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docs/rfcs/0005-event-vocabulary.md
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— Publish the vocabulary on quarry.evt.<repo>.<noun>.<action>
RFC 0005 picked zit.evt., which the fold consumer already claims with a trailing wildcard — every vocabulary event would have been handed to the artifact parser. Own stream, own root, tests pinning both. (user: dmestas, size: 30265) [annotate] [blame] [check-ins using]
- Feature Name: `event-vocabulary` (one named event stream, three consumers) - Start Date: 2026-08-24 - Status: Draft for review - Depends on: RFC 0001 §4 (event bus), §5 (disposability), §6 (CI), §8 (OLTP) - Source authority: fossil `www/hooks.md` and `src/alerts.c` (both read from the mirror this forge serves), GitHub's webhook event reference, Gitea's webhook documentation, GitLab's project webhook events ## Summary [summary]: #summary quarry names the things that happen in a repository, once, in a vocabulary that pipelines, webhooks and notifications all subscribe to. An event is a **noun and an action** — `ticket.closed`, `landing.opened`, `branch.created` — carried on the bus that already exists, with a payload shape declared per noun. A pipeline runs because something **happened**, because the **clock** said so, or because a **person asked**. dagnats already implements all three — cron, NATS-subject, webhook and durable-HTTP triggers, with debounce — so quarry builds no scheduler and no subscription plumbing. What quarry owes is **well-named subjects** (§2.3), and the vocabulary is the subject hierarchy. Creating a trigger is still a forge act, gated on fossil's `a` capability so a repository's own admin owns its automation (§2.4). Today there are two and a half paths and no vocabulary. Webhooks derive an event's kind by slicing a notification's idempotency string. CI does not use events at all: it polls the index for new check-ins behind a per-repository watermark. Notifications have their own workflow names. Adding one more trigger — a landing opening, say — means either a third path or generalising anyway, so this RFC generalises first. The vocabulary is the load-bearing part, and the reason this is an RFC rather than a commit: a pipeline definition names events in its `on:` clause, so an event name is a **published interface**. Renaming one breaks every pipeline in every repository that used it, in a system where the pipeline definition is itself a versioned artifact in someone else's store. ## Motivation [motivation]: #motivation ### What exists `ci.Trigger` runs after every fold. It asks the index for check-ins newer than a watermark, reads `ci/*.json` at each one, registers the definition **at that check-in**, and starts a run. `pollCI` later polls unfinished runs and, on a terminal status, mints a `ci-pass` / `ci-fail` tag on the check-in. That is a complete, working pipeline trigger for exactly one event, with the event's identity left implicit. Four things in it are check-in-shaped: | | today | needed | |---|---|---| | trigger | poll `NewCheckins(watermark)` | subscribe to a named event | | payload | `{repo, checkin, branch, date, user, comment, cloneUrl, pipeline}` | per-noun, common envelope | | watermark | one check-in per repository | per subscription | | verdict sink | `WriteTag(verdict, checkin, runID)` | per-noun; a landing wants a reply | Every one of those blocks the landing trigger (quarry ticket `49323c33`), and none of them is made easier by doing the landing trigger first. ### What the field does Four vocabularies were read before proposing a fifth. **Fossil hooks** (`www/hooks.md`) are artifact-level and carry no semantics at all. Three types — `after-receive`, `before-commit`, `commit-msg` — and the after-receive hook's stdin is a list of artifact hashes with human-readable descriptions. There is no "on branch created" or "on merge". The doc states its purpose plainly: to "start up a background testing or CI process". **Fossil alerts** (`src/alerts.c`) carry fossil's only semantic vocabulary, as subscription letters on the `subscriber.ssub` column: a Announcements c Check-ins f Forum posts n New forum threads r Replies to my posts t Ticket changes u User permission changes w Wiki changes x Edits to forum posts Eight types. It splits the forum four ways by verb, and has no event for a branch, a tag, a technote or a merge. **GitHub** publishes 75 webhook events, most of which are not about version control: roughly six VCS core, fifteen collaboration, eight CI, ten security scanning, fifteen governance, and twenty platform and commerce events (marketplace, sponsorships, apps, Pages, Projects). quarry has a concept for about twenty of them. **Gitea** publishes about 27, **GitLab** 15. ### The shape decision The three forges disagree about the axis, and the disagreement is the design question: - **GitHub**: one event per noun, with an `action` field. `issues` fires for `opened`, `closed`, `labeled`, `assigned`, `edited`. - **Gitea**: one event per noun-verb pair. `issue_assign`, `issue_label`, `issue_milestone` and `issue_comment` are four separate events. - **GitLab**: coarse nouns, verbs folded into the payload. - **Fossil alerts**: mostly nouns, but `f`/`n`/`r`/`x` split the forum by verb. **quarry takes GitHub's.