fix: encode Responses image and file inputs as wire shapes, not IR enums - #530
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WalkthroughThe Responses codec now converts image and file sources into valid ChangesResponses media translation
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: ⚪ Minimal · up to The change corrects Responses image and file request encoding, with the reported regression tests and workspace checks passing. No actionable merge-blocking risk remains; adding documentation for the crate-visible helpers is a small maintainability follow-up. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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In `@crates/switchyard-translation/src/codecs/openai_chat/buffered.rs`:
- Line 1054: Add doc comments to the crate-visible helper functions
openai_image_part, openai_file_part, and the additional helpers at the
referenced locations, describing each conversion or fallback behavior;
explicitly document that openai_image_part and openai_file_part return None for
unmappable sources.
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crates/switchyard-translation/src/codecs/openai_chat/buffered.rscrates/switchyard-translation/src/codecs/openai_chat/mod.rscrates/switchyard-translation/src/codecs/responses/buffered.rscrates/switchyard-translation/tests/request_translation.rs
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@shoemoney Thanks for putting up the PR. I would highly appreciate a humanly written PR description which I can consume better and do a proper review. |
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Fixed in 302bf87: input_file now flattens file_id/file_data/filename to the top level instead of nesting under "file", and the request_translation.rs assertion is updated to match. |
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Added doc comments to openai_image_part, image_source_text, openai_file_part, and file_source_text in a2804eb. |
The Responses wire carries an `input_file` payload directly on the content block, while OpenAI Chat nests it under a `file` object. `decode_file_source` handled the nested shape for both `file_id` and `file_data`, but on the flat shape it read only `file_id` -- a flat `file_data` fell through to `FileSource::Raw`. That is not a cosmetic loss. Chat's raw file encoder maps only Anthropic `document` blocks and returns `None` for anything else, so the fallback drops the block: a Responses request carrying base64 file content loses the file entirely on the way to a Chat backend, silently and with no diagnostic. Read a direct `file_data`/`filename` pair as `FileSource::FileData`. A Chat block cannot reach that branch, having matched the nested one above, so the existing shapes decode unchanged. Scoped to the decode path only. The encoder side of Responses image and file content is fixed separately in NVIDIA-NeMo#530, which explicitly left this case out. Signed-off-by: Oleksandr Pronin <pronin.alx@gmail.com>
The Responses wire carries an `input_file` payload directly on the content block, while OpenAI Chat nests it under a `file` object. `decode_file_source` handled the nested shape for both `file_id` and `file_data`, but on the flat shape it read only `file_id` -- a flat `file_data` fell through to `FileSource::Raw`. That is not a cosmetic loss. Chat's raw file encoder maps only Anthropic `document` blocks and returns `None` for anything else, so the fallback drops the block: a Responses request carrying base64 file content loses the file entirely on the way to a Chat backend, silently and with no diagnostic. Read a direct `file_data`/`filename` pair as `FileSource::FileData`. A Chat block cannot reach that branch, having matched the nested one above, so the existing shapes decode unchanged. Scoped to the decode path only. The encoder side of Responses image and file content is fixed separately in #530, which explicitly left this case out. Signed-off-by: Oleksandr Pronin <pronin.alx@gmail.com>
Brings the deploy line to 4022b67, 11 commits after the 2026-09-01 sync. Included is bb011ca (NVIDIA-NeMo#590), our own flat input_file decode fix, which is now upstream's code rather than a local carry. One conflict, in crates/switchyard-translation/tests/request_translation.rs, and both sides of it are ours: this branch carries the three Responses-image encode tests from the local encode fix (upstream NVIDIA-NeMo#530, still open, supersedes that work), while origin/main now carries NVIDIA-NeMo#590's decode test. They were appended at the same point in the file and test different directions of the codec, so both sets are kept -- 58 tests in that binary, 53 from the merge base plus 3 ours plus 2 upstream's. The config loader conflict this merge line usually produces did not recur: responses_reasoning, responses_tool_images and the base_instructions override all survived unchanged. cargo build / test / fmt / clippy: 705 passed, 0 failed, fmt clean, clippy 0.
