diff --git a/internal/adapter/cli/run_test.go b/internal/adapter/cli/run_test.go
index 7b06d8c..ef0e61f 100644
--- a/internal/adapter/cli/run_test.go
+++ b/internal/adapter/cli/run_test.go
@@ -662,42 +662,29 @@ func TestRunCommandVarsOptional(t *testing.T) {
 }
 
 func TestRunCommandSucceedsWithPromptAndProfileDirsFromConfig(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
 
 	ts := newTestLLMServer("from-config-dirs", nil)
 	defer ts.Close()
 
-	writePromptFile(t, promptDir, "prompt.default", "local-default")
-	writeProfileFile(t, profileDir, "local-default", ts.URL+"/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.default", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", ts.URL+"/v1", "profile-model")
 	configPath := writeAppConfigFile(t, fmt.Sprintf(`
 prompt_dir: %s
 profile_dir: %s
-`, promptDir, profileDir))
+`, lib.promptDir, lib.profileDir))
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := runCommand([]string{
+	code, stdout, stderr := runCLICommand(t, runCommand, []string{
 		"--config", configPath,
 		"--prompt", "prompt.default",
 		"--input", "transcript=" + inputPath,
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if stdout.String() != "from-config-dirs" {
-		t.Fatalf("unexpected stdout output: %q", stdout.String())
+	if stdout != "from-config-dirs" {
+		t.Fatalf("unexpected stdout output: %q", stdout)
 	}
 }
 
@@ -706,28 +693,15 @@ func TestRenderCommandDefaultFormatTextIncludesPreparedDetailsAndNoSecrets(t *te
 	const secret = "super-secret-render-key"
 	t.Setenv(envName, secret)
 
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello transcript"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
 
-	writePromptFileWithTemplate(t, promptDir, "prompt.render", "local-default", "Date {{.session_date}} - Summarize: {{input \"transcript\"}}")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
+	writePromptFileWithTemplate(t, lib.promptDir, "prompt.render", "local-default", "Date {{.session_date}} - Summarize: {{input \"transcript\"}}")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.render",
 		"--profile", "local-default",
 		"--input", "transcript=" + inputPath,
@@ -739,15 +713,15 @@ func TestRenderCommandDefaultFormatTextIncludesPreparedDetailsAndNoSecrets(t *te
 		"--top-p", "0.2",
 		"--timeout", "20s",
 		"--api-key-env", envName,
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if stderr.Len() != 0 {
-		t.Fatalf("expected empty stderr on success, got %q", stderr.String())
+	if stderr != "" {
+		t.Fatalf("expected empty stderr on success, got %q", stderr)
 	}
 
-	out := stdout.String()
+	out := stdout
 	for _, want := range []string{
 		"prompt: prompt.render",
 		"selected_profile_id: local-default",
@@ -774,111 +748,72 @@ func TestRenderCommandDefaultFormatTextIncludesPreparedDetailsAndNoSecrets(t *te
 }
 
 func TestRenderCommandSucceedsWithPromptAndProfileDirsFromConfig(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello transcript"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
 
-	writePromptFile(t, promptDir, "prompt.render", "local-default")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.render", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
 	configPath := writeAppConfigFile(t, fmt.Sprintf(`
 prompt_dir: %s
 profile_dir: %s
-`, promptDir, profileDir))
+`, lib.promptDir, lib.profileDir))
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
 		"--config", configPath,
 		"--prompt", "prompt.render",
 		"--input", "transcript=" + inputPath,
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if !strings.Contains(stdout.String(), "prompt: prompt.render") {
-		t.Fatalf("expected rendered output, got %q", stdout.String())
+	if !strings.Contains(stdout, "prompt: prompt.render") {
+		t.Fatalf("expected rendered output, got %q", stdout)
 	}
 }
 
 func TestRenderCommandExplicitTextFormatWorks(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello transcript"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
 
-	writePromptFile(t, promptDir, "prompt.render", "local-default")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.render", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.render",
 		"--input", "transcript=" + inputPath,
 		"--format", "text",
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if !strings.Contains(stdout.String(), "prompt: prompt.render") {
-		t.Fatalf("expected text output for explicit --format text, got %q", stdout.String())
+	if !strings.Contains(stdout, "prompt: prompt.render") {
+		t.Fatalf("expected text output for explicit --format text, got %q", stdout)
 	}
 }
 
 func TestRenderCommandExplicitJSONFormatOutputsValidJSON(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello transcript"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
 
-	writePromptFile(t, promptDir, "prompt.render", "local-default")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.render", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.render",
 		"--input", "transcript=" + inputPath,
 		"--format", "json",
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
 
 	var payload map[string]any
-	if err := json.Unmarshal(stdout.Bytes(), &payload); err != nil {
-		t.Fatalf("expected valid json output, got %v\nbody=%s", err, stdout.String())
+	if err := json.Unmarshal([]byte(stdout), &payload); err != nil {
+		t.Fatalf("expected valid json output, got %v\nbody=%s", err, stdout)
 	}
 	if payload["prompt_id"] != "prompt.render" {
 		t.Fatalf("expected prompt_id, got %#v", payload["prompt_id"])
@@ -910,38 +845,25 @@ func TestRenderCommandUnknownFormatFailsClearly(t *testing.T) {
 }
 
 func TestRenderCommandOutWritesToFile(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello transcript"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	outPath := filepath.Join(tmp, "render.txt")
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
+	outPath := filepath.Join(lib.rootDir, "render.txt")
 
-	writePromptFile(t, promptDir, "prompt.render", "local-default")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.render", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "profile-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.render",
 		"--input", "transcript=" + inputPath,
 		"--out", outPath,
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if stdout.Len() != 0 {
-		t.Fatalf("expected empty stdout when --out is set, got %q", stdout.String())
+	if stdout != "" {
+		t.Fatalf("expected empty stdout when --out is set, got %q", stdout)
 	}
 	out, err := os.ReadFile(outPath)
 	if err != nil {
@@ -953,36 +875,23 @@ func TestRenderCommandOutWritesToFile(t *testing.T) {
 }
 
 func TestRenderCommandPromptDefaultProfileWorksThroughCLIPath(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
 
-	writePromptFile(t, promptDir, "prompt.default", "local-default")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "default-model")
+	writePromptFile(t, lib.promptDir, "prompt.default", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "default-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.default",
 		"--input", "transcript=" + inputPath,
-	}, &stdout, &stderr)
+	})
 
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	out := stdout.String()
+	out := stdout
 	if !strings.Contains(out, "selected_profile_id: local-default") {
 		t.Fatalf("expected prompt default profile in output, got %q", out)
 	}
@@ -992,38 +901,25 @@ func TestRenderCommandPromptDefaultProfileWorksThroughCLIPath(t *testing.T) {
 }
 
 func TestRenderCommandExplicitProfileOverridesPromptDefault(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
 
-	writePromptFile(t, promptDir, "prompt.default", "local-default")
-	writeProfileFile(t, profileDir, "local-default", "http://127.0.0.1:1/v1", "default-model")
-	writeProfileFile(t, profileDir, "quality", "http://127.0.0.1:1/v1", "quality-model")
+	writePromptFile(t, lib.promptDir, "prompt.default", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", "http://127.0.0.1:1/v1", "default-model")
+	writeProfileFile(t, lib.profileDir, "quality", "http://127.0.0.1:1/v1", "quality-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := renderCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.default",
 		"--profile", "quality",
 		"--input", "transcript=" + inputPath,
-	}, &stdout, &stderr)
+	})
 
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	out := stdout.String()
+	out := stdout
 	if !strings.Contains(out, "selected_profile_id: quality") {
 		t.Fatalf("expected explicit profile in output, got %q", out)
 	}
@@ -1033,104 +929,67 @@ func TestRenderCommandExplicitProfileOverridesPromptDefault(t *testing.T) {
 }
 
 func TestRunCommandPromptDefaultProfileWorksThroughCLIPath(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
 
 	ts := newTestLLMServer("default-output", nil)
 	defer ts.Close()
 
-	writePromptFile(t, promptDir, "prompt.default", "local-default")
-	writeProfileFile(t, profileDir, "local-default", ts.URL+"/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.default", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", ts.URL+"/v1", "profile-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := runCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, runCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.default",
 		"--input", "transcript=" + inputPath,
-	}, &stdout, &stderr)
+	})
 
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if stdout.String() != "default-output" {
-		t.Fatalf("unexpected stdout output: %q", stdout.String())
+	if stdout != "default-output" {
+		t.Fatalf("unexpected stdout output: %q", stdout)
 	}
-	if !strings.Contains(stderr.String(), "selected_profile=local-default") {
-		t.Fatalf("expected selected profile in summary, got %q", stderr.String())
+	if !strings.Contains(stderr, "selected_profile=local-default") {
+		t.Fatalf("expected selected profile in summary, got %q", stderr)
 	}
 }
 
 func TestRunCommandExplicitProfileOverridesPromptDefault(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
 
 	defaultServer := newTestLLMServer("from-default", nil)
 	defer defaultServer.Close()
 	overrideServer := newTestLLMServer("from-override", nil)
 	defer overrideServer.Close()
 
-	writePromptFile(t, promptDir, "prompt.default", "local-default")
-	writeProfileFile(t, profileDir, "local-default", defaultServer.URL+"/v1", "default-model")
-	writeProfileFile(t, profileDir, "quality", overrideServer.URL+"/v1", "quality-model")
+	writePromptFile(t, lib.promptDir, "prompt.default", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", defaultServer.URL+"/v1", "default-model")
+	writeProfileFile(t, lib.profileDir, "quality", overrideServer.URL+"/v1", "quality-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := runCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, runCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.default",
 		"--profile", "quality",
 		"--input", "transcript=" + inputPath,
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
-	if stdout.String() != "from-override" {
-		t.Fatalf("expected explicit profile output, got %q", stdout.String())
+	if stdout != "from-override" {
+		t.Fatalf("expected explicit profile output, got %q", stdout)
 	}
-	if !strings.Contains(stderr.String(), "selected_profile=quality") {
-		t.Fatalf("expected selected profile quality, got %q", stderr.String())
+	if !strings.Contains(stderr, "selected_profile=quality") {
+		t.Fatalf("expected selected profile quality, got %q", stderr)
 	}
 }
 
 func TestRunCommandRuntimeFlagsOverrideSelectedProfileValues(t *testing.T) {
-	tmp := t.TempDir()
-	promptDir := filepath.Join(tmp, "prompts")
-	profileDir := filepath.Join(tmp, "profiles")
-	if err := os.MkdirAll(promptDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.MkdirAll(profileDir, 0o755); err != nil {
-		t.Fatal(err)
-	}
-	inputPath := filepath.Join(tmp, "transcript.md")
-	if err := os.WriteFile(inputPath, []byte("hello"), 0o644); err != nil {
-		t.Fatal(err)
-	}
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
 
 	var baseHits int32
 	baseServer := newTestLLMServer("base", &baseHits)
@@ -1147,14 +1006,12 @@ func TestRunCommandRuntimeFlagsOverrideSelectedProfileValues(t *testing.T) {
 	}))
 	defer overrideServer.Close()
 
-	writePromptFile(t, promptDir, "prompt.default", "local-default")
-	writeProfileFile(t, profileDir, "local-default", baseServer.URL+"/v1", "profile-model")
+	writePromptFile(t, lib.promptDir, "prompt.default", "local-default")
+	writeProfileFile(t, lib.profileDir, "local-default", baseServer.URL+"/v1", "profile-model")
 
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	code := runCommand([]string{
-		"--prompt-dir", promptDir,
-		"--profile-dir", profileDir,
+	code, stdout, stderr := runCLICommand(t, runCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
 		"--prompt", "prompt.default",
 		"--input", "transcript=" + inputPath,
 		"--llm-base-url", overrideServer.URL + "/v1",
@@ -1163,9 +1020,9 @@ func TestRunCommandRuntimeFlagsOverrideSelectedProfileValues(t *testing.T) {
 		"--max-tokens", "55",
 		"--top-p", "0.2",
 		"--timeout", "20s",
-	}, &stdout, &stderr)
+	})
 	if code != ExitOK {
-		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr.String())
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
 	}
 	if atomic.LoadInt32(&baseHits) != 0 {
 		t.Fatalf("expected base profile endpoint not to be hit, got %d", baseHits)
@@ -1173,8 +1030,8 @@ func TestRunCommandRuntimeFlagsOverrideSelectedProfileValues(t *testing.T) {
 	if atomic.LoadInt32(&overrideHits) != 1 {
 		t.Fatalf("expected override endpoint to be hit once, got %d", overrideHits)
 	}
-	if stdout.String() != "override" {
-		t.Fatalf("unexpected stdout output: %q", stdout.String())
+	if stdout != "override" {
+		t.Fatalf("unexpected stdout output: %q", stdout)
 	}
 	if !strings.Contains(observedBody, `"model":"override-model"`) {
 		t.Fatalf("expected override model in request body, got %s", observedBody)
@@ -1209,6 +1066,49 @@ func TestWriteOutputAndSummaryUseSeparateWriters(t *testing.T) {
 	}
 }
 
+type cliTestLibrary struct {
+	rootDir    string
+	promptDir  string
+	profileDir string
+}
+
+func newCLITestLibrary(t *testing.T) *cliTestLibrary {
+	t.Helper()
+	root := t.TempDir()
+	lib := &cliTestLibrary{
+		rootDir:    root,
+		promptDir:  filepath.Join(root, "prompts"),
+		profileDir: filepath.Join(root, "profiles"),
+	}
+	if err := os.MkdirAll(lib.promptDir, 0o755); err != nil {
+		t.Fatalf("failed to create prompt fixture directory: %v", err)
+	}
+	if err := os.MkdirAll(lib.profileDir, 0o755); err != nil {
+		t.Fatalf("failed to create profile fixture directory: %v", err)
+	}
+	return lib
+}
+
+func (l *cliTestLibrary) writeInputFile(t *testing.T, name, body string) string {
+	t.Helper()
+	path := filepath.Join(l.rootDir, name)
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("failed to create input fixture directory: %v", err)
+	}
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatalf("failed to write input fixture: %v", err)
+	}
+	return path
+}
+
+func runCLICommand(t *testing.T, command func([]string, io.Writer, io.Writer) int, args []string) (int, string, string) {
+	t.Helper()
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	code := command(args, &stdout, &stderr)
+	return code, stdout.String(), stderr.String()
+}
+
 func writePromptFile(t *testing.T, dir, id, defaultProfile string) {
 	t.Helper()
 	writePromptFileWithTemplate(t, dir, id, defaultProfile, "Summarize: {{input \"transcript\"}}")