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backend/examples/plugin/scheduler/README.md

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+# Scheduler Plugin
+
+This plugin demonstrates the CLIProxyAPI C ABI scheduler capability from Go.
+
+It implements:
+
+- `plugin.register`
+- `plugin.reconfigure`
+- `scheduler.pick`
+
+The plugin can select a configured auth ID, delegate routing to a built-in scheduler, or reject scheduler picks.
+
+## Configuration
+
+Add the plugin under `plugins.configs`:
+
+```yaml
+plugins:
+  configs:
+    scheduler:
+      enabled: true
+      priority: 1
+      auth_id: ""
+      delegate: ""
+      deny: false
+```
+
+Fields:
+
+- `auth_id`: selects this auth ID when it appears in the scheduler candidates.
+- `delegate`: delegates selection to a built-in scheduler. Supported values are `""`, `fill-first`, and `round-robin`.
+- `deny`: returns a scheduler error when set to `true`.
+
+Behavior:
+
+- When `deny` is `true`, the plugin returns an error envelope with code `scheduler_denied`.
+- When `delegate` is `fill-first` or `round-robin`, the plugin returns `DelegateBuiltin` and marks the pick as handled.
+- When `delegate` is any other non-empty value, the plugin leaves the pick unhandled.
+- When `delegate` is empty and `auth_id` exists in the candidates, the plugin returns that auth ID and marks the pick as handled.
+- When no rule matches, the plugin leaves the pick unhandled.
+
+## Build
+
+From this directory:
+
+```bash
+cd go
+go build -buildmode=c-shared -o /tmp/cliproxy-scheduler-plugin.so .
+rm -f /tmp/cliproxy-scheduler-plugin.so /tmp/cliproxy-scheduler-plugin.h
+```