diff --git a/docs/ops/deploy.md b/docs/ops/deploy.md
index f5bfb0082..e22a1d7f7 100644
--- a/docs/ops/deploy.md
+++ b/docs/ops/deploy.md
@@ -59,3 +59,20 @@ roll back:
    dev --create-only --name vX_Y_Z_rollback_<col>`), edit the SQL,
    commit, and re-deploy. Never `migrate resolve --rolled-back` against
    production unless you've taken a fresh `pg_dump` first.
+
+## Verify the served version
+
+The queued-deploy status is **not** the source of truth — the version
+`/api/version` actually answers is. A BuildKit layer-cache hit can
+re-ship the prior image even when Coolify reports a clean deploy, so
+always confirm the served build after a deploy:
+
+```sh
+# Asserts prod + demo serve 1.9.0, prints each target's buildSha,
+# exits non-zero on a mismatch or timeout after a bounded retry loop.
+pnpm dlx tsx scripts/assert-deploy.ts 1.9.0
+```
+
+Pass `--only=prod` / `--only=demo` to check a single target, or
+`--attempts=N --interval=ms` to widen the retry window while a slow
+pull settles.
diff --git a/scripts/assert-deploy.ts b/scripts/assert-deploy.ts
new file mode 100644
index 000000000..ea1e677d7
--- /dev/null
+++ b/scripts/assert-deploy.ts
@@ -0,0 +1,169 @@
+#!/usr/bin/env tsx
+/**
+ * Post-deploy version assertion.
+ *
+ * Polls `/api/version` on production + demo and asserts the running
+ * build's `data.version` matches an expected value, printing each
+ * target's `buildSha`. Exits non-zero on a mismatch or after the retry
+ * window elapses — so a CI step or a manual deploy can fail loudly when
+ * the `:latest` pull served the prior image (the recurring BuildKit
+ * layer-cache pitfall where Coolify reports "deployed" while
+ * `/api/version` still answers the old number).
+ *
+ * Run it after every deploy — the queued-deploy status is not the source
+ * of truth, the served version is:
+ *
+ *   pnpm dlx tsx scripts/assert-deploy.ts <expected-version>
+ *
+ * Examples:
+ *
+ *   # assert both prod + demo serve 1.9.0
+ *   pnpm dlx tsx scripts/assert-deploy.ts 1.9.0
+ *
+ *   # assert prod only
+ *   pnpm dlx tsx scripts/assert-deploy.ts 1.9.0 --only=prod
+ *
+ *   # widen the retry window (default 24 attempts × 5s = 2 min)
+ *   pnpm dlx tsx scripts/assert-deploy.ts 1.9.0 --attempts=60 --interval=5000
+ *
+ * Pure script — strips the leading `v` from the expected version so both
+ * `v1.9.0` and `1.9.0` work. No app-library import, no runtime wiring;
+ * the standalone image never ships this file.
+ */
+
+interface Target {
+  name: string;
+  url: string;
+}
+
+const TARGETS: Record<string, Target> = {
+  prod: { name: "prod", url: "https://healthlog.bombeck.io/api/version" },
+  demo: { name: "demo", url: "https://demo.healthlog.dev/api/version" },
+};
+
+interface VersionPayload {
+  version?: string;
+  buildSha?: string | null;
+  builtAt?: string | null;
+}
+
+function parseArgs(argv: string[]): {
+  expected: string;
+  attempts: number;
+  intervalMs: number;
+  only: string | null;
+} {
+  const positional: string[] = [];
+  let attempts = 24;
+  let intervalMs = 5_000;
+  let only: string | null = null;
+
+  for (const arg of argv) {
+    if (arg.startsWith("--attempts=")) {
+      attempts = Number.parseInt(arg.slice("--attempts=".length), 10);
+    } else if (arg.startsWith("--interval=")) {
+      intervalMs = Number.parseInt(arg.slice("--interval=".length), 10);
+    } else if (arg.startsWith("--only=")) {
+      only = arg.slice("--only=".length);
+    } else {
+      positional.push(arg);
+    }
+  }
+
+  const expected = (positional[0] ?? "").trim().replace(/^v/, "");
+  if (!expected) {
+    console.error(
+      "usage: pnpm dlx tsx scripts/assert-deploy.ts <expected-version> [--only=prod|demo] [--attempts=N] [--interval=ms]",
+    );
+    process.exit(2);
+  }
+  if (!Number.isFinite(attempts) || attempts < 1) attempts = 24;
+  if (!Number.isFinite(intervalMs) || intervalMs < 0) intervalMs = 5_000;
+
+  return { expected, attempts, intervalMs, only };
+}
+
+const sleep = (ms: number): Promise<void> =>
+  new Promise((res) => setTimeout(res, ms));
+
+/** One probe. Returns the parsed payload or null on any transport / shape error. */
+async function probe(url: string): Promise<VersionPayload | null> {
+  try {
+    const res = await fetch(url, {
+      redirect: "manual",
+      signal: AbortSignal.timeout(10_000),
+      headers: { accept: "application/json" },
+    });
+    if (!res.ok) return null;
+    const body = (await res.json()) as { data?: VersionPayload } | null;
+    return body?.data ?? null;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Poll one target until its served version matches `expected` or the
+ * retry window elapses. Resolves true on a match, false otherwise.
+ */
+async function assertTarget(
+  target: Target,
+  expected: string,
+  attempts: number,
+  intervalMs: number,
+): Promise<boolean> {
+  for (let attempt = 1; attempt <= attempts; attempt += 1) {
+    const payload = await probe(target.url);
+    const version = payload?.version?.trim() ?? null;
+    if (version === expected) {
+      console.log(
+        `[${target.name}] OK version=${version} buildSha=${payload?.buildSha ?? "—"}`,
+      );
+      return true;
+    }
+    const seen = version ?? "unreachable";
+    console.log(
+      `[${target.name}] attempt ${attempt}/${attempts}: expected ${expected}, got ${seen}`,
+    );
+    if (attempt < attempts) await sleep(intervalMs);
+  }
+  console.error(
+    `[${target.name}] FAIL: ${target.url} did not report ${expected} within ${attempts} attempts`,
+  );
+  return false;
+}
+
+async function main(): Promise<void> {
+  const { expected, attempts, intervalMs, only } = parseArgs(
+    process.argv.slice(2),
+  );
+
+  let selected: Target[];
+  if (only) {
+    const picked = TARGETS[only];
+    if (!picked) {
+      console.error(`unknown --only target: ${only} (use prod or demo)`);
+      process.exit(2);
+    }
+    selected = [picked];
+  } else {
+    selected = Object.values(TARGETS);
+  }
+
+  console.log(
+    `Asserting version ${expected} on: ${selected.map((t) => t.name).join(", ")}`,
+  );
+
+  // Probe targets in parallel; each runs its own bounded retry loop.
+  const results = await Promise.all(
+    selected.map((t) => assertTarget(t, expected, attempts, intervalMs)),
+  );
+
+  if (results.every((ok) => ok)) {
+    console.log("All targets serve the expected version.");
+    process.exit(0);
+  }
+  process.exit(1);
+}
+
+void main();