Add --stdin flag for eval command (#348)

Adds --stdin flag to read JavaScript from stdin, enabling heredoc usage
for multiline scripts without shell escaping issues.

.changeset/stdin-eval.md

@@ -0,0 +1,5 @@
+---
+"agent-browser": patch
+---
+
+Add --stdin flag for eval command to read JavaScript from stdin, enabling heredoc usage for multiline scripts

README.md

@@ -77,7 +77,7 @@ agent-browser upload <sel> <files>    # Upload files
 agent-browser screenshot [path]       # Take screenshot (--full for full page, saves to a temporary directory if no path)
 agent-browser pdf <path>              # Save as PDF
 agent-browser snapshot                # Accessibility tree with refs (best for AI)
-agent-browser eval <js>               # Run JavaScript
+agent-browser eval <js>               # Run JavaScript (-b for base64, --stdin for piped input)
 agent-browser connect <port>          # Connect to browser via CDP
 agent-browser close                   # Close browser (aliases: quit, exit)
 ```

cli/src/commands.rs

@@ -1,5 +1,6 @@
 use base64::{engine::general_purpose::STANDARD, Engine};
 use serde_json::{json, Value};
+use std::io::{self, BufRead};
 
 use crate::flags::Flags;
 
@@ -419,24 +420,37 @@ pub fn parse_command(args: &[String], flags: &Flags) -> Result<Value, ParseError
 
         // === Eval ===
         "eval" => {
-            let (is_base64, script_parts): (bool, &[&str]) =
+            // Check for flags: -b/--base64 or --stdin
+            let (is_base64, is_stdin, script_parts): (bool, bool, &[&str]) =
                 if rest.first() == Some(&"-b") || rest.first() == Some(&"--base64") {
-                    (true, &rest[1..])
+                    (true, false, &rest[1..])
+                } else if rest.first() == Some(&"--stdin") {
+                    (false, true, &rest[1..])
                 } else {
-                    (false, rest.as_slice())
+                    (false, false, rest.as_slice())
                 };
-            let raw_script = script_parts.join(" ");
-            let script = if is_base64 {
-                let decoded = STANDARD.decode(&raw_script).map_err(|_| ParseError::InvalidValue {
-                    message: "Invalid base64 encoding".to_string(),
-                    usage: "eval -b <base64-encoded-script>",
-                })?;
-                String::from_utf8(decoded).map_err(|_| ParseError::InvalidValue {
-                    message: "Base64 decoded to invalid UTF-8".to_string(),
-                    usage: "eval -b <base64-encoded-script>",
-                })?
+
+            let script = if is_stdin {
+                // Read script from stdin
+                let stdin = io::stdin();
+                let lines: Vec<String> = stdin.lock().lines()
+                    .map(|l| l.unwrap_or_default())
+                    .collect();
+                lines.join("\n")
             } else {
-                raw_script
+                let raw_script = script_parts.join(" ");
+                if is_base64 {
+                    let decoded = STANDARD.decode(&raw_script).map_err(|_| ParseError::InvalidValue {
+                        message: "Invalid base64 encoding".to_string(),
+                        usage: "eval -b <base64-encoded-script>",
+                    })?;
+                    String::from_utf8(decoded).map_err(|_| ParseError::InvalidValue {
+                        message: "Base64 decoded to invalid UTF-8".to_string(),
+                        usage: "eval -b <base64-encoded-script>",
+                    })?
+                } else {
+                    raw_script
+                }
             };
             Ok(json!({ "id": id, "action": "evaluate", "script": script }))
         }

cli/src/output.rs

@@ -885,6 +885,7 @@ Executes JavaScript code in the browser context and returns the result.
 
 Options:
   -b, --base64         Decode script from base64 (avoids shell escaping issues)
+  --stdin              Read script from stdin (useful for heredocs/multiline)
 
 Global Options:
   --json               Output as JSON
@@ -895,6 +896,12 @@ Examples:
   agent-browser eval "window.location.href"
   agent-browser eval "document.querySelectorAll('a').length"
   agent-browser eval -b "ZG9jdW1lbnQudGl0bGU="
+
+  # Read from stdin with heredoc
+  cat <<'EOF' | agent-browser eval --stdin
+  const links = document.querySelectorAll('a');
+  links.length;
+  EOF
 "##
         }
 

skills/agent-browser/references/commands.md

@@ -189,14 +189,21 @@ agent-browser dialog dismiss        # Dismiss dialog
 
 ```bash
 agent-browser eval "document.title"          # Simple expressions only
-agent-browser eval -b "<base64>"             # Any JavaScript (recommended)
+agent-browser eval -b "<base64>"             # Any JavaScript (base64 encoded)
+agent-browser eval --stdin                   # Read script from stdin
 ```
 
-Use `-b`/`--base64` for reliable execution. Shell escaping with nested quotes and special characters is error-prone.
+Use `-b`/`--base64` or `--stdin` for reliable execution. Shell escaping with nested quotes and special characters is error-prone.
 
 ```bash
 # Base64 encode your script, then:
 agent-browser eval -b "ZG9jdW1lbnQucXVlcnlTZWxlY3RvcignW3NyYyo9Il9uZXh0Il0nKQ=="
+
+# Or use stdin with heredoc for multiline scripts:
+cat <<'EOF' | agent-browser eval --stdin
+const links = document.querySelectorAll('a');
+Array.from(links).map(a => a.href);
+EOF
 ```
 
 ## State Management