diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index baa42d6f..d7a909de 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -46,6 +46,7 @@ jobs:
             sudo bastille cmd node sh -lc 'su -l indiekit -c "cd /usr/local/indiekit && if ! (grep -Eq \"^SECRET=.*\" .env && grep -Eq \"^PASSWORD_SECRET=.*\" .env); then echo \"Missing SECRET or PASSWORD_SECRET in /usr/local/indiekit/.env\"; exit 1; fi"'
 
             # Validate startup prerequisites before touching the running service.
+            sudo bastille cmd node sh -lc 'su -l indiekit -c "cd /usr/local/indiekit && NODE_ENV=production node scripts/preflight-production-security.mjs"'
             sudo bastille cmd node sh -lc 'su -l indiekit -c "cd /usr/local/indiekit && NODE_ENV=production node scripts/preflight-mongo-connection.mjs"'
 
             # Restart asynchronously to avoid hanging SSH sessions when rc scripts keep stdout open.
@@ -67,6 +68,7 @@ jobs:
             echo "Indiekit process not found after restart."
             sudo bastille cmd node sh -lc "tail -n 120 ${restart_log} || true"
             sudo bastille cmd node sh -lc 'service indiekit onestatus || true'
+            sudo bastille cmd node sh -lc 'su -l indiekit -c "cd /usr/local/indiekit && NODE_ENV=production node scripts/preflight-production-security.mjs" || true'
             sudo bastille cmd node sh -lc 'su -l indiekit -c "cd /usr/local/indiekit && NODE_ENV=production node scripts/preflight-mongo-connection.mjs" || true'
             exit 1
       # Optionally reload nginx on web jail
diff --git a/README.md b/README.md
index 0c87114c..7f17cf9e 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,9 @@
 - When `INDIEKIT_ADMIN_URL` is set, config wires absolute auth endpoints/callback base (`/auth`, `/auth/token`, `/auth/introspect`) to that URL to keep login redirects on `/admin/*`.
 - Login uses `PASSWORD_SECRET` (bcrypt hash), not `INDIEKIT_PASSWORD`.
 - If no `PASSWORD_SECRET` exists yet, open `/admin/auth/new-password` once to generate it.
+- If login appears passwordless, first check for an existing authenticated session cookie. Use `/session/logout` (or `/admin/session/logout` behind proxy) to force a fresh login challenge.
+- Upstream IndieKit auto-authenticates in dev mode (`NODE_ENV=development`). This repository patches that behavior so dev auto-auth only works when `INDIEKIT_ALLOW_DEV_AUTH=1` is explicitly set.
+- Production startup now fails closed when auth/session settings are unsafe (`NODE_ENV` not `production`, `INDIEKIT_ALLOW_DEV_AUTH=1`, weak `SECRET`, missing/invalid `PASSWORD_SECRET`, or empty-password hash).
 - Post management UI should use `/posts` (`@indiekit/endpoint-posts.mountPath`).
 - Do not set post-management `mountPath` to frontend routes like `/blog`, otherwise backend publishing can be shadowed by the public site.
 
