diff --git a/src/auth.js b/src/auth.js
index 596290b..1059046 100644
--- a/src/auth.js
+++ b/src/auth.js
@@ -3,6 +3,7 @@ import { betterAuth } from "better-auth";
 import { admin, magicLink, jwt } from "better-auth/plugins";
 import { oauthProvider } from "@better-auth/oauth-provider";
 import appConfig from "./config.js";
+import { getGithubUserInfo } from "./auth/github-provider.js";
 import { devMagicLinks } from "./dev/magic-links.js";
 import { buildMagicLinkPayload } from "./app/utils/magic-link-email.js";
 
@@ -35,6 +36,9 @@ export const auth = betterAuth({
     github: {
       clientId: appConfig.social.github.id,
       clientSecret: appConfig.social.github.secret,
+      // Resolve the account email from /user/emails (primary + verified) so
+      // returning GitHub users match their existing planner accounts.
+      getUserInfo: getGithubUserInfo,
     },
   },
   telemetry: {
diff --git a/src/auth/github-provider.js b/src/auth/github-provider.js
new file mode 100644
index 0000000..b1cb113
--- /dev/null
+++ b/src/auth/github-provider.js
@@ -0,0 +1,62 @@
+// GitHub requires a descriptive User-Agent on API requests.
+const GITHUB_API = "https://api.github.com";
+const USER_AGENT = "codebar-auth";
+
+/**
+ * GET a GitHub API endpoint with the user's access token.
+ * Returns parsed JSON, or null on a non-2xx response.
+ */
+async function githubFetch(path, accessToken) {
+  try {
+    const res = await fetch(`${GITHUB_API}${path}`, {
+      headers: {
+        Authorization: `Bearer ${accessToken}`,
+        "User-Agent": USER_AGENT,
+        Accept: "application/vnd.github+json",
+      },
+    });
+    if (!res.ok) return null;
+    return res.json();
+  } catch {
+    // Fail soft: a network error here must not turn the OAuth callback into a
+    // 500. Better Auth's default getUserInfo returns null on failure too.
+    return null;
+  }
+}
+
+/**
+ * Build the better-auth GitHub user from GitHub's profile + email endpoints.
+ *
+ * Resolves the email the same way the planner's legacy omniauth-github
+ * integration did: prefer the primary and verified address from
+ * /user/emails. Better Auth's default prioritises /user.email (the public
+ * profile email), which routinely differs from the primary account email and
+ * made returning users appear to be new signups.
+ *
+ * Returns the shape better-auth's github provider getUserInfo hook expects:
+ * `{ user, data }`.
+ */
+export async function getGithubUserInfo({ accessToken }) {
+  const [profile, emails] = await Promise.all([
+    githubFetch("/user", accessToken),
+    githubFetch("/user/emails", accessToken),
+  ]);
+
+  const primary = emails?.find((e) => e.primary && e.verified);
+  const email = primary?.email || profile?.email || emails?.[0]?.email || "";
+  const emailVerified =
+    primary !== undefined
+      ? true
+      : (emails?.some((e) => e.email === email && e.verified) ?? false);
+
+  return {
+    user: {
+      id: String(profile?.id ?? ""),
+      name: profile?.name || profile?.login || "",
+      email,
+      image: profile?.avatar_url,
+      emailVerified,
+    },
+    data: profile,
+  };
+}
diff --git a/test/unit/github-provider.test.js b/test/unit/github-provider.test.js
new file mode 100644
index 0000000..ee17722
--- /dev/null
+++ b/test/unit/github-provider.test.js
@@ -0,0 +1,103 @@
+import { test } from "tap";
+import { getGithubUserInfo } from "../../src/auth/github-provider.js";
+
+const originalFetch = global.fetch;
+
+function mockFetch(routes) {
+  global.fetch = async (url) => {
+    const path = new URL(url).pathname;
+    const body = routes[path];
+    if (!body) {
+      return { ok: false, json: async () => null };
+    }
+    return { ok: true, json: async () => body };
+  };
+}
+
+function afterFetch(t) {
+  t.after(() => {
+    global.fetch = originalFetch;
+  });
+}
+
+test("prefers primary verified email over the public profile email", async (t) => {
+  afterFetch(t);
+  mockFetch({
+    "/user": {
+      id: 12345678,
+      login: "jdoe",
+      name: "Jane Doe",
+      email: "jane@example.com",
+    },
+    "/user/emails": [
+      { email: "jane@example.com", primary: false, verified: true },
+      { email: "jane.doe@work.example", primary: true, verified: true },
+    ],
+  });
+
+  const { user } = await getGithubUserInfo({ accessToken: "token" });
+
+  t.equal(user.email, "jane.doe@work.example");
+  t.equal(user.emailVerified, true);
+  t.equal(user.id, "12345678");
+  t.equal(user.name, "Jane Doe");
+});
+
+test("falls back to the public profile email when no primary is verified", async (t) => {
+  afterFetch(t);
+  mockFetch({
+    "/user": {
+      id: 1,
+      login: "alice",
+      name: "Alice",
+      email: "alice@example.com",
+    },
+    "/user/emails": [
+      { email: "alice@example.com", primary: true, verified: false },
+    ],
+  });
+
+  const { user } = await getGithubUserInfo({ accessToken: "token" });
+
+  t.equal(user.email, "alice@example.com");
+  t.equal(user.emailVerified, false);
+});
+
+test("uses the public profile email when /user/emails has no entries", async (t) => {
+  afterFetch(t);
+  mockFetch({
+    "/user": { id: 2, login: "bob", email: "bob@example.com" },
+    "/user/emails": [],
+  });
+
+  const { user } = await getGithubUserInfo({ accessToken: "token" });
+
+  t.equal(user.email, "bob@example.com");
+});
+
+test("falls back to the first listed email when profile email is blank", async (t) => {
+  afterFetch(t);
+  mockFetch({
+    "/user": { id: 3, login: "carol" },
+    "/user/emails": [
+      { email: "carol@example.com", primary: true, verified: true },
+    ],
+  });
+
+  const { user } = await getGithubUserInfo({ accessToken: "token" });
+
+  t.equal(user.email, "carol@example.com");
+  t.equal(user.emailVerified, true);
+});
+
+test("returns a user without throwing when GitHub call throws", async (t) => {
+  afterFetch(t);
+  global.fetch = async () => {
+    throw new Error("network down");
+  };
+
+  const { user } = await getGithubUserInfo({ accessToken: "token" });
+
+  t.equal(user.email, "");
+  t.equal(user.emailVerified, false);
+});