diff --git a/Game/scripts/match_net.gd b/Game/scripts/match_net.gd
index da5afc60..9e04186e 100644
--- a/Game/scripts/match_net.gd
+++ b/Game/scripts/match_net.gd
@@ -54,6 +54,7 @@ var local_player_name := "Player"
 var join_authorisation := ""
 var require_join_authorisation := false
 var _allowed_join_authorisations: Dictionary = {}
+var _active_join_peers: Dictionary = {} # opaque authorisation -> peer_id
 var _join_authorisation_context: Dictionary = {}
 
 # Test hook (tests/match_net_smoke.gd): set false before connecting to
@@ -89,6 +90,7 @@ func _on_disconnected_from_server() -> void:
 func _on_shutting_down() -> void:
 	roster.clear()
 	_allowed_join_authorisations.clear()
+	_active_join_peers.clear()
 	_join_authorisation_context.clear()
 	require_join_authorisation = false
 
@@ -118,6 +120,10 @@ func _on_peer_disconnected(peer_id: int) -> void:
 
 
 func _remove_player(peer_id: int) -> void:
+	for token in _active_join_peers.keys():
+		if int(_active_join_peers[token]) == peer_id:
+			_active_join_peers.erase(token)
+			break
 	if not roster.has(peer_id):
 		return
 	roster.erase(peer_id)
@@ -185,6 +191,9 @@ func _hello(protocol_version: int, tick_hz: int, player_name: String, supplied_j
 	if require_join_authorisation and not _valid_join_authorisation(supplied_join_authorisation):
 		await _reject(peer_id, "join authorisation rejected")
 		return
+	if require_join_authorisation and _active_join_peers.has(supplied_join_authorisation):
+		await _reject(peer_id, "join authorisation already in use")
+		return
 	if player_name.length() > MAX_INPUT_LENGTH:
 		await _reject(peer_id, "player name too long")
 		return
@@ -199,6 +208,8 @@ func _hello(protocol_version: int, tick_hz: int, player_name: String, supplied_j
 
 	var team := _pick_balanced_team()
 	roster[peer_id] = PlayerInfo.new(peer_id, clean_name, team, false)
+	if require_join_authorisation:
+		_active_join_peers[supplied_join_authorisation] = peer_id
 	player_joined.emit(peer_id, clean_name)   # local: the broadcast below is call_remote, never loops back to the server itself
 	_welcome.rpc_id(peer_id)
 	_player_joined.rpc(peer_id, clean_name, team, false)   # broadcast, includes the new peer itself
@@ -229,6 +240,10 @@ func _valid_join_authorisation(token: String) -> bool:
 		and expiry > Time.get_unix_time_from_system()
 
