diff --git a/assets/shell-integration/bash/elyterminal.bash b/assets/shell-integration/bash/elyterminal.bash
index 7b1134f..913cf8e 100644
--- a/assets/shell-integration/bash/elyterminal.bash
+++ b/assets/shell-integration/bash/elyterminal.bash
@@ -13,6 +13,16 @@ else
   [ -r ~/.bashrc ] && builtin source ~/.bashrc
 fi
 _ely_prompt() {
-  builtin printf '\e]7;file://%s\a\e]2;%s\a' "${PWD//\%/%25}" "${PWD##*/}"
+  builtin local ret=$? LC_ALL=C char url= i title
+  for (( i = 0; i < ${#PWD}; i++ )); do
+    char=${PWD:i:1}
+    case $char in
+      [[:cntrl:]]|%) builtin printf -v char '%%%02X' "'$char" ;;
+    esac
+    url+=$char
+  done
+  title=${PWD##*/}
+  builtin printf '\e]7;file://%s\a\e]2;%s\a' "$url" "${title//[[:cntrl:]]/}"
+  builtin return $ret
 }
 PROMPT_COMMAND="_ely_prompt${PROMPT_COMMAND:+;$PROMPT_COMMAND}"
diff --git a/assets/shell-integration/fish/vendor_conf.d/elyterminal.fish b/assets/shell-integration/fish/vendor_conf.d/elyterminal.fish
index 30bf31d..476affc 100644
--- a/assets/shell-integration/fish/vendor_conf.d/elyterminal.fish
+++ b/assets/shell-integration/fish/vendor_conf.d/elyterminal.fish
@@ -7,6 +7,6 @@ end
 set -e ELY_FISH_XDG_DATA_DIRS
 if status is-interactive
     function _ely_prompt --on-event fish_prompt
-        printf '\e]7;file://%s\a' (string replace -a % %25 -- $PWD)
+        printf '\e]7;file://%s\a' (string escape --style=url -- $PWD)
     end
 end
diff --git a/assets/shell-integration/pwsh/elyterminal.ps1 b/assets/shell-integration/pwsh/elyterminal.ps1
index 87b2dda..5771d31 100644
--- a/assets/shell-integration/pwsh/elyterminal.ps1
+++ b/assets/shell-integration/pwsh/elyterminal.ps1
@@ -1,13 +1,15 @@
 # ELYTerminal: wrap the prompt to report folder and title.
 $global:ElyPrompt = $function:prompt
 function global:prompt {
+    $text = & $global:ElyPrompt
     $folder = $executionContext.SessionState.Path.CurrentLocation
     if ($folder.Provider.Name -eq 'FileSystem') {
-        $path = $folder.ProviderPath.Replace('\', '/').Replace('%', '%25')
+        $parts = $folder.ProviderPath.Replace('\', '/') -split '/'
+        $path = ($parts | ForEach-Object { [Uri]::EscapeDataString($_) }) -join '/'
         if (-not $path.StartsWith('/')) { $path = "/$path" }
-        $leaf = Split-Path -Leaf $folder.ProviderPath
+        $leaf = (Split-Path -Leaf $folder.ProviderPath) -replace '\p{Cc}', ''
         $esc, $bel = [char]27, [char]7
         [Console]::Write("$esc]7;file://$path$bel$esc]2;$leaf$bel")
     }
-    & $global:ElyPrompt
+    $text
 }
diff --git a/assets/shell-integration/zsh/.zshenv b/assets/shell-integration/zsh/.zshenv
index 8ed927f..5414977 100644
--- a/assets/shell-integration/zsh/.zshenv
+++ b/assets/shell-integration/zsh/.zshenv
@@ -8,7 +8,15 @@ fi
 [[ -r "${ZDOTDIR:-$HOME}/.zshenv" ]] && builtin source "${ZDOTDIR:-$HOME}/.zshenv"
 if [[ -o interactive ]]; then
   _ely_precmd() {
-    builtin printf '\e]7;file://%s\a\e]2;%s\a' "${PWD//\%/%25}" "${${PWD:t}:-/}"
+    builtin local ret=$? LC_ALL=C char url=
+    for char in ${(s::)PWD}; do
+      case $char in
+        [[:cntrl:]]|%) builtin printf -v char '%%%02X' "'$char" ;;
+      esac
+      url+=$char
+    done
+    builtin printf '\e]7;file://%s\a\e]2;%s\a' "$url" "${${${PWD:t}:-/}//[[:cntrl:]]/}"
+    builtin return ret
   }
   _ely_preexec() {
     builtin printf '\e]2;%s\a' "${1//[[:cntrl:]]/}"
diff --git a/src/term/shell.rs b/src/term/shell.rs
index 60f2705..e141cf4 100644
--- a/src/term/shell.rs
+++ b/src/term/shell.rs
@@ -1,5 +1,6 @@
 use std::{
     env, fs,
+    io::ErrorKind,
     path::{Path, PathBuf},
 };
 
