diff --git a/.gitea/workflows/publish-workspace-server-image.yml b/.gitea/workflows/publish-workspace-server-image.yml
index e9ca5ec2..00bd6e2d 100644
--- a/.gitea/workflows/publish-workspace-server-image.yml
+++ b/.gitea/workflows/publish-workspace-server-image.yml
@@ -59,6 +59,25 @@ jobs:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
+      # Health check: verify Docker daemon is accessible before attempting any
+      # build steps. This fails loudly at step 1 when the runner's docker.sock
+      # is inaccessible (e.g. permission change, daemon restart, or group-membership
+      # drift) rather than silently continuing to step 2 where `docker build`
+      # fails deep in the process with a cryptic ECR auth error that doesn't
+      # surface the root cause.  Also reports the daemon version so operator
+      # can correlate with runner host logs.
+      - name: Verify Docker daemon access
+        run: |
+          set -euo pipefail
+          echo "::group::Docker daemon health check"
+          docker info 2>&1 | head -5 || {
+            echo "::error::Docker daemon is not accessible at /var/run/docker.sock"
+            echo "::error::Check: (1) daemon is running, (2) runner user is in docker group, (3) sock permissions are 660+"
+            exit 1
+          }
+          echo "Docker daemon OK"
+          echo "::endgroup::"
+
       # Pre-clone manifest deps before docker build.
       #
       # Why: workspace-template-* repos on Gitea are private. The pre-fix
diff --git a/.github/workflows/publish-canvas-image.yml b/.github/workflows/publish-canvas-image.yml
index 5f0faf12..6d345978 100644
--- a/.github/workflows/publish-canvas-image.yml
+++ b/.github/workflows/publish-canvas-image.yml
@@ -54,6 +54,22 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
+      # Health check: verify Docker daemon is accessible before attempting any
+      # build steps. This fails loudly at step 1 when the runner's docker.sock
+      # is inaccessible rather than silently continuing to the build step
+      # where docker build fails deep in ECR auth with a cryptic error.
+      - name: Verify Docker daemon access
+        run: |
+          set -euo pipefail
+          echo "::group::Docker daemon health check"
+          docker info 2>&1 | head -5 || {
+            echo "::error::Docker daemon is not accessible at /var/run/docker.sock"
+            echo "::error::Check: (1) daemon running, (2) runner user in docker group, (3) sock perms 660+"
+            exit 1
+          }
+          echo "Docker daemon OK"
+          echo "::endgroup::"
+
       - name: Compute tags
         id: tags
         shell: bash
diff --git a/.github/workflows/publish-workspace-server-image.yml b/.github/workflows/publish-workspace-server-image.yml
index 2a1b8b17..7d981c93 100644
--- a/.github/workflows/publish-workspace-server-image.yml
+++ b/.github/workflows/publish-workspace-server-image.yml
@@ -107,6 +107,22 @@ jobs:
         run: |
           echo "sha=${GITHUB_SHA::7}" >> "$GITHUB_OUTPUT"
 
+      # Health check: verify Docker daemon is accessible before attempting any
+      # build steps. This fails loudly at step 1 when the runner's docker.sock
+      # is inaccessible rather than silently continuing to the build step
+      # where docker build fails deep in ECR auth with a cryptic error.
+      - name: Verify Docker daemon access
+        run: |
+          set -euo pipefail
+          echo "::group::Docker daemon health check"
+          docker info 2>&1 | head -5 || {
+            echo "::error::Docker daemon is not accessible at /var/run/docker.sock"
+            echo "::error::Check: (1) daemon running, (2) runner user in docker group, (3) sock perms 660+"
+            exit 1
+          }
+          echo "Docker daemon OK"
+          echo "::endgroup::"
+
       # Pre-clone manifest deps before docker build (Task #173 fix).
       #
       # Why pre-clone: post-2026-05-06, every workspace-template-* repo on
diff --git a/workspace-server/internal/handlers/admin_workspace_images.go b/workspace-server/internal/handlers/admin_workspace_images.go
index 68bc50f1..95af3c91 100644
--- a/workspace-server/internal/handlers/admin_workspace_images.go
+++ b/workspace-server/internal/handlers/admin_workspace_images.go
@@ -71,10 +71,17 @@ func TemplateImageRef(runtime string) string {
 
