diff --git a/README.md b/README.md
index 9cf5917..4f37e51 100644
--- a/README.md
+++ b/README.md
@@ -190,13 +190,21 @@ flowchart TD
     FindRoot --> CheckLucafile{Lucafile exists<br/>in repo root?}
 
     CheckLucafile -->|No| Exit2([Exit: no Lucafile])
-    CheckLucafile -->|Yes| CheckLuca{luca command<br/>available?}
+    CheckLucafile -->|Yes| CheckLuca{luca installed &<br/>version correct?}
 
-    CheckLuca -->|No| LogNotFound["Log: not found, installing"]
-    CheckLuca -->|Yes| CheckVersion{".luca-version"<br/>matches installed?}
+    CheckLuca -->|Yes| RunInstall
+    CheckLuca -->|No| CheckTTY{Interactive<br/>terminal?}
 
-    CheckVersion -->|Yes or no file| RunInstall
-    CheckVersion -->|No| LogMismatch["Log: version mismatch<br/>(installed vs required)"]
+    CheckTTY -->|"No TTY (e.g. GUI Git client)"| LucaMissing{luca<br/>installed?}
+    LucaMissing -->|No| WarnNoTTYAbsent["⚠️ Non-interactive: luca absent<br/>skipping install — run from terminal"]
+    LucaMissing -->|"Yes, wrong version"| WarnNoTTYMismatch["⚠️ Non-interactive: version mismatch<br/>skipping self-update — run from terminal"]
+
+    WarnNoTTYAbsent --> Exit3([Exit: skip — no binary available])
+    WarnNoTTYMismatch --> RunInstall
+
+    CheckTTY -->|TTY present| LucaMissing2{luca<br/>installed?}
+    LucaMissing2 -->|No| LogNotFound["Log: not found, installing"]
+    LucaMissing2 -->|"Yes, wrong version"| LogMismatch["Log: version mismatch<br/>(installed vs required)"]
 
     LogNotFound --> Download[Download & run<br/>install.sh]
     LogMismatch --> Download
@@ -211,16 +219,16 @@ flowchart TD
     CheckResult -->|Yes| Success[✅ Tools synchronized]
     CheckResult -->|No| Warning[⚠️ Some tools may<br/>have failed]
 
-    Success --> NotifyPath
-    Warning --> NotifyPath
-
-    NotifyPath["ℹ️ PATH will update<br/>on next prompt"]
-    NotifyPath --> Exit3([Exit: done])
+    Success --> Exit4([Exit: done])
+    Warning --> Exit4
 
