DeepSeek V4 Flash repeatedly returns "Sensitive words detected" as session context grows

Description

Describe the bug

When using deepseek-v4-flash through the AgentRouter provider in OpenCode Desktop, the API repeatedly returns a Sensitive words detected error after the session/context becomes larger.

A fresh session works normally at first. However, after working for some time and accumulating more context, the error starts occurring repeatedly.

Creating a new session temporarily fixes the problem, but after the new session becomes larger, the same error happens again.

Steps to reproduce
Open OpenCode Desktop.
Start a new session.
Use deepseek-v4-flash through the AgentRouter provider.
Continue working on a project for some time, including tool calls and file operations.
As the session/context grows, the API eventually starts returning Sensitive words detected.
Starting a new session temporarily resolves the problem.
After the new session grows again, the problem returns.
Expected behavior

The session should continue working normally as the context grows and OpenCode performs context compaction/pruning.

If a context or provider limitation is reached, OpenCode should ideally provide a clear error indicating the actual cause rather than repeatedly returning Sensitive words detected.

Actual behavior

The same error repeatedly occurs:

Sensitive words detected (request id: 20260911014456241868416bvdpbw7yy5Kes)

The exact prompt or word causing the filter cannot be identified.

The most consistent pattern is:

New session → works normally → context grows → Sensitive words detected → new session fixes it temporarily → context grows again → error returns

Environment
OS: Windows 11
OpenCode Desktop: v1.18.30
Provider: AgentRouter
Model: deepseek-v4-flash
Additional information

This makes long-running sessions difficult to use because I have to repeatedly create new sessions to continue working.

I suspect this could be related to context compaction/pruning, accumulated multi-turn message history, tool-call history, or the way the accumulated context is sent through the AgentRouter provider to DeepSeek V4 Flash.

I have not been able to reproduce the issue with a specific sensitive word or prompt.

I can provide additional logs or diagnostic information if needed.

Plugins

No response

OpenCode version

v1.18.30

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

windows 11

Terminal

No response