diff --git a/backend/migrate_add_client_portal.py b/backend/migrate_add_client_portal.py
new file mode 100644
index 0000000..bc66f72
--- /dev/null
+++ b/backend/migrate_add_client_portal.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+"""
+Database migration: Client Portal (M1).
+
+Adds the authoritative client link to projects:
+  - projects.client_id  (TEXT, nullable)  -> clients.id
+
+The `clients` and `client_access_tokens` tables are created automatically by
+SQLAlchemy `create_all` at app startup (they're brand-new tables), so this
+migration only handles the column that create_all won't add to an existing
+`projects` table.
+
+Run once per database:
+    docker exec terra-view-terra-view-1 python3 backend/migrate_add_client_portal.py
+"""
+
+import sqlite3
+from pathlib import Path
+
+
+def migrate():
+    possible_paths = [
+        Path("data/seismo_fleet.db"),
+        Path("data/sfm.db"),
+        Path("data/seismo.db"),
+    ]
+    db_path = next((p for p in possible_paths if p.exists()), None)
+    if db_path is None:
+        print(f"Database not found in any of: {[str(p) for p in possible_paths]}")
+        print("A fresh DB created via models.py will include projects.client_id automatically.")
+        return
+
+    print(f"Using database: {db_path}")
+    conn = sqlite3.connect(db_path)
+    cursor = conn.cursor()
+
+    cursor.execute("PRAGMA table_info(projects)")
+    existing = {row[1] for row in cursor.fetchall()}
+
+    if "client_id" not in existing:
+        try:
+            cursor.execute("ALTER TABLE projects ADD COLUMN client_id TEXT")
+            print("✓ Added column: projects.client_id (TEXT)")
+        except sqlite3.OperationalError as e:
+            print(f"✗ Failed to add projects.client_id: {e}")
+    else:
+        print("○ Column already exists: projects.client_id")
+
+    conn.commit()
+    conn.close()
+    print("\n✓ Client-portal migration complete.")
+    print("  Note: `clients` + `client_access_tokens` tables auto-create on app startup.")
+
+
+if __name__ == "__main__":
+    migrate()
diff --git a/backend/models.py b/backend/models.py
index aae3039..8c5d5e9 100644
--- a/backend/models.py
+++ b/backend/models.py
@@ -192,6 +192,7 @@ class Project(Base):
 
     # Project metadata
     client_name = Column(String, nullable=True, index=True)  # Client name (e.g., "PJ Dick")
+    client_id = Column(String, nullable=True, index=True)    # FK -> clients.id; authoritative portal link (client_name kept for display)
     site_address = Column(String, nullable=True)
     site_coordinates = Column(String, nullable=True)  # "lat,lon"
     start_date = Column(Date, nullable=True)
@@ -704,3 +705,37 @@ class PendingDeployment(Base):
 
     created_at = Column(DateTime, default=datetime.utcnow)
     updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+
+# ============================================================================
+# CLIENT PORTAL — read-only, scoped client access (see docs/CLIENT_PORTAL.md)
+# ============================================================================
+
+class Client(Base):
+    """A portal client (customer org). Owns one or more Projects via
+    Project.client_id; their portal surfaces only those projects' locations.
+    Read-only — clients never control devices."""
+    __tablename__ = "clients"
+
+    id = Column(String, primary_key=True, index=True)        # UUID
+    name = Column(String, nullable=False)                    # display name, e.g. "PJ Dick"
+    slug = Column(String, nullable=False, unique=True, index=True)  # URL-safe handle
+    contact_email = Column(String, nullable=True)            # for M4 magic-link
+    active = Column(Boolean, default=True)                   # False = portal access off
+    created_at = Column(DateTime, default=datetime.utcnow)
+
+
+class ClientAccessToken(Base):
+    """Interim 'magic URL' gate (M1-M3). The raw secret lives in the link and is
+    shown once on creation; only its sha256 is stored here. Revoke by setting
+    revoked_at. In M4 this is replaced behind get_current_client() without
+    touching routes/templates."""
+    __tablename__ = "client_access_tokens"
+
+    id = Column(String, primary_key=True, index=True)        # UUID
+    client_id = Column(String, nullable=False, index=True)   # FK -> clients.id
+    token_hash = Column(String, nullable=False, index=True)  # sha256 hex of the secret
+    label = Column(String, nullable=True)                    # e.g. "Dave's link"
+    created_at = Column(DateTime, default=datetime.utcnow)
+    last_used_at = Column(DateTime, nullable=True)
+    revoked_at = Column(DateTime, nullable=True)             # set = link no longer works