​

Breaking Change: Authentication by Default

• Loopback by default. PHOENIX_HOST defaults to 127.0.0.1 for HTTP, gRPC, and Prometheus, and authentication stays off there. A non-loopback address, such as 0.0.0.0 or ::, turns authentication on.
• Docker requires an API key. The image sets PHOENIX_HOST=::, so configure trace exporters and API clients with an API key, or set PHOENIX_ENABLE_AUTH=false. The Helm chart’s authentication default is unchanged.
• PHOENIX_SECRET is optional. Without it, Phoenix signs tokens with a key stored in the database, but anyone with a copy of the database can then decrypt saved credentials. Settings → Secrets warns admins when this applies. Setting or changing PHOENIX_SECRET makes saved credentials unreadable, so re-enter them.
• Other changes: phoenix serve --host is removed in favor of PHOENIX_HOST, launch_app honors the authentication settings, the default admin password must be changed before it can open a session, and browser sign-out no longer ends CLI or MCP OAuth2 sessions.

PHOENIX_HOST=0.0.0.0 phoenix serve --port 6006

​

DECISION and AGENT Annotator Kinds

• DECISION marks annotations produced by a decision model, and AGENT marks annotations produced by an AI agent.
• Works for every annotation target: spans, documents, traces, sessions, and experiment runs, across REST, GraphQL, both SDKs, and the UI.
• In px, --annotator-kind on annotate and the *-annotations delete commands accepts both. Older servers reject the new kinds.

from phoenix.client import Client

client = Client()
client.spans.add_span_annotation(
    span_id="67f6740bbe1ddc3f",
    annotation_name="intent",
    annotator_kind="DECISION",
    label="refund_request",
)

import { addSpanAnnotation } from "@arizeai/phoenix-client/spans";

await addSpanAnnotation({
  spanAnnotation: {
    spanId: "67f6740bbe1ddc3f",
    name: "intent",
    annotatorKind: "DECISION",
    label: "refund_request",
  },
});

​

Harbor: Reference Outputs and Agent Responses

• Agent responses become run output. The final text turn of the agent’s ATIF trajectory renders as Markdown in experiment comparisons, even with trace_mode=null.
• Optional reference outputs. Point a task at a JSON file under its tests/ directory, and the plugin stores it as the dataset example’s output. Tasks opt in one at a time.

[metadata.arize-phoenix]
reference_output_path = "tests/expected.json"

​

Session Turn Previews and PXI Model Search

• Preview a session turn. Hover over a turn in a session, or move to it with the arrow keys, to see its trace and root span evals, timing, tokens, and cost without opening the trace.
• Search for a PXI model. The PXI model picker shows Current, Recent, and Recommended models, searches every configured provider, and lets you type any model name and pick a provider for it. Settings → Assistant uses the same picker.

​

Client Updates: Trace Filters, Span Sorting, and Dataset Labels

• filter on get_traces, sessions.list, and get_sessions_dataframe takes the same expressions as the UI and deprecates error, min_latency_ms, and max_latency_ms. Requires Phoenix server 20.12.0+.
• sort and order on get_spans return spans by start time instead of insertion order. Requires Phoenix server 20.16.0+.
• Dataset label helpers in @arizeai/phoenix-client/datasets create, list, update, and delete global labels, and add, remove, or replace the labels on a dataset selected by name or GlobalID.

from phoenix.client import Client

client = Client()
slow_failures = client.traces.get_traces(
    project_identifier="my-project",
    filter="error_count > 0 and latency_ms >= 1000",
)
latest_spans = client.spans.get_spans(
    project_identifier="my-project",
    sort="start_time",
    order="desc",
)

import {
  addLabelToDataset,
  createDatasetLabel,
} from "@arizeai/phoenix-client/datasets";

const label = await createDatasetLabel({ name: "golden", color: "#00cc88" });
await addLabelToDataset({
  dataset: { datasetName: "support-tickets" },
  labelId: label.id,
});

​

Built-in Model Prices Update Without an Upgrade

• Prices never roll back. Phoenix applies a price table only when it is newer than the one in use, so restarts, downgrades, and mixed-version replicas keep the latest prices.
• Settings → Models shows the table’s date, for example “Built-in prices from Oct 14, 2026”. Custom models are never changed by an update.
• Opt out with PHOENIX_DISABLE_MODEL_COST_AUTO_UPDATE=true. Air-gapped deployments with PHOENIX_ALLOW_EXTERNAL_RESOURCES=false skip the fetch too.

​

Additional Improvements

• Members can view sandbox settings in read-only mode, while only admins can change them.
• Prompt version responses include created_at in the REST API and both SDKs’ types.
• IPv6 hosts work end to end: PHOENIX_HOST=:: binds dual-stack, and the clients turn IPv6 PHOENIX_HOST values into valid URLs.
• Server telemetry redacts personal data, including credentials and customer content, from exported logs and spans.
• Experiment run errors are easier to read, and the annotation score chart sizes its y-axis to the data.
• Python prompt helpers keep Anthropic extra_body, treat the developer role as system for Anthropic and Google, and keep a label of 0 when logging annotation dataframes.