diff --git a/monitor.toml.example b/monitor.toml.example
index 4827aeb8..7da6c822 100644
--- a/monitor.toml.example
+++ b/monitor.toml.example
@@ -52,6 +52,12 @@ base_image_max_age = 86400
 # Uncomment to skip cached Servo repo updates.
 # dont_update_cached_servo_repo = true
 
+# Create libvirt guests for profile templates as “ci-template-<profile_name>.0”. Namespace must not be used by anything else!
+# libvirt_template_guest_prefix = "ci-template"
+
+# Create libvirt guests for image rebuilds as “ci-rebuild-<profile_name>.0”. Namespace must not be used by anything else!
+# libvirt_rebuild_guest_prefix = "ci-rebuild"
+
 # Create libvirt guests for runners as “ci-runner-<profile_name>.0”. Namespace must not be used by anything else!
 # libvirt_runner_guest_prefix = "ci-runner"
 
diff --git a/monitor/settings/src/lib.rs b/monitor/settings/src/lib.rs
index dae6c75f..db453684 100644
--- a/monitor/settings/src/lib.rs
+++ b/monitor/settings/src/lib.rs
@@ -80,6 +80,8 @@ pub struct Toml {
     pub main_repo_path: String,
     base_image_max_age: u64,
     dont_update_cached_servo_repo: Option<bool>,
+    libvirt_template_guest_prefix: Option<String>,
+    libvirt_rebuild_guest_prefix: Option<String>,
     libvirt_runner_guest_prefix: Option<String>,
     pub available_1g_hugepages: usize,
     pub available_normal_memory: MemorySize,
@@ -242,6 +244,18 @@ impl Toml {
         self.queue_member.unwrap_or(false)
     }
 
+    pub fn libvirt_template_guest_prefix(&self) -> &str {
+        self.libvirt_template_guest_prefix
+            .as_deref()
+            .unwrap_or("ci-template")
+    }
+
+    pub fn libvirt_rebuild_guest_prefix(&self) -> &str {
+        self.libvirt_rebuild_guest_prefix
+            .as_deref()
+            .unwrap_or("ci-rebuild")
+    }
+
     pub fn libvirt_runner_guest_prefix(&self) -> &str {
         self.libvirt_runner_guest_prefix
             .as_deref()
diff --git a/monitor/settings/src/profile.rs b/monitor/settings/src/profile.rs
index 9af58f1f..3680fc96 100644
--- a/monitor/settings/src/profile.rs
+++ b/monitor/settings/src/profile.rs
@@ -1,3 +1,4 @@
+use jane_eyre::eyre::{self, OptionExt};
 use serde::{Deserialize, Serialize};
 
 use crate::{TOML, units::MemorySize};
@@ -20,8 +21,24 @@ pub enum ImageType {
 }
 
 impl Profile {
-    pub fn profile_guest_name(&self) -> String {
-        format!("{}", self.profile_name)
+    pub fn snapshot_path_slug(&self, snapshot_name: &str) -> String {
+        format!("{}@{snapshot_name}", self.profile_name)
+    }
+
+    pub fn template_guest_name(&self, snapshot_name: &str) -> String {
+        format!(
+            "{}-{}@{snapshot_name}",
+            TOML.libvirt_template_guest_prefix(),
+            self.profile_name
+        )
+    }
+
+    pub fn rebuild_guest_name(&self, snapshot_name: &str) -> String {
+        format!(
+            "{}-{}@{snapshot_name}",
+            TOML.libvirt_rebuild_guest_prefix(),
+            self.profile_name
+        )
     }
 
     pub fn runner_guest_name(&self, id: usize) -> String {
@@ -33,3 +50,23 @@ impl Profile {
         )
     }
 }
+
+pub fn parse_template_guest_name(template_guest_name: &str) -> eyre::Result<(&str, &str)> {
+    let prefix = format!("{}-", TOML.libvirt_template_guest_prefix());
+    let (profile_key, snapshot_name) = template_guest_name
+        .strip_prefix(&prefix)
+        .ok_or_eyre("Failed to strip template guest prefix")?
+        .split_once("@")
+        .ok_or_eyre("Failed to split snapshot path slug into profile key and snapshot name")?;
+    Ok((profile_key, snapshot_name))
+}
+
+pub fn parse_rebuild_guest_name(rebuild_guest_name: &str) -> eyre::Result<(&str, &str)> {
+    let prefix = format!("{}-", TOML.libvirt_rebuild_guest_prefix());
+    let (profile_key, snapshot_name) = rebuild_guest_name
+        .strip_prefix(&prefix)
+        .ok_or_eyre("Failed to strip rebuild guest prefix")?
+        .split_once("@")
+        .ok_or_eyre("Failed to split snapshot path slug into profile key and snapshot name")?;
+    Ok((profile_key, snapshot_name))
+}
diff --git a/monitor/src/image.rs b/monitor/src/image.rs
index 64f62e3c..cf93c90b 100644
--- a/monitor/src/image.rs
+++ b/monitor/src/image.rs
@@ -4,10 +4,10 @@ pub mod windows10;
 
 use core::str;
 use std::{
-    collections::BTreeMap,
+    collections::{BTreeMap, BTreeSet},
     ffi::OsStr,
-    fs::{create_dir_all, read_dir, read_link, remove_file, set_permissions, File},
-    io::{ErrorKind, Seek, Write},
+    fs::{create_dir_all, read_dir, remove_file, set_permissions, File},
+    io::{Seek, Write},
     mem::take,
     os::unix::fs::PermissionsExt,
     path::{Path, PathBuf},
@@ -17,13 +17,17 @@ use std::{
 
 use bytesize::ByteSize;
 use chrono::{SecondsFormat, Utc};
-use cmd_lib::{run_cmd, spawn_with_output};
+use cmd_lib::{run_cmd, run_fun, spawn_with_output};
 use jane_eyre::eyre::{self, bail, OptionExt};
-use settings::{profile::Profile, TOML};
-use tracing::{debug, error, info, trace, warn};
+use settings::{
+    profile::{parse_rebuild_guest_name, parse_template_guest_name, Profile},
+    TOML,
+};
+use tracing::{debug, error, info, warn};
 
 use crate::{
-    policy::{base_images_path, runner_images_path, Policy},
+    libvirt::{list_rebuild_guests, list_template_guests},
+    policy::{runner_images_path, template_or_rebuild_images_path, Policy},
     shell::{log_output_as_info, reflink_or_copy_with_warning},
 };
 
@@ -37,10 +41,39 @@ pub struct Rebuilds {
 struct Rebuild {
     thread: JoinHandle<eyre::Result<()>>,
     snapshot_name: String,
+    guest_name: String,
 }
 
 impl Rebuilds {
     pub fn run(&mut self, policy: &mut Policy) -> eyre::Result<()> {
+        // Clean up any dangling resources from past rebuilds.
+        let current_known_rebuild_guest_names = self
+            .rebuild_guest_names()
+            .into_iter()
+            .map(|(_key, guest_name)| guest_name)
+            .collect::<BTreeSet<_>>();
+        for rebuild_guest_name in list_rebuild_guests()? {
+            if !current_known_rebuild_guest_names.contains(&rebuild_guest_name) {
+                undefine_libvirt_guest(&rebuild_guest_name)?;
+                let (profile_key, snapshot_name) =
+                    match parse_rebuild_guest_name(&rebuild_guest_name) {
+                        Ok(result) => result,
+                        Err(error) => {
+                            warn!(?error, "Failed to clean up bad image files");
+                            continue;
+                        }
+                    };
+                let Some(profile) = policy.profile(profile_key) else {
+                    warn!(
+                        ?profile_key,
+                        "Failed to clean up bad image files: Unknown profile"
+                    );
+                    continue;
+                };
+                delete_template(profile, snapshot_name)?;
+            }
+        }
+
         let mut profiles_needing_rebuild = BTreeMap::default();
         let mut cached_servo_repo_was_just_updated = false;
 
