Release v0.24.0v0.24.0

Bring unit test coverage from ~75% to 85.1% project-wide. All internal
packages now exceed 80% coverage. Refactored cmd entrypoints to extract
testable run() functions with injectable seams.

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

22 files changed, 3043 insertions, 34 deletions

diff --git a/cmd/hexai-mcp-server/main.go b/cmd/hexai-mcp-server/main.go
index 557172f..1f52616 100644
--- a/cmd/hexai-mcp-server/main.go
+++ b/cmd/hexai-mcp-server/main.go
@@ -4,7 +4,7 @@ package main
 import (
 	"flag"
 	"fmt"
-	"log"
+	"io"
 	"os"
 
 	"codeberg.org/snonux/hexai/internal"
@@ -12,6 +12,12 @@ import (
 	"codeberg.org/snonux/hexai/internal/hexaimcp"
 )
 
+// Seams for testing: override in tests to avoid launching real MCP server.
+var (
+	runMCP      = hexaimcp.Run
+	runBackfill = hexaimcp.RunBackfill
+)
+
 // printDeprecationWarning outputs a deprecation notice to stderr explaining
 // that hexai-mcp-server is experimental and not actively maintained.
 func printDeprecationWarning() {
@@ -36,6 +42,17 @@ Use at your own risk.
 	fmt.Fprintln(os.Stderr, warning)
 }
 
+// mcpOptions holds the parsed command-line flags for the MCP server.
+type mcpOptions struct {
+	logPath          string
+	configPath       string
+	promptsDir       string
+	slashCommandSync bool
+	slashCommandDir  string
+	syncAll          bool
+	showVersion      bool
+}
+
 func main() {
 	printDeprecationWarning()
 
@@ -49,33 +66,45 @@ func main() {
 	showVersion := flag.Bool("version", false, "print version and exit")
 	flag.Parse()
 
-	if *showVersion {
-		fmt.Println(internal.Version)
-		return
+	opts := mcpOptions{
+		logPath:          *logPath,
+		configPath:       *configPath,
+		promptsDir:       *promptsDir,
+		slashCommandSync: *slashCommandSync,
+		slashCommandDir:  *slashCommandDir,
+		syncAll:          *syncAll,
+		showVersion:      *showVersion,
+	}
+	if err := run(opts, os.Stdin, os.Stdout, os.Stderr); err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
 	}
+}
 
-	// If prompts-dir is specified, set environment variable for RunWithFactory
-	if *promptsDir != "" {
-		os.Setenv("HEXAI_MCP_PROMPTS_DIR", *promptsDir)
+// run executes the MCP server logic with the given options and I/O streams.
+func run(opts mcpOptions, stdin io.Reader, stdout, stderr io.Writer) error {
+	// Set environment variables for RunWithFactory based on flag values
+	if opts.promptsDir != "" {
+		os.Setenv("HEXAI_MCP_PROMPTS_DIR", opts.promptsDir)
 	}
-	if *slashCommandSync {
+	if opts.slashCommandSync {
 		os.Setenv("HEXAI_MCP_SLASHCOMMAND_SYNC", "true")
 	}
-	if *slashCommandDir != "" {
-		os.Setenv("HEXAI_MCP_SLASHCOMMAND_DIR", *slashCommandDir)
+	if opts.slashCommandDir != "" {
+		os.Setenv("HEXAI_MCP_SLASHCOMMAND_DIR", opts.slashCommandDir)
 	}
 
-	// Handle backfill operation
-	if *syncAll {
-		if err := hexaimcp.RunBackfill(*logPath, *configPath); err != nil {
-			log.Fatalf("backfill error: %v", err)
-		}
-		return
+	if opts.showVersion {
+		fmt.Fprintln(stdout, internal.Version)
+		return nil
 	}
 
-	if err := hexaimcp.Run(*logPath, *configPath, os.Stdin, os.Stdout, os.Stderr); err != nil {
-		log.Fatalf("server error: %v", err)
+	// Handle backfill operation
+	if opts.syncAll {
+		return runBackfill(opts.logPath, opts.configPath)
 	}
+
+	return runMCP(opts.logPath, opts.configPath, stdin, stdout, stderr)
 }
 