@@ -68,11 +71,13 @@
 - `start.sh` is intentionally ignored by Git (`.gitignore`) so server secrets are not committed.
 - Use `start.example.sh` as the tracked template and keep real credentials in environment variables (or `.env` on the server).
 - Startup scripts parse `.env` with the `dotenv` parser (not shell `source`), so values containing spaces are handled safely.
-- Startup scripts run preflight + patch helpers before boot (`scripts/preflight-mongo-connection.mjs`, `scripts/patch-lightningcss.mjs`, `scripts/patch-endpoint-media-scope.mjs`, `scripts/patch-endpoint-media-sharp-runtime.mjs`, `scripts/patch-frontend-sharp-runtime.mjs`, `scripts/patch-endpoint-files-upload-route.mjs`, `scripts/patch-endpoint-files-upload-locales.mjs`, `scripts/patch-frontend-serviceworker-file.mjs`, `scripts/patch-conversations-collection-guards.mjs`).
+- Startup scripts run preflight + patch helpers before boot (`scripts/preflight-production-security.mjs`, `scripts/preflight-mongo-connection.mjs`, `scripts/patch-lightningcss.mjs`, `scripts/patch-endpoint-media-scope.mjs`, `scripts/patch-endpoint-media-sharp-runtime.mjs`, `scripts/patch-frontend-sharp-runtime.mjs`, `scripts/patch-endpoint-files-upload-route.mjs`, `scripts/patch-endpoint-files-upload-locales.mjs`, `scripts/patch-frontend-serviceworker-file.mjs`, `scripts/patch-conversations-collection-guards.mjs`, `scripts/patch-indieauth-devmode-guard.mjs`).
+- The production security preflight blocks startup on insecure auth/session configuration and catches empty-password bcrypt hashes.
 - The media scope patch fixes a known upstream issue where file uploads can fail if the token scope is `create update delete` without explicit `media`.
 - The media sharp runtime patch makes image transformation resilient on FreeBSD: if `sharp` cannot load, uploads continue without resize/rotation instead of crashing the server process.
 - The frontend sharp runtime patch makes icon generation non-fatal on FreeBSD when `sharp` cannot load, preventing startup crashes in asset controller imports.
 - The files upload route patch fixes browser multi-upload by posting to `/files/upload` (session-authenticated) instead of direct `/media` calls without bearer token.
 - The files upload locale patch adds missing `files.upload.dropText`/`files.upload.browse`/`files.upload.submitMultiple` labels in endpoint locale files so UI text does not render raw translation keys.
 - The frontend serviceworker patch ensures `@indiekit/frontend/lib/serviceworker.js` exists at runtime to avoid ENOENT in the offline/service worker route.
-- The conversations guard patch prevents `Cannot read properties of undefined (reading 'find')` when the `conversation_items` collection is temporarily unavailable.
\ No newline at end of file
+- The conversations guard patch prevents `Cannot read properties of undefined (reading 'find')` when the `conversation_items` collection is temporarily unavailable.
+- The indieauth dev-mode guard patch prevents accidental production auth bypass by requiring explicit `INDIEKIT_ALLOW_DEV_AUTH=1` to enable dev auto-login.
diff --git a/package.json b/package.json
index ea9b89d0..9b03ea31 100644
--- a/package.json
+++ b/package.json
@@ -4,8 +4,8 @@
   "description": "",
   "main": "index.js",
   "scripts": {
-    "postinstall": "node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-conversations-collection-guards.mjs",
-    "serve": "node scripts/preflight-mongo-connection.mjs && node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-conversations-collection-guards.mjs && node node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs",
+    "postinstall": "node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-conversations-collection-guards.mjs && node scripts/patch-indieauth-devmode-guard.mjs",
+    "serve": "export NODE_ENV=${NODE_ENV:-production} INDIEKIT_DEBUG=${INDIEKIT_DEBUG:-0} && node scripts/preflight-production-security.mjs && node scripts/preflight-mongo-connection.mjs && node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-conversations-collection-guards.mjs && node scripts/patch-indieauth-devmode-guard.mjs && node node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "keywords": [],
diff --git a/scripts/patch-indieauth-devmode-guard.mjs b/scripts/patch-indieauth-devmode-guard.mjs
new file mode 100644
index 00000000..67127567
--- /dev/null
+++ b/scripts/patch-indieauth-devmode-guard.mjs
