diff --git a/harness/clipboard.go b/harness/clipboard.go
new file mode 100644
index 0000000..512dfa8
--- /dev/null
+++ b/harness/clipboard.go
@@ -0,0 +1,69 @@
+// Clipboard support for /copy: put text on the system clipboard from a terminal
+// app, with no third-party dependency. Two independent paths are used so the
+// text lands whether sesh runs locally or over SSH, and whether or not the
+// terminal allows programmatic clipboard writes.
+package harness
+
+import (
+	"encoding/base64"
+	"fmt"
+	"os/exec"
+	"runtime"
+	"strings"
+)
+
+// osc52 is the terminal "set clipboard" escape sequence: the terminal itself
+// base64-decodes the payload and stores it, so it reaches the clipboard even
+// across an SSH hop. The "c" selection is the system clipboard.
+func osc52(text string) string {
+	return "\033]52;c;" + base64.StdEncoding.EncodeToString([]byte(text)) + "\007"
+}
+
+// setClipboard copies text by two independent paths so it lands in as many
+// setups as possible: OSC 52 through the terminal (works over SSH, but some
+// terminals and a default tmux drop it) and a local clipboard tool when one is
+// on PATH (reliable locally and through tmux, but not over SSH). It reports
+// which paths ran so the caller can tell the user, and warn when none did.
+func setClipboard(text string) (tool string, osc bool) {
+	if t, ok := activeConsole.(*tuiConsole); ok {
+		t.mu.Lock()
+		fmt.Fprint(t.out, osc52(text)) // invisible to the terminal; leaves the footer alone
+		t.mu.Unlock()
+		osc = true
+	}
+	return localCopy(text), osc
+}
+
+// localCopy pipes text to the first platform clipboard tool found on PATH,
+// returning its name, or "" when none is available or none succeeds.
+func localCopy(text string) string {
+	for _, tool := range clipboardTools() {
+		if _, err := exec.LookPath(tool[0]); err != nil {
+			continue
+		}
+		cmd := exec.Command(tool[0], tool[1:]...)
+		cmd.Stdin = strings.NewReader(text)
+		if cmd.Run() == nil {
+			return tool[0]
+		}
+	}
+	return ""
+}
+
+// clipboardTools is the per-platform list of clipboard writers, in preference
+// order. Each entry is the command and its args; stdin carries the text.
+func clipboardTools() [][]string {
+	switch runtime.GOOS {
+	case "darwin":
+		return [][]string{{"pbcopy"}}
+	case "windows":
+		return [][]string{{"clip"}}
+	default: // linux, the BSDs
+		return [][]string{
+			{"wl-copy"},                          // Wayland
+			{"xclip", "-selection", "clipboard"}, // X11
+			{"xsel", "--clipboard", "--input"},   // X11
+			{"clip.exe"},                         // WSL bridge to the Windows clipboard
+		}
+	}
+}
diff --git a/harness/clipboard_test.go b/harness/clipboard_test.go
new file mode 100644
index 0000000..eefd2f3
--- /dev/null
+++ b/harness/clipboard_test.go
@@ -0,0 +1,37 @@
+package harness
+
+import (
+	"testing"
+
+	"github.com/mike-diff/sesh/agent"
+)
+
+// TestLastAssistantText: /copy reaches back past trailing tool/user turns and
+// past a tool-call-only assistant turn (which has no text) to the last response
+// the user actually saw. Breaker: walk the history forward, or drop the
+// non-empty check, and the wrong turn (or none) is copied.
+func TestLastAssistantText(t *testing.T) {
+	r := &repl{history: []agent.Turn{
+		{Role: "user", Text: "first"},
+		{Role: "assistant", Text: "older answer"},
+		{Role: "user", Text: "second"},
+		{Role: "assistant", Text: "newer answer"},
+		{Role: "assistant", Text: ""}, // a tool-call-only turn carries no text
+		{Role: "tool"},
+	}}
+	if got := r.lastAssistantText(); got != "newer answer" {
+		t.Fatalf("lastAssistantText = %q, want %q", got, "newer answer")
+	}
+	if got := (&repl{}).lastAssistantText(); got != "" {
+		t.Fatalf("empty history must yield no text, got %q", got)
+	}
+}
+
+// TestOSC52 pins the clipboard escape sequence to the wire format terminals
+// expect (a real external contract): ESC ] 52 ; c ; <base64> BEL. Breaker:
+// wrong selection char, wrong terminator, or unencoded payload.
