diff --git a/bun.lock b/bun.lock
index 12089398..fa6a3269 100644
--- a/bun.lock
+++ b/bun.lock
@@ -1788,7 +1788,7 @@
 
     "@types/mysql": ["@types/mysql@2.15.27", "", { "dependencies": { "@types/node": "*" } }, "sha512-YfWiV16IY0OeBfBCk8+hXKmdTKrKlwKN1MNKAPBu5JYxLwBEZl7QzeEpGnlZb3VMGJrrGmB84gXiH+ofs/TezA=="],
 
-    "@types/node": ["@types/node@25.0.7", "", { "dependencies": { "undici-types": "~7.16.0" } }, "sha512-C/er7DlIZgRJO7WtTdYovjIFzGsz0I95UlMyR9anTb4aCpBSRWe5Jc1/RvLKUfzmOxHPGjSE5+63HgLtndxU4w=="],
+    "@types/node": ["@types/node@25.0.8", "", { "dependencies": { "undici-types": "~7.16.0" } }, "sha512-powIePYMmC3ibL0UJ2i2s0WIbq6cg6UyVFQxSCpaPxxzAaziRfimGivjdF943sSGV6RADVbk0Nvlm5P/FB44Zg=="],
 
     "@types/normalize-package-data": ["@types/normalize-package-data@2.4.4", "", {}, "sha512-37i+OaWTh9qeK4LSHPsyRC7NahnGotNuZvjLSgcPzblpHB3rrCJxAOgI5gCdKm7coonsaX1Of0ILiTcnZjbfxA=="],
 
diff --git a/internal/api/src/routes/auth/auth.server.ts b/internal/api/src/routes/auth/auth.server.ts
index ec8384e8..4cc68e20 100644
--- a/internal/api/src/routes/auth/auth.server.ts
+++ b/internal/api/src/routes/auth/auth.server.ts
@@ -302,6 +302,28 @@ async function handleOAuthCallback(
       password: null,
     });
 
+    // Auto-join team organizations (self-hosted mode)
+    if (c.env.autoJoinOrganizations) {
+      const teamOrgs = await db.selectTeamOrganizations();
+      if (teamOrgs.length === 0) {
+        // First user: create default org, make them owner
+        await db.insertOrganizationWithMembership({
+          name: "default",
+          kind: "organization",
+          created_by: user.id,
+        });
+      } else {
+        // Subsequent users: add as member to all existing team orgs
+        for (const org of teamOrgs) {
+          await db.insertOrganizationMembership({
+            organization_id: org.id,
+            user_id: user.id,
+            role: "member",
+          });
+        }
+      }
+    }
+
     // consume single-use invite (mark accepted)
     if (usedInviteId) {
       try {
@@ -926,6 +948,28 @@ export default function mountAuth(server: APIServer) {
         email_verified: emailVerified,
       });
 
+      // Auto-join team organizations (self-hosted mode)
+      if (c.env.autoJoinOrganizations) {
+        const teamOrgs = await db.selectTeamOrganizations();
+        if (teamOrgs.length === 0) {
+          // First user: create default org, make them owner
+          await db.insertOrganizationWithMembership({
+            name: "default",
+            kind: "organization",
+            created_by: user.id,
+          });
+        } else {
+          // Subsequent users: add as member to all existing team orgs
+          for (const org of teamOrgs) {
+            await db.insertOrganizationMembership({
+              organization_id: org.id,
+              user_id: user.id,
+              role: "member",
+            });
+          }
+        }
+      }
+
       // Sync user to telemetry system (async, don't block)
       if (c.env.sendTelemetryEvent) {
         c.env
diff --git a/internal/api/src/server.ts b/internal/api/src/server.ts
index 698850cd..0944d99e 100644
--- a/internal/api/src/server.ts
+++ b/internal/api/src/server.ts
@@ -236,6 +236,9 @@ export interface Bindings {
 
   readonly serverVersion: string;
 
+  /** When true, auto-add new users to all existing team organizations (self-hosted mode) */
+  readonly autoJoinOrganizations?: boolean;
+
   // Optional AWS credentials used by platform logging to CloudWatch
   readonly AWS_ACCESS_KEY_ID?: string;
   readonly AWS_SECRET_ACCESS_KEY?: string;
diff --git a/internal/database/src/querier.ts b/internal/database/src/querier.ts
index a03a9284..8aae626f 100644
--- a/internal/database/src/querier.ts
+++ b/internal/database/src/querier.ts
@@ -326,6 +326,15 @@ export default class Querier {
   }
 
   // selectOrganizationMembershipsByUserID fetches all organization memberships for a user.
+  // selectTeamOrganizations fetches all team (non-personal) organizations.
+  public async selectTeamOrganizations(): Promise<Organization[]> {
+    return this.db
+      .select()
+      .from(organization)
+      .where(eq(organization.kind, "organization"));
+  }
+
+
   public async selectOrganizationMembershipsByUserID(userId: string): Promise<
     Array<{
       organization_membership: OrganizationMembership;
diff --git a/packages/server/src/server.ts b/packages/server/src/server.ts
index f263efca..0bc5f5e8 100644
--- a/packages/server/src/server.ts
+++ b/packages/server/src/server.ts
@@ -130,6 +130,7 @@ export async function startServer(options: ServerOptions) {
           {
             AUTH_SECRET: authSecret,
             NODE_ENV: "development",
+            autoJoinOrganizations: true,
             serverVersion: pkg.version,
             ONBOARDING_AGENT_BUNDLE_URL:
               "https://artifacts.blink.host/starter-agent/bundle.tar.gz",