diff --git a/modules/mesh-build-node/.gitignore b/modules/mesh-build-node/.gitignore
index f7604aaaa..ce26533a5 100644
--- a/modules/mesh-build-node/.gitignore
+++ b/modules/mesh-build-node/.gitignore
@@ -1 +1,3 @@
-mesh-build-node
+# the binary, built at the module or in its command directory; never the command directory itself
+/mesh-build-node
+/cmd/mesh-build-node/mesh-build-node
diff --git a/modules/mesh-build-node/cmd/mesh-build-node/build.go b/modules/mesh-build-node/cmd/mesh-build-node/build.go
index 4627c2c7a..086bd7c01 100644
--- a/modules/mesh-build-node/cmd/mesh-build-node/build.go
+++ b/modules/mesh-build-node/cmd/mesh-build-node/build.go
@@ -13,6 +13,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -37,6 +38,27 @@ type artifact struct {
 	Language    string   `json:"language"`
 	Entrypoints []string `json:"entrypoints"`
 	External    []string `json:"external"`
+	// Paths are the directories of a package artifact, relative to the module's: one, holding its package.json and
+	// its package-lock.json (as a Go package's, mesh-build-go gopackage.go); none means the module's directory.
+	Paths []string `json:"paths"`
+}
+
+// packageDir is the directory of a package artifact relative to its module's directory in dir: the one path it names
+// when that is a directory of the module holding a package.json (the contracts folders: ts/seats/<seat>/, each with its
+// own lock, ADR 0634 section 8), else the module's directory itself (a package that names no path, or source paths
+// beside the module's package.json: today's form).
+func (a artifact) packageDir(dir string) string {
+	if len(a.Paths) != 1 {
+		return "."
+	}
+	p := path.Clean(strings.TrimSuffix(a.Paths[0], "/"))
+	if p == "." || path.IsAbs(p) || p == ".." || strings.HasPrefix(p, "../") {
+		return "."
+	}
+	if _, err := os.Stat(filepath.Join(dir, filepath.FromSlash(p), "package.json")); err != nil {
+		return "."
+	}
+	return p
 }
 
 // BuildResult is what a passed build step says.
@@ -88,7 +110,8 @@ func (m *Module) build(ctx context.Context, args map[string]any) (any, error) {
 		return nil, err
 	}
 	if a.Kind == "package" {
-		return m.buildPackage(ctx, workspace, module, root, dir, a, publish)
+		at := a.packageDir(dir)
+		return m.buildPackage(ctx, workspace, module, root, filepath.Join(dir, filepath.FromSlash(at)), at, a, publish)
 	}
 	if why, err := lockProblem(dir, module); err != nil || why != "" {
 		if err == nil {
diff --git a/modules/mesh-build-node/cmd/mesh-build-node/check.go b/modules/mesh-build-node/cmd/mesh-build-node/check.go
index 651688ac4..cda4b1ca5 100644
--- a/modules/mesh-build-node/cmd/mesh-build-node/check.go
+++ b/modules/mesh-build-node/cmd/mesh-build-node/check.go
@@ -16,6 +16,7 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 	"time"
@@ -99,78 +100,89 @@ func (m *Module) test(ctx context.Context, args map[string]any) (any, error) {
 	if err != nil {
 		return nil, err
 	}
-	scripts, err := packageScripts(dir)
-	if err != nil {
-		return nil, err
-	}
-	sources, err := typeScriptFiles(dir)
-	if err != nil {
-		return nil, err
-	}
 	res := &TestResult{Workspace: workspace, Module: module, Level: level, By: sdkstep.By("mesh-build-node")}
 	script := "test"
 	if level == "integration" {
 		script = "test:integration"
 	}
-	hasScript := scripts[script] != ""
-	if level == "integration" && !hasScript {
-		res.Passed, res.NoTests, res.Why = true, true, "no tests: the package has no test:integration script"
-		return res, nil
-	}
-	if !hasScript && len(sources) == 0 {
-		res.Passed, res.NoTests, res.Why = true, true, "no tests: the package has no test script and no .ts files"
-		return res, nil
-	}
-	if err := m.provide(root); err != nil {
-		return nil, fmt.Errorf("providing the toolchain's packages to the workspace: %w", err)
-	}
 	where := module
 	if where == "" {
 		where = "."
