docs/ARCHITECTURE.md

# 9Router Architecture

_Last updated: 2026-02-06_

## Executive Summary

9Router is a local AI routing gateway and dashboard built on Next.js.
It provides a single OpenAI-compatible endpoint (`/v1/*`) and routes traffic across multiple upstream providers with translation, fallback, token refresh, and usage tracking.

Core capabilities:

- OpenAI-compatible API surface for CLI/tools
- Request/response translation across provider formats
- Model combo fallback (multi-model sequence)
- Account-level fallback (multi-account per provider)
- OAuth + API-key provider connection management
- Local persistence for providers, keys, aliases, combos, settings, pricing
- Usage/cost tracking and request logging
- Optional cloud sync for multi-device/state sync

Primary runtime model:

- Next.js app routes under `src/app/api/*` implement both dashboard APIs and compatibility APIs
- A shared SSE/routing core in `src/sse/*` + `open-sse/*` handles provider execution, translation, streaming, fallback, and usage

## Scope and Boundaries

### In Scope

- Local gateway runtime
- Dashboard management APIs
- Provider authentication and token refresh
- Request translation and SSE streaming
- Local state + usage persistence
- Optional cloud sync orchestration

### Out of Scope

- Cloud service implementation behind `NEXT_PUBLIC_CLOUD_URL`
- Provider SLA/control plane outside local process
- External CLI binaries themselves (Claude CLI, Codex CLI, etc.)

## High-Level System Context

```mermaid
flowchart LR
    subgraph Clients[Developer Clients]
        C1[Claude Code]
        C2[Codex CLI]
        C3[OpenClaw / Droid / Cline / Continue / Roo]
        C4[Custom OpenAI-compatible clients]
        BROWSER[Browser Dashboard]
    end

    subgraph Router[9Router Local Process]
        API[V1 Compatibility API\n/v1/*]
        DASH[Dashboard + Management API\n/api/*]
        CORE[SSE + Translation Core\nopen-sse + src/sse]
        DB[(db.json)]
        UDB[(usage.json + log.txt)]
    end

    subgraph Upstreams[Upstream Providers]
        P1[OAuth Providers\nClaude/Codex/Gemini/Qwen/iFlow/GitHub/Kiro/Cursor/Antigravity]
        P2[API Key Providers\nOpenAI/Anthropic/OpenRouter/GLM/Kimi/MiniMax]
        P3[Compatible Nodes\nOpenAI-compatible / Anthropic-compatible]
    end

    subgraph Cloud[Optional Cloud Sync]
        CLOUD[Cloud Sync Endpoint\nNEXT_PUBLIC_CLOUD_URL]
    end

    C1 --> API
    C2 --> API
    C3 --> API
    C4 --> API
    BROWSER --> DASH

    API --> CORE
    DASH --> DB
    CORE --> DB
    CORE --> UDB

    CORE --> P1
    CORE --> P2
    CORE --> P3

    DASH --> CLOUD
```

## Core Runtime Components

## 1) API and Routing Layer (Next.js App Routes)

Main directories:

- `src/app/api/v1/*` and `src/app/api/v1beta/*` for compatibility APIs
- `src/app/api/*` for management/configuration APIs
- Next rewrites in `next.config.mjs` map `/v1/*` to `/api/v1/*`

Important compatibility routes:

- `src/app/api/v1/chat/completions/route.js`
- `src/app/api/v1/messages/route.js`
- `src/app/api/v1/responses/route.js`
- `src/app/api/v1/models/route.js`
- `src/app/api/v1/messages/count_tokens/route.js`
- `src/app/api/v1beta/models/route.js`
- `src/app/api/v1beta/models/[...path]/route.js`

Management domains:

- Auth/settings: `src/app/api/auth/*`, `src/app/api/settings/*`
- Providers/connections: `src/app/api/providers*`
- Provider nodes: `src/app/api/provider-nodes*`
- OAuth: `src/app/api/oauth/*`
- Keys/aliases/combos/pricing: `src/app/api/keys*`, `src/app/api/models/alias`, `src/app/api/combos*`, `src/app/api/pricing`
- Usage: `src/app/api/usage/*`
- Sync/cloud: `src/app/api/sync/*`, `src/app/api/cloud/*`
- CLI tooling helpers: `src/app/api/cli-tools/*`

## 2) SSE + Translation Core

Main flow modules:

