fix(agent): only treat shell marker as completion when a valid exit code follows

Addresses review feedback on #4740: a command that reads from stdin (e.g.
`cat` with no args, `read`, `head -n1`) can consume and echo the injected
marker command before it runs. That echoed line contains the marker substring
but no valid trailing exit status, so the in-line indexOf match would treat it
as completion, leave exitCode null (reported as success), and let the real
command keep owning the session.

Only set completed when the text following the marker parses as the expected
exit-code integer; otherwise keep reading (restoring the previous timeout/
restart behavior for stdin-consuming commands). Added a regression test that
runs `cat` and asserts it times out instead of falsely completing.

Author: logicwu0

spring-ai-alibaba-agent-framework/src/main/java/com/alibaba/cloud/ai/graph/agent/tools/ShellSessionManager.java

@@ -392,26 +392,29 @@ private CommandResult collectOutput(String marker, long deadline, int maxOutputL
 					// follow-up echo command, so it usually arrives on its own line. But when the
 					// command's output has no trailing newline (e.g. `cat` of a file without a final
 					// newline, or `printf` without `\n`), the line reader merges that trailing output
-					// and the marker into a single line. Searching for the marker anywhere in the line
-					// keeps completion detection working, and any real output preceding the marker is
-					// preserved. See #4740.
+					// and the marker into a single line, so we look for the marker anywhere in the
+					// line and preserve any real output that precedes it.
+					//
+					// We only treat the line as completion when the text following the marker parses
+					// as the expected exit-status integer. A command that reads from stdin (e.g.
+					// `cat`, `read`, `head -n1`) can consume and echo the injected marker command
+					// itself before it ever runs; that echoed line contains the marker substring but
+					// no valid trailing exit code, so it must NOT be treated as completion (otherwise
+					// the command would be falsely reported as a successful run while still owning the
+					// session). See #4740.
 					if ("stdout".equals(outputLine.source)) {
 						int markerIndex = line.indexOf(marker);
 						if (markerIndex >= 0) {
-							String afterMarker = line.substring(markerIndex + marker.length()).trim();
-							if (!afterMarker.isEmpty()) {
-								try {
-									exitCode = Integer.parseInt(afterMarker.split("\\s+")[0]);
-								} catch (NumberFormatException e) {
-									// Ignore
+							Integer parsedExitCode = parseExitCode(line.substring(markerIndex + marker.length()));
+							if (parsedExitCode != null) {
+								exitCode = parsedExitCode;
+								// Keep any real output that was merged onto the marker line.
+								line = line.substring(0, markerIndex);
+								completed = true;
+								if (line.isEmpty()) {
+									break;
 								}
 							}
-							// Keep any real output that was merged onto the marker line.
-							line = line.substring(0, markerIndex);
-							completed = true;
-							if (line.isEmpty()) {
-								break;
-							}
 						}
 					}
 
@@ -449,6 +452,24 @@ private CommandResult collectOutput(String marker, long deadline, int maxOutputL
 			return new CommandResult(output, exitCode, timedOut, truncatedByLines,
 				truncatedByBytes, totalLines, totalBytes);
 		}
+
+		/**
+		 * Parse the exit status that the completion marker echoes after it (e.g. the {@code 0}
+		 * in {@code <marker> 0}). Returns {@code null} when the text is empty or its first token
+		 * is not an integer, which signals that this occurrence of the marker is not a genuine
+		 * completion line (for example the marker command echoed back by a stdin-reading command).
+		 */
+		private Integer parseExitCode(String afterMarker) {
+			String trimmed = afterMarker.trim();
+			if (trimmed.isEmpty()) {
+				return null;
+			}
+			try {
+				return Integer.parseInt(trimmed.split("\\s+")[0]);
+			} catch (NumberFormatException e) {
+				return null;
+			}
+		}
 	}
 
 	/**

spring-ai-alibaba-agent-framework/src/test/java/com/alibaba/cloud/ai/graph/agent/tools/ShellSessionManagerTest.java

@@ -28,6 +28,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /**
  * Tests for {@link ShellSessionManager} command output collection.
@@ -111,4 +112,31 @@ void normalOutputWithTrailingNewlineStillWorks() throws Exception {
 		}
 	}
 
+	@Test
+	@Timeout(value = 30, unit = TimeUnit.SECONDS)
+	void stdinReadingCommandDoesNotFalselyCompleteOnEchoedMarker() throws Exception {
+		Path workspace = Files.createTempDirectory("shell_session_test_");
+		// Short timeout: this command can never complete normally, so keep the expected
+		// timeout/restart fast.
+		ShellSessionManager manager = ShellSessionManager.builder()
+			.workspaceRoot(workspace)
+			.commandTimeout(3000)
+			.build();
+		RunnableConfig config = RunnableConfig.builder().threadId("test-thread").build();
+		manager.initialize(config);
+		try {
+			// `cat` with no argument reads from the session's stdin and consumes/echoes the
+			// injected marker command before it ever runs. The echoed line contains the marker
+			// substring but no valid trailing exit code, so it must NOT be treated as completion
+			// — otherwise the command would be falsely reported as a successful (exitCode == null)
+			// run while still owning the session. It should time out and restart instead.
+			ShellSessionManager.CommandResult result = manager.executeCommand("cat", config);
+
+			assertTrue(result.isTimedOut(), "stdin-consuming command must not falsely complete on echoed marker");
+		}
+		finally {
+			manager.cleanup(config);
+		}
+	}
+
 }