diff --git a/plugins/codeman/skills/codeman/SKILL.md b/plugins/codeman/skills/codeman/SKILL.md
index 621748ae..c6c85f4a 100644
--- a/plugins/codeman/skills/codeman/SKILL.md
+++ b/plugins/codeman/skills/codeman/SKILL.md
@@ -348,6 +348,7 @@ sendwait() {
   case "$p" in *$'\n'*|*$'\r'*)
     p=$(printf '%s\n' "$p" | tr '\r' '\n' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//' -e '/^$/d' | paste -sd ' ' -) ;;
   esac
+  [ -n "$p" ] || { echo "sendwait: empty prompt" >&2; return 1; }
   # `wait:"stop,exit"`, never the `wait:true` default set: that set also carries
   # `idle`, which is INFERRED from output stabilization and flaps mid-turn. On a
   # dsh worker whose TUI repaints rarely the session reads `idle` while the model
diff --git a/plugins/codeman/skills/codeman/preamble.sh b/plugins/codeman/skills/codeman/preamble.sh
index b6dd5f42..a0e95a32 100644
--- a/plugins/codeman/skills/codeman/preamble.sh
+++ b/plugins/codeman/skills/codeman/preamble.sh
@@ -247,6 +247,7 @@ sendwait() {
   case "$p" in *$'\n'*|*$'\r'*)
     p=$(printf '%s\n' "$p" | tr '\r' '\n' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//' -e '/^$/d' | paste -sd ' ' -) ;;
   esac
+  [ -n "$p" ] || { echo "sendwait: empty prompt" >&2; return 1; }
   # `wait:"stop,exit"`, never the `wait:true` default set: that set also carries
   # `idle`, which is INFERRED from output stabilization and flaps mid-turn. On a
   # dsh worker whose TUI repaints rarely the session reads `idle` while the model
diff --git a/plugins/codeman/skills/codeman/reference/verbs.md b/plugins/codeman/skills/codeman/reference/verbs.md
index a4f43d5a..fa91a749 100644
--- a/plugins/codeman/skills/codeman/reference/verbs.md
+++ b/plugins/codeman/skills/codeman/reference/verbs.md
@@ -304,11 +304,12 @@ Codeman types the text and sends Enter **only when the input contains a carriage
 return**; without it your command sits unsubmitted on the worker's prompt and
 everything downstream times out. No response field catches this: `delivered:true`
 means "written to the pane", **not** "submitted". With `useMux`, newlines are kept: the
-text goes in as one paste, and the `\r` submits all of it. **`sendwait` takes one line,
+text goes in as one paste, and the `\r` submits all of it. **`sendwait` sends one line,
 though:** its Enter loop and the server's submit check cannot reliably recognise a
-multi-line paste, so a multi-line prompt to a freshly spawned worker can sit unsent in
-Claude Code's Enter-ignore window. Join the lines, or put long multi-line content in a
-file ([§5.9](#59-big-input-via-the-workspace)). Build the body with `jq -n`
+multi-line paste, so a multi-line prompt to a freshly spawned worker could sit unsent in
+Claude Code's Enter-ignore window. `sendwait` therefore joins the lines with a space,
+which loses their layout; put long multi-line content in a file
+([§5.9](#59-big-input-via-the-workspace)). Build the body with `jq -n`
 for any prompt you did not author as a literal, because the inline
 `-d '{"input":"'"$P"'\r"}'` pattern breaks on the first double quote, backslash or `$`
 in a real prompt:
diff --git a/skills/codeman/SKILL.md b/skills/codeman/SKILL.md
index 621748ae..c6c85f4a 100644
--- a/skills/codeman/SKILL.md
+++ b/skills/codeman/SKILL.md
@@ -348,6 +348,7 @@ sendwait() {
   case "$p" in *$'\n'*|*$'\r'*)
     p=$(printf '%s\n' "$p" | tr '\r' '\n' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//' -e '/^$/d' | paste -sd ' ' -) ;;
   esac
