diff --git a/apps/api/src/common/oidc-forwarded-proto.spec.ts b/apps/api/src/common/oidc-forwarded-proto.spec.ts
new file mode 100644
index 0000000..5af9cc7
--- /dev/null
+++ b/apps/api/src/common/oidc-forwarded-proto.spec.ts
@@ -0,0 +1,52 @@
+import { normalizeOidcForwardedProto } from './oidc-forwarded-proto';
+
+describe('normalizeOidcForwardedProto', () => {
+  it('corrects an OIDC request when the trusted public issuer uses HTTPS', () => {
+    const request = {
+      method: 'GET',
+      originalUrl: '/oidc/auth?client_id=test',
+      headers: { 'x-forwarded-proto': 'http' },
+    };
+
+    const result = normalizeOidcForwardedProto(request, 'https://auth.example.com', true);
+
+    expect(result).toEqual({ corrected: true, path: '/oidc/auth', previousProto: 'http' });
+    expect(request.headers['x-forwarded-proto']).toBe('https');
+  });
+
+  it('also corrects interaction routes used to finish login and consent', () => {
+    const request = { originalUrl: '/interaction/uid/login', headers: {} as Record<string, string> };
+
+    const result = normalizeOidcForwardedProto(request, 'https://auth.example.com', true);
+
+    expect(result.corrected).toBe(true);
+    expect(request.headers['x-forwarded-proto']).toBe('https');
+  });
+
+  it('does not alter unrelated API requests', () => {
+    const request = { originalUrl: '/api/account', headers: { 'x-forwarded-proto': 'http' } };
+
+    const result = normalizeOidcForwardedProto(request, 'https://auth.example.com', true);
+
+    expect(result.corrected).toBe(false);
+    expect(request.headers['x-forwarded-proto']).toBe('http');
+  });
+
+  it('does not override the protocol when proxy trust is disabled', () => {
+    const request = { originalUrl: '/oidc/auth', headers: { 'x-forwarded-proto': 'http' } };
+
+    const result = normalizeOidcForwardedProto(request, 'https://auth.example.com', false);
+
+    expect(result.corrected).toBe(false);
+    expect(request.headers['x-forwarded-proto']).toBe('http');
+  });
+
+  it('does not force HTTPS for a configured HTTP issuer', () => {
+    const request = { originalUrl: '/oidc/auth', headers: { 'x-forwarded-proto': 'http' } };
+
+    const result = normalizeOidcForwardedProto(request, 'http://localhost:8080', true);
+
+    expect(result.corrected).toBe(false);
+    expect(request.headers['x-forwarded-proto']).toBe('http');
+  });
+});
diff --git a/apps/api/src/common/oidc-forwarded-proto.ts b/apps/api/src/common/oidc-forwarded-proto.ts
new file mode 100644
index 0000000..ceb75f9
--- /dev/null
+++ b/apps/api/src/common/oidc-forwarded-proto.ts
@@ -0,0 +1,58 @@
+import type { IncomingHttpHeaders } from 'node:http';
+
+interface OidcProxyRequest {
+  method?: string;
+  originalUrl?: string;
+  url?: string;
+  headers: IncomingHttpHeaders;
+}
+
+export interface OidcForwardedProtoResult {
+  corrected: boolean;
+  path: string;
+  previousProto?: string;
+}
+
+export function normalizeOidcForwardedProto(
+  request: OidcProxyRequest,
+  issuer: string | undefined,
+  trustProxy: boolean,
+): OidcForwardedProtoResult {
+  const path = (request.originalUrl ?? request.url ?? '/').split('?', 1)[0];
+  const previousProto = headerValue(request.headers['x-forwarded-proto']);
+
+  if (!trustProxy || !isOidcPath(path) || !isHttpsUrl(issuer) || previousProto === 'https') {
+    return { corrected: false, path, previousProto };
+  }
+
+  request.headers['x-forwarded-proto'] = 'https';
+  return { corrected: true, path, previousProto };
+}
+
+function isOidcPath(path: string): boolean {
+  return (
+    path === '/oidc' ||
+    path.startsWith('/oidc/') ||
+    path === '/interaction' ||
+    path.startsWith('/interaction/') ||
+    path === '/.well-known' ||
+    path.startsWith('/.well-known/')
+  );
+}
+
+function isHttpsUrl(value?: string): boolean {
+  if (!value) {
+    return false;
+  }
+
+  try {
+    return new URL(value).protocol === 'https:';
+  } catch {
+    return false;
+  }
+}
+
+function headerValue(value: string | string[] | undefined): string | undefined {
+  const firstValue = Array.isArray(value) ? value[0] : value;
+  return firstValue?.split(',', 1)[0].trim().toLowerCase() || undefined;
+}
diff --git a/apps/api/src/main.ts b/apps/api/src/main.ts
index 1b22490..a78a1aa 100644
--- a/apps/api/src/main.ts
+++ b/apps/api/src/main.ts
@@ -1,8 +1,9 @@
 import 'reflect-metadata';
-import { ValidationPipe } from '@nestjs/common';
+import { Logger, ValidationPipe } from '@nestjs/common';
 import { NestFactory } from '@nestjs/core';
 import express, { NextFunction, Request, Response } from 'express';
 import { AppModule } from './app.module';
+import { normalizeOidcForwardedProto } from './common/oidc-forwarded-proto';
 
 async function bootstrap() {
   const app = await NestFactory.create(AppModule, { bodyParser: false });
@@ -12,6 +13,26 @@ async function bootstrap() {
     credentials: true,
   });
 
+  const oidcProxyLogger = new Logger('OidcProxyProtocol');
+  app.use((request: Request, _response: Response, next: NextFunction) => {
+    const result = normalizeOidcForwardedProto(
+      request,
+      process.env.OIDC_ISSUER,
+      process.env.OIDC_TRUST_PROXY === 'true',
+    );
+    if (result.corrected) {
+      oidcProxyLogger.warn(
+        `[OIDC_FORWARDED_PROTO_CORRECTED] ${JSON.stringify({
+          method: request.method,
+          path: result.path,
+          receivedProto: result.previousProto,
+          effectiveProto: 'https',
+        })}`,
+      );
+    }
+    next();
+  });
+
   const jsonParser = express.json();
   const formParser = express.urlencoded({ extended: false });
   app.use((request: Request, response: Response, next: NextFunction) => {