feat(cli): make sdk-config authoritative for generation

[bears4barrett]

Description

Makes sdk-config.yml authoritative when generating SDKs with fern generate --sdk-config.

Changes

• Builds API workspaces directly from SDK Config sources and targets.
• Avoids loading or validating generators.yml when --sdk-config is provided.
• Supports OpenAPI, AsyncAPI, and GraphQL sources.
• Propagates SDK Config package and output settings through sdk-gen-api.
• Rejects --group with --sdk-config, since SDK Config targets are authoritative.
• Updates fern sdk migrate to omit generatorVersion, allowing targets to use the latest supported generator.
• Removes the obsolete logic that matched SDK Config targets against generators.yml groups.

Backwards compatibility

Generation without --sdk-config continues through the existing generators.yml path unchanged.

Hand-authored generatorVersion values remain supported as exact pins. When omitted, the CLI resolves the latest supported generator during generation.

Testing

• Added SDK Config workspace construction coverage.
• Added project-loading coverage without generators.yml.
• Added remote request package and output propagation coverage.
• Updated migration unit and end-to-end tests to verify generatorVersion is omitted.

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[nitpickybot]

AI Review Summary

This PR makes sdk-config.yml authoritative for fern generate --sdk-config, replacing generators.yml group matching with an in-memory OSSWorkspace built from SDK Config sources/targets. Overall the approach is coherent, but the removal of validateSdkConfigImportSettings drops a validation path, and a few details in createSdkConfigWorkspace (temp file extension for remote specs, silently dropping extra overlays vs. failing, output path handling) deserve a second look.

• 🟡 2 warning(s)
• 🔵 2 suggestion(s)

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AI Review

🔵 suggestion — packages/cli/cli/src/commands/generate/createSdkConfigWorkspace.ts (line 160)

Failing hard when a source declares more than one overlay is fine, but the surrounding code then silently uses only overlays[0]. Since a single overlay is supported and >1 throws, the intent is clear — just note that any future schema change allowing multiple overlays will hit this hard error at generation time rather than at config parse time. Consider surfacing this constraint in the SDK Config schema validation instead, so users learn about it before running generation.

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This review is complete for the current scope. Addressing all critical and warning findings above satisfies the review; suggestions are optional. Request another review only if subsequent changes introduce new behavior or materially expand the pull request's scope.

[devin-ai-integration]

Devin Review found 5 potential issues.

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[github-actions]

Docs Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-09-16T04:06:27Z).

Fixture	main	PR	Delta
docs	268.5s (n=5)	196.9s (35 versions)	-71.6s (-26.7%)

Docs generation runs fern generate --docs --preview end-to-end against the benchmark fixture with 35 API versions (each version: markdown processing + OpenAPI-to-IR + FDR upload).
Delta is computed against the nightly baseline on main.
Baseline from nightly run(s) on main (latest: 2026-09-16T04:06:27Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-09-16 16:29 UTC

[github-actions]

SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-09-16T04:06:27Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
csharp-sdk	square	95s (n=5)	113s (n=5)	79s	-16s (-16.8%)
go-sdk	square	134s (n=5)	295s (n=5)	147s	+13s (+9.7%)
java-sdk	square	221s (n=5)	272s (n=5)	199s	-22s (-10.0%)
php-sdk	square	78s (n=5)	N/A	56s	-22s (-28.2%)
python-sdk	square	157s (n=5)	252s (n=5)	157s	+0s (+0.0%)
ruby-sdk-v2	square	102s (n=5)	148s (n=5)	111s	+9s (+8.8%)
rust-sdk	square	181s (n=5)	208s (n=5)	150s	-31s (-17.1%)
swift-sdk	square	58s (n=5)	435s (n=5)	54s	-4s (-6.9%)
ts-sdk	square	170s (n=5)	167s (n=5)	134s	-36s (-21.2%)

main (generator): generator-only time via --skip-scripts (includes Docker image build, container startup, IR parsing, and code generation — this is the same Docker-based flow customers use via fern generate). main (E2E): full customer-observable time including build/test scripts (nightly baseline, informational). Delta is computed against generator-only baseline.
⚠️ = generation exited with a non-zero exit code (timing may not reflect a successful run).
Baseline from nightly runs on main (latest: 2026-09-16T04:06:27Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-09-16 16:31 UTC