Patch memory hole cleaner, and bounce version

lib3270j/src/main/java/haus/nightmare/lib3270j/ConnectionConfig.java

@@ -70,7 +70,7 @@ public class ConnectionConfig {
     private int tcpUserTimeoutMs = 0;
 
     // Framing buffer sanity limits (RFC 885 / RFC 2355 EOR protection)
-    public static final int DEFAULT_MAX_FRAMING_BUFFER_SIZE = 1048576; // 1MB (supports dense GDDM graphics, symbol sets, and DFT transfers)
+    public static final int DEFAULT_MAX_FRAMING_BUFFER_SIZE = 131072; // 128KB (2x max 64KB structured field; covers multi-SF GDDM + PS loads)
     private int maxFramingBufferSize = DEFAULT_MAX_FRAMING_BUFFER_SIZE;
 
     // Host operating system type (TSO, CMS, CICS)

lib3270j/src/main/java/haus/nightmare/lib3270j/Version.java

@@ -8,7 +8,7 @@ public final class Version {
     /**
      * Hardcoded fallback release version matching build.gradle and pom coordinates.
      */
-    public static final String VERSION = "1.2.4";
+    public static final String VERSION = "1.3.0";
 
     /**
      * Canonical library name.
@@ -22,7 +22,7 @@ public final class Version {
      * Inspects the package implementation version first (populated when loaded from a JAR),
      * and falls back to the compile-time {@link #VERSION} constant if null or blank.
      *
-     * @return the version string (e.g. "1.2.4")
+     * @return the version string (e.g. "1.3.0")
      */
     public static String getVersion() {
         Package pkg = Version.class.getPackage();

lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/DataStreamProcessor.java

@@ -41,10 +41,12 @@ public class DataStreamProcessor {
     private haus.nightmare.lib3270j.input.InputProcessor inputProcessor;
 
     // Graphics & Programmed Symbols
+    private static final int MAX_GOCA_ACCUMULATOR_SIZE = 262144; // 256KB cap (4x advertised 63KB QR_SEGMENT limit)
     private final haus.nightmare.lib3270j.graphics.ProgramSymbolManager programSymbolManager = new haus.nightmare.lib3270j.graphics.ProgramSymbolManager();
     private final haus.nightmare.lib3270j.graphics.GraphicsPlane graphicsPlane = new haus.nightmare.lib3270j.graphics.GraphicsPlane(720, 384);
     private final haus.nightmare.lib3270j.graphics.GocaDecoder gocaDecoder = new haus.nightmare.lib3270j.graphics.GocaDecoder(graphicsPlane);
-    private final java.io.ByteArrayOutputStream gocaAccumulator = new java.io.ByteArrayOutputStream();
+    private final FastByteBuffer gocaAccumulator = new FastByteBuffer(8192, MAX_GOCA_ACCUMULATOR_SIZE);
+    private boolean gocaDiscardMode = false;
     private int currentGocaSubtype = 0;
 
     // Phase 10: Auto-Unlock & Contention Resolution State
@@ -1539,32 +1541,58 @@ public class DataStreamProcessor {
 
