fix: validate empty user messages to prevent Anthropic API 400 errors#3322
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fix: validate empty user messages to prevent Anthropic API 400 errors#3322
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When user messages have empty content (e.g., Discord @mention-only messages, unrecognized attachments), the Anthropic API rejects the request with 'user messages must have non-empty content'. Changes: - anthropic_adapter.py: Add empty content validation for user messages (string and list formats), matching the existing pattern for assistant and tool messages. Empty content gets '(empty message)' placeholder. - discord.py: Defense-in-depth check at gateway layer to catch empty messages before they enter session history. - Add 4 regression tests covering empty string, whitespace-only, empty list, and empty text block scenarios. Fixes #3143
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Mar 29, 2026
…NousResearch#3322) When user messages have empty content (e.g., Discord @mention-only messages, unrecognized attachments), the Anthropic API rejects the request with 'user messages must have non-empty content'. Changes: - anthropic_adapter.py: Add empty content validation for user messages (string and list formats), matching the existing pattern for assistant and tool messages. Empty content gets '(empty message)' placeholder. - discord.py: Defense-in-depth check at gateway layer to catch empty messages before they enter session history. - Add 4 regression tests covering empty string, whitespace-only, empty list, and empty text block scenarios. Fixes NousResearch#3143 Co-authored-by: Bartok9 <bartok9@users.noreply.github.com>
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Summary
Salvaged from PR #3149 by @Bartok9 — cherry-picked onto current main with original authorship preserved.
Root cause
Empty user messages (Discord @mention-only, unrecognized attachments) pass through
convert_messages_to_anthropic()without validation. Anthropic rejects with 400:user messages must have non-empty content. The session breaks permanently until/reset.The adapter already validated empty
assistant(→"(empty)") andtool(→"(no output)") messages, but notusermessages.Fix
"(empty message)"placeholderValidation
python -m pytest tests/test_anthropic_adapter.py -n0 -q→ 81 passedCloses #3149
Fixes #3143
Co-authored-by: Bartok9 bartok9@users.noreply.github.com