The gateway's nginx + dnsmasq no longer run in their own nspawn container.
`nix/host-modules/hive-gateway/default.nix` loses the
`containers.hive-gateway` wrapper and everything that existed only to punch
holes in it: `privateNetwork = false`, `CAP_NET_ADMIN`, five bind mounts,
its own `stateVersion`, `networking.firewall.enable = false`,
`networking.resolvconf.enable = false`, and the `hive-gateway-resolv`
path+service pair. 465 -> 303 lines.
The container never bought isolation here. It shared the host netns by
necessity — nginx binds the host's :80/:443, dnsmasq answers on the bridge —
so each of those settings was undoing a boundary the gateway could not
afford in the first place.
Four things made it more than a deletion, none of them visible in the nix
diff:
- The self-signed cert service also imports the hive CA leaf, so removing it
with the container would have left nginx naming a missing cert file, which
it refuses to load at all.
- The nginx reload is a hive-priv verb. It still needs root, but no longer
for the reason its doc gave, and `--machine=` was both transport and
scope — so the unit name is now hard-coded in the helper as the
containment.
- The lifecycle verb named a container that stops existing.
- `journalctl -M hive-gateway` had no machine to enter.
Per the operator's ruling, the operator verb keeps working and agents lose
it. `InfraContainer` answered three questions that used to share an answer;
it now splits into `name()` (identity), `target()` (Container vs HostUnit),
`service_unit()` (the systemd unit), and `agent_restartable()`, which the
MCP restart path checks before the capability so the refusal cannot read as
"ask for infra_admin". `SIBLING_CONTAINERS` drops the gateway — it gates the
requests that name a container as a string — while `FromStr` still accepts
it, because that answers what a name is, not who may act on it. The
dashboard's gateway journal reads host journald filtered to `nginx.service`.
Prose was corrected where it only named a location, and re-argued where the
container was doing security work: a `0666` per-agent socket was safe
because only the gateway container had the directory bind-mounted. There is
no mount now, so the directory permissions are the whole of the access
control — the constraint holds, its mechanism doesn't.
Gate: nix fmt / clippy --all-targets -D warnings / cargo test all clean (710
tests); hivectl-cli.md regenerated from the clap tree. The nix eval was run
in both TLS shapes at this commit: every delta in the rendered
virtualHosts is one of the three intended path moves, dnsmasq settings are
byte-identical, and the absence probe flips true -> false with bindMounts
emptied.
21 of 28 non-test call sites now insert directly. power.rs compiles.
The only remaining errors are server.rs's 5, which are blocked: those
sites feed the returned id into HostResponse::queued -> `queued_dags`,
a wire field hivectl polls via QueueDag. Removing the container without
answering that breaks hivectl's wait/progress loop; asked on the issue.
Also swept the deleted symbol out of prose, not just code:
- docs/coordinator.md: "the submit layer (job_queue/submit.rs)" ->
the power layer (job_queue/power.rs), and "submits" -> "inserts".
- templates.rs module doc: points at super::power for the power ops.
- lifecycle_ops.rs module doc: says which path each op takes now.
- mod.rs's insert_group comment restated the open issue verbatim
("a DAG is addressed by its container node, which submit inserts
itself"). Replaced with what is actually true for that path.
Dashboard behaviour deltas worth review: insert failures are now
logged per agent instead of swallowed, and UPDATE-ALL emits one queue
snapshot after the loop rather than one per agent.
argus caught `approvals.md` still describing the old serial chain under the old
node name. Grepping the name across *all* tracked files rather than just `*.rs`
turned up three more, all in `coordinator.md`: the node-inventory rows for `Swap`
and the bookkeeping tail, and the rebuild shape diagram.
Three of the four were in the file I had edited in the previous commit to add the
brace section, which is the point worth recording: I grepped the *concept* I had
changed (`lease`) and the *symbol* I had renamed, but scoped the rename grep to
Rust. Neither pass could see an old node name sitting in prose.
Also adds the missing `AgentWindow` row to the node inventory.
The pre-push comment-block lint rejected two 40-line doc blocks, correctly: the
module doc and `rebuild_subtree`'s now carry the trigger and a pointer, and the
reasoning lives in a new `#### Braces` section.
