feat(manifest): U5 — booths that say who posted them and why

The index card showed a name, an item count and a countdown, and nothing
the poster chose. An agent with something to show therefore had no way to
make the booth say "look at this" and posted a URL to the link board
instead — which is why 145 of that board's 210 rows (69%) ended up
pointing at booths that had already been swept. The board was absorbing a
job it was never shaped for. This is the shape.

Each booth carries `.booth.json` — {handle, title, why, created} — written
by the CLI from $ALTHING_HANDLE, and the provenance line renders on both
index lanes and on the booth page header.

WHAT IS WHERE

- booth/manifest.py, stdlib-only and importing nothing from booth.* either:
  scripts/booth imports it under the system python3 with no venv, and a
  cross-import between two stdlib-only modules is a second way for that
  invariant to break. It joins the shared test_stdlib_only list and keeps
  a stricter copy of its own.
- The read is lenient and cannot raise. list_booths touches every booth on
  every index load, so a manifest that cannot be parsed costs that booth's
  provenance and nothing else. That is the v0.2.2 lesson applied before the
  same mistake rather than after it.
- Absent and damaged render differently — `unannounced` and `unreadable`.
  Folding "cannot be read" into "never said" would hide the one case
  somebody has to go and fix.
- Re-announcing preserves `created`. A second `booth add` sharpening the
  why is not a second appearance of the booth.
- The write is atomic (invariant 5); the temp file is itself a dotfile, so
  no listing can see it mid-write.

THREE OPERATOR CALLS, 2026-09-22

Flags on the existing new/add verbs rather than a separate `announce` verb
(a second step is the step that gets forgotten, which is the rot's own
mechanism). Unannounced booths get a quiet marker rather than nothing — the
convention is only adoptable if the gap is visible. U5 adds provenance only
and does NOT add a second index ordering keyed on announcement time; that
is a different surface needing its own stated rule, parked for v1.1.

NO EXEMPTION LIST

A pickup booth and the standing link board are created by the service, so
they announce themselves with handle `booth`, which is true rather than
manufactured. One rule — a booth with no manifest is unannounced — instead
of a growing set of special cases.

ALSO

tests/test_booth.py's keep/release assertion was slicing the page on the
bare word `boothhead`, which has lived in the stylesheet far longer than
the assertion has; it was reading CSS and passing on luck, and went red the
first time a new rule landed above the old one. Same assertion, aimed at
the markup. A U5 test had the mirror-image bug: pytest derives tmp_path
from the test name and the index renders data_dir, so a test named
`test_an_unannounced_booth_says_so` put the needle in the haystack itself
and passed against a template that did not yet exist.

310 tests (304 before this unit's CLI half). Live service restarted, 26/26
booth pages verified 200, end-to-end smoke through the real CLI.

NOT TAGGED. The cold contract-review panel is still in flight and the
code-review and bug-hunt gates have not run. Tagging with a gate
outstanding is what made v0.2.0 premature.

booth/app.py

@@ -141,6 +141,12 @@ from booth.inline import (  # noqa: E402
     has_placeholders,
     place as place_asks,
 )
+from booth.manifest import (  # noqa: E402
+    MANIFEST_FILE,
+    SERVICE_HANDLE,
+    read_manifest,
+    write_manifest,
+)
 from booth.links import (  # noqa: E402
     LINK_LOCK,
     LINKS_FILE,
@@ -273,6 +279,11 @@ def list_booths(data_dir: Path, ttl_seconds: float, now: float | None = None) ->
         # — which is why marks live in one file per booth rather than a sidecar
         # per mark. This loop runs on every index page load.
         marks = marks_for(child)
+        # The booth's own announcement — who posted it and why. One more small
+        # read per booth, beside the marks read already here, and `read_manifest`
+        # cannot raise for the same reason `marks_for` must not: this loop runs
+        # over EVERY booth on every index page load.
+        manifest = read_manifest(child)
         kinds = {"image": 0, "video": 0, "audio": 0, "other": 0}
         thumb_url = None
         thumb_blurred = False
@@ -290,6 +301,7 @@ def list_booths(data_dir: Path, ttl_seconds: float, now: float | None = None) ->
             {
                 "name": child.name,
                 "name_url": quote(child.name, safe=""),
+                "manifest": manifest,
                 "count": len(items),
                 "kinds": kinds,
                 "thumb_url": thumb_url,
@@ -748,6 +760,10 @@ def create_app(
                 },
                 "booth_marks": marks_for_target(marks, None),
                 "uploaded": (booth / UPLOAD_MARKER).exists(),
+                # The same provenance line the index card carries. Deliberate:
+                # a booth URL handed to the operator lands HERE, never on the
+                # index, and job 5 is "operator, look at this".
+                "manifest": read_manifest(booth),
                 "expires_in": max(0.0, ttl_seconds - booth_age_seconds(booth)),
             },
         )
@@ -1086,9 +1102,17 @@ def create_app(
         dest = data_dir / booth_id
         dest.mkdir(parents=True)
         (dest / UPLOAD_MARKER).write_text("")  # stamp as an upload (dotfile, not listed)
+        # A booth the SERVICE made says so, rather than being exempted from the
+        # unannounced marker. One rule instead of an exemption list, and the
+        # handle is true: nobody's agent posted this, the browser did.
+        write_manifest(dest, SERVICE_HANDLE, title=booth_id,
+                       why="browser upload, for pickup")
 
         total = 0
-        used: set = {UPLOAD_MARKER}
+        # Both markers are belt-and-braces: `safe_upload_name` strips leading
+        # dots, so an uploaded file can never be named either of them. Listed
+        # anyway so the set says what the directory already contains.
+        used: set = {UPLOAD_MARKER, MANIFEST_FILE}
         try:
             for i, f in enumerate(files):
                 name = _dedupe_name(safe_upload_name(f.filename, f"file-{i + 1}"), used)