 // ghcrAuthHeader returns the base64-encoded JSON auth payload Docker's
 // ImagePull expects in PullOptions.RegistryAuth, or empty string when no
-// GHCR_USER/GHCR_TOKEN env is set (lets public images pull through).
+// GHCR_USER/GHCR_TOKEN env is set (lets public images pull through and lets
+// ECR's credential-helper-driven flow take over without a stale GHCR
+// payload masking it).
 //
 // The Docker SDK doesn't read ~/.docker/config.json — every authenticated
-// pull needs an explicit RegistryAuth string.
+// pull needs an explicit RegistryAuth string. The serveraddress field is
+// resolved from provisioner.RegistryHost() so it tracks MOLECULE_IMAGE_REGISTRY
+// when the operator points the platform at a private mirror (e.g. ECR).
+// Leaving it hardcoded to "ghcr.io" caused the engine to match the wrong
+// auth entry post-suspension when MOLECULE_IMAGE_REGISTRY was flipped to
+// the AWS ECR mirror (RFC #229).
 func ghcrAuthHeader() string {
 	user := strings.TrimSpace(os.Getenv("GHCR_USER"))
 	token := strings.TrimSpace(os.Getenv("GHCR_TOKEN"))
@@ -84,7 +91,7 @@ func ghcrAuthHeader() string {
 	payload := map[string]string{
 		"username":      user,
 		"password":      token,
-		"serveraddress": "ghcr.io",
+		"serveraddress": provisioner.RegistryHost(),
 	}
 	js, err := json.Marshal(payload)
 	if err != nil {
diff --git a/workspace-server/internal/handlers/admin_workspace_images_test.go b/workspace-server/internal/handlers/admin_workspace_images_test.go
index 26e61f95..411cba5a 100644
--- a/workspace-server/internal/handlers/admin_workspace_images_test.go
+++ b/workspace-server/internal/handlers/admin_workspace_images_test.go
@@ -9,6 +9,7 @@ import (
 func TestGHCRAuthHeader_NoEnvReturnsEmpty(t *testing.T) {
 	t.Setenv("GHCR_USER", "")
 	t.Setenv("GHCR_TOKEN", "")
+	t.Setenv("MOLECULE_IMAGE_REGISTRY", "")
 	if got := ghcrAuthHeader(); got != "" {
 		t.Errorf("expected empty (no auth → public-only), got %q", got)
 	}
@@ -29,6 +30,10 @@ func TestGHCRAuthHeader_PartialEnvReturnsEmpty(t *testing.T) {
 }
 
 func TestGHCRAuthHeader_EncodesDockerEnginePayload(t *testing.T) {
+	// Default registry env (unset → ghcr.io/molecule-ai) means the
+	// serveraddress field should resolve to ghcr.io. Pin both env vars so the
+	// test is hermetic regardless of the host's MOLECULE_IMAGE_REGISTRY.
+	t.Setenv("MOLECULE_IMAGE_REGISTRY", "")
 	t.Setenv("GHCR_USER", "alice")
 	t.Setenv("GHCR_TOKEN", "fake-tok-value")
 	got := ghcrAuthHeader()
@@ -54,7 +59,41 @@ func TestGHCRAuthHeader_EncodesDockerEnginePayload(t *testing.T) {
 	}
 }
 
