diff --git a/cli/assets/completions/_usage b/cli/assets/completions/_usage
index 4c97636a..4a26c589 100644
--- a/cli/assets/completions/_usage
+++ b/cli/assets/completions/_usage
@@ -25,11 +25,15 @@ _usage() {
 
   local spec_file="${TMPDIR:-/tmp}/usage__usage_spec_usage.spec"
   usage --usage-spec >| "$spec_file"
-  local -a completions=()
-  while IFS= read -r line; do
-    completions+=("$line")
-  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${words[@]}")
-  _describe 'completions' completions -S ''
+  local -a completions=() inserts=()
+  local needs_menu=0 display insert
+  while IFS=$'\t' read -r display insert; do
+    completions+=("$display")
+    inserts+=("$insert")
+    [[ "$insert" == "'"* ]] && needs_menu=1
+  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${(Q)words[@]}")
+  (( needs_menu )) && compstate[insert]=menu
+  _describe 'completions' completions inserts -U -Q -S ''
   return 0
 }
 
diff --git a/cli/src/cli/complete_word.rs b/cli/src/cli/complete_word.rs
index 19578b70..168e96ff 100644
--- a/cli/src/cli/complete_word.rs
+++ b/cli/src/cli/complete_word.rs
@@ -59,13 +59,20 @@ impl CompleteWord {
                     }
                 }
                 "zsh" => {
-                    let c = zsh_escape(&c);
-                    if any_descriptions {
-                        let description = zsh_escape(&description);
-                        println!("{c}:{description}")
+                    // Two tab-separated columns per line:
+                    //   1. `value:description` (or just `value`) for _describe's
+                    //      menu rendering and prefix matching, with `:` `(` `)`
+                    //      `[` `]` escaped as `_describe` requires.
+                    //   2. The shell-quoted form that `compadd -Q` should insert
+                    //      verbatim — wrapped in single quotes when the value
+                    //      contains shell metacharacters, raw otherwise.
+                    let display = if any_descriptions {
+                        format!("{}:{}", zsh_escape(&c), zsh_escape(&description))
                     } else {
-                        println!("{c}")
-                    }
+                        zsh_escape(&c)
+                    };
+                    let insert = zsh_shell_quote(&c);
+                    println!("{display}\t{insert}")
                 }
                 _ => miette::bail!("unsupported shell: {}", shell),
             }
@@ -372,6 +379,25 @@ fn zsh_escape(s: &str) -> String {
         .replace(']', "\\]")
 }
 
+/// Wrap a completion value in single quotes if any character would otherwise
+/// be interpreted by the shell. The result is meant to be inserted by
+/// `compadd -Q` verbatim, so the user sees consistent single-quote quoting
+/// instead of zsh's default mix of backslash and single-quote styles.
+fn zsh_shell_quote(s: &str) -> String {
+    fn safe(c: char) -> bool {
+        matches!(c,
+            'a'..='z' | 'A'..='Z' | '0'..='9'
+            | '_' | '-' | '.' | '/' | ':' | '@' | '+' | '=' | '%' | ','
+        )
+    }
+    if !s.is_empty() && s.chars().all(safe) {
+        return s.to_string();
+    }
+    // Wrap in single quotes; close-open dance escapes any internal apostrophes.
+    let escaped = s.replace('\'', "'\\''");
+    format!("'{escaped}'")
+}
+
 fn sh(script: &str) -> XXResult<String> {
     let output = Command::new("sh")
         .arg("-c")
diff --git a/cli/tests/complete_word.rs b/cli/tests/complete_word.rs
index 293cf3f2..90ad7a63 100644
--- a/cli/tests/complete_word.rs
+++ b/cli/tests/complete_word.rs
@@ -293,20 +293,27 @@ fn complete_word_escaped_colons_in_completions() {
 #[test]
 fn complete_word_zsh_escapes_parens_and_brackets() {
     // zsh's _describe interprets parentheses as glob qualifiers and brackets
-    // as character classes, so they must be escaped in completion output.
+    // as character classes, so they must be escaped in the display column.
+    // The second (insert) column is shell-quoted for `compadd -Q`.
     // See: https://github.com/jdx/usage/issues/558
     let mut c = cmd("parens-in-descriptions.usage.kdl", Some("zsh"));
     c.args(["--", "run", ""]);
     c.assert().success().stdout(
-        "connect\\:server:Connect server \\(Hot Reload\\)\ntest\\:unit:Run tests \\[fast\\]\nbuild:Build project\n",
+        "connect\\:server:Connect server \\(Hot Reload\\)\tconnect:server\n\
+         test\\:unit:Run tests \\[fast\\]\ttest:unit\n\
+         build:Build project\tbuild\n",
     );
 }
 
