Module repl 

In-process minimal REPL — defect --repl.

Does not use ACP or TUI: reads one line from stdin as a prompt, runs one turn, and prints the session event stream to stdout as plain colored text. Its purpose is a convenient entry point for “hand-crafting prompts during development to quickly test agent behavior”, not a polished frontend for end users.

The entire module is gated by the repl feature (see Cargo.toml) — when the feature is disabled, this code is not compiled and owo-colors / crossterm are not pulled in.

Why line editing is done manually

Initially we relied on the terminal’s canonical (cooked) mode for line editing, which had two bugs: backspace could erase the prompt, and deleting Chinese characters removed bytes instead of whole Unicode chars. So we switch to raw mode during line reading and handle it ourselves: maintain a String buffer (where pop() naturally deletes by char), and on each key press redraw by “carriage return + clear line + redraw prompt+buffer” — the prompt is redrawn and thus cannot be erased, and CJK wide characters work correctly because the terminal advances the cursor by display width. Raw mode is only active during line reading; event rendering during a turn still runs in cooked mode, so \n works normally.

We use crossterm for raw mode and key event parsing (consistent across Linux / macOS / Windows) — its event::read() returns already-parsed KeyEvent values (multi-byte chars are delivered directly, no need to manually assemble UTF-8), and raw mode switching is cross-platform.

Relationship with the ACP path

Reuses the same AgentCore: creates a session with Frontend::Cli, and uses local LocalFsBackend / LocalShellBackend (the REPL runs on the local machine, files and commands are executed directly, no delegation). The event stream consumption logic is a minimal version of the defect-acp event pump — that one translates events into wire notifications, while this one translates them into terminal text.

Functions

run

Run an interactive REPL until stdin EOF (Ctrl-D) or until :q / :quit / :exit is read.