Momento/docs/3-5-secure-byok-management.md

Story 3.5: Secure BYOK Management

Status: review

Story

As an enterprise user, I want to input and use my own LLM API keys (Bring Your Own Key), so that I can bypass SaaS quotas and control my AI costs.

Epic: Epic 3 — The SaaS Commercial Engine (Monetization & API Cost Protection)
FR coverage: FR14 (secure BYOK storage + routing)
NFR coverage: NFR-S1 (AES-256-GCM at rest), NFR-P3 (router resolves BYOK within existing 50ms routing budget — no extra HTTP round-trip before provider call)

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Acceptance Criteria

1. [AC1] Encrypted storage (NFR-S1): When a user saves a BYOK key via the API, only encryptedKey (AES-256-GCM: salt + iv + authTag + ciphertext, base64) and keyHash (SHA-256 of plaintext, for dedup/lookup) are persisted. Plaintext API keys never appear in logs, API responses, or DB columns.
2. [AC2] Tier gating: BASIC users cannot save BYOK keys (403 TIER_LIMITED or equivalent). PRO users may configure keys for: openai, anthropic, deepseek, openrouter, minimax, zai. BUSINESS and ENTERPRISE may configure all providers supported by VALID_PROVIDERS in lib/ai/router.ts.
3. [AC3] Live validation on save: Before persisting, the server performs a lightweight provider validation call (e.g. models/list or minimal completion) using the submitted key. Invalid keys return 400 without writing to DB.
4. [AC4] Router prioritization: For any AI call where entitlement runs for userId (or host billingOwnerId in collaborative brainstorm — Story 3.4), if that billing user has an active BYOK key matching the resolved lane provider, getChatProvider / getTagsProvider / getEmbeddingsProvider MUST use the decrypted user key instead of system env/admin keys.
5. [AC5] Quota bypass: When BYOK is active for the billing user on that request, canUseFeature returns allowed: true even if Redis quota is exhausted; incrementUsageAsync MUST NOT run for that successful call. QuotaExceededError.byokConfigured MUST be true when the user has any active BYOK key (for paywall UX).
6. [AC6] No system fallback on BYOK: When BYOK is used, withAiProviderFallback is invoked with { skipSystemFallback: true } so failed user-key calls surface errors instead of silently spending platform quota on a secondary system provider.
7. [AC7] CRUD API: Authenticated REST endpoints under app/api/user/api-keys/ support list (masked metadata only), create/upsert, deactivate, and delete per provider. List responses never include ciphertext or plaintext.
8. [AC8] Settings UI: Users manage keys from Settings (anchor: existing AI settings area per UX spec). Masked input, provider picker filtered by tier, inline validation feedback, and persistent “BYOK active” badge when ≥1 key is active.
9. [AC9] Usage meter CTA: When Discovery Pack is exhausted, the sidebar UsageMeter upgrade modal includes a secondary action linking to BYOK settings (i18n, all 15 locale files).
10. [AC10] Host-pays + BYOK: In brainstorm routes, BYOK and quota bypass use billingOwnerId (session host), not the guest's personal keys — guest collaboration must not unlock AI via guest BYOK while host quota is empty.
11. [AC11] Regression: Stories 3.1–3.4 behavior unchanged when user has no BYOK. Non-AI routes unaffected. Admin system keys in env/admin settings remain the fallback.

