# Execution: kvm2, a clean-room libvirt/KVM provider built from the provider contract

Plan: [docs/plans/2026-09-16-1333-kvm2-provider.md](../plans/2026-09-16-1333-kvm2-provider.md)

- [x] Step 0 — Plan file and branch
- [x] Step 1 — The spec, `docs/kvm2-provider-spec.md`
- [x] Step 2 — Config wiring, IDs, state mapping, classify
- [x] Step 3 — Pure builders: domain and volume XML, metadata, seed
- [x] Step 4 — Transport, seam, decorator, fakes
- [x] Step 5 — Image cache and pool-space precheck
- [x] Step 6 — The four contract methods
- [x] Step 7 — Checker and the CRD comment
- [ ] Step 8 — Deployment files, Makefile, integration test
- [ ] Step 9 — Documentation
- [ ] Step 10 — Milestone review
- [ ] Step 11 — Real-host validation, changelog, MR

## Step 0 — Plan file and branch

`main` was fast-forwarded to the merge of PR #7 (`0dc25a1`), which carries the
three provider documents, and `feat/kvm2-provider` was cut from it. The plan
was committed alone as `854856c`. The pre-existing local modification of
`.claude/settings.json` stays uncommitted throughout.

## Step 1 — The spec, `docs/kvm2-provider-spec.md`

2026-09-16 13:37. Written by the orchestrator, not a subagent, since the spec
is the "specifics" a user hands to the implementer. All 24 entries answered;
every Evidence line cites the v1 user guide, the 2026-09-04 execution log, a
go-libvirt symbol, or the contract. Nothing was taken from
`internal/provider/kvm/`.

Design choices that go beyond the user's profile answers, all recorded in the
spec: an adoption guard on `Create` (foreign UID is Permanent), a pool-space
precheck mapped to `ErrQuotaExceeded`, a dedicated connection for image
downloads so a cancelled poll cannot cut one off, the Checker on fresh
connections rather than the pool, SSH authentication and host-key failures
classified Permanent (v1 retried them forever), SSH material re-read on every
dial so rotation needs no restart, kvm2's own metadata namespace (no adoption
of v1 domains), and the shared `validateKVM` refactored to take the block name
so messages say `kvm2.`.

Checks run on the spec:

```sh
grep -c '^\*\*Answer:\*\*$' docs/kvm2-provider-spec.md      # 0 blank answers
grep -n 'internal/provider/kvm/' docs/kvm2-provider-spec.md   # empty
```

plus the axis-code check against contract §4 headings and the path-existence
loop from the docs-split log. All clean.

Worth noting: the spec's entry 21 lists the concrete test name for every
contract §11 item, so the later steps' briefs can quote it rather than
re-derive the mapping.

## Step 2 — Config wiring, IDs, state mapping, classify

2026-09-16 16:38. First subagent step. The brief named the allowed files,
the spec entries, the test names and the prohibition on
`internal/provider/kvm/`; the agent reported nothing opened there, with one
honest caveat: a `golangci-lint` run printed seven single source lines from
v1 files among its findings, which it did not act on. The review greps
(`grep -rn 'provider/kvm"' internal/provider/kvm2/`, the v1 identifier
smell list) are clean.

What landed: `ProviderConfig.KVM2` reusing `KVMConfig`, `setBlocks`, the
allow-list and dispatch in `Config.validate`, `validateKVM` refactored into
`validateKVMBlock(prefix, block, c)` with `validateKVM` kept as a wrapper so
v1 messages and tests are untouched, `"kvm2": kvm2.New` in `cmd/main.go`
(both type lists in one commit), and the package skeleton: `kvm2.go`
(`New` never dials, warns on unreadable files, `withDefaults`, `host`,
`wrapErr`, stubbed methods), `id.go`, `state.go`, `errors.go` with 34
`classify` rows.

Decisions the agent made that the spec left open, all accepted: `New`
checks file existence only (parsing belongs to the dialer); `withDefaults`
copies hosts and images; `firstIPv4` also drops an address whose type tag and
literal disagree; there is no explicit `fs.ErrNotExist` branch in `classify`
because it falls to the Transient default anyway.

Commands as run by the agent and re-run by the orchestrator:

```sh
go vet ./... && go build ./... && go test -race -count=1 ./internal/provider/... ./cmd/...
go test -short ./...
```

All packages `ok`.

Worth noting: `bin/golangci-lint` panics inside staticcheck's IR builder on
this machine (`unexpected expr: *ast.KeyValueExpr` on stdlib `internal/poll`)
because the local toolchain is Go 1.27.0 while `go.mod` says 1.26 and the
bundled staticcheck predates it; it reproduces on untouched packages, so lint
is deferred to Step 10 with a toolchain note. The `.claude/settings.json`
modification is still local and uncommitted.