@@ -118,6 +151,7 @@ impl Rebuilds {
                 Rebuild {
                     thread,
                     snapshot_name: snapshot_name.clone(),
+                    guest_name: profile.rebuild_guest_name(&snapshot_name),
                 },
             );
         }
@@ -142,6 +176,13 @@ impl Rebuilds {
 
         Ok(())
     }
+
+    pub fn rebuild_guest_names(&self) -> BTreeMap<String, String> {
+        self.rebuilds
+            .iter()
+            .map(|(profile_key, rebuild)| (profile_key.clone(), rebuild.guest_name.clone()))
+            .collect()
+    }
 }
 
 #[tracing::instrument]
@@ -170,10 +211,9 @@ fn rebuild_with_rust(
 ) -> Result<(), eyre::Error> {
     info!(?snapshot_name, "Starting image rebuild");
 
-    let base_images_path = create_base_images_dir(&profile)?;
-    undefine_libvirt_guest(&profile.profile_guest_name())?;
+    let base_images_path = create_template_or_rebuild_images_dir(&profile)?;
 
-    match match match &*profile.profile_name {
+    match match &*profile.profile_name {
         "servo-macos13" => macos13::rebuild(
             &base_images_path,
             &profile,
@@ -233,76 +273,27 @@ fn rebuild_with_rust(
         other => todo!("Rebuild not yet implemented: {other}"),
     } {
         result @ Ok(()) => {
-            prune_images(&profile)?;
+            prune_templates(&profile)?;
             result
         }
         Err(error) => {
             warn!(?error, "Image rebuild error");
-            delete_image(&profile, snapshot_name);
+            delete_template(&profile, snapshot_name)?;
             Err(error)
         }
-    } {
-        result => {
-            // After a rebuild attempt, the base guest should always use the symlinks to the last known good image.
-            // On success, these will be the new image files. On failure, these will be the old image files.
-            match &*profile.profile_name {
-                "servo-macos13" => {
-                    macos13::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-macos14" => {
-                    macos13::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-macos15" => {
-                    macos13::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-ubuntu2204" => {
-                    ubuntu2204::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-ubuntu2204-bench" => {
-                    ubuntu2204::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-ubuntu2204-rust" => {
-                    ubuntu2204::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-ubuntu2204-wpt" => {
-                    ubuntu2204::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                "servo-windows10" => {
-                    windows10::redefine_base_guest_with_symlinks(&base_images_path, &profile)?;
-                }
-                other => {
-                    todo!("Redefining base guest with symlinks not implemented: {other}")
-                }
-            }
-            result
-        }
-    }
-}
-
-pub fn prune_images(profile: &Profile) -> eyre::Result<()> {
-    match &*profile.profile_name {
-        "servo-macos13" => macos13::prune_images(profile),
-        "servo-macos14" => macos13::prune_images(profile),
-        "servo-macos15" => macos13::prune_images(profile),
-        "servo-ubuntu2204" => ubuntu2204::prune_images(profile),
-        "servo-ubuntu2204-bench" => ubuntu2204::prune_images(profile),
-        "servo-ubuntu2204-rust" => ubuntu2204::prune_images(profile),
-        "servo-ubuntu2204-wpt" => ubuntu2204::prune_images(profile),
-        "servo-windows10" => windows10::prune_images(profile),
-        other => todo!("Image pruning not yet implemented: {other}"),
     }
 }
 
-pub fn delete_image(profile: &Profile, snapshot_name: &str) {
+pub fn delete_template(profile: &Profile, snapshot_name: &str) -> eyre::Result<()> {
     match &*profile.profile_name {
-        "servo-macos13" => macos13::delete_image(profile, snapshot_name),
-        "servo-macos14" => macos13::delete_image(profile, snapshot_name),
-        "servo-macos15" => macos13::delete_image(profile, snapshot_name),
-        "servo-ubuntu2204" => ubuntu2204::delete_image(profile, snapshot_name),
-        "servo-ubuntu2204-bench" => ubuntu2204::delete_image(profile, snapshot_name),
-        "servo-ubuntu2204-rust" => ubuntu2204::delete_image(profile, snapshot_name),
-        "servo-ubuntu2204-wpt" => ubuntu2204::delete_image(profile, snapshot_name),
-        "servo-windows10" => windows10::delete_image(profile, snapshot_name),
+        "servo-macos13" => macos13::delete_template(profile, snapshot_name),
+        "servo-macos14" => macos13::delete_template(profile, snapshot_name),
+        "servo-macos15" => macos13::delete_template(profile, snapshot_name),
+        "servo-ubuntu2204" => ubuntu2204::delete_template(profile, snapshot_name),
+        "servo-ubuntu2204-bench" => ubuntu2204::delete_template(profile, snapshot_name),
+        "servo-ubuntu2204-rust" => ubuntu2204::delete_template(profile, snapshot_name),
+        "servo-ubuntu2204-wpt" => ubuntu2204::delete_template(profile, snapshot_name),
+        "servo-windows10" => windows10::delete_template(profile, snapshot_name),
         other => todo!("Image pruning not yet implemented: {other}"),
     }
 }
@@ -323,20 +314,35 @@ pub fn register_runner(profile: &Profile, runner_guest_name: &str) -> eyre::Resu
 
 pub fn create_runner(
     profile: &Profile,
+    snapshot_name: &str,
     runner_guest_name: &str,
     runner_id: usize,
 ) -> eyre::Result<String> {
     match &*profile.profile_name {
-        "servo-macos13" => macos13::create_runner(profile, runner_guest_name, runner_id),
-        "servo-macos14" => macos13::create_runner(profile, runner_guest_name, runner_id),
-        "servo-macos15" => macos13::create_runner(profile, runner_guest_name, runner_id),
-        "servo-ubuntu2204" => ubuntu2204::create_runner(profile, runner_guest_name, runner_id),
+        "servo-macos13" => {
+            macos13::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
+        "servo-macos14" => {
+            macos13::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
+        "servo-macos15" => {
+            macos13::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
+        "servo-ubuntu2204" => {
+            ubuntu2204::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
         "servo-ubuntu2204-bench" => {
-            ubuntu2204::create_runner(profile, runner_guest_name, runner_id)
+            ubuntu2204::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
+        "servo-ubuntu2204-rust" => {
+            ubuntu2204::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
+        "servo-ubuntu2204-wpt" => {
+            ubuntu2204::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
+        }
+        "servo-windows10" => {
+            windows10::create_runner(profile, snapshot_name, runner_guest_name, runner_id)
         }
-        "servo-ubuntu2204-rust" => ubuntu2204::create_runner(profile, runner_guest_name, runner_id),
-        "servo-ubuntu2204-wpt" => ubuntu2204::create_runner(profile, runner_guest_name, runner_id),
-        "servo-windows10" => windows10::create_runner(profile, runner_guest_name, runner_id),
         other => todo!("Runner creation not yet implemented: {other}"),
     }
 }
@@ -359,8 +365,8 @@ pub fn destroy_runner(
     }
 }
 
-pub(self) fn create_base_images_dir(profile: &Profile) -> eyre::Result<PathBuf> {
-    let base_images_path = base_images_path(profile);
+pub(self) fn create_template_or_rebuild_images_dir(profile: &Profile) -> eyre::Result<PathBuf> {
+    let base_images_path = template_or_rebuild_images_path(profile);
     debug!(?base_images_path, "Creating base images subdirectory");
     create_dir_all(&base_images_path)?;
 
@@ -375,67 +381,51 @@ pub(self) fn create_runner_images_dir() -> eyre::Result<PathBuf> {
     Ok(runner_images_path)
 }
 
