## Why
Unread queue-only messages prevented idle agents from unloading, and sending a
message to an evicted agent reloaded its session. Pending mail should not require
an idle recipient to occupy a loaded thread slot.
## What changed
- Retain queue-only mail in an in-memory runtime mailbox when a session unloads.
Queue new messages for locally evicted agents without reloading them or
starting a turn.
- Add `AgentControl::take_mailbox` and `AgentControl::watch_mailbox` so sessions
can consume retained mail and react to host mailbox notifications.
- Preserve message order across eviction, reload, and subsequent follow-ups.
Keep agents with outstanding durable sleep or turn-triggering mail loaded,
and discard retained mail when an agent is removed or its tree shuts down.
## Testing
Add integration coverage for retaining mail across eviction, sending while
unloaded, and ordering messages around a follow-up after reload. Add a host
controller test verifying that mailbox notifications wake `wait_agent` and
that the message is delivered exactly once.
GitOrigin-RevId: 4b55647f9ee9d1aaf3753f0688863bda81617327
## What changed
Expose `ThreadManager::request_agent_tree_shutdown` and an `AgentTreeShutdown::wait` handle. Requests reject new starts in the shared runtime, cancel pending startup, and signal every session in that tree, including delegates outside the thread registry. Waiting covers admitted operations and session teardown, and reports cleanup or persistence writer failures. Other root trees remain unaffected; registry removal and persistence handoff remain caller responsibilities.
Retain tree membership through startup, cancelled spawn cleanup, residency eviction, and completion watchers. Release persistence resources before returning startup failures, and stop completion watchers during tree shutdown without reporting shutdown as a child result.
## Testing
Add coverage for tree isolation, children removed from the registry, delegate teardown, cancellation during required MCP initialization, aborted teardown, persistence writer failures, and successful retry after a failed resume releases its writer.
GitOrigin-RevId: a109e25adf23d20baf7595891099947050c6b6b5
## What changed
- Make `LocalThreadStore` default to paginated history while retaining explicit legacy mode.
- Explicitly use paginated history for Guardian review sessions and allow in-memory stores to create paginated threads.
- Rename full-history resume, fork, and subagent helpers to identify them as legacy APIs, and document the paginated alternatives.
- Reject `thread/revert` for ephemeral threads and prevent the TUI from replaying or attaching to ephemeral agent threads.
## Testing
Add coverage for preserving the default and explicitly selected history modes and conversation context across restart, and for retaining context after rejected ephemeral reverts. Extend Guardian checkpoint coverage across both history modes and verify that saved reviews use paginated history.
GitOrigin-RevId: 870239eb3757018159ee4f230a009c97d38ac5b7
## What changed
Add `otel.log_agent_responses`, disabled by default and requiring an OTLP HTTP or gRPC log exporter. Emit `codex.agent_response` for completed `final_answer` messages from main agents and spawned task agents, with session, turn, item, and available parent/root attribution.
Strip memory citations from exported text, preserve the stored answer, and cap responses at 64 KiB on a UTF-8 character boundary. Include the original byte length and a truncation flag, and suppress duplicate item completions within each turn. Exclude commentary and non-task agents.
## Testing
Extend configuration tests for default-off and explicit opt-in behavior, the agent execution test for main/subagent response attribution, and the log-buffer test for response-event exclusion.
GitOrigin-RevId: eacda1150de2e6bac2c667d71b57214b0a086f1a
## Why
Accepted inter-agent messages can still be waiting in the submission queue when a worker appears idle. Evicting that worker can lose the queued work, while cancelling an eviction caller can leave shutdown unfinished and allow delivery to a closing runtime.
## What changed
- Pin V2 recipients until queued submissions are handled or dropped, and verify that delivery targets the registered runtime.
- Move `Submission` into core so it can carry the residency guard through queue handoffs.
- Give eviction exclusive access to each runtime and keep it counted against capacity until removal. Run teardown in a separate task so it completes even if its caller is cancelled, and remove registry and residency entries together.
