---
specification: API Commons Errors
specificationVersion: '0.1'
provider: Université de Montréal
providerId: universite-de-montreal
generated: '2026-08-30'
method: probed
source: live probes of the SADVR API, 2026-08-30, plus the institution's own technical documentation
description: >-
  Error behaviour of the Université de Montréal SADVR API, the institution's one genuinely
  institution-operated contract. UdeM documents a three-code model — 200, 400, 500 — and states
  that on 400 or 500 the body is the error message in JSON. Live probing shows the deployed edge
  does not honour that: unmatched routes fall through to an HTML 404 that the documentation never
  mentions.
documented:
  source: https://wiki.umontreal.ca/spaces/DOC/pages/294781211/API+REST+%E2%80%93+Description+technique
  codes:
  - code: 200
    meaning: OK. Body is a JSON object with the payload under `data`.
  - code: 400
    meaning: Bad request — the request is missing elements or references values that do not exist.
    body: JSON error message
  - code: 500
    meaning: Internal server error — a bug in the SADVR service.
    body: JSON error message
observed:
- code: 200
  contentType: application/json
  detail: >-
    Confirmed on 15 routes. Success payloads are always wrapped in a `data` array; the SOLR search
    routes add a sibling `paginationSOLR` object with numFound, start and rows.
  evidence:
    url: https://www.recherche.umontreal.ca/vitrine/rest/api/1.8/umontreal/ressource/faculte
    status: 200
- code: 404
  contentType: text/html
  documented: false
  detail: >-
    UNDOCUMENTED. An unmatched route returns a 693-byte styled HTML page, not the JSON error the
    documentation promises. A client parsing the response as JSON gets a decode error rather than
    a usable message. This is the defect that made the June 2026 profile of this repo conclude the
    whole API was dead — a single wrong path segment (`ressource/langues` for `ressource/langue`)
    produced an HTML 404 that read as a decommissioned endpoint.
  evidence:
  - url: https://www.recherche.umontreal.ca/vitrine/rest/api/1.8/umontreal/ressource/langues
    status: 404
  - url: https://www.recherche.umontreal.ca/vitrine/rest/api/1.8/umontreal/ressource/secteur_recherche
    status: 404
  - url: https://www.recherche.umontreal.ca/vitrine/rest/api/1.8/umontreal/ressource/ettbaffilie
    status: 404
- code: 301
  documented: false
  detail: >-
    Every documented base URL redirects. https://www.recherche.umontreal.ca/vitrine/rest/api/1.8/...
    is rewritten to https://recherche.umontreal.ca/vitrine/rest/public/api/1.8/... — the www prefix
    is dropped and a `public` segment is inserted. Clients that do not follow redirects get nothing.
    The documentation does not mention the `public` segment, though two example URLs on the page
    accidentally contain it.
  evidence:
    url: https://www.recherche.umontreal.ca/vitrine/rest/api/1.8/umontreal/ressource/faculte
    status: 200
    effectiveUrl: https://recherche.umontreal.ca/vitrine/rest/public/api/1.8/umontreal/ressource/faculte
documentation_drift:
- issue: Route names in the documentation table do not match the deployment.
  detail: >-
    Three routes listed in UdeM's own service table 404 as written — `ressource/secteurrech`
    (documented) and `ressource/secteur_recherche` (in the example list) both fail, as does
    `ressource/etablaffilie` / `ressource/ettbaffilie`. `ressource/uniteadmin` is documented and
    was not independently confirmed.
- issue: Version drift inside a single page.
  detail: >-
    The page names 1.7 as the root prefix, marks it as a test environment, and then gives every
    example at 1.8. Only 1.8 answers; 1.6, 1.7, 1.9 and 2.0 all 404. The page was last updated
    2024-02-08.
- issue: A documented parameter is documented as broken.
  detail: >-
    The `sort` parameter on the SOLR search routes is documented as accepted but non-functional,
    because ordering is lost when the API reformats the SOLR result set. Recorded in the OpenAPI
    as deprecated.
retry_guidance: >-
  No Retry-After header and no rate-limit headers are emitted on any response. The
  /idext/individu response for a single faculty is 11 MB; harvest politely and filter by faculty
  or department rather than pulling the unfiltered population.