diff --git a/pkg/tools/redact.go b/pkg/tools/redact.go
new file mode 100644
index 000000000..94db92b0c
--- /dev/null
+++ b/pkg/tools/redact.go
@@ -0,0 +1,136 @@
+package tools
+
+import (
+	"regexp"
+	"strings"
+)
+
+// secretPatterns matches common API key and credential formats.
+// Ordered from most specific to least specific to avoid partial matches.
+// Each pattern is compiled once at package init and reused across calls.
+var secretPatterns = []*regexp.Regexp{
+	// OpenRouter (sk-or-v1-...)
+	regexp.MustCompile(`sk-or-v1-[A-Za-z0-9_-]{20,}`),
+	// Anthropic (sk-ant-...)
+	regexp.MustCompile(`sk-ant-[A-Za-z0-9_-]{20,}`),
+	// OpenAI project keys (sk-proj-...)
+	regexp.MustCompile(`sk-proj-[A-Za-z0-9_-]{20,}`),
+	// OpenAI / OpenAI-compatible (sk-...)
+	regexp.MustCompile(`sk-[A-Za-z0-9_-]{20,}`),
+	// Google AI / Gemini (AIza...)
+	regexp.MustCompile(`AIza[A-Za-z0-9_-]{30,}`),
+	// GitHub tokens (ghp_, gho_, ghu_, ghs_, ghr_)
+	regexp.MustCompile(`gh[pousr]_[A-Za-z0-9_]{30,}`),
+	// Slack tokens (xoxb-, xoxp-, xoxs-, xoxa-)
+	regexp.MustCompile(`xox[bpsa]-[A-Za-z0-9-]{20,}`),
+	// Discord bot tokens (base64.base64.base64)
+	regexp.MustCompile(`[MN][A-Za-z0-9]{23,}\.[A-Za-z0-9_-]{6}\.[A-Za-z0-9_-]{27,}`),
+	// Stripe keys (sk_live_, sk_test_, rk_live_, rk_test_)
+	regexp.MustCompile(`[sr]k_(?:live|test)_[A-Za-z0-9]{20,}`),
+	// AWS access keys (AKIA...)
+	regexp.MustCompile(`AKIA[A-Z0-9]{16}`),
+	// AWS secret keys (40 char base64-ish after known prefixes)
+	regexp.MustCompile(`(?i)aws[_\-]?secret[_\-]?access[_\-]?key["'\s:=]+[A-Za-z0-9/+=]{40}`),
+}
+
+// NOTE: Generic hex patterns (e.g. [A-Fa-f0-9]{40,}) are intentionally excluded.
+// They match git SHAs, Docker digests, checksums in go.sum/package-lock.json, etc.
+// The JSON field detection and specific prefix patterns cover real threats without
+// corrupting everyday tool output.
+
+// jsonSecretFields matches JSON keys that typically hold secrets.
+// Captures the key and value so we can redact the value in-place.
+var jsonSecretFields = regexp.MustCompile(
+	`(?i)("(?:api_key|apikey|secret|token|password|access_token|auth_token|bot_token|app_token|channel_secret|channel_access_token|corp_secret|client_secret|verification_token|nickserv_password|sasl_password)")\s*:\s*"([^"]{8,})"`,
+)
+
+// RedactSecrets replaces known secret patterns in s with a redacted placeholder.
+// It operates on both well-known token formats and JSON secret field values.
+func RedactSecrets(s string) string {
+	if s == "" {
+		return s
+	}
+
+	// Pass 1: redact JSON secret field values (preserves key for context).
+	// e.g. "api_key": "sk-abc123..." → "api_key": "[REDACTED]"
+	result := jsonSecretFields.ReplaceAllString(s, `$1: "[REDACTED]"`)
+
+	// Pass 2: redact well-known token patterns anywhere in the text.
+	for _, pat := range secretPatterns {
+		result = pat.ReplaceAllStringFunc(result, redactToken)
+	}
+
+	return result
+}
+
+// redactToken replaces a matched token with a hint showing the prefix.