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@ayushag-nv Circling back on the description you asked about — I found it had gone stale against the code and I've rewritten it. Specifically: the No code changed with this; it's the description only. The three checks on the head commit (DCO, Validate PR title, CodeRabbit) are green. If you see a red "Commitlint" run, that workflow is failing at startup on every branch in the repo right now, including your own internal ones — not something from this PR. |
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@grahamking I tested the before and after here against OpenAI. The old image shape gets a 400 because image_url is an object, while the corrected shape succeeds. The old nested file shape also gets a 400, while the flat file fields in this PR succeed. The bug and the proposed wire format both check out. Right now the Responses encoder takes the ImageSource/FileSource IR, builds Chat JSON with the existing helpers, then reshapes it into Responses JSON. That reuses the base64 and raw-source handling, but couples Responses to the Chat shape and copies the full inline payload. We could encode directly from the IR instead. That matches the other codec paths and avoids the extra copy, but repeats some source-mapping logic. I am leaning that way, but wanted your take before asking the contributor to change it. |
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Thank for for the contribution @shoemoney. The team is discussing the design question raised by @afourniernv and we hope to get back with an answer next week! |
The Responses request encoder splatted ImageSource and FileSource into
input_image and input_file blocks verbatim. Both enums are adjacently
tagged (serde tag = "type", content = "data"), so a Chat client image
{"type":"image_url","image_url":{"url":...,"detail":"high"}} came out as
{"type":"input_image","image_url":{"type":"url","data":{...}}}. OpenAI's
/v1/responses requires image_url to be a string and rejects the request
with 400. FileSource::FileId became {"file":{"type":"file_id","data":...}},
a shape even this repo's own decode_file_source cannot read back, so
chained Switchyard hops broke too.
Reuse the Chat mappings (openai_image_part, openai_file_part) and lift
them into the flat Responses layout: image_url as a plain string or data
URI with an optional detail field, and file parts keyed under "file"
exactly as decode_file_source expects. Unmappable sources fall back to
text with a lossy diagnostic, matching the Chat encoder.
Sibling precedent: PR NVIDIA-NeMo#470 (merged 2026-08-20, fixes NVIDIA-NeMo#468) gave the
Anthropic buffered encoder exactly this treatment, data-URI/base64
mapping for image sources, and openai_chat/buffered.rs has always mapped
the enum properly via openai_image_part; the Responses encoder twin
never got either fix.
Signed-off-by: Jeremy Schoemaker <jeremy@shoemoney.com>
responses_file_part renamed the Chat file part's type to input_file but
left the file payload nested under a "file" key, matching neither of
OpenAI's /v1/responses input_file shapes ({"type":"input_file",
"file_id":...} or {"type":"input_file","file_data":...,"filename":...}),
so the server rejected the request with 400.
Lift the fields from the Chat mapping to the top level instead of
renaming the type in place. Updates the file-part assertion in
request_translation.rs to the flattened shape; the image-part assertion
was already correct.
Signed-off-by: Jeremy Schoemaker <jeremy@shoemoney.com>
Documents openai_image_part, image_source_text, openai_file_part, and file_source_text now that the Responses encoder re-exports and calls them; notes that the two mapping functions return None for unmappable sources and fall back to the two text functions. Signed-off-by: Jeremy Schoemaker <jeremy@shoemoney.com>
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Force-push is a rebase onto |
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@shoemoney I dug through the codec paths again and I think we should change this before landing. We share decode helpers today, but this would be the only encoder that builds another codec's wire shape and then reads it back. Can we pull out just the common image/file payload, then let Chat and Responses build their own content blocks? That keeps the raw-source handling shared and avoids copying large inline payloads. |
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@shoemoney I think the overall fix is correct. What makes me nervous is that no other encoder builds another codec’s wire shape and then reads it back, which is why I asked Graham to take a look. |
Signed-off-by: Alex Fournier <afournier@nvidia.com>
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@shoemoney I pushed the small refactor we discussed. The shared image/file mapping is now private common code, and Chat and Responses each build their own output shape. I also added the Anthropic document case to the existing test. Workspace tests and clippy pass locally. |
Signed-off-by: Alex Fournier <afournier@nvidia.com>
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Tested this through switchyard-server against OpenAI Responses in both buffered and streaming modes. I also checked the file shape through the codec and a local HTTP capture. Looks good.