 // defaultLogPath returns the default MCP log file path in the state directory.
diff --git a/cmd/hexai-mcp-server/main_test.go b/cmd/hexai-mcp-server/main_test.go
new file mode 100644
index 0000000..cf48954
--- /dev/null
+++ b/cmd/hexai-mcp-server/main_test.go
@@ -0,0 +1,166 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"os"
+	"strings"
+	"testing"
+
+	"codeberg.org/snonux/hexai/internal"
+)
+
+func TestPrintDeprecationWarning(t *testing.T) {
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to create pipe: %v", err)
+	}
+
+	oldStderr := os.Stderr
+	os.Stderr = w
+	defer func() { os.Stderr = oldStderr }()
+
+	printDeprecationWarning()
+
+	if err := w.Close(); err != nil {
+		t.Fatalf("failed to close pipe writer: %v", err)
+	}
+
+	b, err := io.ReadAll(r)
+	if err != nil {
+		t.Fatalf("failed to read pipe: %v", err)
+	}
+
+	output := string(b)
+	for _, want := range []string{"DEPRECATION NOTICE", "EXPERIMENTAL", "NOT ACTIVELY MAINTAINED"} {
+		if !strings.Contains(output, want) {
+			t.Errorf("expected %q in output, got %q", want, output)
+		}
+	}
+}
+
+func TestDefaultLogPath(t *testing.T) {
+	path := defaultLogPath()
+	if path == "" {
+		t.Fatal("expected non-empty log path")
+	}
+	if !strings.HasSuffix(path, "hexai-mcp-server.log") {
+		t.Errorf("expected path to end with hexai-mcp-server.log, got %q", path)
+	}
+}
+
+func TestRun_ShowVersion(t *testing.T) {
+	var stdout bytes.Buffer
+	opts := mcpOptions{showVersion: true}
+	if err := run(opts, nil, &stdout, nil); err != nil {
+		t.Fatalf("run --version: %v", err)
+	}
+	got := strings.TrimSpace(stdout.String())
+	if got != internal.Version {
+		t.Fatalf("expected version %q, got %q", internal.Version, got)
+	}
+}
+
+func TestRun_SetsPromptsDir(t *testing.T) {
+	t.Setenv("HEXAI_MCP_PROMPTS_DIR", "")
+	opts := mcpOptions{showVersion: true, promptsDir: "/tmp/test-prompts"}
+	var stdout bytes.Buffer
+	if err := run(opts, nil, &stdout, nil); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	if got := os.Getenv("HEXAI_MCP_PROMPTS_DIR"); got != "/tmp/test-prompts" {
+		t.Fatalf("expected HEXAI_MCP_PROMPTS_DIR=/tmp/test-prompts, got %q", got)
+	}
+}
+
+func TestRun_SetsSlashCommandSync(t *testing.T) {
+	t.Setenv("HEXAI_MCP_SLASHCOMMAND_SYNC", "")
+	opts := mcpOptions{showVersion: true, slashCommandSync: true}
+	var stdout bytes.Buffer
+	if err := run(opts, nil, &stdout, nil); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	if got := os.Getenv("HEXAI_MCP_SLASHCOMMAND_SYNC"); got != "true" {
+		t.Fatalf("expected HEXAI_MCP_SLASHCOMMAND_SYNC=true, got %q", got)
+	}
+}
+
+func TestRun_SetsSlashCommandDir(t *testing.T) {
+	t.Setenv("HEXAI_MCP_SLASHCOMMAND_DIR", "")
+	opts := mcpOptions{showVersion: true, slashCommandDir: "/tmp/test-cmds"}
+	var stdout bytes.Buffer
+	if err := run(opts, nil, &stdout, nil); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	if got := os.Getenv("HEXAI_MCP_SLASHCOMMAND_DIR"); got != "/tmp/test-cmds" {
+		t.Fatalf("expected HEXAI_MCP_SLASHCOMMAND_DIR=/tmp/test-cmds, got %q", got)
+	}
+}
+
+func TestRun_SyncAll(t *testing.T) {
+	old := runBackfill
+	t.Cleanup(func() { runBackfill = old })
+
+	var gotLog, gotConfig string
+	runBackfill = func(logPath, configPath string) error {
+		gotLog = logPath
+		gotConfig = configPath
+		return nil
+	}
+
+	opts := mcpOptions{syncAll: true, logPath: "/tmp/test.log", configPath: "/tmp/cfg.toml"}
+	if err := run(opts, nil, nil, nil); err != nil {
+		t.Fatalf("run syncAll: %v", err)
+	}
+	if gotLog != "/tmp/test.log" {
+		t.Fatalf("expected logPath=/tmp/test.log, got %q", gotLog)
+	}
+	if gotConfig != "/tmp/cfg.toml" {
+		t.Fatalf("expected configPath=/tmp/cfg.toml, got %q", gotConfig)
+	}
+}
+
+func TestRun_SyncAllError(t *testing.T) {
+	old := runBackfill
+	t.Cleanup(func() { runBackfill = old })
+
+	wantErr := errors.New("backfill failed")
+	runBackfill = func(_, _ string) error { return wantErr }
+
+	opts := mcpOptions{syncAll: true}
+	if err := run(opts, nil, nil, nil); !errors.Is(err, wantErr) {
+		t.Fatalf("expected backfill error, got: %v", err)
+	}
+}
+
+func TestRun_MCPServer(t *testing.T) {
+	old := runMCP
+	t.Cleanup(func() { runMCP = old })
+
+	called := false
+	runMCP = func(logPath, configPath string, stdin io.Reader, stdout, stderr io.Writer) error {
+		called = true
+		return nil
+	}
+
+	opts := mcpOptions{logPath: "/tmp/mcp.log"}
+	if err := run(opts, nil, nil, nil); err != nil {
+		t.Fatalf("run MCP: %v", err)
+	}
+	if !called {
+		t.Fatal("expected runMCP to be called")
+	}
+}
+
+func TestRun_MCPServerError(t *testing.T) {
+	old := runMCP
+	t.Cleanup(func() { runMCP = old })
+
+	wantErr := errors.New("server failed")
+	runMCP = func(_, _ string, _ io.Reader, _, _ io.Writer) error { return wantErr }
+
+	if err := run(mcpOptions{}, nil, nil, nil); !errors.Is(err, wantErr) {
+		t.Fatalf("expected server error, got: %v", err)
+	}
+}
diff --git a/cmd/hexai-tmux-action/main.go b/cmd/hexai-tmux-action/main.go
index 6249de3..715c41f 100644
--- a/cmd/hexai-tmux-action/main.go
+++ b/cmd/hexai-tmux-action/main.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io"
 	"os"
 	"strings"
 
