fix(agent-framework): detect shell completion marker on output without trailing newline

When a command's stdout has no trailing newline (e.g. cat of a file
without a final newline, or printf without \n), the line reader merges
the trailing output and the completion marker into a single line, so
ShellSession#collectOutput never matched the marker via startsWith and
hung until the command timed out.

Detect the marker anywhere in the line via indexOf, preserve any real
output preceding it, and parse the exit code after it.

Closes #4740

Author: logicwu0

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

@@ -386,18 +386,33 @@ private CommandResult collectOutput(String marker, long deadline, int maxOutputL
 					}
 
 					String line = outputLine.content;
-
-					// Check for completion marker (only in stdout)
-					if ("stdout".equals(outputLine.source) && line.startsWith(marker)) {
-						String[] parts = line.split(" ", 2);
-						if (parts.length > 1) {
-							try {
-								exitCode = Integer.parseInt(parts[1].trim());
-							} catch (NumberFormatException e) {
-								// Ignore
+					boolean completed = false;
+
+					// Detect the completion marker (only in stdout). The marker is emitted by a
+					// 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.
+					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
+								}
+							}
+							// Keep any real output that was merged onto the marker line.
+							line = line.substring(0, markerIndex);
+							completed = true;
+							if (line.isEmpty()) {
+								break;
 							}
 						}
-						break;
 					}
 
 					totalLines++;
@@ -420,6 +435,10 @@ private CommandResult collectOutput(String marker, long deadline, int maxOutputL
 						truncatedByLines = true;
 					}
 
+					if (completed) {
+						break;
+					}
+
 				} catch (InterruptedException e) {
 					Thread.currentThread().interrupt();
 					break;

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

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2025-2026 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.alibaba.cloud.ai.graph.agent.tools;
+
+import com.alibaba.cloud.ai.graph.RunnableConfig;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Timeout;
+import org.junit.jupiter.api.condition.DisabledOnOs;
+import org.junit.jupiter.api.condition.OS;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+/**
+ * Tests for {@link ShellSessionManager} command output collection.
+ *
+ * <p>
+ * Reproduces #4740: a command whose output does not end with a newline (e.g. {@code cat}
+ * of a file without a trailing newline) caused the completion marker to be merged onto the
+ * last output line, so it was never detected and {@code collectOutput} hung until the
+ * command timed out.
+ */
+@DisabledOnOs(OS.WINDOWS)
+class ShellSessionManagerTest {
+
+	private ShellSessionManager newManager(Path workspace) {
+		return ShellSessionManager.builder()
+			.workspaceRoot(workspace)
+			.commandTimeout(10000)
+			.build();
+	}
+
+	@Test
+	@Timeout(value = 20, unit = TimeUnit.SECONDS)
+	void outputWithoutTrailingNewlineIsCapturedAndDoesNotHang() throws Exception {
+		Path workspace = Files.createTempDirectory("shell_session_test_");
+		ShellSessionManager manager = newManager(workspace);
+		RunnableConfig config = RunnableConfig.builder().threadId("test-thread").build();
+		manager.initialize(config);
+		try {
+			// printf without \n leaves no trailing newline, so the marker is merged onto
+			// this line. Before the fix this hung until the command timed out.
+			ShellSessionManager.CommandResult result = manager
+				.executeCommand("printf 'hello-no-newline'", config);
+
+			assertFalse(result.isTimedOut(), "command should not time out");
+			assertEquals("hello-no-newline", result.getOutput());
+			assertEquals(0, result.getExitCode());
+		}
+		finally {
+			manager.cleanup(config);
+		}
+	}
+
+	@Test
+	@Timeout(value = 20, unit = TimeUnit.SECONDS)
+	void exitCodeIsParsedWhenMergedWithOutput() throws Exception {
+		Path workspace = Files.createTempDirectory("shell_session_test_");
+		ShellSessionManager manager = newManager(workspace);
+		RunnableConfig config = RunnableConfig.builder().threadId("test-thread").build();
+		manager.initialize(config);
+		try {
+			// Output has no trailing newline AND the command fails: the non-zero exit code
+			// must still be parsed from the line the marker was merged onto.
+			ShellSessionManager.CommandResult result = manager
+				.executeCommand("printf 'oops' && false", config);
+
+			assertFalse(result.isTimedOut(), "command should not time out");
+			assertEquals("oops", result.getOutput());
+			assertEquals(1, result.getExitCode());
+		}
+		finally {
+			manager.cleanup(config);
+		}
+	}
+
+	@Test
+	@Timeout(value = 20, unit = TimeUnit.SECONDS)
+	void normalOutputWithTrailingNewlineStillWorks() throws Exception {
+		Path workspace = Files.createTempDirectory("shell_session_test_");
+		ShellSessionManager manager = newManager(workspace);
+		RunnableConfig config = RunnableConfig.builder().threadId("test-thread").build();
+		manager.initialize(config);
+		try {
+			ShellSessionManager.CommandResult result = manager.executeCommand("printf 'a\\nb\\n'", config);
+
+			assertFalse(result.isTimedOut(), "command should not time out");
+			assertEquals("a\nb", result.getOutput());
+			assertEquals(0, result.getExitCode());
+		}
+		finally {
+			manager.cleanup(config);
+		}
+	}
+
+}