title	AI API
description	AI provider endpoints for model selection, chat completion, and cost estimation

AI API

Endpoints for interacting with AI models through a unified provider layer. These endpoints are served by the backend API service, not the web application. They are available at the backend base URL, which may differ from the web API base URL depending on your deployment.

These endpoints are internal backend endpoints and are not exposed through the web application's /api routes. All /api/ai/* endpoints require bearer token (API key) authentication — the authenticate middleware is applied to the entire /api/ai router mount. The chat and cost estimation endpoints additionally require a valid subscription plan via header-based plan enforcement. All POST requests must include the Content-Type: application/json header.

All /api/ai/* endpoints share a rate limit of 30 requests per minute per IP, not just the chat endpoint.

Health check

GET /api/ai/health

Returns the availability status of configured AI providers. This endpoint is public and does not require authentication.

Response

{
  "status": "healthy",
  "providers": {
    "openrouter": true
  },
  "timestamp": "2026-03-19T00:00:00Z"
}

The status field is healthy when the OpenRouter provider is reachable and degraded when it is not. Only the OpenRouter provider is checked.

Error response

When the provider check fails, the response uses status: "error" and includes the error message:

{
  "status": "error",
  "error": "Provider connection failed"
}

Code	Description
503	AI service unavailable

List models

GET /api/ai/models

Returns all available AI models across providers. This endpoint is public and does not require authentication.

Response

{
  "models": [
    {
      "id": "anthropic/claude-sonnet-4-20250514",
      "name": "Claude Sonnet",
      "provider": "openrouter",
      "description": "Fast, intelligent model for everyday tasks",
      "tags": ["chat", "code"],
      "inputCost": 0.003,
      "outputCost": 0.015,
      "contextWindow": 200000,
      "available": true
    }
  ],
  "count": 1,
  "openrouter": 1,
  "timestamp": "2026-03-19T00:00:00Z"
}

Errors

Code	Description
500	Failed to fetch models

List models by provider

GET /api/ai/models/:provider

This endpoint is public and does not require authentication.

Path parameters

Parameter	Type	Description
`provider`	string	Provider name (for example, `openrouter`)

Response

{
  "provider": "openrouter",
  "models": [],
  "count": 0,
  "timestamp": "2026-03-19T00:00:00Z"
}

Select model

POST /api/ai/models/select

Requires bearer token authentication and a valid subscription plan.

Automatically selects the best model for a given task type.

Request body

Field	Type	Required	Description
`taskType`	string	No	Type of task (default: `general`)

Response

{
  "model": {
    "id": "anthropic/claude-sonnet-4-20250514",
    "provider": "openrouter"
  },
  "taskType": "general",
  "timestamp": "2026-03-19T00:00:00Z"
}

Errors

Code	Description
401	Unauthorized — missing or invalid bearer token
402	Valid subscription required
404	No models available

Chat completion

POST /api/ai/chat

Send a chat completion request through the unified AI provider layer. The model is auto-selected if not specified.

This endpoint requires a valid subscription plan. Requests without a recognized plan or active Stripe subscription receive a 402 response. The requested model must also be available on your plan — see plan-based model access below.

The chat endpoint uses header-based authentication. Access control is enforced through the x-user-plan and x-stripe-subscription-id headers. When a database is available, the plan middleware cross-references the x-stripe-subscription-id header against the user's record in the database to prevent subscription forgery. The plan stored in the database is used instead of the header value. If the database is unavailable, the middleware falls back to header-based validation with a format check on the subscription ID. Admin emails (configured via ADMIN_EMAILS) bypass both plan and subscription requirements.

Request headers

The following headers are required for plan enforcement:

Header	Type	Required	Description
`x-user-plan`	string	Yes	Subscription plan name (`label`, `solo`, `collective`, or `network`)
`x-user-email`	string	No	User email. Admin emails bypass plan restrictions.
`x-stripe-subscription-id`	string	Yes	Active Stripe subscription ID

Request body

Field	Type	Required	Description
`messages`	array	Yes	Array of message objects with `role` (`user`, `assistant`, or `system`) and `content`
`model`	string	No	Model ID. Auto-selected based on `taskType` if omitted. Must be allowed by your plan.
`taskType`	string	No	Used for auto-selection when `model` is omitted
`temperature`	number	No	Sampling temperature
`top_p`	number	No	Nucleus sampling parameter
`max_tokens`	number	No	Maximum tokens in the response
`algorithmMode`	boolean	No	When `true`, injects the PAI Algorithm system prompt into the conversation. This enables a 7-phase structured problem-solving format (Observe, Think, Plan, Build, Execute, Verify, Learn) for the agent's responses. The system prompt is prepended to the messages array only if no existing system message already contains the Algorithm phases. Defaults to `false`.