booth/manifest.py

@@ -0,0 +1,164 @@
+"""A booth's own announcement — who posted it, and why.
+
+U5. The index card used to show a name, an item count and a countdown, and
+nothing the poster chose. An agent with something to show therefore had no way
+to make the booth say "look at this" and posted a URL to the link board
+instead — which is why 145 of that board's 210 rows (69%) ended up pointing at
+booths that had already been swept. The board was absorbing a job it was never
+shaped for. This is the shape.
+
+    .booth.json  ->  {"handle": ..., "title": ..., "why": ..., "created": ...}
+
+⚠ STDLIB ONLY, and it imports nothing from `booth.*` either.
+
+`scripts/booth` — the CLI every fleet session uses — imports this module
+directly under the system `python3` with no venv, through a `python3 -c`
+heredoc no AST extractor can see. A single third-party import here breaks
+`booth new` and `booth add` on every host, and the failure surfaces in an
+agent's session rather than in ours. The ban extends to sibling `booth` modules:
+importing `marks` to reuse its atomic write would drag marks' own import list
+into this one's, so the four-line pattern is copied instead. `test_stdlib_only`
+in tests/test_manifest.py is the only thing standing here.
+
+Contract: docs/contracts/u5_booth_manifest.contract.md.
+"""
+from __future__ import annotations
+
+import json
+import os
+from dataclasses import dataclass
+from datetime import datetime
+from pathlib import Path
+
+MANIFEST_FILE = ".booth.json"
+
+# A `why` renders inside a card's sub-line, so it is one line by construction
+# rather than by convention — enforced at the WRITE so nothing downstream has to
+# remember. The caps are display budgets, not storage limits.
+HANDLE_MAX = 64
+TITLE_MAX = 120
+WHY_MAX = 200
+
+# The handle a booth created by the service itself carries. A pickup booth and
+# the standing link board are made by the Booth, not by an agent, and saying so
+# is true rather than manufactured — which is the whole reason there is no
+# exemption list. One rule: a booth with no manifest is unannounced.
+SERVICE_HANDLE = "booth"
+
+
+@dataclass(frozen=True)
+class Manifest:
+    """One booth's announcement.
+
+    `handle` is an althing agent handle, or `SERVICE_HANDLE` for a booth the
+    Booth made. `error` is a read-time verdict and is never stored.
+    """
+
+    handle: str
+    title: str
+    why: str
+    created: str
+    error: str | None = None
+
+
+def _one_line(value, limit: int) -> str:
+    if not isinstance(value, str):
+        return ""
+    return " ".join(value.split())[:limit]
+
+
+def _now() -> str:
+    return datetime.now().astimezone().isoformat(timespec="seconds")
+
+
+def read_manifest(booth: Path) -> Manifest | None:
+    """This booth's announcement, or None if it never made one.
+
+    LENIENT, AND IT NEVER RAISES (INV-2). `list_booths` calls this once per
+    booth on every index page load, so a read that can raise is a service-wide
+    outage wearing a single-booth bug's clothes. That is not hypothetical: a
+    poisoned `.marks.json` did exactly that to `/` and `/healthz` across all 25
+    live booths, and the fix shipped in v0.2.2. Same posture, applied before the
+    same mistake rather than after it.
+
+    Absent -> None. Present but unreadable -> a Manifest carrying `error`, so a
+    card can say `unreadable` instead of quietly showing the same thing as a
+    booth that never announced (INV-5). Folding the two together would hide the
+    one case somebody has to go and fix.
+
+    Only `handle` is required. A hand-written manifest is a supported input —
+    the file is plain JSON in a folder the operator owns, and half the point of
+    the Booth is that a booth is just a directory.
+    """
+    booth = Path(booth)
+    path = booth / MANIFEST_FILE
+    try:
+        text = path.read_text(encoding="utf-8")
+    except FileNotFoundError:
+        return None
+    except (OSError, UnicodeDecodeError) as exc:
+        return _broken(booth, f"cannot be read: {exc}")
+    if not text.strip():
+        return _broken(booth, "is empty")
+    try:
+        raw = json.loads(text)
+    except ValueError as exc:
+        return _broken(booth, f"is not valid JSON: {exc}")
+    if not isinstance(raw, dict):
+        return _broken(booth, "is not a JSON object")
+
+    handle = _one_line(raw.get("handle"), HANDLE_MAX)
+    if not handle:
+        return _broken(booth, "names no handle")
+    return Manifest(
+        handle=handle,
+        title=_one_line(raw.get("title"), TITLE_MAX) or booth.name,
+        why=_one_line(raw.get("why"), WHY_MAX),
+        created=_one_line(raw.get("created"), 64),
+    )
+
+
+def _broken(booth: Path, reason: str) -> Manifest:
+    return Manifest(handle="", title=booth.name, why="", created="",
+                    error=f"{MANIFEST_FILE} {reason}")
+
+
+def write_manifest(booth: Path, handle: str, *, title: str = "",
+                   why: str = "") -> Manifest:
+    """Announce a booth, atomically (CLAUDE.md invariant 5).
+
+    Temp file + `os.replace`, because the CLI writes this in one process while
+    the browser reads it in another — a reader must never see a half-written
+    document. The temp file is itself a dotfile (`.booth.json.tmp`), so no
+    listing, gallery or zip can see it mid-write either.
+
+    RE-ANNOUNCING PRESERVES `created` (INV-3). It is when the booth APPEARED,
+    and saying something more about it later is not a second appearance —
+    `booth add` on an existing booth is the common case, where the poster drops
+    the second batch and sharpens the why. A `created` that cannot be read back
+    is replaced rather than guessed at: a stamp that is silently wrong is worse
+    than one that is silently new.
+    """
+    booth = Path(booth)
+    booth.mkdir(parents=True, exist_ok=True)
+    prior = read_manifest(booth)
+    created = prior.created if prior and not prior.error and prior.created else _now()
+
+    record = Manifest(
+        handle=_one_line(handle, HANDLE_MAX) or SERVICE_HANDLE,
+        title=_one_line(title, TITLE_MAX) or booth.name,
+        why=_one_line(why, WHY_MAX),
+        created=created,
+    )
+    path = booth / MANIFEST_FILE
+    tmp = path.with_suffix(path.suffix + ".tmp")
+    tmp.write_text(
+        json.dumps(
+            {"handle": record.handle, "title": record.title,
+             "why": record.why, "created": record.created},
+            ensure_ascii=False, indent=2,
+        ) + "\n",
+        encoding="utf-8",
+    )
+    os.replace(tmp, path)
+    return record

