diff --git a/server.py b/server.py
index d10162a..f1d06f6 100644
--- a/server.py
+++ b/server.py
@@ -437,6 +437,55 @@ async def discard_run(run_id: str, username: str = Depends(get_required_user)):
     return {"discarded": True, "run_id": run_id}
 
 
+@app.delete("/ui/runs/{run_id}/discard", response_class=HTMLResponse)
+async def ui_discard_run(run_id: str, request: Request):
+    """HTMX handler: discard a run."""
+    current_user = get_user_from_cookie(request)
+    if not current_user:
+        return '<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Login required</div>'
+
+    run = load_run(run_id)
+    if not run:
+        return '<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Run not found</div>'
+
+    # Check ownership
+    actor_id = f"@{current_user}@{L2_DOMAIN}"
+    if run.username not in (current_user, actor_id):
+        return '<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Access denied</div>'
+
+    # Failed runs can always be deleted
+    if run.status != "failed":
+        # Check if activity exists for this run
+        activity = cache_manager.get_activity(run_id)
+
+        if activity:
+            can_discard, reason = cache_manager.can_discard_activity(run_id)
+            if not can_discard:
+                return f'<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Cannot discard: {reason}</div>'
+
+            success, msg = cache_manager.discard_activity(run_id)
+            if not success:
+                return f'<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Failed to discard: {msg}</div>'
+        else:
+            # Legacy run - check L2 shared status
+            items_to_check = list(run.inputs or [])
+            if run.output_hash:
+                items_to_check.append(run.output_hash)
+
+            for content_hash in items_to_check:
+                if cache_manager.l2_checker.is_shared(content_hash):
+                    return f'<div class="bg-red-900/50 border border-red-700 text-red-300 px-4 py-3 rounded-lg mb-4">Cannot discard: item {content_hash[:16]}... is published to L2</div>'
+
+    # Remove from Redis
+    redis_client.delete(f"{RUNS_KEY_PREFIX}{run_id}")
+
+    return '''
+    <div class="bg-green-900/50 border border-green-700 text-green-300 px-4 py-3 rounded-lg mb-4">
+        Run deleted. <a href="/runs" class="underline">Back to runs</a>
+    </div>
+    '''
+
+
 @app.get("/run/{run_id}")
 async def run_detail(run_id: str, request: Request):
     """Run detail. HTML for browsers, JSON for APIs."""
@@ -590,6 +639,22 @@ async def run_detail(run_id: str, request: Request):
             </div>
             '''
 
+        # Delete section
+        delete_html = f'''
+        <div class="border-t border-dark-500 pt-6 mt-6">
+            <h2 class="text-lg font-semibold text-white mb-3">Delete Run</h2>
+            <p class="text-sm text-gray-400 mb-4">
+                {"This run failed and can be deleted." if run.status == "failed" else "Delete this run and its associated cache entries."}
+            </p>
+            <div id="delete-result"></div>
+            <button hx-delete="/ui/runs/{run.run_id}/discard" hx-target="#delete-result" hx-swap="innerHTML"
+                    hx-confirm="Are you sure you want to delete this run? This cannot be undone."
+                    class="px-4 py-2 bg-red-600 hover:bg-red-700 text-white font-medium rounded-lg transition-colors">
+                Delete Run
+            </button>
+        </div>
+        '''
+
         output_link = ""
         if run.output_hash:
             output_link = f'''<div class="bg-dark-600 rounded-lg p-4">
@@ -661,6 +726,7 @@ async def run_detail(run_id: str, request: Request):
             </div>
 
             {publish_html}
+            {delete_html}
         </div>
         '''