-pub(self) fn prune_base_image_files(profile: &Profile, prefix: &str) -> eyre::Result<()> {
-    let base_images_path = base_images_path(profile);
-    info!(?base_images_path, "Pruning base image files");
-    create_dir_all(&base_images_path)?;
-
-    let matches_prefix = |target: &str| {
-        target
-            .strip_prefix(prefix)
-            .and_then(move |f| f.strip_prefix("@"))
-            .is_some()
-    };
-
-    // Check the symlink target for the most recent successful build.
-    let mut symlink = match read_link(base_images_path.join(prefix)) {
-        Ok(result) => Some(result),
-        Err(error) if error.kind() == ErrorKind::NotFound => None,
-        Err(other) => Err(other)?,
-    };
-
-    // The symlink target should be of the form `{prefix}@{snapshot_name}`.
-    if let Some(target) = symlink.as_ref() {
-        let target = target.to_str().ok_or_eyre("Unsupported path")?;
-        if !matches_prefix(target) {
-            warn!(target, "Unexpected symlink target format");
-            symlink.take();
+pub(self) fn prune_templates(profile: &Profile) -> eyre::Result<()> {
+    // Build a sorted list of template guest names for this profile.
+    let mut snapshot_names = vec![];
+    for template_guest_name in list_template_guests()? {
+        if let Ok((profile_key, snapshot_name)) = parse_template_guest_name(&template_guest_name) {
+            if profile_key == profile.profile_name {
+                snapshot_names.push(snapshot_name.to_owned());
+            }
+        } else {
+            undefine_libvirt_guest(&template_guest_name)?;
         }
     }
+    snapshot_names.sort();
+
+    // Delete all of those templates, except the three most recent.
+    // Since the snapshot names are RFC 3339 timestamps, we can use the sorted order (until year 10000).
+    let keep_snapshots = snapshot_names.clone().into_iter().rev().take(3);
+    let delete_snapshots = snapshot_names.iter().rev().skip(3);
+    for snapshot_name in delete_snapshots {
+        delete_template(profile, snapshot_name)?;
+    }
+
+    // Now delete any files that are not associated with a known snapshot.
+    let keep_snapshots = keep_snapshots.collect::<BTreeSet<_>>();
+    let base_images_path = template_or_rebuild_images_path(profile);
+    info!(?base_images_path, "Pruning base image files");
+    create_dir_all(&base_images_path)?;
 
-    // Build a sorted list of filenames starting with `{prefix}@`.
-    let mut filenames = vec![];
     for entry in read_dir(&base_images_path)? {
         let filename = entry?.file_name();
         let filename = filename.to_str().ok_or_eyre("Unsupported path")?;
-        if matches_prefix(filename) {
-            filenames.push(filename.to_owned());
-        }
-    }
-    filenames.sort();
-
-    // Delete all of those files, except the most recent successful build and up to three builds before that.
-    // Since the snapshot names are RFC 3339 timestamps, we can use the sorted order (until year 10000).
-    // FIXME: past images may be bad, if the monitor was restarted during an image build.
-    let mut filenames = filenames.iter().rev();
-    while let Some(filename) = filenames.next() {
-        if let Some(target) = symlink.as_ref() {
-            if Path::new(filename) == target {
-                trace!(filename, "Keeping");
-                filenames.next();
-                filenames.next();
-                filenames.next();
-                continue;
+        if let Some((_base, snapshot_name)) = filename.split_once("@") {
+            if !keep_snapshots.contains(snapshot_name) {
+                delete_template_or_rebuild_image_file(profile, filename);
             }
+        } else {
+            delete_template_or_rebuild_image_file(profile, filename);
         }
-        delete_base_image_file(profile, filename);
     }
 
     Ok(())
 }
 
-pub(self) fn delete_base_image_file(profile: &Profile, filename: &str) {
-    let base_images_path = base_images_path(profile);
+pub(self) fn delete_template_or_rebuild_image_file(profile: &Profile, filename: &str) {
+    let base_images_path = template_or_rebuild_images_path(profile);
     let path = base_images_path.join(filename);
     info!(?path, "Deleting");
     if let Err(error) = remove_file(&path) {
@@ -537,10 +527,20 @@ pub fn start_libvirt_guest(guest_name: &str) -> eyre::Result<()> {
 
 pub(self) fn wait_for_guest(guest_name: &str, timeout: Duration) -> eyre::Result<()> {
     let timeout = timeout.as_secs();
-    info!("Waiting for guest to shut down (max {timeout} seconds)"); // normally ~37 seconds
+    info!("Waiting for guest to shut down (max {timeout} seconds)");
     if !run_cmd!(time virsh event --timeout $timeout -- $guest_name lifecycle).is_ok() {
         bail!("`virsh event` failed or timed out!");
     }
+    for _ in 0..100 {
+        if run_fun!(virsh domstate -- $guest_name)?.trim_ascii() == "shut off" {
+            return Ok(());
+        }
+    }
+
+    bail!("Guest did not shut down as expected")
+}
 
+pub(self) fn rename_guest(old_guest_name: &str, new_guest_name: &str) -> eyre::Result<()> {
+    run_cmd!(virsh domrename -- $old_guest_name $new_guest_name)?;
     Ok(())
 }
diff --git a/monitor/src/image/macos13.rs b/monitor/src/image/macos13.rs
index 76c522ba..e4885f53 100644
--- a/monitor/src/image/macos13.rs
+++ b/monitor/src/image/macos13.rs
@@ -12,14 +12,15 @@ use jane_eyre::eyre::OptionExt;
 use settings::profile::Profile;
 use tracing::warn;
 
-use crate::image::create_base_images_dir;
+use crate::data::get_profile_data_path;
 use crate::image::create_runner_images_dir;
-use crate::image::delete_base_image_file;
+use crate::image::delete_template_or_rebuild_image_file;
 use crate::image::libvirt_change_media;
-use crate::image::prune_base_image_files;
+use crate::image::rename_guest;
 use crate::image::undefine_libvirt_guest;
 use crate::image::CdromImage;
 use crate::policy::runner_image_path;
+use crate::policy::template_or_rebuild_image_path;
 use crate::shell::atomic_symlink;
 use crate::shell::log_output_as_info;
 use crate::shell::reflink_or_copy_with_warning;
@@ -36,10 +37,11 @@ pub(super) fn rebuild(
     wait_duration: Duration,
 ) -> eyre::Result<()> {
     let base_images_path = base_images_path.as_ref();
-    let profile_guest_name = &profile.profile_guest_name();
+    let profile_name = &profile.profile_name;
+    let snapshot_path_slug = &profile.snapshot_path_slug(snapshot_name);
+    let rebuild_guest_name = &profile.rebuild_guest_name(snapshot_name);
 
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
-    let initial_contents_path = format!("/var/lib/libvirt/images/{profile_guest_name}.clean.img");
+    let initial_contents_path = format!("/var/lib/libvirt/images/{profile_name}.clean.img");
     let base_image_path = create_disk_image(
         base_images_path,
         snapshot_name,
@@ -47,64 +49,49 @@ pub(super) fn rebuild(
         Path::new(&initial_contents_path),
     )?;
 
-    define_base_guest(profile, &base_image_path, &[])?;
+    define_base_guest(profile, snapshot_name, &base_image_path, &[])?;
     let ovmf_vars_clean_path =
-        format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{profile_guest_name}.clean.fd");
+        format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{profile_name}.clean.fd");
     let ovmf_vars_path =
-        format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{profile_guest_name}.fd");
+        format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{snapshot_path_slug}.fd");
     copy(ovmf_vars_clean_path, ovmf_vars_path)?;
-    start_libvirt_guest(profile_guest_name)?;
-    wait_for_guest(profile_guest_name, wait_duration)?;
+    start_libvirt_guest(rebuild_guest_name)?;
+    wait_for_guest(rebuild_guest_name, wait_duration)?;
 
