diff --git a/crates/cli/src/commands/templates.rs b/crates/cli/src/commands/templates.rs
index 8f1b0dd4e..75acce21d 100644
--- a/crates/cli/src/commands/templates.rs
+++ b/crates/cli/src/commands/templates.rs
@@ -8,6 +8,7 @@ use std::{fmt::Write, process::ExitCode};
 
 use anyhow::{Context as _, bail};
 use camino::Utf8PathBuf;
+use chrono::DateTime;
 use clap::Parser;
 use figment::Figment;
 use mas_config::{
@@ -34,6 +35,12 @@ enum Subcommand {
         /// The directory must either not exist or be empty.
         #[arg(long = "out-dir")]
         out_dir: Option<Utf8PathBuf>,
+
+        /// Attempt to remove 'unstable' template input data such as asset
+        /// hashes, in order to make renders more reproducible between
+        /// versions.
+        #[arg(long = "stabilise")]
+        stabilise: bool,
     },
 }
 
@@ -41,7 +48,7 @@ impl Options {
     pub async fn run(self, figment: &Figment) -> anyhow::Result<ExitCode> {
         use Subcommand as SC;
         match self.subcommand {
-            SC::Check { out_dir } => {
+            SC::Check { out_dir, stabilise } => {
                 let _span = info_span!("cli.templates.check").entered();
 
                 let template_config = TemplatesConfig::extract_or_default(figment)
@@ -59,9 +66,17 @@ impl Options {
                 let captcha_config = CaptchaConfig::extract_or_default(figment)
                     .map_err(anyhow::Error::from_boxed)?;
 
-                let clock = SystemClock::default();
-                // XXX: we should disallow SeedableRng::from_entropy
-                let mut rng = rand_chacha::ChaChaRng::from_entropy();
+                let now = if stabilise {
+                    DateTime::from_timestamp_secs(0).unwrap()
+                } else {
+                    SystemClock::default().now()
+                };
+                let rng = if stabilise {
+                    rand_chacha::ChaChaRng::from_seed([42; 32])
+                } else {
+                    // XXX: we should disallow SeedableRng::from_entropy
+                    rand_chacha::ChaChaRng::from_entropy()
+                };
                 let url_builder =
                     mas_router::UrlBuilder::new("https://example.com/".parse()?, None, None);
                 let site_config = site_config_from_config(
@@ -79,7 +94,7 @@ impl Options {
                     true,
                 )
                 .await?;
-                let all_renders = templates.check_render(clock.now(), &mut rng)?;
+                let all_renders = templates.check_render(now, &rng)?;
 
                 if let Some(out_dir) = out_dir {
                     // Save renders to disk.
diff --git a/crates/templates/src/context.rs b/crates/templates/src/context.rs
index 597683a03..c32691c4c 100644
--- a/crates/templates/src/context.rs
+++ b/crates/templates/src/context.rs
@@ -106,9 +106,9 @@ pub trait TemplateContext: Serialize {
     ///
     /// This is then used to check for template validity in unit tests and in
     /// the CLI (`cargo run -- templates check`)
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -144,9 +144,9 @@ pub(crate) fn sample_list<T: TemplateContext>(samples: Vec<T>) -> BTreeMap<Sampl
 }
 
 impl TemplateContext for () {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -181,9 +181,9 @@ impl<T> std::ops::Deref for WithLanguage<T> {
 }
 
 impl<T: TemplateContext> TemplateContext for WithLanguage<T> {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -192,7 +192,9 @@ impl<T: TemplateContext> TemplateContext for WithLanguage<T> {
         locales
             .iter()
             .flat_map(|locale| {
-                T::sample(now, rng, locales)
+                // Make samples deterministic between locales
+                let mut rng = rng.clone();
+                T::sample(now, &mut rng, locales)
                     .into_iter()
                     .map(|(sample_id, sample)| {
                         (
@@ -218,9 +220,9 @@ pub struct WithCsrf<T> {
 }
 
 impl<T: TemplateContext> TemplateContext for WithCsrf<T> {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -251,9 +253,9 @@ pub struct WithSession<T> {
 }
 
 impl<T: TemplateContext> TemplateContext for WithSession<T> {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -289,9 +291,9 @@ pub struct WithOptionalSession<T> {
 }
 
 impl<T: TemplateContext> TemplateContext for WithOptionalSession<T> {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -340,9 +342,9 @@ impl Serialize for EmptyContext {
 }
 
 impl TemplateContext for EmptyContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -368,9 +370,9 @@ impl IndexContext {
 }
 