booth/templates/_provenance.html

@@ -0,0 +1,17 @@
+{# THE ANNOUNCEMENT — who posted this booth and why. Defined ONCE and called
+   from both index lanes and the booth page header: the kept lane is a separate
+   block, and patching only the ephemeral one would leave the durable,
+   most-looked-at boards with exactly the defect this closes.
+
+   Four states, and `unannounced` is distinct from `unreadable` on purpose —
+   folding "cannot be read" into "never said" hides the one case somebody has to
+   go and fix. The classes are the test hooks; the words are for the operator. #}
+{% macro provenance(m) -%}
+  {% if m is none %}
+    <div class="prov prov-none">unannounced</div>
+  {% elif m.error %}
+    <div class="prov prov-broken" title="{{ m.error }}">unreadable</div>
+  {% else %}
+    <div class="prov"><span class="prov-who">{{ m.handle }}</span>{% if m.why %} · <span class="prov-why">{{ m.why }}</span>{% endif %}</div>
+  {% endif %}
+{%- endmacro %}

booth/templates/base.html

@@ -255,6 +255,22 @@
   .card .name:hover{text-decoration:none;color:var(--aus-bright-cyan)}
   .card .sub{color:var(--fg-3);font-size:.72rem;font-family:var(--font-mono);letter-spacing:.03em;margin-top:.3rem}
 
+  /* THE ANNOUNCEMENT — who posted this booth and why (U5). Same size and
+     rhythm as .sub above it, because it is the same class of information: a
+     second line of card metadata, not a heading. The handle carries the only
+     colour, so a scan down the index reads as a column of posters. */
+  .prov{margin-top:.28rem;font-size:.72rem;font-family:var(--font-mono);
+    letter-spacing:.03em;color:var(--fg-3);line-height:1.45;
+    overflow-wrap:anywhere}
+  .prov-who{color:var(--fg-2)}
+  .prov-why{color:var(--fg-3)}
+  /* Quiet on purpose. 26 booths arrived before this convention existed and
+     rsync keeps making more, so the marker has to be visible-if-you-look and
+     never a badge shouting 26 times. `unreadable` gets the warning tint
+     because, unlike `unannounced`, it is something somebody has to fix. */
+  .prov-none{color:var(--fg-muted);font-style:italic}
+  .prov-broken{color:var(--aus-bright-yellow,#e8c547);font-style:italic;cursor:help}
+
   .wipe{position:absolute;top:.5rem;right:.5rem;margin:0}
   /* ★ keep, mirroring .wipe on the other shoulder of the card. Same
      hover-to-reveal language as .release in the kept lane. */
@@ -408,6 +424,9 @@
   .boothhead h1{margin:0;font-family:var(--font-display);font-weight:600;font-size:1.5rem;
     letter-spacing:-.01em;word-break:break-word;flex:1 1 auto;color:var(--fg-0)}
   .boothhead .sub{color:var(--fg-3);font-size:.74rem;font-family:var(--font-mono);letter-spacing:.06em}
+  /* Its own row under the title, not another chip in the flex line — a `why`
+     can run to WHY_MAX and would otherwise shove the zip link around. */
+  .boothhead .prov{flex:0 0 100%;margin-top:-.35rem}
   .wipe-lg{position:static}
   /* red-outline danger button — legible on the dark canvas, fills on hover */
   .wipe-lg button{width:auto;height:auto;padding:.42rem .85rem;border-radius:var(--radius-md);

booth/templates/booth.html

@@ -1,4 +1,5 @@
 {% extends "base.html" %}
+{% from "_provenance.html" import provenance %}
 {# The blur toggle, defined ONCE. There are three item branches in this file
    (doc / media / other) and the first cut of this feature patched only one of
    them, so docs rendered with no control at all. A macro makes "patched two of
@@ -58,6 +59,7 @@
   <h1>{{ name }}</h1>
   <span class="sub">{% if uploaded %}<span class="badge">⬆ pickup</span> {% endif %}{% if board %}{{ board|length }} link{{ '' if board|length == 1 else 's' }}{% if items %} · {{ items|length }} file{{ '' if items|length == 1 else 's' }}{% endif %}{% else %}{% if marks_open %}<span class="badge badge-mark">{{ marks_open }} open</span> · {% endif %}{{ items|length }} item{{ '' if items|length == 1 else 's' }} · expires in {{ expires_in|dur }}{% endif %}</span>
   {% if items %}<a class="dl-link" href="/b/{{ name_url }}/?download=1" title="download this booth as a zip">⬇ zip</a>{% endif %}
+  {{ provenance(manifest) }}
     {# A durable multi-writer board gets no one-click wipe — same rule as the
        kept lane on the index. Remove rows with the per-row ×, or release the
        board from the index and wipe it from there. #}

booth/templates/index.html

@@ -1,4 +1,5 @@
 {% extends "base.html" %}
+{% from "_provenance.html" import provenance %}
 {% block content %}
 <form class="uploader" method="post" action="/upload" enctype="multipart/form-data">
   <label class="drop" for="booth-files">
@@ -39,6 +40,7 @@
       <div class="meta">
         <a class="name" href="/b/{{ b.name_url }}/">{{ b.name }}</a>
         <div class="sub">{{ b.count }} item{{ '' if b.count == 1 else 's' }} · kept · <a class="dl-link" href="/b/{{ b.name_url }}/?download=1" title="download this booth as a zip">⬇ zip</a></div>
+        {{ provenance(b.manifest) }}
       </div>
       {# There IS a × here now (operator, 2026-09-21). The old rule was
          release-then-find-it-in-the-other-lane, on the theory that two
@@ -110,6 +112,7 @@
       <div class="meta">
         <a class="name" href="/b/{{ b.name_url }}/">{{ b.name }}</a>
         <div class="sub">{{ b.count }} item{{ '' if b.count == 1 else 's' }} · expires in {{ b.expires_in|dur }} · <a class="dl-link" href="/b/{{ b.name_url }}/?download=1" title="download this booth as a zip">⬇ zip</a></div>
+        {{ provenance(b.manifest) }}
       </div>
       {# Promote to the kept lane. The /keep route and the `booth keep` CLI verb
          both predate this button; until 2026-09-19 the UI could only RELEASE a

persistent-memory.md

@@ -26,7 +26,18 @@ _As of 2026-09-22:_
   the deploy. U1 `ce598b3`; U2 `c7f9437` released as `v0.2.0`, then `5e41108` as
   `v0.2.1` (four contract-panel findings), then `v0.2.2` carrying the
   **bug-hunt panel's** nine (below).
-- **U5 is the next unit** (operator, 2026-09-21): **self-announcing booths.**
+- **U5 is IMPLEMENTED and unreleased** as of 2026-09-22. `booth/manifest.py`
+  (stdlib-only, INV-1), `.booth.json` per booth, the provenance line on both
+  index lanes and the booth page header, `--why` / `--title` on `booth new` and
+  `booth add`, and the link board + pickup booths announcing themselves as the
+  service's own. 310 tests, live service restarted, 26/26 booth pages verified
+  200 and all 26 rendering `unannounced`. **Deliberately NOT tagged yet**: the
+  cold `/heid-contract-review` panel is still in flight and the code-review and
+  bug-hunt gates have not run. That ordering is the 2026-09-21 lesson applied —
+  a release whose gate is outstanding is premature even when the tier is right.
+  Contract: `docs/contracts/u5_booth_manifest.contract.md` (carries its own
+  seam-review section).
+- **U5's original framing** (operator, 2026-09-21): **self-announcing booths.**
   `.booth.json` carrying `{handle, title, why, created}`, written by the CLI from
   `$ALTHING_HANDLE`; the index card gains provenance and a one-line purpose, and
   the index becomes the "what landed" feed the link board was being used as. It

scripts/booth

@@ -3,8 +3,10 @@
 # folder under $BOOTH_DATA_DIR; this is sugar over mkdir/cp so you get the URL
 # back.
 #
-#   booth new    <name>                 make an empty booth, print its URL
-#   booth add    <name> <file>...       copy files into a booth (creates it), print URL
+#   booth new    <name> [--why W] [--title T]
+#                                       make an empty booth, print its URL
+#   booth add    <name> <file>... [--why W] [--title T]
+#                                       copy files into a booth (creates it), print URL
 #   booth url    <name>                 print a booth's URL
 #   booth ls                            list booths (kept ones marked ★)
 #   booth rm     <name>                 wipe a booth now (TTL would eventually anyway)
@@ -75,6 +77,18 @@
 # URLs that then drown in terminal scrollback. They go on a standing kept board
 # instead, with provenance, so they outlive the session that produced them.
 #
+# ANNOUNCE YOUR BOOTH. `--why` is one line saying what the operator is looking
+# at and why he should care; it lands on the index card and on the booth page
+# beside your handle, taken from $ALTHING_HANDLE. It is optional and nothing
+# breaks without it — but a booth that cannot say what it is has no way to ask
+# for attention except by posting its URL somewhere, which is exactly how the
+# link board came to be 69% dead rows. The booth is the place to say it.
+#
+#   booth add r18-ab out/*.png --why "pick the denoiser, left column is v3"
+#
+# Re-announcing (a second `new` or `add` on the same booth) updates the why and
+# KEEPS the original creation stamp: the booth appeared once.
+#
 # On a host that is NOT nh3-dev, rsync into the data dir instead, e.g.:
 #   rsync -a ./out/  nh3-dev:booth-data/my-run/
 set -euo pipefail
@@ -85,23 +99,76 @@ KEEP=".forever"                                    # must match KEEP_MARKER in b
 BLUR=".blurred"   # one booth-relative item path per line; see `blur` below
 LINKS_BOARD="${BOOTH_LINKS_BOARD:-links}"
 
+# `--why` / `--title` for `new` and `add`. Pulled out of "$@" wherever they
+# appear, so `booth add b *.png --why "..."` and `booth add b --why "..." *.png`
+# both work — a glob is usually last and a flag usually after it, but nothing
+# enforces that and a session should not have to care.
+WHY=""; TITLE=""; ARGS=()
+strip_announce_flags() {
+  ARGS=()
+  while [ $# -gt 0 ]; do
+    case "$1" in
+      --why)     [ $# -ge 2 ] || usage; WHY="$2";   shift 2 ;;
+      --title)   [ $# -ge 2 ] || usage; TITLE="$2"; shift 2 ;;
+      --why=*)   WHY="${1#--why=}";     shift ;;
+      --title=*) TITLE="${1#--title=}"; shift ;;
+      *) ARGS+=("$1"); shift ;;
+    esac
+  done
+}
+
+# Announce a booth. Goes through booth/manifest.py rather than printf-ing JSON
+# from the shell, because a why containing a quote, a backslash or a newline is
+# not an edge case — it is a sentence somebody wrote.
+announce() {
+  BOOTH_SRC="$(cd "$(dirname -- "$(readlink -f -- "$0")")/.." && pwd)" \
+  BOOTH_ANN_DIR="$1" BOOTH_ANN_HANDLE="$2" \
+  BOOTH_ANN_TITLE="${3:-}" BOOTH_ANN_WHY="${4:-}" python3 -c '
+import os, pathlib, sys
+sys.path.insert(0, os.environ["BOOTH_SRC"])
+try:
+    from booth.manifest import write_manifest
+    write_manifest(pathlib.Path(os.environ["BOOTH_ANN_DIR"]),
+                   os.environ["BOOTH_ANN_HANDLE"],
+                   title=os.environ["BOOTH_ANN_TITLE"],
+                   why=os.environ["BOOTH_ANN_WHY"])
+except Exception as exc:
+    # A booth that could not announce itself is still a booth. Say so on stderr
+    # and carry on: failing `booth add` over its metadata would lose the files
+    # the session just copied, which is a far worse trade.
+    print(f"booth: could not write the announcement: {exc}", file=sys.stderr)
+'
+}
+
+# Who is posting. The same chain `link` uses for its rows, so provenance means
+# the same thing on the board and on the card.
+whoami_handle() {
+  echo "${ALTHING_HANDLE:-${BOOTH_SOURCE:-$(hostname -s 2>/dev/null || echo unknown)}}"
+}
+
 usage() {
-  echo "usage: booth {new <name>|add <name> <file>...|url <name>|ls|rm <name>|keep <name>|unkeep <name>|blur <name> <file>...|unblur <name> <file>...|link <url> [description]|links|unlink <id|index>|ask <name> <id> <prompt> <option>... [--no-notes]|marks <name> [--wait [SECS]]|asks <name> (deprecated alias for marks)|answer <name> <id> [--wait [SECS]]|marks-import <name>}" >&2
+  echo "usage: booth {new <name> [--why W] [--title T]|add <name> <file>... [--why W] [--title T]|url <name>|ls|rm <name>|keep <name>|unkeep <name>|blur <name> <file>...|unblur <name> <file>...|link <url> [description]|links|unlink <id|index>|ask <name> <id> <prompt> <option>... [--no-notes]|marks <name> [--wait [SECS]]|asks <name> (deprecated alias for marks)|answer <name> <id> [--wait [SECS]]|marks-import <name>}" >&2
   exit 2
 }
 
