diff --git a/package.json b/package.json
index 92ae762d..73767958 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
   "scripts": {
     "preinstall": "node -e \"var v = +process.versions.node.split('.')[0]; if (v < 22) { console.error('Node 22 or newer required (got ' + process.versions.node + '). Run: nvm use 22'); process.exit(1); }\"",
     "gen:index": "bun run ./scripts/gen-index.ts",
+    "fix:env": "bun run ./scripts/fix-env.ts",
     "gen:ecosystem": "bun run --env-file=.env ./scripts/gen-ecosystem.ts",
     "predev": "bun run ./scripts/gen-index.ts",
     "dev": "bun --env-file=.env --watch src/server.tsx",
diff --git a/scripts/fix-env.ts b/scripts/fix-env.ts
new file mode 100644
index 00000000..9cb9d34b
--- /dev/null
+++ b/scripts/fix-env.ts
@@ -0,0 +1,14 @@
+// `bun run fix:env` — give every variable in `.env` the `OFFICERDEV_` prefix.
+//
+// A thin front for `servers/env-prefix.ts`, which is where the rules live. Deliberately that way round:
+// the same conversion runs on every restart from the server settings screen, and a router reaching into
+// `scripts/` to do it would make a maintenance script part of the request path.
+
+import { join } from 'node:path';
+import { fixEnvFile } from '../src/servers/env-prefix';
+
+const path = process.argv[2] ?? join(process.cwd(), '.env');
+const { changed, alreadyPrefixed } = fixEnvFile(path);
+
+if (changed.length) console.log(`[fix:env] prefixed ${changed.length}: ${changed.join(', ')}`);
+else console.log(`[fix:env] nothing to do (${alreadyPrefixed} already prefixed)`);
diff --git a/scripts/gen-index.ts b/scripts/gen-index.ts
index 14443f5e..0b1ad5a1 100644
--- a/scripts/gen-index.ts
+++ b/scripts/gen-index.ts
@@ -27,17 +27,23 @@ const output = join(root, 'src/apps/officer-web/index.gen.html');
 const argUrl = process.argv[2]?.trim();
 
 const envPath = join(root, '.env');
-if (!argUrl && !process.env.PUBLIC_URL && existsSync(envPath)) {
+// Prefixed first, bare as the fallback — the same rule every other consumer follows. This script reads
+// the file itself rather than relying on the environment, because it is run by hand as often as by the
+// setup, and `bun run gen:index` in a bare shell has no `.env` loaded.
+const envValue = (): string | undefined => process.env.OFFICERDEV_PUBLIC_URL ?? process.env.PUBLIC_URL;
+
+if (!argUrl && !envValue() && existsSync(envPath)) {
   for (const line of (await Bun.file(envPath).text()).split('\n')) {
-    const match = line.match(/^\s*PUBLIC_URL\s*=\s*(.*)$/);
-    if (match) process.env.PUBLIC_URL = match[1]!.trim().replace(/^["']|["']$/g, '');
+    // Either spelling, so a file that has been through `bun run fix:env` and one that has not both work.
+    const match = line.match(/^\s*(?:OFFICERDEV_)?PUBLIC_URL\s*=\s*(.*)$/);
+    if (match) process.env.OFFICERDEV_PUBLIC_URL = match[1]!.trim().replace(/^["']|["']$/g, '');
   }
 }
 
-const publicUrl = (argUrl || process.env.PUBLIC_URL || '').replace(/\/+$/, '');
+const publicUrl = (argUrl || envValue() || '').replace(/\/+$/, '');
 if (!publicUrl) {
   console.error('[gen-index] no public URL. Pass one — `bun gen:index https://officer.example.com` —');
-  console.error('[gen-index] or set PUBLIC_URL in .env.');
+  console.error('[gen-index] or set OFFICERDEV_PUBLIC_URL in .env.');
   process.exit(1);
 }
 
diff --git a/scripts/rename-capabilities-to-permissions.ts b/scripts/rename-capabilities-to-permissions.ts
index 8ccdec84..a1ba55f7 100644
--- a/scripts/rename-capabilities-to-permissions.ts
+++ b/scripts/rename-capabilities-to-permissions.ts
@@ -37,7 +37,7 @@ import postgres from 'postgres';
 // `role === 'Super Admin'` before it reads the table at all, so the account that can fix things can
 // always sign in. Non-owners degrade to core-only until the rename completes.
 
