VertexAiMemoryBankService.search_memory never returns MemoryEntry.custom_metadata, even though the write path treats it as first-class

[Yatsuiii]

Summary

search_memory (line ~542) constructs every returned MemoryEntry with only author, content, and timestamp:

memory_events.append(
    MemoryEntry(
        author='user',
        content=types.Content(
            parts=[types.Part(text=fact)],
            role='user',
        ),
        timestamp=update_time.isoformat() if update_time else None,
    )
)

MemoryEntry.custom_metadata (memory_entry.py) is never populated, even though memory.metadata -- the underlying Vertex Memory object already in scope in that same loop (memory = retrieved_memory.memory) -- carries it.

This is not a guess about what metadata is for: this same file's write path already reads MemoryEntry.custom_metadata as meaningful input. _add_memories_via_create merges it via _merge_custom_metadata_for_memory (line ~901) into what actually gets written. The write side treats the field as real; the read side drops it.

Live verification (not just source reading)

Created a memory directly against a real Vertex AI Memory Bank instance with metadata attached, then retrieved it:

Created. Now retrieving...
name: projects/.../locations/us-central1/reasoningEngines/.../memories/9019122152674164736
fact: ADK issue verification: metadata round-trip test.
metadata: {'verify_key': MemoryMetadataValue(string_value='verify_value_123')}
cleaned up

The underlying SDK's retrieved_memory.memory.metadata is genuinely populated and correct. VertexAiMemoryBankService.search_memory just never reads it into the MemoryEntry it returns.

Why this matters

A caller that writes custom_metadata at creation time -- an application-specific identifier used to correlate a memory back to its source, for example -- has no way to get it back through search_memory, ADK's own documented read path. No error, no warning; the field is silently empty on every returned MemoryEntry.

Suggested fix

memory_events.append(
    MemoryEntry(
        author='user',
        content=types.Content(
            parts=[types.Part(text=fact)],
            role='user',
        ),
        timestamp=update_time.isoformat() if update_time else None,
        custom_metadata={
            k: getattr(v, 'string_value', v)
            for k, v in (memory.metadata or {}).items()
        },
    )
)

(getattr(v, 'string_value', v) unwraps Vertex's MemoryMetadataValue oneof shape -- happy to adjust to match whatever convention is preferred, or open a PR with this change if useful.)

Context

Found while building an agent-memory governance project on top of this SDK client. Filing as a report against the read-side gap specifically, since the write side already treats this data as meaningful and documented.