@@ -0,0 +1,57 @@
+import { access, readFile, writeFile } from "node:fs/promises";
+
+const candidates = [
+  "node_modules/@indiekit/indiekit/lib/indieauth.js",
+];
+
+const oldCode = `if (devMode) {
+        request.session.access_token = process.env.NODE_ENV;
+        request.session.scope = "create update delete media";
+      } else if (!process.env.PASSWORD_SECRET) {`;
+
+const newCode = `if (devMode && process.env.INDIEKIT_ALLOW_DEV_AUTH === "1") {
+        request.session.access_token = process.env.NODE_ENV;
+        request.session.scope = "create update delete media";
+      } else if (!process.env.PASSWORD_SECRET) {`;
+
+async function exists(path) {
+  try {
+    await access(path);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+let checked = 0;
+let patched = 0;
+
+for (const filePath of candidates) {
+  if (!(await exists(filePath))) {
+    continue;
+  }
+
+  checked += 1;
+
+  const source = await readFile(filePath, "utf8");
+
+  if (source.includes(newCode)) {
+    continue;
+  }
+
+  if (!source.includes(oldCode)) {
+    continue;
+  }
+
+  const updated = source.replace(oldCode, newCode);
+  await writeFile(filePath, updated, "utf8");
+  patched += 1;
+}
+
+if (checked === 0) {
+  console.log("[postinstall] No indieauth middleware files found");
+} else if (patched === 0) {
+  console.log("[postinstall] indieauth dev-mode guard already patched");
+} else {
+  console.log(`[postinstall] Patched indieauth dev-mode guard in ${patched} file(s)`);
+}
diff --git a/scripts/preflight-production-security.mjs b/scripts/preflight-production-security.mjs
new file mode 100644
index 00000000..7a871cf3
--- /dev/null
+++ b/scripts/preflight-production-security.mjs
@@ -0,0 +1,66 @@
+import "dotenv/config";
+
+import bcrypt from "bcrypt";
+
+const strictMode = process.env.REQUIRE_SECURITY !== "0";
+const nodeEnv = (process.env.NODE_ENV || "").toLowerCase();
+
+function failOrWarn(message) {
+  if (strictMode) {
+    console.error(message);
+    process.exit(1);
+  }
+
+  console.warn(`${message} Continuing because strict mode is disabled.`);
+}
+
+if (nodeEnv !== "production") {
+  failOrWarn(
+    `[preflight] NODE_ENV must be "production" for secure startup (received "${process.env.NODE_ENV || "(unset)"}").`,
+  );
+}
+
+if (process.env.INDIEKIT_ALLOW_DEV_AUTH === "1") {
+  failOrWarn(
+    "[preflight] INDIEKIT_ALLOW_DEV_AUTH=1 is not allowed in production.",
+  );
+}
+
+const secret = process.env.SECRET || "";
+if (secret.length < 32) {
+  failOrWarn(
+    "[preflight] SECRET must be set and at least 32 characters long.",
+  );
+}
+
+const passwordSecret = process.env.PASSWORD_SECRET || "";
+if (!passwordSecret) {
+  failOrWarn("[preflight] PASSWORD_SECRET is required.");
+}
+
+if (!/^\$2[aby]\$\d{2}\$/.test(passwordSecret)) {
+  failOrWarn(
+    "[preflight] PASSWORD_SECRET must be a bcrypt hash (starts with $2a$, $2b$, or $2y$).",
+  );
+}
+
+try {
+  const emptyPasswordValid = await bcrypt.compare("", passwordSecret);
+  if (emptyPasswordValid) {
+    failOrWarn(
+      "[preflight] PASSWORD_SECRET matches an empty password. Generate a non-empty password hash via /auth/new-password.",
+    );
+  }
+} catch (error) {
+  failOrWarn(
+    `[preflight] PASSWORD_SECRET could not be validated with bcrypt: ${error.message}`,
+  );
+}
+
+if (process.env.INDIEKIT_PASSWORD) {
+  console.warn(
+    "[preflight] INDIEKIT_PASSWORD is set but ignored by core auth. Use PASSWORD_SECRET only.",
+  );
+}
+
+console.log("[preflight] Production auth configuration OK");
diff --git a/start.example.sh b/start.example.sh
index 4f1eca9a..86080437 100644
--- a/start.example.sh
+++ b/start.example.sh
@@ -37,6 +37,9 @@ export NODE_ENV="production"
 export INDIEKIT_DEBUG="0"
 unset DEBUG
 
+# Verify production auth/session hardening before launching server.
+/usr/local/bin/node scripts/preflight-production-security.mjs
+
 # Verify MongoDB credentials/connectivity before launching server.
 /usr/local/bin/node scripts/preflight-mongo-connection.mjs
 
@@ -49,5 +52,6 @@ unset DEBUG
 /usr/local/bin/node scripts/patch-endpoint-files-upload-locales.mjs
 /usr/local/bin/node scripts/patch-frontend-serviceworker-file.mjs
 /usr/local/bin/node scripts/patch-conversations-collection-guards.mjs
+/usr/local/bin/node scripts/patch-indieauth-devmode-guard.mjs
 
 exec /usr/local/bin/node node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs