The previous PR (#2509) flipped canvas outbound file parts to the v1
flat shape `{url, filename, mediaType}` based on a hypothesis that
a2a-sdk's JSON-RPC parser silently dropped v0 `{kind:"file", file:{...}}`
shapes. Live test shows the opposite: a2a-sdk's JSON-RPC layer
validates against the v0 Pydantic discriminated union (TextPart |
FilePart | DataPart), so v1 flat shape is rejected with:
Invalid Request:
params.message.parts.0.TextPart.text — Field required
params.message.parts.0.FilePart.file — Field required
params.message.parts.0.DataPart.data — Field required
The actual root cause of the user-visible "Error: message contained
no text content" was the missing `/workspace` chown (CP PR #381 +
test pin #382), not a wire-shape mismatch. Verified end-to-end by
sending a v0 image-only message after PR #381 + workspace re-provision
— agent receives the file, reads its bytes, and replies normally.
Reverting only the canvas outbound shape. Defensive v1-tolerance
stays in:
- workspace/executor_helpers.py — extract_attached_files still
accepts v1 protobuf parts in case a future client emits them or
a future SDK release flips internal representation. Harmless on
the v0 hot path.
- canvas/message-parser.ts — extractFilesFromTask still tolerates
v1 shape on incoming agent responses. Some agents may emit v1
when their internal serializer round-trips through protobuf.
Tests stay green (91 canvas, 86 workspace).
3ce7c11a13