                     if (flags == 0x80) { // SPAN_FIRST
                         gocaAccumulator.reset();
+                        gocaDiscardMode = false;
                         currentGocaSubtype = sfSubId;
                         if (orderLen > 0) {
-                            gocaAccumulator.write(data, orderOffset, orderLen);
+                            try {
+                                gocaAccumulator.write(data, orderOffset, orderLen);
+                            } catch (FramingBufferOverflowException e) {
+                                log.warning("GOCA accumulator exceeded " + MAX_GOCA_ACCUMULATOR_SIZE + " bytes on SPAN_FIRST; discarding spanned object");
+                                gocaAccumulator.reset();
+                                gocaDiscardMode = true;
+                            }
                         }
                     } else if (flags == 0x00) { // SPAN_MIDDLE
-                        if (orderLen > 0) {
-                            gocaAccumulator.write(data, orderOffset, orderLen);
+                        if (orderLen > 0 && !gocaDiscardMode) {
+                            try {
+                                gocaAccumulator.write(data, orderOffset, orderLen);
+                            } catch (FramingBufferOverflowException e) {
+                                log.warning("GOCA accumulator exceeded " + MAX_GOCA_ACCUMULATOR_SIZE + " bytes on SPAN_MIDDLE; discarding spanned object");
+                                gocaAccumulator.reset();
+                                gocaDiscardMode = true;
+                            }
                         }
                     } else if (flags == 0x40) { // SPAN_LAST
-                        if (orderLen > 0) {
-                            gocaAccumulator.write(data, orderOffset, orderLen);
+                        if (!gocaDiscardMode) {
+                            if (orderLen > 0) {
+                                try {
+                                    gocaAccumulator.write(data, orderOffset, orderLen);
+                                } catch (FramingBufferOverflowException e) {
+                                    log.warning("GOCA accumulator exceeded " + MAX_GOCA_ACCUMULATOR_SIZE + " bytes on SPAN_LAST; discarding spanned object");
+                                    gocaAccumulator.reset();
+                                    gocaDiscardMode = true;
+                                }
+                            }
+                            if (!gocaDiscardMode) {
+                                byte[] fullStream = gocaAccumulator.toByteArray();
+                                gocaAccumulator.reset();
+                                log.info(String.format("GOCA stream SPAN_LAST assembled: %d bytes", fullStream.length));
+                                try {
+                                    java.nio.file.Files.write(java.nio.file.Paths.get("/Users/rudi/Projects/j3270/captured_goca.bin"), fullStream);
+                                } catch (Exception ignored) {}
+                                if (currentGocaSubtype == haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJCNTL_SUB) {
+                                    gocaDecoder.processProcedureOrders(fullStream, 0, fullStream.length);
+                                } else {
+                                    gocaDecoder.decodeStream(fullStream, 0, fullStream.length);
+                                }
+                                notifyScreenUpdated();
+                            }
                         }
-                        byte[] fullStream = gocaAccumulator.toByteArray();
                         gocaAccumulator.reset();
-                        log.info(String.format("GOCA stream SPAN_LAST assembled: %d bytes", fullStream.length));
-                        try {
-                            java.nio.file.Files.write(java.nio.file.Paths.get("/Users/rudi/Projects/j3270/captured_goca.bin"), fullStream);
-                        } catch (Exception ignored) {}
-                        if (currentGocaSubtype == haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJCNTL_SUB) {
-                            gocaDecoder.processProcedureOrders(fullStream, 0, fullStream.length);
-                        } else {
-                            gocaDecoder.decodeStream(fullStream, 0, fullStream.length);
-                        }
-                        notifyScreenUpdated();
+                        gocaDiscardMode = false;
                     } else { // SPAN_ONLY (0xC0)
                         gocaAccumulator.reset();
+                        gocaDiscardMode = false;
                         log.info(String.format("GOCA stream SPAN_ONLY: %d bytes", orderLen));
                         if (sfSubId == haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJCNTL_SUB) {
                             gocaDecoder.processProcedureOrders(data, orderOffset, orderLen);

lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/FastByteBuffer.java

@@ -18,7 +18,7 @@ import java.util.Arrays;
 public class FastByteBuffer extends OutputStream {
 
     public static final int DEFAULT_INITIAL_CAPACITY = 32768;
-    public static final int DEFAULT_MAX_CAPACITY = 1048576; // 1MB (matches modern x3270 PDS_MAX for dense GDDM / GOCA vector graphics)
+    public static final int DEFAULT_MAX_CAPACITY = 131072; // 128KB (2x max 64KB structured field; covers multi-SF GDDM + PS loads)
 
     private final int initialCapacity;
     private int maxCapacity;

lib3270j/src/main/java/haus/nightmare/lib3270j/printer/PD3270.java

@@ -24,6 +24,9 @@ public class PD3270 {
     private String destination;
     private boolean open = false;
 
+    /** Maximum size of in-memory print capture buffer (1 MB) to prevent unbounded heap growth. */
+    public static final int MAX_MEMORY_CAPTURE_SIZE = 1048576;
+
     private OutputStream targetOutputStream;
     private Writer targetWriter;
     private Process pipeProcess;
@@ -33,6 +36,13 @@ public class PD3270 {
     private int pageCount = 0;
     private Charset outputCharset = StandardCharsets.UTF_8;
 
