diff --git a/.gds/bundle.lock.yaml b/.gds/bundle.lock.yaml
index 9d6b1a1..4205530 100644
--- a/.gds/bundle.lock.yaml
+++ b/.gds/bundle.lock.yaml
@@ -4,14 +4,14 @@ schema_version: 1
 bundle:
   version: "0.9.7-dev"
   release_sequence: 0
-  source_tree_digest: "sha256:c8582e4ff6726dc451444553411d81bf681dbcb03db409987de1db35c016f723"
-  digest: "sha256:f8b44694166c4358ee247362f0d3ec725c421bc681018ad8bea526250440b16b"
+  source_tree_digest: "sha256:4c7e5f20f939b7c78e0d3432c61d62f0b01d7fade56621491da307d656463448"
+  digest: "sha256:3b2e0e5abf1515b37407f609e7e35034136c5acea5ad46f37c67aac17f3ed93a"
 
 projection:
-  input_digest: "sha256:033f6d802a41abddbad4bb0375ca2ad899c2c5651409c3e9541b229179a4248c"
-  output_digest: "sha256:3ff85f46591c1c6d1479bb305adf866d64537f94345fac5185acba78b0738a6f"
+  input_digest: "sha256:924e25d3b7a56d3966975e735ec39f9eec2bca3420b0d4ee6af6e6e07d5191e0"
+  output_digest: "sha256:91c917a3497b68e1c5d6ab372a072a43f0e34f4815511b341357e5b0721b04aa"
   files:
     - path: ".gds/compiled-policy.json"
       digest: "sha256:9f498788bdc34e52a0ab793c536e0e6a7b360c2e1a20446cbf03ed51986cdc6f"
     - path: ".github/workflows/gds-ci.yml"
-      digest: "sha256:387375f2ea62d4971ae8051ad1d13aa3c0d42ef9e7695a6df40d636808cc06d6"
+      digest: "sha256:4f263ba0c7c0e71d2eaeacca25f1fbdaa43cac912d12a178b00dee26c051f932"
diff --git a/.github/workflows/gds-ci.yml b/.github/workflows/gds-ci.yml
index c5bf77b..5269820 100644
--- a/.github/workflows/gds-ci.yml
+++ b/.github/workflows/gds-ci.yml
@@ -1,8 +1,8 @@
 # GENERATED FILE - DO NOT EDIT DIRECTLY
 # generator: gds
 # bundle: 0.9.7-dev
-# source-tree-digest: sha256:c8582e4ff6726dc451444553411d81bf681dbcb03db409987de1db35c016f723
-# input-digest: sha256:033f6d802a41abddbad4bb0375ca2ad899c2c5651409c3e9541b229179a4248c
+# source-tree-digest: sha256:4c7e5f20f939b7c78e0d3432c61d62f0b01d7fade56621491da307d656463448
+# input-digest: sha256:924e25d3b7a56d3966975e735ec39f9eec2bca3420b0d4ee6af6e6e07d5191e0
 # output-digest: sha256:4ef1ee2fcc42927eaedef9c85f7b421f87e5cc75ff7055ef520216a00f7d4b74
 # edit-source:
 #   - .gds/repository.yaml
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c9b47b4..8833c57 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ Versioning.
 
 ## [Unreleased]
 
+- Resolve read-only harness detection, rendering, inspection, evaluation and
+  device reconciliation against the consumed engine module in external estates;
+  preserve estate-relative input paths and explicit mutation targets.
+
 - Observe installed Devin CLI as the eighth catalogue identity while retaining
   seven verified execution adapters. Bind per-mapping runtime evidence policy
   and refuse unproven Devin configuration projections or runtime-proof claims.
diff --git a/core/app/harness_adapter.go b/core/app/harness_adapter.go
index 9c813e5..652ccd0 100644
--- a/core/app/harness_adapter.go
+++ b/core/app/harness_adapter.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/NDDev-OpenNetwork/github-device-sync/core/domain"
 	"github.com/NDDev-OpenNetwork/github-device-sync/core/harness"
+	"github.com/NDDev-OpenNetwork/github-device-sync/core/projections"
 )
 
