MAI Cloud dictation keeps only the last few seconds in Japanese when Show Transcript is enabled

Type: Bug

## Summary

In the latest VS Code Insiders build containing #332970, I found an issue when using MAI Cloud dictation in Japanese.

When `Show Transcript` is enabled, only the last few seconds of the dictation remain after stopping.

With the same Japanese dictation, the result changes depending on the `Show Transcript` setting:

* **Show Transcript ON**
→ Only the last few seconds remain after stopping.
* **Show Transcript OFF**
→ This issue does not occur. Instead, the behavior returns to the previous one, where only about the first 60 seconds of a longer dictation remain.

In Japanese, the transcript shown while dictating does not seem to accumulate the full utterance. Instead, it appears to behave like a rolling window, with older text disappearing as new text is recognized.

When I tried the same thing in English, the finalized portion of the transcript appeared to accumulate much more normally.

As an additional check, I also tried Chinese and was able to reproduce behavior similar to Japanese.

This makes me wonder whether the MAI Cloud interim transcription behavior differs depending on the language, and whether the logic added in #332970 does not work correctly for some languages.

Also, when `Show Transcript` is disabled, the behavior returns to the issue I previously described in #332324, where longer MAI Cloud dictation loses the transcript after around the 60-second mark. So the original issue also appears to still be present.

## Expected behavior

Enabling or disabling `Show Transcript` should not change the final transcription that remains after stopping dictation.

## Related

* #332324
* #332970

VS Code version: Code - Insiders 1.136.0-insider (d5ceefbe0b296c4d8fbbf3664aff8cad73cd1b5d, 2026-08-28T16:34:03Z)
OS version: Windows_NT x64 10.0.26200
Modes:

System Info

|Item|Value|
|---|---|
|CPUs|12th Gen Intel(R) Core(TM) i7-1250U (12 x 1882)|
|GPU Status|2d_canvas: enabled
GPU0: VENDOR= 0x8086, DEVICE=0x46aa [Intel(R) Iris(R) Xe Graphics], DRIVER_VENDOR=Intel, DRIVER_VERSION=31.0.101.5186 *ACTIVE*
GPU1: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.8972
Machine model name:
Machine model version:
direct_rendering_display_compositor: disabled_off_ok
gpu_compositing: enabled
multiple_raster_threads: enabled_on
opengl: enabled_on
rasterization: enabled
raw_draw: disabled_off_ok
skia_graphite: disabled_off
trees_in_viz: disabled_off
video_decode: enabled
video_encode: enabled
webgl: enabled
webgpu: enabled
webnn: disabled_off|
|Load (avg)|undefined|
|Memory (System)|15.70GB (2.42GB free)|
|Process Argv|--crash-reporter-id 98d91960-4115-410f-a9ae-b3a83e40f4c5|
|Screen Reader|no|
|VM|0%|
Extensions (1)

Name|Identifier|Author|Version
---|---|---|---
Japanese Language Pack for Visual Studio Code|ms-ceintl.vscode-language-pack-ja|MS-CEINTL|1.131.2026082318