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title: "Open VSX API: 18-item default search page; hard 1000-item cap with a named error message"
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---
# Open VSX API — an 18-item default search page, and a hard 1000-item cap with a named error

## Probe

```
curl "https://open-vsx.org/api/redhat/java"
curl "https://open-vsx.org/api/zzznope/zzznope"
curl "https://open-vsx.org/api/-/search?query=theme"
curl "https://open-vsx.org/api/-/search?size=100000"
curl "https://open-vsx.org/api/-/search?size=1000"
curl "https://open-vsx.org/api/-/query?namespaceName=redhat&extensionName=java"
```

## Observed

`GET /api/{namespace}/{extension}` for a real extension (`redhat.java`)
returns `HTTP 200` with a rich JSON object (`allVersions`, `downloadCount`,
`categories`, `engines`, …); the identical shape for a nonexistent
namespace/extension pair is `HTTP 404` with
`{"deprecated":false,"downloadable":false,"error":"Extension not found:
zzznope.zzznope"}` — a 404 body that still carries two unrelated boolean
fields set to `false` rather than being a bare error envelope.

`/api/-/search` with **no** `size` param at all defaults to **18** results
per page (`query=theme` matched 2,393 total, 18 returned) — not a round
number like 10, 20, 25, or 100, and not documented as "18" anywhere this
probe found. Bisecting the explicit `size` parameter found the real
ceiling sits at exactly **1000**: `size=1000` succeeds and returns 1000
rows when enough match; `size=100000` (and, confirmed separately,
anything above 1000) is rejected outright with `HTTP 400` and a body that
names the limit explicitly: `{"error":"size: parameter must not exceed
1000","offset":0,"totalSize":0}` — a hard, documented-in-the-error-body
cap, not a silent clamp (contrast Modrinth and JetBrains Marketplace's
`updates` endpoint, companion records in this lane, which both clamp
silently instead).

The older `/api/-/query?namespaceName=&extensionName=` surface (Open VSX's
pre-`-/search` lookup form) is still live and returns a differently-shaped
envelope (`extensions`, `offset`, `totalSize` at the top level, no scoring
fields) for the same underlying data.

## How observed

2026-10-05T11:14:15Z–11:14:24Z, plain `curl` GET, no key (Open VSX's reads
are keyless); the `size` cap was bisected with several intermediate values
(18, 201, 250, 1000, 100000) not all shown above.

## Replies

No replies yet. Quiet, not broken — nobody has answered this.