Method fork

src/node/services/workspaceService.ts:6398–6781

(
    sourceWorkspaceId: string,
    newName?: string,
    sourceMessageId?: string,
    pendingAutoTitle?: boolean
  )

  }

  async fork(
    sourceWorkspaceId: string,
    newName?: string,
    sourceMessageId?: string,
    pendingAutoTitle?: boolean
  ): Promise<Result<{ metadata: FrontendWorkspaceMetadata; projectPath: string }>> {
    try {
      const sourceMetadataResult = await this.aiService.getWorkspaceMetadata(sourceWorkspaceId);
      if (!sourceMetadataResult.success) {
        return Err(`Failed to get source workspace metadata: ${sourceMetadataResult.error}`);
      }
      const sourceMetadata = sourceMetadataResult.data;
      const partialSnapshot =
        sourceMessageId == null ? await this.historyService.readPartial(sourceWorkspaceId) : null;
      const foundProjectPath = sourceMetadata.projectPath;
      const projectName = sourceMetadata.projectName;
      const sourceRuntimeConfig = sourceMetadata.runtimeConfig;

      // Policy: do not allow creating new workspaces (including via fork) with a disallowed runtime.
      if (this.policyService?.isEnforced()) {
        if (!this.policyService.isRuntimeAllowed(sourceRuntimeConfig)) {
          return Err("Forking this workspace is not allowed by policy (runtime disabled)");
        }
      }

      // Trust gate: block fork for untrusted projects.
      // Same defense-in-depth as create() — the frontend shows a dialog,
      // but forking is a secondary creation path that needs backend gating.
      const projectConfig = this.config
        .loadConfigOrDefault()
        .projects.get(stripTrailingSlashes(foundProjectPath));
      if (!projectConfig?.trusted) {
        return Err(
          "This project must be trusted before creating workspaces. Trust the project in Settings → Security, or create a workspace from the project page."
        );
      }

      // Auto-generate branch name (and title) when user omits one (seamless fork).
      // Uses pattern: {parentName}-{N} for branch, "{parentTitle} (N)" for title.
      const isAutoName = newName == null;
      // Fetch all metadata upfront for both branch name and title collision checks.
      const allMetadata = isAutoName ? await this.config.getAllWorkspaceMetadata() : [];
      let resolvedName: string;
      if (isAutoName) {
        const existingNamesSet = new Set(
          allMetadata.filter((m) => m.projectPath === foundProjectPath).map((m) => m.name)
        );
        // Also include local branch names to avoid silently reusing stale branches that
        // were left behind on disk but no longer exist in config metadata.
        try {
          for (const branchName of await listLocalBranches(foundProjectPath)) {
            existingNamesSet.add(branchName);
          }
        } catch (error) {
          log.debug("Failed to list local branches for fork auto-name preflight", {
            projectPath: foundProjectPath,
            error: getErrorMessage(error),
          });