Migrating Rust provider connectors to pure-Harn packages

GitHub, Slack, Linear, and Notion provider business logic now ships in pure-Harn connector packages. Harn core keeps only the shared connector primitives, so Harn Cloud and self-hosted orchestrators can adopt connector fixes, new event families, and provider API changes without waiting for a Harn core release.

This guide is the migration path for an orchestrator that still has an old manifest or deployment model from before the pure-Harn package cutover.

The cron, generic webhook, A2A push, and stream connectors stay in Harn core and are not affected by this migration. HMAC verification, raw-body access, signature header constants, and signing primitives also stay in core so that pure-Harn connectors do not need to reimplement them.

What is changing

Each first-party provider has a pure-Harn replacement that exposes the same event shape through the connector contract v1 surface:

Provider	Pure-Harn package
GitHub	https://github.com/burin-labs/harn-github-connector
Slack	https://github.com/burin-labs/harn-slack-connector
Linear	https://github.com/burin-labs/harn-linear-connector
Notion	https://github.com/burin-labs/harn-notion-connector

Manifests opt into the pure-Harn replacement by declaring a [[providers]] table that points connector = { harn = "..." } at the package's connector module. Provider-specific Rust fallbacks are no longer registered for GitHub, Slack, Linear, or Notion, so the override is the canonical path for those providers.

Cutover checklist

The cutover is intentionally per-provider so that an orchestrator can soak one provider on the pure-Harn implementation before moving the rest.

1. Install the package. Add the package as a dependency and run harn install --locked.

   harn add github.com/burin-labs/harn-github-connector@v0.2.0
   harn install --locked
   

2. Run the contract check. Confirm the package matches the connector contract and your supported event families.

   harn connector check . --provider github
   

   For Notion, also exercise the poll path:

   harn connector check . --provider notion --run-poll-tick
   

3. Add a [[providers]] override. Tell the orchestrator to load the pure-Harn module for this provider.

   [[providers]]
   id = "github"
   connector = { harn = "vendor/harn-github-connector/src/lib.harn" }
   

   Leave existing trigger entries unchanged. Triggers with provider = "github" automatically resolve through the new connector once the override is in place.

4. Run a fixture check. Feed canonical webhook bodies through the pure-Harn package and assert the resulting TriggerEvent kind / dedupe_key / provider_payload shapes match the payloads your handlers expect. The connector testkit (docs/src/connectors/testkit.md) has the primitives needed to stage a RawInbound and capture the normalized event in tests.

   First-party connector packages run a parity matrix against the Rust payload shapes in their own CI. If your handlers depend on a vendor field that is not in the parity fixtures, add it to your local [connector_contract] fixture set before cutover.

5. Roll out and verify. Deploy the manifest change. The orchestrator logs a one-line confirmation when it loads the Harn module. harn doctor reports trigger:<id> as via <provider>, so existing health checks keep working.

Harn cloud specifics

Managed Harn Cloud orchestrators load pure-Harn connector packages through the same [[providers]] mechanism documented above. Connector packages are resolved through the package manager so the cutover is a manifest change, not a Harn Cloud release.

What stays in core

The following primitives stay in Harn core and continue to be the only supported way to express their respective concerns:

• The cron connector (docs/src/connectors/cron.md).
• The generic webhook connector with HMAC verification, including the webhook-signature / webhook-timestamp / webhook-id Standard Webhooks-style headers (docs/src/connectors/webhook.md).
• HMAC verification helpers under harn_vm::connectors::hmac, including the canonical signature-header constants used by GitHub, Slack, Linear, Notion, Stripe, and Standard Webhooks.
• The A2A push connector and the stream connector for queue-shaped ingress.
• Raw HTTP request access (raw_body, headers) and signing primitives.

Pure-Harn provider connectors compose these primitives — they do not duplicate them.

Removal status

The Harn core prerequisites are complete:

• The connector contract conformance harness validates pure-Harn replacements through the same adapter path Harn Cloud and self-hosted orchestrators use.
• NormalizeResult v1, poll_tick, hot-path effect policy, transport primitives, structured concurrency, and the connector testkit are in core.
• The OAuth / connect CLI and package manager give connector packages a stable install + auth path.
• First-party package CI owns parity fixtures for GitHub, Slack, Linear, and Notion so provider payload behavior can evolve with package releases.

Do not add provider-specific Rust connector business logic in this repository; service connectors should be packages that register with connector = { harn = "..." }.