Link a W&B run to trace function calls

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Summary: Associate Weave traces with W&B runs for experiment tracking

Original Documentation

Documentation Index#

Fetch the complete documentation index at: https://docs.wandb.ai/llms.txt Use this file to discover all available pages before exploring further.

Associate Weave traces with W&B runs for experiment tracking

View a W&B run in the Traces table#

With W&B Weave, you can trace function calls in your code and link them directly to the W&B runs in which they were executed. When you trace a function with @weave.op() and call it inside a wandb.init() context, Weave automatically associates the trace with the W&B run. Links to any associated runs are shown in the Traces table.

The following Python code shows how traced Ops are linked to W&B runs when executed inside a wandb.init() context. These traces appear in the Weave UI and are associated with the corresponding run.

To view a W&B run as a Weave trace:

  1. In the terminal, install dependencies.
    pip install wandb weave
    ```

2. Log in to W\&B.

```bash
    wandb login
    ```

3. In the following script, replace `your-team-name/your-project-name` with your actual W\&B entity/project:

```python
    import wandb
    import weave

    def example_wandb(projname):
        # Split projname into entity and project
        entity, project = projname.split("/", 1)

        # Initialize Weave context for tracing
        weave.init(projname)

        # Define a traceable Op
        @weave.op()
        def say(message: str) -> str:
            return f"I said: {message}"

        # First W&B run
        with wandb.init(
            entity=entity,
            project=project,
            notes="Experiment 1",
            tags=["baseline", "paper1"],
        ) as run:
            say("Hello, world!")
            say("How are you!")
            run.log({"messages": 2})

        # Second W&B run
        with wandb.init(
            entity=entity,
            project=project,
            notes="Experiment 2",
            tags=["baseline", "paper1"],
        ) as run:
            say("Hello, world from experiment 2!")
            say("How are you!")
            run.log({"messages": 2})

    if __name__ == "__main__":
        # Replace this with your actual W&B username/project
        example_wandb("your-team-name/your-project-name")
    ```

4. Run the script.

```bash
    python weave_trace_with_wandb.py
    ```

5. Navigate to [https://weave.wandb.ai](https://weave.wandb.ai) and select your project.
6. In the **Weave project sidebar**, click **Traces**.  Links to any associated runs are displayed in the Traces table.
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  <span class="tab-start" data-tab-title="TypeScript"></span>
```plaintext
    This feature is not available for the TypeScript SDK yet.
    ```
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Link last verified June 7, 2026. View original ↗
Source: Weights & Biases Docs
Link last verified: 2026-04-05