# R12 — Final cutoff

Environment: fs-50; Linux 6.8.0-117-generic x86_64; Node v26.12.1; Playwright 1.60.0; Chrome Headless Shell 157.0.8103.38; isolated dev:server, T3CODE_DEV_SEED=0, fresh per-checkout SQLite; synthetic Fx fixture; RPC/MCP over loopback; UTC timestamps.

Scripted interaction (same inputs on both revisions; generated ids differ): Delay dark emulateMedia by 15750ms, then status and a fresh action after settlement. R09 also supplies a late rejection.

What differed: Before returns success inside the broker grace. After returns one timeout around T+500ms; late real completion does not replace it and fresh actions retain the host.

## C2 steps and timestamps

Before step times (UTC):

```jsonl
{"time":"2026-11-10T11:32:32.133Z","tool":"preview_open","caller":0,"args":{"reuseExistingTab":false,"open":false}}
{"time":"2026-11-10T11:32:32.383Z","tool":"preview_set_appearance","caller":0,"args":{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","colorScheme":"dark"}}
{"time":"2026-11-10T11:32:50.270Z","tool":"preview_status","caller":0,"args":{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480"}}
{"time":"2026-11-10T11:32:50.300Z","tool":"preview_evaluate","caller":0,"args":{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","expression":"document.body.dataset.probe=\"ok\"; \"ok\""}}
{"time":"2026-11-10T11:32:50.352Z","tool":"t3_preview_close","caller":0,"args":{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480"}}
```

After step times (UTC):

```jsonl
{"time":"2026-11-10T11:31:44.730Z","tool":"preview_open","caller":0,"args":{"reuseExistingTab":false,"open":false}}
{"time":"2026-11-10T11:31:46.120Z","tool":"preview_set_appearance","caller":0,"args":{"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","colorScheme":"dark"}}
{"time":"2026-11-10T11:32:03.740Z","tool":"preview_status","caller":0,"args":{"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406"}}
{"time":"2026-11-10T11:32:03.763Z","tool":"preview_evaluate","caller":0,"args":{"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","expression":"document.body.dataset.probe=\"ok\"; \"ok\""}}
{"time":"2026-11-10T11:32:03.817Z","tool":"t3_preview_close","caller":0,"args":{"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406"}}
```

<a id="before"></a>
## Before — C2

SHA: [fa2f4ff2a2](https://github.com/pingdotgg/t3code/commit/fa2f4ff2a2bac5ac92e07749f6b83b0003d642a0)

Agent-visible results (status/list fields selected; error text verbatim):

```jsonl
{"time":"2026-11-10T11:32:32.380Z","tool":"preview_open","caller":0,"result":{"isError":false,"selectedStatusFields":{"available":true,"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","url":null,"loading":false,"control":{"owner":"agent","ownedByCaller":true,"generation":0},"dialog":null,"viewportSetting":{"_tag":"fill"},"viewport":{"width":1280,"height":800},"tabs":[{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","owner":"agent","ownedByCaller":true}]}}}
{"time":"2026-11-10T11:32:48.168Z","tool":"preview_set_appearance","caller":0,"result":{"isError":false,"structuredContent":{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","colorScheme":"dark"}}}
{"time":"2026-11-10T11:32:50.300Z","tool":"preview_status","caller":0,"result":{"isError":false,"selectedStatusFields":{"available":true,"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","url":null,"loading":false,"control":{"owner":"agent","ownedByCaller":true,"generation":0},"dialog":null,"viewportSetting":{"_tag":"fill"},"viewport":{"width":1280,"height":800},"tabs":[{"tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","owner":"agent","ownedByCaller":true}]}}}
{"time":"2026-11-10T11:32:50.351Z","tool":"preview_evaluate","caller":0,"result":{"isError":false,"structuredContent":{"value":"ok"}}}
{"time":"2026-11-10T11:32:50.385Z","tool":"t3_preview_close","caller":0,"result":{"isError":false,"structuredContent":{}}}
```