 	}
+	targets, err := testTargets(dir, where)
+	if err != nil {
+		return nil, err
+	}
 	var check, run time.Duration
 	var failed []Failure
-	// a command that could not start is not a verdict: the step fails. One that ran and said no is.
-	ran := func(name string, r forgekey.Ran, report string) error {
-		if r.Err != "" {
-			return fmt.Errorf("%s could not be run: status %d %s: %s", name, r.Status, r.Err, firstLine(r.Stderr))
-		}
-		if r.Status != 0 {
-			failed = append(failed, testFailures(where, name, dir, r, report)...)
-		}
-		return nil
-	}
-	if len(sources) > 0 {
-		// A package that builds (a build or prepare script, which the fetch's --ignore-scripts never runs) is emitted
-		// by tsc into the workspace, shut off like every run step, so its tests find what they import of its own output
-		// (issue 1869: mesh-sdk's tests import ../dist); any other is type-checked without emitting.
-		name, line := "type-check", m.typeCheck(dir, sources)
-		if emit := m.emitBuild(dir, scripts); emit != nil {
-			name, line = "build", emit
-		}
-		start := m.now()
-		r := m.runIn(ctx, root, false, dir, nil, "node", line...)
-		check = m.now().Sub(start)
-		if err := ran(name, r, ""); err != nil {
+	tested := false
+	for _, tg := range targets {
+		scripts, err := packageScripts(tg.dir)
+		if err != nil {
 			return nil, err
 		}
-		res.Ran = append(res.Ran, name)
-	}
-	if hasScript && len(failed) == 0 {
-		start := m.now()
-		// node --test writes its TAP report to a file of the workspace (issue 1901), whatever the script prints itself
-		report := filepath.Join(root, ".mesh-node-test-"+level+".tap")
-		_ = os.Remove(report)
-		env := []string{"PATH=" + binDir(root) + ":" + pathOrDefault(), "npm_config_cache=" + filepath.Join(m.Toolchain.Paths.Cache, "npm"),
-			"NODE_OPTIONS=" + buildstep.NodeTestOptions(report)}
-		r := m.runIn(ctx, root, false, dir, env, "npm", scriptArgs(script)...)
-		run = m.now().Sub(start)
-		tap, _ := os.ReadFile(report)
-		_ = os.Remove(report)
-		if err := ran(script, r, string(tap)); err != nil {
+		sources, err := typeScriptFiles(tg.dir)
+		if err != nil {
 			return nil, err
 		}
-		res.Ran = append(res.Ran, script)
+		hasScript := scripts[script] != ""
+		if (level == "integration" && !hasScript) || (!hasScript && len(sources) == 0) {
+			continue
+		}
+		tested = true
+		if err := m.provide(root); err != nil {
+			return nil, fmt.Errorf("providing the toolchain's packages to the workspace: %w", err)
+		}
+		// a command that could not start is not a verdict: the step fails. One that ran and said no is.
+		ran := func(name string, r forgekey.Ran, report string) error {
+			if r.Err != "" {
+				return fmt.Errorf("%s could not be run: status %d %s: %s", name, r.Status, r.Err, firstLine(r.Stderr))
+			}
+			if r.Status != 0 {
+				failed = append(failed, testFailures(tg.where, name, tg.dir, r, report)...)
+			}
+			return nil
+		}
+		if len(sources) > 0 {
+			// A package that builds (a build or prepare script, which the fetch's --ignore-scripts never runs) is emitted
+			// by tsc into the workspace, shut off like every run step, so its tests find what they import of its own output
+			// (issue 1869: mesh-sdk's tests import ../dist); any other is type-checked without emitting.
