Show failed Codex image generations in the chat (#5810)

When a Codex image request fails, Codex completes the imageGeneration
item with status "failed", an empty result, and an optional failure
record. The image mapper only knew how to render a successful image, so
it returned nothing and the item vanished from the live timeline and
from reopened history. Failed items now map to a failed image_generation
tool call carrying the failure details.

Closes #5619

Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>
Co-authored-by: 3ae3ae <83870598+3ae3ae@users.noreply.github.com>

packages/server/src/server/agent/providers/codex-app-server-agent.test.ts

@@ -6192,6 +6192,107 @@ describe("Codex app-server provider", () => {
     ]);
   });
 
+  test.each([
+    [
+      "a usage limit",
+      { type: "usageLimitExceeded", limitId: "image_gen", resetsAt: 1786150800 },
+      { type: "usageLimitExceeded", limitId: "image_gen", resetsAt: 1786150800 },
+    ],
+    ["no failure details", null, { message: "Image generation failed" }],
+  ])(
+    "emits failed imageGeneration items with %s as failed tool calls",
+    (_label, failure, expectedError) => {
+      const session = createSession();
+      const events: AgentStreamEvent[] = [];
+      session.subscribe((event) => events.push(event));
+
+      asInternals(session).handleNotification("item/completed", {
+        item: {
+          id: "image-generation-failed",
+          type: "imageGeneration",
+          status: "failed",
+          revisedPrompt: "paint a blue whale",
+          result: "",
+          transparentBackground: null,
+          failure,
+          savedPath: null,
+        },
+      });
+
+      expect(events).toEqual([
+        {
+          type: "timeline",
+          provider: "codex",
+          turnId: "test-turn",
+          item: {
+            type: "tool_call",
+            callId: "image-generation-failed",
+            name: "image_generation",
+            status: "failed",
+            error: expectedError,
+            detail: {
+              type: "unknown",
+              input: { prompt: "paint a blue whale" },
+              output: null,
+            },
+          },
+        },
+      ]);
+    },
+  );
+
+  test("keeps failed imageGeneration items in persisted history", async () => {
+    const session = createSession();
+    session.client = {
+      request: vi.fn(async () => ({
+        thread: {
+          turns: [
+            {
+              items: [
+                {
+                  type: "imageGeneration",
+                  id: "image-generation-failed",
+                  status: "failed",
+                  revisedPrompt: "paint a blue whale",
+                  result: "",
+                  transparentBackground: null,
+                  failure: { type: "usageLimitExceeded", limitId: "image_gen", resetsAt: null },
+                  savedPath: null,
+                },
+              ],
+            },
+          ],
+        },
+      })),
+    };
+
+    await asInternals(session).loadPersistedHistory(session.client);
+
+    const history: AgentStreamEvent[] = [];
+    for await (const event of session.streamHistory()) {
+      history.push(event);
+    }
+
+    expect(history).toEqual([
+      {
+        type: "timeline",
+        provider: "codex",
+        item: {
+          type: "tool_call",
+          callId: "image-generation-failed",
+          name: "image_generation",
+          status: "failed",
+          error: { type: "usageLimitExceeded", limitId: "image_gen", resetsAt: null },
+          detail: {
+            type: "unknown",
+            input: { prompt: "paint a blue whale" },
+            output: null,
+          },
+        },
+      },
+    ]);
+  });
+
   test("emits usage_updated on token usage updates and keeps usage on turn completion", () => {
     const session = createSession();
     const events: AgentStreamEvent[] = [];

packages/server/src/server/agent/providers/codex-app-server-agent.ts

@@ -1949,6 +1949,15 @@ function mapCodexThreadImageItem(
     });
   }
 
+  if (normalizedItem.status === "failed") {
+    return mapCodexToolCallEnvelope({
+      callId: firstStringField(normalizedItem, ["id"]),
+      name: "image_generation",
+      input: { prompt: firstStringField(normalizedItem, ["revisedPrompt", "revised_prompt"]) },
+      error: normalizedItem.failure ?? { message: "Image generation failed" },
+    });
+  }
+
   const savedPath = firstStringField(normalizedItem, ["savedPath", "saved_path"]);
   const result = codexImageOutputFromResult(normalizedItem.result);
   return renderProviderImageOutputAsAssistantMarkdown(