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Align with spec #3002: optional clientInfo, serverInfo in result _meta (#3143)

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Max 2026-07-23 12:00:36 +01:00 • committed by GitHub
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10
docs/protocol-versions.md
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@ -68,10 +68,10 @@ A pin is a promise *you* make: you already know the server speaks that version.
A pin is not a discovery. Print `client.server_info` and the price is right there:
```text
name='' title=None version='' description=None website_url=None icons=None
None
```
The client never asked the server who it is, so `server_info` is a blank. `client.server_capabilities`
The client never asked the server who it is, so `server_info` is `None`. `client.server_capabilities`
is the same story: every capability is `None`. Tool calls still work (the protocol needs none of it);
code that reads `server_capabilities` to decide what to offer does not.
@ -87,7 +87,7 @@ ValueError: mode must be 'legacy', 'auto', or one of ['2026-07-28']; got '2025-0
The probe is cheap, but it is still a round trip you pay on every reconnect, and the answer almost never changes.
So keep it. After an `auto` connection, `client.session.discover_result` holds the exact `DiscoverResult` the server sent: its `supported_versions`, its `capabilities`, its `server_info`, its `instructions`. Hand it back as `prior_discover=` the next time:
So keep it. After an `auto` connection, `client.session.discover_result` holds the exact `DiscoverResult` the server sent: its `supported_versions`, its `capabilities`, its `instructions`, and the identity the server stamped into the result's `_meta`. Hand it back as `prior_discover=` the next time:
```python title="client.py" hl_lines="15 17"
--8<-- "docs_src/protocol_versions/tutorial004.py"
@ -112,7 +112,7 @@ The second connection made **zero** negotiation round trips and still knows exac
| --- | --- | --- |
| `Client(target)` | one `server/discover` probe; the `initialize` handshake if it fails | the newest version both sides speak, whichever era |
| `Client(target, mode="legacy")` | the `initialize` handshake | a handshake-era version; server-initiated requests work |
| `Client(target, mode="2026-07-28")` | none | that version, pinned, with a blank `server_info` |
| `Client(target, mode="2026-07-28")` | none | that version, pinned, with `server_info` as `None` |
| `Client(target, mode="2026-07-28", prior_discover=saved)` | none | that version, pinned, *and* the identity you saved last time |
## Recap
@ -121,7 +121,7 @@ The second connection made **zero** negotiation round trips and still knows exac
* `mode="auto"` is the default: probe, fall back. Leave it alone unless one of the other three rows describes you.
* `client.protocol_version` is always the answer to "what did I get?".
* `mode="legacy"` forces the handshake. It is what you need for server-initiated requests: sampling, push elicitation, `message_handler`.
* A version pin (`mode="2026-07-28"`) sends no negotiation traffic at all, at the cost of a blank `server_info`.
* A version pin (`mode="2026-07-28"`) sends no negotiation traffic at all, at the cost of `client.server_info` being `None`.
* `prior_discover=` pays that cost back: save `client.session.discover_result`, reconnect with it, get both.
A modern connection has no push channel, so how does a 2026 server ask you a question mid-call? It returns it: **[Multi-round-trip requests](handlers/multi-round-trip.md)**.