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Where It Runs

Agentforce Vibes 2.0 ships with Claude Sonnet 4.5 as the default LLM for developer assistance. The same model is available as a first-class option inside Prompt Builder, Atlas Reasoning, and the Trust Layer model router for Agentforce agents — selectable per Topic and per Action. Enterprises running BYO LLM on the Anthropic API integrate Sonnet 4.5 directly into CRM agents, custom workflows, and customer service deflection without going through Agentforce, typically via Named Credential and an External Service.

Deployment surfaces in 2026:
  - Vibes 2.0 (developer IDE assist)
  - Atlas Reasoning planner (when configured)
  - Prompt Builder template execution
  - Custom Apex via Anthropic API + Named Credential
  - Slack workflow automations via the Anthropic Slack app
  - Heroku-hosted services calling Anthropic API

Why Sonnet 4.5

Strong multi-step reasoning. Excellent tool-use reliability — the model picks the right tool, supplies well-formed arguments, and recovers gracefully from tool errors more often than its predecessors and most peers. Anthropic positions it as capable of building software and accomplishing business tasks autonomously over hours-long horizons. For agent orchestration, these traits matter more than raw token throughput. Latency lands competitive with GPT-5 mini-tier and slower than Haiku-tier models — appropriate for Topic routing and Action planning, less so for high-volume single-turn classification.

Enterprise Tier Fit

Anthropic’s Team and Enterprise tiers cover licensed Claude usage with a Business Associate Agreement, SOC 2 Type II evidence, and zero data retention by default. Production apps use the API with the same underlying model — no functional difference between Claude.ai-served and API-served Sonnet 4.5. Many enterprises maintain both: interactive Team subscriptions for analysts and engineers, plus API integration for application embedding. Pricing as of April 2026: $3 per million input tokens, $15 per million output tokens, with 90% discount on cached input via prompt caching.

Practical Configuration

For Agentforce, route Topic classification to a faster cheaper model (Haiku or xGen) and reserve Sonnet 4.5 for Action planning and complex reasoning steps. This two-tier pattern cuts cost 50–70% with negligible quality loss on routing accuracy. Always pair with prompt caching for system prompts and stable retrieval contexts.

HttpRequest req = new HttpRequest();
req.setEndpoint('callout:Anthropic_API/v1/messages');
req.setMethod('POST');
req.setHeader('content-type', 'application/json');
req.setBody(JSON.serialize(new Map<String,Object>{
    'model' => 'claude-sonnet-4-5-20260219',
    'max_tokens' => 1024,
    'system' => systemPromptCached,    // mark for cache
    'messages' => messages
}));

Comparison Notes

Evaluate Sonnet 4.5 for your agent reasoning layer with side-by-side runs against GPT-5, Gemini 2.5 Pro, and Salesforce xGen on your specific workloads. Sonnet 4.5 typically wins on multi-step tool-use traces and on long-context refactoring; GPT-5 wins on raw code generation throughput; xGen wins on Apex and Flow XML edge cases. Defaults are starting points; tune per use case using your eval set, not vendor benchmarks.

When to Skip

Skip Sonnet 4.5 for high-volume single-turn classification (use Haiku-tier), for sub-second latency requirements (use a smaller fast model), or for workloads requiring on-prem deployment (Anthropic is API-only).

What to Do This Week

Pick one Agentforce Topic, swap the underlying model from default to Claude Sonnet 4.5, and run your eval set. Compare cost per call and accuracy. Decide based on data, not defaults.

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