Pumpkin-MC/Pumpkin · warning · InventoryError

Invalid inventory packet

Error message

Invalid inventory packet

What it means

InventoryError::InvalidPacket is raised when a received inventory interaction packet (window click, drag, etc.) is malformed or fails validation while being processed from the network. The library throws it because it cannot map the packet payload onto a legal inventory operation (bad slot data, inconsistent drag payload, or impossible action). It protects server-side inventory state from being corrupted by client input.

Solutions

1. Inspect the packet handler that produced the error and validate the client's reported window ID, state ID, and slot indices against the server's open container before applying it.
2. Check whether the client is vanilla; non-vanilla or outdated client mods frequently send non-conformant inventory packets.
3. If it occurs on the server you develop with Pumpkin, add logging of the raw packet fields to identify which field fails validation.
4. If the packet is genuinely malformed, disconnect or ignore the offending packet; this is a client-protocol violation, not a server bug.

Example fix

// before: blindly applying packet data
player.apply_click(packet.slot, packet.button);
// after: validate before applying
if player.open_container().is_none() || !packet.slot.is_valid_for(container) {
    return Err(InventoryError::InvalidPacket);
}
player.apply_click(packet.slot, packet.button);

// Rust: validate before applying an inventory packet
fn packet_is_valid(open: Option<&Container>, pkt: &ClickPacket) -> bool {
    open.is_some() && (pkt.slot as usize) < open.unwrap().size()
}

fn open_container(player: &Player) -> Option<&Container> { player.open_container() }

match player.handle_inventory_packet(pkt) {
    Err(InventoryError::InvalidPacket) => log::warn!("bad packet from {}", player.id()),
    Err(e) => return Err(e.into()),
    Ok(()) => {}
}

When it happens

Trigger: A client sends a ClickContainer/CloseContainer/creative-inventory packet whose fields cannot be validated against the open container; a drag packet is malformed; the packet references slots that cannot be resolved to a valid operation during packet handling.

Common situations: A modified or buggy client sends crafted inventory packets; a client and server disagree about the open window ID or state after a desync; plugins/protocol changes cause packets to be parsed with the wrong layout.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Invalid slot
• Player ' ' tried to interact with a closed container
• Multiple players dragging in a container at once
• Out of order dragging
• Player does not have enough permissions

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/401de39f1584f63a. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-inventory/src/error.rs:27

    /// Failed to acquire a lock on an inventory or slot.
    #[error("Unable to lock")]
    LockError,
    /// The specified slot index is invalid or out of bounds.
    #[error("Invalid slot")]
    InvalidSlot,
    /// A player attempted to interact with a container that is closed.
    ///
    /// The parameter is the player's entity ID.
    #[error("Player '{0}' tried to interact with a closed container")]
    ClosedContainerInteract(i32),
    /// Multiple players attempted to drag items in the same container simultaneously.
    #[error("Multiple players dragging in a container at once")]
    MultiplePlayersDragging,
    /// Drag operation was performed out of order (e.g., end before start).
    #[error("Out of order dragging")]
    OutOfOrderDragging,
    /// The received inventory packet is malformed or invalid.
    #[error("Invalid inventory packet")]
    InvalidPacket,
    /// The player lacks permission to perform this inventory operation.
    #[error("Player does not have enough permissions")]
    PermissionError,
}

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