diff --git a/src/db/migrations/007_runtime-service-metadata.ts b/src/db/migrations/007_runtime-service-metadata.ts
index 61ac6bb..70a076e 100644
--- a/src/db/migrations/007_runtime-service-metadata.ts
+++ b/src/db/migrations/007_runtime-service-metadata.ts
@@ -6,9 +6,14 @@ import {
   fillCanonicalChannelOwnerLeaseMetadata,
   fillCanonicalPairedTaskMetadata,
   fillCanonicalServiceHandoffMetadata,
+  inferExecutionLeaseServiceIdFromCanonicalMetadata,
 } from '../canonical-role-metadata.js';
 import { normalizeStoredAgentType } from '../room-registration.js';
-import { tableHasColumn, tryExecMigration } from './helpers.js';
+import {
+  getTableColumns,
+  tableHasColumn,
+  tryExecMigration,
+} from './helpers.js';
 import type { SchemaMigrationDefinition } from './types.js';
 
 interface StoredPairedTaskServiceRow {
@@ -52,6 +57,17 @@ interface StoredWorkItemServiceRow {
   delivery_role?: string | null;
 }
 
+interface LegacyExecutionLeaseServiceRow {
+  rowid: number;
+  role: string;
+  owner_service_id?: string | null;
+  reviewer_service_id?: string | null;
+  arbiter_service_id?: string | null;
+  owner_agent_type?: string | null;
+  reviewer_agent_type?: string | null;
+  arbiter_agent_type?: string | null;
+}
+
 function normalizePairedRole(
   role: string | null | undefined,
 ): 'owner' | 'reviewer' | 'arbiter' | null {
@@ -354,10 +370,110 @@ function backfillCanonicalWorkItemServiceIds(database: Database): void {
   tx(rows);
 }
 
+function backfillLegacyExecutionLeaseServiceShadows(database: Database): void {
+  if (
+    !tableHasColumn(
+      database,
+      'paired_task_execution_leases',
+      'claimed_service_id',
+    )
+  ) {
+    return;
+  }
+
+  const pairedTasksTable = database
+    .prepare(
+      `
+        SELECT 1
+          FROM sqlite_master
+         WHERE type = 'table'
+           AND name = 'paired_tasks'
+      `,
+    )
+    .get();
+  if (!pairedTasksTable) {
+    return;
+  }
+
+  const pairedTaskColumns = getTableColumns(database, 'paired_tasks');
+  const selectPairedTaskColumn = (columnName: string): string =>
+    pairedTaskColumns.includes(columnName)
+      ? `paired_tasks.${columnName} AS ${columnName}`
+      : `NULL AS ${columnName}`;
+
+  const rows = database
+    .prepare(
+      `
+        SELECT
+          paired_task_execution_leases.rowid AS rowid,
+          paired_task_execution_leases.role AS role,
+          ${selectPairedTaskColumn('owner_service_id')},
+          ${selectPairedTaskColumn('reviewer_service_id')},
+          ${selectPairedTaskColumn('arbiter_service_id')},
+          ${selectPairedTaskColumn('owner_agent_type')},
+          ${selectPairedTaskColumn('reviewer_agent_type')},
+          ${selectPairedTaskColumn('arbiter_agent_type')}
+        FROM paired_task_execution_leases
+        LEFT JOIN paired_tasks
+          ON paired_tasks.id = paired_task_execution_leases.task_id
+       WHERE paired_task_execution_leases.claimed_service_id IS NULL
+      `,
+    )
+    .all() as LegacyExecutionLeaseServiceRow[];
+
+  if (rows.length === 0) {
+    return;
+  }
+
+  const update = database.prepare(
+    `
+      UPDATE paired_task_execution_leases
+         SET claimed_service_id = ?
+       WHERE rowid = ?
+         AND claimed_service_id IS NULL
+    `,
+  );
+  const tx = database.transaction(
+    (leaseRows: LegacyExecutionLeaseServiceRow[]) => {
+      for (const row of leaseRows) {
+        const claimedServiceId =
+          inferExecutionLeaseServiceIdFromCanonicalMetadata(row);
+        if (!claimedServiceId) {
+          continue;
+        }
+
+        update.run(claimedServiceId, row.rowid);
+      }
+    },
+  );
+
+  tx(rows);
+}
+
 export const RUNTIME_SERVICE_METADATA_MIGRATION = {
   version: 7,
   name: 'runtime_service_metadata',
   apply(database) {
+    for (const statement of [
+      `ALTER TABLE service_handoffs ADD COLUMN intended_role TEXT`,
+      `ALTER TABLE service_handoffs ADD COLUMN source_role TEXT`,
+      `ALTER TABLE service_handoffs ADD COLUMN target_role TEXT`,
+      `ALTER TABLE service_handoffs ADD COLUMN source_agent_type TEXT`,
+      `ALTER TABLE service_handoffs ADD COLUMN source_service_id TEXT`,
+      `ALTER TABLE service_handoffs ADD COLUMN target_service_id TEXT`,
+      `ALTER TABLE paired_tasks ADD COLUMN owner_service_id TEXT`,
+      `ALTER TABLE paired_tasks ADD COLUMN reviewer_service_id TEXT`,
+      `ALTER TABLE paired_tasks ADD COLUMN owner_agent_type TEXT`,
+      `ALTER TABLE paired_tasks ADD COLUMN reviewer_agent_type TEXT`,
+      `ALTER TABLE paired_tasks ADD COLUMN arbiter_agent_type TEXT`,
+      `ALTER TABLE paired_task_execution_leases ADD COLUMN expires_at TEXT`,
+      `ALTER TABLE paired_task_execution_leases ADD COLUMN claimed_service_id TEXT`,
+      `ALTER TABLE work_items ADD COLUMN delivery_role TEXT`,
+      `ALTER TABLE work_items ADD COLUMN service_id TEXT`,
+    ]) {
+      tryExecMigration(database, statement);
+    }
+
     for (const column of [
       'owner_service_id',
       'reviewer_service_id',
@@ -372,9 +488,22 @@ export const RUNTIME_SERVICE_METADATA_MIGRATION = {
       );
     }
 
