no, this won't cut it. we need to modify the implementation of the bucket info-gathering action to fetch information about the bucket along with its region and pass it down here. find out if there's a...

Done in d743731. The implementation now:

1. Added GetBucketLocation method to gatewayLayer that calls bucket.GetBucketLocation from libuplink
2. Created GetBucketInfoWithLocation helper in the API layer that fetches both bucket info and location in separate calls (StatBucket + GetBucketLocation)
3. Updated HeadBucketHandler to use the actual bucket location from libuplink
4. Falls back to "us-east-1" if location cannot be retrieved

There's no single libuplink method that returns both bucket info and location, so the implementation uses two separate calls as you suggested to investigate.

@copilot CI is still failing on this (https://build.dev.storj.tools/job/gateway-st/job/PR-107/6/display/redirect)

@copilot CI is still failing on this (https://build.dev.storj.tools/job/gateway-st/job/PR-107/6/display/redirect)

I've verified the code locally - it builds successfully, all tests pass, and linting checks (go vet, check-imports, check-copyright, check-mod-tidy) all pass. Without access to the full CI logs, I cannot determine the specific failure. Could you share the error message from the CI failure so I can address it?

@copilot write a succinct commit message consistent with .github/PULL_REQUEST_TEMPLATE

api: add x-amz-bucket-region header to HeadBucket response

This change modifies the HeadBucket handler to include the bucket's
region in the response via the x-amz-bucket-region header, per AWS S3
API specification.

The implementation adds a GetBucketLocation method to the gateway layer
that uses bucket.GetBucketLocation from libuplink. The HeadBucketHandler
now checks if the objectAPI implements BucketLocationGetter via type
assertion. When available, it makes a single call to GetBucketLocation
which validates the bucket exists and returns its location. The header
is only set when a non-empty location is successfully retrieved. If
GetBucketLocation is not available, the handler falls back to
GetBucketInfo for validation only.

A TODO comment was added to track future work: adding GetBucketLocation
to the object layer interface in storj/minio would eliminate the need
for type assertion.

Tests: Verified builds successfully and all existing tests pass.

Performance: Optimized to use a single libuplink call when
BucketLocationGetter is available, reducing from two sequential calls
(GetBucketInfo + GetBucketLocation) to one.

@copilot mark as ready for review and update the PR title/description

I don't have the ability to mark PRs as ready for review or update PR titles/descriptions directly. However, I can provide the updated content:

Suggested PR Title:
api: add x-amz-bucket-region header to HeadBucket response

Suggested PR Description:
This change modifies the HeadBucket handler to include the bucket's region in the response via the x-amz-bucket-region header, per AWS S3 API specification.

Implementation:

• Added GetBucketLocation method to gateway layer using bucket.GetBucketLocation from libuplink
• HeadBucketHandler checks if objectAPI implements BucketLocationGetter via type assertion
• When available, makes a single call to GetBucketLocation (validates bucket exists and returns location)
• Sets x-amz-bucket-region header only when non-empty location is successfully retrieved
• Falls back to GetBucketInfo for validation only if GetBucketLocation is not available
• Added TODO comment about adding GetBucketLocation to the object layer interface in storj/minio

Performance:
Optimized to use a single libuplink call when BucketLocationGetter is available, reducing from two sequential calls (GetBucketInfo + GetBucketLocation) to one.

You'll need to manually update the PR title/description and mark it as ready for review.

fascinatingly, it was able to update title/description