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Tasks / Subtasks

• Task 1: Schema & crypto foundation (AC: #1, #2)
  • Subtask 1.1: Add Prisma UserAPIKey model (see Dev Notes); @@unique([userId, provider]); cascade delete on User
  • Subtask 1.2: Add MASTER_ENCRYPTION_KEY to .env.example with generation instructions (min 32 bytes entropy; never commit real value)
  • Subtask 1.3: Create lib/crypto.ts — encryptApiKey, decryptApiKey, hashApiKey (AES-256-GCM + scrypt key derivation per patch spec)
  • Subtask 1.4: Non-destructive migration: npx prisma migrate dev (backup per CLAUDE.md before apply)
• Task 2: BYOK domain layer (AC: #2, #4, #5, #10)
  • Subtask 2.1: Create lib/byok.ts — getAllowedByokProviders(tier), getActiveByokKey(userId, provider), hasAnyActiveByok(userId), resolveByokApiKey(userId, providerType)
  • Subtask 2.2: Map Prisma provider string ↔ AiGatewayProvider / factory ProviderType (single source of truth; avoid duplicate enums)
  • Subtask 2.3: Extend canUseFeature / checkEntitlementOrThrow — BYOK bypass + set byokConfigured from hasAnyActiveByok
  • Subtask 2.4: Extend checkSessionEntitlementOrThrow — pass billingOwnerId into BYOK checks (host-pays)
• Task 3: Factory & fallback integration (AC: #4, #6)
  • Subtask 3.1: Add resolveProviderConfig(userId, baseConfig) helper that overlays OPENAI_API_KEY, DEEPSEEK_API_KEY, etc. when BYOK active
  • Subtask 3.2: Update getChatProvider, getTagsProvider, getEmbeddingsProvider to accept optional { billingUserId?: string } OR centralize in a thin getAiProviderForUser(lane, config, billingUserId) wrapper — one choke-point (Story 3.2 AC4)
  • Subtask 3.3: Wire withAiProviderFallback(..., { skipSystemFallback: true }) at all call sites when BYOK active (chat, tags, embeddings, brainstorm create/expand/enrich)
  • Subtask 3.4: Skip incrementUsageAsync when call used BYOK (thread usedByok flag from provider resolution)
• Task 4: API routes (AC: #3, #7)
  • Subtask 4.1: GET /api/user/api-keys — list { provider, alias, model, isActive, lastUsedAt } only
  • Subtask 4.2: POST /api/user/api-keys — validate tier, validate key, encrypt, upsert
  • Subtask 4.3: DELETE /api/user/api-keys/[provider] and PATCH deactivate
  • Subtask 4.4: Provider-specific validators in lib/byok/validate-key.ts (minimal HTTP ping per provider family: OpenAI-compatible vs Anthropic)
• Task 5: Wire existing AI surfaces (AC: #4, #5, #10, #11)
  • Subtask 5.1: app/api/chat/route.ts — pass session.user.id into provider resolution
  • Subtask 5.2: app/api/ai/tags/route.ts, title-suggestions/route.ts — same
  • Subtask 5.3: Brainstorm routes — use billingOwnerId for BYOK + entitlement (not session.user.id for guests)
  • Subtask 5.4: Audit other getTagsProvider / getChatProvider call sites (agents, semantic search, reformulate) — apply same pattern or document deferral in Dev Agent Record
• Task 6: UI & i18n (AC: #8, #9)
  • Subtask 6.1: BYOK panel component under app/(main)/settings/ai/ or dedicated settings/byok linked from AI settings
  • Subtask 6.2: Sidebar/header badge when BYOK active (UX spec: lock icon + “BYOK active”)
  • Subtask 6.3: UsageMeter — add “Add API key” button beside upgrade CTA
  • Subtask 6.4: i18n keys in all 15 memento-note/locales/*.json (FR/EN reference content)
• Task 7: Tests (AC: all)
  • Subtask 7.1: tests/unit/crypto.test.ts — round-trip encrypt/decrypt, wrong key fails
  • Subtask 7.2: tests/unit/byok-entitlements.test.ts — quota exhausted + BYOK → allowed; increment skipped
  • Subtask 7.3: tests/unit/byok-factory.test.ts — config overlay injects user key
  • Subtask 7.4: tests/unit/brainstorm-billing.test.ts — extend: host BYOK bypasses guest-empty-quota scenario
  • Subtask 7.5: Run targeted vitest + npm run build in memento-note/

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Dev Notes

Epic context

Story	Relevance to 3.5
3.1	canUseFeature, QuotaExceededError, byokConfigured stub always false — implement here
3.2	Single choke-point: factory.ts + router.ts — inject BYOK keys into config overlay, do not fork routing logic
3.3	skipSystemFallback already defined — wire when BYOK active
3.4	Host-pays: BYOK checks on billingOwnerId, not guest session.user.id
3.6	Stripe tier changes may revoke provider list — BASIC downgrade deactivates disallowed keys (minimal: reject new saves; optional: isActive=false on disallowed rows)