@@ -11,6 +12,10 @@ import (
 	"codeberg.org/snonux/hexai/internal/hexaiaction"
 )
 
+// runCommand is the seam for testing: override in tests to avoid launching
+// the real tmux action.
+var runCommand = hexaiaction.RunCommand
+
 func main() {
 	infile := flag.String("infile", "", "Read input from this file instead of stdin")
 	outfile := flag.String("outfile", "", "Write output to this file instead of stdout")
@@ -22,16 +27,38 @@ func main() {
 	tmuxPercent := flag.Int("tmux-percent", 33, "tmux split size percentage (1-100)")
 	flag.Parse()
 
-	opts := hexaiaction.Options{
-		Infile: *infile, Outfile: *outfile,
-		UIChild: *uiChild, TmuxTarget: *tmuxTarget, TmuxSplit: *tmuxSplit, TmuxPercent: *tmuxPercent,
-	}
-	ctx := context.Background()
-	if path := strings.TrimSpace(*configPath); path != "" {
-		ctx = hexaiaction.WithConfigPath(ctx, path)
+	opts := actionOptions{
+		infile: *infile, outfile: *outfile,
+		uiChild: *uiChild, configPath: *configPath,
+		tmuxTarget: *tmuxTarget, tmuxSplit: *tmuxSplit, tmuxPercent: *tmuxPercent,
 	}
-	if err := hexaiaction.RunCommand(ctx, opts, os.Stdin, os.Stdout, os.Stderr); err != nil {
+	if err := run(opts, os.Stdin, os.Stdout, os.Stderr); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
 }
+
+// actionOptions holds the parsed command-line flags for hexai-tmux-action.
+type actionOptions struct {
+	infile      string
+	outfile     string
+	uiChild     bool
+	configPath  string
+	tmuxTarget  string
+	tmuxSplit   string
+	tmuxPercent int
+}
+
+// run builds the hexaiaction.Options and context, then delegates to runCommand.
+func run(opts actionOptions, stdin io.Reader, stdout, stderr io.Writer) error {
+	haOpts := hexaiaction.Options{
+		Infile: opts.infile, Outfile: opts.outfile,
+		UIChild: opts.uiChild, TmuxTarget: opts.tmuxTarget,
+		TmuxSplit: opts.tmuxSplit, TmuxPercent: opts.tmuxPercent,
+	}
+	ctx := context.Background()
+	if path := strings.TrimSpace(opts.configPath); path != "" {
+		ctx = hexaiaction.WithConfigPath(ctx, path)
+	}
+	return runCommand(ctx, haOpts, stdin, stdout, stderr)
+}
diff --git a/cmd/hexai-tmux-action/main_test.go b/cmd/hexai-tmux-action/main_test.go
new file mode 100644
index 0000000..8abd420
--- /dev/null
+++ b/cmd/hexai-tmux-action/main_test.go
@@ -0,0 +1,63 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"io"
+	"testing"
+
+	"codeberg.org/snonux/hexai/internal/hexaiaction"
+)
+
+func TestRun_DelegatesToRunCommand(t *testing.T) {
+	old := runCommand
+	t.Cleanup(func() { runCommand = old })
+
+	var gotOpts hexaiaction.Options
+	runCommand = func(_ context.Context, opts hexaiaction.Options, _ io.Reader, _, _ io.Writer) error {
+		gotOpts = opts
+		return nil
+	}
+
+	opts := actionOptions{
+		infile: "in.txt", outfile: "out.txt",
+		tmuxSplit: "h", tmuxPercent: 50,
+	}
+	if err := run(opts, nil, nil, nil); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	if gotOpts.Infile != "in.txt" || gotOpts.Outfile != "out.txt" {
+		t.Fatalf("unexpected opts: %+v", gotOpts)
+	}
+	if gotOpts.TmuxSplit != "h" || gotOpts.TmuxPercent != 50 {
+		t.Fatalf("unexpected tmux opts: %+v", gotOpts)
+	}
+}
+
+func TestRun_WithConfigPath(t *testing.T) {
+	old := runCommand
+	t.Cleanup(func() { runCommand = old })
+
+	runCommand = func(_ context.Context, _ hexaiaction.Options, _ io.Reader, _, _ io.Writer) error {
+		return nil
+	}
+
+	opts := actionOptions{configPath: "  /tmp/test.toml  ", tmuxSplit: "v", tmuxPercent: 33}
+	if err := run(opts, nil, nil, nil); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+}
+
+func TestRun_Error(t *testing.T) {
+	old := runCommand
+	t.Cleanup(func() { runCommand = old })
+
+	wantErr := errors.New("action failed")
+	runCommand = func(_ context.Context, _ hexaiaction.Options, _ io.Reader, _, _ io.Writer) error {
+		return wantErr
+	}
+
+	if err := run(actionOptions{}, nil, nil, nil); !errors.Is(err, wantErr) {
+		t.Fatalf("expected error, got: %v", err)
+	}
+}
diff --git a/cmd/hexai-tmux-edit/main.go b/cmd/hexai-tmux-edit/main.go
index ea3330b..6d0e75e 100644
--- a/cmd/hexai-tmux-edit/main.go
+++ b/cmd/hexai-tmux-edit/main.go
@@ -21,6 +21,9 @@ import (
 	"codeberg.org/snonux/hexai/internal/tmuxedit"
 )
 
+// runTmuxEdit is the seam for testing: override in tests to avoid real tmux.
+var runTmuxEdit = tmuxedit.Run
+
 func main() {
 	defaultPath := appconfig.DefaultConfigPath()
 	configPath := flag.String("config", "", fmt.Sprintf("path to config file (default: %s)", defaultPath))
@@ -28,13 +31,19 @@ func main() {
 	pane := flag.String("pane", "", "tmux target pane ID (e.g. %%5)")
 	flag.Parse()
 
-	opts := tmuxedit.Options{
-		ConfigPath: strings.TrimSpace(*configPath),
-		Agent:      strings.TrimSpace(*agent),
-		Pane:       strings.TrimSpace(*pane),
-	}
-	if err := tmuxedit.Run(opts); err != nil {
+	opts := buildOptions(*configPath, *agent, *pane)
+	if err := runTmuxEdit(opts); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
 }
+
+// buildOptions constructs tmuxedit.Options from the parsed flag values,
+// trimming whitespace from each field.
+func buildOptions(configPath, agent, pane string) tmuxedit.Options {
+	return tmuxedit.Options{
+		ConfigPath: strings.TrimSpace(configPath),
+		Agent:      strings.TrimSpace(agent),
+		Pane:       strings.TrimSpace(pane),
+	}
+}
diff --git a/cmd/hexai-tmux-edit/main_test.go b/cmd/hexai-tmux-edit/main_test.go
new file mode 100644
index 0000000..fc2364c
--- /dev/null
+++ b/cmd/hexai-tmux-edit/main_test.go
@@ -0,0 +1,59 @@
+package main
+
+import (
+	"errors"
+	"testing"
+
+	"codeberg.org/snonux/hexai/internal/tmuxedit"
+)
+
+func TestBuildOptions_AllEmpty(t *testing.T) {
+	opts := buildOptions("", "", "")
+	if opts.ConfigPath != "" || opts.Agent != "" || opts.Pane != "" {
+		t.Fatalf("expected all empty, got %+v", opts)
+	}
+}
+
+func TestBuildOptions_TrimsWhitespace(t *testing.T) {
+	opts := buildOptions("  /tmp/cfg.toml  ", "  claude  ", "  %5  ")
+	if opts.ConfigPath != "/tmp/cfg.toml" {
+		t.Fatalf("expected trimmed config path, got %q", opts.ConfigPath)
+	}
+	if opts.Agent != "claude" {
+		t.Fatalf("expected trimmed agent, got %q", opts.Agent)
+	}
+	if opts.Pane != "%5" {
+		t.Fatalf("expected trimmed pane, got %q", opts.Pane)
+	}
+}
+
+func TestRunTmuxEdit_Success(t *testing.T) {
+	old := runTmuxEdit
+	t.Cleanup(func() { runTmuxEdit = old })
+
+	var gotOpts tmuxedit.Options
+	runTmuxEdit = func(opts tmuxedit.Options) error {
+		gotOpts = opts
+		return nil
+	}
+
+	opts := buildOptions("/tmp/cfg.toml", "cursor", "%3")
+	if err := runTmuxEdit(opts); err != nil {
+		t.Fatalf("runTmuxEdit: %v", err)
+	}
+	if gotOpts.ConfigPath != "/tmp/cfg.toml" || gotOpts.Agent != "cursor" || gotOpts.Pane != "%3" {
+		t.Fatalf("unexpected opts: %+v", gotOpts)
+	}
+}
+
+func TestRunTmuxEdit_Error(t *testing.T) {
+	old := runTmuxEdit
+	t.Cleanup(func() { runTmuxEdit = old })
+
+	wantErr := errors.New("tmux not found")
+	runTmuxEdit = func(_ tmuxedit.Options) error { return wantErr }
+
+	if err := runTmuxEdit(tmuxedit.Options{}); !errors.Is(err, wantErr) {
+		t.Fatalf("expected error, got: %v", err)
+	}
+}
diff --git a/cmd/hexai/main_test.go b/cmd/hexai/main_test.go
index 531a11f..7c20cc4 100644
--- a/cmd/hexai/main_test.go
+++ b/cmd/hexai/main_test.go
@@ -5,6 +5,8 @@ import (
 	"os"
 	"strings"
 	"testing"
+
+	"codeberg.org/snonux/hexai/internal/appconfig"
 )
 
 func TestMain_Version(t *testing.T) {
@@ -25,6 +27,115 @@ func TestMain_Version(t *testing.T) {
 	}
 }
 
+func TestSplitConfigPath(t *testing.T) {
+	tests := []struct {
+		name     string
+		args     []string
+		wantPath string
