zylon-ai/private-gpt · error · ValueError

Chat history contains multiple user blocks. This is not supp

Error message

Chat history contains multiple user blocks. This is not supported.

What it means

Raised by _assert_only_one_user_block when the history splits into more than one user block (multiple user turns separated by assistant replies). repair_with_tools is a single-turn reduction — it only accepts one user block — so multi-turn conversations must be reduced (e.g. condensed) before this repair path.

Source

Thrown at private_gpt/components/chat/processors/chat_history/memory/utils/repairs.py:209

            )


def _assert_only_one_user_block(
    chat_history: list[ChatMessage],
) -> None:
    """Assert that the chat history contains exactly one user block.

    This is used to ensure that the chat history
    is clean and contains only one user block.
    """
    if not chat_history:
        return

    matrix = get_user_blocks(chat_history)
    if not matrix:
        raise ValueError("Chat history does not contain any user messages.")
    if len(matrix) > 1:
        raise ValueError(
            "Chat history contains multiple user blocks. This is not supported."
        )

View on GitHub (pinned to 4a030776a3)

Solutions

Condense/trim history to the last user block before calling repair_with_tools()
Use repair_without_tools() if multiple blocks are expected and tools are absent
Split the session into per-turn requests and repair only the current turn

Example fix

# before
repaired = repair_with_tools(conversation_messages)

# after
# keep only the last user block
from private_gpt.components.chat.processors.chat_history.memory.utils.splitting import get_user_blocks
blocks = get_user_blocks(conversation_messages)
repaired = repair_with_tools(blocks[-1])

Defensive patterns

Strategy: validation

Validate before calling

blocks = get_user_blocks(conversation_messages)
if len(blocks) > 1:
    conversation_messages = blocks[-1]  # reduce to the last user block before repair_with_tools

Type guard

def is_single_user_block(history: list[ChatMessage]) -> bool:
    return len(get_user_blocks(history)) <= 1

Try / catch

try:
    repaired = repair_with_tools(conversation_messages)
except ValueError as e:
    if "multiple user blocks" in str(e):
        repaired = repair_with_tools(get_user_blocks(conversation_messages)[-1])
    else:
        raise

Prevention

Condense multi-turn sessions to the last user block before the tools repair path
Use repair_without_tools for general multi-turn histories
Document the single-block contract of repair_with_tools at its call sites

When it happens

Trigger: Calling repair_with_tools() on a full multi-turn conversation containing two or more user messages with assistant replies between them.

Common situations: Feeding an entire chat session into the tools path without prior condensation; a session loader appending prior turns; conflating repair_with_tools with the general repair_without_tools path (which tolerates multiple blocks).

Related errors

AI-assisted analysis of zylon-ai/private-gpt@4a030776a3 (2026-08-15). Data as JSON: /api/errors/285afca7c24b2996. Report an issue: GitHub.