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Error Recovery Flow

1. Overview​

Related Golden Flow: flow-04-single-agent-llm-enrichment

In autonomous systems, failures are inevitable. MPLP provides a structured way to detect, log, and recover from errors using the Trace Module for observation and Plan Module for state management.

Recovery Workflow:​

  1. Detection: A step execution fails (exception, timeout, or validation failure).
  2. Emission: The runtime emits a Trace event with status failed.
  3. Analysis: The recovery logic (Kernel Duty) inspects the error type.
  4. Action: The runtime applies a recovery strategy (Retry, Skip, or Rollback).
  5. Update: The Plan and Trace are updated to reflect the recovery action.

2. Normative Example​

2.1 Failed Trace Segment (JSON)​

When a step fails, the corresponding trace segment is marked as failed:

{
  "segment_id": "seg-step-2",
  "label": "Call Weather API",
  "status": "failed",
  "started_at": "2025-12-22T11:00:00Z",
  "finished_at": "2025-12-22T11:00:05Z",
  "attributes": {
    "error_type": "timeout_error",
    "retry_count": 0,
    "message": "Upstream API failed to respond within 5000ms"
  }
}

2.2 Recovery Event​

The runtime then emits a recovery event to the Trace:

{
  "event_id": "evt-rec-001",
  "type": "recovery.retry_initiated",
  "timestamp": "2025-12-22T11:00:06Z",
  "detail": {
    "target_segment_id": "seg-step-2",
    "strategy": "exponential_backoff",
    "next_attempt_at": "2025-12-22T11:00:10Z"
  }
}

3. Recovery Strategies​

StrategyPlan State ChangeTrace Impact
RetryStep status reset to pending.New span created for attempt.
SkipStep status set to skipped.Segment marked skipped.
RollbackPlan reverted to last checkpoint.Trace segments after checkpoint invalidated.
AbortPlan status set to failed.Trace terminated.

4. Implementation Details​

4.1 Error Propagation​

Errors must propagate from the L3 Execution layer to the L2 Trace layer. A conformant runtime must ensure that the root_span of the Trace correctly reflects the aggregate status of its segments.

4.2 Deterministic Rollback​

When a Rollback is triggered, the runtime must use the Value State Layer (VSL) to restore the agent's memory and state to the exact values recorded at the target checkpoint.