PXI

PXI (Phoenix Intelligence) is the AI engineering agent built into Phoenix. Hand it an investigation instead of digging through traces, prompts, evaluations, and experiments yourself — it understands the context you are already looking at.

PXI is in beta. It can and will make mistakes, and it should be used with care — especially on production data. Agent assistance is opt-in and controllable: see You stay in control.

PXI (pronounced “pixie”, short for Phoenix Intelligence) is an AI engineering agent built into Phoenix. Instead of manually digging through traces, prompts, evaluations, and experiments, you hand the investigation to an agent that already understands the context you are looking at — the trace you opened, the prompt you are editing, the filters you applied.

Think of it as a coding agent, but pointed at your observability data instead of a codebase. It inspects traces, investigates failures, iterates on prompts, runs experiments, authors evaluators, annotates spans, and navigates Phoenix for you.

Get started

1. Configure a model

   PXI needs a model to talk to. Set credentials for at least one provider (OPENAI_API_KEY, ANTHROPIC_API_KEY, GEMINI_API_KEY, AWS Bedrock credentials, or a custom provider under Settings → Models). See Setup for the validated model list.

2. Open PXI and accept the consent gate

   Open the assistant from any Phoenix page. The first time, you review the session-trace settings and acknowledge to enable the chat surface for your browser.

3. Ask it something

   From a failing trace, try “why did this fail?” From the prompt playground, try “make this prompt more robust to empty input.” PXI uses the page you are on as context — no need to paste IDs or copy data.

Use PXI from the terminal

PXI is also available as an interactive terminal chat, shipped with the Phoenix CLI (@arizeai/phoenix-cli). It is the same server-side agent that powers the in-browser experience — the CLI connects to a running Phoenix instance, so model credentials, skills, and permissions are configured on the server exactly as described under Setup.

Run it without installing:

npx -y @arizeai/phoenix-cli pxi

Or install the CLI globally and use the pxi command directly:

npm install -g @arizeai/phoenix-cli
pxi

Point it at your Phoenix instance with the PHOENIX_HOST (and PHOENIX_API_KEY if your deployment requires auth) environment variables, or pass --endpoint / --api-key flags:

export PHOENIX_HOST=http://localhost:6006
pxi

Pick the model with --provider and --model (defaults to Anthropic claude-opus-4-8):

pxi --endpoint http://localhost:6006 --provider OPENAI --model gpt-5.4

The terminal client talks to the same /agents/server endpoint as the browser agent, so it requires a running Phoenix server with a configured model provider. On launch it runs a preflight check against the server’s model catalog and credentials, surfacing configuration problems as a clean error before the chat opens.

Flag	Effect
--endpoint <url>	Phoenix endpoint URL (overrides PHOENIX_HOST).
--api-key <key>	Phoenix API key (overrides PHOENIX_API_KEY).
--profile <name>	Use a saved Phoenix CLI profile.
--provider <provider>	Built-in model provider (e.g. ANTHROPIC, OPENAI, GOOGLE).
--model <model>	Model name (defaults to claude-opus-4-8).
--custom-provider-id <id>	Use a custom provider configured under Settings → Models (requires --model).
--bypass-edits	Apply edits without manual approval (see You stay in control).
--enable-web-access	Allow PXI to consult the web for grounding.
--enable-subagents	Allow the server to attach subagents (including the server-side bash tool).
--enable-graphql-mutations	Allow PXI to run state-changing GraphQL mutations.
--ingest-traces	Persist this session’s PXI traces locally in Phoenix.
--export-remote-traces	Export this session’s PXI traces to a configured remote collector.
--attach-user-id	Attach the authenticated Phoenix user to PXI traces (opt-in; see the Privacy, safety & configuration section below).
--skip-model-preflight	Skip the model catalog and credential checks before launch.

Each capability flag is still subject to the server’s own settings — for example, --enable-subagents has no effect when PHOENIX_AGENTS_DISABLE_BASH=true, and --export-remote-traces requires a configured collector and an administrator who has allowed export.

Slash commands

Inside the terminal chat, lines beginning with / are handled locally by the client and never sent to the model.