@@ -50,8 +51,14 @@ impl ShellIntegration {
 pub fn install(dir: &Path) -> anyhow::Result<()> {
     for (name, text) in SCRIPTS {
         let path = dir.join(name);
-        if fs::read_to_string(&path).is_ok_and(|kept| kept == text) {
-            continue;
+        match fs::read_to_string(&path) {
+            Ok(kept) if kept == text => continue,
+            Ok(_) => {}
+            Err(error) if matches!(error.kind(), ErrorKind::NotFound | ErrorKind::InvalidData) => {}
+            Err(error) => {
+                return Err(error)
+                    .with_context(|| format!("shell integration: cannot read {}", path.display()));
+            }
         }
         let folder = path
             .parent()
@@ -98,11 +105,12 @@ pub fn launch(shell: &str, cwd: PathBuf, dir: &Path) -> anyhow::Result<Launch> {
         }
         "fish" => {
             let previous = env::var("XDG_DATA_DIRS").unwrap_or_default();
-            let data = if previous.is_empty() {
-                format!("{}:/usr/local/share:/usr/share", script("fish"))
+            let rest = if previous.is_empty() {
+                "/usr/local/share:/usr/share"
             } else {
-                format!("{}:{previous}", script("fish"))
+                &previous
             };
+            let data = format!("{}:{rest}", dir.display());
             launch.env.push(("XDG_DATA_DIRS".into(), data));
             launch.env.push(("ELY_FISH_XDG_DATA_DIRS".into(), previous));
         }
@@ -113,8 +121,12 @@ pub fn launch(shell: &str, cwd: PathBuf, dir: &Path) -> anyhow::Result<Launch> {
                 vec![
                     "-NoLogo".into(),
                     "-NoExit".into(),
+                    "-ExecutionPolicy".into(),
+                    "Bypass".into(),
                     "-Command".into(),
-                    format!(". '{file}'"),
+                    format!(
+                        "try {{ . '{file}' }} catch {{ [Console]::Error.WriteLine(\"ELYTerminal: shell integration failed: $_\"); exit 1 }}"
+                    ),
                 ],
             ));
         }
diff --git a/src/term/shell/tests.rs b/src/term/shell/tests.rs
index 1099223..13bb41a 100644
--- a/src/term/shell/tests.rs
+++ b/src/term/shell/tests.rs
@@ -1,10 +1,13 @@
 use std::time::{Duration, Instant};
 
-use alacritty_terminal::event::Event;
+use alacritty_terminal::{event::Event, grid::Dimensions, index::Line};
 use futures::channel::mpsc::TryRecvError;
 
 use super::*;
-use crate::term::{PtyEvent, spawn};
+use crate::term::{Pty, PtyEvent, spawn};
+
+/// A folder name with a space, a percent, a bell and a newline.
+const INNER: &str = "in ner%\u{7}x\ny";
 
 /// A fresh folder under the temp dir, by its real path.
 fn folder(name: &str) -> PathBuf {
@@ -21,88 +24,135 @@ fn installed(shell: &str) -> String {
         .args(["-c", &format!("command -v {shell}")])
         .output()
         .expect("sh runs");
-    let path = String::from_utf8(found.stdout).expect("utf-8");
     assert!(found.status.success(), "{shell} is not installed");
-    path.trim().to_string()
+    String::from_utf8(found.stdout)
+        .expect("utf-8")
+        .trim()
+        .to_string()
 }
 
