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Perplexity

Perplexity (https://api.perplexity.ai) hosts the Sonar family of web-aware reasoning models behind an OpenAI-style chat-completions interface. The extension ships a dedicated factory for it because Perplexity diverges from the standard OpenAI shape in two material ways:

  • The chat-completions endpoint is POST /chat/completions — without the /v1/ prefix used by NVIDIA NIM, OpenAI, and most compatible providers.

  • The Sonar API does not accept response_format: json_object, so JSON mode is disabled at the protocol level. Prompts that require structured output still work through prompt-level instruction.

Do not point the Generic (OpenAI-compatible) backend at https://api.perplexity.ai — Generic targets /v1/chat/completions and will return 404 Not Found. Use this dedicated Perplexity backend instead.

Requirements

  • A Perplexity API account and an API key (starts with pplx-…).

  • Network access to api.perplexity.ai.

Setup

  1. Sign in at perplexity.ai/settings/api and generate an API key.

  2. Pick a Sonar model (for example sonar-pro).

  3. Configure the backend in the AI Backend settings tab.

Configuration

Setting
Default
Description

Preferred Backend

perplexity

Select backend.

Base URL

https://api.perplexity.ai

Override only if you proxy Perplexity through your own gateway.

Model

(empty)

Sonar model identifier, e.g. sonar-pro.

API Key

(empty)

Your pplx-… token. Sent as Authorization: Bearer ….

Extra Headers

(empty)

Optional extra Header: value lines if a gateway requires them.

Timeout

120

Request timeout in seconds (accepted range: 30-3600).

A working baseline:

Supported Models

The extension does not maintain a model allowlist: it sends the free-form Model value unchanged. Use a currently supported Sonar model ID from Perplexity's API catalog; sonar-pro is only an example, not an extension default.

Capabilities

Capability
Value

Streaming

Not functionally decoded. The request currently sets stream: true, but the production parser expects one complete JSON document and emits one UI chunk.

JSON mode

No — response_format=json_object is not supported by Sonar. Use prompt-level instructions for structured output.

System role

Yes — agent profiles are delivered as the system message.

Auto-start

Not applicable (cloud backend).

The lack of protocol-level JSON mode means structured scanner workflows—notably batch passive analysis and adaptive payload generation—fall back to a text-mode parser. The parser scans the model output for fenced JSON blocks first, then a top-level { / [, then individual field regexes as a last resort. It recovers from prose preambles and markdown wrappers but is more brittle than a response_format=json_object constraint: malformed JSON or schemas with unexpected fields are silently dropped. Keep confidence thresholds conservative when using Perplexity for scanner workflows.

There is also a response-framing limitation: the normal request sets stream: true, while the Montoya transport buffers the body and the shared backend parser calls readTree on that body as one JSON document. Actual SSE data: frames are not decoded on this path. A provider/gateway that returns a non-streaming JSON envelope can work; strict SSE output can fail parsing.

Privacy Considerations

Perplexity is a cloud backend. The same guidance as other cloud providers applies:

  • Keep privacy mode at STRICT or BALANCED (the default) for real targets.

  • Review the context preview dialog before sending auto-captured traffic.

  • Review the Privacy Modes page for redaction patterns.

Health Check Traffic

While Perplexity is the selected backend, the top-bar status check runs about every 5 seconds and sends a fixed, non-streaming "Hey" completion with max_tokens: 16. The current health-check provider uses the shared direct HTTP client rather than Burp's Montoya transport. It contains no captured Burp context, but it bypasses Burp's upstream proxy/Proxy history and may count toward quota or billing. Normal chat and scanner requests still use Montoya.

Output Token Limits

The extension sets max_tokens automatically per request type:

Request Type

max_tokens

Chat

4096

Scanner (single request)

2048

Scanner (batch analysis)

4096

Payload generation

1024

Troubleshooting

  • 401 Unauthorized: verify the API key is a valid pplx-… token and not expired.

  • 404 Not Found: confirm the Base URL is https://api.perplexity.ai (no /v1 suffix). The factory targets /chat/completions directly.

  • 400 Bad Request mentioning response_format: a request tried to force JSON mode against Sonar. Disable the JSON-mode toggle for that request or switch to a backend that supports it.

  • model_not_found / invalid_model: confirm the model ID matches Perplexity's catalog exactly.

  • Slow first token: Sonar models are shared infrastructure; brief cold starts are expected.

  • Extra headers: add them only if your organization routes requests through a gateway.

Retry Behavior

Classified transient transport exceptions trigger up to 6 total attempts with five possible delays (500 / 1000 / 1500 / 2000 / 3000 ms). HTTP error responses are not retried inside the same call, although 429/5xx responses count toward the connection's circuit breaker. Each actual retry is recorded in the AI Request Logger as a RETRY activity. After 5 recorded transient failures, that connection allows one half-open model request after 30 seconds.

Related Pages

PreviousNVIDIA NIM
NextAnthropic (API)

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