** Under Gitea's rule every new verb is a new permanent event name, and the name is a published interface. Under GitHub's, a subscriber can ask for `ticket` and get every change, or `ticket.closed` and get one, and adding a verb later costs nothing. Fossil's split shows the cost of the other choice inside one product: `f` and `n` and `x` are three names for three verbs on one noun, and a subscriber who wants "any forum activity" must name all three and remember to add the fourth when it appears. ## Guide-level explanation [guide-level-explanation]: #guide-level-explanation An event is `noun.action`, published on a subject that carries the repository: zit.evt.<repo>.<noun>.<action> A workflow subscribes with a dagnats subject trigger, so the selecting is NATS' and quarry adds no syntax of its own: zit.evt.quarry.landing.opened one repository, one action zit.evt.*.landing.opened that action anywhere zit.evt.quarry.ticket.* every ticket action in one repository zit.evt.quarry.> everything in one repository A pipeline with no trigger of its own still runs on `checkin.created`, which is today's behaviour, so every pipeline already in a repository keeps working without being edited. Every event carries the same envelope, and a payload keyed by its noun: ```json { "event": "landing.opened", "repo": "quarry", "at": "2026-08-24T09:48:57.123", "actor": "dmestas", "id": "activity:landing:9802c157…", "payload": { "landing": "9802c157…", "branch": "wiki-struct", "target": "trunk" } } ``` `id` is the idempotency key. It is stable for one occurrence of one event, and it is how a consumer that sees an event twice can tell that it has. ## Reference-level explanation [reference-level-explanation]: #reference-level-explanation ### §1 The vocabulary Nouns and their actions. An action marked † is not yet raised by any code path and is reserved so that adding it later is not a vocabulary change. | noun | actions | payload | |---|---|---| | `checkin` | `created` | hash, branch, parents, user, comment | | `branch` | `created`, `moved`, `closed`† | name, tip, previous tip | | `tag` | `created`, `removed`† | name, target, value | | `ticket` | `opened`, `changed`, `closed`, `reopened` | id, title, fields changed | | `wiki` | `edited`, `created`, `deleted` | title, hash | | `technote` | `created`, `edited` | event id, hash | | `forum` | `posted`, `replied`, `edited`†, `moderated` | thread root, post hash | | `landing` | `opened`, `commented`, `accepted`, `rejected` | id, branch, target | | `ci` | `started`, `completed` | run id, checkin or landing, verdict | | `mirror` | `pulled`, `failed` | url, artifacts received | | `repo` | `created`, `removed`, `settings` | name | | `clone` | `cloned`, `fetched` | actor or anonymous, artifacts sent | | `account` | `added`, `caps`, `removed` | account, repository, caps | Fourteen nouns, thirty-odd actions. For comparison: fossil's alerts name eight things, GitHub's 75 events name about twenty that quarry has a concept for. **Clone counts.** `clone.*` is observable because every sync request goes through one place: `Fronter` proxies `POST /r/{repo}/xfer` and already runs a `ReadGate` per request, so the choke point exists. Counting *fetches* is free at that point. Distinguishing a **clone** — a first fetch by a peer holding nothing — from an incremental pull requires reading the request body, since that distinction lives in the sync protocol's announcement and nowhere else. Both counts are operational per §2.1 and so are recorded in OLTP as they happen; the bus carries notice of a row that already exists. GitHub reports clones and *unique cloners* separately. Uniqueness needs an identity to count by, and a sync request may be anonymous, so quarry counts unique by account where there is one and reports anonymous clones as a separate figure rather than guessing at a person behind an address. Three of these exist in no other forge, and are here because quarry has the concept and an operator needs the hook: `technote` (fossil has the artifact but no alert for it), `mirror` (a forge that tracks 25 upstreams needs to fire on a failed pull), and `landing`. ### §2 What the bus is, verified Read from `internal/events/events.go` rather than assumed, because §2's promises depend on it: ```go desired := &nats.StreamConfig{ Retention: nats.LimitsPolicy, Discard: nats.DiscardOld, MaxBytes: 1 << 30, // 1 GiB ceiling across all repos MaxAge: time.Hour, // live window; older needs a reindex } ``` **The stream is a one-hour live window, not a log of record.