Rename express/ to backend/ and update references

Update paths in sync.sh, master/main.go, and CLAUDE.md to reflect
the directory rename.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/diachron/auth/index.ts

@@ -0,0 +1,20 @@
+// index.ts
+//
+// Barrel export for auth module.
+//
+// NOTE: authRoutes is NOT exported here to avoid circular dependency:
+// services.ts → auth/index.ts → auth/routes.ts → services.ts
+// Import authRoutes directly from "./auth/routes" instead.
+
+export { hashPassword, verifyPassword } from "./password";
+export { type AuthResult, AuthService } from "./service";
+export { type AuthStore, InMemoryAuthStore } from "./store";
+export { generateToken, hashToken, SESSION_COOKIE_NAME } from "./token";
+export {
+    type AuthMethod,
+    Session,
+    type SessionData,
+    type TokenId,
+    type TokenType,
+    tokenLifetimes,
+} from "./types";

backend/diachron/auth/password.spec.ts

@@ -0,0 +1,80 @@
+// Tests for auth/password.ts
+// Pure unit tests - no database needed
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { hashPassword, verifyPassword } from "./password";
+
+describe("password", () => {
+    describe("hashPassword", () => {
+        it("returns a scrypt formatted hash", async () => {
+            const hash = await hashPassword("testpassword");
+            assert.ok(hash.startsWith("$scrypt$"));
+        });
+
+        it("includes all scrypt parameters", async () => {
+            const hash = await hashPassword("testpassword");
+            const parts = hash.split("$");
+            // Format: $scrypt$N$r$p$salt$hash
+            assert.equal(parts.length, 7);
+            assert.equal(parts[0], "");
+            assert.equal(parts[1], "scrypt");
+            // N, r, p should be numbers
+            assert.ok(!Number.isNaN(parseInt(parts[2], 10)));
+            assert.ok(!Number.isNaN(parseInt(parts[3], 10)));
+            assert.ok(!Number.isNaN(parseInt(parts[4], 10)));
+        });
+
+        it("generates different hashes for same password (different salt)", async () => {
+            const hash1 = await hashPassword("testpassword");
+            const hash2 = await hashPassword("testpassword");
+            assert.notEqual(hash1, hash2);
+        });
+    });
+
+    describe("verifyPassword", () => {
+        it("returns true for correct password", async () => {
+            const hash = await hashPassword("correctpassword");
+            const result = await verifyPassword("correctpassword", hash);
+            assert.equal(result, true);
+        });
+
+        it("returns false for incorrect password", async () => {
+            const hash = await hashPassword("correctpassword");
+            const result = await verifyPassword("wrongpassword", hash);
+            assert.equal(result, false);
+        });
+
+        it("throws for invalid hash format", async () => {
+            await assert.rejects(
+                verifyPassword("password", "invalid-hash"),
+                /Invalid password hash format/,
+            );
+        });
+
+        it("throws for non-scrypt hash", async () => {
+            await assert.rejects(
+                verifyPassword("password", "$bcrypt$10$salt$hash"),
+                /Invalid password hash format/,
+            );
+        });
+
+        it("works with empty password", async () => {
+            const hash = await hashPassword("");
+            const result = await verifyPassword("", hash);
+            assert.equal(result, true);
+        });
+
+        it("works with unicode password", async () => {
+            const hash = await hashPassword("p@$$w0rd\u{1F511}");
+            const result = await verifyPassword("p@$$w0rd\u{1F511}", hash);
+            assert.equal(result, true);
+        });
+
+        it("is case sensitive", async () => {
+            const hash = await hashPassword("Password");
+            const result = await verifyPassword("password", hash);
+            assert.equal(result, false);
+        });
+    });
+});

backend/diachron/auth/password.ts

@@ -0,0 +1,70 @@
+// password.ts
+//
+// Password hashing using Node.js scrypt (no external dependencies).
+// Format: $scrypt$N$r$p$salt$hash (all base64)
+
+import {
+    randomBytes,
+    type ScryptOptions,
+    scrypt,
+    timingSafeEqual,
+} from "node:crypto";
+
+// Configuration
+const SALT_LENGTH = 32;
+const KEY_LENGTH = 64;
+const SCRYPT_PARAMS: ScryptOptions = {
+    N: 16384, // CPU/memory cost parameter (2^14)
+    r: 8, // Block size
+    p: 1, // Parallelization
+};
+
+// Promisified scrypt with options support
+function scryptAsync(
+    password: string,
+    salt: Buffer,
+    keylen: number,
+    options: ScryptOptions,
+): Promise<Buffer> {
+    return new Promise((resolve, reject) => {
+        scrypt(password, salt, keylen, options, (err, derivedKey) => {
+            if (err) {
+                reject(err);
+            } else {
+                resolve(derivedKey);
+            }
+        });
+    });
+}
+
+async function hashPassword(password: string): Promise<string> {
+    const salt = randomBytes(SALT_LENGTH);
+    const hash = await scryptAsync(password, salt, KEY_LENGTH, SCRYPT_PARAMS);
+
+    const { N, r, p } = SCRYPT_PARAMS;
+    return `$scrypt$${N}$${r}$${p}$${salt.toString("base64")}$${hash.toString("base64")}`;
+}
+
+async function verifyPassword(
+    password: string,
+    stored: string,
+): Promise<boolean> {
+    const parts = stored.split("$");
+    if (parts[1] !== "scrypt" || parts.length !== 7) {
+        throw new Error("Invalid password hash format");
+    }
+
+    const [, , nStr, rStr, pStr, saltB64, hashB64] = parts;
+    const salt = Buffer.from(saltB64, "base64");
+    const storedHash = Buffer.from(hashB64, "base64");
+
+    const computedHash = await scryptAsync(password, salt, storedHash.length, {
+        N: parseInt(nStr, 10),
+        r: parseInt(rStr, 10),
+        p: parseInt(pStr, 10),
+    });
+
+    return timingSafeEqual(storedHash, computedHash);
+}
+
+export { hashPassword, verifyPassword };

backend/diachron/auth/routes.ts

@@ -0,0 +1,231 @@
+// routes.ts
+//
+// Authentication route handlers.
+
+import { z } from "zod";
+import { contentTypes } from "../content-types";
+import { httpCodes } from "../http-codes";
+import { request } from "../request";
+import type { Call, Result, Route } from "../types";
+import {
+    forgotPasswordInputParser,
+    loginInputParser,
+    registerInputParser,
+    resetPasswordInputParser,
+} from "./types";
+
+// Helper for JSON responses
+const jsonResponse = (
+    code: (typeof httpCodes.success)[keyof typeof httpCodes.success],
+    data: object,
+): Result => ({
+    code,
+    contentType: contentTypes.application.json,
+    result: JSON.stringify(data),
+});
+
+const errorResponse = (
+    code: (typeof httpCodes.clientErrors)[keyof typeof httpCodes.clientErrors],
+    error: string,
+): Result => ({
+    code,
+    contentType: contentTypes.application.json,
+    result: JSON.stringify({ error }),
+});
+
+// POST /auth/login
+const loginHandler = async (call: Call): Promise<Result> => {
+    try {
+        const body = call.request.body;
+        const { email, password } = loginInputParser.parse(body);
+
+        const result = await request.auth.login(email, password, "cookie", {
+            userAgent: call.request.get("User-Agent"),
+            ipAddress: call.request.ip,
+        });
+
+        if (!result.success) {
+            return errorResponse(
+                httpCodes.clientErrors.Unauthorized,
+                result.error,
+            );
+        }
+
+        return jsonResponse(httpCodes.success.OK, {
+            token: result.token,
+            user: {
+                id: result.user.id,
+                email: result.user.email,
+                displayName: result.user.displayName,
+            },
+        });
+    } catch (error) {
+        if (error instanceof z.ZodError) {
+            return errorResponse(
+                httpCodes.clientErrors.BadRequest,
+                "Invalid input",
+            );
+        }
+        throw error;
+    }
+};
+
+// POST /auth/logout
+const logoutHandler = async (call: Call): Promise<Result> => {
+    const token = request.auth.extractToken(call.request);
+    if (token) {
+        await request.auth.logout(token);
+    }
+
+    return jsonResponse(httpCodes.success.OK, { message: "Logged out" });
+};
+
+// POST /auth/register
+const registerHandler = async (call: Call): Promise<Result> => {
+    try {
+        const body = call.request.body;
+        const { email, password, displayName } =
+            registerInputParser.parse(body);
+
+        const result = await request.auth.register(
+            email,
+            password,
+            displayName,
+        );
+
+        if (!result.success) {
+            return errorResponse(httpCodes.clientErrors.Conflict, result.error);
+        }
+
+        // TODO: Send verification email with result.verificationToken
+        // For now, log it for development
+        console.log(
+            `[AUTH] Verification token for ${email}: ${result.verificationToken}`,
+        );
+
+        return jsonResponse(httpCodes.success.Created, {
+            message:
+                "Registration successful. Please check your email to verify your account.",
+            user: {
+                id: result.user.id,
+                email: result.user.email,
+            },
+        });
+    } catch (error) {
+        if (error instanceof z.ZodError) {
+            return errorResponse(
+                httpCodes.clientErrors.BadRequest,
+                "Invalid input",
+            );
+        }
+        throw error;
+    }
+};
+
+// POST /auth/forgot-password
+const forgotPasswordHandler = async (call: Call): Promise<Result> => {
+    try {
+        const body = call.request.body;
+        const { email } = forgotPasswordInputParser.parse(body);
+
+        const result = await request.auth.createPasswordResetToken(email);
+
+        // Always return success (don't reveal if email exists)
+        if (result) {
+            // TODO: Send password reset email
+            console.log(
+                `[AUTH] Password reset token for ${email}: ${result.token}`,
+            );
+        }
+
+        return jsonResponse(httpCodes.success.OK, {
+            message:
+                "If an account exists with that email, a password reset link has been sent.",
+        });
+    } catch (error) {
+        if (error instanceof z.ZodError) {
+            return errorResponse(
+                httpCodes.clientErrors.BadRequest,
+                "Invalid input",
+            );
+        }
+        throw error;
+    }
+};
+
+// POST /auth/reset-password
+const resetPasswordHandler = async (call: Call): Promise<Result> => {
+    try {
+        const body = call.request.body;
+        const { token, password } = resetPasswordInputParser.parse(body);
+
+        const result = await request.auth.resetPassword(token, password);
+
+        if (!result.success) {
+            return errorResponse(
+                httpCodes.clientErrors.BadRequest,
+                result.error,
+            );
+        }
+
+        return jsonResponse(httpCodes.success.OK, {
+            message:
+                "Password has been reset. You can now log in with your new password.",
+        });
+    } catch (error) {
+        if (error instanceof z.ZodError) {
+            return errorResponse(
+                httpCodes.clientErrors.BadRequest,
+                "Invalid input",
+            );
+        }
+        throw error;
+    }
+};
+
+// GET /auth/verify-email?token=xxx
+const verifyEmailHandler = async (call: Call): Promise<Result> => {
+    const url = new URL(call.path, "http://localhost");
+    const token = url.searchParams.get("token");
+
+    if (!token) {
+        return errorResponse(
+            httpCodes.clientErrors.BadRequest,
+            "Missing token",
+        );
+    }
+
+    const result = await request.auth.verifyEmail(token);
+
+    if (!result.success) {
+        return errorResponse(httpCodes.clientErrors.BadRequest, result.error);
+    }
+
+    return jsonResponse(httpCodes.success.OK, {
+        message: "Email verified successfully. You can now log in.",
+    });
+};
+
+// Export routes
+const authRoutes: Route[] = [
+    { path: "/auth/login", methods: ["POST"], handler: loginHandler },
+    { path: "/auth/logout", methods: ["POST"], handler: logoutHandler },
+    { path: "/auth/register", methods: ["POST"], handler: registerHandler },
+    {
+        path: "/auth/forgot-password",
+        methods: ["POST"],
+        handler: forgotPasswordHandler,
+    },
+    {
+        path: "/auth/reset-password",
+        methods: ["POST"],
+        handler: resetPasswordHandler,
+    },
+    {
+        path: "/auth/verify-email",
+        methods: ["GET"],
+        handler: verifyEmailHandler,
+    },
+];
+
+export { authRoutes };

backend/diachron/auth/service.spec.ts

@@ -0,0 +1,419 @@
+// Tests for auth/service.ts
+// Uses InMemoryAuthStore - no database needed
+
+import assert from "node:assert/strict";
+import { beforeEach, describe, it } from "node:test";
+import { AuthService } from "./service";
+import { InMemoryAuthStore } from "./store";
+
+describe("AuthService", () => {
+    let store: InMemoryAuthStore;
+    let service: AuthService;
+
+    beforeEach(() => {
+        store = new InMemoryAuthStore();
+        service = new AuthService(store);
+    });
+
+    describe("register", () => {
+        it("creates a new user", async () => {
+            const result = await service.register(
+                "test@example.com",
+                "password123",
+                "Test User",
+            );
+
+            assert.equal(result.success, true);
+            if (result.success) {
+                assert.equal(result.user.email, "test@example.com");
+                assert.equal(result.user.displayName, "Test User");
+                assert.ok(result.verificationToken.length > 0);
+            }
+        });
+
+        it("fails when email already registered", async () => {
+            await service.register("test@example.com", "password123");
+            const result = await service.register(
+                "test@example.com",
+                "password456",
+            );
+
+            assert.equal(result.success, false);
+            if (!result.success) {
+                assert.equal(result.error, "Email already registered");
+            }
+        });
+
+        it("creates user without displayName", async () => {
+            const result = await service.register(
+                "test@example.com",
+                "password123",
+            );
+
+            assert.equal(result.success, true);
+            if (result.success) {
+                assert.equal(result.user.displayName, undefined);
+            }
+        });
+    });
+
+    describe("login", () => {
+        beforeEach(async () => {
+            // Create and verify a user
+            const result = await service.register(
+                "test@example.com",
+                "password123",
+                "Test User",
+            );
+            if (result.success) {
+                // Verify email to activate user
+                await service.verifyEmail(result.verificationToken);
+            }
+        });
+
+        it("succeeds with correct credentials", async () => {
+            const result = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+            );
+
+            assert.equal(result.success, true);
+            if (result.success) {
+                assert.ok(result.token.length > 0);
+                assert.equal(result.user.email, "test@example.com");
+            }
+        });
+
+        it("fails with wrong password", async () => {
+            const result = await service.login(
+                "test@example.com",
+                "wrongpassword",
+                "cookie",
+            );
+
+            assert.equal(result.success, false);
+            if (!result.success) {
+                assert.equal(result.error, "Invalid credentials");
+            }
+        });
+
+        it("fails with unknown email", async () => {
+            const result = await service.login(
+                "unknown@example.com",
+                "password123",
+                "cookie",
+            );
+
+            assert.equal(result.success, false);
+            if (!result.success) {
+                assert.equal(result.error, "Invalid credentials");
+            }
+        });
+
+        it("fails for inactive user", async () => {
+            // Create a user but don't verify email (stays pending)
+            await service.register("pending@example.com", "password123");
+
+            const result = await service.login(
+                "pending@example.com",
+                "password123",
+                "cookie",
+            );
+
+            assert.equal(result.success, false);
+            if (!result.success) {
+                assert.equal(result.error, "Account is not active");
+            }
+        });
+
+        it("stores metadata", async () => {
+            const result = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+                { userAgent: "TestAgent", ipAddress: "192.168.1.1" },
+            );
+
+            assert.equal(result.success, true);
+        });
+    });
+
+    describe("validateToken", () => {
+        let token: string;
+
+        beforeEach(async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            if (regResult.success) {
+                await service.verifyEmail(regResult.verificationToken);
+            }
+
+            const loginResult = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+            );
+            if (loginResult.success) {
+                token = loginResult.token;
+            }
+        });
+
+        it("returns authenticated for valid token", async () => {
+            const result = await service.validateToken(token);
+
+            assert.equal(result.authenticated, true);
+            if (result.authenticated) {
+                assert.equal(result.user.email, "test@example.com");
+                assert.notEqual(result.session, null);
+            }
+        });
+
+        it("returns unauthenticated for invalid token", async () => {
+            const result = await service.validateToken("invalid-token");
+
+            assert.equal(result.authenticated, false);
+            assert.equal(result.user.isAnonymous(), true);
+            assert.equal(result.session, null);
+        });
+    });
+
+    describe("logout", () => {
+        it("invalidates the session", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            if (regResult.success) {
+                await service.verifyEmail(regResult.verificationToken);
+            }
+
+            const loginResult = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+            );
+            assert.equal(loginResult.success, true);
+            if (!loginResult.success) return;
+
+            const token = loginResult.token;
+
+            // Token should be valid before logout
+            const beforeLogout = await service.validateToken(token);
+            assert.equal(beforeLogout.authenticated, true);
+
+            // Logout
+            await service.logout(token);
+
+            // Token should be invalid after logout
+            const afterLogout = await service.validateToken(token);
+            assert.equal(afterLogout.authenticated, false);
+        });
+    });
+
+    describe("logoutAllSessions", () => {
+        it("invalidates all user sessions", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            if (regResult.success) {
+                await service.verifyEmail(regResult.verificationToken);
+            }
+
+            // Create multiple sessions
+            const login1 = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+            );
+            const login2 = await service.login(
+                "test@example.com",
+                "password123",
+                "bearer",
+            );
+
+            assert.equal(login1.success, true);
+            assert.equal(login2.success, true);
+            if (!login1.success || !login2.success) return;
+
+            // Both should be valid
+            const before1 = await service.validateToken(login1.token);
+            const before2 = await service.validateToken(login2.token);
+            assert.equal(before1.authenticated, true);
+            assert.equal(before2.authenticated, true);
+
+            // Logout all
+            const user = await store.getUserByEmail("test@example.com");
+            const count = await service.logoutAllSessions(user!.id);
+            assert.equal(count, 2);
+
+            // Both should be invalid
+            const after1 = await service.validateToken(login1.token);
+            const after2 = await service.validateToken(login2.token);
+            assert.equal(after1.authenticated, false);
+            assert.equal(after2.authenticated, false);
+        });
+    });
+
+    describe("verifyEmail", () => {
+        it("activates user with valid token", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            assert.equal(regResult.success, true);
+            if (!regResult.success) return;
+
+            const result = await service.verifyEmail(
+                regResult.verificationToken,
+            );
+            assert.equal(result.success, true);
+
+            // User should now be active and can login
+            const loginResult = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+            );
+            assert.equal(loginResult.success, true);
+        });
+
+        it("fails with invalid token", async () => {
+            const result = await service.verifyEmail("invalid-token");
+
+            assert.equal(result.success, false);
+            if (!result.success) {
+                assert.equal(
+                    result.error,
+                    "Invalid or expired verification token",
+                );
+            }
+        });
+
+        it("fails when token already used", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            assert.equal(regResult.success, true);
+            if (!regResult.success) return;
+
+            // First verification succeeds
+            const result1 = await service.verifyEmail(
+                regResult.verificationToken,
+            );
+            assert.equal(result1.success, true);
+
+            // Second verification fails (token deleted)
+            const result2 = await service.verifyEmail(
+                regResult.verificationToken,
+            );
+            assert.equal(result2.success, false);
+        });
+    });
+
+    describe("createPasswordResetToken", () => {
+        it("returns token for existing user", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            assert.equal(regResult.success, true);
+
+            const result =
+                await service.createPasswordResetToken("test@example.com");
+            assert.notEqual(result, null);
+            assert.ok(result!.token.length > 0);
+        });
+
+        it("returns null for unknown email", async () => {
+            const result = await service.createPasswordResetToken(
+                "unknown@example.com",
+            );
+            assert.equal(result, null);
+        });
+    });
+
+    describe("resetPassword", () => {
+        it("changes password with valid token", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "oldpassword",
+            );
+            if (regResult.success) {
+                await service.verifyEmail(regResult.verificationToken);
+            }
+
+            const resetToken =
+                await service.createPasswordResetToken("test@example.com");
+            assert.notEqual(resetToken, null);
+
+            const result = await service.resetPassword(
+                resetToken!.token,
+                "newpassword",
+            );
+            assert.equal(result.success, true);
+
+            // Old password should no longer work
+            const loginOld = await service.login(
+                "test@example.com",
+                "oldpassword",
+                "cookie",
+            );
+            assert.equal(loginOld.success, false);
+
+            // New password should work
+            const loginNew = await service.login(
+                "test@example.com",
+                "newpassword",
+                "cookie",
+            );
+            assert.equal(loginNew.success, true);
+        });
+
+        it("fails with invalid token", async () => {
+            const result = await service.resetPassword(
+                "invalid-token",
+                "newpassword",
+            );
+
+            assert.equal(result.success, false);
+            if (!result.success) {
+                assert.equal(result.error, "Invalid or expired reset token");
+            }
+        });
+
+        it("invalidates all existing sessions", async () => {
+            const regResult = await service.register(
+                "test@example.com",
+                "password123",
+            );
+            if (regResult.success) {
+                await service.verifyEmail(regResult.verificationToken);
+            }
+
+            // Create a session
+            const loginResult = await service.login(
+                "test@example.com",
+                "password123",
+                "cookie",
+            );
+            assert.equal(loginResult.success, true);
+            if (!loginResult.success) return;
+
+            const sessionToken = loginResult.token;
+
+            // Reset password
+            const resetToken =
+                await service.createPasswordResetToken("test@example.com");
+            await service.resetPassword(resetToken!.token, "newpassword");
+
+            // Old session should be invalid
+            const validateResult = await service.validateToken(sessionToken);
+            assert.equal(validateResult.authenticated, false);
+        });
+    });
+});

