Pre-fix WriteFile (templates.go:436) had an `instance_id != ""` branch
that dispatched to writeFileViaEIC (SSH through EC2 Instance Connect),
but ReadFile (templates.go:362) skipped that branch entirely. ReadFile
always tried `findContainer` (which only works for local-Docker
workspaces, not SaaS EC2-per-workspace ones) and fell through to
`resolveTemplateDir` (which returns the seed template, not the
persisted workspace state).
Net effect on production: every Canvas Config tab open against a
SaaS workspace returned 404 "No config.yaml found" because GET
couldn't see what PUT had written. Visible to users after PR #2781
("show-misconfigured-state") surfaced the 404 as an error UX.
Caught by the synth-E2E 7c gate's GET-back assertion, but
misdiagnosed as a "test bug" and the GET assertion was dropped in
PR #2783 (rather than fixed at the source). This PR closes the loop:
1. New `readFileViaEIC` helper in template_files_eic.go that mirrors
writeFileViaEIC's SSH-via-EIC dance and runs `sudo -n cat <path>`.
Returns os.ErrNotExist on missing file (cat exits 1 with empty
stdout under `2>/dev/null`) so the handler maps it cleanly to 404.
2. ReadFile dispatch now mirrors WriteFile's: when `instance_id` is
non-empty, use readFileViaEIC; otherwise fall through to the
local-Docker / template-dir path.
3. ReadFile's DB query expanded to also select instance_id + runtime
(was just name). Three sqlmock-based tests updated to match the
new column shape; the existing local-Docker fallback path stays
green by passing instance_id="" in the mock rows.
Follow-up (separate PR): the synth-E2E 7c gate should restore the
GET-back marker assertion now that the read/write paths are unified.
That'll also catch any future Files API regression in the round-trip.
This PR doesn't touch the gate to keep the scope tight.
Verification:
- go build ./... clean
- full handlers test suite green (0.4s for ReadFile subset; 5.8s
full)
- The 3 ReadFile sqlmock tests still cover the local-Docker fallback
(instance_id=""); SaaS EIC dispatch is covered by the upcoming
re-enabled synth-E2E 7c GET assertion (deferred to follow-up)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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