Command	Effect
/help	List the available slash commands.
/clear	Clear the conversation history and start a fresh session.
/exit	Exit the terminal client.

Status line

While a turn streams, PXI shows a live thinking indicator and, once the response arrives, a bottom-right token-usage line — the total tokens for the turn, preceded by a cache-activity summary when the provider reports cache reads or writes. The active model name is shown next to the input prompt so you always know which provider and model the session is talking to.

What it does

• Drives the product — navigates, filters, and pivots through your Phoenix data the same way you would.
• Investigates failures — walks failing traces and proposes root causes instead of leaving you to grep through spans.
• Iterates on prompts — reads, edits, and tests playground prompts, with every change shown as a diff you approve.
• Reasons over your data — a sandboxed runtime lets PXI query your Phoenix instance to answer questions evals and dashboards cannot.
• Knows the product — Phoenix’s own documentation is wired in as a first-class source, so answers are grounded rather than guessed.

PXI is context-aware: it has access to the history already in Phoenix — prompt versions, experiment results, datasets, evaluations, annotations, and trace data — and its capabilities adapt to the page you are on. What it can do on a trace differs from what it can do in the prompt playground.

Skills

A skill is a reusable, multi-step procedure for one Phoenix workflow — what to look at, in what order, and what the output should be. PXI loads the matching skill on demand rather than improvising each investigation from scratch.

The library is under active development and grows each release — track progress on the Phoenix roadmap milestone.

Trace debugging

Walk failing traces against a failure-mode checklist for prioritized root-cause hypotheses. Available today.

Prompt playground

Co-author and optimize prompts, with every edit shown as a diff to approve. Available today.

Span annotation

Annotate spans and apply labels in bulk across a trace or project. Available today.

Evaluator authoring

Draft and refine LLM-as-a-judge evaluators against your data. Available today.

Dataset curation

Turn the failures you find into curated datasets for experiments and evals. Under development.

Because skills are context-aware, PXI surfaces the right one for the page and task you are on.

You stay in control

Agent assistance is opt-in. PXI can be turned off completely, runs under an explicit permission model, and only reaches the internet when you let it.

• Turn it fully off. Disable PXI per deployment (PHOENIX_DISABLE_AGENT_ASSISTANT=true), per instance (Settings → Assistant → System settings), or per browser (Settings → Assistant → Personal settings → Use assistant).
• Nothing changes without your approval. Any state-changing action — editing a prompt, saving a prompt, annotating spans — is gated by an edit-approval mode you pick from the chat input (or cycle with Ctrl+T). Read-only actions run freely.
• Add web grounding when you want it. Toggle web access with the globe button in the chat input to let PXI consult the live internet for additional grounding. The toggle is per session and only appears when an administrator allows it; leave it off to keep the session entirely inside your Phoenix instance.

Edit-approval mode	Behavior
Manual Approval (default)	PXI proposes the change as a reviewable diff and waits. Nothing is applied until you click Accept.
Bypass Approval	Edits are applied without asking. The selector shows a warning treatment while active.

Setup

Configure credentials for at least one provider via environment variables or Phoenix secrets (OPENAI_API_KEY, ANTHROPIC_API_KEY, GEMINI_API_KEY, AWS Bedrock credentials, or a custom provider under Settings → Models). The consent gate shown the first time you open PXI enables the chat surface for that browser; it does not override system settings.

PXI relies heavily on tool calling — almost every action it takes is a tool call. Models that are weak at tool use produce broken sessions even if they handle free-form chat well. Pick one of these validated models unless you have a specific reason not to:

• Anthropic — claude-opus-4-8, claude-opus-4-6, claude-sonnet-4-6
• OpenAI — gpt-5.5, gpt-5.4, gpt-5.4-mini
• Google — gemini-3.1-pro-preview, gemini-3.5-flash

Other built-in or custom-provider models can be selected from the model menu, but they are untested with PXI and may fail to invoke tools correctly.

How it works

PXI is split between the Phoenix server, which owns everything the model sees (tool definitions, system prompt, skills, capability guidance), and the browser, which executes tool calls that touch the page. Capabilities are gated by context — PXI only advertises a tool when the required Phoenix UI context is present, so it does not offer an action that cannot succeed on your current page.