backend/diachron/auth/service.ts

@@ -0,0 +1,262 @@
+// service.ts
+//
+// Core authentication service providing login, logout, registration,
+// password reset, and email verification.
+
+import type { Request as ExpressRequest } from "express";
+import {
+    type AnonymousUser,
+    anonymousUser,
+    type User,
+    type UserId,
+} from "../user";
+import { hashPassword, verifyPassword } from "./password";
+import type { AuthStore } from "./store";
+import {
+    hashToken,
+    parseAuthorizationHeader,
+    SESSION_COOKIE_NAME,
+} from "./token";
+import { type SessionData, type TokenId, tokenLifetimes } from "./types";
+
+type LoginResult =
+    | { success: true; token: string; user: User }
+    | { success: false; error: string };
+
+type RegisterResult =
+    | { success: true; user: User; verificationToken: string }
+    | { success: false; error: string };
+
+type SimpleResult = { success: true } | { success: false; error: string };
+
+// Result of validating a request/token - contains both user and session
+export type AuthResult =
+    | { authenticated: true; user: User; session: SessionData }
+    | { authenticated: false; user: AnonymousUser; session: null };
+
+export class AuthService {
+    constructor(private store: AuthStore) {}
+
+    // === Login ===
+
+    async login(
+        email: string,
+        password: string,
+        authMethod: "cookie" | "bearer",
+        metadata?: { userAgent?: string; ipAddress?: string },
+    ): Promise<LoginResult> {
+        const user = await this.store.getUserByEmail(email);
+        if (!user) {
+            return { success: false, error: "Invalid credentials" };
+        }
+
+        if (!user.isActive()) {
+            return { success: false, error: "Account is not active" };
+        }
+
+        const passwordHash = await this.store.getUserPasswordHash(user.id);
+        if (!passwordHash) {
+            return { success: false, error: "Invalid credentials" };
+        }
+
+        const valid = await verifyPassword(password, passwordHash);
+        if (!valid) {
+            return { success: false, error: "Invalid credentials" };
+        }
+
+        const { token } = await this.store.createSession({
+            userId: user.id,
+            tokenType: "session",
+            authMethod,
+            expiresAt: new Date(Date.now() + tokenLifetimes.session),
+            userAgent: metadata?.userAgent,
+            ipAddress: metadata?.ipAddress,
+        });
+
+        return { success: true, token, user };
+    }
+
+    // === Session Validation ===
+
+    async validateRequest(request: ExpressRequest): Promise<AuthResult> {
+        // Try cookie first (for web requests)
+        let token = this.extractCookieToken(request);
+
+        // Fall back to Authorization header (for API requests)
+        if (!token) {
+            token = parseAuthorizationHeader(request.get("Authorization"));
+        }
+
+        if (!token) {
+            return { authenticated: false, user: anonymousUser, session: null };
+        }
+
+        return this.validateToken(token);
+    }
+
+    async validateToken(token: string): Promise<AuthResult> {
+        const tokenId = hashToken(token) as TokenId;
+        const session = await this.store.getSession(tokenId);
+
+        if (!session) {
+            return { authenticated: false, user: anonymousUser, session: null };
+        }
+
+        if (session.tokenType !== "session") {
+            return { authenticated: false, user: anonymousUser, session: null };
+        }
+
+        const user = await this.store.getUserById(session.userId as UserId);
+        if (!user || !user.isActive()) {
+            return { authenticated: false, user: anonymousUser, session: null };
+        }
+
+        // Update last used (fire and forget)
+        this.store.updateLastUsed(tokenId).catch(() => {});
+
+        return { authenticated: true, user, session };
+    }
+
+    private extractCookieToken(request: ExpressRequest): string | null {
+        const cookies = request.get("Cookie");
+        if (!cookies) {
+            return null;
+        }
+
+        for (const cookie of cookies.split(";")) {
+            const [name, ...valueParts] = cookie.trim().split("=");
+            if (name === SESSION_COOKIE_NAME) {
+                return valueParts.join("="); // Handle = in token value
+            }
+        }
+        return null;
+    }
+
+    // === Logout ===
+
+    async logout(token: string): Promise<void> {
+        const tokenId = hashToken(token) as TokenId;
+        await this.store.deleteSession(tokenId);
+    }
+
+    async logoutAllSessions(userId: UserId): Promise<number> {
+        return this.store.deleteUserSessions(userId);
+    }
+
+    // === Registration ===
+
+    async register(
+        email: string,
+        password: string,
+        displayName?: string,
+    ): Promise<RegisterResult> {
+        const existing = await this.store.getUserByEmail(email);
+        if (existing) {
+            return { success: false, error: "Email already registered" };
+        }
+
+        const passwordHash = await hashPassword(password);
+        const user = await this.store.createUser({
+            email,
+            passwordHash,
+            displayName,
+        });
+
+        // Create email verification token
+        const { token: verificationToken } = await this.store.createSession({
+            userId: user.id,
+            tokenType: "email_verify",
+            authMethod: "bearer",
+            expiresAt: new Date(Date.now() + tokenLifetimes.email_verify),
+        });
+
+        return { success: true, user, verificationToken };
+    }
+
+    // === Email Verification ===
+
+    async verifyEmail(token: string): Promise<SimpleResult> {
+        const tokenId = hashToken(token) as TokenId;
+        const session = await this.store.getSession(tokenId);
+
+        if (!session || session.tokenType !== "email_verify") {
+            return {
+                success: false,
+                error: "Invalid or expired verification token",
+            };
+        }
+
+        if (session.isUsed) {
+            return { success: false, error: "Token already used" };
+        }
+
+        await this.store.updateUserEmailVerified(session.userId as UserId);
+        await this.store.deleteSession(tokenId);
+
+        return { success: true };
+    }
+
+    // === Password Reset ===
+
+    async createPasswordResetToken(
+        email: string,
+    ): Promise<{ token: string } | null> {
+        const user = await this.store.getUserByEmail(email);
+        if (!user) {
+            // Don't reveal whether email exists
+            return null;
+        }
+
+        const { token } = await this.store.createSession({
+            userId: user.id,
+            tokenType: "password_reset",
+            authMethod: "bearer",
+            expiresAt: new Date(Date.now() + tokenLifetimes.password_reset),
+        });
+
+        return { token };
+    }
+
+    async resetPassword(
+        token: string,
+        newPassword: string,
+    ): Promise<SimpleResult> {
+        const tokenId = hashToken(token) as TokenId;
+        const session = await this.store.getSession(tokenId);
+
+        if (!session || session.tokenType !== "password_reset") {
+            return { success: false, error: "Invalid or expired reset token" };
+        }
+
+        if (session.isUsed) {
+            return { success: false, error: "Token already used" };
+        }
+
+        const passwordHash = await hashPassword(newPassword);
+        await this.store.setUserPassword(
+            session.userId as UserId,
+            passwordHash,
+        );
+
+        // Invalidate all existing sessions (security: password changed)
+        await this.store.deleteUserSessions(session.userId as UserId);
+
+        // Delete the reset token
+        await this.store.deleteSession(tokenId);
+
+        return { success: true };
+    }
+
+    // === Token Extraction Helper (for routes) ===
+
+    extractToken(request: ExpressRequest): string | null {
+        // Try Authorization header first
+        const token = parseAuthorizationHeader(request.get("Authorization"));
+        if (token) {
+            return token;
+        }
+
+        // Try cookie
+        return this.extractCookieToken(request);
+    }
+}

backend/diachron/auth/store.spec.ts

@@ -0,0 +1,321 @@
+// Tests for auth/store.ts (InMemoryAuthStore)
+// Pure unit tests - no database needed
+
+import assert from "node:assert/strict";
+import { after, before, beforeEach, describe, it } from "node:test";
+import type { UserId } from "../user";
+import { InMemoryAuthStore } from "./store";
+import { hashToken } from "./token";
+import type { TokenId } from "./types";
+
+describe("InMemoryAuthStore", () => {
+    let store: InMemoryAuthStore;
+
+    beforeEach(() => {
+        store = new InMemoryAuthStore();
+    });
+
+    describe("createUser", () => {
+        it("creates a user with pending status", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+                displayName: "Test User",
+            });
+
+            assert.equal(user.email, "test@example.com");
+            assert.equal(user.displayName, "Test User");
+            assert.equal(user.status, "pending");
+        });
+
+        it("creates a user without displayName", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            assert.equal(user.email, "test@example.com");
+            assert.equal(user.displayName, undefined);
+        });
+
+        it("generates a unique id", async () => {
+            const user1 = await store.createUser({
+                email: "test1@example.com",
+                passwordHash: "hash123",
+            });
+            const user2 = await store.createUser({
+                email: "test2@example.com",
+                passwordHash: "hash456",
+            });
+
+            assert.notEqual(user1.id, user2.id);
+        });
+    });
+
+    describe("getUserByEmail", () => {
+        it("returns user when found", async () => {
+            await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const user = await store.getUserByEmail("test@example.com");
+            assert.notEqual(user, null);
+            assert.equal(user!.email, "test@example.com");
+        });
+
+        it("is case-insensitive", async () => {
+            await store.createUser({
+                email: "Test@Example.COM",
+                passwordHash: "hash123",
+            });
+
+            const user = await store.getUserByEmail("test@example.com");
+            assert.notEqual(user, null);
+        });
+
+        it("returns null when not found", async () => {
+            const user = await store.getUserByEmail("notfound@example.com");
+            assert.equal(user, null);
+        });
+    });
+
+    describe("getUserById", () => {
+        it("returns user when found", async () => {
+            const created = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const user = await store.getUserById(created.id);
+            assert.notEqual(user, null);
+            assert.equal(user!.id, created.id);
+        });
+
+        it("returns null when not found", async () => {
+            const user = await store.getUserById("nonexistent" as UserId);
+            assert.equal(user, null);
+        });
+    });
+
+    describe("getUserPasswordHash", () => {
+        it("returns hash when found", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const hash = await store.getUserPasswordHash(user.id);
+            assert.equal(hash, "hash123");
+        });
+
+        it("returns null when not found", async () => {
+            const hash = await store.getUserPasswordHash(
+                "nonexistent" as UserId,
+            );
+            assert.equal(hash, null);
+        });
+    });
+
+    describe("setUserPassword", () => {
+        it("updates password hash", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "oldhash",
+            });
+
+            await store.setUserPassword(user.id, "newhash");
+
+            const hash = await store.getUserPasswordHash(user.id);
+            assert.equal(hash, "newhash");
+        });
+    });
+
+    describe("updateUserEmailVerified", () => {
+        it("sets user status to active", async () => {
+            const created = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+            assert.equal(created.status, "pending");
+
+            await store.updateUserEmailVerified(created.id);
+
+            const user = await store.getUserById(created.id);
+            assert.equal(user!.status, "active");
+        });
+    });
+
+    describe("createSession", () => {
+        it("creates a session with token", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { token, session } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() + 3600000),
+            });
+
+            assert.ok(token.length > 0);
+            assert.equal(session.userId, user.id);
+            assert.equal(session.tokenType, "session");
+            assert.equal(session.authMethod, "cookie");
+        });
+
+        it("stores metadata", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { session } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() + 3600000),
+                userAgent: "Mozilla/5.0",
+                ipAddress: "127.0.0.1",
+            });
+
+            assert.equal(session.userAgent, "Mozilla/5.0");
+            assert.equal(session.ipAddress, "127.0.0.1");
+        });
+    });
+
+    describe("getSession", () => {
+        it("returns session when found and not expired", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { token } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() + 3600000), // 1 hour from now
+            });
+
+            const tokenId = hashToken(token) as TokenId;
+            const session = await store.getSession(tokenId);
+            assert.notEqual(session, null);
+            assert.equal(session!.userId, user.id);
+        });
+
+        it("returns null for expired session", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { token } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() - 1000), // Expired 1 second ago
+            });
+
+            const tokenId = hashToken(token) as TokenId;
+            const session = await store.getSession(tokenId);
+            assert.equal(session, null);
+        });
+
+        it("returns null for nonexistent session", async () => {
+            const session = await store.getSession("nonexistent" as TokenId);
+            assert.equal(session, null);
+        });
+    });
+
+    describe("deleteSession", () => {
+        it("removes the session", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { token } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() + 3600000),
+            });
+
+            const tokenId = hashToken(token) as TokenId;
+            await store.deleteSession(tokenId);
+
+            const session = await store.getSession(tokenId);
+            assert.equal(session, null);
+        });
+    });
+
+    describe("deleteUserSessions", () => {
+        it("removes all sessions for user", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { token: token1 } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() + 3600000),
+            });
+
+            const { token: token2 } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "bearer",
+                expiresAt: new Date(Date.now() + 3600000),
+            });
+
+            const count = await store.deleteUserSessions(user.id);
+            assert.equal(count, 2);
+
+            const session1 = await store.getSession(
+                hashToken(token1) as TokenId,
+            );
+            const session2 = await store.getSession(
+                hashToken(token2) as TokenId,
+            );
+            assert.equal(session1, null);
+            assert.equal(session2, null);
+        });
+
+        it("returns 0 when user has no sessions", async () => {
+            const count = await store.deleteUserSessions(
+                "nonexistent" as UserId,
+            );
+            assert.equal(count, 0);
+        });
+    });
+
+    describe("updateLastUsed", () => {
+        it("updates lastUsedAt timestamp", async () => {
+            const user = await store.createUser({
+                email: "test@example.com",
+                passwordHash: "hash123",
+            });
+
+            const { token } = await store.createSession({
+                userId: user.id,
+                tokenType: "session",
+                authMethod: "cookie",
+                expiresAt: new Date(Date.now() + 3600000),
+            });
+
+            const tokenId = hashToken(token) as TokenId;
+            const beforeUpdate = await store.getSession(tokenId);
+            assert.equal(beforeUpdate!.lastUsedAt, undefined);
+
+            await store.updateLastUsed(tokenId);
+
+            const afterUpdate = await store.getSession(tokenId);
+            assert.ok(afterUpdate!.lastUsedAt instanceof Date);
+        });
+    });
+});