 cmd="${1:-}"; shift || true
 case "$cmd" in
   new)
+    strip_announce_flags "$@"
+    set -- ${ARGS+"${ARGS[@]}"}
     [ $# -ge 1 ] || usage
     mkdir -p -- "$DATA/$1"
+    announce "$DATA/$1" "$(whoami_handle)" "$TITLE" "$WHY"
     echo "$URL/b/$1/"
     ;;
   add)
+    strip_announce_flags "$@"
+    set -- ${ARGS+"${ARGS[@]}"}
     [ $# -ge 2 ] || usage
     name="$1"; shift
     mkdir -p -- "$DATA/$name"
     cp -- "$@" "$DATA/$name/"
+    announce "$DATA/$name" "$(whoami_handle)" "$TITLE" "$WHY"
     echo "$URL/b/$name/"
     ;;
   url)
@@ -177,6 +244,11 @@ case "$cmd" in
     board="$DATA/$LINKS_BOARD"
     mkdir -p -- "$board"
     : > "$board/$KEEP"                             # the board is durable by definition
+    # The board announces itself as the SERVICE's, not as any one agent's:
+    # seventeen handles post to it, so no handle owns it. Idempotent — a second
+    # link keeps the original creation stamp.
+    announce "$board" "booth" "$LINKS_BOARD" \
+      "the standing link board — every agent session posts here"
     # Provenance, because a bare URL is unreadable three days later: who posted
     # it, from where, and when.
     who="${ALTHING_HANDLE:-${BOOTH_SOURCE:-$(hostname -s 2>/dev/null || echo unknown)}}"

tests/test_booth.py

@@ -1537,7 +1537,13 @@ def test_booth_page_offers_keep_when_ephemeral_and_release_when_kept(client):
     _png(d / "x.png")
 
     body = c.get("/b/bo/").text
-    assert "☆ keep" in body and "release" not in body.split("boothhead")[1][:900]
+    # Sliced on the ELEMENT, not the bare word: `boothhead` has appeared in the
+    # stylesheet this page carries since long before this assertion, so
+    # `split("boothhead")[1]` was reading CSS and passing on luck. It went red
+    # the first time a new rule landed above the old one (U5's .prov), which is
+    # the only reason anybody noticed. Same assertion, aimed at the markup.
+    head = body.split('class="boothhead"')[1][:900]
+    assert "☆ keep" in body and "release" not in head
 
     c.post("/b/bo/keep", data={"next": "/b/bo/"}, follow_redirects=False)
     body = c.get("/b/bo/").text

