Errors and limits

Status codes

gRPC	HTTP	Cause	What to do
INVALID_ARGUMENT	400	A malformed expression, an out-of-range limit, an option not supported by this RPC, a resume token that does not match the request, or an ambiguous workspace name without organization. The message says which.	Fix the request.
UNAUTHENTICATED	401	An authorization header that is present but malformed, invalid or expired.	Refresh the token.
PERMISSION_DENIED	403	No read access to the workspace, or it does not exist. Anonymous callers get this for any non-public workspace.	Check the workspace and your credentials.
NOT_FOUND	404	A named project, run, experiment or environment does not exist.	Fix the name.
UNIMPLEMENTED	501	An RPC or option that is declared but not served.	Use a documented alternative.
INTERNAL	500	An unexpected server error.	Retry with backoff.
UNAVAILABLE	503	A dependency is temporarily unavailable.	Retry with backoff.
CANCELLED	504	The request exceeded the server’s timeout (15 seconds by default).	Narrow the request or page smaller, then retry.

REST error bodies are plain text. Every Query API RPC is read-only, so any request can be retried safely; the Python SDK retries UNAVAILABLE and INTERNAL up to four times with exponential backoff starting at 100 ms.

Paging limits

RPCs	Parameter	Default	Maximum
ListProjects, ListRuns, ListExperiments, ListDirectories, ListRLEnvironments	limit	50	1,000
RunsFilter (in across-runs requests)	limit	server default	100
ListSpans	limit	50	1,000 (and limit + offset ≤ 1,000 across several runs)
ListTraceSpans	limit	1,000	10,000
Discovery and attribute RPCs	limit	50–100	10,000
ListSeriesSummaries	limit (series per run)	100	10,000
ListFloatSeries	maxPointsPerPage	1,000,000	10,000,000
ListFloatSeriesBuckets, ListFloatSeriesTimestampBuckets, ListRLEnvironmentFloatSeriesBuckets	bucketsCount	1,000	5,000
	maxBucketsPerPage	1,000,000	1,000,000
ListHistogramSeries	maxPointsPerPage	1,000	10,000
ListScatterSeries	maxDataPointsPerPage	100,000	1,000,000
GetSpanPayload	maxDataLength (bytes)	1 MiB	16 MiB

Request limits

Item	Limit
Runs in ListMetricDefinitions / BrowseMetricDefinitions	1,000
Runs in the RL …AcrossRuns discovery RPCs	1–100
Environments in RL metric discovery and ListRLEnvironmentFloatSeriesBuckets	1,000
Runs in ListSpans	10
Span ids in GetSpanPayload	1–100
Label keys in ListSeriesLabelValues	10
Request message size	4 MiB
Request timeout	15 seconds

AggregateRLEnvironmentSeries additionally rejects requests that would produce more output points or series than the server is configured to allow; narrow the range, request buckets or filter environments.

Timeouts are defaults; a self-hosted deployment may configure them differently.