fix(openapi): add type discriminator to DestinationUpdate union

[leggetter]

Summary

Two distinct-but-intertwined bugs in destination PATCH, both rooted in the spec. This PR fixes both at the source.

Bug 1 — Wire-serialization (runtime, silent failure)

PATCH requests that try to update part of a non-Webhook destination's config silently fail. The API returns 200 OK, but the destination's config is unchanged.

Concretely — calling the TS SDK to change an AWS SQS destination's queue URL:

await outpost.destinations.update("test-tenant", "des_123", {
  config: { queueUrl: "https://sqs.us-west-2.amazonaws.com/.../updated-queue" },
});

The TS-facing field is queueUrl (camelCase), which the SQS outbound schema is supposed to remap to queue_url (snake_case) on the wire. But the request actually goes out as { "config": { "queueUrl": "..." } } — camelCase reaches the server. Merge-patch doesn't recognize the key, leaves queue_url untouched, and the response shows the old queue.

Why: the DestinationUpdate oneOf has no discriminator (removed in 8be278c5, May 2025, when type wasn't yet accepted on PATCH). Without one, the SDK picks a union variant by structural shape-matching. DestinationUpdateHookdeck's config: {} (intent: "no updatable config"; OpenAPI: "any value allowed") wins for every partial-config payload because it accepts anything. Hookdeck's variant has no field-name remap — that's the actual mis-serialization. Affects AWS SQS, S3, Kinesis, RabbitMQ, GCP Pub/Sub, Azure Service Bus, and Kafka partial-config updates.

Bug 2 — Typing (compile-time, blocks correct usage)

Even fully correct payloads couldn't be expressed as partial updates. The spec referenced the full *Config / *Credentials schemas — which require their fields — from the DestinationUpdate* variants. So:

// Before this PR — TS error: `queueUrl` is required on AWSSQSConfig
update("t", "id", { config: { endpoint: "https://..." } });

The OpenAPI source even acknowledges the gap with inline comments like # queue_url is required here, but PATCH means it's optional. The fix has been a TODO note in production.

Fix

• Add type (required, enum-locked) to every DestinationUpdate* variant and discriminator: propertyName: type on the union (mirrors DestinationCreate) → resolves Bug 1.
• Introduce 17 new *ConfigUpdate / *CredentialsUpdate companion schemas (all-optional fields, RFC 7396 merge-patch documented) and reference these from DestinationUpdate* variants → resolves Bug 2.
• Remove config: {} from DestinationUpdateHookdeck. Hookdeck has no updatable config; HookdeckCredentialsUpdate handles partial credential updates.

Server-side merge-patch landed in bd7701b5 (April 2026), so the runtime side is already correct — only the spec needed to catch up.

TS SDK typing after regen

DestinationUpdate becomes a true discriminated union — type: "aws_sqs" literal types narrow config to the matching *ConfigUpdate. Examples:

update("t", "id", { config: { queueUrl: "x" } });
// ❌ Missing required `type`

update("t", "id", { type: "aws_sqs", config: { streamName: "x" } });
// ❌ `streamName` doesn't exist on AWSSQSConfigUpdate (it's `queueUrl` / `endpoint`)

update("t", "id", { type: "aws_kinesis", config: { streamName: "x" } });
// ✅ Narrowed to DestinationUpdateAWSKinesis; only Kinesis fields allowed; partial config ok

IDE autocomplete on config: now shows only fields valid for the chosen type.

(Zod note: the regen emits z.union([…]), not z.discriminatedUnion(…). Functionally equivalent here — every variant requires type: z.literal("…"), so only the matching variant parses. Speakeasy's choice; not worth chasing in this PR.)

Spec changes

• type added to every DestinationUpdate* variant: required, enum-locked, documented as immutable on PATCH.
• discriminator: propertyName: type added to DestinationUpdate.
• 17 new *ConfigUpdate / *CredentialsUpdate companion schemas — all fields optional, RFC 7396 merge-patch documented. Variants now reference these instead of the full *Config / *Credentials.
• config: {} removed from DestinationUpdateHookdeck.

Consumer impact

Consumer	Impact
Typed SDK (TS / Python / Go)	Breaking after regen. update() payloads must include type: '<destination>'. Compile-error otherwise.
Raw HTTP	Server still accepts PATCH without type at runtime — calls keep working but are spec-noncompliant. Server-side enforcement is a separate decision.
API ref docs / code samples / MCP server	Regenerated as part of the SDK regen PR.

What's NOT in this PR (deliberately)

• SDK regen — bot-driven via .github/workflows/sdk_generation_outpost_*.yaml. Tests here were validated locally against a TS regen (1.4.1); CI compile-check on this PR will fail until the regen PR lands.
• Server-side enforcement of required type — separate decision.
• CI for spec-sdk-tests — confirmed none exists today (verified across .github/workflows and .speakeasy). Follow-up PR.

spec-sdk-tests changes (knock-on)

• type: '<destination>' inserted into 46 updateDestination payloads across 9 files.
• Paginator response shape fixed (response.result.models) in events.test.ts / tenants.test.ts — supersedes fix/spec-sdk-tests-paginator-shape.
• SDK retries enabled (backoff on 429/5xx) in utils/sdk-client.ts — managed-Outpost rate limits no longer flake tests.
• Cleanup parallelized in webhook-merge-patch after hook (15 destinations × serial DELETE was exceeding mocha's 10s hook timeout).
• console.warn('Failed to cleanup destination:', error) → safe String(error) form in all 17 cleanup hooks (node util.inspect was crashing on SDK errors with getter-only descriptors).

Test status

Against managed Outpost (api.outpost.hookdeck.com), locally with regen'd TS SDK 1.4.1:

	Passing	Failing	Pending
Before	133	14	15
After	152	0	15

The 15 pending are the same skipped tests as before (Hookdeck token verification, GCP Pub/Sub validation gaps — pre-existing backend limitations).

Also of note: spec-sdk-tests/TEST_STATUS.md had attributed the AWS Kinesis partial-config update failure to a "backend bug." It's the same SDK-side dispatch issue this PR fixes — the Kinesis test should pass after regen and can be un-skipped in a follow-up.

Test plan

• Spec validates (swagger-cli validate) — re-run on final branch state.
• SDK regen PR merges → CI compile-check goes green on this PR.
• Full spec-sdk-tests run against managed Outpost — re-run on final branch state: 152 passing / 0 failing / 15 pending.
• Add spec-sdk-tests CI workflow — tracked in Add CI workflow for spec-sdk-tests (SDK acceptance testing) #921.
• Decide whether to enforce required type server-side (follow-up).

🤖 Generated with Claude Code