+  [ -n "$p" ] || { echo "sendwait: empty prompt" >&2; return 1; }
   # `wait:"stop,exit"`, never the `wait:true` default set: that set also carries
   # `idle`, which is INFERRED from output stabilization and flaps mid-turn. On a
   # dsh worker whose TUI repaints rarely the session reads `idle` while the model
diff --git a/skills/codeman/preamble.sh b/skills/codeman/preamble.sh
index b6dd5f42..a0e95a32 100644
--- a/skills/codeman/preamble.sh
+++ b/skills/codeman/preamble.sh
@@ -247,6 +247,7 @@ sendwait() {
   case "$p" in *$'\n'*|*$'\r'*)
     p=$(printf '%s\n' "$p" | tr '\r' '\n' | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//' -e '/^$/d' | paste -sd ' ' -) ;;
   esac
+  [ -n "$p" ] || { echo "sendwait: empty prompt" >&2; return 1; }
   # `wait:"stop,exit"`, never the `wait:true` default set: that set also carries
   # `idle`, which is INFERRED from output stabilization and flaps mid-turn. On a
   # dsh worker whose TUI repaints rarely the session reads `idle` while the model
diff --git a/skills/codeman/reference/verbs.md b/skills/codeman/reference/verbs.md
index a4f43d5a..fa91a749 100644
--- a/skills/codeman/reference/verbs.md
+++ b/skills/codeman/reference/verbs.md
@@ -304,11 +304,12 @@ Codeman types the text and sends Enter **only when the input contains a carriage
 return**; without it your command sits unsubmitted on the worker's prompt and
 everything downstream times out. No response field catches this: `delivered:true`
 means "written to the pane", **not** "submitted". With `useMux`, newlines are kept: the
-text goes in as one paste, and the `\r` submits all of it. **`sendwait` takes one line,
+text goes in as one paste, and the `\r` submits all of it. **`sendwait` sends one line,
 though:** its Enter loop and the server's submit check cannot reliably recognise a
-multi-line paste, so a multi-line prompt to a freshly spawned worker can sit unsent in
-Claude Code's Enter-ignore window. Join the lines, or put long multi-line content in a
-file ([§5.9](#59-big-input-via-the-workspace)). Build the body with `jq -n`
+multi-line paste, so a multi-line prompt to a freshly spawned worker could sit unsent in
+Claude Code's Enter-ignore window. `sendwait` therefore joins the lines with a space,
+which loses their layout; put long multi-line content in a file
+([§5.9](#59-big-input-via-the-workspace)). Build the body with `jq -n`
 for any prompt you did not author as a literal, because the inline
 `-d '{"input":"'"$P"'\r"}'` pattern breaks on the first double quote, backslash or `$`
 in a real prompt:
diff --git a/test/agent-skill-sendwait.test.ts b/test/agent-skill-sendwait.test.ts
index d0d45e53..b38d412f 100644
--- a/test/agent-skill-sendwait.test.ts
+++ b/test/agent-skill-sendwait.test.ts
@@ -47,6 +47,7 @@ function sentInput(prompt: string): string {
   `;
   try {
     execFileSync('bash', ['-c', script], {
+      stdio: ['ignore', 'pipe', 'pipe'],
       env: {
         PATH: process.env.PATH,
         HOME: process.env.HOME,
@@ -74,6 +75,10 @@ describe.skipIf(!hasJq)('preamble sendwait', () => {
     expect(sentInput(prompt)).toBe(toSingleLine(prompt) + '\r');
   });
 
+  it('refuses a prompt made only of blank lines instead of sending a bare Enter', () => {
+    expect(() => sentInput('  \n \t\n')).toThrow(/sendwait: empty prompt/);
+  });
+
   it('leaves a single-line prompt, glob characters included, as it was', () => {
     expect(sentInput('fix * in ?.ts  ')).toBe('fix * in ?.ts  \r');
   });