+    private void appendToMemoryStream(byte[] data, int offset, int length) {
+        int remaining = MAX_MEMORY_CAPTURE_SIZE - memoryStream.size();
+        if (remaining > 0) {
+            memoryStream.write(data, offset, Math.min(length, remaining));
+        }
+    }
+
     public PD3270() {
         this(new PrinterConfig());
     }
@@ -102,7 +112,7 @@ public class PD3270 {
         }
 
         try {
-            memoryStream.write(data, offset, length);
+            appendToMemoryStream(data, offset, length);
             byteCount += length;
 
             if (targetOutputStream != null) {
@@ -129,7 +139,7 @@ public class PD3270 {
         }
         try {
             byte[] b = String.valueOf(c).getBytes(outputCharset);
-            memoryStream.write(b);
+            appendToMemoryStream(b, 0, b.length);
             byteCount += b.length;
 
             if (targetWriter != null) {
@@ -158,7 +168,7 @@ public class PD3270 {
         }
         try {
             byte[] b = s.getBytes(outputCharset);
-            memoryStream.write(b);
+            appendToMemoryStream(b, 0, b.length);
             byteCount += b.length;
 
             if (targetWriter != null) {

lib3270j/src/main/java/haus/nightmare/lib3270j/printer/PrinterConfig.java

@@ -54,7 +54,7 @@ public class PrinterConfig {
     private long autoFlushTimeoutMs = 2000;
     private int graphicErrorAction = PrinterConstants.GEA_NO_SUBSTITUTION;
     private char graphicErrorReplacementChar = '?';
-    public static final int DEFAULT_MAX_FRAMING_BUFFER_SIZE = 1048576; // 1MB
+    public static final int DEFAULT_MAX_FRAMING_BUFFER_SIZE = 131072; // 128KB
     private int maxFramingBufferSize = DEFAULT_MAX_FRAMING_BUFFER_SIZE;
 
     public PrinterConfig() {

lib3270j/src/main/java/haus/nightmare/lib3270j/printer/Telnet3270EP.java

@@ -61,14 +61,16 @@ public class Telnet3270EP implements Runnable {
     private static final int MAX_PRINTER_SUBNEG_SIZE = 8192;
     private final int maxFramingBufferSize;
     private boolean recordDiscardMode = false;
-    private final ByteArrayOutputStream recordBuffer;
+    private boolean subnegDiscardMode = false;
+    private final haus.nightmare.lib3270j.datastream.FastByteBuffer recordBuffer;
     private final ByteArrayOutputStream subnegBuffer = new ByteArrayOutputStream();
     private boolean inSubnegotiation = false;
 
     public Telnet3270EP(PrinterConfig config) {
         this.config = config != null ? config : new PrinterConfig();
         this.maxFramingBufferSize = this.config.getMaxFramingBufferSize();
-        this.recordBuffer = new ByteArrayOutputStream(Math.min(32768, this.maxFramingBufferSize));
+        this.recordBuffer = new haus.nightmare.lib3270j.datastream.FastByteBuffer(
+                Math.min(32768, this.maxFramingBufferSize), this.maxFramingBufferSize);
         this.pd = new PD3270(this.config);
         this.translator = new EbcdicTranslator(this.config.getCodePage());
         this.scs = new PrintSCS3270(this.config, this.pd, this.translator);
@@ -79,7 +81,8 @@ public class Telnet3270EP implements Runnable {
     public Telnet3270EP(PrinterConfig config, PD3270 pd, EbcdicTranslator translator) {
         this.config = config != null ? config : new PrinterConfig();
         this.maxFramingBufferSize = this.config.getMaxFramingBufferSize();
-        this.recordBuffer = new ByteArrayOutputStream(Math.min(32768, this.maxFramingBufferSize));
+        this.recordBuffer = new haus.nightmare.lib3270j.datastream.FastByteBuffer(
+                Math.min(32768, this.maxFramingBufferSize), this.maxFramingBufferSize);
         this.pd = pd != null ? pd : new PD3270(this.config);
         this.translator = translator != null ? translator : new EbcdicTranslator(this.config.getCodePage());
         this.scs = new PrintSCS3270(this.config, this.pd, this.translator);
@@ -384,21 +387,30 @@ public class Telnet3270EP implements Runnable {
                     if (idx < end && (data[idx] & 0xFF) == TelnetConstants.SE) {
                         idx++;
                         inSubnegotiation = false;
-                        processSubnegotiation(subnegBuffer.toByteArray());
+                        if (!subnegDiscardMode) {
+                            processSubnegotiation(subnegBuffer.toByteArray());
+                        }
                         subnegBuffer.reset();
+                        subnegDiscardMode = false;
                     } else if (idx < end && (data[idx] & 0xFF) == TelnetConstants.IAC) {
-                        if (subnegBuffer.size() < MAX_PRINTER_SUBNEG_SIZE) {
-                            subnegBuffer.write(TelnetConstants.IAC);
+                        if (!subnegDiscardMode) {
+                            if (subnegBuffer.size() < MAX_PRINTER_SUBNEG_SIZE) {
+                                subnegBuffer.write(TelnetConstants.IAC);
+                            } else {
+                                log.warning("Printer subnegotiation exceeded " + MAX_PRINTER_SUBNEG_SIZE + " bytes; discarding until IAC SE");
+                                subnegBuffer.reset();
+                                subnegDiscardMode = true;
+                            }
                         }
                         idx++;
                     }
-                } else {
+                } else if (!subnegDiscardMode) {
                     if (subnegBuffer.size() < MAX_PRINTER_SUBNEG_SIZE) {
                         subnegBuffer.write(b);
                     } else {
-                        log.warning("Printer subnegotiation exceeded " + MAX_PRINTER_SUBNEG_SIZE + " bytes; aborting SB");
+                        log.warning("Printer subnegotiation exceeded " + MAX_PRINTER_SUBNEG_SIZE + " bytes; discarding until IAC SE");
                         subnegBuffer.reset();
-                        inSubnegotiation = false;
+                        subnegDiscardMode = true;
                     }
                 }
                 continue;
@@ -414,6 +426,7 @@ public class Telnet3270EP implements Runnable {
                         break;
                     case TelnetConstants.SB:
                         inSubnegotiation = true;
+                        subnegDiscardMode = false;
                         subnegBuffer.reset();
                         break;
                     case TelnetConstants.EOR:

