diff --git a/.github/workflows/windows-arm64.yml b/.github/workflows/windows-arm64.yml
index 2a8144a5b..2cedc1a57 100644
--- a/.github/workflows/windows-arm64.yml
+++ b/.github/workflows/windows-arm64.yml
@@ -28,8 +28,8 @@ permissions:
 
 jobs:
   windows-arm64:
-    # Immutable supporting workflow revision until the new install contract lands upstream.
-    uses: storytold/craft-common-actions/.github/workflows/windows-arm64.yml@fa5ef18780cf5e7d5d3b8de068de56cffc83cac5
+    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
+    uses: storytold/craft-common-actions/.github/workflows/windows-arm64.yml@main
     with:
       app-name: effectcraft
       app-dir: EffectCraft
diff --git a/AGENTS.md b/AGENTS.md
index 24abee6a1..24287ff9a 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -144,3 +144,8 @@ as PhotoCraft does with `cargo xtask corpus`.
   GitHub profiles). Never hand-edit `contributors.json`.
 - Maintainers refresh the stats with `python3 ../../craftrules/scripts/contributors.py .` (it also
   re-verifies who wrote each `people.toml` entry; `--check` only verifies).
+
+## CI workflows
+- Workflows in `.github/workflows/` call the shared workflows in [`storytold/craft-common-actions`](https://github.com/storytold/craft-common-actions) at `@main`, with their inputs and secrets. No other jobs: if no shared workflow does what's needed, it doesn't go here.
+- Don't add or change CI in a feature or fix PR. If the existing workflows can't build or test a change, link an existing craft-common-actions issue or PR, or open a new issue, or a PR only for a small fix that is safe for every app and does not increase CI time.
+- Some workflow files here still run their own jobs. Don't add to them. Moving a job into craft-common-actions is its own task, never part of another PR, and the job stays here until a shared workflow runs it.
diff --git a/CLAUDE.md b/CLAUDE.md
index 21f2df36b..7bd0e7422 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -30,3 +30,8 @@ EffectCraft is a clean-room, open-source, pure-Rust motion graphics and visual e
 - For UI work, **look at the result**. Headless (no window, works while the user is busy on the machine): `cargo run -p effectcraft-ui-egui --example snapshot -- --out ui.png --step '{"method":"engine.execute","params":{"command":"layer.select","params":{"layers":["#2"]}}}'` (steps are control-channel requests; `--script steps.jsonl`; `{"method":"snap","params":{"path":…}}` for intermediate shots). Or drive the live app via the control channel and take `ui.screenshot` (needs the window visible on screen).
 - After Effects reference: drive AE via ExtendScript (`osascript -e 'tell application "Adobe After Effects 2026" to DoScriptFile "x.jsx"'`) and capture only AE's window (`screencapture -l <windowid>`); keep captures in `plan/aftereffects/ref/` (gitignored), never commit them, never capture the Home screen.
 - Parallel agents: separate git worktrees and `CARGO_TARGET_DIR=target/agent-<name>`; keep every `Cargo.toml` valid (the `crates/*` glob).
+
+## CI workflows
+- Workflows in `.github/workflows/` call the shared workflows in [`storytold/craft-common-actions`](https://github.com/storytold/craft-common-actions) at `@main`, with their inputs and secrets. No other jobs: if no shared workflow does what's needed, it doesn't go here.
+- Don't add or change CI in a feature or fix PR. If the existing workflows can't build or test a change, link an existing craft-common-actions issue or PR, or open a new issue, or a PR only for a small fix that is safe for every app and does not increase CI time.
+- Some workflow files here still run their own jobs. Don't add to them. Moving a job into craft-common-actions is its own task, never part of another PR, and the job stays here until a shared workflow runs it.
diff --git a/Cargo.lock b/Cargo.lock
index 629fc65e9..e55969e6f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1454,6 +1454,7 @@ dependencies = [
  "kurbo",
  "log",
  "rayon",
+ "same-file",
  "serde",
  "serde_json",
  "thiserror 2.0.21",
@@ -4292,7 +4293,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7d8fae84b431384b68627d0f9b3b1245fcf9f46f6c0e3dc902e9dce64edd1967"
 dependencies = [
  "libc",
- "windows-sys 0.45.0",
+ "windows-sys 0.61.2",
 ]
 
 [[package]]
@@ -4884,9 +4885,9 @@ dependencies = [
 
 [[package]]
 name = "roxmltree"
-version = "0.21.1"
+version = "0.21.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f1964b10c76125c36f8afe190065a4bf9a87bf324842c05701330bba9f1cacbb"
+checksum = "9da7f59328b09405b181fee1018925fad50f157afb43c0c0f5c522c256dd5907"
 dependencies = [
  "memchr",
 ]
@@ -7469,9 +7470,9 @@ dependencies = [
 
 [[package]]
 name = "zip"
-version = "9.1.0"
+version = "9.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2886b00003a72c4ccee3f42cfc34908d33b2508a74d827dc2a4244706475c704"
+checksum = "1156b39d142a34b999c2310a50455e0cb3760bf7efad0122f796d813bee26ccb"
 dependencies = [
  "crc32fast",
  "flate2",
diff --git a/Cargo.toml b/Cargo.toml
index c101c489c..24791c08d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -74,6 +74,7 @@ skrifa = { version = "0.44", default-features = false, features = ["std"] }
 harfrust = { version = "0.12", default-features = false, features = ["std"] }
 exr = "1.74"
 image = { version = "0.25", default-features = false, features = ["png", "jpeg"] }
+same-file = "1.0"
 
 # media codecs + containers: FilmCraft's pure-Rust crates, pinned to a revision (plan/adr/0001).
 # Only `crates/media`, `crates/export` and `crates/interchange` may depend on these.
diff --git a/apps/effectcraft-cli/src/main.rs b/apps/effectcraft-cli/src/main.rs
index db6394b21..fd77162ed 100644
--- a/apps/effectcraft-cli/src/main.rs
+++ b/apps/effectcraft-cli/src/main.rs
@@ -890,6 +890,7 @@ fn render(args: &Args, json_out: bool) -> Result<(), Failure> {
             r["outputModuleSummary"].as_str().unwrap_or("")
         );
     }
+    let attempted: std::collections::HashSet<u64> = s.project.render_queue.iter().filter(|i| i.is_queued()).map(|i| i.id).collect();
     s.execute("renderQueue.render", json!({"wait": false})).map_err(err)?;
     let tty = std::io::IsTerminal::is_terminal(&std::io::stderr());
     // `--progress`: one line per update for a program reading stderr (a terminal gets the live line).
@@ -928,7 +929,7 @@ fn render(args: &Args, json_out: bool) -> Result<(), Failure> {
     }
     let mut results = vec![];
     let mut failed = vec![];
-    for it in s.project.render_queue.iter().filter(|i| i.render && i.started.is_some()) {
+    for it in s.project.render_queue.iter().filter(|i| attempted.contains(&i.id)) {
         let name = s.project.item(it.comp).map(|i| i.name.clone()).unwrap_or_else(|| "?".into());
         match &it.status {
             RenderStatus::Done => {
diff --git a/apps/effectcraft-cli/tests/it/cli.rs b/apps/effectcraft-cli/tests/it/cli.rs
index bcab79c8b..7a770fa87 100644
--- a/apps/effectcraft-cli/tests/it/cli.rs
+++ b/apps/effectcraft-cli/tests/it/cli.rs
@@ -605,6 +605,49 @@ fn a_failed_render_under_run_and_exec_exits_1() {
     assert!(v["error"].as_str().is_some_and(|e| e.starts_with("T: ")), "{v}");
 }
 
+/// A source refusal happens before encoding and has no started timestamp. It must still
+/// fail the CLI, while the valid queue item finishes and the imported frame stays intact.
+#[test]
+fn a_partly_protected_queue_exits_1_under_render_run_and_exec() {
+    let root = tmp("protected-mixed-queue");
+    let _ = std::fs::remove_dir_all(&root);
+    std::fs::create_dir_all(&root).unwrap();
+    let source = root.join("source_00000.png");
+    image::RgbaImage::from_pixel(4, 4, image::Rgba([40, 80, 120, 255])).save(&source).unwrap();
+    let original = std::fs::read(&source).unwrap();
+    let project = root.join("q.ecproj");
+    let good = root.join("good.gif");
+    let import = json!({"paths": [source]}).to_string();
+    let blocked = json!({"format": "png", "output": root.join("source_[#####].png")}).to_string();
+    let valid = json!({"format": "gif", "output": good}).to_string();
+    ok_json(&[
+        "run",
+        "--empty",
+        "--save-as",
+        project.to_str().unwrap(),
+        "comp.new",
+        r#"{"name":"Main","width":16,"height":16,"frameRate":10,"duration":0.1}"#,
+        "layer.newSolid",
+        "{}",
+        "file.import",
+        &import,
+        "renderQueue.add",
+        &blocked,
+        "renderQueue.add",
+        &valid,
+    ]);
+    let p = project.to_str().unwrap();
+    for args in [vec!["render", "--queue", "--project", p], vec!["run", p, "renderQueue.render", "{}"], vec!["exec", "renderQueue.render", "--project", p]] {
+        std::fs::write(&good, b"previous output").unwrap();
+        let (code, result) = run_json(&args);
+        assert_eq!(code, 1, "{args:?}: {result}");
+        assert!(result["error"].as_str().is_some_and(|e| e.contains("footage") && e.contains("source_00000.png")), "{result}");
+        assert_eq!(std::fs::read(&source).unwrap(), original);
+        assert!(std::fs::read(&good).unwrap().starts_with(b"GIF8"), "the valid item still rendered");
+    }
+    std::fs::remove_dir_all(root).unwrap();
+}
+
 /// `render --bitrate` (#440) targets the bitrate in VP9 WebM.
 #[test]
 fn render_bitrate_applies_to_vp9_webm() {
diff --git a/crates/engine/Cargo.toml b/crates/engine/Cargo.toml
index 7104bc1cc..4bb488569 100644
--- a/crates/engine/Cargo.toml
+++ b/crates/engine/Cargo.toml
@@ -39,3 +39,7 @@ rayon = { workspace = true }
 image = { workspace = true }
 web-time = { workspace = true }
 exr = { workspace = true }
+
+# Native only: the volume's own identity for a file, to tell that a hard link is the footage it leads to.
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+same-file = { workspace = true }
diff --git a/crates/engine/src/cmd/comp_more.rs b/crates/engine/src/cmd/comp_more.rs
index 83c49bad2..824966cb3 100644
--- a/crates/engine/src/cmd/comp_more.rs
+++ b/crates/engine/src/cmd/comp_more.rs
@@ -96,8 +96,11 @@ fn queue_frame(s: &mut Session, p: &Value) -> Result<Value> {
     }
     if let Some(path) = str_p(p, "path") {
         it.output.output = path.to_string();
-    } else if !it.output.format.is_sequence() {
-        it.output.output = "[compName]_frame.[fileExtension]".into();
+    } else {
+        if !it.output.format.is_sequence() {
+            it.output.output = "[compName]_frame.[fileExtension]".into();
+        }
+        s.avoid_sources(&mut it);
     }
     let id = s.edit("Save Frame As", None, |proj, _| {
         it.id = proj.render_queue.iter().map(|i| i.id).max().unwrap_or(0) + 1;
diff --git a/crates/engine/src/cmd/proxy.rs b/crates/engine/src/cmd/proxy.rs
index 99650875c..58b147e89 100644
--- a/crates/engine/src/cmd/proxy.rs
+++ b/crates/engine/src/cmd/proxy.rs
@@ -191,6 +191,8 @@ fn create_proxy(s: &mut Session, p: &Value) -> Result<Value> {
     it.output.channels = Channels::Rgba;
     if let Some(o) = str_p(p, "path").or(str_p(p, "output")) {
         it.output.output = o.to_string();
+    } else {
+        s.avoid_sources(&mut it);
     }
     it.post_render = PostRenderAction::SetProxy;
     let id = s.edit("Create Proxy", None, |proj, _| {
diff --git a/crates/engine/src/cmd/render_queue.rs b/crates/engine/src/cmd/render_queue.rs
index 00e078372..a3934c537 100644
--- a/crates/engine/src/cmd/render_queue.rs
+++ b/crates/engine/src/cmd/render_queue.rs
@@ -550,6 +550,9 @@ fn add(s: &mut Session, p: &Value) -> Result<Value> {
         object.remove("template");
     }
     apply_output(&mut it.output, &templates, s.state.region_of_interest, &output_params, "renderQueue.add")?;
+    if str_p(p, "output").or(str_p(p, "path")).is_none() {
+        s.avoid_sources(&mut it);
+    }
     if let Some(l) = enum_p(p, "log", "renderQueue.add", RenderLog::parse, "errorsOnly|plusSettings|plusPerFrameInfo")? {
         it.log = l;
     }
@@ -696,8 +699,18 @@ fn render(s: &mut Session, p: &Value) -> Result<Value> {
     {
         log::warn!("{e}");
     }
+    let queued: std::collections::HashSet<u64> = s.project.render_queue.iter().filter(|i| i.is_queued()).map(|i| i.id).collect();
     let ids = s.start_render(wait).map_err(EngineError::Other)?;
-    let items: Vec<Value> = s.project.render_queue.iter().enumerate().filter(|(_, i)| ids.contains(&i.id)).map(|(k, i)| item_json(s, i, k)).collect();
+    // Source refusals fail before the exporter starts. Report them just like encoding
+    // failures, so CLI/MCP callers do not mistake a partly refused queue for full success.
+    let items: Vec<Value> = s
+        .project
+        .render_queue
+        .iter()
+        .enumerate()
+        .filter(|(_, i)| ids.contains(&i.id) || (queued.contains(&i.id) && matches!(i.status, RenderStatus::Failed(_))))
+        .map(|(k, i)| item_json(s, i, k))
+        .collect();
     Ok(json!({"rendering": s.is_rendering(), "items": items}))
 }
 