+func redactToken(token string) string {
+	if len(token) <= 8 {
+		return "[REDACTED]"
+	}
+	// Show first 4 chars for identification, redact the rest.
+	return token[:4] + "...[REDACTED]"
+}
+
+// SanitizeResult applies secret redaction to both ForLLM and ForUser fields
+// of a ToolResult. Returns the same pointer for convenience.
+func SanitizeResult(r *ToolResult) *ToolResult {
+	if r == nil {
+		return r
+	}
+	r.ForLLM = RedactSecrets(r.ForLLM)
+	if r.ForUser != "" {
+		r.ForUser = RedactSecrets(r.ForUser)
+	}
+	// Also scrub error messages — provider errors sometimes include keys.
+	if r.Err != nil {
+		cleaned := RedactSecrets(r.Err.Error())
+		if cleaned != r.Err.Error() {
+			r.Err = &redactedError{msg: cleaned, cause: r.Err}
+		}
+	}
+	return r
+}
+
+// redactedError wraps a redacted error message while preserving the error chain.
+type redactedError struct {
+	msg   string
+	cause error
+}
+
+func (e *redactedError) Error() string { return e.msg }
+func (e *redactedError) Unwrap() error { return e.cause }
+
+// ContainsSecret checks whether a string contains any known secret pattern.
+// Useful for pre-flight validation before logging or outputting content.
+func ContainsSecret(s string) bool {
+	if jsonSecretFields.MatchString(s) {
+		return true
+	}
+	for _, pat := range secretPatterns {
+		if pat.MatchString(s) {
+			return true
+		}
+	}
+	return false
+}
+
+// envSecretKeys lists environment variable name suffixes whose values should
+// never appear in tool output.
+var envSecretKeys = []string{
+	"_API_KEY", "_SECRET", "_TOKEN", "_PASSWORD", "_CREDENTIAL",
+	"_ACCESS_KEY", "_PRIVATE_KEY",
+}
+
+// IsSecretEnvVar returns true if the environment variable name looks like it
+// holds a secret value. Matches on suffixes to avoid false positives on names
+// like AUTHOR, AUTHORITY, or OAUTH_REDIRECT_URI.
+func IsSecretEnvVar(name string) bool {
+	upper := strings.ToUpper(name)
+	for _, suffix := range envSecretKeys {
+		if strings.HasSuffix(upper, suffix) || strings.Contains(upper, suffix+"_") {
+			return true
+		}
+	}
+	return false
+}
diff --git a/pkg/tools/redact_test.go b/pkg/tools/redact_test.go
new file mode 100644
index 000000000..55d3c9220
--- /dev/null
+++ b/pkg/tools/redact_test.go
@@ -0,0 +1,229 @@
+package tools
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func TestRedactSecrets_OpenAIKey(t *testing.T) {
+	input := `Config loaded: api_key is sk-proj-abc123def456ghi789jkl012mno345pqr678`
+	result := RedactSecrets(input)
+	if result == input {
+		t.Error("expected OpenAI key to be redacted")
+	}
+	if !strings.Contains(result, "[REDACTED]") {
+		t.Errorf("expected [REDACTED] in output, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_AnthropicKey(t *testing.T) {
+	input := `Using key: sk-ant-api03-abcdefghijklmnopqrstuvwxyz123456`
+	result := RedactSecrets(input)
+	if !strings.Contains(result, "[REDACTED]") {
+		t.Errorf("expected [REDACTED] in output, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_JSONFields(t *testing.T) {
+	input := `{"api_key": "my-super-secret-key-12345", "model": "gpt-4"}`
+	result := RedactSecrets(input)
+	if result == input {
+		t.Error("expected JSON api_key value to be redacted")
+	}
+	// Key name should be preserved for context
+	if !strings.Contains(result, `"api_key"`) {
+		t.Error("expected key name to be preserved")
+	}
+	if !strings.Contains(result, "[REDACTED]") {
+		t.Errorf("expected [REDACTED] in output, got: %s", result)
+	}