 
+func is_join_authorisation_active(token: String) -> bool:
+	return not token.is_empty() and _active_join_peers.has(token)
+
+
 # Strips control/formatting characters (so a name can't corrupt a log line
 # or blow out UI layout with e.g. embedded newlines) and clamps to display
 # length. Input is already bounded to MAX_INPUT_LENGTH by the caller before
diff --git a/Game/tests/cases/test_match_net.gd b/Game/tests/cases/test_match_net.gd
index 77ea62e3..c1a38bb4 100644
--- a/Game/tests/cases/test_match_net.gd
+++ b/Game/tests/cases/test_match_net.gd
@@ -54,3 +54,6 @@ func test_allocated_join_authorisation_is_allowlisted_and_bound_to_server() -> v
 	wrong_claims["ServerID"] = "other-server"
 	var wrong_token := Marshalls.raw_to_base64(JSON.stringify({"Authorisation": wrong_claims, "Signature": "trusted-signature"}).to_utf8_buffer())
 	assert_true(not match_net._valid_join_authorisation(wrong_token), "wrong server claim is rejected")
+	assert_true(not match_net.is_join_authorisation_active(token), "validated token is not active before admission")
+	match_net._active_join_peers[token] = 42
+	assert_true(match_net.is_join_authorisation_active(token), "active token is visible to the duplicate-admission guard")
diff --git a/multiplayer-todo.md b/multiplayer-todo.md
index c3d87230..381f2225 100644
--- a/multiplayer-todo.md
+++ b/multiplayer-todo.md
@@ -1229,7 +1229,7 @@ the local/CI/community transport, not a silent production fallback.
 |---|---|---|
 | 8.39 `[D:8.3,8.14,8.17]` | **IN PROGRESS.** `MatchmakingState` now projects queue → proposal → allocation/process-ready/assignment-ready/connect/live plus terminal failure states; autoload `ControlPlaneClient` provides authenticated queue create/recovery/heartbeat/cancel and proposal response requests with idempotency/revision headers; `matchmaking.tscn`/`matchmaking.gd` expose the state and authoritative actions from the main menu; authenticated proposal recovery now reconciles missed proposal events and expires them at read time; the Go API publishes targeted authenticated revisioned queue/proposal/assignment events and the Godot client consumes state/proposal/assignment events, fetching the authoritative assignment after assignment readiness; the API can now use the durable participant-scoped proposal provider for both recovery and accept/decline mutations | `test_matchmaking_state.gd`, `test_control_plane_client.gd`, `test_matchmaking_ui.gd`, `TestProposalRecoveryIsParticipantScopedAndExpiresAtReadBoundary`, `TestAuthenticatedWebSocketDeliversOnlyTargetedRevisionedEvents`, `TestStateChangingAPIActionsPublishTargetedEvents`, `TestProposalRecoveryUsesDurableBackendAndRemainsParticipantScoped` and store proposal SQL tests reject stale/gapped/conflicting updates, validate endpoint/token/payload normalization, preserve idempotent duplicates, and guarantee visible phase/terminal copy; wiring durable allocation events into the outbox, wait/latency explanations and Godot runtime verification remain |
 | 8.40 `[D:8.3,8.14]` | **IN PROGRESS.** Pure Go revisioned replica reducer rejects gaps for REST resync, makes duplicate/out-of-order events idempotent, and resumes from the authoritative snapshot revision; authenticated queue-ticket recovery now has an owner-checked REST read; Godot client projection persists non-secret ticket/proposal state, forces authoritative recovery after restart, and can replay a lost queue-create response with the original ticket/idempotency key; the Go API now exposes an authenticated `/v1/events` WebSocket with bounded per-player queues, strict upgrade/vocabulary validation and REST-resync-safe slow-client failure; Godot `ControlPlaneClient` can connect to the stream using Godot 4.7's handshake-header API, consume validated events, automatically reconnect with bounded backoff, and trigger REST recovery on projection gaps and stream return; `OutboxDispatcher` now provides ordered at-least-once delivery after durable commit; assignment recovery events carry the durable assignment revision without leaking it into REST JSON; prediction startup now distinguishes the sequence-0 warm-up acknowledgement from genuine missing/evicted history, preventing a false hard-snap during a live match | `server/domain/sync.go`, `server/api/events.go`, `server/api/service.go`, `server/store/outbox.go`, `service_test.go`, `outbox_test.go`, `matchmaking_state.gd`, `control_plane_client.gd`, `local_prediction_history.gd`, `net_ship_predictor.gd` and tests cover gap, snapshot, replay, same-revision conflict, owner-only ticket recovery, expired-ticket terminal handling, malformed restart snapshots, API-level duplicate-create replay/conflict, authenticated handshake/key rejection, targeted event delivery, exactly-once slow-subscriber closure, invalid-event rejection, delivery-before-ack failure ordering, assignment event/response revision separation and prediction warm-up/hard-resync separation; Godot 4.7.1 headless project parse and 143-test unit harness pass with compatibility rendering, and a two-process ENet authoritative match smoke passes spawn, movement, prediction, 0% snapshot loss and 0 hard snaps; wiring the dispatcher to a production WebSocket/Redis worker and live multi-process control-plane/game verification remain |
