Release 2.4.0 step 2: merge v2/main into main and cut the release

[cliffhall]

Milestone v2.4.0

The fourth v2/main → main milestone merge, cutting 2.4.0. This is step 2 of the release procedure in Cutting a release; step 1 (the version bump on v2/main) is #2141 / #2142.

main currently holds 2.3.0 (merged via #2053 / #2054) and has not moved since — no dependabot PR landed on it directly this cycle. v2/main has accumulated 31 merged PRs (200 non-merge commits) on top of it.

Scope

1. Branch from main, merge origin/v2/main.
2. Open a PR against main and run npm run ci green on the merged tree.
3. After merge: tag origin/main as bare 2.4.0 and draft the GitHub Release — publishing runs pack:verify, asserts the tag matches package.json, and publishes the latest dist-tag.

The version bump is not part of this issue — it lands on v2/main first (#2142), which is the whole point of the #2010 procedure change, and arrives here as part of the payload.

Conflicts

None expected. A trial merge of main with v2/main + the bump went through clean, with no conflicted paths — unlike the v2.3.0 merge, where #2004 (dependabot, npm_and_yarn group) had landed on main only and collided on the version field. Nothing has landed on main since #2054, so main is unchanged from the state v2/main last merged into it.

Re-run the trial merge before opening the PR anyway: a dependabot PR merged to main in the interim would reintroduce exactly the lockfile conflict the last two merges hit, and the security bumps must survive it.

Payload

Group	PRs
Release mechanics	#2142 (bump to 2.4.0 — #2141)
MCP Apps	#2100 (dedicated app origin for _meta.ui.domain — #2056), #2083 (negotiated app-rendered form elicitations — #1854), #2098 (read UI resource metadata from _meta.ui — #2055), #2107 (render an App from the installed tarball in pack:verify — #2003)
OAuth / secrets	#2113 (pass the challenge's resource_metadata URL to SDK auth() — #2071), #2136 (keep the server's path in the fallback authorization-server URL — #2110), #2118 (persist the requested scope when the token response omits it — #2117), #2114 (per-server refresh_token opt-out — #2068), #2105 (don't answer token_expired from an unknowable local expiry — #2051), #2115 (open the monitoring sidebar when a connect fails during OAuth — #2108), #2076 (file-backed and in-memory SecretStore for hosts with no keychain — #1950), #2088 (a real cross-process lock on the secrets file — #2082)
Protocol / runtime	#2135 (carry the in-progress SSE frame across chunk boundaries — #2134), #2099 (route the proxy through undici's own fetch and keep undici external — #2067), #2094 (complex JSON values in request _meta — #1910)
Tools / forms / UI	#2121 (flag unportable tool schemas in all three clients — #1005), #2109 (multiline tool string arguments — #2042), #2139 (take the enlarge button out of the tab order — #2138), #2131 (keep the pagination toggle on the last write across a server switch — #2095), #2091 (roll a failed settings write back to what actually landed — #2089), #2087 (surface a failed post-write server-list reload — #1914), #2106 (state the expected shape when dropping a CSP source — #2064)
CLI / config	#2119 (carry a landed stdio env/cwd onto the config it connects with — #2096), #2112 (apply a server's persisted mcp.json metadata — #2093)
Lint / tooling / CI	#2090 (--max-warnings 0 on every lint scope — #2085), #2116 (pin esbuild past GHSA-g7r4-m6w7-qqqr in web/cli/tui — #2062), #2120 (build test-servers unconditionally from one shared helper — #2111), #2092 (three small cleanups flagged in the v2.2.0 merge review — #2000), #2103 (remove the Claude Code GitHub Actions workflow — #2102), #2070 (drop the redundant PR-head checkout from claude.yml — #2069)

After merge

• Close this issue manually and move its card to Done — Closes #N does not fire on a PR targeting main from a merge branch until it actually merges there, and the merge PR uses References by convention.
• Close out the v2.4.0 milestone, moving anything still open on it to v2.5.0.