-    let base_image_filename = Path::new(
-        base_image_path
-            .file_name()
-            .expect("Guaranteed by make_disk_image"),
-    );
-    atomic_symlink(base_image_filename, base_image_symlink_path)?;
-
-    Ok(())
-}
-
-pub(super) fn redefine_base_guest_with_symlinks(
-    base_images_path: impl AsRef<Path>,
-    profile: &Profile,
-) -> Result<(), eyre::Error> {
-    let base_images_path = base_images_path.as_ref();
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
-    undefine_libvirt_guest(&profile.profile_guest_name())?;
-    define_base_guest(profile, &base_image_symlink_path, &[])?;
+    let template_guest_name = &profile.template_guest_name(snapshot_name);
+    rename_guest(rebuild_guest_name, template_guest_name)?;
+    let snapshot_symlink_path =
+        get_profile_data_path(&profile.profile_name, Path::new("snapshot"))?;
+    atomic_symlink(snapshot_name, snapshot_symlink_path)?;
 
     Ok(())
 }
 
 fn define_base_guest(
     profile: &Profile,
+    snapshot_name: &str,
     base_image_path: &dyn AsRef<OsStr>,
     cdrom_images: &[CdromImage],
 ) -> eyre::Result<()> {
-    let profile_guest_name = &profile.profile_guest_name();
+    let clean_guest_name = &format!("{}.clean", profile.profile_name);
+    let rebuild_guest_name = &profile.rebuild_guest_name(snapshot_name);
     let base_image_path = base_image_path
         .as_ref()
         .to_str()
         .ok_or_eyre("Unsupported path")?;
     // Clone the hand-made clean guest, since we can’t yet automate the macOS install
-    run_cmd!(virt-clone --preserve-data --check path_in_use=off -o $profile_guest_name.clean -n $profile_guest_name --nvram /var/lib/libvirt/images/OSX-KVM/OVMF_VARS.$profile_guest_name.fd --skip-copy sda -f $base_image_path --skip-copy sdc)?;
-    libvirt_change_media(profile_guest_name, cdrom_images)?;
+    run_cmd!(virt-clone --preserve-data --check path_in_use=off -o $clean_guest_name -n $rebuild_guest_name --nvram /var/lib/libvirt/images/OSX-KVM/OVMF_VARS.$clean_guest_name.fd --skip-copy sda -f $base_image_path --skip-copy sdc)?;
+    libvirt_change_media(rebuild_guest_name, cdrom_images)?;
 
     Ok(())
 }
 
-pub(super) fn prune_images(profile: &Profile) -> eyre::Result<()> {
-    prune_base_image_files(profile, "base.img")?;
-
+pub(super) fn delete_template(profile: &Profile, snapshot_name: &str) -> eyre::Result<()> {
+    undefine_libvirt_guest(&profile.template_guest_name(snapshot_name))?;
+    delete_template_or_rebuild_image_file(profile, &format!("base.img@{snapshot_name}"));
     Ok(())
 }
 
-pub(super) fn delete_image(profile: &Profile, snapshot_name: &str) {
-    delete_base_image_file(profile, &format!("base.img@{snapshot_name}"));
-}
-
 pub fn register_runner(profile: &Profile, runner_guest_name: &str) -> eyre::Result<String> {
     monitor::github::register_runner(
         runner_guest_name,
@@ -115,27 +102,28 @@ pub fn register_runner(profile: &Profile, runner_guest_name: &str) -> eyre::Resu
 
 pub fn create_runner(
     profile: &Profile,
+    snapshot_name: &str,
     runner_guest_name: &str,
     runner_id: usize,
 ) -> eyre::Result<String> {
     let pipe = || |reader| log_output_as_info(reader);
-    let profile_guest_name = &profile.profile_name;
+    let snapshot_path_slug = &profile.snapshot_path_slug(snapshot_name);
+    let template_guest_name = &profile.template_guest_name(snapshot_name);
 
     // Copy images in the monitor, not with `virt-clone --auto-clone --reflink`,
     // because the latter can’t be parallelised without causing errors.
-    let base_images_path = create_base_images_dir(profile)?;
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
+    let template_base_img = template_or_rebuild_image_path(profile, snapshot_name, "base.img");
     create_runner_images_dir()?;
-    let runner_base_image_path = runner_image_path(runner_id, "base.img");
-    reflink_or_copy_with_warning(&base_image_symlink_path, &runner_base_image_path)?;
+    let runner_base_img = runner_image_path(runner_id, "base.img");
+    reflink_or_copy_with_warning(&template_base_img, &runner_base_img)?;
 
     let ovmf_vars_base_path =
-        format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{profile_guest_name}.clean.fd");
+        format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{snapshot_path_slug}.fd");
     let ovmf_vars_path =
         format!("/var/lib/libvirt/images/OSX-KVM/OVMF_VARS.{runner_guest_name}.fd");
     copy(ovmf_vars_base_path, ovmf_vars_path)?;
 
-    spawn_with_output!(virt-clone -o $profile_guest_name -n $runner_guest_name --nvram /var/lib/libvirt/images/OSX-KVM/OVMF_VARS.$runner_guest_name.fd --preserve-data --skip-copy sda -f $runner_base_image_path --skip-copy sdc 2>&1)?.wait_with_pipe(&mut pipe())?;
+    spawn_with_output!(virt-clone -o $template_guest_name -n $runner_guest_name --nvram /var/lib/libvirt/images/OSX-KVM/OVMF_VARS.$runner_guest_name.fd --preserve-data --skip-copy sda -f $runner_base_img --skip-copy sdc 2>&1)?.wait_with_pipe(&mut pipe())?;
 
     Ok(runner_guest_name.to_owned())
 }
diff --git a/monitor/src/image/ubuntu2204.rs b/monitor/src/image/ubuntu2204.rs
index a5981720..96f4c99f 100644
--- a/monitor/src/image/ubuntu2204.rs
+++ b/monitor/src/image/ubuntu2204.rs
@@ -7,18 +7,18 @@ use bytesize::ByteSize;
 use cmd_lib::run_cmd;
 use cmd_lib::spawn_with_output;
 use jane_eyre::eyre;
-use jane_eyre::eyre::OptionExt;
 use settings::profile::Profile;
 use tracing::info;
 use tracing::warn;
 
 use crate::data::get_profile_configuration_path;
-use crate::image::create_base_images_dir;
+use crate::data::get_profile_data_path;
 use crate::image::create_runner_images_dir;
-use crate::image::delete_base_image_file;
-use crate::image::prune_base_image_files;
+use crate::image::delete_template_or_rebuild_image_file;
+use crate::image::rename_guest;
 use crate::image::undefine_libvirt_guest;
 use crate::policy::runner_image_path;
+use crate::policy::template_or_rebuild_image_path;
 use crate::shell::atomic_symlink;
 use crate::shell::log_output_as_info;
 use crate::shell::reflink_or_copy_with_warning;
@@ -38,16 +38,14 @@ pub(super) fn rebuild(
     wait_duration: Duration,
 ) -> eyre::Result<()> {
     let base_images_path = base_images_path.as_ref();
-    let profile_guest_name = &profile.profile_guest_name();
+    let rebuild_guest_name = &profile.rebuild_guest_name(snapshot_name);
     let profile_configuration_path = get_profile_configuration_path(&profile, None)?;
-    let config_iso_symlink_path = base_images_path.join(format!("config.iso"));
     let config_iso_filename = format!("config.iso@{snapshot_name}");
     let config_iso_path = base_images_path.join(&config_iso_filename);
     let config_iso_path = config_iso_path.to_str().expect("Unsupported path");
     info!(config_iso_path, "Creating config image file");
     run_cmd!(genisoimage -V CIDATA -R -f -o $config_iso_path $profile_configuration_path/user-data $profile_configuration_path/meta-data)?;
 
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
     let os_image_path = IMAGE_DEPS_DIR
         .join("ubuntu2204")
         .join("jammy-server-cloudimg-amd64.raw");
@@ -60,53 +58,33 @@ pub(super) fn rebuild(
 
     define_base_guest(
         profile,
+        snapshot_name,
         &base_image_path,
         &[CdromImage::new("sda", config_iso_path)],
     )?;
-    start_libvirt_guest(profile_guest_name)?;
-    wait_for_guest(profile_guest_name, wait_duration)?;
+    start_libvirt_guest(rebuild_guest_name)?;
+    wait_for_guest(rebuild_guest_name, wait_duration)?;
 