That move surfaced a third doc the resource change had falsified. The scheduler's
lease-acquirer list still named `StopForUpdate` / `Swap` / `Signal` / `Drain`,
all of which are now exempt. The list now separates container-affecting nodes
from braces, and says why the rebuild subtree's members are exempt for a
different reason than `MetaSync` / `Prebuild`: they do touch the container, but
their brace holds the lease above them.
The deletion PR removed the types but left ~10 sites still describing
them. Two are real breakage rather than staleness: rustdoc intra-doc
links to deleted items ([NodeView::kind] and [Self::snapshot] in
job_queue/mod.rs). Neither clippy --all-targets -D warnings nor cargo
test resolves intra-doc links, so the tree was green with both already
dangling.
The rest reassert facts the deletion made false: docs/coordinator.md
documented the event as RebuildQueueChanged { seq, queue: [DagView...] }
with a per-node field list, and three sites pointed at the removed
/api/state.rebuild_queue endpoint.
One is pointer rot rather than a rename, and no grep for a deleted name
finds it: SchedulesChanged justified itself as "same snapshot-shape
rationale as RebuildQueueChanged" -- which the deletion turned into the
one event that is not a snapshot. Repointed at TombstonesChanged /
MetaInputsChanged, in both the Rust doc and the dashboard doc.
Two are pre-existing and strictly out of scope, swept under the
pfadfinderregel because the same grep surfaced them: hive-sh4re/README
advertised a jobs module that crate has not had since the host-sock
split, and hive-host-sock/README claimed its own payload types live in
hive-sh4re.
Docs and comments only -- no behaviour, no API, no test changes.
Resources were derived from the node's kind: `templates::node` called
`NodeKind::resource_deps()`, which fanned out to `needs_build_slot` /
`needs_lease` / `needs_meta_window`. That made the requirement a property
of the *kind*, so a kind that happened to run under an ancestor already
holding the resource could get away with declaring nothing.
Three did. `Start`, `Stop` and `PostSwap` appear in none of the three
predicates, and that was only safe because one construction site fans
them out from inside a lease-holding `Reconcile` — a fact about today's
DAG shape, not about the nodes.
Each of the 41 construction sites now says what it holds. `Start` /
`Stop` / `PostSwap` declare the agent lease; per the contract that is a
re-entrant borrow, which a new test pins rather than argues.
`running_transients` reads the node's declared deps instead of
re-deriving from the kind. That closes the blank-pill gap: the pill went
blank during container start, stop and the post-swap tail because the
declaration was missing, not because the filter was wrong.
The deleted predicates carried the only written record of three design
decisions; each moved to the `Resource` variant it constrains rather than
dying with its function.
The submit-time petgraph `toposort` this described is gone — a cycle
needs an edge pointing at a node declared later, and a handle only
exists for a node already declared. Say why the validation pass is
absent rather than leaving a description of one that isn't there.
`templates.rs`'s module doc was 35 lines and over the comment-block
lint's max; it now points here for the reasoning instead of restating
it, and drops the power-op paragraph that `submit.rs` already owns.
The queue carried a per-DAG `HookKind` that fired an inline side effect
from outside the graph when a container rolled up terminal. mara asked
three times why this could not be an ordinary node; the answer in the
code was a doc-comment claiming a node could not work, and it was wrong.
`DepWhen::AfterAny` already existed with two live users, and a weak edge
is satisfied by a `Cancelled` dep, so a tail node runs on success,
failure and cancel alike. What was genuinely missing was smaller than a
hook: a node had no way to learn how the work it followed ended.
So: `Claim` now carries `deps: Vec<DepOutcome>`, snapshotted at claim
time from the graph the scheduler already holds (no `hive-jobq` change).
`Claim::deps_state()` / `deps_error()` roll that up, and two new kinds
consume it — `ResolveApproval { approval_id }` and `EmitRebuilt { agent }`.
Templates append one as a group-root with `AfterAny` edges onto the DAG's
other group roots; a root's state is its subtree's roll-up, so that
covers every node without fanning out to each of them.
Deleted: `HookKind`, `DagSpec.hook`, `NodeKind::Dag.hook`, `DagMeta.hook`,
`TerminalDag`, `terminal_dag()`, `terminal_summary()`, `dag_agents()`,
`dag_rollup()`, `fire_terminal_hook()`, `run_terminal_hook()`,
`emit_rebuilt()`. `complete_node` returns `()`.
