Files
codex/codex-rs
T
jif 4e803a017c feat: add v2 agent residency lru (#26632)
## Why

Multi-agent v2 treats agents as durable logical agents, not just live
entries in `ThreadManager`. After the reload-on-delivery change, a v2
agent can be addressed even if its thread is not currently loaded.

This PR adds the next layer: loaded v2 subagents can be paged out of
`ThreadManager` when the session has too many resident agents. That
keeps residency separate from logical identity and prepares the stack
for making v2 concurrency count active execution instead of existing
agents.

## What Changed

- Add an `AgentControl`-scoped LRU for resident v2 subagents.
- Reserve residency before spawning or reloading a v2 subagent.
- If resident capacity is full, unload the least-recently-used idle v2
subagent from `ThreadManager`.
- Keep `ThreadManager` as a primitive loaded-thread store; it does not
own the LRU policy.
- Keep unloaded agents registered and durable so they can be reloaded by
the delivery path.
- Preserve the existing v2 cap semantics by using the derived non-root
v2 cap for residency.

Eviction is intentionally conservative. A thread is unloadable only when
it is a v2 subagent, has completed or errored, has no active turn, and
has no pending mailbox work. Before removal, the rollout is materialized
and flushed.

## Assumptions And Non-Goals

- PR #26623 provides the reload-on-delivery path for unloaded v2 agents.
- `ThreadManager` membership means loaded/resident, not logical agent
existence.
- `AgentRegistry` remains the logical identity/metadata source for v2
agents that may be unloaded.
- `list_agents` remains a recent/resident view for now.
- This does not change active execution concurrency; that is the next
PR.
- This does not change `close_agent` semantics.
- This does not change or remove `resume_agent`.
- This does not add a new residency config knob.

## Stack

1. V2 durable lookup and reload on delivery (#26623) - reload unloaded
v2 agents before delivering follow-up/input.
2. V2 residency LRU (this PR) - unload idle resident v2 agents from
`ThreadManager` when resident capacity is full.
3. V2 active-execution concurrency - count running non-root v2 turns
instead of logical agents.
4. V2 close/interrupt semantics - make v2 close interrupt the current
turn without deleting durable identity.
5. V2 resume cleanup - remove the manual resume surface for v2 while
keeping internal reload support.

## Validation

- Added focused coverage for the residency LRU eviction path.
- Local clippy/check/tests were not run; CI will cover them.
4e803a017c · 2026-06-08 10:24:48 +02:00
History
..
2026-05-18 21:33:05 -07:00
2026-06-04 09:16:03 -07:00