diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 7eab3b30c..3da36ee85 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -172,6 +172,7 @@
 - Fixed OAuth `launchUrl` advertisement for flows whose redirect never returns to the local callback server: custom-scheme redirects (e.g. GitLab Duo's `vscode://` URI, which `new URL` parses without complaint) and fixed non-loopback hosts no longer receive a `http://localhost:<port>/launch` copy target that misrepresents the callback endpoint and resolves nowhere for remote users.
 - Codex load balancing: clear stale persisted and in-memory usage-limit blocks for an `openai-codex` account when a fresh live usage report shows it is allowed and below all limits, including broker-backed gateway snapshots, so traffic returns to recovered accounts instead of funneling to one sibling.
 - Fixed Cursor `max_mode` requests to send discovered max-mode metadata on both model payload fields. ([#4797](https://github.com/can1357/oh-my-pi/issues/4797))
+- Fixed `auth-broker` config discovery ignoring nested `auth.broker.url` / `auth.broker.token` YAML keys. `readConfigYaml` only read the literal flat dotted key, so standard nested YAML was silently dropped; it now resolves both nested and flat forms (nested wins). ([#4734](https://github.com/can1357/oh-my-pi/issues/4734))
 
 ## [16.3.11] - 2026-07-06
 
diff --git a/packages/ai/src/auth-broker/discover.ts b/packages/ai/src/auth-broker/discover.ts
index 71ef2c5fe..7cb08cb26 100644
--- a/packages/ai/src/auth-broker/discover.ts
+++ b/packages/ai/src/auth-broker/discover.ts
@@ -72,6 +72,26 @@ interface ConfigSnapshot {
 	token?: string;
 }
 
+/**
+ * Resolve a dotted config key (e.g. `auth.broker.url`) against a parsed YAML
+ * record, accepting both nested form (`auth: { broker: { url } }`) and the
+ * legacy flat literal-dot key (`"auth.broker.url": ...`). Nested wins when both
+ * are present. Returns the value only when it is a string.
+ */
+function readDottedString(record: Record<string, unknown>, dottedKey: string): string | undefined {
+	let current: unknown = record;
+	for (const segment of dottedKey.split(".")) {
+		if (current === null || typeof current !== "object" || Array.isArray(current)) {
+			current = undefined;
+			break;
+		}
+		current = (current as Record<string, unknown>)[segment];
+	}
+	if (typeof current === "string") return current;
+	const flat = record[dottedKey];
+	return typeof flat === "string" ? flat : undefined;
+}
+
 async function readConfigYaml(agentDir: string): Promise<ConfigSnapshot> {
 	for (const filename of MAIN_CONFIG_FILENAMES) {
 		const configPath = path.join(agentDir, filename);
@@ -80,9 +100,8 @@ async function readConfigYaml(agentDir: string): Promise<ConfigSnapshot> {
 			const parsed = YAML.parse(raw);
 			if (!parsed || typeof parsed !== "object" || Array.isArray(parsed)) return {};
 			const record = parsed as Record<string, unknown>;
-			const url = typeof record["auth.broker.url"] === "string" ? (record["auth.broker.url"] as string) : undefined;
-			const token =
-				typeof record["auth.broker.token"] === "string" ? (record["auth.broker.token"] as string) : undefined;
+			const url = readDottedString(record, "auth.broker.url");
+			const token = readDottedString(record, "auth.broker.token");
 			return { url, token };
 		} catch (err) {
 			if (isEnoent(err)) continue;
diff --git a/packages/ai/test/auth-broker-nested-config.test.ts b/packages/ai/test/auth-broker-nested-config.test.ts
new file mode 100644
index 000000000..b2f69e1fa
--- /dev/null
+++ b/packages/ai/test/auth-broker-nested-config.test.ts
@@ -0,0 +1,65 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import * as fs from "node:fs/promises";
+import * as os from "node:os";
+import * as path from "node:path";
+import { resolveAuthBrokerConfig } from "@oh-my-pi/pi-ai/auth-broker";
+import { removeWithRetries } from "../../utils/src/temp";
+import { withEnv } from "./helpers";
+
+const CLEAR_BROKER_ENV = {
+	OMP_AUTH_BROKER_URL: undefined,
+	OMP_AUTH_BROKER_TOKEN: undefined,
+} as const;
+
+describe("auth-broker config.yml key resolution", () => {
+	let agentDir = "";
+
+	beforeEach(async () => {
+		agentDir = await fs.mkdtemp(path.join(os.tmpdir(), "pi-ai-auth-broker-config-"));
+	});
+
+	afterEach(async () => {
+		if (agentDir) await removeWithRetries(agentDir);
+		agentDir = "";
+	});
+
+	async function writeConfig(yaml: string): Promise<void> {
+		await Bun.write(path.join(agentDir, "config.yml"), yaml);
+	}
+
+	test("nested YAML keys resolve broker url and token", async () => {
+		await writeConfig(
+			["auth:", "  broker:", "    url: https://broker.example", "    token: nested-token", ""].join("\n"),
+		);
+		await withEnv(CLEAR_BROKER_ENV, async () => {
+			const config = await resolveAuthBrokerConfig({ agentDir });
+			expect(config).toEqual({ url: "https://broker.example", token: "nested-token" });
+		});
+	});
+
+	test("legacy flat dotted keys still resolve", async () => {
+		await writeConfig(['"auth.broker.url": https://flat.example', '"auth.broker.token": flat-token', ""].join("\n"));
+		await withEnv(CLEAR_BROKER_ENV, async () => {
+			const config = await resolveAuthBrokerConfig({ agentDir });
+			expect(config).toEqual({ url: "https://flat.example", token: "flat-token" });
+		});
+	});
+
+	test("nested value wins over the flat dotted key", async () => {
+		await writeConfig(
+			[
+				'"auth.broker.url": https://flat.example',
+				'"auth.broker.token": flat-token',
+				"auth:",
+				"  broker:",
+				"    url: https://nested.example",
+				"    token: nested-token",
+				"",
+			].join("\n"),
+		);
+		await withEnv(CLEAR_BROKER_ENV, async () => {
+			const config = await resolveAuthBrokerConfig({ agentDir });
+			expect(config).toEqual({ url: "https://nested.example", token: "nested-token" });
+		});
+	});
+});