-/// Starts `shell` with integration in a fresh folder, cds once, and returns folders and titles it reported.
-fn reports(shell: &str) -> (PathBuf, Vec<PathBuf>, Vec<String>) {
-    crate::testlog::init();
-    let root = folder(&format!(
-        "shell-{}",
-        shell.rsplit('/').next().expect("a name")
-    ));
-    let (dir, home, start) = (
-        root.join("integration"),
-        root.join("home"),
-        root.join("start"),
-    );
-    let inner = start.join("in ner%");
-    for made in [&home, &inner] {
-        fs::create_dir_all(made).expect("a folder");
-    }
-    install(&dir).expect("scripts install");
-    let mut launch = launch(shell, start.clone(), &dir).expect("a launch");
-    launch.env.push(("HOME".into(), home.display().to_string()));
-    let mut pty = spawn(&launch, (80, 24), (8, 16), 100).expect("the shell starts");
-    let (mut folders, mut titles) = (Vec::new(), Vec::new());
-    let deadline = Instant::now() + Duration::from_secs(20);
-    let mut asked = false;
-    while !folders.contains(&inner) {
-        assert!(
-            Instant::now() < deadline,
-            "{shell} reported {folders:?} and {titles:?} on\n{}",
-            screen(&pty)
+/// A shell started with integration under a fake HOME, and what it reported.
+struct Run {
+    shell: String,
+    pty: Pty,
+    root: PathBuf,
+    start: PathBuf,
+    folders: Vec<PathBuf>,
+    titles: Vec<String>,
+    deadline: Instant,
+}
+
+impl Run {
+    /// Starts `shell` in a fresh folder; `files` go under its HOME first.
+    fn start(shell: &str, files: &[(&str, &str)]) -> Self {
+        crate::testlog::init();
+        let root = folder(&format!(
+            "shell-{}",
+            shell.rsplit('/').next().expect("a name")
+        ));
+        let (dir, home, start) = (
+            root.join("integration"),
+            root.join("home"),
+            root.join("start"),
         );
-        match pty.events.try_recv() {
-            Ok(PtyEvent::Folder(folder)) => folders.push(folder),
-            Ok(PtyEvent::Term(Event::Title(title))) => titles.push(title),
-            Ok(PtyEvent::Term(Event::PtyWrite(reply))) => pty.write(reply.into_bytes()),
-            Ok(PtyEvent::Term(Event::ChildExit(status))) => {
-                panic!("{shell} ended, {status}, after {folders:?}")
+        fs::create_dir_all(start.join(INNER)).expect("the inner folder");
+        fs::create_dir_all(&home).expect("home");
+        for (name, text) in files {
+            let path = home.join(name);
+            fs::create_dir_all(path.parent().expect("a folder")).expect("a home folder");
+            fs::write(path, text).expect("a home file");
+        }
+        install(&dir).expect("scripts install");
+        let mut launch = launch(shell, start.clone(), &dir).expect("a launch");
+        launch.env.push(("HOME".into(), home.display().to_string()));
+        let pty = spawn(&launch, (100, 30), (8, 16), 100).expect("the shell starts");
+        Self {
+            shell: shell.into(),
+            pty,
+            root,
+            start,
+            folders: Vec::new(),
+            titles: Vec::new(),
+            deadline: Instant::now() + Duration::from_secs(30),
+        }
+    }
+
+    /// Reads events, answering the shell's terminal queries, until `done` holds.
+    fn until(&mut self, what: &str, done: impl Fn(&Self) -> bool) {
+        while !done(self) {
+            assert!(
+                Instant::now() < self.deadline,
+                "{}: no {what}; folders {:?}, titles {:?}, screen\n{}",
+                self.shell,
+                self.folders,
+                self.titles,
+                self.screen()
+            );
+            match self.pty.events.try_recv() {
+                Ok(PtyEvent::Folder(folder)) => self.folders.push(folder),
+                Ok(PtyEvent::Term(Event::Title(title))) => self.titles.push(title),
+                Ok(PtyEvent::Term(Event::PtyWrite(reply))) => self.pty.write(reply.into_bytes()),
+                Ok(PtyEvent::Term(Event::ChildExit(status))) => {
+                    panic!("{} ended, {status}:\n{}", self.shell, self.screen())
+                }
+                Ok(_) => {}
+                Err(TryRecvError::Closed) => panic!("{}'s events ended", self.shell),
+                Err(TryRecvError::Empty) => std::thread::sleep(Duration::from_millis(10)),
             }
-            Ok(_) => {}
-            Err(TryRecvError::Closed) => panic!("{shell}'s events ended"),
-            Err(TryRecvError::Empty) => std::thread::sleep(Duration::from_millis(10)),
-        }
-        if !asked && folders.contains(&start) {
-            pty.write(format!("cd '{}'\r", inner.display()).into_bytes());
-            asked = true;
         }
     }
-    pty.write(&b"exit\r"[..]);
-    loop {
-        assert!(
-            Instant::now() < deadline,
-            "{shell} did not exit:\n{}",
-            screen(&pty)
-        );
-        match pty.events.try_recv() {
-            Ok(PtyEvent::Term(Event::ChildExit(_))) | Err(TryRecvError::Closed) => break,
-            Ok(PtyEvent::Term(Event::Title(title))) => titles.push(title),
-            Ok(PtyEvent::Term(Event::PtyWrite(reply))) => pty.write(reply.into_bytes()),
-            Ok(_) => {}
-            Err(TryRecvError::Empty) => std::thread::sleep(Duration::from_millis(10)),
-        }
-    }
-    drop(pty);
-    fs::remove_dir_all(&root).expect("cleanup");
-    (start, folders, titles)
-}
 
