re-uploading work

work-summary/2026-02-04-timer-sensor-discriminator-fix.md

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+# Timer Sensor Discriminator Fix
+
+**Date**: 2026-02-04  
+**Status**: ✅ Fixed  
+**Type**: Bug Fix
+
+## Problem
+
+The timer sensor was failing to start timers with the error:
+
+```
+Failed to start timer for rule 1: Failed to parse trigger_params as TimerConfig
+```
+
+## Root Cause
+
+The timer sensor's `TimerConfig` enum is defined as a **tagged union** using serde's `#[serde(tag = "type")]`:
+
+```rust
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum TimerConfig {
+    Interval { interval: u64, unit: TimeUnit },
+    Cron { expression: String },
+    DateTime { fire_at: DateTime<Utc> },
+}
+```
+
+This requires JSON with a `type` discriminator field:
+
+```json
+{
+  "type": "interval",
+  "interval": 1,
+  "unit": "seconds"
+}
+```
+
+However, the `trigger_params` stored in the rule table was missing the `type` field:
+
+```json
+{
+  "interval": 1,
+  "unit": "seconds"
+}
+```
+
+Without the discriminator, serde couldn't deserialize the enum variant, causing the parse error.
+
+## Investigation Steps
+
+1. Observed error in sensor logs
+2. Checked database for `trigger_params` content
+3. Found parameters were correct but missing `type` field
+4. Examined `TimerConfig` enum definition in `crates/sensor-timer/src/types.rs`
+5. Identified the tagged union requirement
+
+## Solution
+
+**Immediate Fix**: Manually added the `type` field to existing rule:
+
+```sql
+UPDATE rule 
+SET trigger_params = jsonb_set(trigger_params, '{type}', '"interval"') 
+WHERE trigger_ref = 'core.intervaltimer';
+```
+
+**Result**: Timer sensor now working correctly, firing events every second.
+
+## Not Related to JSON Schema Migration
+
+This issue was **NOT caused by the JSON Schema format migration**. This is a separate data format issue:
+
+- **Schema format**: How parameter definitions are structured (inline vs standard JSON Schema)
+- **Data format**: How parameter values are stored (with or without type discriminator)
+
+The JSON Schema migration only affected the **parameter schema definitions** in YAML files and the database. It did not affect the **parameter values** stored in rules.
+
+## Proper Long-Term Fix
+
+The issue should be fixed at the source - when rules are created. The system should automatically add the appropriate `type` discriminator to `trigger_params` based on the `trigger_ref`:
+
+| Trigger Ref | Type Value |
+|-------------|------------|
+| `core.intervaltimer` | `"interval"` |
+| `core.crontimer` | `"cron"` |
+| `core.datetimetimer` | `"datetime"` |
+
+### Implementation Options
+
+1. **Database Trigger**: Add a PostgreSQL trigger to automatically inject the `type` field
+2. **API Layer**: Add the `type` field in the API when creating/updating rules
+3. **Repository Layer**: Add the `type` field in the rule repository's create/update methods
+4. **Timer Sensor**: Make the timer sensor more flexible to infer type from trigger_ref
+
+**Recommended**: Option 3 (Repository Layer) - keep the logic in Rust code where it's testable and maintainable.
+
+## Files Involved
+
+- `crates/sensor-timer/src/types.rs` - Defines `TimerConfig` enum with tagged union
+- `crates/sensor-timer/src/timer_manager.rs` - Deserializes `TimerConfig` from rule params
+- Database: `rule` table, `trigger_params` column
+
+## Verification
+
+After applying the fix:
+
+```bash
+# Check rule parameters
+docker compose exec -T postgres psql -U attune -d attune \
+  -c "SELECT id, ref, jsonb_pretty(trigger_params) FROM rule;"
+
+# Verify timer is working
+docker compose logs sensor | grep "Timer fired"
+```
+
+Expected output:
+- Rule parameters include `"type": "interval"`
+- Sensor logs show "Timer fired for rule 1, created event X" every second
+- Events are being created in the database
+
+## Action Items
+
+- [ ] Implement automatic `type` field injection in rule repository
+- [ ] Add validation to ensure timer trigger params include required `type` field
+- [ ] Update rule creation tests to verify `type` field is present
+- [ ] Consider making timer sensor more lenient (infer type from trigger_ref)
+- [ ] Document the required format for timer trigger parameters
+
+## Conclusion
+
+The timer sensor is now operational. The issue was a missing discriminator field in the stored parameter data, not a problem with the JSON Schema migration. The system needs a proper fix to automatically add the `type` field when creating rules with timer triggers.