+// TestGHCRAuthHeader_RespectsRegistryEnv pins the RFC #229 fix: when
+// MOLECULE_IMAGE_REGISTRY points at a private mirror (e.g. AWS ECR), the
+// Docker engine auth payload's serveraddress must reflect that mirror's
+// host so credential matching lands on the right entry. Pre-fix this was
+// hardcoded to "ghcr.io" and silently dropped the override.
+func TestGHCRAuthHeader_RespectsRegistryEnv(t *testing.T) {
+	t.Setenv("GHCR_USER", "alice")
+	t.Setenv("GHCR_TOKEN", "fake-tok-value")
+	t.Setenv("MOLECULE_IMAGE_REGISTRY", "004947743811.dkr.ecr.us-east-2.amazonaws.com/molecule-ai")
+
+	got := ghcrAuthHeader()
+	if got == "" {
+		t.Fatal("expected non-empty auth header")
+	}
+	raw, err := base64.URLEncoding.DecodeString(got)
+	if err != nil {
+		t.Fatalf("auth header is not valid base64-url: %v", err)
+	}
+	var payload map[string]string
+	if err := json.Unmarshal(raw, &payload); err != nil {
+		t.Fatalf("decoded auth is not valid JSON: %v (raw=%s)", err, raw)
+	}
+	want := "004947743811.dkr.ecr.us-east-2.amazonaws.com"
+	if payload["serveraddress"] != want {
+		t.Errorf("serveraddress: got %q, want %q (must follow MOLECULE_IMAGE_REGISTRY host)",
+			payload["serveraddress"], want)
+	}
+	// Sanity: the org-path portion must NOT leak into serveraddress.
+	if payload["serveraddress"] == "004947743811.dkr.ecr.us-east-2.amazonaws.com/molecule-ai" {
+		t.Error("serveraddress must be host-only, not host+org-path")
+	}
+}
+
 func TestGHCRAuthHeader_TrimsWhitespace(t *testing.T) {
+	t.Setenv("MOLECULE_IMAGE_REGISTRY", "")
 	// .env lines often have trailing newlines or accidental spaces. Without
 	// trimming, a stray space would produce an auth payload the engine
 	// rejects with a confusing 401.
diff --git a/workspace-server/internal/handlers/external_connection.go b/workspace-server/internal/handlers/external_connection.go
index 320e761e..ef213ae0 100644
--- a/workspace-server/internal/handlers/external_connection.go
+++ b/workspace-server/internal/handlers/external_connection.go
@@ -121,7 +121,7 @@ curl -fsS -X POST "{{PLATFORM_URL}}/registry/register" \
 // operators whose external agent IS a Claude Code session (laptop or
 // remote dev VM); routes the workspace's A2A traffic into the running
 // Claude Code session as conversation turns via MCP. The plugin source
-// lives at github.com/Molecule-AI/molecule-mcp-claude-channel — polling
+// lives at git.moleculesai.app/molecule-ai/molecule-mcp-claude-channel — polling
 // based, no tunnel required (uses /workspaces/:id/activity?since_secs=,
 // platform-side support shipped in #2300).
 const externalChannelTemplate = `# Claude Code channel — bridges this workspace's A2A traffic into your
@@ -134,8 +134,8 @@ const externalChannelTemplate = `# Claude Code channel — bridges this workspac
 #    The plugin is NOT on Anthropic's default allowlist, so a one-time
 #    marketplace-add is needed before install:
 #
-#      /plugin marketplace add Molecule-AI/molecule-mcp-claude-channel
-#      /plugin install molecule@molecule-mcp-claude-channel
+#      /plugin marketplace add https://git.moleculesai.app/molecule-ai/molecule-mcp-claude-channel.git
+#      /plugin install molecule@molecule-channel
 #
 #    Then either run /reload-plugins or restart Claude Code so the
 #    plugin is registered.
@@ -154,7 +154,7 @@ chmod 600 ~/.claude/channels/molecule/.env
 #    flag to opt in — without it, you'll see "not on the approved channels
 #    allowlist" on startup.
 claude --dangerously-load-development-channels \
-  --channels plugin:molecule@molecule-mcp-claude-channel
+  --channels plugin:molecule@molecule-channel
 
 # You should see on stderr:
 #   molecule channel: connected — watching 1 workspace(s) at {{PLATFORM_URL}}
@@ -176,7 +176,7 @@ claude --dangerously-load-development-channels \
 # add the plugin to allowedChannelPlugins in claude.ai admin settings.
 #
 # Multi-workspace: comma-separate IDs and tokens (same order). See
-# https://github.com/Molecule-AI/molecule-mcp-claude-channel for
+# https://git.moleculesai.app/molecule-ai/molecule-mcp-claude-channel for
 # pairing flow, push-mode upgrade, and v0.2 roadmap.
 