+		wantRest []string
+	}{
+		{
+			name:     "no args",
+			args:     nil,
+			wantPath: "",
+			wantRest: []string{},
+		},
+		{
+			name:     "no config flag",
+			args:     []string{"-version", "hello"},
+			wantPath: "",
+			wantRest: []string{"-version", "hello"},
+		},
+		{
+			name:     "--config with separate value",
+			args:     []string{"--config", "/tmp/cfg.toml", "-version"},
+			wantPath: "/tmp/cfg.toml",
+			wantRest: []string{"-version"},
+		},
+		{
+			name:     "-config with separate value",
+			args:     []string{"-config", "/tmp/cfg.toml", "extra"},
+			wantPath: "/tmp/cfg.toml",
+			wantRest: []string{"extra"},
+		},
+		{
+			name:     "--config= form",
+			args:     []string{"--config=/tmp/cfg.toml", "extra"},
+			wantPath: "/tmp/cfg.toml",
+			wantRest: []string{"extra"},
+		},
+		{
+			name:     "-config= form",
+			args:     []string{"-config=/tmp/cfg.toml", "extra"},
+			wantPath: "/tmp/cfg.toml",
+			wantRest: []string{"extra"},
+		},
+		{
+			name:     "--config as last arg without value",
+			args:     []string{"extra", "--config"},
+			wantPath: "",
+			wantRest: []string{"extra"},
+		},
+		{
+			name:     "-config as last arg without value",
+			args:     []string{"-config"},
+			wantPath: "",
+			wantRest: []string{},
+		},
+		{
+			name:     "path with whitespace is trimmed",
+			args:     []string{"--config", "  /tmp/cfg.toml  "},
+			wantPath: "/tmp/cfg.toml",
+			wantRest: []string{},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			gotPath, gotRest := splitConfigPath(tc.args)
+			if gotPath != tc.wantPath {
+				t.Errorf("path = %q, want %q", gotPath, tc.wantPath)
+			}
+			if len(gotRest) != len(tc.wantRest) {
+				t.Fatalf("rest len = %d, want %d; got %v", len(gotRest), len(tc.wantRest), gotRest)
+			}
+			for i := range gotRest {
+				if gotRest[i] != tc.wantRest[i] {
+					t.Errorf("rest[%d] = %q, want %q", i, gotRest[i], tc.wantRest[i])
+				}
+			}
+		})
+	}
+}
+
+func TestPickDefaultModel(t *testing.T) {
+	cfg := appconfig.App{
+		OllamaModel:    "llama3",
+		AnthropicModel: "claude-sonnet",
+		OpenAIModel:    "gpt-4o",
+	}
+	tests := []struct {
+		provider string
+		want     string
+	}{
+		{"ollama", "llama3"},
+		{"Ollama", "llama3"},
+		{"  OLLAMA  ", "llama3"},
+		{"anthropic", "claude-sonnet"},
+		{"Anthropic", "claude-sonnet"},
+		{"openai", "gpt-4o"},
+		{"unknown-provider", "gpt-4o"},
+		{"", "gpt-4o"},
+	}
+	for _, tc := range tests {
+		t.Run(tc.provider, func(t *testing.T) {
+			got := pickDefaultModel(cfg, tc.provider)
+			if got != tc.want {
+				t.Errorf("pickDefaultModel(%q) = %q, want %q", tc.provider, got, tc.want)
+			}
+		})
+	}
+}
+
 func TestMain_TPSSimulation(t *testing.T) {
 	oldArgs := os.Args
 	defer func() { os.Args = oldArgs }()
diff --git a/internal/editor/editor_test.go b/internal/editor/editor_test.go
index 06cc165..260fb85 100644
--- a/internal/editor/editor_test.go
+++ b/internal/editor/editor_test.go
@@ -1,11 +1,32 @@
 package editor
 
 import (
+	"errors"
 	"os"
 	"path/filepath"
 	"testing"
 )
 
+// TestRunEditor_Default exercises the default RunEditor function with a harmless command.
+func TestRunEditor_Default(t *testing.T) {
+	t.Setenv("HEXAI_EDITOR", "true") // /usr/bin/true — exits 0 immediately
+	tmp := filepath.Join(t.TempDir(), "test.md")
+	if err := os.WriteFile(tmp, []byte("hello"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := RunEditor("true", tmp); err != nil {
+		t.Fatalf("RunEditor with 'true': %v", err)
+	}
+}
+
+// TestRunEditor_Default_BadCommand verifies RunEditor returns an error for a nonexistent command.
+func TestRunEditor_Default_BadCommand(t *testing.T) {
+	err := RunEditor("nonexistent-editor-cmd-12345", "/dev/null")
+	if err == nil {
+		t.Fatal("expected error for nonexistent editor command")
+	}
+}
+
 func TestResolve_EnvPriority(t *testing.T) {
 	t.Setenv("HEXAI_EDITOR", "ed1")
 	t.Setenv("EDITOR", "ed2")
@@ -20,6 +41,26 @@ func TestResolve_EnvPriority(t *testing.T) {
 	}
 }
 
+// TestResolve_NoEditor verifies the error when neither HEXAI_EDITOR nor EDITOR is set.
+func TestResolve_NoEditor(t *testing.T) {
+	t.Setenv("HEXAI_EDITOR", "")
+	t.Setenv("EDITOR", "")
+	_, err := Resolve()
+	if err == nil {
+		t.Fatal("expected error when no editor is configured")
+	}
+}
+
+// TestResolve_WhitespaceOnly verifies that whitespace-only values are treated as empty.
+func TestResolve_WhitespaceOnly(t *testing.T) {
+	t.Setenv("HEXAI_EDITOR", "   ")
+	t.Setenv("EDITOR", "  \t ")
+	_, err := Resolve()
+	if err == nil {
+		t.Fatal("expected error for whitespace-only editor values")
+	}
+}
+
 func TestOpenTempAndEdit_UsesRunEditor(t *testing.T) {
 	old := RunEditor
 	t.Cleanup(func() { RunEditor = old })
@@ -42,3 +83,102 @@ func TestOpenTempAndEdit_UsesRunEditor(t *testing.T) {
 		t.Fatalf("expected .md suffix: %s", capturedPath)
 	}
 }
+
+// TestOpenTempAndEdit_NoEditor verifies error propagation when no editor is configured.
+func TestOpenTempAndEdit_NoEditor(t *testing.T) {
+	t.Setenv("HEXAI_EDITOR", "")
+	t.Setenv("EDITOR", "")
+	_, err := OpenTempAndEdit(nil)
+	if err == nil {
+		t.Fatal("expected error when no editor is set")
+	}
+}
+
+// TestOpenTempAndEdit_NilInitial verifies that nil initial content works (empty file).
+func TestOpenTempAndEdit_NilInitial(t *testing.T) {
+	old := RunEditor
+	t.Cleanup(func() { RunEditor = old })
+	t.Setenv("HEXAI_EDITOR", "dummy")
+	RunEditor = func(editor, path string) error {
+		// simulate user writing content into a file that started empty
+		return os.WriteFile(path, []byte("result"), 0o600)
+	}
+	out, err := OpenTempAndEdit(nil)
+	if err != nil {
+		t.Fatalf("OpenTempAndEdit with nil initial: %v", err)
+	}
+	if out != "result" {
+		t.Fatalf("unexpected content: %q", out)
+	}
+}
+
+// TestOpenTempAndEdit_EmptyInitial verifies that empty (zero-length) initial content
+// skips the write branch but still works end-to-end.
+func TestOpenTempAndEdit_EmptyInitial(t *testing.T) {
+	old := RunEditor
+	t.Cleanup(func() { RunEditor = old })
+	t.Setenv("HEXAI_EDITOR", "dummy")
+	RunEditor = func(editor, path string) error {
