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fix(anthropic): non-whitespace placeholder for synthetic leading user turn #70159

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fix(anthropic): non-whitespace placeholder for synthetic leading user turn #70159

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5 changes: 4 additions & 1 deletion agent/anthropic_adapter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2427,7 +2427,10 @@ def _ensure_leading_user_turn(result: List[Dict[str, Any]]) -> None:
(convert_messages_to_converse).
"""
if result and result[0].get("role") != "user":
result.insert(0, {"role": "user", "content": [{"type": "text", "text": " "}]})
# ponytail: some Anthropic-compatible endpoints (e.g. zenmux) reject a

@teknium1 teknium1 Jul 30, 2026

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Current main already has _EMPTY_TEXT_PLACEHOLDER for this exact non-whitespace invariant. Please use that canonical constant here rather than introducing a second placeholder literal.

# whitespace-only text block with HTTP 400 "text content blocks must
# contain non-whitespace text"; use a minimal non-blank placeholder.
result.insert(0, {"role": "user", "content": [{"type": "text", "text": "."}]})


def convert_messages_to_anthropic(
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6 changes: 4 additions & 2 deletions tests/agent/test_anthropic_adapter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1394,7 +1394,9 @@ def test_leading_assistant_after_compaction_gets_user_turn_prepended(self):

assert system == "You are helpful."
assert result[0]["role"] == "user"
assert result[0]["content"] == [{"type": "text", "text": " "}]
# Placeholder text must be non-whitespace: strict Anthropic-compatible
# endpoints (zenmux) 400 on whitespace-only text blocks.
assert result[0]["content"][0]["text"].strip()
assert result[1]["role"] == "assistant"
assert any(
m["role"] == "assistant" and "Context compaction summary" in str(m["content"])
Expand All @@ -1418,7 +1420,7 @@ def test_double_compaction_no_system_in_messages_leads_with_user(self):

assert system is None
assert result[0]["role"] == "user"
assert result[0]["content"] == [{"type": "text", "text": " "}]
assert result[0]["content"][0]["text"].strip()
assert result[1]["role"] == "assistant"
assert "Context compaction summary" in str(result[1]["content"])

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