Pi

← all harnesses · parser: crates/core/src/session/pi.rs

The simplest of the eight to read, and the one that records its own costs most completely. What it does not record is anything about the context window or the outcome of a tool call, and those two gaps are the whole of its ─ column.

Where it lives

$PI_CODING_AGENT_SESSION_DIR, or $PI_CODING_AGENT_DIR/sessions, or ~/.pi/agent/sessions — checked in that order (config::PI_SESSIONS_ROOT). Two variables rather than one because Pi lets the session store move independently of the agent directory. Everything below the root is swept with rglob(root, ".jsonl").

The format

JSONL, with three record types cctop reads:

• session — id, cwd, timestamp. Both the id and the start time come from here, and a file without one is skipped entirely.
• session_info — name, which becomes the row’s title.
• message — message.role, message.model, message.timestamp (epoch milliseconds), message.usage, and message.content[] blocks of type toolCall.

usage carries input, output, cacheRead, cacheWrite, cacheWrite1h, reasoning, totalTokens, and a nested cost object with input, output, cacheRead, cacheWrite and total. The 1h cache-write figure is a subset of cacheWrite, so the 5m bucket is the remainder — .min(cache_write) guards against a file that says otherwise.

Discovery parses the whole file, unlike every other JSONL harness here, which reads a bounded head and tail. There is no header record that carries the last-activity time, so the last message’s timestamp has to be found by reading to the end. It is worth knowing if Pi sessions ever get long: this is the one discovery path whose cost grows with transcript size.

Cost

Reported, and preserved exactly rather than re-derived from the model id. The one exception is a turn Pi priced at nothing while reporting tokens — what a provider it has no rates for produces — which is priced from LiteLLM instead, since reporting real spend as free hides it. Same rule as OpenCode’s, same FallbackRates helper. See What the cost figures mean.

What cannot be extracted

Context is ─. loader::read_tail has no context reader for Pi. The transcript records what each turn consumed but never how full the window stood afterwards, and there is no ceiling recorded either.

Tool outcomes are ─. Pi records the call — name, arguments, id — and nothing about how it ended. Provider::records_tool_outcomes is false for Pi precisely so ERR% reads as unavailable: a transcript with no failures in it and a transcript that cannot express one look identical, and drawing 0% would put a reassuring figure on a row that earned nothing of the sort.

Liveness

pi --session <id> puts the id on the command line, so the match is exact (proc::session_value), and node running a script whose stem is pi counts as well. pi --session <id> is also the resume command.

Waiting-for-input is read off the tail like the file harnesses: a message record whose content holds a toolCall named for an input request (session::is_input_request_tool).

cctop installs no hooks into Pi — it is not one of hook::HARNESSES — so everything on a Pi row is forensic.