> A comprehensive, beginner-friendly guide to the **omniroute** multi-provider AI proxy router.
---
## 1. What Is omniroute?
omniroute is a **proxy router** that sits between AI clients (Claude CLI, Codex, Cursor IDE, etc.) and AI providers (Anthropic, Google, OpenAI, AWS, GitHub, etc.). It solves one big problem:
> **Different AI clients speak different "languages" (API formats), and different AI providers expect different "languages" too.** omniroute translates between them automatically.
Think of it like a universal translator at the United Nations — any delegate can speak any language, and the translator converts it for any other delegate.
---
## 2. Architecture Overview
```mermaid
graph LR
subgraph Clients
A[Claude CLI]
B[Codex]
C[Cursor IDE]
D[OpenAI-compatible]
end
subgraph omniroute
E[Handler Layer]
F[Translator Layer]
G[Executor Layer]
H[Services Layer]
end
subgraph Providers
I[Anthropic Claude]
J[Google Gemini]
K[OpenAI / Codex]
L[GitHub Copilot]
M[AWS Kiro]
N[Antigravity]
O[Cursor API]
end
A --> E
B --> E
C --> E
D --> E
E --> F
F --> G
G --> I
G --> J
G --> K
G --> L
G --> M
G --> N
G --> O
H -.-> E
H -.-> G
```
### Core Principle: Hub-and-Spoke Translation
All format translation passes through **OpenAI format as the hub**:
```
Client Format → [OpenAI Hub] → Provider Format (request)
Provider Format → [OpenAI Hub] → Client Format (response)
```
This means you only need **N translators** (one per format) instead of **N²** (every pair).
| `constants.ts` | `PROVIDERS` object with base URLs, OAuth credentials (defaults), headers, and default system prompts for every provider. Also defines `HTTP_STATUS`, `ERROR_TYPES`, `COOLDOWN_MS`, `BACKOFF_CONFIG`, and `SKIP_PATTERNS`. |
| `credentialLoader.ts` | Loads external credentials from `data/provider-credentials.json` and merges them over the hardcoded defaults in `PROVIDERS`. Keeps secrets out of source control while maintaining backwards compatibility. |
| `providerModels.ts` | Central model registry: maps provider aliases → model IDs. Functions like `getModels()`, `getProviderByAlias()`. |
| `codexInstructions.ts` | System instructions injected into Codex requests (editing constraints, sandbox rules, approval policies). |
| `defaultThinkingSignature.ts` | Default "thinking" signatures for Claude and Gemini models. |
| `ollamaModels.ts` | Schema definition for local Ollama models (name, size, family, quantization). |
| `provider.ts` | **Format detection** (`detectFormat`): analyzes request body structure to identify Claude/OpenAI/Gemini/Antigravity/Responses formats (includes `max_tokens` heuristic for Claude). Also: URL building, header building, thinking config normalization. Supports `openai-compatible-*` and `anthropic-compatible-*` dynamic providers. |
| `model.ts` | Model string parsing (`claude/model-name` → `{provider: "claude", model: "model-name"}`), alias resolution with collision detection, input sanitization (rejects path traversal/control chars), and model info resolution with async alias getter support. |
| `combo.ts` | **Combo models**: chains of fallback models. If model A fails with a fallback-eligible error, try model B, then C, etc. Returns actual upstream status codes. |
| `usage.ts` | Fetches quota/usage data from provider APIs (GitHub Copilot quotas, Antigravity model quotas, Codex rate limits, Kiro usage breakdowns, Claude settings). |
| `accountSelector.ts` | Smart account selection with scoring algorithm: considers priority, health status, round-robin position, and cooldown state to pick the optimal account for each request. |
| `contextManager.ts` | Request context lifecycle management: creates and tracks per-request context objects with metadata (request ID, timestamps, provider info) for debugging and logging. |
| `ipFilter.ts` | IP-based access control: supports allowlist and blocklist modes. Validates client IP against configured rules before processing API requests. |
| `sessionManager.ts` | Session tracking with client fingerprinting: tracks active sessions using hashed client identifiers, monitors request counts, and provides session metrics. |
