Engine panic in Container.AttachDependencyResultsKinds while resolving Go.env

Summary

The test-split:test-interface CI check panicked while resolving Go.env:

panic while resolving Go.env: runtime error: index out of range [2] with length 2

Trace ID: 747d6720abca0470be378b52598715d8

Inspect with:

dagger trace 747d6720abca0470be378b52598715d8

Stack

The first application frame is:

github.com/dagger/dagger/core.(*Container).AttachDependencyResultsKinds
    /app/core/container.go:1141
github.com/dagger/dagger/dagql.(*Cache).attachDependencyResults
    /app/dagql/cache.go:4785
github.com/dagger/dagger/dagql.(*Cache).initCompletedResult
    /app/dagql/cache.go:4712

The DagQL resolver recovered the panic in dagql.(*Server).resolvePath and reported it as an internal check error.

Suspected cause

AttachDependencyResultsKinds iterates and indexes the mutable field separately:

for i := range container.Mounts {
    mnt := &container.Mounts[i]
}

For iteration i == 2 to panic with a current length of 2, the loop must have captured a longer slice before container.Mounts was replaced or shortened. Lazy container materialization assigns a cloned mount slice to the same field, so this looks like unsynchronized concurrent or re-entrant evaluation/attachment of a shared cached container result.

Go.env appears to be the resolver that exposed the race rather than the source of the invalid index.

Context

• Check: test-split:test-interface
• PR where observed: #14109
• PR head: e75f6d9bb2bf7a2e677b836eb0575ffa1c749f45
• Current main inspected: 371244c89e9a754096c440dd97e00aa8a1c25031
• The relevant core/container.go, dagql/cache.go, and lazy-state code is unchanged by #14109, so this appears to be a pre-existing engine race.
• The failure is scheduling/cache-state dependent and was found during a CI rerun.

Expected behavior

Concurrent or re-entrant lazy evaluation and dependency attachment must not mutate a container mount slice while it is being traversed. The resolver should return normally or report a regular error rather than panic.