+			name, line := "type-check", m.typeCheck(tg.dir, sources)
+			if emit := m.emitBuild(tg.dir, scripts); emit != nil {
+				name, line = "build", emit
+			}
+			start := m.now()
+			r := m.runIn(ctx, root, false, tg.dir, nil, "node", line...)
+			check += m.now().Sub(start)
+			if err := ran(name, r, ""); err != nil {
+				return nil, err
+			}
+			res.Ran = appendOnce(res.Ran, name)
+		}
+		if hasScript && len(failed) == 0 {
+			start := m.now()
+			// node --test writes its TAP report to a file of the workspace (issue 1901), whatever the script prints itself
+			report := filepath.Join(root, ".mesh-node-test-"+level+".tap")
+			_ = os.Remove(report)
+			env := []string{"PATH=" + binDir(root) + ":" + pathOrDefault(), "npm_config_cache=" + filepath.Join(m.Toolchain.Paths.Cache, "npm"),
+				"NODE_OPTIONS=" + buildstep.NodeTestOptions(report)}
+			r := m.runIn(ctx, root, false, tg.dir, env, "npm", scriptArgs(script)...)
+			run += m.now().Sub(start)
+			tap, _ := os.ReadFile(report)
+			_ = os.Remove(report)
+			if err := ran(script, r, string(tap)); err != nil {
+				return nil, err
+			}
+			res.Ran = appendOnce(res.Ran, script)
+		}
+	}
+	if !tested {
+		res.Passed, res.NoTests = true, true
+		res.Why = "no tests: the package has no test script and no .ts files"
+		if level == "integration" {
+			res.Why = "no tests: the package has no test:integration script"
+		}
+		return res, nil
 	}
 	res.Failed = failed
 	var why []string
@@ -294,3 +306,56 @@ func typeScriptFiles(dir string) ([]string, error) {
 	})
 	return out, err
 }
+
+// testTarget is a directory whose tests a level runs, and the name it is reported under.
+type testTarget struct{ dir, where string }
+
+// testTargets are the directories a module's tests run in: each TypeScript package artifact's own path when every
+// package the module declares names one (ADR 0634 §8: its package.json, its lock, its tests), else the module's
+// directory.
+func testTargets(dir, where string) ([]testTarget, error) {
+	whole := []testTarget{{dir, where}}
+	raw, err := os.ReadFile(filepath.Join(dir, "module.json"))
+	if err != nil {
+		return whole, nil
+	}
+	var mj struct {
+		Build struct {
+			Artifacts []artifact `json:"artifacts"`
+		} `json:"build"`
+	}
+	if json.Unmarshal(raw, &mj) != nil {
+		return whole, nil
+	}
+	var out []testTarget
+	seen := map[string]bool{}
+	for _, a := range mj.Build.Artifacts {
+		if a.Language != "typescript" {
+			continue
+		}
+		if a.Kind != "package" {
+			return whole, nil // a bundle is tested in its module's directory
+		}
+		at := a.packageDir(dir)
+		if at == "." {
+			return whole, nil
+		}
+		if !seen[at] {
+			seen[at] = true
+			out = append(out, testTarget{filepath.Join(dir, filepath.FromSlash(at)), path.Join(where, at)})
+		}
+	}
+	if len(out) == 0 {
+		return whole, nil
+	}
+	return out, nil
+}
+
+func appendOnce(list []string, s string) []string {
+	for _, x := range list {
+		if x == s {
+			return list
+		}
+	}
+	return append(list, s)
+}
diff --git a/modules/mesh-build-node/cmd/mesh-build-node/fetch.go b/modules/mesh-build-node/cmd/mesh-build-node/fetch.go
index e758fab70..bd6343ecd 100644
--- a/modules/mesh-build-node/cmd/mesh-build-node/fetch.go
+++ b/modules/mesh-build-node/cmd/mesh-build-node/fetch.go
@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -210,8 +211,8 @@ func (m *Module) fetchInto(ctx context.Context, req sdkstep.FetchRequest, group
 	return res, nil
 }
 
-// typeScriptModules are the directories of the tree whose module.json declares a typescript artifact, relative to
-// it, in order.
