feat(providers): resolve LinkCode Gateway as a Codex-native endpoint

[xiaoland]

Client half of CODE-603. The server half is arcboxlabs/linkcodehq#50.

LinkCode Cloud now serves POST /v1/responses at the same base URL, so the LinkCode Gateway
service gains an openai-responses variant and Codex resolves it as native instead of
reporting an incompatible protocol.

Codex ≥ 0.122 rejects wire_api = "chat" outright, so this variant is the only thing standing
between Codex and the Gateway; nothing else in the client hard-codes chat-only for this service,
since the settings incompatibility notice derives from resolveBinding.

Verification

• resolve regression test flipped from unavailable / protocol-unsupported to
  native / openai-responses; 26 tests in the providers package pass, Biome clean.
• End to end with the real Codex binary this repo pins (@openai/codex 0.144.6) against the
  server branch: a completed turn on openai/gpt-5.3-codex, and a full tool round trip on
  anthropic/claude-sonnet-5 — Claude called exec_command, Codex executed it, Claude
  summarized the output.

Note

The server serves Responses for 46 of the 75 catalog models, while /v1/models still advertises
all of them, so the model picker can offer a model that returns 404 model_not_found for Codex.
That is tracked in CODE-620 and needs a client-side decision as well as the server field.

[linear-code]

CODE-603

[Copilot]

Pull request overview

Enables the LinkCode Gateway service to be resolved as a Codex-native endpoint by adding an openai-responses variant, aligning the client-side provider catalog with the Gateway now serving POST /v1/responses at the same base URL. This updates the provider resolution logic outcome (via catalog data) so Codex no longer reports an incompatible protocol for LinkCode Gateway.

Changes:

• Add an openai-responses protocol variant for the linkcode-gateway service in the provider catalog.
• Update the resolveBinding regression test to expect Codex to resolve LinkCode Gateway as native using openai-responses.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/foundation/providers/src/catalog.ts	Adds the openai-responses variant for LinkCode Gateway at the same /v1 base URL so Codex can bind natively.
packages/foundation/providers/src/tests/resolve.test.ts	Updates expectations to verify Codex resolves LinkCode Gateway as native / openai-responses while other agents continue to use the appropriate wire.

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[greptile-apps]

Greptile Summary

Adds an OpenAI Responses variant to LinkCode Gateway so Codex can resolve it as a native endpoint.

• Keeps the existing OpenAI Chat variant for other supported agents.
• Updates resolver coverage to assert each agent’s expected protocol and Codex’s native Gateway binding.

Confidence Score: 5/5

The PR appears safe to merge, with no unacknowledged blocking or independently actionable issues identified.

The new catalog variant is selected only for Codex, existing agents retain their prior bindings, and legacy catalog-derived endpoints remain eligible for per-agent resolution.

Important Files Changed

Filename	Overview
packages/foundation/providers/src/catalog.ts	Adds the Gateway’s OpenAI Responses capability at the existing base URL without changing sibling-agent protocol precedence.
packages/foundation/providers/src/tests/resolve.test.ts	Updates LinkCode Gateway resolution coverage to verify Codex uses OpenAI Responses while existing agents retain OpenAI Chat behavior.

_{Reviews (1): Last reviewed commit: "feat(providers): resolve LinkCode Gatewa..." | Re-trigger Greptile}