** It is a transport between the store and the index, and the durable truth is the pair either side of it: the store (authority) and the publisher cursor in the KV bucket, which advances only after a fold succeeds. A consumer that falls outside the window does not catch up by replaying; it rebuilds from the store. Two consequences this RFC must respect rather than wish away: 1. **A consumer down for an hour has missed events permanently.** CI's current watermark-and-poll survives that, because it reads the index, which is durable. A naive move to bus subscriptions would trade a robust trigger for a fragile one — §2.1 is how that is avoided. 2. **Per-node durable consumers each read the whole stream** (limits retention was chosen over work-queue for exactly this: every node must fold every event). So three consumers subscribing independently is the shape the bus was already built for. ### §2.0 A gap is detectable, but only if you look The documentation does not say what a consumer sees when MaxAge drops a message it has not read, so it was measured against this forge's own embedded NATS (`internal/events/gap_test.go`). Three messages aged out unread: stream first_seq=7 last_seq=7 msgs=1 consumer ack_floor=3 delivered=3 pending=1 Two facts, and the design turns on the second: 1. **The gap is visible**: `first_seq - ack_floor - 1` = 3. A consumer can know exactly how many messages it lost. 2. **Nothing tells it.** The next `Fetch` succeeds and returns the message *after* the gap. `pending` counts only what survives. A consumer that does not compare sequences carries on with a hole in its view and no error. So the window is not silent data loss *if* every consumer checks. That turns "a consumer down for an hour has missed events" into something recoverable: **Every consumer MUST compare the stream's `first_seq` against its own `ack_floor` on each fetch.** On a gap, a consumer of derived events rebuilds from the index (§2.1); a consumer of operational events reads the OLTP rows it missed. Neither is expensive, and the alternative is a forge that is quietly wrong after any hour of downtime. ### §2.1 Two classes of event, and why the distinction is load-bearing The one-hour window is survivable for some events and not others, and the line is whether the event is derivable from the DAG: **Derived events** — `checkin`, `branch`, `tag`, `ticket`, `wiki`, `technote`, `forum`, `landing`. Every one is a reading of artifacts the store holds. A consumer that missed one can re-derive it by walking the index, exactly as the ingest pipeline rebuilds after a gap. A missed event costs latency, not truth. **Operational events** — `ci`, `mirror`, `repo`, `account`, `clone`. None of these is in the DAG. `mirror.failed` is a fact about a network attempt; `account.caps` is OLTP state; a clone is a request that happened. If the delivery is missed, the fact is gone. So operational events MUST be recorded in OLTP as they are raised, and the bus carries a notification of a record that already exists. Derived events need no such backing — the store is their backing. This is not symmetry for its own sake: it is the difference between a `mirror.failed` an operator can page on and one that silently did not happen. ### §2.2 Delivery semantics, which the medium decides Fossil's hook documentation states the constraint, and quarry inherits it rather than choosing it: > A push might not deliver all of the artifacts for a checkin. If Fossil knows > that a /xfer HTTP request is incomplete, it will defer running the > after-receive push for 60 seconds, or until a complete /xfer request is > received. This helps to prevent after-receive hooks from running when > incomplete checkins exist in the repository, **but it does not provide hard > guarantees, as there is no way to do that in a distributed system.** So: 1. **At-least-once.** A consumer may see an event twice. `id` is the idempotency key and a consumer that acts on an event MUST be idempotent under it. quarry's own notification plane already works this way. 2. **Possibly batched.** Fossil warns that two pushes' artifacts "might be combined into a single after-receive callback". quarry's fold has the same property; a single fold can produce many events, and a consumer must not assume one event per delivery. 3. **Possibly partial.** An event may describe state that is still arriving. A consumer that needs the whole picture reads the index at handling time rather than trusting the payload to be complete. 4. **Ordered within a repository, not across.