diff --git a/canvas/src/components/tabs/ConfigTab.tsx b/canvas/src/components/tabs/ConfigTab.tsx
index 7d177ebf..4bf4b09f 100644
--- a/canvas/src/components/tabs/ConfigTab.tsx
+++ b/canvas/src/components/tabs/ConfigTab.tsx
@@ -104,6 +104,13 @@ interface RuntimeOption {
 // Fallback used when /templates can't be fetched (offline, older backend).
 // Keep in sync with manifest.json workspace_templates as a defensive default.
 // Model + env suggestions only flow when the backend is reachable.
+// Runtimes that manage their own config outside the platform's config.yaml
+// template. For these, a missing config.yaml is expected — the user manages
+// config via the runtime's own mechanism (e.g. hermes edits
+// ~/.hermes/config.yaml on the workspace EC2 via the Terminal tab or its
+// own CLI). Showing a "No config.yaml found" error for these is misleading.
+const RUNTIMES_WITH_OWN_CONFIG = new Set<string>(["hermes", "external"]);
+
 const FALLBACK_RUNTIME_OPTIONS: RuntimeOption[] = [
   { value: "", label: "LangGraph (default)", models: [] },
   { value: "claude-code", label: "Claude Code", models: [] },
@@ -134,14 +141,50 @@ export function ConfigTab({ workspaceId }: Props) {
   const loadConfig = useCallback(async () => {
     setLoading(true);
     setError(null);
+
+    // ALWAYS load workspace metadata first (runtime + model). These are the
+    // source of truth regardless of whether the runtime uses our config.yaml
+    // template. Without this the form falls back to empty/default values on
+    // a hermes workspace (which doesn't use our template), creating the
+    // appearance that the saved runtime is unset — and worse, clicking Save
+    // would silently flip `runtime` from `hermes` back to the dropdown
+    // default `LangGraph`. See GH #1894.
+    let wsMetadataRuntime = "";
+    let wsMetadataModel = "";
+    try {
+      const ws = await api.get<{ runtime?: string }>(`/workspaces/${workspaceId}`);
+      wsMetadataRuntime = (ws.runtime || "").trim();
+    } catch { /* fall back to config.yaml */ }
+    try {
+      const m = await api.get<{ model?: string }>(`/workspaces/${workspaceId}/model`);
+      wsMetadataModel = (m.model || "").trim();
+    } catch { /* non-fatal */ }
+
     try {
       const res = await api.get<{ content: string }>(`/workspaces/${workspaceId}/files/config.yaml`);
       const parsed = parseYaml(res.content);
       setOriginalYaml(res.content);
       setRawDraft(res.content);
-      setConfig({ ...DEFAULT_CONFIG, ...parsed } as ConfigData);
+      // Merge: config.yaml wins for fields it declares, but workspace metadata
+      // wins for runtime + model when config.yaml doesn't set them.
+      const merged = { ...DEFAULT_CONFIG, ...parsed } as ConfigData;
+      if (!merged.runtime && wsMetadataRuntime) merged.runtime = wsMetadataRuntime;
+      if (!merged.model && wsMetadataModel) merged.model = wsMetadataModel;
+      setConfig(merged);
     } catch {
-      setError("No config.yaml found");
+      // No platform-managed config.yaml. Some runtimes (hermes, external)
+      // manage their own config outside this template; that's expected, not
+      // an error. Populate the form from workspace metadata so the user
+      // still sees the saved runtime + model.
+      const runtimeManagesOwnConfig = RUNTIMES_WITH_OWN_CONFIG.has(wsMetadataRuntime);
+      if (!runtimeManagesOwnConfig) {
+        setError("No config.yaml found");
+      }
+      setConfig({
+        ...DEFAULT_CONFIG,
+        runtime: wsMetadataRuntime,
+        model: wsMetadataModel,
+      } as ConfigData);
     } finally {
       setLoading(false);
     }
@@ -511,6 +554,13 @@ export function ConfigTab({ workspaceId }: Props) {
       {error && (
         <div className="mx-3 mb-2 px-3 py-1.5 bg-red-900/30 border border-red-800 rounded text-xs text-red-400">{error}</div>
       )}
+      {!error && RUNTIMES_WITH_OWN_CONFIG.has(config.runtime || "") && (
+        <div className="mx-3 mb-2 px-3 py-1.5 bg-zinc-900/50 border border-zinc-700 rounded text-xs text-zinc-400">
+          {config.runtime === "hermes"
+            ? "Hermes manages its own config at ~/.hermes/config.yaml on the workspace host. Edit it via the Terminal tab or the hermes CLI, not this form."
+            : "This runtime manages its own config outside the platform template."}
+        </div>
+      )}
       {success && (
         <div className="mx-3 mb-2 px-3 py-1.5 bg-green-900/30 border border-green-800 rounded text-xs text-green-400">Saved</div>
       )}