diff --git a/config/config.example.json b/config/config.example.json
index d87f711d0..d9e417724 100644
--- a/config/config.example.json
+++ b/config/config.example.json
@@ -391,7 +391,13 @@
       "enabled": true,
       "enable_deny_patterns": true,
       "custom_deny_patterns": null,
-      "custom_allow_patterns": null
+      "custom_allow_patterns": null,
+      "tirith": {
+        "enabled": false,
+        "bin": "tirith",
+        "timeout_seconds": 5,
+        "fail_open": true
+      }
     },
     "skills": {
       "enabled": true,
diff --git a/docs/reference/tools_configuration.md b/docs/reference/tools_configuration.md
index d92f58476..50294d34a 100644
--- a/docs/reference/tools_configuration.md
+++ b/docs/reference/tools_configuration.md
@@ -191,6 +191,7 @@ The exec tool is used to execute shell commands.
 | `enabled`              | bool  | true    | Enable the exec tool                        |
 | `enable_deny_patterns` | bool  | true    | Enable default dangerous command blocking  |
 | `custom_deny_patterns` | array | []      | Custom deny patterns (regular expressions) |
+| `tirith.enabled`       | bool  | false   | Enable optional Tirith pre-exec scanning   |
 
 ### Disabling the Exec Tool
 
@@ -219,6 +220,96 @@ PICOCLAW_TOOLS_EXEC_ENABLED=false
 - **`enable_deny_patterns`**: Set to `false` to completely disable the default dangerous command blocking patterns
 - **`custom_deny_patterns`**: Add custom deny regex patterns; commands matching these will be blocked
 
+### Optional Tirith Security Scan
+
+PicoClaw can run [Tirith](https://github.com/sheeki03/tirith) before executing a command. This is disabled by default
+and has no path lookup or subprocess overhead unless explicitly enabled.
+
+Tirith analyzes command text for content-level threats such as homograph and punycode URLs, pipe-to-interpreter
+chains (`curl | bash`, `wget | sh`, PowerShell `iwr | iex`, and wrapper variants with `sudo` / `env`), base64
+decode-execute chains, terminal-control injection, suspicious package or URL installs, insecure transport, shortened
+URLs, and credential or file exfiltration patterns. If the local Tirith installation has its signed threat-intelligence
+database installed, `tirith check` can also apply package, hostname, and IP reputation matches.
+
+PicoClaw does not download, install, vendor, or bundle Tirith. Install Tirith separately, then enable it in config:
+
+```json
+{
+  "tools": {
+    "exec": {
+      "tirith": {
+        "enabled": true,
+        "bin": "tirith",
+        "timeout_seconds": 5,
+        "fail_open": true
+      }
+    }
+  }
+}
+```
+
+| Config | Type | Default | Description |
+|--------|------|---------|-------------|
+| `tirith.enabled` | bool | `false` | Run Tirith before command execution |
+| `tirith.bin` | string | `"tirith"` | Tirith binary name from `PATH`, or an explicit absolute/relative path. Empty values are treated as `"tirith"` |
+| `tirith.timeout_seconds` | int | `5` | Scanner timeout in seconds |
+| `tirith.fail_open` | bool | `true` | Allow commands if Tirith is missing or the scanner fails operationally |
+
+Explicit relative `tirith.bin` paths are resolved from PicoClaw's process working directory. Directories are rejected
+on all platforms, and non-executable regular files are rejected on Unix.
+
+Environment variables:
+
+```bash
+PICOCLAW_TOOLS_EXEC_TIRITH_ENABLED=true
+PICOCLAW_TOOLS_EXEC_TIRITH_BIN=tirith
+PICOCLAW_TOOLS_EXEC_TIRITH_TIMEOUT_SECONDS=5
+PICOCLAW_TOOLS_EXEC_TIRITH_FAIL_OPEN=true
+```
+
+For this integration, PicoClaw starts `tirith check` with a temporary local-only policy. The pre-exec check disables
+Tirith threat-DB auto-update, remote policy credentials inherited from the environment, live OSV/deps.dev enrichment,
+Google Safe Browsing enrichment, and supplemental phishing/abuse.ch feed downloads. Local threat-database files that
+are already installed remain available to Tirith, but PicoClaw does not install, update, or download them during
+command execution.
+
+Install methods depend on the Tirith project release you choose. Common options include:
+
+```bash
+brew install sheeki03/tap/tirith
+cargo install tirith
+tirith threat-db update  # optional, enables local threat-intelligence database matches
+```
+
+You can also download a release binary from the Tirith project. PicoClaw only needs the final `tirith` executable
+to be on `PATH` or configured with `tools.exec.tirith.bin`.
+
+Supported prebuilt platform coverage is determined by the Tirith binary you install. Common Tirith release targets
+include macOS x86_64/aarch64, Linux x86_64/aarch64, and Windows x86_64. PicoClaw passes `--shell posix` on non-Windows
+systems and `--shell powershell` on Windows to match its command execution path.
+
+PicoClaw runs:
+
+```text
+tirith check --format json --non-interactive --no-daemon --shell <mode> -- <command>
+```
+
+Tirith's exit code is the verdict source of truth:
+
+| Exit code | PicoClaw behavior |
+|-----------|-------------------|
+| `0` | Allow |
+| `1` | Block |
+| `2` | Log a warning and allow |
+| Other scanner failure | Allow when `fail_open=true`; block when `fail_open=false` |
+
+Direct non-interactive `tirith check` normally returns `0`, `1`, or `2`. PicoClaw also handles Tirith's warn-ack exit
+defensively by logging and allowing, but it is not expected in normal non-interactive use.
+
+Tirith scans the top-level `exec` command before PicoClaw starts the process. It does not inspect later `write` or
+`send-keys` input sent into an already-running background or PTY session, and it does not recursively inspect child
+processes spawned by the command after it starts.