 # Need help?
@@ -258,7 +258,7 @@ claude mcp add molecule -s user -- env \
 // externalPythonTemplate uses molecule-sdk-python's RemoteAgentClient +
 // A2AServer (PR #13 in that repo). Until the SDK cuts a v0.y release
 // to PyPI the snippet pins git+main.
-const externalPythonTemplate = `# pip install 'git+https://github.com/Molecule-AI/molecule-sdk-python.git@main'
+const externalPythonTemplate = `# pip install 'git+https://git.moleculesai.app/molecule-ai/molecule-sdk-python.git@main'
 
 import asyncio
 from molecule_agent import RemoteAgentClient, A2AServer
@@ -307,7 +307,7 @@ if __name__ == "__main__":
 // A2A traffic into the running hermes gateway as platform messages
 // via the molecule-channel plugin.
 //
-// The plugin (Molecule-AI/hermes-channel-molecule) is a hermes
+// The plugin (molecule-ai/hermes-channel-molecule on Gitea) is a hermes
 // platform adapter that:
 //   1. Spawns ``python -m molecule_runtime.a2a_mcp_server`` as a
 //      stdio MCP subprocess (separate from any hermes-side MCP
@@ -336,7 +336,7 @@ const externalHermesChannelTemplate = `# Hermes channel — bridges this workspa
 #
 # 1. Install the runtime + plugin:
 pip install molecule-ai-workspace-runtime
-pip install 'git+https://github.com/Molecule-AI/hermes-channel-molecule.git'
+pip install 'git+https://git.moleculesai.app/molecule-ai/hermes-channel-molecule.git'
 
 # 2. Export the workspace credentials:
 export MOLECULE_WORKSPACE_ID={{WORKSPACE_ID}}
@@ -366,7 +366,7 @@ hermes gateway --replace
 # by the plugin's molecule_runtime MCP subprocess).
 #
 # Source + issue tracker:
-# https://github.com/Molecule-AI/hermes-channel-molecule
+# https://git.moleculesai.app/molecule-ai/hermes-channel-molecule
 
