AgentEngineSandboxCodeExecutor sends 'contents' but Vertex SDK reads 'content' — input file payload silently dropped

[Number531]

Summary

AgentEngineSandboxCodeExecutor.execute_code() builds the per-file dict with key 'contents' (plural), but the Vertex AI SDK reads the singular key 'content'. Result: when an agent passes input files via CodeExecutionInput.input_files, the file is created in the sandbox's working directory with its declared name but zero bytes. No exception is raised; the agent just sees an empty file.

This is a sibling of #5480 (external-delete recovery class mismatch), which I filed earlier from the same investigation.

Versions

• google-adk 1.31.0 (latest, 2026-04-16) — bug present
• google-adk 1.27.2 — bug present (initial discovery)
• Verified by reading src/google/adk/code_executors/agent_engine_sandbox_code_executor.py directly at the v1.31.0 tag.

Code paths

Producer side — src/google/adk/code_executors/agent_engine_sandbox_code_executor.py (v1.31.0, ~line 147):

if code_execution_input.input_files:
    input_data['files'] = [
        {
            'name': f.name,
            'contents': f.content,        # ← writes 'contents'
            'mimeType': f.mime_type,
        }
        for f in code_execution_input.input_files
    ]

Consumer side — vertexai/_genai/sandboxes.py (~line 641, current SDK):

for file in input_data.get("files", []):
    file_name = file.get("name", "")
    input_chunks.append(
        types.Chunk(
            mime_type=file.get("mimeType", ""),
            data=file.get("content", b""),    # ← reads 'content', not 'contents'
            metadata={"attributes": {"file_name": file_name.encode("utf-8")}},
        )
    )

The data=file.get("content", b"") falls through to the default b"" because the dict only has 'contents'. The Chunk is created with empty data.

Reproduction

1. Build any code-executor agent with code_executor=AgentEngineSandboxCodeExecutor(...).
2. Pass a non-empty CodeExecutionInput.input_files=[File(name='data.csv', content=<some bytes>, mime_type='text/csv')].
3. Have the agent run import pandas as pd; print(pd.read_csv('data.csv')).
4. Observe pandas.errors.EmptyDataError: No columns to parse from file — because data.csv exists but contains zero bytes.

Fix

One-line change. In agent_engine_sandbox_code_executor.py, the dict key should be 'content' (singular) to match what vertexai/_genai/sandboxes.py reads:

input_data['files'] = [
    {
        'name': f.name,
        'content': f.content,             # was: 'contents'
        'mimeType': f.mime_type,
    }
    for f in code_execution_input.input_files
]

Workaround

For projects that need to ship before this is fixed upstream, subclassing AgentEngineSandboxCodeExecutor and overriding execute_code() with a near-verbatim copy of the upstream method plus the corrected key works. (We also patch the related #5480 in the same subclass.) Happy to share the reference implementation if helpful.

Related

• AgentEngineSandboxCodeExecutor: external-delete recovery catches wrong exception class (genai.ClientError vs api_core.NotFound) #5480 — Sibling bug in the same file (external-delete recovery catches wrong exception class)
• AgentEngineSandboxCodeExecutor uses wrong JSON field names for stdout/stderr #3690 — Earlier related field-name-mismatch bug in this executor (stdout/stderr keys)

[klateefa]

@Number531 The issue is caused by a small key mismatch.The executor is sending file data using contents, but the Vertex sandbox is only checking for content. Because of this, the file gets created but ends up empty.Changing contents to content fixes the problem and the file data is passed correctly.
This looks like a simple fix, and PR #5505 seems to address it
Can you try this and let me know if the issue persists?