Polytope expects wrong number of fields

[uandrae]

The following request for 12 fields

(polytope) a000864@c22681:~/git/polytope-examples (main)$  cat aac6.py 
from polytope.api import Client

collection = "deode"
c = Client( address="polytope.ecmwf.int")

request = {
    "class": "d1",
    "dataset": "on-demand-extremes-dt",
    "expver": "aac6",
    "stream": "oper",
    "date": 20230820,
    "time": "1200",
    "type": "fc",
    "levtype": "ml",
    "levelist": [89,90],
    "georef": "u09tvk",
    "param": [129,260238],
    "step": [0,1,2],
}

print(c.retrieve("deode", request, pointer=False))

Generates

...
Matched datasource mars-deode
mars - EROR - 2026-06-09 08:48:06 Exception: UserError: 12 messages retrieved out of 9 expected
mars - EROR - 2026-06-09 08:48:06 ** UserError: 12 messages retrieved out of 9 expected Caught in  (/home/debian/git/mars-client-cpp/eckit/src/eckit/runtime/Tool.cc:31 start)
mars - EROR - 2026-06-09 08:48:06 ** Exception terminates mars-client

Adding "expect": 12 returns a successful correct retrieval. The problem makes it difficult to use polytope in a general way. The error is reproduced using hash a1fc98ca58b9173e5d2a734cf8933f7c0c499dcb of this repo.

[peshence]

Thank you for your report! This is caused by an underlying mars-client/metkit issue. I've reported it to the relevant team.