## Step 3 — Pure builders: domain and volume XML, metadata, seed

2026-09-16 16:55. Second subagent step, new files only: `xml.go`,
`metadata.go`, `volume.go`, `seed.go` and their tests (26 tests). The
domain XML is built from `encoding/xml` structs, both disks are
`type="file"` with resolved paths (the AppArmor lesson), UEFI is the default
with the secure-boot feature disabled, the metadata element parses with or
without its namespace declaration, and the seed ISO is staged under
`os.TempDir()` (the library uses `os.MkdirTemp("", "")`, so `TMPDIR` is
honoured; the test points it at a `t.TempDir()` and asserts nothing is left
behind).

Decisions the agent made, all accepted: `buildDomainXML` defaults an empty
disk format to qcow2 and rejects anything but qcow2 or raw;
`buildVolumeXML` rejects a non-positive capacity; `buildSeedISO` rejects an
empty name; the guest-agent script still runs the enable-and-start step when
the agent is already installed; the multipart boundary is random, so
vendor-data is not byte-deterministic across calls (the seed is rebuilt every
Create anyway).

Commands:

```sh
gofmt -l ./internal/provider/kvm2 ; go vet ./internal/provider/kvm2/ && go test -race -count=1 ./internal/provider/kvm2/
go build ./... && go test -short ./...
```

All `ok`. Review greps for a v1 import or v1 identifiers are empty; the only
`type="volume"` in the package is the comment explaining why it is not used.
The agent reported "files read outside the allowed set: none".

## Step 4 — Transport, seam, decorator, fakes

2026-09-16 17:42. Third subagent step, the largest: `backend.go` (the
ctx-first seam `backend`, the production adapter `libvirtBackend`, a
generic `call[T]` helper with per-call budgets and the abandon policy),
`ssh.go` (credentials read on every dial, stage-tagged `dialError`, the
forwarded socket, keepalive), `hosts.go` (`hostTable` with a per-host
channel semaphore so waiting for a dial ends with the caller's ctx,
`dialFresh` for dedicated connections, the production `libvirtDialer`
starting the `kvm2.dial` span and applying the decorator once),
`observe.go` (one span `kvm2.<Method>` and one `libvirt call` line per
RPC), plus an in-memory `fakeBackend`, an in-process SSH server and 41
tests. The agent also drove the real adapter over go-libvirt's own
`libvirttest` mock through a `net.Pipe`, which the brief did not ask for.

Abandon policy as built: a call that outlives its ctx or budget kills the
link (closes the socket and the SSH client), returns Transient wrapping the
ctx or deadline error, and other in-flight calls on that connection fail once
with go-libvirt's `ErrInterrupted`; the next `get` redials. Results travel
through a channel so a late-finishing abandoned call never writes into its
caller's frame; the agent reported that the first `-race` run caught exactly
that bug in an earlier version.

Decisions the agent made, accepted: liveness is a separate unexported
interface so the reflection test over `backend` stays at the 20 RPCs plus
`Close`; `Close` sends a bounded `ConnectClose` before killing the link;
`observe` and the dialer take `...tracing.Option` so tests can inject a
recording tracer provider, as `provider.WithTracing` does.

Clean-room note: three type names coincide with names v1 uses
(`dialError`, `dialStage`, `hostEntry`). The brief described each concept
("an error type that records which stage failed", "a per-host entry") so the
names follow from the description; the greps for a v1 import and for the
listed v1 identifiers are empty and the agent attested to reading nothing
under `internal/provider/kvm/`.

Commands (agent and orchestrator):

```sh
gofmt -l ./internal/provider/kvm2 ; go vet ./internal/provider/kvm2/ && go test -race -count=2 ./internal/provider/kvm2/
go build ./... && go test -short ./...
grep -n 'context.Background()' internal/provider/kvm2/*.go | grep -v _test.go   # empty
```

All `ok`; the agent also ran the timing-sensitive tests at `-count=8`.

## Step 5 — Image cache and pool-space precheck

2026-09-16 18:11. Fourth subagent step: `image.go` and `image_test.go`
(27 tests), plus additive changes to `fake_test.go` (a `twin()` sharing
state with its own call log, so a test can tell the pooled connection from
the dedicated one) and `kvm2.go` (`http` client, budgets and tracing
options behind functional options, so `New` is unchanged). The pipeline:
marker lookup and bounded read on the pooled connection, then a GET bound to
ctx plus the 20-minute cap under a `kvm2.download` span, `StorageVolCreateXML`
and a streamed `StorageVolUpload` through sha256 on a fresh connection,
`StoragePoolRefresh`, and the marker written last; every failure after the
volume exists discards it with the cancellation stripped from ctx so the
cleanup RPC still runs.

