Compare

Use POST /v1/chat/compare when you want to run the same conversation across multiple models and inspect the results side by side.

How it works

1. Fan-out: All requested models are called concurrently. The total wall-clock time is roughly that of the slowest model, not the sum of all models.
2. Error isolation: If a single model fails or times out (hard timeout of 120s), the others continue unaffected. Partial results are returned with a partial: true flag.
3. Synthesis (default): After all models respond, a separate comparison LLM analyzes the responses and produces a structured evaluation covering accuracy, completeness, clarity, and a recommendation.
4. Skip synthesis (optional): By setting skip_comparison: true, you can skip the synthesis step and receive only the raw model outputs. This is useful for parallel streaming UIs that perform their own comparison.
5. Rate limiting and Billing: The entire comparison counts as a single request against your rate limits (RPM/RPD). However, billing tracks each model call plus the comparison call as separate usage events (N+1 events).
6. Streaming: Two streaming modes are available by setting stream: true. With synthesis enabled, fan-out is non-streaming, but the final comparison text is streamed token-by-token. If skip_comparison: true is set, each fan-out model streams its tokens in real-time concurrently, tagged by model name.

Basic request

$
curl https://api.meshapi.ai/v1/chat/compare \
>
  -H "Authorization: Bearer <YOUR_RSK_KEY>" \
>
  -H "Content-Type: application/json" \
>
  -d '{
>
    "models": [
>
      "openai/gpt-4o-mini",
>
      "anthropic/claude-3.5-haiku"
>
    ],
>
    "messages": [
>
      { "role": "user", "content": "Explain vector search in two sentences." }
>
    ]
>
  }'

Request fields

Response shape

The response includes:

• the compared model list
• one result per model
• optional synthesized comparison text
• latency and request metadata

Streaming (SSE)

Set "stream": true to receive a text/event-stream with typed events. There are two streaming modes:

Mode 1: With comparison (skip_comparison: false, default)

Fan-out models are non-streaming (full response collected per model), then the comparison LLM streams token-by-token.

Mode 2: Skip comparison (skip_comparison: true)

Each fan-out model streams tokens in real time concurrently, tagged by model name. No comparison LLM is called.

SDK coverage

• Node: client.compare.create(...)
• Python: client.compare.create(...)
• Go: client.Compare.Create(...)
• Java: client.compare().create(...)

Streaming compare is also available in the SDKs through their compare stream methods when you want incremental events instead of a single final JSON response.

When to use compare

• Evaluate multiple candidate models for a task
• Compare cost/quality trade-offs before choosing a default
• Build internal prompt evaluations with a stable request shape