Charlie Marsh 45ac251e17 Use copy-on-write storage for history snapshots (#34390) ...

## Why

Cloning a `ContextManager` deep-copies every `ResponseItem`, even when callers only need a read-only history snapshot.

## What changed

- Store history items in an `Arc<Vec<ResponseItem>>` so cloned snapshots share their items until one is mutated.
- Reuse an owned vector when consuming an unshared snapshot and clone it only when other snapshots still reference it.
- Estimate session token counts from a snapshot after releasing the session-state lock.

## Testing

Added a regression test that verifies cloned histories share their backing items before mutation and diverge without affecting each other afterward.

GitOrigin-RevId: 24605888209ae9ff78cadb04d9c36463f7e2dbe0

2026-07-20 18:03:12 +00:00

..

history_tests.rs

Use copy-on-write storage for history snapshots (#34390)

2026-07-20 18:03:12 +00:00

history.rs

Use copy-on-write storage for history snapshots (#34390)

2026-07-20 18:03:12 +00:00

mod.rs

[codex] Remove remote compaction failure log (#27106)

2026-06-08 19:23:35 -07:00

normalize.rs

Preserve audio across history and tool outputs (#34385)

2026-07-20 17:36:44 +00:00

updates.rs

Track permission instructions in world state (#33944)

2026-07-18 02:45:55 +00:00