Streaming is asserted by counting: a hook on the dedicated fake's upload
snapshots how many bytes the 64 MiB test server had written when the upload
began, and asserts under 16 MiB. The agent chose that over a process-wide
`MemStats` delta because the tests run in parallel.

Decisions the agent made, accepted: the base volume is created on the
dedicated connection (nothing exists if the dial fails); `Accept-Encoding:
identity` is sent so transparent gunzip cannot hide the Content-Length; a
marker whose content is not 64 hex characters counts as debris;
`Content-Length: 0` is its own Permanent error; the image lock is a
one-slot channel so a waiter gives up with its ctx instead of sitting out a
transfer; the fetch logger is derived after the span starts so its lines
carry the span ID (the agent's first test run caught that).

Commands (agent and orchestrator):

```sh
gofmt -l ./internal/provider/kvm2 ; go vet ./internal/provider/kvm2/ && go test -race -count=2 ./internal/provider/kvm2/
go build ./... && go test -short ./...
grep -n 'io.ReadAll\|bytes.Buffer' internal/provider/kvm2/image.go            # empty
grep -n 'context.Background()' internal/provider/kvm2/*.go | grep -v _test.go  # empty
```

All `ok`. Attestation: "files read outside the allowed set: none".

## Step 6 — The four contract methods

2026-09-16 18:36. Fifth subagent step: `create.go`, `get.go`, `delete.go`,
`list.go` and five test files (the package now has 150 top-level tests).
Create follows spec entry 10 step for step under a per-name lock, with the
adoption guard, the quota precheck, the image cache, an overlay that is
reused and a seed that is always rebuilt, file-type disks from resolved
paths, the metadata element in the define call, and a wait for running
capped at two minutes. Get maps only `ErrNoDomain` to NotFound, prefers the
guest agent over ARP, and reads UID and CreatedAt back every time. Delete is
idempotent at every step and a no-op success for an unconfigured host.
ListByTag fails whole per host and skips single unreadable domains.

Decisions the agent made, accepted: the adoption path also waits for
running, so a repeat Create on a shut-off domain blocks like a first one;
`address` and `ListByTag` propagate ctx cancellation instead of reading it as
"no address" or "skip", so a cancelled Get is Transient rather than a false
Provisioning; NotFound from Get gets its own V(1) line because polling to
NotFound is expected; the domain XML rides on the `domain defined` line at
V(2). Flagged, not solved: adopting a paused domain fails Transient on every
retry (`DomainCreate` refuses and the wait expires), which the spec does not
cover; recorded as a known gap for the docs step.

The agent found a one-word conflict between the brief and the spec
(`DomainAffectCurrent` versus `DomainAffectConfig` for `DomainGetMetadata`);
the code uses `DomainAffectCurrent`, and spec entry 8 was corrected to
match in this commit.

Commands (agent and orchestrator):

```sh
gofmt -l ./internal/provider/kvm2 ; go vet ./internal/provider/kvm2/ && go test -race -count=2 ./internal/provider/kvm2/
go build ./... && go test -short ./...
grep -n 'CloudInit' internal/provider/kvm2/create.go          # only len(req.CloudInit) and the seed builder call
grep -n 'not implemented' internal/provider/kvm2/*.go          # empty
grep -n 'provider.Wrap(' internal/provider/kvm2/*.go | grep -v _test.go | grep -v 'p.name'   # empty
```

All `ok`. Attestation: "files read outside the allowed set: none".

## Step 7 — Checker and the CRD comment

2026-09-16 18:52. Sixth subagent step: `check.go` and `check_test.go`
(ten tests, the reasons table has 19 rows). Every host is checked
concurrently on a fresh dedicated connection that is closed when the probe
ends; the pooled table is never consulted, which the test proves with a
counting dialer. Details fill in as facts arrive, so a `PoolNotFound`
verdict still says which libvirt version answered. The `status.type` comment
in `api/v1alpha1/providerhealth_types.go` gained `kvm2` and `make manifests`
changed only the CRD's description line:

```sh
make manifests && git diff --stat config/ api/
#  api/v1alpha1/providerhealth_types.go                    | 2 +-
#  config/crd/bases/crawl.example.com_providerhealths.yaml | 2 +-
```

Decisions the agent made, accepted: a dial that runs out of time is
`Unreachable` (the host did not answer), and `Timeout` is reserved for ctx or
budget expiry on an established connection; `Close` runs synchronously in
the probe so the close-count assertion is deterministic, at the cost of up
to five seconds past ctx if a disconnect hangs on a live link.

The agent also reported that the `captureContext` helper in `kvm2_test.go`
appends to an unlocked slice, which the race detector flagged once `Check`
logged from several goroutines. The helper was outside its allowed file set,
so it built its own locked capture; the orchestrator fixed `captureContext`
with a mutex in this commit and re-ran the package at `-race -count=3`.

Attestation: "files read outside the allowed set: none".