TPI: Agent Host Binaries Download Progress Notification

[Giuspepe]

Refs: #322919

• macOS @chrmarti
• windows @kycutler
• linux @eleanorjboyd

Complexity: 3

Authors: @Giuspepe

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Context

VS Code ships the Claude and Codex agents but not their native SDK binaries for the agent host, those are downloaded on demand from the CDN the first time a session of that provider starts, then cached on disk. The tarballs are 70-95 MB, so on a cold cache the first session used to block for several seconds with no feedback. This feature shows a progress notification while the SDK downloads.

Set up

The download only fires on a cold cache, so you must clear it before each run:

rm -rf "$HOME/Library/Application Support/Code - Insiders/agent-host/sdk-cache/claude"
rm -rf "$HOME/Library/Application Support/Code - Insiders/agent-host/sdk-cache/codex"

Codex must be enabled, if it doesn't appear in the session-type picker, set "chat.agentHost.codexAgent.enabled": true (and "chat.agents.claude.preferAgentHost": true, "chat.agentHost.claudeAgent.enabled": true for Claude).

Test

1. Quit Insiders
2. Clear the SDK cache for Codex/Claude (see Set up)
3. Open Insiders
4. Start a New Session in a valid workspace folder, pick Codex in the "with ▾" picker, type any message, and Send. - ✅ A "Downloading Codex agent…" notification appears (bottom-right) with a progress bar that advances 0→100%.
   • ✅ When the download completes, the notification dismisses on its own and the session starts.
5. Repeat steps 2–3 for Claude → expect a "Downloading Claude agent…" notification.

Verify no duplicate / stuck notifications

5. Clear the Codex cache again, restart, start a Codex session and Send so the download begins.
6. While it's still downloading, click New Session (⌘N / Ctrl+N) several times (Codex stays selected).
   • ✅ There is still exactly one download notification — clicking New Session does not stack additional ones.
7. While a download is in progress, open a New Session and switch the picker to a different provider (e.g. Claude).
   • ✅ The in-progress notification keeps advancing and dismisses normally on completion — it does not freeze or get left behind.

Notes

• The download runs in the agent-host process; the notification is rendered in the app regardless of whether the host is local or remote (WSL/SSH).
• If AI features are disabled (chat.disableAIFeatures), no notification should appear.
• A second session of the same provider started during a download shares the single notification (one download, one indicator).

[eleanorjboyd]

note for @digitarald you command to remove the cache is likely different since you would be on windows