diff a/src/jdk.incubator.code/share/classes/jdk/incubator/code/InternalAbstractOp.java b/src/jdk.incubator.code/share/classes/jdk/incubator/code/InternalAbstractOp.java
--- /dev/null
+++ b/src/jdk.incubator.code/share/classes/jdk/incubator/code/InternalAbstractOp.java
@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) 2024, 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.incubator.code;
+
+import jdk.incubator.code.dialect.core.CoreType;
+import jdk.incubator.code.dialect.core.FunctionType;
+import jdk.incubator.code.extern.OpWriter;
+
+import java.util.*;
+
+sealed abstract class InternalAbstractOp implements Op permits AbstractOp, AbstractOp.Terminating {
+
+    // Set when op is placed in a block or as a root operation, otherwise null when unplaced
+    // @@@ stable value?
+    Result result;
+
+    // null if not specified
+    // @@@ stable value?
+    Location location;
+
+    final List<Value> operands;
+
+    /**
+     * Constructs an operation with a list of operands.
+     *
+     * @param operands the list of operands, a copy of the list is performed if required.
+     * @throws IllegalArgumentException if an operand's declaring block is built.
+     */
+    protected InternalAbstractOp(List<? extends Value> operands) {
+        for (Value operand : operands) {
+            if (operand.isBuilt()) {
+                throw new IllegalArgumentException("Operand's declaring block is built: " + operand);
+            }
+        }
+        this.operands = List.copyOf(operands);
+    }
+
+    /**
+     * Constructs an operation with operands mapped from, and location copied from, the given operation.
+     * <p>
+     * The constructed operation's operands are the values mapped, in order, from the given operation's operands using
+     * the given code context. The new operation's location is the given operation's location, if any.
+     *
+     * @param that the operation
+     * @param cc   the code context
+     * @throws IllegalArgumentException if an operation's operand has no context mapping
+     * @throws IllegalArgumentException if a mapped value's declaring block is built.
+     */
+    protected InternalAbstractOp(InternalAbstractOp that, CodeContext cc) {
+        this(cc.getValues(that.operands));
+        this.location = that.location;
+    }
+
+    @Override
+    public final void setLocation(Location l) {
+        // @@@ Fail if location != null?
+        if (isRoot() || (result != null && result.block.isBuilt())) {
+            throw new IllegalStateException("Built operation");
+        }
+
+        location = l;
+    }
+
+    @Override
+    public final Location location() {
+        return location;
+    }
+
+    @Override
+    public final Block parent() {
+        if (isRoot() || result == null) {
+            return null;
+        }
+
+        if (!result.block.isBuilt()) {
+            throw new IllegalStateException("Parent block is unobservable");
+        }
+
+        return result.block;
+    }
+
+    @Override
+    public final List<Body> children() {
+        return bodies();
+    }
+
+    /**
+     * {@inheritDoc}
+     * @implSpec this implementation returns an unmodifiable empty list.
+     */
+    @Override
+    public List<Body> bodies() {
+        return List.of();
+    }
+
+    @Override
+    public final Result result() {
+        return result == Result.ROOT_RESULT ? null : result;
+    }
+
+    @Override
+    public final List<Value> operands() {
+        return operands;
+    }
+
+    @Override
+    public final FunctionType opSignature() {
+        List<CodeType> operandTypes = operands.stream().map(Value::type).toList();
+        return CoreType.functionType(resultType(), operandTypes);
+    }
+
+    @Override
+    public final List<Value> capturedValues() {
+        Set<Value> cvs = new LinkedHashSet<>();
+
+        Deque<Body> bodyStack = new ArrayDeque<>();
+        for (Body childBody : bodies()) {
+            Body.capturedValues(cvs, bodyStack, childBody);
+        }
+        return new ArrayList<>(cvs);
+    }
+
+    @Override
+    public final void buildAsRoot() {
+        if (result == Result.ROOT_RESULT) {
+            return;
+        }
+        if (!bodies().stream().allMatch(Body::isIsolated)) {
+            throw new IllegalStateException("One of the operation bodies is not isolated");
+        }
+        if (!operands().isEmpty()) {
+            throw new IllegalStateException("Operation has operands");
+        }
+        if (!successors().isEmpty()) {
+            throw new IllegalStateException("Operation has successors");
+        }
+        if (result != null) {
+            throw new IllegalStateException("Operation is placed in a block");
+        }
+        result = Result.ROOT_RESULT;
+    }
+
+    @Override
+    public final boolean isRoot() {
+        return result == Result.ROOT_RESULT;
+    }
+
+    @Override
+    public final boolean isPlacedInBlock() {
+        return !isRoot() && result != null;
+    }
+
+    @Override
+    public final String toText() {
+        return OpWriter.toText(this);
+    }
+}