Load-bearing details:
- `JobQueue::cancel` spares tail nodes instead of cancelling the whole
subtree, and returns `bool`. Without this a cancelled approval DAG
would dangle its approval forever — the hazard `tests.rs` already
named. The spared tail's deps are `Cancelled`, which satisfies its weak
edge, so the scheduler claims it and it resolves the row as cancelled.
`hive-jobq` anticipated exactly this: `cancel_node`'s doc already says
to settle afterwards so "a weak-edge terminal node observing the
cancellation" can advance.
- The existing `complete(container)` call after cancelling is kept and is
deliberately a no-op when a tail was spared (a non-terminal child parks
the container back in `Finishing`), so power ops still settle
synchronously with no branch.
- `DeployTail` is NOT `is_tail()`: it does real compensating work, and a
cancelled DAG has nothing to compensate.
- `exec::failure_reason` falls back to `first_error(dag_id)` because a
group root that rolled up `Failed` from a child carries no error of its
own — without it every tail-reported failure would lose its reason.
- `EmitRebuilt` is per agent, so a multi-agent DAG reports each agent's
own outcome rather than painting all of them with the DAG roll-up.
- `ResolveApproval` is agentless: the approval row already names its
agent, and that is also what lets one tail close a multi-agent DAG.
Transients-derived-from-running-nodes and the frontend's node-kind
strings stay out of this change; they touch iris's slice and review
better next to their own diff.
The PR added CPUWeight=/IOWeight= to the drop-in but left the prose
docs describing a two-setting file. Covers the cap-vs-share
distinction, the hive-wide-only scope (no resource-limits.json
override), and the iocost/BFQ caveat that makes IOWeight= inert on
most hosts.
The `step` label was taken off the wire in #2661, when each deploy phase
became a first-class DAG node. Since then it has been written but never
read: `NodeRuntime` derives only `Debug, Default, Clone` — no serde — so
the field could not reach any client, and the only reads of it were the
dedup checks inside its own setters. This deletes the machinery.
Removed:
- `NodeRuntime.step`, `set_step`, `set_step_running`, and the
`rt.step = None` clear in `complete_node`. `NodeRuntime` keeps its
remaining `build_log_id` field (deliberately still a struct — collapsing
it to a bare `Option<i64>` would churn every call site for no gain).
- `Ctx::step` and its ~15 call sites in `job_queue/exec.rs`. `Ctx` itself
stays: it is the build-log sink, which `run_prebuild` and `run_swap`
still use.
- `Coordinator::set_queue_step` and its 11 callers in `actions.rs`.
- `JobQueue::running_node_of`, reachable only from `set_queue_step`.
- `swap_update`'s `on_step` parameter and its one body call.
- The `set_step_only_on_running_and_signals_change` test.
Dropping the calls orphaned parameters, which are removed with their call
sites: `ctx` on ten executors that used it only as a step sink, and
`queue_entry_id` on `run_deploy_merge_verify` / `run_deploy_apply` /
`run_finalize_deploy` plus both `coord` and `queue_entry_id` on
`prepare_applied_target`. `run_deploy_tail` KEEPS its `queue_entry_id` —
that one has a genuine surviving use (the build-log link in the failure
comment posted to the PR).
One behavioural change, called out so it is not mistaken for a dropped
dashboard refresh: `Ctx::step` and `set_queue_step` each emitted a
`rebuild_queue_changed` snapshot when the label changed, and those
emissions go away with them. This is safe — the snapshot payload has no
step field, so those pushes carried nothing a client could observe. Real
state transitions still emit from the scheduler's claim and completion
paths, from `submit`, and from the three `actions.rs` sites. Net effect is
strictly fewer redundant SSE pushes.
Docs: `docs/coordinator.md` still listed `step` as a `NodeView` wire field
and `docs/web-ui/dashboard.md` documented a cyan `↳ <step>` sub-line under
each queue row. Neither has existed since #2661 — both corrected here, plus
the `job_queue/model.rs` module doc.
Not touched: `frontend/packages/dashboard/src/system-sections.css` has a
dead `.rqe-step` rule with no JS referencing it. Left for the frontend
owner rather than deleted here.