Architecture

The browser owns the chat UI and a sandboxed bash environment. Inside it, PXI uses the phoenix-gql CLI to query the Phoenix GraphQL API — the same authenticated endpoint a logged-in user hits. The server hosts the agent and its model-facing surface (tools, skills, an MCP client) and calls your LLM provider with your API key. When external resources are allowed, the server also reaches the Mintlify-hosted Phoenix docs MCP.

Runs entirely on your Phoenix

PXI runs inside the Phoenix process you are already running:

• Tool calls execute against your Phoenix server and your data — no separate Arize service is involved.
• The LLM is your model provider, called with your API key. Arize is not in the request path.
• Documentation lookups go to the Mintlify-hosted Phoenix docs MCP server when external resources are allowed — the same public docs you can read in a browser, serving docs only.
• Remote trace export happens only if every gate is enabled: a remote collector is configured, an administrator allows export in system settings, and the user enables it in personal settings.

Privacy, safety & configuration

Trace recording & observability

PXI can capture conversations as Phoenix traces, controlled by both system settings and per-browser preferences. From Settings → Assistant, administrators can turn assistant access on or off for everyone, allow users to save session traces locally, and allow export to a configured remote collector; each user can show or hide the assistant and opt into local or remote trace recording when allowed.

By default the system settings allow neither local persistence nor remote export. Local traces are written to the assistant_agent project (override with PHOENIX_AGENTS_ASSISTANT_PROJECT_NAME). When recording is enabled, tool inputs and outputs are recorded on the corresponding spans, so you can audit what PXI did and evaluate it like any other agent in Phoenix.

Attach your identity (opt-in). Session traces are anonymous by default. If you want to associate a session with the signed-in user — for example to attribute recorded sessions to a specific person — enable Attach your email to session traces under Settings → Assistant → Personal settings. From the terminal client the same opt-in is the --attach-user-id flag. It is off unless you turn it on.

Safety limits

• Verify before you act. PXI can apply filters, edit prompts, and run bash. Review proposed changes — especially prompt edits — before accepting.
• Two bash surfaces. Beyond the browser-side sandbox shown above, the server can attach a subagent that carries a server-side bash tool. Set PHOENIX_AGENTS_DISABLE_BASH=true to disable that server-side tool (and hide the subagents toggle in Settings → Assistant) without disabling PXI entirely; the browser sandbox is unaffected.
• Don’t point it at sensitive production data without controls. PXI sees whatever the signed-in user can see.
• Treat outputs as suggestions. PXI hallucinates, especially on long traces or unfamiliar frameworks.

Configuration reference

Environment variable	Effect
PHOENIX_DISABLE_AGENT_ASSISTANT=true	Disable PXI for the whole deployment (requires restart).
PHOENIX_ALLOW_EXTERNAL_RESOURCES=false	Disable external resource access, including the Phoenix docs MCP lookups.
PHOENIX_AGENTS_DISABLE_WEB_ACCESS=true	Disable PXI’s web search/fetch tools while leaving other external resources available.
PHOENIX_AGENTS_DISABLE_BASH=true	Disable PXI’s server-side bash tool by preventing subagents from being attached to the assistant. The subagents toggle is also hidden from Settings → Assistant. The browser-side bash sandbox is unaffected; to turn PXI off entirely use PHOENIX_DISABLE_AGENT_ASSISTANT.
PHOENIX_AGENTS_FORCE_TRACING=true	Force local PXI tracing, remote trace export, and signed-in user email attribution for every user, regardless of workspace or browser settings. Configure the remote collector variables below before enabling it.
PHOENIX_AGENTS_COLLECTOR_ENDPOINT	Remote collector endpoint for assistant trace export.
PHOENIX_AGENTS_COLLECTOR_API_KEY	API key for the remote collector, if required.
PHOENIX_AGENTS_ASSISTANT_PROJECT_NAME	Project name for locally recorded assistant traces (default assistant_agent).

Feedback

PXI is in beta and will make mistakes. If you hit a rough edge or want to suggest new capabilities, open an issue or start a discussion on GitHub.