-| 8.41 `[D:7.8,8.9,8.31,8.40]` | **IN PROGRESS.** Authenticated `GET /v1/assignments/{matchId}` now exposes only a validated, player-scoped assignment view including the hosted endpoint; Godot `AssignmentState`/`ControlPlaneClient.fetch_assignment()` bind the response to the authenticated player, recheck expiry, validate and retain the endpoint, and `connect_to_assignment()` now starts only the validated ENet/Steam transport after assignment readiness; the opaque join authorisation is carried in the MatchNet hello payload rather than the endpoint URL; allocated Godot servers now fail closed unless an operator-mounted JSON roster of control-plane signed envelopes is present, and MatchNet checks exact token membership plus match/server/protocol/slot/expiry claims before admitting a peer; migration 0002 and the Go store adapter now persist/recover the complete player-scoped assignment projection with conflict-safe identical replay; `AssignmentProviderFromStore` wires that durable projection into the API injection point; `SaveAssignments` publishes a complete signed roster atomically instead of allowing partial player visibility; `SaveVerifiedAssignmentRoster` rechecks signed claims before deriving player rows | `server/api/service.go`, `store_adapters.go`, `service_test.go`, `assignment_state.gd`, `control_plane_client.gd`, `match_net.gd`, `server_boot.gd`, `server_config.gd`, `test_assignment_state.gd`, `test_control_plane_client.gd`, `test_match_net.gd`, `server/contracts/v1/openapi.json`, `server/migrations/0002_assignments.sql` and `server/store/assignment_sql.go` cover participant/identity/expiry/shape/transport/endpoint boundaries, player-scoped schema keys, expiry-filtered reads, assignment upsert conflict handling, atomic batch validation, signed-claim binding, strict endpoint splitting, allowlisted claim rejection and 145-test Godot compatibility coverage; cryptographic signature verification inside the Godot process, SDR relay-ticket installation, reconnect generation fencing and live Godot/PostgreSQL verification remain |
+| 8.41 `[D:7.8,8.9,8.31,8.40]` | **IN PROGRESS.** Authenticated `GET /v1/assignments/{matchId}` now exposes only a validated, player-scoped assignment view including the hosted endpoint; Godot `AssignmentState`/`ControlPlaneClient.fetch_assignment()` bind the response to the authenticated player, recheck expiry, validate and retain the endpoint, and `connect_to_assignment()` now starts only the validated ENet/Steam transport after assignment readiness; the opaque join authorisation is carried in the MatchNet hello payload rather than the endpoint URL; allocated Godot servers now fail closed unless an operator-mounted JSON roster of control-plane signed envelopes is present, and MatchNet checks exact token membership plus match/server/protocol/slot/expiry claims before admitting a peer, rejects concurrent reuse of an active token, and releases it on disconnect; migration 0002 and the Go store adapter now persist/recover the complete player-scoped assignment projection with conflict-safe identical replay; `AssignmentProviderFromStore` wires that durable projection into the API injection point; `SaveAssignments` publishes a complete signed roster atomically instead of allowing partial player visibility; `SaveVerifiedAssignmentRoster` rechecks signed claims before deriving player rows | `server/api/service.go`, `store_adapters.go`, `service_test.go`, `assignment_state.gd`, `control_plane_client.gd`, `match_net.gd`, `server_boot.gd`, `server_config.gd`, `test_assignment_state.gd`, `test_control_plane_client.gd`, `test_match_net.gd`, `server/contracts/v1/openapi.json`, `server/migrations/0002_assignments.sql` and `server/store/assignment_sql.go` cover participant/identity/expiry/shape/transport/endpoint boundaries, player-scoped schema keys, expiry-filtered reads, assignment upsert conflict handling, atomic batch validation, signed-claim binding, strict endpoint splitting, allowlisted claim rejection, duplicate active-token rejection and 145-test Godot compatibility coverage; cryptographic signature verification inside the Godot process, SDR relay-ticket installation, reconnect generation fencing and live Godot/PostgreSQL verification remain |
 | 8.42 `[D:8.22,8.23,8.24,8.40]` | **IN PROGRESS.** `RankedProfileState` and `ControlPlaneClient.fetch_ranked_profile()` expose the backend-authoritative rating/RD/volatility/games/tier/provisional/season view; matchmaking UI displays provisional/tier status without client-side rating math | `test_control_plane_client.gd` validates profile shape, numeric safety and provisional display; ranked profile fetch/display, committed revision after reconnect, abandon status and season countdown remain dependent on live auth/backend events and Godot runtime verification |
 | 8.43 `[D:8.39,8.40,8.41]` | **IN PROGRESS.** Matchmaking client now distinguishes expired queue recovery, session expiry, missing records and retryable control-plane outages; a 401 clears the in-memory token, emits `session_expired` and disables retry until a new session is configured; terminal messages remain visible and active searches are not falsely failed on transient errors | `MatchmakingState` and `ControlPlaneClient` tests cover explicit expiry and the existing terminal/retry-safe state paths; decline, version mismatch, regional outage retry UI, failed reconnect, duplicate-action recovery and live Godot verification remain |