tests/test_cli.py

@@ -119,3 +119,91 @@ def test_answer_on_a_note_id_says_no_such_pick(booth):
     r = run(data, "answer", "b", "note-1")
     assert r.returncode == NO_SUCH_PICK
     assert "no such pick" in r.stderr
+
+
+# ---- U5: self-announcing booths ---------------------------------------------
+
+
+def _manifest(booth_dir):
+    import sys
+    sys.path.insert(0, str(pathlib.Path(__file__).parent.parent))
+    from booth.manifest import read_manifest
+    return read_manifest(booth_dir)
+
+
+def test_new_announces_the_booth(tmp_path):
+    """`$ALTHING_HANDLE` is the whole provenance story: the session already has
+    it, so the booth can say who made it without anybody typing a name."""
+    env = {**os.environ, "ALTHING_HANDLE": "shutter-dev"}
+    r = subprocess.run([str(SCRIPT), "new", "r18-ab", "--why", "pick the winner"],
+                       capture_output=True, text=True, timeout=30,
+                       env={**env, "BOOTH_DATA_DIR": str(tmp_path),
+                            "BOOTH_URL": "http://booth.invalid"})
+    assert r.returncode == 0, r.stderr
+    m = _manifest(tmp_path / "r18-ab")
+    assert m.handle == "shutter-dev"
+    assert m.why == "pick the winner"
+
+
+def test_new_without_a_why_is_still_legal(tmp_path):
+    """The flags are optional and existing call sites keep working. A booth
+    that says only who made it is still a booth that said something."""
+    r = subprocess.run([str(SCRIPT), "new", "scratch"], capture_output=True,
+                       text=True, timeout=30,
+                       env={**os.environ, "ALTHING_HANDLE": "booth-dev",
+                            "BOOTH_DATA_DIR": str(tmp_path),
+                            "BOOTH_URL": "http://booth.invalid"})
+    assert r.returncode == 0, r.stderr
+    m = _manifest(tmp_path / "scratch")
+    assert m.handle == "booth-dev" and m.why == ""
+
+
+def test_add_announces_and_still_copies_the_files(tmp_path):
+    """`add` is the verb most sessions actually use — it creates the booth AND
+    fills it — so the why has to ride on it or it rides nowhere."""
+    src = tmp_path / "src"
+    src.mkdir()
+    (src / "a.txt").write_text("content")
+    r = subprocess.run([str(SCRIPT), "add", "r18-ab", str(src / "a.txt"),
+                        "--why", "second pass", "--title", "R18 A/B"],
+                       capture_output=True, text=True, timeout=30,
+                       env={**os.environ, "ALTHING_HANDLE": "booth-dev",
+                            "BOOTH_DATA_DIR": str(tmp_path),
+                            "BOOTH_URL": "http://booth.invalid"})
+    assert r.returncode == 0, r.stderr
+    assert (tmp_path / "r18-ab" / "a.txt").read_text() == "content"
+    m = _manifest(tmp_path / "r18-ab")
+    assert m.why == "second pass" and m.title == "R18 A/B"
+
+
+def test_add_re_announcing_keeps_the_original_created(tmp_path):
+    """The common shape: `new` opens the booth, `add` drops the second batch and
+    sharpens the why. The booth appeared once."""
+    env = {**os.environ, "ALTHING_HANDLE": "booth-dev",
+           "BOOTH_DATA_DIR": str(tmp_path), "BOOTH_URL": "http://booth.invalid"}
+    src = tmp_path / "a.txt"
+    src.write_text("x")
+    subprocess.run([str(SCRIPT), "new", "b", "--why", "first"], check=True,
+                   capture_output=True, timeout=30, env=env)
+    first = _manifest(tmp_path / "b").created
+    subprocess.run([str(SCRIPT), "add", "b", str(src), "--why", "sharper"],
+                   check=True, capture_output=True, timeout=30, env=env)
+
+    after = _manifest(tmp_path / "b")
+    assert after.created == first
+    assert after.why == "sharper"
+
+
+def test_the_link_board_announces_itself_as_the_booths_own(tmp_path):
+    """No exemption list. The standing board is made by the service and posted
+    to by seventeen handles, so no single agent owns it — `booth` is the
+    truthful answer, and it keeps the rule to one line."""
+    r = subprocess.run([str(SCRIPT), "link", "http://example.invalid", "a thing"],
+                       capture_output=True, text=True, timeout=30,
+                       env={**os.environ, "ALTHING_HANDLE": "booth-dev",
+                            "BOOTH_DATA_DIR": str(tmp_path),
+                            "BOOTH_URL": "http://booth.invalid"})
+    assert r.returncode == 0, r.stderr
+    m = _manifest(tmp_path / "links")
+    assert m is not None and m.handle == "booth"
+    assert m.why

