{CALL_HTTP_HANDLER_DUNDER} returned unexpected code {code}.

Error message

{CALL_HTTP_HANDLER_DUNDER} returned unexpected code {code}. HTTP handlers should return code 0 or trap.

What it means

Error "{CALL_HTTP_HANDLER_DUNDER} returned unexpected code {code}. HTTP handlers should return code 0 or trap." thrown in clockworklabs/SpacetimeDB.

Source

Thrown at crates/core/src/host/wasmtime/wasmtime_module.rs:882

                    op.timestamp.to_micros_since_unix_epoch() as u64,
                    request_source.0,
                    request_body_source.0,
                    response_sink,
                    response_body_sink,
                ),
            )
            .await;

        store.data_mut().terminate_dangling_anon_tx();

        let (stats, result_bytes, response_body_bytes) =
            finish_http_handler_opcall(store, budget, response_sink, response_body_sink);

        let call_result = call_result.and_then(|code| {
            (code == 0)
                .then_some((result_bytes.into(), response_body_bytes.into()))
                .ok_or_else(|| {
                anyhow::anyhow!(
                    "{CALL_HTTP_HANDLER_DUNDER} returned unexpected code {code}. HTTP handlers should return code 0 or trap."
                )
                })
        });

        let res = module_host_actor::HttpHandlerExecuteResult { stats, call_result };

        let tx_offset = store.data_mut().take_procedure_tx_offset();

        (res, tx_offset)
    }
}

fn set_store_fuel(store: &mut impl AsContextMut, fuel: WasmtimeFuel) {
    store.as_context_mut().set_fuel(fuel.0).unwrap();
}

fn get_store_fuel(store: &impl AsContext) -> WasmtimeFuel {

View on GitHub (pinned to 524b4487d9)

When it happens

Trigger: Thrown at crates/core/src/host/wasmtime/wasmtime_module.rs:882 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of clockworklabs/SpacetimeDB@524b4487d9 (2026-08-16). Data as JSON: /api/errors/7ec632d086515a6d. Report an issue: GitHub.