DioxusLabs/dioxus · error

visible fragment placement requires a fallback insertion sit

Error message

visible fragment placement requires a fallback insertion site

What it means

Internal diffing invariant: a visible fragment placement run had no anchor element or fallback insertion site to insert relative to. Means the surrounding mounted tree is inconsistent with the diff plan.

Source

Thrown at packages/core/src/diff/iterator.rs:422

        }

        let stable_edges = StableFragmentEdges::new(new, &new_mounts, &anchorable, self.dom);
        for range in plan.placement_runs(&stable_edges.live_stable) {
            let context = self.context();
            let runtime = self.dom.runtime.clone();
            let dom = &mut *self.dom;
            let mut replaced_nodes = Vec::new();
            if let Some(to) = self.to.as_deref_mut() {
                let site = stable_edges
                    .next_first(range.end)
                    .map(InsertionSite::before)
                    .or_else(|| {
                        stable_edges
                            .prev_last(range.start)
                            .map(InsertionSite::after)
                    })
                    .or(fallback_site)
                    .expect("visible fragment placement requires a fallback insertion site");
                site.create_and_place_with_result(to, runtime, |to| {
                    let mut state = DiffState::new_with_context(dom, Some(to), context);
                    let nodes = state.create_or_diff_placed_range(
                        &inputs,
                        &plan,
                        range.clone(),
                        &mut new_mounts,
                        &mut replaced_nodes,
                    );
                    (nodes, nodes)
                });
            } else {
                let mut state = DiffState::new_with_context(dom, None, context);
                state.create_or_diff_placed_range(
                    &inputs,
                    &plan,
                    range.clone(),
                    &mut new_mounts,

View on GitHub (pinned to 24f6a829df)

Solutions

1. This is an internal diffing invariant about fragment placement. Report it with a minimal reproduction to the Dioxus issue tracker.

When it happens

Trigger: Thrown at packages/core/src/diff/iterator.rs:422 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of DioxusLabs/dioxus@24f6a829df (2026-08-23). Data as JSON: /api/errors/eff15ae021455a78. Report an issue: GitHub.