 impl TemplateContext for IndexContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -414,9 +416,9 @@ impl AppContext {
 }
 
 impl TemplateContext for AppContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -447,9 +449,9 @@ impl ApiDocContext {
 }
 
 impl TemplateContext for ApiDocContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -539,9 +541,9 @@ pub struct LoginContext {
 }
 
 impl TemplateContext for LoginContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -647,9 +649,9 @@ pub struct RegisterContext {
 }
 
 impl TemplateContext for RegisterContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -690,9 +692,9 @@ pub struct PasswordRegisterContext {
 }
 
 impl TemplateContext for PasswordRegisterContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -732,9 +734,9 @@ pub struct ConsentContext {
 }
 
 impl TemplateContext for ConsentContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -790,9 +792,9 @@ pub struct PolicyViolationContext {
 }
 
 impl TemplateContext for PolicyViolationContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -865,9 +867,9 @@ pub struct CompatSsoContext {
 }
 
 impl TemplateContext for CompatSsoContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -927,9 +929,9 @@ impl EmailRecoveryContext {
 }
 
 impl TemplateContext for EmailRecoveryContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -992,9 +994,9 @@ impl EmailVerificationContext {
 }
 
 impl TemplateContext for EmailVerificationContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1067,9 +1069,9 @@ impl RegisterStepsVerifyEmailContext {
 }
 
 impl TemplateContext for RegisterStepsVerifyEmailContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1107,9 +1109,9 @@ impl RegisterStepsEmailInUseContext {
 }
 
 impl TemplateContext for RegisterStepsEmailInUseContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1162,9 +1164,9 @@ impl RegisterStepsDisplayNameContext {
 }
 
 impl TemplateContext for RegisterStepsDisplayNameContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<chrono::Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1217,9 +1219,9 @@ impl RegisterStepsRegistrationTokenContext {
 }
 
 impl TemplateContext for RegisterStepsRegistrationTokenContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<chrono::Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1268,9 +1270,9 @@ impl RecoveryStartContext {
 }
 
 impl TemplateContext for RecoveryStartContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1310,9 +1312,9 @@ impl RecoveryProgressContext {
 }
 
 impl TemplateContext for RecoveryProgressContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1356,9 +1358,9 @@ impl RecoveryExpiredContext {
 }
 
 impl TemplateContext for RecoveryExpiredContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1420,9 +1422,9 @@ impl RecoveryFinishContext {
 }
 
 impl TemplateContext for RecoveryFinishContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1469,9 +1471,9 @@ impl UpstreamExistingLinkContext {
 }
 
 impl TemplateContext for UpstreamExistingLinkContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1507,9 +1509,9 @@ impl UpstreamSuggestLink {
 }
 
 impl TemplateContext for UpstreamSuggestLink {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1636,9 +1638,9 @@ impl UpstreamRegister {
 }
 
 impl TemplateContext for UpstreamRegister {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1722,9 +1724,9 @@ impl DeviceLinkContext {
 }
 
 impl TemplateContext for DeviceLinkContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1756,9 +1758,9 @@ impl DeviceConsentContext {
 }
 
 impl TemplateContext for DeviceConsentContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1801,9 +1803,9 @@ impl AccountInactiveContext {
 }
 
 impl TemplateContext for AccountInactiveContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1837,9 +1839,9 @@ impl DeviceNameContext {
 }
 
 impl TemplateContext for DeviceNameContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1863,9 +1865,9 @@ pub struct FormPostContext<T> {
 }
 
 impl<T: TemplateContext> TemplateContext for FormPostContext<T> {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<Utc>,
-        rng: &mut impl Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -1945,9 +1947,9 @@ impl std::fmt::Display for ErrorContext {
 }
 
 impl TemplateContext for ErrorContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: chrono::DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
@@ -2039,9 +2041,9 @@ impl NotFoundContext {
 }
 
 impl TemplateContext for NotFoundContext {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         _now: DateTime<Utc>,
-        _rng: &mut impl Rng,
+        _rng: &mut R,
         _locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
diff --git a/crates/templates/src/context/captcha.rs b/crates/templates/src/context/captcha.rs
index 3daafb745..32c2d1068 100644
--- a/crates/templates/src/context/captcha.rs
+++ b/crates/templates/src/context/captcha.rs
@@ -11,6 +11,7 @@ use minijinja::{
     Value,
     value::{Enumerator, Object},
 };
+use rand::Rng;
 use serde::Serialize;
 