@@ -788,6 +801,9 @@ fn pre_render(s: &mut Session, p: &Value) -> Result<Value> {
     it.output = templates.default_output_module(TemplateSlot::PreRender);
     it.output.output = "[compName]_prerender.[fileExtension]".into();
     apply_output(&mut it.output, &templates, s.state.region_of_interest, p, "render.preRender")?;
+    if str_p(p, "output").or(str_p(p, "path")).is_none() {
+        s.avoid_sources(&mut it);
+    }
     it.post_render = PostRenderAction::ImportAndReplace;
     let id = s.edit("Pre-render", None, |proj, _| {
         it.id = proj.render_queue.iter().map(|i| i.id).max().unwrap_or(0) + 1;
@@ -813,6 +829,9 @@ fn save_current_preview(s: &mut Session, p: &Value) -> Result<Value> {
     let mut item = RenderQueueItem::new(0, cid);
     item.output = OutputModule::for_format(format);
     item.output.output = path.clone();
+    if let Some(refusal) = s.check_outputs(&[vec![(item.clone(), path.clone())]]).first() {
+        return Err(EngineError::Other(refusal.reason.clone()));
+    }
     let job = crate::ExportJob {
         project: &s.project,
         footage: s.footage.as_ref(),
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index a7484a3f8..0cc9a7189 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -18,6 +18,7 @@ pub mod history;
 mod home;
 mod interchange;
 pub mod menus;
+mod output_guard;
 pub mod preview;
 pub mod render_queue;
 pub mod scriptui;
diff --git a/crates/engine/src/output_guard.rs b/crates/engine/src/output_guard.rs
new file mode 100644
index 000000000..5d4dc289e
--- /dev/null
+++ b/crates/engine/src/output_guard.rs
@@ -0,0 +1,435 @@
+//! Protect files the project reads from render outputs (#1743).
+//!
+//! This guard is independent of replacement consent and export staging: it never authorizes
+//! overwriting ordinary outputs or opens a second confirmation flow. Those belong to the
+//! exporter. Existing aliases are compared by native file identity, including hard links.
+//! Missing sources remain protected by their normalized path. Checks happen before dispatch;
+//! filesystem changes between the check and the write require exporter-side revalidation.
+
+use std::collections::{HashMap, HashSet};
+use std::path::{Component, Path, PathBuf};
+use std::sync::Arc;
+
+use effectcraft_project::render_queue::{RenderQueueItem, log_path, numbered_template, sequence_frame, sequence_path};
+use effectcraft_project::{Footage, ItemKind};
+
+use crate::Session;
+
+/// Volumes on Windows and macOS ignore case unless they were set up not to.
+const IGNORES_CASE: bool = cfg!(any(windows, target_os = "macos"));
+
+/// How many frames are looked at one by one for a sequence whose folder cannot be read at once
+/// (its frame number is in a folder's name).
+const PROBE_LIMIT: u64 = 100_000;
+
+/// How far a default output name is numbered (`_1` … `_1000`) before it is left to the check at
+/// render time.
+const MAX_NUMBER: u32 = 1_000;
+
+/// What reads a file the project depends on.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum Source {
+    /// A footage item, by name.
+    Footage(Arc<str>),
+    /// An item's proxy, by the item's name.
+    Proxy(Arc<str>),
+    /// The project file.
+    Project,
+}
+
+impl Source {
+    /// Why `path`, a file this reads, cannot be a render's output.
+    pub(crate) fn refusal(&self, path: &str) -> String {
+        match self {
+            Source::Footage(name) => format!("{path} is the footage “{name}” of this project, and a render never replaces footage; choose another Output To"),
+            Source::Proxy(name) => format!("{path} is the proxy of “{name}”, and a render never replaces a proxy; choose another Output To"),
+            Source::Project => format!("{path} is this project's own file, and a render never replaces it; choose another Output To"),
+        }
+    }
+}
+
+/// The files the project reads: footage (every frame of a sequence), proxies and the project file.
+#[derive(Default)]
+pub(crate) struct Protected {
+    files: Vec<(PathBuf, Source)>,
+    by_path: HashMap<String, usize>,
+    /// Hashes of native identities, built once. Handles are closed after indexing so long
+    /// sequences do not exhaust the process's file descriptors. Hash hits are verified with
+    /// native handle equality; a hash collision cannot make another file a protected source.
+    #[cfg(not(target_arch = "wasm32"))]
+    by_identity: std::sync::OnceLock<HashMap<u64, Vec<usize>>>,
+    #[cfg(all(test, not(target_arch = "wasm32")))]
+    identity_reads: std::sync::atomic::AtomicUsize,
+}
+
+impl Protected {
+    pub(crate) fn of(s: &Session) -> Protected {
+        let mut found = Protected::default();
+        for item in s.project.items.values() {
+            let name: Arc<str> = item.name.as_str().into();
+            if let ItemKind::Footage(f) = &item.kind {
+                found.add_footage(s, f, &Source::Footage(name.clone()));
+            }
+            if let Some(proxy) = &item.proxy {
+                found.add_footage(s, &proxy.footage, &Source::Proxy(name));
+            }
+        }
+        if let Some(path) = s.path.as_deref().filter(|p| !p.is_empty()) {
+            found.add(PathBuf::from(path), Source::Project);
+        }
+        found
+    }
+
+    fn add_footage(&mut self, s: &Session, f: &Footage, source: &Source) {
+        for stored in std::iter::once(&f.path).chain(&f.sequence).filter(|p| !p.is_empty()) {
+            // The file the media layer opens for the path the project stores.
+            let path = s.stored_path(stored).unwrap_or_else(|_| PathBuf::from(stored));
+            self.add(path, source.clone());
+        }
+    }
+
+    fn add(&mut self, path: PathBuf, source: Source) {
+        self.by_path.entry(key(&path)).or_insert(self.files.len());
+        self.files.push((path, source));
+    }
+
+    pub(crate) fn is_empty(&self) -> bool {
+        self.files.is_empty()
+    }
+
+    /// The source at this normalized path or native file identity. A new output only needs
+    /// its path lookup and one failed filesystem probe; existing outputs build the index once.
+    pub(crate) fn find(&self, path: &Path) -> Option<&Source> {
+        self.by_path.get(&key(path)).and_then(|i| self.files.get(*i)).map(|(_, source)| source).or_else(|| self.alias_of(path))
+    }
+
+    #[cfg(not(target_arch = "wasm32"))]
+    fn handle(&self, path: &Path) -> Option<same_file::Handle> {
+        #[cfg(test)]
+        self.identity_reads.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
+        // Opening a FIFO can wait for a writer. Only regular files can be protected media;
+        // preserve the old size-indexed lookup's exclusion of special files and directories.
+        if !std::fs::metadata(path).ok()?.is_file() {
+            return None;
+        }
+        same_file::Handle::from_path(path).ok()
+    }
+
+    /// Hashes narrow the search, while native handle equality also checks any hash collisions.
+    #[cfg(not(target_arch = "wasm32"))]
+    fn alias_of(&self, path: &Path) -> Option<&Source> {
+        let output = self.handle(path)?;
+        let indexed = self.by_identity.get_or_init(|| {
+            let mut ids: HashMap<u64, Vec<usize>> = HashMap::new();
+            for (i, (known, _)) in self.files.iter().enumerate() {
+                if let Some(handle) = self.handle(known) {
+                    ids.entry(identity_hash(&handle)).or_default().push(i);
+                }
+            }
+            ids
+        });
+        indexed.get(&identity_hash(&output))?.iter().find_map(|i| {
+            let (known, source) = self.files.get(*i)?;
+            (self.handle(known)? == output).then_some(source)
+        })
+    }
+
+    #[cfg(target_arch = "wasm32")]
+    fn alias_of(&self, _: &Path) -> Option<&Source> {
+        None
+    }
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+fn identity_hash(handle: &same_file::Handle) -> u64 {
+    use std::hash::{Hash, Hasher};
+    let mut hash = std::collections::hash_map::DefaultHasher::new();
+    handle.hash(&mut hash);
+    hash.finish()
+}
+
+/// `path` made absolute, with `.` and `..` resolved by name alone (no file is looked at).
+fn lexical(path: &Path) -> PathBuf {
+    let absolute = std::path::absolute(path).unwrap_or_else(|_| path.to_path_buf());
+    let mut out = PathBuf::new();
+    for part in absolute.components() {
+        match part {
+            Component::CurDir => {}
+            Component::ParentDir => match out.components().next_back() {
+                Some(Component::Normal(_)) => {
+                    out.pop();
+                }
+                Some(Component::RootDir | Component::Prefix(_)) => {}
+                _ => out.push(".."),
+            },
+            other => out.push(other.as_os_str()),
+        }
+    }
+    out
+}
+
+/// The name a path is compared by: absolute, resolved by name, without case where volumes ignore it.
+fn key(path: &Path) -> String {
+    let parts: Vec<String> = lexical(path).components().map(|c| c.as_os_str().to_string_lossy().into_owned()).collect();
+    fold(&parts.join("/"))
+}
+
+fn fold(name: &str) -> String {
+    if IGNORES_CASE { name.to_lowercase() } else { name.to_string() }
+}
+
+#[cfg(test)]
+fn same_file(a: &Path, b: &Path) -> bool {
+    if key(a) == key(b) {
+        return true;
+    }
+    #[cfg(not(target_arch = "wasm32"))]
+    return same_file::is_same_file(a, b).unwrap_or(false);
+    #[cfg(target_arch = "wasm32")]
+    false
+}
+
+/// Whether a file (or a link, even one leading nowhere) is at `path`.
+fn exists(path: &str) -> bool {
+    std::fs::symlink_metadata(path).is_ok_and(|m| !m.is_dir())
+}
+
+/// The files of a numbered sequence (`count` frames from `first`) that are on disk: its folder is
+/// read once, not asked about frame by frame.
+fn frames_on_disk(path: &str, first: i64, count: u64) -> Result<Vec<PathBuf>, String> {
+    let last = first.saturating_add(i64::try_from(count).unwrap_or(i64::MAX));
+    let p = Path::new(path);
+    let dir = p.parent().filter(|d| !d.as_os_str().is_empty()).unwrap_or(Path::new("."));
+    let name = p.file_name().map(|n| n.to_string_lossy().into_owned());
+    let Some(name) = name.filter(|_| !dir.to_string_lossy().contains('#')) else {
+        // The frame number is in a folder's name: every frame has a folder of its own.
+        if count > PROBE_LIMIT {
+            return Err(format!(
+                "cannot safely check {count} output frames with a number in a folder name (limit {PROBE_LIMIT}); choose a fixed output folder or a shorter range"
+            ));
+        }
+        return Ok((0..count)
+            .map(|k| sequence_path(path, first.saturating_add(i64::try_from(k).unwrap_or(i64::MAX))))
+            .filter(|frame| exists(frame))
+            .map(PathBuf::from)
+            .collect());
+    };
+    let pattern = fold(&name);
+    let entries = match std::fs::read_dir(dir) {
+        Ok(entries) => entries,
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(Vec::new()),
+        Err(e) => return Err(format!("cannot check render output folder {}: {e}", dir.display())),
+    };
+    Ok(entries
+        .filter_map(Result::ok)
+        .filter(|e| sequence_frame(&pattern, &fold(&e.file_name().to_string_lossy())).is_some_and(|frame| (first..last).contains(&frame)))
+        .filter(|e| !e.file_type().is_ok_and(|t| t.is_dir()))
+        .map(|e| e.path())
+        .collect())
+}
+
+/// A queue item refused before any of its output modules are dispatched.
+#[derive(Clone, Debug, PartialEq)]
+pub(crate) struct Refused {
+    pub item: u64,
+    pub reason: String,
+}
+
+impl Session {
+    /// The files the project reads.
+    pub(crate) fn protected_files(&self) -> Protected {
+        Protected::of(self)
+    }
+
+    /// Reject protected outputs and ranges that cannot be checked completely. Ordinary-file
+    /// replacement consent is left to the exporter, independently of this source guard.
+    pub(crate) fn check_outputs(&self, items: &[Vec<(RenderQueueItem, String)>]) -> Vec<Refused> {
+        if cfg!(target_arch = "wasm32") {
+            return Vec::new();
+        }
+        let protected = self.protected_files();
+        let mut seen = HashSet::new();
+        let mut refused = Vec::new();
+        for (item, path) in items.iter().flatten() {
+            if seen.contains(&item.id) {
+                continue;
+            }
+            let reason = match self.check_output(&protected, item, path) {
+                Ok(reason) => reason,
+                Err(reason) => Some(reason),
+            };
+            if let Some(reason) = reason {
+                seen.insert(item.id);
+                refused.push(Refused { item: item.id, reason });
+            }
+        }
+        refused
+    }
+
+    fn check_output(&self, protected: &Protected, item: &RenderQueueItem, path: &str) -> Result<Option<String>, String> {
+        if protected.is_empty() {
+            return Ok(None);
+        }
+        let sequence = item.output.format.is_sequence();
+        // Skip Existing Files leaves existing frames untouched, but not the render log.
+        let frames = if sequence && !item.settings.skip_existing {
+            match self.project.comp(item.comp) {
+                Some(comp) => frames_on_disk(path, item.settings.first_frame(comp), item.settings.frame_count(comp))?,
+                None => Vec::new(),
+            }
+        } else {
+            Vec::new()
+        };
+        let log = log_path(path);
+        let movie = (!sequence).then_some(Path::new(path));
+        Ok(frames
+            .iter()
+            .map(PathBuf::as_path)
+            .chain(movie)
+            .chain(Some(Path::new(&log)))
+            .find_map(|path| protected.find(path).map(|source| source.refusal(&path.to_string_lossy()))))
+    }
+
+    /// A new item's default output must not be a file the project reads: `[compName]_1`,
+    /// `[compName]_2`… take its place (and avoid the queue's other outputs), as After Effects
+    /// numbers a second item of the same composition. An output nothing is in the way of keeps
+    /// the composition's own name, and one the caller chose is not touched: rendering it is
+    /// refused instead.
+    pub(crate) fn avoid_sources(&self, item: &mut RenderQueueItem) {
+        if cfg!(target_arch = "wasm32") {
+            return;
+        }
+        let protected = self.protected_files();
+        if protected.is_empty() {
+            return;
+        }
+        let template = item.output.output.clone();
+        let mut taken: Option<HashSet<String>> = None;
+        'candidate: for n in 0..=MAX_NUMBER {
+            item.output.output = if n == 0 { template.clone() } else { numbered_template(&template, n) };
+            let Ok(outputs) = self.outputs_of(item, None) else { break };
+            for (module, path) in &outputs {
+                match self.check_output(&protected, module, path) {
+                    Ok(Some(_)) => continue 'candidate,
+                    Err(_) => break 'candidate,
+                    Ok(None) => {}
+                }
+            }
+            // Only a name that had to move is kept clear of the other items.
+            let others = if n == 0 { None } else { Some(taken.get_or_insert_with(|| self.queue_output_keys())) };
+            if others.is_none_or(|others| !outputs.iter().any(|(_, path)| others.contains(&key(Path::new(path))))) {
+                return;
+            }
+        }
+        item.output.output = template;
+    }
+
+    /// [`key`] of every output of the queue's items.
+    fn queue_output_keys(&self) -> HashSet<String> {
+        self.project.render_queue.iter().filter_map(|it| self.outputs_of(it, None).ok()).flatten().map(|(_, path)| key(Path::new(&path))).collect()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[cfg(not(target_arch = "wasm32"))]
+    fn unrelated_same_size_frames_are_indexed_once() {
+        let dir = std::env::temp_dir().join(format!("effectcraft-identity-index-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        let mut protected = Protected::default();
+        for i in 0..128 {
+            let source = dir.join(format!("source{i}")).join("plate.png");
+            let output = dir.join(format!("output{i}")).join("plate.png");
+            for path in [&source, &output] {
+                std::fs::create_dir_all(path.parent().unwrap()).unwrap();
+                std::fs::write(path, b"same-size frame").unwrap();
+            }
+            protected.add(source, Source::Footage(format!("plate{i}").into()));
+        }
+        for i in 0..128 {
+            assert!(protected.find(&dir.join(format!("output{i}")).join("plate.png")).is_none());
+        }
+        assert_eq!(protected.identity_reads.load(std::sync::atomic::Ordering::Relaxed), 256, "one source-index pass plus one lookup per output");
+        let alias = dir.join("renamed.png");
+        std::fs::hard_link(dir.join("source64").join("plate.png"), &alias).unwrap();
+        assert_eq!(protected.find(&alias), Some(&Source::Footage("plate64".into())));
+        assert_eq!(protected.identity_reads.load(std::sync::atomic::Ordering::Relaxed), 258, "native equality verifies a matching identity");
+        std::fs::remove_dir_all(dir).unwrap();
+    }
+
+    #[test]
+    fn folder_numbered_sequences_are_never_partially_checked() {
+        let pattern = std::env::temp_dir().join("frames[######]").join("plate.png").to_string_lossy().into_owned();
+        let error = frames_on_disk(&pattern, 0, PROBE_LIMIT + 1).unwrap_err();
+        assert!(error.contains("cannot safely check") && error.contains("100000"), "{error}");
+        assert!(frames_on_disk(&pattern, 0, u64::MAX).is_err());
+    }
+
+    #[test]
+    #[cfg(not(target_arch = "wasm32"))]
+    fn non_file_outputs_do_not_build_the_identity_index() {
+        let protected = Protected::default();
+        assert!(protected.find(&std::env::temp_dir()).is_none());
+        assert!(protected.by_identity.get().is_none());
+    }
+
+    #[test]
+    fn paths_compare_by_name_once_resolved() {
+        let here = std::env::current_dir().unwrap();
+        assert_eq!(key(Path::new("a/b/../c.mp4")), key(Path::new("a/c.mp4")));
+        assert_eq!(key(Path::new("./a/c.mp4")), key(&here.join("a/c.mp4")));
+        assert_ne!(key(Path::new("a/c.mp4")), key(Path::new("b/c.mp4")));
+        assert_eq!(key(Path::new(&format!("{}x", "../".repeat(64)))), key(Path::new(&format!("{}x", "../".repeat(80)))), "past the root stays at the root");
+        assert_eq!(IGNORES_CASE, key(Path::new("A/C.MP4")) == key(Path::new("a/c.mp4")));
+    }
+
+    #[test]
+    fn a_file_is_the_same_file_under_every_spelling_the_volume_allows() {
+        let dir = std::env::temp_dir().join(format!("effectcraft-output-guard-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(dir.join("sub")).unwrap();
+        std::fs::write(dir.join("clip.mov"), b"x").unwrap();
+        std::fs::write(dir.join("other.mov"), b"y").unwrap();
+        assert!(same_file(&dir.join("clip.mov"), &dir.join("sub").join("..").join("clip.mov")));
+        assert!(!same_file(&dir.join("clip.mov"), &dir.join("other.mov")));
+        // Nothing there yet: only the name decides.
+        assert!(same_file(&dir.join("gone.mov"), &dir.join("sub").join("..").join("gone.mov")));
+        assert!(!same_file(&dir.join("gone.mov"), &dir.join("clip.mov")));
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn a_sequences_folder_is_read_once_for_its_frames() {
+        let dir = std::env::temp_dir().join(format!("effectcraft-output-frames-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(dir.join("a_00003.png")).unwrap(); // a folder is not a frame
+        for name in ["a_00001.png", "a_00002.png", "a_0004.png", "a_00004.jpg", "b_00002.png", "a_00009.png"] {
+            std::fs::write(dir.join(name), b"x").unwrap();
+        }
+        let pattern = dir.join("a_[#####].png").to_string_lossy().into_owned();
+        let names = |frames: Vec<PathBuf>| {
+            let mut names: Vec<String> = frames.iter().filter_map(|f| f.file_name()).map(|n| n.to_string_lossy().into_owned()).collect();
+            names.sort();
+            names
+        };
+        assert_eq!(
+            names(frames_on_disk(&pattern, 0, 5).unwrap()),
+            ["a_00001.png", "a_00002.png"],
+            "frames 0-4: not the 4-digit one, the jpg, the folder or frame 9"
+        );
+        assert_eq!(names(frames_on_disk(&pattern, 2, 1).unwrap()), ["a_00002.png"]);
+        assert_eq!(names(frames_on_disk(&pattern, 9, 100).unwrap()), ["a_00009.png"]);
+        assert_eq!(names(frames_on_disk(&pattern, 0, u64::MAX).unwrap()), ["a_00001.png", "a_00002.png", "a_00009.png"], "a hostile frame count is not walked");
+        // A frame number in a folder's name: each frame has its own folder.
+        std::fs::create_dir_all(dir.join("f02")).unwrap();
+        std::fs::write(dir.join("f02").join("x.png"), b"x").unwrap();
+        let in_folder = dir.join("f[##]").join("x.png").to_string_lossy().into_owned();
+        assert_eq!(names(frames_on_disk(&in_folder, 0, 4).unwrap()), ["x.png"]);
+        // A folder that is not there holds nothing.
+        assert!(frames_on_disk(&dir.join("none").join("a_[#####].png").to_string_lossy(), 0, 5).unwrap().is_empty());
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+}
diff --git a/crates/engine/src/render_queue.rs b/crates/engine/src/render_queue.rs
index d8f8cf7b5..1ff91e8e8 100644
--- a/crates/engine/src/render_queue.rs
+++ b/crates/engine/src/render_queue.rs
@@ -442,10 +442,46 @@ impl Session {
         self.render_job.as_ref().map(|j| j.shared.snapshot())
     }
 