 func (services *Services) RenderHarnessAdapter(
@@ -155,8 +156,9 @@ func (services *Services) EvaluateHarnessAdapter(
 	}
 	options.RuntimeDriver = normalizePath(options.RuntimeDriver)
 	options.EvidenceDirectory = normalizePath(options.EvidenceDirectory)
+	engineRoot := projections.ResolveDevelopmentSourceLayout(info.WorktreeRoot).EngineRoot
 	run, findings := harness.Evaluate(
-		ctx, info.WorktreeRoot, harnessID, options, services.Schemas, services.Now(), nil,
+		ctx, engineRoot, harnessID, options, services.Schemas, services.Now(), nil,
 	)
 	exitClass := domain.ExitSuccess
 	if run.Result == "not-proven" {
@@ -192,7 +194,8 @@ func (services *Services) resolveHarnessAdapter(
 		envelope := envelopeForError(command, path, err)
 		return nil, &envelope
 	}
-	adapter, findings := harness.NewAdapter(info.WorktreeRoot, harnessID, services.Schemas)
+	engineRoot := projections.ResolveDevelopmentSourceLayout(info.WorktreeRoot).EngineRoot
+	adapter, findings := harness.NewAdapter(engineRoot, harnessID, services.Schemas)
 	if len(findings) != 0 {
 		envelope := domain.NewEnvelope(command, classifyFindings(findings), nil, findings...)
 		return nil, &envelope
diff --git a/core/app/harness_external_estate_test.go b/core/app/harness_external_estate_test.go
new file mode 100644
index 0000000..2fd43b8
--- /dev/null
+++ b/core/app/harness_external_estate_test.go
@@ -0,0 +1,110 @@
+package app
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"github.com/NDDev-OpenNetwork/github-device-sync/core/domain"
+	"github.com/NDDev-OpenNetwork/github-device-sync/core/harness"
+)
+
+func TestHarnessObservationsUseConsumedEngineInExternalEstate(t *testing.T) {
+	_, current, _, _ := runtime.Caller(0)
+	source := filepath.Clean(filepath.Join(filepath.Dir(current), "..", ".."))
+	root := t.TempDir()
+	engine := filepath.Join(root, "modules", "github-device-sync")
+	for _, directory := range []string{"harnesses", "skills", "docs", "tests/harness"} {
+		if err := copyAppTestTree(source, engine, directory); err != nil {
+			t.Fatal(err)
+		}
+	}
+	runCompletionGraphGit(t, root, "init", "-q")
+	runCompletionGraphGit(t, root, "-c", "user.name=Fixture", "-c", "user.email=fixture@example.invalid",
+		"-c", "commit.gpgsign=false", "commit", "--allow-empty", "-qm", "fixture")
+	// An estate-local decoy must not replace the consumed catalogue.
+	if err := os.Mkdir(filepath.Join(root, "harnesses"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "harnesses", "capability-registry.yaml"), []byte("invalid: true\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	bin := t.TempDir()
+	for _, name := range []string{"agy", "claude", "codex", "cursor-agent", "devin", "grok", "opencode", "pi"} {
+		if err := os.WriteFile(filepath.Join(bin, name), []byte("#!/bin/sh\n[ \"$1\" = --version ] || exit 42\nprintf 'fixture 1.2.3\\n'\n"), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	t.Setenv("PATH", bin+string(os.PathListSeparator)+os.Getenv("PATH"))
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	services, err := NewServices(DefaultClock)
+	if err != nil {
+		t.Fatal(err)
+	}
+	request := harness.RenderRequest{SkillProfile: "core", Scope: "project"}
+	target := t.TempDir()
+	t.Run("detect-one-and-all", func(t *testing.T) {
+		one := services.DetectHarness(t.Context(), root, "devin")
+		if one.ExitClass != domain.ExitSuccess || one.Data.(harness.RuntimeObservation).Version != "fixture 1.2.3" {
+			t.Fatalf("external detection: %+v", one)
+		}
+		all := services.DetectHarness(t.Context(), root, "all")
+		if len(all.Data.(harness.RuntimeDetectionReport).Harnesses) != len(harness.CanonicalIDs) {
+			t.Fatalf("external catalogue not observed: %+v", all)
+		}
+	})
+	t.Run("render-inspect-and-doctor", func(t *testing.T) {
+		baseline, findings := harness.NewAdapter(source, "codex", services.Schemas)
+		if len(findings) != 0 {
+			t.Fatal(findings)
+		}
+		want, findings := baseline.Render(request)
+		if len(findings) != 0 {
+			t.Fatal(findings)
+		}
+		render := services.RenderHarnessAdapter(t.Context(), root, "codex", request)
+		if render.ExitClass != domain.ExitSuccess || render.Data.(harness.AdapterCandidate).CandidateDigest != want.CandidateDigest {
+			t.Fatalf("external rendering differs from canonical source: %+v", render)
+		}
+		inspect := services.InspectHarnessAdapter(t.Context(), root, "codex", target, request)
+		if inspect.ExitClass != domain.ExitSuccess || inspect.Data.(harness.AdapterInspection).CandidateDigest != want.CandidateDigest {
+			t.Fatalf("external inspection: %+v", inspect)
+		}
+		doctor := services.DoctorHarnessAdapter(t.Context(), root, "codex", target, request)
+		if doctor.Data == nil || doctor.Data.(harness.AdapterDoctorReport).Runtime.Version != "fixture 1.2.3" {
+			t.Fatalf("external doctor: %+v", doctor)
+		}
+	})
+	t.Run("installed-only-plan-remains-refused", func(t *testing.T) {
+		plan := services.PlanHarnessAdapter(t.Context(), root, "devin", target, request, "install")
+		if !appHasFinding(plan, "GDS_HARNESS_PROJECT_SKILLS_NOT_PROVEN") || plan.Mutation.Attempted {
+			t.Fatalf("unproven configuration was permitted: %+v", plan)
+		}
+	})
+	t.Run("evaluation-without-model-execution", func(t *testing.T) {
+		result := services.EvaluateHarnessAdapter(t.Context(), root, "codex", harness.EvalOptions{
+			SkillProfile: "core", ModelLabel: "not-proven", ExecutionProfile: "read-only",
+		})
+		run, ok := result.Data.(harness.EvalRun)
+		if !ok || run.Profile.ID != "codex" || appHasFinding(result, "GDS_INPUT_READ_FAILED") || result.Mutation.Attempted {
+			t.Fatalf("external evaluation did not resolve the consumed contract: %+v", result)
+		}
+	})
+	t.Run("device-reconciliation", func(t *testing.T) {
+		result := services.ReconcileDeviceHarnesses(t.Context(), HarnessSyncOptions{
+			Path: root, DevicePath: filepath.Join(source, "estate", "devices", "example-user-ubuntu-1.yaml"),
+			TargetRoot: target, SkillProfile: "core", Scope: "project",
+		})
+		if _, ok := result.Data.(HarnessSyncData); !ok || appHasFinding(result, "GDS_INPUT_READ_FAILED") {
+			t.Fatalf("external reconciliation did not inspect the consumed catalogue: %+v", result)
+		}
+	})
+	for _, directory := range []string{home, target} {
+		entries, err := os.ReadDir(directory)
+		if err != nil || len(entries) != 0 {
+			t.Fatalf("read-only operation changed %s: %v %v", directory, entries, err)
+		}
+	}
+}
diff --git a/core/app/harness_sync.go b/core/app/harness_sync.go
index 494bcbc..e12983d 100644
--- a/core/app/harness_sync.go
+++ b/core/app/harness_sync.go
@@ -9,6 +9,7 @@ import (
 	"github.com/NDDev-OpenNetwork/github-device-sync/core/domain"
 	"github.com/NDDev-OpenNetwork/github-device-sync/core/harness"
 	"github.com/NDDev-OpenNetwork/github-device-sync/core/materialize"
+	"github.com/NDDev-OpenNetwork/github-device-sync/core/projections"
 	"github.com/NDDev-OpenNetwork/github-device-sync/core/workspace"
 )
 
