diff --git a/cmd/mesh-controller/upgrades.go b/cmd/mesh-controller/upgrades.go
index 7f8bc8e2..7570fb79 100644
--- a/cmd/mesh-controller/upgrades.go
+++ b/cmd/mesh-controller/upgrades.go
@@ -79,7 +79,7 @@ func (f following) Upgraded(ctx context.Context, u link.Upgraded) error {
 	// `rebuild`, a `replay` registered — was sent here one machine after another without any judging; it
 	// now waits for a gate like any other build, and the release plan walks it through the machines, one
 	// at a time, each judged.
-	fmt.Printf("%s moved to %s outside a plan; a release plan sends it to %s, one machine at a time, each judged "+
+	fmt.Printf("%s moved to %s outside a plan; a release plan sends it to %s, one machine first and then the rest at once, each judged "+
 		"(`upgrade backlog` lists what waits)\n", u.Module, shortCommit(u.Commit), readableList(on))
 	return nil
 }
diff --git a/cmd/mesh-controller/walk_said.go b/cmd/mesh-controller/walk_said.go
index ddb724e4..3e5d9bad 100644
--- a/cmd/mesh-controller/walk_said.go
+++ b/cmd/mesh-controller/walk_said.go
@@ -177,6 +177,12 @@ func walkReached(p inventory.Plan, running func(string) []string) map[string][]s
 			reached = appendNew(reached, r.Gate.Machines...)
 			carried(r.Gate)
 		}
+		for _, g := range r.Gates {
+			if g != nil && !g.Pending {
+				reached = appendNew(reached, g.Machines...)
+				carried(g)
+			}
+		}
 		for _, tier := range p.Tiers {
 			for _, m := range tier {
 				for _, n := range running(m) {
diff --git a/internal/builder/builder.go b/internal/builder/builder.go
index c2c1cbf9..728ce83e 100644
--- a/internal/builder/builder.go
+++ b/internal/builder/builder.go
@@ -1088,6 +1088,16 @@ func one(ctx context.Context, run Runner, publish Publisher,
 			return catalogue.Built{}, fmt.Errorf("%s: building %s failed: %w", module, a.Name, err)
 		}
 		say("image", "built, publishing")
+		// Its bases linked into its repository first, so the push needs none of their blobs from this
+		// machine's store, which may not hold them (novox/hq issue 694). Said and not fatal: a push
+		// from a store that holds them works without, and one that fails says which blob it lacked.
+		if lender, can := publish.(BaseLender); can {
+			if n, err := lender.LendBases(ctx, module+"/"+a.Name, buildArgValues(args)); err != nil {
+				say("image", "its bases could not all be linked into %s/%s before the push: %v", module, a.Name, err)
+			} else if n > 0 {
+				say("image", "%d blob(s) of its bases linked into %s/%s before the push", n, module, a.Name)
+			}
+		}
 		reference, err := publish.PublishImage(ctx, local, module+"/"+a.Name)
 		if err != nil {
 			return catalogue.Built{}, err
@@ -1439,6 +1449,19 @@ func standingOn(ctx context.Context, manifest catalogue.Manifest, held map[strin
 	return args, resolved, nil
 }
 
+// buildArgValues is what each --build-arg of a build was handed: the bases, as this mesh holds them.
+func buildArgValues(args []string) []string {
+	var values []string
+	for i := 0; i+1 < len(args); i += 2 {
+		if args[i] == "--build-arg" {
+			if _, value, has := strings.Cut(args[i+1], "="); has {
+				values = append(values, value)
+			}
+		}
+	}
+	return values
+}
+
 // compile runs a module's own code through its toolchain, and says where the result is.
 //
 // **In the module's own directory, under the path the toolchain expects.** A module is compiled
diff --git a/internal/builder/check.go b/internal/builder/check.go
index bf0ce5bc..a2107499 100644
--- a/internal/builder/check.go
+++ b/internal/builder/check.go
@@ -103,6 +103,23 @@ type CheckSpec struct {
 	// for the walk to take. None for a group's composed check, whose members' own checks build.
 	Builds    []CheckBuildSpec
 	BuildWith *CheckBuilding
+	// Tests and StoreOnly narrow what the repository's own script runs, for a branch tried before its pull
+	// request (novox/hq issue 686): handed to the script as EnvTests and EnvStoreOnly, which it may read.
+	Tests     string
+	StoreOnly bool
+}
+
+// selection is what a check hands the repository's script to narrow what it runs (novox/hq issue 686): nothing
+// for a pull request's check, which always runs whole.
+func selection(spec CheckSpec) []string {
+	var env []string
+	if spec.Tests != "" {
+		env = append(env, EnvTests+"="+spec.Tests)
+	}
+	if spec.StoreOnly {
+		env = append(env, EnvStoreOnly+"=1")
+	}
+	return env
 }
 
 // GroupHead is one other head of a delivery group's composed check.
@@ -193,6 +210,11 @@ const (
 	// EnvGroup is a delivery group's other heads, as JSON, for the gate (novox/hq ADR 0239); empty for a
 	// pull request checked alone.
 	EnvGroup = "MESH_CHECK_GROUP"
+	// EnvTests is a `go test -run` pattern and EnvStoreOnly is 1 when a branch tried before its pull request
+	// asks for only those tests, or only the store tests (novox/hq issue 686). Never set for a pull request's
+	// check. A script that reads neither runs whole.
+	EnvTests     = "MESH_CHECK_TESTS"
+	EnvStoreOnly = "MESH_CHECK_STORE_ONLY"
 )
 
 // CheckTimeout bounds one check; a check that runs past it is an error, not a pass.
@@ -515,6 +537,7 @@ func Check(ctx context.Context, run Runner, spec CheckSpec, workspace, registry
 		EnvModules + "=" + strings.Join(append(append([]string{}, spec.Modules...), spec.New...), ","),
 		EnvGroup + "=" + groupFile,
 		"GOCACHE=" + filepath.Join(workspace, "go-cache"), "GOMODCACHE=" + filepath.Join(workspace, "go-modules")}
+	env = append(env, selection(spec)...)
 
 	v := CheckVerdict{}
 	modules := append(append([]string{}, spec.Modules...), prefixed("new:", spec.New)...)
diff --git a/internal/builder/check_test.go b/internal/builder/check_test.go
index 92583f5a..1eb5890a 100644
--- a/internal/builder/check_test.go
+++ b/internal/builder/check_test.go
@@ -590,3 +590,15 @@ func TestARepositoryInTwoLanguagesIsCheckedInBoth(t *testing.T) {
 		t.Errorf("a part in a toolchain the mesh does not hold answered %+v — never a pass", layer)
 	}
 }
+
+// A branch tried before its pull request may narrow what the repository's script runs (novox/hq issue 686); a
+// pull request's check is handed nothing, and runs whole.
+func TestOnlyATrysSelectionReachesTheScript(t *testing.T) {
+	if env := selection(CheckSpec{Number: 7}); len(env) != 0 {
+		t.Fatalf("a pull request's check was handed a selection: %v", env)
+	}
+	env := selection(CheckSpec{Tests: "^TestX$", StoreOnly: true})
+	if len(env) != 2 || env[0] != "MESH_CHECK_TESTS=^TestX$" || env[1] != "MESH_CHECK_STORE_ONLY=1" {
+		t.Fatalf("a try's selection: %v", env)
+	}
+}
diff --git a/internal/builder/lend.go b/internal/builder/lend.go
new file mode 100644
index 00000000..d3984647
--- /dev/null
+++ b/internal/builder/lend.go
@@ -0,0 +1,178 @@
+package builder
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"runtime"
+	"strings"
+)
+
+// **A built image's bases are linked into its repository before it is pushed** (novox/hq issue 694).
+//
+// A push reads every blob of the image out of this machine's store, unless the repository it goes to
+// already holds that blob: the runtime asks the registry first, blob by blob, and reads locally only
+// what the registry lacks. A runtime keeping its images in containerd's store — the default for a
+// fresh install from docker 29 on — does not always hold the compressed layers of the base an image
+// was built FROM: a layer whose unpacked form it already had is never fetched. The push of such an
+// image then fails on a layer this machine never had ("not all of them are available locally"), while
+// the very bytes sit in this registry, under the repository the base was mirrored into.
+//
+// So the base's blobs are mounted into the image's repository first. A mount moves no bytes, and once
+// the repository holds a blob the push asks this machine for nothing of it — whichever store the
+// runtime keeps. A runtime that holds every layer (the classic store) is not changed by this: its push
+// finds the same blobs already there.
+
+// BaseLender links what a build's bases hold into the repository its image is about to be pushed to.
+type BaseLender interface {
+	// LendBases mounts every blob of each base this registry holds — for the platform this machine
+	// builds — into `repository`, and answers how many it mounted.
+	LendBases(ctx context.Context, repository string, bases []string) (int, error)
+}
+
+// platformed is an index's entry: a manifest and the platform it is for.
+type platformed struct {
+	descriptor
+	Platform *struct {
+		OS           string `json:"os"`
+		Architecture string `json:"architecture"`
+	} `json:"platform"`
+}
+
+// LendBases mounts each base's blobs into the repository. A base this registry does not hold under its
+// repository — named by tag, or held somewhere else — lends nothing and is no error: the push reads it
+// from this machine's store as before.
+func (r Registry) LendBases(ctx context.Context, repository string, bases []string) (int, error) {
+	mounted := 0
+	for _, base := range bases {
+		name, digest, pinned := strings.Cut(base, "@")
+		if !pinned || !strings.HasPrefix(digest, "sha256:") {
+			continue
+		}
+		where, err := parseReference(name + "@" + digest)
+		if err != nil {
+			continue
+		}
+		from := where.repository
+		if from == repository {
+			continue
+		}
+		blobs, held, err := r.blobsOf(ctx, from, digest)
+		if err != nil {
+			return mounted, fmt.Errorf("reading %s: %w", base, err)
+		}
+		if !held {
+			continue
+		}
+		for _, blob := range blobs {
+			did, err := r.mount(ctx, repository, from, blob)
+			if err != nil {
+				return mounted, fmt.Errorf("linking %s of %s into %s: %w", blob, base, repository, err)
+			}
+			if did {
+				mounted++
+			}
+		}
+	}
+	return mounted, nil
+}
+
+// blobsOf is the config and layers of the manifest under repository@digest — for an index, of each
+// manifest it names for this machine's platform. False when the registry holds no such manifest there.
+func (r Registry) blobsOf(ctx context.Context, repository, digest string) ([]string, bool, error) {
+	body, held, err := r.manifest(ctx, repository, digest)
+	if err != nil || !held {
+		return nil, held, err
+	}
+	var document struct {
+		Manifests []platformed `json:"manifests"`
+		Config    *descriptor  `json:"config"`
+		Layers    []descriptor `json:"layers"`
+	}
+	if err := json.Unmarshal(body, &document); err != nil {
+		return nil, false, fmt.Errorf("%s@%s is not a manifest: %w", repository, digest, err)
+	}
+	var blobs []string
+	if document.Config != nil {
+		blobs = append(blobs, document.Config.Digest)
+	}
+	for _, l := range document.Layers {
+		blobs = append(blobs, l.Digest)
+	}
+	for _, m := range document.Manifests {
+		if m.Platform == nil || m.Platform.OS != runtime.GOOS || m.Platform.Architecture != runtime.GOARCH {
+			continue
+		}
+		more, held, err := r.blobsOf(ctx, repository, m.Digest)
+		if err != nil {
+			return nil, false, err
+		}
+		if held {
+			blobs = append(blobs, more...)
+		}
+	}
+	return blobs, true, nil
+}
+
+// manifest reads one manifest document from this registry; false when it is not there.
+func (r Registry) manifest(ctx context.Context, repository, digest string) ([]byte, bool, error) {
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet,
+		"http://"+r.Address+"/v2/"+repository+"/manifests/"+digest, nil)
+	if err != nil {
+		return nil, false, err
+	}
+	request.Header.Set("Accept", manifestAccept)
+	response, err := r.client().Do(request)
+	if err != nil {
+		return nil, false, fmt.Errorf("cannot reach the registry at %s: %w", r.Address, err)
+	}
+	defer response.Body.Close()
+	if response.StatusCode == http.StatusNotFound {
+		return nil, false, nil
+	}
+	if response.StatusCode != http.StatusOK {
+		return nil, false, fmt.Errorf("%s/%s@%s: %s", r.Address, repository, digest, response.Status)
+	}
+	body, err := io.ReadAll(io.LimitReader(response.Body, 4<<20))
+	return body, err == nil, err
+}
+
+// mount links one blob from one repository into another; false when the repository already held it.
+func (r Registry) mount(ctx context.Context, repository, from, digest string) (bool, error) {
+	base := "http://" + r.Address + "/v2/" + repository
+	if there, err := r.has(ctx, base+"/blobs/"+digest); err != nil {
+		return false, err
+	} else if there {
+		return false, nil
+	}
+	start, err := http.NewRequestWithContext(ctx, http.MethodPost,
+		base+"/blobs/uploads/?mount="+digest+"&from="+from, nil)
+	if err != nil {
+		return false, err
+	}
+	begun, err := r.client().Do(start)
+	if err != nil {
+		return false, fmt.Errorf("cannot reach the registry at %s: %w", r.Address, err)
+	}
+	begun.Body.Close()
+	if begun.StatusCode == http.StatusCreated {
+		return true, nil
+	}
+	if begun.StatusCode == http.StatusAccepted {
+		// Not mounted, and an upload begun in its place: let go of it, so nothing is left half-open.
+		if location := begun.Header.Get("Location"); location != "" {
+			if strings.HasPrefix(location, "/") {
+				location = "http://" + r.Address + location
+			}
+			if cancel, err := http.NewRequestWithContext(ctx, http.MethodDelete, location, nil); err == nil {
+				if done, err := r.client().Do(cancel); err == nil {
+					done.Body.Close()
+				}
+			}
+		}
+		return false, fmt.Errorf("%s did not mount it from %s", r.Address, from)
+	}
+	return false, fmt.Errorf("%s answered %s when asked to mount it from %s", r.Address, begun.Status, from)
+}
diff --git a/internal/builder/lend_test.go b/internal/builder/lend_test.go
new file mode 100644
index 00000000..ff92a998
--- /dev/null
+++ b/internal/builder/lend_test.go
@@ -0,0 +1,140 @@
+package builder
+
+import (
+	"context"
+	"encoding/json"
+	"net/http/httptest"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+// A built image's bases are linked into its repository before it is pushed (novox/hq issue 694): a
+// runtime keeping containerd's image store may not hold a base layer it never had to fetch, and its push
+// asks this machine only for what the repository lacks.
+
+// aBaseForThisMachine puts an index into the registry under `repository`: one manifest for this
+// machine's platform, one for another, and answers the index's digest and each manifest's blobs.
