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b2o2i edited this page May 10, 2026 · 4 revisions

AI Providers

Cross supports five AI providers simultaneously. Each brings different strengths, pricing models, and rate limits. This page helps you choose the right provider for each task and shows how to override the default model for any provider.

For first-time setup (getting API keys, running st-admin --setup), see Onboarding.

Multi-model: since cross-st 0.9.0 you can also run more than one model per provider in the same matrix (e.g. anthropic-opus and anthropic-sonnet competing side-by-side). See Multi-Model for the agent file format.

Quick-pick guide

Provider Best for Free tier Cost
Gemini Daily use, long prompts, getting started ✅ Yes Free / pay-as-you-go
xAI (Grok) Current events, X/Twitter context ⚠️ Limited credits Pay-as-you-go
Anthropic (Claude) Long careful reasoning, writing quality ❌ No Pay-per-token
OpenAI (GPT) Broad general knowledge, reliable baseline ❌ No Pay-per-token
Perplexity (Sonar) Live web search with citations ❌ No Subscription or credits

Run all five at once with st-bang or st-cross — that's the point of Cross.
Use the quick-pick above when you want a single provider for a quick job.

Gemini — gemini

Key: GEMINI_API_KEY · Default model: gemini-2.5-flash
Get a key: aistudio.google.com/app/apikey — free, no credit card

The only provider with a genuinely free API tier. Recommended as the default for new users and for exploratory work.

Free tier limits: 15 req/min · 1,500 req/day · 1M tokens/day — comfortably covers normal Cross usage.

Strengths for Cross:

  • 1M token context window — handles very long cross-product payloads without truncation
  • Fast on gemini-2.5-flash; step up to gemini-2.5-pro for more careful reasoning
  • Reliable JSON and structured output; low hallucination rate on factual domains

Notes: Gemini responses occasionally include safety refusals on politically sensitive topics. If a domain prompt triggers one, try rephrasing or use a different provider as primary.

xAI — xai

Key: XAI_API_KEY · Default model: grok-4-1-fast-reasoning
Get a key: console.x.ai

Grok is trained on X/Twitter data in addition to web text, giving it stronger awareness of recent public discourse and named individuals active on social media.

Strengths for Cross:

  • Often more opinionated and willing to make direct claims — which scores well in fact-checking when the claims are verifiable
  • Strong on current-events and technology domains
  • grok-4-1-fast-reasoning is among the fastest models Cross uses; good speed scores on benchmarks

Notes: Free credits for new accounts burn quickly with Cross's multi-call pattern. Set a spending limit in the xAI console.

Anthropic — anthropic

Key: ANTHROPIC_API_KEY · Default model: claude-opus-4-5
Get a key: console.anthropic.com — credit card required

Claude is known for long, structured, carefully hedged writing. Reports tend to be well-organized with clear claim structure, which helps fact-checkers parse them.

Strengths for Cross:

  • Highest-quality prose in synthesize and quality merge modes (st-merge, st-fix)
  • Excellent at following the Cross prompt format precisely — outputs clean segmented reports
  • Lower tendency toward confident false statements than some other models

Notes: Claude tends to qualify claims heavily. This can reduce fact-check scores on domains where peer AIs penalize hedged language as "Partially True." claude-opus-4-5 is the most capable but also the most expensive per token.

OpenAI — openai

Key: OPENAI_API_KEY · Default model: gpt-4o
Get a key: platform.openai.com — credit card required

GPT-4o is a reliable, well-rounded model. It tends to produce consistent, predictable output — useful as a stable baseline in benchmarks.

Strengths for Cross:

  • Stable output format makes it reliable for Cross's fact-check parsing pipeline
  • Strong performance across most Cross-Stones domains
  • gpt-4o has a 128K token context window — large enough for all Cross payloads

Notes: OpenAI's free tier was removed — a small prepaid credit is required. The API can be slower than Gemini or xAI under load; this shows up in speed scores.

Perplexity — perplexity

Key: PERPLEXITY_API_KEY · Default model: sonar-pro
Get a key: perplexity.ai/settings/api — paid plan or API credits

Perplexity's Sonar models do live web search with citations before generating a response. This makes them uniquely suited to current-events topics where training data cut-offs matter.

Strengths for Cross:

  • Grounded responses — citations reduce hallucination on time-sensitive claims
  • Excellent on research and Q&A domains (research_qa benchmark)
  • Naturally produces claim-level structure that works well with st-fact

Notes: Response times are higher than other providers because each call includes a search step. This shows in speed scores. The citation URLs in the output are preserved in the Cross container but not rendered in the Discourse post.

Overriding the default model

Each provider has a compiled-in default model. To switch to a different model for a provider:

# Set a model override (persisted to .ai_models in the repo root)
st-admin --set-ai-model anthropic=claude-sonnet-4-5

# View all active models
st-admin --show

# Override for a single command only
st-gen --agent anthropic --model claude-sonnet-4-5 my_topic.prompt

Model overrides are stored in .ai_models (one provider=model line per entry). This file is git-ignored — safe for developer-specific settings.

Using multiple providers

Every command that takes --agent also accepts all:

st-gen --agent all my_topic.prompt       # generate once per provider (sequential)
st-bang my_topic.prompt               # generate all providers in parallel (faster)
st-fact --agent all my_topic.json        # fact-check with every provider
st-cross my_topic.json                # full N×N pipeline: generate + fact-check

Related: Onboarding · st-admin · st-bang · st-cross · Cross-Stones

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