diff --git a/README.md b/README.md
index c1fe602..af7cbd6 100644
--- a/README.md
+++ b/README.md
@@ -65,29 +65,17 @@ Installed through a `sitecustomize.py` MetaPathFinder hook, so it runs at interp
 
 ### Auth issues
 
-- **`Anthropic 401 authentication failed`** or **`No Anthropic credentials found`**: Hermes reads Claude subscription credentials from `~/.claude/.credentials.json`. If Claude Code is authenticated (e.g. in macOS Keychain) but that file is missing or stale, Hermes fails even when Claude Code itself works. Fix:
+- **`Anthropic 401 authentication failed`** or **`No Anthropic credentials found`**: Hermes reads Claude subscription credentials from `~/.claude/.credentials.json`. If Claude Code is authenticated (e.g. in macOS Keychain) but that file is missing or stale, Hermes fails even when Claude Code itself works.
+
+  On macOS, `install.sh` v1.1.1+ auto-mirrors the `Claude Code-credentials` Keychain entry into `~/.claude/.credentials.json` on every run, so re-running the installer is usually enough. Full fix:
 
   1. Refresh Claude subscription login:
      ```bash
      claude auth login --claudeai
      ```
-  2. **macOS only** — mirror the Keychain `Claude Code-credentials` entry into the file Hermes reads:
+  2. Re-run the installer to re-mirror credentials (macOS) and reload the patch:
      ```bash
-     python3 - <<'PY'
-     import subprocess
-     from pathlib import Path
-
-     secret = subprocess.check_output(
-         ['security', 'find-generic-password', '-s', 'Claude Code-credentials', '-w'],
-         text=True,
-     ).strip()
-
-     cred_path = Path.home() / '.claude' / '.credentials.json'
-     cred_path.parent.mkdir(parents=True, exist_ok=True)
-     cred_path.write_text(secret)
-     cred_path.chmod(0o600)
-     print(f'wrote {cred_path}')
-     PY
+     ./install.sh
      ```
   3. Remove stale `ANTHROPIC_TOKEN` / `ANTHROPIC_API_KEY` values from `~/.hermes/.env` — they can override subscription auth.
   4. Reset cached credentials:
@@ -99,7 +87,26 @@ Installed through a `sitecustomize.py` MetaPathFinder hook, so it runs at interp
      hermes chat -q 'Reply with exactly: AUTH TEST OK' --provider anthropic -m claude-sonnet-4-6 -Q
      ```
 
-  Credit: this macOS Keychain mirror step was written up by [@DrQbz](https://github.com/DrQbz) in [issue #5](https://github.com/kristianvast/hermes-claude-auth/issues/5).
+  If the auto-mirror doesn't work (e.g. your Keychain entry is under a different service name), mirror it manually:
+  ```bash
+  python3 - <<'PY'
+  import subprocess
+  from pathlib import Path
+
+  secret = subprocess.check_output(
+      ['security', 'find-generic-password', '-s', 'Claude Code-credentials', '-w'],
+      text=True,
+  ).strip()
+
+  cred_path = Path.home() / '.claude' / '.credentials.json'
+  cred_path.parent.mkdir(parents=True, exist_ok=True)
+  cred_path.write_text(secret)
+  cred_path.chmod(0o600)
+  print(f'wrote {cred_path}')
+  PY
+  ```
+
+  Credit: the macOS Keychain mirror approach was written up by [@DrQbz](https://github.com/DrQbz) in [issue #5](https://github.com/kristianvast/hermes-claude-auth/issues/5) and is now automated in `install.sh`.
 