+func aBaseForThisMachine(t *testing.T, dst *aRegistryOfRepositories, repository string) (string, []string, []string) {
+	t.Helper()
+	put := func(arch string) (string, []string) {
+		config := []byte(`{"architecture":"` + arch + `"}`)
+		layer := []byte(arch + " layer bytes")
+		for _, b := range [][]byte{config, layer} {
+			dst.blobs[digestOf(b)] = b
+			dst.link(repository, digestOf(b))
+		}
+		m, _ := json.Marshal(map[string]any{
+			"schemaVersion": 2, "mediaType": mediaManifestOCI,
+			"config": map[string]any{"mediaType": "application/vnd.oci.image.config.v1+json", "digest": digestOf(config), "size": len(config)},
+			"layers": []map[string]any{{"mediaType": "application/vnd.oci.image.layer.v1.tar+gzip", "digest": digestOf(layer), "size": len(layer)}},
+		})
+		dst.manifests[repository+"@"+digestOf(m)] = m
+		return digestOf(m), []string{digestOf(config), digestOf(layer)}
+	}
+	other := "s390x"
+	if runtime.GOARCH == other {
+		other = "amd64"
+	}
+	mine, mineBlobs := put(runtime.GOARCH)
+	theirs, theirBlobs := put(other)
+	index, _ := json.Marshal(map[string]any{
+		"schemaVersion": 2, "mediaType": mediaIndexOCI,
+		"manifests": []map[string]any{
+			{"mediaType": mediaManifestOCI, "digest": mine, "size": 1, "platform": map[string]string{"os": runtime.GOOS, "architecture": runtime.GOARCH}},
+			{"mediaType": mediaManifestOCI, "digest": theirs, "size": 1, "platform": map[string]string{"os": "linux", "architecture": other}},
+		},
+	})
+	dst.manifests[repository+"@"+digestOf(index)] = index
+	return digestOf(index), mineBlobs, theirBlobs
+}
+
+func TestABuildsBaseIsLinkedIntoItsRepositoryBeforeThePush(t *testing.T) {
+	dst := newRegistryOfRepositories()
+	server := httptest.NewServer(dst.handler())
+	defer server.Close()
+	address := strings.TrimPrefix(server.URL, "http://")
+	r := Registry{Address: address}
+
+	const from = "upstream/docker.io/library/golang"
+	index, mine, theirs := aBaseForThisMachine(t, dst, from)
+	bases := []string{
+		address + "/" + from + "@" + index,
+		// Not bases this registry holds: a package version, a tag, an image held nowhere here.
+		"@novox/mesh-sdk@1.2.3",
+		"golang:1-alpine",
+		"elsewhere.invalid/thing@sha256:" + strings.Repeat("e", 64),
+	}
+	n, err := r.LendBases(context.Background(), "mesh-tools-go/build", bases)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Every blob of this machine's platform is in the image's repository, so a push asks this machine's
+	// store for none of them; another platform's are not, since nothing built here stands on them.
+	for _, blob := range mine {
+		if !dst.links["mesh-tools-go/build"][blob] {
+			t.Fatalf("the base's blob %s is not in the image's repository", blob)
+		}
+	}
+	for _, blob := range theirs {
+		if dst.links["mesh-tools-go/build"][blob] {
+			t.Fatalf("another platform's blob %s was linked", blob)
+		}
+	}
+	if n != len(mine) || dst.mounts != len(mine) || dst.uploads != 0 {
+		t.Fatalf("%d linked, %d mounts, %d uploads; want %d mounts and no bytes moved", n, dst.mounts, dst.uploads, len(mine))
+	}
+
+	// Asked again, nothing is mounted twice.
+	if n, err := r.LendBases(context.Background(), "mesh-tools-go/build", bases); err != nil || n != 0 {
+		t.Fatalf("a second lending mounted %d: %v", n, err)
+	}
+}
+
+// A registry that will not mount is said, not hidden: the push is still tried, from the store.
+func TestABaseTheRegistryWillNotMountIsAnError(t *testing.T) {
+	dst := newRegistryOfRepositories()
+	dst.noMount = true
+	server := httptest.NewServer(dst.handler())
+	defer server.Close()
+	address := strings.TrimPrefix(server.URL, "http://")
+	index, _, _ := aBaseForThisMachine(t, dst, "upstream/thing")
+	_, err := Registry{Address: address}.LendBases(context.Background(), "hello/server",
+		[]string{address + "/upstream/thing@" + index})
+	if err == nil || !strings.Contains(err.Error(), "did not mount") {
+		t.Fatalf("a refused mount passed silently: %v", err)
+	}
+}
+
+// lending records what a build lent, and when, against the push.
+type lending struct {
+	*mirroring
+	order []string
+}
+
+func (l *lending) LendBases(_ context.Context, repository string, bases []string) (int, error) {
+	l.order = append(l.order, "lend "+repository+" "+strings.Join(bases, " "))
+	return len(bases), nil
+}
+
+func (l *lending) PublishImage(ctx context.Context, localTag, repository string) (string, error) {
+	l.order = append(l.order, "push "+repository)
+	return l.mirroring.PublishImage(ctx, localTag, repository)
+}
+
+func TestAnImageIsPushedOnlyAfterItsBasesAreLent(t *testing.T) {
+	r, workspace := aRepository(t, anImage, map[string]string{"modules/bus/Dockerfile": "ARG BASE\nFROM ${BASE}"})
+	r.contents["modules/bus/module.json"] = anImage
+	l := &lending{mirroring: &mirroring{recorded: r, at: "127.0.0.1:5000"}}
+	if _, err := Build(context.Background(), r.run, l, "https://forge.invalid/catalogue.git", "modules/bus", "", workspace,
+		nil, Npmrc{}, GitCredential{}, nil); err != nil {
+		t.Fatal(err)
+	}
+	want := []string{
+		"lend bus/server 127.0.0.1:5000/upstream/docker.io/vendor/server@sha256:" + strings.Repeat("1", 64),
+		"push bus/server",
+	}
+	if strings.Join(l.order, "\n") != strings.Join(want, "\n") {
+		t.Fatalf("the build did:\n%s\nwant:\n%s", strings.Join(l.order, "\n"), strings.Join(want, "\n"))
+	}
+}
diff --git a/internal/builder/reuse.go b/internal/builder/reuse.go
index 04a09ce0..2def775d 100644
--- a/internal/builder/reuse.go
+++ b/internal/builder/reuse.go
@@ -257,6 +257,13 @@ func (s scratchPublisher) PublishArchive(ctx context.Context, repository string,
 	return s.to.PublishArchive(ctx, ScratchPrefix+repository, body, digest)
 }
 
+func (s scratchPublisher) LendBases(ctx context.Context, repository string, bases []string) (int, error) {
+	if l, can := s.to.(BaseLender); can {
+		return l.LendBases(ctx, ScratchPrefix+repository, bases)
+	}
+	return 0, nil
+}
+
 func (s scratchPublisher) MirrorImage(ctx context.Context, from, repository string) (string, error) {
 	m, can := s.to.(Mirrorer)
 	if !can {
diff --git a/internal/catalogue/verbs.go b/internal/catalogue/verbs.go
index 673f62f4..a186e558 100644
--- a/internal/catalogue/verbs.go
+++ b/internal/catalogue/verbs.go
@@ -362,6 +362,28 @@ var ControllerVerbs = []Verb{
 			"register": "\"true\" to register what it builds",
 			"older":    "\"true\", with register: even though a newer build of the module is registered",
 		}, []string{"id"}, "register", "older")},
+	// novox/hq issue 686: a builder ran a branch's store tests for the first time in its pull request's merge check.
