[Help] Token limit (8,192) exceeded via Dialogflow CX API while using Gemini 2.5 Flash

Gemini API
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Hi everyone,

I’m a web designer currently building a custom chatbot UI using the Dialogflow CX API and the Gemini 2.5 Flash model for summarization.

I’ve encountered a persistent issue where my custom API-linked messenger triggers a 400 error after just 2-3 conversational turns, whereas the built-in Dialogflow messenger works without issues.

The Error Message:
{“error”:{“code”:400,“message”:“com.google.apps.framework.request.FailedPreconditionException: Token limit exceeded: got 13440, expected less than 8192 Code: FAILED_PRECONDITION”,“status”:“FAILED_PRECONDITION”}}

It seems like my input context window is strictly capped at 8,192 tokens, which is insufficient for my data store (extensive website and YouTube content).

My Questions:

  1. Is this 8,192 token cap a hard limit for Dialogflow CX API calls, even when using Gemini 2.5 Flash?

  2. Why does the built-in messenger handle this differently/better than the API?

  3. Are there any specific configurations or “padding” tricks to expand this limit?
    4. Most importantly, I am currently on a Free Trial / Free Tier account. Is this 8,192 token limit a specific restriction for free users? Would upgrading to a paid/billing account resolve this “Token limit exceeded” issue?

I’m trying to maintain a natural “Tiki-taka” flow for my users, but this error is a major roadblock. Any advice or workarounds would be greatly appreciated!