diff --git a/eo-maven-plugin/src/main/java/org/eolang/maven/Unplace.java b/eo-maven-plugin/src/main/java/org/eolang/maven/Unplace.java
index 6b69f694a4c..e0a14cd5730 100644
--- a/eo-maven-plugin/src/main/java/org/eolang/maven/Unplace.java
+++ b/eo-maven-plugin/src/main/java/org/eolang/maven/Unplace.java
@@ -25,6 +25,7 @@
 
 import java.io.File;
 import java.nio.file.Path;
+import java.util.regex.Pattern;
 
 /**
  * Make program name from a path.
@@ -38,6 +39,11 @@ final class Unplace {
      */
     private final Path parent;
 
+    /**
+     * The file extension.
+     */
+    private final String extension;
+
     /**
      * Ctor.
      * @param dir The name of the parent dir
@@ -51,7 +57,26 @@ final class Unplace {
      * @param dir The name of the parent dir
      */
     Unplace(final Path dir) {
+        this(dir, ".eo");
+    }
+
+    /**
+     * Ctor.
+     * @param dir The name of the parent dir
+     * @param extension The file extension
+     */
+    Unplace(final File dir, final String extension) {
+        this(dir.toPath(), extension);
+    }
+
+    /**
+     * Main Ctor.
+     * @param dir The name of the parent dir
+     * @param extension The file extension
+     */
+    Unplace(final Path dir, final String extension) {
         this.parent = dir;
+        this.extension = extension;
     }
 
     /**
@@ -62,6 +87,9 @@ final class Unplace {
     public String make(final Path file) {
         return file.toString().substring(
             this.parent.toString().length() + 1
-        ).replaceAll(".eo$", "").replace(File.separator, ".");
+        ).replaceAll(
+            Pattern.quote(this.extension).concat("$"),
+            ""
+        ).replace(File.separator, ".");
     }
 }
diff --git a/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojo.java b/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojo.java
index 4c12fd5190c..99b0954771c 100644
--- a/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojo.java
+++ b/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojo.java
@@ -117,6 +117,14 @@ public String description() {
         );
     }
 
+    /**
+     * The tojo phi.
+     * @return The phi.
+     */
+    public Path phi() {
+        return Paths.get(this.attribute(ForeignTojos.Attribute.PHI));
+    }
+
     /**
      * The tojo hash.
      * @return The hash.
@@ -178,6 +186,48 @@ public boolean notParsed() {
         return res;
     }
 
+    /**
+     * Check if the given tojo has not been parsed to phi-expression.
+     *
+     * @return True if the tojo has not been parsed to phi-expression.
+     */
+    public boolean notPhied() {
+        boolean res = true;
+        if (this.delegate.exists(ForeignTojos.Attribute.PHI.getKey())
+            && this.delegate.exists(ForeignTojos.Attribute.XMIR.getKey())) {
+            final Path phi = this.phi();
+            if (phi.toFile().lastModified() >= this.xmir().toFile().lastModified()) {
+                Logger.debug(
+                    this, "Already executed xmir-to-phi: %s to %[file]s (it's newer than the XMIR)",
+                    this.identifier(), phi
+                );
+                res = false;
+            }
+        }
+        return res;
+    }
+
+    /**
+     * Check if the given tojo has not been parsed to XMIR from phi-expression.
+     *
+     * @return True if the tojo has not been parsed from XMIR to phi-expression.
+     */
+    public boolean notUnphied() {
+        boolean res = true;
+        if (this.delegate.exists(ForeignTojos.Attribute.XMIR.getKey())
+            && this.delegate.exists(ForeignTojos.Attribute.PHI.getKey())) {
+            final Path xmir = this.xmir();
+            if (xmir.toFile().lastModified() >= this.phi().toFile().lastModified()) {
+                Logger.debug(
+                    this, "Already executed phi-to-xmir: %s to %[file]s (it's newer than the phi)",
+                    this.identifier(), xmir
+                );
+                res = false;
+            }
+        }
+        return res;
+    }
+
     /**
      * Checks if tojo has hash.
      * @return True if has hash, false otherwise.
@@ -309,6 +359,16 @@ public ForeignTojo withScope(final String scope) {
         return this;
     }
 
+    /**
+     * Set the phi.
+     * @param phi The phi.
+     * @return The tojo itself.
+     */
+    public ForeignTojo withPhi(final Path phi) {
+        this.delegate.set(ForeignTojos.Attribute.PHI.getKey(), phi);
+        return this;
+    }
+
     /**
      * Return the scope of the tojo.
      * @return The scope.
diff --git a/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojos.java b/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojos.java
index a218905f0b9..bef84f838e7 100644
--- a/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojos.java
+++ b/eo-maven-plugin/src/main/java/org/eolang/maven/tojos/ForeignTojos.java
@@ -361,7 +361,12 @@ enum Attribute {
         /**
          * Git SHA of the object in the {@code objectionary/home}.
          */
-        HASH("hash");
+        HASH("hash"),
+
+        /**
+         * Absolute path of the parsed from XMIR to phi-expression file.
+         */
+        PHI("phi");
 
         /**
          * Attribute name.
diff --git a/eo-maven-plugin/src/test/java/org/eolang/maven/UnplaceTest.java b/eo-maven-plugin/src/test/java/org/eolang/maven/UnplaceTest.java
index 63698b7f261..6185a0110e2 100644
--- a/eo-maven-plugin/src/test/java/org/eolang/maven/UnplaceTest.java
+++ b/eo-maven-plugin/src/test/java/org/eolang/maven/UnplaceTest.java
@@ -26,6 +26,8 @@
 import java.nio.file.Paths;
 import org.hamcrest.MatcherAssert;
 import org.hamcrest.Matchers;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
@@ -55,4 +57,31 @@ void makesName(
         );
     }
 
+    @ParameterizedTest
+    @CsvSource({
+        "/tmp/foo/bar, /tmp/foo/bar/a/b/c.phi, a.b.c",
+        "/tmp/foo/bar, /tmp/foo/bar/a/b/.cd.ef.phi, a.b..cd.ef"
+    })
+    void makesNameWithCustomExtension(
+        final String base,
+        final String source,
+        final String name
+    ) {
+        MatcherAssert.assertThat(
+            CatalogsTest.TO_ADD_MESSAGE,
+            new Unplace(Paths.get(base), ".phi").make(
+                Paths.get(source)
+            ),
+            Matchers.equalTo(name)
+        );
+    }
+
+    @Test
+    void interpretsExtensionAsLiteralString() {
+        Assertions.assertDoesNotThrow(
+            () -> new Unplace(Paths.get("/tmp/foo/bar"), "(")
+                .make(Paths.get("/tmp/foo/bar/a/b/c(")),
+            "Extension interpreted not as literal string"
+        );
+    }
 }