feat: add Infron as an open_code gateway provider

[meridah7]

Summary

• What changed: Adds Infron as an open_code gateway provider. Infron is an OpenAI-compatible inference gateway serving the standard <provider>/<model> ids, so wiring it in is a base-URL change rather than a model-mapping exercise: infron/moonshotai/kimi-k2.6 routes the same model the bare id names, and nothing else in a deployment moves.
• Why it changed: It gives deployers a second open-model gateway behind the exact same resolution rules, so switching (or A/B-ing) is an env-var change instead of a fork.

Disclosure: I work on Infron. Everything below is checkable from the diff and the commands under Validation.

File	Change
docker/opencode.json	New. The OpenCode provider block moves out of the two Dockerfiles into one shared file both images COPY, so they cannot drift apart. Declares infron (@ai-sdk/openai-compatible) next to the existing provider.
Dockerfile, go/Dockerfile	Replace the inlined echo '{...}' config with COPY docker/opencode.json.
swe_af/execution/schemas.py	_infron_only_env() + _INFRON_AUTO_DEFAULT_MODEL, following the existing gateway path through _default_runtime, _default_planning_model, and resolve_runtime_models.
go/internal/config/resolve.go	Same, for the Go port (infronOnlyEnv, infronAutoDefaultModel).
agentfield-package.yaml, go/agentfield-package.yaml	INFRON_API_KEY offered as a third llm_provider option.
.env.example, README.md	Document the prefix swap and the auto-select rule.
tests/test_model_config.py, tests/test_dockerfile.py, go/internal/config/config_test.go	Coverage for the new path and for the shared-config invariant.

Behavior

With only an INFRON_API_KEY set (no ANTHROPIC_API_KEY, no other gateway key, no SWE_DEFAULT_RUNTIME), SWE-AF auto-selects the open_code runtime and defaults to infron/deepseek/deepseek-v4-flash — the same rule the existing gateway path already follows, with the prefix swapped.

A gateway key that was already honored before Infron existed keeps precedence. Adding an Infron key never silently reroutes an existing deployment; moving traffic across is an explicit act (drop the other key, or set SWE_DEFAULT_MODEL=infron/...). A provider with no key set is never selected, so shipping both in the image costs nothing at runtime.

Validation

Rebased on main at 7a8dba0 and re-run today.

• make check — python -m pytest tests/ -q: 1154 passed, 1 skipped, 0 failed, plus python -m compileall -q swe_af/ clean
  (note for anyone reproducing: tests/conftest.py requires AGENTFIELD_SERVER to be set to a local address, e.g. AGENTFIELD_SERVER=http://localhost:9999, or every test errors at fixture setup)
• cd go && go test ./... — 27 packages ok, 0 failures (Go 1.23.4)
• cd go && go build ./... clean; gofmt -l internal/config/ clean
• The 81 tests covering this change specifically (tests/test_model_config.py, tests/test_dockerfile.py) pass, including test_both_dockerfiles_share_one_opencode_config, which pins the new shared-config invariant.
• Live smoke test against the gateway: moonshotai/kimi-k2.6, minimax/minimax-m2.5 and z-ai/glm-5.2 over https://llm.onerouter.pro/v1 return well-formed completions with usage accounting, on both the sync and the streaming path, under the same ids already used in the image.

Behavior Impact

• No behavior change — every new path is gated on INFRON_API_KEY being the only gateway key present, and an existing key wins ties.

Notes

• The docker/opencode.json extraction is the one structural change. It was the cleanest way to avoid a ~900-character echo line and to stop the Python and Go images from drifting; test_both_dockerfiles_share_one_opencode_config now pins that. Happy to inline it back into both Dockerfiles if you would rather keep the diff to a single mechanism.
• @ai-sdk/openai-compatible providers are not in models.dev, so the model list has to be explicit. I listed the eight open-weight models SWE-AF realistically uses (Kimi K2.6 / K2.7-Code / K3, DeepSeek V4 Flash/Pro, MiniMax M2.5/M3, GLM-5.2). Easy to extend.
• Companion PR on the SDK side, which is what makes infron/... work for AgentField apps generally: feat(sdk/go/ai): support the Infron gateway agentfield#874. The two are independent; either can land alone.
• Happy to follow up with a joint benchmark on SWE-AF's own workload (same model, both gateways, cost + cache + latency side by side) if that is useful for the docs.

[CLAassistant]

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