 use crate::{TemplateContext, context::SampleIdentifier};
@@ -58,9 +59,9 @@ impl<T> WithCaptcha<T> {
 }
 
 impl<T: TemplateContext> TemplateContext for WithCaptcha<T> {
-    fn sample(
+    fn sample<R: Rng + Clone>(
         now: chrono::DateTime<chrono::prelude::Utc>,
-        rng: &mut impl rand::prelude::Rng,
+        rng: &mut R,
         locales: &[DataLocale],
     ) -> BTreeMap<SampleIdentifier, Self>
     where
diff --git a/crates/templates/src/lib.rs b/crates/templates/src/lib.rs
index 603dcfdf6..a57f718f0 100644
--- a/crates/templates/src/lib.rs
+++ b/crates/templates/src/lib.rs
@@ -471,10 +471,10 @@ impl Templates {
     /// # Errors
     ///
     /// Returns an error if any of the templates fails to render
-    pub fn check_render(
+    pub fn check_render<R: Rng + Clone>(
         &self,
         now: chrono::DateTime<chrono::Utc>,
-        rng: &mut impl Rng,
+        rng: &R,
     ) -> anyhow::Result<BTreeMap<(&'static str, SampleIdentifier), String>> {
         check::all(self, now, rng)
     }
@@ -489,7 +489,7 @@ mod tests {
         #[allow(clippy::disallowed_methods)]
         let now = chrono::Utc::now();
         #[allow(clippy::disallowed_methods)]
-        let mut rng = rand::thread_rng();
+        let rng = rand::thread_rng();
 
         let path = Utf8Path::new(env!("CARGO_MANIFEST_DIR")).join("../../templates/");
         let url_builder = UrlBuilder::new("https://example.com/".parse().unwrap(), None, None);
@@ -517,6 +517,6 @@ mod tests {
         )
         .await
         .unwrap();
-        templates.check_render(now, &mut rng).unwrap();
+        templates.check_render(now, &rng).unwrap();
     }
 }
diff --git a/crates/templates/src/macros.rs b/crates/templates/src/macros.rs
index 95b57f0d9..c6d5e9302 100644
--- a/crates/templates/src/macros.rs
+++ b/crates/templates/src/macros.rs
@@ -78,15 +78,18 @@ macro_rules! register_templates {
             /// # Errors
             ///
             /// Returns an error if any template fails to render with any of the sample.
-            pub(crate) fn all(templates: &Templates, now: chrono::DateTime<chrono::Utc>, rng: &mut impl rand::Rng) -> anyhow::Result<::std::collections::BTreeMap<(&'static str, SampleIdentifier), String>> {
+            pub(crate) fn all<R: Rng + Clone>(templates: &Templates, now: chrono::DateTime<chrono::Utc>, rng: &R) -> anyhow::Result<::std::collections::BTreeMap<(&'static str, SampleIdentifier), String>> {
                 let mut out = ::std::collections::BTreeMap::new();
                 // TODO shouldn't the Rng be independent for each render?
                 $(
-                    out.extend(
-                        $name $(::< $( $generic_default ),*  >)? (templates, now, rng)?
-                            .into_iter()
-                            .map(|(sample_identifier, rendered)| (($template, sample_identifier), rendered))
-                    );
+                    {
+                        let mut rng = rng.clone();
+                        out.extend(
+                            $name $(::< _ $( , $generic_default ),* >)? (templates, now, &mut rng)?
+                                .into_iter()
+                                .map(|(sample_identifier, rendered)| (($template, sample_identifier), rendered))
+                        );
+                    }
                 )*
 
                 Ok(out)
@@ -101,8 +104,8 @@ macro_rules! register_templates {
                 ///
                 /// Returns an error if the template fails to render with any of the sample.
                 pub(crate) fn $name
-                    $(< $( $lt $( : $clt $(+ $dlt )* + TemplateContext )? ),+ >)?
-                    (templates: &Templates, now: chrono::DateTime<chrono::Utc>, rng: &mut impl rand::Rng)
+                    < __R: Rng + Clone $( , $( $lt $( : $clt $(+ $dlt )* + TemplateContext )? ),+ )? >
+                    (templates: &Templates, now: chrono::DateTime<chrono::Utc>, rng: &mut __R)
                 -> anyhow::Result<BTreeMap<SampleIdentifier, String>> {
                     let locales = templates.translator().available_locales();
                     let samples: BTreeMap<SampleIdentifier, $param > = TemplateContext::sample(now, rng, &locales);