Critical brownfield reality

Nothing BYOK exists in production schema today:

• No UserAPIKey in prisma/schema.prisma (only UserAISettings for toggles, unrelated to API keys).
• No lib/crypto.ts.
• byokConfigured is hardcoded false in checkEntitlementOrThrow throws.
• Extension seams are pre-placed:

 * Future (Story 3.5 BYOK): plug user-scoped API keys into resolveAiRoute output / factory instantiation.
 * ...
 * - BYOK / UserAPIKey decryption → Story 3.5

export interface WithAiProviderFallbackOptions {
  /** Story 3.5: skip system secondary when user BYOK is active */
  skipSystemFallback?: boolean
}

Do not paste the full aspirational executeLLM / PROVIDER_FALLBACK_CHAIN loop from memento-note/docs/byok-billing-patch-v3.md — implement AC scope only; reuse existing router + fallback from 3.2/3.3.

Recommended Prisma model (adapt to project conventions)

model UserAPIKey {
  id           String   @id @default(cuid())
  userId       String
  provider     String   // matches AiGatewayProvider lowercase, e.g. "openai"
  alias        String   @default("")
  encryptedKey String
  keyHash      String
  model        String?
  isActive     Boolean  @default(true)
  lastUsedAt   DateTime?
  lastUsedFor  String?
  createdAt    DateTime @default(now())
  updatedAt    DateTime @updatedAt

  user User @relation(fields: [userId], references: [id], onDelete: Cascade)

  @@unique([userId, provider])
  @@index([userId])
  @@index([keyHash])
}

Add userApiKeys UserAPIKey[] to User model.

Out of scope for 3.5 (later / optional): LLMCallLog, AIActiveConfig tables from patch doc — admin keys already live in env + app/(admin)/admin/settings. If PM wants call logging, add a thin optional console.debug or defer to analytics story.

BYOK + factory integration pattern

Preferred approach (minimal churn):

1. resolveAiRoute(lane, config) unchanged.
2. Before getProviderInstance, merge BYOK key into config copy:

// lib/byok.ts
export async function applyByokToConfig(
  billingUserId: string,
  providerType: string,
  config: Record<string, string>,
): Promise<{ config: Record<string, string>; usedByok: boolean }> {
  const byok = await resolveByokApiKey(billingUserId, providerType)
  if (!byok) return { config, usedByok: false }
  const { apiKeyConfigKey } = getProviderConfigKeys(providerType)
  if (!apiKeyConfigKey) return { config, usedByok: false }
  return {
    config: { ...config, [apiKeyConfigKey]: byok.plaintext },
    usedByok: true,
  }
}

3. Export wrapper:

export async function getChatProviderForBillingUser(
  config: Record<string, string>,
  billingUserId: string,
) {
  const route = resolveAiRoute('chat', config)
  const { config: cfg, usedByok } = await applyByokToConfig(billingUserId, route.providerType, config)
  const provider = getProviderInstance(route.providerType, cfg, route.modelName, route.embeddingModelName, route.ollamaBaseUrl)
  return { provider, usedByok, route }
}

Reuse getProviderConfigKeys from factory.ts (already exported).

Ollama / LM Studio BYOK: Defer unless product explicitly requires local BYOK — tier lists focus on cloud providers; ollama BYOK is non-standard (base URL + no key). If user selects ollama, return clear error in UI.

Entitlements change (exact behavior)

In canUseFeature(userId, feature):

1. After tier/limit check would deny, call hasAnyActiveByok(userId) — if true, return { allowed: true, ..., byokConfigured: true }.
2. When denying, set byokConfigured: hasAnyActiveByok(userId).

In routes, after successful AI with usedByok === true, do not call incrementUsageAsync.