-const url = process.env.POSTGRES_URL;
+const url = process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL;
 if (!url) {
   console.error('  POSTGRES_URL is not set. Run from the platform directory so Bun loads .env.');
   process.exit(1);
diff --git a/scripts/setup/officer-setup/lib/env.sh b/scripts/setup/officer-setup/lib/env.sh
index b4d7ec1a..d7a1b8e2 100644
--- a/scripts/setup/officer-setup/lib/env.sh
+++ b/scripts/setup/officer-setup/lib/env.sh
@@ -60,13 +60,22 @@ write_env() {
 #
 # Everything Officer reads at runtime. Kept at 0600 and owned by ${USERNAME}: it
 # holds the token-signing secret and the database credential.
+#
+# EVERY NAME IS PREFIXED \`OFFICERDEV_\`. Bun auto-loads this file into every
+# process started in the platform directory, so a bare PORT or POSTGRES_URL
+# reaches the sidecars, the tools they spawn and anything an agent runs from
+# here — names half the software in the world already uses. Prefixed, they
+# cannot be picked up by accident.
+#
+# Every consumer reads \`OFFICERDEV_X ?? X\`, so an older unprefixed file still
+# works. \`bun run fix:env\` converts one in place.
 
-PORT="${ENV_PORT}"
+OFFICERDEV_PORT="${ENV_PORT}"
 
 # Where Officer is reached from a browser. Not derivable — see the section.
-PUBLIC_URL="${ENV_PUBLIC_URL}"
+OFFICERDEV_PUBLIC_URL="${ENV_PUBLIC_URL}"
 
-POSTGRES_URL="${POSTGRES_URL}"
+OFFICERDEV_POSTGRES_URL="${POSTGRES_URL}"
 
 ENVF
 
diff --git a/src/databases/marketplace_db/drizzle.config.ts b/src/databases/marketplace_db/drizzle.config.ts
index efa10430..673f0ef2 100644
--- a/src/databases/marketplace_db/drizzle.config.ts
+++ b/src/databases/marketplace_db/drizzle.config.ts
@@ -20,7 +20,7 @@ try {
 // because drizzle-kit loads this file outside the workspace's module resolution.
 const url = (() => {
   if (process.env.MARKETPLACE_POSTGRES_URL) return process.env.MARKETPLACE_POSTGRES_URL;
-  const base = process.env.POSTGRES_URL;
+  const base = process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL;
   if (!base) throw new Error('MARKETPLACE_POSTGRES_URL or POSTGRES_URL is required');
   const parsed = new URL(base);
   parsed.pathname = '/officer_marketplace';
diff --git a/src/databases/marketplace_db/src/db.ts b/src/databases/marketplace_db/src/db.ts
index 205a92be..bf37f7d7 100644
--- a/src/databases/marketplace_db/src/db.ts
+++ b/src/databases/marketplace_db/src/db.ts
@@ -31,7 +31,7 @@ export function marketplaceUrl(): string {
   const explicit = process.env.MARKETPLACE_POSTGRES_URL;
   if (explicit) return explicit;
 
-  const base = process.env.POSTGRES_URL;
+  const base = process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL;
   if (!base) throw new Error('MARKETPLACE_POSTGRES_URL or POSTGRES_URL is required');
 
   // Swap only the path. Parsing rather than string-replacing, so a password containing the database
diff --git a/src/databases/officer_db/drizzle.config.ts b/src/databases/officer_db/drizzle.config.ts
index e9c8e431..0c9a7f11 100644
--- a/src/databases/officer_db/drizzle.config.ts
+++ b/src/databases/officer_db/drizzle.config.ts
@@ -20,6 +20,6 @@ export default defineConfig({
   out: './migrations',
   dialect: 'postgresql',
   dbCredentials: {
-    url: process.env.POSTGRES_URL!,
+    url: (process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL)!,
   },
 });
diff --git a/src/databases/officer_db/src/db.ts b/src/databases/officer_db/src/db.ts
index 1bbc2485..50e565f3 100644
--- a/src/databases/officer_db/src/db.ts
+++ b/src/databases/officer_db/src/db.ts
@@ -2,7 +2,11 @@ import { drizzle } from 'drizzle-orm/postgres-js';
 import postgres from 'postgres';
 import * as schema from './schema';
 
