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+# What is diachron?
+
+diachron is a web framework for TypeScript and Node.js.  It uses a Go-based
+master process that handles file watching, building, process management, and
+request proxying.  The application code is TypeScript running on Express.js.
+
+If you're joining a project that uses diachron, this document will orient you.
+
+## Why diachron exists
+
+diachron was built around a few frustrations with mainstream web frameworks:
+
+- **No dev/prod split.**  Most frameworks behave differently in development and
+  production.  diachron doesn't.  The master process watches files, rebuilds,
+  and manages workers the same way everywhere.  There is no `NODE_ENV`.
+
+- **Managed tooling.**  Node.js, pnpm, and other tools are downloaded and
+  pinned to exact versions inside the project.  You don't install them
+  system-wide.  Everyone on the team runs the same binaries.
+
+- **PostgreSQL, directly.**  No ORM, no database abstraction layer.  You write
+  SQL (via Kysely for type safety) and talk to PostgreSQL.  If you need
+  MySQL or SQLite support, this is not the framework for you.
+
+- **Debuggability over magic.**  Everything is explicit and inspectable.
+  Logging and observability are first-class concerns, not afterthoughts.
+
+diachron is inspired by the
+[Taking PHP Seriously](https://slack.engineering/taking-php-seriously/) essay
+from Slack Engineering.  It's designed for small to medium systems (what we
+call "Ring 0 and Ring 1") -- not heavy-compliance or banking-scale
+applications.
+
+## How it works
+
+When you run `./master`, the following happens:
+
+1. The Go master process starts and watches your TypeScript source files.
+2. It builds the backend using `@vercel/ncc`, producing a single bundled JS
+   file.
+3. It starts one or more Node.js worker processes running your Express app.
+4. It proxies HTTP requests from port 8080 to the workers.
+5. When you edit a source file, it rebuilds and restarts the workers
+   automatically.
+6. If a worker crashes, it restarts automatically.
+
+There is no separate "dev server" or "hot module replacement."  The master
+process is the only way to run the application.
+
+## Project structure
+
+A diachron project looks like this:
+
+```
+.
+├── DIACHRON.md      # This file (framework overview for newcomers)
+├── master/          # Go master process (framework-owned)
+├── logger/          # Go logging service (framework-owned)
+├── diachron/        # Managed binaries, shims, framework library
+│   ├── AGENTS.md    # Guide for AI coding agents
+│   ├── binaries/    # Downloaded Node.js, pnpm (gitignored)
+│   ├── cmd.d/       # Commands available via ./cmd
+│   ├── shims/       # Wrappers that use managed binaries
+│   └── ...
+├── backend/         # Your application code
+│   ├── app.ts       # Entry point
+│   ├── routes.ts    # Route definitions
+│   ├── handlers.ts  # Route handlers
+│   ├── services.ts  # Service layer
+│   ├── types.ts     # Application types
+│   ├── config.ts    # Application configuration
+│   └── diachron/    # Framework library code (framework-owned)
+├── cmd              # Run managed commands (./cmd pnpm install, etc.)
+├── develop          # Development-only commands (./develop reset-db, etc.)
+├── mgmt             # Management commands safe for production
+├── sync.sh          # Install/update all dependencies
+├── master           # The compiled master binary (after sync)
+└── docker-compose.yml
+```
+
+### File ownership
+
+There are two owners of files in a diachron project:
+
+- **You own** everything in `backend/` (except `backend/diachron/`), plus
+  `docker-compose.yml`, `package.json`, and anything else you create.
+- **The framework owns** `master/`, `logger/`, `diachron/`,
+  `backend/diachron/`, and the top-level scripts (`cmd`, `develop`, `mgmt`,
+  `sync.sh`, `check.sh`).
+
+Don't modify framework-owned files.  This separation keeps framework upgrades
+clean.
+
+## Getting started
+
+```bash
+# Install dependencies and build the master process
+./sync.sh
+
+# Start the application
+./master
+```
+
+The app will be available at `http://localhost:8080`.
+
+You need Linux or macOS on x86_64.  For the full stack (database, Redis,
+etc.), you also need `docker compose`.