 # Need help?
 #   Documentation: https://doc.moleculesai.app/docs/guides/external-agent-registration
diff --git a/workspace-server/internal/handlers/external_connection_test.go b/workspace-server/internal/handlers/external_connection_test.go
index cd843693..0b9a0fa3 100644
--- a/workspace-server/internal/handlers/external_connection_test.go
+++ b/workspace-server/internal/handlers/external_connection_test.go
@@ -75,3 +75,46 @@ func TestExternalMcpTemplates_UseMoleculeMcpWrapper(t *testing.T) {
 		}
 	}
 }
+
+// TestExternalTemplates_NoBrokenMoleculeAIGitHubURLs pins the invariant
+// that operator-facing snippets never embed github.com URLs pointing at
+// Molecule-AI repos.
+//
+// Why: the Molecule-AI GitHub org was suspended 2026-05-06 and the
+// canonical SCM is now git.moleculesai.app. Any `pip install
+// git+https://github.com/Molecule-AI/...` or marketplace-add Molecule-AI/
+// URL emitted to an external operator hits a 404 / org-suspended page,
+// breaking onboarding silently. RFC #229 P2-5.
+//
+// Third-party github URLs (gin, openai/codex, NousResearch/hermes-agent
+// upstream issue trackers, npm @openai/codex) remain valid — only
+// Molecule-AI/ paths are broken.
+func TestExternalTemplates_NoBrokenMoleculeAIGitHubURLs(t *testing.T) {
+	templates := map[string]string{
+		"externalCurlTemplate":          externalCurlTemplate,
+		"externalChannelTemplate":       externalChannelTemplate,
+		"externalUniversalMcpTemplate":  externalUniversalMcpTemplate,
+		"externalPythonTemplate":        externalPythonTemplate,
+		"externalHermesChannelTemplate": externalHermesChannelTemplate,
+		"externalCodexTemplate":         externalCodexTemplate,
+		"externalOpenClawTemplate":      externalOpenClawTemplate,
+	}
+	// Substrings that imply the snippet is pointing an operator at the
+	// suspended Molecule-AI GitHub org.
+	bannedSubstrings := []string{
+		"github.com/Molecule-AI/",
+		"github.com/molecule-ai/",
+		// Bare `Molecule-AI/<repo>` form used by `/plugin marketplace add`
+		// resolves through GitHub by default — explicit Gitea URL is
+		// required post-suspension.
+		"marketplace add Molecule-AI/",
+		"marketplace add molecule-ai/",
+	}
+	for name, body := range templates {
+		for _, banned := range bannedSubstrings {
+			if strings.Contains(body, banned) {
+				t.Errorf("%s contains %q — Molecule-AI GitHub org is suspended; use git.moleculesai.app/molecule-ai/<repo> instead (RFC #229 P2-5)", name, banned)
+			}
+		}
+	}
+}
diff --git a/workspace-server/internal/imagewatch/watch.go b/workspace-server/internal/imagewatch/watch.go
index d39d57f3..7e038b35 100644
--- a/workspace-server/internal/imagewatch/watch.go
+++ b/workspace-server/internal/imagewatch/watch.go
@@ -29,6 +29,7 @@ import (
 	"time"
 
 	"github.com/Molecule-AI/molecule-monorepo/platform/internal/handlers"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/provisioner"
 )
 
 // DefaultInterval is the polling cadence. Runtime publishes happen at most
@@ -127,20 +128,32 @@ func (w *Watcher) tick(ctx context.Context, fetch digestFetcher) {
 	}
 }
 
-// remoteDigest queries GHCR for the current manifest digest of the
-// workspace-template-<runtime>:latest image. Uses the Docker Registry V2
-// HTTP API: get a bearer token, then HEAD the manifest.
+// remoteDigest queries the configured registry for the current manifest
+// digest of the workspace-template-<runtime>:latest image. Uses the Docker
+// Registry V2 HTTP API: get a bearer token, then HEAD the manifest.
+//
+// Registry host is resolved from provisioner.RegistryHost() so the watcher
+// follows MOLECULE_IMAGE_REGISTRY in production tenants. Pre-RFC #229 this
+// was hardcoded to ghcr.io, which silently broke image-watch in tenants
+// pointed at the AWS ECR mirror.
 //
 // Auth: if GHCR_USER+GHCR_TOKEN are set, basic-auth the token request
 // (works for both public and private images). If unset, anonymous token
 // (works for public images only — every workspace template is public).
+//
+// NOTE: the bearer-token negotiation in fetchPullToken speaks GHCR's
+// `/token` flavor of the Docker Registry V2 spec. ECR uses a different
+// auth path (`aws ecr get-authorization-token` → SigV4 + basic-auth header).
+// Wiring ECR auth here is tracked as a follow-up; until then, operators on
+// ECR should keep IMAGE_AUTO_REFRESH=false and the watcher will fail loudly
+// at the token fetch instead of pulling from ghcr.io behind their back.
 func (w *Watcher) remoteDigest(ctx context.Context, runtime string) (string, error) {
 	repo := "molecule-ai/workspace-template-" + runtime
 	tok, err := w.fetchPullToken(ctx, repo)
 	if err != nil {
 		return "", fmt.Errorf("pull token: %w", err)
 	}
-	manifestURL := fmt.Sprintf("https://ghcr.io/v2/%s/manifests/latest", repo)
+	manifestURL := fmt.Sprintf("https://%s/v2/%s/manifests/latest", provisioner.RegistryHost(), repo)
 	req, err := http.NewRequestWithContext(ctx, "HEAD", manifestURL, nil)
 	if err != nil {
 		return "", err
@@ -171,14 +184,22 @@ func (w *Watcher) remoteDigest(ctx context.Context, runtime string) (string, err
 	return digest, nil
 }
 
