diff --git a/apps/backend/src/lib/ai/ai-query-handlers.test.ts b/apps/backend/src/lib/ai/ai-query-handlers.test.ts
index a7a5df424..4a4d866fe 100644
--- a/apps/backend/src/lib/ai/ai-query-handlers.test.ts
+++ b/apps/backend/src/lib/ai/ai-query-handlers.test.ts
@@ -49,10 +49,12 @@ vi.mock("ai", async (importOriginal) => {
 });
 
 import { logAiQuery } from "@/lib/ai/loggers/ai-query-logger";
+import { logIfMcpToolCall } from "@/lib/ai/loggers/mcp-call-logger";
 import { handleStreamMode } from "./ai-query-handlers";
 import type { CommonLogFields } from "./types";
 
 const mockedLogAiQuery = vi.mocked(logAiQuery);
+const mockedLogIfMcpToolCall = vi.mocked(logIfMcpToolCall);
 
 const baseCommon: CommonLogFields = {
   correlationId: "test-correlation-id",
@@ -89,6 +91,7 @@ function makeCtx(): Parameters<typeof handleStreamMode>[0] {
 beforeEach(() => {
   hoisted.capturedCallbacks.current = undefined;
   mockedLogAiQuery.mockClear();
+  mockedLogIfMcpToolCall.mockClear();
 });
 
 describe("handleStreamMode terminal callback logging", () => {
@@ -180,4 +183,39 @@ describe("handleStreamMode terminal callback logging", () => {
     expect(mockedLogAiQuery).toHaveBeenCalledTimes(1);
     expect(mockedLogAiQuery).toHaveBeenCalledWith(expect.objectContaining({ type: "failure" }));
   });
+
+  // --- MCP call logging on stream failure ---------------------------------
+  // A failed MCP-backed question must still land in mcp_call_log (with its
+  // error) so it appears in the MCP Review workflow instead of vanishing.
+
+  const mcpCtx = () => ({
+    ...makeCtx(),
+    mcpCallMetadata: { toolName: "ask_hexclave", reason: "test", userPrompt: "prompt" },
+    conversationIdForLog: "conversation-1",
+  });
+
+  it("logs the MCP call with the error when a stream with mcpCallMetadata errors", () => {
+    handleStreamMode(mcpCtx());
+    hoisted.capturedCallbacks.current!.onError!({ error: new Error("upstream model error") });
+    expect(mockedLogIfMcpToolCall).toHaveBeenCalledTimes(1);
+    expect(mockedLogIfMcpToolCall).toHaveBeenCalledWith(expect.objectContaining({
+      errorMessage: expect.stringContaining("upstream model error"),
+    }));
+  });
+
+  it("logs the MCP call with the error when a stream with mcpCallMetadata aborts", () => {
+    handleStreamMode(mcpCtx());
+    hoisted.capturedCallbacks.current!.onAbort!();
+    expect(mockedLogIfMcpToolCall).toHaveBeenCalledTimes(1);
+    expect(mockedLogIfMcpToolCall).toHaveBeenCalledWith(expect.objectContaining({
+      errorMessage: expect.stringContaining("Stream aborted"),
+    }));
+  });
+
+  it("logs the MCP call at most once on rapid-fire abort+error", () => {
+    handleStreamMode(mcpCtx());
+    hoisted.capturedCallbacks.current!.onAbort!();
+    hoisted.capturedCallbacks.current!.onError!({ error: new DOMException("aborted", "AbortError") });
+    expect(mockedLogIfMcpToolCall).toHaveBeenCalledTimes(1);
+  });
 });
diff --git a/apps/backend/src/lib/ai/ai-query-handlers.ts b/apps/backend/src/lib/ai/ai-query-handlers.ts
index d7fd10d31..83ef13ec8 100644
--- a/apps/backend/src/lib/ai/ai-query-handlers.ts
+++ b/apps/backend/src/lib/ai/ai-query-handlers.ts
@@ -48,6 +48,23 @@ export function handleStreamMode(ctx: ModeContext & {
   // SpacetimeDB and trip the UNIQUE(correlation_id) constraint on the second
   // insert. Guard with a single boolean — the first terminal callback wins.
   let logged = false;
+  const logStreamFailure = (err: unknown) => {
+    clearTimeout(timeoutId);
+    if (logged) return;
+    logged = true;
+    logAiQuery({ type: "failure", common, startedAt, err, partialSteps: completedSteps });
+    logIfMcpToolCall({
+      mcpCallMetadata,
+      conversationIdForLog,
+      correlationId,
+      messages,
+      steps: completedSteps,
+      text: "",
+      startedAt,
+      modelId: String(model.modelId),
+      errorMessage: err instanceof Error ? err.stack ?? `${err.name}: ${err.message}` : String(err),
+    });
+  };
   const result = streamText({
     model,
     messages: messagesWithCachedSystemPrompt,
@@ -80,24 +97,8 @@ export function handleStreamMode(ctx: ModeContext & {
         modelId: String(model.modelId),
       });
     },
-    onError: ({ error }) => {
-      clearTimeout(timeoutId);
-      if (logged) return;
-      logged = true;
-      logAiQuery({ type: "failure", common, startedAt, err: error, partialSteps: completedSteps });
-    },
-    onAbort: () => {
-      clearTimeout(timeoutId);
-      if (logged) return;
-      logged = true;
-      logAiQuery({
-        type: "failure",
-        common,
-        startedAt,
-        err: new Error("Stream aborted (client disconnect or timeout)"),
-        partialSteps: completedSteps,
-      });
-    },
+    onError: ({ error }) => logStreamFailure(error),
+    onAbort: () => logStreamFailure(new Error("Stream aborted (client disconnect or timeout)")),
   });
   return {
     statusCode: 200,