+
+## The command system
+
+diachron has three types of commands, separated by intent and safety:
+
+- **`./cmd <command>`** -- Run managed tools (node, pnpm, tsx, etc.).  These
+  use the project's pinned versions, not whatever is installed on your system.
+
+  ```bash
+  ./cmd pnpm install
+  ./cmd pnpm test
+  ```
+
+- **`./mgmt <command>`** -- Management commands that are safe to run in
+  production.  Migrations, user management, that sort of thing.
+
+  ```bash
+  ./mgmt migrate
+  ./mgmt add-user
+  ```
+
+- **`./develop <command>`** -- Development commands that may be destructive.
+  Database resets, fixture loading, etc.  These are gated in production.
+
+  ```bash
+  ./develop reset-db
+  ./develop db           # Open a database shell
+  ```
+
+The rule of thumb: if you'd run it at 3am while tired and worried, it's a
+`mgmt` command.  If it destroys data on purpose, it's a `develop` command.
+
+## Key concepts
+
+### Call and Result
+
+diachron wraps Express's `Request` and `Response` in its own types called
+`Call` and `Result`.  This avoids shadowing and keeps the framework's
+interface distinct from Express internals.  Your handlers receive a `Call`
+and return a `Result`.
+
+### Routes
+
+Routes are defined as data (arrays of `Route` objects in `routes.ts`), not
+through decorators or method chaining.  The framework processes them into
+Express handlers.
+
+### No environment variables for behavior
+
+There is no `NODE_ENV`, no `DEBUG`, no mode switching.  Configuration that
+must vary between deployments (database URLs, secrets) lives in
+configuration files, but the application's behavior doesn't branch on
+environment.
+
+## Further reading
+
+- `README.md` -- Project introduction and requirements
+- `diachron/AGENTS.md` -- Guide for AI coding agents
+- `docs/` -- Design documents and philosophy
+- `docs/commands.md` -- Detailed explanation of the command system
+- `docs/concentric-circles.md` -- What diachron is (and isn't) designed for
diff --git a/backend/services.ts b/backend/services.ts
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+// This is a sample file provided by diachron.  You are encouraged to modify it.
+
+// Application services go here.  A service encapsulates a capability that
+// handlers depend on: database queries, external API calls, business logic
+// that doesn't belong in a handler.
+//
+// The framework provides core services via `core` (from ./diachron/core):
+// core.database, core.logging, core.misc, etc.  This file is for your
+// application's own services.
+
+import { core } from "./diachron/core";
+
+const db = core.database.db;
+
+export { db };
diff --git a/backend/types.ts b/backend/types.ts
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+// This is a sample file provided by diachron.  You are encouraged to modify it.
+
+// Application-specific types go here.  Framework types (Call, Result, Route,
+// Handler, etc.) are defined in ./diachron/types and should be imported from
+// there.
+//
+// This file is for your domain types: the nouns and shapes that are specific
+// to your application.
diff --git a/diachron/AGENTS.md b/diachron/AGENTS.md
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+# Working with diachron (Agent Guide)
+
+This document helps AI coding agents work effectively with projects built on
+the diachron framework.  It covers the conventions, commands, and structures
+you need to know.
+
+## Quick orientation
+
+diachron is a TypeScript/Express web framework with a Go master process.
+Your application code lives in `backend/`.  The framework owns `master/`,
+`logger/`, `diachron/`, and `backend/diachron/`.
+
+**Do not modify framework-owned files** unless explicitly asked to work on
+the framework itself.
+
+## Running the application
+
+```bash
+./sync.sh       # Install dependencies (run once, or after pulling changes)
+./master        # Start the application (watches files, rebuilds, proxies)
+```
+
+By default, the app listens on port 8080 (proxy) and workers run on
+ports starting at 3000.
+
+## Commands you'll need
+
+All tools (node, pnpm, tsx, etc.) are managed by the framework.  Do not
+invoke system-installed versions.
+
+```bash
+./cmd pnpm install          # Install npm packages
+./cmd pnpm test             # Run tests
+./cmd pnpm biome check .    # Lint (run from backend/)
+./develop db                # Open database shell
+./develop reset-db          # Drop and recreate database
+./develop migrate           # Run migrations (development)
+./mgmt migrate              # Run migrations (production-safe)
+```
+
+### Formatting and linting
+
+```bash
+cd backend && ../cmd pnpm biome check --write .
