Mirrors PR-C's Upload migration: replaces the docker-cp tar-stream
extraction with a streaming HTTP GET to the workspace's own
/internal/file/read endpoint. Closes the SaaS gap for downloads —
without this PR, GET /workspaces/:id/chat/download still returns 503
on Railway-hosted SaaS even after A+B+C+F land.
Stacks: PR-A #2313 → PR-B #2314 → PR-C #2315 → PR-F #2319 → this PR.
Why a single broad /internal/file/read instead of /internal/chat/download:
Today's chat_files.go::Download already accepts paths under any of the
four allowed roots {/configs, /workspace, /home, /plugins} — it's not
strictly chat. Future PRs (template export, etc.) will reuse this
endpoint via the same forward pattern; reusing avoids three near-
identical handlers (one per domain) with duplicated path-safety logic.
Path safety is duplicated on platform + workspace sides — defence in
depth via two parallel checks, not "trust the workspace."
Changes:
* workspace/internal_file_read.py — Starlette handler. Validates path
(must be absolute, under allowed roots, no traversal, canonicalises
cleanly). lstat (not stat) so a symlink at the path doesn't redirect
the read. Streams via FileResponse (no buffering). Mirrors Go's
contentDispositionAttachment for Content-Disposition header.
* workspace/main.py — registers GET /internal/file/read alongside the
POST /internal/chat/uploads/ingest from PR-B.
* scripts/build_runtime_package.py — adds internal_file_read to
TOP_LEVEL_MODULES so the publish-runtime cascade rewrites its
imports correctly. Also includes the PR-B additions
(internal_chat_uploads, platform_inbound_auth) since this branch
was rooted before PR-B's drift-gate fix; merge-clean alphabetic
additions.
* workspace-server/internal/handlers/chat_files.go — Download
rewritten as streaming HTTP GET forward. Resolves workspace URL +
platform_inbound_secret (same shape as Upload), builds GET request
with path query param, propagates response headers (Content-Type /
Content-Length / Content-Disposition) + body. Drops archive/tar
+ mime imports (no longer needed). Drops Docker-exec branch entirely
— Download is now uniform across self-hosted Docker and SaaS EC2.
* workspace-server/internal/handlers/chat_files_test.go — replaces
TestChatDownload_DockerUnavailable (stale post-rewrite) with 4
new tests:
- TestChatDownload_WorkspaceNotInDB → 404 on missing row
- TestChatDownload_NoInboundSecret → 503 on NULL column
(with RFC #2312 detail in body)
- TestChatDownload_ForwardsToWorkspace_HappyPath → forward shape
(auth header, GET method, /internal/file/read path) + headers
propagated + body byte-for-byte
- TestChatDownload_404FromWorkspacePropagated → 404 from
workspace propagates (NOT remapped to 500)
Existing TestChatDownload_InvalidPath path-safety tests preserved.
* workspace/tests/test_internal_file_read.py — 21 tests covering
_validate_path matrix (absolute, allowed roots, traversal, double-
slash, exact-match-on-root), 401 on missing/wrong/no-secret-file
bearer, 400 on missing path/outside-root/traversal, 404 on missing
file, happy-path streaming with correct Content-Type +
Content-Disposition, special-char escaping in Content-Disposition,
symlink-redirect-rejection (lstat-not-stat protection).
Test results:
* go test ./internal/handlers/ ./internal/wsauth/ — green
* pytest workspace/tests/ — 1292 passed (was 1272 before PR-D)
Refs #2312 (parent RFC), #2308 (chat upload+download 503 incident).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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