Closes: #2664
The config-PR deploy's apply node still did the whole container rebuild
inline, through the last surviving `lifecycle::rebuild_no_meta` call. It
now merges, opens the two-phase meta deploy, and returns the ordinary
rebuild chain as a subgraph the scheduler grafts into the live DAG under
it. A new `FinalizeDeploy` node, gated on that graft, plants the deploy
tag and commits the staged lock.
Net effect: "did the agent come back up?" is answered by `Reconcile`
succeeding, the same way it is for every other rebuild, instead of by a
fused inline start — and each deploy phase is its own queue node, so the
dashboard shows which one is running.
The grafted nodes root on the apply node, so they land inside
`DeployWindow`'s subtree and re-enter the meta window and build slot it
already holds rather than deadlocking against them. The new happy-path
test runs on a one-slot queue specifically to pin that down.
`FinalizeDeploy`'s two git writes are fatal, deliberately: they are what
tells `DeployTail` a deploy confirmed good, so a node that merely warned
on them could report success while leaving the tail looking at the git
state of a failure — and the tail would then roll a good deploy back.
The trailing `meta::finalize_deploy` stays warn-only, since by then the
container already runs the new config.
The `failed/<id>` annotated tag moves into the tail, which is now the
only place holding a failed deploy. It reads the reason off the DAG via
a new `JobQueue::first_error`, and is gated on `main` having actually
moved — the rollback ref is parked *before* the merge, so its existence
alone does not mean a merge happened, and a pre-merge rejection must not
tag the previous, innocent head.
Removing the last inline rebuild orphaned a chain of now-dead code:
`rebuild_no_meta`, `container_exists`, `Coordinator::set_queue_build_log`
and `JobQueue::set_build_log_id_running`, all deleted here.
Rewrite the approval flow's step 4 as the three phases, with the reason
the rollback state is a git ref, and refresh the coordinator's node
inventory + dispatch table. Fix four doc comments that still pointed at
the deleted `run_merge_config_pr`.
The two-phase approval deploy keeps a bumped `flake.lock` staged
uncommitted for the whole container build, so no other meta mutation may
land inside that span — until now enforced by a process-global
`meta::exclusive()` mutex held inside each executor fn.
A `MutexGuard` cannot outlive the fn that takes it, which is what blocks
decomposing the opaque `ApprovalDeploy` node into scheduler-visible
sub-nodes: the window has to span them. Replace the mutex with
`Resource::MetaWindow`, a global capacity-1 queue resource declared by
every meta-mutating node kind (`NodeKind::needs_meta_window`). Resources
are held by a subtree root across its whole subtree, so a later increment
can hang the deploy's phases under one window-holding parent.
Same global serialisation as before, and the scheduler now blocks a node
from being claimed rather than parking a worker on a mutex.
Split the rebuild's meta preamble out of `Prebuild` into a new `MetaSync`
node. `Prebuild` must NOT hold the window: the old mutex was deliberately
scoped to drop before the multi-minute toplevel build, which only reads
the store, and a cap-1 global held across it would serialise every
agent's rebuild behind every other's. `MetaSync` is a sibling root that
`Prebuild` deps `AfterOk` on — not its parent, since a parent's resource
covers its whole subtree and would reintroduce exactly that problem.
Queue tests: shape assertions gain the extra node, which is the point of
the change (phases become nodes). The concurrency invariants are intact
but observed one step later — the `MetaSync` heads take turns on the
window, exactly as the runtime mutex made them, so those tests now
complete the heads before asserting that the prebuilds overlap.
The #2439 agent-per-node chain removed submit-time dedup, DAG parent_id, and
child-DAG fan-out (everything grows in-DAG via append_subgraph). Update three
stale spots in docs/coordinator.md: the DAG is no longer a dedup unit;
in-DAG-appended nodes (not fan-out child DAGs) surface under the same polled
DAG id; and there is no cancel_children / parent-child cascade anymore.
Since the boot sweep (#2450) and meta-update cascade (#2476) became
single DAGs that grow subgraphs in-place, nothing constructs the old
fan-out anchors/parents anymore:
- NodeKind::Noop (the old boot_root grouping anchor) — no constructors.
- Template::StartupSweep / Source::StartupSweep (the old fan-out parent
template + cascade-child source) — replaced by Template::Boot and
Source::AutoUpdate/MetaUpdate respectively.
