diff --git a/packages/app/src/app/components/session/artifact-markdown-editor.tsx b/packages/app/src/app/components/session/artifact-markdown-editor.tsx
index 1370194b..3f26426f 100644
--- a/packages/app/src/app/components/session/artifact-markdown-editor.tsx
+++ b/packages/app/src/app/components/session/artifact-markdown-editor.tsx
@@ -67,7 +67,9 @@ export default function ArtifactMarkdownEditor(props: ArtifactMarkdownEditorProp
       setError(writeDisabledReason());
       return;
     }
-    if (!target) return;
+    if (!target) {
+      return;
+    }
     if (!isMarkdown(target)) {
       setError("Only markdown files are supported.");
       return;
@@ -193,8 +195,7 @@ export default function ArtifactMarkdownEditor(props: ArtifactMarkdownEditorProp
     }
 
     const target = path();
-    if (!target) return;
-    if (loading() || pendingReason() === "switch") return;
+    if (!target || loading() || pendingReason() === "switch") return;
 
     const active = loadedPath();
     if (!active) {
diff --git a/packages/app/src/app/pages/session.tsx b/packages/app/src/app/pages/session.tsx
index e9c74304..b570be9e 100644
--- a/packages/app/src/app/pages/session.tsx
+++ b/packages/app/src/app/pages/session.tsx
@@ -722,6 +722,17 @@ export default function SessionView(props: SessionViewProps) {
       return "";
     }
 
+    if (root) {
+      const rootSegments = root.split("/").filter(Boolean);
+      const workspaceFolderName = rootSegments[rootSegments.length - 1]?.toLowerCase();
+      if (workspaceFolderName) {
+        const workspaceMarker = `workspaces/${workspaceFolderName}/`;
+        const markerIndex = fileKey.indexOf(workspaceMarker);
+        if (markerIndex >= 0) return normalized.slice(markerIndex + workspaceMarker.length);
+        if (fileKey.endsWith(`workspaces/${workspaceFolderName}`)) return "";
+      }
+    }
+
     let relative = normalized.replace(/^\.\/+/, "");
     if (!relative) return "";
 
@@ -739,15 +750,28 @@ export default function SessionView(props: SessionViewProps) {
     if (/^\/+workspace\//i.test(relative)) {
       relative = relative.replace(/^\/+workspace\//i, "");
     }
+
     if (relative.startsWith("/") || relative.startsWith("~") || /^[a-zA-Z]:\//.test(relative)) return "";
     if (relative.split("/").some((part) => part === "." || part === "..")) return "";
+
+    if (/com\.[^/]+\.(openwork|opencode)/i.test(relative)) return "";
+
     return relative;
   };
 
   const openMarkdownEditor = (file: string) => {
+    if (!props.openworkServerClient) {
+      setToastMessage("Cannot open file: not connected to OpenWork server.");
+      return;
+    }
+    if (!props.openworkServerWorkspaceId) {
+      setToastMessage("Cannot open file: no workspace selected.");
+      return;
+    }
+
     const relative = toWorkspaceRelativeForApi(file);
     if (!relative) {
-      setToastMessage("Only worker-relative files can be opened here.");
+      setToastMessage(`Cannot open file: path "${file}" is not within the workspace.`);
       return;
     }
     if (!/\.(md|mdx|markdown)$/i.test(relative)) {
diff --git a/packages/app/src/app/utils/index.ts b/packages/app/src/app/utils/index.ts
index a53c9df0..98efd229 100644
--- a/packages/app/src/app/utils/index.ts
+++ b/packages/app/src/app/utils/index.ts
@@ -800,6 +800,44 @@ const ARTIFACT_PATH_PATTERN =
 const ARTIFACT_OUTPUT_SCAN_LIMIT = 4000;
 const ARTIFACT_OUTPUT_SKIP_TOOLS = new Set(["webfetch"]);
 
+// Patterns that indicate a path is a truncated system/absolute path rather than a workspace-relative path
+const TRUNCATED_SYSTEM_PATH_PATTERNS = [
+  /com\.[^/]+\.(openwork|opencode)/i, // macOS app bundle identifiers
+  /\.openwork\.dev\//i, // OpenWork dev paths
+  /Application Support\//i, // macOS Application Support
+  /AppData[/\\]/i, // Windows AppData
+  /\.local\/share\//i, // Linux XDG data
+  /workspaces\/[^/]+\/workspaces\//i, // Nested workspaces paths (clearly malformed)
+];
+
+/**
+ * Clean up an artifact path to extract the workspace-relative portion.
+ * Returns null if the path should be rejected entirely.
+ */
+function cleanArtifactPath(rawPath: string): string | null {
+  const normalized = rawPath.trim().replace(/[\\/]+/g, "/");
+  if (!normalized) return null;
+
+  // Check if this looks like a truncated system path
+  for (const pattern of TRUNCATED_SYSTEM_PATH_PATTERNS) {
+    if (pattern.test(normalized)) {
+      // Try to extract just the relative part after "workspaces/<name>/"
+      const workspacesMatch = normalized.match(/workspaces\/[^/]+\/(.+)$/i);
+      if (workspacesMatch && workspacesMatch[1]) {
+        const relative = workspacesMatch[1];
+        // Validate the extracted path doesn't still contain system patterns
+        if (!TRUNCATED_SYSTEM_PATH_PATTERNS.some((p) => p.test(relative))) {
+          return relative;
+        }
+      }
+      // Reject the path entirely if we can't extract a clean relative path
+      return null;
+    }
+  }
+
+  return normalized;
+}
+
 type DeriveArtifactsOptions = {
   maxMessages?: number;
 };
@@ -906,19 +944,19 @@ export function deriveArtifacts(list: MessageWithParts[], options: DeriveArtifac
       if (matches.size === 0) return;
 
       matches.forEach((match) => {
-        const normalizedPath = match.trim().replace(/[\\/]+/g, "/");
-        if (!normalizedPath) return;
+        const cleanedPath = cleanArtifactPath(match);
+        if (!cleanedPath) return;
 
-        const key = normalizedPath.toLowerCase();
-        const name = normalizedPath.split("/").pop() ?? normalizedPath;
-        const id = `artifact-${encodeURIComponent(normalizedPath)}`;
+        const key = cleanedPath.toLowerCase();
+        const name = cleanedPath.split("/").pop() ?? cleanedPath;
+        const id = `artifact-${encodeURIComponent(cleanedPath)}`;
 
         // Delete and re-add to move to end (most recent)
         if (results.has(key)) results.delete(key);
         results.set(key, {
           id,
           name,
-          path: normalizedPath,
+          path: cleanedPath,
           kind: "file" as const,
           size: state.size ? String(state.size) : undefined,
           messageId: messageId || undefined,