Semantic gRPC for Plugins

Since Sigil 0.35.0, the host supports the additive Host API 1.3 interface sigil:host/grpc-unary@1.3.0 under plugin manifest schema 4. Existing schema 1–3 and Host API 1.0–1.2 imports remain unchanged.

The host supports exactly three Temporal WorkflowService methods: StartWorkflowExecution, DescribeWorkflowExecution, and GetWorkflowExecutionHistory. This is not a generic gRPC client. Reflection, streaming, connection pooling, hidden retries, and mTLS are not supported.

Temporal 0.1.1

The plugin exports three operations with fixed host RPC aliases:

Lua export	Profile RPC alias	Caller timeout ceiling
`start-workflow-execution`	`start`	10,000 ms
`describe-workflow-execution`	`describe`	10,000 ms
`get-workflow-execution-history`	`history`	65,000 ms for close-event waiting; 10,000 ms for all-events

Each request supplies a named profile and a positive timeout-millis no greater than that operation’s ceiling. Host profile and scenario deadlines can lower the effective timeout further. Grant only the aliases needed by the scenario, with their exact WorkflowService paths and read/mutation kinds.

Start requires exactly two ordered json/plain payloads and a caller-owned request-id. Its protobuf identity is fixed to sigil-temporal@0.1.0; the operator’s request policy must match. Describe and History select the latest run by workflow-id; they do not accept an explicit run ID.

History accepts only these flag combinations:

`filter`	`wait-new-event`	`skip-archival`	Maximum `timeout-millis`
`"close-event"`	`true`	`true`	65,000
`"all-events"`	`false`	`false`	10,000

Each History call returns one page. The caller passes the opaque next-page-token explicitly to request another page. No operation retries, polls, or reconnects internally. See the versioned Temporal README for the operator configuration and full caller contract.

Temporal 0.1.0’s immutable manifest still requires >=0.35.0, <0.36.0. The 0.1.1 minimum-only range removes that minor ceiling, not the exact host interface or schema checks. It does not certify an unmeasured future host.

Project-side Lua companion

Temporal 0.1.1 includes an opt-in Lua companion. Copy the version-pinned file into your scenario’s lib/temporal.lua and record its hash with the caller change. Official plugin acquisition does not install this file. require("lib.temporal") callers must declare wasm.temporal, even when using only its decoder; the standalone sigil.json.decode builtin instead needs no plugin capability.

Helper	Contract
`run(request, options)`	Starts once, then polls Describe; returns the full Describe response (`value.status.number`), not a status string.
`wait_after_start(request, options)`	Polls an already-started workflow without another Start. Only RUNNING and typed post-start NOT_FOUND are retryable.
`history(selector, options)`	Bounded History traversal; derives both flags from the required filter and preserves event order.
`result(selector, options)`	Reads close-event History; distinguishes completed ordered payloads, including an empty list, from `not-completed`.
`decode_json(payload, options)`	Explicitly decodes one `json/plain` payload layer; preserves raw payloads and never guesses a second decoding step.

Polling requires explicit attempt/interval bounds. History and result require explicit page, event, byte and per-call timeout bounds; result takes no filter. Repeated tokens and exhausted bounds return helper errors, never partial success or a fabricated workflow TIMED_OUT. Byte accounting covers returned WIT strings, not process memory or cumulative transport bytes. Set a scenario deadline as well: attempts are not elapsed seconds, and host deadlines still win. Do not swallow RPC, sleep or checkpoint exceptions. A checkpoint may signal cancellation but must not mutate requests or issue RPCs/sleep.

Preserve ordered binary payloads and metadata before interpreting them. An empty completed payload list is not missing completion; JSON null is not no payload. The decoder preserves exact signed 64-bit integers and empty object/array shape, but rejects fractions, out-of-range integers, duplicate keys and malformed JSON. Unsupported encoding returns a companion error; builtin JSON failures throw. If an application explicitly stores JSON inside a JSON string or field, decode that further layer at the application boundary, not automatically.

Handle helper/infrastructure failures before product assertions, and do not mask an already-measured non-COMPLETED product outcome with an unnecessary result read. Start is never retried. started=false has no presence information, and successful effect="applied" may describe an existing execution, not creation by this call. Describe/History still select by workflow ID, not Start’s returned run ID. See Start semantics and the complete helper contract.

CAPI accepted the exact 0.1.1-rc.1 package and copied companion on Sigil 0.35.1: five profiles, 10 scenarios, 319 unchanged assertions and both expected-RED fingerprints. Its supplemental real histories fit in one page; repeated tokens, empty completed payloads and cancellation/deadline races were not exercised. The later diagnostic addendum did not rerun the full suite. This evidence is scoped to that RC and caller adoption, not a separate stable-artifact CAPI run or proof that every server/payload shape works.

Authority belongs to the host

The component supplies profile/RPC aliases, protobuf bytes, and limits that can only lower host ceilings. It cannot select socket addresses, TLS roots, SNI, or raw request headers, and it never receives credentials. Only explicitly allowlisted response metadata is returned to the component. Before secret lookup or socket access, the host validates the frozen profile and canonical application request.

Execution requires all of these independently:

A verified immutable package and exact project requirement/lock, admitted by the project’s source policy.
A schema-4 manifest importing Host API 1.3 and requesting grpc-unary, with no raw network/secret imports or requests.
Source admission under the grpc-unary capability allowlist.
The scenario’s exact wasm.<name> capability and matching operator grants.
A request satisfying temporal-workflow-v0: namespace, workflow prefix, Start workflow type/task queue/identity, and payload shape are constrained. The caller owns the Start request ID.