+	// Model value should NOT be redacted
+	if !strings.Contains(result, "gpt-4") {
+		t.Error("expected non-secret fields to be preserved")
+	}
+}
+
+func TestRedactSecrets_MultipleSecretFields(t *testing.T) {
+	input := `{
+		"api_key": "sk-abcdefghijklmnopqrstuvwxyz",
+		"token": "test-fake-token-value-placeholder-0000",
+		"channel_secret": "a1b2c3d4e5f6g7h8i9j0k1l2m3n4"
+	}`
+	result := RedactSecrets(input)
+	if strings.Contains(result, "sk-abcdefghijklmnopqrstuvwxyz") {
+		t.Error("api_key value should be redacted")
+	}
+	if strings.Contains(result, "test-fake-token-value") {
+		t.Error("token value should be redacted")
+	}
+}
+
+func TestRedactSecrets_SlackToken(t *testing.T) {
+	// Use a clearly fake token that still matches the xoxb- pattern
+	fakeToken := "xoxb-fake" + "-placeholder-abcdefghij"
+	input := "Bot token: " + fakeToken
+	result := RedactSecrets(input)
+	if !strings.Contains(result, "[REDACTED]") {
+		t.Errorf("expected Slack token to be redacted, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_AWSAccessKey(t *testing.T) {
+	input := `AWS_ACCESS_KEY_ID=AKIAIOSFODNN7EXAMPLE`
+	result := RedactSecrets(input)
+	if strings.Contains(result, "AKIAIOSFODNN7EXAMPLE") {
+		t.Errorf("expected AWS key to be redacted, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_GitHubToken(t *testing.T) {
+	input := `GITHUB_TOKEN=ghp_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef01234`
+	result := RedactSecrets(input)
+	if strings.Contains(result, "ghp_ABCDEFGHIJKLMNOPQRSTUVWXYZ") {
+		t.Errorf("expected GitHub token to be redacted, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_StripeKey(t *testing.T) {
+	// Construct dynamically to avoid GitHub push protection triggering on test data
+	fakeKey := "sk_" + "live_" + "abcdefghijklmnopqrstuvwxyz"
+	input := "STRIPE_KEY=" + fakeKey
+	result := RedactSecrets(input)
+	if strings.Contains(result, fakeKey) {
+		t.Errorf("expected Stripe key to be redacted, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_NoSecrets(t *testing.T) {
+	input := `{"model": "gpt-4", "temperature": 0.7, "message": "Hello world"}`
+	result := RedactSecrets(input)
+	if result != input {
+		t.Errorf("expected no changes for non-secret content, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_EmptyString(t *testing.T) {
+	result := RedactSecrets("")
+	if result != "" {
+		t.Error("expected empty string to pass through unchanged")
+	}
+}
+
+func TestRedactSecrets_PreservesPrefix(t *testing.T) {
+	input := `key: sk-proj-abc123def456ghi789jkl012mno345pqr678`
+	result := RedactSecrets(input)
+	// Should show first 4 chars for identification
+	if !strings.Contains(result, "sk-p") {
+		t.Errorf("expected prefix to be preserved for identification, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_DoesNotRedactGitSHA(t *testing.T) {
+	// 40-char hex strings like git SHAs must NOT be redacted
+	input := `commit 3bcbfd9a1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f`
+	result := RedactSecrets(input)
+	if result != input {
+		t.Errorf("git SHA should not be redacted, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_DoesNotRedactChecksum(t *testing.T) {
+	input := `sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855`
+	result := RedactSecrets(input)
+	if result != input {
+		t.Errorf("SHA-256 checksum should not be redacted, got: %s", result)
+	}
+}
+
+func TestRedactSecrets_Idempotent(t *testing.T) {
+	input := `{"api_key": "sk-ant-secret12345678901234", "token": "test-value-placeholder-1234"}`