-    let base_image_filename = Path::new(
-        base_image_path
-            .file_name()
-            .expect("Guaranteed by make_disk_image"),
-    );
-    atomic_symlink(config_iso_filename, config_iso_symlink_path)?;
-    atomic_symlink(base_image_filename, base_image_symlink_path)?;
-
-    Ok(())
-}
-
-pub(super) fn redefine_base_guest_with_symlinks(
-    base_images_path: impl AsRef<Path>,
-    profile: &Profile,
-) -> Result<(), eyre::Error> {
-    let base_images_path = base_images_path.as_ref();
-    let config_iso_symlink_path = base_images_path.join(format!("config.iso"));
-    let config_iso_symlink_path = config_iso_symlink_path
-        .to_str()
-        .ok_or_eyre("Unsupported path")?;
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
-    undefine_libvirt_guest(&profile.profile_guest_name())?;
-    define_base_guest(
-        profile,
-        &base_image_symlink_path,
-        &[CdromImage::new("sda", &config_iso_symlink_path)],
-    )?;
+    let template_guest_name = &profile.template_guest_name(snapshot_name);
+    rename_guest(rebuild_guest_name, template_guest_name)?;
+    let snapshot_symlink_path =
+        get_profile_data_path(&profile.profile_name, Path::new("snapshot"))?;
+    atomic_symlink(snapshot_name, snapshot_symlink_path)?;
 
     Ok(())
 }
 
 fn define_base_guest(
     profile: &Profile,
+    snapshot_name: &str,
     base_image_path: &dyn AsRef<OsStr>,
     cdrom_images: &[CdromImage],
 ) -> eyre::Result<()> {
-    let profile_guest_name = &profile.profile_guest_name();
+    let rebuild_guest_name = &profile.rebuild_guest_name(snapshot_name);
     let guest_xml_path = get_profile_configuration_path(&profile, Path::new("guest.xml"))?;
     define_libvirt_guest(
         &profile.profile_name,
-        profile_guest_name,
+        rebuild_guest_name,
         guest_xml_path,
         &[&"-f", &base_image_path],
         cdrom_images,
@@ -115,40 +93,35 @@ fn define_base_guest(
     Ok(())
 }
 
-pub(super) fn prune_images(profile: &Profile) -> eyre::Result<()> {
-    prune_base_image_files(profile, "config.iso")?;
-    prune_base_image_files(profile, "base.img")?;
-
+pub(super) fn delete_template(profile: &Profile, snapshot_name: &str) -> eyre::Result<()> {
+    undefine_libvirt_guest(&profile.template_guest_name(snapshot_name))?;
+    delete_template_or_rebuild_image_file(profile, &format!("config.iso@{snapshot_name}"));
+    delete_template_or_rebuild_image_file(profile, &format!("base.img@{snapshot_name}"));
     Ok(())
 }
 
-pub(super) fn delete_image(profile: &Profile, snapshot_name: &str) {
-    delete_base_image_file(profile, &format!("config.iso@{snapshot_name}"));
-    delete_base_image_file(profile, &format!("base.img@{snapshot_name}"));
-}
-
 pub fn register_runner(profile: &Profile, runner_guest_name: &str) -> eyre::Result<String> {
     monitor::github::register_runner(runner_guest_name, &profile.github_runner_label, "/a")
 }
 
 pub fn create_runner(
     profile: &Profile,
+    snapshot_name: &str,
     runner_guest_name: &str,
     runner_id: usize,
 ) -> eyre::Result<String> {
     let pipe = || |reader| log_output_as_info(reader);
-    let profile_guest_name = &profile.profile_guest_name();
+    let template_guest_name = &profile.template_guest_name(snapshot_name);
 
     // Copy images in the monitor, not with `virt-clone --auto-clone --reflink`,
     // because the latter can’t be parallelised without causing errors.
     // TODO copy config.iso?
-    let base_images_path = create_base_images_dir(profile)?;
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
+    let template_base_img = template_or_rebuild_image_path(profile, snapshot_name, "base.img");
     create_runner_images_dir()?;
-    let runner_base_image_path = runner_image_path(runner_id, "base.img");
-    reflink_or_copy_with_warning(&base_image_symlink_path, &runner_base_image_path)?;
+    let runner_base_img = runner_image_path(runner_id, "base.img");
+    reflink_or_copy_with_warning(&template_base_img, &runner_base_img)?;
 
-    spawn_with_output!(virt-clone -o $profile_guest_name -n $runner_guest_name --preserve-data -f $runner_base_image_path 2>&1)?
+    spawn_with_output!(virt-clone -o $template_guest_name -n $runner_guest_name --preserve-data -f $runner_base_img 2>&1)?
         .wait_with_pipe(&mut pipe())?;
 
     Ok(runner_guest_name.to_owned())
diff --git a/monitor/src/image/windows10.rs b/monitor/src/image/windows10.rs
index 6b5ec422..07b818de 100644
--- a/monitor/src/image/windows10.rs
+++ b/monitor/src/image/windows10.rs
@@ -7,18 +7,18 @@ use bytesize::ByteSize;
 use cmd_lib::run_cmd;
 use cmd_lib::spawn_with_output;
 use jane_eyre::eyre;
-use jane_eyre::eyre::OptionExt;
 use settings::profile::Profile;
 use tracing::info;
 use tracing::warn;
 
 use crate::data::get_profile_configuration_path;
-use crate::image::create_base_images_dir;
+use crate::data::get_profile_data_path;
 use crate::image::create_runner_images_dir;
-use crate::image::delete_base_image_file;
-use crate::image::prune_base_image_files;
+use crate::image::delete_template_or_rebuild_image_file;
+use crate::image::rename_guest;
 use crate::image::undefine_libvirt_guest;
 use crate::policy::runner_image_path;
+use crate::policy::template_or_rebuild_image_path;
 use crate::shell::atomic_symlink;
 use crate::shell::log_output_as_info;
 use crate::shell::reflink_or_copy_with_warning;
@@ -38,16 +38,14 @@ pub(super) fn rebuild(
     wait_duration: Duration,
 ) -> eyre::Result<()> {
     let base_images_path = base_images_path.as_ref();
-    let profile_guest_name = &profile.profile_guest_name();
+    let rebuild_guest_name = &profile.rebuild_guest_name(snapshot_name);
     let profile_configuration_path = get_profile_configuration_path(&profile, None)?;
-    let config_iso_symlink_path = base_images_path.join(format!("config.iso"));
     let config_iso_filename = format!("config.iso@{snapshot_name}");
     let config_iso_path = base_images_path.join(&config_iso_filename);
     let config_iso_path = config_iso_path.to_str().expect("Unsupported path");
     info!(config_iso_path, "Creating config image file");
     run_cmd!(genisoimage -J -f -o $config_iso_path $profile_configuration_path/autounattend.xml)?;
 
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
     let base_image_path =
         create_disk_image(base_images_path, snapshot_name, base_image_size, None)?;
 
@@ -62,6 +60,7 @@ pub(super) fn rebuild(
 
     define_base_guest(
         profile,
+        snapshot_name,
         &base_image_path,
         &[
             CdromImage::new("sdb", installer_iso_path),
@@ -69,64 +68,29 @@ pub(super) fn rebuild(
             CdromImage::new("sdd", config_iso_path),
         ],
     )?;
-    start_libvirt_guest(profile_guest_name)?;
-    wait_for_guest(profile_guest_name, wait_duration)?;
+    start_libvirt_guest(rebuild_guest_name)?;
+    wait_for_guest(rebuild_guest_name, wait_duration)?;
 