+	{Name: "try", Description: "Try a pushed branch or commit before its pull request (novox/hq issue 686): the build " +
+		"seat merges it into the repository's trunk and runs the repository's own merge-check.sh on the merge, in the " +
+		"toolchain containers and against the throwaway store and bus a pull request's merge check gets. Answers at " +
+		"once with an id; asked again with that id it waits up to 20 s and answers pass, fail or error, how long it " +
+		"took and the lines naming what failed — or that it is still waiting or running, to ask again. Sets no " +
+		"status on the forge, registers and builds nothing, runs no merge gate, counts as a check in the build queue " +
+		"(after deliveries and after every pull request's check, however long it waits) and is bounded as one. One " +
+		"try of a commit at a time — a second ask answers the first's id — and at most four waiting or running in " +
+		"all: a fifth is refused. Only for a repository of the mesh; the ref must be on the forge.",
+		Input: schema(map[string]string{
+			"repository": "the repository on the forge, owner/name; with ref",
+			"ref":        "the branch or commit to try, as pushed to the forge",
+			"base": "the branch it is merged into (the repository's default branch when none is named). The " +
+				"merge-check.sh that runs is that branch's, never the ref's own: the same trust as a pull request's base",
+			"tests": "only the tests this `go test -run` pattern names, where the repository's merge-check.sh reads " +
+				"MESH_CHECK_TESTS; a script that does not runs whole",
+			"store-only": "\"true\": only the repository's store tests, where its merge-check.sh reads " +
+				"MESH_CHECK_STORE_ONLY",
+			"id": "instead of a repository: the id a try answered, to read what came of it",
+		}, nil, "store-only"),
+		Replaces: []string{"sh merge-check.sh", "docker run postgres"}},
 	// novox/hq ADR 0350 §5: asked by the delivery's owner when the forge says a pull request closed unmerged.
 	{Name: "forget-checks", Description: "Let go of every build a pull request's merge checks made for its merge in " +
 		"the artifact store's scratch namespace (novox/hq ADR 0350 §5): asked when it closed unmerged; a merged one's go " +
diff --git a/internal/inventory/plans.go b/internal/inventory/plans.go
index fd86c2b9..c9f712cf 100644
--- a/internal/inventory/plans.go
+++ b/internal/inventory/plans.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 	"strings"
 	"time"
 
@@ -391,6 +392,65 @@ type PlanGate struct {
 	// reports its module's container left running because it said busy, the judging waits and has not
 	// started; once it reports the container replaced, Since is moved to then. Nil when nothing waited.
 	Busy *GateBusy `json:"busy,omitempty"`
+	// Pending says the send this gate judges is kept and not yet made (novox/hq ADR 0353 §8): a controller that
+	// takes over reads the machine's last send before making it, and never sends it twice.
+	Pending bool `json:"pending,omitempty"`
+	// Silent says the machine reported nothing on its send within ApplySilentAfter (novox/hq ADR 0353 §4): left,
+	// neither failed nor put back.
+	Silent bool `json:"silent,omitempty"`
+	// TookOver names the gate whose readings this one took over (novox/hq ADR 0353 §7): another walk's judging of
+	// the same build on the same machine, which this gate goes on from instead of starting from zero.
+	TookOver string `json:"took_over,omitempty"`
+}
+
+// TakeReadings makes this gate go on from another's readings of the same build on the same machine (novox/hq ADR
+// 0353 §7): when the judging began, when each machine applied, the passes counted and when, and what each found.
+// A module's own count is taken only for the modules this gate judges.
+func (g *PlanGate) TakeReadings(from *PlanGate, modules []string, id string) {
+	if from == nil {
+		return
+	}
+	if from.Since != nil {
+		since := *from.Since
+		g.Since = &since
+	}
+	for n, s := range from.Sent {
+		if slices.Contains(g.Machines, n) {
+			if g.Sent == nil {
+				g.Sent = map[string]SentDeclaration{}
+			}
+			g.Sent[n] = s
+		}
+	}
+	for n, at := range from.Applied {
+		if slices.Contains(g.Machines, n) {
+			if g.Applied == nil {
+				g.Applied = map[string]time.Time{}
+			}
+			g.Applied[n] = at
+		}
+	}
+	g.Passes, g.Faulted, g.HealthySeen, g.Last = from.Passes, from.Faulted, from.HealthySeen, from.Last
+	if from.LastPass != nil {
+		at := *from.LastPass
+		g.LastPass = &at
+	}
+	for _, m := range modules {
+		if n, counted := from.Healthy[m]; counted {
+			if g.Healthy == nil {
+				g.Healthy = map[string]int{}
+			}
+			g.Healthy[m] = n
+		}
+		if at, counted := from.HealthyAt[m]; counted {
+			if g.HealthyAt == nil {
+				g.HealthyAt = map[string]time.Time{}
+			}
+			g.HealthyAt[m] = at
+		}
+	}
+	g.Readings = append([]GateReading(nil), from.Readings...)