-    /// Start rendering every queued item. `wait`: block until done (otherwise a background thread
-    /// renders, or the [`Session::offload`] worker; call [`Session::poll_render`] regularly).
-    /// Returns the ids being rendered. Without threads or an offload (wasm32) the render always
-    /// runs to completion before this returns.
+    /// The (item, resolved output path) of each output of `it`: one per output module and, with
+    /// Segment Sequences / Segment Movie Files, per segment. `formats`: the ones that can be
+    /// written (`None`: all). Fails with the status the item gets instead.
+    pub(crate) fn outputs_of(&self, it: &RenderQueueItem, formats: Option<&[OutputFormat]>) -> Result<Vec<(RenderQueueItem, String)>, RenderStatus> {
+        let mut modules = vec![];
+        for om in it.output_modules() {
+            let mut m = it.clone();
+            m.output = om.clone();
+            match self.resolve_output(&m) {
+                Some(p) if formats.is_none_or(|f| f.contains(&om.format)) => {
+                    // Settings ▸ Export: Append Bit Depth to File Name, Segment Sequences /
+                    // Movie Files.
+                    let bits = output_bits(om.format, self.project.settings.bit_depth);
+                    let p = self.prefs.output_name(&p, bits);
+                    modules.extend(self.segments(&m, &p));
+                }
+                Some(_) => return Err(RenderStatus::Failed(format!("{} export is not available", om.format.label()))),
+                None if self.project.comp(it.comp).is_none() => return Err(RenderStatus::Failed("composition missing".into())),
+                None => return Err(RenderStatus::NeedsOutput),
+            }
+        }
+        Ok(modules)
+    }
+
+    /// What the next Render would write: for each queued item its [`Session::outputs_of`], and
+    /// the status of each queued item that has none.
+    pub(crate) fn queued_outputs(&self, formats: &[OutputFormat]) -> (Vec<Vec<(RenderQueueItem, String)>>, Vec<(u64, RenderStatus)>) {
+        let (mut items, mut problems) = (Vec::new(), Vec::new());
+        for it in self.project.render_queue.iter().filter(|i| i.is_queued()) {
+            match self.outputs_of(it, Some(formats)) {
+                Ok(modules) => items.push(modules),
+                Err(status) => problems.push((it.id, status)),
+            }
+        }
+        (items, problems)
+    }
+
+    /// Start rendering every queued item, refusing outputs that replace footage, proxies or
+    /// the project file. Other existing outputs keep the exporter's usual replacement policy.
+    /// `wait`: block until done, otherwise render in the background and poll regularly.
     pub fn start_render(&mut self, wait: bool) -> Result<Vec<u64>, String> {
         let offload = self.offload.clone().filter(|_| !wait);
         let wait = wait || (cfg!(target_arch = "wasm32") && offload.is_none());
@@ -455,46 +491,33 @@ impl Session {
         self.poll_render();
         let exporter = self.exporter.clone().ok_or("export is not available in this build")?;
         let formats = exporter.formats();
-        let mut items = Vec::new();
-        let mut needs_output = Vec::new();
-        for it in self.project.render_queue.iter().filter(|i| i.is_queued()) {
-            let mut modules = vec![];
-            let mut problem = None;
-            for om in it.output_modules() {
-                let mut m = it.clone();
-                m.output = om.clone();
-                match self.resolve_output(&m) {
-                    Some(p) if formats.contains(&om.format) => {
-                        // Settings ▸ Export: Append Bit Depth to File Name, Segment Sequences /
-                        // Movie Files.
-                        let bits = output_bits(om.format, self.project.settings.bit_depth);
-                        let p = self.prefs.output_name(&p, bits);
-                        modules.extend(self.segments(&m, &p));
-                    }
-                    Some(_) => problem = Some(RenderStatus::Failed(format!("{} export is not available", om.format.label()))),
-                    None if self.project.comp(it.comp).is_none() => problem = Some(RenderStatus::Failed("composition missing".into())),
-                    None => problem = Some(RenderStatus::NeedsOutput),
-                }
-                if problem.is_some() {
-                    break;
-                }
-            }
-            match problem {
-                Some(st) => needs_output.push((it.id, st)),
-                None => items.push(modules),
-            }
-        }
-        if !needs_output.is_empty() {
+        let (mut items, mut problems) = self.queued_outputs(&formats);
+        let refused = self.check_outputs(&items);
+        items.retain(|modules| modules.first().is_none_or(|(it, _)| !refused.iter().any(|r| r.item == it.id)));
+        problems.extend(refused.iter().map(|r| (r.item, RenderStatus::Failed(r.reason.clone()))));
+        if !problems.is_empty() {
             let p = Arc::make_mut(&mut self.project);
-            for (id, st) in needs_output {
+            for (id, st) in problems {
                 if let Some(i) = p.render_queue.iter_mut().find(|i| i.id == id) {
                     i.status = st;
                 }
             }
             self.bump();
         }
+        if let Some(first) = refused.first() {
+            let message = if refused.len() == 1 {
+                format!("Not rendered: {}", first.reason)
+            } else {
+                format!("{} items were not rendered; first: {}", refused.len(), first.reason)
+            };
+            self.events.push(Event::Toast { message, error: true });
+        }
         if items.is_empty() {
-            return Err("nothing is queued: add a composition (Composition ▸ Add to Render Queue) and tick Render".into());
+            return Err(match refused.as_slice() {
+                [] => "nothing is queued: add a composition (Composition ▸ Add to Render Queue) and tick Render".into(),
+                [only] => only.reason.clone(),
+                [first, ..] => format!("{} items would replace files the project reads; first: {}", refused.len(), first.reason),
+            });
         }
         let ids: Vec<u64> = items.iter().filter_map(|m| m.first().map(|(i, _)| i.id)).collect();
         if let Some(off) = offload {
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 26092967f..050f78957 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -36,6 +36,7 @@ mod panels;
 mod project_items;
 mod proxy;
 mod quick_offset;
+mod render_overwrite;
 mod replace_source;
 mod rig3d;
 pub(crate) mod roto;
diff --git a/crates/engine/src/tests/render_overwrite.rs b/crates/engine/src/tests/render_overwrite.rs
new file mode 100644
index 000000000..420763da2
--- /dev/null
+++ b/crates/engine/src/tests/render_overwrite.rs
@@ -0,0 +1,606 @@
+//! Rendering never replaces a file the project reads (#1743). Ordinary-file replacement
+//! behavior stays with the exporter and its confirmation API.
+
+use std::path::{Path, PathBuf};
+use std::sync::{Arc, Mutex};
+
+use effectcraft_color::Label;
+use effectcraft_project::render_queue::{OutputFormat, RenderStatus, sequence_path};
+use effectcraft_project::{Footage, FootageKind, ItemId, ItemKind};
+use effectcraft_time::Tick;
+use serde_json::{Value, json};
+
+use crate::{ExportJob, ExportResult, Exporter, Session};
+
+const SOURCE: &[u8] = b"SOURCE FOOTAGE";
+const EARLIER: &[u8] = b"AN EARLIER RENDER";
+const RENDERED: &[u8] = b"RENDERED";
+
+/// An exporter that writes like the real one: `RENDERED` at the job's path, or at the path of
+/// every frame for a sequence (leaving the frames that exist alone when the item skips them).
+#[derive(Default)]
+struct Writer {
+    jobs: Mutex<Vec<String>>,
+}
+
+impl Exporter for Writer {
+    fn formats(&self) -> Vec<OutputFormat> {
+        OutputFormat::ALL.to_vec()
+    }
+    fn export(&self, job: &ExportJob, _: &mut dyn FnMut(u64, u64) -> bool) -> Result<ExportResult, String> {
+        self.jobs.lock().unwrap().push(job.path.to_string());
+        let comp = job.project.comp(job.item.comp).ok_or("no comp")?;
+        let paths: Vec<String> = if job.item.output.format.is_sequence() {
+            let first = job.item.settings.first_frame(comp);
+            (0..job.item.settings.frame_count(comp)).map(|k| sequence_path(job.path, first + k as i64)).collect()
+        } else {
+            vec![job.path.to_string()]
+        };
+        for path in &paths {
+            if job.item.settings.skip_existing && Path::new(path).exists() {
+                continue;
+            }
+            if let Some(dir) = Path::new(path).parent() {
+                std::fs::create_dir_all(dir).map_err(|e| e.to_string())?;
+            }
+            std::fs::write(path, RENDERED).map_err(|e| e.to_string())?;
+        }
+        Ok(ExportResult { path: paths.first().cloned().unwrap_or_default(), ..Default::default() })
+    }
+}
+
+/// A session whose project is saved in a fresh folder (the footage goes there too), with an
+/// exporter that writes real files.
+struct Fixture {
+    s: Session,
+    writer: Arc<Writer>,
+    dir: PathBuf,
+}
+
+impl Fixture {
+    fn new(name: &str) -> Fixture {
+        let dir = std::env::temp_dir().join("effectcraft-render-overwrite").join(format!("{}-{name}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        let mut s = Session::default();
+        let writer = Arc::new(Writer::default());
+        s.exporter = Some(writer.clone());
+        s.execute("file.saveAs", json!({"path": dir.join("Project.ecproj").to_string_lossy()})).unwrap();
+        Fixture { s, writer, dir }
+    }
+
+    fn path(&self, file: &str) -> PathBuf {
+        self.dir.join(file)
+    }
+
+    fn text(&self, file: &str) -> String {
+        self.path(file).to_string_lossy().into_owned()
+    }
+
+    fn read(&self, file: &str) -> Vec<u8> {
+        std::fs::read(self.path(file)).unwrap()
+    }
+
+    fn write(&self, file: &str, bytes: &[u8]) {
+        std::fs::write(self.path(file), bytes).unwrap();
+    }
+
+    /// A video file in the project's folder, imported.
+    fn footage(&mut self, file: &str) -> ItemId {
+        self.write(file, SOURCE);
+        let f = Footage {
+            path: self.text(file),
+            kind: FootageKind::Video,
+            width: 64,
+            height: 36,
+            has_video: true,
+            duration: Tick::from_seconds_f64(1.0),
+            ..Default::default()
+        };
+        Arc::make_mut(&mut self.s.project).add_item(file, Label::None, None, ItemKind::Footage(f))
+    }
+
+    /// Numbered stills in the project's folder, imported as one image sequence.
+    fn sequence(&mut self, name: &str, frames: std::ops::Range<u32>) -> ItemId {
+        let files: Vec<String> = frames
+            .map(|n| {
+                let file = format!("{name}_{n:05}.png");
+                self.write(&file, SOURCE);
+                self.text(&file)
+            })
+            .collect();
+        let f = Footage {
+            path: files[0].clone(),
+            kind: FootageKind::Sequence,
+            sequence: files,
+            width: 16,
+            height: 16,
+            has_video: true,
+            duration: Tick::from_seconds_f64(0.5),
+            ..Default::default()
+        };
+        Arc::make_mut(&mut self.s.project).add_item(&format!("{name}_[00000-00004].png"), Label::None, None, ItemKind::Footage(f))
+    }
+
+    /// A five-frame composition.
+    fn comp(&mut self, name: &str) {
+        self.s.execute("comp.new", json!({"name": name, "width": 16, "height": 16, "frameRate": 10, "duration": 0.5})).unwrap();
+    }
+
+    /// The output path of queue item `index` (0-based).
+    fn output(&self, index: usize) -> PathBuf {
+        PathBuf::from(self.s.resolve_output(&self.s.project.render_queue[index]).unwrap())
+    }
+
+    /// The paths the exporter was started for.
+    fn exported(&self) -> Vec<String> {
+        self.writer.jobs.lock().unwrap().clone()
+    }
+
+    fn render(&mut self, params: Value) -> crate::Result<Value> {
+        self.s.execute("renderQueue.render", params)
+    }
+}
+
+impl Drop for Fixture {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.dir);
+    }
+}
+
+fn link(target: &Path, link: &Path) -> std::io::Result<()> {
+    #[cfg(unix)]
+    return std::os::unix::fs::symlink(target, link);
+    #[cfg(windows)]
+    return std::os::windows::fs::symlink_file(target, link);
+    #[cfg(not(any(unix, windows)))]
+    {
+        let _ = (target, link);
+        Err(std::io::ErrorKind::Unsupported.into())
+    }
+}
+
+/// A folder that leads to `target`: a symbolic link, or on Windows, where that takes a privilege
+/// most accounts lack, a junction.
+fn link_dir(target: &Path, link: &Path) -> std::io::Result<()> {
+    #[cfg(unix)]
+    return std::os::unix::fs::symlink(target, link);
+    #[cfg(windows)]
+    return std::os::windows::fs::symlink_dir(target, link).or_else(|_| {
+        let made = std::process::Command::new("cmd").args(["/C", "mklink", "/J"]).arg(link).arg(target).output()?;
+        if made.status.success() { Ok(()) } else { Err(std::io::Error::other(String::from_utf8_lossy(&made.stdout).into_owned())) }
+    });
+    #[cfg(not(any(unix, windows)))]
+    {
+        let _ = (target, link);
+        Err(std::io::ErrorKind::Unsupported.into())
+    }
+}
+
+/// The report: save a new project beside `footage.mp4`, import it, make a composition from it
+/// (it is named after the file), add that to the Render Queue and click Render. The composition's
+/// default output is `<project folder>/footage.mp4`, the footage itself.
+#[test]
+fn a_comp_made_from_footage_does_not_render_over_it() {
+    let mut f = Fixture::new("comp-from-footage");
+    let footage = f.footage("footage.mp4");
+    f.s.state.project_selection = vec![footage];
+    f.s.execute("file.newCompFromSelection", json!({"addToRenderQueue": true})).unwrap();
+    assert_eq!(f.s.project.render_queue.len(), 1);
+    f.render(json!({})).unwrap();
+    assert_eq!(f.read("footage.mp4"), SOURCE, "the footage is still the footage");
+    assert_eq!(f.s.project.render_queue[0].status, RenderStatus::Done);
+    // The default name stepped aside: the render sits next to it.
+    assert_eq!(f.output(0), f.path("footage_1.mp4"));
+    assert_eq!(f.read("footage_1.mp4"), RENDERED);
+    // Another item for the same composition takes the next free number.
+    f.s.execute("renderQueue.add", json!({})).unwrap();
+    assert_eq!(f.output(1), f.path("footage_2.mp4"));
+}
+
+#[test]
+fn an_output_that_is_the_footage_is_refused_with_or_without_overwrite() {
+    for (n, params) in [json!({}), json!({"overwrite": true})].into_iter().enumerate() {
+        let mut f = Fixture::new(&format!("explicit-footage-{n}"));
+        f.footage("clip.mov");
+        f.comp("Main");
+        let clip = f.text("clip.mov");
+        f.s.execute("renderQueue.add", json!({"format": "prores", "output": clip})).unwrap();
+        let e = f.render(params).unwrap_err().to_string();
+        assert!(e.contains("clip.mov") && e.contains("footage"), "{e}");
+        assert_eq!(f.read("clip.mov"), SOURCE);
+        assert!(f.exported().is_empty(), "the exporter was not started");
+        let RenderStatus::Failed(why) = &f.s.project.render_queue[0].status else { panic!("{:?}", f.s.project.render_queue[0].status) };
+        assert!(why.contains("clip.mov"), "{why}");
+    }
+}
+
+/// An item that would replace the footage fails on its own; the rest of the queue renders.
+#[test]
+fn the_rest_of_the_queue_renders_when_one_item_would_replace_footage() {
+    let mut f = Fixture::new("one-refused");
+    f.footage("clip.mov");
+    f.comp("Main");
+    let clip = f.text("clip.mov");
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": clip})).unwrap();
+    let ok = f.text("main.mp4");
+    f.s.execute("renderQueue.add", json!({"output": ok})).unwrap();
+    let r = f.render(json!({})).unwrap();
+    assert_eq!(f.read("clip.mov"), SOURCE);
+    assert_eq!(f.read("main.mp4"), RENDERED);
+    assert!(matches!(f.s.project.render_queue[0].status, RenderStatus::Failed(_)));
+    assert_eq!(f.s.project.render_queue[1].status, RenderStatus::Done);
+    assert!(r["items"].as_array().unwrap().iter().any(|i| i["status"].get("Failed").is_some()), "the reply includes the refused item: {r}");
+    assert!(r["items"].as_array().unwrap().iter().any(|i| i["status"] == "Done"), "{r}");
+}
+
+#[test]
+fn the_project_file_is_never_an_output() {
+    let mut f = Fixture::new("project-file");
+    // A project saved under a name a movie could have.
+    let name = f.text("final.mp4");
+    f.s.execute("file.saveAs", json!({"path": name})).unwrap();
+    f.comp("final");
+    f.s.execute("renderQueue.add", json!({})).unwrap();
+    assert_eq!(f.output(0), f.path("final_1.mp4"), "the default name moves aside");
+    f.s.execute("renderQueue.remove", json!({"index": 1})).unwrap();
+    f.s.execute("renderQueue.add", json!({"output": name})).unwrap();
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("final.mp4") && e.contains("project"), "{e}");
+    assert!(std::fs::read_to_string(f.path("final.mp4")).unwrap().contains("\"schema\""), "the project file is still a project");
+}
+
+#[test]
+fn a_proxy_is_not_an_output_either() {
+    let mut f = Fixture::new("proxy");
+    f.footage("clip.mov");
+    f.write("proxy.mov", SOURCE);
+    f.comp("Main");
+    let proxy = Footage { path: f.text("proxy.mov"), kind: FootageKind::Video, has_video: true, ..Default::default() };
+    let comp = f.s.active_comp_id().unwrap();
+    Arc::make_mut(&mut f.s.project).item_mut(comp).unwrap().proxy = Some(Box::new(effectcraft_project::Proxy { footage: proxy, enabled: true }));
+    let target = f.text("proxy.mov");
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": target})).unwrap();
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("proxy"), "{e}");
+    assert_eq!(f.read("proxy.mov"), SOURCE);
+}
+
+/// Recreating a default proxy writes a new file and attaches it, without replacing the proxy
+/// the project is currently reading. Explicitly choosing that protected path is still refused.
+#[test]
+fn creating_a_proxy_again_chooses_a_new_default_and_attaches_it() {
+    struct Probe;
+    impl crate::Importer for Probe {
+        fn probe(&self, path: &str) -> Result<Footage, String> {
+            if !Path::new(path).is_file() {
+                return Err("proxy file missing".into());
+            }
+            Ok(Footage {
+                path: path.into(),
+                kind: if path.ends_with(".png") { FootageKind::Still } else { FootageKind::Video },
+                width: 16,
+                height: 16,
+                has_video: true,
+                ..Default::default()
+            })
+        }
+    }
+    for kind in ["movie", "still"] {
+        let mut f = Fixture::new(&format!("recreate-proxy-{kind}"));
+        f.s.importer = Some(Arc::new(Probe));
+        f.comp("Main");
+        let comp = f.s.active_comp_id().unwrap();
+        f.s.execute("file.createProxy", json!({"kind": kind})).unwrap();
+        f.render(json!({})).unwrap();
+        let first = f.s.project.item(comp).unwrap().proxy.as_ref().unwrap().footage.path.clone();
+        assert_eq!(std::fs::read(&first).unwrap(), RENDERED);
+
+        f.s.execute("file.createProxy", json!({"kind": kind})).unwrap();
+        f.render(json!({})).unwrap();
+        let second = f.s.project.item(comp).unwrap().proxy.as_ref().unwrap().footage.path.clone();
+        assert_ne!(second, first, "the replacement proxy gets its own file");
+        assert_eq!(std::fs::read(&second).unwrap(), RENDERED);
+        assert_eq!(std::fs::read(&first).unwrap(), RENDERED);
+        assert_eq!(f.exported().len(), 2);
+
+        // For a still proxy, an explicit output is the sequence pattern, not its first
+        // rendered frame (a bare PNG name would have another frame number appended).
+        let protected_output = f.output(1);
+        f.s.execute("file.createProxy", json!({"kind": kind, "path": protected_output})).unwrap();
+        let error = f.render(json!({})).unwrap_err().to_string();
+        assert!(error.contains("never replaces a proxy"), "{error}");
+        assert_eq!(f.exported().len(), 2);
+    }
+}
+
+/// A pre-render becomes imported footage. Its old output stays protected even from the
+/// same queue item; issuing Pre-render again supplies a fresh default output instead.
+#[test]
+fn refreshing_a_pre_render_uses_a_new_default_without_exempting_imported_footage() {
+    struct Probe;
+    impl crate::Importer for Probe {
+        fn probe(&self, path: &str) -> Result<Footage, String> {
+            if !Path::new(path).is_file() {
+                return Err("pre-render missing".into());
+            }
+            Ok(Footage { path: path.into(), kind: FootageKind::Video, width: 16, height: 16, has_video: true, ..Default::default() })
+        }
+    }
+    let mut f = Fixture::new("refresh-pre-render");
+    f.s.importer = Some(Arc::new(Probe));
+    f.comp("Main");
+    f.s.execute("render.preRender", json!({"format": "gif"})).unwrap();
+    let first = f.output(0);
+    f.render(json!({})).unwrap();
+    f.s.execute("renderQueue.setRender", json!({"index": 1, "render": true})).unwrap();
+    let error = f.render(json!({})).unwrap_err().to_string();
+    assert!(error.contains("footage"), "{error}");
+    assert_eq!(std::fs::read(&first).unwrap(), RENDERED);
+    assert_eq!(f.exported().len(), 1);
+    f.s.execute("renderQueue.setRender", json!({"index": 1, "render": false})).unwrap();
+    f.s.execute("render.preRender", json!({"format": "gif"})).unwrap();
+    let second = f.output(1);
+    assert_ne!(first, second);
+    f.render(json!({})).unwrap();
+    assert_eq!(std::fs::read(first).unwrap(), RENDERED);
+    assert_eq!(std::fs::read(second).unwrap(), RENDERED);
+    assert_eq!(f.exported().len(), 2);
+}
+
+/// Exercise the engine's import and project serialization paths, rather than injecting a
+/// Footage item directly. The importer reads dimensions from a real, generated PNG.
+#[test]
+fn imported_footage_stays_protected_after_the_project_is_reopened() {
+    struct PngProbe;
+    impl crate::Importer for PngProbe {
+        fn probe(&self, path: &str) -> Result<Footage, String> {
+            let (width, height) = image::image_dimensions(path).map_err(|e| e.to_string())?;
+            Ok(Footage { path: path.into(), kind: FootageKind::Still, width, height, has_video: true, ..Default::default() })
+        }
+    }
+    let mut f = Fixture::new("import-reopen");
+    f.s.importer = Some(Arc::new(PngProbe));
+    let path = f.path("plate_00002.png");
+    image::RgbaImage::from_pixel(4, 4, image::Rgba([40, 80, 120, 255])).save(&path).unwrap();
+    let original = std::fs::read(&path).unwrap();
+    let result = f.s.execute("file.import", json!({"paths": [path]})).unwrap();
+    assert_eq!(result["items"].as_array().unwrap().len(), 1);
+    f.comp("Main");
+    f.s.execute("renderQueue.add", json!({"format": "png", "output": f.text("plate_[#####].png")})).unwrap();
+    f.s.execute("file.save", json!({})).unwrap();
+    f.s.execute("file.open", json!({"path": f.text("Project.ecproj")})).unwrap();
+    let error = f.render(json!({})).unwrap_err().to_string();
+    assert!(error.contains("plate_00002.png") && error.contains("footage"), "{error}");
+    assert_eq!(std::fs::read(&path).unwrap(), original);
+    assert!(f.exported().is_empty());
+}
+
+#[test]
+fn a_protected_frame_past_the_probe_limit_is_not_rendered() {
+    struct LastFrame(PathBuf);
+    impl Exporter for LastFrame {
+        fn formats(&self) -> Vec<OutputFormat> {
+            vec![OutputFormat::PngSequence]
+        }
+        fn export(&self, _: &ExportJob, _: &mut dyn FnMut(u64, u64) -> bool) -> Result<ExportResult, String> {
+            // A synthetic exporter writes only the vulnerable late frame, so a broken guard
+            // can be reproduced without creating 100,001 output directories.
+            std::fs::write(&self.0, RENDERED).map_err(|e| e.to_string())?;
+            Ok(ExportResult { path: self.0.to_string_lossy().into_owned(), ..Default::default() })
+        }
+    }
+    let mut f = Fixture::new("late-frame");
+    std::fs::create_dir_all(f.path("f100000")).unwrap();
+    f.footage("f100000/plate.png");
+    f.comp("Main");
+    f.s.execute("comp.settings", json!({"duration": 10000.1})).unwrap();
+    f.s.exporter = Some(Arc::new(LastFrame(f.path("f100000/plate.png"))));
+    f.s.execute("renderQueue.add", json!({"format": "png", "output": f.text("f[######]/plate.png")})).unwrap();
+    let error = f.render(json!({})).unwrap_err().to_string();
+    assert!(error.contains("cannot safely check"), "{error}");
+    assert_eq!(f.read("f100000/plate.png"), SOURCE);
+}
+
+/// A numbered sequence is footage frame by frame: one colliding frame is enough, and nothing of
+/// the item is rendered.
+#[test]
+fn a_sequence_never_replaces_one_of_its_footage_frames() {
+    let mut f = Fixture::new("sequence");
+    f.sequence("shot", 0..5);
+    f.comp("shot");
+    // The default name steps aside as a whole: shot_1_00000.png …
+    f.s.execute("renderQueue.add", json!({"format": "png"})).unwrap();
+    assert_eq!(f.output(0), f.path("shot_1_[#####].png"));
+    f.render(json!({})).unwrap();
+    for n in 0..5 {
+        assert_eq!(f.read(&format!("shot_{n:05}.png")), SOURCE, "frame {n}");
+        assert_eq!(f.read(&format!("shot_1_{n:05}.png")), RENDERED, "frame {n}");
+    }
+
+    // Named by hand, one frame of five is a footage file.
+    let mut f = Fixture::new("sequence-one-frame");
+    f.write("shot_00002.png", SOURCE);
+    let still = Footage { path: f.text("shot_00002.png"), kind: FootageKind::Still, width: 16, height: 16, has_video: true, ..Default::default() };
+    Arc::make_mut(&mut f.s.project).add_item("shot_00002.png", Label::None, None, ItemKind::Footage(still));
+    f.comp("shot");
+    let pattern = f.text("shot_[#####].png");
+    f.s.execute("renderQueue.add", json!({"format": "png", "output": pattern})).unwrap();
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("shot_00002.png"), "{e}");
+    assert_eq!(f.read("shot_00002.png"), SOURCE);
+    assert!(!f.path("shot_00000.png").exists(), "the frames before it were not rendered either");
+    assert!(f.exported().is_empty());
+}
+
+#[test]
+fn ordinary_existing_outputs_keep_the_exporters_replacement_policy() {
+    let mut f = Fixture::new("earlier-render");
+    f.comp("Main");
+    f.s.execute("renderQueue.add", json!({"output": f.text("render.mp4")})).unwrap();
+    f.write("render.mp4", EARLIER);
+    f.render(json!({})).unwrap();
+    assert_eq!(f.read("render.mp4"), RENDERED);
+    assert_eq!(f.s.project.render_queue[0].status, RenderStatus::Done);
+}
+
+#[test]
+fn a_render_with_nothing_in_the_way_needs_no_flag() {
+    let mut f = Fixture::new("free");
+    f.comp("Main");
+    f.s.execute("renderQueue.add", json!({})).unwrap();
+    assert_eq!(f.output(0), f.path("Main.mp4"), "no footage in the way: the comp's own name");
+    f.render(json!({})).unwrap();
+    assert_eq!(f.read("Main.mp4"), RENDERED);
+}
+
+/// Skip Existing Files leaves the frames that exist alone, so they need no answer.
+#[test]
+fn a_sequence_that_skips_existing_frames_needs_no_flag() {
+    let mut f = Fixture::new("skip-existing");
+    f.comp("Main");
+    let pattern = f.text("render_[#####].png");
+    f.s.execute("renderQueue.add", json!({"format": "png", "output": pattern, "skipExisting": true})).unwrap();
+    for n in 0..3 {
+        f.write(&format!("render_{n:05}.png"), EARLIER);
+    }
+    f.render(json!({})).unwrap();
+    assert_eq!(f.read("render_00002.png"), EARLIER);
+    assert_eq!(f.read("render_00003.png"), RENDERED);
+    // Ordinary files still follow the exporter's replacement policy when skipping is off.
+    f.s.execute("renderQueue.setRenderSettings", json!({"index": 1, "skipExisting": false})).unwrap();
+    f.render(json!({})).unwrap();
+    assert_eq!(f.read("render_00002.png"), RENDERED);
+}
+
+/// A link is another name for the file it points to.
+#[test]
+fn a_link_to_the_footage_is_the_footage() {
+    let mut f = Fixture::new("link");
+    f.footage("clip.mov");
+    f.comp("Main");
+    let alias = f.path("render.mov");
+    if link(&f.path("clip.mov"), &alias).is_err() {
+        eprintln!("this account cannot make symbolic links: skipped");
+        return;
+    }
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": f.text("render.mov")})).unwrap();
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("render.mov") && e.contains("footage"), "{e}");
+    assert_eq!(f.read("clip.mov"), SOURCE);
+    assert!(std::fs::symlink_metadata(&alias).unwrap().file_type().is_symlink(), "the link was not replaced either");
+}
+
+/// A hard link to the footage under another name is the same file on disk: replacing it would truncate the footage.
+#[test]
+fn a_hard_link_to_the_footage_is_the_footage() {
+    let mut f = Fixture::new("hardlink");
+    f.footage("clip.mov");
+    f.comp("Main");
+    if std::fs::hard_link(f.path("clip.mov"), f.path("render.mov")).is_err() {
+        eprintln!("this volume cannot make hard links: skipped");
+        return;
+    }
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": f.text("render.mov")})).unwrap();
+    // not even with overwrite
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("render.mov") && e.contains("footage"), "{e}");
+    assert_eq!(f.read("clip.mov"), SOURCE);
+    assert_eq!(f.read("render.mov"), SOURCE, "the other name still leads to the footage");
+    assert!(f.exported().is_empty(), "nothing was rendered");
+}
+
+/// A copy of the footage has its size and bytes, but it is another file: an earlier render may replace it.
+#[test]
+fn a_copy_of_the_footage_is_not_the_footage() {
+    let mut f = Fixture::new("copy");
+    f.footage("clip.mov");
+    f.comp("Main");
+    std::fs::copy(f.path("clip.mov"), f.path("copy.mov")).unwrap();
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": f.text("copy.mov")})).unwrap();
+    f.render(json!({})).unwrap();
+    assert_eq!(f.read("copy.mov"), RENDERED);
+    assert_eq!(f.read("clip.mov"), SOURCE, "the footage is as it was");
+}
+
+/// Footage imported through a linked folder is the same file as the one in the real folder.
+#[test]
+fn footage_reached_through_a_linked_folder_is_still_footage() {
+    let mut f = Fixture::new("linked-folder");
+    std::fs::create_dir_all(f.path("real")).unwrap();
+    std::fs::write(f.path("real").join("clip.mov"), SOURCE).unwrap();
+    if link_dir(&f.path("real"), &f.path("linked")).is_err() {
+        eprintln!("this account cannot link folders: skipped");
+        return;
+    }
+    let via_link =
+        Footage { path: f.path("linked").join("clip.mov").to_string_lossy().into_owned(), kind: FootageKind::Video, has_video: true, ..Default::default() };
+    Arc::make_mut(&mut f.s.project).add_item("clip.mov", Label::None, None, ItemKind::Footage(via_link));
+    f.comp("Main");
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": f.path("real").join("clip.mov").to_string_lossy()})).unwrap();
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("footage"), "{e}");
+    assert_eq!(std::fs::read(f.path("real").join("clip.mov")).unwrap(), SOURCE);
+}
+
+/// Where the volume ignores case, `CLIP.MOV` is `clip.mov`.
+#[test]
+fn another_spelling_of_the_footage_name_is_the_footage_where_the_volume_ignores_case() {
+    let mut f = Fixture::new("case");
+    f.footage("clip.mov");
+    f.comp("Main");
+    if !f.path("CLIP.MOV").exists() {
+        eprintln!("this volume tells the two names apart: skipped");
+        return;
+    }
+    let shouting = f.text("CLIP.MOV");
+    f.s.execute("renderQueue.add", json!({"format": "prores", "output": shouting})).unwrap();
+    let e = f.render(json!({"overwrite": true})).unwrap_err().to_string();
+    assert!(e.contains("footage"), "{e}");
+    assert_eq!(f.read("clip.mov"), SOURCE);
+}
+
+#[test]
+fn save_current_preview_never_replaces_footage() {
+    let mut f = Fixture::new("preview");
+    f.footage("clip.mov");
+    f.comp("Main");
+    let clip = f.text("clip.mov");
+    let e = f.s.execute("render.saveCurrentPreview", json!({"path": clip})).unwrap_err().to_string();
+    assert!(e.contains("clip.mov") && e.contains("footage"), "{e}");
+    assert_eq!(f.read("clip.mov"), SOURCE);
+    assert!(f.exported().is_empty());
+    // Anywhere else it renders.
+    let elsewhere = f.text("preview.mp4");
+    f.s.execute("render.saveCurrentPreview", json!({"path": elsewhere})).unwrap();
+    assert_eq!(f.read("preview.mp4"), RENDERED);
+}
+
+#[test]
+fn save_current_preview_checks_sequence_frames_as_well_as_the_pattern() {
+    let mut f = Fixture::new("preview-sequence");
+    f.sequence("plate", 0..5);
+    f.comp("Main");
+    let error = f.s.execute("render.saveCurrentPreview", json!({"path": f.text("plate_[#####].png")})).unwrap_err().to_string();
+    assert!(error.contains("plate_000") && error.contains("footage"), "{error}");
+    for frame in 0..5 {
+        assert_eq!(f.read(&format!("plate_{frame:05}.png")), SOURCE);
+    }
+    assert!(f.exported().is_empty());
+}
+
+/// A watched folder renders unattended; delete the status file to render a project again.
+#[test]
+fn a_watched_folder_still_renders_a_project_again_over_its_outputs() {
+    let mut f = Fixture::new("watch");
+    f.comp("Main");
+    let out = f.text("Main.mp4");
+    f.s.execute("renderQueue.add", json!({"output": out})).unwrap();
+    f.s.execute("file.save", json!({})).unwrap();
+    f.write("Main.mp4", EARLIER);
+    let folder = f.dir.to_string_lossy().into_owned();
+    let done = crate::commands::watch_folder::poll(&mut f.s, &folder).unwrap();
+    assert_eq!(done.len(), 1, "{done:?}");
+    assert_eq!(done[0]["state"], "done", "{:?}", done[0]);
+    assert_eq!(f.read("Main.mp4"), RENDERED);
+}
diff --git a/crates/project/src/render_queue.rs b/crates/project/src/render_queue.rs
index 1a829630c..c40096905 100644
--- a/crates/project/src/render_queue.rs
+++ b/crates/project/src/render_queue.rs
@@ -1477,22 +1477,56 @@ pub fn expand_template(template: &str, format: OutputFormat, v: &TemplateVars) -
 /// Replace the first run of `#` (optionally in brackets, `[####]`) with the zero-padded frame
 /// number. Paths without a run get `_NNNNN` before the extension.
 pub fn sequence_path(path: &str, frame: i64) -> String {
+    let (before, width, after) = sequence_parts(path);
+    format!("{before}{frame:0width$}{after}")
+}
+
+/// A sequence output path around its frame number: what comes before it, how many digits it is
+/// padded to and what comes after (`out/a_[#####].png` → `out/a_`, 5, `.png`).
+pub fn sequence_parts(path: &str) -> (String, usize, String) {
     if let Some(start) = path.find('#') {
         let len = path[start..].chars().take_while(|c| *c == '#').count();
         let (mut a, mut b) = (start, start + len);
-        if a > 0 && path.as_bytes()[a - 1] == b'[' && path.as_bytes().get(b) == Some(&b']') {
+        if a > 0 && path.as_bytes().get(a - 1) == Some(&b'[') && path.as_bytes().get(b) == Some(&b']') {
             a -= 1;
             b += 1;
         }
-        return format!("{}{:0width$}{}", &path[..a], frame, &path[b..], width = len);
+        return (path[..a].to_string(), len, path[b..].to_string());
     }
     let p = std::path::Path::new(path);
     match p.extension() {
-        Some(ext) => format!("{}_{frame:05}.{}", p.with_extension("").to_string_lossy(), ext.to_string_lossy()),
-        None => format!("{path}_{frame:05}"),
+        Some(ext) => (format!("{}_", p.with_extension("").to_string_lossy()), 5, format!(".{}", ext.to_string_lossy())),
+        None => (format!("{path}_"), 5, String::new()),
     }
 }
 