lib3270j/src/main/java/haus/nightmare/lib3270j/telnet/TelnetFSM.java

@@ -54,6 +54,7 @@ public class TelnetFSM {
 
     // Sanity cap for Telnet subnegotiation parameters (RFC 1091, RFC 1572, RFC 2355)
     private static final int MAX_SUBNEG_BUFFER_SIZE = 8192;
+    private boolean sbDiscardMode = false;
 
     // Reusable single-byte scratch buffer for plain NVT data dispatch (Phase 27.5 / T1-C)
     private final byte[] nvtSingleByteScratch = new byte[1];
@@ -229,6 +230,7 @@ public class TelnetFSM {
         ttypeIndex = 0;
         luIndex = 0;
         recordDiscardMode = false;
+        sbDiscardMode = false;
         ibuf.reset();
         sbbuf.reset();
 
@@ -401,7 +403,13 @@ public class TelnetFSM {
     private void processIAC(int c) {
         switch (c) {
             case IAC: // Escaped IAC — literal 0xFF
-                appendInboundByte(c);
+                if ((connectionState == ConnectionState.CONNECTED_NVT || connectionState == ConnectionState.CONNECTED_NVT_CHAR)
+                        && !(hisOpts[TELOPT_BINARY] && hisOpts[TELOPT_EOR])) {
+                    nvtSingleByteScratch[0] = (byte) c;
+                    nvtProcessor.processNVTData(nvtSingleByteScratch, 0, 1);
+                } else {
+                    appendInboundByte(c);
+                }
                 state = TNS_DATA;
                 break;
             case EOR: // End of record — process accumulated 3270 data
@@ -419,6 +427,7 @@ public class TelnetFSM {
             case DONT: state = TNS_DONT; break;
             case SB:
                 sbbuf.reset();
+                sbDiscardMode = false;
                 state = TNS_SB;
                 break;
             case GA:
@@ -585,14 +594,14 @@ public class TelnetFSM {
     private void processSB(int c) {
         if (c == IAC) {
             state = TNS_SB_IAC;
-        } else {
+        } else if (!sbDiscardMode) {
             if (sbbuf.size() < MAX_SUBNEG_BUFFER_SIZE) {
                 sbbuf.write(c);
             } else {
                 log.warning("Telnet subnegotiation exceeded " + MAX_SUBNEG_BUFFER_SIZE +
-                        " bytes without IAC SE; discarding and aborting SB");
+                        " bytes without IAC SE; discarding until IAC SE");
                 sbbuf.reset();
-                state = TNS_DATA;
+                sbDiscardMode = true;
             }
         }
     }
@@ -602,21 +611,34 @@ public class TelnetFSM {
     private void processSBIAC(int c) {
         if (c == SE) {
             // Sub-negotiation complete
-            byte[] sbData = sbbuf.toByteArray();
-            sbbuf.reset();
-            processSubNegotiation(sbData);
+            if (!sbDiscardMode) {
+                byte[] sbData = sbbuf.toByteArray();
+                sbbuf.reset();
+                processSubNegotiation(sbData);
+            } else {
+                sbbuf.reset();
+                sbDiscardMode = false;
+            }
             state = TNS_DATA;
         } else if (c == IAC) {
             // Escaped IAC within sub-negotiation
-            if (sbbuf.size() < MAX_SUBNEG_BUFFER_SIZE) {
-                sbbuf.write(IAC);
+            if (!sbDiscardMode) {
+                if (sbbuf.size() < MAX_SUBNEG_BUFFER_SIZE) {
+                    sbbuf.write(IAC);
+                } else {
+                    log.warning("Telnet subnegotiation exceeded " + MAX_SUBNEG_BUFFER_SIZE +
+                            " bytes without IAC SE; discarding until IAC SE");
+                    sbbuf.reset();
+                    sbDiscardMode = true;
+                }
             }
             state = TNS_SB;
         } else {
-            // Shouldn't happen, but recover
+            // Unexpected command after IAC inside SB (e.g. missing SE): abort SB and process command
             log.warning("Unexpected byte " + c + " after IAC in SB");
             sbbuf.reset();
-            state = TNS_DATA;
+            sbDiscardMode = false;
+            processIAC(c);
         }
     }
 