+	g.TookOver = id
 }
 
 // GateBusy is a first-node gate's wait for a busy container (novox/hq ADR 0335 §4).
@@ -477,9 +537,17 @@ type CarriedMove struct {
 type PlanRelease struct {
 	Order []string `json:"order"`
 	Next  int      `json:"next"`
-	// Gate is the machine being judged; nil between machines.
+	// Gate is the first machine being judged; nil between machines.
 	Gate *PlanGate `json:"gate,omitempty"`
-	Done []string  `json:"done,omitempty"`
+	// Rest says the first machine passed (novox/hq ADR 0353 §1): every other machine is sent at once, each judged by
+	// its own gate in Gates, by machine — a build no gate passed going to one machine of a step only (§2).
+	Rest  bool                 `json:"rest,omitempty"`
+	Gates map[string]*PlanGate `json:"gates,omitempty"`
+	// Failed are the machines of the rest whose gate failed, and Silent those that said nothing on their send
+	// within ApplySilentAfter (ADR 0353 §3 and §4).
+	Failed []string `json:"failed,omitempty"`
+	Silent []string `json:"silent,omitempty"`
+	Done   []string `json:"done,omitempty"`
 	// Skipped are the machines not heard from when their turn came, left as they were.
 	Skipped []string `json:"skipped,omitempty"`
 	// By is the person who released it, empty when the mesh did.
diff --git a/internal/link/build.go b/internal/link/build.go
index 6eb16588..73384e9f 100644
--- a/internal/link/build.go
+++ b/internal/link/build.go
@@ -164,6 +164,30 @@ type CheckRequest struct {
 	// each, from the merge it judged, into the scratch namespace once it has judged and not failed, for the walk to
 	// take. A build seat from before it builds nothing, and the walk builds as before.
 	Builds []CheckBuild `json:"builds,omitempty"`
+	// Try marks a branch tried before its pull request (novox/hq issue 686): the repository's own check for a
+	// pushed branch or commit, asked by a builder through the controller's `try` verb. Its outcome is read from
+	// the build's log (StepTried) and said to nobody: no status on the forge, nothing recorded or registered,
+	// nothing built for a merge. Tests narrows what the repository's script runs to the tests a pattern names,
+	// and StoreOnly to its store tests; a script that reads neither runs whole.
+	Try       bool   `json:"try,omitempty"`
+	Tests     string `json:"tests,omitempty"`
+	StoreOnly bool   `json:"store-only,omitempty"`
+}
+
+// StepTried is the step a build seat says a try's outcome under, in the build's log: one line, a Tried as JSON
+// (novox/hq issue 686).
+const StepTried = "tried"
+
+// Tried is what came of a branch tried before its pull request (novox/hq issue 686): the verdict of the
+// repository's own check for the ref merged into the trunk, how long it took, and the lines that name what
+// failed, picked from the whole of its output (issue 460).
+type Tried struct {
+	Verdict string   `json:"verdict"`
+	Summary string   `json:"summary"`
+	Took    string   `json:"took"`
+	Head    string   `json:"head,omitempty"`
+	Trunk   string   `json:"trunk,omitempty"`
+	Failed  []string `json:"failed,omitempty"`
 }
 
 // CheckBuild is one module a check builds for its merge: from the merge it made when Merged — a module built from
diff --git a/internal/link/builds.go b/internal/link/builds.go
index 7fe20541..f372d056 100644
--- a/internal/link/builds.go
+++ b/internal/link/builds.go
@@ -96,8 +96,27 @@ type BuildStart struct {
 	// an earlier taker left unfinished — most often a build agent replaced mid-build — and started
 	// again from the beginning (novox/hq issue 594). 0 from a machine that predates it.
 	Delivery int `json:"delivery,omitempty"`
+	// Try marks the start of a branch tried before its pull request (novox/hq issue 686), which names no
+	// repository and no ref (startOf).
+	Try bool `json:"try,omitempty"`
 }
 
+// startOf is what a build machine says of the ask it took. **A try's start names no repository and no commit**
+// (novox/hq issue 686): the forge's holder writes mesh/merge-gate pending on an open pull request whose head is
+// the commit a start names, and a try of that head is no check of the pull request — nothing on the forge moves
+// for a try. Its id, machine and time are all the queue reads of a start.
+func startOf(r BuildRequest, on string, delivery int, at time.Time) BuildStart {
+	s := BuildStart{ID: r.ID, Repository: r.Repository, Path: r.Path, Ref: r.Ref, On: on,
+		At: at.UTC().Format(time.RFC3339Nano), Delivery: delivery}
+	if IsTry(r) {
+		s.Repository, s.Path, s.Ref, s.Try = "", "", "", true
+	}
+	return s
+}
+
+// IsTry says an ask is a branch tried before its pull request (novox/hq issue 686).