-const { POSTGRES_URL } = process.env;
+// Prefixed first, bare as the fallback. Bun auto-loads `.env` into every process started in this
+// directory, so an unprefixed POSTGRES_URL reaches sidecars and anything an agent spawns — none of
+// which has business holding a database credential. `bun run fix:env` does the rename; the fallback
+// is what lets an install that has not run it keep working.
+const POSTGRES_URL = process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL;
 
 if (!POSTGRES_URL) {
   throw new Error('POSTGRES_URL environment variable is required');
diff --git a/src/servers/api/dav/router.ts b/src/servers/api/dav/router.ts
index 02b56924..42a2f77e 100644
--- a/src/servers/api/dav/router.ts
+++ b/src/servers/api/dav/router.ts
@@ -43,7 +43,7 @@ davRouter.post('/provision/ios', async (ctx) => {
 
   // The profile has to name a host, and PUBLIC_URL is the only place that knows the one a phone can
   // actually reach — the request's own Host header is whatever the reverse proxy forwarded.
-  const publicUrl = process.env.PUBLIC_URL;
+  const publicUrl = process.env.OFFICERDEV_PUBLIC_URL ?? process.env.PUBLIC_URL;
   if (!publicUrl) throw errors.INTERNAL_SERVER_ERROR('PUBLIC_URL is not set; cannot build a profile');
 
   let url: URL;
diff --git a/src/servers/api/server-settings/server-settings.ts b/src/servers/api/server-settings/server-settings.ts
index ff926c5d..8179700f 100644
--- a/src/servers/api/server-settings/server-settings.ts
+++ b/src/servers/api/server-settings/server-settings.ts
@@ -1,6 +1,7 @@
 import { createRouter } from '../../create-router';
 import { rebuildFrontend } from '../../plugins/generate';
 import { isKnownToPm2, restartProcess } from '../../app-store/pm2';
+import { fixEnvFile } from '../../env-prefix';
 import { PLATFORM_DIR } from '../../data-path';
 import { readdirSync, existsSync } from 'node:fs';
 import { join } from 'node:path';
@@ -66,10 +67,27 @@ serverSettingsRouter.post('/restart', async (ctx) => {
     return ctx.json({ ok: false, error: 'not running under PM2 — restart it the way you started it' }, 400);
   }
 
+  // Convert `.env` to the `OFFICERDEV_` prefix on the way past.
+  //
+  // Here rather than at boot, because a restart is the one moment the file can be rewritten and the
+  // change take effect in the same breath — the process about to start is the one that reads it. Doing
+  // it at boot would rewrite a file the running process had already loaded.
+  //
+  // Idempotent and non-fatal: an already-converted file is not even written, and a failure must not stop
+  // a restart the owner asked for. Every consumer still reads the unprefixed name as a fallback, so the
+  // worst case is that nothing changed.
+  let envFixed: string[] = [];
+  try {
+    envFixed = fixEnvFile(join(PLATFORM_DIR, '.env')).changed;
+    if (envFixed.length) console.log(`[env] prefixed on restart: ${envFixed.join(', ')}`);
+  } catch (err) {
+    console.error('[env] could not prefix .env —', err instanceof Error ? err.message : err);
+  }
+
   setTimeout(() => {
     void restartProcess('officer', PLATFORM_DIR);
   }, 250);
-  return ctx.json({ ok: true, restartingIn: 250 });
+  return ctx.json({ ok: true, restartingIn: 250, envFixed });
 });
 