Explicit installation before plugin add makes acquisition visible and works with older hosts. Sigil 0.35.0’s add can instead acquire missing packages through verified remote installation. For an existing lock with an empty cache, run sigil plugin sync before adding or upgrading Temporal, so the other pinned dependencies are available. Then install and add temporal@0.1.1, run plugin sync, and inspect its exact official-github-provenance-v1 proof tuple. plugin test --path cannot supply this adapter’s frozen project owner, even with a local:path allowance.

Operator configuration

Configure the source policy under [plugins.trust.capability_allowlist].grpc-unary, then bind a profile under [plugins.grants.<plugin>.grpc.<profile>] to a named network endpoint. The profile freezes its transport, authority, RPC aliases, request policy, request/response metadata, and byte/deadline limits. A source allowlist alone does not grant a method or create provenance.

In Sigil 0.35.1, unused-network-grant warnings recognize endpoints referenced by gRPC and SigV4 profiles, not just raw network capability. Referenced endpoints are not reported as unused. Unused extras still produce unused plugin network grants ignored with an unused_endpoints count, never endpoint names or targets. This diagnostic does not grant raw guest networking or change route admission.

Request metadata is closed, not an arbitrary user-header map: it requires temporal-namespace, supported-server-versions, caller-type, client-name, and client-version. Namespace must match the request policy. The other values are operator-pinned bounded ASCII.

The logical grant target, published socket, and protocol :authority are distinct. For an endpoint target workflow:7233 published on a different port, bind it explicitly with --plugin-route workflow:7233=http://127.0.0.1:49172, or use a structured endpoint-map entry with logical_port = 7233. An omitted authority port stays omitted; it is never inferred from the socket. See route configuration.

For direct TLS, select transport = "h2-tls", endpoint tls = "direct", a tls_server_name matching the authority’s DNS host, and operator-selected roots. bearer_secret names an allowed scenario environment variable, never its value. Do not also grant it as a raw secret. Credentials are acquired lazily only after certificate, SNI, and exact h2 ALPN verification. An unused missing credential does not abort a run; a selected missing one fails closed. Bearer credentials over h2c are forbidden.

Diagnose a pre-send denial

Since Sigil 0.35.1, human output from sigil run and sigil scenario run includes a closed operator hint for gRPC authorization failures. Common categories point to the constraint to inspect:

Hint prefix	What to check
`grpc.profile`	The named profile exists in the plugin’s frozen grant.
`grpc.rpc-alias`	The internal alias (`start`, `describe`, or `history`), not the Lua export name, appears in the selected profile’s `rpcs` map.
`grpc.request.identity`	`request_policy.identity` matches the plugin’s fixed caller identity; do not derive it from the release version.
`grpc.request.history-flags`	Close-event requests use both flags `true`; all-events requests use both `false`, as shown above.

Only the first failure is reported. Fixing an alias can reveal an independent identity mismatch on the next run. Hints never echo request or policy values, payload bytes, secrets, or the alias inventory. JSON, ledger, replay, and agent-safe feedback omit this private hint.

These pre-send host failures latch PLUGIN_CAPABILITY_DENIED for authorization. Internal host-to-WASM kinds distinguish denied from invalid-request; the Temporal adapter maps exchange failures to infrastructure/host-failure and the sticky host fault throws after export. Do not expect distinct Lua-returned kinds for these denials. A malformed RPC alias can instead fail at configuration load, before any run report exists; inspect stderr. Human hints are not JSON fields. Do not weaken the grant or retry an ambiguous Start. A caught sticky failure cannot be converted into a passing run.

Limits and outcomes

Endpoint connection and cumulative bidirectional HTTP/2 plaintext-byte quotas are shared across calls, not reset by each RPC. Request/response protobuf ceilings are at most 4 MiB, independently of plugin memory and fuel. Overall, connect, and I/O waits obey the earliest applicable profile, caller, outer-call, and scenario deadline; progress does not restart the whole-call budget.

A maximum-sized message is not guaranteed to fit the default 64 MiB runtime budget. Canonical lifting allocates host values and consumes transfer fuel. A measured 4 MiB response fixture reaches Lua under max_memory = "256MiB"; the default instead fails without returning partial data. Even 256 MiB is not a universal sizing guarantee: guest memory and other retained values still share the budget.

A complete nonzero gRPC status is a typed server result. Authorization, transport, malformed-request/response, cancellation, and resource faults latch infrastructure failure. pcall, ignored results, or a later guest success cannot clear it; further exchanges on that store are denied.

Trusted direct-run reports may include grpc_send_state: not-sent, headers-sent, message-partial, or message-sent. This describes observed transmission, not whether the server committed a mutation. It never authorizes automatic retry. Holdout-safe eval feedback remains generic.

Credential-fragment filtering and wiping cover selected Sigil-owned buffers. They do not promise transformed-secret detection or erasure of guest, Wasmtime, TLS-library, kernel, or process-wide memory.

Replay

Ordinary replay reads and verifies pinned evidence without executing plugins or selecting credentials. Semantic source, profile, RPC classification, and transport identities are revalidated.

Live replay rejects a selected plugin if its frozen profile contains any mutation RPC, before deployment—even if the scenario would use a read alias. --live is not mutation authorization. Read-only live replay uses frozen policy/roots with current lazy credentials and must pass ordinary execution checks. Baseline verdicts are separate from PR comparison status; a PR MATCH is not proof of fresh baseline success.