Worker Previews JSON schema for `previews.observability` requires top-level Worker properties

[NuroDev]

Summary

Currently if you try and add a observability property to your previews object in your Wrangler config it will give you the following warning:

Missing property "compatibility_flags".
Missing property "jsx_factory".
Missing property "jsx_fragment".
Missing property "migrations".
Missing property "exports".
Missing property "triggers".
Missing property "rules".
Missing property "build".
Missing property "logfwdr".
Missing property "python_modules".
[...]

It seems one of the types or JSDoc types that the JSON schema is generated from is incorrect and is pulling in the type for the top-level config rather than just the observability types.

Reproduction

Paste this in as your wrangler.jsonc config and your editors LSP should warn you about previews.observability missing a large number of properties.

{
	"$schema": "node_modules/wrangler/config-schema.json",
	"name": "my-worker",
	"main": "src/index.ts",
	"compatibility_date": "2026-06-16",
	"compatibility_flags": ["nodejs_compat"],
	"observability": {
		"enabled": true,
	},
	"previews": {
		"observability": {
			"enabled": true,
		},
	},
}

[workers-devprod]

Automated triage

Issue assessment

• Actionability: ✅ Actionable.
• Type: Bug.
• Reproduction: Automatic attempt requested.
• Labels:
  • package:wrangler (high)
  • feature:types (medium)
  • product:deploy-config (medium)

Actionability and missing information

Wrangler's generated config schema makes previews.observability require top-level worker config properties, so editors warn it is missing compatibility_flags, migrations, exports and others; a minimal wrangler.jsonc and expected behavior are provided.

Reproduction reason: A minimal wrangler.jsonc is provided; validating its previews.observability against the generated config schema should reproduce the spurious missing-property warnings.

Reproduction

• Result: ✅ Reproduced.
• Summary: Reproduced cloudflare/workers-sdk issue 15793 with wrangler 4.136.3: the issue's exact wrangler.jsonc fails schema validation at previews.observability with ten Missing-property LSP warnings; a config without previews validates cleanly. Fixture in /workspace/reproduction-output.

Evidence and attempted steps

Steps attempted:

1. Created a minimal project with the exact wrangler.jsonc from the issue (previews.observability = {enabled: true}), a trivial src/index.ts, and pinned wrangler version 4.136.3 (latest published at run time).
   • Command: pnpm install (project with wrangler 4.136.3, vscode-json-languageservice 5.7.2, jsonc-parser 3.3.1, ajv 8.20.0)
2. Validated wrangler.jsonc against node_modules/wrangler/config-schema.json using vscode-json-languageservice, the editor LSP engine that emits the issue's Missing-property message format.
   • Command: pnpm run reproduce (node validate.mjs)
3. Cross-checked with the independent ajv draft-07 validator and ran a baseline (same config without the previews block) to rule out a broken setup.
   • Command: node validate.mjs (ajv cross-check + baseline without previews)

Expected behavior: previews.observability should accept {"enabled": true} without warnings, mirroring the top-level observability property, which has no required properties and only documents enabled, head_sampling_rate, redact_query_string, issues, logs and traces.

Observed behavior: Editor-LSP validation produced exactly the diagnostics quoted in the issue, in the same order and format, all pointing at the previews.observability key: Missing property "compatibility_flags"., "jsx_factory"., "jsx_fragment"., "migrations"., "exports"., "triggers"., "rules"., "build"., "logfwdr"., "python_modules"., plus "Property enabled is not allowed." The independent ajv validator reported the same violations at /previews/observability, confirming the schema artifact is defective rather than one tool behavior. A baseline config identical except without the previews block produced zero diagnostics in both validators. Schema inspection matches: PreviewsConfig.properties.observability references an anonymous interface whose required list is the ten top-level config properties, while top-level observability correctly references the Observability definition.

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