-// fetchPullToken negotiates a short-lived bearer token from GHCR's token
-// endpoint scoped to repo:pull. GHCR requires a token even for anonymous
-// pulls of public images.
+// fetchPullToken negotiates a short-lived bearer token from the registry's
+// `/token` endpoint scoped to repo:pull. GHCR requires a token even for
+// anonymous pulls of public images.
+//
+// Registry host follows provisioner.RegistryHost() so the request goes to
+// the same registry the rest of the platform pulls from. The `service`
+// query parameter mirrors the host because GHCR (and most registries
+// implementing the Docker Registry V2 token spec) validate it against the
+// realm/service the auth challenge advertised. ECR doesn't implement this
+// flow — see remoteDigest's note on the ECR auth follow-up.
 func (w *Watcher) fetchPullToken(ctx context.Context, repo string) (string, error) {
+	host := provisioner.RegistryHost()
 	q := url.Values{}
-	q.Set("service", "ghcr.io")
+	q.Set("service", host)
 	q.Set("scope", "repository:"+repo+":pull")
-	tokURL := "https://ghcr.io/token?" + q.Encode()
+	tokURL := "https://" + host + "/token?" + q.Encode()
 	req, err := http.NewRequestWithContext(ctx, "GET", tokURL, nil)
 	if err != nil {
 		return "", err
diff --git a/workspace-server/internal/imagewatch/watch_test.go b/workspace-server/internal/imagewatch/watch_test.go
index b29d17a3..662e5113 100644
--- a/workspace-server/internal/imagewatch/watch_test.go
+++ b/workspace-server/internal/imagewatch/watch_test.go
@@ -3,6 +3,9 @@ package imagewatch
 import (
 	"context"
 	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
 	"sync"
 	"testing"
 
@@ -160,6 +163,100 @@ func TestTick_DigestFetchErrorSkipsRuntime(t *testing.T) {
 	}
 }
 