     style Exit1 fill:#FFE4B5
     style Exit2 fill:#FFE4B5
+    style Exit3 fill:#FFE4B5
     style ErrorExit fill:#FFB6C1
     style Success fill:#90EE90
+    style WarnNoTTYAbsent fill:#FFE4B5
+    style WarnNoTTYMismatch fill:#FFE4B5
 ```
 
 ---
@@ -336,8 +344,14 @@ sequenceDiagram
     G->>PC: Trigger post-checkout
     PC->>PC: Check for Lucafile
     PC->>PC: Check luca version vs .luca-version
-    PC->>IS: Run install.sh if missing or version mismatch
-    IS-->>PC: Done
+    alt TTY present and update needed
+        PC->>IS: Run install.sh
+        IS-->>PC: Done
+    else No TTY and luca absent
+        PC->>PC: ⚠️ Skip — non-interactive, no binary
+    else No TTY and version mismatch
+        PC->>PC: ⚠️ Skip self-update — non-interactive
+    end
     PC->>L: luca install --quiet
     L->>L: Install/update tools
     L-->>PC: Done
diff --git a/post-checkout b/post-checkout
index 164d77b..8c852cf 100755
--- a/post-checkout
+++ b/post-checkout
@@ -129,27 +129,40 @@ log_info "Found $FOUND_SPEC, synchronizing tools..."
 
 # Check if Luca is installed and version is correct, install/update if not
 if ! is_luca_installed || ! is_luca_version_correct; then
-    if ! is_luca_installed; then
-        log_info "Luca not found, installing..."
+    if [ ! -t 0 ]; then
+        # No TTY — sudo cannot prompt for a password (e.g. GUI Git client).
+        # Skip the self-update and fall through to luca install below.
+        if ! is_luca_installed; then
+            log_warning "Non-interactive environment detected (e.g. GUI Git client). Luca is not installed — skipping automatic installation. Please run the setup from a terminal."
+            exit 0
+        else
+            REQUIRED=$(cat "$VERSION_FILE")
+            INSTALLED=$(luca --version 2>/dev/null)
+            log_warning "Non-interactive environment detected (e.g. GUI Git client). Luca version mismatch (installed: $INSTALLED, required: $REQUIRED) — skipping automatic update. Please run the setup from a terminal to apply the correct version."
+        fi
     else
-        REQUIRED=$(cat "$VERSION_FILE")
-        INSTALLED=$(luca --version 2>/dev/null)
-        log_info "Luca version mismatch (installed: $INSTALLED, required: $REQUIRED), updating..."
-    fi
+        if ! is_luca_installed; then
+            log_info "Luca not found, installing..."
+        else
+            REQUIRED=$(cat "$VERSION_FILE")
+            INSTALLED=$(luca --version 2>/dev/null)
+            log_info "Luca version mismatch (installed: $INSTALLED, required: $REQUIRED), updating..."
+        fi
 
-    if command -v curl >/dev/null 2>&1; then
-        /bin/bash -c "$(curl -fsSL $INSTALL_SCRIPT_URL)"
-        INSTALL_RESULT=$?
+        if command -v curl >/dev/null 2>&1; then
+            /bin/bash -c "$(curl -fsSL $INSTALL_SCRIPT_URL)"
+            INSTALL_RESULT=$?
 
-        if [ $INSTALL_RESULT -ne 0 ]; then
-            log_error "Failed to install Luca"
+            if [ $INSTALL_RESULT -ne 0 ]; then
+                log_error "Failed to install Luca"
+                exit 1
+            fi
+
+            log_success "Luca installed"
+        else
+            log_error "curl is required to install Luca"
             exit 1
         fi
-
-        log_success "Luca installed"
-    else
-        log_error "curl is required to install Luca"
-        exit 1
     fi
 fi
 
diff --git a/tests/post_checkout.bats b/tests/post_checkout.bats
index 55e0096..1284932 100644
--- a/tests/post_checkout.bats
+++ b/tests/post_checkout.bats
@@ -86,7 +86,7 @@ setup() {
     fi
 }
 
-@test "luca absent: curl called to install when luca not in PATH" {
+@test "luca absent, no-tty: skips installation with informative message and exits 0" {
     cp "$FIXTURE_DIR/Lucafile" "$FAKE_REPO/Lucafile"
     # Build a PATH that has git/curl mocks but NOT luca
     local no_luca_bin="$BATS_TEST_TMPDIR/no_luca_bin"
@@ -95,11 +95,15 @@ setup() {
         ln -sf "$TESTS_DIR/test_helper/mocks/$mock" "$no_luca_bin/$mock"
     done
 
-    # Intentionally omit /usr/local/bin to ensure real luca is not found
+    # Intentionally omit /usr/local/bin to ensure real luca is not found.
+    # bats runs without a TTY so the non-interactive path is exercised.
     run env PATH="$no_luca_bin:/usr/bin:/bin" \
         "$REPO_ROOT/post-checkout" prev_ref new_ref 1
 
-    assert_output --partial "installing"
+    assert_success
+    assert_output --partial "Non-interactive environment"
+    assert_output --partial "skipping automatic installation"
+    assert_output --partial "terminal"
 }
 
 # ---------------------------------------------------------------------------
@@ -142,15 +146,29 @@ setup() {
     refute_output --partial "installing"
 }
 
-@test "version check: luca version mismatch triggers reinstall with mismatch message" {
+@test "version check, no-tty: version mismatch shows warning with installed and required versions" {
     cp "$FIXTURE_DIR/Lucafile" "$FAKE_REPO/Lucafile"
     echo "v2.0.0" > "$FAKE_REPO/.luca-version"  # differs from MOCK_LUCA_VERSION (v1.0.0)
 
     run "$REPO_ROOT/post-checkout" prev_ref new_ref 1
 
+    assert_output --partial "Non-interactive environment"
     assert_output --partial "version mismatch"
     assert_output --partial "v1.0.0"
     assert_output --partial "v2.0.0"
+    assert_output --partial "terminal"
+}
+
+@test "version check, no-tty: version mismatch still runs luca install" {
+    cp "$FIXTURE_DIR/Lucafile" "$FAKE_REPO/Lucafile"
+    echo "v2.0.0" > "$FAKE_REPO/.luca-version"  # differs from MOCK_LUCA_VERSION (v1.0.0)
+
+    run "$REPO_ROOT/post-checkout" prev_ref new_ref 1
+
+    assert_success
+    assert_output --partial "Tools synchronized successfully"
+    run grep "luca install --quiet --no-install-post-checkout-git-hook" "$MOCK_LUCA_CALL_LOG"
+    assert_success
 }
 
 @test "version check: no .luca-version file skips version check" {