Files
PaperClipAI/server
DottaandClaude Opus 5.5 e8a3f1f6f2 feat(recovery): prove a replaced container's records gone through a fenced controller epoch (#20054)
## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - After a restart, the control plane settles in-progress records
(leases, claims, intents) only once it proves their owner process is
gone
> - The proof compares host and PID space, so a stamp from a replaced
container or a rebooted machine stays unprovable forever, and its
records never settle
> - Self-hosted users on Docker, Kubernetes and Fly hit this on every
redeploy; a Railway deployment with an exclusive volume is covered by
`deployment_replaced` (#20026)
> - This pull request adds a fenced controller epoch: each boot holds a
database lease, and an expired boot is fenced so its records can be
proven gone
> - The benefit is that work stranded by a replaced container is
recovered, without keeping an idle database awake

## Linked Issues or Issue Description

Follow-up to #20026 and the Phase 2 durable-ownership data. Related:
#19965 (owner stamps), #19883 (process space). No duplicate PR was
found.

**What happened?**

A record stamped by a server process in another container reports
`different_process_space`. A dead PID elsewhere is never proof, so the
record stays `unprovable` and is never settled. Every redeploy of a
self-hosted container leaves such records behind.

**Expected behavior**

A record owned by a server boot that was replaced (stopped cleanly, or
lost its lease and was fenced) is proven gone and settled exactly once.
A live boot's records stay with it. An idle server issues no recurring
queries.

**Steps to reproduce**

1. Run Paperclip in a container and start work, so an environment lease
is stamped by that boot.
2. Replace the container. The new container has a new PID namespace.
3. The ownership reconciler reports `different_process_space`
(unprovable) for the old lease, forever.

**Paperclip version or commit**

`master` before this PR.

## What Changed

- New `controller_instances` table (migration 0449): boot id, epoch
(bigserial), process space, pid, a lease on the database clock,
`fenced_at` / `fenced_by_epoch`, `stopped_at`.
- `controller-instance-lease.ts`, registered with the shared
delivery-work coordinator (`controller-instance-lease` queue, runs
during drain):
- **Holds work → renews; idle → silent.** One upsert creates the row on
first use and extends the lease only if the boot holds work: a stamp
within the last 90 s, or a stamp whose ownership write may still be
pending (held until the server's tracked work settles, capped at 10
minutes; a renewal that sees some other held record does not clear it,
so a slow ownership write cannot be outlived), or an in-progress record
held by its boot id. Those records are active environment leases,
in-flight cleanup claims, sandbox creation intents, workspace finalize
attempts, agent lifecycle steps, native finalizer and cleanup leases
(`lease_holder` bound to the token), open native coordinator claims, and
running legacy runs. Renewal runs every 30 s while the boot holds work.
When it finds none, the lease lapses and the worker sleeps until the
next stamp (`onControllerStamp`).
- **No idle trailing statements.** When the server's last tracked work
settles, the worker re-checks holdings at once, at most every 5 s (the
rate limit also absorbs the worker's own run). So the last check happens
with the work, not 30 s later.
- **Quiesce, don't crash.** Each renewal has a 10 s bound. A failed or
timed-out renewal applies an internal task drain, so no new work is
dispatched. A recovered renewal resumes. The boot exits only after 60 s
of failure (counted from the first failed attempt's start) while it
still holds work, or at once when it finds itself fenced.
- **Fence on demand, by a newer epoch.** For a stamp from another host
or PID space, the prover reads that boot's row:
    - `stopped` or `fenced`: gone.
    - live lease: alive.
- otherwise, the boot's last sign of life is the later of its lease
expiry and the record's last write plus the TTL. Within 30 s of that,
the owner stays `alive` (`controller_lease_grace`), so the settle watch
keeps rechecking. After that, the prover fences the boot, but only with
a lease row of its own (created on demand) and only an older epoch.
  - A graceful shutdown records `stopped_at`.
- A reconciliation pass that settles nothing (`record: false` or
`settle: false`) never fences and never creates the boot's row.
- `owner-proof.ts`: these proofs apply only to server-held records. A
stamp with a recorded process group stays unprovable, because agent
processes can outlive their server. The reconciler passes each record's
`updatedAt` to the proof.
- `task-admission.ts`:
- the quiesce drain never replaces an operator's drain, and has no idle
owner, so HTTP stays open;
- a `subscribeIdleWorkSettled` hook fires when the last tracked work
finishes.
- Off on a Railway deployment with an exclusive volume (it has its own
replacement proof). `PAPERCLIP_CONTROLLER_INSTANCE_LEASE=on|off`
overrides this. A stateless Railway service keeps the lease. A server
without its own lease row never fences.
- `maintenance-server-routes.test.ts`: in the post-run quiet window, the
lease may check once more that the run's records were released. The test
now excludes those statements, then asserts that the lease issues
nothing in a further window.
- Docs: `doc/execution-semantics.md`; the Phase 2 data doc records the
two known gaps.

## Verification

- `controller-instance-lease.test.ts` (15 cases):
- a replaced container with all Railway variables empty is fenced and
settled exactly once over two passes;
  - a live lease is alive;
- an owner in grace, and work written after an idle lapse, stay alive
and watched;
  - an older epoch never fences a newer one;
- no fencing without its own lease row (off or unregistered), and an
idle prover creates its row on demand;
  - a stopped boot is gone;
  - process-group stamps stay unprovable;
- idle issues zero statements, and one upsert renews only while records
are held;
  - **a 45 s outage:** quiesced, no exit, resumes;
- **a renewal that never answers:** bounded, and the boot exits on time;
- **a 70 s outage:** exits at 60–65 s, and the successor recovers the
work exactly once;
  - fenced: stops;
  - the settle re-check;
- graceful stop; off on a volume-exclusive Railway deployment, on for a
stateless one, and the on/off override;
  - a running legacy run keeps the lease live.
- Red, with the proof's instance check removed: the replaced-container,
live, stopped and successor cases fail.
- Wider: task-drain, idle-sleep, idle-local-work, owner-proof and
ownership suites, plus the maintenance quiet-window tests. Server
low-memory typecheck is clean.

## Risks

- **Clock skew.** The proof compares a record's `updatedAt` (often the
writer's clock) with the lease (database clock). The 30 s grace absorbs
ordinary skew.
- **A new exit path exists.** A server whose database is unreachable for
more than 60 s while it holds work now exits, after first quiescing.
This is the intended safety backstop.
- **Bounded trailing activity.** A lease that holds work issues one
statement every 30 s, plus at most one check when its work settles. An
idle server issues none.
- **Boots from before this release** have no row, and their records stay
unprovable. The board "mark owner gone" action for those follows in a
separate PR.

## Model Used

- Anthropic Claude Opus 5.5 (`claude-opus-5-5`), via Claude Code with
tool use.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-08 11:06:32 -06:00
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