 ### Billing / routing issues
 
diff --git a/anthropic_billing_bypass.py b/anthropic_billing_bypass.py
index 345921c..86af169 100644
--- a/anthropic_billing_bypass.py
+++ b/anthropic_billing_bypass.py
@@ -87,11 +87,16 @@ Version history
   header, ``?beta=true`` query param on ``/v1/messages``.  Addresses the
   "Third-party apps now draw from your extra usage, not your plan limits"
   400 error introduced by Anthropic's 2026-04-14+ validator tightening.
+- 1.1.1 (2026-04-22): Installer only — ``install.sh`` now auto-mirrors the
+  ``Claude Code-credentials`` macOS Keychain entry into
+  ``~/.claude/.credentials.json`` on Darwin hosts, so the oneliner works
+  end-to-end on macOS without a manual post-install step.  Bypass module
+  itself is unchanged; version bump tracks the release.
 """
 
 from __future__ import annotations
 
-__version__ = "1.1.0"
+__version__ = "1.1.1"
 
 import hashlib
 import inspect
diff --git a/install.sh b/install.sh
index c5b5934..4e592eb 100755
--- a/install.sh
+++ b/install.sh
@@ -61,6 +61,27 @@ fi
 chmod 644 "$SITECUSTOMIZE"
 printf "${GREEN}[✓] Installed hook into %s${RESET}\n" "$SITECUSTOMIZE"
 
+# macOS: hermes-agent reads Claude subscription credentials from
+# ~/.claude/.credentials.json, but Claude Code on macOS stores them in
+# Keychain only.  Mirror the Keychain entry into the file so auth works
+# out of the box.  No-op on Linux (Claude Code writes the file directly).
+if [ "$(uname -s)" = "Darwin" ]; then
+    CRED_FILE="$HOME/.claude/.credentials.json"
+    if KEYCHAIN_CRED="$(security find-generic-password -s 'Claude Code-credentials' -w 2>/dev/null)"; then
+        mkdir -p "$(dirname "$CRED_FILE")"
+        if [ ! -f "$CRED_FILE" ] || [ "$(cat "$CRED_FILE" 2>/dev/null)" != "$KEYCHAIN_CRED" ]; then
+            printf '%s' "$KEYCHAIN_CRED" > "$CRED_FILE"
+            chmod 600 "$CRED_FILE"
+            printf "${GREEN}[✓] Mirrored Claude Code credentials from Keychain → %s${RESET}\n" "$CRED_FILE"
+        else
+            printf "${GREEN}[✓] Claude Code credentials file already matches Keychain${RESET}\n"
+        fi
+    elif [ ! -f "$CRED_FILE" ]; then
+        printf "${YELLOW}[!] macOS detected but no 'Claude Code-credentials' Keychain entry found${RESET}\n"
+        printf "    Run: claude auth login --claudeai\n"
+    fi
+fi
+
 if systemctl --user is-active hermes-gateway.service >/dev/null 2>&1; then
     systemctl --user restart hermes-gateway.service
     printf "${GREEN}[✓] Restarted hermes-gateway.service${RESET}\n"
diff --git a/tests/test_install.sh b/tests/test_install.sh
index ad619e1..0e1d81b 100755
--- a/tests/test_install.sh
+++ b/tests/test_install.sh
@@ -139,6 +139,92 @@ else
     fail "$T5" "install.sh or uninstall.sh --purge exited non-zero"
 fi
 