** The bus preserves order per repository because the fold does; nothing orders two repositories against each other, and nothing should be written that needs it. ### §2.3 Three trigger sources, of which events are one A pipeline runs because something happened, because the clock said so, or because a person asked. Only the first is an event, and conflating the three is how "on:" ends up meaning two different things. | source | `on:` | what it carries | |---|---|---| | **event** | `checkin.created`, `landing.opened` | the event envelope of §1 | | **schedule** | `schedule: "0 * * * *"` | the fire time and the ref it runs against | | **dispatch** | `dispatch: true` | the actor and any inputs they supplied | This is GitHub's split (`schedule`, `workflow_dispatch`) and it is the right one: a cron run has no actor and no artifact, and a dispatched run has an actor but nothing happened. Forcing either into the event envelope would mean a payload full of fields that are empty by construction, which is how a schema stops meaning anything. **Schedules and dispatches are OLTP state**, not artifacts. A schedule is a forge configuration — which repository, which pipeline, which cron expression, enabled or not — and it is exactly the shape of the existing `webhook` table. Both are per-repository, and both survive a reindex because neither is derived from the DAG. **dagnats already has all four sources, and more.** Read from `internal/trigger/types.go` rather than probed over HTTP — the probe was the wrong lens, because triggers are NATS- and KV-native and CLI-created, so nothing about them answers on a URL: ```go type TriggerDef struct { Cron *CronConfig // {Expression} Subject *SubjectConfig // {Subject} — a NATS subject, wildcards included Webhook *WebhookConfig // {Path, Secret} — POST /hooks/{path} HTTP *HTTPConfig // durable endpoints, /api/{path}, with a respond step External *ExternalTriggerConfig // trigger kinds contributed by workers Debounce *DebounceConfig // {Period, Timeout, Key} } ``` and its envelope's own comment states the property §2.3 was about to ask for: *"the standard workflow input produced by all trigger types. Workflows always know how they were triggered."* So quarry builds no scheduler, no dispatch plumbing, and no subscription mechanism. **What quarry owes the engine is well-named subjects**, and the vocabulary of §1 is exactly that. ### §2.3.1 The subject namespace is the interface Events publish to: quarry.evt.<repo>.<noun>.<action> and NATS wildcards do the selecting, so the `on:` clause this RFC first proposed is unnecessary — a workflow's own `triggers` array already says it: | subscription | subject filter | |---|---| | every landing opened, anywhere | `quarry.evt.*.landing.opened` | | everything in one repository | `quarry.evt.quarry.>` | | every ticket action | `quarry.evt.*.ticket.*` | | one repository's CI | `quarry.evt.quarry.ci.*` | This is why noun-and-action was the right shape for a second reason the motivation did not know: **the vocabulary is a subject hierarchy**, and Gitea's `issue_assign` naming would have flattened it into strings a wildcard cannot take apart. The root is `quarry.`, not `zit.`, and the first draft of this section had it wrong. `zit.evt.>` is already the ingest stream's namespace, and the fold consumer subscribes to `zit.evt.<repo>.>` — a trailing wildcard that would not merely share a stream with the vocabulary but hand every vocabulary event to a parser expecting an artifact. The better reason arrived with the blunt one: `zit.` is zit's DAG transport, and `ci`, `mirror`, `account` and `clone` name things zit has never heard of. These are the **forge's** events. So the vocabulary gets its own stream, `QUARRYEVT` on `quarry.evt.>`, following the precedent the webhook dispatcher already set with `QUARRYHOOK`. Limits retention, not work-queue: a workflow reacting to `landing.opened` must not consume the event out from under a webhook subscribed to the same subject. The practical consequence for §1: the noun and action MUST be single tokens with no dots, because a dot is the subject separator. Every name in the vocabulary already obeys this; it is now a rule rather than an accident. ### §2.3.2 Debounce, and one resolved question `DebounceConfig{Period, Timeout, Key}` delays a run until events stop arriving, resetting on each new one, with a hard upper bound. That answers the RFC's own first unresolved question — whether `branch.moved` fires per fold or per check-in — and answers it better than either option: **fire per check-in and let the subscriber debounce.** A ten-commit push then runs one build for a pipeline that debounces and ten for one that does not, and the choice belongs to the pipeline rather than to quarry. Coalescing at the source would have taken it away from both. ### §2.3.3 One bus, or two For a dagnats subject trigger to see a quarry event, both must be on the same NATS. Today a quarry deployment runs two: its own embedded server for ingest, and dagnats' for workflow execution. The seam already exists — `events.Connect(url)` joins an external cluster and is what the multi-node flag uses, with `events.Start(dir)` embedding one otherwise. Pointing quarry at dagnats' NATS makes the two into one bus and the subject triggers work with no bridge. Two constraints on doing it, both real: - The external server MUST allow `max_payload` of at least 8 MiB. Parsed artifacts ride quarry's stream whole, and NATS' 1 MiB default rejects large-store manifests. - quarry's stream is a one-hour window sized for ingest (§2.0). dagnats' own streams have their own retention. Sharing a server is not sharing a stream, and