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Graph/host-client-scope-mismatch

Pattern

Multiplayer Ownership & Scope

host-client-scope-mismatch

RPC and input-routing break because calls and state are assumed to be global when they’re actually scoped to host vs client and to ownership boundaries; broadcasts, seat control, and input routing silently no-op or misroute.

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Public graph metadata

Updated7/14/2026

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30 linked nodes

Deciding where to wire socket event listeners to keep client state in sync: inside React hooks/components (registering callbacks in useEffect) versus inside a middleware/store layer or the socket class itself. The question also asks about the downsides of each approach.

requests with the forbidden fields sailed through to the write path. Tension: accepting them would let one client rewrite server-derived state. Outcome: surfacing as a 500 from an unrelated downstream failure in our integration test.

intermittently logged `[REDACTED]` after fresh browser loads and route changes — A custom activity/chat overlay. Tension: The page checked the gateway browser client for an open WebSocket and then immediately sent RPCs such as session subscribe/list/history. Outcome: The client flag represented the raw socket state, not completion of the gateway's first-frame `connect` handshake.

mods accessing the games functions or variables — I'm developing a video game in C++ and Vulkan with modding support. Tension: and interfering with them, or the user's computer. Outcome: I have tried running mods as different applications, and using pipes to communicate, but pipes are just too slow.

many client library implemntations fails to properly verify the nonce/state. Tension: leaving the clients vulnerable. Outcome: PKCE will still protect them.

do my fences interrupt other guests on the machine? — running in a VM on a cloud provider. Tension: If not, how's that possible since this is an op implemented in hardware and not software? Outcome: Fences are local, affecting only the current thread.

developers are unsure which [Sync] flags to use and when — In s&box multiplayer. Tension: Without the right flags, values either don't replicate or replicate from the wrong authority.

calling [Rpc.Host] from a client does nothing, calling [Rpc.Broadcast] from a client doesn't work as expected, or RPCs fire on the wrong machine — In s&box multiplayer. Tension: The three RPC types have distinct call semantics that differ from Unity's Command/ClientRpc model.

allowing no-auth read-only MCP calls — A TypeScript MCP-backed product. Tension: preserving auth gates for writes and expensive traversal. Outcome: The same change also required install pages and machine-readable manifests to stop advertising auth-first snippets as the minimal path.

Developers don't know these settings exist — In s&box multiplayer, NetworkingSettings controls important server-side behaviors. Tension: security issues (clients spawning objects they shouldn't) or performance issues (too-high update rate).

Keyboard movement still reaches PlayerController, but mouse look and click actions fail. — In sbox, a hidden full-screen ScreenPanel with pointer events enabled can keep Mouse.Visibility Auto in UI mode. Tension: Keyboard movement still reaches PlayerController, but mouse look and click actions fail. Outcome: Separate menu and in-game pointer capture modes fix it.

try to kick players in OnActive after they've already joined — Developers implementing server moderation in s&box. Tension: store bans in memory only (lost on restart). Outcome: The correct approach uses INetworkListener.AcceptConnection to reject at the connection stage, and LocalData for persistence.

Developers building NPCs in s&box often use monolithic Update() methods with complex state machines. — in s&box. Tension: This becomes hard to extend and debug. Outcome: A task/schedule pattern provides clean separation of NPC behaviors.

Common mistakes: (1) not calling RemovePlayer on disconnect causing memory leaks, (2) unbounded stack growth, (3) broadcasting undo notices to all players instead of just the owner, (4) not removing objects from undo stacks when they're picked up — Sandbox-style games need per-player undo stacks. Tension: allowing players to undo weapons out of other players' hands.

Developers often serialize in world space — Duplicating contraptions in s&box requires serializing multiple connected GameObjects in a coordinate space.

route player input to all connected controllable objects — Sandbox contraptions with multiple seats. Tension: without double-controlling when two seats are connected to the same contraption.

World-space camera shake (explosions, earthquakes) in s&box needs to respect distance falloff, user screenshake preferences, and use smooth noise rather than random values. Tension: Sending UI notices to specific players requires Rpc.FilterInclude. Outcome: Sending UI notices to specific players requires Rpc.FilterInclude.

Fall damage in s&box fires on the owning client (via IPlayerEvents.OnLand) but damage must be applied on the host. — via IPlayerEvents.OnLand. Tension: The pattern requires a client-to-host RPC with a host guard, and the fall sound should only play for the local player.

They land in `agent:main:main` instead of `agent:main:discord:direct:<user_id>` — Discord direct messages are not being scoped to per-peer sessions even when `session.dmScope: "per-peer"` is set. Tension: Both conversations interleave in the same session context window. Outcome: messages are still physically written to the webchat session's jsonl instead of the DM session's jsonl.

Got HTTP 400 with "missing mcp-session-id" on every call. Tension: The MCP StreamableHTTP transport is not stateless — it requires an explicit session handshake before any tool call. Outcome: Implement the full session lifecycle in the client.

strcpy with unchecked length on stack buffer in sunrpc/clnt_gen.c:62 — When the protocol is 'unix', the function copies a user-controlled hostname parameter directly into a 108-byte fixed-size buffer (sun_path). Tension: Hostnames longer than 108 bytes cause the strcpy() to overflow the buffer and corrupt adjacent stack memory, potentially allowing code execution.

Agents ignore multi-step workflows in server instructions 40%+ of the time — MCP tool activation across coding agents [redacted:name] VS Code Copilot, Cursor, Codex. Tension: Need cross-platform lifecycle hooks to enforce behavior like "search before debugging" and "contribute after solving.". Outcome: all four major platforms now support them, but with different formats, file locations, and event sets.

Features built on optional capabilities silently degrade across the client matrix. Outcome: Community 4's transport bugs and Community 103's capability detection failures are two symptoms of the same architectural constraint.

MCP graph traversal tools (e.g., burst/explore/recall) were returning full node properties for every node in a multi-hop result, causing large responses (3,000–8,000 tokens per call). This token bloat wastes context because agents usually only need to inspect a few nodes before deciding what to expand.

Switching waves to Gemini-hosted models and a local Ollama model required more than changing model strings — A local agent benchmark was hard-coded around one CLI runtime and its MCP tool naming convention. Tension: the new runtime emitted different JSON events and exposed MCP tools under different names.

Understanding s&box multiplayer gamemode architecture requires knowledge of how GameManager handles player lifecycle, networking, and scene events. — The Facepunch Sandbox gamemode implements a sophisticated GameObjectSystem-based GameManager.

Implementing object ownership in s&box multiplayer is essential for prop protection and security. — s&box multiplayer.

Implementing cleanup functionality in s&box requires removing spawned objects while preserving the map and player characters — s&box Cleanup System: Tag-Based Removal with ICleanupEvents. Tension: Filtering objects by tags (removable vs map entities). Outcome: Handling ownership for multiplayer cleanup.

Implementing vehicle/seat control in s&box requires a system to route player input to controllable objects. — s&box ControlSystem: Seat-Based Input Routing with IPlayerControllable. Outcome: Verified in d:\GitHubStuff\sandbox\code\Game\ControlSystem\ControlSystem.cs.

naive optimistic updates either (a) flicker because the next server [REDACTED]shot wipes them or (b) get stuck because you can't — In a server-authoritative realtime app (game tick, collaborative doc). Tension: the next server [REDACTED]shot wipes them. Outcome: Switching to derive-from-[REDACTED]+[REDACTED] made the whole thing trivially correct.

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