+/// The frame number `candidate` is the file of, when `path` (a sequence output path) writes it:
+/// the inverse of [`sequence_path`].
+pub fn sequence_frame(path: &str, candidate: &str) -> Option<i64> {
+    let (before, width, after) = sequence_parts(path);
+    let digits = candidate.strip_prefix(before.as_str())?.strip_suffix(after.as_str())?;
+    let frame: i64 = digits.parse().ok()?;
+    (format!("{frame:0width$}") == digits).then_some(frame)
+}
+
+/// `template` with `_n` added to the name: before the frame-number run of a sequence, else before
+/// the extension (`[compName].[fileExtension]` → `[compName]_1.[fileExtension]`,
+/// `[compName]_[#####].[fileExtension]` → `[compName]_1_[#####].[fileExtension]`).
+pub fn numbered_template(template: &str, n: u32) -> String {
+    let at = match template.find('#') {
+        Some(hash) => {
+            // The run's `[`, then the separator that sets it off from the name.
+            let run = if template[..hash].ends_with('[') { hash - 1 } else { hash };
+            if template[..run].ends_with(['_', '-', '.', ' ']) { run - 1 } else { run }
+        }
+        None => {
+            let name = template.rfind(['/', '\\']).map_or(0, |i| i + 1);
+            template[name..].rfind('.').map_or(template.len(), |i| name + i)
+        }
+    };
+    format!("{}_{n}{}", &template[..at], &template[at..])
+}
+
 /// Make a name safe as a file name component.
 pub fn sanitize(name: &str) -> String {
     name.chars().map(|c| if matches!(c, '/' | '\\' | ':' | '*' | '?' | '"' | '<' | '>' | '|') { '_' } else { c }).collect()
@@ -1512,6 +1546,44 @@ mod tests {
         assert_eq!(sequence_path("a.png", 3), "a_00003.png");
     }
 