lib3270j/src/test/java/haus/nightmare/lib3270j/Phase30LibraryDistributionTest.java

@@ -66,7 +66,7 @@ public class Phase30LibraryDistributionTest {
         String setupShContent = Files.readString(setupSh.toPath());
         assertTrue(setupShContent.contains("lib3270j.jar"), "setup.sh must package lib3270j.jar");
         assertTrue(setupShContent.contains("Implementation-Title: lib3270j"), "setup.sh must set Implementation-Title: lib3270j");
-        assertTrue(setupShContent.contains("Implementation-Version: 1.2.4"), "setup.sh must set Implementation-Version: 1.2.4");
+        assertTrue(setupShContent.contains("Implementation-Version: 1.3.0"), "setup.sh must set Implementation-Version: 1.3.0");
 
         // 3. setup.ps1
         File setupPs1 = new File(projectRoot, "setup.ps1");
@@ -74,7 +74,7 @@ public class Phase30LibraryDistributionTest {
         String setupPs1Content = Files.readString(setupPs1.toPath());
         assertTrue(setupPs1Content.contains("lib3270j.jar"), "setup.ps1 must package lib3270j.jar");
         assertTrue(setupPs1Content.contains("Implementation-Title: lib3270j"), "setup.ps1 must set Implementation-Title: lib3270j");
-        assertTrue(setupPs1Content.contains("Implementation-Version: 1.2.4"), "setup.ps1 must set Implementation-Version: 1.2.4");
+        assertTrue(setupPs1Content.contains("Implementation-Version: 1.3.0"), "setup.ps1 must set Implementation-Version: 1.3.0");
     }
 
     @Test
@@ -112,12 +112,12 @@ public class Phase30LibraryDistributionTest {
     @DisplayName("Phase 30.2: Maven local published artifacts exist and validate if maven-publish was executed")
     public void testMavenLocalPublishedArtifacts() throws Exception {
         String userHome = System.getProperty("user.home");
-        File m2ArtifactDir = new File(userHome, ".m2/repository/haus/nightmare/j3270/lib3270j/1.2.4");
+        File m2ArtifactDir = new File(userHome, ".m2/repository/haus/nightmare/j3270/lib3270j/1.3.0");
         if (m2ArtifactDir.exists()) {
-            File pomFile = new File(m2ArtifactDir, "lib3270j-1.2.4.pom");
-            File jarFile = new File(m2ArtifactDir, "lib3270j-1.2.4.jar");
-            File sourcesFile = new File(m2ArtifactDir, "lib3270j-1.2.4-sources.jar");
-            File javadocFile = new File(m2ArtifactDir, "lib3270j-1.2.4-javadoc.jar");
+            File pomFile = new File(m2ArtifactDir, "lib3270j-1.3.0.pom");
+            File jarFile = new File(m2ArtifactDir, "lib3270j-1.3.0.jar");
+            File sourcesFile = new File(m2ArtifactDir, "lib3270j-1.3.0-sources.jar");
+            File javadocFile = new File(m2ArtifactDir, "lib3270j-1.3.0-javadoc.jar");
 
