diff --git a/.changeset/fn-6193-merger-deleted-task.md b/.changeset/fn-6193-merger-deleted-task.md
new file mode 100644
index 0000000000..b646f69c68
--- /dev/null
+++ b/.changeset/fn-6193-merger-deleted-task.md
@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Fix merger AI commit finalization so deleted tasks no longer crash settings resolution while the merge is completing.
diff --git a/packages/engine/src/__tests__/merger-settings-degrade.test.ts b/packages/engine/src/__tests__/merger-settings-degrade.test.ts
new file mode 100644
index 0000000000..f7f8b9cdf3
--- /dev/null
+++ b/packages/engine/src/__tests__/merger-settings-degrade.test.ts
@@ -0,0 +1,43 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { BUILTIN_WORKFLOW_SETTINGS, type Settings } from "@fusion/core";
+import { mergeEffectiveSettings } from "../effective-settings.js";
+
+const PROJECT = "proj-1";
+
+function baseSettings(): Settings {
+  const catalogDefaults = Object.fromEntries(
+    BUILTIN_WORKFLOW_SETTINGS
+      .filter((setting) => setting.default !== undefined)
+      .map((setting) => [setting.id, setting.default]),
+  );
+  return {
+    ...catalogDefaults,
+    persistAgentToolOutput: false,
+    executionProvider: "project-anthropic",
+    executionModelId: "claude-project",
+  } as unknown as Settings;
+}
+
+describe("merger settings degrade path", () => {
+  it("uses a fallback task id so deleted-task getTask failures still return base settings", async () => {
+    const taskId = "FN-6193-DELETED";
+    const store = {
+      getTask: vi.fn(async () => {
+        throw new Error(`Task ${taskId} not found`);
+      }),
+      getTaskWorkflowSelection: vi.fn(() => {
+        throw new Error(`Task ${taskId} not found`);
+      }),
+      getWorkflowDefinition: vi.fn(async () => undefined),
+      getWorkflowSettingValues: vi.fn(() => ({})),
+      getWorkflowSettingsProjectId: vi.fn(() => PROJECT),
+    };
+    const base = baseSettings();
+
+    const taskForSettings = await store.getTask(taskId).catch(() => ({ id: taskId } as const));
+    const merged = await mergeEffectiveSettings(store as any, taskForSettings, base);
+
+    expect(merged).toEqual(base);
+  });
+});
diff --git a/packages/engine/src/merger.ts b/packages/engine/src/merger.ts
index d76103d78b..81fe69852a 100644
--- a/packages/engine/src/merger.ts
+++ b/packages/engine/src/merger.ts
@@ -11679,9 +11679,10 @@ async function runAiAgentForCommit(params: AiAgentParams): Promise<{ success: bo
   // Merge per-task effective workflow settings (U3, KTD-3) — this worker re-fetches
   // settings independently of aiMergeTask, so apply the same merge here (covers the
   // titleSummarizer lane reads in resolveSafeCommitBody). Behavior-inert by default.
+  const taskForSettings = await store.getTask(taskId).catch(() => ({ id: taskId } as const));
   const settings = await mergeEffectiveSettings(
     store,
-    await store.getTask(taskId),
+    taskForSettings,
     await store.getSettings(),
   );