Module conversation_window 

The window a conversation is cut to when it is held or handed over.

One window, applied at every boundary. The transport’s copy of a seat’s conversation lives in one, and a Connected cuts a resume’s whole transcript to one before it rides an update - so a read that was 2.5 GiB on the seat #2150 was filed from is not copied per subscriber. The fan-out’s ring is sized from the same caps, because a ring exists to fill a copy that is behind.

A window is bounded by frames and by bytes. The count alone let a giant seat’s window weigh 319 MiB (measured 2026-10-17 on the seat #1637 was filed from, in the frames a read serves - CONVERSATION_CAP_BYTES names the basis, and why the file’s own lines read as about half of it) - and it is not the window’s own weight that bites: a page is cut from the window, so a ceiling ABOVE the newest twenty turns changes nothing a reader feels. CONVERSATION_CAP_BYTES carries where the byte ceiling’s number comes from and what it deliberately changes on the seats that reach it: a page there is the window whole rather than the newest twenty turns, and the history above it is reached the way any window’s is, a more below the floor answered from the transcript.

And both cuts land on a turn’s first frame. A window starting part-way through a turn serves its first turn with the head missing, so what the cap sheds is counted to a frame a turn opens at - one cut, shared by both entry points, and crate::conversation_turns is where a turn opens. The one case with no whole turn to land on is a turn heavier than both ceilings and their slack: there the cut is made inside it, and the frames it keeps are the newest ones.

Re-exports

use forge_primitives::Message; 🔒

Structs

Budget 🔒

The two ceilings one cut answers to, as a value.

Counted 🔒

A writer that only counts, so weighing a frame does not allocate a copy of it.

Shed

What a window’s cut shed: the frames it dropped, and the thinking growth the drop took out of the newest turn.

Window

One conversation’s newest window, and what each frame in it weighs.

Constants

CONVERSATION_CAP

How many messages one copy of a conversation keeps.

CONVERSATION_CAP_BYTES

How many bytes one copy of a conversation keeps, as frames weigh on the wire.

CONVERSATION_SLACK

How far past the cap a copy may grow before the drop runs.

CONVERSATION_SLACK_BYTES

How far past the byte cap a copy may grow before the drop runs. A quarter of the cap, as the count’s slack is, and it is also the room a turn crossing the byte line is kept whole in.

WINDOW 🔒

The ceilings the shipped window answers to.

Functions

front_of 🔒

Where the window’s front moves to in messages: the first frame of the oldest turn it keeps.

line_by_bytes 🔒

The first frame of sizes whose tail weighs no more than cap.

thinking_in 🔒

The thinking growth a run of frames stands for: the sum of the deltas on the turn’s own counters among them.

turn_counter 🔒

The growth a frame stands for when it is the turn’s own thinking counter, not a dispatched sub-agent’s.

weighted_from 🔒

What sizes[from..] weighs together.

wire_bytes 🔒

What a frame weighs on the wire: its JSON, which is what a page carries.