diff --git a/packages/core/src/database/migration.ts b/packages/core/src/database/migration.ts
index 90dee8acbf3b..0b259ee527eb 100644
--- a/packages/core/src/database/migration.ts
+++ b/packages/core/src/database/migration.ts
@@ -21,6 +21,23 @@ export function apply(db: Database) {
       const tables = yield* db.all<{ name: string }>(
         sql`SELECT name FROM sqlite_master WHERE type = 'table' AND name NOT LIKE 'sqlite_%'`,
       )
+      if (tables.some((table) => table.name === "migration")) {
+        // A newer build may have migrated this database already. Running old
+        // SQL against a newer schema fails at query time with an opaque
+        // "SQL logic error", so refuse upfront. Unknown ids sorting before our
+        // newest migration are retired ids (e.g. 20260530232709_lovely_romulus)
+        // and stay allowed.
+        const known = new Set(migrations.map((migration) => migration.id))
+        const latest = migrations.reduce((max, migration) => (migration.id > max ? migration.id : max), "")
+        const newer = (yield* db.all<{ id: string }>(sql`SELECT id FROM ${sql.identifier("migration")}`))
+          .map((row) => row.id)
+          .filter((id) => !known.has(id) && id > latest)
+          .sort()
+        if (newer.length > 0)
+          return yield* Effect.die(
+            `Database was migrated by a newer version of opencode (unknown migration: ${newer[newer.length - 1]}). Refusing to start against a newer schema; please update this installation.`,
+          )
+      }
       if (tables.some((table) => table.name === "session")) return yield* applyOnly(db, migrations)
       if (tables.length > 0) return yield* Effect.die("Database is not empty and has no session table")
       yield* db.transaction((tx) =>
diff --git a/packages/core/test/database-migration.test.ts b/packages/core/test/database-migration.test.ts
index b381cc7418a3..6c6ecbafde10 100644
--- a/packages/core/test/database-migration.test.ts
+++ b/packages/core/test/database-migration.test.ts
@@ -111,6 +111,30 @@ describe("DatabaseMigration", () => {
     ).rejects.toThrow("Database is not empty and has no session table")
   })
 
+  test("refuses a database migrated by a newer version", async () => {
+    await expect(
+      run(
+        Effect.gen(function* () {
+          const db = yield* makeDb
+          yield* DatabaseMigration.apply(db)
+          yield* db.run(sql`INSERT INTO migration (id, time_completed) VALUES ('99991231000000_from_the_future', 1)`)
+          yield* DatabaseMigration.apply(db)
+        }),
+      ),
+    ).rejects.toThrow("newer version of opencode")
+  })
+
+  test("allows unknown migration ids older than the newest known migration", async () => {
+    await run(
+      Effect.gen(function* () {
+        const db = yield* makeDb
+        yield* DatabaseMigration.apply(db)
+        yield* db.run(sql`INSERT INTO migration (id, time_completed) VALUES ('20260530232709_lovely_romulus', 1)`)
+        yield* DatabaseMigration.apply(db)
+      }),
+    )
+  })
+
   test("backfills existing Context Epoch rows to the build agent", async () => {
     await run(
       Effect.gen(function* () {