+    /// `sequence_frame` reads back what `sequence_path` writes, and nothing else.
+    #[test]
+    fn sequence_frames_read_back() {
+        for path in ["out/a_[#####].png", "a###.tif", "a.png", "/x/[compName]/shot_[##].exr", "noext", "dir.v2/clip"] {
+            for frame in [0, 7, 42, 99_999, 123_456, -3] {
+                assert_eq!(sequence_frame(path, &sequence_path(path, frame)), Some(frame), "{path} {frame}");
+            }
+        }
+        let (before, width, after) = sequence_parts("out/a_[#####].png");
+        assert_eq!((before.as_str(), width, after.as_str()), ("out/a_", 5, ".png"));
+        let (before, width, after) = sequence_parts("a.png");
+        assert_eq!((before.as_str(), width, after.as_str()), ("a_", 5, ".png"));
+        // Other numbers, other widths, other names are not frames of the sequence.
+        assert_eq!(sequence_frame("a_[#####].png", "a_0042.png"), None, "padded to four");
+        assert_eq!(sequence_frame("a_[####].png", "a_+042.png"), None, "a sign is not padding");
+        assert_eq!(sequence_frame("a_[#####].png", "a_00042.jpg"), None);
+        assert_eq!(sequence_frame("a_[#####].png", "b_00042.png"), None);
+        assert_eq!(sequence_frame("a_[#####].png", "a_00x42.png"), None);
+        assert_eq!(sequence_frame("a_[#####].png", "a_.png"), None);
+        assert_eq!(sequence_frame("a_[#####].png", "a_99999999999999999999.png"), None, "too big for a frame number");
+    }
+
+    #[test]
+    fn numbered_templates() {
+        assert_eq!(numbered_template(DEFAULT_TEMPLATE, 1), "[compName]_1.[fileExtension]");
+        assert_eq!(numbered_template(DEFAULT_SEQUENCE_TEMPLATE, 2), "[compName]_2_[#####].[fileExtension]");
+        assert_eq!(numbered_template("[compName]_frame.[fileExtension]", 3), "[compName]_frame_3.[fileExtension]");
+        assert_eq!(numbered_template("out/[compName]###.png", 1), "out/[compName]_1###.png");
+        assert_eq!(numbered_template("my.dir/clip", 4), "my.dir/clip_4", "a dot in a folder is not an extension");
+        assert_eq!(numbered_template("clip.v2.mov", 1), "clip.v2_1.mov");
+        assert_eq!(numbered_template("", 1), "_1");
+        assert_eq!(numbered_template("#", 1), "_1#");
+        assert_eq!(numbered_template("[#]", 1), "_1[#]");
+        // A numbered default is still a default: it expands to the numbered name.
+        let v = TemplateVars { comp_name: "footage", project_name: "P", width: 64, height: 36, frame_rate: 30.0, start_frame: 0, end_frame: 29 };
+        assert_eq!(expand_template(&numbered_template(DEFAULT_TEMPLATE, 1), OutputFormat::H264, &v), "footage_1.mp4");
+    }
+
     #[test]
     fn set_format_fixes_names() {
         let mut m = OutputModule::default();
diff --git a/crates/ui-egui/src/i18n.rs b/crates/ui-egui/src/i18n.rs
index 14afe59cc..7f4a77989 100644
--- a/crates/ui-egui/src/i18n.rs
+++ b/crates/ui-egui/src/i18n.rs
@@ -1874,7 +1874,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("comp.settings", "Composition Settings...", "コンポジション設定..."),
     ("comp.setPosterTime", "Set Poster Time", "ポスター時間を設定"),
     ("comp.trimToWorkArea", "Trim Comp to Work Area", "コンポジションをワークエリアにトリミング"),
-    ("comp.cropToRegionOfInterest", "Crop Comp to Region of Interest", "コンポジションを目標範囲にクロップ"),
+    ("comp.cropToRegionOfInterest", "Crop Comp to Region of Interest", "コンポジションを関心領域にクロップ"),
     ("comp.cropToLayerBounds", "Crop Comp to Selected Layer(s) Bounds", "コンポジションを選択レイヤーの境界にクロップ"),
     ("render.addOutputModule", "Add Output Module", "出力モジュールを追加"),
     ("", "Preview", "プレビュー"),
@@ -1927,7 +1927,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.mask.reset", "Reset Mask", "マスクをリセット"),
     ("layer.mask.remove", "Remove Mask", "マスクを削除"),
     ("layer.mask.removeAll", "Remove All Masks", "すべてのマスクを削除"),
-    ("track.mask", "Track Mask", "マスクをトラック"),
+    ("track.mask", "Track Mask", "マスクをトラッキング"),
     ("", "Mode", "モード"),
     ("layer.mask.mode", "None", "なし"),
     ("layer.mask.mode", "Add", "加算"),
@@ -1992,8 +1992,8 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.transform", "Fit to Comp Height", "コンポジションの高さに合わせる"),
     ("layer.autoOrient", "Auto-Orient...", "自動方向..."),
     ("", "Time", "時間"),
-    ("layer.enableTimeRemap", "Enable Time Remapping", "タイムリマップ使用可能"),
-    ("layer.timeReverse", "Time-Reverse Layer", "時間反転レイヤー"),
+    ("layer.enableTimeRemap", "Enable Time Remapping", "時間リマップを有効化"),
+    ("layer.timeReverse", "Time-Reverse Layer", "レイヤーを時間反転"),
     ("layer.timeStretch", "Time Stretch...", "時間伸縮..."),
     ("layer.freezeFrame", "Freeze Frame", "フレームを固定"),
     ("layer.freezeOnLastFrame", "Freeze On Last Frame", "最後のフレームで固定"),
@@ -2061,7 +2061,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.trackMatte", "Matte with Layer Above", "上のレイヤーをマットにする"),
     ("layer.trackMatte", "Matte with Layer Below", "下のレイヤーをマットにする"),
     ("", "Layer Styles", "レイヤースタイル"),
-    ("layer.style.options", "Layer Style Options...", "レイヤースタイルオプション..."),
+    ("layer.style.options", "Layer Style Options...", "レイヤースタイルのオプション..."),
     ("layer.style.convertToEditable", "Convert to Editable Styles", "編集可能なスタイルに変換"),
     ("layer.style.showAll", "Show All", "すべてを表示"),
     ("layer.style.removeAll", "Remove All", "すべてを削除"),
@@ -2090,7 +2090,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.create", "Convert to Editable Text", "編集可能なテキストに変換"),
     ("layer.create", "Create Shapes from Text", "テキストからシェイプを作成"),
     ("layer.create", "Create Masks from Text", "テキストからマスクを作成"),
-    ("layer.create", "Create Shapes from Vector Layer", "ベクトルレイヤーからシェイプを作成"),
+    ("layer.create", "Create Shapes from Vector Layer", "ベクターレイヤーからシェイプを作成"),
     ("layer.create", "Create Keyframes from Data", "データからキーフレームを作成"),
     ("layer.create", "Null Controllers for Positional Points", "位置のポイント用ヌルコントローラー"),
     ("layer.create", "Null Controllers for Path Points", "パスのポイント用ヌルコントローラー"),
@@ -2140,7 +2140,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.applyTextPreset", "Jitter", "ジッター"),
     ("layer.applyTextPreset", "Drop In Lines", "行をドロップイン"),
     ("anim.addKeyframe", "Add Keyframe", "キーフレームを追加"),
-    ("keys.toggleHold", "Toggle Hold Keyframe", "停止したキーフレームの切り替え"),
+    ("keys.toggleHold", "Toggle Hold Keyframe", "ホールドキーフレームの切り替え"),
     ("keys.setMuted", "Mute Keyframes", "キーフレームをミュート"),
     ("keys.setMuted", "Unmute Keyframes", "キーフレームのミュートを解除"),
     ("keys.interpolation", "Keyframe Interpolation...", "キーフレーム補間法..."),
@@ -2156,7 +2156,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.sequence", "Sequence Layers...", "シーケンスレイヤー..."),
     ("keys.timeReverse", "Time-Reverse Keyframes", "時間反転キーフレーム"),
     ("", "Animate Text", "テキストをアニメート"),
-    ("layer.enablePerChar3D", "Enable Per-character 3D", "文字ごとの3Dを使用可能にする"),
+    ("layer.enablePerChar3D", "Enable Per-character 3D", "文字ごとの3Dを有効化"),
     ("layer.addTextAnimator", "Anchor Point", "アンカーポイント"),
     ("layer.addTextAnimator", "Position", "位置"),
     ("layer.addTextAnimator", "Scale", "スケール"),
@@ -2168,7 +2168,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.addTextAnimator", "RGB", "RGB"),
     ("layer.addTextAnimator", "Hue", "色相"),
     ("layer.addTextAnimator", "Saturation", "彩度"),
-    ("layer.addTextAnimator", "Brightness", "明度"),
+    ("layer.addTextAnimator", "Brightness", "明るさ"),
     ("", "Stroke Color", "線のカラー"),
     ("layer.addTextAnimator", "Stroke Width", "線幅"),
     ("", "Front", "前面"),
@@ -2190,12 +2190,12 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("text.removeAllAnimators", "Remove All Text Animators", "すべてのテキストアニメーターを削除"),
     ("prop.setExpression", "Add Expression", "エクスプレッションを追加"),
     ("essential.addProperty", "Add Property to Essential Graphics", "エッセンシャルグラフィックスにプロパティを追加"),
-    ("prop.separateDimensions", "Separate Dimensions", "次元に分割"),
-    ("track.camera", "Track Camera", "カメラをトラック"),
+    ("prop.separateDimensions", "Separate Dimensions", "次元を分離"),
+    ("track.camera", "Track Camera", "カメラをトラッキング"),
     ("track.warpStabilizer", "Warp Stabilizer VFX", "ワープスタビライザーVFX"),
-    ("track.motion", "Track Motion", "モーションをトラック"),
-    ("track.stabilize", "Stabilize Motion", "モーションをスタビライズ"),
-    ("track.property", "Track this Property", "このプロパティをトラック"),
+    ("track.motion", "Track Motion", "モーションをトラッキング"),
+    ("track.stabilize", "Stabilize Motion", "モーションを安定化"),
+    ("track.property", "Track this Property", "このプロパティをトラッキング"),
     ("anim.reveal", "Reveal Properties with Keyframes", "キーフレームのあるプロパティを表示"),
     ("anim.reveal", "Reveal Properties with Animation", "アニメーションのあるプロパティを表示"),
     ("anim.reveal", "Reveal All Modified Properties", "変更されたすべてのプロパティを表示"),
@@ -2275,7 +2275,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("window.workspace", "Default", "初期設定"),
     ("window.workspace", "Review", "レビュー"),
     ("window.workspace", "Learn", "学習"),
-    ("window.workspace", "Small Screen", "小画面"),
+    ("window.workspace", "Small Screen", "小さい画面"),
     ("window.workspace", "Standard", "標準"),
     ("window.workspace", "All Panels", "すべてのパネル"),
     ("window.workspace", "Animation", "アニメーション"),
diff --git a/crates/ui-egui/src/i18n/ui.rs b/crates/ui-egui/src/i18n/ui.rs
index 67a131d75..ec70e3197 100644
--- a/crates/ui-egui/src/i18n/ui.rs
+++ b/crates/ui-egui/src/i18n/ui.rs
@@ -456,7 +456,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("None", "なし"),
     ("Not applied: tick it in the list to add it.", "未適用：リストでチェックを入れると追加されます。"),
     ("Not assigned", "未割り当て"),
-    ("Note: Shadows are only cast from layers with Cast Shadows enabled.", "注意：シャドウは「シャドウを投影」が有効なレイヤーからのみ投影されます。"),
+    ("Note: Shadows are only cast from layers with Cast Shadows enabled.", "注意：「シャドウを落とす」が有効なレイヤーだけがシャドウを落とします。"),
     ("Notify", "通知"),
     ("OK", "OK"),
     ("Offset:", "オフセット:"),
@@ -538,7 +538,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Select a command to change its shortcut.", "ショートカットを変更するコマンドを選択してください。"),
     ("Select a layer to see its effects", "レイヤーを選択するとエフェクトが表示されます"),
     ("Select a layer to see its properties", "レイヤーを選択するとプロパティが表示されます"),
-    ("({}) Selected Objects", "({}) 個の選択されたオブジェクト"),
+    ("({}) Selected Objects", "選択したオブジェクト（{}）"),
     (
         "Select a layer with a mask or shape path (or the path property), or Puppet pins.",
         "マスクまたはシェイプパスのあるレイヤー（またはパスプロパティ）か、パペットピンを選択してください。",
@@ -686,7 +686,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Import Image Sequence", "画像シーケンスを読み込み"),
     ("Import PDF / Illustrator File", "PDF / Illustratorファイルを読み込み"),
     ("Import Photoshop File", "Photoshopファイルを読み込み"),
-    ("Interpret Unlabeled Alpha As", "ラベルのないアルファを変換"),
+    ("Interpret Unlabeled Alpha As", "ラベルのないアルファの解釈"),
     ("Join the ArtCraft Discord", "ArtCraftのDiscordに参加"),
     ("Mercury GPU Acceleration ({})", "Mercury GPUアクセラレーション（{}）"),
     ("Mercury Software Only", "Mercuryソフトウェアのみ"),
@@ -804,7 +804,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Cycle Mask Colors", "新規マスクに別のカラーを使用"),
     ("Use Gradients", "グラデーションを使用"),
     ("Menu Bar", "メニューバー"),
-    ("Grids & Guides", "グリッド＆ガイド"),
+    ("Grids & Guides", "グリッドとガイド"),
     ("Gridline Every", "グリッドの間隔"),
     ("Subdivisions", "分割数"),
     ("Style", "スタイル"),
@@ -836,7 +836,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Ask User", "ユーザーに確認"),
     ("Guess", "推測"),
     ("Ignore", "無視"),
-    ("Straight", "そのまま"),
+    ("Straight", "ストレート"),
     ("Premultiplied", "プリマルチプライ"),
     ("Default Drag Import As", "複数アイテムのドラッグ読み込みの初期設定"),
     ("Footage", "フッテージ"),
@@ -886,7 +886,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Scripting & Expressions", "スクリプトとエクスプレッション"),
     ("Application Scripting", "アプリケーションのスクリプト"),
     ("Allow Scripts to Write Files and Access Network", "スクリプトによるファイルへの書き込みとネットワークへのアクセスを許可"),
-    ("Warn User When Executing Files", "ファイルの実行時にカーソルに警告"),
+    ("Warn User When Executing Files", "ファイルの実行時にユーザーに警告"),
     ("Enable JavaScript Debugger", "JavaScript デバッガーを使用"),
     ("Expressions Editor", "エクスプレッションエディター"),
     ("Font Size", "フォントサイズ"),
@@ -895,7 +895,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Auto-complete", "オートコンプリート"),
     ("Bracket Matching", "対応する括弧をハイライト"),
     ("Word Wrap", "折り返し"),
-    ("Show Expression Error Banner", "式のエラーがある場合に警告バナーを表示"),
+    ("Show Expression Error Banner", "エクスプレッションのエラーがある場合に警告バナーを表示"),
     (
         "Expressions use the JavaScript engine. Script errors report their file and line in the Script Console; there is no step debugger.",
         "エクスプレッションはJavaScriptエンジンを使用します。スクリプトのエラーはファイルと行をスクリプトコンソールに報告します。ステップ実行デバッガーはありません。",
@@ -1004,8 +1004,8 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Create Shapes from Vector Layer", "ベクターレイヤーからシェイプを作成"),
     ("Create Shapes from Text", "テキストからシェイプを作成"),
     ("Create Masks from Text", "テキストからマスクを作成"),
-    ("New Mask", "新しいマスク"),
-    ("Center In View", "ビュー内で中央揃え"),
+    ("New Mask", "新規マスク"),
+    ("Center In View", "ビューの中央に配置"),
     ("Fit to Comp", "コンポジションに合わせる"),
     ("Flip Horizontal", "水平方向に反転"),
     ("Flip Vertical", "垂直方向に反転"),
@@ -1034,8 +1034,8 @@ const JAPANESE: &[(&str, &str)] = &[
     ("All Transform Properties", "すべてのトランスフォームプロパティ"),
     ("Line Anchor", "行のアンカー"),
     ("Line Spacing", "行間"),
-    ("Character Offset", "文字オフセット"),
-    ("Character Value", "文字値"),
+    ("Character Offset", "文字のオフセット"),
+    ("Character Value", "文字の値"),
     ("Fill Color: RGB", "塗りの色: RGB"),
     ("Fill Color: Hue", "塗りの色: 色相"),
     ("Fill Color: Saturation", "塗りの色: 彩度"),
@@ -1061,7 +1061,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("ScriptUI Panel", "ScriptUI パネル"),
     ("Lumetri Scopes", "Lumetri スコープ"),
     ("Media Browser", "メディアブラウザー"),
-    ("Content-Aware Fill", "コンテンツに応じた塗り"),
+    ("Content-Aware Fill", "コンテンツに応じた塗りつぶし"),
     ("Create Nulls From Paths", "パスからヌルを作成"),
     ("VR Comp Editor", "VR コンポジションエディター"),
     ("Media Duration", "メディアの長さ"),
@@ -1096,7 +1096,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Background Color", "背景色"),
     ("Basic", "基本"),
     ("Shutter Angle", "シャッター角度"),
-    ("Shutter Phase", "シャッター位相"),
+    ("Shutter Phase", "シャッターフェーズ"),
     ("Samples Per Frame", "フレームあたりのサンプル数"),
     ("Adaptive Sample Limit", "適応サンプル数の上限"),
     ("X and Y", "X と Y"),
diff --git a/crates/ui-egui/src/panels/markers_ui.rs b/crates/ui-egui/src/panels/markers_ui.rs
index cc08f223d..03c45d32b 100644
--- a/crates/ui-egui/src/panels/markers_ui.rs
+++ b/crates/ui-egui/src/panels/markers_ui.rs
@@ -296,21 +296,13 @@ fn marker(app: &mut EffectcraftApp, ui: &mut egui::Ui, p: &egui::Painter, comp:
                 hx += 5.0;
             }
         }
-        p.line_segment([pos2(xe, y0), pos2(xe, y0 + h)], Stroke::new(1.0, col));
     }
-    p.add(egui::Shape::convex_polygon(marker_shape(x, y0, h), col, Stroke::NONE));
     if !m.comment.is_empty() {
         // The name sits in a small outlined box beside the flag, as in After Effects. It is drawn in the theme's field
         // colours, so it follows Dark, Darker and Light.
         let galley = p.layout_no_wrap(m.comment.lines().next().unwrap_or_default().to_string(), Tokens::ui(10.0), t.text);
-        let (box_w, mut box_x) = (galley.size().x + 8.0, x + 6.0);
-        // A duration that ends under the box would be hidden by its fill: the box steps past the end cap instead.
-        if let Some(xe) = end
-            && xe > box_x
-            && xe < box_x + box_w
-        {
-            box_x = xe + 3.0;
-        }
+        let box_w = galley.size().x + 8.0;
+        let box_x = name_box_x(x, box_w, end, p.clip_rect());
         let box_rect = Rect::from_min_size(pos2(box_x, y0), vec2(box_w, h.max(galley.size().y + 2.0)));
         p.rect(box_rect, t.radius_sm, t.field_bg, Stroke::new(1.0, t.field_border), egui::StrokeKind::Inside);
         p.galley(pos2(box_rect.min.x + 4.0, box_rect.center().y - galley.size().y / 2.0), galley, t.text);
@@ -385,6 +377,33 @@ fn marker(app: &mut EffectcraftApp, ui: &mut egui::Ui, p: &egui::Painter, comp:
     });
 }
 
