## Summary

Step 7 of the incremental extraction tracked in #655, directly against
current `main` after #684. This is read-only configuration reporting,
not historical work outcomes or child controls.

- Extend standard child configuration from model-only reports to
complete reported model/reasoning-effort snapshots. Every select offers
only its observed current value; neither parent values nor requested
spawn arguments supply child values.
- Preserve the existing model-source precedence and model labels. Newer
observations remove unset/unavailable effort, including empty snapshots
when no fields remain reportable. A model change cannot carry the
previous model's effort.
- Keep recorded configuration historical. Reattachment drops cached
confirmation; fresh observations and verified, loaded provider metadata
establish current configuration after the actual response write,
including whole JSON-RPC batches.
- Run optional metadata reads outside the notification lane and rejoin
that lane only to publish. Newer observations, unload/close, or another
attachment invalidate late results. Reads verify the physical child ID
and immediate parent without loading or changing the child.
- Ignore foreign runtime starts for history-only children; copied
associations do not establish current configuration or ownership.

V1 standard opt-in, v2 defaults, empty child capabilities, mutation
restrictions, and AIR's existing contract remain unchanged. AIR's only
source change is exporting the existing source-priority constant for
reuse. Dependencies and generated app-server types are untouched.
Existing AIR and parent-session snapshots have no changes.

## Review size

9 files, +653/-36 lines. About four fifths of the additions are
tests/snapshots. Runtime changes stay within the standard router, its
server wiring, and a small shared snapshot builder used by live and
historical reporting.

## Validation

- `npm run typecheck`
- `npm test`: **2,028 passed**, 39 skipped. Includes **33 new v1/v2 wire
regressions**, with one v2-only batch case skipped on v1.
- `npm run build`
- `npm run test:integration`: **15 passed** against real Codex 0.164.0
and a local mock Responses API. Native child tests now compare reported
effort with the child's actual Responses request, both initially and
after parent reattachment.
- `npm run bundle:all`: all six platform targets compiled.
- `npm run codex-test -- -p 'Reply with exactly child-configuration-ok.
Do not read files or use tools.' -c <isolated-scratch-directory> -o
summary`: live-model smoke completed with `end_turn`.
- `git diff --check`

Wire tests cover complete singleton snapshots,
effort-only/unknown/cleared values, model changes, source precedence and
pre-announcement buffering, no-op mutation rejection, changed and
unchanged reattachment snapshots, full and no-replay attachment, delayed
batches, pending reads without blocked output, newer native settings,
late reads across attachments/unload/close, untrusted metadata, and
historical-only configuration.

The full live-model E2E suite was not run. Cross-platform bundles were
compiled, not executed on each target OS.

## Protocol / reference check

- Specification `main` at `53620d0b325d6815b3cff1ca7e909351d488fdf0`:
[RFD child
configuration](https://github.com/agentclientprotocol/agent-client-protocol/blob/53620d0b325d6815b3cff1ca7e909351d488fdf0/docs/rfds/subagents.mdx#L252-L285)
supplies the proposed child reporting, singleton-choice, and
reattachment semantics. Existing draft configuration notifications
require complete state in
[v1](https://github.com/agentclientprotocol/agent-client-protocol/blob/53620d0b325d6815b3cff1ca7e909351d488fdf0/docs/protocol/v1/draft/session-config-options.mdx#L337-L368)
and
[v2](https://github.com/agentclientprotocol/agent-client-protocol/blob/53620d0b325d6815b3cff1ca7e909351d488fdf0/docs/protocol/v2/draft/session-config-options.mdx#L333-L382).
- TypeScript SDK `main` at `c7e07388feed7a530f8211d0dae4951cb6d26d09`,
with the installed SDK **2.0.2** used for real wire decoding/schema
checks. SDK runtime evidence is separate from the specification; the
existing actual-write response boundary and ordered session-transition
helper are reused, not replaced.
- Codex's generated `Thread` metadata documents model/effort as current
configured values when loaded, or persisted values otherwise. Readback
accepts only loaded, correctly parented children; persisted metadata
alone does not confirm current configuration.

Historical work outcomes remain the next extraction. This PR does not
merge or replace #655 wholesale.