the two must not be configured as if it were. ### §2.4 Who may schedule and who may dispatch dagnats stores the trigger; quarry decides who may ask for one. Creating a schedule or dispatching a run is repository configuration and spends the engine's time, so both follow RFC 0004's rule: they take **`a`** — fossil's Admin capability, the same letter that already gates `repo.update`, `repo.reindex`, `ticket.config(write)` and the mirror verbs. That the record lives in dagnats' KV rather than quarry's OLTP does not move the gate: the forge is what knows who holds `a` on a repository, and an engine that trusted its callers would let any of them schedule work on anyone's. That answers "repo admins should have these" in fossil's own vocabulary rather than by inventing a role: an account holding `a` on a repository can create, edit, disable and delete its schedules, and can dispatch a run. An account without it can see that a schedule exists — a pipeline that runs nightly is not a secret from the people reading the repository — and cannot change it. Deliberately NOT a new capability letter. RFC 0004 §6's rule is that a letter which exists in fossil carries its fossil meaning and a surface which exists only in quarry names an existing letter rather than minting one; a forge that grows private letters stops being a fossil forge by increments. One consequence worth stating: **`a` excludes `s`**, so a repository admin may schedule work on their own repository and not on anyone else's, and a fleet-wide schedule is a site-admin action. That falls out of the cap model rather than needing its own rule. ### §3 Handlers do not run inside the fold Fossil again: > Fossil holds a write transaction on the repository while the after-receive > hook is running. A hook that writes to the repository it was fired by therefore deadlocks. The same is true here for a different reason: quarry mints artifacts through the lease holder, and the fold is not it. **An event handler that mints an artifact runs outside the fold, through the lease holder, asynchronously.** The CI verdict already obeys this by accident of structure — `pollCI` runs on a timer, not in the ingest path. This RFC makes it a rule rather than an accident, because the landing verdict (`700b22b6`) would otherwise be written from exactly the wrong place. ### §4 One stream, three consumers | consumer | today | after | |---|---|---| | webhooks | `Raise()` from `fireNotify`, kind sliced out of a TxnID | subscribes by name | | CI | polls `NewCheckins` behind a watermark | subscribes by name | | notifications | own workflow names | subscribes by name | The watermark does not disappear: it becomes per-subscription rather than per-repository, because two consumers may be at different positions and one falling behind must not advance the other. ### §5 Verdict sinks A CI run's verdict is an artifact, because 0001 §6's no-hostage rule says the result must clone with the repository. Which artifact depends on the noun that triggered it: - `checkin.created` → a `ci-pass` / `ci-fail` **tag on the check-in**, as today. - `landing.opened` and `landing.commented` → a **reply in the landing's thread**. A landing is a forum thread; a verdict is commentary on a moment, a moving branch earns several, and tags do not accumulate. This is the shape quarry ticket `700b22b6` settled on and this RFC does not revisit it. The rule generalises: **the verdict takes the shape of the thing it judges.** ### §6 What is deliberately absent Named so the absence reads as a decision rather than an oversight: - **No security scanning events.** GitHub has ten. quarry scans nothing, and an event for a scan nobody runs is a promise to nobody. - **No package or registry events.** quarry hosts no packages. - **No marketplace, sponsorship, or app-installation events.** These are GitHub-the-product, not forge-the-idea. - **No `star` or `watch`.** quarry has subscriptions, which are a truthful signal about wanting to be told things; stars are a popularity one. - **No `fork`.** A zit clone is not an event in the origin: the origin does not learn of it, and an event it cannot honestly raise should not be named. - **No `before-*` events.** Every event here is a statement that something HAPPENED. A veto hook — fossil's `before-commit` — is a different mechanism with different failure modes (what does a forge do when a hook times out?), and mixing "tell me" with "may I" in one vocabulary is how both get harder. The last one is the one most likely to be asked for later. It should be its own RFC, and it should not reuse these names. ## Drawbacks [drawbacks]: #drawbacks **A published vocabulary is hard to change.