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✅ Action performedComments resolved. Approval is disabled; enable |
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@shoemoney applied the boundary fix. Ty for your contribution! |
129 commits, 2026-09-04..2026-09-21. Every conflict was this branch's own work meeting upstream's version of the same idea, so the merge was four decisions across 32 hunks rather than 32 edits. Retired, because upstream now does the job: base_instructions and vision were one hunk, not two -- both are arguments to codex_model_entry_json, and NVIDIA-NeMo#693 deleted that function in favour of serving "models": []. Keeping either meant keeping the whole catalog. Checked before deciding rather than after: the 20,903-byte file the deployment serves is Codex's OWN prompt, and 17 long lines sampled across it are all present in the codex 0.155.1 binary. Upstream's empty catalog makes Codex fall back to that same text, so this is behaviour-preserving. vision survives differently -- NVIDIA-NeMo#750 turns the route capability into a rejection gate, which is what the carry wanted, and images still flow because default_input_modalities is [Text, Image]. extra_body_override is superseded by NVIDIA-NeMo#666, whose commit message describes the exact bug the carry was written for: extra_body only fills keys the caller left out. All three live uses in routes.toml are reasoning.effort and nothing else, so NVIDIA-NeMo#666 covers 100% of them -- and it is better, knowing the wire-specific key per format and rejecting the setting on Anthropic clients. 53ab915's Responses image/file encoding is superseded by NVIDIA-NeMo#530, the retirement AGENTS.md said would come due when it landed. Kept, ported to their new homes: the three responses_* policies (reasoning, tool_images, custom_tools) and the custom classifier verdict logging, which now sits inside NVIDIA-NeMo#630's Category rewrite -- routed=false there covers three causes it did not before, so the verdict text beside it is what tells them apart. config.rs and server/lib.rs were taken from upstream wholesale and the kept features re-applied at their new homes, per AGENTS.md; resolving them hunk-wise left dead machinery behind that compiled fine and served nothing. Proven byte-level, not by a green suite: git diff against origin/main returns 0 lines for vision, base_instructions and codex_model_entry_json, and 1 for extra_body_override -- a comment recording where the test came from. Divergence is now 1,248 insertions and 12 deletions, essentially three self-contained modules plus their tests, where before it reached into the config loader, the server, the route and the client backend. 880 tests pass. The e2e test written against extra_body_override before this merge now runs against reasoning_effort, asserting exactly what it did: the target's value beats the caller's and sibling keys survive. The carry was retired; the behaviour was not. One loss, accepted: /v1/decision no longer reports the per-target override, because upstream's DecisionTarget does not carry it.
4 participants
What
Fix the OpenAI Responses request encoder so image and file content uses Responses wire shapes instead of serialized protocol enums.
Why
A Chat image routed to an OpenAI Responses backend was encoded with an object under image_url. The Responses API requires a string there and rejected the request with a 400. Files had the same underlying problem: the encoder serialized Switchyard protocol enums instead of the flat Responses wire format.
Same-format round trips usually replay the preserved request, so they did not expose this. Fresh Chat-to-Responses and Anthropic-to-Responses translations did.
How tested
API impact
No public Rust or Python API changes. The observable change is limited to correcting invalid Responses request bodies.
Checklist