feat(go): read idempotency-key generation config from the IR

[devin-ai-integration]

Description

Linear ticket: N/A

Read centralized sdkConfig.idempotencyKeyGeneration from the IR instead of a Go generator-specific config flag. The generated Go behavior is unchanged: eligible methods receive a UUIDv4 fallback only when the caller did not provide the configured header.

Changes Made

• Gate the UUID helper and endpoint injection from the IR's configured header name and method list.
• Bring in the synthetic-invocation config fallback so seed threads the CLI-only auto-generate-idempotency-key key into the IR.
• Upgrade the Go v2 packages to @fern-fern/ir-sdk 67.11.0 and regenerate the opt-in idempotency fixture.
• Updated README.md generator (if applicable)

Testing

• Unit tests added/updated
• Manual testing completed
• pnpm turbo run compile test --filter @fern-api/go-sdk --filter @fern-api/api-workspace-commons
• go test ./... in generators/go
• pnpm seed test --generator go-sdk --fixture idempotency-headers --local --skip-scripts --parallel 1
• go test ./... in both regenerated idempotency fixture outputs
• pnpm check

Link to Devin session: https://app.devin.ai/sessions/315ea45e9da84294a994c0e162b4eec6
Requested by: @cadesark

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[devin-ai-integration]

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[nitpickybot]

AI Review Summary

Ports the TS auto-generate idempotency key feature to the Go v2 SDK generator. The implementation is clean and the caller-wins precedence logic is sound. One concern: the injected key isn't captured before retries, and there's a minor consideration about idempotency semantics on PUT.

• 🔵 1 suggestion(s)

[nitpickybot]

🔵 suggestion

The Idempotency-Key is set once on the headers bag before the request is issued, then reused across retries via the retrier (which replays the same *http.Request). That's correct — retries keep the same key, which is exactly what you want for idempotency. Just confirm the retrier doesn't rebuild the request per-attempt (from caller.go it reuses req, so this holds). No change needed, flagging for reviewer awareness.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 1 additional finding.

[github-actions]

SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-07-13T05:08:13Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
csharp-sdk	square	76s (n=5)	115s (n=5)	64s	-12s (-15.8%)
go-sdk	square	139s (n=5)	285s (n=5)	131s	-8s (-5.8%)
java-sdk	square	226s (n=5)	267s (n=5)	234s	+8s (+3.5%)
php-sdk	square	61s (n=5)	85s (n=5)	49s	-12s (-19.7%)
python-sdk	square	135s (n=5)	241s (n=5)	129s	-6s (-4.4%)
ruby-sdk-v2	square	94s (n=5)	124s (n=5)	83s	-11s (-11.7%)
rust-sdk	square	169s (n=5)	176s (n=5)	159s	-10s (-5.9%)
swift-sdk	square	58s (n=5)	433s (n=5)	51s	-7s (-12.1%)
ts-sdk	square	127s (n=5)	128s (n=5)	118s	-9s (-7.1%)

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: 2026-07-13T05:08:13Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-07-13 23:46 UTC

[devin-ai-integration]

Tested the regenerated Go SDK locally through the seed harness and against an httptest.Server.

• Passed: POST without a caller key sent a valid UUIDv4 Idempotency-Key.
• Passed: declared WithIdempotencyKey("declared-key") remained unchanged.
• Passed: generic header-bag value header-bag-key remained unchanged.
• Passed: DELETE sent no idempotency key.
• Passed: baseline and opt-in generated fixtures both pass go test ./....
• Note: default seed parallelism hit an ENOTEMPTY race between the root and nested outputs; --parallel 1 passed both fixtures (2/2).

Generated injection and commands

headers.Set("Idempotency-Key", core.GenerateIdempotencyKey())

pnpm seed test --generator go-sdk --fixture idempotency-headers --local --skip-scripts --parallel 1
2/2 test cases passed

=== RUN   TestIdempotencyKeyRuntimeBehavior
--- PASS: TestIdempotencyKeyRuntimeBehavior (0.00s)
PASS

Session: https://app.devin.ai/sessions/315ea45e9da84294a994c0e162b4eec6

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[github-actions]

Docs Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-07-13T05:08:13Z).

Fixture	main	PR	Delta
docs	241.5s (n=5)	242.9s (35 versions)	+1.4s (+0.6%)

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: 2026-07-13T05:08:13Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-07-13 23:43 UTC