diff --git a/release-notes/CREDITS b/release-notes/CREDITS
index 6f5d21a88..8e8f4b199 100644
--- a/release-notes/CREDITS
+++ b/release-notes/CREDITS
@@ -76,3 +76,6 @@ PJ Fanning (@pjfanning)
 * Contributed #763: (protobuf) Use `VarHandle` for multi-byte primitive reads
   and writes in `ProtobufParser` / `ProtobufGenerator`
  (3.3.0)
+* Contributed #781: (smile) `SmileGenerator.writeNumber(String)` should validate
+  number length against configured `StreamReadConstraints`, not global defaults
+ (3.3.0)
diff --git a/release-notes/VERSION b/release-notes/VERSION
index 34c5dfd62..d498ab9cc 100644
--- a/release-notes/VERSION
+++ b/release-notes/VERSION
@@ -38,6 +38,9 @@ implementations)
 #767: (smile) Use more efficient `String` construction wrt "Compact Strings"
   for "short" ASCII text values of async parser
  (fix by @cowtowncoder, w/ Claude code)
+#781: (smile) `SmileGenerator.writeNumber(String)` should validate number length
+  against configured `StreamReadConstraints`, not global defaults
+ (contributed by @pjfanning)
 
 3.2.3 (not yet released)
 
diff --git a/smile/src/main/java/tools/jackson/dataformat/smile/SmileGenerator.java b/smile/src/main/java/tools/jackson/dataformat/smile/SmileGenerator.java
index fce5d2b4e..ca5361f09 100644
--- a/smile/src/main/java/tools/jackson/dataformat/smile/SmileGenerator.java
+++ b/smile/src/main/java/tools/jackson/dataformat/smile/SmileGenerator.java
@@ -2761,12 +2761,10 @@ protected UnsupportedOperationException _notSupported() {
 
     /**
      * We need access to some reader-side constraints for safety-check within
-     * number decoding for {@linl #writeNumber(String)}: for now we need to
-     * rely on global defaults; should be ok for basic safeguarding.
-     *
-     * @since 2.17
+     * number decoding for {@link #writeNumber(String)}: these are the ones
+     * configured for the underlying factory, accessed via {@link IOContext}.
      */
     protected StreamReadConstraints _streamReadConstraints() {
-        return StreamReadConstraints.defaults();
+        return _ioContext.streamReadConstraints();
     }
 }
diff --git a/smile/src/test/java/tools/jackson/dataformat/smile/gen/SmileGeneratorNumbersTest.java b/smile/src/test/java/tools/jackson/dataformat/smile/gen/SmileGeneratorNumbersTest.java
index 2b27bd1ee..e0b28b171 100644
--- a/smile/src/test/java/tools/jackson/dataformat/smile/gen/SmileGeneratorNumbersTest.java
+++ b/smile/src/test/java/tools/jackson/dataformat/smile/gen/SmileGeneratorNumbersTest.java
@@ -1,14 +1,21 @@
 package tools.jackson.dataformat.smile.gen;
 
 import java.io.ByteArrayOutputStream;
+import java.math.BigInteger;
 import java.util.Arrays;
 
 import org.junit.jupiter.api.Test;
 
+import tools.jackson.core.JsonParser;
+import tools.jackson.core.JsonToken;
+import tools.jackson.core.StreamReadConstraints;
+import tools.jackson.core.exc.StreamConstraintsException;
+
 import tools.jackson.dataformat.smile.*;
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
 
 public class SmileGeneratorNumbersTest
     extends BaseTestForSmile
@@ -203,6 +210,42 @@ public void testNumbersAsString() throws Exception
         assertEquals(10, out.toByteArray().length);
     }
 
+    // [dataformats-binary#781]: `writeNumber(String)` should use the factory's
+    // `StreamReadConstraints` for its number-length guard, not global defaults
+    @Test
+    public void testNumbersAsStringLengthLimit() throws Exception
+    {
+        final int maxLen = 20;
+        SmileFactory f = smileFactoryBuilder(false, false, false)
+                .streamReadConstraints(StreamReadConstraints.builder()
+                        .maxNumberLength(maxLen).build())
+                .build();
+        final String tooLongInt = "1".repeat(maxLen + 1);
+        final String tooLongDec = "1." + "1".repeat(maxLen - 1);
+
+        for (String num : new String[] { tooLongInt, tooLongDec }) {
+            ByteArrayOutputStream out = new ByteArrayOutputStream();
+            try (SmileGenerator gen = (SmileGenerator) f.createGenerator(out)) {
+                gen.writeNumber(num);
+                fail("Should not pass for: "+num);
+            } catch (StreamConstraintsException e) {
+                verifyException(e, "Number value length (" + (maxLen + 1)
+                        + ") exceeds the maximum allowed (" + maxLen + ",");
+            }
+        }
+
+        // And conversely, one at the limit is fine
+        final String atLimit = "1".repeat(maxLen);
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        try (SmileGenerator gen = (SmileGenerator) f.createGenerator(out)) {
+            gen.writeNumber(atLimit);
+        }
+        try (JsonParser p = f.createParser(out.toByteArray())) {
+            assertEquals(JsonToken.VALUE_NUMBER_INT, p.nextToken());
+            assertEquals(new BigInteger(atLimit), p.getBigIntegerValue());
+        }
+    }
+
     // [dataformats-binary#608]
     @Test
     public void testFloat32FromSpecEncoding() throws Exception