-    let base_image_filename = Path::new(
-        base_image_path
-            .file_name()
-            .expect("Guaranteed by make_disk_image"),
-    );
-    atomic_symlink(config_iso_filename, config_iso_symlink_path)?;
-    atomic_symlink(base_image_filename, base_image_symlink_path)?;
-
-    Ok(())
-}
-
-pub(super) fn redefine_base_guest_with_symlinks(
-    base_images_path: impl AsRef<Path>,
-    profile: &Profile,
-) -> Result<(), eyre::Error> {
-    let base_images_path = base_images_path.as_ref();
-    let config_iso_symlink_path = base_images_path.join(format!("config.iso"));
-    let config_iso_symlink_path = config_iso_symlink_path
-        .to_str()
-        .ok_or_eyre("Unsupported path")?;
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
-
-    let installer_iso_path = IMAGE_DEPS_DIR
-        .join("windows10")
-        .join("Win10_22H2_English_x64v1.iso");
-    let installer_iso_path = installer_iso_path.to_str().expect("Unsupported path");
-    let drivers_iso_path = IMAGE_DEPS_DIR
-        .join("windows10")
-        .join("virtio-win-0.1.240.iso");
-    let drivers_iso_path = drivers_iso_path.to_str().expect("Unsupported path");
-
-    undefine_libvirt_guest(&profile.profile_guest_name())?;
-    define_base_guest(
-        profile,
-        &base_image_symlink_path,
-        &[
-            CdromImage::new("sdb", installer_iso_path),
-            CdromImage::new("sdc", drivers_iso_path),
-            CdromImage::new("sdd", &config_iso_symlink_path),
-        ],
-    )?;
+    let template_guest_name = &profile.template_guest_name(snapshot_name);
+    rename_guest(rebuild_guest_name, template_guest_name)?;
+    let snapshot_symlink_path =
+        get_profile_data_path(&profile.profile_name, Path::new("snapshot"))?;
+    atomic_symlink(snapshot_name, snapshot_symlink_path)?;
 
     Ok(())
 }
 
 fn define_base_guest(
     profile: &Profile,
+    snapshot_name: &str,
     base_image_path: &dyn AsRef<OsStr>,
     cdrom_images: &[CdromImage],
 ) -> eyre::Result<()> {
-    let profile_guest_name = &profile.profile_guest_name();
+    let rebuild_guest_name = &profile.rebuild_guest_name(snapshot_name);
     let guest_xml_path = get_profile_configuration_path(&profile, Path::new("guest.xml"))?;
     define_libvirt_guest(
         &profile.profile_name,
-        profile_guest_name,
+        rebuild_guest_name,
         guest_xml_path,
         &[&"-f", &base_image_path],
         cdrom_images,
@@ -135,40 +99,35 @@ fn define_base_guest(
     Ok(())
 }
 
-pub(super) fn prune_images(profile: &Profile) -> eyre::Result<()> {
-    prune_base_image_files(profile, "config.iso")?;
-    prune_base_image_files(profile, "base.img")?;
-
+pub(super) fn delete_template(profile: &Profile, snapshot_name: &str) -> eyre::Result<()> {
+    undefine_libvirt_guest(&profile.template_guest_name(snapshot_name))?;
+    delete_template_or_rebuild_image_file(profile, &format!("config.iso@{snapshot_name}"));
+    delete_template_or_rebuild_image_file(profile, &format!("base.img@{snapshot_name}"));
     Ok(())
 }
 
-pub(super) fn delete_image(profile: &Profile, snapshot_name: &str) {
-    delete_base_image_file(profile, &format!("config.iso@{snapshot_name}"));
-    delete_base_image_file(profile, &format!("base.img@{snapshot_name}"));
-}
-
 pub fn register_runner(profile: &Profile, runner_guest_name: &str) -> eyre::Result<String> {
     monitor::github::register_runner(runner_guest_name, &profile.github_runner_label, r"C:\a")
 }
 
 pub fn create_runner(
     profile: &Profile,
+    snapshot_name: &str,
     runner_guest_name: &str,
     runner_id: usize,
 ) -> eyre::Result<String> {
     let pipe = || |reader| log_output_as_info(reader);
-    let profile_guest_name = &profile.profile_guest_name();
+    let template_guest_name = &profile.template_guest_name(snapshot_name);
 
     // Copy images in the monitor, not with `virt-clone --auto-clone --reflink`,
     // because the latter can’t be parallelised without causing errors.
     // TODO copy config.iso?
-    let base_images_path = create_base_images_dir(profile)?;
-    let base_image_symlink_path = base_images_path.join(format!("base.img"));
+    let template_base_img = template_or_rebuild_image_path(profile, snapshot_name, "base.img");
     create_runner_images_dir()?;
-    let runner_base_image_path = runner_image_path(runner_id, "base.img");
-    reflink_or_copy_with_warning(&base_image_symlink_path, &runner_base_image_path)?;
+    let runner_base_img = runner_image_path(runner_id, "base.img");
+    reflink_or_copy_with_warning(&template_base_img, &runner_base_img)?;
 
-    spawn_with_output!(virt-clone -o $profile_guest_name -n $runner_guest_name --preserve-data -f $runner_base_image_path 2>&1)?
+    spawn_with_output!(virt-clone -o $template_guest_name -n $runner_guest_name --preserve-data -f $runner_base_img 2>&1)?
         .wait_with_pipe(&mut pipe())?;
 
     Ok(runner_guest_name.to_owned())
diff --git a/monitor/src/libvirt.rs b/monitor/src/libvirt.rs
index b5c48823..231a9090 100644
--- a/monitor/src/libvirt.rs
+++ b/monitor/src/libvirt.rs
@@ -12,6 +12,30 @@ use tracing::debug;
 
 use crate::shell::log_output_as_trace;
 
+pub fn list_template_guests() -> eyre::Result<Vec<String>> {
+    // Output is not filtered by prefix, so we must filter it ourselves.
+    let prefix = format!("{}-", TOML.libvirt_template_guest_prefix());
+    let result = run_fun!(virsh list --name --all)?;
+    let result = result
+        .split_terminator('\n')
+        .filter(|name| name.starts_with(&prefix))
+        .map(str::to_owned);
+
+    Ok(result.collect())
+}
+
+pub fn list_rebuild_guests() -> eyre::Result<Vec<String>> {
+    // Output is not filtered by prefix, so we must filter it ourselves.
+    let prefix = format!("{}-", TOML.libvirt_rebuild_guest_prefix());
+    let result = run_fun!(virsh list --name --all)?;
+    let result = result
+        .split_terminator('\n')
+        .filter(|name| name.starts_with(&prefix))
+        .map(str::to_owned);
+
+    Ok(result.collect())
+}
+
 pub fn list_runner_guests() -> eyre::Result<Vec<String>> {
     // Output is not filtered by prefix, so we must filter it ourselves.
     let prefix = format!("{}-", TOML.libvirt_runner_guest_prefix());
diff --git a/monitor/src/main.rs b/monitor/src/main.rs
index c8280477..78f53095 100644
--- a/monitor/src/main.rs
+++ b/monitor/src/main.rs
@@ -53,7 +53,7 @@ use crate::{
     id::IdGen,
     image::{start_libvirt_guest, Rebuilds},
     libvirt::list_runner_guests,
-    policy::{base_image_path, Override, Policy, RunnerCounts},
+    policy::{Override, Policy, RunnerCounts},
     runner::{Runners, Status},
 };
 
