diff --git a/experiments/shell/keyboard.hpp b/experiments/shell/keyboard.hpp
index 546a1edc..cb9e2028 100644
--- a/experiments/shell/keyboard.hpp
+++ b/experiments/shell/keyboard.hpp
@@ -76,12 +76,30 @@ class KeyboardEncoder {
             return {true, modifier == 1 ? std::string("\x1b[") + final :
                 std::string("\x1b[1;") + std::to_string(modifier) + final, false};
         }
+        // F1..F4 use the SS3 letters; F5 and later use the xterm tilde numbers.
+        // The tilde numbers follow the VT/xterm table rather than the physical
+        // order so that applications see the same codes as other terminals.
+        static constexpr char ss3_function[] = {'P', 'Q', 'R', 'S'};
+        if (key >= 0x70 && key <= 0x73)
+        if (key >= 0x70 && key <= 0x73) {
+            const char letter = ss3_function[key - 0x70];
+            if (modifier == 1) return {true, std::string("\x1bO") + letter, false};
+            return {true, std::string("\x1b[1;") + std::to_string(modifier) + letter, false};
+        }
         int number = 0;
         switch (key) {
         case 0x2d: number = 2; break; // Insert
         case 0x2e: number = 3; break; // Delete
         case 0x21: number = 5; break; // PageUp
         case 0x22: number = 6; break; // PageDown
+        case 0x74: number = 15; break; // F5
+        case 0x75: number = 17; break; // F6
+        case 0x76: number = 18; break; // F7
+        case 0x77: number = 19; break; // F8
+        case 0x78: number = 20; break; // F9
+        case 0x79: number = 21; break; // F10
+        case 0x7a: number = 23; break; // F11
+        case 0x7b: number = 24; break; // F12
         default: return {};
         }
         return {true, "\x1b[" + std::to_string(number) +
diff --git a/experiments/shell/keyboard_test.cpp b/experiments/shell/keyboard_test.cpp
index 317f6fe9..6a248cff 100644
--- a/experiments/shell/keyboard_test.cpp
+++ b/experiments/shell/keyboard_test.cpp
@@ -45,6 +45,18 @@ int main() {
               "application mode must not rewrite modified cursor keys");
         check(KeyboardEncoder::key_down(0x2e, {}, true).bytes == "\x1b[3~",
               "application mode must not rewrite editing keys");
+        // F1..F4 are SS3 letters; F5..F12 use the xterm tilde numbers.
+        const std::vector<std::pair<uint32_t,std::string>> functions{
+            {0x70,"\x1bOP"}, {0x71,"\x1bOQ"}, {0x72,"\x1bOR"}, {0x73,"\x1bOS"},
+            {0x74,"\x1b[15~"}, {0x75,"\x1b[17~"}, {0x76,"\x1b[18~"}, {0x77,"\x1b[19~"},
+            {0x78,"\x1b[20~"}, {0x79,"\x1b[21~"}, {0x7a,"\x1b[23~"}, {0x7b,"\x1b[24~"}};
+        for (const auto& entry : functions) {
+            const auto encoded = KeyboardEncoder::key_down(entry.first);
+            check(encoded.handled && encoded.bytes == entry.second && !encoded.skip_translate,
+                  "function key encoding");
+        }
+        check(KeyboardEncoder::key_down(0x70, {false,true,false,false}).bytes == "\x1b[1;5P",
+              "modified F1 must use the CSI modifier form");
         check(KeyboardEncoder::key_down(0x24, {false,true,false,false}).bytes == "\x1b[1;5H", "Ctrl Home");
         check(KeyboardEncoder::key_down(0x2e, {true,false,true,false}).bytes == "\x1b[3;4~", "Shift Alt Delete");
         check(!KeyboardEncoder::key_down(0x09).handled, "plain Tab belongs only to WM_CHAR");