diff --git a/backend/src/handlers/test_admin.rs b/backend/src/handlers/test_admin.rs
index b6c40ce..917ccbf 100644
--- a/backend/src/handlers/test_admin.rs
+++ b/backend/src/handlers/test_admin.rs
@@ -98,6 +98,13 @@ pub async fn truncate_all(
     // surviving ticket is a dangling reference to a user that no longer exists.
     state.sse_tickets.clear();
 
+    // Invalidate any in-flight/queued compression task spawned by the previous test. Without this a
+    // task still waiting on the concurrency semaphore wakes AFTER this wipe, fails to find its
+    // (now-deleted) file, and broadcasts upload-error/upload-deleted into the NEXT test's SSE
+    // stream. (Export workers are already inert across a truncate: they are epoch-guarded on the
+    // event row, and truncate gives the event a fresh random UUID, so their writes match nothing.)
+    state.compression.bump_generation();
+
     Ok(StatusCode::NO_CONTENT)
 }
 
diff --git a/backend/src/handlers/upload.rs b/backend/src/handlers/upload.rs
index 0edcc5a..e0fdbd2 100644
--- a/backend/src/handlers/upload.rs
+++ b/backend/src/handlers/upload.rs
@@ -416,6 +416,15 @@ pub async fn edit_upload(
 
     // Caption update + hashtag wipe-then-relink in one transaction, so a crash
     // mid-relink can't leave the upload with its hashtags stripped.
+    //
+    // Editing is intentionally allowed while uploads are locked or the gallery is released — like
+    // comments and likes, the lock freezes *new uploads* only (USER_JOURNEYS §9.3). But a caption
+    // is embedded in the HTML viewer keepsake (the ZIP holds media only — see export.rs), so an
+    // edit AFTER release must regenerate the viewer, or the downloadable keepsake keeps showing the
+    // old caption forever while the live feed shows the new one. Same atomicity as delete_upload:
+    // the edit and its invalidation share one tx so a dropped handler can't leave them disagreeing.
+    // `Affects::ViewerOnly` carries the finished ZIP forward (the media didn't change); when the
+    // gallery isn't released, `invalidate_and_arm` returns None and this is a no-op.
     let mut tx = state.pool.begin().await?;
     if let Some(ref caption) = body.caption {
         Upload::update_caption(&mut *tx, upload_id, Some(caption)).await?;
@@ -427,7 +436,16 @@ pub async fn edit_upload(
             Hashtag::link_to_upload(&mut *tx, upload_id, h.id).await?;
         }
     }
+    let regen = crate::services::export::invalidate_and_arm(
+        &mut tx,
+        &state.config.event_slug,
+        crate::services::export::Affects::ViewerOnly,
+    )
+    .await?;
     tx.commit().await?;
+    if let Some(r) = regen {
+        crate::handlers::host::start_regen(&state, r);
+    }
 
     Ok(StatusCode::OK)
 }
diff --git a/backend/src/services/compression.rs b/backend/src/services/compression.rs
index 44813c0..29fcb1b 100644
--- a/backend/src/services/compression.rs
+++ b/backend/src/services/compression.rs
@@ -1,4 +1,5 @@
 use std::path::{Path, PathBuf};
+use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
 
 use anyhow::{Context, Result};
@@ -15,6 +16,10 @@ pub struct CompressionWorker {
     pool: PgPool,
     media_path: PathBuf,
     sse_tx: broadcast::Sender<SseEvent>,
+    /// Bumped whenever the underlying data is reset out from under in-flight work (only the e2e
+    /// TRUNCATE does this today). A task captures the value at spawn and abandons itself if it has
+    /// changed by the time it runs — see `process`.
+    generation: Arc<AtomicU64>,
 }
 
 impl CompressionWorker {
@@ -24,14 +29,32 @@ impl CompressionWorker {
             pool,
             media_path,
             sse_tx,
+            generation: Arc::new(AtomicU64::new(0)),
         }
     }
 
+    /// Invalidate all in-flight and queued compression work. Called by the e2e TRUNCATE endpoint:
+    /// truncating deletes the upload rows and wipes `media/`, so a worker that was queued on the
+    /// semaphore when the wipe happened would otherwise wake in the NEXT test, fail to find its
+    /// file, and broadcast `upload-error` / `upload-deleted` into that test's live SSE stream —
+    /// corrupting any test that asserts on toasts or feed contents. Bumping the generation makes
+    /// those stale tasks return silently instead. A no-op in production (never called there).
+    pub fn bump_generation(&self) {
+        self.generation.fetch_add(1, Ordering::SeqCst);
+    }
+
     /// Spawn a background task to process an uploaded file.
     pub fn process(&self, upload_id: Uuid, original_path: String, mime_type: String) {
         let worker = self.clone();
+        let born_at = worker.generation.load(Ordering::SeqCst);
         tokio::spawn(async move {
             let _permit = worker.semaphore.acquire().await;
+            // The data this task was queued against may have been reset while it waited for a permit
+            // (e2e TRUNCATE). If so, its file and row are gone; doing anything — including
+            // broadcasting a failure — would leak into an unrelated test. Abandon quietly.
+            if worker.generation.load(Ordering::SeqCst) != born_at {
+                return;
+            }
             match worker.do_process(upload_id, &original_path, &mime_type).await {
                 Ok(_) => {
                     tracing::info!("compression completed for upload {upload_id}");