- Entry: `src/sse/handlers/chat.js`
- Core orchestration: `open-sse/handlers/chatCore.js`
- Provider execution adapters: `open-sse/executors/*`
- Format detection/provider config: `open-sse/services/provider.js`
- Model parse/resolve: `src/sse/services/model.js`, `open-sse/services/model.js`
- Account fallback logic: `open-sse/services/accountFallback.js`
- Translation registry: `open-sse/translator/index.js`
- Stream transformations: `open-sse/utils/stream.js`, `open-sse/utils/streamHandler.js`
- Usage extraction/normalization: `open-sse/utils/usageTracking.js`

## 3) Persistence Layer

Primary state DB:

- `src/lib/localDb.js`
- file: `${DATA_DIR}/db.json` (or `~/.9router/db.json` when `DATA_DIR` is unset)
- entities: providerConnections, providerNodes, modelAliases, combos, apiKeys, settings, pricing

Usage DB:

- `src/lib/usageDb.js`
- files: `~/.9router/usage.json`, `~/.9router/log.txt`
- note: currently independent from `DATA_DIR`

## 4) Auth + Security Surfaces

- Dashboard cookie auth: `src/proxy.js`, `src/app/api/auth/login/route.js`
- API key generation/verification: `src/shared/utils/apiKey.js`
- Provider secrets persisted in `providerConnections` entries
- Optional proxy support for upstream calls via env proxy variables (`open-sse/utils/proxyFetch.js`)

## 5) Cloud Sync

- Scheduler init: `src/lib/initCloudSync.js`, `src/shared/services/initializeCloudSync.js`
- Periodic task: `src/shared/services/cloudSyncScheduler.js`
- Control route: `src/app/api/sync/cloud/route.js`

## Request Lifecycle (`/v1/chat/completions`)

```mermaid
sequenceDiagram
    autonumber
    participant Client as CLI/SDK Client
    participant Route as /api/v1/chat/completions
    participant Chat as src/sse/handlers/chat
    participant Core as open-sse/handlers/chatCore
    participant Model as Model Resolver
    participant Auth as Credential Selector
    participant Exec as Provider Executor
    participant Prov as Upstream Provider
    participant Stream as Stream Translator
    participant Usage as usageDb

    Client->>Route: POST /v1/chat/completions
    Route->>Chat: handleChat(request)
    Chat->>Model: parse/resolve model or combo

    alt Combo model
        Chat->>Chat: iterate combo models (handleComboChat)
    end

    Chat->>Auth: getProviderCredentials(provider)
    Auth-->>Chat: active account + tokens/api key

    Chat->>Core: handleChatCore(body, modelInfo, credentials)
    Core->>Core: detect source format
    Core->>Core: translate request to target format
    Core->>Exec: execute(provider, transformedBody)
    Exec->>Prov: upstream API call
    Prov-->>Exec: SSE/JSON response
    Exec-->>Core: response + metadata

    alt 401/403
        Core->>Exec: refreshCredentials()
        Exec-->>Core: updated tokens
        Core->>Exec: retry request
    end

    Core->>Stream: translate/normalize stream to client format
    Stream-->>Client: SSE chunks / JSON response

    Stream->>Usage: extract usage + persist history/log
```

## Combo + Account Fallback Flow

```mermaid
flowchart TD
    A[Incoming model string] --> B{Is combo name?}
    B -- Yes --> C[Load combo models sequence]
    B -- No --> D[Single model path]

    C --> E[Try model N]
    E --> F[Resolve provider/model]
    D --> F

    F --> G[Select account credentials]
    G --> H{Credentials available?}
    H -- No --> I[Return provider unavailable]
    H -- Yes --> J[Execute request]

    J --> K{Success?}
    K -- Yes --> L[Return response]
    K -- No --> M{Fallback-eligible error?}

    M -- No --> N[Return error]
    M -- Yes --> O[Mark account unavailable cooldown]
    O --> P{Another account for provider?}
    P -- Yes --> G
    P -- No --> Q{In combo with next model?}
    Q -- Yes --> E
    Q -- No --> R[Return all unavailable]
```

Fallback decisions are driven by `open-sse/services/accountFallback.js` using status codes and error-message heuristics.

## OAuth Onboarding and Token Refresh Lifecycle

```mermaid
sequenceDiagram
    autonumber
    participant UI as Dashboard UI
    participant OAuth as /api/oauth/[provider]/[action]
    participant ProvAuth as Provider Auth Server
    participant DB as localDb
    participant Test as /api/providers/[id]/test
    participant Exec as Provider Executor

    UI->>OAuth: GET authorize or device-code
    OAuth->>ProvAuth: create auth/device flow
    ProvAuth-->>OAuth: auth URL or device code payload
    OAuth-->>UI: flow data

    UI->>OAuth: POST exchange or poll
    OAuth->>ProvAuth: token exchange/poll
    ProvAuth-->>OAuth: access/refresh tokens
    OAuth->>DB: createProviderConnection(oauth data)
    OAuth-->>UI: success + connection id

    UI->>Test: POST /api/providers/[id]/test
    Test->>Exec: validate credentials / optional refresh
    Exec-->>Test: valid or refreshed token info
    Test->>DB: update status/tokens/errors
    Test-->>UI: validation result
```

Refresh during live traffic is executed inside `open-sse/handlers/chatCore.js` via executor `refreshCredentials()`.