+fn name_box_x(x: f32, width: f32, end: Option<f32>, clip: Rect) -> f32 {
+    let start = x + 6.0;
+    let right = match end {
+        Some(end) if end > start && end < start + width => end + 3.0,
+        _ => start,
+    };
+    if right + width <= clip.right() {
+        return right;
+    }
+    let left = x - 6.0 - width;
+    if left >= clip.left() {
+        return left;
+    }
+    start
+}
+
+/// Flags and duration handles sit above every name box in their marker strip.
+fn marker_glyphs(p: &egui::Painter, tokens: &Tokens, tm: TMap, marker: &Marker, time: f64, y0: f32, y1: f32) {
+    let color = marker_color(tokens, marker.label);
+    let h = (y1 - y0).min(10.0);
+    p.add(egui::Shape::convex_polygon(marker_shape(tm.x(time), y0, h), color, Stroke::NONE));
+    if marker.duration > Tick(0) {
+        let end = tm.x(time + marker.duration.seconds());
+        p.line_segment([pos2(end, y0), pos2(end, y0 + h)], Stroke::new(1.0, color));
+    }
+}
+
 /// Composition markers in the ruler strip `[y0, y1]`, protected regions over `rows`.
 pub(crate) fn comp_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, comp: &Comp, tm: TMap, strip: Rect, rows: Rect) {
     let p = ui.painter().with_clip_rect(strip);
@@ -398,6 +417,9 @@ pub(crate) fn comp_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, comp: &C
     for (i, m) in comp.markers.iter().enumerate() {
         marker(app, ui, &p, comp, tm, m, m.time.seconds(), MarkerRef { layer: None, index: i }, strip.min.y, strip.max.y);
     }
+    for m in &comp.markers {
+        marker_glyphs(&p, &app.tokens, tm, m, m.time.seconds(), strip.min.y, strip.max.y);
+    }
 }
 
 /// The composition marker bin at the right end of the time ruler (`bin`), as in After Effects
@@ -439,6 +461,9 @@ pub(crate) fn layer_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, clip: R
     for (i, m) in layer.markers.iter().enumerate() {
         marker(app, ui, &p, comp, tm, m, layer.comp_time(m.time).seconds(), MarkerRef { layer: Some(layer.id.0), index: i }, r.min.y + 3.0, r.max.y - 3.0);
     }
+    for m in &layer.markers {
+        marker_glyphs(&p, &app.tokens, tm, m, layer.comp_time(m.time).seconds(), r.min.y + 3.0, r.max.y - 3.0);
+    }
 }
 
 /// The nested comp's markers on a precomp layer's bar (`markers.nested`).
@@ -488,6 +513,21 @@ fn nested_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, p: &egui::Painter
 mod tests {
     use super::*;
 
+    #[test]
+    fn duration_name_box_stays_visible_near_the_right_clip_edge() {
+        let clip = Rect::from_min_max(pos2(0.0, 0.0), pos2(100.0, 20.0));
+        let x = name_box_x(70.0, 20.0, Some(85.0), clip);
+        assert!(x >= clip.left() && x + 20.0 <= clip.right());
+        assert!(x + 20.0 < 70.0 - 4.0, "the left-hand box must not cover its own marker flag");
+        assert!(85.0 < x || 85.0 > x + 20.0, "the end cap must remain outside the box");
+        assert_eq!(name_box_x(20.0, 20.0, Some(35.0), clip), 38.0);
+        for end in [None, Some(72.0), Some(110.0)] {
+            let x = name_box_x(90.0, 20.0, end, clip);
+            assert!(x >= clip.left() && x + 20.0 <= clip.right(), "all right-edge names must remain visible: {end:?}");
+            assert!(x + 20.0 < 90.0 - 4.0);
+        }
+    }
+
     #[test]
     fn marker_dialog_reads_and_writes_every_field() {
         let mut s = effectcraft_engine::Session::default();
diff --git a/crates/ui-egui/tests/it/gpu_test.rs b/crates/ui-egui/tests/it/gpu_test.rs
new file mode 100644
index 000000000..0156fbb4d
--- /dev/null
+++ b/crates/ui-egui/tests/it/gpu_test.rs
@@ -0,0 +1,43 @@
+//! Shared device-creation gate for the integration-test executable.
+
+static GPU_TEST_LOCK: std::sync::Mutex<()> = std::sync::Mutex::new(());
+
+thread_local! {
+    static HELD: std::cell::Cell<bool> = const { std::cell::Cell::new(false) };
+}
+
+pub(crate) struct Guard {
+    held: Option<std::sync::MutexGuard<'static, ()>>,
+}
+
+impl Drop for Guard {
+    fn drop(&mut self) {
+        if self.held.is_some() {
+            HELD.with(|held| held.set(false));
+        }
+    }
+}
+
+/// GPU-backed harnesses hold this for their whole test; screenshots may enter it again.
+pub(crate) fn lock() -> Guard {
+    let held = if HELD.with(std::cell::Cell::get) {
+        None
+    } else {
+        let guard = GPU_TEST_LOCK.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+        HELD.with(|held| held.set(true));
+        Some(guard)
+    };
+    Guard { held }
+}
+
+/// Plain harnesses create their GPU renderer lazily on the first screenshot.
+pub(crate) trait RenderSerial {
+    fn render_serialized(&mut self) -> Result<image::RgbaImage, String>;
+}
+
+impl<State> RenderSerial for egui_kittest::Harness<'_, State> {
+    fn render_serialized(&mut self) -> Result<image::RgbaImage, String> {
+        let _device = lock();
+        self.render().map_err(|error| format!("{error:?}"))
+    }
+}
diff --git a/crates/ui-egui/tests/it/main.rs b/crates/ui-egui/tests/it/main.rs
index 7d38e3089..17fe06cae 100644
--- a/crates/ui-egui/tests/it/main.rs
+++ b/crates/ui-egui/tests/it/main.rs
@@ -1,5 +1,6 @@
 //! The crate's integration tests, one binary (each module is a former `tests/<name>.rs`).
 
+mod gpu_test;
 mod native_menu_text_keys;
 mod render_queue_snapshot;
 mod shared_docking_ui;
diff --git a/crates/ui-egui/tests/it/render_queue_snapshot.rs b/crates/ui-egui/tests/it/render_queue_snapshot.rs
index d054511af..27054119d 100644
--- a/crates/ui-egui/tests/it/render_queue_snapshot.rs
+++ b/crates/ui-egui/tests/it/render_queue_snapshot.rs
@@ -2,6 +2,7 @@
 //! adapter); run with
 //! `RQ_SNAPSHOT=/abs/out.png cargo test -p effectcraft-ui-egui --test it render_queue_snapshot:: -- --ignored`.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::render_queue::RenderStatus;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -34,7 +35,7 @@ fn render_queue_panel_snapshot() {
     h.ctx.data_mut(|d| d.insert_temp(egui::Id::unique("rq-ui"), (ids, None::<u64>)));
     h.state_mut().show_panel(effectcraft_ui_egui::dock::PanelKind::RenderQueue);
     h.run_steps(4);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     let out = std::env::var("RQ_SNAPSHOT").unwrap_or_else(|_| concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out/render_queue.png").into());
     if let Some(d) = std::path::Path::new(&out).parent() {
         std::fs::create_dir_all(d).unwrap();
@@ -57,7 +58,7 @@ fn templates_dialog_snapshot() {
     let mut h = Harness::builder().with_size(egui::vec2(1400.0, 900.0)).build_eframe(|_| app.take().expect("app"));
     h.run_steps(4);
     assert!(h.state().dialog.is_some(), "the Templates dialog is open");
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     let out = std::env::var("RQ_TEMPLATES_SNAPSHOT").unwrap_or_else(|_| concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out/rq_templates.png").into());
     if let Some(d) = std::path::Path::new(&out).parent() {
         std::fs::create_dir_all(d).unwrap();
diff --git a/crates/ui-egui/tests/it/ui_3d.rs b/crates/ui-egui/tests/it/ui_3d.rs
index a654f745c..0f7a10b7e 100644
--- a/crates/ui-egui/tests/it/ui_3d.rs
+++ b/crates/ui-egui/tests/it/ui_3d.rs
@@ -2,6 +2,7 @@
 //! with wgpu and writes PNGs when `EC_SNAPSHOT_DIR` is set (`cargo test -p effectcraft-ui-egui
 //! --test it ui_3d:: -- --ignored`); the other test only runs the UI logic.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::render::three_d::View3D;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -109,6 +110,7 @@ fn camera_and_light_dialogs_create_layers() {
 #[test]
 #[ignore = "renders with wgpu; run with --ignored (set EC_SNAPSHOT_DIR to keep PNGs)"]
 fn snapshot() {
+    let _device = crate::gpu_test::lock();
     let dir = std::env::var("EC_SNAPSHOT_DIR").ok();
     let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).with_pixels_per_point(1.0).wgpu().build_eframe(|_| app());
     let shots: [(&str, Option<&str>); 4] =
@@ -118,7 +120,7 @@ fn snapshot() {
             h.state_mut().session.execute(c, json!({})).unwrap();
         }
         settle(&mut h);
-        let img = h.render().expect("render");
+        let img = h.render_serialized().expect("render");
         if let Some(d) = &dir {
             img.save(format!("{d}/ui3d_{name}.png")).unwrap();
         }
@@ -126,14 +128,14 @@ fn snapshot() {
     let ctx = h.ctx.clone();
     effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "layer.newCamera", json!({})).unwrap();
     h.run_steps(3);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Some(d) = &dir {
         img.save(format!("{d}/ui3d_camera_dialog.png")).unwrap();
     }
     h.state_mut().dialog = None;
     effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "layer.newLight", json!({})).unwrap();
     h.run_steps(3);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Some(d) = &dir {
         img.save(format!("{d}/ui3d_light_dialog.png")).unwrap();
     }
@@ -143,7 +145,7 @@ fn snapshot() {
     h.state_mut().session.execute("layer.select", json!({"layers": ["Card Blue"]})).unwrap();
     effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "timeline.reveal.rotation", json!({})).unwrap();
     settle(&mut h);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Some(d) = &dir {
         img.save(format!("{d}/ui3d_reveal_rotation.png")).unwrap();
     }
diff --git a/crates/ui-egui/tests/it/ui_blank_context_menus.rs b/crates/ui-egui/tests/it/ui_blank_context_menus.rs
index 52417326f..84080be08 100644
--- a/crates/ui-egui/tests/it/ui_blank_context_menus.rs
+++ b/crates/ui-egui/tests/it/ui_blank_context_menus.rs
@@ -1,4 +1,5 @@
 //! Right-click actions in the blank Project and Timeline areas, and on Timeline property names.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::ItemKind;
 use effectcraft_ui_egui::dock::WorkspaceExt as _;
@@ -20,7 +21,7 @@ fn rect(h: &Harness<'_, EffectcraftApp>, id: &str) -> Rect {
 }
 fn snapshot(h: &mut Harness<'_, EffectcraftApp>, name: &str) {
     if let Ok(dir) = std::env::var("BLANK_CONTEXT_MENU_SNAPSHOTS") {
-        h.render().unwrap().save(format!("{dir}/{name}.png")).unwrap();
+        h.render_serialized().unwrap().save(format!("{dir}/{name}.png")).unwrap();
     }
 }
 fn right_click(h: &mut Harness<'_, EffectcraftApp>, p: Pos2) {
diff --git a/crates/ui-egui/tests/it/ui_camera_tracker.rs b/crates/ui-egui/tests/it/ui_camera_tracker.rs
index 8c4be61a7..619d7c7c5 100644
--- a/crates/ui-egui/tests/it/ui_camera_tracker.rs
+++ b/crates/ui-egui/tests/it/ui_camera_tracker.rs
@@ -3,6 +3,7 @@
 //! The solve is a synthetic one written into the effect (the analysis itself is tested in the
 //! engine and track crates).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::effects::camera_tracker as ct;
 use effectcraft_engine::track::camtrack::{CameraSolve, ShotType, SolveMethod, SolvedFrame, SolvedPoint};
@@ -186,6 +187,7 @@ fn blender_export_button_opens_python_dialog_and_writes_scene() {
     let shot = std::env::var("EFFECTCRAFT_BLENDER_UI_SNAPSHOT").ok();
     let builder = Harness::builder().with_size(egui::vec2(1600.0, 1000.0));
     let builder = if shot.is_some() { builder.wgpu() } else { builder };
+    let _device = shot.is_some().then(crate::gpu_test::lock);
     let mut h = builder.build_eframe(|_| a);
     h.state_mut().show_panel(PanelKind::EffectControls);
     h.run_steps(5);
@@ -272,6 +274,7 @@ fn settle(h: &mut Harness<'_, EffectcraftApp>) {
 #[test]
 #[ignore = "analyses the demo's 3D Showcase and renders with wgpu; run with --ignored (set EC_SNAPSHOT_DIR to keep PNGs)"]
 fn snapshot_showcase_track() {
+    let _device = crate::gpu_test::lock();
     let dir = std::env::var("EC_SNAPSHOT_DIR").ok();
     let mut s = Session::default();
     s.execute("file.openDemoProject", json!({})).unwrap();
@@ -290,7 +293,7 @@ fn snapshot_showcase_track() {
     h.input_mut().events.push(egui::Event::PointerMoved(r.center() + egui::vec2(12.0, 12.0)));
     h.run_steps(2);
     if let Some(d) = &dir {
-        h.render().expect("render").save(format!("{d}/camera_tracker_hover.png")).unwrap();
+        h.render_serialized().expect("render").save(format!("{d}/camera_tracker_hover.png")).unwrap();
     }
     let sel: Vec<u64> = pts.iter().take(5).filter_map(|i| i.rsplit('.').next()?.parse().ok()).collect();
     h.state_mut().session.execute("camera.selectPoints", json!({"points": sel})).unwrap();
@@ -298,6 +301,6 @@ fn snapshot_showcase_track() {
     h.state_mut().session.execute("layer.select", json!({"layers": ["#3"]})).unwrap();
     settle(&mut h);
     if let Some(d) = &dir {
-        h.render().expect("render").save(format!("{d}/camera_tracker_solid.png")).unwrap();
+        h.render_serialized().expect("render").save(format!("{d}/camera_tracker_solid.png")).unwrap();
     }
 }
diff --git a/crates/ui-egui/tests/it/ui_character_eyedropper.rs b/crates/ui-egui/tests/it/ui_character_eyedropper.rs
index ea2578a0d..ea4eecd99 100644
--- a/crates/ui-egui/tests/it/ui_character_eyedropper.rs
+++ b/crates/ui-egui/tests/it/ui_character_eyedropper.rs
@@ -1,4 +1,5 @@
 //! Character Fill and Stroke can sample a displayed Composition pixel.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, commands::text_edit::layer_doc, project::LayerId};
 use effectcraft_ui_egui::{
     EffectcraftApp,
@@ -37,6 +38,7 @@ fn settle(h: &mut Harness<'_, EffectcraftApp>) {
 
 #[test]
 fn character_fill_eyedropper_samples_viewer_and_keeps_text_selection() {
+    let _device = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"width": 320, "height": 180, "duration": 2})).unwrap();
     s.execute("layer.newSolid", json!({"name": "Background", "color": "#20c040"})).unwrap();
@@ -64,6 +66,7 @@ fn character_fill_eyedropper_samples_viewer_and_keeps_text_selection() {
 
 #[test]
 fn character_stroke_eyedropper_samples_viewer() {
+    let _device = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"width": 320, "height": 180, "duration": 2})).unwrap();
     s.execute("layer.newSolid", json!({"name": "brat green", "color": "#8ACE00"})).unwrap();
@@ -79,7 +82,7 @@ fn character_stroke_eyedropper_samples_viewer() {
     settle(&mut h);
     click_auto(&mut h, "character.stroke.eyedropper");
     if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-        h.render().unwrap().save(format!("{dir}/character-eyedropper.png")).unwrap();
+        h.render_serialized().unwrap().save(format!("{dir}/character-eyedropper.png")).unwrap();
     }
     let sample = comp_to_screen(&h.ctx, [20.0, 20.0]).unwrap();
     click(&mut h, sample);
diff --git a/crates/ui-egui/tests/it/ui_dock_resize.rs b/crates/ui-egui/tests/it/ui_dock_resize.rs
index 863fe697e..11ca740cb 100644
--- a/crates/ui-egui/tests/it/ui_dock_resize.rs
+++ b/crates/ui-egui/tests/it/ui_dock_resize.rs
@@ -1,5 +1,6 @@
 //! Shared pane resizing in the full application, including application shortcut ownership.
 
