From f8dfd9de33b4ebb8b7f510ec191545ed6d65a087 Mon Sep 17 00:00:00 2001
From: Aryan Falahatpisheh <aryanfalahat@gmail.com>
Date: Wed, 3 Jun 2026 13:12:12 -0400
Subject: [PATCH 1/2] Improve error parsing for billing errors

---
 src/apiv2.spec.ts | 14 ++++++++++++++
 src/apiv2.ts      |  6 +++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/apiv2.spec.ts b/src/apiv2.spec.ts
index 96652879b6f..1de401aa59d 100644
--- a/src/apiv2.spec.ts
+++ b/src/apiv2.spec.ts
@@ -162,6 +162,20 @@ describe("apiv2", () => {
       expect(nock.isDone()).to.be.true;
     });
 
+    it("should handle non-JSON error responses gracefully even when responseType is json", async () => {
+      const xml =
+        "<?xml version='1.0' encoding='UTF-8'?><Error><Code>BillingDisabled</Code></Error>";
+      nock("https://example.com").get("/path/to/foo").reply(403, xml);
+
+      const c = new Client({ urlPrefix: "https://example.com" });
+      const r = c.request({
+        method: "GET",
+        path: "/path/to/foo",
+      });
+      await expect(r).to.eventually.be.rejectedWith(FirebaseError, /BillingDisabled/);
+      expect(nock.isDone()).to.be.true;
+    });
+
     it("should error with a FirebaseError if an error happens", async () => {
       nock("https://example.com").get("/path/to/foo").replyWithError("boom");
 
diff --git a/src/apiv2.ts b/src/apiv2.ts
index c9b716f9609..e012bf216cf 100644
--- a/src/apiv2.ts
+++ b/src/apiv2.ts
@@ -477,7 +477,11 @@ export class Client {
               } catch (err: unknown) {
                 // JSON-parse errors are useless. Log the response for better debugging.
                 this.logResponse(res, text, options);
-                throw new FirebaseError(`Unable to parse JSON: ${err}`);
+                if (res.status >= 400) {
+                  body = text as unknown as ResT;
+                } else {
+                  throw new FirebaseError(`Unable to parse JSON: ${err}`);
+                }
               }
             }
           } else if (options.responseType === "xml") {

From d3bcc5633f4c17e8b4ff6c1e54c9be6e99903b5d Mon Sep 17 00:00:00 2001
From: Aryan Falahatpisheh <aryanfalahat@gmail.com>
Date: Tue, 16 Jun 2026 20:12:28 -0400
Subject: [PATCH 2/2] clean up error handling for billing specifically

---
 src/apphosting/secrets/index.spec.ts | 18 ++++++++++++++++++
 src/apphosting/secrets/index.ts      |  3 ++-
 src/error.ts                         |  3 ++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/apphosting/secrets/index.spec.ts b/src/apphosting/secrets/index.spec.ts
index 5dc86eb8253..e76c8f36597 100644
--- a/src/apphosting/secrets/index.spec.ts
+++ b/src/apphosting/secrets/index.spec.ts
@@ -189,6 +189,24 @@ describe("secrets", () => {
         undefined,
       );
     });
+
+    it("appends original message for 403 errors", async () => {
+      gcsm.getSecret.withArgs("project", "secret").rejects(new Error("Forbidden"));
+
+      await expect(secrets.upsertSecret("project", "secret")).to.be.rejectedWith("Unexpected error loading secret: Forbidden");
+    });
+
+    it("appends original message for 400 errors", async () => {
+      gcsm.getSecret.withArgs("project", "secret").rejects(new Error("Bad Request"));
+
+      await expect(secrets.upsertSecret("project", "secret")).to.be.rejectedWith("Unexpected error loading secret: Bad Request");
+    });
+
+    it("appends original message for other errors", async () => {
+      gcsm.getSecret.withArgs("project", "secret").rejects(new Error("Internal Error"));
+
+      await expect(secrets.upsertSecret("project", "secret")).to.be.rejectedWith("Unexpected error loading secret: Internal Error");
+    });
   });
 
   describe("toMulti", () => {
diff --git a/src/apphosting/secrets/index.ts b/src/apphosting/secrets/index.ts
index c85f0645abc..531b5b09f19 100644
--- a/src/apphosting/secrets/index.ts
+++ b/src/apphosting/secrets/index.ts
@@ -198,7 +198,8 @@ export async function upsertSecret(
     existing = await gcsm.getSecret(project, secret);
   } catch (err: unknown) {
     if (getErrStatus(err) !== 404) {
-      throw new FirebaseError("Unexpected error loading secret", { original: getError(err) });
+      const original = getError(err);
+      throw new FirebaseError(`Unexpected error loading secret: ${original.message}`, { original });
     }
     await gcsm.createSecret(project, secret, gcsm.labels("apphosting"), location);
     return true;
diff --git a/src/error.ts b/src/error.ts
index e85ddeaef71..30db9bb8b83 100644
--- a/src/error.ts
+++ b/src/error.ts
@@ -117,7 +117,8 @@ export function isBillingError(e: {
   return !!e.context?.body?.error?.details?.find((d) => {
     return (
       d.violations?.find((v) => v.type === "serviceusage/billing-enabled") ||
-      d.reason === "UREQ_PROJECT_BILLING_NOT_FOUND"
+      d.reason === "UREQ_PROJECT_BILLING_NOT_FOUND" ||
+      d.reason === "BILLING_DISABLED"
     );
   });
 }