+func TestOSC52(t *testing.T) {
+	if got := osc52("hi"); got != "\033]52;c;aGk=\007" {
+		t.Fatalf("osc52 = %q, want ESC]52;c;aGk=BEL", got)
+	}
+}
diff --git a/harness/help.go b/harness/help.go
index 4ae9b5b..3634dc6 100644
--- a/harness/help.go
+++ b/harness/help.go
@@ -54,6 +54,7 @@ SESSION COMMANDS (interactive; tab completes)
   /chain                       show this conversation's handoff chain and ledger
   /compact                     summarize in place (lossier than /handoff)
   /settings                    session settings picker: show thinking
+  /copy                        copy the last response to the clipboard (clean source)
   /help                        command and key reference
   exit, /exit, ctrl-d          quit (prints sesh -resume <id>)
 
diff --git a/harness/repl.go b/harness/repl.go
index 02075df..a3816fa 100644
--- a/harness/repl.go
+++ b/harness/repl.go
@@ -280,6 +280,7 @@ var slashCommands = []slashCommand{
 	{name: "/chain", run: func(r *repl, _ string) { r.chainCmd() }},
 	{name: "/compact", run: func(r *repl, _ string) { r.compactCmd() }},
 	{name: "/settings", run: func(r *repl, _ string) { r.settingsCmd() }},
+	{name: "/copy", run: func(r *repl, _ string) { r.copyCmd() }},
 	{name: "/help", run: func(r *repl, _ string) { r.helpCmd() }},
 	{name: "/exit", quit: true},
 	{name: "/quit", quit: true},
@@ -344,6 +345,42 @@ func (r *repl) contextCmd(arg string) {
 	emit("%s  context window set to %s tokens%s; automatic handoff at 80%%%s\n\n", dim, kTokens(n), note, reset)
 }
 
+// copyCmd puts the last assistant response on the clipboard as its raw markdown
+// source: clean by construction, free of the terminal's line wrapping and the
+// renderer's indentation that a mouse-selected copy carries.
+func (r *repl) copyCmd() {
+	text := r.lastAssistantText()
+	if text == "" {
+		emit("%s  nothing to copy yet%s\n\n", dim, reset)
+		return
+	}
+	tool, osc := setClipboard(text)
+	var via string
+	switch {
+	case tool != "" && osc:
+		via = tool + " + OSC 52"
+	case tool != "":
+		via = tool
+	case osc:
+		via = "OSC 52"
+	default:
+		emit("%s  no clipboard available: install wl-copy/xclip/xsel, or enable OSC 52 in your terminal%s\n\n", red, reset)
+		return
+	}
+	emit("%s  copied last response to clipboard, %d lines (%s)%s\n\n", dim, 1+strings.Count(text, "\n"), via, reset)
+}
+
+// lastAssistantText returns the most recent assistant turn that carried text;
+// turns that only made tool calls have none. Empty when nothing has been said.
+func (r *repl) lastAssistantText() string {
+	for i := len(r.history) - 1; i >= 0; i-- {
+		if r.history[i].Role == "assistant" && r.history[i].Text != "" {
+			return r.history[i].Text
+		}
+	}
+	return ""
+}
+
 // settingsCmd opens the session-settings picker: arrows pick a setting, enter
 // toggles it, and the menu reopens with the new value until cancelled. These
 // are policies for THIS session; durable knobs live in files (providers.json,
@@ -395,11 +432,12 @@ func (r *repl) helpCmd() {
   /chain                 show this conversation's handoff chain and its ledger
   /compact               summarize history in place (lossier than /handoff)
   /settings              session settings picker (show thinking)
+  /copy                  copy the last response to the clipboard (clean source)
   /help                  this help
   exit, /exit            quit (ctrl-d works too); prints how to resume
-keys: ctrl-c cancels the running turn (twice quits) · shift+enter or ctrl-j
-      inserts a newline · up/down history · tab completes · pastes over 3
-      lines collapse to a [snippet] sent in full
+keys: ctrl-c cancels the running turn (twice quits) · shift+enter, ctrl-j, or
+      \+enter inserts a newline · up/down history · tab completes · pastes over
+      3 lines collapse to a [snippet] sent in full
 config: ~/.sesh/ holds providers.json, credentials, SYSTEM.md, statusline
 %s
 `, dim, reset)