+
 ### Default Blocked Command Patterns
 
 By default, PicoClaw blocks the following dangerous commands:
diff --git a/pkg/config/config.go b/pkg/config/config.go
index 53eaef059..3496a234b 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -928,13 +928,25 @@ type CronToolsConfig struct {
 	AllowCommand       bool `                                 json:"allow_command"        env:"PICOCLAW_TOOLS_CRON_ALLOW_COMMAND"`
 }
 
+type TirithConfig struct {
+	Enabled        bool   `env:"ENABLED"         json:"enabled"`
+	Bin            string `env:"BIN"             json:"bin"`
+	TimeoutSeconds int    `env:"TIMEOUT_SECONDS" json:"timeout_seconds"`
+	FailOpen       bool   `env:"FAIL_OPEN"       json:"fail_open"`
+}
+
 type ExecConfig struct {
-	ToolConfig          `         envPrefix:"PICOCLAW_TOOLS_EXEC_"`
-	EnableDenyPatterns  bool     `                                 json:"enable_deny_patterns"  env:"PICOCLAW_TOOLS_EXEC_ENABLE_DENY_PATTERNS"`
-	AllowRemote         bool     `                                 json:"allow_remote"          env:"PICOCLAW_TOOLS_EXEC_ALLOW_REMOTE"`
-	CustomDenyPatterns  []string `                                 json:"custom_deny_patterns"  env:"PICOCLAW_TOOLS_EXEC_CUSTOM_DENY_PATTERNS"`
-	CustomAllowPatterns []string `                                 json:"custom_allow_patterns" env:"PICOCLAW_TOOLS_EXEC_CUSTOM_ALLOW_PATTERNS"`
-	TimeoutSeconds      int      `                                 json:"timeout_seconds"       env:"PICOCLAW_TOOLS_EXEC_TIMEOUT_SECONDS"` // 0 means use default (60s)
+	ToolConfig `envPrefix:"PICOCLAW_TOOLS_EXEC_"`
+
+	EnableDenyPatterns  bool     `json:"enable_deny_patterns"  env:"PICOCLAW_TOOLS_EXEC_ENABLE_DENY_PATTERNS"`
+	AllowRemote         bool     `json:"allow_remote"          env:"PICOCLAW_TOOLS_EXEC_ALLOW_REMOTE"`
+	CustomDenyPatterns  []string `json:"custom_deny_patterns"  env:"PICOCLAW_TOOLS_EXEC_CUSTOM_DENY_PATTERNS"`
+	CustomAllowPatterns []string `json:"custom_allow_patterns" env:"PICOCLAW_TOOLS_EXEC_CUSTOM_ALLOW_PATTERNS"`
+
+	// 0 means use default (60s)
+	TimeoutSeconds int `json:"timeout_seconds" env:"PICOCLAW_TOOLS_EXEC_TIMEOUT_SECONDS"`
+
+	Tirith TirithConfig `json:"tirith" envPrefix:"PICOCLAW_TOOLS_EXEC_TIRITH_"`
 }
 
 type SkillsToolsConfig struct {
diff --git a/pkg/config/config_test.go b/pkg/config/config_test.go
index d744e15dc..5af80bbb6 100644
--- a/pkg/config/config_test.go
+++ b/pkg/config/config_test.go
@@ -1233,6 +1233,118 @@ func TestDefaultConfig_ExecAllowRemoteEnabled(t *testing.T) {
 	}
 }
 
+func TestDefaultConfig_TirithDisabled(t *testing.T) {
+	cfg := DefaultConfig()
+	if cfg.Tools.Exec.Tirith.Enabled {
+		t.Fatal("DefaultConfig().Tools.Exec.Tirith.Enabled should be false")
+	}
+	if cfg.Tools.Exec.Tirith.Bin != "tirith" {
+		t.Fatalf("DefaultConfig().Tools.Exec.Tirith.Bin = %q, want tirith", cfg.Tools.Exec.Tirith.Bin)
+	}
+	if cfg.Tools.Exec.Tirith.TimeoutSeconds != 5 {
+		t.Fatalf("DefaultConfig().Tools.Exec.Tirith.TimeoutSeconds = %d, want 5", cfg.Tools.Exec.Tirith.TimeoutSeconds)
+	}
+	if !cfg.Tools.Exec.Tirith.FailOpen {
+		t.Fatal("DefaultConfig().Tools.Exec.Tirith.FailOpen should be true")
+	}
+}
+
+func TestLoadConfig_TirithNestedKeysAndEnv(t *testing.T) {
+	dir := t.TempDir()
+	configPath := filepath.Join(dir, "config.json")
+	raw := `{
+  "version": 3,
+  "tools": {
+    "exec": {
+      "tirith": {
+        "enabled": true,
+        "bin": "/usr/local/bin/tirith",
+        "timeout_seconds": 7,
+        "fail_open": false
+      }
+    }
+  }
+}`
+	if err := os.WriteFile(configPath, []byte(raw), 0o600); err != nil {
+		t.Fatalf("WriteFile() error: %v", err)
+	}
+
+	cfg, err := LoadConfig(configPath)
+	if err != nil {
+		t.Fatalf("LoadConfig() error: %v", err)
+	}
+	if !cfg.Tools.Exec.Tirith.Enabled {
+		t.Fatal("Tirith.Enabled = false, want true")
+	}
+	if cfg.Tools.Exec.Tirith.Bin != "/usr/local/bin/tirith" {
+		t.Fatalf("Tirith.Bin = %q", cfg.Tools.Exec.Tirith.Bin)
+	}
+	if cfg.Tools.Exec.Tirith.TimeoutSeconds != 7 {
+		t.Fatalf("Tirith.TimeoutSeconds = %d, want 7", cfg.Tools.Exec.Tirith.TimeoutSeconds)
+	}
+	if cfg.Tools.Exec.Tirith.FailOpen {
+		t.Fatal("Tirith.FailOpen = true, want false")
+	}
+
+	t.Setenv("PICOCLAW_TOOLS_EXEC_TIRITH_ENABLED", "false")
+	t.Setenv("PICOCLAW_TOOLS_EXEC_TIRITH_BIN", "/opt/tirith")
+	t.Setenv("PICOCLAW_TOOLS_EXEC_TIRITH_TIMEOUT_SECONDS", "11")
+	t.Setenv("PICOCLAW_TOOLS_EXEC_TIRITH_FAIL_OPEN", "true")
+
+	cfg, err = LoadConfig(configPath)
+	if err != nil {
+		t.Fatalf("LoadConfig() with env error: %v", err)
+	}
+	if cfg.Tools.Exec.Tirith.Enabled {
+		t.Fatal("env Tirith.Enabled = true, want false")
+	}
+	if cfg.Tools.Exec.Tirith.Bin != "/opt/tirith" {
+		t.Fatalf("env Tirith.Bin = %q, want /opt/tirith", cfg.Tools.Exec.Tirith.Bin)
+	}
+	if cfg.Tools.Exec.Tirith.TimeoutSeconds != 11 {
+		t.Fatalf("env Tirith.TimeoutSeconds = %d, want 11", cfg.Tools.Exec.Tirith.TimeoutSeconds)
+	}
+	if !cfg.Tools.Exec.Tirith.FailOpen {
+		t.Fatal("env Tirith.FailOpen = false, want true")
+	}
+}
+
+func TestLoadConfig_TirithOldPRKeysAreUnknown(t *testing.T) {
+	dir := t.TempDir()
+	configPath := filepath.Join(dir, "config.json")
+	raw := `{
+  "version": 3,
+  "tools": {
+    "exec": {
+      "tirith": {
+        "tirith_enabled": true,
+        "tirith_bin": "tirith",
+        "tirith_timeout": 5,
+        "tirith_fail_open": true
+      }
+    }
+  }
+}`
+	if err := os.WriteFile(configPath, []byte(raw), 0o600); err != nil {
+		t.Fatalf("WriteFile() error: %v", err)
+	}
+
+	_, err := LoadConfig(configPath)
+	if err == nil {
+		t.Fatal("expected old Tirith PR keys to be rejected as unknown")
+	}
+	for _, field := range []string{
+		"tools.exec.tirith.tirith_enabled",
+		"tools.exec.tirith.tirith_bin",
+		"tools.exec.tirith.tirith_timeout",
+		"tools.exec.tirith.tirith_fail_open",
+	} {
+		if !strings.Contains(err.Error(), field) {
+			t.Fatalf("expected unknown field %s in error, got %q", field, err.Error())
+		}
+	}
+}
+
 func TestDefaultConfig_FilterSensitiveDataEnabled(t *testing.T) {
 	cfg := DefaultConfig()
 	if !cfg.Tools.FilterSensitiveData {
diff --git a/pkg/config/defaults.go b/pkg/config/defaults.go
index 6171f4626..657bbd69d 100644
--- a/pkg/config/defaults.go
+++ b/pkg/config/defaults.go
@@ -381,6 +381,12 @@ func DefaultConfig() *Config {
 				EnableDenyPatterns: true,
 				AllowRemote:        true,
 				TimeoutSeconds:     60,
+				Tirith: TirithConfig{
+					Enabled:        false,
+					Bin:            "tirith",
+					TimeoutSeconds: 5,
+					FailOpen:       true,
+				},
 			},
 			Skills: SkillsToolsConfig{
 				ToolConfig: ToolConfig{
diff --git a/pkg/tools/shell.go b/pkg/tools/shell.go
index a570ac9ec..ea50ca776 100644
--- a/pkg/tools/shell.go
+++ b/pkg/tools/shell.go
@@ -44,6 +44,7 @@ type ExecTool struct {
 	restrictToWorkspace bool
 	allowRemote         bool
 	sessionManager      *SessionManager
+	tirithConfig        TirithConfig
 }
 
 var (
@@ -168,6 +169,22 @@ func NewExecToolWithConfig(
 		timeout = time.Duration(cfg.Tools.Exec.TimeoutSeconds) * time.Second
 	}
 
+	tirithCfg := TirithConfig{
+		Enabled:  false,
+		BinPath:  "tirith",
+		Timeout:  5,
+		FailOpen: true,
+	}
+	if cfg != nil {
+		tc := cfg.Tools.Exec.Tirith
+		tirithCfg = TirithConfig{
+			Enabled:  tc.Enabled,
+			BinPath:  tc.Bin,
+			Timeout:  tc.TimeoutSeconds,
+			FailOpen: tc.FailOpen,
+		}
+	}
+
 	return &ExecTool{
 		workingDir:          workingDir,
 		timeout:             timeout,
@@ -178,6 +195,7 @@ func NewExecToolWithConfig(
 		restrictToWorkspace: restrict,
 		allowRemote:         allowRemote,
 		sessionManager:      getSessionManager(),
+		tirithConfig:        tirithCfg,
 	}, nil
 }
 
@@ -322,6 +340,11 @@ func (t *ExecTool) executeRun(ctx context.Context, args map[string]any) *ToolRes
 		return ErrorResult(guardError)
 	}
 
+	// Tirith content-level security gate (after cheap regex guards)
+	if tirithError := tirithGuard(ctx, command, cwd, t.tirithConfig); tirithError != "" {
+		return ErrorResult(tirithError)
+	}
+
 	// Re-resolve symlinks immediately before execution to shrink the TOCTOU window
 	// between validation and cmd.Dir assignment.
 	if t.restrictToWorkspace && t.workingDir != "" && cwd != t.workingDir {
diff --git a/pkg/tools/tirith.go b/pkg/tools/tirith.go
new file mode 100644
index 000000000..ff5d0980e
--- /dev/null
+++ b/pkg/tools/tirith.go
@@ -0,0 +1,543 @@
+// Package tools integrates Tirith pre-exec security scanning.
+//
+// Tirith (https://github.com/sheeki03/tirith) is a terminal security tool
+// that scans commands for content-level threats: homograph/punycode URLs,
+// pipe-to-interpreter patterns, base64 decode-execute chains, terminal
+// injection, suspicious packages/URLs, insecure transport, and local
+// threat-intelligence matches when configured in Tirith.
+//
+// PicoClaw invokes a locally installed Tirith binary when explicitly enabled.
+// It does not download, install, vendor, or bundle Tirith, and it disables
+// Tirith auto-update / live enrichment for this pre-exec check.
+package tools
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+	"unicode"
+	"unicode/utf8"
+)
+
+const (
+	tirithDefaultBin       = "tirith"
+	tirithDefaultTimeout   = 5
+	tirithStdoutLimitBytes = 256 * 1024
+	tirithStderrLimitBytes = 8 * 1024
+	tirithMaxFindings      = 50
+	tirithMaxSummaryRunes  = 500
+)
+
+var tirithScrubbedEnvVars = map[string]struct{}{
+	"TIRITH":                       {},
+	"TIRITH_POLICY_ROOT":           {},
+	"TIRITH_SERVER_URL":            {},
+	"TIRITH_API_KEY":               {},
+	"TIRITH_ALLOW_HTTP":            {},
+	"GOOGLE_SAFE_BROWSING_API_KEY": {},
+	"GOOGLE_SAFE_BROWSING_KEY":     {},
+	"SAFE_BROWSING_API_KEY":        {},
+	"ABUSECH_AUTH_KEY":             {},
+	"ABUSE_CH_AUTH_KEY":            {},
+	"URLHAUS_AUTH_KEY":             {},
+	"THREATFOX_AUTH_KEY":           {},
+}
+
+const tirithLocalOnlyPolicy = `policy_server_url: null
+policy_server_api_key: null
+allow_bypass_env: false
+allow_bypass_env_noninteractive: false
+threat_intel:
+  auto_update_hours: 0
+  osv_enabled: false
+  deps_dev_enabled: false
+  google_safe_browsing_key: null
+  abusech_auth_key: null
+  phishing_army_enabled: false
+`
+
+// TirithConfig holds Tirith security scanner settings (tools-internal).
+// Mapped from config.TirithConfig at ExecTool construction time.
+type TirithConfig struct {
+	Enabled  bool
+	BinPath  string
+	Timeout  int
+	FailOpen bool
+}
+
+var tirithWarningCache = struct {
+	sync.Mutex
+	seen map[string]struct{}
+}{
+	seen: make(map[string]struct{}),
+}
+
+// tirithGuard scans a command with tirith for content-level threats.