backend/diachron/auth/store.ts

@@ -0,0 +1,164 @@
+// store.ts
+//
+// Authentication storage interface and in-memory implementation.
+// The interface allows easy migration to PostgreSQL later.
+
+import { AuthenticatedUser, type User, type UserId } from "../user";
+import { generateToken, hashToken } from "./token";
+import type { AuthMethod, SessionData, TokenId, TokenType } from "./types";
+
+// Data for creating a new session (tokenId generated internally)
+export type CreateSessionData = {
+    userId: string;
+    tokenType: TokenType;
+    authMethod: AuthMethod;
+    expiresAt: Date;
+    userAgent?: string;
+    ipAddress?: string;
+};
+
+// Data for creating a new user
+export type CreateUserData = {
+    email: string;
+    passwordHash: string;
+    displayName?: string;
+};
+
+// Abstract interface for auth storage - implement for PostgreSQL later
+export interface AuthStore {
+    // Session operations
+    createSession(
+        data: CreateSessionData,
+    ): Promise<{ token: string; session: SessionData }>;
+    getSession(tokenId: TokenId): Promise<SessionData | null>;
+    updateLastUsed(tokenId: TokenId): Promise<void>;
+    deleteSession(tokenId: TokenId): Promise<void>;
+    deleteUserSessions(userId: UserId): Promise<number>;
+
+    // User operations
+    getUserByEmail(email: string): Promise<User | null>;
+    getUserById(userId: UserId): Promise<User | null>;
+    createUser(data: CreateUserData): Promise<User>;
+    getUserPasswordHash(userId: UserId): Promise<string | null>;
+    setUserPassword(userId: UserId, passwordHash: string): Promise<void>;
+    updateUserEmailVerified(userId: UserId): Promise<void>;
+}
+
+// In-memory implementation for development
+export class InMemoryAuthStore implements AuthStore {
+    private sessions: Map<string, SessionData> = new Map();
+    private users: Map<string, User> = new Map();
+    private usersByEmail: Map<string, string> = new Map();
+    private passwordHashes: Map<string, string> = new Map();
+    private emailVerified: Map<string, boolean> = new Map();
+
+    async createSession(
+        data: CreateSessionData,
+    ): Promise<{ token: string; session: SessionData }> {
+        const token = generateToken();
+        const tokenId = hashToken(token);
+
+        const session: SessionData = {
+            tokenId,
+            userId: data.userId,
+            tokenType: data.tokenType,
+            authMethod: data.authMethod,
+            createdAt: new Date(),
+            expiresAt: data.expiresAt,
+            userAgent: data.userAgent,
+            ipAddress: data.ipAddress,
+        };
+
+        this.sessions.set(tokenId, session);
+        return { token, session };
+    }
+
+    async getSession(tokenId: TokenId): Promise<SessionData | null> {
+        const session = this.sessions.get(tokenId);
+        if (!session) {
+            return null;
+        }
+
+        // Check expiration
+        if (new Date() > session.expiresAt) {
+            this.sessions.delete(tokenId);
+            return null;
+        }
+
+        return session;
+    }
+
+    async updateLastUsed(tokenId: TokenId): Promise<void> {
+        const session = this.sessions.get(tokenId);
+        if (session) {
+            session.lastUsedAt = new Date();
+        }
+    }
+
+    async deleteSession(tokenId: TokenId): Promise<void> {
+        this.sessions.delete(tokenId);
+    }
+
+    async deleteUserSessions(userId: UserId): Promise<number> {
+        let count = 0;
+        for (const [tokenId, session] of this.sessions) {
+            if (session.userId === userId) {
+                this.sessions.delete(tokenId);
+                count++;
+            }
+        }
+        return count;
+    }
+
+    async getUserByEmail(email: string): Promise<User | null> {
+        const userId = this.usersByEmail.get(email.toLowerCase());
+        if (!userId) {
+            return null;
+        }
+        return this.users.get(userId) ?? null;
+    }
+
+    async getUserById(userId: UserId): Promise<User | null> {
+        return this.users.get(userId) ?? null;
+    }
+
+    async createUser(data: CreateUserData): Promise<User> {
+        const user = AuthenticatedUser.create(data.email, {
+            displayName: data.displayName,
+            status: "pending", // Pending until email verified
+        });
+
+        this.users.set(user.id, user);
+        this.usersByEmail.set(data.email.toLowerCase(), user.id);
+        this.passwordHashes.set(user.id, data.passwordHash);
+        this.emailVerified.set(user.id, false);
+
+        return user;
+    }
+
+    async getUserPasswordHash(userId: UserId): Promise<string | null> {
+        return this.passwordHashes.get(userId) ?? null;
+    }
+
+    async setUserPassword(userId: UserId, passwordHash: string): Promise<void> {
+        this.passwordHashes.set(userId, passwordHash);
+    }
+
+    async updateUserEmailVerified(userId: UserId): Promise<void> {
+        this.emailVerified.set(userId, true);
+
+        // Update user status to active
+        const user = this.users.get(userId);
+        if (user) {
+            // Create new user with active status
+            const updatedUser = AuthenticatedUser.create(user.email, {
+                id: user.id,
+                displayName: user.displayName,
+                status: "active",
+                roles: [...user.roles],
+                permissions: [...user.permissions],
+            });
+            this.users.set(userId, updatedUser);
+        }
+    }
+}

backend/diachron/auth/token.spec.ts

@@ -0,0 +1,94 @@
+// Tests for auth/token.ts
+// Pure unit tests - no database needed
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import {
+    generateToken,
+    hashToken,
+    parseAuthorizationHeader,
+    SESSION_COOKIE_NAME,
+} from "./token";
+
+describe("token", () => {
+    describe("generateToken", () => {
+        it("generates a non-empty string", () => {
+            const token = generateToken();
+            assert.equal(typeof token, "string");
+            assert.ok(token.length > 0);
+        });
+
+        it("generates unique tokens", () => {
+            const tokens = new Set<string>();
+            for (let i = 0; i < 100; i++) {
+                tokens.add(generateToken());
+            }
+            assert.equal(tokens.size, 100);
+        });
+
+        it("generates base64url encoded tokens", () => {
+            const token = generateToken();
+            // base64url uses A-Z, a-z, 0-9, -, _
+            assert.match(token, /^[A-Za-z0-9_-]+$/);
+        });
+    });
+
+    describe("hashToken", () => {
+        it("returns a hex string", () => {
+            const hash = hashToken("test-token");
+            assert.match(hash, /^[a-f0-9]+$/);
+        });
+
+        it("returns consistent hash for same input", () => {
+            const hash1 = hashToken("test-token");
+            const hash2 = hashToken("test-token");
+            assert.equal(hash1, hash2);
+        });
+
+        it("returns different hash for different input", () => {
+            const hash1 = hashToken("token-1");
+            const hash2 = hashToken("token-2");
+            assert.notEqual(hash1, hash2);
+        });
+
+        it("returns 64 character hash (SHA-256)", () => {
+            const hash = hashToken("test-token");
+            assert.equal(hash.length, 64);
+        });
+    });
+
+    describe("parseAuthorizationHeader", () => {
+        it("returns null for undefined header", () => {
+            assert.equal(parseAuthorizationHeader(undefined), null);
+        });
+
+        it("returns null for empty string", () => {
+            assert.equal(parseAuthorizationHeader(""), null);
+        });
+
+        it("returns null for non-bearer auth", () => {
+            assert.equal(parseAuthorizationHeader("Basic abc123"), null);
+        });
+
+        it("returns null for malformed header", () => {
+            assert.equal(parseAuthorizationHeader("Bearer"), null);
+            assert.equal(parseAuthorizationHeader("Bearer token extra"), null);
+        });
+
+        it("extracts token from valid bearer header", () => {
+            assert.equal(parseAuthorizationHeader("Bearer abc123"), "abc123");
+        });
+
+        it("is case-insensitive for Bearer keyword", () => {
+            assert.equal(parseAuthorizationHeader("bearer abc123"), "abc123");
+            assert.equal(parseAuthorizationHeader("BEARER abc123"), "abc123");
+        });
+    });
+
+    describe("SESSION_COOKIE_NAME", () => {
+        it("is defined", () => {
+            assert.equal(typeof SESSION_COOKIE_NAME, "string");
+            assert.ok(SESSION_COOKIE_NAME.length > 0);
+        });
+    });
+});

backend/diachron/auth/token.ts

@@ -0,0 +1,42 @@
+// token.ts
+//
+// Token generation and hashing utilities for authentication.
+// Raw tokens are never stored - only their SHA-256 hashes.
+
+import { createHash, randomBytes } from "node:crypto";
+
+const TOKEN_BYTES = 32; // 256 bits of entropy
+
+// Generate a cryptographically secure random token
+function generateToken(): string {
+    return randomBytes(TOKEN_BYTES).toString("base64url");
+}
+
+// Hash token for storage (never store raw tokens)
+function hashToken(token: string): string {
+    return createHash("sha256").update(token).digest("hex");
+}
+
+// Parse token from Authorization header
+function parseAuthorizationHeader(header: string | undefined): string | null {
+    if (!header) {
+        return null;
+    }
+
+    const parts = header.split(" ");
+    if (parts.length !== 2 || parts[0].toLowerCase() !== "bearer") {
+        return null;
+    }
+
+    return parts[1];
+}
+
+// Cookie name for web sessions
+const SESSION_COOKIE_NAME = "diachron_session";
+
+export {
+    generateToken,
+    hashToken,
+    parseAuthorizationHeader,
+    SESSION_COOKIE_NAME,
+};

backend/diachron/auth/types.spec.ts

@@ -0,0 +1,253 @@
+// Tests for auth/types.ts
+// Pure unit tests - no database needed
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { z } from "zod";
+import { AuthenticatedUser, anonymousUser } from "../user";
+import {
+    authMethodParser,
+    forgotPasswordInputParser,
+    loginInputParser,
+    registerInputParser,
+    resetPasswordInputParser,
+    Session,
+    sessionDataParser,
+    tokenLifetimes,
+    tokenTypeParser,
+} from "./types";
+
+describe("auth/types", () => {
+    describe("tokenTypeParser", () => {
+        it("accepts valid token types", () => {
+            assert.equal(tokenTypeParser.parse("session"), "session");
+            assert.equal(
+                tokenTypeParser.parse("password_reset"),
+                "password_reset",
+            );
+            assert.equal(tokenTypeParser.parse("email_verify"), "email_verify");
+        });
+
+        it("rejects invalid token types", () => {
+            assert.throws(() => tokenTypeParser.parse("invalid"));
+        });
+    });
+
+    describe("authMethodParser", () => {
+        it("accepts valid auth methods", () => {
+            assert.equal(authMethodParser.parse("cookie"), "cookie");
+            assert.equal(authMethodParser.parse("bearer"), "bearer");
+        });
+
+        it("rejects invalid auth methods", () => {
+            assert.throws(() => authMethodParser.parse("basic"));
+        });
+    });
+
+    describe("sessionDataParser", () => {
+        it("accepts valid session data", () => {
+            const data = {
+                tokenId: "abc123",
+                userId: "user-1",
+                tokenType: "session",
+                authMethod: "cookie",
+                createdAt: new Date(),
+                expiresAt: new Date(),
+            };
+            const result = sessionDataParser.parse(data);
+            assert.equal(result.tokenId, "abc123");
+            assert.equal(result.userId, "user-1");
+        });
+
+        it("coerces date strings to dates", () => {
+            const data = {
+                tokenId: "abc123",
+                userId: "user-1",
+                tokenType: "session",
+                authMethod: "cookie",
+                createdAt: "2025-01-01T00:00:00Z",
+                expiresAt: "2025-01-02T00:00:00Z",
+            };
+            const result = sessionDataParser.parse(data);
+            assert.ok(result.createdAt instanceof Date);
+            assert.ok(result.expiresAt instanceof Date);
+        });
+
+        it("accepts optional fields", () => {
+            const data = {
+                tokenId: "abc123",
+                userId: "user-1",
+                tokenType: "session",
+                authMethod: "cookie",
+                createdAt: new Date(),
+                expiresAt: new Date(),
+                lastUsedAt: new Date(),
+                userAgent: "Mozilla/5.0",
+                ipAddress: "127.0.0.1",
+                isUsed: true,
+            };
+            const result = sessionDataParser.parse(data);
+            assert.equal(result.userAgent, "Mozilla/5.0");
+            assert.equal(result.ipAddress, "127.0.0.1");
+            assert.equal(result.isUsed, true);
+        });
+    });
+
+    describe("loginInputParser", () => {
+        it("accepts valid login input", () => {
+            const result = loginInputParser.parse({
+                email: "test@example.com",
+                password: "secret",
+            });
+            assert.equal(result.email, "test@example.com");
+            assert.equal(result.password, "secret");
+        });
+
+        it("rejects invalid email", () => {
+            assert.throws(() =>
+                loginInputParser.parse({
+                    email: "not-an-email",
+                    password: "secret",
+                }),
+            );
+        });
+
+        it("rejects empty password", () => {
+            assert.throws(() =>
+                loginInputParser.parse({
+                    email: "test@example.com",
+                    password: "",
+                }),
+            );
+        });
+    });
+
+    describe("registerInputParser", () => {
+        it("accepts valid registration input", () => {
+            const result = registerInputParser.parse({
+                email: "test@example.com",
+                password: "password123",
+                displayName: "Test User",
+            });
+            assert.equal(result.email, "test@example.com");
+            assert.equal(result.password, "password123");
+            assert.equal(result.displayName, "Test User");
+        });
+
+        it("accepts registration without displayName", () => {
+            const result = registerInputParser.parse({
+                email: "test@example.com",
+                password: "password123",
+            });
+            assert.equal(result.displayName, undefined);
+        });
+
+        it("rejects password shorter than 8 characters", () => {
+            assert.throws(() =>
+                registerInputParser.parse({
+                    email: "test@example.com",
+                    password: "short",
+                }),
+            );
+        });
+    });
+
+    describe("forgotPasswordInputParser", () => {
+        it("accepts valid email", () => {
+            const result = forgotPasswordInputParser.parse({
+                email: "test@example.com",
+            });
+            assert.equal(result.email, "test@example.com");
+        });
+
+        it("rejects invalid email", () => {
+            assert.throws(() =>
+                forgotPasswordInputParser.parse({
+                    email: "invalid",
+                }),
+            );
+        });
+    });
+
+    describe("resetPasswordInputParser", () => {
+        it("accepts valid reset input", () => {
+            const result = resetPasswordInputParser.parse({
+                token: "abc123",
+                password: "newpassword",
+            });
+            assert.equal(result.token, "abc123");
+            assert.equal(result.password, "newpassword");
+        });
+
+        it("rejects empty token", () => {
+            assert.throws(() =>
+                resetPasswordInputParser.parse({
+                    token: "",
+                    password: "newpassword",
+                }),
+            );
+        });
+
+        it("rejects password shorter than 8 characters", () => {
+            assert.throws(() =>
+                resetPasswordInputParser.parse({
+                    token: "abc123",
+                    password: "short",
+                }),
+            );
+        });
+    });
+
+    describe("tokenLifetimes", () => {
+        it("defines session lifetime", () => {
+            assert.ok(tokenLifetimes.session > 0);
+            // 30 days in ms
+            assert.equal(tokenLifetimes.session, 30 * 24 * 60 * 60 * 1000);
+        });
+
+        it("defines password_reset lifetime", () => {
+            assert.ok(tokenLifetimes.password_reset > 0);
+            // 1 hour in ms
+            assert.equal(tokenLifetimes.password_reset, 1 * 60 * 60 * 1000);
+        });
+
+        it("defines email_verify lifetime", () => {
+            assert.ok(tokenLifetimes.email_verify > 0);
+            // 24 hours in ms
+            assert.equal(tokenLifetimes.email_verify, 24 * 60 * 60 * 1000);
+        });
+    });
+
+    describe("Session", () => {
+        it("wraps authenticated session", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                id: "user-1",
+            });
+            const sessionData = {
+                tokenId: "token-1",
+                userId: "user-1",
+                tokenType: "session" as const,
+                authMethod: "cookie" as const,
+                createdAt: new Date(),
+                expiresAt: new Date(),
+            };
+            const session = new Session(sessionData, user);
+
+            assert.equal(session.isAuthenticated(), true);
+            assert.equal(session.getUser(), user);
+            assert.equal(session.getData(), sessionData);
+            assert.equal(session.tokenId, "token-1");
+            assert.equal(session.userId, "user-1");
+        });
+
+        it("wraps anonymous session", () => {
+            const session = new Session(null, anonymousUser);
+
+            assert.equal(session.isAuthenticated(), false);
+            assert.equal(session.getUser(), anonymousUser);
+            assert.equal(session.getData(), null);
+            assert.equal(session.tokenId, undefined);
+            assert.equal(session.userId, undefined);
+        });
+    });
+});

backend/diachron/auth/types.ts

@@ -0,0 +1,96 @@
+// types.ts
+//
+// Authentication types and Zod schemas.
+
+import { z } from "zod";
+
+// Branded type for token IDs (the hash, not the raw token)
+export type TokenId = string & { readonly __brand: "TokenId" };
+
+// Token types for different purposes
+export const tokenTypeParser = z.enum([
+    "session",
+    "password_reset",
+    "email_verify",
+]);
+export type TokenType = z.infer<typeof tokenTypeParser>;
+
+// Authentication method - how the token was delivered
+export const authMethodParser = z.enum(["cookie", "bearer"]);
+export type AuthMethod = z.infer<typeof authMethodParser>;
+
+// Session data schema - what gets stored
+export const sessionDataParser = z.object({
+    tokenId: z.string().min(1),
+    userId: z.string().min(1),
+    tokenType: tokenTypeParser,
+    authMethod: authMethodParser,
+    createdAt: z.coerce.date(),
+    expiresAt: z.coerce.date(),
+    lastUsedAt: z.coerce.date().optional(),
+    userAgent: z.string().optional(),
+    ipAddress: z.string().optional(),
+    isUsed: z.boolean().optional(), // For one-time tokens
+});
+
+export type SessionData = z.infer<typeof sessionDataParser>;
+
+// Input validation schemas for auth endpoints
+export const loginInputParser = z.object({
+    email: z.string().email(),
+    password: z.string().min(1),
+});
+
+export const registerInputParser = z.object({
+    email: z.string().email(),
+    password: z.string().min(8),
+    displayName: z.string().optional(),
+});
+
+export const forgotPasswordInputParser = z.object({
+    email: z.string().email(),
+});
+
+export const resetPasswordInputParser = z.object({
+    token: z.string().min(1),
+    password: z.string().min(8),
+});
+
+// Token lifetimes in milliseconds
+export const tokenLifetimes: Record<TokenType, number> = {
+    session: 30 * 24 * 60 * 60 * 1000, // 30 days
+    password_reset: 1 * 60 * 60 * 1000, // 1 hour
+    email_verify: 24 * 60 * 60 * 1000, // 24 hours
+};
+
+// Import here to avoid circular dependency at module load time
+import type { User } from "../user";
+
+// Session wrapper class providing a consistent interface for handlers.
+// Always present on Call (never null), but may represent an anonymous session.
+export class Session {
+    constructor(
+        private readonly data: SessionData | null,
+        private readonly user: User,
+    ) {}
+
+    getUser(): User {
+        return this.user;
+    }
+
+    getData(): SessionData | null {
+        return this.data;
+    }
+
+    isAuthenticated(): boolean {
+        return !this.user.isAnonymous();
+    }
+
+    get tokenId(): string | undefined {
+        return this.data?.tokenId;
+    }
+
+    get userId(): string | undefined {
+        return this.data?.userId;
+    }
+}