 #[test]
 fn complete_word_zsh_escapes_colons_without_descriptions() {
+    // Display column has `\:` escapes for `_describe`; insert column has the
+    // raw value (no shell-quoting needed — colons aren't shell-special).
     let mut c = cmd("zsh-colons-without-descriptions.usage.kdl", Some("zsh"));
     c.args(["--", "run", ""]);
-    c.assert().success().stdout("test\\:git\ntest\\:nvim\n");
+    c.assert()
+        .success()
+        .stdout("test\\:git\ttest:git\ntest\\:nvim\ttest:nvim\n");
 }
 
 fn cmd(example: &str, shell: Option<&str>) -> Command {
diff --git a/cli/tests/shell_completions_integration.rs b/cli/tests/shell_completions_integration.rs
index 7f92851f..49d60ae0 100644
--- a/cli/tests/shell_completions_integration.rs
+++ b/cli/tests/shell_completions_integration.rs
@@ -565,6 +565,96 @@ echo "COMPLETION_TEST_DONE"
     let _ = fs::remove_dir_all(&temp_dir);
 }
 
+/// Regression test for https://github.com/jdx/usage/issues/634
+///
+/// `usage complete-word --shell zsh` emits two tab-separated columns per
+/// match — `<display>\t<insert>` — and the generated completion script feeds
+/// those to `_describe ... -U -Q -S ''` so values with spaces are inserted
+/// with consistent single-quote quoting (e.g. `'Alice Alice'`) instead of
+/// zsh's default mix of backslash and single-quote styles.
+#[test]
+fn test_zsh_completion_quotes_choices_with_spaces() {
+    if skip_if_shell_missing("zsh") {
+        return;
+    }
+
+    let usage_bin = build_usage_binary();
+
+    let temp_dir = env::temp_dir().join(format!(
+        "usage_zsh_choices_quote_test_{}",
+        std::process::id()
+    ));
+    fs::create_dir_all(&temp_dir).unwrap();
+
+    let spec = r#"
+arg "<course>" required {
+  choices "A B & C"
+}
+arg "<recipient>" required {
+  choices "Alice Alice" "Bob Bob" "Carol Carol"
+}
+"#;
+    let spec_kdl_file = temp_dir.join("testcli.kdl");
+    fs::write(&spec_kdl_file, spec).unwrap();
+
+    // 1. The raw `complete-word --shell zsh` output for the recipient arg
+    //    should be tab-separated, with the insert column pre-quoted.
+    let raw = Command::new(&usage_bin)
+        .args(["complete-word", "--shell", "zsh", "-f"])
+        .arg(spec_kdl_file.to_str().unwrap())
+        .args(["--", "testcli", "A B & C", ""])
+        .output()
+        .expect("Failed to run complete-word");
+    let raw_stdout = String::from_utf8_lossy(&raw.stdout);
+    let expected_lines = [
+        "Alice Alice\t'Alice Alice'",
+        "Bob Bob\t'Bob Bob'",
+        "Carol Carol\t'Carol Carol'",
+    ];
+    for line in expected_lines {
+        assert!(
+            raw_stdout.lines().any(|l| l == line),
+            "Expected `{line}` in complete-word output, got:\n{raw_stdout}"
+        );
+    }
+
+    // 2. The simple unquoted case still emits a tab + the raw value as the
+    //    insert column (no surrounding quotes).
+    let raw_simple = Command::new(&usage_bin)
+        .args(["complete-word", "--shell", "zsh", "-s"])
+        .arg(r#"arg "<env>" { choices "dev" "prod" }"#)
+        .args(["--", "testcli", ""])
+        .output()
+        .expect("Failed to run complete-word");
+    let simple_stdout = String::from_utf8_lossy(&raw_simple.stdout);
+    assert!(
+        simple_stdout.lines().any(|l| l == "dev\tdev"),
+        "Expected `dev\\tdev` in complete-word output, got:\n{simple_stdout}"
+    );
+
