diff --git a/CHANGELOG.md b/CHANGELOG.md
index dd7a99d..d310c9b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,20 @@
 ## [Unreleased]
 
+### Fixed
+
+- **Play upload keystore no longer bakes a trailing newline into the stored
+  password** (MOB-71). `Mix.shell().prompt/1` returns the whole input line
+  including the trailing `\n`, and `MobDev.GooglePlay.SetupWizard.generate_keystore/2`
+  passed that value verbatim to both `keytool -storepass` and
+  `android/keystore.properties`. The keystore then contained a password
+  ending in `\n` that Gradle read literally on every subsequent release
+  signing — a value nobody could re-type at the next Play upload, and only
+  discovered when a signed AAB fails to upload with a stack trace deep
+  inside `bundletool`. The three prompts (passphrase, name, org) are now
+  trimmed at the source (`prompt_trimmed/2`), and
+  `keystore_properties_content/1` is extracted and public so the trim is
+  covered by revert-verified unit tests.
+
 ### Changed
 
 - **`mix mob.deploy` now freezes an explicit target set before doing work**
diff --git a/lib/mob_dev/google_play/setup_wizard.ex b/lib/mob_dev/google_play/setup_wizard.ex
index 0abdcc2..dc860b1 100644
--- a/lib/mob_dev/google_play/setup_wizard.ex
+++ b/lib/mob_dev/google_play/setup_wizard.ex
@@ -122,9 +122,9 @@ defmodule MobDev.GooglePlay.SetupWizard do
 
   defp generate_keystore(shell, path) do
     shell.info("")
-    passphrase = shell.prompt("  Keystore passphrase (remember this — back it up!): ")
-    name = shell.prompt("  Your full name: ")
-    org = shell.prompt("  Organisation (or your name): ")
+    passphrase = prompt_trimmed(shell, "  Keystore passphrase (remember this — back it up!): ")
+    name = prompt_trimmed(shell, "  Your full name: ")
+    org = prompt_trimmed(shell, "  Organisation (or your name): ")
 
     args = [
       "-genkey",
@@ -169,15 +169,39 @@ defmodule MobDev.GooglePlay.SetupWizard do
 
   defp write_keystore_properties(path, passphrase) do
     unless File.exists?(path) do
-      File.write!(path, """
-      storeFile=upload_jks.keystore
-      storePassword=#{passphrase}
-      keyAlias=upload
-      keyPassword=#{passphrase}
-      """)
+      File.write!(path, keystore_properties_content(passphrase))
     end
   end
 
+  @doc """
+  Render the `android/keystore.properties` file body for `passphrase`.
+
+  The passphrase is trimmed so a trailing newline from `Mix.shell().prompt/1`
+  (or leading/trailing whitespace pasted from a password manager) cannot be
+  baked into the stored password — Gradle's signing config reads the file
+  literally, so a `storePassword=secret\\n` line signs releases with a
+  password nobody can retype on the next upload. See MOB-71.
+  """
+  @spec keystore_properties_content(binary()) :: binary()
+  def keystore_properties_content(passphrase) when is_binary(passphrase) do
+    trimmed = String.trim(passphrase)
+
+    """
+    storeFile=upload_jks.keystore
+    storePassword=#{trimmed}
+    keyAlias=upload
+    keyPassword=#{trimmed}
+    """
+  end
+
+  # `Mix.shell().prompt/1` includes the trailing newline in its return value;
+  # a raw passphrase carries that newline everywhere it is used — the keytool
+  # `-storepass` arg, the `keystore.properties` file, the -dname CN/O fields.
+  # Trimming at the source is safer than fixing each call site downstream.
+  defp prompt_trimmed(shell, question) do
+    shell.prompt(question) |> String.trim()
+  end
+
   defp step_manual_account_creation(shell, dry?) do
     shell.info("")
     shell.info(yellow() <> "── Manual prerequisite steps ──" <> reset())
diff --git a/test/mob_dev/google_play/setup_wizard_test.exs b/test/mob_dev/google_play/setup_wizard_test.exs
index d09da71..5ceb73d 100644
--- a/test/mob_dev/google_play/setup_wizard_test.exs
+++ b/test/mob_dev/google_play/setup_wizard_test.exs
@@ -9,6 +9,7 @@ defmodule MobDev.GooglePlay.SetupWizardTest do
 
   alias MobDev.GooglePlay.CloudSetup
   alias MobDev.GooglePlay.PlaySetup
+  alias MobDev.GooglePlay.SetupWizard
 
   # ── Key filename derivation ──────────────────────────────────────────────────
   # Mirrors the logic in SetupWizard.default_key_filename/1.
@@ -130,4 +131,42 @@ defmodule MobDev.GooglePlay.SetupWizardTest do
         end
     end
   end
+
+  # ── keystore.properties passphrase handling (MOB-71) ─────────────────────────
+
+  describe "keystore_properties_content/1" do
+    test "does NOT bake a trailing newline from Mix.shell().prompt/1 into the stored password" do
+      # `Mix.shell().prompt/1` returns the whole line including the trailing
+      # \n. Before MOB-71 that newline flowed straight into `-storepass` at
+      # keytool time AND into `keystore.properties`, so Gradle later signed
+      # every release with `secret\n` — a password nobody can retype on the
+      # next Play upload. Revert the `String.trim/1` in
+      # `keystore_properties_content/1` and this assertion fails: the file
+      # would contain `storePassword=secret\n\nkeyAlias=...`.
+      content = SetupWizard.keystore_properties_content("secret\n")
+
+      assert content =~ ~r/^storePassword=secret$/m
+      assert content =~ ~r/^keyPassword=secret$/m
+      refute content =~ "storePassword=secret\n\n"
+    end
+
+    test "strips leading/trailing whitespace so a pasted password does not carry surrounding blanks" do
+      # Password managers often add a leading space when auto-typing into a
+      # terminal prompt; users occasionally add a trailing space by habit.
+      # Either would produce a keystore Gradle can never open again.
+      content = SetupWizard.keystore_properties_content("  secret  ")
+
+      assert content =~ ~r/^storePassword=secret$/m
+      assert content =~ ~r/^keyPassword=secret$/m
+    end
+
+    test "leaves an already-clean passphrase alone" do
+      content = SetupWizard.keystore_properties_content("secret")
+
+      assert content =~ ~r/^storePassword=secret$/m
+      assert content =~ ~r/^keyPassword=secret$/m
+      assert content =~ ~r/^storeFile=upload_jks\.keystore$/m
+      assert content =~ ~r/^keyAlias=upload$/m
+    end
+  end
 end