backend/diachron/basic/login.spec.ts

@@ -0,0 +1,24 @@
+// Tests for basic/login.ts
+// These tests verify the route structure and export
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { loginRoute } from "./login";
+
+describe("basic/login", () => {
+    describe("loginRoute", () => {
+        it("has correct path", () => {
+            assert.equal(loginRoute.path, "/login");
+        });
+
+        it("handles GET and POST methods", () => {
+            assert.ok(loginRoute.methods.includes("GET"));
+            assert.ok(loginRoute.methods.includes("POST"));
+            assert.equal(loginRoute.methods.length, 2);
+        });
+
+        it("has a handler function", () => {
+            assert.equal(typeof loginRoute.handler, "function");
+        });
+    });
+});

backend/diachron/basic/login.ts

@@ -0,0 +1,62 @@
+import { SESSION_COOKIE_NAME } from "../auth/token";
+import { tokenLifetimes } from "../auth/types";
+import { request } from "../request";
+import { html, redirect, render } from "../request/util";
+import type { Call, Result, Route } from "../types";
+
+const loginHandler = async (call: Call): Promise<Result> => {
+    if (call.method === "GET") {
+        const c = await render("basic/login", {});
+        return html(c);
+    }
+
+    // POST - handle login
+    const { email, password } = call.request.body;
+
+    if (!email || !password) {
+        const c = await render("basic/login", {
+            error: "Email and password are required",
+            email,
+        });
+        return html(c);
+    }
+
+    const result = await request.auth.login(email, password, "cookie", {
+        userAgent: call.request.get("User-Agent"),
+        ipAddress: call.request.ip,
+    });
+
+    if (!result.success) {
+        const c = await render("basic/login", {
+            error: result.error,
+            email,
+        });
+        return html(c);
+    }
+
+    // Success - set cookie and redirect to home
+    const redirectResult = redirect("/");
+    redirectResult.cookies = [
+        {
+            name: SESSION_COOKIE_NAME,
+            value: result.token,
+            options: {
+                httpOnly: true,
+                secure: false, // Set to true in production with HTTPS
+                sameSite: "lax",
+                maxAge: tokenLifetimes.session,
+                path: "/",
+            },
+        },
+    ];
+
+    return redirectResult;
+};
+
+const loginRoute: Route = {
+    path: "/login",
+    methods: ["GET", "POST"],
+    handler: loginHandler,
+};
+
+export { loginRoute };

backend/diachron/basic/logout.spec.ts

@@ -0,0 +1,24 @@
+// Tests for basic/logout.ts
+// These tests verify the route structure and export
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { logoutRoute } from "./logout";
+
+describe("basic/logout", () => {
+    describe("logoutRoute", () => {
+        it("has correct path", () => {
+            assert.equal(logoutRoute.path, "/logout");
+        });
+
+        it("handles GET and POST methods", () => {
+            assert.ok(logoutRoute.methods.includes("GET"));
+            assert.ok(logoutRoute.methods.includes("POST"));
+            assert.equal(logoutRoute.methods.length, 2);
+        });
+
+        it("has a handler function", () => {
+            assert.equal(typeof logoutRoute.handler, "function");
+        });
+    });
+});

backend/diachron/basic/logout.ts

@@ -0,0 +1,38 @@
+import { SESSION_COOKIE_NAME } from "../auth/token";
+import { request } from "../request";
+import { redirect } from "../request/util";
+import type { Call, Result, Route } from "../types";
+
+const logoutHandler = async (call: Call): Promise<Result> => {
+    // Extract token from cookie and invalidate the session
+    const token = request.auth.extractToken(call.request);
+    if (token) {
+        await request.auth.logout(token);
+    }
+
+    // Clear the cookie and redirect to login
+    const redirectResult = redirect("/login");
+    redirectResult.cookies = [
+        {
+            name: SESSION_COOKIE_NAME,
+            value: "",
+            options: {
+                httpOnly: true,
+                secure: false,
+                sameSite: "lax",
+                maxAge: 0,
+                path: "/",
+            },
+        },
+    ];
+
+    return redirectResult;
+};
+
+const logoutRoute: Route = {
+    path: "/logout",
+    methods: ["GET", "POST"],
+    handler: logoutHandler,
+};
+
+export { logoutRoute };

backend/diachron/basic/routes.spec.ts

@@ -0,0 +1,73 @@
+// Tests for basic/routes.ts
+// These tests verify the route structure and exports
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { routes } from "./routes";
+
+describe("basic/routes", () => {
+    describe("routes object", () => {
+        it("exports routes as an object", () => {
+            assert.equal(typeof routes, "object");
+        });
+
+        it("contains hello route", () => {
+            assert.ok("hello" in routes);
+            assert.equal(routes.hello.path, "/hello");
+            assert.ok(routes.hello.methods.includes("GET"));
+        });
+
+        it("contains home route", () => {
+            assert.ok("home" in routes);
+            assert.equal(routes.home.path, "/");
+            assert.ok(routes.home.methods.includes("GET"));
+        });
+
+        it("contains login route", () => {
+            assert.ok("login" in routes);
+            assert.equal(routes.login.path, "/login");
+        });
+
+        it("contains logout route", () => {
+            assert.ok("logout" in routes);
+            assert.equal(routes.logout.path, "/logout");
+        });
+
+        it("all routes have handlers", () => {
+            for (const [name, route] of Object.entries(routes)) {
+                assert.equal(
+                    typeof route.handler,
+                    "function",
+                    `Route ${name} should have a handler function`,
+                );
+            }
+        });
+
+        it("all routes have methods array", () => {
+            for (const [name, route] of Object.entries(routes)) {
+                assert.ok(
+                    Array.isArray(route.methods),
+                    `Route ${name} should have methods array`,
+                );
+                assert.ok(
+                    route.methods.length > 0,
+                    `Route ${name} should have at least one method`,
+                );
+            }
+        });
+
+        it("all routes have path string", () => {
+            for (const [name, route] of Object.entries(routes)) {
+                assert.equal(
+                    typeof route.path,
+                    "string",
+                    `Route ${name} should have a path string`,
+                );
+                assert.ok(
+                    route.path.startsWith("/"),
+                    `Route ${name} path should start with /`,
+                );
+            }
+        });
+    });
+});

backend/diachron/basic/routes.ts

@@ -0,0 +1,51 @@
+import { DateTime } from "ts-luxon";
+import { get, User } from "../hydrators/user";
+import { request } from "../request";
+import { html, render } from "../request/util";
+import type { Call, Result, Route } from "../types";
+import { loginRoute } from "./login";
+import { logoutRoute } from "./logout";
+
+const routes: Record<string, Route> = {
+    hello: {
+        path: "/hello",
+        methods: ["GET"],
+        handler: async (_call: Call): Promise<Result> => {
+            const now = DateTime.now();
+            const c = await render("basic/hello", { now });
+
+            return html(c);
+        },
+    },
+    home: {
+        path: "/",
+        methods: ["GET"],
+        handler: async (_call: Call): Promise<Result> => {
+            const _auth = request.auth;
+            const me = request.session.getUser();
+
+            const id = me.id;
+            console.log(`*** id: ${id}`);
+
+            const u = await get(id);
+
+            const email = u?.email || "anonymous@example.com";
+            const name = u?.display_name || "anonymous";
+            const showLogin = me.isAnonymous();
+            const showLogout = !me.isAnonymous();
+
+            const c = await render("basic/home", {
+                name,
+                email,
+                showLogin,
+                showLogout,
+            });
+
+            return html(c);
+        },
+    },
+    login: loginRoute,
+    logout: logoutRoute,
+};
+
+export { routes };

backend/diachron/cli.ts

@@ -0,0 +1,55 @@
+import { parseArgs } from "node:util";
+
+const { values } = parseArgs({
+    options: {
+        listen: {
+            type: "string",
+            short: "l",
+        },
+        "log-address": {
+            type: "string",
+            default: "8085",
+        },
+    },
+    strict: true,
+    allowPositionals: false,
+});
+
+function parseListenAddress(listen: string | undefined): {
+    host: string;
+    port: number;
+} {
+    const defaultHost = "127.0.0.1";
+    const defaultPort = 3500;
+
+    if (!listen) {
+        return { host: defaultHost, port: defaultPort };
+    }
+
+    const lastColon = listen.lastIndexOf(":");
+    if (lastColon === -1) {
+        // Just a port number
+        const port = parseInt(listen, 10);
+        if (Number.isNaN(port)) {
+            throw new Error(`Invalid listen address: ${listen}`);
+        }
+        return { host: defaultHost, port };
+    }
+
+    const host = listen.slice(0, lastColon);
+    const port = parseInt(listen.slice(lastColon + 1), 10);
+
+    if (Number.isNaN(port)) {
+        throw new Error(`Invalid port in listen address: ${listen}`);
+    }
+
+    return { host, port };
+}
+
+const listenAddress = parseListenAddress(values.listen);
+const logAddress = parseListenAddress(values["log-address"]);
+
+export const cli = {
+    listen: listenAddress,
+    logAddress,
+};

backend/diachron/content-types.ts

@@ -0,0 +1,122 @@
+// This file belongs to the framework.  You are not expected to modify it.
+
+export type ContentType = string;
+
+// tx claude https://claude.ai/share/344fc7bd-5321-4763-af2f-b82275e9f865
+const contentTypes = {
+    text: {
+        plain: "text/plain",
+        html: "text/html",
+        css: "text/css",
+        javascript: "text/javascript",
+        xml: "text/xml",
+        csv: "text/csv",
+        markdown: "text/markdown",
+        calendar: "text/calendar",
+    },
+    image: {
+        jpeg: "image/jpeg",
+        png: "image/png",
+        gif: "image/gif",
+        svgPlusXml: "image/svg+xml",
+        webp: "image/webp",
+        bmp: "image/bmp",
+        ico: "image/x-icon",
+        tiff: "image/tiff",
+        avif: "image/avif",
+    },
+    audio: {
+        mpeg: "audio/mpeg",
+        wav: "audio/wav",
+        ogg: "audio/ogg",
+        webm: "audio/webm",
+        aac: "audio/aac",
+        midi: "audio/midi",
+        opus: "audio/opus",
+        flac: "audio/flac",
+    },
+    video: {
+        mp4: "video/mp4",
+        webm: "video/webm",
+        xMsvideo: "video/x-msvideo",
+        mpeg: "video/mpeg",
+        ogg: "video/ogg",
+        quicktime: "video/quicktime",
+        xMatroska: "video/x-matroska",
+    },
+    application: {
+        json: "application/json",
+        pdf: "application/pdf",
+        zip: "application/zip",
+        xWwwFormUrlencoded: "application/x-www-form-urlencoded",
+        octetStream: "application/octet-stream",
+        xml: "application/xml",
+        gzip: "application/gzip",
+        javascript: "application/javascript",
+        ld_json: "application/ld+json",
+        msword: "application/msword",
+        vndOpenxmlformatsOfficedocumentWordprocessingmlDocument:
+            "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+        vndMsExcel: "application/vnd.ms-excel",
+        vndOpenxmlformatsOfficedocumentSpreadsheetmlSheet:
+            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+        vndMsPowerpoint: "application/vnd.ms-powerpoint",
+        vndOpenxmlformatsOfficedocumentPresentationmlPresentation:
+            "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+        sql: "application/sql",
+        graphql: "application/graphql",
+        wasm: "application/wasm",
+        xTar: "application/x-tar",
+        x7zCompressed: "application/x-7z-compressed",
+        xRarCompressed: "application/x-rar-compressed",
+    },
+    multipart: {
+        formData: "multipart/form-data",
+        byteranges: "multipart/byteranges",
+    },
+    font: {
+        woff: "font/woff",
+        woff2: "font/woff2",
+        ttf: "font/ttf",
+        otf: "font/otf",
+    },
+};
+
+export { contentTypes };
+
+/*
+
+possible additions for later
+
+Looking at what's there, here are a few gaps that might be worth filling:
+Streaming/Modern Web:
+
+application/x-ndjson or application/jsonlines - newline-delimited JSON (popular for streaming APIs)
+text/event-stream - Server-Sent Events
+
+API/Data Exchange:
+
+application/yaml or text/yaml - YAML files
+application/protobuf - Protocol Buffers
+application/msgpack - MessagePack
+
+Archives you're missing:
+
+application/x-bzip2 - bzip2 compression
+
+Images:
+
+image/heic - HEIC/HEIF (common on iOS)
+
+Fonts:
+
+application/vnd.ms-fontobject - EOT fonts (legacy but still seen)
+
+Text:
+
+text/rtf - Rich Text Format
+
+The most impactful would probably be text/event-stream (if you do any SSE), application/x-ndjson (common in modern APIs), and maybe text/yaml. The rest are more situational.
+But honestly, what you have covers 95% of common web development scenarios. You can definitely add as you go when you encounter specific needs!
+
+*/

backend/diachron/context.ts

@@ -0,0 +1,27 @@
+// context.ts
+//
+// Request-scoped context using AsyncLocalStorage.
+// Allows services to access request data (like the current user) without
+// needing to pass Call through every function.
+
+import { AsyncLocalStorage } from "node:async_hooks";
+import { anonymousUser, type User } from "./user";
+
+type RequestContext = {
+    user: User;
+};
+
+const asyncLocalStorage = new AsyncLocalStorage<RequestContext>();
+
+// Run a function within a request context
+function runWithContext<T>(context: RequestContext, fn: () => T): T {
+    return asyncLocalStorage.run(context, fn);
+}
+
+// Get the current user from context, or AnonymousUser if not in a request
+function getCurrentUser(): User {
+    const context = asyncLocalStorage.getStore();
+    return context?.user ?? anonymousUser;
+}
+
+export { getCurrentUser, runWithContext, type RequestContext };

backend/diachron/core/index.ts

@@ -0,0 +1,48 @@
+import nunjucks from "nunjucks";
+import { db, migrate, migrationStatus } from "../database";
+import { getLogs, log } from "../logging";
+
+// FIXME: This doesn't belong here; move it somewhere else.
+const conf = {
+    templateEngine: () => {
+        return {
+            renderTemplate: (template: string, context: object) => {
+                return nunjucks.renderString(template, context);
+            },
+        };
+    },
+};
+
+const database = {
+    db,
+    migrate,
+    migrationStatus,
+};
+
+const logging = {
+    log,
+    getLogs,
+};
+
+const random = {
+    randomNumber: () => {
+        return Math.random();
+    },
+};
+
+const misc = {
+    sleep: (ms: number) => {
+        return new Promise((resolve) => setTimeout(resolve, ms));
+    },
+};
+
+// Keep this asciibetically sorted
+const core = {
+    conf,
+    database,
+    logging,
+    misc,
+    random,
+};
+
+export { core };

backend/diachron/database.spec.ts

@@ -0,0 +1,285 @@
+// Tests for database.ts
+// Requires test PostgreSQL: docker compose -f docker-compose.test.yml up -d
+
+import assert from "node:assert/strict";
+import { after, before, beforeEach, describe, it } from "node:test";
+import {
+    connectionConfig,
+    db,
+    migrate,
+    migrationStatus,
+    PostgresAuthStore,
+    pool,
+    raw,
+    rawPool,
+} from "./database";
+import type { UserId } from "./user";
+
+describe("database", () => {
+    before(async () => {
+        // Run migrations to set up schema
+        await migrate();
+    });
+
+    after(async () => {
+        await pool.end();
+    });
+
+    describe("connectionConfig", () => {
+        it("has required fields", () => {
+            assert.ok("host" in connectionConfig);
+            assert.ok("port" in connectionConfig);
+            assert.ok("user" in connectionConfig);
+            assert.ok("password" in connectionConfig);
+            assert.ok("database" in connectionConfig);
+        });
+
+        it("port is a number", () => {
+            assert.equal(typeof connectionConfig.port, "number");
+        });
+    });
+
+    describe("raw", () => {
+        it("executes raw SQL queries", async () => {
+            const result = await raw<{ one: number }>("SELECT 1 as one");
+            assert.equal(result.length, 1);
+            assert.equal(result[0].one, 1);
+        });
+
+        it("supports parameterized queries", async () => {
+            const result = await raw<{ sum: number }>(
+                "SELECT $1::int + $2::int as sum",
+                [2, 3],
+            );
+            assert.equal(result[0].sum, 5);
+        });
+    });
+
+    describe("db (Kysely instance)", () => {
+        it("can execute SELECT queries", async () => {
+            const result = await db
+                .selectFrom("users")
+                .select("id")
+                .limit(1)
+                .execute();
+
+            // May be empty, just verify it runs
+            assert.ok(Array.isArray(result));
+        });
+    });
+
+    describe("rawPool", () => {
+        it("is a pg Pool instance", () => {
+            assert.ok(rawPool.query !== undefined);
+        });
+
+        it("can execute queries", async () => {
+            const result = await rawPool.query("SELECT 1 as one");
+            assert.equal(result.rows[0].one, 1);
+        });
+    });
+
+    describe("migrate", () => {
+        it("runs without error when migrations are up to date", async () => {
+            // Should not throw
+            await migrate();
+        });
+    });
+
+    describe("migrationStatus", () => {
+        it("returns applied and pending arrays", async () => {
+            const status = await migrationStatus();
+
+            assert.ok(Array.isArray(status.applied));
+            assert.ok(Array.isArray(status.pending));
+        });
+
+        it("shows framework migrations as applied", async () => {
+            const status = await migrationStatus();
+
+            // At least the users migration should be applied
+            const hasUsersMigration = status.applied.some((m) =>
+                m.includes("users"),
+            );
+            assert.ok(hasUsersMigration);
+        });
+    });
+
+    describe("PostgresAuthStore", () => {
+        let store: PostgresAuthStore;
+
+        before(() => {
+            store = new PostgresAuthStore();
+        });
+
+        beforeEach(async () => {
+            // Clean up test data before each test
+            await rawPool.query("DELETE FROM sessions");
+            await rawPool.query("DELETE FROM user_credentials");
+            await rawPool.query("DELETE FROM user_emails");
+            await rawPool.query("DELETE FROM users");
+        });
+
+        describe("createUser", () => {
+            it("creates a user with pending status", async () => {
+                const user = await store.createUser({
+                    email: "test@example.com",
+                    passwordHash: "hash123",
+                    displayName: "Test User",
+                });
+
+                assert.equal(user.email, "test@example.com");
+                assert.equal(user.displayName, "Test User");
+                assert.equal(user.status, "pending");
+            });
+
+            it("stores the password hash", async () => {
+                const user = await store.createUser({
+                    email: "test@example.com",
+                    passwordHash: "secrethash",
+                });
+
+                const hash = await store.getUserPasswordHash(user.id);
+                assert.equal(hash, "secrethash");
+            });
+        });
+
+        describe("getUserByEmail", () => {
+            it("returns user when found", async () => {
+                await store.createUser({
+                    email: "find@example.com",
+                    passwordHash: "hash",
+                });
+
+                const user = await store.getUserByEmail("find@example.com");
+                assert.notEqual(user, null);
+                assert.equal(user!.email, "find@example.com");
+            });
+
+            it("is case-insensitive", async () => {
+                await store.createUser({
+                    email: "UPPER@EXAMPLE.COM",
+                    passwordHash: "hash",
+                });
+
+                const user = await store.getUserByEmail("upper@example.com");
+                assert.notEqual(user, null);
+            });
+
+            it("returns null when not found", async () => {
+                const user = await store.getUserByEmail("notfound@example.com");
+                assert.equal(user, null);
+            });
+        });
+
+        describe("getUserById", () => {
+            it("returns user when found", async () => {
+                const created = await store.createUser({
+                    email: "test@example.com",
+                    passwordHash: "hash",
+                });
+
+                const user = await store.getUserById(created.id);
+                assert.notEqual(user, null);
+                assert.equal(user!.id, created.id);
+            });
+
+            it("returns null when not found", async () => {
+                const user = await store.getUserById(
+                    "00000000-0000-0000-0000-000000000000" as UserId,
+                );
+                assert.equal(user, null);
+            });
+        });
+
+        describe("setUserPassword", () => {
+            it("updates the password hash", async () => {
+                const user = await store.createUser({
+                    email: "test@example.com",
+                    passwordHash: "oldhash",
+                });
+
+                await store.setUserPassword(user.id, "newhash");
+
+                const hash = await store.getUserPasswordHash(user.id);
+                assert.equal(hash, "newhash");
+            });
+        });
+
+        describe("updateUserEmailVerified", () => {
+            it("sets user status to active", async () => {
+                const created = await store.createUser({
+                    email: "test@example.com",
+                    passwordHash: "hash",
+                });
+                assert.equal(created.status, "pending");
+
+                await store.updateUserEmailVerified(created.id);
+
+                const user = await store.getUserById(created.id);
+                assert.equal(user!.status, "active");
+            });
+        });
+
+        describe("session operations", () => {
+            let userId: UserId;
+
+            beforeEach(async () => {
+                const user = await store.createUser({
+                    email: "session@example.com",
+                    passwordHash: "hash",
+                });
+                userId = user.id;
+            });
+
+            it("creates and retrieves sessions", async () => {
+                const { token, session } = await store.createSession({
+                    userId,
+                    tokenType: "session",
+                    authMethod: "cookie",
+                    expiresAt: new Date(Date.now() + 3600000),
+                });
+
+                assert.ok(token.length > 0);
+                assert.equal(session.userId, userId);
+                assert.equal(session.tokenType, "session");
+            });
+
+            it("deletes sessions", async () => {
+                const { session } = await store.createSession({
+                    userId,
+                    tokenType: "session",
+                    authMethod: "cookie",
+                    expiresAt: new Date(Date.now() + 3600000),
+                });
+
+                await store.deleteSession(session.tokenId as any);
+
+                // Session should be soft-deleted (revoked)
+                const retrieved = await store.getSession(
+                    session.tokenId as any,
+                );
+                assert.equal(retrieved, null);
+            });
+
+            it("deletes all user sessions", async () => {
+                await store.createSession({
+                    userId,
+                    tokenType: "session",
+                    authMethod: "cookie",
+                    expiresAt: new Date(Date.now() + 3600000),
+                });
+
+                await store.createSession({
+                    userId,
+                    tokenType: "session",
+                    authMethod: "bearer",
+                    expiresAt: new Date(Date.now() + 3600000),
+                });
+
+                const count = await store.deleteUserSessions(userId);
+                assert.equal(count, 2);
+            });
+        });
+    });
+});

backend/diachron/database.ts

@@ -0,0 +1,548 @@
+// database.ts
+// PostgreSQL database access with Kysely query builder and simple migrations
+
+import * as fs from "node:fs";
+import * as path from "node:path";
+import {
+    type Generated,
+    Kysely,
+    PostgresDialect,
+    type Selectable,
+    sql,
+} from "kysely";
+import { Pool } from "pg";
+import type {
+    AuthStore,
+    CreateSessionData,
+    CreateUserData,
+} from "./auth/store";
+import { generateToken, hashToken } from "./auth/token";
+import type { SessionData, TokenId } from "./auth/types";
+import type { Domain } from "./types";
+import { AuthenticatedUser, type User, type UserId } from "./user";
+
+// Connection configuration (supports environment variable overrides)
+const connectionConfig = {
+    host: process.env.DB_HOST ?? "localhost",
+    port: Number(process.env.DB_PORT ?? 5432),
+    user: process.env.DB_USER ?? "diachron",
+    password: process.env.DB_PASSWORD ?? "diachron",
+    database: process.env.DB_NAME ?? "diachron",
+};
+
+// Database schema types for Kysely
+// Generated<T> marks columns with database defaults (optional on insert)
+interface UsersTable {
+    id: string;
+    status: Generated<string>;
+    display_name: string | null;
+    created_at: Generated<Date>;
+    updated_at: Generated<Date>;
+}
+
+interface UserEmailsTable {
+    id: string;
+    user_id: string;
+    email: string;
+    normalized_email: string;
+    is_primary: Generated<boolean>;
+    is_verified: Generated<boolean>;
+    created_at: Generated<Date>;
+    verified_at: Date | null;
+    revoked_at: Date | null;
+}
+
+interface UserCredentialsTable {
+    id: string;
+    user_id: string;
+    credential_type: Generated<string>;
+    password_hash: string | null;
+    created_at: Generated<Date>;
+    updated_at: Generated<Date>;
+}
+
+interface SessionsTable {
+    id: Generated<string>;
+    token_hash: string;
+    user_id: string;
+    user_email_id: string | null;
+    token_type: string;
+    auth_method: string;
+    created_at: Generated<Date>;
+    expires_at: Date;
+    revoked_at: Date | null;
+    ip_address: string | null;
+    user_agent: string | null;
+    is_used: Generated<boolean | null>;
+}
+
+interface Database {
+    users: UsersTable;
+    user_emails: UserEmailsTable;
+    user_credentials: UserCredentialsTable;
+    sessions: SessionsTable;
+}
+
+// Create the connection pool
+const pool = new Pool(connectionConfig);
+
+// Create the Kysely instance
+const db = new Kysely<Database>({
+    dialect: new PostgresDialect({ pool }),
+});
+
+// Raw pool access for when you need it
+const rawPool = pool;
+
+// Execute raw SQL (for when Kysely doesn't fit)
+async function raw<T = unknown>(
+    query: string,
+    params: unknown[] = [],
+): Promise<T[]> {
+    const result = await pool.query(query, params);
+    return result.rows as T[];
+}
+
+// ============================================================================
+// Migrations
+// ============================================================================
+
+// Migration file naming convention:
+//   yyyy-mm-dd_ss_description.sql
+//   e.g., 2025-01-15_01_initial.sql, 2025-01-15_02_add_users.sql
+//
+// Migrations directory: express/migrations/
+
+const FRAMEWORK_MIGRATIONS_DIR = path.join(__dirname, "diachron/migrations");
+const APP_MIGRATIONS_DIR = path.join(__dirname, "migrations");
+const MIGRATIONS_TABLE = "_migrations";
+
+interface MigrationRecord {
+    id: number;
+    name: string;
+    applied_at: Date;
+}
+
+// Ensure migrations table exists
+async function ensureMigrationsTable(): Promise<void> {
+    await pool.query(`
+        CREATE TABLE IF NOT EXISTS ${MIGRATIONS_TABLE} (
+            id SERIAL PRIMARY KEY,
+            name TEXT NOT NULL UNIQUE,
+            applied_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+        )
+    `);
+}
+
+// Get list of applied migrations
+async function getAppliedMigrations(): Promise<string[]> {
+    const result = await pool.query<MigrationRecord>(
+        `SELECT name FROM ${MIGRATIONS_TABLE} ORDER BY name`,
+    );
+    return result.rows.map((r) => r.name);
+}
+
+// Get pending migration files
+function getMigrationFiles(kind: Domain): string[] {
+    const dir = kind === "fw" ? FRAMEWORK_MIGRATIONS_DIR : APP_MIGRATIONS_DIR;
+
+    if (!fs.existsSync(dir)) {
+        return [];
+    }
+
+    const root = __dirname;
+
+    const mm = fs
+        .readdirSync(dir)
+        .filter((f) => f.endsWith(".sql"))
+        .filter((f) => /^\d{4}-\d{2}-\d{2}_\d{2}-/.test(f))
+        .map((f) => `${dir}/${f}`)
+        .map((f) => f.replace(`${root}/`, ""))
+        .sort();
+
+    return mm;
+}
+
+// Run a single migration
+async function runMigration(filename: string): Promise<void> {
+    // const filepath = path.join(MIGRATIONS_DIR, filename);
+    const filepath = filename;
+    const content = fs.readFileSync(filepath, "utf-8");
+
+    process.stdout.write(`  Migration: ${filename}...`);
+
+    // Run migration in a transaction
+    const client = await pool.connect();
+    try {
+        await client.query("BEGIN");
+        await client.query(content);
+        await client.query(
+            `INSERT INTO ${MIGRATIONS_TABLE} (name) VALUES ($1)`,
+            [filename],
+        );
+        await client.query("COMMIT");
+        console.log(" ✓");
+    } catch (err) {
+        console.log(" ✗");
+        const message = err instanceof Error ? err.message : String(err);
+        console.error(`    Error: ${message}`);
+        await client.query("ROLLBACK");
+        throw err;
+    } finally {
+        client.release();
+    }
+}
+
+function getAllMigrationFiles() {
+    const fw_files = getMigrationFiles("fw");
+    const app_files = getMigrationFiles("app");
+    const all = [...fw_files, ...app_files];
+
+    return all;
+}
+
+// Run all pending migrations
+async function migrate(): Promise<void> {
+    await ensureMigrationsTable();
+
+    const applied = new Set(await getAppliedMigrations());
+    const all = getAllMigrationFiles();
+    const pending = all.filter((all) => !applied.has(all));
+
+    if (pending.length === 0) {
+        console.log("No pending migrations");
+        return;
+    }
+
+    console.log(`Applying ${pending.length} migration(s):`);
+    for (const file of pending) {
+        await runMigration(file);
+    }
+}
+
+// List migration status
+async function migrationStatus(): Promise<{
+    applied: string[];
+    pending: string[];
+}> {
+    await ensureMigrationsTable();
+    const applied = new Set(await getAppliedMigrations());
+    const ff = getAllMigrationFiles();
+    return {
+        applied: ff.filter((ff) => applied.has(ff)),
+        pending: ff.filter((ff) => !applied.has(ff)),
+    };
+}
+
+// ============================================================================
+// PostgresAuthStore - Database-backed authentication storage
+// ============================================================================
+
+class PostgresAuthStore implements AuthStore {
+    // Session operations
+
+    async createSession(
+        data: CreateSessionData,
+    ): Promise<{ token: string; session: SessionData }> {
+        const token = generateToken();
+        const tokenHash = hashToken(token);
+
+        const row = await db
+            .insertInto("sessions")
+            .values({
+                token_hash: tokenHash,
+                user_id: data.userId,
+                token_type: data.tokenType,
+                auth_method: data.authMethod,
+                expires_at: data.expiresAt,
+                user_agent: data.userAgent ?? null,
+                ip_address: data.ipAddress ?? null,
+            })
+            .returningAll()
+            .executeTakeFirstOrThrow();
+
+        const session: SessionData = {
+            tokenId: row.token_hash,
+            userId: row.user_id,
+            tokenType: row.token_type as SessionData["tokenType"],
+            authMethod: row.auth_method as SessionData["authMethod"],
+            createdAt: row.created_at,
+            expiresAt: row.expires_at,
+            userAgent: row.user_agent ?? undefined,
+            ipAddress: row.ip_address ?? undefined,
+            isUsed: row.is_used ?? undefined,
+        };
+
+        return { token, session };
+    }
+
+    async getSession(tokenId: TokenId): Promise<SessionData | null> {
+        const row = await db
+            .selectFrom("sessions")
+            .selectAll()
+            .where("token_hash", "=", tokenId)
+            .where("expires_at", ">", new Date())
+            .where("revoked_at", "is", null)
+            .executeTakeFirst();
+
+        if (!row) {
+            return null;
+        }
+
+        return {
+            tokenId: row.token_hash,
+            userId: row.user_id,
+            tokenType: row.token_type as SessionData["tokenType"],
+            authMethod: row.auth_method as SessionData["authMethod"],
+            createdAt: row.created_at,
+            expiresAt: row.expires_at,
+            userAgent: row.user_agent ?? undefined,
+            ipAddress: row.ip_address ?? undefined,
+            isUsed: row.is_used ?? undefined,
+        };
+    }
+
+    async updateLastUsed(_tokenId: TokenId): Promise<void> {
+        // The new schema doesn't have last_used_at column
+        // This is now a no-op; session activity tracking could be added later
+    }
+
+    async deleteSession(tokenId: TokenId): Promise<void> {
+        // Soft delete by setting revoked_at
+        await db
+            .updateTable("sessions")
+            .set({ revoked_at: new Date() })
+            .where("token_hash", "=", tokenId)
+            .execute();
+    }
+
+    async deleteUserSessions(userId: UserId): Promise<number> {
+        const result = await db
+            .updateTable("sessions")
+            .set({ revoked_at: new Date() })
+            .where("user_id", "=", userId)
+            .where("revoked_at", "is", null)
+            .executeTakeFirst();
+
+        return Number(result.numUpdatedRows);
+    }
+
+    // User operations
+
+    async getUserByEmail(email: string): Promise<User | null> {
+        // Find user through user_emails table
+        const normalizedEmail = email.toLowerCase().trim();
+
+        const row = await db
+            .selectFrom("user_emails")
+            .innerJoin("users", "users.id", "user_emails.user_id")
+            .select([
+                "users.id",
+                "users.status",
+                "users.display_name",
+                "users.created_at",
+                "users.updated_at",
+                "user_emails.email",
+            ])
+            .where("user_emails.normalized_email", "=", normalizedEmail)
+            .where("user_emails.revoked_at", "is", null)
+            .executeTakeFirst();
+
+        if (!row) {
+            return null;
+        }
+        return this.rowToUser(row);
+    }
+
+    async getUserById(userId: UserId): Promise<User | null> {
+        // Get user with their primary email
+        const row = await db
+            .selectFrom("users")
+            .leftJoin("user_emails", (join) =>
+                join
+                    .onRef("user_emails.user_id", "=", "users.id")
+                    .on("user_emails.is_primary", "=", true)
+                    .on("user_emails.revoked_at", "is", null),
+            )
+            .select([
+                "users.id",
+                "users.status",
+                "users.display_name",
+                "users.created_at",
+                "users.updated_at",
+                "user_emails.email",
+            ])
+            .where("users.id", "=", userId)
+            .executeTakeFirst();
+
+        if (!row) {
+            return null;
+        }
+        return this.rowToUser(row);
+    }
+
+    async createUser(data: CreateUserData): Promise<User> {
+        const userId = crypto.randomUUID();
+        const emailId = crypto.randomUUID();
+        const credentialId = crypto.randomUUID();
+        const now = new Date();
+        const normalizedEmail = data.email.toLowerCase().trim();
+
+        // Create user record
+        await db
+            .insertInto("users")
+            .values({
+                id: userId,
+                display_name: data.displayName ?? null,
+                status: "pending",
+                created_at: now,
+                updated_at: now,
+            })
+            .execute();
+
+        // Create user_email record
+        await db
+            .insertInto("user_emails")
+            .values({
+                id: emailId,
+                user_id: userId,
+                email: data.email,
+                normalized_email: normalizedEmail,
+                is_primary: true,
+                is_verified: false,
+                created_at: now,
+            })
+            .execute();
+
+        // Create user_credential record
+        await db
+            .insertInto("user_credentials")
+            .values({
+                id: credentialId,
+                user_id: userId,
+                credential_type: "password",
+                password_hash: data.passwordHash,
+                created_at: now,
+                updated_at: now,
+            })
+            .execute();
+
+        return new AuthenticatedUser({
+            id: userId,
+            email: data.email,
+            displayName: data.displayName,
+            status: "pending",
+            roles: [],
+            permissions: [],
+            createdAt: now,
+            updatedAt: now,
+        });
+    }
+
+    async getUserPasswordHash(userId: UserId): Promise<string | null> {
+        const row = await db
+            .selectFrom("user_credentials")
+            .select("password_hash")
+            .where("user_id", "=", userId)
+            .where("credential_type", "=", "password")
+            .executeTakeFirst();
+
+        return row?.password_hash ?? null;
+    }
+
+    async setUserPassword(userId: UserId, passwordHash: string): Promise<void> {
+        const now = new Date();
+
+        // Try to update existing credential
+        const result = await db
+            .updateTable("user_credentials")
+            .set({ password_hash: passwordHash, updated_at: now })
+            .where("user_id", "=", userId)
+            .where("credential_type", "=", "password")
+            .executeTakeFirst();
+
+        // If no existing credential, create one
+        if (Number(result.numUpdatedRows) === 0) {
+            await db
+                .insertInto("user_credentials")
+                .values({
+                    id: crypto.randomUUID(),
+                    user_id: userId,
+                    credential_type: "password",
+                    password_hash: passwordHash,
+                    created_at: now,
+                    updated_at: now,
+                })
+                .execute();
+        }
+
+        // Update user's updated_at
+        await db
+            .updateTable("users")
+            .set({ updated_at: now })
+            .where("id", "=", userId)
+            .execute();
+    }
+
+    async updateUserEmailVerified(userId: UserId): Promise<void> {
+        const now = new Date();
+
+        // Update user_emails to mark as verified
+        await db
+            .updateTable("user_emails")
+            .set({
+                is_verified: true,
+                verified_at: now,
+            })
+            .where("user_id", "=", userId)
+            .where("is_primary", "=", true)
+            .execute();
+
+        // Update user status to active
+        await db
+            .updateTable("users")
+            .set({
+                status: "active",
+                updated_at: now,
+            })
+            .where("id", "=", userId)
+            .execute();
+    }
+
+    // Helper to convert database row to User object
+    private rowToUser(row: {
+        id: string;
+        status: string;
+        display_name: string | null;
+        created_at: Date;
+        updated_at: Date;
+        email: string | null;
+    }): User {
+        return new AuthenticatedUser({
+            id: row.id,
+            email: row.email ?? "unknown@example.com",
+            displayName: row.display_name ?? undefined,
+            status: row.status as "active" | "suspended" | "pending",
+            roles: [], // TODO: query from RBAC tables
+            permissions: [], // TODO: query from RBAC tables
+            createdAt: row.created_at,
+            updatedAt: row.updated_at,
+        });
+    }
+}
+
+// ============================================================================
+// Exports
+// ============================================================================
+
+export {
+    db,
+    raw,
+    rawPool,
+    pool,
+    migrate,
+    migrationStatus,
+    connectionConfig,
+    PostgresAuthStore,
+    type Database,
+};