** That is the point, and also the cost: a name chosen badly here is one every pipeline in every store repeats. The mitigation is the reserved actions in §1 and the noun-plus-action shape, which absorbs new verbs without new names. **One stream is a single point of failure** where today CI's polling is independently robust: if the bus stops, CI stops. The watermark survives, so nothing is lost, but a stalled bus becomes a stalled forge in a way a stalled poll loop is not. §2's at-least-once rule and per-subscription watermarks are what make recovery a replay rather than a repair. **Schedules and dispatches put quarry in the business of running things nobody asked for at that moment.** A cron pipeline consumes engine time on a repository whose owner may have forgotten it exists, and unlike an event-driven run there is no push to point at. The `a` requirement in §2.4 bounds who can create one; nothing here bounds how many, and a per-repository ceiling is probably wanted before this ships. **Fourteen nouns is more than fossil has and fewer than GitHub.** Both comparisons will be made, and neither is the argument: the set is what quarry can honestly raise today plus what it will raise next. ## Rationale and alternatives [rationale-and-alternatives]: #rationale-and-alternatives **Do the landing trigger without a vocabulary.** Rejected: all four generalisations in the motivation table are needed for it anyway, and the result is a third trigger path. Ticket `49323c33` says so in its own words — "rides the existing event plane … rather than growing a second trigger path". **Adopt fossil's after-receive shape: hand the handler a list of artifacts.** Rejected. It is honest and it is what fossil does, but it pushes the whole interpretation problem to every consumer: each pipeline would re-derive "is this a new branch" from artifact hashes, and they would derive it differently. quarry already folds artifacts into meaning; the event stream should carry the meaning it already has. **Adopt Gitea's noun_verb naming.** Rejected in §Motivation: every new verb becomes a permanent name. **Use GitHub's names verbatim where they overlap.** Tempting for recognisability, and rejected in two places: `issues` is called `ticket` here because that is what fossil calls it and fossil compatibility is the north star, and `pull_request` is called `landing` because it is not one — nothing is transported and nobody requests a pull (zit#127). ## Prior art [prior-art]: #prior-art - **dagnats**: a DAG workflow engine on NATS, with cron, NATS-subject, webhook, durable-HTTP and worker-contributed trigger kinds, plus debounce and a trigger envelope that tells a workflow how it was fired. Quarry's HTTP use of it (`/workflows`, `/runs`) is the small corner of its surface; the trigger system lives in NATS and KV, which is why it is invisible to an HTTP probe. Everything §2.3 needs already exists there. - **fossil** `www/hooks.md`: three hook types, artifact-level, no vocabulary. Its warning about distributed delivery is quoted in §2 and is the reason this RFC does not promise exactly-once. - **fossil** `src/alerts.c`: eight subscription letters, the only semantic event vocabulary fossil has. - **GitHub**: 75 events, noun-plus-action. The layering (VCS / collaboration / CI / security / governance / platform) is the useful part; most of the events are for products quarry does not have. - **Gitea**: ~27 events, noun_verb. - **GitLab**: 15 coarse events, verbs in the payload. ## Unresolved questions [unresolved-questions]: #unresolved-questions 1. ~~Does `branch.moved` fire per check-in or per fold?~~ **Resolved** in §2.3.2: per check-in, because dagnats' debounce lets each pipeline decide whether to coalesce. Choosing at the source would take the choice from both. 2. **Should `ci.completed` be subscribable?** It would let a pipeline trigger on another pipeline, which is either composition or a foot-gun. GitHub allows it (`workflow_run`) and guards against recursion. Deferred until something needs it. 3. **How does a subscription express "my repository only" versus fleet-wide?** The webhook plane is per-repository today; CI is per-repository; a fleet-wide subscriber (an operator watching `mirror.failed` across 25 stores) has no way to say so. 4. ~~JetStream delivery guarantees have not been traced.~~ **Resolved** and folded into §2: the stream is a one-hour window with limits retention and per-node durable consumers, and the durable truth is the store plus the publisher cursor. The consequence — that operational events need OLTP backing and derived ones do not — is §2.1. ## Future possibilities [future-possibilities]: #future-possibilities - **Veto hooks** — fossil's `before-commit` and `commit-msg`, as their own RFC. - **Fleet-wide subscriptions**, resolving question 3. - **Event replay** — the bus retains the log, so "re-run every pipeline for the last hour" is a cursor rewind rather than new machinery. Attractive after an outage, and dangerous without §2's idempotency rule. - **`ci.completed` composition**, resolving question 2. - **Traffic beyond clones.** Once `clone.*` is recorded, page views and unique visitors are the same shape and the same storage. Worth doing only if somebody asks: a forge that counts everything it can is how an OLTP that was "small by construction" stops being.