Add support for idempotency keys

packages/docs/docs/roadmap.mdx

@@ -16,10 +16,10 @@ description: What's coming next for OpenWorkflow
 - ✅ Workflow versioning
 - ✅ Workflow cancelation
 - ✅ Configurable retry policies
+- ✅ Idempotency keys
 
 ## Coming Soon
 
-- Idempotency keys
 - Rollback / compensation functions
 - Signals for external events
 - Native OpenTelemetry integration

packages/docs/docs/workflows.mdx

@@ -177,6 +177,26 @@ defineWorkflow(
 Any `retryPolicy` fields you omit fall back to defaults. See
 [Retries](/docs/retries) for the full behavior and defaults.
 
+### Idempotency Key (Optional)
+
+You can prevent duplicate run creation by providing an idempotency key, though
+there is a performance cost to checking for duplicates, so use this only when
+necessary:
+
+```ts
+const handle = await ow.runWorkflow(
+  sendWelcomeEmail.spec,
+  { userId: "user_123" },
+  { idempotencyKey: "welcome-email:user_123" },
+);
+```
+
+Within a given namespace, when an existing run matches the same
+`workflowName` + `idempotencyKey`, OpenWorkflow returns that existing run
+immediately. This dedupe window is built-in and lasts 24 hours from the original
+run creation time. The same `idempotencyKey` used in a different namespace will
+create a separate run.
+
 ## Workflow Function Parameters
 
 The workflow function receives an object with three properties:

packages/openworkflow/CHANGELOG.md

@@ -1,5 +1,11 @@
 # openworkflow
 
+## Unreleased
+
+- Add workflow-scoped idempotency keys via
+  `ow.runWorkflow(spec, input, { idempotencyKey })`
+- Built-in run idempotency dedupe period is 24 hours from run creation time
+
 ## 0.6.7
 
 - Add support for Bun as an alternative to Node

packages/openworkflow/README.md

@@ -67,6 +67,7 @@ For more details, check out our [docs](https://openworkflow.dev/docs).
 - ✅ **Long pauses** - Sleep for seconds or months
 - ✅ **Scheduled runs** - Start workflows at a specific time
 - ✅ **Parallel execution** - Run steps concurrently
+- ✅ **Idempotency keys** - Deduplicate repeated run requests (24h window)
 - ✅ **No extra servers** - Uses your existing database
 - ✅ **Dashboard included** - Monitor and debug workflows
 - ✅ **Production ready** - PostgreSQL and SQLite support