## Testing
Add a regression test covering queued follow-up delivery, eviction refusal while mail is pending, cancelled eviction completing teardown, rejection of late delivery, and capacity reuse after removal.
GitOrigin-RevId: d6de3d68cb6b911942e9ddfc05c65b3741b796b2
## What changed
- Remove the private-desktop opt-out from elevated and unelevated Windows sandbox launches.
- Remove `windows.sandbox_private_desktop` and its managed requirement and API fields. Warn users to remove the obsolete setting.
- Require a private desktop name when launching through the Windows sandbox wrapper and command runner.
## Testing
Add coverage for the obsolete-setting migration warning and update wrapper tests to verify a live private desktop is passed and a missing desktop name is rejected.
GitOrigin-RevId: c7135f8d211aac8d812180691c2c1e433d77cde4
## What changed
- Accept `windows.sandbox = "mxc"` and preserve the selected backend through environment configuration, command execution, patch writes, and sandbox metadata.
- Treat MXC as enabled in the TUI and report Windows sandbox readiness as `ready`, avoiding legacy setup prompts.
- Keep `allowed_sandbox_implementations` scoped to the legacy elevated and unelevated backends without restricting MXC.
- Default `windows.sandbox_private_desktop` to `false` for MXC while retaining `true` for legacy sandboxes.
## Testing
Add coverage for MXC configuration precedence, legacy requirement handling, sandbox selection, and TUI state. Add a Wine integration test that verifies command and patch routing fails when native MXC is unavailable and reports `windows_mxc` in turn metadata.
GitOrigin-RevId: e2162447d0750f60753864c92a20e02a7f297bca
## Why
Persisted turn-start events lack the originating root turn ID, so they cannot directly associate child turns with the root turn that initiated them.
## What changed
- Add optional `root_turn_id` to `TurnStartedEvent`. Use the inherited root turn ID when available, otherwise the turn's own ID.
- Centralize turn-start emission for regular turns, shell commands, and manual compaction so they record attribution consistently.
- Carry attribution into `ThreadHistoryTurnChange` when processing turn-start events and retain it through completion in the history builder.
- Keep older records compatible by defaulting missing attribution to `None`.
## Testing
Add coverage for root and child turn attribution, persistence when tool collisions fail a turn before sampling, history change propagation, and deserialization of older turn-start records.
GitOrigin-RevId: 54a80b828ca7d1c4c19f13d468c01d052e1b9130
## What changed
- Add effective workspace roots to `EnvironmentConfig` and use them when
materializing permission profiles and filesystem context.
- Preserve selection roots for thread-owned configurations while allowing a
ready environment attachment to supply its resolved roots.
- Propagate resolved roots to child environments and validate both command and
`apply_patch` writes in owner-provided secondary workspaces.
GitOrigin-RevId: 1832c168ce1fc37fa67efc2a472998ab4f448c70
## What changed
- Add Windows sandbox mode, private-desktop behavior, and legacy Landlock selection to each `EnvironmentConfig`.
- Centralize sandbox context construction on `TurnEnvironment`, preserving environment-owned permissions, paths, and backend settings while applying additional permission grants.
- Use the environment-derived context for project instructions, capability discovery, file uploads, and filesystem-oriented tools.
## Testing
- Verify capability discovery uses the selected environment's permission profile and sandbox backends when they differ from the thread defaults.
GitOrigin-RevId: 7ae2fed90c8ada950f2e8431e571e9b2c793c291
## Why
Multi-Agent V2 children are owned by their parent at runtime. Resuming an
unloaded child directly could rebuild it from caller-provided settings instead
of the parent's current authority.
## What changed
- Route child reloads through their loaded immediate parent and reject direct
cold resume when that parent is unavailable.
- Preserve the child's recorded model, provider, reasoning effort, and role
while inheriting the parent's execution policy and MCP extensions.
- Validate cached environments against the parent, intersect local permission
profiles, and reject stale remote or workspace-root configurations.
- Keep paginated cold-resume token usage attribution when attaching to the
reloaded child.