+    // 3. The generated zsh completion script wires these two columns into
+    //    `_describe` with `-U -Q` so zsh inserts the pre-quoted value verbatim.
+    let gen = Command::new(&usage_bin)
+        .args(["generate", "completion", "zsh", "testcli", "-f"])
+        .arg(spec_kdl_file.to_str().unwrap())
+        .output()
+        .expect("Failed to generate zsh completion");
+    let script = String::from_utf8_lossy(&gen.stdout);
+    let expected_fragments = [
+        "(Q)words",                                          // unquote user input
+        r#"IFS=$'\t' read -r display insert"#,               // tab-separated
+        "_describe 'completions' completions inserts -U -Q", // -U -Q on _describe
+    ];
+    for fragment in expected_fragments {
+        assert!(
+            script.contains(fragment),
+            "Expected `{fragment}` in generated script:\n{script}"
+        );
+    }
+
+    let _ = fs::remove_dir_all(&temp_dir);
+}
+
 #[test]
 fn test_powershell_completion_integration() {
     if skip_if_shell_missing("pwsh") {
@@ -726,19 +816,23 @@ cmd other help="Another subcommand"
     let spec_file = temp_dir.join("test.spec");
     fs::write(&spec_file, usage_spec).unwrap();
 
-    // Test zsh output format: should be `name:description` for _describe
+    // Test zsh output format: each line is `<display>\t<insert>` where
+    // <display> is `name:description` (or `name`) for `_describe`'s menu
+    // rendering, and <insert> is the shell-quoted form to insert verbatim
+    // via `compadd -Q`.
     let output = run_complete_word(&usage_bin, "zsh", &spec_file, &["testcli", ""]);
     let lines: Vec<&str> = output.lines().collect();
 
-    // Should have completions with description format "name:description"
     assert!(
-        lines.iter().any(|l| l.contains("sub:A subcommand")),
-        "Expected 'sub:A subcommand' in zsh output, got: {:?}",
+        lines.iter().any(|l| *l == "sub:A subcommand\tsub"),
+        "Expected 'sub:A subcommand\\tsub' in zsh output, got: {:?}",
         lines
     );
     assert!(
-        lines.iter().any(|l| l.contains("other:Another subcommand")),
-        "Expected 'other:Another subcommand' in zsh output, got: {:?}",
+        lines
+            .iter()
+            .any(|l| *l == "other:Another subcommand\tother"),
+        "Expected 'other:Another subcommand\\tother' in zsh output, got: {:?}",
         lines
     );
 
diff --git a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-2.snap b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-2.snap
index 38eabe3e..9e52f375 100644
--- a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-2.snap
+++ b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-2.snap
@@ -31,11 +31,15 @@ _mycli() {
   if [[ ! -f "$spec_file" ]]; then
     mycli complete --usage >| "$spec_file"
   fi
-  local -a completions=()
-  while IFS= read -r line; do
-    completions+=("$line")
-  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${words[@]}")
-  _describe 'completions' completions -S ''
+  local -a completions=() inserts=()
+  local needs_menu=0 display insert
+  while IFS=$'\t' read -r display insert; do
+    completions+=("$display")
+    inserts+=("$insert")
+    [[ "$insert" == "'"* ]] && needs_menu=1
+  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${(Q)words[@]}")
+  (( needs_menu )) && compstate[insert]=menu
+  _describe 'completions' completions inserts -U -Q -S ''
   return 0
 }
 
