Add Block Preview Skill

You manage block visibility gating in Sim — hiding blocks from every discovery surface (toolbar, cmd+K search, copilot @-mentions, agent tool picker, mothership VFS/metadata/tools, Access Control list, public docs/catalog) while never gating execution of already-placed instances.

The model

Three levers, evaluated in apps/sim/lib/core/config/block-visibility.ts and folded into the registry accessors (apps/sim/blocks/registry.ts):

1. preview: true on the BlockConfig (static, in code) — the block is default-hidden EVERYWHERE (hosted, self-hosted, dev, SSR) until revealed. Fail-closed.

2. The hosted block-visibility AppConfig document — per-block rule keyed by the existing block type:

   {
     "<block-type>": {
       "enabled": false,        // required. true = GA (visible to everyone)
       "orgIds": ["org_..."],   // optional allowlist clauses (any match reveals)
       "userIds": ["user_..."],
       "adminEnabled": true     // platform admins (user.role === 'admin')
     }
   }

3. PREVIEW_BLOCKS env (comma-separated block types) — the off-AppConfig reveal path for self-hosters and local dev.

A revealed block that is not globally GA (enabled !== true, or env-revealed) renders with a " (Preview)" name suffix on discovery surfaces. getBlock() stays pure, so placed instances keep their canonical name and always execute.

Lifecycle of a preview block

1. Author the block normally (/add-block etc.) and set preview: true on its BlockConfig. Ship no BlockMeta and no docs until GA — check-block-registry deliberately skips preview blocks in meta coverage, and generate-docs skips them at every gate.
2. Local dev: set PREVIEW_BLOCKS=<block-type> in your env to see it (with the suffix).
3. Merge/deploy. The block's code is live everywhere but visible nowhere — no AppConfig rule exists and self-hosters have no env entry.

4. Hosted preview: add a rule to the block-visibility AppConfig document and start a deployment (no code deploy):

   • Admins only: { "enabled": false, "adminEnabled": true }
   • Design-partner org: { "enabled": false, "orgIds": ["org_123"] }
   • GA via config (code cleanup pending): { "enabled": true } — suffix disappears everywhere within ~30s (AppConfig TTL) + client refetch.

   Same runbook as feature-flags: edit the hosted document, aws appconfig start-deployment with the sim-<env>-fast strategy (see the infra README).

5. GA cleanup: delete preview: true from the block (now visible to self-hosters on their next upgrade), add its BlockMeta + regen docs, and drop the AppConfig entry. For a v2 upgrade, this is also when v1 gets hideFromToolbar: true (the superseded-version paradigm).

Kill switch (shipped blocks)

To pull an already-GA block from discovery surfaces on hosted (incident, deprecation): add { "<block-type>": { "enabled": false } } to the document. Allowlist clauses can carve out exceptions. Execution is NOT stopped — workflows already using the block keep running; the kill switch only prevents new placement/discovery.

Invariants (do not violate)

• Execution is never gated. The executor, serializer, drop-naming, and isBlockTypeAccessControlExempt resolve via pure getBlock. Do not add visibility checks to execution paths.
• Clone-not-remove: gated blocks stay in getAllBlocks() output as clones with hideFromToolbar: true — .find-by-type consumers rely on this. Never filter them out.
• Keys are registry block types. Never custom_block_* (parse drops them — custom blocks have their own enabled/disabled lifecycle).
• The shared hidden-predicate is isHiddenUnder (apps/sim/blocks/visibility/context.ts). Never restate the preview/disabled rule inline at a new consumer.
• Process-global caches stay ungated. getStaticComponentFiles (VFS) and getExposedIntegrationTools build the ungated universe; per-viewer filtering happens at stamp/consumer time. Never move gating into a shared builder.
• Gating is surface hiding, not secrecy — the full config ships in the client JS bundle. Anything truly secret cannot be a registered block.

Tests

Evaluation semantics: apps/sim/lib/core/config/block-visibility.test.ts. Registry projection: apps/sim/blocks/visibility/visibility.test.ts. When gating behavior changes, extend those — mock isPlatformAdmin for the admin clause; use the local withAppConfig harness.