48 lines
1.3 KiB
Markdown
48 lines
1.3 KiB
Markdown
# Backend Integration and History Bridge
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This engine uses adapter-based backend integration so core runtime logic can run
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with or without an external backend service.
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## Runtime Modes
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Configure with environment variables:
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- `BACKEND_MODE=auto|http|disabled`
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- `BACKEND_URL`
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- `BACKEND_TIMEOUT_SEC`
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- `HISTORY_ENABLED=true|false`
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Mode behavior:
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- `auto`: use HTTP backend adapter only when `BACKEND_URL` is set.
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- `http`: force HTTP backend adapter (falls back to null adapter when URL is missing).
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- `disabled`: force null adapter and run engine-only.
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## Architecture
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- Ports: `core/ports/backend.py`
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- Adapters: `app/backend_adapters.py`
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- Compatibility wrappers: `app/backend_client.py`
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`Session` and `DuplexPipeline` receive backend capabilities via injected adapter
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methods instead of hard-coding backend client imports.
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## Async History Writes
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Session history persistence is handled by `core/history_bridge.py`.
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Design:
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- transcript writes are queued with `put_nowait` (non-blocking turn path)
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- background worker drains queue
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- failed writes retry with exponential backoff
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- finalize waits briefly for queue drain before sending call finalize
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- finalize is idempotent
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Related settings:
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- `HISTORY_QUEUE_MAX_SIZE`
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- `HISTORY_RETRY_MAX_ATTEMPTS`
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- `HISTORY_RETRY_BACKOFF_SEC`
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- `HISTORY_FINALIZE_DRAIN_TIMEOUT_SEC`
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