+func IsTry(r BuildRequest) bool { return r.Check != nil && r.Check.Try }
+
 // Restarted is how a build handed out again says so (novox/hq issue 594), in its log and in its check's
 // report, so a second run never reads as the first. Neutral on why: a holder replaced mid-build, a paused
 // holder handing an ask back as it arrived, and a bus that held its acknowledgements past the wait all
diff --git a/internal/link/builds_nats.go b/internal/link/builds_nats.go
index c7d0c67e..5ec3b9c1 100644
--- a/internal/link/builds_nats.go
+++ b/internal/link/builds_nats.go
@@ -401,10 +401,7 @@ func (b *natsBuild) Done() error { return b.msg.Ack() }
 // Began publishes that this machine has taken the build, into the stream like the outcome, so a
 // reader that asks afterwards sees when it started as well as how it ended.
 func (b *natsBuild) Began(ctx context.Context) error {
-	body, err := json.Marshal(BuildStart{
-		ID: b.request.ID, Repository: b.request.Repository, Path: b.request.Path,
-		Ref: b.request.Ref, On: b.on, At: time.Now().UTC().Format(time.RFC3339Nano), Delivery: b.delivery,
-	})
+	body, err := json.Marshal(startOf(b.request, b.on, b.delivery, time.Now()))
 	if err != nil {
 		return err
 	}
diff --git a/internal/link/queue.go b/internal/link/queue.go
index 50865ef8..3bbbb8a2 100644
--- a/internal/link/queue.go
+++ b/internal/link/queue.go
@@ -427,6 +427,9 @@ func ReadCheckBuilds(ctx context.Context, js *broker.JetStream, seat string, pul
 // safeKey is an id that can be a key, and a subject token, as it is: a build id, never a pattern.
 var safeKey = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)
 
+// SafeBuildID says an id can be a subject token as it is: a build's id, never a pattern.
+func SafeBuildID(id string) bool { return safeKey.MatchString(id) }
+
 // Cancelled is what the controller writes for an ask it cancelled.
 type Cancelled struct {
 	At  string `json:"at"`
diff --git a/internal/link/queue_order.go b/internal/link/queue_order.go
index 449618f9..90e68f50 100644
--- a/internal/link/queue_order.go
+++ b/internal/link/queue_order.go
@@ -26,6 +26,8 @@ import (
 //   - a check that has waited CheckWaitsAtMost goes before every delivery asked after it, so no check
 //     waits for ever behind a stream of deliveries;
 //   - within a kind, first come, first served, by when it was asked;
+//   - a branch tried before its pull request goes after everything else, however long it has waited: it is
+//     never promoted ahead of a delivery, and never ahead of a pull request's check (novox/hq issue 686);
 //   - an ask whose kind cannot be told counts as a check: a delivery taken late breaks a budget, a check
 //     taken late breaks nothing.
 //
@@ -64,8 +66,12 @@ func (a QueuedAsk) askedOrStored() time.Time {
 // QueueOrder is the order the waiting asks are to be handed out in, now: the deliveries and every check
 // that has waited CheckWaitsAtMost, by when each was asked, then the other checks, by when each was asked.
 func QueueOrder(waiting []QueuedAsk, now time.Time) []QueuedAsk {
-	var first, then []QueuedAsk
+	var first, then, tries []QueuedAsk
 	for _, a := range waiting {
+		if IsTry(a.Request) {
+			tries = append(tries, a)
+			continue
+		}
 		if KindOf(a.Request) == KindCheck && now.Sub(a.askedOrStored()) < CheckWaitsAtMost {
 			then = append(then, a)
 			continue
@@ -82,7 +88,8 @@ func QueueOrder(waiting []QueuedAsk, now time.Time) []QueuedAsk {
 	}
 	byAsking(first)
 	byAsking(then)
-	return append(first, then...)
+	byAsking(tries)
+	return append(append(first, then...), tries...)
 }
 
 // toMove is the asks to move to the tail, in this order, for the queue to stand as order says: everything
diff --git a/internal/link/try_test.go b/internal/link/try_test.go
new file mode 100644
index 00000000..f434dc18
--- /dev/null
+++ b/internal/link/try_test.go
@@ -0,0 +1,55 @@
+package link
+
+import (
+	"encoding/json"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+// The start of a try names no repository and no commit (novox/hq issue 686): the forge's holder writes
+// mesh/merge-gate pending on the open pull request whose head a start names, and nothing on the forge moves
+// for a try. A pull request's check still names both.
+func TestATrysStartNamesNoCommitTheForgeCouldMatch(t *testing.T) {
+	sha := strings.Repeat("c0ffee", 7)[:40]
+	at := time.Date(2026, 10, 14, 0, 0, 0, 0, time.UTC)
+	try := BuildRequest{ID: "build-1", Repository: "https://forge/novox/a.git", Ref: sha,
+		Check: &CheckRequest{Owner: "novox", Repo: "a", Try: true}}
+	body, _ := json.Marshal(startOf(try, "ace", 1, at))
+	if strings.Contains(string(body), sha) || strings.Contains(string(body), "novox/a") {
+		t.Fatalf("a try's start names what the forge matches a pull request by: %s", body)
+	}
+	if s := startOf(try, "ace", 2, at); s.ID != "build-1" || s.On != "ace" || !s.Try || s.Delivery != 2 || s.At == "" {
+		t.Fatalf("a try's start lost what the queue reads: %+v", s)
+	}
+	pull := try
+	pull.Check = &CheckRequest{Owner: "novox", Repo: "a", Number: 7}
+	if s := startOf(pull, "ace", 1, at); s.Ref != sha || s.Repository == "" || s.Try {
+		t.Fatalf("a pull request's check's start: %+v", s)
+	}
+}
+
+// A try stays behind every delivery and every pull request's check, however long it has waited: the ten
+// minutes that put a check ahead of later deliveries never promote a try (novox/hq issue 686).