+use crate::gpu_test::RenderSerial;
 use craft_ui::docking::{Divider, DockArea, Hit};
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -16,7 +17,7 @@ fn snapshots(h: &mut Harness<'_, EffectcraftApp>, directory: Option<&std::path::
         let ctx = h.ctx.clone();
         h.state_mut().set_theme(&ctx, theme);
         h.run_steps(3);
-        h.render().unwrap().save(directory.join(format!("effectcraft-{phase}-{name}.png"))).unwrap();
+        h.render_serialized().unwrap().save(directory.join(format!("effectcraft-{phase}-{name}.png"))).unwrap();
     }
     let ctx = h.ctx.clone();
     h.state_mut().set_theme(&ctx, ThemeKind::Dark);
@@ -32,6 +33,7 @@ fn first_size(h: &Harness<'_, EffectcraftApp>) -> f32 {
 
 #[test]
 fn focused_dock_resize_owns_arrows_and_keeps_pointer_dragging() {
+    let _device = crate::gpu_test::lock();
     let mut session = Session::default();
     session.execute("comp.new", json!({"name": "Split test", "width": 160, "height": 90, "duration": 1})).unwrap();
     session.execute("layer.newSolid", json!({"name": "Selected", "color": [1.0, 0.0, 0.0, 1.0]})).unwrap();
diff --git a/crates/ui-egui/tests/it/ui_env_light_gpu.rs b/crates/ui-egui/tests/it/ui_env_light_gpu.rs
index e88f0a2a4..185980fb6 100644
--- a/crates/ui-egui/tests/it/ui_env_light_gpu.rs
+++ b/crates/ui-egui/tests/it/ui_env_light_gpu.rs
@@ -44,6 +44,7 @@ fn same_adapter(name: String) -> eframe::egui_wgpu::WgpuSetup {
 /// viewer's GPU frames change when the light is added.
 #[test]
 fn environment_light_lights_the_scene_on_the_gpu() {
+    let _device = crate::gpu_test::lock();
     let Some(probe) = effectcraft_gpu::Gpu::headless() else {
         eprintln!("no GPU adapter: skipping");
         return;
diff --git a/crates/ui-egui/tests/it/ui_font_search.rs b/crates/ui-egui/tests/it/ui_font_search.rs
index 77984cf6b..44b650be4 100644
--- a/crates/ui-egui/tests/it/ui_font_search.rs
+++ b/crates/ui-egui/tests/it/ui_font_search.rs
@@ -1,4 +1,5 @@
 //! Real keyboard/pointer coverage for the font menus in both text panels.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, commands::text_edit::layer_doc, project::LayerId};
 use effectcraft_ui_egui::{EffectcraftApp, dock::PanelKind};
 use egui::{Event, Key, Modifiers, PointerButton};
@@ -29,6 +30,7 @@ fn type_text(h: &mut Harness<'_, EffectcraftApp>, text: &str) {
 
 #[test]
 fn font_search_filters_selects_and_undoes_in_both_panels() {
+    let _device = crate::gpu_test::lock();
     for (panel, prefix) in [(PanelKind::Character, "character.font"), (PanelKind::Properties, "properties.text.font")] {
         let mut s = Session::default();
         s.execute("comp.new", json!({"width": 320, "height": 180})).unwrap();
@@ -56,7 +58,7 @@ fn font_search_filters_selects_and_undoes_in_both_panels() {
         assert!(!rows.is_empty());
         assert!(rows.iter().all(|r| r.label.to_lowercase().contains("jetbrains")));
         if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-            h.render().unwrap().save(format!("{dir}/{prefix}-search.png")).unwrap();
+            h.render_serialized().unwrap().save(format!("{dir}/{prefix}-search.png")).unwrap();
         }
         assert_eq!(layer_doc(&h.state().session, LayerId(lid)).unwrap().font, "Inter", "typing only filters");
         key(&mut h, Key::Enter);
@@ -76,7 +78,7 @@ fn font_search_filters_selects_and_undoes_in_both_panels() {
         // Reopening clears the previous query, and mouse selection still works.
         h.run_steps(2);
         if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-            h.render().unwrap().save(format!("{dir}/{prefix}-reopened.png")).unwrap();
+            h.render_serialized().unwrap().save(format!("{dir}/{prefix}-reopened.png")).unwrap();
         }
         assert!(h.state().auto.query(&format!("{prefix}.option.")).len() > 1);
         type_text(&mut h, "JetBrains");
diff --git a/crates/ui-egui/tests/it/ui_gpu.rs b/crates/ui-egui/tests/it/ui_gpu.rs
index 643d99492..d5d432db3 100644
--- a/crates/ui-egui/tests/it/ui_gpu.rs
+++ b/crates/ui-egui/tests/it/ui_gpu.rs
@@ -53,6 +53,7 @@ fn small_session() -> Session {
 /// composites on the CPU. The worker is held on a gate so the "preparing" state is observable.
 #[test]
 fn the_interface_draws_and_composites_on_the_cpu_while_the_gpu_compositor_is_built() {
+    let _device = crate::gpu_test::lock();
     if !any_adapter() {
         eprintln!("no wgpu adapter: skipping");
         return;
@@ -111,6 +112,7 @@ fn the_interface_draws_and_composites_on_the_cpu_while_the_gpu_compositor_is_bui
 /// thread, not under the UI: the window keeps drawing on the CPU and says why.
 #[test]
 fn a_compositor_build_that_panics_leaves_the_viewer_on_the_cpu() {
+    let _device = crate::gpu_test::lock();
     if !any_adapter() {
         eprintln!("no wgpu adapter: skipping");
         return;
@@ -153,6 +155,7 @@ fn same_adapter(name: String) -> eframe::egui_wgpu::WgpuSetup {
 
 #[test]
 fn viewer_draws_gpu_frames_that_match_the_cpu() {
+    let _device = crate::gpu_test::lock();
     let Some(probe) = effectcraft_gpu::Gpu::headless() else {
         eprintln!("no GPU adapter: skipping");
         return;
diff --git a/crates/ui-egui/tests/it/ui_guide_layers.rs b/crates/ui-egui/tests/it/ui_guide_layers.rs
index 37158658f..92196f5f1 100644
--- a/crates/ui-egui/tests/it/ui_guide_layers.rs
+++ b/crates/ui-egui/tests/it/ui_guide_layers.rs
@@ -1,6 +1,7 @@
 //! Guide Layer in the layer context menus (Timeline rows and the Composition viewer), a plain item
 //! (no check mark) that toggles the switch on the selection, and the guide mark by a guide layer's
 //! name.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::LayerId;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -45,7 +46,7 @@ fn guide(h: &Harness<'_, EffectcraftApp>, id: LayerId) -> bool {
 
 fn snapshot(h: &mut Harness<'_, EffectcraftApp>, name: &str) {
     if let Ok(dir) = std::env::var("GUIDE_LAYER_SNAPSHOTS") {
-        h.render().unwrap().save(format!("{dir}/{name}.png")).unwrap();
+        h.render_serialized().unwrap().save(format!("{dir}/{name}.png")).unwrap();
     }
 }
 
diff --git a/crates/ui-egui/tests/it/ui_layer_source_picker.rs b/crates/ui-egui/tests/it/ui_layer_source_picker.rs
index 78a0f8821..ca10e4249 100644
--- a/crates/ui-egui/tests/it/ui_layer_source_picker.rs
+++ b/crates/ui-egui/tests/it/ui_layer_source_picker.rs
@@ -3,6 +3,7 @@
 //! Effect Controls' layer parameters (a Displacement Map's layer) pick through the same widget,
 //! and both write an undoable `prop.set`.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::keyframe::Value;
 use effectcraft_engine::project::LayerId;
@@ -183,6 +184,7 @@ fn effect_controls_layer_param_picks_through_the_shared_widget() {
 #[test]
 #[ignore = "renders with wgpu; run with --ignored (set EC_SNAPSHOT_DIR to keep PNGs)"]
 fn snapshot_source_dropdown_open_and_chosen() {
+    let _device = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"name": "Main", "width": 1280, "height": 720, "frameRate": 30, "duration": 5})).unwrap();
     s.execute("comp.settings", json!({"renderer": "advanced3D"})).unwrap();
@@ -200,7 +202,7 @@ fn snapshot_source_dropdown_open_and_chosen() {
     h.run_steps(4);
     let save = |h: &mut Harness<'_, EffectcraftApp>, name: &str| {
         if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-            h.render().expect("render").save(format!("{dir}/{name}")).expect("save");
+            h.render_serialized().expect("render").save(format!("{dir}/{name}")).expect("save");
         }
     };
     save(&mut h, "source_unset.png");
diff --git a/crates/ui-egui/tests/it/ui_marker_names.rs b/crates/ui-egui/tests/it/ui_marker_names.rs
index 99adf41f3..190bd77bb 100644
--- a/crates/ui-egui/tests/it/ui_marker_names.rs
+++ b/crates/ui-egui/tests/it/ui_marker_names.rs
@@ -8,16 +8,13 @@ use effectcraft_ui_egui::theme::ThemeKind;
 use egui_kittest::Harness;
 use serde_json::json;
 
-/// One render at a time: two tests creating a GPU device together crash some Vulkan loaders.
-static RENDER: std::sync::Mutex<()> = std::sync::Mutex::new(());
-
 fn close(got: [u8; 4], want: egui::Color32) -> bool {
     got[..3].iter().zip(want.to_array()).all(|(a, b)| a.abs_diff(b) <= 3)
 }
 
 #[test]
 fn the_name_box_follows_the_theme() {
-    let _one_at_a_time = RENDER.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _one_at_a_time = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"name": "Song", "width": 640, "height": 360, "duration": 4})).unwrap();
     s.execute("layer.newSolid", json!({"name": "Bed", "color": "#204060", "width": 640, "height": 360})).unwrap();
@@ -58,7 +55,7 @@ fn the_name_box_follows_the_theme() {
 /// stays visible: the cap is drawn, the bar shows left of it, and the box starts after it.
 #[test]
 fn a_short_duration_stays_visible_beside_the_name_box() {
-    let _one_at_a_time = RENDER.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _one_at_a_time = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"name": "Song", "width": 640, "height": 360, "duration": 4})).unwrap();
     s.execute("layer.newSolid", json!({"name": "Bed", "color": "#204060", "width": 640, "height": 360})).unwrap();
@@ -95,3 +92,29 @@ fn a_short_duration_stays_visible_beside_the_name_box() {
     let fill = at(xe + 3.0 + 2.5, mid);
     assert!(close(fill, tokens.field_bg), "the box begins after the end cap: {fill:?}, field_bg {:?}", tokens.field_bg);
 }
+
+#[test]
+fn a_later_name_box_does_not_hide_an_earlier_duration_cap() {
+    let _one_at_a_time = crate::gpu_test::lock();
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"width": 640, "height": 360, "duration": 4})).unwrap();
+    s.execute("markers.set", json!({"new": true, "time": 1.0, "duration": 0.5, "label": "Red"})).unwrap();
+    s.execute("markers.set", json!({"new": true, "time": 1.3, "comment": "This name overlaps the earlier endpoint", "label": "Blue"})).unwrap();
+    let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).build_eframe(move |_| EffectcraftApp::new(s));
+    h.run_steps(5);
+    let a = h.state().auto.find("timeline.marker.0").unwrap().rect;
+    let b = h.state().auto.find("timeline.marker.1").unwrap().rect;
+    let x = |r: [f32; 4]| r[0] + r[2] / 2.0;
+    let end = x(a) + (x(b) - x(a)) * 0.5 / 0.3;
+    let y = a[1] + 1.0 + (a[3] - 1.0).min(10.0) / 2.0;
+    let image = h.render().unwrap();
+    if let Some(dir) = std::env::var_os("MARKER_NAMES_SNAPSHOT") {
+        image.save(std::path::Path::new(&dir).join("marker-overlapping-cap.png")).unwrap();
+    }
+    let scale = image.width() as f32 / 1600.0;
+    let cap = (-1..=1)
+        .map(|offset| image.get_pixel(((end + offset as f32) * scale) as u32, (y * scale) as u32).0)
+        .max_by_key(|pixel| i32::from(pixel[0]) - i32::from(pixel[1]))
+        .unwrap();
+    assert!(i32::from(cap[0]) - i32::from(cap[1]) > 40, "the earlier red duration cap stays above the later name: {cap:?}");
+}
diff --git a/crates/ui-egui/tests/it/ui_media_browser_cache.rs b/crates/ui-egui/tests/it/ui_media_browser_cache.rs
index ddfc53e22..44ca9dd81 100644
--- a/crates/ui-egui/tests/it/ui_media_browser_cache.rs
+++ b/crates/ui-egui/tests/it/ui_media_browser_cache.rs
@@ -1,3 +1,4 @@
+use crate::gpu_test::RenderSerial;
 use std::sync::{
     Arc, Mutex,
     atomic::{AtomicBool, Ordering},
@@ -140,6 +141,6 @@ fn browser_cache_refreshes_filters_navigates_and_recovers_from_errors() {
     assert_eq!(names(&listing(&h, false).1), ["Sub", "Added.csv", "Clip.csv", "From action.csv"]);
     assert!(h.state().auto.find("mediaBrowser.entry.Clip.csv").is_some());
     if let Ok(path) = std::env::var("MEDIA_BROWSER_SNAPSHOT") {
-        h.render().unwrap().save(path).unwrap();
+        h.render_serialized().unwrap().save(path).unwrap();
     }
 }
diff --git a/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs b/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs
index dff60ddd0..8372b2be5 100644
--- a/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs
+++ b/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs
@@ -1,3 +1,4 @@
+use crate::gpu_test::RenderSerial;
 use std::sync::Arc;
 
 use effectcraft_engine::{
@@ -74,7 +75,7 @@ fn file_folder_and_virtual_paths_copy_from_the_context_menu_without_document_cha
         if name == "作品 clip.csv"
             && let Ok(file) = std::env::var("MEDIA_BROWSER_COPY_SNAPSHOT")
         {
-            h.render().unwrap().save(file).unwrap();
+            h.render_serialized().unwrap().save(file).unwrap();
         }
         assert_eq!(click(&mut h, &id, PointerButton::Primary), [path]);
         h.run_steps(3);
diff --git a/crates/ui-egui/tests/it/ui_menus.rs b/crates/ui-egui/tests/it/ui_menus.rs
index 8501f6b52..512f1f376 100644
--- a/crates/ui-egui/tests/it/ui_menus.rs
+++ b/crates/ui-egui/tests/it/ui_menus.rs
@@ -1,6 +1,7 @@
 //! The menu bar from the keyboard, and the app's shortcuts waiting while a menu is open (#279)
 //! (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::EffectcraftApp;
 use egui::{Event, Key, Modifiers, Pos2, Rect, pos2, vec2};
@@ -226,7 +227,7 @@ fn relink_is_reachable_through_the_dependencies_menu() {
     h.run_steps(8);
     let relink = h.query_by_label_contains("Relink Missing Footage").unwrap().rect();
     if let Some(path) = std::env::var_os("EFFECTCRAFT_RELINK_MENU_SNAPSHOT") {
-        h.render().unwrap().save(path).unwrap();
+        h.render_serialized().unwrap().save(path).unwrap();
     }
     click_at(&mut h, relink.center());
     assert!(picked.get());
diff --git a/crates/ui-egui/tests/it/ui_panels.rs b/crates/ui-egui/tests/it/ui_panels.rs
index 6d06c6bf7..2c2d650e9 100644
--- a/crates/ui-egui/tests/it/ui_panels.rs
+++ b/crates/ui-egui/tests/it/ui_panels.rs
@@ -2,6 +2,7 @@
 //! registers its automation ids; the Footage panel's buttons edit into the comp; the Progress
 //! panel lists and cancels a job; Lumetri Scopes switch scope through their dropdown.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_ui_egui::dock::WorkspaceExt as _;
 use std::sync::Arc;
 
@@ -448,7 +449,7 @@ fn panels_snapshot() {
         }
         open(&mut h, panel);
         h.run_steps(3);
-        let img = h.render().expect("render");
+        let img = h.render_serialized().expect("render");
         img.save(format!("{dir}/{panel}{scope}.png")).unwrap();
     }
 }
diff --git a/crates/ui-egui/tests/it/ui_presets_folder.rs b/crates/ui-egui/tests/it/ui_presets_folder.rs
index e11efe944..1bcd9189c 100644
--- a/crates/ui-egui/tests/it/ui_presets_folder.rs
+++ b/crates/ui-egui/tests/it/ui_presets_folder.rs
@@ -1,5 +1,6 @@
 //! Effects & Presets: copy the configured folder path through the contents menu.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::panels::effects_presets::PresetFile;
 use effectcraft_ui_egui::{ControlRequest, EffectcraftApp, control, dock::PanelKind};
@@ -52,7 +53,7 @@ fn presets_menu_copies_the_configured_folder_without_editing_the_project() {
         click(&mut h, "effects.menu");
         h.run_steps(3);
         if let Ok(path) = std::env::var("PRESETS_FOLDER_SNAPSHOT") {
-            h.render().unwrap().save(path).unwrap();
+            h.render_serialized().unwrap().save(path).unwrap();
         }
         assert_eq!(click(&mut h, "effects.copyPresetsFolderPath"), [expected.as_str()]);
         h.run_steps(2);
@@ -156,7 +157,7 @@ fn shared_preset_rows_search_apply_and_undo_the_selected_definition() {
         assert_eq!(h.state().session.active_comp().unwrap().layers[0].props.prop("transform/opacity").unwrap().value.as_f64(), expected);
         assert_eq!(h.state().session.history.undo.len(), history + 1);
         if let Ok(dir) = std::env::var("PRESET_CACHE_SNAPSHOTS") {
-            h.render().unwrap().save(format!("{dir}/{name}.png")).unwrap();
+            h.render_serialized().unwrap().save(format!("{dir}/{name}.png")).unwrap();
         }
         h.state_mut().session.execute("edit.undo", json!({})).unwrap();
         h.run_steps(2);
diff --git a/crates/ui-egui/tests/it/ui_script_console.rs b/crates/ui-egui/tests/it/ui_script_console.rs
index e705a20b7..9430bc7a2 100644
--- a/crates/ui-egui/tests/it/ui_script_console.rs
+++ b/crates/ui-egui/tests/it/ui_script_console.rs
@@ -1,6 +1,7 @@
 //! Window ▸ Script Console: the panel shows, runs JavaScript through `script.run` (persistent
 //! context) and logs output, results and errors (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_ui_egui::EffectcraftApp;
 use effectcraft_ui_egui::dock::PanelKind;
 use egui_kittest::Harness;
@@ -59,7 +60,7 @@ fn script_console_snapshot() {
     }
     h.state_mut().ui.script_console.input = "app.project.numItems".into();
     h.run_steps(3);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     let out = std::env::var("SC_SNAPSHOT").unwrap_or_else(|_| concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out/script_console.png").into());
     if let Some(d) = std::path::Path::new(&out).parent() {
         std::fs::create_dir_all(d).unwrap();
diff --git a/crates/ui-egui/tests/it/ui_scriptui.rs b/crates/ui-egui/tests/it/ui_scriptui.rs
index 0a924bb65..a905ebc5a 100644
--- a/crates/ui-egui/tests/it/ui_scriptui.rs
+++ b/crates/ui-egui/tests/it/ui_scriptui.rs
@@ -2,6 +2,7 @@
 //! windows (clicks reach the script's handlers), the branching History panel, and the Window /
 //! File ▸ Scripts menus listing scripts (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_ui_egui::EffectcraftApp;
 use effectcraft_ui_egui::dock::PanelKind;
 use effectcraft_ui_egui::dock::WorkspaceExt as _;
@@ -210,6 +211,7 @@ fn history_panel_jumps_between_branches() {
 /// onDraw fills of concave paths and real images (drawImage, image controls), rendered.
 #[test]
 fn on_draw_concave_fills_and_images_render() {
+    let _device = crate::gpu_test::lock();
     let dir = std::env::temp_dir().join(format!("effectcraft-scriptui-img-{}", std::process::id()));
     std::fs::create_dir_all(&dir).unwrap();
     let png = dir.join("green.png");
@@ -244,7 +246,7 @@ fn on_draw_concave_fills_and_images_render() {
     let g = &win.root.children[0];
     assert!(matches!(&g.draw[1], effectcraft_engine::scriptui::DrawOp::Image { image: Some(i), .. } if i.src.as_deref() == Some(png.as_str())));
     assert_eq!(win.root.children[1].image.as_ref().and_then(|i| i.src.clone()).as_deref(), Some(png.as_str()));
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Ok(d) = std::env::var("EC_SNAPSHOT_DIR") {
         img.save(format!("{d}/scriptui_paint.png")).unwrap();
     }
diff --git a/crates/ui-egui/tests/it/ui_tabs.rs b/crates/ui-egui/tests/it/ui_tabs.rs
index 5fc3d8598..cc9e56041 100644
--- a/crates/ui-egui/tests/it/ui_tabs.rs
+++ b/crates/ui-egui/tests/it/ui_tabs.rs
@@ -2,6 +2,7 @@
 //! as its own Timeline tab (not a rename, and not in place of the comp shown), the tabs switch and
 //! close comps, and a dragged tab lands where its insertion mark shows.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::ItemId;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -135,7 +136,7 @@ fn tab_drag_snapshot() {
     }
     let dir = concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out");
     std::fs::create_dir_all(dir).unwrap();
-    h.render().expect("render").save(format!("{dir}/tab-drag.png")).unwrap();
+    h.render_serialized().expect("render").save(format!("{dir}/tab-drag.png")).unwrap();
 }
 