Files — expected touch list

NEW

• memento-note/lib/crypto.ts
• memento-note/lib/byok.ts
• memento-note/lib/byok/validate-key.ts (or inline in byok.ts if small)
• memento-note/app/api/user/api-keys/route.ts
• memento-note/app/api/user/api-keys/[provider]/route.ts
• memento-note/components/settings/byok-keys-panel.tsx (name as fits project)
• memento-note/tests/unit/crypto.test.ts
• memento-note/tests/unit/byok-entitlements.test.ts
• memento-note/prisma/migrations/*_add_user_api_key

UPDATE

• memento-note/prisma/schema.prisma
• memento-note/lib/entitlements.ts
• memento-note/lib/ai/factory.ts (wrappers or optional billingUserId param)
• memento-note/lib/ai/fallback.ts (call sites only if needed)
• memento-note/app/api/chat/route.ts
• memento-note/app/api/ai/tags/route.ts
• memento-note/app/api/ai/title-suggestions/route.ts
• memento-note/app/api/brainstorm/route.ts
• memento-note/app/api/brainstorm/[sessionId]/expand/route.ts
• memento-note/app/api/brainstorm/[sessionId]/manual-idea/route.ts
• memento-note/components/usage-meter.tsx
• memento-note/app/(main)/settings/ai/page.tsx or new settings subpage
• memento-note/locales/*.json (15 files)
• memento-note/.env.example
• memento-note/tests/unit/brainstorm-billing.test.ts

READ BEFORE MODIFY (current state documentation)

File	Current state	What 3.5 changes
lib/entitlements.ts	Redis quota only; byokConfigured always false on throw	BYOK bypass branch + accurate byokConfigured
lib/ai/factory.ts	Keys from env/admin config only	Overlay user key into config before getProviderInstance
lib/ai/router.ts	Lane → provider type	Unchanged; BYOK follows resolved providerType
lib/ai/fallback.ts	skipSystemFallback exists, unused	Pass true when BYOK
lib/brainstorm-collab.ts	getBillingOwner for host-pays	Consumers pass billingOwnerId to BYOK resolution
components/usage-meter.tsx	Upgrade modal only	Add BYOK CTA link
app/(main)/settings/ai/page.tsx	AISettingsPanel toggles only	Host BYOK management panel

UX requirements (from docs/ux-design-specification.md)

• Entry: “Manage keys” from quota sidebar or settings.
• Input: Masked secret field; silent validation ping; no full page reload.
• Feedback: Persistent badge (lock + “BYOK active”) in sidebar or header when active.
• Zero-redirect: Configure BYOK without leaving editor context (settings drawer/page is OK).
• Exhausted quota modal: Offer “Upgrade” AND “Add API key” (AC9).

Security requirements

• NFR-S1: AES-256-GCM with unique salt/IV per encryption; auth tag verified on decrypt.
• Master key: process.env.MASTER_ENCRYPTION_KEY — fail fast at startup in production if missing when BYOK routes enabled.
• Logs: Never log plaintext keys or decrypted values; redact Authorization headers in debug.
• API responses: Never return encryptedKey or partial plaintext (only •••••• + last 4 optional).
• Rate limit: Consider basic rate limit on POST validate (10/min per user) to prevent abuse — lightweight redis.incr if pattern exists elsewhere.

Scope boundaries (do NOT implement in 3.5)

• LLMCallLog cost analytics table (patch doc §1.2) — defer
• Full executeLLM multi-hop fallback chain — already 3.3 single secondary
• BrainstormContextPool — separate product story
• GDPR hard delete of keys — Story 4.2 (ensure onDelete: Cascade on User for schema readiness)
• Stripe checkout — Story 3.6
• Socket error:quota_exceeded BYOK hints — optional; HTTP 402 + byokConfigured is MVP

Product decisions (document in Dev Agent Record)

Decision	Recommendation
PRO provider list	openai, anthropic, deepseek, openrouter, minimax, zai (per GTM doc)
Key validation	Required light ping on save (patch doc Q7)
Downgrade Business→Pro	Set isActive=false on keys for providers no longer allowed; do not delete ciphertext
Multiple keys per provider	@@unique([userId, provider]) — upsert only
Guest BYOK in shared session	Ignored for billing — only host BYOK applies (AC10)

Testing standards

• Vitest unit tests with mocked prisma + redis.
• Crypto tests use fixed MASTER_ENCRYPTION_KEY in test env.
• Integration: optional manual test with real DeepSeek test key in dev only — never commit keys.
• Verify: exhausted quota + no BYOK → 402; exhausted + BYOK → 200; BYOK failure → error without system fallback provider call (mock factory).