@@ -504,24 +504,16 @@ fn monitor_thread() -> eyre::Result<()> {
             },
         ) in profile_runner_counts.iter()
         {
-            let profile = policy.profile(key).ok_or_eyre("Failed to get profile")?;
-            let image = policy
-                .base_image_snapshot(key)
-                .map(|snapshot| match profile.image_type {
-                    settings::profile::ImageType::Rust => base_image_path(profile, &**snapshot)
-                        .as_os_str()
-                        .to_str()
-                        .expect("Guaranteed by base_image_path()")
-                        .to_owned(),
-                });
-            info!("profile {key}: {healthy}/{target} healthy runners ({idle} idle, {reserved} reserved, {busy} busy, {started_or_crashed} started or crashed, {excess_healthy} excess healthy, {wanted} wanted), image {:?} age {image_age:?}", image);
+            let snapshot = policy.base_image_snapshot(key);
+            info!("profile {key}: {healthy}/{target} healthy runners ({idle} idle, {reserved} reserved, {busy} busy, {started_or_crashed} started or crashed, {excess_healthy} excess healthy, {wanted} wanted), snapshot {snapshot:?} age {image_age:?}");
         }
         for (_id, runner) in policy.runners() {
             runner.log_info();
         }
 
-        policy.update_screenshots();
-        policy.update_ipv4_addresses_for_profile_guests();
+        let rebuild_guest_names = image_rebuilds.rebuild_guest_names();
+        policy.update_screenshots(&rebuild_guest_names);
+        policy.update_ipv4_addresses_for_rebuild_guests(&rebuild_guest_names);
 
         if TOML.destroy_all_non_busy_runners() {
             let non_busy_runners = policy
@@ -689,14 +681,14 @@ fn monitor_thread() -> eyre::Result<()> {
                     // GET /github-jitconfig request both happen in step (2) without step (1) in between, we won’t know
                     // the IPv4 address, so let’s update the IPv4 addresses before continuing.
                     policy.update_ipv4_addresses_for_runner_guests()?;
-                    policy.update_ipv4_addresses_for_profile_guests();
+                    policy.update_ipv4_addresses_for_rebuild_guests(&rebuild_guest_names);
 
                     let result = policy
                         .boot_script_for_runner_guest(remote_addr.clone())
                         .transpose()
                         .or_else(|| {
                             policy
-                                .boot_script_for_profile_guest(remote_addr)
+                                .boot_script_for_rebuild_guest(remote_addr)
                                 .transpose()
                         })
                         .transpose()
diff --git a/monitor/src/policy.rs b/monitor/src/policy.rs
index 2cd919c3..eff1534b 100644
--- a/monitor/src/policy.rs
+++ b/monitor/src/policy.rs
@@ -9,7 +9,7 @@ use std::{
     time::{Duration, SystemTime, UNIX_EPOCH},
 };
 
-use cfg_if::cfg_if;
+use chrono::DateTime;
 use itertools::Itertools;
 use jane_eyre::eyre::{self, bail, Context, OptionExt};
 use mktemp::Temp;
@@ -265,7 +265,8 @@ impl Policy {
         profile: &Profile,
         id: usize,
     ) -> eyre::Result<JoinHandle<eyre::Result<String>>> {
-        if self.base_image_snapshot(&profile.profile_name).is_none() {
+        let Some(base_image_snapshot) = self.base_image_snapshot(&profile.profile_name).cloned()
+        else {
             bail!(
                 "Tried to create runner, but profile has no base image snapshot (profile {})",
                 profile.profile_name
@@ -299,7 +300,7 @@ impl Policy {
                             .write_all(github_api_registration.as_bytes())?;
                     }
 
-                    create_runner(&profile, &runner_guest_name, id)
+                    create_runner(&profile, &base_image_snapshot, &runner_guest_name, id)
                 }
             }
         }))
@@ -471,26 +472,9 @@ impl Policy {
         let now = SystemTime::now()
             .duration_since(UNIX_EPOCH)
             .wrap_err("Failed to get current time")?;
-        let creation_time = match profile.image_type {
-            ImageType::Rust => {
-                let base_image_path = base_image_path(profile, &**base_image_snapshot);
-                let Some(mtime) = base_image_mtime(profile, &base_image_path) else {
-                    return Ok(None);
-                };
-                match mtime.duration_since(UNIX_EPOCH) {
-                    Ok(result) => result,
-                    Err(error) => {
-                        debug!(
-                            profile.profile_name,
-                            ?base_image_path,
-                            ?error,
-                            "Failed to calculate image age"
-                        );
-                        return Ok(None);
-                    }
-                }
-            }
-        };
+        let creation_time = DateTime::parse_from_rfc3339(&base_image_snapshot)?
+            .signed_duration_since(DateTime::UNIX_EPOCH)
+            .to_std()?;
 
         Ok(Some(now - creation_time))
     }
@@ -506,13 +490,16 @@ impl Policy {
         Ok(())
     }
 
-    pub fn update_ipv4_addresses_for_profile_guests(&mut self) {
-        for (key, profile) in self.profiles.iter() {
-            let ipv4_address = get_ipv4_address(&profile.profile_guest_name());
-            let entry = self.ipv4_addresses.entry(key.clone()).or_default();
+    pub fn update_ipv4_addresses_for_rebuild_guests(
+        &mut self,
+        rebuild_guest_names: &BTreeMap<String, String>,
+    ) {
+        for (profile_key, guest_name) in rebuild_guest_names {
+            let ipv4_address = get_ipv4_address(&guest_name);
+            let entry = self.ipv4_addresses.entry(profile_key.clone()).or_default();
             if ipv4_address != *entry {
                 info!(
-                    "IPv4 address changed for profile guest {key}: {:?} -> {:?}",
+                    "IPv4 address changed for profile guest {profile_key}: {:?} -> {:?}",
                     *entry, ipv4_address
                 );
             }
@@ -520,7 +507,7 @@ impl Policy {
         }
     }
 
-    pub fn boot_script_for_profile_guest(
+    pub fn boot_script_for_rebuild_guest(
         &self,
         remote_addr: web::auth::RemoteAddr,
     ) -> eyre::Result<Option<String>> {
@@ -571,24 +558,20 @@ impl Policy {
             .filter(|(_id, runner)| runner.status() == Status::Idle)
     }
 
-    pub fn update_screenshots(&self) {
+    pub fn update_screenshots(&self, rebuild_guest_names: &BTreeMap<String, String>) {
         if let Some(runners) = self.runners.as_ref() {
             runners.update_screenshots();
         }
-        for (_key, profile) in self.profiles() {
-            if let Err(error) = self.try_update_screenshot(profile) {
-                debug!(
-                    profile.profile_name,
-                    ?error,
-                    "Failed to update screenshot for profile guest"
-                );
+        for (profile_key, guest_name) in rebuild_guest_names {
+            if let Err(error) = self.try_update_screenshot(&profile_key, &guest_name) {
+                debug!(guest_name, ?error, "Failed to update screenshot for guest");
             }
         }
     }
 
-    fn try_update_screenshot(&self, profile: &Profile) -> eyre::Result<()> {
-        let output_dir = get_profile_data_path(&profile.profile_name, None)?;
-        update_screenshot(&profile.profile_guest_name(), &output_dir)?;
+    fn try_update_screenshot(&self, profile_key: &str, guest_name: &str) -> eyre::Result<()> {
+        let output_dir = get_profile_data_path(&profile_key, None)?;
+        update_screenshot(guest_name, &output_dir)?;
 
         Ok(())
     }
@@ -870,7 +853,7 @@ impl Policy {
     }
 }
 
-pub fn base_images_path(profile: &Profile) -> PathBuf {
+pub fn template_or_rebuild_images_path(profile: &Profile) -> PathBuf {
     Path::new("/var/lib/libvirt/images/base").join(&profile.profile_name)
 }
 
@@ -878,15 +861,12 @@ pub fn runner_images_path() -> PathBuf {
     PathBuf::from("/var/lib/libvirt/images/runner")
 }
 