tests/test_manifest.py

@@ -0,0 +1,345 @@
+"""U5 — self-announcing booths.
+
+A booth carries `.booth.json` saying who posted it and why, and the index card
+and the booth page render it. Closes job 5 (`Announce`) — the job nobody named,
+whose absence is the measured cause of 145 dead link rows.
+
+See docs/contracts/u5_booth_manifest.contract.md.
+"""
+import ast
+import json
+import os
+import pathlib
+import sys
+
+import pytest
+
+from booth.manifest import MANIFEST_FILE, Manifest, read_manifest, write_manifest
+
+
+# ---- slice 1: the record and its storage ------------------------------------
+
+
+def test_an_announcement_round_trips(tmp_path):
+    b = tmp_path / "r18-ab"
+    b.mkdir()
+    written = write_manifest(b, "booth-dev", why="pick the winning denoiser")
+
+    assert (b / MANIFEST_FILE).is_file()
+    got = read_manifest(b)
+    assert got == written
+    assert got.handle == "booth-dev"
+    assert got.why == "pick the winning denoiser"
+    assert got.error is None
+
+
+def test_the_title_falls_back_to_the_directory_name(tmp_path):
+    """A booth always has a display name. `title` is the one the poster chose
+    when there is one, and the folder name is a perfectly good one when there
+    is not — an empty heading on a card is worse than a plain one."""
+    b = tmp_path / "r18-ab"
+    b.mkdir()
+    assert write_manifest(b, "booth-dev").title == "r18-ab"
+    assert write_manifest(b, "booth-dev", title="R18 A/B").title == "R18 A/B"
+
+
+def test_a_booth_that_never_announced_reads_as_none(tmp_path):
+    """The normal case for every booth that predates this unit, and for every
+    booth that arrives by rsync — the documented path for any host that is not
+    nh3-dev, which never runs the CLI at all."""
+    b = tmp_path / "quiet"
+    b.mkdir()
+    assert read_manifest(b) is None
+    assert read_manifest(tmp_path / "does-not-exist") is None
+
+
+def test_one_line_by_construction_not_by_convention(tmp_path):
+    """`why` renders inside a card's sub-line, so a newline in it would break
+    the card rather than the field. Truncation and newline-stripping happen at
+    the WRITE, so nothing downstream has to remember."""
+    b = tmp_path / "b"
+    b.mkdir()
+    m = write_manifest(b, "booth-dev", why="first line\nsecond line\r\nthird")
+    assert "\n" not in m.why and "\r" not in m.why
+    assert "first line" in m.why and "second line" in m.why
+
+    long = write_manifest(b, "booth-dev", why="x" * 5000)
+    assert len(long.why) <= 200
+    assert len(write_manifest(b, "y" * 500).handle) <= 64
+    assert len(write_manifest(b, "booth-dev", title="t" * 500).title) <= 120
+
+
+# ---- slice 2: the read cannot raise (INV-2) ---------------------------------
+
+
+@pytest.mark.parametrize(
+    "payload",
+    [
+        b"{truncated",                       # not JSON at all
+        b"[]",                               # JSON, wrong shape
+        b'"a string"',                       # JSON, wronger shape
+        b"null",
+        b'{"handle": 7}',                    # right shape, wrong type
+        b'{"why": "no handle here"}',        # the one required field missing
+        b"\xff\xfe not utf-8",
+        b"",
+    ],
+    ids=["truncated", "list", "string", "null", "wrong-type", "no-handle",
+         "not-utf8", "empty"],
+)
+def test_a_damaged_manifest_never_raises(tmp_path, payload):
+    """INV-2. `list_booths` calls this once per booth on every index page load,
+    so a read that can raise is a service-wide outage wearing a single-booth
+    bug's clothes. That is not a hypothetical — a poisoned `.marks.json` did
+    exactly that to `/` and `/healthz` across all 25 booths, and the fix shipped
+    in v0.2.2. The same reader posture, applied before the same mistake."""
+    b = tmp_path / "b"
+    b.mkdir()
+    (b / MANIFEST_FILE).write_bytes(payload)
+
+    got = read_manifest(b)
+    assert isinstance(got, Manifest)
+    assert got.error, "a damaged manifest read clean"
+
+
+def test_damaged_is_not_the_same_as_absent(tmp_path):
+    """INV-5. Silently folding "cannot be read" into "never announced" would
+    hide the one case somebody has to go and fix."""
+    absent = tmp_path / "absent"
+    absent.mkdir()
+    damaged = tmp_path / "damaged"
+    damaged.mkdir()
+    (damaged / MANIFEST_FILE).write_text("{oops")
+
+    assert read_manifest(absent) is None
+    assert read_manifest(damaged).error
+
+
+def test_a_manifest_the_module_did_not_write_still_reads(tmp_path):
+    """Hand-written is a supported input: the file is plain JSON in a folder the
+    operator owns, and half the point is that a booth is just a directory. Only
+    `handle` is required; everything else has a default."""
+    b = tmp_path / "b"
+    b.mkdir()
+    (b / MANIFEST_FILE).write_text(json.dumps({"handle": "shutter-dev"}))
+
+    got = read_manifest(b)
+    assert got.handle == "shutter-dev" and got.error is None
+    assert got.title == "b"
+    assert got.why == ""
+
+
+# ---- slice 3: re-announcement (INV-3) ---------------------------------------
+
+
+def test_re_announcing_preserves_created(tmp_path):
+    """INV-3. `created` is when the booth APPEARED. Saying something more about
+    it later is not a second appearance, and a `booth add` on an existing booth
+    is the common case — the poster adds the second batch and sharpens the why."""
+    b = tmp_path / "b"
+    b.mkdir()
+    first = write_manifest(b, "booth-dev", why="first pass")
+    second = write_manifest(b, "booth-dev", why="second pass, sharper")
+
+    assert second.created == first.created
+    assert second.why == "second pass, sharper"
+
+
+def test_re_announcing_over_a_damaged_file_does_not_inherit_its_created(tmp_path):
+    """A `created` that cannot be read back is replaced rather than guessed at.
+    The alternative is a stamp that is silently wrong, which is worse than one
+    that is silently new."""
+    b = tmp_path / "b"
+    b.mkdir()
+    (b / MANIFEST_FILE).write_text("{not json")
+
+    m = write_manifest(b, "booth-dev", why="rescued")
+    assert m.created and m.error is None
+    assert read_manifest(b).why == "rescued"
+
+
+# ---- slice 4: the write is atomic, and invisible to every listing -----------
+
+
+def test_the_write_is_atomic(tmp_path):
+    """INV-5 of CLAUDE.md. The CLI writes this in one process while the browser
+    reads it in another, so a reader must never see a half-written document."""
+    b = tmp_path / "b"
+    b.mkdir()
+    write_manifest(b, "booth-dev", why="x")
+    assert not list(b.glob("*.tmp")), "a temp file survived the write"
+
+
+def test_a_manifest_is_not_an_item(tmp_path):
+    """The whole integration story: it is a DOTFILE, so the existing
+    `startswith('.')` skip in `booth_items` already keeps it out of tiles,
+    counts and zips. No new exclusion rule anywhere. Asserted rather than
+    assumed, because the claim is load-bearing for the contract's scope."""
+    from booth.app import zip_booth
+    from booth.items import booth_items
+
+    b = tmp_path / "b"
+    b.mkdir()
+    (b / "a.txt").write_text("real content")
+    write_manifest(b, "booth-dev", why="x")
+
+    assert [i.rel for i in booth_items(b)] == ["a.txt"]
+    assert MANIFEST_FILE not in zip_booth(b).decode("latin-1")
+
+
+def test_announcing_is_activity(tmp_path):
+    """A manifest is a dotfile but not a `.lock` dotfile, so `_newest_mtime`
