Piped Mode

When stdin is not a terminal (i.e., input is piped), yoyo reads all of stdin as a single prompt, processes it, and exits. This works like single-prompt mode but takes input from a pipe instead of a flag.

Usage

echo "explain this code" | yoyo
cat prompt.txt | yoyo
git diff | yoyo

When to use it

Piped mode is useful for:

Passing file contents as part of the prompt
Chaining with other commands in a pipeline
Feeding structured input from scripts

Examples

Review a git diff:

git diff HEAD~1 | yoyo --system "Review this diff for bugs."

Analyze a file:

cat src/main.rs | yoyo --system "Find all potential panics in this Rust code."

Process command output:

cargo test 2>&1 | yoyo --system "Explain these test failures and suggest fixes."

Detection

yoyo detects piped mode automatically by checking if stdin is a terminal. If it is not, piped mode activates. If stdin is a terminal, interactive REPL mode starts instead.

If piped input is empty, yoyo exits with an error: No input on stdin.

Structured output (`--output-format`)

Piped and single-prompt modes accept --output-format <fmt>:

text (default) — just the response text.
json — a single JSON object with the final result.
stream-json — newline-delimited JSON (NDJSON): one yoagent AgentEvent per line, emitted in real time as the agent works.

The stream-json stream is the raw yoagent AgentEvent serialization — internally tagged on a "type" field, camelCase keys, full fidelity (no lossy translation). The first line is always {"type":"agentStart"} and the last is {"type":"agentEnd", ...}. Tool activity appears as toolExecutionStart / toolExecutionEnd, and assistant text arrives as messageStart / messageUpdate / messageEnd. Turn boundaries are turnStart / turnEnd.

echo "list the files" | yoyo --output-format stream-json

{"type":"agentStart"}
{"type":"turnStart", ...}
{"type":"messageStart", ...}
{"type":"toolExecutionStart","toolCallId":"...","toolName":"bash","args":{...}}
{"type":"toolExecutionEnd","toolCallId":"...", ...}
{"type":"messageEnd", ...}
{"type":"agentEnd", ...}

The exact set of fields on each event is defined by yoagent — see its messages & events reference for the authoritative contract.

Quiet mode

When both stdin and stdout are piped (fully scripted usage), yoyo automatically enables quiet mode, suppressing informational config: and context: loading messages on stderr. You can also enable this explicitly with --quiet or -q:

echo "fix the test" | yoyo -q > result.md  # explicit quiet
echo "fix the test" | yoyo > result.md     # auto-quiet (both pipes detected)

The YOYO_QUIET=1 environment variable also enables quiet mode.

Slash commands aren't dispatched in piped mode

Slash commands (/doctor, /status, /help, etc.) belong to the interactive REPL — they depend on REPL state that piped mode doesn't have. If you pipe a slash command into yoyo, it won't run it; it would only get sent to the model as a literal string and waste a turn of tokens.

Instead, yoyo detects this case, prints a one-line warning to stderr, and exits with status code 2. Use one of these alternatives:

yoyo doctor                       # run the subcommand directly
yoyo --prompt "/doctor"           # send the literal text to the agent
yoyo                              # interactive REPL

yoyo documentation