Drops the three variants + their as_str arms + the Noop executor arm, and
refreshes the stale fan-out/anchor doc comments (Boot/MetaUpdate/Source
docs, coordinator.md, dashboard.md). Frontend: the queue-kind glyph moves
from the dead startup_sweep to boot (which had none), and the dead
rqe-source-startup_sweep style is dropped.
No behaviour change — pure dead-variant removal.
With the meta-update cascade (#2476) and startup sweep (#2450) folded
into single DAGs that grow per-agent subgraphs via append_subgraph,
nothing links parent/child DAGs anymore — parent_id is dead.
hive-c0re: drop parent_id from Dag/DagSpec (+ the DagView copy); delete
append_children and cancel_children (no callers); simplify trim_history
(no more terminal-parent-with-live-children guard — a one-big-DAG is
terminal only when its whole graph settles); drop the rebuild() parent_id
param; QueueDag returns just the polled DAG (no fan-out children to
gather). hive-sh4re: drop the DagView.parent_id wire field.
frontend: a multi-step op is one DAG now, so renderRebuildQueue drops the
childrenOf/orphans cross-DAG grouping and renders each entry flat; its
per-agent subgraphs render as nodes within the one row (split by deps).
Removed the dead rqe-child style + isChild plumbing.
Docs + the child-DAG queue tests updated/removed to match.
MetaLock's non-sweep completion now grows one rebuild subgraph per
affected agent into the same DAG (append_subgraph), replacing the
fan-out-child-DAGs + cancel_children dance. Drops NodeOutput.fanout and
scheduler's fanout_specs. meta_update DAG carries Rebuilding transient so
each cascade agent gets crash-watch suppression at Swap (the property the
old child Rebuild DAGs held via their own transient); MetaLock head needs
no lease so the pseudo-agent gets no pill.
append_children/parent_id and child-DAG tests are intentionally left for
the #2453 capstone.
Hive-wide `stop` / `start` / `restart` emit ONE DAG with a per-agent
subgraph each (concurrent on their own leases) instead of N DAGs — and each
subgraph is now built dynamically from the agent's live running state rather
than a fixed template shape:
- online agent: the full stop→reconcile (restart: stop-for-update→reconcile)
chain; `graceful` prepends signal→drain.
- offline agent: just `SetWanted → Reconcile` (nothing to quiesce/stop; a
restart of a down agent is really a start).
The head `SetWanted` (intent) and tail `Reconcile` (convergence guarantee)
are always present; only the mechanical `Signal`/`Drain`/`StopForUpdate`
nodes are state-conditional. Keeping `Reconcile` in every shape closes the
TOCTOU window — a race-up between the `is_running` read and node exec is
still converged in-DAG (with `StopForUpdate`-noop as the backstop) — with no
reliance on an external reconcile sweep.
The state-aware assembly needs an async `is_running` read, so it moves out
of the pure/sync `templates.rs` into `submit.rs`, layered as pure
`*_chain(running)` → pure `*_spec(targets)` (the unit-test seam) → async
`*_many` (reads live state + submits). `templates.rs` keeps only the shared
pure primitives (`node`/`after_ok`/`rebuild_nodes`).
Callers await the now-async submit fns (server, dashboard, socket_server).
Tests exercise both the online and offline shapes via the pure `*_spec`
seam. docs/coordinator.md shapes updated.
- multi_agent_restart_is_one_dag_with_concurrent_per_agent_subgraphs:
two agents restart in one DAG; both SetWanted heads are roots, each
acquiring its own agent's lease concurrently. Existing single-agent
shape/lease tests updated for the templates::restart(&[..], graceful)
signature.
- coordinator.md + templates.rs module doc: restart takes an agent list;
a hive-wide restart is one DAG with N per-agent subgraphs.
- builds.js NODE_KIND_LABEL: 'set wanted' (and the previously-missing
'noop') so the new head node renders with a label, not the raw kind.
- docs/coordinator.md + templates.rs module doc: the power-op DAG shapes
now show the head SetWanted node; SetWanted added to the lease-needing
list with the atomicity rationale.
DagView no longer has a DAG-level agent, so consumers derive it from the
per-node agents:
- hivectl dag_progress.rs: dag_agents(d) helper (distinct node agents,
comma-joined) in place of d.agent.
- dashboard builds.js: entryAgents(entry) helper likewise for the
rebuild-queue card + live-log header + cancel confirms.