 serverSettingsRouter.get('/settings', async (ctx) => {
diff --git a/src/servers/env-prefix.test.ts b/src/servers/env-prefix.test.ts
new file mode 100644
index 00000000..30c48f61
--- /dev/null
+++ b/src/servers/env-prefix.test.ts
@@ -0,0 +1,53 @@
+import { describe, expect, test } from 'bun:test';
+import { prefixEnvText } from './env-prefix';
+
+// This rewrites the file the whole platform reads its database credential from, and it runs on every
+// restart from the settings screen. The tests are about what it must NOT do.
+
+describe('prefixing', () => {
+  test('renames an ordinary variable', () => {
+    expect(prefixEnvText('PORT="9000"').text).toBe('OFFICERDEV_PORT="9000"');
+  });
+
+  test('leaves the value completely alone, including an = inside it', () => {
+    const line = 'POSTGRES_URL="postgresql://u:p=a=ss@127.0.0.1:5432/officer"';
+    expect(prefixEnvText(line).text).toBe(`OFFICERDEV_${line}`);
+  });
+
+  test('is idempotent — it runs on every restart', () => {
+    const once = prefixEnvText('PORT="9000"').text;
+    const twice = prefixEnvText(once);
+    expect(twice.text).toBe(once);
+    expect(twice.changed).toEqual([]);
+    expect(twice.alreadyPrefixed).toBe(1);
+  });
+});
+
+describe('what it must not touch', () => {
+  test('comments and blank lines survive', () => {
+    const text = '# the port\n\nPORT="9000"\n# trailing note\n';
+    const out = prefixEnvText(text).text;
+    expect(out).toContain('# the port');
+    expect(out).toContain('# trailing note');
+    expect(out.split('\n').length).toBe(text.split('\n').length);
+  });
+
+  test('a commented-out assignment stays commented out', () => {
+    expect(prefixEnvText('# PORT="9000"').text).toBe('# PORT="9000"');
+  });
+
+  test('variables belonging to other software are left alone', () => {
+    // Prefixing one of these does not rename a variable, it deletes it: nothing reads OFFICERDEV_PATH.
+    for (const key of ['NODE_ENV', 'PATH', 'HOME', 'TZ']) {
+      expect(prefixEnvText(`${key}=x`).text).toBe(`${key}=x`);
+    }
+  });
+
+  test('an `export` prefix is preserved', () => {
+    expect(prefixEnvText('export PORT=9000').text).toBe('export OFFICERDEV_PORT=9000');
+  });
+
+  test('a line that is not an assignment passes through', () => {
+    expect(prefixEnvText('this is not an env line').text).toBe('this is not an env line');
+  });
+});
diff --git a/src/servers/env-prefix.ts b/src/servers/env-prefix.ts
new file mode 100644
index 00000000..5e61985f
--- /dev/null
+++ b/src/servers/env-prefix.ts
@@ -0,0 +1,79 @@
+import { existsSync, readFileSync, writeFileSync } from 'node:fs';
+
+// Giving every variable in `.env` the `OFFICERDEV_` prefix.
+//
+// ── Why prefix at all ──
+//
+// `PORT`, `PUBLIC_URL` and `POSTGRES_URL` are names half the software in the world uses. Bun auto-loads
+// `.env` into EVERY process started in the platform directory, so a bare `PORT` reaches the sidecars,
+// the tools they spawn and anything an agent runs from here — and a bare `POSTGRES_URL` reaches things
+// with no business holding a database credential. Prefixed, they cannot be picked up by accident.
+//
+// ── Why every consumer still reads both ──
+//
+// `process.env.OFFICERDEV_X ?? process.env.X`, everywhere. An install that has not been converted keeps
+// working, which is what makes this safe to ship before every machine has run it. The unprefixed name is
+// the fallback, never the source.
+//
+// ── Idempotent, because it runs unattended ──
+//
+// This runs on every restart from the server settings screen, not only when somebody types
+// `bun run fix:env`. An already-prefixed line is left exactly as it is, and a file that needs no change
+// is not written at all — writing an identical file still moves its mtime.
+
+const PREFIX = 'OFFICERDEV_';
+
+/**
+ * Names that must NOT be prefixed.
+ *
+ * These are read by other software rather than by Officer: `NODE_ENV` is the runtime's, `PATH` and
+ * `HOME` are the operating system's. Prefixing one does not rename a variable, it deletes it.
+ */
+const LEAVE_ALONE = new Set(['NODE_ENV', 'PATH', 'HOME', 'SHELL', 'USER', 'LANG', 'TZ', 'TMPDIR', 'XDG_DATA_HOME']);
+
+export type FixEnvResult = { changed: string[]; alreadyPrefixed: number; path: string };
+
+/** Rewrite one env file's text. Pure, so the rules are testable without a filesystem. */
+export function prefixEnvText(text: string): { text: string; changed: string[]; alreadyPrefixed: number } {
+  const changed: string[] = [];
+  let alreadyPrefixed = 0;
+
+  const out = text.split('\n').map((line) => {
+    // Comments, blanks and anything that is not `KEY=…` pass through untouched. A `.env` is usually
+    // commented, and losing that would be a poor trade for a rename.
+    //
+    // `export` is captured rather than skipped so it can be put back — dropping it would change what the
+    // line does in a shell that sources this file.
+    const match = line.match(/^(\s*)(export\s+)?([A-Za-z_][A-Za-z0-9_]*)(\s*=)(.*)$/);
+    if (!match) return line;
+
+    const [, indent, exported, key, eq, value] = match as unknown as [
+      string,
+      string,
+      string | undefined,
+      string,
+      string,
+      string,
+    ];
+
+    if (key.startsWith(PREFIX)) {
+      alreadyPrefixed += 1;
+      return line;
+    }
+    if (LEAVE_ALONE.has(key)) return line;
+
+    changed.push(key);
+    return `${indent}${exported ?? ''}${PREFIX}${key}${eq}${value}`;
+  });
+
+  return { text: out.join('\n'), changed, alreadyPrefixed };
+}
+
+/** Apply it to a file. Returns what changed; writes nothing when nothing did. */
+export function fixEnvFile(path: string): FixEnvResult {
+  if (!existsSync(path)) return { changed: [], alreadyPrefixed: 0, path };
+  const before = readFileSync(path, 'utf8');
+  const { text, changed, alreadyPrefixed } = prefixEnvText(before);
+  if (text !== before) writeFileSync(path, text);
+  return { changed, alreadyPrefixed, path };
+}
diff --git a/src/servers/officer-url.mjs b/src/servers/officer-url.mjs
index 0ff14fc1..23158689 100644
--- a/src/servers/officer-url.mjs
+++ b/src/servers/officer-url.mjs
@@ -20,7 +20,7 @@
 //
 // So: no default anywhere, and this throws. Same posture as jwt.ts with JWT_SECRET.
 