+    database.exec(`
+      UPDATE paired_task_execution_leases
+         SET expires_at = COALESCE(
+           expires_at,
+           strftime('%Y-%m-%dT%H:%M:%fZ', 'now', '+10 minutes')
+         )
+    `);
+    database.exec(`
+      CREATE INDEX IF NOT EXISTS idx_paired_task_execution_leases_expires_at
+        ON paired_task_execution_leases(expires_at)
+    `);
+
     backfillCanonicalPairedTaskServiceIds(database);
     backfillCanonicalChannelOwnerServiceIds(database);
     backfillCanonicalServiceHandoffServiceIds(database);
     backfillCanonicalWorkItemServiceIds(database);
+    backfillLegacyExecutionLeaseServiceShadows(database);
   },
 } satisfies SchemaMigrationDefinition;
diff --git a/src/db/schema.ts b/src/db/schema.ts
index 55e1bc4..5a7531f 100644
--- a/src/db/schema.ts
+++ b/src/db/schema.ts
@@ -1,12 +1,7 @@
 import { Database } from 'bun:sqlite';
 
-import { inferExecutionLeaseServiceIdFromCanonicalMetadata } from './canonical-role-metadata.js';
 import { buildPairedTurnAttemptId } from './paired-turn-attempts.js';
-import {
-  getTableColumns,
-  tableHasColumn,
-  tryExecMigration,
-} from './migrations/helpers.js';
+import { tableHasColumn, tryExecMigration } from './migrations/helpers.js';
 
 // Legacy monolithic migration bundle kept for compatibility with databases
 // that predate ordered schema migration tracking. New schema changes belong in
@@ -145,17 +140,6 @@ function tableHasForeignKey(
   return false;
 }
 
-interface LegacyExecutionLeaseServiceRow {
-  rowid: number;
-  role: string;
-  owner_service_id?: string | null;
-  reviewer_service_id?: string | null;
-  arbiter_service_id?: string | null;
-  owner_agent_type?: string | null;
-  reviewer_agent_type?: string | null;
-  arbiter_agent_type?: string | null;
-}
-
 interface PairedTurnAttemptTimingRow {
   turn_id: string;
   attempt_no: number;
@@ -2076,160 +2060,14 @@ export function applyPairedTurnAttemptProvenanceConstraints(
   }
 }
 
-function backfillLegacyExecutionLeaseServiceShadows(database: Database): void {
-  if (
-    !tableHasColumn(
-      database,
-      'paired_task_execution_leases',
-      'claimed_service_id',
-    )
-  ) {
-    return;
-  }
-
-  const pairedTasksTable = database
-    .prepare(
-      `
-        SELECT 1
-          FROM sqlite_master
-         WHERE type = 'table'
-           AND name = 'paired_tasks'
-      `,
-    )
-    .get();
-  if (!pairedTasksTable) {
-    return;
-  }
-
-  const pairedTaskColumns = getTableColumns(database, 'paired_tasks');
-  const selectPairedTaskColumn = (columnName: string): string =>
-    pairedTaskColumns.includes(columnName)
-      ? `paired_tasks.${columnName} AS ${columnName}`
-      : `NULL AS ${columnName}`;
-
-  const rows = database
-    .prepare(
-      `
-        SELECT
-          paired_task_execution_leases.rowid AS rowid,
-          paired_task_execution_leases.role AS role,
-          ${selectPairedTaskColumn('owner_service_id')},
-          ${selectPairedTaskColumn('reviewer_service_id')},
-          ${selectPairedTaskColumn('arbiter_service_id')},
-          ${selectPairedTaskColumn('owner_agent_type')},
-          ${selectPairedTaskColumn('reviewer_agent_type')},
-          ${selectPairedTaskColumn('arbiter_agent_type')}
-        FROM paired_task_execution_leases
-        LEFT JOIN paired_tasks
-          ON paired_tasks.id = paired_task_execution_leases.task_id
-       WHERE paired_task_execution_leases.claimed_service_id IS NULL
-      `,
-    )
-    .all() as LegacyExecutionLeaseServiceRow[];
-
-  if (rows.length === 0) {
-    return;
-  }
-
-  const update = database.prepare(
-    `
-      UPDATE paired_task_execution_leases
-         SET claimed_service_id = ?
-       WHERE rowid = ?
-         AND claimed_service_id IS NULL
-    `,
-  );
-  const tx = database.transaction(
-    (leaseRows: LegacyExecutionLeaseServiceRow[]) => {
-      for (const row of leaseRows) {
-        const claimedServiceId =
-          inferExecutionLeaseServiceIdFromCanonicalMetadata(row);
-        if (!claimedServiceId) {
-          continue;
-        }
-        update.run(claimedServiceId, row.rowid);
-      }
-    },
-  );
-
-  tx(rows);
-}
-
 export function applyLegacySchemaMigrations(
   database: Database,
   _args: {
     assistantName: string;
   },
 ): void {
-  tryExecMigration(
-    database,
-    `ALTER TABLE service_handoffs ADD COLUMN intended_role TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE service_handoffs ADD COLUMN source_role TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE service_handoffs ADD COLUMN target_role TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE service_handoffs ADD COLUMN source_agent_type TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE service_handoffs ADD COLUMN source_service_id TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE service_handoffs ADD COLUMN target_service_id TEXT`,
-  );
-
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_tasks ADD COLUMN owner_agent_type TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_tasks ADD COLUMN reviewer_agent_type TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_tasks ADD COLUMN arbiter_agent_type TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_tasks ADD COLUMN owner_service_id TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_tasks ADD COLUMN reviewer_service_id TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_task_execution_leases ADD COLUMN expires_at TEXT`,
-  );
-  tryExecMigration(
-    database,
-    `ALTER TABLE paired_task_execution_leases ADD COLUMN claimed_service_id TEXT`,
-  );
-  database.exec(`
-    UPDATE paired_task_execution_leases
-       SET expires_at = COALESCE(
-         expires_at,
-         strftime('%Y-%m-%dT%H:%M:%fZ', 'now', '+10 minutes')
-       )
-  `);
-  // Legacy lease rows predate claimed_service_id. Infer the original service
-  // from paired-task role metadata when possible instead of blanket-marking
-  // everything as the current service, which would let startup cleanup delete
-  // leases that belong to another runtime.
-  backfillLegacyExecutionLeaseServiceShadows(database);
-  database.exec(`
-    CREATE INDEX IF NOT EXISTS idx_paired_task_execution_leases_expires_at
-      ON paired_task_execution_leases(expires_at)
-  `);
+  // Some legacy columns must exist before later numbered migrations can run.
+  // `work_items.service_id` / `delivery_role` are referenced by v4 indexes.
   tryExecMigration(
     database,
     `ALTER TABLE work_items ADD COLUMN delivery_role TEXT`,