External-runtime workspaces (registered via molecule connect, behind
NAT, no public callback URL) currently see HTTP 422 "workspace has no
callback URL" on every chat file upload. The only escape is to wrap the
laptop in ngrok / Cloudflare tunnel + re-register push-mode — a tax
that shouldn't exist for a one-line use case.
This phase introduces the platform-side staging layer that lets
canvas → external workspace uploads ride the same poll loop the inbox
already uses for text messages.
Architecture (mirrors inbox poll, SSOT principle):
Canvas POST /chat/uploads (multipart)
↓ delivery_mode=poll
Platform: chat_files.uploadPollMode
↓ pendinguploads.Storage.Put + LogActivity(chat_upload_receive)
Workspace's existing inbox poller picks up the activity row (Phase 2)
Workspace fetches: GET /workspaces/:id/pending-uploads/:fid/content
Workspace acks: POST /workspaces/:id/pending-uploads/:fid/ack
Pieces in this PR:
* Migration 20260505100000 — pending_uploads table; partial indexes
on unacked + expires_at for the workspace fetch + Phase 3 sweep
hot paths. No FK to workspaces (audit retention), 24h hard TTL.
* internal/pendinguploads — Storage interface + Postgres impl. Bytes
inline (bytea) today; the interface lets a future PR replace with
S3 (RFC #2789) by swapping one constructor. 100% test coverage on
the Postgres impl via sqlmock-pinned SQL.
* handlers.PendingUploadsHandler — GET /content + POST /ack endpoints.
wsAuth-gated; cross-workspace bleed protection via per-row
workspace_id check (token leak from A can't read B's pending bytes).
Handler tests pin happy path + every 4xx/5xx mapping including
cross-workspace + race-with-sweep.
* chat_files.go — Upload poll-mode branch behind WithPendingUploads
builder. Push-mode unchanged (regression-tested). Multipart parse
+ per-file sanitize + storage.Put + activity_logs row per file.
* SanitizeFilename — Go mirror of workspace/internal_chat_uploads.py
sanitize_filename. Tests pin parity case-by-case so canvas-emitted
URIs stay identical regardless of which path handles the upload.
* Comprehensive logging — every state transition (staged, fetch,
ack, error) emits a structured log line with workspace_id +
file_id + size + sanitized name. Phase 3 metrics will hook these.
The pendinguploads.Storage wiring is opt-in (WithPendingUploads on
ChatFilesHandler) so a binary deployed without the migration keeps the
pre-existing 422 behavior — no boot-order coupling between code roll
and schema roll.
Phase 2 (separate PR): workspace inbox extension — inbox_uploads.py
fetches via the GET endpoint, writes to /workspace/.molecule/chat-
uploads/, acks, and rewrites the URI from platform-pending: → workspace:
so the agent's existing send-attachments path needs no changes.
Phase 3: GC sweep + dashboards. Phase 4: poll-mode E2E on staging.
Tests:
* 100% coverage on pendinguploads (sqlmock-pinned SQL drift gate).
* Functional 100% on new handler code (uncovered branches are
documented defensive duplicates: uuid re-parse, multipart Open
error, Writer.Write fail — none reproducible in unit tests).
* Push-mode + NULL delivery_mode regression tests pin no behavior
change for existing workspaces.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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