-/// The screen's rows, for a failure's message.
-fn screen(pty: &crate::term::Pty) -> String {
-    use alacritty_terminal::{grid::Dimensions, index::Line};
-    let term = pty.term.lock();
-    (0..term.screen_lines())
-        .map(|line| {
-            let row = &term.grid()[Line(line as i32)];
-            let text: String = row.into_iter().map(|cell| cell.c).collect();
-            text.trim_end().to_string()
-        })
-        .collect::<Vec<_>>()
-        .join("\n")
+    fn send(&self, line: &str) {
+        self.pty.write(format!("{line}\r").into_bytes());
+    }
+
+    fn shows(&self, text: &str) -> bool {
+        self.screen().contains(text)
+    }
+
+    fn screen(&self) -> String {
+        let term = self.pty.term.lock();
+        (0..term.screen_lines())
+            .map(|line| {
+                let row = &term.grid()[Line(line as i32)];
+                let text: String = row.into_iter().map(|cell| cell.c).collect();
+                text.trim_end().to_string()
+            })
+            .collect::<Vec<_>>()
+            .join("\n")
+    }
+
+    /// The prompt's folder, the script loaded by `probe`, then a cd into the inner folder.
+    fn walk(&mut self, probe: &str) {
+        let start = self.start.clone();
+        self.until("first folder", |run| run.folders.contains(&start));
+        assert_eq!(self.folders[0], start);
+        self.send(probe);
+        self.until("loaded script", |run| run.shows("ELY-LOADED"));
+        self.send("cd in*");
+        let inner = start.join(INNER);
+        self.until("inner folder", |run| run.folders.contains(&inner));
+    }
+
+    fn finish(mut self) {
+        self.send("exit");
+        loop {
+            assert!(
+                Instant::now() < self.deadline,
+                "{} did not exit",
+                self.shell
+            );
+            match self.pty.events.try_recv() {
+                Ok(PtyEvent::Term(Event::ChildExit(_))) | Err(TryRecvError::Closed) => break,
+                Ok(PtyEvent::Term(Event::PtyWrite(reply))) => self.pty.write(reply.into_bytes()),
+                Ok(_) => {}
+                Err(TryRecvError::Empty) => std::thread::sleep(Duration::from_millis(10)),
+            }
+        }
+        let root = self.root.clone();
+        drop(self);
+        fs::remove_dir_all(&root).expect("cleanup");
+    }
 }
 
 #[test]
@@ -111,46 +161,84 @@ fn the_scripts_install_once_and_mend_a_changed_one() {
     install(&dir).expect("installs");
     let zshenv = dir.join("zsh/.zshenv");
     assert_eq!(fs::read_to_string(&zshenv).expect("written"), SCRIPTS[0].1);
-    fs::write(&zshenv, "changed").expect("write");
+    fs::write(&zshenv, [0xff, 0xfe]).expect("write");
     install(&dir).expect("installs again");
     assert_eq!(fs::read_to_string(&zshenv).expect("mended"), SCRIPTS[0].1);
     fs::remove_dir_all(dir).expect("cleanup");
 }
 
