Expert blueprint for signal-driven architecture using "Signal Up, Call Down" pattern for loose coupling. Covers typed signals, signal chains, one-shot connections, and AutoLoad event buses. Use when implementing event systems OR decoupling nodes. Keywords signal, emit, connect, CONNECT_ONE_SHOT, CON

NEVER Do in Signal Architecture NEVER use the legacy string based Object.connect() — Typos result in silent failures. Always use signal.connect( callback) for compile time validation. NEVER use signals to dictate behavior top down — Signals are past tense events (e.g., "died"). Use direct method calls for commands (e.g., "kill"). NEVER connect a signal twice to the same Callable — This throws an ERR INVALID PARAMETER at runtime unless using the Object.CONNECT REFERENCE COUNTED flag to stack connections. NEVER use a Global Signal Bus for local data — Pollutes global state and makes debugging harder. Use local connections for scene specific logic. NEVER assume callbacks must accept all signal arguments — Use unbind() to drop unwanted parameters and keep your API clean. NEVER create circular signal dependencies — A signals B, B signals back to A? Use a mediator (parent or AutoLoad) to break the loop. NEVER skip signal typing — signal moved without types lacks editor support. Always use signal moved(dir: Vector2) . NEVER forget to disconnect dynamic signals — Ghost connections cause "call on null instance" errors. Disconnect in exit tree() or when retargeting ([disconnect ghost signals.gd](scripts/disconnect ghost signals.gd)). NEVER emit signals with immediate side effects on the emitter — If died.emit() calls queue free() , listeners might fail to respond. Emit first. NEVER use signals for high frequency data streams — Sending 1000+ signals/second (like per particle updates) is inefficient. Use shared arrays or direct buffers. Signal Up / Call Down Children → parents: past tense signals ( health changed , died ). Parents → children: direct calls / properties ( apply damage , play anim ). Siblings: parent mediator or carefully scoped Autoload bus — never sibling hard refs. Use signals for: UI presses, death → game over, loot → inventory, cross scene bus events. Use direct calls for: parent commanding child, local property access. Decision Tree: Where to Connect Scope Pattern MANDATORY script Child notifies parent / UI Local signal.connect in parent ready [signal up call down pattern.gd](scripts/signal up call down pattern.gd) Parent orchestrates children Method calls down (not signals) same Cross scene / systems (achievements, save) Autoload bus [global signal bus router.gd](scripts/global signal bus router.gd) / [global event bus.gd](scripts/global event bus.gd) Linear async steps (load → fade → spawn) await signal sequence [await signal sequencing.gd](scripts/await signal sequencing.gd) / [complex signal sequencer.gd](scripts/complex signal sequencer.gd) Retarget tracking (new enemy) Disconnect old first [disconnect ghost signals.gd](scripts/disconnect ghost signals.gd) One shot / physics safe CONNECT ONE SHOT / CONNECT DEFERRED [one shot deferred connections.gd](scripts/one shot deferred connections.gd) Extra context / drop args Callable.bind / unbind [callable bind context.gd](scripts/callable bind context.gd) / [unbind unwanted args.gd](scripts/unbind unwanted args.gd) Available Scripts [signal up call down pattern.gd](scripts/signal up call down pattern.gd) — MANDATORY before hierarchy wiring. [global signal bus router.gd](scripts/global signal bus router.gd) / [global event bus.gd](scripts/global event bus.gd) — MANDATORY before Autoload buses. [disconnect ghost signals.gd](scripts/disconnect ghost signals.gd) — MANDATORY when switching tracked emitters. [await signal sequencing.gd](scripts/await signal sequencing.gd) / [complex signal sequencer.gd](scripts/complex signal sequencer.gd) — MANDATORY for multi step awaits. [safe dynamic connections.gd](scripts/safe dynamic connections.gd) — is connected guards. [one shot deferred connections.gd](scripts/one shot deferred connections.gd) — one shot / deferred flags. [callable bind context.gd](scripts/callable bind context.gd) / [unbind unwanted args.gd](scripts/unbind unwanted args.gd) — bind/unbind. [track signal emitter source.gd](scripts/track signal emitter source.gd) — CONNECT APPEND SOURCE OBJECT . [signal debugger.gd](scripts/signal debugger.gd) / [signal spy.gd](scripts/signal spy.gd) — debug / test spies. Lambda Capture Cleanup (complete) Godot auto disconnects most connections when a node frees. Exception: lambdas that capture locals — you must disconnect manually. Prefer named methods or [disconnect ghost signals.gd](scripts/disconnect ghost signals.gd) when retargeting. CONNECT REFERENCE COUNTED — Correct Semantics CONNECT REFERENCE COUNTED means multiple identical connects share one connection with a refcount (connect N times / disconnect N times). It is not "auto cleanup when the emitter frees" and does not fix capturing lambda leaks. Auto cleanup on free: normal connections to Object methods (non capturing) are cleared when either side is freed. Capturing lambdas: always manual disconnect (see above). One shot auto remove after fire: CONNECT ONE SHOT . Deep recipes (on demand) LLM ignorance rule: if a general agent would not know it before reading, it lives here or in scripts/ — never delete, only move. Topic Reference Patterns 1–7 + gotchas [implementation patterns.md](references/implementation patterns.md) Reference Progressive disclosure: open Official