fix(coding-agent): preserve codex web search backend error diagnostics

The Codex SSE `type:"error"` branch read only top-level `code`/`message`,
so backend rejections emitted under a nested `error` or `response.error`
object collapsed to `Codex error (): Unknown error`, hiding the cause
(e.g. a regional/model-snapshot rejection). `response.failed` similarly
dropped the error code.

Add a shared `extractCodexSseError` that reads top-level, nested `error`,
and `response.error` envelopes, and wire both error paths through it so
the backend code and message survive in `SearchProviderError`. The
existing `web_search_call` requirement is untouched.

Fixes #7200

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed Codex web search collapsing backend errors to `Codex error (): Unknown error`; the SSE error parser now preserves the backend code and message from top-level, nested `error`, and `response.error` envelopes ([#7200](https://github.com/can1357/oh-my-pi/issues/7200)).
+
 ## [17.2.2] - 2026-07-31
 
 ### Added

packages/coding-agent/src/web/search/providers/codex.ts

@@ -407,6 +407,30 @@ function buildCodexHeaders(
 	return headers;
 }
 
+/**
+ * Extracts a backend error `{code, message}` from a Codex SSE event, tolerating
+ * the envelope shapes the ChatGPT Codex backend emits: top-level `{code,message}`,
+ * a nested `error` object, and a `response.error` object (as in `response.failed`).
+ * Without this the nested shapes collapse to `Codex error (): Unknown error`,
+ * discarding the backend diagnostic — e.g. a regional/model-snapshot rejection (#7200).
+ */
+function extractCodexSseError(rawEvent: Record<string, unknown>): { code: string; message: string } {
+	const candidates: unknown[] = [
+		rawEvent,
+		rawEvent.error,
+		(rawEvent.response as { error?: unknown } | undefined)?.error,
+	];
+	let code = "";
+	let message = "";
+	for (const candidate of candidates) {
+		if (!candidate || typeof candidate !== "object") continue;
+		const record = candidate as Record<string, unknown>;
+		if (!code && typeof record.code === "string" && record.code) code = record.code;
+		if (!message && typeof record.message === "string" && record.message) message = record.message;
+	}
+	return { code, message };
+}
+
 /**
  * Calls the Codex Responses API with web search tool enabled.
  * The caller provides the exact model id to send; retry / fallback policy
@@ -558,13 +582,14 @@ async function callCodexSearch(
 				}
 			}
 		} else if (eventType === "error") {
-			const code = (rawEvent as { code?: string }).code ?? "";
-			const message = (rawEvent as { message?: string }).message ?? "Unknown error";
-			throw new SearchProviderError("codex", `Codex error (${code}): ${message}`, 500);
+			const { code, message } = extractCodexSseError(rawEvent);
+			throw new SearchProviderError("codex", `Codex error (${code}): ${message || "Unknown error"}`, 500);
 		} else if (eventType === "response.failed") {
-			const resp = (rawEvent as { response?: { error?: { message?: string } } }).response;
-			const errorMessage = resp?.error?.message ?? "Request failed";
-			throw new SearchProviderError("codex", `Codex request failed: ${errorMessage}`, 500);
+			const { code, message } = extractCodexSseError(rawEvent);
+			const detail = code
+				? `Codex request failed (${code}): ${message || "Request failed"}`
+				: `Codex request failed: ${message || "Request failed"}`;
+			throw new SearchProviderError("codex", detail, 500);
 		}
 	}
 

packages/coding-agent/test/tools/web-search-codex.test.ts

@@ -752,4 +752,44 @@ describe("searchCodex model selection", () => {
 		expect(result.model).toBe("gpt-5.6-terra");
 		expect(result.sources).toEqual([{ title: "Example Article", url: "https://example.com/article" }]);
 	});
+
+	it("preserves a nested type:error code and message instead of Unknown error (#7200)", async () => {
+		delete process.env.PI_CODEX_WEB_SEARCH_MODEL;
+		const sse = [
+			`data: ${JSON.stringify({
+				type: "error",
+				error: {
+					code: "unsupported_region",
+					message: "web_search is not available for this workspace's data residency region.",
+				},
+			})}`,
+			"",
+		].join("\n");
+		const fetchMock: FetchImpl = () =>
+			Promise.resolve(new Response(sse, { status: 200, headers: { "Content-Type": "text/event-stream" } }));
+
+		await expect(searchCodex(makeSearchParams("nested error envelope", fetchMock))).rejects.toThrow(
+			"Codex error (unsupported_region): web_search is not available for this workspace's data residency region.",
+		);
+	});
+
+	it("preserves a structured response.failed error code and message (#7200)", async () => {
+		delete process.env.PI_CODEX_WEB_SEARCH_MODEL;
+		const sse = [
+			`data: ${JSON.stringify({
+				type: "response.failed",
+				response: {
+					id: "resp_failed",
+					error: { code: "model_snapshot_unavailable", message: "The requested model snapshot is unavailable." },
+				},
+			})}`,
+			"",
+		].join("\n");
+		const fetchMock: FetchImpl = () =>
+			Promise.resolve(new Response(sse, { status: 200, headers: { "Content-Type": "text/event-stream" } }));
+
+		await expect(searchCodex(makeSearchParams("structured failure", fetchMock))).rejects.toThrow(
+			"Codex request failed (model_snapshot_unavailable): The requested model snapshot is unavailable.",
+		);
+	});
 });