@@ -71,6 +72,7 @@ func (services *Services) ReconcileDeviceHarnesses(
 	// currently holds. Two selected harnesses that share a skill root collide on
 	// an empty root too, where no on-disk evidence of the conflict exists yet.
 	claims := map[string][]harness.AdapterFile{}
+	engineRoot := projections.ResolveDevelopmentSourceLayout(info.WorktreeRoot).EngineRoot
 	for _, id := range harness.CanonicalIDs {
 		// A selected harness that cannot be rendered is a hard error: the device
 		// cannot converge on it. An unselected one is skipped instead, so an
@@ -78,7 +80,7 @@ func (services *Services) ReconcileDeviceHarnesses(
 		// the same separation ValidateSelected already makes. It is recorded, not
 		// swallowed: an unobservable entry could be a leftover install, and
 		// removing what cannot be seen is never safe.
-		adapter, adapterFindings := harness.NewAdapter(info.WorktreeRoot, id, services.Schemas)
+		adapter, adapterFindings := harness.NewAdapter(engineRoot, id, services.Schemas)
 		if len(adapterFindings) != 0 {
 			if wanted[id] {
 				return domain.NewEnvelope(
diff --git a/core/app/services.go b/core/app/services.go
index a2e2fce..ad00457 100644
--- a/core/app/services.go
+++ b/core/app/services.go
@@ -1323,10 +1323,11 @@ func (services *Services) DetectHarness(
 	}
 	var report any
 	var findings []domain.Finding
+	engineRoot := projections.ResolveDevelopmentSourceLayout(info.WorktreeRoot).EngineRoot
 	if harnessID == "all" {
-		report, findings = harness.DetectAll(ctx, info.WorktreeRoot, services.Schemas)
+		report, findings = harness.DetectAll(ctx, engineRoot, services.Schemas)
 	} else {
-		report, findings = harness.Detect(ctx, info.WorktreeRoot, harnessID, services.Schemas)
+		report, findings = harness.Detect(ctx, engineRoot, harnessID, services.Schemas)
 	}
 	return domain.NewEnvelope(
 		"gds harness detect", classifyFindings(findings), report, findings...,