PR #1107: Update Anthropic model defaults and skip sampling params on Claude 4.7+

PR #1107 resolves a breakage between laravel/ai's Anthropic gateway and Anthropic's newest Claude releases, and refreshes the package's default model choices in the same pass. Claude 4.7 and later models reject requests that carry a non-default temperature or top_p with an HTTP 400, which meant agents using #[Temperature] or #[TopP] against those models started failing outright. The gateway now sends sampling parameters only to models that accept them, and the cheapest and smartest default text models move to claude-haiku-5-5 and claude-opus-5-5 respectively. If you're upgrading from v1.1.0, the change is mostly transparent, but there are a few behavioral details worth knowing.

Category: 3 (Fix)

New default models: Haiku 5.5 and Opus 5.5

The cheapestTextModel() and smartestTextModel() fallbacks on AnthropicProvider have been updated:

// Before (v1.1.0)
'claude-haiku-4-5-20251001'  // cheapest
'claude-fable-5-1'           // smartest

// After
'claude-haiku-5-5'           // cheapest
'claude-opus-5-5'            // smartest

These defaults only apply when you don't name a model explicitly and haven't overridden the values in configuration. If you pin models in config/ai.php, your values still win:

'providers' => [
    'anthropic' => [
        'models' => [
            'text' => [
                'cheapest' => 'claude-haiku-4-5-20251001',
            ],
        ],
    ],
],

The practical effect is that #[UseCheapestModel]-style resolution now lands on Haiku 5.5 instead of a dated Haiku 4.5 snapshot, and smartest resolution lands on Opus 5.5 instead of Fable 5.1.

Why Claude 4.7+ requests failed

Anthropic tightened its API for Claude 4.7 and later: sending a non-default temperature or top_p returns a 400. Because laravel/ai always forwarded those options when the attributes were present, a perfectly valid agent could start throwing as soon as it was pointed at a new model:

#[UseCheapestModel]
#[Temperature(0.7)]
class SummarizerAgent implements Agent
{
    use Promptable;

    public function instructions(): string
    {
        return 'Summarize the given text in one sentence.';
    }
}

On v1.1.0, once the cheapest default resolved to a 4.7+ generation model, this agent's requests were rejected before generation even started. The failure was confusing because nothing in your code changed — only the default model behind it.

How request building works now

The Anthropic gateway gained a supportsSamplingParameters() check built around this pattern:

/^claude-(3-|(opus|sonnet|haiku)-4(-[0-6])?(-\d{8})?$)/

In practice:

• claude-3-* and claude-opus|sonnet|haiku-4 up through 4.6 (including dated snapshots like claude-sonnet-4-5-20250929) accept sampling parameters, so temperature and top_p are sent as before.
• Claude 4.7+ and the 5.x family — claude-haiku-5-5, claude-opus-5-5, claude-fable-5-1, and so on — get both keys omitted entirely. #[Temperature] and #[TopP] are silently ignored on those models rather than causing a 400.

There's a second, subtler rule: on supported models, top_p is now only sent when temperature is not set. If an agent defines both #[Temperature(0.7)] and #[TopP(0.8)], temperature wins and top_p is dropped. Previously both keys were forwarded together.

Upgrade impact from v1.1.0

For most applications this is a drop-in patch, but check three things:

1. Default drift. If you relied on the cheapest or smartest defaults, your traffic moves to Haiku 5.5 / Opus 5.5. That changes cost, latency, and output characteristics. Pin models or override the config values if you need the old behavior.
2. Ignored attributes. On Claude 4.7+ models, #[Temperature] and #[TopP] no longer error — they're simply not sent. If you depended on sampling for output variance, that variance is gone on those models.
3. top_p precedence. Agents that set both attributes on a 3.x or 4.0–4.6 model will now only send temperature. Re-run any evaluations that tuned top_p alongside a temperature.

No configuration migration is required and no public API changed — the fix is entirely in how Anthropic request bodies are assembled.

Takeaways

• Cheapest default is now claude-haiku-5-5; smartest default is now claude-opus-5-5.
• temperature and top_p are only sent to claude-3-* and Claude 4.0–4.6 models.
• On Claude 4.7+, sampling attributes are ignored instead of triggering HTTP 400 errors.
• When both attributes are set on a supported model, temperature wins and top_p is omitted.
• Pin explicit models or override the config defaults to keep behavior stable across upgrades.

Sources

• Pull request #1107
• Release v1.2.0