feat(tools): create_project_from_template

Generates a new repo from mathias/template-go-web via Gitea's generate
API, then substitutes __PROJECT_NAME__ and __MODULE_PATH__ placeholders
in six known files (best-effort, partial failure surfaced in result).

Validates name regex, allowlist, template flag, and destination
non-existence before generating. Adds Template field to gitea.Repo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/gitea-mcp/main.go

@@ -41,6 +41,7 @@ func main() {
 	reg.Register(tools.NewIssueComment(giteaClient, ownerAllow))
 	reg.Register(tools.NewPRComment(giteaClient, ownerAllow))
 	reg.Register(tools.NewPRFilesDiff(giteaClient, ownerAllow))
+	reg.Register(tools.NewCreateProjectFromTemplate(giteaClient, ownerAllow, "mathias", "template-go-web"))
 
 	mcpSrv := mcp.NewServer(mcp.ServerOptions{
 		Registry: reg,

internal/gitea/repos.go

@@ -15,6 +15,7 @@ type Repo struct {
 	Private       bool   `json:"private"`
 	CloneURL      string `json:"clone_url"`
 	HTMLURL       string `json:"html_url"`
+	Template      bool   `json:"template"`
 }
 
 func (c *Client) ListRepos(ctx context.Context, owner string, page, limit int) ([]Repo, error) {

internal/gitea/templates.go

@@ -0,0 +1,72 @@
+package gitea
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// GenerateFromTemplateArgs is the request body for POST /repos/{owner}/{repo}/generate.
+type GenerateFromTemplateArgs struct {
+	Owner         string `json:"owner"`
+	Name          string `json:"name"`
+	Description   string `json:"description,omitempty"`
+	Private       bool   `json:"private"`
+	DefaultBranch string `json:"default_branch,omitempty"`
+	GitContent    bool   `json:"git_content"` // include all template files
+}
+
+// GenerateFromTemplate creates a new repository from a template via POST /repos/{tmplOwner}/{tmplName}/generate.
+func (c *Client) GenerateFromTemplate(ctx context.Context, tmplOwner, tmplName string, args GenerateFromTemplateArgs) (*Repo, error) {
+	p := fmt.Sprintf("/api/v1/repos/%s/%s/generate", tmplOwner, tmplName)
+	payload, err := json.Marshal(args)
+	if err != nil {
+		return nil, err
+	}
+	body, status, err := c.PostJSON(ctx, p, payload)
+	if err != nil {
+		return nil, err
+	}
+	if err := MapStatus(status, body); err != nil {
+		return nil, err
+	}
+	var r Repo
+	if err := json.Unmarshal(body, &r); err != nil {
+		return nil, err
+	}
+	return &r, nil
+}
+
+// SubstituteFile reads a file from the given branch, applies string replacements,
+// and writes it back if any changes were made. Best-effort — returns a wrapped error
+// that includes the file path.
+func (c *Client) SubstituteFile(ctx context.Context, owner, repo, branch, path string, replacements map[string]string) error {
+	fc, err := c.GetFileContents(ctx, owner, repo, path, branch)
+	if err != nil {
+		return fmt.Errorf("read %s: %w", path, err)
+	}
+	decoded, err := base64.StdEncoding.DecodeString(fc.Content)
+	if err != nil {
+		return fmt.Errorf("decode %s: %w", path, err)
+	}
+	content := string(decoded)
+	for k, v := range replacements {
+		content = strings.ReplaceAll(content, k, v)
+	}
+	if content == string(decoded) {
+		return nil // no changes, skip write
+	}
+	encoded := base64.StdEncoding.EncodeToString([]byte(content))
+	_, err = c.UpsertFile(ctx, owner, repo, path, UpsertFileArgs{
+		Branch:  branch,
+		Content: encoded,
+		Message: "Apply template substitutions",
+		Sha:     fc.Sha,
+	})
+	if err != nil {
+		return fmt.Errorf("write %s: %w", path, err)
+	}
+	return nil
+}

internal/gitea/templates_test.go

@@ -0,0 +1,156 @@
+package gitea_test
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"sync/atomic"
+	"testing"
+
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGenerateFromTemplate(t *testing.T) {
+	var capturedBody []byte
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "/api/v1/repos/mathias/template-go-web/generate", r.URL.Path)
+		assert.Equal(t, http.MethodPost, r.Method)
+		var err error
+		capturedBody, err = io.ReadAll(r.Body)
+		require.NoError(t, err)
+		w.WriteHeader(http.StatusCreated)
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{
+			"name":"new-svc",
+			"full_name":"mathias/new-svc",
+			"default_branch":"main",
+			"description":"A new service",
+			"private":true,
+			"clone_url":"http://gitea.example.com/mathias/new-svc.git",
+			"html_url":"http://gitea.example.com/mathias/new-svc",
+			"template":false
+		}`))
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	repo, err := c.GenerateFromTemplate(context.Background(), "mathias", "template-go-web", gitea.GenerateFromTemplateArgs{
+		Owner:       "mathias",
+		Name:        "new-svc",
+		Description: "A new service",
+		Private:     true,
+		GitContent:  true,
+	})
+	require.NoError(t, err)
+
+	// Verify the captured POST body contains the expected fields.
+	var payload map[string]any
+	require.NoError(t, json.Unmarshal(capturedBody, &payload))
+	assert.Equal(t, "mathias", payload["owner"])
+	assert.Equal(t, "new-svc", payload["name"])
+	assert.Equal(t, "A new service", payload["description"])
+	assert.Equal(t, true, payload["private"])
+	assert.Equal(t, true, payload["git_content"])
+
+	// Verify the decoded repo fields.
+	assert.Equal(t, "new-svc", repo.Name)
+	assert.Equal(t, "mathias/new-svc", repo.FullName)
+	assert.Equal(t, "main", repo.DefaultBranch)
+	assert.Equal(t, "A new service", repo.Description)
+	assert.True(t, repo.Private)
+	assert.Equal(t, "http://gitea.example.com/mathias/new-svc.git", repo.CloneURL)
+	assert.Equal(t, "http://gitea.example.com/mathias/new-svc", repo.HTMLURL)
+}
+
+func TestSubstituteFileApplies(t *testing.T) {
+	originalContent := "module __MODULE_PATH__\n\ngo 1.22\n"
+	encoded := base64.StdEncoding.EncodeToString([]byte(originalContent))
+
+	var capturedPutBody []byte
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			assert.Equal(t, "/api/v1/repos/mathias/new-svc/contents/go.mod", r.URL.Path)
+			assert.Equal(t, "main", r.URL.Query().Get("ref"))
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"path":"go.mod","sha":"abc123","size":30,"content":"` + encoded + `","encoding":"base64"}`))
+		case http.MethodPut:
+			assert.Equal(t, "/api/v1/repos/mathias/new-svc/contents/go.mod", r.URL.Path)
+			var err error
+			capturedPutBody, err = io.ReadAll(r.Body)
+			require.NoError(t, err)
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(`{"content":{"path":"go.mod","sha":"newsha","html_url":""},"commit":{"sha":"commitsha","html_url":""}}`))
+		default:
+			t.Errorf("unexpected method %s", r.Method)
+			w.WriteHeader(http.StatusMethodNotAllowed)
+		}
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	err := c.SubstituteFile(context.Background(), "mathias", "new-svc", "main", "go.mod", map[string]string{
+		"__MODULE_PATH__": "gitea.d-ma.be/mathias/new-svc",
+	})
+	require.NoError(t, err)
+
+	// Verify the PUT body contains the substituted content.
+	require.NotNil(t, capturedPutBody, "PUT should have been called")
+	var payload map[string]string
+	require.NoError(t, json.Unmarshal(capturedPutBody, &payload))
+
+	decoded, err := base64.StdEncoding.DecodeString(payload["content"])
+	require.NoError(t, err)
+	assert.Contains(t, string(decoded), "gitea.d-ma.be/mathias/new-svc")
+	assert.NotContains(t, string(decoded), "__MODULE_PATH__")
+	assert.Equal(t, "abc123", payload["sha"])
+	assert.Equal(t, "Apply template substitutions", payload["message"])
+}
+
+func TestSubstituteFileNoChangeSkipsWrite(t *testing.T) {
+	originalContent := "module gitea.d-ma.be/mathias/existing\n\ngo 1.22\n"
+	encoded := base64.StdEncoding.EncodeToString([]byte(originalContent))
+
+	var putCount atomic.Int32
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"path":"go.mod","sha":"abc123","size":40,"content":"` + encoded + `","encoding":"base64"}`))
+		case http.MethodPut:
+			putCount.Add(1)
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(`{"content":{"path":"go.mod","sha":"newsha","html_url":""},"commit":{"sha":"c","html_url":""}}`))
+		}
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	// Replacements that don't match anything in the content.
+	err := c.SubstituteFile(context.Background(), "mathias", "new-svc", "main", "go.mod", map[string]string{
+		"__MODULE_PATH__": "gitea.d-ma.be/mathias/new-svc",
+	})
+	require.NoError(t, err)
+	assert.Equal(t, int32(0), putCount.Load(), "PUT should not be called when content is unchanged")
+}
+
+func TestSubstituteFileReadError(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+		_, _ = w.Write([]byte(`{"message":"file not found"}`))
+	}))
+	defer srv.Close()
+
+	c := gitea.NewClient(srv.URL, "tok")
+	err := c.SubstituteFile(context.Background(), "mathias", "new-svc", "main", "go.mod", map[string]string{
+		"__MODULE_PATH__": "gitea.d-ma.be/mathias/new-svc",
+	})
+	require.Error(t, err)
+	assert.True(t, errors.Is(err, gitea.ErrNotFound), "error should wrap ErrNotFound, got: %v", err)
+}

internal/tools/create_project_from_template.go

@@ -0,0 +1,146 @@
+package tools
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"regexp"
+
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/registry"
+)
+
+var nameRe = regexp.MustCompile(`^[a-z][a-z0-9-]{1,38}[a-z0-9]$`)
+
+var substitutionFiles = []string{
+	"go.mod",
+	"Taskfile.yml",
+	"Dockerfile",
+	".gitea/workflows/cd.yml",
+	"README.md",
+	".context/PROJECT.md",
+}
+
+func substitutions(owner, name string) map[string]string {
+	return map[string]string{
+		"__PROJECT_NAME__": name,
+		"__MODULE_PATH__":  "gitea.d-ma.be/" + owner + "/" + name,
+	}
+}
+
+// CreateProjectFromTemplate is the exported type so tests can reference it.
+type CreateProjectFromTemplate struct {
+	c             *gitea.Client
+	a             *allowlist.Allowlist
+	templateOwner string
+	templateName  string
+}
+
+func NewCreateProjectFromTemplate(c *gitea.Client, a *allowlist.Allowlist, tmplOwner, tmplName string) *CreateProjectFromTemplate {
+	return &CreateProjectFromTemplate{c: c, a: a, templateOwner: tmplOwner, templateName: tmplName}
+}
+
+func (t *CreateProjectFromTemplate) Descriptor() registry.ToolDescriptor {
+	return registry.ToolDescriptor{
+		Name:        "create_project_from_template",
+		Description: "Create a new project repo from the template, applying placeholder substitutions to known files.",
+		InputSchema: json.RawMessage(`{
+			"type":"object",
+			"properties":{
+				"owner":{"type":"string"},
+				"name":{"type":"string","pattern":"^[a-z][a-z0-9-]{1,38}[a-z0-9]$"},
+				"description":{"type":"string"},
+				"private":{"type":"boolean"}
+			},
+			"required":["owner","name"]
+		}`),
+	}
+}
+
+type createProjectArgs struct {
+	Owner       string `json:"owner"`
+	Name        string `json:"name"`
+	Description string `json:"description"`
+	Private     bool   `json:"private"`
+}
+
+type createProjectResult struct {
+	FullName         string   `json:"full_name"`
+	HTMLURL          string   `json:"html_url"`
+	CloneURL         string   `json:"clone_url"`
+	DefaultBranch    string   `json:"default_branch"`
+	FilesSubstituted []string `json:"files_substituted"`
+	PartialFailure   string   `json:"partial_failure,omitempty"`
+}
+
+func (t *CreateProjectFromTemplate) Call(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
+	var args createProjectArgs
+	if err := parseArgs(raw, &args); err != nil {
+		return nil, err
+	}
+
+	// Allowlist check first.
+	if err := t.a.Check(args.Owner); err != nil {
+		return nil, err
+	}
+
+	// Validate name format.
+	if !nameRe.MatchString(args.Name) {
+		return nil, fmt.Errorf("name %q does not match pattern %s: %w", args.Name, nameRe.String(), gitea.ErrValidation)
+	}
+
+	// Verify template exists and is marked as a template repo.
+	tmpl, err := t.c.GetRepo(ctx, t.templateOwner, t.templateName)
+	if err != nil {
+		return nil, fmt.Errorf("template lookup: %w", err)
+	}
+	if !tmpl.Template {
+		return nil, fmt.Errorf("repo %s/%s is not marked as template: %w", t.templateOwner, t.templateName, gitea.ErrValidation)
+	}
+
+	// Verify destination doesn't already exist.
+	if _, err := t.c.GetRepo(ctx, args.Owner, args.Name); err == nil {
+		return nil, fmt.Errorf("destination %s/%s already exists: %w", args.Owner, args.Name, gitea.ErrConflict)
+	} else if !errors.Is(err, gitea.ErrNotFound) {
+		return nil, fmt.Errorf("destination check: %w", err)
+	}
+
+	// Generate repo from template.
+	newRepo, err := t.c.GenerateFromTemplate(ctx, t.templateOwner, t.templateName, gitea.GenerateFromTemplateArgs{
+		Owner:       args.Owner,
+		Name:        args.Name,
+		Description: args.Description,
+		Private:     args.Private,
+		GitContent:  true,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("generate: %w", err)
+	}
+
+	result := createProjectResult{
+		FullName:      newRepo.FullName,
+		HTMLURL:       newRepo.HTMLURL,
+		CloneURL:      newRepo.CloneURL,
+		DefaultBranch: newRepo.DefaultBranch,
+	}
+
+	// Substitute placeholders in known files (best-effort).
+	repls := substitutions(args.Owner, args.Name)
+	branch := newRepo.DefaultBranch
+	for _, path := range substitutionFiles {
+		if err := t.c.SubstituteFile(ctx, args.Owner, args.Name, branch, path, repls); err != nil {
+			// Files that don't exist in this template are silently skipped.
+			if errors.Is(err, gitea.ErrNotFound) {
+				continue
+			}
+			// Any other error halts the substitution pass with partial_failure recorded.
+			result.PartialFailure = fmt.Sprintf("%s: %v", path, err)
+			break
+		}
+		result.FilesSubstituted = append(result.FilesSubstituted, path)
+	}
+
+	return textOK(result)
+}

internal/tools/create_project_from_template_test.go

@@ -0,0 +1,266 @@
+package tools_test
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/allowlist"
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/gitea"
+	"gitea.d-ma.be/mathias/gitea-mcp/internal/tools"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// substitutionFileList matches the tool's internal list — used to drive fake server routing.
+var substitutionFileList = []string{
+	"go.mod",
+	"Taskfile.yml",
+	"Dockerfile",
+	".gitea/workflows/cd.yml",
+	"README.md",
+	".context/PROJECT.md",
+}
+
+// contentWithPlaceholder is a template file body that contains the placeholder.
+const contentWithPlaceholder = "# __PROJECT_NAME__\nmodule __MODULE_PATH__\n"
+
+func encodedContent(s string) string {
+	return base64.StdEncoding.EncodeToString([]byte(s))
+}
+
+// fileContentsJSON returns a JSON FileContents object for the given path.
+func fileContentsJSON(path string) string {
+	enc := encodedContent(contentWithPlaceholder)
+	return fmt.Sprintf(`{"path":%q,"sha":"sha-%s","size":40,"content":%q,"encoding":"base64"}`,
+		path, strings.ReplaceAll(path, "/", "-"), enc)
+}
+
+// fileWriteResultJSON returns a minimal FileWriteResult JSON.
+func fileWriteResultJSON(path string) string {
+	return fmt.Sprintf(`{"content":{"path":%q,"sha":"newsha","html_url":""},"commit":{"sha":"c","html_url":""}}`, path)
+}
+
+// newTemplateRepoJSON returns a JSON Repo marked as template.
+func newTemplateRepoJSON(name string, isTemplate bool) string {
+	return fmt.Sprintf(`{"name":%q,"full_name":"mathias/%s","default_branch":"main","description":"","private":false,"clone_url":"http://gitea.example.com/mathias/%s.git","html_url":"http://gitea.example.com/mathias/%s","template":%v}`,
+		name, name, name, name, isTemplate)
+}
+
+// newGeneratedRepoJSON returns the JSON for the newly generated repo.
+func newGeneratedRepoJSON(name string) string {
+	return fmt.Sprintf(`{"name":%q,"full_name":"mathias/%s","default_branch":"main","description":"","private":false,"clone_url":"http://gitea.example.com/mathias/%s.git","html_url":"http://gitea.example.com/mathias/%s","template":false}`,
+		name, name, name, name)
+}
+
+func newCreateProjectTool(srvURL string) *tools.CreateProjectFromTemplate {
+	c := gitea.NewClient(srvURL, "tok")
+	a := allowlist.New([]string{"mathias"})
+	return tools.NewCreateProjectFromTemplate(c, a, "mathias", "template-go-web")
+}
+
+// TestCreateProjectHappyPath: all 6 files served and substituted.
+func TestCreateProjectHappyPath(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch {
+		// Template repo lookup
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/template-go-web":
+			_, _ = w.Write([]byte(newTemplateRepoJSON("template-go-web", true)))
+
+		// Destination repo lookup — 404 means it doesn't exist yet
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/new-svc":
+			w.WriteHeader(http.StatusNotFound)
+			_, _ = w.Write([]byte(`{"message":"not found"}`))
+
+		// Generate
+		case r.Method == http.MethodPost && r.URL.Path == "/api/v1/repos/mathias/template-go-web/generate":
+			w.WriteHeader(http.StatusCreated)
+			_, _ = w.Write([]byte(newGeneratedRepoJSON("new-svc")))
+
+		// File contents GET — handle all 6 substitution files
+		case r.Method == http.MethodGet && strings.HasPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/"):
+			filePath := strings.TrimPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/")
+			_, _ = w.Write([]byte(fileContentsJSON(filePath)))
+
+		// File contents PUT — handle all 6 substitution files
+		case r.Method == http.MethodPut && strings.HasPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/"):
+			filePath := strings.TrimPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/")
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(fileWriteResultJSON(filePath)))
+
+		default:
+			t.Errorf("unexpected request: %s %s", r.Method, r.URL.Path)
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}))
+	defer srv.Close()
+
+	tool := newCreateProjectTool(srv.URL)
+	result, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"mathias","name":"new-svc","description":"A new service"}`))
+	require.NoError(t, err)
+
+	var out struct {
+		FullName         string   `json:"full_name"`
+		HTMLURL          string   `json:"html_url"`
+		CloneURL         string   `json:"clone_url"`
+		DefaultBranch    string   `json:"default_branch"`
+		FilesSubstituted []string `json:"files_substituted"`
+		PartialFailure   string   `json:"partial_failure,omitempty"`
+	}
+	require.NoError(t, json.Unmarshal(result, &out))
+
+	assert.Equal(t, "mathias/new-svc", out.FullName)
+	assert.Equal(t, "http://gitea.example.com/mathias/new-svc", out.HTMLURL)
+	assert.Equal(t, "main", out.DefaultBranch)
+	assert.ElementsMatch(t, substitutionFileList, out.FilesSubstituted)
+	assert.Empty(t, out.PartialFailure)
+}
+
+// TestCreateProjectNameRegexFailure: invalid name returns ErrValidation without hitting network.
+func TestCreateProjectNameRegexFailure(t *testing.T) {
+	tool := tools.NewCreateProjectFromTemplate(
+		gitea.NewClient("http://unused", ""),
+		allowlist.New([]string{"mathias"}),
+		"mathias", "template-go-web",
+	)
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"mathias","name":"INVALID_NAME"}`))
+	require.Error(t, err)
+	assert.ErrorIs(t, err, gitea.ErrValidation)
+}
+
+// TestCreateProjectAllowlistRejects: owner not in allowlist returns error.
+func TestCreateProjectAllowlistRejects(t *testing.T) {
+	tool := tools.NewCreateProjectFromTemplate(
+		gitea.NewClient("http://unused", ""),
+		allowlist.New([]string{"mathias"}),
+		"mathias", "template-go-web",
+	)
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"evil","name":"new-svc"}`))
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "allowlist")
+}
+
+// TestCreateProjectTemplateNotTemplate: template repo exists but is not marked as template.
+func TestCreateProjectTemplateNotTemplate(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		// Template lookup returns a non-template repo.
+		if r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/template-go-web" {
+			_, _ = w.Write([]byte(newTemplateRepoJSON("template-go-web", false)))
+			return
+		}
+		t.Errorf("unexpected request: %s %s", r.Method, r.URL.Path)
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer srv.Close()
+
+	tool := newCreateProjectTool(srv.URL)
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"mathias","name":"new-svc"}`))
+	require.Error(t, err)
+	assert.ErrorIs(t, err, gitea.ErrValidation)
+}
+
+// TestCreateProjectDestinationExists: destination repo already exists.
+func TestCreateProjectDestinationExists(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch {
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/template-go-web":
+			_, _ = w.Write([]byte(newTemplateRepoJSON("template-go-web", true)))
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/new-svc":
+			// Destination exists — return 200.
+			_, _ = w.Write([]byte(newTemplateRepoJSON("new-svc", false)))
+		default:
+			t.Errorf("unexpected request: %s %s", r.Method, r.URL.Path)
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}))
+	defer srv.Close()
+
+	tool := newCreateProjectTool(srv.URL)
+	_, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"mathias","name":"new-svc"}`))
+	require.Error(t, err)
+	assert.ErrorIs(t, err, gitea.ErrConflict)
+}
+
+// TestCreateProjectMidPassSubstitutionFailure: the 4th file (.gitea/workflows/cd.yml) PUT fails;
+// the first 3 are substituted, partial_failure is populated, no Go error is returned.
+func TestCreateProjectMidPassSubstitutionFailure(t *testing.T) {
+	// Files that should succeed (index 0-2 in substitutionFileList).
+	successFiles := map[string]bool{
+		"go.mod":       true,
+		"Taskfile.yml": true,
+		"Dockerfile":   true,
+	}
+	// The 4th file (index 3) is .gitea/workflows/cd.yml — its PUT returns 500.
+	failFile := ".gitea/workflows/cd.yml"
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch {
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/template-go-web":
+			_, _ = w.Write([]byte(newTemplateRepoJSON("template-go-web", true)))
+
+		case r.Method == http.MethodGet && r.URL.Path == "/api/v1/repos/mathias/new-svc":
+			w.WriteHeader(http.StatusNotFound)
+			_, _ = w.Write([]byte(`{"message":"not found"}`))
+
+		case r.Method == http.MethodPost && r.URL.Path == "/api/v1/repos/mathias/template-go-web/generate":
+			w.WriteHeader(http.StatusCreated)
+			_, _ = w.Write([]byte(newGeneratedRepoJSON("new-svc")))
+
+		case r.Method == http.MethodGet && strings.HasPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/"):
+			filePath := strings.TrimPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/")
+			_, _ = w.Write([]byte(fileContentsJSON(filePath)))
+
+		case r.Method == http.MethodPut && strings.HasPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/"):
+			filePath := strings.TrimPrefix(r.URL.Path, "/api/v1/repos/mathias/new-svc/contents/")
+			if filePath == failFile {
+				// Simulate upstream 500.
+				w.WriteHeader(http.StatusInternalServerError)
+				_, _ = w.Write([]byte(`{"message":"internal server error"}`))
+				return
+			}
+			if !successFiles[filePath] {
+				t.Errorf("unexpected PUT for file: %s", filePath)
+				w.WriteHeader(http.StatusNotFound)
+				return
+			}
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(fileWriteResultJSON(filePath)))
+
+		default:
+			t.Errorf("unexpected request: %s %s", r.Method, r.URL.Path)
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}))
+	defer srv.Close()
+
+	tool := newCreateProjectTool(srv.URL)
+	result, err := tool.Call(context.Background(), json.RawMessage(`{"owner":"mathias","name":"new-svc"}`))
+	// Best-effort: no Go error returned, partial state in result.
+	require.NoError(t, err)
+
+	var out struct {
+		FullName         string   `json:"full_name"`
+		FilesSubstituted []string `json:"files_substituted"`
+		PartialFailure   string   `json:"partial_failure,omitempty"`
+	}
+	require.NoError(t, json.Unmarshal(result, &out))
+
+	// First 3 files should be in FilesSubstituted.
+	assert.Len(t, out.FilesSubstituted, 3)
+	assert.Contains(t, out.FilesSubstituted, "go.mod")
+	assert.Contains(t, out.FilesSubstituted, "Taskfile.yml")
+	assert.Contains(t, out.FilesSubstituted, "Dockerfile")
+	assert.NotContains(t, out.FilesSubstituted, failFile)
+
+	// partial_failure should be non-empty.
+	assert.NotEmpty(t, out.PartialFailure, "partial_failure should be populated on mid-pass failure")
+}