 #[test]
-fn zsh_reports_its_folder_and_title() {
-    let (start, folders, titles) = reports(&installed("zsh"));
-    assert_eq!(folders[0], start);
-    assert!(titles.contains(&"start".to_string()), "{titles:?}");
+fn a_script_it_cannot_read_fails_the_install() {
+    use std::os::unix::fs::PermissionsExt;
+    let dir = folder("unreadable");
+    install(&dir).expect("installs");
+    let bash = dir.join("bash/elyterminal.bash");
+    fs::set_permissions(&bash, fs::Permissions::from_mode(0o200)).expect("200");
+    let error = install(&dir).expect_err("an unreadable script fails");
+    fs::set_permissions(&bash, fs::Permissions::from_mode(0o600)).expect("600");
     assert!(
-        titles.iter().any(|title| title.starts_with("cd ")),
-        "{titles:?}"
+        format!("{error:#}").contains("bash/elyterminal.bash"),
+        "{error:#}"
     );
+    fs::remove_dir_all(dir).expect("cleanup");
 }
 
 #[test]
-fn bash_reports_its_folder_and_title() {
-    let (start, folders, titles) = reports(&installed("bash"));
-    assert_eq!(folders[0], start);
-    assert!(titles.contains(&"in ner%".to_string()), "{titles:?}");
+fn zsh_reports_its_folder_byte_for_byte_and_its_titles() {
+    let mut run = Run::start(&installed("zsh"), &[]);
+    run.walk("(( $+functions[_ely_precmd] )) && echo ELY-LOAD''ED");
+    run.until("title", |run| {
+        run.titles.iter().any(|title| title == "in ner%xy")
+    });
+    assert!(
+        run.titles.contains(&"cd in*".to_string()),
+        "{:?}",
+        run.titles
+    );
+    run.finish();
 }
 
 #[test]
-fn fish_reports_its_folder_and_keeps_its_own_title() {
-    let (start, folders, titles) = reports(&installed("fish"));
-    assert_eq!(folders[0], start);
-    assert!(
-        titles.iter().any(|title| title.ends_with("start")),
-        "{titles:?}"
-    );
+fn bash_reports_its_folder_byte_for_byte_and_keeps_the_status() {
+    let status = r#"PROMPT_COMMAND='printf "USER_STATUS=%s\n" "$?"'"#;
+    let files = [(".bashrc", status), (".bash_profile", status)];
+    let mut run = Run::start(&installed("bash"), &files);
+    run.walk("declare -F _ely_prompt >/dev/null && echo ELY-LOAD''ED");
+    run.until("title", |run| {
+        run.titles.iter().any(|title| title == "in ner%xy")
+    });
+    run.send("false");
+    run.until("kept status", |run| run.shows("USER_STATUS=1"));
+    run.finish();
+}
+
+#[test]
+fn fish_loads_its_script_and_restores_its_data_dirs() {
+    let mut run = Run::start(&installed("fish"), &[]);
+    run.walk("functions -q _ely_prompt; and echo ELY-LOAD''ED");
+    let previous = env::var("XDG_DATA_DIRS").unwrap_or_default();
+    run.send(r#"echo "DIRS[$ELY_FISH_XDG_DATA_DIRS][$XDG_DATA_DIRS]""#);
+    let restored = format!("DIRS[][{previous}]");
+    run.until("restored dirs", |run| run.shows(&restored));
+    run.finish();
 }
 
 #[cfg(target_os = "macos")]
 #[test]
-fn powershell_reports_its_folder_and_title() {
-    let (start, folders, titles) = reports(&installed("pwsh"));
-    assert_eq!(folders[0], start);
-    assert!(titles.contains(&"in ner%".to_string()), "{titles:?}");
+fn powershell_reports_its_folder_byte_for_byte_and_keeps_the_status() {
+    let prompt = r#"function global:prompt { "USER_SUCCESS=$? > " }"#;
+    let files = [(
+        ".config/powershell/Microsoft.PowerShell_profile.ps1",
+        prompt,
+    )];
+    let mut run = Run::start(&installed("pwsh"), &files);
+    run.walk("if ($global:ElyPrompt) { 'ELY-LOAD' + 'ED' }");
+    run.until("title", |run| {
+        run.titles.iter().any(|title| title == "in ner%xy")
+    });
+    run.send("/usr/bin/false");
+    run.until("kept status", |run| run.shows("USER_SUCCESS=False"));
+    run.finish();
 }
 
 #[test]