diff --git a/README.md b/README.md
index b1d3a0a..688b4be 100644
--- a/README.md
+++ b/README.md
@@ -78,6 +78,7 @@ Environment variables (prefix `WHENCE_`):
 | `age` / `rage` | encrypt, decrypt |
 | `git` | push, pull, fetch, clone, signed commit |
 | `gpg` / `gpg2` | sign, decrypt, encrypt, verify |
+| `cosign` | sign, sign-blob, attest (PIV / PKCS#11) |
 | `ssh` / `scp` / `sftp` | authenticate |
 | browsers | WebAuthn / passkey |
 
diff --git a/e2e/README.md b/e2e/README.md
index ed33d27..9f593b3 100644
--- a/e2e/README.md
+++ b/e2e/README.md
@@ -43,6 +43,7 @@ a PASS / FAIL / SKIP matrix and exits non-zero if anything failed.
 | `ssh` | `ssh-keygen -t ed25519-sk` | FIDO2 PIN set on the key |
 | `age` | `age -d` via `age-plugin-yubikey` | PIV identity (best-effort) |
 | browser | opens webauthn.io in your default browser | a passkey/WebAuthn credential |
+| `cosign` | `cosign sign-blob --key <pkcs11>` | PIV key via `WHENCE_E2E_COSIGN_KEY` (PKCS#11) |
 
 The watcher is granted only the eBPF caps (`cap_bpf`, `cap_perfmon`,
 `cap_sys_admin`). An agent-mediated touch (gpg, pass, sops, …) is attributed to
@@ -64,6 +65,7 @@ Tools whose credential isn't present are **SKIP**ped with a reason.
 | `WHENCE_E2E_GPG_KEY` | first secret key | GPG key fingerprint to use |
 | `E2E_TOUCH_TIMEOUT` | `60` | seconds to wait for each touch |
 | `E2E_DEBUG` | `0` | `1` runs the watcher with `-verbose` and prints, per test, the full process call stack the classifier saw (plus how the gpg/ssh-agent client was resolved) — use it to explain a misclassification |
+| `WHENCE_E2E_COSIGN_KEY` | _(unset)_ | PIV PKCS#11 key URI for the cosign test (skipped if unset) |
 
 ## Requirements
 
diff --git a/e2e/run.sh b/e2e/run.sh
index 242e9ab..abf82b3 100755
--- a/e2e/run.sh
+++ b/e2e/run.sh
@@ -309,8 +309,22 @@ test_browser() {
 	show_stack
 }
 
+test_cosign() {
+	command -v cosign >/dev/null || { record cosign SKIP "cosign not installed"; return; }
+	local key="${WHENCE_E2E_COSIGN_KEY:-}"
+	[ -n "$key" ] || { record cosign SKIP "set WHENCE_E2E_COSIGN_KEY to a PIV PKCS#11 key URI (touch-policy=always)"; return; }
+	ask_run "cosign — sign a blob with your PIV key ($key)" || { record cosign SKIP "skipped"; return; }
+	printf 'whence-touche-e2e\n' > "$WORK/cosign-blob.txt"
+	touch_now; mark
+	if timeout "$TOUCH_TIMEOUT" cosign sign-blob --yes --key "$key" "$WORK/cosign-blob.txt" >"$WORK/cosign.log" 2>&1; then
+		finish cosign cosign
+	else
+		record cosign FAIL "cosign sign-blob failed/timed out (see $WORK/cosign.log)"
+	fi
+}
+
 # --- driver -------------------------------------------------------------------
-ALL=(gpg pass gopass sops git ssh age browser)
+ALL=(gpg pass gopass sops git ssh age browser cosign)
 if [ "$#" -gt 0 ]; then SELECTED=("$@"); else SELECTED=("${ALL[@]}"); fi
 