+    counts it. Creating or re-announcing a booth resets its TTL, which is right:
+    both are somebody touching it. The lock exemption added in v0.2.2 is for
+    machinery a READ path creates; this is a deliberate write."""
+    from booth.app import booth_age_seconds
+
+    b = tmp_path / "b"
+    b.mkdir()
+    old = 1_000_000_000
+    os.utime(b, (old, old))
+
+    write_manifest(b, "booth-dev", why="look at this")
+    assert booth_age_seconds(b, now=old + 90_000) < 86_400
+
+
+def test_stdlib_only():
+    """INV-4, and the reason this module exists separately from anything that
+    imports a third-party package. `scripts/booth` imports it under the system
+    python3 with NO venv, through a `python3 -c` heredoc no AST extractor can
+    see. It must also not import `booth.*`: a cross-import between two
+    stdlib-only modules is a second way for the invariant to break."""
+    src = pathlib.Path(__file__).parent.parent / "booth" / "manifest.py"
+    roots = set()
+    for node in ast.walk(ast.parse(src.read_text())):
+        if isinstance(node, ast.Import):
+            roots.update(a.name.split(".")[0] for a in node.names)
+        elif isinstance(node, ast.ImportFrom) and node.level == 0 and node.module:
+            roots.add(node.module.split(".")[0])
+    assert not (roots - set(sys.stdlib_module_names)), (
+        f"booth/manifest.py imports outside the stdlib: "
+        f"{sorted(roots - set(sys.stdlib_module_names))}"
+    )
+
+
+# ---- slice 5: what the operator actually sees -------------------------------
+
+
+@pytest.fixture
+def client(tmp_path):
+    from fastapi.testclient import TestClient
+
+    from booth.app import create_app
+    return TestClient(create_app(tmp_path, ttl_hours=24, start_sweeper=False)), tmp_path
+
+
+def _booth(data, name, *, kept=False):
+    b = data / name
+    b.mkdir()
+    (b / "a.txt").write_text("content")
+    if kept:
+        (b / ".forever").touch()
+    return b
+
+
+@pytest.mark.parametrize("kept", [False, True], ids=["ephemeral", "kept"])
+def test_the_index_card_carries_the_announcement(client, kept):
+    """BOTH LANES. Kept boards render first and are a separate block in
+    index.html, so patching only the ephemeral lane would leave the 15 kept
+    booths — the durable, most-looked-at ones — with exactly the defect this
+    unit closes. Same lesson as the `blurtoggle` macro: three branches, one
+    definition; here it is two lanes and one rule."""
+    c, data = client
+    b = _booth(data, "r18-ab", kept=kept)
+    write_manifest(b, "booth-dev", why="pick the winning denoiser")
+
+    html = c.get("/").text
+    assert "booth-dev" in html
+    assert "pick the winning denoiser" in html
+
+
+@pytest.mark.parametrize("kept", [False, True], ids=["ephemeral", "kept"])
+def test_a_booth_that_never_spoke_up_is_marked(client, kept):
+    """All 26 live booths are in this state, and rsync keeps making more. The
+    marker is what makes the convention adoptable at all: the link board rotted
+    to 69% precisely because nothing ever showed which rows were dead.
+
+    ASSERTED ON THE CLASS, not on the word, and the test is named around it.
+    `pytest`'s `tmp_path` is derived from the TEST NAME and the index renders
+    `data_dir` in its empty-state hint — so a test called
+    `test_an_unannounced_booth_says_so` put the literal string "unannounced"
+    into the page and passed against a template that did not yet exist. A
+    structural hook cannot be spelled by accident — though it has to be the
+    rendered ELEMENT and not the bare class, since base.html ships a
+    `.prov-none{...}` rule into the very same page."""
+    c, data = client
+    _booth(data, "quiet", kept=kept)
+
+    html = c.get("/").text
+    assert 'class="prov prov-none"' in html
+    assert "unannounced" in html
+
+
+def test_a_damaged_manifest_reads_differently_from_an_absent_one(client):
+    """INV-5 on the surface the operator looks at, not just in the reader."""
+    c, data = client
+    b = _booth(data, "damaged")
+    (b / MANIFEST_FILE).write_text("{oops")
+
+    html = c.get("/").text
+    assert 'class="prov prov-broken"' in html
+    assert "unreadable" in html
+    assert c.get("/b/damaged/").status_code == 200
+
+
+def test_an_announced_booth_with_no_why_shows_only_its_handle(client):
+    """`booth new x` with no --why is legal and common. The card shows who made
+    it and does not invent a purpose or leave a dangling separator."""
+    c, data = client
+    b = _booth(data, "scratch")
+    write_manifest(b, "booth-dev")
+
+    html = c.get("/").text
+    assert "booth-dev" in html
+    assert 'class="prov prov-none"' not in html
+
+
+def test_the_booth_page_header_carries_it_too(client):
+    """Deliberate scope, not creep: a booth URL handed to the operator lands
+    HERE, never on the index. Job 5 is 'operator, look at this', so the page he
+    actually opens is where the answer has to be."""
+    c, data = client
+    b = _booth(data, "r18-ab")
+    write_manifest(b, "booth-dev", why="pick the winning denoiser")
+
+    html = c.get("/b/r18-ab/").text
+    assert "booth-dev" in html
+    assert "pick the winning denoiser" in html
+
+
+def test_a_poisoned_manifest_cannot_take_down_the_index(client):
+    """The v0.2.2 lesson, asserted for the new reader before it can repeat:
+    `list_booths` touches every booth on every page load, so one bad file must
+    cost that booth's provenance and nothing else."""
+    c, data = client
+    _booth(data, "good")
+    bad = _booth(data, "bad")
+    (bad / MANIFEST_FILE).write_bytes(b"\xff\xfe not utf-8 at all")
+
+    assert c.get("/").status_code == 200
+    assert c.get("/healthz").status_code == 200
+
+
+def test_a_pickup_booth_announces_itself_as_the_booths_own(client):
+    """No exemption list. A booth the service made says the service made it,
+    which is true — and it keeps the rule to one line: a booth with no manifest
+    is unannounced."""
+    c, data = client
+    r = c.post("/upload", files=[("files", ("a.txt", b"hello", "text/plain"))],
+               follow_redirects=False)
+    assert r.status_code in (200, 303)
+
+    booth = next(p for p in data.iterdir() if p.is_dir())
+    got = read_manifest(booth)
+    assert got is not None and got.handle == "booth"
+    assert 'class="prov prov-none"' not in c.get("/").text

tests/test_marks.py

@@ -276,12 +276,15 @@ def test_as_dict_round_trips_through_json(tmp_path):
 # ---- the stdlib-only invariant (INV-5) --------------------------------------
 
 
-@pytest.mark.parametrize("module", ["marks", "asks", "links"])
+@pytest.mark.parametrize("module", ["marks", "asks", "links", "manifest"])
 def test_stdlib_only(module):
     """INV-5. scripts/booth imports these under the system python3 with NO venv,
     through a `python3 -c` heredoc that no AST extractor can see — so nothing
     but this test stands between a casual third-party import and `booth ask`
     breaking on every fleet host."""
+    # `manifest` also carries a stricter copy in tests/test_manifest.py, which
+    # additionally forbids importing `booth.*` — a cross-import between two
+    # stdlib-only modules is a second way for this invariant to break.
     src = pathlib.Path(__file__).parent.parent / "booth" / f"{module}.py"
     tree = ast.parse(src.read_text())
     roots = set()