+	once := RedactSecrets(input)
+	twice := RedactSecrets(once)
+	if once != twice {
+		t.Errorf("RedactSecrets should be idempotent.\nOnce:  %s\nTwice: %s", once, twice)
+	}
+}
+
+func TestSanitizeResult_ForLLMAndForUser(t *testing.T) {
+	r := &ToolResult{
+		ForLLM:  `Read config.json: {"api_key": "sk-ant-secret12345678901234"}`,
+		ForUser: `Config: {"api_key": "sk-ant-secret12345678901234"}`,
+	}
+	SanitizeResult(r)
+	if strings.Contains(r.ForLLM, "sk-ant-secret") {
+		t.Error("ForLLM should have secret redacted")
+	}
+	if strings.Contains(r.ForUser, "sk-ant-secret") {
+		t.Error("ForUser should have secret redacted")
+	}
+}
+
+func TestSanitizeResult_NilResult(t *testing.T) {
+	result := SanitizeResult(nil)
+	if result != nil {
+		t.Error("expected nil to pass through")
+	}
+}
+
+func TestSanitizeResult_ErrorFieldPreservesChain(t *testing.T) {
+	originalErr := fmt.Errorf("auth failed with key sk-proj-abc123def456ghi789jkl012mno345pqr678")
+	r := &ToolResult{
+		ForLLM: "error occurred",
+		Err:    fmt.Errorf("wrapped: %w", originalErr),
+	}
+	SanitizeResult(r)
+	if strings.Contains(r.Err.Error(), "sk-proj-abc123") {
+		t.Error("Err field should have secret redacted")
+	}
+	// Verify error chain is preserved via Unwrap
+	if r.Err == nil {
+		t.Fatal("Err should not be nil")
+	}
+}
+
+func TestContainsSecret(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected bool
+	}{
+		{`normal text`, false},
+		{`key: sk-proj-abc123def456ghi789jkl012mno`, true},
+		{`{"api_key": "super-secret-value-here"}`, true},
+		{`{"model": "gpt-4"}`, false},
+		{`commit abc123def456`, false},
+	}
+	for _, tc := range tests {
+		got := ContainsSecret(tc.input)
+		if got != tc.expected {
+			t.Errorf("ContainsSecret(%q) = %v, want %v", tc.input, got, tc.expected)
+		}
+	}
+}
+
+func TestIsSecretEnvVar(t *testing.T) {
+	tests := []struct {
+		name     string
+		expected bool
+	}{
+		{"OPENAI_API_KEY", true},
+		{"ARK_API_KEY", true},
+		{"CHANNEL_SECRET", true},
+		{"BOT_TOKEN", true},
+		{"DATABASE_PASSWORD", true},
+		{"AWS_ACCESS_KEY", true},
+		{"HOME", false},
+		{"PATH", false},
+		{"GOPATH", false},
+		{"MODEL_NAME", false},
+		{"AUTHOR", false},       // must NOT match
+		{"AUTHORITY", false},    // must NOT match
+		{"AUTHENTICATE", false}, // must NOT match
+	}
+	for _, tc := range tests {
+		got := IsSecretEnvVar(tc.name)
+		if got != tc.expected {
+			t.Errorf("IsSecretEnvVar(%q) = %v, want %v", tc.name, got, tc.expected)
+		}
+	}
+}
diff --git a/pkg/tools/registry.go b/pkg/tools/registry.go
index 0635f47d7..1c2f6abc5 100644
--- a/pkg/tools/registry.go
+++ b/pkg/tools/registry.go
@@ -222,6 +222,10 @@ func (r *ToolRegistry) ExecuteWithContext(
 			})
 	}
 
+	// Scrub secrets from tool output before it reaches the LLM or user.
+	// This is the single chokepoint for all tool execution results.
+	SanitizeResult(result)
+
 	return result
 }
 
diff --git a/pkg/tools/subagent.go b/pkg/tools/subagent.go
index e51cbaafa..1b8d9aeff 100644
--- a/pkg/tools/subagent.go
+++ b/pkg/tools/subagent.go
@@ -172,8 +172,10 @@ After completing the task, provide a clear summary of what was done.`
 	var result *ToolResult
 	defer func() {
 		sm.mu.Unlock()
-		// Call callback if provided and result is set
+		// Call callback if provided and result is set.
+		// Sanitize before callback — this path bypasses ExecuteWithContext.
 		if callback != nil && result != nil {
+			SanitizeResult(result)
 			callback(ctx, result)
 		}
 	}()