+func TestATryIsNeverHandedOutBeforeADeliveryOrAPullRequestsCheck(t *testing.T) {
+	now := time.Date(2026, 10, 12, 12, 0, 0, 0, time.UTC)
+	try := func(seq uint64, id string, asked time.Time) QueuedAsk {
+		a := anAsk(seq, id, asked, true)
+		a.Request.Check.Try = true
+		return a
+	}
+	waiting := []QueuedAsk{
+		try(1, "try-old", now.Add(-40*time.Minute)),
+		try(2, "try-young", now.Add(-time.Minute)),
+		anAsk(3, "check-young", now.Add(-2*time.Minute), true),
+		anAsk(4, "delivery", now.Add(-time.Minute), false),
+	}
+	want := []string{"delivery", "check-young", "try-old", "try-young"}
+	if got := idsOf(QueueOrder(waiting, now)); !reflect.DeepEqual(got, want) {
+		t.Fatalf("handed out as %v, want %v", got, want)
+	}
+	if !SafeBuildID("build-20261014T000000-1a2b") || SafeBuildID("x.>") || SafeBuildID("*") || SafeBuildID("") {
+		t.Fatal("an id that is a pattern passes for a build's id")
+	}
+}
diff --git a/merge-check.sh b/merge-check.sh
index e1e85687..36de3711 100755
--- a/merge-check.sh
+++ b/merge-check.sh
@@ -54,11 +54,26 @@ if [ -n "$unformatted" ]; then
 fi
 CGO_ENABLED=0 go vet ./...
 
-if command -v gcc >/dev/null 2>&1; then
-	CGO_ENABLED=1 go test -race -count=1 -timeout 30m ./...
+suite() {
+	if command -v gcc >/dev/null 2>&1; then
+		CGO_ENABLED=1 go test -race -count=1 -timeout 30m "$@"
+	else
+		echo "NOT RACE-CHECKED: the toolchain holds no C compiler; the suite runs without the race detector"
+		CGO_ENABLED=0 go test -count=1 -timeout 30m "$@"
+	fi
+}
+# **A branch tried before its pull request may ask for a part** (novox/hq issue 686): the controller's `try` verb
+# hands MESH_CHECK_TESTS, a `go test -run` pattern, or MESH_CHECK_STORE_ONLY=1. A pull request's merge check is
+# handed neither and always runs whole; a part that passes is said as a part, never as the check.
+if [ -n "${MESH_CHECK_TESTS:-}" ]; then
+	echo "TRIED IN PART: only the tests matching $MESH_CHECK_TESTS, in every package"
+	suite -run "$MESH_CHECK_TESTS" ./...
+	exit 0
+fi
+if [ "${MESH_CHECK_STORE_ONLY:-}" = 1 ]; then
+	echo "TRIED IN PART: only the store tests listed in testdata/store-tests"
 else
-	echo "NOT RACE-CHECKED: the toolchain holds no C compiler; the suite runs without the race detector"
-	CGO_ENABLED=0 go test -count=1 -timeout 30m ./...
+	suite ./...
 fi
 
 # **The store tests listed ran** (novox/hq issue 459): a test that needs the store skips without one, and a skip
diff --git a/module.json b/module.json
index 1b84a8c4..538f5cca 100644
--- a/module.json
+++ b/module.json
@@ -77,6 +77,7 @@
     "replay",
     "kill",
     "forget-checks",
+    "try",
     "pause",
     "resume",
     "hand-act",
diff --git a/testdata/store-tests b/testdata/store-tests
index d3af9659..62ca1239 100644
--- a/testdata/store-tests
+++ b/testdata/store-tests
@@ -64,3 +64,14 @@
 ./internal/inventory TestPlacementMovesOutOfTheSettingsLayers
 ./internal/inventory TestASettingRoutesPlacementBesideTheLayer
 ./cmd/mesh-controller TestADeclarationIsTheSameAfterPlacementMoves
+./cmd/mesh-controller TestAReleaseSendsTheRestAtOnceAfterTheFirstPasses
+./cmd/mesh-controller TestARestMachineThatFailsIsPutBackAloneAndTheOthersAreJudgedOn
+./cmd/mesh-controller TestAWalkTakesOverTheReadingsOfAGateJudgingTheSameBuildThere
+./cmd/mesh-controller TestAFirstSendMadeAndNotKeptIsNotSentAgain
+./cmd/mesh-controller TestAReleaseSendKeptAndMadeIsNotMadeAgain
+./cmd/mesh-controller TestAFirstMachineThatFailsStillStopsTheWalk
+./cmd/mesh-controller TestTheControlNodeIsSentLastInAStep
+./cmd/mesh-controller TestARestMachineSilentPastItsBoundIsLeftAndSaid
+./cmd/mesh-controller TestANoMoveTierWaitsForNoNewReport
+./cmd/mesh-controller TestOneProviderDownAndThreeConsumersFailingAreOneCondition
+./cmd/mesh-controller TestAConsumerFailingBesideAHealthyProviderIsItsOwn