-const raw = process.env.PORT;
+const raw = process.env.OFFICERDEV_PORT ?? process.env.PORT;
 
 if (!raw) {
   throw new Error(
diff --git a/src/servers/os-user-postgres.ts b/src/servers/os-user-postgres.ts
index e0c2d367..e1375b41 100644
--- a/src/servers/os-user-postgres.ts
+++ b/src/servers/os-user-postgres.ts
@@ -223,7 +223,7 @@ const TEMPLATE_ISOLATION_SQL = [
  * their side.
  */
 export async function ensureTemplateIsolation(): Promise<{ ok: true } | { ok: false; error: string }> {
-  const url = process.env.POSTGRES_URL;
+  const url = (process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL);
   if (!url) return { ok: false, error: 'POSTGRES_URL is not set' };
 
   let target: string;
@@ -315,7 +315,7 @@ export async function provisionPostgresRole(params: {
     }
 
     if (passwordSet && password) {
-      const { host, port } = pgpassTarget(process.env.POSTGRES_URL);
+      const { host, port } = pgpassTarget((process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL));
 
       // Written twice, on purpose, and they are not redundant.
       //
@@ -428,7 +428,7 @@ const DB_NAME_RE = /^[a-zA-Z0-9._-]{1,63}$/;
 export async function dropPostgresRole(osUser: string): Promise<DropRoleResult> {
   if (!ROLE_NAME_RE.test(osUser)) return { ok: false, error: `'${osUser}' is not a usable Postgres role name` };
 
-  const url = process.env.POSTGRES_URL;
+  const url = (process.env.OFFICERDEV_POSTGRES_URL ?? process.env.POSTGRES_URL);
   if (!url) return { ok: false, error: 'POSTGRES_URL is not set' };
 
   try {