Investigation: chat issue links silently fail (root cause in vscode-pull-request-github)

[Copilot]

Clicking an issue link like vscode-insiders://github.vscode-pull-request-github/open-issue-webview?uri=https://github.com/microsoft/vscode-tools/issues/964 in chat does nothing. No code changes are made in this repo — investigation shows the bug lives in microsoft/vscode-pull-request-github.

Root cause

The click flows correctly through vscode core: markdownRenderer.activateLink → openerService.open → RelayURLService → main URL service → ext-host → GHPR UriHandler → fromOpenIssueWebviewUri.

In microsoft/vscode-pull-request-github (src/common/uri.ts):

• fromOpenOrCheckoutPullRequestWebviewUri accepts both the legacy JSON query and the simplified uri=https://github.com/owner/repo/pull/N format.
• fromOpenIssueWebviewUri only accepts the JSON query — it does JSON.parse(uri.query.split('&')[0]), which throws on uri=https://... and silently returns undefined.

The LM emits the simplified format by analogy with the PR skill (src/lm/skills/create-pull-request/SKILL.md), so the issue handler never resolves and the webview is never opened.

Recommended fix (in vscode-pull-request-github, not here)

Mirror the PR variant in fromOpenIssueWebviewUri:

const queryParams = new URLSearchParams(uri.query);
const uriParam = queryParams.get('uri');
if (uriParam) {
    const m = /^https?:\/\/github\.com\/(?<owner>[^\/]+)\/(?<repo>[^\/]+)\/issues\/(?<issueNumber>\d+)$/.exec(uriParam);
    if (m?.groups) {
        const params = { owner: m.groups.owner, repo: m.groups.repo, issueNumber: parseInt(m.groups.issueNumber, 10) };
        if (!validateOpenWebviewParams(params.owner, params.repo, params.issueNumber.toString())) { return; }
        return params;
    }
}
// fall back to existing JSON parsing

The issue should be transferred to microsoft/vscode-pull-request-github.