Example request

{
  "messages": [
    { "role": "system", "content": "You are a helpful assistant." },
    { "role": "user", "content": "Hello!" }
  ],
  "temperature": 0.7,
  "max_tokens": 1024
}

Example request with Algorithm mode

When algorithmMode is enabled, the agent responds using a structured 7-phase format for non-trivial tasks:

{
  "messages": [
    { "role": "user", "content": "Audit the authentication flow for security issues" }
  ],
  "algorithmMode": true
}

Response

Returns a structured response with the following shape:

{
  "id": "chatcmpl-abc123",
  "model": "anthropic/claude-sonnet-4-20250514",
  "provider": "openrouter",
  "message": {
    "role": "assistant",
    "content": "Hello! How can I help you today?"
  },
  "usage": {
    "prompt_tokens": 25,
    "completion_tokens": 10,
    "total_tokens": 35
  },
  "timestamp": "2026-03-19T00:00:00Z"
}

Errors

Code	Description
400	Messages array is required and must be non-empty
402	Valid subscription required. Returned when the plan header is missing or unrecognized (`PLAN_REQUIRED`), when there is no active Stripe subscription (`SUBSCRIPTION_REQUIRED`), or when the subscription ID in the request header does not match the subscription on file for the authenticated user (`SUBSCRIPTION_MISMATCH`).
403	Model not available on your plan (`MODEL_RESTRICTED`). The response includes an `allowedModels` array listing the models your plan supports.
404	No models available
429	Monthly token quota exceeded for this plan (`QUOTA_EXCEEDED`). Resets at the start of the next calendar month.
500	AI provider error

402 error examples

{
  "success": false,
  "error": "Valid subscription required. Choose a plan at /pricing",
  "code": "PLAN_REQUIRED"
}

When the subscription ID sent in the x-stripe-subscription-id header does not match the subscription stored in the database for the authenticated user:

{
  "success": false,
  "error": "Subscription mismatch. Please sign out and back in.",
  "code": "SUBSCRIPTION_MISMATCH"
}

403 error example

{
  "error": "Model openai/gpt-4-turbo not available on your plan. Upgrade for more models.",
  "code": "MODEL_RESTRICTED",
  "allowedModels": ["openai/gpt-4o-mini", "google/gemini-2.0-flash"]
}

Token quotas

Token quotas are enforced per user on a calendar-month basis. Each chat completion request checks the user's cumulative token usage for the current month against their plan limit before calling the AI provider. Requests that would exceed the quota are rejected with a 429 status and a QUOTA_EXCEEDED error code. The quota resets automatically at the start of each calendar month.

Usage is tracked in the model_metrics table. Each successful and failed chat request logs the model, token counts, latency, and outcome for auditing and quota enforcement.

Plan	Monthly token limit
`solo`	2,000,000
`collective`	6,000,000
`label`	20,000,000
`network`	Unlimited

429 error example

{
  "error": "Monthly token quota exceeded for plan \"solo\". Used 2,000,000 of 2,000,000 tokens. Quota resets at the start of next month.",
  "code": "QUOTA_EXCEEDED"
}

If the database is temporarily unreachable, quota enforcement fails open — the request proceeds without a usage check. A warning is logged server-side.

Plan-based model access

Each subscription plan grants access to a specific set of AI models. The chat endpoint enforces these limits automatically via the plan middleware.

Plan	Price	Models	Agent limit	Skill limit	A2A messages/day
`solo`	£29/mo	`openai/gpt-4o-mini`, `google/gemini-2.0-flash`, `xiaomi/mimo-v2-pro`	1	3	100
`collective`	£69/mo	`openai/gpt-4o-mini`, `openai/gpt-4o`, `google/gemini-2.0-flash`, `anthropic/claude-3.5-sonnet`, `xiaomi/mimo-v2-pro`	3	10	500
`label`	£149/mo	`openai/gpt-4o-mini`, `openai/gpt-4o`, `openai/gpt-4-turbo`, `google/gemini-2.0-flash`, `anthropic/claude-3.5-sonnet`, `anthropic/claude-3-opus`, `xiaomi/mimo-v2-pro`	10	25	2,000
`network`	£499/mo	All models	100	100	10,000

Admin users are automatically granted network-level access regardless of their subscription plan.

The plan middleware (x-user-plan header) enforces model access, skill limits, and A2A message quotas. The provisioning endpoint enforces separate agent creation limits: solo 1, collective 3, label 10, network unlimited. The agent count is per-user across all plans — all active agents count toward the current plan's limit. The provisioning limits determine how many agents you can create, while the middleware limits in the table above apply to per-request AI model access and skill usage.

Model fallbacks

The backend AI service uses a tier-based fallback system. Each tier has a primary model and one or more fallback models. When the primary model is unavailable, times out, or returns an error, the system automatically retries the request using the next fallback model in order. Each model attempt is bounded by a configurable timeout (default 30 seconds) to prevent hangs.

Tier	Primary model	Fallback models
`reasoning`	`deepseek/deepseek-r1`	`meta-llama/llama-3.3-70b-instruct`, `moonshotai/kimi-k2.5`
`coding`	`qwen/qwen-2.5-coder-32b-instruct`	`deepseek/deepseek-r1`, `google/gemini-2.0-flash-001`
`fast`	`meta-llama/llama-3.3-70b-instruct`	`mistralai/mistral-7b-instruct`, `google/gemini-2.0-flash-001`
`creative`	`moonshotai/kimi-k2.5`	`deepseek/deepseek-r1`, `meta-llama/llama-3.3-70b-instruct`

Fallback routing is handled transparently. The response always indicates which model ultimately served the request via the model field. All tier-based requests are routed through OpenRouter.

Task-based model selection

In addition to provider-level fallbacks, the backend AI service uses tag-based model selection that picks the best available model based on the type of work being performed. When you specify a taskType, the system searches the available OpenRouter models for matching capability tags and selects the first match.

Task type	Matching tags
`coding`	`coding`, `logic`
`analysis`	`analysis`
`creative`	`creative`
`long`	`long-context`
`general`	`general`, `balanced`

When no model matches the requested task tags, the first available model from the OpenRouter catalog is used as a fallback. All task-based requests are routed through OpenRouter.

Algorithm mode

The chat endpoint supports an optional structured problem-solving mode called PAI Algorithm mode. When enabled via the algorithmMode parameter, a system prompt is injected that instructs the model to process non-trivial tasks using a 7-phase format:

Phase	Name	Purpose
1	Observe	Reverse-engineer the request: what was asked, what was implied, and what is not wanted. Produce 3–5 Ideal State Criteria (ISC).
2	Think	Select capabilities and a composition pattern (Pipeline, TDD Loop, Fan-out, or Gate).
3	Plan	Define concrete numbered steps with clear handoffs.
4	Build	Create artifacts such as files, configs, or code.
5	Execute	Run the work using the selected capabilities.
6	Verify	Test each ISC criterion with evidence, marking each as pass or fail.
7	Learn	Summarize what worked, what didn't, and what to improve.

The Algorithm system prompt is prepended to the messages array as a system message. If the messages already contain a system message with Algorithm phase markers, the prompt is not duplicated. For simple greetings or acknowledgments, the model skips the 7-phase format and responds naturally.

Algorithm mode is opt-in and does not affect billing or model selection. It only modifies the system prompt sent to the model. Based on Daniel Miessler's TheAlgorithm v0.2.24.

Estimate cost

POST /api/ai/estimate-cost

Requires bearer token authentication and a valid subscription plan.

Estimate the cost of a request based on token counts and model pricing.

Request body

Field	Type	Required	Description
`model`	string	Yes	Model ID
`inputTokens`	number	Yes	Number of input tokens
`outputTokens`	number	Yes	Number of output tokens

Response

{
  "model": "anthropic/claude-sonnet-4-20250514",
  "inputTokens": 1000,
  "outputTokens": 500,
  "estimatedCost": 0.0045,
  "currency": "USD",
  "timestamp": "2026-03-19T00:00:00Z"
}

Errors

Code	Description
400	Model, inputTokens, and outputTokens are all required
401	Unauthorized — missing or invalid bearer token
402	Valid subscription required

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AI API

Health check

Response

Error response

List models

Response

Errors

List models by provider

Path parameters

Response

Select model

Request body

Response

Errors

Chat completion

Request headers

Request body

Example request

Example request with Algorithm mode

Response

Errors

402 error examples

403 error example

Token quotas

429 error example

Plan-based model access

Model fallbacks

Task-based model selection

Algorithm mode

Estimate cost

Request body

Response

Errors

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AI API

Health check

Response

Error response

List models

Response

Errors

List models by provider

Path parameters

Response

Select model

Request body

Response

Errors

Chat completion

Request headers

Request body

Example request

Example request with Algorithm mode

Response

Errors

402 error examples

403 error example

Token quotas

429 error example

Plan-based model access

Model fallbacks

Task-based model selection

Algorithm mode

Estimate cost

Request body

Response

Errors