+```
+
+### Building Go code
+
+```bash
+cd master && go build
+cd logger && go build
+```
+
+### Quality checks
+
+```bash
+./check.sh                  # shellcheck + golangci-lint
+```
+
+## Application structure
+
+### Where to put code
+
+| What                     | Where                       |
+|--------------------------|-----------------------------|
+| Application entry point  | `backend/app.ts`            |
+| Route definitions        | `backend/routes.ts`         |
+| Route handlers           | `backend/handlers.ts`       |
+| Service layer            | `backend/services.ts`       |
+| Application types        | `backend/types.ts`          |
+| Application config       | `backend/config.ts`         |
+| Database migrations      | `backend/migrations/`       |
+| Framework library code   | `backend/diachron/`         |
+
+### Types and naming
+
+- HTTP request wrapper: `Call` (not Request)
+- HTTP response wrapper: `Result` (not Response)
+- Route definitions: arrays of `Route` objects
+- Handlers: functions that take a `Call` and return a `Result`
+
+These names are intentional.  Use them consistently.
+
+Import framework types from `./diachron/types`:
+
+```typescript
+import type { Call, Result, Route, Handler } from "./diachron/types";
+```
+
+Application-specific domain types go in `backend/types.ts`.
+
+### Services
+
+Application services go in `backend/services.ts`.  Framework services are
+accessed through the `core` object:
+
+```typescript
+import { core } from "./diachron/core";
+
+core.database.db     // Kysely database instance
+core.logging.log     // Logging
+core.misc.sleep      // Utilities
+```
+
+### Exports
+
+When a TypeScript file exports symbols, they should be listed in
+alphabetical order.
+
+## Database
+
+diachron uses PostgreSQL exclusively, accessed through Kysely (type-safe
+query builder).  There is no ORM.
+
+- Write SQL via Kysely, not raw query strings (unless Kysely can't express
+  the query)
+- Migrations live in `backend/migrations/`
+- Run `./develop codegen` after schema changes to regenerate Kysely types
+
+## Key conventions
+
+### No dev/prod distinction
+
+There is no `NODE_ENV`.  The application behaves identically everywhere.
+Do not introduce environment-based branching.
+
+### Managed tooling
+
+Never reference globally installed `node`, `npm`, `npx`, or `pnpm`.
+Always use `./cmd node`, `./cmd pnpm`, etc.
+
+### File ownership boundary
+
+```
+You may edit:          backend/* (except backend/diachron/)
+Do not edit:           master/*, logger/*, diachron/*, backend/diachron/*
+```
+
+If a task requires framework changes, confirm with the user first.
+
+### Command safety tiers
+
+- `./cmd` -- Tool wrappers, always safe
+- `./mgmt` -- Production-safe operations (migrations, user management)
+- `./develop` -- Destructive operations, development only
+
+Never use `./develop` commands against production data.
+
+## Common tasks
+
+### Add a new route
+
+1. Define the route in `backend/routes.ts` as a `Route` object
+2. Implement the handler in `backend/handlers.ts`
+3. Add any needed types to `backend/types.ts`
+
+### Add a database migration
+
+1. Create a migration file in `backend/migrations/`
+2. Run `./develop migrate` to apply it
+3. Run `./develop codegen` to regenerate Kysely types
+
+### Install a package
+
+```bash
+cd backend && ../cmd pnpm add <package>
+```
+
+### Run a one-off TypeScript script
+
+```bash
+./develop tsx backend/path/to/script.ts
+```
+
+## Things to avoid
+
+- Do not introduce `.env` files or `dotenv` without checking with the
+  team first.  The configuration story is still being decided.
+- Do not introduce webpack, vite, or other bundlers.  The master process
+  handles building via `@vercel/ncc`.
+- Do not add express middleware directly.  Use the framework's route
+  processing in `backend/diachron/routing.ts`.
+- Do not use `npm` or globally installed `pnpm`.  Use `./cmd pnpm`.
+- Do not add `NODE_ENV` checks or development/production branches.