             assertTrue(pomFile.exists() && pomFile.length() > 0, "POM file must exist and be non-empty");
             assertTrue(jarFile.exists() && jarFile.length() > 0, "JAR file must exist and be non-empty");
@@ -127,7 +127,7 @@ public class Phase30LibraryDistributionTest {
             String pomXml = Files.readString(pomFile.toPath());
             assertTrue(pomXml.contains("<groupId>haus.nightmare.j3270</groupId>"), "POM must contain groupId");
             assertTrue(pomXml.contains("<artifactId>lib3270j</artifactId>"), "POM must contain artifactId");
-            assertTrue(pomXml.contains("<version>1.2.4</version>"), "POM must contain version 1.2.4");
+            assertTrue(pomXml.contains("<version>1.3.0</version>"), "POM must contain version 1.3.0");
             assertTrue(pomXml.contains("The Unlicense"), "POM must contain Unlicense");
             assertFalse(pomXml.contains("Apache"), "lib3270j POM must not contain Apache license");
             assertFalse(pomXml.contains("<dependencies>"), "lib3270j POM must have zero external dependencies");

lib3270j/src/test/java/haus/nightmare/lib3270j/datastream/FastByteBufferTest.java

@@ -165,6 +165,7 @@ public class FastByteBufferTest {
 
         buf.write(chunk, 0, 64);
         assertEquals(128, buf.size());
+        assertEquals(128, buf.buffer().length);
 
         // Writing one more byte must throw FramingBufferOverflowException
         assertThrows(FramingBufferOverflowException.class, () -> buf.write(0xFF));
@@ -180,10 +181,10 @@ public class FastByteBufferTest {
     }
 
     @Test
-    @DisplayName("FastByteBuffer default maxCapacity is 1048576 bytes (1MB)")
+    @DisplayName("FastByteBuffer default maxCapacity is 131072 bytes (128KB)")
     public void testDefaultMaxCapacity() {
         FastByteBuffer buf = new FastByteBuffer();
         assertEquals(FastByteBuffer.DEFAULT_MAX_CAPACITY, buf.getMaxCapacity());
-        assertEquals(1048576, buf.getMaxCapacity());
+        assertEquals(131072, buf.getMaxCapacity());
     }
 }

lib3270j/src/test/java/haus/nightmare/lib3270j/telnet/FramingBufferBoundedCapTest.java

@@ -72,7 +72,7 @@ public class FramingBufferBoundedCapTest {
     }
 
     @Test
-    @DisplayName("Framing buffer caps at 1MB and enters discard mode if stream lacks IAC EOR")
+    @DisplayName("Framing buffer caps at 128KB and enters discard mode if stream lacks IAC EOR")
     public void testFramingBufferOverflowDiscardsUntilEor() {
         fsm.onConnected();
 
@@ -82,19 +82,19 @@ public class FramingBufferBoundedCapTest {
         feedBytes(IAC, DO, TELOPT_BINARY);
         feedBytes(IAC, WILL, TELOPT_BINARY);
 
-        assertEquals(1048576, fsm.getMaxFramingBufferSize(), "Default framing buffer cap should be 1MB (1048576 bytes)");
+        assertEquals(131072, fsm.getMaxFramingBufferSize(), "Default framing buffer cap should be 128KB (131072 bytes)");
         assertFalse(fsm.isRecordDiscardMode());
 
-        // Feed chunks totaling over 1MB without any IAC EOR delimiter
+        // Feed chunks totaling over 128KB without any IAC EOR delimiter
         byte[] chunk = new byte[8192];
         Arrays.fill(chunk, (byte) 0xC1); // EBCDIC 'A'
 
-        for (int i = 0; i < 128; i++) {
-            fsm.feedBytes(chunk, 0, chunk.length); // 128 * 8192 = 1,048,576 bytes
+        for (int i = 0; i < 16; i++) {
+            fsm.feedBytes(chunk, 0, chunk.length); // 16 * 8192 = 131,072 bytes
         }
         assertFalse(fsm.isRecordDiscardMode(), "Buffer should be at exact cap without overflowing yet");
 