backend/diachron/deps.ts

@@ -0,0 +1,7 @@
+// Database
+//export { Client as PostgresClient } from "https://deno.land/x/postgres@v0.19.3/mod.ts";
+//export type { ClientOptions as PostgresOptions } from "https://deno.land/x/postgres@v0.19.3/mod.ts";
+
+// Redis
+//export { connect as redisConnect } from "https://deno.land/x/redis@v0.37.1/mod.ts";
+//export type { Redis } from "https://deno.land/x/redis@v0.37.1/mod.ts";

backend/diachron/develop/clear-db.ts

@@ -0,0 +1,17 @@
+import { connectionConfig, migrate, pool } from "../database";
+import { dropTables, exitIfUnforced } from "./util";
+
+async function main(): Promise<void> {
+    exitIfUnforced();
+
+    try {
+        await dropTables();
+    } finally {
+        await pool.end();
+    }
+}
+
+main().catch((err) => {
+    console.error("Failed to clear database:", err.message);
+    process.exit(1);
+});

backend/diachron/develop/reset-db.ts

@@ -0,0 +1,26 @@
+// reset-db.ts
+// Development command to wipe the database and apply all migrations from scratch
+
+import { connectionConfig, migrate, pool } from "../database";
+import { dropTables, exitIfUnforced } from "./util";
+
+async function main(): Promise<void> {
+    exitIfUnforced();
+
+    try {
+        await dropTables();
+
+        console.log("");
+        await migrate();
+
+        console.log("");
+        console.log("Database reset complete.");
+    } finally {
+        await pool.end();
+    }
+}
+
+main().catch((err) => {
+    console.error("Failed to reset database:", err.message);
+    process.exit(1);
+});

backend/diachron/develop/util.ts

@@ -0,0 +1,42 @@
+// FIXME: this is at the wrong level of specificity
+
+import { connectionConfig, migrate, pool } from "../database";
+
+const exitIfUnforced = () => {
+    const args = process.argv.slice(2);
+
+    // Require explicit confirmation unless --force is passed
+    if (!args.includes("--force")) {
+        console.error("This will DROP ALL TABLES in the database!");
+        console.error(`  Database: ${connectionConfig.database}`);
+        console.error(
+            `  Host: ${connectionConfig.host}:${connectionConfig.port}`,
+        );
+        console.error("");
+        console.error("Run with --force to proceed.");
+        process.exit(1);
+    }
+};
+
+const dropTables = async () => {
+    console.log("Dropping all tables...");
+
+    // Get all table names in the public schema
+    const result = await pool.query<{ tablename: string }>(`
+            SELECT tablename FROM pg_tables
+            WHERE schemaname = 'public'
+        `);
+
+    if (result.rows.length > 0) {
+        // Drop all tables with CASCADE to handle foreign key constraints
+        const tableNames = result.rows
+            .map((r) => `"${r.tablename}"`)
+            .join(", ");
+        await pool.query(`DROP TABLE IF EXISTS ${tableNames} CASCADE`);
+        console.log(`Dropped ${result.rows.length} table(s)`);
+    } else {
+        console.log("No tables to drop");
+    }
+};
+
+export { dropTables, exitIfUnforced };

backend/diachron/execution-context-schema.ts

@@ -0,0 +1,13 @@
+import { z } from "zod";
+
+export const executionContextSchema = z.object({
+    diachron_root: z.string(),
+});
+
+export type ExecutionContext = z.infer<typeof executionContextSchema>;
+
+export function parseExecutionContext(
+    env: Record<string, string | undefined>,
+): ExecutionContext {
+    return executionContextSchema.parse(env);
+}

backend/diachron/execution-context.spec.ts

@@ -0,0 +1,38 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { ZodError } from "zod";
+
+import {
+    executionContextSchema,
+    parseExecutionContext,
+} from "./execution-context-schema";
+
+describe("parseExecutionContext", () => {
+    it("parses valid executionContext with diachron_root", () => {
+        const env = { diachron_root: "/some/path" };
+        const result = parseExecutionContext(env);
+        assert.deepEqual(result, { diachron_root: "/some/path" });
+    });
+
+    it("throws ZodError when diachron_root is missing", () => {
+        const env = {};
+        assert.throws(() => parseExecutionContext(env), ZodError);
+    });
+
+    it("strips extra fields not in schema", () => {
+        const env = {
+            diachron_root: "/some/path",
+            EXTRA_VAR: "should be stripped",
+        };
+        const result = parseExecutionContext(env);
+        assert.deepEqual(result, { diachron_root: "/some/path" });
+        assert.equal("EXTRA_VAR" in result, false);
+    });
+});
+
+describe("executionContextSchema", () => {
+    it("requires diachron_root to be a string", () => {
+        const result = executionContextSchema.safeParse({ diachron_root: 123 });
+        assert.equal(result.success, false);
+    });
+});

backend/diachron/execution-context.ts

@@ -0,0 +1,5 @@
+import { parseExecutionContext } from "./execution-context-schema";
+
+const executionContext = parseExecutionContext(process.env);
+
+export { executionContext };

backend/diachron/handlers.spec.ts

@@ -0,0 +1,71 @@
+// Tests for handlers.ts
+// These tests use mock Call objects
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import type { Request as ExpressRequest } from "express";
+import { Session } from "./auth/types";
+import { contentTypes } from "./content-types";
+import { multiHandler } from "./handlers";
+import { httpCodes } from "./http-codes";
+import type { Call } from "./types";
+import { anonymousUser } from "./user";
+
+// Helper to create a minimal mock Call
+function createMockCall(overrides: Partial<Call> = {}): Call {
+    const defaultSession = new Session(null, anonymousUser);
+    return {
+        pattern: "/test",
+        path: "/test",
+        method: "GET",
+        parameters: {},
+        request: {} as ExpressRequest,
+        user: anonymousUser,
+        session: defaultSession,
+        ...overrides,
+    };
+}
+
+describe("handlers", () => {
+    describe("multiHandler", () => {
+        it("returns OK status", async () => {
+            const call = createMockCall({ method: "GET" });
+            const result = await multiHandler(call);
+
+            assert.equal(result.code, httpCodes.success.OK);
+        });
+
+        it("returns text/plain content type", async () => {
+            const call = createMockCall();
+            const result = await multiHandler(call);
+
+            assert.equal(result.contentType, contentTypes.text.plain);
+        });
+
+        it("includes method in result", async () => {
+            const call = createMockCall({ method: "POST" });
+            const result = await multiHandler(call);
+
+            assert.ok(result.result.includes("POST"));
+        });
+
+        it("includes a random number in result", async () => {
+            const call = createMockCall();
+            const result = await multiHandler(call);
+
+            // Result format: "that was GET (0.123456789)"
+            assert.match(result.result, /that was \w+ \(\d+\.?\d*\)/);
+        });
+
+        it("works with different HTTP methods", async () => {
+            const methods = ["GET", "POST", "PUT", "PATCH", "DELETE"] as const;
+
+            for (const method of methods) {
+                const call = createMockCall({ method });
+                const result = await multiHandler(call);
+
+                assert.ok(result.result.includes(method));
+            }
+        });
+    });
+});

backend/diachron/handlers.ts

@@ -0,0 +1,19 @@
+import { contentTypes } from "./content-types";
+import { core } from "./core";
+import { httpCodes } from "./http-codes";
+import type { Call, Handler, Result } from "./types";
+
+const multiHandler: Handler = async (call: Call): Promise<Result> => {
+    const code = httpCodes.success.OK;
+    const rn = core.random.randomNumber();
+
+    const retval: Result = {
+        code,
+        result: `that was ${call.method} (${rn})`,
+        contentType: contentTypes.text.plain,
+    };
+
+    return retval;
+};
+
+export { multiHandler };

backend/diachron/http-codes.ts

@@ -0,0 +1,76 @@
+// This file belongs to the framework.  You are not expected to modify it.
+
+export type HttpCode = {
+    code: number;
+    name: string;
+    description?: string;
+};
+type Group = "success" | "redirection" | "clientErrors" | "serverErrors";
+type CodeDefinitions = {
+    [K in Group]: {
+        [K: string]: HttpCode;
+    };
+};
+
+// tx claude https://claude.ai/share/344fc7bd-5321-4763-af2f-b82275e9f865
+const httpCodes: CodeDefinitions = {
+    success: {
+        OK: { code: 200, name: "OK", description: "" },
+        Created: { code: 201, name: "Created" },
+        Accepted: { code: 202, name: "Accepted" },
+        NonAuthoritativeInformation: {
+            code: 203,
+            name: "Non-Authoritative Information",
+        },
+        NoContent: { code: 204, name: "No Content" },
+        ResetContent: { code: 205, name: "Reset Content" },
+        PartialContent: { code: 206, name: "Partial Content" },
+    },
+    redirection: {
+        MultipleChoices: { code: 300, name: "Multiple Choices" },
+        MovedPermanently: { code: 301, name: "Moved Permanently" },
+        Found: { code: 302, name: "Found" },
+        SeeOther: { code: 303, name: "See Other" },
+        NotModified: { code: 304, name: "Not Modified" },
+        TemporaryRedirect: { code: 307, name: "Temporary Redirect" },
+        PermanentRedirect: { code: 308, name: "Permanent Redirect" },
+    },
+    clientErrors: {
+        BadRequest: { code: 400, name: "Bad Request" },
+        Unauthorized: { code: 401, name: "Unauthorized" },
+        PaymentRequired: { code: 402, name: "Payment Required" },
+        Forbidden: { code: 403, name: "Forbidden" },
+        NotFound: { code: 404, name: "Not Found" },
+        MethodNotAllowed: { code: 405, name: "Method Not Allowed" },
+        NotAcceptable: { code: 406, name: "Not Acceptable" },
+        ProxyAuthenticationRequired: {
+            code: 407,
+            name: "Proxy Authentication Required",
+        },
+        RequestTimeout: { code: 408, name: "Request Timeout" },
+        Conflict: { code: 409, name: "Conflict" },
+        Gone: { code: 410, name: "Gone" },
+        LengthRequired: { code: 411, name: "Length Required" },
+        PreconditionFailed: { code: 412, name: "Precondition Failed" },
+        PayloadTooLarge: { code: 413, name: "Payload Too Large" },
+        URITooLong: { code: 414, name: "URI Too Long" },
+        UnsupportedMediaType: { code: 415, name: "Unsupported Media Type" },
+        RangeNotSatisfiable: { code: 416, name: "Range Not Satisfiable" },
+        ExpectationFailed: { code: 417, name: "Expectation Failed" },
+        ImATeapot: { code: 418, name: "I'm a teapot" },
+        UnprocessableEntity: { code: 422, name: "Unprocessable Entity" },
+        TooManyRequests: { code: 429, name: "Too Many Requests" },
+    },
+    serverErrors: {
+        InternalServerError: { code: 500, name: "Internal Server Error" },
+        NotImplemented: { code: 501, name: "Not Implemented" },
+        BadGateway: { code: 502, name: "Bad Gateway" },
+        ServiceUnavailable: { code: 503, name: "Service Unavailable" },
+        GatewayTimeout: { code: 504, name: "Gateway Timeout" },
+        HTTPVersionNotSupported: {
+            code: 505,
+            name: "HTTP Version Not Supported",
+        },
+    },
+};
+export { httpCodes };

backend/diachron/hydrators/hydrator.ts

@@ -0,0 +1,29 @@
+import { Kysely, PostgresDialect } from "kysely";
+import { Pool } from "pg";
+import { connectionConfig } from "../database";
+import type { DB } from "../../generated/db";
+
+const db = new Kysely<DB>({
+    dialect: new PostgresDialect({
+        pool: new Pool(connectionConfig),
+    }),
+    log(event) {
+        if (event.level === "query") {
+            // FIXME: Wire this up to the logging system
+            console.log("SQL:", event.query.sql);
+            console.log("Params:", event.query.parameters);
+        }
+    },
+});
+
+abstract class Hydrator<T> {
+    public db: Kysely<DB>;
+
+    protected abstract table: string;
+
+    constructor() {
+        this.db = db;
+    }
+}
+
+export { Hydrator, db };

backend/diachron/hydrators/index.ts

@@ -0,0 +1 @@
+export type Hydrators = {};

backend/diachron/hydrators/tests/setup.ts

@@ -0,0 +1,44 @@
+// Test setup for hydrator tests
+// Run: DB_PORT=5433 DB_USER=diachron_test DB_PASSWORD=diachron_test DB_NAME=diachron_test npx tsx --test tests/*.test.ts
+
+import { Pool } from "pg";
+import { connectionConfig, migrate } from "../../database";
+
+const pool = new Pool(connectionConfig);
+
+export async function setupTestDatabase(): Promise<void> {
+    await migrate();
+}
+
+export async function cleanupTables(): Promise<void> {
+    // Clean in reverse dependency order
+    await pool.query("DELETE FROM user_emails");
+    await pool.query("DELETE FROM users");
+}
+
+export async function teardownTestDatabase(): Promise<void> {
+    await pool.end();
+}
+
+export async function insertTestUser(data: {
+    id: string;
+    displayName: string;
+    status: string;
+    email: string;
+}): Promise<void> {
+    const emailId = crypto.randomUUID();
+    const normalizedEmail = data.email.toLowerCase().trim();
+
+    await pool.query(
+        `INSERT INTO users (id, display_name, status) VALUES ($1, $2, $3)`,
+        [data.id, data.displayName, data.status],
+    );
+
+    await pool.query(
+        `INSERT INTO user_emails (id, user_id, email, normalized_email, is_primary)
+         VALUES ($1, $2, $3, $4, true)`,
+        [emailId, data.id, data.email, normalizedEmail],
+    );
+}
+
+export { pool };

backend/diachron/hydrators/tests/user.spec.ts

@@ -0,0 +1,98 @@
+// Tests for user hydrator
+// Run with: cd express && DB_PORT=5433 DB_USER=diachron_test DB_PASSWORD=diachron_test DB_NAME=diachron_test ../cmd npx tsx --test diachron/hydrators/tests/user.test.ts
+
+import assert from "node:assert/strict";
+import { after, before, beforeEach, describe, it } from "node:test";
+import { get } from "../user";
+import {
+    cleanupTables,
+    insertTestUser,
+    setupTestDatabase,
+    teardownTestDatabase,
+} from "./setup";
+
+describe("user hydrator", () => {
+    before(async () => {
+        await setupTestDatabase();
+    });
+
+    after(async () => {
+        await teardownTestDatabase();
+    });
+
+    beforeEach(async () => {
+        await cleanupTables();
+    });
+
+    describe("get", () => {
+        it("returns null for non-existent user", async () => {
+            const result = await get("00000000-0000-0000-0000-000000000000");
+            assert.equal(result, null);
+        });
+
+        it("returns user when found", async () => {
+            const userId = "cfae0a19-6515-4813-bc2d-1e032b72b203";
+            await insertTestUser({
+                id: userId,
+                displayName: "Test User",
+                status: "active",
+                email: "test@example.com",
+            });
+
+            const result = await get(userId);
+
+            assert.notEqual(result, null);
+            assert.equal(result!.id, userId);
+            assert.equal(result!.display_name, "Test User");
+            assert.equal(result!.status, "active");
+            assert.equal(result!.email, "test@example.com");
+        });
+
+        it("validates user data with zod parser", async () => {
+            const userId = crypto.randomUUID();
+            await insertTestUser({
+                id: userId,
+                displayName: "Valid User",
+                status: "active",
+                email: "valid@example.com",
+            });
+
+            const result = await get(userId);
+
+            // If we get here without throwing, parsing succeeded
+            assert.notEqual(result, null);
+            assert.equal(typeof result!.id, "string");
+            assert.equal(typeof result!.email, "string");
+        });
+
+        it("returns user with pending status", async () => {
+            const userId = crypto.randomUUID();
+            await insertTestUser({
+                id: userId,
+                displayName: "Pending User",
+                status: "pending",
+                email: "pending@example.com",
+            });
+
+            const result = await get(userId);
+
+            assert.notEqual(result, null);
+            assert.equal(result!.status, "pending");
+        });
+
+        it("returns user with suspended status", async () => {
+            const userId = crypto.randomUUID();
+            await insertTestUser({
+                id: userId,
+                displayName: "Suspended User",
+                status: "suspended",
+                email: "suspended@example.com",
+            });
+
+            const result = await get(userId);
+
+            assert.notEqual(result, null);
+            assert.equal(result!.status, "suspended");
+        });
+    });
+});

