## Why
Fixes#18718.
After rewinding a thread, `/copy` could still copy the latest assistant
response from before the rewind. The transcript cells were rolled back,
but the copy source was a single `last_agent_markdown` cache that was
not synchronized with backtracking, so the visible conversation and
copied content could diverge.
## What changed
`ChatWidget` now keeps a bounded copy history for the most recent 32
assistant responses, keyed by the visible user-turn count. When local
rollback trims transcript cells, the copy cache is trimmed to the same
surviving user-turn count so `/copy` uses the latest visible assistant
response.
If the user rewinds past the retained copy window, `/copy` now reports:
```text
Cannot copy that response after rewinding. Only the most recent 32 responses are available to /copy.
```
The change also adds coverage for copying the latest surviving response
after rollback and for the over-limit rewind message.
## Verification
- Manually resumed a synthetic 35-turn session, rewound within the
retained window, and verified `/copy` copied the surviving response.
- Manually rewound past the retained window and verified `/copy` showed
the 32-response limit message.
- `cargo test -p codex-tui slash_copy`
- `just fix -p codex-tui`
- `cargo insta pending-snapshots`
Note: `cargo test -p codex-tui` currently fails on unrelated model
catalog and snapshot drift around the default model changing to
`gpt-5.4`; the focused `/copy` tests pass after fixing the new test
setup.
Fixes stale test fixtures left after the active bundled model catalog
updates in #18586 and #18388. Those changes made `gpt-5.4` the current
default and removed several older hardcoded slugs, which left Windows
Bazel shards failing TUI and config tests.
What changed:
- Refresh TUI model migration, availability NUX, plan-mode, status, and
snapshot fixtures to use active bundled model slugs.
- Update the config edit test expectation for the TOML-quoted
`"gpt-5.2"` migration key.
- Move the model catalog tests into
`codex-rs/tui/src/app/tests/model_catalog.rs` so touching them does not
trip the blob-size policy for `app.rs`.
Verification:
- CI Bazel/lint checks are expected to cover the affected test shards.
## Why
`skills/list` refreshes are best-effort metadata updates. If one fails
during startup or thread switching, the TUI should keep running and show
enough detail to diagnose the app-server failure instead of leaving the
user with only a log entry.
This addresses the recoverability and observability issue reported in
#16914.
## What Changed
- Preserve the full startup `skills/list` error chain before sending it
back through the app event queue.
- Surface failed skills refreshes as recoverable TUI error messages
while still logging the warning.
This is related to the recent bug fix from [PR
#18370](https://github.com/openai/codex/pull/18370).
## Summary
This PR aims to improve integration between the realtime model and the
codex agent by sharing more context with each other. In particular, we
now share full realtime conversation transcript deltas in addition to
the delegation message.
realtime_conversation.rs now turns a handoff into:
```
<realtime_delegation>
<input>...</input>
<transcript_delta>...</transcript_delta>
</realtime_delegation>
```
## Implementation notes
The transcript is accumulated in the realtime websocket layer as parsed
realtime events arrive. When a background-agent handoff is requested,
the current transcript snapshot is copied onto the handoff event and
then serialized by `realtime_conversation.rs` into the hidden realtime
delegation envelope that Codex receives as user-turn context.
For Realtime V2, the session now explicitly enables input audio
transcription, and the parser handles the relevant input/output
transcript completion events so the snapshot includes both user speech
and realtime model responses. The delegation `<input>` remains the
actual handoff request, while `<transcript_delta>` carries the
surrounding conversation history for context.
Reviewers should note that the transcript payload is intended for Codex
context sharing, not UI rendering. The realtime delegation envelope
should stay hidden from the user-facing transcript surface, while still
being included in the background-agent turn so Codex can answer with the
same conversational context the realtime model had.
rhan-oai