Best possible solution:

Keep the merged scoped-cache and Control UI responsiveness fixes, and do not merge this superseded branch's process-wide cache.

Do we have a high-confidence way to reproduce the issue?

Yes for the code path, without rerunning a live large-store benchmark in this review. The current source and the merged #77187 proof show sessions.list row building repeatedly reached resolver/isCliProvider work on large stores.

Is this the best way to solve the issue?

No, this PR is no longer the best way to solve it. The safer solution is the merged per-sessions.list scoped resolver cache from #77187 plus the already-merged Control UI refresh bound from #80657.

Security review:

Security review cleared: The diff only changes local TypeScript UI/model-selection code and tests, with no dependency, workflow, permission, secret, package-script, or artifact execution changes.

What I checked:

• PR diff adds long-lived CLI-provider cache: The proposed cache key is only the normalized provider plus configured cliBackends keys, while the function still depends on runtime and setup-registry backend lookup state. (src/agents/model-selection-cli.ts:14, bb401f95c247)
• Current checkout already bounds chat-final refreshes: At current checkout SHA 5d4a8b0, terminal chat events call loadSessions with activeMinutes, agentId, and CHAT_SESSIONS_REFRESH_LIMIT. (ui/src/ui/app-gateway.ts:682, 5d4a8b00721a)
• Merged Control UI overlap fix: fix(control-ui): keep channel statuses responsive #80657 merged as 6b3cd90 and its discussion explicitly says it covers this PR's chat-side session refresh bounds while leaving CLI-provider caching as separate follow-up work. (ui/src/ui/app-gateway.ts:682, 6b3cd9043ee6)
• Merged scoped resolver-cache supersedes remaining backend optimization: Fix/sessions list resolver cache #77187 merged as e4cee2e and its body identifies resolveSessionDisplayModelIdentityRef/isCliProvider as the hot path, then scopes resolver caches to a single sessions.list call. (src/gateway/session-utils.ts:1539, e4cee2eb697f)
• Current source shows why a process-wide cache is risky: isCliProvider reads resolveRuntimeCliBackends() and resolvePluginSetupCliBackendRuntime(); plugin runtime state can change via setActivePluginRegistry, and setup backend resolution is keyed by plugin metadata/config fingerprints that this PR's cache key omits. (src/agents/model-selection-cli.ts:12, 5d4a8b00721a)
• PR proof and live state: The PR body reports that the targeted local test command could not run, and live PR metadata reports mergeStateStatus DIRTY / mergeable CONFLICTING after later main changes. (bb401f95c247)

Likely related people:

• BunsDev: Authored and merged the Control UI responsiveness work that covers this PR's chat-side session refresh overlap and left the split-path guidance on this PR. (role: recent Control UI responsiveness contributor; confidence: high; commits: 6b3cd9043ee6, d9f0eaa3e5fa, 4935e24c7a7f; files: ui/src/ui/app-chat.ts, ui/src/ui/app-gateway.ts, ui/src/ui/app-gateway.sessions.node.test.ts)
• rolandrscheel: Authored the merged scoped resolver-cache PR that supersedes this branch's remaining backend/model-selection performance goal. (role: recent sessions-list performance contributor; confidence: high; commits: e4cee2eb697f, aeac10f5cea7; files: src/gateway/session-utils.ts, src/agents/model-selection-cli.ts)
• vincentkoc: Recent history for src/agents/model-selection-cli.ts includes the CLI provider/runtime split that this PR changes. (role: adjacent model-selection runtime contributor; confidence: medium; commits: d7fcd23091e1; files: src/agents/model-selection-cli.ts)

Codex review notes: model gpt-5.5, reasoning high; reviewed against 5d4a8b00721a; fix evidence: commit e4cee2eb697f, main fix timestamp 2026-05-14T04:20:40Z.