+		return os.WriteFile(path, []byte("  trimmed  "), 0o600)
+	}
+	out, err := OpenTempAndEdit([]byte{})
+	if err != nil {
+		t.Fatalf("OpenTempAndEdit with empty initial: %v", err)
+	}
+	if out != "trimmed" {
+		t.Fatalf("expected trimmed content, got %q", out)
+	}
+}
+
+// TestOpenTempAndEdit_EditorError verifies that an editor failure propagates the error.
+func TestOpenTempAndEdit_EditorError(t *testing.T) {
+	old := RunEditor
+	t.Cleanup(func() { RunEditor = old })
+	t.Setenv("HEXAI_EDITOR", "dummy")
+	editorErr := errors.New("editor crashed")
+	RunEditor = func(editor, path string) error {
+		return editorErr
+	}
+	_, err := OpenTempAndEdit([]byte("some content"))
+	if err == nil {
+		t.Fatal("expected error when editor fails")
+	}
+	if !errors.Is(err, editorErr) {
+		t.Fatalf("expected editor error, got: %v", err)
+	}
+}
+
+// TestOpenTempAndEdit_EditorDeletesFile verifies error when the editor removes the temp file.
+func TestOpenTempAndEdit_EditorDeletesFile(t *testing.T) {
+	old := RunEditor
+	t.Cleanup(func() { RunEditor = old })
+	t.Setenv("HEXAI_EDITOR", "dummy")
+	RunEditor = func(editor, path string) error {
+		// simulate the editor deleting the file
+		return os.Remove(path)
+	}
+	_, err := OpenTempAndEdit([]byte("content"))
+	if err == nil {
+		t.Fatal("expected error when temp file is deleted by editor")
+	}
+}
+
+// TestOpenTempAndEdit_TempFileCleanup verifies the temp file is removed after success.
+func TestOpenTempAndEdit_TempFileCleanup(t *testing.T) {
+	old := RunEditor
+	t.Cleanup(func() { RunEditor = old })
+	t.Setenv("HEXAI_EDITOR", "dummy")
+	var capturedPath string
+	RunEditor = func(editor, path string) error {
+		capturedPath = path
+		return os.WriteFile(path, []byte("done"), 0o600)
+	}
+	_, err := OpenTempAndEdit(nil)
+	if err != nil {
+		t.Fatalf("OpenTempAndEdit: %v", err)
+	}
+	// The deferred os.Remove should have cleaned up the temp file
+	if _, err := os.Stat(capturedPath); !os.IsNotExist(err) {
+		t.Fatalf("temp file was not cleaned up: %s", capturedPath)
+	}
+}
diff --git a/internal/gotest/heuristics_test.go b/internal/gotest/heuristics_test.go
index 831262d..6597238 100644
--- a/internal/gotest/heuristics_test.go
+++ b/internal/gotest/heuristics_test.go
@@ -12,6 +12,22 @@ func TestParsePackageName(t *testing.T) {
 	}
 }
 
+func TestParsePackageName_TabAfterName(t *testing.T) {
+	// Covers the tab-trimming branch in ParsePackageName.
+	lines := []string{"package mypkg\t// tab then comment"}
+	if got := ParsePackageName(lines); got != "mypkg" {
+		t.Fatalf("got %q, want %q", got, "mypkg")
+	}
+}
+
+func TestParsePackageName_SpaceAfterName(t *testing.T) {
+	// Covers the space-trimming branch (no comment, just trailing space).
+	lines := []string{"package mypkg "}
+	if got := ParsePackageName(lines); got != "mypkg" {
+		t.Fatalf("got %q, want %q", got, "mypkg")
+	}
+}
+
 func TestFindFunctionAtLine_NoBody(t *testing.T) {
 	lines := []string{"func X(a int)", "// comment"}
 	start, end := FindFunctionAtLine(lines, 0)
@@ -20,6 +36,81 @@ func TestFindFunctionAtLine_NoBody(t *testing.T) {
 	}
 }
 