+// TestRemoteDigest_RegistryHostFollowsEnv pins the RFC #229 fix: with
+// MOLECULE_IMAGE_REGISTRY pointed at a private mirror, the watcher's HTTP
+// calls (token endpoint + manifest HEAD) must hit that mirror's host, not
+// the hardcoded ghcr.io of the pre-fix code path. We stand up an httptest
+// server, point MOLECULE_IMAGE_REGISTRY at its host, and assert both
+// endpoints get hit on it.
+//
+// Without this test, a future refactor could revert the helper indirection
+// and the watcher would silently go back to talking to ghcr.io even when
+// the platform is configured for ECR — exactly the bug RFC #229 is closing.
+func TestRemoteDigest_RegistryHostFollowsEnv(t *testing.T) {
+	var (
+		mu              sync.Mutex
+		tokenHits       int
+		manifestHits    int
+		lastTokenURL    string
+		lastManifestURL string
+	)
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		defer mu.Unlock()
+		switch {
+		case strings.HasPrefix(r.URL.Path, "/token"):
+			tokenHits++
+			lastTokenURL = r.URL.String()
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"token":"fake-bearer"}`))
+		case strings.HasPrefix(r.URL.Path, "/v2/") && strings.Contains(r.URL.Path, "/manifests/latest"):
+			manifestHits++
+			lastManifestURL = r.URL.Path
+			w.Header().Set("Docker-Content-Digest", "sha256:cafef00d")
+			w.WriteHeader(http.StatusOK)
+		default:
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}))
+	defer srv.Close()
+
+	// httptest.Server.URL is "http://127.0.0.1:NNNN". RegistryHost() works
+	// over the host:port portion (provisioner.RegistryPrefix takes the env
+	// verbatim), so we strip the scheme and append "/molecule-ai" to mimic
+	// the prefix shape MOLECULE_IMAGE_REGISTRY actually uses in production.
+	host := strings.TrimPrefix(srv.URL, "http://")
+	t.Setenv("MOLECULE_IMAGE_REGISTRY", host+"/molecule-ai")
+
+	w := newTestWatcher(&fakeRefresher{}, "claude-code")
+	// Use the test-server URL scheme by overriding the http client only —
+	// remoteDigest constructs https://<host>/... internally. We need the
+	// watcher to hit our http server, so swap the URL scheme by injecting
+	// a transport that rewrites https→http for this test.
+	w.http = &http.Client{Transport: rewriteToHTTP{}}
+
+	digest, err := w.remoteDigest(context.Background(), "claude-code")
+	if err != nil {
+		t.Fatalf("remoteDigest failed: %v", err)
+	}
+	if digest != "sha256:cafef00d" {
+		t.Errorf("digest: got %q, want sha256:cafef00d", digest)
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if tokenHits != 1 {
+		t.Errorf("token endpoint hits: got %d, want 1 (watcher must hit configured registry, not ghcr.io)", tokenHits)
+	}
+	if manifestHits != 1 {
+		t.Errorf("manifest HEAD hits: got %d, want 1 (watcher must hit configured registry, not ghcr.io)", manifestHits)
+	}
+	// service= query param must reflect the configured host so registries
+	// that validate the param (GHCR-style spec) accept the request.
+	if !strings.Contains(lastTokenURL, "service="+host) && !strings.Contains(lastTokenURL, "service=127.0.0.1") {
+		t.Errorf("token URL service param not host-derived: got %q", lastTokenURL)
+	}
+	wantManifestPath := "/v2/molecule-ai/workspace-template-claude-code/manifests/latest"
+	if lastManifestURL != wantManifestPath {
+		t.Errorf("manifest path: got %q, want %q", lastManifestURL, wantManifestPath)
+	}
+}
+
+// rewriteToHTTP is a tiny RoundTripper that flips https→http so the watcher
+// (which builds https URLs from the configured registry host) can target an
+// httptest.Server that only speaks http. Production code paths still go
+// over https; this is a unit-test seam only.
+type rewriteToHTTP struct{}
+
+func (rewriteToHTTP) RoundTrip(req *http.Request) (*http.Response, error) {
+	if req.URL.Scheme == "https" {
+		clone := req.Clone(req.Context())
+		clone.URL.Scheme = "http"
+		req = clone
+	}
+	return http.DefaultTransport.RoundTrip(req)
+}
+
 func TestShortDigest(t *testing.T) {
 	cases := map[string]string{
 		"sha256:abcdef0123456789":     "sha256:abcdef012345",
diff --git a/workspace-server/internal/provisioner/registry.go b/workspace-server/internal/provisioner/registry.go
index 209411a4..74334882 100644
--- a/workspace-server/internal/provisioner/registry.go
+++ b/workspace-server/internal/provisioner/registry.go
@@ -3,6 +3,7 @@ package provisioner
 import (
 	"fmt"
 	"os"
+	"strings"
 )
 
 // defaultRegistryPrefix is the upstream OSS face for all workspace template
@@ -62,6 +63,32 @@ func RegistryPrefix() string {
 	return defaultRegistryPrefix
 }
 