diff --git a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-3.snap b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-3.snap
index f5abd836..afbe39e5 100644
--- a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-3.snap
+++ b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh-3.snap
@@ -54,11 +54,15 @@ cmd plugin {
     }
 }
 __USAGE_EOF__
-  local -a completions=()
-  while IFS= read -r line; do
-    completions+=("$line")
-  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${words[@]}")
-  _describe 'completions' completions -S ''
+  local -a completions=() inserts=()
+  local needs_menu=0 display insert
+  while IFS=$'\t' read -r display insert; do
+    completions+=("$display")
+    inserts+=("$insert")
+    [[ "$insert" == "'"* ]] && needs_menu=1
+  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${(Q)words[@]}")
+  (( needs_menu )) && compstate[insert]=menu
+  _describe 'completions' completions inserts -U -Q -S ''
   return 0
 }
 
diff --git a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh.snap b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh.snap
index 7ba3e9f6..830a92b3 100644
--- a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh.snap
+++ b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh.snap
@@ -29,11 +29,15 @@ _mycli() {
 
   local spec_file="${TMPDIR:-/tmp}/usage__usage_spec_mycli.spec"
   mycli complete --usage >| "$spec_file"
-  local -a completions=()
-  while IFS= read -r line; do
-    completions+=("$line")
-  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${words[@]}")
-  _describe 'completions' completions -S ''
+  local -a completions=() inserts=()
+  local needs_menu=0 display insert
+  while IFS=$'\t' read -r display insert; do
+    completions+=("$display")
+    inserts+=("$insert")
+    [[ "$insert" == "'"* ]] && needs_menu=1
+  done < <(command usage complete-word --shell zsh -f "$spec_file" -- "${(Q)words[@]}")
+  (( needs_menu )) && compstate[insert]=menu
+  _describe 'completions' completions inserts -U -Q -S ''
   return 0
 }
 
diff --git a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh_init.snap b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh_init.snap
index 65fd804f..091a58b0 100644
--- a/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh_init.snap
+++ b/lib/src/complete/snapshots/usage__complete__zsh__tests__complete_zsh_init.snap
@@ -19,12 +19,15 @@ _usage_default_complete() {
         local first
         if IFS= read -r first < "$cmdpath" 2>/dev/null && [[ "$first" == "#!"*"usage"* ]]; then
             if (( ${+commands[usage]} )); then
-                local -a completions=()
-                local line
-                while IFS= read -r line; do
-                    completions+=("$line")
-                done < <(command usage complete-word --shell zsh -f "$cmdpath" --cword=$((CURRENT - 1)) -- "${words[@]}")
-                _describe 'completions' completions -S ''
+                local -a completions=() inserts=()
+                local needs_menu=0 display insert
+                while IFS=$'\t' read -r display insert; do
+                  completions+=("$display")
+                  inserts+=("$insert")
+                  [[ "$insert" == "'"* ]] && needs_menu=1
+                done < <(command usage complete-word --shell zsh -f "$cmdpath" --cword=$((CURRENT - 1)) -- "${(Q)words[@]}")
+                (( needs_menu )) && compstate[insert]=menu
+                _describe 'completions' completions inserts -U -Q -S ''
                 return $?
             fi
         fi
diff --git a/lib/src/complete/zsh.rs b/lib/src/complete/zsh.rs
index 43b279ff..5f874ed1 100644
--- a/lib/src/complete/zsh.rs
+++ b/lib/src/complete/zsh.rs
@@ -1,6 +1,39 @@
 use crate::complete::CompleteOptions;
 use heck::ToSnakeCase;
 