+# macOS Keychain mirror tests — fake `uname -s` → Darwin and a fake
+# `security find-generic-password` via PATH shims so install.sh takes the
+# Darwin branch without an actual Mac.
+FAKE_BIN="$FAKE_HOME/fakebin"
+mkdir -p "$FAKE_BIN"
+cat > "$FAKE_BIN/uname" <<'UNAME_EOF'
+#!/usr/bin/env bash
+if [ "${1:-}" = "-s" ]; then
+    echo Darwin
+    exit 0
+fi
+exec /usr/bin/uname "$@"
+UNAME_EOF
+chmod +x "$FAKE_BIN/uname"
+
+FAKE_CRED='{"oauth":{"accessToken":"sk-ant-fake","refreshToken":"rt-fake","expiresAt":0}}'
+cat > "$FAKE_BIN/security" <<SECURITY_EOF
+#!/usr/bin/env bash
+if [ "\${1:-}" = "find-generic-password" ] && [ "\${2:-}" = "-s" ] \\
+    && [ "\${3:-}" = "Claude Code-credentials" ] && [ "\${4:-}" = "-w" ]; then
+    printf '%s' '$FAKE_CRED'
+    exit 0
+fi
+exit 1
+SECURITY_EOF
+chmod +x "$FAKE_BIN/security"
+
+# Test 6: Fresh macOS install mirrors Keychain → ~/.claude/.credentials.json
+T6="Test 6: macOS install mirrors Keychain credentials to credentials.json"
+rm -rf "$FAKE_HOME/.claude"
+if PATH="$FAKE_BIN:$PATH" "$REPO_DIR/install.sh" >/dev/null 2>&1; then
+    ok=1
+    CRED_FILE="$FAKE_HOME/.claude/.credentials.json"
+    assert_file_exists "$T6" "$CRED_FILE" || ok=0
+    if [ -f "$CRED_FILE" ]; then
+        actual="$(cat "$CRED_FILE")"
+        if [ "$actual" != "$FAKE_CRED" ]; then
+            fail "$T6" "credentials content mismatch: got '$actual'"
+            ok=0
+        fi
+        mode="$(python3 -c "import os, sys; print(oct(os.stat(sys.argv[1]).st_mode)[-3:])" "$CRED_FILE")"
+        if [ "$mode" != "600" ]; then
+            fail "$T6" "credentials file mode is $mode, expected 600"
+            ok=0
+        fi
+    fi
+    [ "$ok" -eq 1 ] && pass "$T6"
+else
+    fail "$T6" "install.sh exited non-zero under faked macOS"
+fi
+
+# Test 7: Idempotent macOS re-install does not rewrite file with identical content
+T7="Test 7: macOS re-install does not rewrite identical credentials"
+CRED_FILE="$FAKE_HOME/.claude/.credentials.json"
+if [ -f "$CRED_FILE" ]; then
+    mtime_before="$(python3 -c "import os, sys; print(os.stat(sys.argv[1]).st_mtime_ns)" "$CRED_FILE")"
+    sleep 1
+    if PATH="$FAKE_BIN:$PATH" "$REPO_DIR/install.sh" >/dev/null 2>&1; then
+        mtime_after="$(python3 -c "import os, sys; print(os.stat(sys.argv[1]).st_mtime_ns)" "$CRED_FILE")"
+        if [ "$mtime_before" != "$mtime_after" ]; then
+            fail "$T7" "credentials file rewritten despite identical content"
+        else
+            pass "$T7"
+        fi
+    else
+        fail "$T7" "install.sh exited non-zero on idempotent macOS re-run"
+    fi
+else
+    fail "$T7" "Test 6 did not produce a credentials file; cannot run idempotency check"
+fi
+
+# Test 8: macOS install with no Keychain entry leaves credentials file absent
+T8="Test 8: macOS install with missing Keychain entry leaves no file"
+rm -rf "$FAKE_HOME/.claude"
+cat > "$FAKE_BIN/security" <<'SECURITY_FAIL_EOF'
+#!/usr/bin/env bash
+exit 1
+SECURITY_FAIL_EOF
+chmod +x "$FAKE_BIN/security"
+
+if PATH="$FAKE_BIN:$PATH" "$REPO_DIR/install.sh" >/dev/null 2>&1; then
+    assert_file_not_exists "$T8" "$FAKE_HOME/.claude/.credentials.json" && pass "$T8"
+else
+    fail "$T8" "install.sh exited non-zero when Keychain entry absent"
+fi
+
 TOTAL=$((PASS + FAIL))
 printf '\n%d/%d tests passed\n' "$PASS" "$TOTAL"
 [ "$FAIL" -eq 0 ]