-pub fn base_image_path<'snap>(
+pub fn template_or_rebuild_image_path(
     profile: &Profile,
-    snapshot_name: impl Into<Option<&'snap str>>,
+    snapshot_name: &str,
+    filename: impl AsRef<str>,
 ) -> PathBuf {
-    if let Some(snapshot_name) = snapshot_name.into() {
-        base_images_path(profile).join(format!("base.img@{snapshot_name}"))
-    } else {
-        base_images_path(profile).join("base.img")
-    }
+    template_or_rebuild_images_path(profile).join(format!("{}@{snapshot_name}", filename.as_ref()))
 }
 
 pub fn runner_image_path(runner_id: usize, filename: impl AsRef<str>) -> PathBuf {
@@ -894,72 +874,26 @@ pub fn runner_image_path(runner_id: usize, filename: impl AsRef<str>) -> PathBuf
 }
 
 fn read_base_image_snapshot(profile: &Profile) -> eyre::Result<Option<String>> {
-    let path = base_image_path(profile, None);
+    let path = get_profile_data_path(&profile.profile_name, Path::new("snapshot"))?;
     if let Ok(path) = read_link(path) {
-        let path = path.to_str().ok_or_eyre("Symlink target is unsupported")?;
-        let (_, snapshot_name) = path
-            .split_once("@")
-            .ok_or_eyre("Symlink target has no snapshot name")?;
+        let snapshot_name = path.to_str().ok_or_eyre("Symlink target is unsupported")?;
         return Ok(Some(snapshot_name.to_owned()));
     }
 
     Ok(None)
 }
 
-cfg_if! {
-    if #[cfg(not(test))] {
-        fn base_image_mtime(profile: &Profile, base_image_path: impl AsRef<Path>) -> Option<SystemTime> {
-            let base_image_path = base_image_path.as_ref();
-            let metadata = match std::fs::metadata(&base_image_path) {
-                Ok(result) => result,
-                Err(error) => {
-                    debug!(
-                        profile.profile_name,
-                        ?base_image_path,
-                        ?error,
-                        "Failed to get file metadata"
-                    );
-                    return None;
-                }
-            };
-
-            Some(metadata.modified().expect("Guaranteed by platform"))
-        }
-    } else {
-        use std::cell::RefCell;
-
-        thread_local! {
-            static BASE_IMAGE_MTIMES: RefCell<BTreeMap<String, SystemTime>> = RefCell::new(BTreeMap::new());
-        }
-
-        fn base_image_mtime(_profile: &Profile, base_image_path: impl AsRef<Path>) -> Option<SystemTime> {
-            let base_image_path = base_image_path.as_ref().to_str().expect("Unsupported path");
-
-            BASE_IMAGE_MTIMES.with_borrow(|mtimes| mtimes.get(base_image_path).copied())
-        }
-
-        fn set_base_image_mtime_for_test(base_image_path: &str, mtime: impl Into<Option<SystemTime>>) {
-            BASE_IMAGE_MTIMES.with_borrow_mut(|mtimes| {
-                if let Some(mtime) = mtime.into() {
-                    mtimes.insert(base_image_path.to_owned(), mtime);
-                } else {
-                    mtimes.remove(base_image_path);
-                }
-            });
-        }
-    }
-}
-
 #[cfg(test)]
 mod test {
     use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
+    use chrono::{SecondsFormat, Utc};
     use jane_eyre::eyre;
     use monitor::github::{ApiRunner, ApiRunnerLabel};
     use settings::{profile::Profile, TOML};
 
     use crate::{
-        policy::{set_base_image_mtime_for_test, Override, RunnerChanges},
+        policy::{Override, RunnerChanges},
         runner::{set_runner_created_time_for_test, Runners, Status},
     };
 
@@ -1089,6 +1023,9 @@ mod test {
         Runners::new(registrations, guest_names)
     }
 
+    fn snapshot_now_minus_seconds(delta: u64) -> String {
+        (Utc::now() - Duration::from_secs(delta)).to_rfc3339_opts(SecondsFormat::Nanos, true)
+    }
     fn system_time_minus_seconds(delta: u64) -> SystemTime {
         SystemTime::now()
             .checked_sub(Duration::from_secs(delta))
@@ -1189,14 +1126,11 @@ mod test {
         );
 
         // Images need rebuild, because they are too old.
-        let too_old = system_time_minus_seconds(86500);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/linux/base.img@", too_old);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/macos/base.img@", too_old);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/windows/base.img@", too_old);
-        policy.set_base_image_snapshot("linux", "")?;
-        policy.set_base_image_snapshot("macos", "")?;
-        policy.set_base_image_snapshot("windows", "")?;
-        policy.set_base_image_snapshot("wpt", "")?;
+        let too_old = snapshot_now_minus_seconds(86500);
+        policy.set_base_image_snapshot("linux", &too_old)?;
+        policy.set_base_image_snapshot("macos", &too_old)?;
+        policy.set_base_image_snapshot("windows", &too_old)?;
+        policy.set_base_image_snapshot("wpt", &too_old)?;
         assert_eq!(
             policy.compute_runner_changes()?,
             RunnerChanges {
@@ -1212,10 +1146,10 @@ mod test {
         );
 
         // Empty state.
-        let fresh = system_time_minus_seconds(0);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/linux/base.img@", fresh);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/macos/base.img@", fresh);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/windows/base.img@", fresh);
+        let fresh = snapshot_now_minus_seconds(0);
+        policy.set_base_image_snapshot("linux", &fresh)?;
+        policy.set_base_image_snapshot("macos", &fresh)?;
+        policy.set_base_image_snapshot("windows", &fresh)?;
         assert_eq!(
             policy.compute_runner_changes()?,
             RunnerChanges {
@@ -1440,15 +1374,11 @@ mod test {
             ]
             .into(),
         )?;
-        let fresh = system_time_minus_seconds(0);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/linux/base.img@", fresh);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/macos/base.img@", fresh);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/windows/base.img@", fresh);
-        set_base_image_mtime_for_test("/var/lib/libvirt/images/base/wpt/base.img@", fresh);
-        policy.set_base_image_snapshot("linux", "")?;
-        policy.set_base_image_snapshot("macos", "")?;
-        policy.set_base_image_snapshot("windows", "")?;
-        policy.set_base_image_snapshot("wpt", "")?;
+        let fresh = snapshot_now_minus_seconds(0);
+        policy.set_base_image_snapshot("linux", &fresh)?;
+        policy.set_base_image_snapshot("macos", &fresh)?;
+        policy.set_base_image_snapshot("windows", &fresh)?;
+        policy.set_base_image_snapshot("wpt", &fresh)?;
 
         // Proposed create counts should be adjusted for critical runners, regardless of whether
         // those runners fit the current policy.
@@ -1482,21 +1412,10 @@ mod test {
             ]
             .into(),
         )?;
-        set_base_image_mtime_for_test(
-            "/var/lib/libvirt/images/base/linux/base.img@",
-            SystemTime::now(),
-        );
-        set_base_image_mtime_for_test(
-            "/var/lib/libvirt/images/base/windows/base.img@",
-            SystemTime::now(),
-        );
-        set_base_image_mtime_for_test(
-            "/var/lib/libvirt/images/base/macos/base.img@",
-            SystemTime::now(),
-        );
-        policy.set_base_image_snapshot("linux", "")?;
-        policy.set_base_image_snapshot("windows", "")?;
-        policy.set_base_image_snapshot("macos", "")?;
+        let now = snapshot_now_minus_seconds(0);
+        policy.set_base_image_snapshot("linux", &now)?;
+        policy.set_base_image_snapshot("windows", &now)?;
+        policy.set_base_image_snapshot("macos", &now)?;
 
         // If the runners are not yet known, refuse the request.
         assert!(policy.try_override([].into()).is_err());
@@ -1576,11 +1495,8 @@ mod test {
         );
 
         // The image is ready. Let’s create runners.
-        set_base_image_mtime_for_test(
-            "/var/lib/libvirt/images/base/wpt/base.img@",
-            SystemTime::now(),
-        );
-        policy.set_base_image_snapshot("wpt", "")?;
+        let now = snapshot_now_minus_seconds(0);
+        policy.set_base_image_snapshot("wpt", &now)?;
         assert_eq!(
             policy.compute_runner_changes()?,
             RunnerChanges {