The system prompt can omit plugin and MCP error lists, and warms something extra on Windows.
A condition strips plugin details from the prompt; what makes it hold is not visible.
What's wrong with this entry?
Prompt construction now awaits an extra warm-up step on Windows, and under a condition derived from the current configuration it sends empty plugin, plugin-error, plugin-warning and MCP-server-error lists instead of the real ones. What makes that condition hold is not visible from the built code.
fastModeDisabledReason
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Related
Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.
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v2.1.219
Opus 5 gets an extra system-prompt instruction restricting AgentTool, workflows and deep-research
Both mention system prompt
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v2.1.219
Opus 5 carries an extra system-prompt block and suppresses subagent nudges
Both mention system prompt
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v2.1.229
Bash tool prompt always carries the full git commit instructions
Both mention system prompt