diff --git a/cli/examples/custom-commit-templater/main.rs b/cli/examples/custom-commit-templater/main.rs
index edb78fd843..e3ae01a664 100644
--- a/cli/examples/custom-commit-templater/main.rs
+++ b/cli/examples/custom-commit-templater/main.rs
@@ -17,19 +17,24 @@ use jj_cli::commit_templater::{CommitTemplateBuildFnTable, CommitTemplateLanguag
 use jj_cli::template_builder::TemplateLanguage;
 use jj_cli::template_parser::{self, TemplateParseError};
 use jj_cli::templater::{TemplateFunction, TemplatePropertyError};
+use jj_lib::backend::CommitId;
 use jj_lib::commit::Commit;
+use jj_lib::extensions_map::ExtensionsMap;
 use jj_lib::object_id::ObjectId;
+use jj_lib::repo::Repo;
+use jj_lib::revset::RevsetExpression;
+use once_cell::sync::OnceCell;
 
 struct HexCounter;
 
-fn num_digits_in_id(commit: Commit) -> Result<i64, TemplatePropertyError> {
+fn num_digits_in_id(id: &CommitId) -> i64 {
     let mut count = 0;
-    for ch in commit.id().hex().chars() {
+    for ch in id.hex().chars() {
         if ch.is_ascii_digit() {
             count += 1;
         }
     }
-    Ok(count)
+    count
 }
 
 fn num_char_in_id(commit: Commit, ch_match: char) -> Result<i64, TemplatePropertyError> {
@@ -42,14 +47,57 @@ fn num_char_in_id(commit: Commit, ch_match: char) -> Result<i64, TemplatePropert
     Ok(count)
 }
 
+struct MostDigitsInId {
+    count: OnceCell<i64>,
+}
+
+impl MostDigitsInId {
+    fn new() -> Self {
+        Self {
+            count: OnceCell::new(),
+        }
+    }
+
+    fn count(&self, repo: &dyn Repo) -> i64 {
+        *self.count.get_or_init(|| {
+            RevsetExpression::all()
+                .evaluate_programmatic(repo)
+                .unwrap()
+                .iter()
+                .map(|id| num_digits_in_id(&id))
+                .max()
+                .unwrap_or(0)
+        })
+    }
+}
+
 impl CommitTemplateLanguageExtension for HexCounter {
     fn build_fn_table<'repo>(&self) -> CommitTemplateBuildFnTable<'repo> {
         let mut table = CommitTemplateBuildFnTable::empty();
+        table.commit_methods.insert(
+            "has_most_digits",
+            |language, _build_context, property, call| {
+                template_parser::expect_no_arguments(call)?;
+                let most_digits = language
+                    .cache_extension::<MostDigitsInId>()
+                    .unwrap()
+                    .count(language.repo());
+                Ok(
+                    language.wrap_boolean(TemplateFunction::new(property, move |commit| {
+                        Ok(num_digits_in_id(commit.id()) == most_digits)
+                    })),
+                )
+            },
+        );
         table.commit_methods.insert(
             "num_digits_in_id",
             |language, _build_context, property, call| {
                 template_parser::expect_no_arguments(call)?;
-                Ok(language.wrap_integer(TemplateFunction::new(property, num_digits_in_id)))
+                Ok(
+                    language.wrap_integer(TemplateFunction::new(property, |commit| {
+                        Ok(num_digits_in_id(commit.id()))
+                    })),
+                )
             },
         );
         table.commit_methods.insert(
@@ -78,6 +126,10 @@ impl CommitTemplateLanguageExtension for HexCounter {
 
         table
     }
+
+    fn build_cache_extensions(&self, extensions: &mut ExtensionsMap) {
+        extensions.insert(MostDigitsInId::new());
+    }
 }
 
 fn main() -> std::process::ExitCode {
diff --git a/cli/src/commit_templater.rs b/cli/src/commit_templater.rs
index e45759dc69..60a0a6fdd7 100644
--- a/cli/src/commit_templater.rs
+++ b/cli/src/commit_templater.rs
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::any::Any;
 use std::cmp::max;
 use std::collections::HashMap;
 use std::io;
@@ -20,6 +21,7 @@ use std::rc::Rc;
 use itertools::Itertools as _;
 use jj_lib::backend::{ChangeId, CommitId};
 use jj_lib::commit::Commit;
+use jj_lib::extensions_map::ExtensionsMap;
 use jj_lib::hex_util::to_reverse_hex;
 use jj_lib::id_prefix::IdPrefixContext;
 use jj_lib::object_id::ObjectId as _;
@@ -42,6 +44,8 @@ use crate::text_util;
 
 pub trait CommitTemplateLanguageExtension {
     fn build_fn_table<'repo>(&self) -> CommitTemplateBuildFnTable<'repo>;
+
+    fn build_cache_extensions(&self, extensions: &mut ExtensionsMap);
 }
 
 pub struct CommitTemplateLanguage<'repo> {
@@ -50,6 +54,7 @@ pub struct CommitTemplateLanguage<'repo> {
     id_prefix_context: &'repo IdPrefixContext,
     build_fn_table: CommitTemplateBuildFnTable<'repo>,
     keyword_cache: CommitKeywordCache,
+    cache_extensions: ExtensionsMap,
 }
 
 impl<'repo> CommitTemplateLanguage<'repo> {
@@ -62,15 +67,22 @@ impl<'repo> CommitTemplateLanguage<'repo> {
         extension: Option<&dyn CommitTemplateLanguageExtension>,
     ) -> Self {
         let mut build_fn_table = CommitTemplateBuildFnTable::builtin();
+        let mut cache_extensions = ExtensionsMap::empty();
+
+        // TODO: Extension methods should be refactored to be plural, to support
+        // multiple extensions in a dynamic load environment
         if let Some(extension) = extension {
             build_fn_table.merge(extension.build_fn_table());
+            extension.build_cache_extensions(&mut cache_extensions);
         }
+
         CommitTemplateLanguage {
             repo,
             workspace_id: workspace_id.clone(),
             id_prefix_context,
             build_fn_table,
             keyword_cache: CommitKeywordCache::default(),
+            cache_extensions,
         }
     }
 }
@@ -156,6 +168,10 @@ impl<'repo> CommitTemplateLanguage<'repo> {
         &self.keyword_cache
     }
 
+    pub fn cache_extension<T: Any>(&self) -> Option<&T> {
+        self.cache_extensions.get::<T>()
+    }
+
     pub fn wrap_commit(
         &self,
         property: impl TemplateProperty<Commit, Output = Commit> + 'repo,