## Testing
Add coverage for owner validation, nested-parent reloads, permission and
environment changes, role instruction restoration, paginated usage replay,
and app-server child resume behavior.
GitOrigin-RevId: 84014762bcdb57f94fc23974c9c1af55dc1babf1
## What changed
- Use `exec_command` and `write_stdin` as the shell tool surface.
- Treat legacy `default`, `local`, and `shell_command` model metadata as `unified_exec`.
- Remove obsolete shell-selection configuration and runtime paths while preserving the feature and policy gates for zsh fork execution.
GitOrigin-RevId: d743cbe598630d73052f1fecad680c4cde17977d
## Why
Environment-owned permission profiles and workspace roots must remain effective
without being persisted or restored as thread-owned settings.
## What changed
- Keep thread settings snapshots and restore data separate from the effective
configuration supplied by the primary environment.
- Use resolved environment permissions, active profiles, workspace roots, and
network policy when building turn context and session events.
- Preserve environment selections when agents are evicted, resumed, or spawned,
and validate owner configuration when it becomes ready.
- Start memory initialization only after the primary environment is configured.
## Testing
- Extend remote-environment and multi-agent tests to cover settings persistence,
owner permission profiles, workspace roots, spawning, eviction, and resume.
GitOrigin-RevId: d82f126981cd0190233020bbdd61d96c70558868
## What changed
- Restore a V2 agent's inherited environment selections when reloading its
thread after residency eviction.
- Keep the restored execution environment and its tools available when the
agent receives a follow-up task.
## Testing
- Add an integration test that evicts and reloads a V2 agent, then verifies
its environment selection and `exec_command` tool are preserved.
GitOrigin-RevId: a5d4ad0fa465c717b32b7ae6807486429187a41d
## What changed
- Allow multi-agent v2 parents to spawn any visible model that has not explicitly disabled multi-agent support.
- Expose collaboration tools to child agents only when their selected model supports multi-agent v2, keeping legacy models as leaf workers.
- Preserve a worker's selected model when reloading it into residency.
- Propagate multi-agent capability metadata to Amazon Bedrock model entries so delegation is gated consistently.
## Testing
- Cover model selection, leaf-worker tool visibility, Bedrock capability handling, and model preservation after reload.
GitOrigin-RevId: 1457adb1a09806d1f0621311d5a42a6815b9dd4e
## Summary
Multi-agent v2 tools now use the fixed `collaboration` namespace when
namespace tools are available. This keeps the model-visible hint and the
actual tool surface aligned around `functions.collaboration.*`, without
exposing an unshipped namespace knob to users.
The PR also removes the old `features.multi_agent_v2.tool_namespace`
config/schema surface, updates the MAv2 test fixtures for namespaced
calls, and fixes stale `TurnContext.features` references that were
breaking `codex-core` builds.
## Changes
- Expose MAv2 tools under `collaboration` instead of relying on a
configurable namespace.
- Remove `tool_namespace` from MAv2 TOML config, resolved config,
validation, schema, and tests.
- Update tool-planning and integration fixtures to assert or emit
namespaced MAv2 tool calls.
- Read feature state through `TurnContext.config.features` in the
multi-agent mode context paths.
## Testing
- `just write-config-schema`
- `just test -p codex-features`
## Why
Multi-Agent V2 concurrency should count active non-root turns, not
resident or durable agent threads. The limit is intentionally best
effort: admission checks are synchronous, but concurrent successful
checks may overshoot slightly.
## What changed
- Keep one root-derived execution limit on the shared `AgentControl`.
- Count active V2 subagent turns with an RAII guard owned by
`RunningTask`.
- Check capacity before spawning or starting an idle agent, including
direct app-server `turn/start` submissions.
- Preserve queued delivery for agents that are already running.
- Exempt automatic idle continuations so `/goal` work is not dropped
when capacity is temporarily full.
- Keep root and V1 turns outside this limiter.
## Test coverage
- `execution_guards_count_active_v2_subagent_turns`
- `execution_guards_ignore_root_and_v1_turns`
- `v2_nested_spawn_checks_shared_active_execution_capacity`
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