-        // Now feed an additional chunk exceeding the 1MB cap without IAC EOR
+        // Now feed an additional chunk exceeding the 128KB cap without IAC EOR
         fsm.feedBytes(chunk, 0, 100);
 
         assertTrue(fsm.isRecordDiscardMode(), "FSM must enter recordDiscardMode when cap is exceeded without IAC EOR");
@@ -156,45 +156,56 @@ public class FramingBufferBoundedCapTest {
     }
 
     @Test
-    @DisplayName("Telnet subnegotiation buffer caps at 8KB if stream lacks IAC SE")
+    @DisplayName("Telnet subnegotiation buffer caps at 8KB if stream lacks IAC SE without leaking into data buffer")
     public void testSubnegotiationBufferCap() {
         fsm.onConnected();
+        feedBytes(IAC, DO, TELOPT_EOR);
+        feedBytes(IAC, WILL, TELOPT_EOR);
+        feedBytes(IAC, DO, TELOPT_BINARY);
+        feedBytes(IAC, WILL, TELOPT_BINARY);
 
         // Begin subnegotiation: IAC SB TELOPT_TTYPE
         feedBytes(IAC, SB, TELOPT_TTYPE);
 
         // Feed > 8192 bytes without IAC SE
-        byte[] largeSb = new byte[8200];
+        byte[] largeSb = new byte[9000];
         Arrays.fill(largeSb, (byte) 'X');
         fsm.feedBytes(largeSb, 0, largeSb.length);
 
-        // Feed a regular byte: should be back in TNS_DATA, not accumulating in SB
-        feedBytes(IAC, NOP);
-        // Ensure no exception and session remains operational
-        assertTrue(true);
+        // Overflowing SB bytes must NOT leak into the 3270 framing buffer while waiting for IAC SE
+        assertEquals(0, fsm.getCurrentFramingBufferSize(), "Overflowing SB bytes must not leak into ibuf");
+
+        // Terminate the subnegotiation with IAC SE
+        feedBytes(IAC, SE);
+        assertEquals(0, fsm.getCurrentFramingBufferSize());
+
+        // Subsequent 3270 data record should be processed cleanly
+        byte[] valid3270 = new byte[] { (byte) 0xF5, (byte) 0xC2, (byte) 0x11, 0x00, 0x00, (byte) 0xC1, (byte) IAC, (byte) EOR };
+        fsm.feedBytes(valid3270, 0, valid3270.length);
+        assertEquals('A', screenBuffer.getDisplayCell(0).ucs4);
     }
 
     @Test
-    @DisplayName("Printer framing buffer caps at 1MB and enters discard mode without IAC EOR")
+    @DisplayName("Printer framing buffer caps at 128KB and enters discard mode without IAC EOR")
     public void testPrinterFramingBufferCap() throws Exception {
         PrinterConfig pcfg = new PrinterConfig("localhost", 23);
-        assertEquals(1048576, pcfg.getMaxFramingBufferSize());
+        assertEquals(131072, pcfg.getMaxFramingBufferSize());
 
         Telnet3270EP printer = new Telnet3270EP(pcfg);
-        assertEquals(1048576, printer.getMaxFramingBufferSize());
+        assertEquals(131072, printer.getMaxFramingBufferSize());
         assertFalse(printer.isRecordDiscardMode());
 
         Method processIncoming = Telnet3270EP.class.getDeclaredMethod("processIncomingBytes", byte[].class, int.class, int.class);
         processIncoming.setAccessible(true);
 
-        byte[] chunk = new byte[32768];
+        byte[] chunk = new byte[8192];
         Arrays.fill(chunk, (byte) 0x40);
 
-        for (int i = 0; i < 33; i++) {
-            processIncoming.invoke(printer, chunk, 0, chunk.length); // 33 * 32768 = 1,081,344 bytes > 1,048,576
+        for (int i = 0; i < 17; i++) {
+            processIncoming.invoke(printer, chunk, 0, chunk.length); // 17 * 8192 = 139,264 bytes > 131,072
         }
 
-        assertTrue(printer.isRecordDiscardMode(), "Printer must enter discard mode when record exceeds 1MB");
+        assertTrue(printer.isRecordDiscardMode(), "Printer must enter discard mode when record exceeds 128KB");
 
         // Send IAC EOR
         byte[] eor = new byte[] { (byte) IAC, (byte) EOR };