## Why
A process host should be discarded and rebuilt after critical actor or
V8 failure, while the existing in-process production path must keep its
current cell-error semantics. This change establishes that failure
boundary without adding the host process or remote client.
## What changed
- add optional task-failure supervision to the transport-neutral
code-mode session runtime
- report Tokio cell-actor failures and V8 runtime-thread panics to a
host-provided fail-stop handler
- preserve the existing handler-less in-process behavior
- make host-owned cell ID allocation fail before numeric wraparound
## Follow-up
The V8 panic signal surfaced here should also be consumed by the
`InProcessCodeModeSession` manager in a future change so it can fail the
affected cell. This PR intentionally leaves the handler-less in-process
behavior unchanged while putting the required panic tracking in place.
## Stack
This is **2 of 4** in the process-owned code-mode session stack.
- #30108 is merged into `main`
- The next PR targets this branch
## Validation
- `just test -p codex-code-mode` — 53 passed
- `just argument-comment-lint -p codex-code-mode`
- `just fix -p codex-code-mode`
Remove this unused API. This API is insidious in that it implies that
alive state should be determinable from the caller, and implies that a
preflight should indicate routing. Lets drop this, and handle errors
correctly from a failed session in the future.
## Summary
- Retain the first pre-observation `yield_control()` boundary when a
cell completes before observation.
- Deliver the preserved yield before the buffered completion.
- Keep later unattached yields as no-ops.
## Why
Create followed by the initial wait must preserve the former execute
response boundary even when the script runs to completion first.
## Impact
The first wait observes the same initial yield boundary as before create
and observe were decoupled.
## Validation
- Focused initial-yield signature regression passed.
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch:
`cconger/code-mode-runtime-compact-03e2-observation-delivery`.
## Summary
- Give each session and cell a hierarchical cancellation token.
- Track cell tasks so shutdown waits for admitted actors without polling
the registry.
- Make shutdown authoritative across concurrent admission and
non-cooperative callbacks.
## Why
A best-effort registry scan can miss cells admitted concurrently or
blocked behind the registry lock.
## Impact
Session shutdown reliably stops every admitted cell and rejects new work
once shutdown begins.
## Validation
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch: `cconger/code-mode-runtime-compact-03c-terminal-state`.
## Summary
- Introduce a single cell terminal-state machine for completion and
termination.
- Make stored-value commits atomic with the winning terminal outcome.
- Buffer terminal results for later observation and cover
termination-before-commit behavior.
## Why
Completion, termination, observation, and stored-value updates must
agree on one linearized outcome under cancellation races.
## Impact
Terminal delivery becomes deterministic and terminated cells cannot
commit state after termination wins.
## Validation
- Focused terminal-state regression passed.
- Stack-tip validation: `just test -p codex-code-mode -p
codex-code-mode-protocol` (70 passed).
- Parent branch:
`cconger/code-mode-runtime-compact-03b-session-runtime`.