Relevant server milestones:

```jsonl
{"time":"2026-11-10T11:31:22.851Z","event":"host.connected","connectionId":"bb0cd425-09b7-4a2b-a500-62416afd6798"}
{"time":"2026-11-10T11:31:54.934Z","event":"host.connected","connectionId":"746164df-43f7-443a-b8a2-62c5ea4dfe2c"}
{"time":"2026-11-10T11:32:13.712Z","event":"host.connected","connectionId":"c8993c19-f16f-4c48-a9be-fb75b6d77a37"}
{"time":"2026-11-10T11:32:32.166Z","event":"request.start","operation":"open","requestId":"preview-65","tabId":"tab_7_bea12b60-c14f-4580-bb58-2b38123bd480","timeoutMs":660000,"connectionId":"c8993c19-f16f-4c48-a9be-fb75b6d77a37"}
{"time":"2026-11-10T11:32:32.366Z","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","event":"tab.created","detail":{"desktop":false,"isolatedContext":true}}
{"time":"2026-11-10T11:32:32.406Z","event":"request.start","operation":"setColorScheme","requestId":"preview-66","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","timeoutMs":15000,"connectionId":"c8993c19-f16f-4c48-a9be-fb75b6d77a37"}
{"time":"2026-11-10T11:32:32.406Z","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","event":"emulateMedia.start","detail":[{"colorScheme":"dark"}]}
{"time":"2026-11-10T11:32:48.162Z","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","event":"emulateMedia.end","detail":{}}
{"time":"2026-11-10T11:32:50.288Z","event":"request.start","operation":"status","requestId":"preview-68","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","timeoutMs":15000,"connectionId":"c8993c19-f16f-4c48-a9be-fb75b6d77a37"}
{"time":"2026-11-10T11:32:50.337Z","event":"request.start","operation":"evaluate","requestId":"preview-69","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","timeoutMs":15000,"connectionId":"c8993c19-f16f-4c48-a9be-fb75b6d77a37"}
{"time":"2026-11-10T11:32:50.376Z","event":"request.start","operation":"close","requestId":"preview-71","tabId":"tab_8_bea12b60-c14f-4580-bb58-2b38123bd480","timeoutMs":15000,"connectionId":"c8993c19-f16f-4c48-a9be-fb75b6d77a37"}
```

<a id="after"></a>
## After — C2

SHA: [b088b88d19](https://github.com/pingdotgg/t3code/commit/b088b88d19fb0edc43f754da2e1d199bda70d6d8)

Agent-visible results (status/list fields selected; error text verbatim):

```jsonl
{"time":"2026-11-10T11:31:46.120Z","tool":"preview_open","caller":0,"result":{"isError":false,"selectedStatusFields":{"available":true,"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","url":null,"loading":false,"control":{"owner":"agent","ownedByCaller":true,"generation":0},"dialog":null,"viewportSetting":{"_tag":"fill"},"viewport":{"width":1280,"height":800},"tabs":[{"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","owner":"agent","ownedByCaller":true}]}}}
{"time":"2026-11-10T11:32:01.638Z","tool":"preview_set_appearance","caller":0,"result":{"content":[{"type":"text","text":"Preview automation setColorScheme timed out after 15000ms."}],"isError":true}}
{"time":"2026-11-10T11:32:03.763Z","tool":"preview_status","caller":0,"result":{"isError":false,"selectedStatusFields":{"available":true,"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","url":null,"loading":false,"control":{"owner":"agent","ownedByCaller":true,"generation":0},"dialog":null,"viewportSetting":{"_tag":"fill"},"viewport":{"width":1280,"height":800},"tabs":[{"tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","owner":"agent","ownedByCaller":true}]}}}
{"time":"2026-11-10T11:32:03.816Z","tool":"preview_evaluate","caller":0,"result":{"isError":false,"structuredContent":{"value":"ok"}}}
{"time":"2026-11-10T11:32:03.843Z","tool":"t3_preview_close","caller":0,"result":{"isError":false,"structuredContent":{}}}
```

Relevant server milestones:

```jsonl
{"time":"2026-11-10T11:29:29.949Z","event":"host.connected","connectionId":"09b81d2d-300e-436a-8035-a1f18530f0d1"}
{"time":"2026-11-10T11:31:45.523Z","event":"request.start","operation":"open","requestId":"preview-50","tabId":"tab_6_bd9d2d9d-727d-4676-b1e8-9554a31f1406","timeoutMs":660000,"connectionId":"09b81d2d-300e-436a-8035-a1f18530f0d1"}
{"time":"2026-11-10T11:31:46.101Z","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","event":"tab.created","detail":{"desktop":false,"isolatedContext":true}}
{"time":"2026-11-10T11:31:46.133Z","event":"request.start","operation":"setColorScheme","requestId":"preview-51","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","timeoutMs":15000,"connectionId":"09b81d2d-300e-436a-8035-a1f18530f0d1"}
{"time":"2026-11-10T11:31:46.133Z","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","event":"emulateMedia.start","detail":[{"colorScheme":"dark"}]}
{"time":"2026-11-10T11:32:01.892Z","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","event":"emulateMedia.end","detail":{}}
{"time":"2026-11-10T11:32:03.747Z","event":"request.start","operation":"status","requestId":"preview-52","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","timeoutMs":15000,"connectionId":"09b81d2d-300e-436a-8035-a1f18530f0d1"}
{"time":"2026-11-10T11:32:03.792Z","event":"request.start","operation":"evaluate","requestId":"preview-53","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","timeoutMs":15000,"connectionId":"09b81d2d-300e-436a-8035-a1f18530f0d1"}
{"time":"2026-11-10T11:32:03.838Z","event":"request.start","operation":"close","requestId":"preview-55","tabId":"tab_7_bd9d2d9d-727d-4676-b1e8-9554a31f1406","timeoutMs":15000,"connectionId":"09b81d2d-300e-436a-8035-a1f18530f0d1"}
```

AI-assisted; verified with the tests and tools listed above.