+// typeScriptModules are the directories of the tree that a typescript artifact of a module.json is built in, relative to
+// it, in order: the module's directory for a bundle, the artifact's path for a package.
 func (m *Module) typeScriptModules(ctx context.Context, tree string) (dirs []string, packages map[string]bool, err error) {
 	r := m.Run(ctx, m.baseEnv(), "git", "-C", tree, "ls-files", "--", "module.json", "*/module.json")
 	if r.Status != 0 || r.Err != "" {
@@ -237,13 +238,21 @@ func (m *Module) typeScriptModules(ctx context.Context, tree string) (dirs []str
 		if json.Unmarshal(raw, &mj) != nil {
 			continue // a module.json the build step will refuse by name, not a fetch's business
 		}
+		// A bundle is built in its module's directory, a package in its own path (ADR 0634 §8: as at a repository's
+		// root, each package with its own lock); the first artifact to claim a directory decides it.
 		for _, a := range mj.Build.Artifacts {
-			if a.Language == "typescript" {
-				d := filepath.ToSlash(filepath.Dir(l))
-				dirs = append(dirs, d)
-				packages[d] = a.Kind == "package"
-				break
+			if a.Language != "typescript" {
+				continue
 			}
+			d := filepath.ToSlash(filepath.Dir(l))
+			if a.Kind == "package" {
+				d = path.Join(d, a.packageDir(filepath.Join(tree, filepath.FromSlash(d))))
+			}
+			if _, seen := packages[d]; seen {
+				continue
+			}
+			dirs = append(dirs, d)
+			packages[d] = a.Kind == "package"
 		}
 	}
 	sort.Strings(dirs)
diff --git a/modules/mesh-build-node/cmd/mesh-build-node/package.go b/modules/mesh-build-node/cmd/mesh-build-node/package.go
index 0663f180a..713d76c6c 100644
--- a/modules/mesh-build-node/cmd/mesh-build-node/package.go
+++ b/modules/mesh-build-node/cmd/mesh-build-node/package.go
@@ -469,11 +469,13 @@ func fetchCommit(ctx context.Context, run forgekey.Runner, dir, remote, commit,
 // (publish) publishes it, from this module's own process with the registry's write credential, which no run step is
 // given: a version the registry lacks is published; the same packed file already there is done without a publish;
 // another packed file under that version fails `version taken:`. The reference is <name>@<version>, answered only when
-// the registry holds this build's file; a candidate answers its digest alone.
-func (m *Module) buildPackage(ctx context.Context, workspace, module, root, dir string, a artifact, publish bool) (any, error) {
-	rel := module
-	if rel == "" {
-		rel = "."
+// the registry holds this build's file; a candidate answers its digest alone. dir is the package's directory, at its
+// place in the module's.
+func (m *Module) buildPackage(ctx context.Context, workspace, module, root, dir, at string, a artifact, publish bool) (any, error) {
+	// rel is the package's directory in the workspace, as the fetch installed it (the shims lie under it).
+	rel := path.Join(module, at)
+	if module == "" {
+		rel = path.Join(".", at)
 	}
 	p, err := m.buildAndPack(ctx, root, dir, rel, publish)
 	if err != nil {
diff --git a/modules/mesh-build-node/cmd/mesh-build-node/package_paths_test.go b/modules/mesh-build-node/cmd/mesh-build-node/package_paths_test.go
new file mode 100644
index 000000000..98dd5f781
--- /dev/null
+++ b/modules/mesh-build-node/cmd/mesh-build-node/package_paths_test.go
@@ -0,0 +1,93 @@
+package main
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// A folder module (mesh-contracts' root, a domain folder) declares several package artifacts, each at its own path
+// with its own package.json and package-lock.json and none at the module's directory (ADR 0634 section 8).