- docs/coordinator.md: lease prose (node-agent-keyed, global per agent),
wire shape (NodeView.agent, no DagView.agent), and dropped the removed
dedup section.
mara's review on #2436: no submit-await-submit composition, even
server-side. Adds Template::GracefulRestart (Signal -> Drain ->
StopForUpdate -> Reconcile, wanted=Up) mirroring how Restart already
does StopForUpdate -> Reconcile, plus submit::graceful_restart and
templates::graceful_restart. handle_restart_scoped now submits exactly
one DAG per agent up front for both the graceful and non-graceful
case -- no await_dags in the loop anymore.
every agent lifecycle verb on the admin socket (rebuild / restart /
restart-all / kill / stop / start) now submits job-queue DAGs and
returns their ids; hivectl polls the new HostRequest::QueueDag and
prints a live node-chain progress line per DAG (fan-out children
included), exiting non-zero on failure — --no-wait opts out. DagView
and the queue wire enums move to hive_sh4re::jobs (wire types live in
the shared crate); the last fused rebuild path (lifecycle::rebuild)
is gone. tracker: #2166
- deploy-window gate (meta::exclusive) + path-limited meta commits:
a perm/lock/topology commit can no longer sweep an ApprovalDeploy's
staged flake.lock and neuter abort_deploy (regression test included)
- cancel surfaces now buffer terminal roll-ups the scheduler drains,
so a queued approval DAG cancelled by the operator resolves its
approval instead of dangling, and cancelled power ops revert their
wanted flip to the observed state
- hivectl restart / restart-all ride the queue (lease serialization,
transient guard) and restart sets wanted=Up like the old kill+start
- exactly one Rebuilt event per rebuild DAG, emitted at terminal
- StopForUpdate pre-seeds a missing agent_power row from the pre-stop
observation so a rebuild can't strand an unknown agent offline
- history trim keeps terminal fan-out parents with live children
- audit_log back on db::open; swarm.js badge for reconcile DAGs
coordinator.md rewrites the queue section (node inventory, DAG shapes,
resources, desired-state reconciliation, boot reconcile); approvals.md
+ persistence.md + hivectl --graceful help updated to match. agent_power
lives in broker.sqlite like approvals/questions (own connection + busy
timeout) instead of a separate db file.
- .prettierrc: proseWrap=preserve (no prose reflow)
- .prettierignore: exclude hivectl-cli.md (auto-generated) + 11 docs
with multi-line list-item continuations prettier would strip to col 0
(CommonMark limitation in prettier's list handling)
- format 16 markdown files: cosmetic only (*→_, table alignment,
heading normalisation) — verified no broken continuations, idempotent
coordinator.md: GracefulStop entry referenced the old bare /kill/<agent>
path with the lax graceful=1 bool — update to /api/kill/<agent>?graceful=true.
approvals.md: the auto-update badge description referenced /rebuild/<name>
(bare, no /api/ prefix) — update to /api/rebuild/<name>.
Port-range, network-isolation, state-dir, web-UI-port, priv allowlist,
and rebuild-source mentions now refer to the root/bootstrap container
rather than 'the manager' — no structural manager exists (root-ness is
topological). Real artifact names (the manager.nix template toplevel,
/run/hyperhive/manager/mcp.sock) are left as-is.
Three host-level NixOS options in services.hyperhive.c0re were
undocumented. Add a new 'Host-level resource + performance options'
section to coordinator.md covering:
- agentCpuQuota (default 200%) — CPUQuota= drop-in per container
- agentMemoryMax (default 4G) — MemoryMax= drop-in per container
- preBuildAgentTemplates (default false) — pre-fetch agent closures
into host nix store; trade system closure size for first-spawn speed;
warn against enabling on aarch64 hosts
add QueueKind::PermChange — dashboard tool-group and capability
handlers no longer write the shared JSON files inline. instead they
enqueue a PermChange entry; the FIFO worker applies the file write
then calls rebuild_agent so the updated env var takes effect.
concurrent batch-apply actions for different agents previously raced
on tool-groups.json / capabilities.json (last write wins, earlier
change silently dropped). serialising through the queue prevents this.
dedup check extended with perm-type discriminant so tool-groups and
capabilities changes for the same agent are kept as distinct entries
and never collapse into one slot.