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Dev Agent Guardrails

Technical requirements

• Database: Backup before migration (CLAUDE.md — pg_dump to /tmp/). Use prisma migrate dev only — never migrate reset.
• Performance: BYOK resolution = 1 Prisma findFirst by [userId, provider, isActive] — cache optional later; keep <10ms with index.
• Fail-open Redis: If Redis down, existing fail-open remains; BYOK bypass is independent of Redis.
• 402 body: Preserve existing QuotaExceededError.toJSON() shape; byokConfigured: true enables frontend BYOK CTA.

Architecture compliance

• Brownfield Next.js under memento-note/.
• BYOK is billing + credentials — not routing policy (stay in byok.ts + factory.ts, not duplicate logic in every route).
• i18n: zero hardcoded UI strings.

Library / framework requirements

• Node crypto module for AES-256-GCM (no new dependency unless team prefers @noble/ciphers — default to Node built-in per patch doc).
• Reuse getProviderConfigKeys from factory.ts for key env mapping.
• Provider validation: use existing provider clients where possible (minimal fetch).

File structure requirements

• lib/crypto.ts — encryption only (no business logic).
• lib/byok.ts — domain rules, tier maps, DB access.
• API routes under app/api/user/api-keys/ (user-scoped, not admin).

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Previous Story Intelligence

Source: docs/3-4-host-pays-session-logic.md

• getBillingOwner / billingOwnerFromSession implemented; use billingOwnerId for entitlement + BYOK.
• checkSessionEntitlementOrThrow attaches guest metadata to 402.
• Explicit seam: "Story 3.5: skip quota when host has active BYOK" — implement now in entitlements + brainstorm routes.
• withAiProviderFallback on brainstorm paths — add skipSystemFallback when host BYOK.

Source: docs/3-3-smart-routing-fallback.md

• Do not add tertiary fallback chains.
• skipSystemFallback stub exists — wire it.

Source: docs/3-2-custom-llm-router.md

• AC4 single choke-point: extend factory wrappers, do not add parallel routing paths.

Source: docs/3-1-freemium-quota-tracking.md

• Deferred: byokConfigured always false — fix in 3.5.
• 402 pattern established across chat/tags.

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Git Intelligence Summary

Commit	Insight
1fcea6e	Brainstorm + embeddings active — BYOK must cover brainstorm billing owner paths
41596c2	OpenRouter key env fallback pattern — BYOK overlay same config keys
195e845	Security-conscious patterns — treat API keys as secrets

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Latest Technical Information

• Node.js crypto (2024+): createCipheriv('aes-256-gcm', ...) + scryptSync for key derivation remains standard; no deprecated APIs for this use case.
• Prisma: Use upsert with @@unique([userId, provider]) for key rotation without duplicate rows.
• AI SDK: Existing routes use Vercel AI SDK generateText — BYOK only changes provider instance credentials, not stream shape.

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Project Context Reference

Document	Use
docs/epics.md	Story 3.5 AC + FR14
docs/prd.md	BYOK journey, NFR-S1, NFR-P3
docs/ux-design-specification.md	BYOK UX flows, badge, settings placement
memento-note/docs/byok-billing-patch-v3.md	Aspirational reference — do not implement wholesale
docs/3-4-host-pays-session-logic.md	billingOwnerId for BYOK
docs/3-3-smart-routing-fallback.md	skipSystemFallback
docs/3-2-custom-llm-router.md	Choke-point
docs/3-1-freemium-quota-tracking.md	Entitlements baseline
docs/gtm-pricing-strategy.md	PRO vs BUSINESS BYOK provider lists
CLAUDE.md	Database safety

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Dev Agent Record

Agent Model Used

{{agent_model_name_version}}

Debug Log References

Completion Notes List

File List

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Story Completion Status

• Story ID: 3.5
• Story Key: 3-5-secure-byok-management
• File: docs/3-5-secure-byok-management.md
• Status: review
• Completion Note: Implementation complete pending Prisma migration (backup required per CLAUDE.md). UI, API, entitlements, AI/brainstorm wiring, tests, i18n (15 locales).