The `future.unstable_subResourceIntegrity` flag has been sta

Error message

The `future.unstable_subResourceIntegrity` flag has been stabilized and moved to a top-level `config.subResourceIntegrity` field

What it means

Fatal config-validation error: `future.unstable_subResourceIntegrity` was stabilized. The option now lives as the top-level `config.subResourceIntegrity` boolean (default false, resolved at config.ts line 755), so keeping the old future key aborts readConfig with instructions to move it. SRI adds integrity hashes to prerendered/asset tags; only the location changed, not the behavior.

Source

Thrown at packages/react-router-dev/config/config.ts:740

    }
    if (
      "unstable_middleware" in futureConfig ||
      "v8_middleware" in futureConfig
    ) {
      return err(
        "The `future.v8_middleware` flag has been removed because middleware is now always enabled",
      );
    }
    if (
      "unstable_trailingSlashAwareDataRequests" in futureConfig ||
      "v8_trailingSlashAwareDataRequests" in futureConfig
    ) {
      return err(
        "The `future.v8_trailingSlashAwareDataRequests` flag has been removed because trailing slash-aware data requests are now the default behavior",
      );
    }
    if ("unstable_subResourceIntegrity" in futureConfig) {
      return err(
        "The `future.unstable_subResourceIntegrity` flag has been stabilized and moved to a top-level `config.subResourceIntegrity` field",
      );
    }
  }

  let future: FutureConfig = {
    unstable_enableNodeReadableStream:
      userAndPresetConfigs.future?.unstable_enableNodeReadableStream ?? false,
    unstable_optimizeDeps:
      userAndPresetConfigs.future?.unstable_optimizeDeps ?? false,
  };

  let allowedActionOrigins = userAndPresetConfigs.allowedActionOrigins ?? false;
  let splitRouteModules = userAndPresetConfigs.splitRouteModules ?? true;
  let subResourceIntegrity = userAndPresetConfigs.subResourceIntegrity ?? false;

  let reactRouterConfig: ResolvedReactRouterConfig = deepFreeze({
    appDirectory,

View on GitHub (pinned to 6beaca3952)

Solutions

Move the option to the top level: replace `future: { unstable_subResourceIntegrity: true }` with `subResourceIntegrity: true`
Keep the value semantics: true enables SRI, omit/false disables — nothing else changed
Re-run typegen so `.react-router/types` reflect the top-level field
Remove any `satisfies FutureConfig` typing that still lists the old key

Example fix

// before - react-router.config.ts
import type { Config } from "@react-router/dev";
export default {
  future: { unstable_subResourceIntegrity: true },
} satisfies Config;

// after
export default {
  subResourceIntegrity: true,
} satisfies Config;

Defensive patterns

Strategy: validation

Validate before calling

import fs from "node:fs";
let cfg = fs.readFileSync("react-router.config.ts", "utf8");
if (cfg.includes("unstable_subResourceIntegrity")) {
  throw new Error("Move `future.unstable_subResourceIntegrity` to top-level `subResourceIntegrity`");
}

Type guard

// guard the moved option on a parsed config object
function hasTopLevelSRI(cfg: unknown): cfg is { subResourceIntegrity: boolean } {
  if (typeof cfg !== "object" || cfg === null) return false;
  let f = (cfg as { future?: Record<string, unknown> }).future;
  return !(f && "unstable_subResourceIntegrity" in f);
}

Try / catch

try {
  let result = await readConfig(root);
} catch (e) {
  if (e instanceof Error && e.message.includes("subResourceIntegrity")) {
    // rewrite future.unstable_subResourceIntegrity -> top-level subResourceIntegrity, retry once
  } else throw e;
}

Prevention

Watch stabilization notes: unstable_ flags that stabilize usually relocate to top-level config fields
Prefer top-level options over future.* flags in new configs; future flags are inherently temporary
Re-run `react-router typegen` after every upgrade so relocated fields surface in types

When it happens

Trigger: Any config-loading run where `future` contains the `unstable_subResourceIntegrity` key (there is no v8_ alias for this one — only the unstable name is checked).

Common situations: Apps that enabled SRI when it was unstable and upgraded after stabilization; configs written from older docs; the flag being spread into `future` via a shared object.

Related errors

AI-assisted analysis of remix-run/react-router@6beaca3952 (2026-08-18). Data as JSON: /api/errors/d0573d92a1bf4c4e. Report an issue: GitHub.