feat(server): resolve GitHub issues and prepare an issue worktree thread

[Artic0din]

Problem

There is no way to start agent work from a GitHub issue.
The user has to read the issue on GitHub, create a branch and worktree by hand, and paste the issue into the composer.
This PR is the server half of the fork experiment tracked in #1.

Change

• git.resolveIssue reads one issue through gh issue view, behind a new optional getIssue capability on source control providers. Only GitHub implements it; other hosts get "Only GitHub issues are supported."
• git.prepareIssueThread resolves the issue, then creates a worktree on issue/<number>-<slug> from the default branch and runs the project setup script.
• Starting the same issue again reuses its worktree, even if the issue title changed since. An existing branch without a worktree is checked out instead of recreated.
• A stale worktree registration (folder deleted by hand) is pruned first. An issue branch checked out in the main repo is refused rather than handed back as a worktree.
• A pull request number or URL is rejected with "#N is a pull request, not an issue." A missing number says "Issue N not found."

The web dialog that calls these RPCs follows in a stacked PR for #3.

Scope and approval

Fork-only experiment, tracked in #1 and #2.
Upstream context: pingdotgg#11067 suggests "creating a thread from an issue can follow" the first Issues slice. This change deliberately has no issue browsing UI.

Verification

• 388 tests pass across the 9 touched test files (GitManager, GitWorkflowService, GitHubSourceControlProvider, GitHubCli, VcsProcess, GitHubPullRequestCli, shared git, contracts git and rpc).
• New tests: issue reference parsing, branch naming (emoji-only and "Update" titles), resolve by number, open and merged PR numbers rejected, missing issue, unsupported host, worktree created from main, reuse on second start, reuse after a title change, existing branch without a worktree, deleted worktree folder, branch checked out in the main repo.
• apps/server and packages/contracts typecheck clean.
• Real gh against this fork: a fork issue URL resolves; a bare 1 resolves against origin (upstream) and hits upstream PR feat: start agent work from a GitHub issue #1, which is how the merged-PR bug was found and fixed.
• Not checked: the UI (lands in the next PR).

Release note: Agents can start work from a GitHub issue in its own worktree (server support).

Fixes #2

Implemented by Claude Opus 5.5 (1M context) in Claude Code, running inside T3 Code.

🤖 Generated with Claude Code

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-06T03:04:16.348179Z	eb9b318	New commits
🔒 Security Review	✅ Completed 2026-10-05T09:37:38.087498Z	6dec9d3	PR opened

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[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="apps/server/src/git/GitManager.ts" line_range="2405-2414" />
<code_context>
+      const existing =
+        localRefs.find((ref) => ref.name === branch) ??
+        localRefs.find((ref) => ref.name.startsWith(issueBranchPrefix));
+      if (existing?.worktreePath) {
+        const rootWorktreePath = yield* canonicalizeExistingPath(input.cwd);
+        if ((yield* canonicalizeExistingPath(existing.worktreePath)) === rootWorktreePath) {
+          return yield* new GitManagerError({
+            operation: "prepareIssueThread",
+            cwd: input.cwd,
+            detail: `${existing.name} is already checked out in the main repo. Switch the main repo off that branch to start a worktree thread.`,
+          });
+        }
+        return { issue, branch: existing.name, worktreePath: existing.worktreePath };
+      }
+
</code_context>
<issue_to_address>
**issue (bug_risk):** The main-checkout comparison canonicalizes `input.cwd` rather than the repository root, so a request whose `cwd` is a subdirectory of the main repository is treated as a different worktree and returns the main checkout as the issue worktree even though that branch is checked out in the main repo.

**Triggers:** When `cwd` points to a subdirectory inside the repository and the matching issue branch is checked out in the main checkout.

**Suggested fix:** Resolve `input.cwd` to the Git worktree root before comparing it with `existing.worktreePath`, or obtain the root from Git directly.
</issue_to_address>

Fix all in Cursor

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[Artic0din]

Pushed 64abefd: fix(server): keep the issue capability when routing to a provider.

The manual pass for #5 found that SourceControlProviderRegistry.bindProviderContext rebuilt each provider without the optional getIssue capability, so every real project reported "Only GitHub issues are supported". The earlier GitManager tests injected the provider directly and bypassed the registry. New test: 'keeps the issue capability on a resolved GitHub provider' (failed first, passes now; registry suite 13/13).

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💡 Codex Review

t3code/apps/server/src/git/GitManager.ts

Lines 2570 to 2572 in eb9b318

	if (yield* refExists(`refs/remotes/${remote}/${baseBranch}`)) {
	return `${remote}/${baseBranch}`;
	}

Return the fully qualified remote default ref

When the default exists only as origin/main and the repository also has a valid local branch named origin/main, this verifies the unambiguous refs/remotes/origin/main but then returns the short name. GitVcsDriver.createWorktree passes that short name as the start commit; on Git 2.43 this produces warning: refname 'origin/main' is ambiguous followed by fatal: ambiguous object name: 'origin/main', so the issue worktree cannot be created. Return the same fully qualified remote ref that was verified.

---

t3code/apps/server/src/git/GitManager.ts

Lines 2461 to 2465 in eb9b318

	if (cwdPath === existingPath || cwdPath.startsWith(`${existingPath}${path.sep}`)) {
	return yield* new GitManagerError({
	operation: "prepareIssueThread",
	cwd: input.cwd,
	detail: `${existing.name} is already checked out in the main repo. Switch the main repo off that branch to start a worktree thread.`,

Reuse the current linked worktree

When the registered project is itself a linked Git worktree already checked out on this issue branch, cwdPath equals or falls under existingPath, so this reports that the branch is in the main checkout and refuses the request. Git projects rooted at linked worktrees— including registered monorepo subdirectories inside one—therefore cannot use the advertised same-issue reuse behavior even though existing.worktreePath is exactly the worktree that should be returned; distinguish the primary checkout from a linked worktree before rejecting it.

---

t3code/apps/web/src/components/ChatView.tsx

Lines 2866 to 2868 in eb9b318

	if (activeProject?.environmentId !== input.environmentId) {
	throw new Error(
	"This project moved to another environment while the worktree was created. Close this dialog and start the issue again.",

Validate against the current environment after preparation

When automatic environment selection moves the draft while prepareIssueThread is pending, the in-flight handleConfirm invocation still holds the onPrepared callback from the render where the request began, and that callback captured the old activeProject. This comparison therefore sees the old environment on both sides and passes, after which the stale openOrReuseProjectDraftThread closure can attach the old environment's worktree path to the draft that has moved; read the draft's current project/environment from a ref or store when preparation completes instead of validating captured render state.

AGENTS.md reference: AGENTS.md:L75-L75

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