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feat(client): accept a cached era verdict on ConnectOptions.prior (#2511)

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Felix Weinberger 2026-07-17 17:25:02 +01:00 • committed by GitHub
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6
docs/protocol-versions.md
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@ -74,6 +74,12 @@ The rejection is a typed, local `SdkError` — nothing reaches the server beyond
ERA_NEGOTIATION_FAILED: Version negotiation failed: the server did not offer pinned protocol version 2026-07-28 via server/discover (no fallback in pin mode)
```
## Skip the probe with a cached verdict
`mode: 'auto'` pays the probe on every fresh connect. A host that already knows the server's era — from a registry entry, or an earlier connection's outcome — skips it by supplying `ConnectOptions.prior`, the exported `PriorDiscovery` type: `{ kind: 'modern', discover }` adopts a previously obtained `DiscoverResult` with zero round trips, and `{ kind: 'legacy' }` goes straight to the `initialize` handshake.
Freshness is the host's job, not the SDK's: a stale modern verdict fails loudly at the first request, but a stale legacy verdict succeeds silently against an upgraded server — so date cached legacy verdicts in your own storage and stop supplying them past your policy horizon. [Caching discovery verdicts](./advanced/gateway.md#caching-discovery-verdicts) shows the full loop, including the re-probe that re-populates the cache.
## Understand the probe
`probe` bounds the `server/discover` round trip that `'auto'` and a pin run before anything else.