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docs: add CJK language limitation warning for Gemini 2.5 models #2187

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docs: add CJK language limitation warning for Gemini 2.5 models
shanujans Mar 18, 2026
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docs: add CJK language limitation warning for Gemini 2.5 models
shanujans Mar 18, 2026
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23 changes: 20 additions & 3 deletions codegen_instructions.md
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,16 @@ client = genai.Client()
- **Gemini 2.0 Series**: `gemini-2.0-flash`, `gemini-2.0-flash-lite`
- **Gemini 2.5 Series**: `gemini-2.5-flash`, `gemini-2.5-pro`

> **⚠️ Known limitation — Gemini 2.5 series (CJK languages):** All Gemini 2.5
> models (`gemini-2.5-flash`, `gemini-2.5-pro`, `gemini-2.5-flash-lite`)
> currently fail to correctly process CJK (Japanese, Chinese, Korean) text
> input via the REST API. The model may interpret valid UTF-8 CJK characters as
> garbled/corrupted text. Google Search Grounding is also affected —
> `webSearchQueries` returns empty `[]` for CJK input on these models.
> **If your application requires CJK language input, use `gemini-3-pro-preview`
> or another Gemini 3.x model as a workaround until this is resolved.**
> See [issue #2134](https://github.com/googleapis/python-genai/issues/2134).

- Do not use the following deprecated models (or their variants like
`gemini-1.5-flash-latest`):
- **Prohibited:** `gemini-1.5-flash`
Expand Down Expand Up @@ -410,7 +420,6 @@ response = client.models.generate_content(
contents='What is the weather in Boston?',
config=types.GenerateContentConfig(
tools=[get_current_weather] # Make the function available to the model as a tool

),
)

Expand Down Expand Up @@ -457,6 +466,14 @@ print(f"Search Pages: {', '.join([site.web.title for site in response.candidates
The output `response.text` will likely not be in JSON format, do not attempt to
parse it as JSON.

> **⚠️ Known limitation — CJK languages with Gemini 2.5:** Search Grounding
> does not work correctly with CJK (Japanese, Chinese, Korean) input on any
> Gemini 2.5 model. `webSearchQueries` returns an empty list `[]` and the model
> treats the input as garbled text. English input on the same models works
> correctly. **Use a Gemini 3.x model (e.g. `gemini-3-pro-preview`) for Search
> Grounding with CJK queries.**
> See [issue #2134](https://github.com/googleapis/python-genai/issues/2134).

## Media Generation

### Generate Images
Expand Down Expand Up @@ -635,7 +652,7 @@ response = client.models.generate_content(
print(response.text)
```

## Other APIs
## Other APIs

The list of APIs and capabilities above are not comprehensive. If users ask you
to generate code for a capability not provided above, refer them to
Expand All @@ -647,4 +664,4 @@ ai.google.dev/gemini-api/docs.
- API Keys and Authentication: ai.google.dev/gemini-api/docs/api-key
- Models: ai.google.dev/models
- API Pricing: ai.google.dev/pricing
- Rate Limits: ai.google.dev/rate-limits
- Rate Limits: ai.google.dev/rate-limits