diff --git a/index.ts b/index.ts
index 968a9ec..265bc86 100644
--- a/index.ts
+++ b/index.ts
@@ -147,6 +147,12 @@ export function runWorker(payload: unknown, signal: AbortSignal): Promise<Worker
       reject(abortError());
       return;
     }
+    if (!existsSync(WORKER_PATH)) {
+      reject(new Error(
+        `SnapCompact worker source is missing at ${WORKER_PATH}; reinstall or reload the extension from a checkout that still exists`,
+      ));
+      return;
+    }
     let input: string;
     try {
       input = JSON.stringify(payload);
@@ -980,9 +986,12 @@ export function createSnapcompactExtension(dependencies: SnapcompactDependencies
             notify(ctx, `SnapCompact unavailable; preserved history with native text compaction: ${message}`, "warning");
             return { compaction };
           } catch (migrationError) {
+            const fallbackMessage = migrationError instanceof Error
+              ? migrationError.message
+              : String(migrationError);
             notify(
               ctx,
-              `SnapCompact failed and retained the existing archive: ${migrationError instanceof Error ? migrationError.message : String(migrationError)}`,
+              `SnapCompact visual compaction failed: ${message}. Its text fallback also failed, so the existing archive was retained: ${fallbackMessage}`,
               "error",
             );
             return { cancel: true };
diff --git a/test/integration.mjs b/test/integration.mjs
index 97297d6..12ba527 100644
--- a/test/integration.mjs
+++ b/test/integration.mjs
@@ -43,11 +43,12 @@ const prep = (messages, previousSummary) => ({
   settings: { enabled: true, reserveTokens: 16384, keepRecentTokens: 20000 },
 });
 const controller = new AbortController();
+const notifications = [];
 let branch = [];
 const ctx = {
   cwd: process.cwd(),
-  hasUI: false,
-  ui: { notify() {} },
+  hasUI: true,
+  ui: { notify(message, level) { notifications.push({ message, level }); } },
   model: { ...model },
   modelRegistry: { async getApiKeyAndHeaders() { throw new Error("auth should not be needed in this test"); } },
   sessionManager: {
@@ -231,6 +232,16 @@ console.warn = () => {};
 const workerFailureWithArchive = await before({ type: "session_before_compact", preparation: prep(nextMessages, first.compaction.summary), branchEntries: branch, customInstructions: undefined, signal: controller.signal }, ctx);
 console.warn = originalWarn;
 if (workerFailureWithArchive?.cancel !== true) throw new Error("worker failure with an existing archive did not cancel safely");
+const retainedNotice = notifications.at(-1);
+if (
+  retainedNotice?.level !== "error" ||
+  !retainedNotice.message.includes("SnapCompact visual compaction failed: SnapCompact worker failed") ||
+  !retainedNotice.message.includes("maxArchiveTokens must be positive") ||
+  !retainedNotice.message.includes("text fallback also failed") ||
+  !retainedNotice.message.includes("existing archive was retained")
+) {
+  throw new Error(`worker failure notice hid the primary error: ${JSON.stringify(retainedNotice)}`);
+}
 ctx.model = { ...model, input: ["text"], contextWindow: 20000, maxTokens: 4096 };
 console.warn = () => {};
 const manual = await before({ type: "session_before_compact", preparation: prep(nextMessages, first.compaction.summary), branchEntries: branch, customInstructions: "focus on tests", signal: controller.signal }, ctx);