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AI SDK errors and fixes: 2 guides

Real AI SDK failures, each with the error you'll see, the cause and steps that worked. 2 of 2 fixed upstream. Search within AI SDK.

Fixed: 2

AI SDKFixed (verified)
Disabling ListAgents throws NoSuchToolError during HarnessAgent construction
Constructing HarnessAgent with inactiveTools: ['ListAgents'] throws AI_NoSuchToolError before a session starts. The message is Model tried to call unavailable tool 'ListAgents'.
Last checked Oct 19, 2026#tool-calls#error-messages2 steps →
AI SDKFixed (verified)
WorkflowAgent fails on an image or file URL when workflow fetch is unavailable
WorkflowAgent.stream() fails before the first model call when a message contains a URL file or image part. The line is AI_DownloadError: Failed to download https://…/image.png: Error: Global "fetch" is unavailable in workflow functions.
Last checked Oct 19, 2026#transport#error-messages2 steps →

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