 /// A precomp layer's bar shows its comp's markers; a double-click opens that comp at the marker.
diff --git a/crates/ui-egui/tests/it/ui_theme_favorites.rs b/crates/ui-egui/tests/it/ui_theme_favorites.rs
index 1b700f51f..424b28c49 100644
--- a/crates/ui-egui/tests/it/ui_theme_favorites.rs
+++ b/crates/ui-egui/tests/it/ui_theme_favorites.rs
@@ -1,3 +1,4 @@
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, config::MemoryConfig, prefs::Prefs};
 use effectcraft_ui_egui::{EffectcraftApp, menus};
 use egui::{Event, Modifiers, PointerButton, Pos2, pos2, vec2};
@@ -49,7 +50,7 @@ fn star_controls_save_and_favorite_menu_selects_the_family() {
     assert_eq!(h.state().session.prefs.appearance.favorite_themes, vec!["light"]);
     if let Some(path) = std::env::var_os("FAVORITES_SCREENSHOT_DIR") {
         std::fs::create_dir_all(&path).unwrap();
-        h.render().unwrap().save(std::path::Path::new(&path).join("effectcraft-favorites.png")).unwrap();
+        h.render_serialized().unwrap().save(std::path::Path::new(&path).join("effectcraft-favorites.png")).unwrap();
     }
     assert_eq!(h.state().session.prefs.appearance.appearance_mode, "dark");
     let p = at(&h, "settings.ok");
diff --git a/crates/ui-egui/tests/it/ui_viewer.rs b/crates/ui-egui/tests/it/ui_viewer.rs
index 41cf5fe43..48bc36a44 100644
--- a/crates/ui-egui/tests/it/ui_viewer.rs
+++ b/crates/ui-egui/tests/it/ui_viewer.rs
@@ -2,6 +2,7 @@
 //! interest drawing, rulers and guides, snapping, the shape Pen and motion-path key drags
 //! (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::commands::shape_tool::PaintKind;
 use effectcraft_engine::project::LayerId;
@@ -448,7 +449,7 @@ fn mid_drag(h: &mut Harness<'_, EffectcraftApp>, from: Pos2, to: Pos2, mods: egu
         h.input_mut().events.push(Event::PointerMoved(from + (to - from) * (i as f32 / 8.0)));
         h.step();
     }
-    h.render().expect("the mid-drag frame")
+    h.render_serialized().expect("the mid-drag frame")
 }
 
 /// Release the button where the drag left it.
@@ -490,7 +491,7 @@ fn shape_drag_ghost_shows_the_tools_own_shape_while_dragging() {
         h.state_mut().ui.tool = tool;
         settle_viewer(&mut h);
         let (a, b) = (screen(&h, from), screen(&h, to));
-        let before = h.render().expect("the frame before the drag");
+        let before = h.render_serialized().expect("the frame before the drag");
         let mid = mid_drag(&mut h, a, b, egui::Modifiers::default());
         let fill = fill_rgb(&h);
 
@@ -526,7 +527,7 @@ fn shape_drag_ghost_normalises_the_same_way_as_the_release() {
         h.state_mut().ui.tool = Tool::Ellipse;
         settle_viewer(&mut h);
         let (a, b) = (screen(&h, from.map(|v| v as f32)), screen(&h, to.map(|v| v as f32)));
-        let before = h.render().expect("the frame before the drag");
+        let before = h.render_serialized().expect("the frame before the drag");
         // Measured with the button down, so this is the ghost and not the committed shape.
         let mid = mid_drag(&mut h, a, b, mods);
         let on = [centre[0] as f32 + size[0] as f32 / 4.0, centre[1] as f32 + size[1] as f32 / 4.0];
@@ -595,7 +596,7 @@ fn a_layer_drag_moves_the_picture_while_the_button_is_down() {
     h.input_mut().events.push(Event::PointerButton { pos: from, button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
     h.step();
     // Where the layer is not (yet): the plate behind it.
-    let plate = px_at(&h.render().unwrap(), &h, [440.0, 200.0]);
+    let plate = px_at(&h.render_serialized().unwrap(), &h, [440.0, 200.0]);
 
     // Drag in small steps, still holding the button, and give the renders a chance to land.
     let mut moved = false;
@@ -606,7 +607,7 @@ fn a_layer_drag_moves_the_picture_while_the_button_is_down() {
         std::thread::sleep(std::time::Duration::from_millis(15));
         // 30 comp px behind the pointer: inside the layer, well away from its outline, its anchor
         // icon and where it started.
-        let at = px_at(&h.render().expect("mid-drag frame"), &h, [320.0 + 200.0 * (i as f32 / 40.0) - 30.0, 200.0]);
+        let at = px_at(&h.render_serialized().expect("mid-drag frame"), &h, [320.0 + 200.0 * (i as f32 / 40.0) - 30.0, 200.0]);
         if i >= 30 && delta(at, plate) > 30 {
             moved = true;
             break;
diff --git a/crates/ui-egui/tests/it/ui_viewers.rs b/crates/ui-egui/tests/it/ui_viewers.rs
index 833ab0a60..bfbcad51e 100644
--- a/crates/ui-egui/tests/it/ui_viewers.rs
+++ b/crates/ui-egui/tests/it/ui_viewers.rs
@@ -2,6 +2,7 @@
 //! comp goes to an unlocked viewer (a new one when every viewer is locked); a click on another
 //! viewer makes it the active one; closing a viewer forgets it.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::ItemId;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -171,5 +172,5 @@ fn viewers_snapshot() {
     h.run_steps(4);
     let dir = concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out");
     std::fs::create_dir_all(dir).unwrap();
-    h.render().unwrap().save(format!("{dir}/viewers.png")).unwrap();
+    h.render_serialized().unwrap().save(format!("{dir}/viewers.png")).unwrap();
 }
diff --git a/crates/ui-egui/tests/it/ui_visual_review.rs b/crates/ui-egui/tests/it/ui_visual_review.rs
index 70cc5ed84..6d079f1f5 100644
--- a/crates/ui-egui/tests/it/ui_visual_review.rs
+++ b/crates/ui-egui/tests/it/ui_visual_review.rs
@@ -1,5 +1,6 @@
 //! Opt-in visual review of every built-in panel, workspaces and common dialogs.
 //! Original fixture; captures are review outputs, not shipped assets.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::{Dialog, EffectcraftApp, dock::PanelKind};
 use egui_kittest::Harness;
@@ -19,18 +20,18 @@ fn all_ui_review_captures() {
         std::sync::Arc::make_mut(&mut s.project).settings.gpu_acceleration = false;
         let mut h = Harness::builder().with_size(size).build_eframe(|_| EffectcraftApp::new(s));
         h.run_steps(4);
-        h.render().unwrap().save(out.join(format!("{label}-workspace.png"))).unwrap();
+        h.render_serialized().unwrap().save(out.join(format!("{label}-workspace.png"))).unwrap();
         let ctx = h.ctx.clone();
         h.state_mut().set_theme(&ctx, effectcraft_ui_egui::theme::ThemeKind::Light);
         h.run_steps(4);
-        h.render().unwrap().save(out.join(format!("{label}-workspace-light.png"))).unwrap();
+        h.render_serialized().unwrap().save(out.join(format!("{label}-workspace-light.png"))).unwrap();
         h.state_mut().set_theme(&ctx, effectcraft_ui_egui::theme::ThemeKind::Dark);
         for p in PanelKind::ALL {
             h.state_mut().show_panel(p);
             h.state_mut().ui.maximized = Some(p);
             h.run_steps(4);
             assert!(h.state().auto.find(&format!("panel.{}", p.id())).is_some(), "{} opens", p.title());
-            h.render().unwrap().save(out.join(format!("{label}-{}.png", p.id()))).unwrap();
+            h.render_serialized().unwrap().save(out.join(format!("{label}-{}.png", p.id()))).unwrap();
         }
         h.state_mut().ui.maximized = None;
         for (name, dialog) in [
@@ -42,7 +43,7 @@ fn all_ui_review_captures() {
         ] {
             h.state_mut().dialog = Some(dialog);
             h.run_steps(4);
-            h.render().unwrap().save(out.join(format!("{label}-dialog-{name}.png"))).unwrap();
+            h.render_serialized().unwrap().save(out.join(format!("{label}-dialog-{name}.png"))).unwrap();
             h.state_mut().dialog = None;
             h.run_steps(2);
         }
diff --git a/crates/ui-egui/tests/it/ui_web_gpu_storage.rs b/crates/ui-egui/tests/it/ui_web_gpu_storage.rs
index a742226de..024bd1cd0 100644
--- a/crates/ui-egui/tests/it/ui_web_gpu_storage.rs
+++ b/crates/ui-egui/tests/it/ui_web_gpu_storage.rs
@@ -122,6 +122,7 @@ fn cpu_pixels(f: &FrameImage) -> Vec<egui::Color32> {
 
 #[test]
 fn gpu_worker_renders_effect_frames_and_the_disk_cache_survives_a_reload() {
+    let _device = crate::gpu_test::lock();
     let (Some(page_gpu), Some(worker_gpu)) = (Gpu::headless(), Gpu::headless_deferred()) else {
         eprintln!("no GPU adapter: skipped");
         return;
diff --git a/crates/ui-egui/tests/it/ui_web_job_gpu.rs b/crates/ui-egui/tests/it/ui_web_job_gpu.rs
index 9060e1067..8b8914abc 100644
--- a/crates/ui-egui/tests/it/ui_web_job_gpu.rs
+++ b/crates/ui-egui/tests/it/ui_web_job_gpu.rs
@@ -10,10 +10,6 @@ use effectcraft_engine::offload::{Inbox, Offload, Post, WorkerReply, WorkerReque
 use effectcraft_gpu::Gpu;
 use serde_json::json;
 
-/// One device at a time in this test binary: wgpu's OpenGL backend (Mesa llvmpipe on FreeBSD,
-/// Linux without Vulkan) panics or crashes when tests create and drive devices concurrently.
-static GPU_LOCK: Mutex<()> = Mutex::new(());
-
 /// Holds offloaded jobs until the test runs them.
 #[derive(Default)]
 struct Manual(Mutex<Vec<(WorkerRequest, Arc<Inbox>)>>);
@@ -63,7 +59,7 @@ fn page() -> (Session, Arc<Manual>) {
 
 #[test]
 fn render_queue_jobs_render_on_the_worker_gpu() {
-    let _gpu = GPU_LOCK.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _gpu = crate::gpu_test::lock();
     let Some(g) = Gpu::headless_deferred() else {
         eprintln!("no GPU adapter: skipped");
         return;
@@ -102,7 +98,7 @@ fn render_queue_jobs_render_on_the_worker_gpu() {
 
 #[test]
 fn analyses_render_their_input_on_the_worker_gpu() {
-    let _gpu = GPU_LOCK.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _gpu = crate::gpu_test::lock();
     let Some(g) = Gpu::headless_deferred() else {
         eprintln!("no GPU adapter: skipped");
         return;
diff --git a/crates/ui-egui/tests/it/ui_workflow_selection.rs b/crates/ui-egui/tests/it/ui_workflow_selection.rs
index 121c2b888..e7bcedb60 100644
--- a/crates/ui-egui/tests/it/ui_workflow_selection.rs
+++ b/crates/ui-egui/tests/it/ui_workflow_selection.rs
@@ -1,4 +1,5 @@
 //! User-reported selection, Project deletion, and render-queue drop regressions.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, project::LayerId};
 use effectcraft_ui_egui::{Dialog, EffectcraftApp, dock::PanelKind};
 use egui::{Event, Modifiers, PointerButton, Pos2, Rect, pos2, vec2};
@@ -273,7 +274,7 @@ fn viewer_right_click_targets_hit_and_duplicate_preserves_group() {
         }
         assert!(h.state().frames.is_cached(&key));
         h.run_steps(3);
-        h.render().expect("offscreen context menu render").save(out).unwrap();
+        h.render_serialized().expect("offscreen context menu render").save(out).unwrap();
     }
     h.get_by_label("Duplicate").click();
     h.run_steps(3);
@@ -433,7 +434,7 @@ fn workflow_snapshot() {
     }
     assert!(h.state().frames.is_cached(&key), "current composition rendered before capture");
     h.run_steps(3);
-    h.render().expect("offscreen UI render").save(out).unwrap();
+    h.render_serialized().expect("offscreen UI render").save(out).unwrap();
 }
 
 /// Filled rects painted this frame (flattening nested shape lists).
diff --git a/crates/ui-egui/tests/it/viewer_geometry.rs b/crates/ui-egui/tests/it/viewer_geometry.rs
index e3e4128e8..d57a8aa9e 100644
--- a/crates/ui-egui/tests/it/viewer_geometry.rs
+++ b/crates/ui-egui/tests/it/viewer_geometry.rs
@@ -1,5 +1,6 @@
 //! Inspect the actual viewer's painted colors and pointer-driven control geometry.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::{
     EffectcraftApp,
@@ -269,10 +270,10 @@ fn viewer_theme_and_width_visual_matrix() {
 }
 
 fn save_stable_snapshot(h: &mut Harness<'_, EffectcraftApp>, path: &str, width: f32) {
-    let image = h.render().unwrap();
+    let image = h.render_serialized().unwrap();
     image.save(path).unwrap();
     h.run_steps(3);
-    let repeated = h.render().unwrap();
+    let repeated = h.render_serialized().unwrap();
     assert!(image == repeated, "settled synthetic viewer pixels must repeat exactly: {path}");
     if width == 900.0 {
         let times: Vec<_> = h
diff --git a/docs/agents.md b/docs/agents.md
index 7f3fd9ad3..200e7f2ec 100644
--- a/docs/agents.md
+++ b/docs/agents.md
@@ -4,6 +4,10 @@ Everything in EffectCraft is an engine command with a stable id and JSON params.
 panel gestures, the CLI, the control channel and MCP all go through the same commands, so anything a
 user can do, an agent can do too. There are three ways in:
 
+Render-queue outputs cannot replace footage, proxies or the project file. See
+[render source protection](file-format-parity.md#render-source-protection) for aliases, default names and sequence
+limits. This guard does not change ordinary-file overwrite defaults or add another confirmation API.
+
 | Interface | Best for | Needs a window |
 |---|---|---|
 | **MCP** (`effectcraft-cli mcp`) | Claude Code and other MCP clients | no (headless), or yes with `--bridge` |
diff --git a/docs/file-format-parity.md b/docs/file-format-parity.md
index 45e373cda..6eeef1719 100644
--- a/docs/file-format-parity.md
+++ b/docs/file-format-parity.md
@@ -105,6 +105,37 @@ single-file video (Animation / PNG codecs), DPX / Photoshop sequences, MXF, DNxH
 encoders ([hardware-parity.md](hardware-parity.md)), and rendering safely over an existing file
 (#325).
 
+### Render source protection
+
+The render queue refuses an output that would replace footage, an attached proxy, or the
+project file. It checks every output module and segment before dispatching the item. A refused
+item is marked Failed with its reason; other valid queued items can still render. Render logs
+are checked too. No render parameter overrides this protection.
+
+Checks compare normalized paths and native file identities, so an existing symbolic link,
+hard link, junction or Windows short name cannot disguise a source as another output file.
+Source identities are indexed once per check and matching identities are verified. The index
+does not keep file handles open for the lifetime of a long sequence.
+
+Default output names move aside when they would replace a protected file. This also applies to
+Create Proxy: recreating a proxy chooses a new default name and attaches the new proxy, leaving
+the previous proxy file intact. An explicit output path is kept as entered and refused if it
+would replace a protected file.
+
+After Pre-render imports its result, that file is footage too. Re-queueing the same item
+with the same output is refused; run Pre-render again for a fresh default output, or choose
+another Output To. An item's `last_output` is not permission to replace imported footage.
+
+Image-sequence checks inspect existing frames in the requested range. Skip Existing Files leaves
+existing frames alone. If a frame number appears in a folder name, the checker probes each
+frame separately and refuses ranges over 100,000 frames instead of silently checking a prefix.
+Choose a fixed output folder or a shorter range for those exports.
+
+This guard does not introduce an overwrite flag, confirmation dialog, or changed replacement
+defaults for the CLI, scripts or MCP. Replacement consent and staging ordinary output files
+belong to the exporter. The source check runs before export; filesystem changes between that
+check and a write still require exporter-side revalidation.
+
 ## Estimate
 
 **≈ 130–230 h**: `.aep` / `.aepx` import 80–160 h (after the owner decision), wiring TGA / DPX /
@@ -115,5 +146,6 @@ relinking 6–12 h, `.mogrt`-compatible templates 15–30 h (partly parallel wit
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-30 | minor | Render-queue source-protection behavior and limits consolidated here from the standalone page |
 | 2026-10-12 | minor | #324 and #514 marked closed; open `.aep` PRs #251 and #860 noted |
 | 2026-10-10 | major | First file format parity document, from the After Effects 26.5 bundle and this repository's import/export registries |