backend/diachron/hydrators/user.ts

@@ -0,0 +1,59 @@
+import {
+    ColumnType,
+    Generated,
+    Insertable,
+    JSONColumnType,
+    Selectable,
+    Updateable,
+} from "kysely";
+import type { TypeID } from "typeid-js";
+import { z } from "zod";
+import { db, Hydrator } from "./hydrator";
+
+const parser = z.object({
+    // id: z.uuidv7(),
+    id: z.uuid(),
+    display_name: z.string(),
+    // FIXME: status is duplicated elsewhere
+    status: z.union([
+        z.literal("active"),
+        z.literal("suspended"),
+        z.literal("pending"),
+    ]),
+    email: z.email(),
+});
+
+const tp = parser.parse({
+    id: "cfae0a19-6515-4813-bc2d-1e032b72b203",
+    display_name: "foo",
+    status: "active",
+    email: "mw@philologue.net",
+});
+
+export type User = z.infer<typeof parser>;
+
+const get = async (id: string): Promise<null | User> => {
+    const ret = await db
+        .selectFrom("users")
+        .where("users.id", "=", id)
+        .innerJoin("user_emails", "user_emails.user_id", "users.id")
+        .select([
+            "users.id",
+            "users.status",
+            "users.display_name",
+            "user_emails.email",
+        ])
+        .executeTakeFirst();
+
+    if (ret === undefined) {
+        return null;
+    }
+
+    console.dir(ret);
+
+    const parsed = parser.parse(ret);
+
+    return parsed;
+};
+
+export { get };

backend/diachron/interfaces.ts

@@ -0,0 +1,3 @@
+type Brand<K, T> = K & { readonly __brand: T };
+
+export type Extensible = Brand<"Extensible", {}>;

backend/diachron/logging.spec.ts

@@ -0,0 +1,53 @@
+// Tests for logging.ts
+// Note: These tests verify the module structure and types.
+// Full integration tests would require a running logging service.
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+
+// We can't easily test log() and getLogs() without mocking fetch,
+// but we can verify the module exports correctly and types work.
+
+describe("logging", () => {
+    describe("module structure", () => {
+        it("exports log function", async () => {
+            const { log } = await import("./logging");
+            assert.equal(typeof log, "function");
+        });
+
+        it("exports getLogs function", async () => {
+            const { getLogs } = await import("./logging");
+            assert.equal(typeof getLogs, "function");
+        });
+    });
+
+    describe("Message type", () => {
+        // Type-level tests - if these compile, the types are correct
+        it("accepts valid message sources", () => {
+            type MessageSource = "logging" | "diagnostic" | "user";
+            const sources: MessageSource[] = ["logging", "diagnostic", "user"];
+            assert.equal(sources.length, 3);
+        });
+    });
+
+    describe("FilterArgument type", () => {
+        // Type-level tests
+        it("accepts valid filter options", () => {
+            type FilterArgument = {
+                limit?: number;
+                before?: number;
+                after?: number;
+                match?: (string | RegExp)[];
+            };
+
+            const filter: FilterArgument = {
+                limit: 10,
+                before: Date.now(),
+                after: Date.now() - 3600000,
+                match: ["error", /warning/i],
+            };
+
+            assert.ok(filter.limit === 10);
+        });
+    });
+});

backend/diachron/logging.ts

@@ -0,0 +1,73 @@
+// internal-logging.ts
+
+import { cli } from "./cli";
+
+// FIXME: Move this to somewhere more appropriate
+type AtLeastOne<T> = [T, ...T[]];
+
+type MessageSource = "logging" | "diagnostic" | "user";
+
+type Message = {
+    // FIXME: number probably isn't what we want here
+    timestamp?: number;
+    source: MessageSource;
+
+    text: AtLeastOne<string>;
+};
+
+const _m1: Message = { timestamp: 123, source: "logging", text: ["foo"] };
+const _m2: Message = {
+    timestamp: 321,
+    source: "diagnostic",
+    text: ["ok", "whatever"],
+};
+
+type FilterArgument = {
+    limit?: number;
+    before?: number;
+    after?: number;
+
+    // FIXME: add offsets to use instead of or in addition to before/after
+
+    match?: (string | RegExp)[];
+};
+
+const loggerUrl = `http://${cli.logAddress.host}:${cli.logAddress.port}`;
+
+const log = (message: Message) => {
+    const payload = {
+        timestamp: message.timestamp ?? Date.now(),
+        source: message.source,
+        text: message.text,
+    };
+
+    fetch(`${loggerUrl}/log`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(payload),
+    }).catch((err) => {
+        console.error("[logging] Failed to send log:", err.message);
+    });
+};
+
+const getLogs = async (filter: FilterArgument): Promise<Message[]> => {
+    const params = new URLSearchParams();
+    if (filter.limit) {
+        params.set("limit", String(filter.limit));
+    }
+    if (filter.before) {
+        params.set("before", String(filter.before));
+    }
+    if (filter.after) {
+        params.set("after", String(filter.after));
+    }
+
+    const url = `${loggerUrl}/logs?${params.toString()}`;
+    const response = await fetch(url);
+    return response.json();
+};
+
+// FIXME: there's scope for more specialized functions although they
+// probably should be defined in terms of the basic ones here.
+
+export { getLogs, log };

backend/diachron/mgmt/add-user.ts

@@ -0,0 +1,69 @@
+// add-user.ts
+// Management command to create users from the command line
+
+import { hashPassword } from "../auth/password";
+import { PostgresAuthStore, pool } from "../database";
+
+async function main(): Promise<void> {
+    const args = process.argv.slice(2);
+
+    if (args.length < 2) {
+        console.error(
+            "Usage: ./mgmt add-user <email> <password> [--display-name <name>] [--active]",
+        );
+        process.exit(1);
+    }
+
+    const email = args[0];
+    const password = args[1];
+
+    // Parse optional flags
+    let displayName: string | undefined;
+    let makeActive = false;
+
+    for (let i = 2; i < args.length; i++) {
+        if (args[i] === "--display-name" && args[i + 1]) {
+            displayName = args[i + 1];
+            i++;
+        } else if (args[i] === "--active") {
+            makeActive = true;
+        }
+    }
+
+    try {
+        const store = new PostgresAuthStore();
+
+        // Check if user already exists
+        const existing = await store.getUserByEmail(email);
+        if (existing) {
+            console.error(`Error: User with email '${email}' already exists`);
+            process.exit(1);
+        }
+
+        // Hash password and create user
+        const passwordHash = await hashPassword(password);
+        const user = await store.createUser({
+            email,
+            passwordHash,
+            displayName,
+        });
+
+        // Optionally activate user immediately
+        if (makeActive) {
+            await store.updateUserEmailVerified(user.id);
+            console.log(
+                `Created and activated user: ${user.email} (${user.id})`,
+            );
+        } else {
+            console.log(`Created user: ${user.email} (${user.id})`);
+            console.log("  Status: pending (use --active to create as active)");
+        }
+    } finally {
+        await pool.end();
+    }
+}
+
+main().catch((err) => {
+    console.error("Failed to create user:", err.message);
+    process.exit(1);
+});

backend/diachron/migrate.ts

@@ -0,0 +1,45 @@
+// migrate.ts
+// CLI script for running database migrations
+
+import { migrate, migrationStatus, pool } from "./database";
+
+async function main(): Promise<void> {
+    const command = process.argv[2] || "run";
+
+    try {
+        switch (command) {
+            case "run":
+                await migrate();
+                break;
+
+            case "status": {
+                const status = await migrationStatus();
+                console.log("Applied migrations:");
+                for (const name of status.applied) {
+                    console.log(`  ✓ ${name}`);
+                }
+                if (status.pending.length > 0) {
+                    console.log("\nPending migrations:");
+                    for (const name of status.pending) {
+                        console.log(`  • ${name}`);
+                    }
+                } else {
+                    console.log("\nNo pending migrations");
+                }
+                break;
+            }
+
+            default:
+                console.error(`Unknown command: ${command}`);
+                console.error("Usage: migrate [run|status]");
+                process.exit(1);
+        }
+    } finally {
+        await pool.end();
+    }
+}
+
+main().catch((err) => {
+    console.error("Migration failed:", err);
+    process.exit(1);
+});

backend/diachron/migrations/2026-01-01_01-users.sql

@@ -0,0 +1,29 @@
+-- 0001_users.sql
+-- Create users table for authentication
+
+CREATE TABLE users (
+    id UUID PRIMARY KEY,
+    status TEXT NOT NULL DEFAULT 'active',
+    display_name TEXT,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE user_emails (
+    id UUID PRIMARY KEY,
+    user_id UUID NOT NULL REFERENCES users(id),
+    email TEXT NOT NULL,
+    normalized_email TEXT NOT NULL,
+    is_primary BOOLEAN NOT NULL DEFAULT FALSE,
+    is_verified BOOLEAN NOT NULL DEFAULT FALSE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    verified_at TIMESTAMPTZ,
+    revoked_at TIMESTAMPTZ
+);
+
+-- Enforce uniqueness only among *active* emails
+CREATE UNIQUE INDEX user_emails_unique_active
+ON user_emails (normalized_email)
+WHERE revoked_at IS NULL;
+
+

backend/diachron/migrations/2026-01-01_02-sessions.sql

@@ -0,0 +1,26 @@
+-- 0002_sessions.sql
+-- Create sessions table for auth tokens
+
+CREATE TABLE sessions (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    token_hash TEXT UNIQUE NOT NULL,
+    user_id UUID NOT NULL REFERENCES users(id),
+    user_email_id UUID REFERENCES user_emails(id),
+    token_type TEXT NOT NULL,
+    auth_method TEXT NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    expires_at TIMESTAMPTZ NOT NULL,
+    revoked_at TIMESTAMPTZ,
+    ip_address INET,
+    user_agent TEXT,
+    is_used BOOLEAN DEFAULT FALSE
+);
+
+-- Index for user session lookups (logout all, etc.)
+CREATE INDEX sessions_user_id_idx ON sessions (user_id);
+
+-- Index for expiration cleanup
+CREATE INDEX sessions_expires_at_idx ON sessions (expires_at);
+
+-- Index for token type filtering
+CREATE INDEX sessions_token_type_idx ON sessions (token_type);

backend/diachron/migrations/2026-01-01_03-user-credentials.sql

@@ -0,0 +1,17 @@
+-- 0003_user_credentials.sql
+-- Create user_credentials table for password storage (extensible for other auth methods)
+
+CREATE TABLE user_credentials (
+    id UUID PRIMARY KEY,
+    user_id UUID NOT NULL REFERENCES users(id),
+    credential_type TEXT NOT NULL DEFAULT 'password',
+    password_hash TEXT,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Each user can have at most one credential per type
+CREATE UNIQUE INDEX user_credentials_user_type_idx ON user_credentials (user_id, credential_type);
+
+-- Index for user lookups
+CREATE INDEX user_credentials_user_id_idx ON user_credentials (user_id);

backend/diachron/migrations/2026-01-24_01-roles-and-groups.sql

@@ -0,0 +1,20 @@
+CREATE TABLE roles (
+    id UUID PRIMARY KEY,
+    name TEXT UNIQUE NOT NULL,
+    description TEXT
+);
+
+CREATE TABLE groups (
+    id UUID PRIMARY KEY,
+    name TEXT NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE user_group_roles (
+    user_id UUID NOT NULL REFERENCES users(id),
+    group_id UUID NOT NULL REFERENCES groups(id),
+    role_id UUID NOT NULL REFERENCES roles(id),
+    granted_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    revoked_at TIMESTAMPTZ,
+    PRIMARY KEY (user_id, group_id, role_id)
+);

backend/diachron/migrations/2026-01-24_02-capabilities.sql

@@ -0,0 +1,14 @@
+CREATE TABLE capabilities (
+    id UUID PRIMARY KEY,
+    name TEXT UNIQUE NOT NULL,
+    description TEXT
+);
+
+CREATE TABLE role_capabilities (
+    role_id UUID NOT NULL REFERENCES roles(id),
+    capability_id UUID NOT NULL REFERENCES capabilities(id),
+    granted_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    revoked_at TIMESTAMPTZ,
+    PRIMARY KEY (role_id, capability_id)
+);
+

backend/diachron/request/index.ts

@@ -0,0 +1,25 @@
+import { AuthService } from "../auth";
+import { getCurrentUser } from "../context";
+import { PostgresAuthStore } from "../database";
+import type { User } from "../user";
+import { html, redirect, render } from "./util";
+
+const util = { html, redirect, render };
+
+const session = {
+    getUser: (): User => {
+        return getCurrentUser();
+    },
+};
+
+// Initialize auth with PostgreSQL store
+const authStore = new PostgresAuthStore();
+const auth = new AuthService(authStore);
+
+const request = {
+    auth,
+    session,
+    util,
+};
+
+export { request };

backend/diachron/request/util.ts

@@ -0,0 +1,45 @@
+import { contentTypes } from "../content-types";
+import { core } from "../core";
+import { executionContext } from "../execution-context";
+import { httpCodes } from "../http-codes";
+import type { RedirectResult, Result } from "../types";
+import { loadFile } from "../util";
+import { request } from "./index";
+
+type NoUser = {
+    [key: string]: unknown;
+} & {
+    user?: never;
+};
+
+const render = async (path: string, ctx?: NoUser): Promise<string> => {
+    const fullPath = `${executionContext.diachron_root}/templates/${path}.html.njk`;
+    const template = await loadFile(fullPath);
+    const user = request.session.getUser();
+    const context = { user, ...ctx };
+    const engine = core.conf.templateEngine();
+    const retval = engine.renderTemplate(template, context);
+
+    return retval;
+};
+
+const html = (payload: string): Result => {
+    const retval: Result = {
+        code: httpCodes.success.OK,
+        result: payload,
+        contentType: contentTypes.text.html,
+    };
+
+    return retval;
+};
+
+const redirect = (location: string): RedirectResult => {
+    return {
+        code: httpCodes.redirection.SeeOther,
+        contentType: contentTypes.text.plain,
+        result: "",
+        redirect: location,
+    };
+};
+
+export { html, redirect, render };

backend/diachron/types.spec.ts

@@ -0,0 +1,179 @@
+// Tests for types.ts
+// Pure unit tests
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import type { Request as ExpressRequest } from "express";
+import { Session } from "./auth/types";
+import { contentTypes } from "./content-types";
+import { httpCodes } from "./http-codes";
+import {
+    AuthenticationRequired,
+    AuthorizationDenied,
+    type Call,
+    isRedirect,
+    massageMethod,
+    methodParser,
+    type Permission,
+    type RedirectResult,
+    type Result,
+    requireAuth,
+    requirePermission,
+} from "./types";
+import { AuthenticatedUser, anonymousUser } from "./user";
+
+// Helper to create a minimal mock Call
+function createMockCall(overrides: Partial<Call> = {}): Call {
+    const defaultSession = new Session(null, anonymousUser);
+    return {
+        pattern: "/test",
+        path: "/test",
+        method: "GET",
+        parameters: {},
+        request: {} as ExpressRequest,
+        user: anonymousUser,
+        session: defaultSession,
+        ...overrides,
+    };
+}
+
+describe("types", () => {
+    describe("methodParser", () => {
+        it("accepts valid HTTP methods", () => {
+            assert.equal(methodParser.parse("GET"), "GET");
+            assert.equal(methodParser.parse("POST"), "POST");
+            assert.equal(methodParser.parse("PUT"), "PUT");
+            assert.equal(methodParser.parse("PATCH"), "PATCH");
+            assert.equal(methodParser.parse("DELETE"), "DELETE");
+        });
+
+        it("rejects invalid methods", () => {
+            assert.throws(() => methodParser.parse("get"));
+            assert.throws(() => methodParser.parse("OPTIONS"));
+            assert.throws(() => methodParser.parse("HEAD"));
+            assert.throws(() => methodParser.parse(""));
+        });
+    });
+
+    describe("massageMethod", () => {
+        it("converts lowercase to uppercase", () => {
+            assert.equal(massageMethod("get"), "GET");
+            assert.equal(massageMethod("post"), "POST");
+            assert.equal(massageMethod("put"), "PUT");
+            assert.equal(massageMethod("patch"), "PATCH");
+            assert.equal(massageMethod("delete"), "DELETE");
+        });
+
+        it("handles mixed case", () => {
+            assert.equal(massageMethod("Get"), "GET");
+            assert.equal(massageMethod("pOsT"), "POST");
+        });
+
+        it("throws for invalid methods", () => {
+            assert.throws(() => massageMethod("options"));
+            assert.throws(() => massageMethod("head"));
+        });
+    });
+
+    describe("isRedirect", () => {
+        it("returns true for redirect results", () => {
+            const result: RedirectResult = {
+                code: httpCodes.redirection.Found,
+                contentType: contentTypes.text.html,
+                result: "",
+                redirect: "/other",
+            };
+            assert.equal(isRedirect(result), true);
+        });
+
+        it("returns false for non-redirect results", () => {
+            const result: Result = {
+                code: httpCodes.success.OK,
+                contentType: contentTypes.text.html,
+                result: "hello",
+            };
+            assert.equal(isRedirect(result), false);
+        });
+    });
+
+    describe("AuthenticationRequired", () => {
+        it("has correct name and message", () => {
+            const err = new AuthenticationRequired();
+            assert.equal(err.name, "AuthenticationRequired");
+            assert.equal(err.message, "Authentication required");
+        });
+
+        it("is an instance of Error", () => {
+            const err = new AuthenticationRequired();
+            assert.ok(err instanceof Error);
+        });
+    });
+
+    describe("AuthorizationDenied", () => {
+        it("has correct name and message", () => {
+            const err = new AuthorizationDenied();
+            assert.equal(err.name, "AuthorizationDenied");
+            assert.equal(err.message, "Authorization denied");
+        });
+
+        it("is an instance of Error", () => {
+            const err = new AuthorizationDenied();
+            assert.ok(err instanceof Error);
+        });
+    });
+
+    describe("requireAuth", () => {
+        it("returns user for authenticated call", () => {
+            const user = AuthenticatedUser.create("test@example.com");
+            const session = new Session(null, user);
+            const call = createMockCall({ user, session });
+
+            const result = requireAuth(call);
+            assert.equal(result, user);
+        });
+
+        it("throws AuthenticationRequired for anonymous user", () => {
+            const call = createMockCall({ user: anonymousUser });
+
+            assert.throws(() => requireAuth(call), AuthenticationRequired);
+        });
+    });
+
+    describe("requirePermission", () => {
+        it("returns user when they have the permission", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                permissions: ["posts:create" as Permission],
+            });
+            const session = new Session(null, user);
+            const call = createMockCall({ user, session });
+
+            const result = requirePermission(
+                call,
+                "posts:create" as Permission,
+            );
+            assert.equal(result, user);
+        });
+
+        it("throws AuthenticationRequired for anonymous user", () => {
+            const call = createMockCall({ user: anonymousUser });
+
+            assert.throws(
+                () => requirePermission(call, "posts:create" as Permission),
+                AuthenticationRequired,
+            );
+        });
+
+        it("throws AuthorizationDenied when missing permission", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                permissions: ["posts:read" as Permission],
+            });
+            const session = new Session(null, user);
+            const call = createMockCall({ user, session });
+
+            assert.throws(
+                () => requirePermission(call, "posts:create" as Permission),
+                AuthorizationDenied,
+            );
+        });
+    });
+});

