> ## Documentation Index
> Fetch the complete documentation index at: https://arizeai-433a7140.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Release Notes

# Prompt Version Diff View

March 24, 2026

**Available in arize-phoenix 13.18.0+**

The Prompts UI now includes a diff view for comparing two versions of a prompt side by side. Open any prompt version and select a baseline to see exactly what changed between versions — message roles, content additions, tool call arguments, and tool results are all diffed line by line.

* **Side-by-side diff** highlights added and removed lines across the full chat template
* **Works with all template types**: chat templates (with multi-part messages including tool calls and tool results) and string templates
* **Supports all content parts**: text, tool calls, and tool results are each rendered and diffed

# Evals Now Accept Structured Data as Inputs

March 24, 2026

**Available in arize-phoenix-evals 2.12.0+**

Evaluators now accept dicts, lists, and other structured data as template variable values. Previously, non-string inputs were coerced via Python `str()`, which produced invalid JSON for nested objects. Now, structured values are JSON-serialized automatically before being inserted into the prompt.

```python theme={null}
from phoenix.evals.metrics.faithfulness import FaithfulnessEvaluator
from phoenix.evals import LLM

llm = LLM(provider="openai", model="gpt-4o-mini")
evaluator = FaithfulnessEvaluator(llm=llm)

# Structured data is now accepted directly — no manual serialization needed
scores = evaluator.evaluate({
    "input": {"query": "What is the capital of France?", "language": "en"},
    "output": "Paris is the capital of France.",
    "context": ["Paris is the capital of France.", "France is in Western Europe."],
})
```

* **Dicts and lists** are serialized to valid JSON strings (e.g., `{"key": "value"}`) before prompt rendering
* **Plain strings** pass through unchanged — existing evaluator code continues to work without modification
* **Section variables** (`{{#var}}`, `{{^var}}`) in Mustache templates still receive the raw value so pystache can iterate lists and evaluate conditionals

# Built-in Classification Evaluators Accept LLM Invocation Parameters

March 24, 2026

**Available in arize-phoenix-evals 2.12.0+**

Built-in classification evaluators (`FaithfulnessEvaluator`, `CorrectnessEvaluator`, `HallucinationEvaluator`, and others) now accept arbitrary `**kwargs` that are forwarded to the LLM on every evaluation call. Use this to control generation behavior without needing to subclass.

```python theme={null}
from phoenix.evals.metrics.faithfulness import FaithfulnessEvaluator
from phoenix.evals import LLM

llm = LLM(provider="openai", model="gpt-4o-mini")

# Pass LLM invocation parameters directly (e.g., temperature, max_tokens)
evaluator = FaithfulnessEvaluator(llm=llm, temperature=0.0, max_tokens=256)

eval_input = {
    "input": "What is the capital of France?",
    "output": "Paris is the capital of France.",
    "context": "Paris is the capital and largest city of France.",
}
scores = evaluator.evaluate(eval_input)
```

* **Any keyword argument** beyond `llm` is stored as an invocation parameter and forwarded to the underlying LLM client on each call
* Applies to all built-in evaluators: `FaithfulnessEvaluator`, `CorrectnessEvaluator`, `DocumentRelevanceEvaluator`, `RefusalEvaluator`, `ConcisenessEvaluator`, `ToolSelectionEvaluator`, `ToolInvocationEvaluator`, and `ToolResponseHandlingEvaluator`