Preserve plugin session continuity through warm execution and checkpoint recovery (#17820)

doc/plugins/PLUGIN_RUNNER_EXECUTION.md

@@ -23,7 +23,7 @@ bounded `read_file` operation for attachments and deliverables.
 
 Core supports per-turn workspace sessions with Codex, OpenCode, and ACPX.
 OpenCode and ACPX require the existing qualified provider profiles.
-Workspace-free providers are not supported here. Codex warm retention is opt-in through `warmTaskVersion: 1`; ACPX and OpenCode remain per-turn.
+Workspace-free providers are not supported here. Drivers opt into warm retention through `warmTaskVersion: 1`. Core prefers warm execution for new task runs on capable drivers, including ACPX; existing provider admission still determines which harnesses the driver supports.
 The plugin owns project workspace preparation. Core does not prepare or reuse
 a Core Git worktree for a task-only environment.
 Selecting a plain task directory does not add redundant default configuration.
@@ -164,13 +164,20 @@ The existing agent-independent `inspect` and `remove` operations continue to
 protect storage maintenance. Providers that do not declare finalization version 1
 retain the inspection-based completion path. No stored binding migration is required.
 
-## Codex warm task retention
+## Warm task retention
 
 A driver declares `warmTaskVersion: 1`, implements `onEnvironmentResumeLease`,
 and returns `warmTaskVersion: 1` from `describe` only when its execution host
-supports authorized run attachment. Select the agent's warm lifecycle or set
-`runnerLifecycleMode: "warm"` and `runnerIdleTimeoutMs` on its plugin environment.
-Core requires an explicitly selected account. Setup probes remain ephemeral.
+supports authorized run attachment. Newly hired agents targeting such a driver
+are configured for warm execution. Existing agents keep their explicit policy;
+plugin runs without an explicit policy prefer warm execution. There is no
+provider-specific warm gate or additional setting. Existing runs retain their
+admitted lifecycle policy during restart recovery. The existing
+`runnerIdleTimeoutMs` controls bounded retention. Fresh warm admission requires
+a Core-managed credential identity before lease acquisition. Plugin-owned installed
+accounts continue per-turn until such an identity is available; the saved warm
+preference does not bypass account ownership checks. Drivers without warm
+capability and setup probes remain ephemeral.
 
 Plugin task execution does not create a Core-managed GitHub broker. Warm reuse
 and restart recovery use the same broker-ownership rule as initial startup.
@@ -208,4 +215,5 @@ Changes to account, credential generation, workspace, runtime or process policy
 retire the old owner before recovery. A new authority epoch archives the stopped
 checkpoint under its stable archive key and preserves provider session files.
 Warm status monitoring relies on PRP after startup and does not poll an idle
-Launcher. General ACPX warm support is deliberately excluded.
+Launcher. ACPX uses this task-provider contract; other execution transports retain
+their provider-specific lifecycle policies.