[yarikoptic-gitmate]

Summary

This follows up on the review of server-compatibility conditionals in #1963 ("Existing conditionals: removable now?"). Here is what each instance currently reports at /api/info/ (2026-10-28):

Instance	version	schema_version	allowed_schema_versions
DANDI	1.1.1	0.7.0	reported
DANDI sandbox	1.1.0.post1.dev2+g4f8a26029	0.7.0	reported
EMBER	0.0.post1.dev7927+g9e4606812	0.7.0	reported
EMBER sandbox	0.0.post1.dev7926+g7614f3033	0.7.0	reported
LINC	0.0.post6586+g39387b8	0.6.9	not reported
LINC staging	0.0.post7100+g49fd9e7	0.6.9	not reported

LINC is still in use, so anything it needs stays.

Removed

• The dandi-staging check in get_instance(). It could never run: known_instances[dandi_id] raises KeyError first, and on the command line -i only accepts known instances. The id itself was removed in 0.74.0 (Add support for all known instances in short URL format, removed dandi-staging and renamed EMBER* ones into EMBER-DANDI* #1750).
• Retrying downloads on HTTP 400. This was added for Girder (download: we need to retry #87), which was retired in 2021. Retrying the same request does not help with a 400 from dandi-archive or S3.
• The fallback for servers that do not report allowed_schema_versions. When the server's schema was newer than the client's, the client's own ALLOWED_INPUT_SCHEMAS was used in place of the missing field.
  • All DANDI and EMBER instances now report the field (Expose allowed schema versions at /info/ endpoint dandi-archive#2625, 0.19.0).
  • LINC does not report it, but it never reaches this code. That branch only runs when the server's schema is newer than the client's, and LINC's 0.6.9 is older than any schema dandi-cli supports (dandischema >= 0.12.0, i.e. schema >= 0.7.0).
  • A server without the field now accepts no older client schema. That is how dandi-cli behaved before the field existed.
  • The existing test only covered the fallback; new tests cover the field being present and absent.

Kept, with comments saying why

• x-amz-tagging for Zarr uploads is still sent only when the upload URL signs it, and an embargoed upload does not fail without it.
  • DANDI and EMBER sign it for embargoed Zarrs (Only include tagging header in zarr upload URL if zarr is embargoed dandi-archive#2503, 0.12.14).
  • LINC, a fork of dandi-archive 0.3.115, does not sign it and accepts embargoed Zarrs without it.
  • The TODO for the strict check (from Add tagging to zarr upload if embargoed #1685) now names LINC as what it waits for. When that check failed CI in Add tagging to zarr upload if embargoed #1685, the cause was the docker-compose instance not signing the header. That has been fixed since dandi/dandi-archive@9ee8cdd.
• mkzarr() matching both "Zarr already exists" and "dandiset, name must make a unique set". Current dandi-archive sends both. The "unique set" text comes from the DRF upgrade in 1.0.0 (Upgrade djangorestframework dandi-archive#2589), but "Zarr already exists" still comes back when two creations race.
• Not touched: the /server-info → /api/info/ fallback and the pagination fallback. Neither is about server versions.

DEVELOPMENT.md

• LINC is now named alongside DANDI and EMBER as an instance to stay compatible with.
• A shell loop shows what each instance deploys.
• A fallback can go once no known instance can reach it, not only once all instances support the feature.
• EMBER's version cannot be compared with dandi-archive's any more than LINC's can, so deciding support by server version works only for DANDI's own instances.

Not addressed here

Since 0.74.0, dandi upload to LINC has failed in check_schema_version() with Server uses older incompatible schema version 0.6.9; client supports 0.7.0 (or 0.8.0 with dandischema 0.14). The cause is that 0.6.9 is not in ALLOWED_TARGET_SCHEMAS and is in a different MAJOR.MINOR band. Fixing it would mean dandischema downgrading metadata to 0.6.9 (today it goes no lower than 0.6.10), or LINC upgrading its deployment. This PR does not change that behaviour.

Testing

• flake8, codespell and mypy dandi pass.
• The unit tests for check_schema_version(), the metadata downgrade, _check_attempts_and_sleep(), dandi/tests/test_utils.py and dandi/cli/tests/test_instances.py pass locally.
  • test_utils.py::test_server_info fails there only because the environment cannot reach dandiarchive.org; it fails the same way on master.
• The Docker integration tests were not run locally. None of the code changed here depends on them.

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.91%. Comparing base (e4647a6) to head (5213d34).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1973      +/-   ##
==========================================
+ Coverage   90.82%   90.91%   +0.09%     
==========================================
  Files          92       92              
  Lines       14190    14211      +21     
==========================================
+ Hits        12888    12920      +32     
+ Misses       1302     1291      -11     

Flag	Coverage Δ
unittests	90.91% <100.00%> (+0.09%)	⬆️

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