+func TestFindFunctionAtLine_EmptyLines(t *testing.T) {
+	// Covers the empty-lines early return.
+	start, end := FindFunctionAtLine([]string{}, 0)
+	if start != -1 || end != -1 {
+		t.Fatalf("expected -1,-1 for empty input, got %d,%d", start, end)
+	}
+}
+
+func TestFindFunctionAtLine_NegativeIdx(t *testing.T) {
+	// Covers the idx < 0 clamping branch.
+	lines := []string{"func Foo() {", "  return", "}"}
+	start, end := FindFunctionAtLine(lines, -5)
+	if start != 0 || end != 2 {
+		t.Fatalf("expected 0,2 got %d,%d", start, end)
+	}
+}
+
+func TestFindFunctionAtLine_IdxBeyondEnd(t *testing.T) {
+	// Covers the idx >= len(lines) clamping branch.
+	// The last line contains "func " so the backward scan finds it directly.
+	lines := []string{"package main", "", "func Last() { }"}
+	start, end := FindFunctionAtLine(lines, 100)
+	if start != 2 || end != 2 {
+		t.Fatalf("expected 2,2 got %d,%d", start, end)
+	}
+}
+
+func TestFindFunctionAtLine_ClosingBraceBeforeFunc(t *testing.T) {
+	// When scanning backward, hitting '}' before 'func ' means no enclosing function.
+	lines := []string{"func A() {", "}", "  x := 1"}
+	start, end := FindFunctionAtLine(lines, 2)
+	if start != -1 || end != -1 {
+		t.Fatalf("expected -1,-1 got %d,%d", start, end)
+	}
+}
+
+func TestFindFunctionAtLine_NormalFunction(t *testing.T) {
+	// Covers the normal path: finding a complete function with braces.
+	lines := []string{
+		"package main",
+		"",
+		"func Hello() {",
+		"  fmt.Println(\"hi\")",
+		"}",
+	}
+	start, end := FindFunctionAtLine(lines, 3)
+	if start != 2 || end != 4 {
+		t.Fatalf("expected 2,4 got %d,%d", start, end)
+	}
+}
+
+func TestFindFunctionAtLine_UnclosedBrace(t *testing.T) {
+	// Covers the branch where opening brace is seen but never closed.
+	lines := []string{"func Broken() {", "  x := 1"}
+	start, end := FindFunctionAtLine(lines, 0)
+	if start != 0 || end != -1 {
+		t.Fatalf("expected 0,-1 for unclosed brace, got %d,%d", start, end)
+	}
+}
+
+func TestFindFunctionAtLine_NestedBraces(t *testing.T) {
+	// Covers depth tracking with nested braces.
+	lines := []string{
+		"func Nested() {",
+		"  if true {",
+		"    x := 1",
+		"  }",
+		"}",
+	}
+	start, end := FindFunctionAtLine(lines, 2)
+	if start != 0 || end != 4 {
+		t.Fatalf("expected 0,4 got %d,%d", start, end)
+	}
+}
+
 func TestDeriveFuncName(t *testing.T) {
 	if got := DeriveFuncName("func Sum(a int) int { return a }"); got != "Sum" {
 		t.Fatalf("got %q", got)
@@ -29,6 +120,28 @@ func TestDeriveFuncName(t *testing.T) {
 	}
 }
 
+func TestDeriveFuncName_NotAFunc(t *testing.T) {
+	// Covers the early return when line doesn't start with "func ".
+	if got := DeriveFuncName("var x = 1"); got != "" {
+		t.Fatalf("expected empty, got %q", got)
+	}
+}
+
+func TestDeriveFuncName_MultiLine(t *testing.T) {
+	// Covers the firstLine newline-splitting branch.
+	code := "func Multi() {\n  return\n}"
+	if got := DeriveFuncName(code); got != "Multi" {
+		t.Fatalf("got %q, want %q", got, "Multi")
+	}
+}
+
+func TestDeriveFuncName_MethodReceiverNoParenAfter(t *testing.T) {
+	// Covers the case where receiver is parsed but no '(' follows the name.
+	if got := DeriveFuncName("func (t *T) "); got != "" {
+		t.Fatalf("expected empty, got %