diff --git a/fleetd/src/main/java/dev/ltms/fleet/session/GitWorktrees.java b/fleetd/src/main/java/dev/ltms/fleet/session/GitWorktrees.java
index eacffb9..fb0a5fc 100644
--- a/fleetd/src/main/java/dev/ltms/fleet/session/GitWorktrees.java
+++ b/fleetd/src/main/java/dev/ltms/fleet/session/GitWorktrees.java
@@ -140,7 +140,7 @@ public final class GitWorktrees implements Worktrees {
         if (exitCode("git", "-C", repoRoot, "config", "--get", "remote.origin.url") != 0) {
             return;
         }
-        String origin = exec("git", "-C", repoRoot, "config", "--get", "remote.origin.url").trim();
+        String origin = execRedacted("git", "-C", repoRoot, "config", "--get", "remote.origin.url").trim();
         URI uri;
         try {
             uri = new URI(origin);
@@ -156,6 +156,9 @@ public final class GitWorktrees implements Worktrees {
             throw new WorktreeException("origin URL has invalid HTTPS user info; cannot provision safely");
         }
         String cleanOrigin = origin.substring(0, schemeEnd) + origin.substring(userInfoEnd + 1);
+        // Plain exec, not execRedacted, is correct here: this call WRITES cleanOrigin (already
+        // stripped of user-info above) rather than reading a URL back from stdout, so there is
+        // nothing secret left in either its argv or its stdout to redact.
         exec("git", "-C", repoRoot, "remote", "set-url", "origin", cleanOrigin);
         log.info("removed HTTPS user info from forge origin before provisioning worktree");
     }
@@ -165,7 +168,7 @@ public final class GitWorktrees implements Worktrees {
         if (exitCode("git", "-C", worktreePath, "remote", "get-url", "--all", "origin") != 0) {
             return;
         }
-        String origins = exec("git", "-C", worktreePath, "remote", "get-url", "--all", "origin");
+        String origins = execRedacted("git", "-C", worktreePath, "remote", "get-url", "--all", "origin");
         for (String origin : origins.split("\\R")) {
             try {
                 URI uri = new URI(origin);
@@ -328,7 +331,7 @@ public final class GitWorktrees implements Worktrees {
         if (exitCode("git", "-C", repoRoot, "config", "--get", "remote.origin.url") != 0) {
             return;
         }
-        String origin = exec("git", "-C", repoRoot, "config", "--get", "remote.origin.url").trim();
+        String origin = execRedacted("git", "-C", repoRoot, "config", "--get", "remote.origin.url").trim();
         URI uri;
         try {
             uri = new URI(origin);
@@ -711,9 +714,17 @@ public final class GitWorktrees implements Worktrees {
         return exec(Map.of(), true, command);
     }
 
-    /** Shared implementation for {@link #exec(Map, String...)} and {@link #execRedacted(String...)}.
-     *  {@code redactOutput} suppresses captured stdout from both failure messages below. */
-    private String exec(Map<String, String> extraEnv, boolean redactOutput, String... command) {
+    /**
+     * Shared implementation for {@link #exec(Map, String...)} and {@link #execRedacted(String...)}.
+     * {@code redactOutput} suppresses captured stdout from both failure messages below.
+     *
+     * <p>Package-private, not {@code private}: also a test seam, the same way the
+     * {@code afterWorktreeAdded} constructor parameter is. It lets a test drive the redaction
+     * guarantee directly — a synthetic failing command whose stdout carries a test marker passed
+     * through {@code extraEnv} rather than argv — without depending on finding a real git failure
+     * mode that happens to echo a URL onto stdout before exiting non-zero.
+     */
+    String exec(Map<String, String> extraEnv, boolean redactOutput, String... command) {
         String out;
         int code;
         Process p;
diff --git a/fleetd/src/test/java/dev/ltms/fleet/session/GitWorktreesTest.java b/fleetd/src/test/java/dev/ltms/fleet/session/GitWorktreesTest.java
index 033e0be..74e99eb 100644
--- a/fleetd/src/test/java/dev/ltms/fleet/session/GitWorktreesTest.java
+++ b/fleetd/src/test/java/dev/ltms/fleet/session/GitWorktreesTest.java
@@ -17,6 +17,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
@@ -476,6 +477,36 @@ class GitWorktreesTest {
                         + capturedMessages());
     }
 
+    /**
+     * CB-189 review fix. Even a FAILING command that read a credential onto its stdout must never
+     * let that value reach the thrown {@link WorktreeException}'s message — this is gap 4 from the
+     * CB-189 issue, and the reason {@link GitWorktrees#execRedacted} exists at all. Drives the
+     * shared {@code exec}/{@code execRedacted} seam directly (it is package-private for exactly this,
+     * the same way the {@code afterWorktreeAdded} constructor parameter is a test seam) with a
+     * synthetic, non-git command whose stdout carries a marker — passed through the environment,
+     * never through argv, so the marker cannot leak via the command line that IS always printed
+     * unconditionally in the exception message — and which exits non-zero. This isolates the
+     * redaction guarantee itself rather than depending on a specific git failure mode that happens to
+     * echo a URL onto stdout before failing: none of the git subcommands this class actually runs was
+     * found to have one (a corrupted config makes {@code git config --get} fail before it ever reads
+     * the target key, so its output never carries the URL either). The marker is generated per-test
+     * run and injected only by the test, never a real-looking credential, so even a failing assertion
+     * could not itself print a secret.
+     */
+    @Test
+    void execRedactedNeverCopiesFailingCommandOutputIntoTheExceptionMessage(@TempDir Path tmp) {
+        String marker = "cb189-marker-" + System.nanoTime();
+        GitWorktrees worktrees = new GitWorktrees(tmp.toString());
+
+        WorktreeException thrown = assertThrows(WorktreeException.class, () -> worktrees.exec(
+                Map.of("MARKER", marker), true, "sh", "-c", "echo \"$MARKER\"; exit 7"));
+
+        assertNotNull(thrown.getMessage());
+        assertFalse(thrown.getMessage().contains(marker),
+                "a failing command's captured stdout leaked into the exception message: "
+                        + thrown.getMessage());
+    }
+
     /** Neutralizing must not look like work in progress, or a worker would commit it into its PR. */
     @Test
     void theNeutralizedConfigIsNotAPendingLocalModification(@TempDir Path tmp) throws Exception {