Symptom: pasting a screenshot into the canvas chat for a runtime="external"
workspace returned `503 {"error":"workspace container not running"}` —
accurate from the upload handler's POV (no container exists for external
workspaces) but misleading because it implies the container has crashed.
Fix: detect runtime="external" via DB lookup BEFORE the container-find
step and return 422 with:
- error: "file upload not supported for external workspaces"
- detail: explains why + points at admin/secrets workaround +
references issue #2308 for the v0.2 native-support roadmap
- runtime: "external" (machine-readable for clients)
Why 422 not 200/501:
- 422 = Unprocessable Entity — the request is well-formed but the
workspace's runtime can't accept it. Standard REST semantics.
- 200 with empty result would lie; 501 implies the API itself is
unimplemented (it's not — works for non-external workspaces); 503
was the misleading status this PR fixes.
Verified via live E2E against localhost:
- Created `runtime=external,external=true` workspace
- Posted multipart to /workspaces/:id/chat/uploads
- Got 422 with the expected structured body
Unit test (`chat_files_external_test.go`) pins the contract via sqlmock
+ httptest. Notable: the handler is constructed with `templates: nil`
to prove the runtime check happens BEFORE any docker plumbing — if a
future change moves the check below findContainer, the test crashes
on nil-deref instead of silently regressing.
Out of scope (for v0.2 follow-up):
- Native external-workspace file ingest via artifacts table or the
channel-plugin's inbox/ pattern. Requires separate design pass.
Closes#2308
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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