backend/diachron/types.ts

@@ -0,0 +1,117 @@
+// types.ts
+
+// FIXME: split this up into types used by app developers and types internal
+// to the framework.
+import type { Request as ExpressRequest } from "express";
+import type { MatchFunction } from "path-to-regexp";
+import { z } from "zod";
+import type { Session } from "./auth/types";
+import type { ContentType } from "./content-types";
+import type { HttpCode } from "./http-codes";
+import type { Permission, User } from "./user";
+
+const methodParser = z.union([
+    z.literal("GET"),
+    z.literal("POST"),
+    z.literal("PUT"),
+    z.literal("PATCH"),
+    z.literal("DELETE"),
+]);
+
+export type Method = z.infer<typeof methodParser>;
+const massageMethod = (input: string): Method => {
+    const r = methodParser.parse(input.toUpperCase());
+
+    return r;
+};
+
+export type Call = {
+    pattern: string;
+    path: string;
+    method: Method;
+    parameters: object;
+    request: ExpressRequest;
+    user: User;
+    session: Session;
+};
+
+export type InternalHandler = (req: ExpressRequest) => Promise<Result>;
+
+export type Handler = (call: Call) => Promise<Result>;
+export type ProcessedRoute = {
+    matcher: MatchFunction<Record<string, string>>;
+    method: Method;
+    handler: InternalHandler;
+};
+
+export type CookieOptions = {
+    httpOnly?: boolean;
+    secure?: boolean;
+    sameSite?: "strict" | "lax" | "none";
+    maxAge?: number;
+    path?: string;
+};
+
+export type Cookie = {
+    name: string;
+    value: string;
+    options?: CookieOptions;
+};
+
+export type Result = {
+    code: HttpCode;
+    contentType: ContentType;
+    result: string;
+    cookies?: Cookie[];
+};
+
+export type RedirectResult = Result & {
+    redirect: string;
+};
+
+export function isRedirect(result: Result): result is RedirectResult {
+    return "redirect" in result;
+}
+
+export type Route = {
+    path: string;
+    methods: Method[];
+    handler: Handler;
+    interruptable?: boolean;
+};
+
+// Authentication error classes
+export class AuthenticationRequired extends Error {
+    constructor() {
+        super("Authentication required");
+        this.name = "AuthenticationRequired";
+    }
+}
+
+export class AuthorizationDenied extends Error {
+    constructor() {
+        super("Authorization denied");
+        this.name = "AuthorizationDenied";
+    }
+}
+
+// Helper for handlers to require authentication
+export function requireAuth(call: Call): User {
+    if (call.user.isAnonymous()) {
+        throw new AuthenticationRequired();
+    }
+    return call.user;
+}
+
+// Helper for handlers to require specific permission
+export function requirePermission(call: Call, permission: Permission): User {
+    const user = requireAuth(call);
+    if (!user.hasPermission(permission)) {
+        throw new AuthorizationDenied();
+    }
+    return user;
+}
+
+export type Domain = "app" | "fw";
+
+export { methodParser, massageMethod };

backend/diachron/user.spec.ts

@@ -0,0 +1,213 @@
+// Tests for user.ts
+// These are pure unit tests - no database needed
+
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import {
+    AnonymousUser,
+    AuthenticatedUser,
+    anonymousUser,
+    type Permission,
+    type Role,
+} from "./user";
+
+describe("User", () => {
+    describe("AuthenticatedUser.create", () => {
+        it("creates a user with default values", () => {
+            const user = AuthenticatedUser.create("test@example.com");
+
+            assert.equal(user.email, "test@example.com");
+            assert.equal(user.status, "active");
+            assert.equal(user.isAnonymous(), false);
+            assert.deepEqual([...user.roles], []);
+            assert.deepEqual([...user.permissions], []);
+        });
+
+        it("creates a user with custom values", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                id: "custom-id",
+                displayName: "Test User",
+                status: "pending",
+                roles: ["admin"],
+                permissions: ["posts:create"],
+            });
+
+            assert.equal(user.id, "custom-id");
+            assert.equal(user.displayName, "Test User");
+            assert.equal(user.status, "pending");
+            assert.deepEqual([...user.roles], ["admin"]);
+            assert.deepEqual([...user.permissions], ["posts:create"]);
+        });
+    });
+
+    describe("status checks", () => {
+        it("isActive returns true for active users", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                status: "active",
+            });
+            assert.equal(user.isActive(), true);
+        });
+
+        it("isActive returns false for suspended users", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                status: "suspended",
+            });
+            assert.equal(user.isActive(), false);
+        });
+
+        it("isActive returns false for pending users", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                status: "pending",
+            });
+            assert.equal(user.isActive(), false);
+        });
+    });
+
+    describe("role checks", () => {
+        it("hasRole returns true when user has the role", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["admin", "editor"],
+            });
+            assert.equal(user.hasRole("admin"), true);
+            assert.equal(user.hasRole("editor"), true);
+        });
+
+        it("hasRole returns false when user does not have the role", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["user"],
+            });
+            assert.equal(user.hasRole("admin"), false);
+        });
+
+        it("hasAnyRole returns true when user has at least one role", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["editor"],
+            });
+            assert.equal(user.hasAnyRole(["admin", "editor"]), true);
+        });
+
+        it("hasAnyRole returns false when user has none of the roles", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["user"],
+            });
+            assert.equal(user.hasAnyRole(["admin", "editor"]), false);
+        });
+
+        it("hasAllRoles returns true when user has all roles", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["admin", "editor", "user"],
+            });
+            assert.equal(user.hasAllRoles(["admin", "editor"]), true);
+        });
+
+        it("hasAllRoles returns false when user is missing a role", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["admin"],
+            });
+            assert.equal(user.hasAllRoles(["admin", "editor"]), false);
+        });
+    });
+
+    describe("permission checks", () => {
+        it("hasPermission returns true for direct permissions", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                permissions: ["posts:create" as Permission],
+            });
+            assert.equal(
+                user.hasPermission("posts:create" as Permission),
+                true,
+            );
+        });
+
+        it("hasPermission returns true for role-derived permissions", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["admin" as Role],
+            });
+            // admin role has users:read, users:create, users:update, users:delete
+            assert.equal(user.hasPermission("users:read" as Permission), true);
+            assert.equal(
+                user.hasPermission("users:delete" as Permission),
+                true,
+            );
+        });
+
+        it("hasPermission returns false when permission not granted", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["user" as Role],
+            });
+            // user role only has users:read
+            assert.equal(
+                user.hasPermission("users:delete" as Permission),
+                false,
+            );
+        });
+
+        it("can() is a convenience method for hasPermission", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["admin" as Role],
+            });
+            assert.equal(user.can("read", "users"), true);
+            assert.equal(user.can("delete", "users"), true);
+            assert.equal(user.can("create", "posts"), false);
+        });
+    });
+
+    describe("effectivePermissions", () => {
+        it("returns combined direct and role-derived permissions", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                roles: ["user" as Role],
+                permissions: ["posts:create" as Permission],
+            });
+
+            const perms = user.effectivePermissions();
+            assert.equal(perms.has("posts:create" as Permission), true);
+            assert.equal(perms.has("users:read" as Permission), true); // from user role
+        });
+
+        it("returns empty set for user with no roles or permissions", () => {
+            const user = AuthenticatedUser.create("test@example.com");
+            const perms = user.effectivePermissions();
+            assert.equal(perms.size, 0);
+        });
+    });
+
+    describe("serialization", () => {
+        it("toJSON returns plain object", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                id: "test-id",
+                displayName: "Test",
+                status: "active",
+                roles: ["admin"],
+                permissions: ["posts:create"],
+            });
+
+            const json = user.toJSON();
+            assert.equal(json.id, "test-id");
+            assert.equal(json.email, "test@example.com");
+            assert.equal(json.displayName, "Test");
+            assert.equal(json.status, "active");
+            assert.deepEqual(json.roles, ["admin"]);
+            assert.deepEqual(json.permissions, ["posts:create"]);
+        });
+
+        it("toString returns readable string", () => {
+            const user = AuthenticatedUser.create("test@example.com", {
+                id: "test-id",
+            });
+            assert.equal(user.toString(), "User(id test-id)");
+        });
+    });
+
+    describe("AnonymousUser", () => {
+        it("isAnonymous returns true", () => {
+            const user = AnonymousUser.create("anon@example.com");
+            assert.equal(user.isAnonymous(), true);
+        });
+
+        it("anonymousUser singleton is anonymous", () => {
+            assert.equal(anonymousUser.isAnonymous(), true);
+            assert.equal(anonymousUser.id, "-1");
+            assert.equal(anonymousUser.email, "anonymous@example.com");
+        });
+    });
+});

backend/diachron/user.ts

@@ -0,0 +1,232 @@
+// user.ts
+//
+// User model for authentication and authorization.
+//
+// Design notes:
+// - `id` is the stable internal identifier (UUID when database-backed)
+// - `email` is the primary human-facing identifier
+// - Roles provide coarse-grained authorization (admin, editor, etc.)
+// - Permissions provide fine-grained authorization (posts:create, etc.)
+// - Users can have both roles (which grant permissions) and direct permissions
+
+import { z } from "zod";
+
+// Branded type for user IDs to prevent accidental mixing with other strings
+export type UserId = string & { readonly __brand: "UserId" };
+
+// User account status
+const userStatusParser = z.enum(["active", "suspended", "pending"]);
+export type UserStatus = z.infer<typeof userStatusParser>;
+
+// Role - simple string identifier
+const roleParser = z.string().min(1);
+export type Role = z.infer<typeof roleParser>;
+
+// Permission format: "resource:action" e.g. "posts:create", "users:delete"
+const permissionParser = z.string().regex(/^[a-z_]+:[a-z_]+$/, {
+    message: "Permission must be in format 'resource:action'",
+});
+export type Permission = z.infer<typeof permissionParser>;
+
+// Core user data schema - this is what gets stored/serialized
+const userDataParser = z.object({
+    id: z.string().min(1),
+    email: z.email(),
+    displayName: z.string().optional(),
+    status: userStatusParser,
+    roles: z.array(roleParser),
+    permissions: z.array(permissionParser),
+    createdAt: z.coerce.date(),
+    updatedAt: z.coerce.date(),
+});
+
+export type UserData = z.infer<typeof userDataParser>;
+
+// Role-to-permission mappings
+// In a real system this might be database-driven or configurable
+type RolePermissionMap = Map<Role, Permission[]>;
+
+const defaultRolePermissions: RolePermissionMap = new Map([
+    ["admin", ["users:read", "users:create", "users:update", "users:delete"]],
+    ["user", ["users:read"]],
+]);
+
+export abstract class User {
+    protected readonly data: UserData;
+    protected rolePermissions: RolePermissionMap;
+
+    constructor(data: UserData, rolePermissions?: RolePermissionMap) {
+        this.data = userDataParser.parse(data);
+        this.rolePermissions = rolePermissions ?? defaultRolePermissions;
+    }
+
+    // Identity
+    get id(): UserId {
+        return this.data.id as UserId;
+    }
+
+    get email(): string {
+        return this.data.email;
+    }
+
+    get displayName(): string | undefined {
+        return this.data.displayName;
+    }
+
+    // Status
+    get status(): UserStatus {
+        return this.data.status;
+    }
+
+    isActive(): boolean {
+        return this.data.status === "active";
+    }
+
+    // Roles
+    get roles(): readonly Role[] {
+        return this.data.roles;
+    }
+
+    hasRole(role: Role): boolean {
+        return this.data.roles.includes(role);
+    }
+
+    hasAnyRole(roles: Role[]): boolean {
+        return roles.some((role) => this.hasRole(role));
+    }
+
+    hasAllRoles(roles: Role[]): boolean {
+        return roles.every((role) => this.hasRole(role));
+    }
+
+    // Permissions
+    get permissions(): readonly Permission[] {
+        return this.data.permissions;
+    }
+
+    // Get all permissions: direct + role-derived
+    effectivePermissions(): Set<Permission> {
+        const perms = new Set<Permission>(this.data.permissions);
+
+        for (const role of this.data.roles) {
+            const rolePerms = this.rolePermissions.get(role);
+            if (rolePerms) {
+                for (const p of rolePerms) {
+                    perms.add(p);
+                }
+            }
+        }
+
+        return perms;
+    }
+
+    // Check if user has a specific permission (direct or via role)
+    hasPermission(permission: Permission): boolean {
+        // Check direct permissions first
+        if (this.data.permissions.includes(permission)) {
+            return true;
+        }
+
+        // Check role-derived permissions
+        for (const role of this.data.roles) {
+            const rolePerms = this.rolePermissions.get(role);
+            if (rolePerms?.includes(permission)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    // Convenience method: can user perform action on resource?
+    can(action: string, resource: string): boolean {
+        const permission = `${resource}:${action}` as Permission;
+        return this.hasPermission(permission);
+    }
+
+    // Timestamps
+    get createdAt(): Date {
+        return this.data.createdAt;
+    }
+
+    get updatedAt(): Date {
+        return this.data.updatedAt;
+    }
+
+    // Serialization - returns plain object for storage/transmission
+    toJSON(): UserData {
+        return { ...this.data };
+    }
+
+    toString(): string {
+        return `User(id ${this.id})`;
+    }
+
+    abstract isAnonymous(): boolean;
+}
+
+export class AuthenticatedUser extends User {
+    // Factory for creating new users with sensible defaults
+    static create(
+        email: string,
+        options?: {
+            id?: string;
+            displayName?: string;
+            status?: UserStatus;
+            roles?: Role[];
+            permissions?: Permission[];
+        },
+    ): User {
+        const now = new Date();
+        return new AuthenticatedUser({
+            id: options?.id ?? crypto.randomUUID(),
+            email,
+            displayName: options?.displayName,
+            status: options?.status ?? "active",
+            roles: options?.roles ?? [],
+            permissions: options?.permissions ?? [],
+            createdAt: now,
+            updatedAt: now,
+        });
+    }
+
+    isAnonymous(): boolean {
+        return false;
+    }
+}
+
+// For representing "no user" in contexts where user is optional
+export class AnonymousUser extends User {
+    // FIXME: this is C&Ped with only minimal changes.  No bueno.
+    static create(
+        email: string,
+        options?: {
+            id?: string;
+            displayName?: string;
+            status?: UserStatus;
+            roles?: Role[];
+            permissions?: Permission[];
+        },
+    ): AnonymousUser {
+        const now = new Date(0);
+        return new AnonymousUser({
+            id: options?.id ?? crypto.randomUUID(),
+            email,
+            displayName: options?.displayName,
+            status: options?.status ?? "active",
+            roles: options?.roles ?? [],
+            permissions: options?.permissions ?? [],
+            createdAt: now,
+            updatedAt: now,
+        });
+    }
+
+    isAnonymous(): boolean {
+        return true;
+    }
+}
+
+export const anonymousUser = AnonymousUser.create("anonymous@example.com", {
+    id: "-1",
+    displayName: "Anonymous User",
+});

backend/diachron/util.spec.ts

@@ -0,0 +1,61 @@
+// Tests for util.ts
+// Pure unit tests with filesystem
+
+import assert from "node:assert/strict";
+import { mkdir, rm, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import { after, before, describe, it } from "node:test";
+import { loadFile } from "./util";
+
+describe("util", () => {
+    const testDir = join(import.meta.dirname, ".test-util-tmp");
+
+    before(async () => {
+        await mkdir(testDir, { recursive: true });
+    });
+
+    after(async () => {
+        await rm(testDir, { recursive: true, force: true });
+    });
+
+    describe("loadFile", () => {
+        it("loads file contents as string", async () => {
+            const testFile = join(testDir, "test.txt");
+            await writeFile(testFile, "hello world");
+
+            const content = await loadFile(testFile);
+            assert.equal(content, "hello world");
+        });
+
+        it("handles utf-8 content", async () => {
+            const testFile = join(testDir, "utf8.txt");
+            await writeFile(testFile, "hello \u{1F511} world");
+
+            const content = await loadFile(testFile);
+            assert.equal(content, "hello \u{1F511} world");
+        });
+
+        it("handles empty file", async () => {
+            const testFile = join(testDir, "empty.txt");
+            await writeFile(testFile, "");
+
+            const content = await loadFile(testFile);
+            assert.equal(content, "");
+        });
+
+        it("handles multiline content", async () => {
+            const testFile = join(testDir, "multiline.txt");
+            await writeFile(testFile, "line1\nline2\nline3");
+
+            const content = await loadFile(testFile);
+            assert.equal(content, "line1\nline2\nline3");
+        });
+
+        it("throws for nonexistent file", async () => {
+            await assert.rejects(
+                loadFile(join(testDir, "nonexistent.txt")),
+                /ENOENT/,
+            );
+        });
+    });
+});

backend/diachron/util.ts

@@ -0,0 +1,11 @@
+import { readFile } from "node:fs/promises";
+
+// FIXME: Handle the error here
+const loadFile = async (path: string): Promise<string> => {
+    // Specifying 'utf8' returns a string; otherwise, it returns a Buffer
+    const data = await readFile(path, "utf8");
+
+    return data;
+};
+
+export { loadFile };