# Rejected Alternatives — Architecture

Rejected proposals in the **architecture** domain, rationale preserved for the audit trail.

### R-001: Stellaris mod
- **Rejected:** 2026-02-08
- **Reason:** Character system too shallow, multi-empire assumption conflicts with the Settled Reach's single-civilization focus, wormhole-as-infrastructure not achievable within Stellaris modding. Team Leader's experience with Star Trek: New Horizons confirmed that even well-suited IPs struggle with character connection in Stellaris.

### R-002: CK3 total conversion
- **Rejected:** 2026-02-08
- **Reason:** Would require building a space map from scratch within CK3's framework - essentially building a game inside a game. The map system fundamentally doesn't support the complexity needed.

### R-003: Other existing games (Distant Worlds 2, GalCiv IV, Sins of a Solar Empire II, Victoria 3)
- **Rejected:** 2026-02-08
- **Reason:** Each captures at most 40% of what's needed. Smaller modding communities, less mature tools, and none solve the core CK3+Stellaris hybrid requirement.

### R-004: Pure Bevy (Rust) — no Godot
- **Rejected:** 2026-02-09
- **Reason:** No visual editor (level design is code-only). UI framework in flux. API breaks significantly between versions. For a solo developer who needs visual tools for hand-crafted buildings ([D-014](../decisions/scope.md#d-014-v01-map-specification)), Godot's editor is a massive productivity advantage. Bevy's ECS is used — just not its renderer.

### R-005: Pure Godot (GDScript or C#)
- **Rejected:** 2026-02-09
- **Reason:** Scene tree paradigm fights ECS-style simulation. Perception queries ([D-017](../decisions/perception.md#d-017-perception-modes-as-character-build-system)) and information boundaries ([D-010](../decisions/architecture.md#d-010-multiplayer-ready-architectural-baseline)) map naturally to ECS component queries, not scene tree traversal. Multi-core scaling for expanded content impossible in GDScript. Kept as kill-switch fallback if Rust architecture exceeds time budget.

### R-006: Godot + Rust via GDExtension
- **Rejected:** 2026-02-09
- **Reason:** gdext is pre-1.0 with breaking API changes. Godot version upgrades break GDExtension ABI. Thread safety at FFI boundary is CRITICAL risk (`Gd<T>` is `!Send`/`!Sync`). Couples Rust and Godot learning curves. Subprocess/IPC achieves the same architecture without the FFI risk surface, and maps directly to [D-010](../decisions/architecture.md#d-010-multiplayer-ready-architectural-baseline) client-server. See `docs/architecture/risk-godot-rust-bridge.md` for full analysis.

### R-007: Godot + C++ via GDExtension
- **Rejected:** 2026-02-09
- **Reason:** More mature bindings than gdext, but trades Rust's safety guarantees for C++ memory unsafety. No advantage over subprocess/IPC approach. Developer not experienced in C++.

### R-008: Fyrox (pure Rust engine)
- **Rejected:** 2026-02-09
- **Reason:** Single maintainer. ~1/50th of Godot's community. Less documentation, fewer tutorials, weaker AI training data for Claude Code. Single-maintainer risk unacceptable for multi-year project.

### R-009: Custom framework (Rust + raylib/macroquad)
- **Rejected:** 2026-02-09
- **Reason:** Maximum control but you build everything — tilemap rendering, camera, UI, audio, input, asset pipeline. Months before testing a mechanic. The game's hard problems are simulation, not rendering — don't reinvent the rendering wheel.

### R-010: protobuf for client-server serialization
- **Rejected:** 2026-02-09
- **Reason:** Schema evolution across independent deployments is a problem we don't have (one developer, client and server ship together). Poor GDScript support. Rigid schema fights dynamic HUD composition driven by perception modes ([D-017](../decisions/perception.md#d-017-perception-modes-as-character-build-system)). MessagePack's schema-optional nature fits better.

### R-014: Rust rewrite of the Python tooling
- **Rejected:** 2026-08-20 — superseded by [D-263](../decisions/architecture.md#d-263) (one Python CLI, `reach`), which answers [Q-124](../questions/architecture.md#q-124-should-the-python-tooling-be-retooled-into-a-single-rust-cli).
- **Reason:** **Costed down, not argued down.** All three frictions that motivated it — per-script permission prompts, the venv/PATH split between interactive and non-interactive shells, and interpreter startup paid four times per push — are **packaging** problems, and each is fully solved by one bare command on PATH with lazy subcommand loading. None of them requires a different language. Against that, Rust would have to prove **numerical equivalence** for the numpy/scipy/PIL planet-gen path, whose heightmaps are committed build artefacts with goldens standing on them — a genuine porting problem, not a transliteration. It would also make one-off analysis expensive, trading a small recurring cost for a large occasional one in the place the project can least afford it. A hybrid (Rust for the four push-gate checks only, Python for the rest) was also rejected: it reintroduces the two-doors problem the whole exercise exists to remove.
- **Not rejected on principle.** The quality bar this proposal was reaching for — `pql`-calibre, one binary, no interpreter — is the right bar, and D-263 adopts it wholesale minus the language. If the check/gate family ever becomes the dominant push cost *after* lazy loading is measured, this is worth reopening for that family alone, with the measurement in hand.