RUDPClient/openspec/specs/server-authoritative-combat/spec.md

server-authoritative-combat Specification

Purpose

Define the shared server-side combat authority contract that accepts ShootInput, validates sender-scoped fire requests, resolves authoritative hit and damage outcomes, and emits reliable CombatEvent results.

Requirements

Requirement: Server registers and validates ShootInput per peer

The shared server networking path SHALL register ShootInput handling through the server host/runtime composition and SHALL validate each inbound shooting request against the sending managed peer before applying any authoritative combat result. Validation MUST reject malformed numeric input, missing or mismatched player identity, non-increasing shoot ticks for that sender, zero-direction fire requests, and shot requests that do not resolve to a living managed peer either through an explicit targetId or through server-side aim-direction fallback when targetId is omitted.

Scenario: Valid ShootInput is accepted for the sending peer

• WHEN a managed peer sends a well-formed ShootInput whose playerId maps to that sender, whose tick is newer than the sender's last accepted shoot tick, and whose target resolves to another living managed peer either from explicit targetId data or from server-side aim-direction fallback
• THEN the server accepts the request for that sender only
• THEN the sender's last accepted shoot tick is updated without changing other peers' combat bookkeeping

Scenario: Invalid ShootInput is rejected without mutating authoritative combat state

• WHEN a managed peer sends a ShootInput with malformed direction data, a stale tick, a mismatched playerId, or targeting data that resolves to no living non-self managed peer
• THEN the server rejects that request
• THEN no authoritative damage or death state is applied to any peer from that rejected request

Requirement: Server resolves authoritative combat outcomes

The shared server networking path SHALL own final combat resolution for accepted shots, including hit acceptance, damage application, authoritative HP mutation, and death determination. Combat resolution MUST update the authoritative server-owned state of both the attacker and target as needed without delegating gameplay truth to client-side prediction or presentation code.

Scenario: Accepted shot applies damage to the authoritative target state

• WHEN the server accepts a ShootInput that resolves a living managed peer
• THEN it resolves the shot as an authoritative hit against that target
• THEN it reduces the target's authoritative HP according to the configured damage rule before later state snapshots are broadcast

Scenario: Lethal damage marks the authoritative target as dead

• WHEN an accepted shot reduces a target's authoritative HP to zero or below
• THEN the server clamps the target's authoritative HP to zero
• THEN subsequent combat and state broadcast treat that target as dead until a later server-owned lifecycle change resets it

Requirement: Server emits reliable authoritative CombatEvent results

The shared server networking path SHALL emit authoritative combat outcomes through CombatEvent messages using the existing reliable-lane delivery contract. Accepted shots MUST produce reliable events for hit and damage application, and lethal results MUST also produce a death event. Rejected shots MUST produce a reliable ShootRejected event that identifies the attacker and rejected target context.

Scenario: Accepted shot produces authoritative hit and damage events

• WHEN the server resolves an accepted shot that damages a living target
• THEN it broadcasts CombatEvent messages on the reliable lane for the authoritative combat result
• THEN the emitted events identify the attacker, target, damage, and authoritative tick for client-side application

Scenario: Rejected shot produces an authoritative rejection event

• WHEN the server rejects a ShootInput during validation
• THEN it broadcasts a reliable CombatEvent with event type ShootRejected
• THEN clients can observe that rejection without inferring local authoritative damage or hit success