| `signatureCache.ts` | Request signature-based deduplication cache: prevents duplicate requests by caching recent request signatures and returning cached responses for identical requests within a time window. |
| `systemPrompt.ts` | Global system prompt injection: prepends or appends a configurable system prompt to all requests, with per-provider compatibility handling. |
| `thinkingBudget.ts` | Reasoning token budget management: supports passthrough, auto (strip thinking config), custom (fixed budget), and adaptive (complexity-scaled) modes for controlling thinking/reasoning tokens. |
| `wildcardRouter.ts` | Wildcard model pattern routing: resolves wildcard patterns (e.g., `*/claude-*`) to concrete provider/model pairs based on availability and priority. |
#### Token Refresh Deduplication
```mermaid
sequenceDiagram
participant R1 as Request 1
participant R2 as Request 2
participant Cache as refreshPromiseCache
participant OAuth as OAuth Provider
R1->>Cache: getAccessToken("gemini", token)
Cache->>Cache: No in-flight promise
Cache->>OAuth: Start refresh
R2->>Cache: getAccessToken("gemini", token)
Cache->>Cache: Found in-flight promise
Cache-->>R2: Return existing promise
OAuth-->>Cache: New access token
Cache-->>R1: New access token
Cache-->>R2: Same access token (shared)
Cache->>Cache: Delete cache entry
```
#### Account Fallback State Machine
```mermaid
stateDiagram-v2
[*] --> Active
Active --> Error: Request fails (401/429/500)
Error --> Cooldown: Apply backoff
Cooldown --> Active: Cooldown expires
Active --> Active: Request succeeds (reset backoff)
| `usageTracking.ts` | Token usage extraction from any format (Claude/OpenAI/Gemini/Responses), estimation with separate tool/message char-per-token ratios, buffer addition (2000 tokens safety margin), format-specific field filtering, console logging with ANSI colors. |
| `requestLogger.ts` | Legacy file-based request logging helper kept for compatibility. Current deployments should prefer `APP_LOG_TO_FILE` for application logs and the call log pipeline for persisted request artifacts. |
| `bypassHandler.ts` | Intercepts specific patterns from Claude CLI (title extraction, warmup, count) and returns fake responses without calling any provider. Supports both streaming and non-streaming. Intentionally limited to Claude CLI scope. |
| `networkProxy.ts` | Resolves outbound proxy URL for a given provider with precedence: provider-specific config → global config → environment variables (`HTTPS_PROXY`/`HTTP_PROXY`/`ALL_PROXY`). Supports `NO_PROXY` exclusions. Caches config for 30s. |
| `/api/settings/system-prompt` | GET/PUT | Global system prompt injection for all requests |
| `/api/sessions` | GET | Active session tracking and metrics |
| `/api/rate-limits` | GET | Per-account rate limit status |
---
## 5. Key Design Patterns
### 5.1 Hub-and-Spoke Translation
All formats translate through **OpenAI format as the hub**. Adding a new provider only requires writing **one pair** of translators (to/from OpenAI), not N pairs.
### 5.2 Executor Strategy Pattern
Each provider has a dedicated executor class inheriting from `BaseExecutor`. The factory in `executors/index.ts` selects the right one at runtime.
### 5.3 Self-Registering Plugin System
Translator modules register themselves on import via `register()`. Adding a new translator is just creating a file and importing it.
### 5.4 Account Fallback with Exponential Backoff
When a provider returns 429/401/500, the system can switch to the next account, applying exponential cooldowns (1s → 2s → 4s → max 2min).
### 5.5 Combo Model Chains
A "combo" groups multiple `provider/model` strings. If the first fails, fallback to the next automatically.
### 5.6 Stateful Streaming Translation
Response translation maintains state across SSE chunks (thinking block tracking, tool call accumulation, content block indexing) via the `initState()` mechanism.
### 5.7 Usage Safety Buffer
A 2000-token buffer is added to reported usage to prevent clients from hitting context window limits due to overhead from system prompts and format translation.