## Cloud Sync Lifecycle (Enable / Sync / Disable)

```mermaid
sequenceDiagram
    autonumber
    participant UI as Endpoint Page UI
    participant Sync as /api/sync/cloud
    participant DB as localDb
    participant Cloud as External Cloud Sync
    participant Claude as ~/.claude/settings.json

    UI->>Sync: POST action=enable
    Sync->>DB: set cloudEnabled=true
    Sync->>DB: ensure API key exists
    Sync->>Cloud: POST /sync/{machineId} (providers/aliases/combos/keys)
    Cloud-->>Sync: sync result
    Sync->>Cloud: GET /{machineId}/v1/verify
    Sync-->>UI: enabled + verification status

    UI->>Sync: POST action=sync
    Sync->>Cloud: POST /sync/{machineId}
    Cloud-->>Sync: remote data
    Sync->>DB: update newer local tokens/status
    Sync-->>UI: synced

    UI->>Sync: POST action=disable
    Sync->>DB: set cloudEnabled=false
    Sync->>Cloud: DELETE /sync/{machineId}
    Sync->>Claude: switch ANTHROPIC_BASE_URL back to local (if needed)
    Sync-->>UI: disabled
```

Periodic sync is triggered by `CloudSyncScheduler` when cloud is enabled.

## Data Model and Storage Map

```mermaid
erDiagram
    SETTINGS ||--o{ PROVIDER_CONNECTION : controls
    PROVIDER_NODE ||--o{ PROVIDER_CONNECTION : backs_compatible_provider
    PROVIDER_CONNECTION ||--o{ USAGE_ENTRY : emits_usage

    SETTINGS {
      boolean cloudEnabled
      number stickyRoundRobinLimit
      boolean requireLogin
      string password_hash
    }

    PROVIDER_CONNECTION {
      string id
      string provider
      string authType
      string name
      number priority
      boolean isActive
      string apiKey
      string accessToken
      string refreshToken
      string expiresAt
      string testStatus
      string lastError
      string rateLimitedUntil
      json providerSpecificData
    }

    PROVIDER_NODE {
      string id
      string type
      string name
      string prefix
      string apiType
      string baseUrl
    }

    MODEL_ALIAS {
      string alias
      string targetModel
    }

    COMBO {
      string id
      string name
      string[] models
    }

    API_KEY {
      string id
      string name
      string key
      string machineId
      boolean isActive
    }

    USAGE_ENTRY {
      string provider
      string model
      number prompt_tokens
      number completion_tokens
      string connectionId
      string timestamp
    }
```

Physical storage files:

- main state: `${DATA_DIR}/db.json` (or `~/.9router/db.json`)
- usage stats: `~/.9router/usage.json`
- request log lines: `~/.9router/log.txt`
- optional translator/request debug sessions: `<repo>/logs/...`

## Deployment Topology

```mermaid
flowchart LR
    subgraph LocalHost[Developer Host]
        CLI[CLI Tools]
        Browser[Dashboard Browser]
    end

    subgraph ContainerOrProcess[9Router Runtime]
        Next[Next.js Server\nPORT=20128]
        Core[SSE Core + Executors]
        MainDB[(db.json)]
        UsageDB[(usage.json/log.txt)]
    end

    subgraph External[External Services]
        Providers[AI Providers]
        SyncCloud[Cloud Sync Service]
    end

    CLI --> Next
    Browser --> Next
    Next --> Core
    Next --> MainDB
    Core --> MainDB
    Core --> UsageDB
    Core --> Providers
    Next --> SyncCloud
```

## Module Mapping (Decision-Critical)

### Route and API Modules

- `src/app/api/v1/*`, `src/app/api/v1beta/*`: compatibility APIs
- `src/app/api/providers*`: provider CRUD, validation, testing
- `src/app/api/provider-nodes*`: custom compatible node management
- `src/app/api/oauth/*`: OAuth/device-code flows
- `src/app/api/keys*`: local API key lifecycle
- `src/app/api/models/alias`: alias management
- `src/app/api/combos*`: fallback combo management
- `src/app/api/pricing`: pricing overrides for cost calculation
- `src/app/api/usage/*`: usage and logs APIs
- `src/app/api/sync/*` + `src/app/api/cloud/*`: cloud sync and cloud-facing helpers
- `src/app/api/cli-tools/*`: local CLI config writers/checkers