+// RegistryHost returns just the registry host portion of RegistryPrefix() —
+// i.e. everything before the first "/" separator. This is the value that
+// belongs in:
+//
+//   - Docker Engine PullOptions.RegistryAuth payloads (`serveraddress` field)
+//     — the engine matches credentials against host, not host+org-path.
+//   - Docker Registry V2 HTTP API base URLs (e.g. `https://<host>/v2/...`)
+//     — the V2 API is host-rooted; the org-path lives in the manifest path.
+//
+// Examples:
+//
+//	"ghcr.io/molecule-ai"                                    → "ghcr.io"
+//	"123456789012.dkr.ecr.us-east-2.amazonaws.com/molecule-ai" → "123456789012.dkr.ecr.us-east-2.amazonaws.com"
+//	"git.moleculesai.app/molecule-ai"                        → "git.moleculesai.app"
+//
+// If RegistryPrefix() ever returns a bare host (no `/`), we return it as-is
+// rather than letting strings.SplitN produce an empty string — defensive
+// against a misconfiguration where the operator sets just the host.
+func RegistryHost() string {
+	prefix := RegistryPrefix()
+	if i := strings.IndexByte(prefix, '/'); i > 0 {
+		return prefix[:i]
+	}
+	return prefix
+}
+
 // RuntimeImage returns the canonical image reference for the given runtime,
 // using the current RegistryPrefix() and the moving `:latest` tag.
 //
diff --git a/workspace-server/internal/provisioner/registry_test.go b/workspace-server/internal/provisioner/registry_test.go
index 885a6b99..f9c6611c 100644
--- a/workspace-server/internal/provisioner/registry_test.go
+++ b/workspace-server/internal/provisioner/registry_test.go
@@ -127,6 +127,50 @@ func TestComputeRuntimeImages_ReflectsCurrentEnv(t *testing.T) {
 	}
 }
 
+// TestRegistryHost_SplitsHostFromOrgPath pins the contract that callers
+// (Docker auth payloads, registry V2 HTTP base URLs) need: the host portion
+// must be free of the "/molecule-ai" org suffix that appears in the
+// pull-prefix form. Pre-RFC #229, ghcr.io was hardcoded in two places
+// (imagewatch + admin_workspace_images auth payload); this helper is the
+// single source they should resolve from.
+func TestRegistryHost_SplitsHostFromOrgPath(t *testing.T) {
+	cases := []struct {
+		name string
+		env  string
+		want string
+	}{
+		{"default GHCR", "", "ghcr.io"},
+		{"AWS ECR mirror", "004947743811.dkr.ecr.us-east-2.amazonaws.com/molecule-ai", "004947743811.dkr.ecr.us-east-2.amazonaws.com"},
+		{"self-hosted Gitea", "git.moleculesai.app/molecule-ai", "git.moleculesai.app"},
+		// Bare host (no /org) — defensive: return as-is rather than empty.
+		{"bare host no org-path", "registry.example.com", "registry.example.com"},
+		// Multi-level org path — split at the first "/" only.
+		{"nested org path", "registry.example.com/org/sub", "registry.example.com"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("MOLECULE_IMAGE_REGISTRY", tc.env)
+			got := RegistryHost()
+			if got != tc.want {
+				t.Errorf("RegistryHost() with env=%q: got %q, want %q", tc.env, got, tc.want)
+			}
+		})
+	}
+}
+
+// TestRegistryHost_NeverEmpty — guard against a future refactor accidentally
+// returning "" for some edge env value. An empty serveraddress in the
+// Docker engine auth payload, or an empty host in `https:///v2/...`, would
+// silently break image operations.
+func TestRegistryHost_NeverEmpty(t *testing.T) {
+	for _, env := range []string{"", "ghcr.io/molecule-ai", "/leading-slash", "host-only", "host/with/path"} {
+		t.Setenv("MOLECULE_IMAGE_REGISTRY", env)
+		if got := RegistryHost(); got == "" {
+			t.Errorf("RegistryHost() with env=%q returned empty (would break Docker auth + V2 HTTP)", env)
+		}
+	}
+}
+
 // TestKnownRuntimes_AlphabeticalOrder — pin the order so test snapshots
 // (and human readers diffing the file) see deterministic output. Adding a
 // new runtime out of alphabetical order will fail this test, which is the