistency with a redundant guard, not a fix
for a reachable collision. Do it or don't; what the contract may not do is claim
it prevents something. **This is the exact class the seam review exists for: a
scope item the contract asserted from its own reasoning and the sibling's real
surface refutes.**

**SR-2 — the atomic-write pattern transfers cleanly to a dotfile, verified not
assumed.** `marks._write_raw` derives its temp name as
`path.with_suffix(path.suffix + ".tmp")`. For a dotfile with an extension that
is not obviously safe — `Path(".booth.json").stem` is `".booth"`, which looks
alarming — but `.suffix` is `".json"` and the result is `.booth.json.tmp`.
Checked against the interpreter. The temp file is itself a dotfile, so
`booth_items` and `zip_booth` skip it and no reader can see it mid-write.

**SR-3 — the dotfile skips are on `p.name`, and all three use `rglob` or
`iterdir` over the booth.** `items.booth_items` (items.py:182), `app.zip_booth`
(app.py:351) and `marks.import_legacy_asks` (marks.py:656) each test
`p.name.startswith(".")`. A manifest at the booth root is skipped by every one
of them. Confirmed by reading the three loops, not by trusting the claim.

**SR-4 — `test_stdlib_only` is parametrized `["marks", "asks", "links"]`**
(tests/test_marks.py:279) and gains `"manifest"` as a fourth entry. The test's
docstring calls this INV-5 while `CLAUDE.md` calls it invariant 1; that
inconsistency predates this unit and is left alone.

**SR-5 — `.booth.json` is reachable over HTTP at `/b/<name>/.booth.json`.**
`booth_file` refuses only path escapes and non-files, not dotfiles, so a remote
session with no filesystem access can read a booth's announcement the same way
it already polls `/b/<n>/marks.json`. That is a feature and it is now written
down; there is no secret in a manifest, and the Booth has no auth by design.

**SR-6 — `list_booths` returns plain dicts and the templates read them by key.**
`b.manifest` resolves through Jinja's getitem fallback. A None manifest must be
guarded with an explicit `{% if %}` rather than relying on `b.manifest.handle`
rendering as Undefined, because the two lanes' cards differ and a silent
Undefined in one of them is how the kept lane would quietly keep the old defect.

## Out of scope

Deliberately deferred or never. Divergence here is not drift.

- **A second index ordering keyed on `created`** — a "what landed" feed. Operator
  decision, 2026-09-22: parked for v1.1. It is a new ordered collection needing
  its own stated rule, it competes with the existing order for what "the third
  one" means, and it has nothing to sort the 26 manifest-less booths by.
- **`why` in the zip manifest, or a `booth ls` column.** One-liners over the
  same record, neither on the v1 path.
- **Enforcing that a booth MUST announce itself.** `rsync` is the documented
  path for every host that is not nh3-dev and never runs the CLI, so a refusal
  would break the documented workflow. The marker is the whole mechanism.
- **Deleting, expiring or migrating anything based on the manifest.** U4 owns
  lifetime; this unit only describes.
- **Any change to how items, marks, blur, keep or the link board work.** The
  manifest is a dotfile and every existing listing already skips it.
- **Auth, or treating a manifest as trusted.** Standing non-goal; the Booth is
  LAN-internal and a hand-written `.booth.json` is a supported input.
- **Provenance ON a verbatim-`index.html` booth's own page.** Five live booths
  serve the author's HTML raw, and the Booth owns no header there to put a line
  into — it currently reaches those pages through six regexes injected into
  arbitrary markup, which is precisely the defect U3 exists to fix. Their INDEX
  cards carry provenance like everything else; the page itself waits for U3's
  declared embed seam. Verified on `pewpew-ui-brief`: page renders 200, card
  reads `unannounced`.

## Invariants

Numbered INV-1..5 and local to this unit. Where a repo-wide rule is meant it is
named in words — "CLAUDE.md invariant 5", "CLAUDE.md invariant 6" — never by a
bare number, because an earlier draft used `INV-5` for both the repo's
atomic-write rule and this unit's render rule and the collision was caught
3-of-4.

**INV-1 — one module knows the filename.** `booth/manifest.py` is the only
module that names `MANIFEST_FILE`. No route body, template or CLI verb opens or
parses `.booth.json`; `write_manifest` reads it back inside that module, which
is what INV-3 requires and is not an exception to this rule. Falsifiable and
tested: no other file under `booth/` contains the literal `.booth.json`.

**INV-2 — the read cannot raise, AND cannot cost the caller unboundedly.**
`read_manifest` returns for every input: an absent directory, a `.booth.json`
that is a list, a string, `null`, empty, not UTF-8, wrong-typed, missing its
handle, nested deeply enough to overflow the parser's stack, and one larger
than `MANIFEST_MAX_BYTES` — which is refused by `stat` before a byte is read,
because a bound that only constrains the RETURN recreates the outage in slow
motion. Tested per case, the size and depth cases included.

**INV-3 — `created` survives re-announcement.** A second `write_manifest` on the
same booth preserves the first `created`. A prior record carrying `error`, or
one whose `created` is `""`, has no stamp to preserve and gets `now()`. Tested
against a stamp that could not have come from `now()` — `_now()` is whole-second
resolution, so back-to-back writes share a timestamp and a naive test passes
against an implementation that regenerates it every time.

**INV-4 — stdlib-only, and sibling-free** (this is CLAUDE.md invariant 1
extended by one clause). `booth/manifest.py` imports nothing outside the
standard library and nothing from `booth.*` — a cross-import between two
stdlib-only modules is a second way for the repo rule to break. Relative
imports count; the AST walk sees them.

**INV-6 — bytes that could not be read are never destroyed.** When
`write_manifest` replaces a manifest whose read returned `error`, the old bytes
move to `QUARANTINE_FILE` first. This is the doctrine marks made explicit in
v0.2.1 — reads lenient, writes strict, damaged bytes stay on disk — and this
unit contradicted it by replacing outright, so a file that failed on ONE field
lost the others with it, including a `why` the re-announcer may never have kept
anywhere.

It diverges from marks in HOW it honours the rule, and the divergence is the
interesting part. Marks REFUSE the write and answer 409, because the operator's
judgment is not restatable. A manifest QUARANTINES and proceeds, because
refusing would fail `booth add` and lose the files it was mid-way through
copying — and a booth's own description is something its poster can say again.
One fixed quarantine name rather than a timestamped series: nothing prunes a
booth but the sweep, and the most recent damage is the only copy anyone opens.

**INV-5 — unannounced and unreadable render DIFFERENT TEXT.** Not merely
different styling: the words differ (`unannounced` / `unreadable`), so the
distinction survives a stylesheet change and a reader who cannot see colour. A
one-pixel difference would satisfy a looser wording and encode nothing, and the
point is that one of the two states is something somebody has to go and fix.