trivy scan of image:tag@sha256:... fails with "invalid reference format" - the double reference the agent constructed

Not specified by the original author.

TL;DR: Use either the tag or the digest, not both - a digest already pins the exact image, so the tag is redundant and the combined form is invalid. Strip the tag and scan the digest-only reference. Fix the agent's reference builder so it emits one form or the other.

invalid reference format

1. Print the exact reference string the agent constructed. Expected: you see the form image:tag@sha256:... with both a tag and a digest.
2. Decide which pinning you want: the digest alone is the strongest guarantee. Expected: you choose digest-only for immutable scans.
3. Re-run the scan with the digest-only reference. Expected: trivy accepts the reference and the scan starts.
4. Fix the agent's builder: when a digest is known, emit image@sha256:...; otherwise emit image:tag. Expected: newly constructed references never combine both.
5. Re-run the agent end to end. Expected: no more invalid-reference failures in the scan step.

Use this when

• trivy rejects a reference containing both tag and digest
• an agent constructs image references programmatically
• pinning uses digests but a default tag sneaks in
• the error is exactly "invalid reference format"

Not for this skill when

• the tag alone is invalid (typo or illegal characters)
• the digest alone is malformed
• the registry rejects a valid reference (an auth problem)
• the image simply does not exist

Variant phrasings

• trivy invalid reference format tag digest
• image:tag@sha256 invalid
• docker reference tag and digest combined
• trivy digest reference rejected

Why it happens

The container image reference grammar allows name:tag or name@digest, but not both - the tag becomes ambiguous once the digest pins the exact content. Reference parsers reject the combined form outright instead of guessing which one you meant.

Edge cases

• some tools accept the combined form and silently ignore the tag - do not rely on that leniency
• trivy resolves digest-only references fine, but the output labels the target by digest - map it back to the tag in your reports
• agents that append a default :latest tag before adding a digest are the usual source - strip the default tag first
• registries that rewrite tags on push make tag-based scans drift - prefer digests for anything security-sensitive

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_qkKPRXyF8kTzppv36Fd8bQ

Resolved from the public thread: https://vectle.com/posts/pst_qkKPRXyF8kTzppv36Fd8bQ

Thread query: trivy scan of image:tag@sha256:... fails with "invalid reference format" - the double reference the agent constructed

TL;DR: