api version

Q Does /api/v1.1 differ from /api/v1, and which should a client call?

Endpoint GET / and 19 other read-only calls under each prefix

Docs claim The reference documents /api/v1. The deployment's own OpenAPI document, served from both prefixes, gives servers[0].url as /api/v1.1 and never mentions /api/v1.

Actual

20 read-only calls, each made under both prefixes with one bearer token obtained from /api/v1:
  /, /schema, /schema/Shot, /schema/Shot/fields, /schema/Shot/fields/<field>, /preferences,
  /license_info, /spec.json, /schedule/work_day_rules, /webhook/hooks, /entity/shots,
  /entity/shots/<id>, /entity/shots/<id>/followers, /entity/shots/<id>/relationships/project,
  /entity/projects/<id>, /entity/human_users, _search x2, _summarize, _text_search

  19 identical, same status and same body once the prefix is normalised
   1 genuinely different

GET /  is the one, and the whole difference is one field:
  api_version:  v1 -> '1.0'      v1.1 -> '1.1'
  every other key identical, no key present on one and absent on the other

links echo the prefix you called, they do not rewrite it:
  called v1   -> {"self": "/api/v1/entity/shots?...",   "next": "/api/v1/entity/shots?..."}
  called v1.1 -> {"self": "/api/v1.1/entity/shots?...", "next": "/api/v1.1/entity/shots?..."}

/spec.json is byte-identical from both, and both advertise servers[0].url as /api/v1.1.
operations: v1 62, v1.1 62, identical sets True

/api/v1.2  /api/v2  /api/v0  /api/v1.10  /api/version  /api   -> all 404 code 103, detail null

Teaches

• The two prefixes are one API. One token authenticates both, every status matches, and every body matches once the prefix each echoes in its own links is normalised. Everything measured in this corpus was measured on /api/v1 and transfers to /api/v1.1 unchanged.
• links echo the prefix you called. A client that starts on /api/v1.1 stays there through links.next; there is no silent downgrade to follow, and no rewriting to guard against (006_pagination).
• api_version in the root document reports the prefix that served the request, 1.0 or 1.1. It is not a statement about the site, so it cannot be used to discover which versions a deployment offers.
• The version is not discoverable from the API. Both specs advertise only /api/v1.1, yet /api/v1 serves the same 62 operations, and there is no listing of valid prefixes. /api/v1.2 and /api/v2 answer 404 code 103 with detail null, the same shape as any unrouted path (045_webhooks), so a probe cannot tell an unreleased version from a wrong URL.
• Comparing two versions needs two artefacts removed first. Every error body has a per-request errors[].id that changes on every call, and /spec.json contains the literal /api/v1.1 under servers whichever prefix served it. Left in, both read as version differences and neither is one.