+// Call AFTER guardCommand() because cheap regex guards reject known-bad commands first.
+// Returns empty string if allowed, error message if blocked.
+func tirithGuard(ctx context.Context, command, cwd string, cfg TirithConfig) string {
+	if !cfg.Enabled {
+		return ""
+	}
+
+	binPath, cacheKey, err := resolveTirithPath(cfg.BinPath)
+	if err != nil {
+		return tirithScannerFailure(cacheKey, cfg, err)
+	}
+
+	timeout := cfg.Timeout
+	if timeout <= 0 {
+		timeout = tirithDefaultTimeout
+	}
+
+	policyRoot, cleanupPolicy, err := createTirithLocalOnlyPolicyRoot()
+	if err != nil {
+		return tirithScannerFailure(cacheKey, cfg, err)
+	}
+	defer cleanupPolicy()
+
+	parentCtx := ctx
+	ctx, cancel := context.WithTimeout(parentCtx, time.Duration(timeout)*time.Second)
+	defer cancel()
+
+	shellFlag := "posix"
+	if runtime.GOOS == "windows" {
+		shellFlag = "powershell"
+	}
+
+	cmd := exec.Command(binPath, "check", "--format", "json", "--non-interactive",
+		"--no-daemon", "--shell", shellFlag, "--", command)
+	if cwd != "" {
+		cmd.Dir = cwd
+	}
+	cmd.Env = tirithSubprocessEnv(policyRoot)
+	var stdout cappedBuffer
+	var stderr cappedBuffer
+	stdout.limit = tirithStdoutLimitBytes
+	stderr.limit = tirithStderrLimitBytes
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err = runTirithCommand(ctx, cmd)
+	if err != nil {
+		if parentCtx.Err() != nil {
+			return "Tirith security scan canceled"
+		}
+		if errors.Is(ctx.Err(), context.DeadlineExceeded) {
+			return tirithScannerFailure(cacheKey, cfg, fmt.Errorf("timed out after %ds", timeout))
+		}
+		if errors.Is(ctx.Err(), context.Canceled) {
+			return "Tirith security scan canceled"
+		}
+
+		var exitErr *exec.ExitError
+		if errors.As(err, &exitErr) {
+			return tirithHandleExit(exitErr.ExitCode(), stdout.Bytes(), cfg)
+		}
+
+		if stderr.Len() > 0 {
+			err = fmt.Errorf("%w: %s", err, tirithSanitizeText(stderr.String()))
+		}
+		return tirithScannerFailure(cacheKey, cfg, err)
+	}
+
+	return tirithHandleExit(0, stdout.Bytes(), cfg)
+}
+
+func runTirithCommand(ctx context.Context, cmd *exec.Cmd) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
+	prepareCommandForTermination(cmd)
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	done := make(chan error, 1)
+	go func() {
+		done <- cmd.Wait()
+	}()
+
+	select {
+	case err := <-done:
+		return err
+	case <-ctx.Done():
+		_ = terminateProcessTree(cmd)
+		err := <-done
+		if err != nil {
+			return err
+		}
+		return ctx.Err()
+	}
+}
+
+func createTirithLocalOnlyPolicyRoot() (string, func(), error) {
+	root, err := os.MkdirTemp("", "picoclaw-tirith-policy-*")
+	if err != nil {
+		return "", func() {}, fmt.Errorf("create local-only Tirith policy root: %w", err)
+	}
+
+	cleanup := func() {
+		_ = os.RemoveAll(root)
+	}
+
+	policyDir := filepath.Join(root, ".tirith")
+	if err := os.MkdirAll(policyDir, 0o700); err != nil {
+		cleanup()
+		return "", func() {}, fmt.Errorf("create local-only Tirith policy directory: %w", err)
+	}
+
+	policyPath := filepath.Join(policyDir, "policy.yaml")
+	if err := os.WriteFile(policyPath, []byte(tirithLocalOnlyPolicy), 0o600); err != nil {
+		cleanup()
+		return "", func() {}, fmt.Errorf("write local-only Tirith policy: %w", err)
+	}
+
+	return root, cleanup, nil
+}
+
+func tirithSubprocessEnv(policyRoot string) []string {
+	env := make([]string, 0, len(os.Environ())+1)
+	for _, entry := range os.Environ() {
+		name, _, ok := strings.Cut(entry, "=")
+		if !ok {
+			continue
+		}
+		if tirithShouldScrubEnv(name) {
+			continue
+		}
+		env = append(env, entry)
+	}
+	env = append(env, "TIRITH_POLICY_ROOT="+policyRoot)
+	return env
+}
+
+func tirithShouldScrubEnv(name string) bool {
+	_, ok := tirithScrubbedEnvVars[strings.ToUpper(name)]
+	return ok
+}
+
+func tirithHandleExit(exitCode int, jsonOutput []byte, cfg TirithConfig) string {
+	switch exitCode {
+	case 0:
+		return ""
+	case 1:
+		return fmt.Sprintf("Command blocked by Tirith security scan: %s", tirithSummarize(jsonOutput))
+	case 2:
+		log.Printf("[tirith] warning: %s", tirithSummarize(jsonOutput))
+		return ""
+	case 3:
+		log.Printf(
+			"[tirith] warning acknowledgement required; allowing in non-interactive mode: %s",
+			tirithSummarize(jsonOutput),
+		)
+		return ""
+	default:
+		return tirithScannerFailure(
+			normalizeTirithBin(cfg.BinPath),
+			cfg,
+			fmt.Errorf("unexpected exit code %d", exitCode),
+		)
+	}
+}
+
+func tirithScannerFailure(cacheKey string, cfg TirithConfig, err error) string {
+	message := tirithSanitizeText(err.Error())
+	if cfg.FailOpen {
+		tirithLogOncef(cacheKey, "scanner-failure", "[tirith] unavailable (fail-open): %s", message)
+		return ""
+	}
+	return fmt.Sprintf("Tirith security scan failed (fail-closed): %s", message)
+}
+
+func tirithLogOncef(cacheKey, category, format string, args ...any) {
+	cacheKey = normalizeTirithBin(cacheKey)
+	key := cacheKey + "\x00" + category + "\x00" + fmt.Sprintf(format, args...)
+
+	tirithWarningCache.Lock()
+	defer tirithWarningCache.Unlock()
+	if _, ok := tirithWarningCache.seen[key]; ok {
+		return
+	}
+	tirithWarningCache.seen[key] = struct{}{}
+	log.Printf(format, args...)