### Routing and Execution Core

- `src/sse/handlers/chat.js`: request parse, combo handling, account selection loop
- `open-sse/handlers/chatCore.js`: translation, executor dispatch, retry/refresh handling, stream setup
- `open-sse/executors/*`: provider-specific network and format behavior

### Translation Registry and Format Converters

- `open-sse/translator/index.js`: translator registry and orchestration
- Request translators: `open-sse/translator/request/*`
- Response translators: `open-sse/translator/response/*`
- Format constants: `open-sse/translator/formats.js`

### Persistence

- `src/lib/localDb.js`: persistent config/state
- `src/lib/usageDb.js`: usage history and rolling request logs

## Provider Executor Coverage

Specialized executors:

- `antigravity`
- `gemini-cli`
- `github`
- `kiro`
- `codex`
- `cursor`

Default executor path:

- all other providers (including compatible node providers) use `open-sse/executors/default.js`

## Format Translation Coverage

Detected source formats include:

- `openai`
- `openai-responses`
- `claude`
- `gemini`

Target formats include:

- OpenAI chat/Responses
- Claude
- Gemini/Gemini-CLI/Antigravity envelope
- Kiro
- Cursor

Translations are selected dynamically based on source payload shape and provider target format.

## Failure Modes and Resilience

## 1) Account/Provider Availability

- provider account cooldown on transient/rate/auth errors
- account fallback before failing request
- combo model fallback when current model/provider path is exhausted

## 2) Token Expiry

- pre-check and refresh with retry for refreshable providers
- 401/403 retry after refresh attempt in core path

## 3) Stream Safety

- disconnect-aware stream controller
- translation stream with end-of-stream flush and `[DONE]` handling
- usage estimation fallback when provider usage metadata is missing

## 4) Cloud Sync Degradation

- sync errors are surfaced but local runtime continues
- scheduler has retry-capable logic, but periodic execution currently calls single-attempt sync by default

## 5) Data Integrity

- DB shape migration/repair for missing keys
- corrupt JSON reset safeguards for localDb and usageDb

## Observability and Operational Signals

Runtime visibility sources:

- console logs from `src/sse/utils/logger.js`
- per-request usage aggregates in `usage.json`
- textual request status log in `log.txt`
- optional deep request/translation logs under `logs/` when `ENABLE_REQUEST_LOGS=true`
- dashboard usage endpoints (`/api/usage/*`) for UI consumption

## Security-Sensitive Boundaries

- JWT secret (`JWT_SECRET`) secures dashboard session cookie verification/signing
- Initial password fallback (`INITIAL_PASSWORD`, default `123456`) must be overridden in real deployments
- API key HMAC secret (`API_KEY_SECRET`) secures generated local API key format
- Provider secrets (API keys/tokens) are persisted in local DB and should be protected at filesystem level
- Cloud sync endpoints rely on API key auth + machine id semantics

## Environment and Runtime Matrix

Environment variables actively used by code:

- App/auth: `JWT_SECRET`, `INITIAL_PASSWORD`
- Storage: `DATA_DIR`
- Security hashing: `API_KEY_SECRET`, `MACHINE_ID_SALT`
- Logging: `ENABLE_REQUEST_LOGS`
- Sync/cloud URLing: `NEXT_PUBLIC_BASE_URL`, `NEXT_PUBLIC_CLOUD_URL`
- Outbound proxy: `HTTP_PROXY`, `HTTPS_PROXY`, `ALL_PROXY`, `NO_PROXY` and lowercase variants
- Platform/runtime helpers (not app-specific config): `APPDATA`, `NODE_ENV`, `PORT`, `HOSTNAME`

## Known Architectural Notes

1. `usageDb` currently stores under `~/.9router` and does not follow `DATA_DIR`.
2. `/api/v1/route.js` returns a static model list and is not the main models source used by `/v1/models`.
3. Request logger writes full headers/body when enabled; treat log directory as sensitive.
4. Cloud behavior depends on correct `NEXT_PUBLIC_BASE_URL` and cloud endpoint reachability.

## Operational Verification Checklist

- Build from source: `cd /root/dev/9router && npm run build`
- Build Docker image: `cd /root/dev/9router && docker build -t 9router .`
- Start service and verify:
- `GET /api/settings`
- `GET /api/v1/models`
- CLI target base URL should be `http://<host>:20128/v1` when `PORT=20128`