AzureBlobStorage.set() logs "Error setting key %s: %s" with only one argument, so the failure is never logged

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• I have searched the existing issues and this bug is not already filed.
• My model is hosted on OpenAI or Azure. If not, please look at the "model providers" issue and don't file a new one here.
• I believe this is a legitimate bug, not just a question or feature request.

Describe the bug

AzureBlobStorage.set() logs its failure with a format string that has two %s placeholders but supplies one argument:

https://github.com/microsoft/graphrag/blob/main/packages/graphrag-storage/graphrag_storage/azure_blob_storage.py#L195

except Exception:
    logger.exception("Error setting key %s: %s", key)

logging raises TypeError: not enough arguments for format string while rendering the record, catches it internally, drops the record, and writes --- Logging error --- plus a traceback to stderr instead.

The net effect is that when a blob write fails, the diagnostic that was written specifically for that case never reaches the configured log handlers — exactly the moment the log is needed. The exception is swallowed by the bare except, so the failed write is otherwise silent.

Every sibling handler uses one placeholder and one argument, e.g. lines 176 and 251 in the same file (logger.warning("Error getting key %s", key)) and the four handlers in azure_cosmos_storage.py (logger.exception("Error reading item %s", namespaced) etc.). This one call site is the only one with a stray : %s.

Steps to reproduce

Any failing blob write reaches it; the call shape reproduces standalone:

import logging
logging.basicConfig()
log = logging.getLogger("repro")
try:
    raise ValueError("blob upload failed")
except Exception:
    log.exception("Error setting key %s: %s", "output/entities.parquet")

Observed — no log record is emitted, and stderr gets:

--- Logging error ---
Traceback (most recent call last):
  File ".../logging/__init__.py", line 1160, in emit
    msg = self.format(record)
  ...
TypeError: not enough arguments for format string

Dropping the extra : %s emits the intended record (with the traceback that logger.exception appends anyway).

Expected Behavior

The failure is logged through the normal handlers, like every sibling handler in the storage package.

GraphRAG Config Used

Not config-dependent — any configuration using the Azure Blob storage backend.

Logs and screenshots

Included above.

Additional Information

• GraphRAG Version: main (packages/graphrag-storage)
• Python Version: any supported version (stdlib logging behaviour)

Happy to send the one-line PR.

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