RUDPClient/openspec/changes/archive/2026-04-05-fix-authoritative-movement-p2/specs/network-sync-strategy/spec.md

MODIFIED Requirements

Requirement: Authoritative correction prunes acknowledged prediction history

The client sync strategy SHALL reconcile local prediction against authoritative player-state updates by pruning acknowledged movement inputs at or before the authoritative acknowledged movement tick and only reapplying newer pending MoveInput messages. For the controlled player, reconciliation MUST classify authoritative error after replay into a bounded-correction path for small cadence-aligned divergence and an immediate snap path for large divergence. When bounded correction is already active, later authoritative snapshots MUST deterministically replace, fold into, or escalate that correction based on the newest residual error instead of stacking unbounded visual offsets.

Scenario: Reconciliation removes already acknowledged movement inputs

• WHEN the client accepts an authoritative PlayerState update that acknowledges movement tick N
• THEN locally buffered predicted MoveInput messages with tick less than or equal to N are removed from the replay buffer
• THEN only MoveInput messages newer than N remain eligible for re-simulation

Scenario: Small post-replay error uses bounded correction

• WHEN the controlled client finishes replay after accepting an authoritative PlayerState and the remaining position or rotation error stays within the configured bounded-correction threshold
• THEN the client keeps authoritative ownership of the accepted snapshot
• THEN local presentation converges through bounded correction instead of an immediate hard snap on that frame

Scenario: New small error updates active bounded correction

• WHEN the controlled client accepts another authoritative PlayerState before the previous bounded correction has finished and the new residual error still stays within bounded-correction limits
• THEN the sync strategy updates the active bounded correction state using the newest authoritative residual error
• THEN the client does not queue multiple independent correction tails for the same controlled player

Scenario: Failed bounded correction escalates to snap

• WHEN the controlled client detects that the residual error from consecutive authoritative updates exceeds the snap threshold or remains non-convergent beyond the configured correction budget
• THEN the client immediately applies the authoritative transform state
• THEN any active bounded correction state is discarded before later prediction continues from the authoritative baseline