GSD (Get Shit Done) is a mature, actively maintained meta-prompting and context-engineering system that orchestrates AI coding agents (Claude Code, OpenCode, Gemini, Codex, Copilot, Cursor, and 9+ other runtimes) through a structured milestone → phase → plan → execute → verify workflow. The system solves context decay in long AI-assisted coding sessions by maintaining a `.planning/` artifact tree (ROADMAP.md, STATE.md, PLAN.md, SUMMARY.md, VERIFICATION.md) and dispatching focused subagents with fresh 200K-token contexts for each discrete task. The codebase is a dual-package npm monorepo: a legacy CJS CLI (`get-shit-done-cc`) and a modern TypeScript SDK (`@gsd-build/sdk`) with a query-registry architecture, runtime-bridge sync primitive, and generated CJS mirrors that keep both surfaces in parity. The architecture is built around a 'thin orchestrator' pattern where slash-command entry points delegate to workflow markdown files that spawn specialized subagents (planner, executor, verifier, researcher, debugger, code-reviewer) via a registry-backed `gsd-sdk query` dispatch layer. The SDK exposes a `GSD` class that composes plan parsing, config loading, prompt building, and session running into `executePlan()` and `runPhase()` calls, with event-stream telemetry and CLI/WS transports. A `synckit`-based synchronous bridge (`executeForCjs`) lets CJS callers invoke async SDK handlers without subprocess overhead. The query registry resolves commands through a multi-strategy topology (exact, alias, dotted, spaced) with native handlers and transparent CJS fallback. What distinguishes this codebase is the obsessive engineering around installer migrations (transactional, with rollback and user-prompt resolution), cross-runtime path projection (PowerShell/cmd/Git-Bash/POSIX), adversarial parser testing (hostile frontmatter/roadmap fixtures), atomic state writes with file locking, prompt-injection scanning hooks, and a changeset-fragment workflow that eliminates CHANGELOG merge conflicts. The test suite is exceptionally thorough — 400+ test files covering mutation-resistant config validation, golden parity between CJS and SDK, security prompt injection, worktree safety, and regression coverage for 3800+ tracked issues. The system supports 15 AI runtimes with runtime-aware artifact layout, model-profile resolution, and per-agent model overrides.