github/github-mcp-server · warning

failed to get file tree

Error message

failed to get file tree

What it means

Thrown by completePath when client.Git.GetTree(ctx, owner, repo, refVal, true) fails or returns nil. The call fetches the full repository tree recursively; the underlying error is discarded and replaced. The most common real cause is GitHub rejecting a recursive fetch of a very large tree (409 Conflict / 'tree is too large' style errors), but invalid refs and auth failures also land here.

Source

Thrown at pkg/github/repository_resource_completions.go:265

	if refVal == "" {
		refVal = "HEAD"
	}

	// Determine the prefix to complete (directory path or file path)
	prefix := argValue
	if prefix != "" && !strings.HasSuffix(prefix, "/") {
		lastSlash := strings.LastIndex(prefix, "/")
		if lastSlash >= 0 {
			prefix = prefix[:lastSlash+1]
		} else {
			prefix = ""
		}
	}

	// Get the tree for the ref (recursive)
	tree, _, err := client.Git.GetTree(ctx, owner, repo, refVal, true)
	if err != nil || tree == nil {
		return nil, errors.New("failed to get file tree")
	}

	// Collect immediate children of the prefix (files and directories, no duplicates)
	dirs := map[string]struct{}{}
	files := map[string]struct{}{}
	prefixLen := len(prefix)
	for _, entry := range tree.Entries {
		if !strings.HasPrefix(entry.GetPath(), prefix) {
			continue
		}
		rel := entry.GetPath()[prefixLen:]
		if rel == "" {
			continue
		}
		// Only immediate children
		slashIdx := strings.Index(rel, "/")
		if slashIdx >= 0 {
			// Directory: only add the directory name (with trailing slash), prefixed with full path

View on GitHub (pinned to 0ea1f775a7)

Solutions

1. Verify the ref exists (git ls-remote or GET /repos/{owner}/{repo}/git/ref/{ref}) before completing paths
2. For very large repos, avoid recursive tree completion: fetch the root tree non-recursively and walk only the prefix directory
3. Check token scopes/permissions on the target repository
4. Wrap the underlying error with %w so the true HTTP status is visible instead of the generic message
5. Retry once on transient 5xx/network failures

Example fix

// before
tree, _, err := client.Git.GetTree(ctx, owner, repo, refVal, true)
if err != nil || tree == nil {
    return nil, errors.New("failed to get file tree")
}

// after
tree, resp, err := client.Git.GetTree(ctx, owner, repo, refVal, true)
if err != nil {
    return nil, fmt.Errorf("failed to get file tree (ref %s, HTTP %d): %w", refVal, resp.StatusCode, err)
}
if tree == nil {
    return nil, errors.New("failed to get file tree: nil response")
}

// Validate the ref exists before requesting the recursive tree
_, resp, err := client.Git.GetRef(ctx, owner, repo, "refs/heads/"+refVal)
if err != nil || resp == nil {
    // ref invalid; skip path completion
    return nil
}

// Degrade path completion on tree-fetch failure instead of failing the request
values, err := completePath(ctx, client, resolved, argValue)
if err != nil {
    if strings.Contains(err.Error(), "failed to get file tree") {
        return &mcp.CompleteResult{Completion: mcp.CompletionResultDetails{Values: []string{}}}, nil
    }
    return nil, err
}

When it happens

Trigger: Path completion against a repository whose tree exceeds GitHub's recursive-fetch limits (very large monorepos); refVal resolves to a nonexistent branch/SHA/tag; token lacks read access to the repo; transient network/API failure; tree response nil.

Common situations: Autocompleting paths on huge repositories (e.g. linux-scale monorepos); ref segment resolved to a value that was deleted or typo'd; fine-grained PAT without 'Contents: read' on the target repo.

Related errors

• failed to get repositories
• owner or repo not specified
• failed to get GitHub client: %w
• failed to read response body: %w
• failed to read file content: %w

AI-assisted analysis of github/github-mcp-server@0ea1f775a7 (2026-08-15). Data as JSON: /api/errors/dc1c024061c4aafa. Report an issue: GitHub.