Running pig without arguments opens the interactive terminal interface. When input or output is piped or redirected, pig automatically switches to print mode. You can also explicitly choose print, JSON, or RPC mode for scripts and applications.

All modes share the same agent loop, sessions, tools, and extensions. The mode determines how input reaches pig, how output is delivered, and whether the process remains available for subsequent commands.

The SDK is not a CLI mode. It embeds the agent directly into PHP processes. See the SDK Guide when direct in-process PHP integration is preferable to process communication.

Mode	Interface	Lifecycle	Use Case
Interactive	Terminal UI	Runs until user exits	Direct human interaction with pig
Print	Final text on stdout	Single execution	Scripts that need the assistant's final response
JSON	JSONL events on stdout	Single execution	Processes requiring structured execution progress
RPC	JSONL commands, responses & events	Long-running daemon	External programs or other languages controlling pig

Regardless of mode, CLI options independently govern working directory, model selection, tools, and session logging. See Command Line for complete options.

Print mode executes the prompt, writes the final assistant text to stdout, and exits:

pig -p "Summarize the changes in this repository"
# or, with stdout redirected
pig "Summarize the changes in this repository" > summary.txt

--mode text alone does not select print mode: on a terminal it still opens the interactive UI. Use -p to run once.

Use print mode when only the final text is needed for shell pipelines or automation jobs. Intermediate events are not exposed.

Print mode writes errors and warnings to stderr. An assistant turn ending in error or aborted exits with status 1. Print mode with no prompt at all exits with status 0 and prints nothing.

JSON mode writes the session header, followed by newline-delimited JSON (JSONL) events:

pig --mode json "Review this repository" > events.jsonl

All prompts are provided at process launch. The process streams all execution events and exits once complete.

Streaming message_update events emit incremental deltas rather than accumulated snapshots. agent_settled marks the end of all automated work for the current turn.

stdout is reserved strictly for JSONL data. Logs and warnings are directed to stderr. See JSON Event Stream for payload contracts.

RPC mode keeps pig running while an external host process exchanges JSON commands and events over stdin/stdout:

pig --mode rpc --no-session

Commands are JSON objects written to stdin. Responses and events are JSON objects written to stdout, each occupying a single line.

Attaching an id to a command causes pig to echo the same ID in the matching response.

See RPC Protocol, RPC Commands, and JSON Event Stream for protocol details.

• Command Line: Flags and mode options
• JSON Event Stream: Event structure reference
• RPC Protocol: RPC lifecycle, framing, and error handling
• RPC Commands: Command and response contracts
• RPC Extension UI: Extension interactive dialogs
• PHP SDK Guide: In-process PHP integration