+/// The completion loop that both `complete_zsh` (per-bin script) and
+/// `complete_zsh_init` (shebang-fallback handler) need to emit.
+///
+/// `complete-word --shell zsh` emits two tab-separated columns per match:
+/// the display string (`value:description` for `_describe`) and the
+/// shell-quoted insert string. `usage complete-word` already filters by the
+/// typed prefix, so `-U` tells `compadd` not to re-filter (which would
+/// discard our pre-quoted matches whose literal text starts with `'`).
+/// `compstate[insert]=menu` skips longest-common-prefix insertion when
+/// values share a leading quote.
+///
+/// `cw_extra_args` is the extra `complete-word` arguments specific to each
+/// caller (e.g. `-f "$spec_file"` vs `-f "$cmdpath" --cword=$((CURRENT - 1))`).
+/// `indent` is prepended to every emitted line.
+fn render_completion_loop(usage_bin: &str, indent: &str, cw_extra_args: &str) -> String {
+    let template = r#"local -a completions=() inserts=()
+local needs_menu=0 display insert
+while IFS=$'\t' read -r display insert; do
+  completions+=("$display")
+  inserts+=("$insert")
+  [[ "$insert" == "'"* ]] && needs_menu=1
+done < <(command __USAGE_BIN__ complete-word --shell zsh __CW_EXTRA__ -- "${(Q)words[@]}")
+(( needs_menu )) && compstate[insert]=menu
+_describe 'completions' completions inserts -U -Q -S ''"#;
+    template
+        .replace("__USAGE_BIN__", usage_bin)
+        .replace("__CW_EXTRA__", cw_extra_args)
+        .lines()
+        .map(|l| format!("{indent}{l}"))
+        .collect::<Vec<_>>()
+        .join("\n")
+}
+
 pub fn complete_zsh(opts: &CompleteOptions) -> String {
     let usage_bin = &opts.usage_bin;
     let bin = &opts.bin;
@@ -82,15 +115,13 @@ fi"#
         String::new()
     };
 
+    let completion_loop = render_completion_loop(usage_bin, "  ", r#"-f "$spec_file""#);
+
     out.push(format!(
         r#"
   local spec_file="${{TMPDIR:-/tmp}}/usage_{spec_variable}.spec"
   {file_write_logic}
-  local -a completions=()
-  while IFS= read -r line; do
-    completions+=("$line")
-  done < <(command {usage_bin} complete-word --shell zsh -f "$spec_file" -- "${{words[@]}}")
-  _describe 'completions' completions -S ''
+{completion_loop}
   return 0
 }}
 
@@ -120,6 +151,11 @@ fi
 /// command path, peeks the first line, and dispatches to `usage complete-word`
 /// when it's a usage shebang. Otherwise it falls back to `_files`.
 pub fn complete_zsh_init(usage_bin: &str) -> String {
+    let completion_loop = render_completion_loop(
+        usage_bin,
+        "                ",
+        r#"-f "$cmdpath" --cword=$((CURRENT - 1))"#,
+    );
     format!(
         r##"# @generated by usage-cli — auto-completion for usage shebang scripts
 # Source this file from your zshrc to enable <Tab> completion for any command
@@ -138,12 +174,7 @@ _usage_default_complete() {{
         local first
         if IFS= read -r first < "$cmdpath" 2>/dev/null && [[ "$first" == "#!"*"usage"* ]]; then
             if (( ${{+commands[{usage_bin}]}} )); then
-                local -a completions=()
-                local line
-                while IFS= read -r line; do
-                    completions+=("$line")
-                done < <(command {usage_bin} complete-word --shell zsh -f "$cmdpath" --cword=$((CURRENT - 1)) -- "${{words[@]}}")
-                _describe 'completions' completions -S ''
+{completion_loop}
                 return $?
             fi
         fi