+const folderManifest = `{"module":"c","build":{"artifacts":[` +
+	`{"name":"ts-a","kind":"package","language":"typescript","paths":["ts/seats/a"]},` +
+	`{"name":"ts-b","kind":"package","language":"typescript","paths":["ts/seats/b/"]}]}}`
+
+func folderFiles(prefix string) map[string]string {
+	files := map[string]string{prefix + "module.json": folderManifest}
+	for _, s := range []string{"a", "b"} {
+		files[prefix+"ts/seats/"+s+"/package.json"] = `{"name":"@x/` + s + `","version":"0.1.0","scripts":{"build":"tsc","test":"node --test"}}`
+		files[prefix+"ts/seats/"+s+"/package-lock.json"] = `{"lockfileVersion":3}`
+		files[prefix+"ts/seats/"+s+"/index.ts"] = "export const v = 1;\n"
+	}
+	return files
+}
+
+// The fetch installs each package artifact at its path from the lock there, and finds no lock missing at the module.
+func TestAFolderModulesPackagesAreInstalledEachAtItsPath(t *testing.T) {
+	m, f := fetchMachine(t, folderFiles("modules/c/"), nil)
+	out, err := m.fetch(context.Background(), fetchArgs)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := out.(FetchResult)
+	if len(r.Modules) != 2 || r.Modules[0] != "modules/c/ts/seats/a" || r.Modules[1] != "modules/c/ts/seats/b" || len(r.Installed) != 2 {
+		t.Errorf("result = %+v, want both package directories found and installed", r)
+	}
+	var prefixes []string
+	for _, c := range npmCalls(f) {
+		for i, a := range c.args {
+			if a == "--prefix" {
+				prefixes = append(prefixes, strings.TrimPrefix(c.args[i+1], filepath.Join(m.Work, r.Workspace, "tree")))
+			}
+		}
+	}
+	if len(prefixes) != 2 || prefixes[0] != "/modules/c/ts/seats/a" || prefixes[1] != "/modules/c/ts/seats/b" {
+		t.Errorf("npm ci ran with --prefix %v, want each package's own directory", prefixes)
+	}
+}
+
+// The build runs the package's script and pack in its own path, and the test level runs in each path.
+func TestAFolderModulesPackageIsBuiltAndTestedInItsPath(t *testing.T) {
+	m, f, work := newMachine(t)
+	workspaceWith(t, work, folderFiles(""))
+	f.effect = func(c call) {
+		if c.name == "npm" && len(c.args) > 0 && c.args[0] == "pack" {
+			for i, a := range c.args {
+				if a == "--pack-destination" {
+					write(t, filepath.Join(c.args[i+1], "x.tgz"), "packed", 0o644)
+				}
+			}
+		}
+	}
+	if _, err := m.build(context.Background(), map[string]any{"workspace": "w1", "module": ".", "artifact": "ts-b"}); err != nil {
+		t.Fatal(err)
+	}
+	want := filepath.Join(work, "w1", "tree", "ts", "seats", "b")
+	built := 0
+	for _, c := range f.calls {
+		if c.name == "npm" {
+			built++
+			if c.dir != want {
+				t.Errorf("%s ran in %s, want %s", joined(c), c.dir, want)
+			}
+		}
+	}
+	if built != 2 {
+		t.Errorf("%d npm commands, want the build and the pack", built)
+	}
+	f.calls = nil
+	res, err := m.test(context.Background(), testArgs("unit"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	tests := map[string]bool{}
+	for _, c := range f.calls {
+		if c.name == "npm" {
+			tests[c.dir] = true
+		}
+	}
+	if r := res.(*TestResult); !r.Passed || len(tests) != 2 || !tests[want] || !tests[filepath.Join(work, "w1", "tree", "ts", "seats", "a")] {
+		t.Errorf("unit level = %+v, ran tests in %v, want both package paths", r, tests)
+	}
+}