LibreChat/api/server
Danny Avila 20cd00c492
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🖼️ feat: Return Sandbox Images From read_file as Viewable Artifacts (#14277)
* 🖼️ feat: Return Sandbox Images From `read_file` as Viewable Artifacts

The code-execution sandbox `read_file` path refused every image
extension because it reads files via `cat` over codeapi's JSON `/exec`
transport, which lossily corrupts non-UTF-8 bytes. The skill-file read
path already surfaced images as artifacts; this brings the sandbox path
to parity so an agent can actually see a chart/screenshot it reads.

- `readSandboxImage` (process.js): a Python base64 reader over `/exec`
  with an in-sandbox size guard so oversize images never cross the wire;
  base64 is ASCII-safe where `cat` corrupts.
- `handleSandboxImageRead` (handlers.ts): byte-integrity check (guards
  against a truncated `/exec` stdout), MIME resolved purely from the
  magic-byte sniff (extension only routes; a mislabeled non-image falls
  back to the bash hint), and graceful degradation on every failure mode.
- Shared `buildImageArtifactResult` used by both read paths; the result's
  `artifact.content` image_url reaches the UI (tool-end callbacks save it
  as an attachment) and the LLM (SDK folds it into the model-visible
  message for Anthropic/OpenAI/Google).

*  test: Sync read_file code-only description assertions with image wording

* 🛡️ fix: Harden sandbox image reads (regular-file guard, completeness check)

Addresses Codex review on PR #14277:

- readSandboxImage now os.stat's the target and rejects non-regular files
  (FIFOs, sockets, /dev/* symlinks) via stat.S_ISREG, and bounds the read at
  limit+1 bytes — a device/FIFO can no longer stream unbounded into memory
  until the request times out.
- handleSandboxImageRead validates completeness (not just the magic header):
  PNG must end with the IEND trailer and WebP's RIFF size must match the byte
  length, so a truncated/interrupted image degrades to the bash hint instead
  of being sent as a corrupt image_url. JPEG/GIF stay header-level (they can
  carry trailing metadata; a strict end-marker would risk false rejections).

* 🩹 fix: Chunk sandbox image reads to fit the runner stdout cap

Inlining any real image failed with "is an image file (.png) and cannot
be read as text". Root cause: readSandboxImage base64-encodes the file to
STDOUT, but the runner caps stdout at SANDBOX_OUTPUT_MAX_SIZE (1024 bytes
by default) and SIGKILLs the job on overflow (status OL), truncating the
JSON mid-base64. The parse then threw and the handler degraded to the
binary hint. The in-sandbox MAX_BINARY_BYTES=5MB guard never fired because
the *transport*, not the file size, is the real ceiling: a 5MB image needs
~6.8MB of stdout. Reproduced against a live MicroVM — a 186KB matplotlib
PNG died with 'stdout length exceeded' at exactly the 65536-byte cap.

Read the file in windows instead: each /exec pulls  raw bytes at an
offset and base64s only that slice, so every response stays under the cap
regardless of how the runner is configured; the chunks are reassembled and
verified against the sandbox-reported total. Verified end-to-end on a real
MicroVM: 25KB and 186KB PNGs both round-trip byte-exact (sha256 match).

Also:
- Detect the truncation explicitly (status OL) and name the fixable cause
  (chunk size / SANDBOX_OUTPUT_MAX_SIZE) instead of "unexpected output".
- Parse the LAST stdout line so a shell banner can't break the read, and
  include a stdout snippet when it genuinely is unparseable.
- LIBRECHAT_CODE_IMAGE_CHUNK_BYTES (default 32KB) tunes the window.
- Tests drive the real reader against a mocked /exec transport rather than
  mocking readSandboxImage, which is why the existing suite stayed green
  through this bug.

* 🎯 fix: Cap sandbox inline images at 1MB, separate from skill-file reads

The sandbox and skill-file image paths shared MAX_BINARY_BYTES (5MB), but
their transports differ: skill files stream from storage, while sandbox
bytes come back base64 over /exec stdout under the runner's output cap, so
the reader windows the file and cost scales in round-trips (~160 at 5MB vs
~32 at 1MB). Nothing is gained by allowing more — vision providers
downsample to ~1.5-2k px regardless, so multi-MB originals buy no fidelity
while grinding through round-trips.

Give the sandbox path its own MAX_SANDBOX_INLINE_IMAGE_BYTES (1MB), used
for both the read cap and the over-limit message (which previously quoted
5MB while the reader enforced something else). Skill-file reads keep 5MB.

Verified against a live MicroVM: a 186KB PNG round-trips byte-exact, and a
1.4MB file returns tooLarge in a single round-trip with zero bytes
transferred, degrading to the existing bash_tool hint.
2026-07-16 07:27:33 -04:00
..
controllers 🙊 refactor: Clarify Ask Question Schema Errors and Retry Guidance (#14279) 2026-07-15 11:06:29 -04:00
middleware 💂 fix: Enforce ALLOW_EMAIL_LOGIN on the Backend Login Route (#14180) 2026-07-09 09:55:36 -04:00
routes 🧭 feat: Mid-Run Steering and Queued Messages for Agent Runs (#14220) 2026-07-14 10:11:10 -04:00
services 🖼️ feat: Return Sandbox Images From read_file as Viewable Artifacts (#14277) 2026-07-16 07:27:33 -04:00
utils 🔄 feat: Continue Shared Conversations as Personal Copies (#13714) 2026-06-24 16:27:01 -04:00
cleanup.js 🧹 refactor: Tighten Config Schema Typing and Remove Deprecated Fields (#12452) 2026-03-29 01:10:57 -04:00
experimental.js 🧹 feat: Eager HITL Checkpoint Cleanup (Expiry + Deletion) & Full-Wiring E2E (#14123) 2026-07-05 11:29:30 -04:00
index.js 🧹 feat: Eager HITL Checkpoint Cleanup (Expiry + Deletion) & Full-Wiring E2E (#14123) 2026-07-05 11:29:30 -04:00
index.metrics.spec.js ⚖️ feat: Add Operational Prometheus Metrics (#13265) 2026-05-22 20:47:41 -04:00
index.spec.js ⚙️ refactor: lazy-load React Query Devtools (#13639) 2026-06-10 13:06:20 -04:00
socialLogins.js feat: Make OpenID Token Reuse Window Configurable (#13546) 2026-06-06 15:15:58 -04:00
socialLogins.spec.js feat: Make OpenID Token Reuse Window Configurable (#13546) 2026-06-06 15:15:58 -04:00
telemetry.js 📡 feat: Add Backend OpenTelemetry Tracing (#12909) 2026-05-14 09:08:55 -04:00
telemetry.spec.js 📡 feat: Add Backend OpenTelemetry Tracing (#12909) 2026-05-14 09:08:55 -04:00