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Allow protocol era to be set on an ad-hoc --server-url launch (not just via mcp.json) #2208
Description
Which client?
All / shared core
The problem
protocolEra is only settable as a per-server field in an mcp.json entry. An ad-hoc invocation (--server-url + --header) always gets the default legacy era, in all three clients.
We launch the inspector from a wrapper script that mints a short-lived OAuth token and spawns:
mcp-inspector --transport http --server-url "$URL" --header "Authorization: Bearer $TOKEN"
To exercise the same server under a non-legacy era we would have to write a config file per launch, which means writing the bearer token to disk.
Solution you have in mind (optional)
A --protocol-era <legacy|auto|modern> flag that feeds settings.protocolEra on the ad-hoc path, the way --connect-timeout feeds settings.connectionTimeout today.
Alternatives or workarounds you have tried
Generating a temporary mcp.json per launch (puts a short-lived credential on disk). In web, switching Protocol Era by hand in Server Settings after every launch; CLI and TUI have no equivalent.
Before you submit
- I searched existing issues and this is not a duplicate.
- This is a request for the Inspector itself, not for the MCP specification or an SDK.
Activity
[-]Protocol era can only be set via mcp.json, not on an ad-hoc --server-url launch[/-][+]Allow protocol era to be set on an ad-hoc --server-url launch (not just via `mcp.json`)[/+]cliffhall commentedon Sep 1, 2026
Triage: Priority Low (total 5)
mcp.json) works but writes a short-lived credential to disk, and CLI/TUI have no in-session equivalentbuglabel, no milestone, unassigned, not a sub-issue, no reporter priority set)Labels applied at triage:
v2,enhancement.Board: #28, Status
Incoming(awaiting maintainer review — no milestone yet).test: discriminate --protocol-era wiring against a modern-only server (…
cliffhall commentedon Sep 14, 2026
Shipped in #2372 (merged into
v2/mainas 634b243):--protocol-era <legacy|auto|modern>now sets the era for an ad-hoc--server-url/ command launch in the web, CLI and TUI clients, so a non-legacy era no longer needs anmcp.jsonentry — and so no bearer token has to be written to disk for it.feat: add --protocol-era launch flag for ad-hoc servers (modelcontext…