[engine-failure] PROJ-582-socratic-transformers-dialogue-based-sel @ tasks: PermanentBackendError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-582-socratic-transformers-dialogue-based-sel** at stage `tasks`.

```
PermanentBackendError: Error code: 400 - {'detail': "'qwen.qwen3.5-122b'"}
```

The project remains schedulable; it will retry on its normal cadence and recover once the underlying defect is fixed. Closing this issue does not require any project-state change.

Start by tracing the `tasks` stage for PROJ-582-socratic-transformers-dialogue-based-sel and the handling of the reported PermanentBackendError, especially the `'qwen.qwen3.5-122b'` detail. Confirm the underlying defect is fixed without changing project state, and verify that the project remains schedulable and recovers on its normal cadence.

Written by the indexing model from the issue text.