Documentation links only when researching a specific API; load Related Skills when routing to a peer domain — do not preload the whole lattice. Official Documentation [Using signals](https://docs.godotengine.org/en/stable/getting started/step by step/signals.html) — Core emit/connect model and why signals decouple nodes without hard references. [Scene organization](https://docs.godotengine.org/en/stable/tutorials/best practices/scene organization.html) — Canonical “signal up, call down” ownership rules that keep parent→child command flows explicit. [Instancing with signals](https://docs.godotengine.org/en/stable/tutorials/scripting/instancing with signals.html) — Emit from spawned scenes so parents/managers receive bullets, loot, and other products without fixed node paths. [Autoloads versus regular nodes](https://docs.godotengine.org/en/stable/tutorials/best practices/autoloads versus regular nodes.html) — When a global EventBus is justified vs when scene local signal wiring is safer. [Singletons (Autoload)](https://docs.godotengine.org/en/stable/tutorials/scripting/singletons autoload.html) — How to register a typed signal bus that survives scene changes. [Signal](https://docs.godotengine.org/en/stable/classes/class signal.html) — Typed Signal API: emit , connect , is connected , and disconnect helpers used throughout this skill. [Callable](https://docs.godotengine.org/en/stable/classes/class callable.html) — bind() / unbind() for injecting or discarding callback context without wrapper lambdas. [Object](https://docs.godotengine.org/en/stable/classes/class object.html) — CONNECT ONE SHOT , CONNECT DEFERRED , CONNECT REFERENCE COUNTED , and CONNECT APPEND SOURCE OBJECT flags. [GDScript basics](https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript basics.html) — Typed signal declarations and await on signals for linear async sequences. [Using SceneTree](https://docs.godotengine.org/en/stable/tutorials/scripting/scene tree.html) — Connection lifetime across enter/exit tree and why dynamic listeners must disconnect when retargeting. [Godot notifications](https://docs.godotengine.org/en/stable/tutorials/best practices/godot notifications.html) — Safe connection timing relative to ready , parent caches, and user signals. [Idle and Physics Processing](https://docs.godotengine.org/en/stable/tutorials/scripting/idle and physics processing.html) — Why deferred signal handlers matter when callbacks mutate physics bodies mid step. Related Skills Prerequisites [godot project foundations](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot project foundations/SKILL.md) — Project layout, Autoload registration, and scene ownership conventions signals plug into. [godot gdscript mastery](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot gdscript mastery/SKILL.md) — Typed Callables, await , and signal syntax required before advanced connect flags and sequencers. [godot autoload architecture](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot autoload architecture/SKILL.md) — Singleton boot order and ownership rules for global EventBus routers (not for local scene events). Complements [godot composition](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot composition/SKILL.md) — Component nodes emit past tense events; parents compose by connecting those signals and calling down. [godot scene management](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot scene management/SKILL.md) — Scene swaps and loaders must reconnect or re emit through buses without ghost listeners. [godot state machine advanced](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot state machine advanced/SKILL.md) — State enter/exit often drives signal fan out; keeps FSM transitions from becoming circular signal graphs. [godot resource data patterns](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot resource data patterns/SKILL.md) — Prefer Resources for shared config; signals carry change events, not duplicated mutable state blobs. [godot testing patterns](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot testing patterns/SKILL.md) — watch signals / spies pair with this skill’s emit contracts for unit and integration tests. [godot ui containers](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot ui containers/SKILL.md) — Buttons and menus should signal intent upward; controllers call down to update Control trees. Downstream / consumers [godot dialogue system](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot dialogue system/SKILL.md) — Line/choice completion events should follow signal up orchestration into UI and quest listeners. [godot ability system](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot ability system/SKILL.md) — Cooldown, cast, and hit payloads need typed signals so HUD/VFX stay decoupled from ability nodes. [godot combat system](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot combat system/SKILL.md) — Damage/death/score chains are the classic signal up fan out into UI, audio, and progression. [godot performance optimization](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot performance optimization/SKILL.md) — Escalate when high frequency emit storms show up; replace per tick signals with buffers or direct reads. Master [godot master](https://github.com/thedivergentai/gd agentic skills/blob/main/skills/godot master/SKILL.md) — Library router and mirrored module entry; open when discovering which Domain Skill owns a cross cutting architecture concern.

godot-signal-architecture