Get model and multiplier show up for Copilot CLI controller API route

[anthonykim1]

Before PR:
We went from being able to show model + token info after: #311769 to the model not showing up until user reloads.

Also not getting anything shown for auto mode before or after both #311769 and this PR branch.
Maybe related to: #303960 (comment)

Edit: Seems like related to controller API path. On latest insiders if you disable controller api setting the models show up without having to refresh.

Summary -> Live model footer comes from request handler's returned ChatResult.details.

• Non-controller route had logic around request flow to build/ return details but the controller route was effectively completing the CLI request and returning {}. So live UI had no details to render.
• Reason why it worked on reload: History rebuild could later recover details from persisted/session data, which is why it looked "fixed after reload" but did not show up on live.
• Controller route now reads model after handleRequest via getCopilotCLIModelDetails.
• Gating this behind setting: "github.copilot.chat.cli.modelDetails.enabled"

Thanks @justschen for helping with auto mode.
Side note: For some reason auto seems to always show sonnet 4.6

[Copilot]

Pull request overview

This PR aims to restore/improve Copilot CLI chat’s ability to display “last used model” (and related detail string) immediately on the first response, including across the untitled→real session swap and history rebuild paths.

Changes:

• Track and surface a “last response model id” derived from assistant.usage to drive the model details badge.
• Improve model-id matching (e.g., dotted vs dashed Claude ids) via aliasing utilities and use those aliases when rebuilding history and resolving preferences.
• Defer the untitled-session swap so the request handler can return ChatResult.details before the swap happens; update/add tests accordingly.

Show a summary per file

File	Description
extensions/copilot/src/extension/chatSessions/vscode-node/copilotCLIChatSessionsContribution.ts	Uses last-response/selected/request model ids to compute details; schedules untitled swap asynchronously.
extensions/copilot/src/extension/chatSessions/vscode-node/test/copilotCLIChatSessionParticipant.spec.ts	Adds assertions for “live” model details and waits for async swap behavior.
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSession.ts	Captures last response model id from assistant.usage and exposes it.
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts	Supplies a model-details-by-id map (with aliases) into history rebuild.
extensions/copilot/src/extension/chatSessions/copilotcli/common/copilotCLITools.ts	Rebuilds turns with per-turn model ids and uses aliased model details when emitting response result.details.
extensions/copilot/src/extension/chatSessions/copilotcli/common/copilotCLIModelIds.ts	New shared alias/equality helpers for Copilot CLI model ids.
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotCli.ts	Adds matchesCopilotCLIModel and uses it for model resolution/defaulting.
extensions/copilot/src/extension/chatSessions/copilotcli/common/test/copilotCLITools.spec.ts	Extends history rebuild tests to cover aliasing and per-turn model changes.
extensions/copilot/src/extension/chatSessions/copilotcli/node/test/copilotcliSession.spec.ts	Ensures assistant.usage model populates getLastResponseModelId().
extensions/copilot/src/extension/chatSessions/copilotcli/node/test/copilotCliModels.spec.ts	Tests dotted↔dashed Claude model id preference resolution.

Copilot's findings

• Files reviewed: 10/10 changed files
• Comments generated: 2

[DonJayamanne]

I think we can get this from the events. hence do not need to store this here.

[justschen]

from the SDK, the usage actually doesn't survive on reloads for some reason.

that session event for assistant.usage is ephemerel which means when we build the session from events only, we don't get back the model id, but we get back auto or undefined, which means it never gets rendered.

[DonJayamanne]

Got it, than you for clarification
Long live our metadata store solution

[justschen]

haha yeah it's a little unfortunate - i don't think there is anything we can do with SDK to turn that to emphemeral: false instead? otherwise this is the best we can do.