XaiModel with tests and stock analysis agent

[brightsparc]

This PR includes support for GrokModel which uses the xai-sdk-python library, which supports chat completion, tool calling, and built-in server side tool calls.

I have included a series of tests, as well as an example for a stock analysis agent that uses search and code execution, and returns results in the form of a local tool call.

python examples/pydantic_ai_examples/stock_analysis_agent.py

🔍 Starting stock analysis...

Query: What was the hottest performing stock on NASDAQ yesterday?

18:32:37.095 stock_analysis_agent run
18:32:37.099   chat grok-4-fast
18:32:37.119     chat.stream grok-4-fast
🔧 Server-side tool: web_search
🔧 Server-side tool: browse_page

✅ Analysis complete!

📊 Top Stock: ATGL
💰 Current Price: $20.00

📈 Buy Analysis:
ATGL surged 139.84% on November 18, 2025, making it the hottest performer on NASDAQ, but pulled back 7.45% today to $20.00. The extreme volatility suggests high risk; without clear fundamental drivers, it's not recommended as a buy for most investors. Suitable only for speculative short-term trades.

📊 Usage Statistics:
   Requests: 1
   Input Tokens: 19150
   Output Tokens: 526
   Total Tokens: 19676
   Server-Side Tools: 7

Below is what the output looks like in logfire. It includes custom spans emmited from the xai-sdk.

Cost is coming back as Unknown so it would be good to understand how we can populate this.

[DouweM]

@brightsparc Thanks Julian! Let me know when this is ready for review or if you have any questions.

[brightsparc]

Due to using otel in our own SDK, I did notice an error when running the pydantic ai code in async.io loop:

Failed to detach context
Traceback (most recent call last):
  File "/Users/julian/workspace/poc/pydantic-ai/.venv/lib/python3.12/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
  File "/Users/julian/workspace/poc/pydantic-ai/.venv/lib/python3.12/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x1055d33d0> at 0x109ca6e00> was created in a different Context

We could disable our tracing with XAI_SDK_DISABLE_TRACING=1, but would be good to understand why this happens.

[DouweM]

Cost is coming back as Unknown so it would be good to understand how we can populate this.

@brightsparc Looks like grok-4-fast is not on https://github.com/pydantic/genai-prices/blob/main/prices/providers/x_ai.yml yet. Contribution welcome! (See contrib docs)

---

Failing tests:

│  tests/test_examples.py             │  test_docs_examples[docs/models/grok.md:34]  │  113            │  256         │  ValueError      │

I believe we just need to add the xAI env var to the list here:

pydantic-ai/tests/test_examples.py

Lines 179 to 182 in c096d99

	env.set('MOONSHOTAI_API_KEY', 'testing')
	env.set('DEEPSEEK_API_KEY', 'testing')
	env.set('OVHCLOUD_API_KEY', 'testing')
	env.set('PYDANTIC_AI_GATEWAY_API_KEY', 'testing')

│  tests/test_examples.py             │  test_docs_examples[docs/models/grok.md:56]  │  113            │              │                  │

This one should be fixed by running uv run pytest --update-examples tests/test_examples.py -k grok.md

│  tests/models/test_instrumented.py  │  test_instrumented_model_stream_break        │  484            │  512         │  AssertionError  │

Looks like we need the new logfire.exception.fingerprint there as well. Not 100% sure why we're suddenly seeing that...

Due to using otel in our own SDK, I did notice an error when running the pydantic ai code in async.io loop:

Do you have example code for me that triggers it?

[brightsparc]

Cost is coming back as Unknown so it would be good to understand how we can populate this.

@brightsparc Looks like grok-4-fast is not on https://github.com/pydantic/genai-prices/blob/main/prices/providers/x_ai.yml yet. Contribution welcome! (See contrib docs)

I will make a separate PR here

Failing tests:

│  tests/test_examples.py             │  test_docs_examples[docs/models/grok.md:34]  │  113            │  256         │  ValueError      │

I believe we just need to add the xAI env var to the list here:

pydantic-ai/tests/test_examples.py

Lines 179 to 182 in c096d99

	env.set('MOONSHOTAI_API_KEY', 'testing')
	env.set('DEEPSEEK_API_KEY', 'testing')
	env.set('OVHCLOUD_API_KEY', 'testing')
	env.set('PYDANTIC_AI_GATEWAY_API_KEY', 'testing')

│  tests/test_examples.py             │  test_docs_examples[docs/models/grok.md:56]  │  113            │              │                  │

Added this:

This one should be fixed by running uv run pytest --update-examples tests/test_examples.py -k grok.md

│  tests/models/test_instrumented.py  │  test_instrumented_model_stream_break        │  484            │  512         │  AssertionError  │

Not sure I follow this

Looks like we need the new logfire.exception.fingerprint there as well. Not 100% sure why we're suddenly seeing that...

Due to using otel in our own SDK, I did notice an error when running the pydantic ai code in async.io loop:

Do you have example code for me that triggers it?

You can run the following command to repo that error:

XAI_API_KEY="a-valid-key" uv run python examples/pydantic_ai_examples/stock_analysis_agent.py