+}
+
+func tirithSummarize(jsonOutput []byte) string {
+	if len(jsonOutput) == 0 {
+		return "security issue detected"
+	}
+	var data struct {
+		Summary  string `json:"summary"`
+		Findings []struct {
+			Severity    string `json:"severity"`
+			Title       string `json:"title"`
+			Message     string `json:"message"`
+			Description string `json:"description"`
+		} `json:"findings"`
+	}
+	if err := json.Unmarshal(jsonOutput, &data); err != nil {
+		return "security issue detected (details unavailable)"
+	}
+
+	if summary := tirithTruncateRunes(tirithSanitizeText(data.Summary), tirithMaxSummaryRunes); summary != "" {
+		return summary
+	}
+
+	limit := len(data.Findings)
+	if limit > tirithMaxFindings {
+		limit = tirithMaxFindings
+	}
+	parts := make([]string, 0, limit)
+	for _, f := range data.Findings[:limit] {
+		title := f.Title
+		if title == "" {
+			title = f.Message
+		}
+		if title == "" {
+			title = f.Description
+		}
+		title = tirithSanitizeText(title)
+		if title == "" {
+			continue
+		}
+		severity := tirithSanitizeText(f.Severity)
+		if severity == "" {
+			parts = append(parts, title)
+		} else {
+			parts = append(parts, fmt.Sprintf("[%s] %s", severity, title))
+		}
+	}
+	if len(parts) == 0 {
+		return "security issue detected"
+	}
+	if len(data.Findings) > limit {
+		return tirithJoinFindingSummary(parts, len(data.Findings)-limit)
+	}
+	return tirithTruncateRunes(strings.Join(parts, "; "), tirithMaxSummaryRunes)
+}
+
+func tirithJoinFindingSummary(parts []string, more int) string {
+	summary := strings.Join(parts, "; ")
+	if more <= 0 {
+		return tirithTruncateRunes(summary, tirithMaxSummaryRunes)
+	}
+
+	suffix := fmt.Sprintf("; ...and %d more", more)
+	summaryRunes := []rune(summary)
+	suffixRunes := []rune(suffix)
+	if len(summaryRunes)+len(suffixRunes) <= tirithMaxSummaryRunes {
+		return summary + suffix
+	}
+	prefixLimit := tirithMaxSummaryRunes - len(suffixRunes)
+	if prefixLimit <= 0 {
+		return tirithTruncateRunes(strings.TrimPrefix(suffix, "; "), tirithMaxSummaryRunes)
+	}
+	prefix := strings.TrimSpace(string(summaryRunes[:prefixLimit]))
+	prefix = strings.TrimSuffix(prefix, ";")
+	if prefix == "" {
+		return strings.TrimPrefix(suffix, "; ")
+	}
+	return prefix + suffix
+}
+
+// resolveTirithPath resolves only a user-installed Tirith binary. It deliberately
+// does not cache failed lookups so installing Tirith after a miss works immediately.
+func resolveTirithPath(configured string) (string, string, error) {
+	normalized := normalizeTirithBin(configured)
+	if isExplicitTirithPath(normalized) {
+		if err := validateTirithPath(normalized); err != nil {
+			return "", normalized, err
+		}
+		return normalized, normalized, nil
+	}
+
+	path, err := exec.LookPath(normalized)
+	if err != nil {
+		return "", normalized, err
+	}
+	if err := validateTirithPath(path); err != nil {
+		return "", normalized, err
+	}
+	return path, normalized, nil
+}
+
+func normalizeTirithBin(configured string) string {
+	bin := strings.TrimSpace(configured)
+	if bin == "" {
+		bin = tirithDefaultBin
+	}
+	if bin == "~" || strings.HasPrefix(bin, "~/") || strings.HasPrefix(bin, `~\`) {
+		if home, err := os.UserHomeDir(); err == nil && home != "" {
+			if bin == "~" {
+				bin = home
+			} else {
+				bin = filepath.Join(home, bin[2:])
+			}
+		}
+	}
+	if isExplicitTirithPath(bin) {
+		cleaned := filepath.Clean(bin)
+		if filepath.IsAbs(cleaned) {
+			return cleaned
+		}
+		if abs, err := filepath.Abs(cleaned); err == nil {
+			return abs
+		}
+		return cleaned
+	}
+	return bin
+}
+
+func isExplicitTirithPath(path string) bool {
+	return filepath.IsAbs(path) ||
+		strings.Contains(path, "/") ||
+		strings.Contains(path, `\`)
+}
+
+func validateTirithPath(path string) error {
+	info, err := os.Stat(path)
+	if err != nil {
+		return err
+	}
+	if info.IsDir() {
+		return fmt.Errorf("%s is a directory", path)
+	}
+	if runtime.GOOS != "windows" && info.Mode()&0o111 == 0 {
+		return fmt.Errorf("%s is not executable", path)
+	}
+	return nil
+}
+
+type cappedBuffer struct {
+	limit int
+	buf   bytes.Buffer
+}
+
+func (b *cappedBuffer) Write(p []byte) (int, error) {
+	written := len(p)
+	if b.limit <= 0 || b.buf.Len() >= b.limit {
+		return written, nil
+	}
+	remaining := b.limit - b.buf.Len()
+	if len(p) > remaining {
+		p = p[:remaining]
+	}
+	_, _ = b.buf.Write(p)
+	return written, nil
+}
+
+func (b *cappedBuffer) Bytes() []byte {
+	return b.buf.Bytes()
+}
+
+func (b *cappedBuffer) String() string {
+	return b.buf.String()
+}
+
+func (b *cappedBuffer) Len() int {
+	return b.buf.Len()
+}
+
+func tirithSanitizeText(input string) string {
+	input = tirithStripANSI(input)
+	var b strings.Builder
+	b.Grow(len(input))
+	for _, r := range input {
+		if tirithDropRune(r) {
+			continue
+		}
+		b.WriteRune(r)
+	}
+	return strings.Join(strings.Fields(b.String()), " ")
+}
+
+func tirithDropRune(r rune) bool {
+	if unicode.IsControl(r) {
+		return true
+	}
+	switch {
+	case r >= '\u202a' && r <= '\u202e':
+		return true
+	case r >= '\u2066' && r <= '\u2069':
+		return true
+	case r >= '\u200b' && r <= '\u200f':
+		return true
+	case r == '\u2060' || r == '\ufeff':
+		return true
+	case r >= '\ufe00' && r <= '\ufe0f':
+		return true
+	case r >= '\U000e0100' && r <= '\U000e01ef':
+		return true
+	case r >= '\U000e0000' && r <= '\U000e007f':
+		return true
+	default:
+		return false
+	}
+}
+
+func tirithStripANSI(input string) string {
+	var b strings.Builder
+	for i := 0; i < len(input); {
+		r, size := utf8.DecodeRuneInString(input[i:])
+		if r != '\x1b' {
+			b.WriteString(input[i : i+size])
+			i += size
+			continue
+		}
+
+		i += size
+		if i >= len(input) {
+			continue
+		}
+		switch input[i] {
+		case '[':
+			i++
+			for i < len(input) {
+				c := input[i]
+				i++
+				if c >= 0x40 && c <= 0x7e {
+					break
+				}
+			}
+		case ']':
+			i++
+			for i < len(input) {
+				if input[i] == 0x07 {
+					i++
+					break
+				}
+				if input[i] == '\x1b' && i+1 < len(input) && input[i+1] == '\\' {
+					i += 2
+					break
+				}
+				i++
+			}
+		default:
+			i++
+		}
+	}
+	return b.String()
+}
+
+func tirithTruncateRunes(s string, limit int) string {
+	if limit <= 0 {
+		return ""
+	}
+	runes := []rune(s)
+	if len(runes) <= limit {
+		return s
+	}
+	return string(runes[:limit]) + "..."
+}
diff --git a/pkg/tools/tirith_test.go b/pkg/tools/tirith_test.go
new file mode 100644
index 000000000..5e4cfb1a8
--- /dev/null
+++ b/pkg/tools/tirith_test.go
@@ -0,0 +1,521 @@
+package tools
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewExecTool_DefaultTirithDisabled(t *testing.T) {
+	tool, err := NewExecTool("", false)
+	require.NoError(t, err)
+	require.False(t, tool.tirithConfig.Enabled)
+	require.Equal(t, "tirith", tool.tirithConfig.BinPath)
+	require.Equal(t, 5, tool.tirithConfig.Timeout)
+	require.True(t, tool.tirithConfig.FailOpen)
+}
+
+func TestTirithGuard_DisabledDoesNotResolve(t *testing.T) {
+	cfg := TirithConfig{
+		Enabled:  false,
+		BinPath:  filepath.Join(t.TempDir(), "missing-tirith"),
+		Timeout:  5,
+		FailOpen: false,
+	}
+	require.Empty(t, tirithGuard(context.Background(), "echo hello", "", cfg))
+}
+
+func TestTirithGuard_MissingBinaryFailOpenAndFailClosed(t *testing.T) {
+	missing := filepath.Join(t.TempDir(), "missing-tirith")
+
+	failOpen := tirithGuard(context.Background(), "echo hello", "", TirithConfig{
+		Enabled:  true,
+		BinPath:  missing,
+		Timeout:  5,
+		FailOpen: true,
+	})
+	require.Empty(t, failOpen)
+
+	failClosed := tirithGuard(context.Background(), "echo hello", "", TirithConfig{
+		Enabled:  true,
+		BinPath:  missing,
+		Timeout:  5,
+		FailOpen: false,
+	})
+	require.Contains(t, failClosed, "fail-closed")
+}
+
+func TestResolveTirithPath_NormalizationAndValidation(t *testing.T) {
+	require.Equal(t, "tirith", normalizeTirithBin(""))
+	require.Equal(t, "tirith", normalizeTirithBin("   "))
+
+	dir := t.TempDir()
+	_, _, err := resolveTirithPath(dir)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "directory")
+
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	if runtime.GOOS == "windows" {
+		t.Setenv("USERPROFILE", home)
+	}
+	homeBin := filepath.Join(home, "tirith")
+	writeExecutableFile(t, homeBin, fakeTirithScript(`printf '{"findings":[]}'`+"\nexit 0\n"))
+	resolved, cacheKey, err := resolveTirithPath("~/tirith")
+	require.NoError(t, err)
+	require.Equal(t, filepath.Clean(homeBin), resolved)
+	require.Equal(t, filepath.Clean(homeBin), cacheKey)
+
+	if runtime.GOOS != "windows" {
+		notExecutable := filepath.Join(t.TempDir(), "tirith")
+		require.NoError(t, os.WriteFile(notExecutable, []byte("#!/bin/sh\nexit 0\n"), 0o644))
+		_, _, err = resolveTirithPath(notExecutable)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "not executable")
+	}
+}
+
+func TestResolveTirithPath_PathLookup(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	dir := t.TempDir()
+	bin := filepath.Join(dir, "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript(`printf '{"findings":[]}'`+"\nexit 0\n"))
+	t.Setenv("PATH", dir+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+	resolved, cacheKey, err := resolveTirithPath("tirith")
+	require.NoError(t, err)
+	require.Equal(t, bin, resolved)
+	require.Equal(t, "tirith", cacheKey)
+}
+
+func TestResolveTirithPath_ExplicitRelativePathDoesNotUsePath(t *testing.T) {
+	dir := t.TempDir()
+	oldWD, err := os.Getwd()
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		require.NoError(t, os.Chdir(oldWD))
+	})
+	require.NoError(t, os.Chdir(dir))
+
+	local := filepath.Join(dir, "tirith")
+	writeExecutableFile(t, local, fakeTirithScript(`printf '{"findings":[]}'`+"\nexit 0\n"))
+
+	pathDir := t.TempDir()
+	pathBin := filepath.Join(pathDir, "tirith")
+	writeExecutableFile(t, pathBin, fakeTirithScript("exit 1\n"))
+	t.Setenv("PATH", pathDir+string(os.PathListSeparator)+os.Getenv("PATH"))
+
+	resolved, cacheKey, err := resolveTirithPath("./tirith")
+	require.NoError(t, err)
+	expected, err := filepath.Abs("tirith")
+	require.NoError(t, err)
+	require.Equal(t, expected, resolved)
+	require.Equal(t, expected, cacheKey)
+}
+
+func TestTirithGuard_DoesNotCacheFailedResolution(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	bin := filepath.Join(t.TempDir(), "tirith")
+	cfg := TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: true}
+
+	require.Empty(t, tirithGuard(context.Background(), "echo first", "", cfg))
+
+	writeExecutableFile(
+		t,
+		bin,
+		fakeTirithScript(`printf '{"findings":[{"severity":"HIGH","title":"later install"}]}'`+"\nexit 1\n"),
+	)
+	got := tirithGuard(context.Background(), "echo second", "", cfg)
+	require.Contains(t, got, "Command blocked by Tirith")
+	require.Contains(t, got, "later install")
+}
+
+func TestTirithGuard_Argv(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	argsFile := filepath.Join(t.TempDir(), "args.txt")
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript(`
+printf '%s\n' "$@" > "$TIRITH_ARGS_FILE"
+printf '{"findings":[]}'
+exit 0
+`))
+	t.Setenv("TIRITH_ARGS_FILE", argsFile)
+
+	got := tirithGuard(
+		context.Background(),
+		"echo hello",
+		"",
+		TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: false},
+	)
+	require.Empty(t, got)
+
+	argsData, err := os.ReadFile(argsFile)
+	require.NoError(t, err)
+	args := strings.Split(strings.TrimSpace(string(argsData)), "\n")
+	require.Equal(t, []string{
+		"check",
+		"--format",
+		"json",
+		"--non-interactive",
+		"--no-daemon",
+		"--shell",
+		"posix",
+		"--",
+		"echo hello",
+	}, args)
+}
+
+func TestTirithGuard_UsesLocalOnlyPolicyEnvironment(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	envFile := filepath.Join(t.TempDir(), "env.txt")
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript(`
+{
+  printf 'policy_root=%s\n' "$TIRITH_POLICY_ROOT"
+  printf 'server=%s\n' "${TIRITH_SERVER_URL-unset}"
+  printf 'api=%s\n' "${TIRITH_API_KEY-unset}"
+  printf 'bypass=%s\n' "${TIRITH-unset}"
+  printf 'allow_http=%s\n' "${TIRITH_ALLOW_HTTP-unset}"
+  printf 'gsb=%s\n' "${GOOGLE_SAFE_BROWSING_API_KEY-unset}"
+  printf 'abusech=%s\n' "${ABUSECH_AUTH_KEY-unset}"
+  printf 'path=%s\n' "${PATH-unset}"
+  printf 'home=%s\n' "${HOME-unset}"
+  printf '%s\n' '---policy---'
+  cat "$TIRITH_POLICY_ROOT/.tirith/policy.yaml"
+} > "$TIRITH_ENV_FILE"
+printf '{"findings":[]}'
+exit 0
+`))
+	t.Setenv("TIRITH_ENV_FILE", envFile)
+	t.Setenv("TIRITH_POLICY_ROOT", "/should/not/be/used")
+	t.Setenv("TIRITH_SERVER_URL", "https://policy.example.invalid")
+	t.Setenv("TIRITH_API_KEY", "secret")
+	t.Setenv("TIRITH", "0")
+	t.Setenv("TIRITH_ALLOW_HTTP", "1")
+	t.Setenv("GOOGLE_SAFE_BROWSING_API_KEY", "gsb-secret")
+	t.Setenv("ABUSECH_AUTH_KEY", "abusech-secret")
+
+	got := tirithGuard(
+		context.Background(),
+		"echo hello",
+		"",
+		TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: false},
+	)
+	require.Empty(t, got)
+
+	data, err := os.ReadFile(envFile)
+	require.NoError(t, err)
+	text := string(data)
+	require.Contains(t, text, "policy_root=")
+	require.NotContains(t, text, "/should/not/be/used")
+	require.Contains(t, text, "server=unset")
+	require.Contains(t, text, "api=unset")
+	require.Contains(t, text, "bypass=unset")
+	require.Contains(t, text, "allow_http=unset")
+	require.Contains(t, text, "gsb=unset")
+	require.Contains(t, text, "abusech=unset")
+	require.Contains(t, text, "path=")
+	require.Contains(t, text, "home=")
+	require.Contains(t, text, "allow_bypass_env: false")
+	require.Contains(t, text, "allow_bypass_env_noninteractive: false")
+	require.Contains(t, text, "auto_update_hours: 0")
+	require.Contains(t, text, "osv_enabled: false")
+	require.Contains(t, text, "deps_dev_enabled: false")
+	require.Contains(t, text, "phishing_army_enabled: false")
+}
+
+func TestTirithGuard_UsesCommandWorkingDirectory(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	cwd := t.TempDir()
+	pwdFile := filepath.Join(t.TempDir(), "pwd.txt")
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript(`
+pwd > "$TIRITH_PWD_FILE"
+printf '{"findings":[]}'
+exit 0
+	`))
+	t.Setenv("TIRITH_PWD_FILE", pwdFile)
+
+	cfg := TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: false}
+	got := tirithGuard(context.Background(), "echo hello", cwd, cfg)
+	require.Empty(t, got)
+
+	data, err := os.ReadFile(pwdFile)
+	require.NoError(t, err)
+	expectedCWD, err := filepath.EvalSymlinks(cwd)
+	require.NoError(t, err)
+	require.Equal(t, expectedCWD, strings.TrimSpace(string(data)))
+}
+
+func TestTirithGuard_ExitCodes(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	tests := []struct {
+		name      string
+		exitCode  int
+		failOpen  bool
+		wantBlock bool
+		wantText  string
+	}{
+		{name: "allow", exitCode: 0, failOpen: false},
+		{name: "block", exitCode: 1, failOpen: false, wantBlock: true, wantText: "Pipe to shell"},
+		{name: "warn", exitCode: 2, failOpen: false},
+		{name: "warn ack defensive", exitCode: 3, failOpen: false},
+		{name: "unknown fail open", exitCode: 9, failOpen: true},
+		{name: "unknown fail closed", exitCode: 9, failOpen: false, wantBlock: true, wantText: "fail-closed"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			bin := filepath.Join(t.TempDir(), "tirith")
+			script := `printf '{"findings":[{"severity":"HIGH","title":"Pipe to shell"}]}'` +
+				"\nexit " + itoa(tt.exitCode) + "\n"
+			writeExecutableFile(t, bin, fakeTirithScript(script))
+
+			cfg := TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: tt.failOpen}
+			got := tirithGuard(context.Background(), "echo hello", "", cfg)
+			if tt.wantBlock {
+				require.NotEmpty(t, got)
+				require.Contains(t, got, tt.wantText)
+			} else {
+				require.Empty(t, got)
+			}
+		})
+	}
+}
+
+func TestTirithGuard_InvalidJSONKeepsExitVerdict(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript("printf 'not json'\nexit 1\n"))
+
+	cfg := TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: false}
+	got := tirithGuard(context.Background(), "echo hello", "", cfg)
+	require.Contains(t, got, "Command blocked by Tirith")
+	require.Contains(t, got, "details unavailable")
+}
+
+func TestTirithGuard_TimeoutUsesFailOpen(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript("sleep 2\nexit 0\n"))
+
+	cfg := TirithConfig{Enabled: true, BinPath: bin, Timeout: 1, FailOpen: true}
+	require.Empty(t, tirithGuard(context.Background(), "echo hello", "", cfg))
+
+	cfg.FailOpen = false
+	got := tirithGuard(context.Background(), "echo hello", "", cfg)
+	require.Contains(t, got, "fail-closed")
+	require.Contains(t, got, "timed out")
+}
+
+func TestRunTirithCommand_CancelKillsProcessTree(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	childPIDFile := filepath.Join(t.TempDir(), "child.pid")
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript(`
+sleep 30 &
+echo $! > "$TIRITH_CHILD_PID_FILE"
+wait
+`))
+	t.Setenv("TIRITH_CHILD_PID_FILE", childPIDFile)
+
+	start := time.Now()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	cmd := exec.Command(bin)
+	cmd.Env = append(os.Environ(), "TIRITH_CHILD_PID_FILE="+childPIDFile)
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- runTirithCommand(ctx, cmd)
+	}()
+
+	require.Eventually(t, func() bool {
+		_, err := os.Stat(childPIDFile)
+		return err == nil
+	}, 5*time.Second, 100*time.Millisecond)
+
+	cancel()
+	var runErr error
+	require.Eventually(t, func() bool {
+		select {
+		case runErr = <-errCh:
+			return true
+		default:
+			return false
+		}
+	}, 5*time.Second, 100*time.Millisecond)
+	require.Error(t, runErr)
+	require.Less(t, time.Since(start), 7*time.Second)
+
+	data, err := os.ReadFile(childPIDFile)
+	require.NoError(t, err)
+	pid, err := strconv.Atoi(strings.TrimSpace(string(data)))
+	require.NoError(t, err)
+	require.Eventually(t, func() bool {
+		return !tirithTestProcessExists(pid)
+	}, 5*time.Second, 100*time.Millisecond)
+}
+
+func TestTirithGuard_ContextCanceledBlocksExecution(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript("sleep 2\nexit 0\n"))
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	got := tirithGuard(ctx, "echo hello", "", TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: true})
+	require.Equal(t, "Tirith security scan canceled", got)
+}
+
+func TestTirithGuard_ParentDeadlineBlocksExecution(t *testing.T) {
+	skipWindowsProcessTest(t)
+
+	bin := filepath.Join(t.TempDir(), "tirith")
+	writeExecutableFile(t, bin, fakeTirithScript("sleep 2\nexit 0\n"))
+
+	ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(-time.Second))
+	defer cancel()
+
+	got := tirithGuard(ctx, "echo hello", "", TirithConfig{Enabled: true, BinPath: bin, Timeout: 5, FailOpen: true})
+	require.Equal(t, "Tirith security scan canceled", got)
+}
+
+func TestCappedBuffer_DiscardReturnsFullWriteLength(t *testing.T) {
+	var buf cappedBuffer
+	buf.limit = 5
+
+	n, err := buf.Write([]byte("abcdef"))
+	require.NoError(t, err)
+	require.Equal(t, 6, n)
+	require.Equal(t, "abcde", buf.String())
+
+	n, err = buf.Write([]byte("ghij"))
+	require.NoError(t, err)
+	require.Equal(t, 4, n)
+	require.Equal(t, "abcde", buf.String())
+}
+
+func TestTirithSummarize_SanitizesAndCapsFindings(t *testing.T) {
+	findings := make([]map[string]string, 0, tirithMaxFindings+5)
+	findings = append(findings, map[string]string{
+		"severity": "\x1b[31mHIGH\x1b[0m",
+		"title":    "bad\u202e\u200b title",
+	})
+	for i := 0; i < tirithMaxFindings+4; i++ {
+		findings = append(findings, map[string]string{"severity": "LOW", "title": "extra"})
+	}
+	payload, err := json.Marshal(map[string]any{"findings": findings})
+	require.NoError(t, err)
+
+	got := tirithSummarize(payload)
+	require.Contains(t, got, "[HIGH] bad title")
+	require.NotContains(t, got, "\x1b")
+	require.NotContains(t, got, "[31m")
+	require.NotContains(t, got, "\u202e")
+	require.NotContains(t, got, "\u200b")
+	require.Contains(t, got, "...and 5 more")
+	require.LessOrEqual(t, len([]rune(got)), tirithMaxSummaryRunes+3)
+}
+
+func TestTirithSummarize_CapsSummary(t *testing.T) {
+	payload, err := json.Marshal(map[string]any{"summary": strings.Repeat("x", tirithMaxSummaryRunes+20)})
+	require.NoError(t, err)
+
+	got := tirithSummarize(payload)
+	require.Len(t, []rune(got), tirithMaxSummaryRunes+3)
+	require.True(t, strings.HasSuffix(got, "..."))
+}
+
+func TestTirithWarningCacheSuppressesRepeatedScannerFailureLogs(t *testing.T) {
+	resetTirithWarningCacheForTest()
+
+	var logs bytes.Buffer
+	previousOutput := log.Writer()
+	previousFlags := log.Flags()
+	log.SetOutput(&logs)
+	log.SetFlags(0)
+	defer func() {
+		log.SetOutput(previousOutput)
+		log.SetFlags(previousFlags)
+	}()
+
+	missing := filepath.Join(t.TempDir(), "missing-tirith")
+	cfg := TirithConfig{Enabled: true, BinPath: missing, Timeout: 5, FailOpen: true}
+	require.Empty(t, tirithGuard(context.Background(), "echo one", "", cfg))
+	require.Empty(t, tirithGuard(context.Background(), "echo two", "", cfg))
+
+	require.Equal(t, 1, strings.Count(logs.String(), "unavailable (fail-open)"))
+}
+
+func TestTirithSummarize_InvalidAndEmptyJSON(t *testing.T) {
+	require.Contains(t, tirithSummarize([]byte("not json")), "details unavailable")
+	require.Equal(t, "security issue detected", tirithSummarize([]byte(`{"findings":[]}`)))
+	require.Equal(t, "security issue detected", tirithSummarize(nil))
+}
+
+func resetTirithWarningCacheForTest() {
+	tirithWarningCache.Lock()
+	defer tirithWarningCache.Unlock()
+	tirithWarningCache.seen = make(map[string]struct{})
+}
+
+func writeExecutableFile(t *testing.T, path, content string) {
+	t.Helper()
+	require.NoError(t, os.WriteFile(path, []byte(content), 0o755))
+	if runtime.GOOS != "windows" {
+		require.NoError(t, os.Chmod(path, 0o755))
+	}
+}
+
+func fakeTirithScript(body string) string {
+	return "#!/bin/sh\n" + body
+}
+
+func skipWindowsProcessTest(t *testing.T) {
+	t.Helper()
+	if runtime.GOOS == "windows" {
+		t.Skip("shell-script Tirith fake is Unix-only")
+	}
+}
+
+func tirithTestProcessExists(pid int) bool {
+	return exec.Command("kill", "-0", itoa(pid)).Run() == nil
+}
+
+func itoa(v int) string {
+	if v == 0 {
+		return "0"
+	}
+	var digits [20]byte
+	i := len(digits)
+	for v > 0 {
+		i--
+		digits[i] = byte('0' + v%10)
+		v /= 10
+	}
+	return string(digits[i:])
+}