PR https://git.cafe/pingdotgg/t3code/pulls/24479
Date: 2026-10-28, Linux Boat VM, Node 24.22.1, system Google Chrome, repository Playwright 1.60.0.
Outcome: UNVERIFIABLE for the changed ACP behavior; native Codex neighboring paths passed.

Main:
$ git worktree add ../main github/main
HEAD 0c80751701 (github/main)
$ timeout 600 vp i
exit 0
$ T3CODE_DEV_SEED=0 setsid nohup vp run dev > /tmp/main-dev.log 2>&1 &
captured launcher PID 109263; server 16733; web 8693; isolated /home/user/main/.t3
Chrome UI paired, added local repository project, selected GPT-6.1-Sol, sent real turns.
Large-output turn used native codex.app-server; completed.
Assistant: both commands exited successfully (0). the unicode tail survived: utf8-tail: café 🦀 你好.
Additional real-repository turn: pwd => /home/user/main; printf neighbor-main-ok => neighbor-main-ok.
Main launcher process group stopped before PR server started; neither main port remained listening.

Candidate:
$ git switch --detach 12f971f1ef5e557a60b00ee5672ccff0f99916bc
$ timeout 600 vp i
exit 0
$ T3CODE_DEV_SEED=0 setsid nohup vp run dev --home-dir /home/user/t3code/.t3 > /tmp/dev.log 2>&1 &
captured launcher PID 120156; server 13773; web 5733; isolated /home/user/t3code/.t3
Chrome UI paired, added /home/user/t3code as a local repository project, selected GPT-6.1-Sol.
Composer requested:
node -e 'process.stdout.write("terminal-neighbor-start\n"); process.stdout.write("x".repeat(17*1024*1024)); process.stdout.write("\nutf8-tail: café 🦀 你好\n")'
then printf neighbor-ok.
Native protocol: codex.app-server; model gpt-6.1-sol; cwd /home/user/t3code.
Large command completion payload was truncated by the native diagnostic logger; no retained-buffer byte count was measured.
printf neighbor-ok: commandExecution completed, exitCode 0, aggregatedOutput neighbor-ok.
turn/completed: status completed, error null.
Client displayed: both commands exited successfully (code 0). the unicode tail survived: utf8-tail: café 🦀 你好.

Follow-up through the same web composer and native provider session:
printf followup-unicode-café; exit 7
=> exitCode 7, aggregatedOutput followup-unicode-café
printf followup-recovered
=> exitCode 0, aggregatedOutput followup-recovered
turn/completed: status completed, error null.
Client displayed both outputs and exit codes.
$ timeout 30 node apps/server/src/bin.ts thread show --base-dir /home/user/t3code/.t3 --messages 4 6bc02ea4-f586-4292-b76d-4334c42d0d6c
completed codex/gpt-6.1-sol; same assistant replies returned by running server.

Focused existing check through Blacksmith:
vp test run packages/provider-acp/src/server/runtimeModel.test.ts
1 file passed; 47 tests passed.

Limitation:
Native CodexDriver creates CodexAdapterV2, bypassing packages/provider-acp.
The changed appendTerminalOutput runs only on ACP terminal_update/terminal_output_chunk notifications.
Standard ACP terminal/create is also a separate clientTerminals buffer (4 MiB default, 8 MiB maximum).
No compatible real ACP terminal-notification provider path was exercised.
The original after-turn 16 MiB buffer-copy bug was NOT reproduced on main, and the PR's real-provider performance improvement was NOT verified.
No mocks, fixtures, protocol injection, source edits, commits, pushes, labels, merges, closes, rebases, or force-pushes.