August 2026 - Arize AX Docs

Create experiments without a dataset

August 5, 2026 New Datasets and Experiments You can now create an experiment scoped to a space instead of a dataset, so runs and results you produced elsewhere can be recorded in Arize AX even when there is no dataset to attach them to. In the Python SDK, pass space in place of dataset to experiments.create(); through the REST API, send space_id instead of dataset_id on POST /v2/experiments and filter dataset-less experiments with the new space_id query parameter on GET /v2/experiments. This extends dataset-less experiment support, previously available in the JavaScript and TypeScript SDK, to Python and the REST API. The code example below creates a standalone experiment in a space:

from arize.experiments import ExperimentTaskFieldNames

# Pass `space` instead of `dataset` to create a standalone experiment
# that is not tied to any dataset.
experiment = client.experiments.create(
    name="my-standalone-experiment",
    space="your-space-name-or-id",
    experiment_runs=[{"output": "the task output"}],
    task_fields=ExperimentTaskFieldNames(output="output"),  # example_id is optional for standalone runs
)

Visit the experiments client documentation to learn more.

Delete spans faster by scoping to a time window

August 5, 2026 Improvement SDKs and REST APIs Deleting spans by ID through DELETE /v2/spans now accepts optional start_time and end_time bounds, so a delete searches only the interval when the spans were ingested instead of the full lookback window. Each bound is independent: omit start_time and it defaults to the start of the lookback window, omit end_time and it defaults to now. The parameters are available across the Python, Go, and TypeScript SDKs. The code example below deletes two spans, scoping the search to a single day:

from datetime import datetime, timezone

# Scope the delete to the day the spans were ingested.
client.spans.delete(
    project="your-project-name-or-id",
    span_ids=["span-id-1", "span-id-2"],
    start_time=datetime(2026, 8, 4, tzinfo=timezone.utc),  # inclusive lower bound
    end_time=datetime(2026, 8, 5, tzinfo=timezone.utc),    # exclusive upper bound
)

Visit the spans client documentation to learn more.

Write new API keys directly to a .env file

August 3, 2026 New CLI Commands The ax api-keys create and ax api-keys create-service-key commands now take an --env-file flag that writes the generated key to ARIZE_API_KEY in a dotenv or .envrc file, so the new credential is written into your local environment and the raw key is never printed to your terminal. The write preserves the file’s existing formatting, and if it fails, the new key is automatically revoked so you are never left with an unusable credential. The code example below creates a key and writes it into a local dotenv file:

# Write the new key as ARIZE_API_KEY into .env.local.
# If the file write fails, the key is automatically revoked.
ax api-keys create --name "Local development" --env-file .env.local

Visit the api-keys CLI documentation to learn more.

Pin evaluators to a specific version, now on every account

July 31, 2026 New Evaluators Evaluator version pinning is now available on every account. Pin an evaluator task to a specific published version and the task keeps running that version when newer versions are published, so a task you have tuned and validated does not change when someone publishes an update. Choose “Latest” when you would rather a task always pick up the newest version. You select the version from the evaluator’s version dropdown wherever you configure the task. Learn more about creating evaluators.

Fixes and improvements

August 3–5, 2026 Evaluators

Improvement Skip a mapping step when building template evals on a project: the {context} variable now maps to the input column automatically.

Tracing and Sessions

Fix Open span details for backfilled spans whose event time differs significantly from their ingestion time.

Dashboards and Visualizations

Fix See dashboard widgets and Actual Class filter values scoped to the date range you selected, rather than the full account lookback.
Fix See correct monthly buckets in metrics and dashboards when your time zone has a non-zero UTC offset.

Webhooks and Events

Improvement Reuse the name of a webhook destination you previously deleted when creating a new one.

Custom Metrics

Fix Filter custom metrics with a contains condition on string-list fields such as agent tool calls.

SDKs and REST APIs

Fix Retrieve task runs from the Python SDK reliably as the API adds new response fields.

​Create experiments without a dataset

​Delete spans faster by scoping to a time window

​Write new API keys directly to a .env file

​Pin evaluators to a specific version, now on every account

​Fixes and improvements

Create experiments without a dataset

Delete spans faster by scoping to a time window

Write new API keys directly to a .env file

Pin evaluators to a specific version, now on every account

Fixes and improvements