diff --git a/CHANGELOG.md b/CHANGELOG.md
index ed4614ce..ac20501b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# Unreleased
+
+## Fixes
+- Gemini CLI: reuse stored OAuth project IDs for quota checks and show clearer setup guidance when the project is missing (#1271)
+
 # v0.4.59 (2026-05-21)
 
 ## Fixes
@@ -508,4 +513,4 @@
 # v0.3.89 (2026-04-13)
 
 ## Improvements
-- Improved dashboard access control by blocking tunnel/Tailscale access when disabled
\ No newline at end of file
+- Improved dashboard access control by blocking tunnel/Tailscale access when disabled
diff --git a/open-sse/services/usage.js b/open-sse/services/usage.js
index 3144302c..26a10f72 100644
--- a/open-sse/services/usage.js
+++ b/open-sse/services/usage.js
@@ -58,13 +58,17 @@ const CLAUDE_CONFIG = {
  * @returns {Object} Usage data with quotas
  */
 export async function getUsageForProvider(connection, proxyOptions = null) {
-  const { provider, accessToken, apiKey, providerSpecificData } = connection;
+  const { provider, accessToken, apiKey, providerSpecificData, projectId } = connection;
+  const providerDataWithProjectId = {
+    ...(providerSpecificData || {}),
+    ...(projectId ? { projectId } : {}),
+  };
 
   switch (provider) {
     case "github":
       return await getGitHubUsage(accessToken, providerSpecificData, proxyOptions);
     case "gemini-cli":
-      return await getGeminiUsage(accessToken, providerSpecificData, proxyOptions);
+      return await getGeminiUsage(accessToken, providerDataWithProjectId, proxyOptions);
     case "antigravity":
       return await getAntigravityUsage(accessToken, providerSpecificData, proxyOptions);
     case "claude":
@@ -222,18 +226,22 @@ async function getGeminiUsage(accessToken, providerSpecificData, proxyOptions =
   }
 
   try {
-    // Resolve project id: prefer connection-stored id, else loadCodeAssist lookup
-    let projectId = providerSpecificData?.projectId || null;
+    // Resolve project id: prefer connection-stored id, else loadCodeAssist lookup.
+    // #1271: OAuth save stores projectId on the connection, not providerSpecificData.
+    let projectId = normalizeCloudCodeProjectId(providerSpecificData?.projectId);
     let plan = "Free";
 
     if (!projectId) {
       const subInfo = await getGeminiSubscriptionInfo(accessToken, proxyOptions);
-      projectId = subInfo?.cloudaicompanionProject || null;
+      projectId = normalizeCloudCodeProjectId(subInfo?.cloudaicompanionProject);
       plan = subInfo?.currentTier?.name || plan;
     }
 
     if (!projectId) {
-      return { plan, message: "Gemini CLI project ID not available." };
+      return {
+        plan,
+        message: "Gemini CLI project ID not available. Reconnect Gemini CLI, or configure a Google Cloud project with Gemini Code Assist access before checking quota.",
+      };
     }
 
     const controller = new AbortController();
@@ -289,6 +297,14 @@ async function getGeminiUsage(accessToken, providerSpecificData, proxyOptions =
   }
 }
 
+function normalizeCloudCodeProjectId(project) {
+  if (typeof project === "string") return project.trim() || null;
+  if (project && typeof project === "object" && typeof project.id === "string") {
+    return project.id.trim() || null;
+  }
+  return null;
+}
+
 /**
  * Get Gemini CLI subscription info via loadCodeAssist
  */
diff --git a/tests/unit/gemini-usage-projectid.test.js b/tests/unit/gemini-usage-projectid.test.js
new file mode 100644
index 00000000..0d06f2ca
--- /dev/null
+++ b/tests/unit/gemini-usage-projectid.test.js
@@ -0,0 +1,87 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+vi.mock("../../open-sse/utils/proxyFetch.js", () => ({
+  proxyAwareFetch: vi.fn(),
+}));
+
+import { proxyAwareFetch } from "../../open-sse/utils/proxyFetch.js";
+import { getUsageForProvider } from "../../open-sse/services/usage.js";
+
+function jsonResponse(body, status = 200) {
+  return new Response(JSON.stringify(body), {
+    status,
+    headers: { "Content-Type": "application/json" },
+  });
+}
+
+describe("Gemini CLI usage project id resolution", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("uses the projectId stored on the provider connection", async () => {
+    proxyAwareFetch.mockResolvedValueOnce(jsonResponse({
+      buckets: [
+        {
+          modelId: "gemini-3-flash-preview",
+          remainingFraction: 0.75,
+          resetTime: "2026-05-25T12:00:00Z",
+        },
+      ],
+    }));
+
+    const usage = await getUsageForProvider({
+      provider: "gemini-cli",
+      accessToken: "token",
+      projectId: "cloud-code-project",
+    });
+
+    expect(proxyAwareFetch).toHaveBeenCalledTimes(1);
+    expect(proxyAwareFetch).toHaveBeenCalledWith(
+      "https://cloudcode-pa.googleapis.com/v1internal:retrieveUserQuota",
+      expect.objectContaining({
+        body: JSON.stringify({ project: "cloud-code-project" }),
+      }),
+      null
+    );
+    expect(usage.quotas["gemini-3-flash-preview"]).toMatchObject({
+      used: 250,
+      total: 1000,
+      remainingPercentage: 75,
+    });
+  });
+
+  it("normalizes project objects returned by loadCodeAssist", async () => {
+    proxyAwareFetch
+      .mockResolvedValueOnce(jsonResponse({
+        cloudaicompanionProject: { id: "project-from-load" },
+        currentTier: { name: "Free" },
+      }))
+      .mockResolvedValueOnce(jsonResponse({ buckets: [] }));
+
+    await getUsageForProvider({
+      provider: "gemini-cli",
+      accessToken: "token",
+    });
+
+    expect(proxyAwareFetch).toHaveBeenLastCalledWith(
+      "https://cloudcode-pa.googleapis.com/v1internal:retrieveUserQuota",
+      expect.objectContaining({
+        body: JSON.stringify({ project: "project-from-load" }),
+      }),
+      null
+    );
+  });
+
+  it("returns actionable guidance when no project id is available", async () => {
+    proxyAwareFetch.mockResolvedValueOnce(jsonResponse({}));
+
+    const usage = await getUsageForProvider({
+      provider: "gemini-cli",
+      accessToken: "token",
+    });
+
+    expect(usage.message).toContain("Reconnect Gemini CLI");
+    expect(usage.message).toContain("Gemini Code Assist");
+  });
+});