Gemini CLI

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

Gemini records a per-turn token breakdown and never a cost, so its money column is inferred from published rates. Its chats also come in two on-disk shapes depending on the release that wrote them, and the parser reads both as one.

Where it lives

$GEMINI_DIR/tmp/<project>/chats/session-*.json{,l}, defaulting to ~/.gemini (config::GEMINI_HOME). The tmp/ reads like something disposable; it is where the transcripts actually live.

Discovery descends exactly two levels — project, then chats/ — rather than globbing. The sibling tool-outputs/ holds a file per tool call and dwarfs the transcripts beside it, so a recursive walk would spend most of its time in a directory with nothing in it cctop wants.

The working directory comes from a .project_root file written beside chats/. Older subtrees are named for a hash of that path with no marker to undo it; those keep an empty label, because a hash rendered in the LABEL column looks like a path and is not one.

Identity, and why it is the filename

Session::session_id is the filename stem, not the sessionId inside the file. Resuming a chat opens a new file under the same sessionId, and the segments are disjoint rather than cumulative — so keying rows on that id would collapse them onto each other and lose every earlier segment’s usage. The filename is unique and is what Gemini itself indexes by.

The start time is parsed straight out of that stem (session-2026-05-14T17-34-79709c93 → minute precision), which is all the table sorts on. Reading it from the file instead would mean deserialising a multi-megabyte JSON conversation during discovery, since the single-object shape has no header to stop at.

The two formats

• Older: one JSON object holding the whole conversation, with a messages array.
• Newer: JSONL — a header line, one line per message, and {"$set": …} patches revising header fields in place.

for_each_record unwraps $set patches and hands them over as plain objects. Every field a patch revises is one the header already declares, so a caller that simply takes the last value it sees ends up with the same header the JSON form states outright.

Tokens, verified

A gemini record’s tokens object carries input, cached, output, thoughts, tool and total. Checked against 605 recorded turns:

• total equals input + output + thoughts + tool, exactly, and
• cached is never among the addends — it is the part of input that was served from context cache, not an addition to it.

So the full-rate input is the uncached remainder, which is the same split Codex reports. thoughts is billed as output, which is how Google bills it and is the larger half of a reasoning turn on Gemini 3. The tool bucket has no rate of its own and reads zero on every turn seen so far, so it is left inside total rather than folded into a bucket that would be charged.

Cost

Estimated, through pricing::resolve_codex. The name is Codex’s; the shape — flat input, cached input, output, no cache-write tier — is Gemini’s billing model too, and a duplicate resolver under a different name would buy nothing.

A session on a bundled Code Assist tier still shows an estimate: nothing in the transcript says which tier it ran on. See What the cost figures mean.

What cannot be extracted

Context is ─. There is no extract_context for Gemini — loader::read_tail returns None for it. The transcript records what a turn consumed but not how full the window was afterwards, and the two are not the same number.

No live process. Gemini takes no session id on its command line, so there is nothing to tie a PID to a chat file; Gemini is not among the providers proc::could_be_agent recognises at all. Rows always read as stopped and the CPU and memory columns stay blank rather than borrowing another session’s figures. Session::resume_argv is None for the same reason.

Tool outcomes are recorded — a call’s status == "error" — so ERR% is real here, unlike Pi’s.

The title is the summary field, which is what Gemini’s own update_topic tool writes; it is the closest thing to a session name the format has.

--install-hooks writes $GEMINI_DIR/settings.json in the same nested shape Claude uses, so a live Gemini session can report the states its file cannot.