 say "Testing: ${SELECTED[*]}"
diff --git a/flake.nix b/flake.nix
index f9266c3..d621a95 100644
--- a/flake.nix
+++ b/flake.nix
@@ -36,6 +36,7 @@
             pkgs.age                # age
             pkgs.rage               # rage
             pkgs.git                # git
+            pkgs.cosign             # cosign (Sigstore signing)
             pkgs.yubikey-manager    # ykman (key diagnostics)
             pkgs.age-plugin-yubikey # age + YubiKey via PIV
             pkgs.libfido2           # fido2-token etc. for FIDO diagnostics
diff --git a/internal/classifier/rules/all.go b/internal/classifier/rules/all.go
index 74bdf43..4eb2f93 100644
--- a/internal/classifier/rules/all.go
+++ b/internal/classifier/rules/all.go
@@ -14,6 +14,7 @@ func All() []classifier.Rule {
 		Age{},
 		Git{},
 		GPG{},
+		Cosign{},
 		Browser{},
 		SSH{},
 	}
diff --git a/internal/classifier/rules/cosign.go b/internal/classifier/rules/cosign.go
new file mode 100644
index 0000000..4afae27
--- /dev/null
+++ b/internal/classifier/rules/cosign.go
@@ -0,0 +1,93 @@
+package rules
+
+import (
+	"strings"
+
+	"github.com/Talgarr/Whence-Touche/internal/classifier"
+)
+
+// Cosign matches cosign (Sigstore) signing operations.
+// https://docs.sigstore.dev/cosign/
+//
+// cosign can sign with a PIV hardware token (touch-policy=always) via its
+// go-piv / PKCS#11 backend, so a sustained touch-wait while cosign runs is a
+// hardware-key signing request.
+type Cosign struct{}
+
+func (Cosign) Match(tree []classifier.Process) (classifier.Classification, bool) {
+	idx, p, ok := classifier.FindFirst(tree, "cosign")
+	if !ok {
+		return classifier.Classification{}, false
+	}
+	action, resource := cosignOperation(p)
+	return classifier.Classification{
+		Tool:     "cosign",
+		Action:   action,
+		Resource: resource,
+		Depth:    idx,
+	}, true
+}
+
+func cosignOperation(p classifier.Process) (action, resource string) {
+	sub, pos := parseCosignArgs(p)
+
+	switch sub {
+	case "sign":
+		action = "sign"
+		resource = pos
+		if resource == "" {
+			resource = "artifact"
+		}
+	case "sign-blob":
+		action = "sign blob"
+		resource = pos
+		if resource == "" {
+			if key, ok := classifier.Arg(p, "--key"); ok {
+				resource = key
+			} else {
+				resource = "blob"
+			}
+		}
+	case "attest":
+		action = "attest"
+		resource = pos
+		if resource == "" {
+			resource = "artifact"
+		}
+	case "generate-key-pair":
+		action = "generate key"
+		resource = "PIV key"
+	default:
+		action = "sign"
+		resource = "artifact"
+	}
+	return
+}
+
+// parseCosignArgs returns the first subcommand token (the first non-flag arg
+// after argv[0]) and the first positional that follows it. A bare flag (e.g.
+// "--key pkcs11:...") consumes the next token as its value so it is not
+// mistaken for a positional.
+func parseCosignArgs(p classifier.Process) (sub, pos string) {
+	skip := false
+	for _, arg := range p.Args[1:] {
+		if skip {
+			skip = false
+			continue
+		}
+		if strings.HasPrefix(arg, "-") {
+			// "--flag=value" is self-contained; "--flag value" eats the next token.
+			if !strings.Contains(arg, "=") {
+				skip = true
+			}
+			continue
+		}
+		if sub == "" {
+			sub = arg
+			continue
+		}
+		pos = arg
+		return
+	}
+	return
+}
diff --git a/internal/classifier/rules/cosign_test.go b/internal/classifier/rules/cosign_test.go
new file mode 100644
index 0000000..40fb32a
--- /dev/null
+++ b/internal/classifier/rules/cosign_test.go
@@ -0,0 +1,72 @@
+package rules
+
+import (
+	"testing"
+
+	"github.com/Talgarr/Whence-Touche/internal/classifier"
+)
+
+func TestCosignMatch(t *testing.T) {
+	cases := []struct {
+		name         string
+		comm         string
+		args         []string
+		wantOK       bool
+		wantTool     string
+		wantAction   string
+		wantResource string
+		wantDepth    int
+	}{
+		{
+			name:         "sign image reference",
+			comm:         "cosign",
+			args:         []string{"cosign", "sign", "ghcr.io/acme/app:1.0"},
+			wantOK:       true,
+			wantTool:     "cosign",
+			wantAction:   "sign",
+			wantResource: "ghcr.io/acme/app:1.0",
+			wantDepth:    0,
+		},
+		{
+			name:         "sign-blob with key flag and file",
+			comm:         "cosign",
+			args:         []string{"cosign", "sign-blob", "--key", "pkcs11:object=signing", "artifact.tar"},
+			wantOK:       true,
+			wantTool:     "cosign",
+			wantAction:   "sign blob",
+			wantResource: "artifact.tar",
+			wantDepth:    0,
+		},
+		{
+			name:   "no match",
+			comm:   "bash",
+			args:   []string{"bash", "-c", "echo hi"},
+			wantOK: false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			tree := []classifier.Process{{PID: 100, Comm: tc.comm, Args: tc.args}}
+			got, ok := Cosign{}.Match(tree)
+			if ok != tc.wantOK {
+				t.Fatalf("Match ok = %v, want %v", ok, tc.wantOK)
+			}
+			if !tc.wantOK {
+				return
+			}
+			if got.Tool != tc.wantTool {
+				t.Errorf("Tool = %q, want %q", got.Tool, tc.wantTool)
+			}
+			if got.Action != tc.wantAction {
+				t.Errorf("Action = %q, want %q", got.Action, tc.wantAction)
+			}
+			if got.Resource != tc.wantResource {
+				t.Errorf("Resource = %q, want %q", got.Resource, tc.wantResource)
+			}
+			if got.Depth != tc.wantDepth {
+				t.Errorf("Depth = %d, want %d", got.Depth, tc.wantDepth)
+			}
+		})
+	}
+}