Sentry MCP: get_event_attachment returns an empty body — download fails schema validation, and listing reports SHA1 of the empty string for every attachment #1267

Environment

SaaS (https://sentry.io/)

Steps to Reproduce

Reproduced on org daniels-sentry-org1 / project javascript-vue-test (EU, https://de.sentry.io),
event 8c365db20f0845c3a71315a943205d83, with two attachments of known content:

1. Send an event with two attachments of different content/size.
2. List them — omit attachmentId:
   get_event_attachment(organizationSlug='daniels-sentry-org1', projectSlug='javascript-vue-test', eventId='8c365db20f0845c3a71315a943205d83')
3. Download one — pass attachmentId='858188125'.
4. Confirm in the Web UI (Issue → Attachments) that both files download intact.

Reproduces with and without explicit regionUrl, on every attachment, across a client restart + connector reconnect.

Expected Result

Step 3 returns the file content as a valid MCP content block. Step 2 reports each attachment's real, distinct SHA1.

Actual Result

1. Download fails every content-block union branch:
   MCP error -32602: Invalid tools/call result: [{
   "code": "invalid_union", "path": ["content", 0],
   "errors": [
   ["type" expected "text", "text" expected string received undefined],
   ["type" expected "image", "data"/"mimeType" expected string received undefined],
   ["type" expected "audio", "data"/"mimeType" expected string received undefined],
   ["name"/"uri" expected string, "type" expected "resource_link"],
   ["resource": ["_meta" expected record received null,
   "text"/"blob" expected string received undefined]]
   ]}]

text/blob/data are all undefined — the response has no content.

2. Listing reports SHA1 of zero bytes for every attachment:

one.log Size: 540 bytes SHA1: da39a3ee5e6b4b0d3255bfef95601890afd80709
two.log Size: 1539 bytes SHA1: da39a3ee5e6b4b0d3255bfef95601890afd80709

That value is SHA1 of empty input (printf '' | shasum -a 1). Note Size is correct while the SHA1 is of nothing — so metadata resolves fine but the body is empty by hashing time. Likely one root cause for both symptoms: the fetch yields zero bytes, so the connector hashes an empty buffer and builds a content block with no data.
3. Separate defect — _meta: null: the resource branch also fails with "_meta" expected record, received null, independently of the missing body. Fixing the download may not fix this.
Web UI is unaffected — the same attachments download intact, so the stored blobs are fine; the fault is in the connector.
Not tenant-specific — originally reported by a customer on a different org; reproduced independently here on a separate org/project with freshly created attachments.

Product Area

Settings - Integrations

Link

https://daniels-sentry-org1.sentry.io/issues/?query=8c365db20f0845c3a71315a943205d83

DSN

daniels-sentry-org1

Version

No response