diff --git a/README.md b/README.md
index ade2f4cf9..5abd4f0e1 100644
--- a/README.md
+++ b/README.md
@@ -129,22 +129,35 @@ For command reference, see [Commands](https://pipenv.pypa.io/en/latest/commands/
 
 ### Shell Completion
 
-To enable completion in fish, add this to your configuration `~/.config/fish/completions/pipenv.fish`:
+Shell completion is powered by [argcomplete](https://kislyuk.github.io/argcomplete/).
+Install the optional dependency first:
 
-    eval (env _PIPENV_COMPLETE=fish_source pipenv)
+    pip install "pipenv[completion]"
+
+For **fish**, add this to `~/.config/fish/completions/pipenv.fish`:
+
+    register-python-argcomplete --shell fish pipenv | source
 
 There is also a [fish plugin](https://github.com/fisherman/pipenv), which will automatically
 activate your subshells for you!
 
-Alternatively, with zsh, add this to your configuration `~/.zshrc`:
+For **zsh**, add this to your `~/.zshrc`:
+
+    autoload -U bashcompinit
+    bashcompinit
+    eval "$(register-python-argcomplete pipenv)"
 
-    eval "$(_PIPENV_COMPLETE=zsh_source pipenv)"
+For **bash** (including Git Bash on Windows), add this to `~/.bashrc` or `~/.bash_profile`:
 
-Alternatively, with bash, add this to your configuration `~/.bashrc` or `~/.bash_profile`:
+    eval "$(register-python-argcomplete pipenv)"
 
-    eval "$(_PIPENV_COMPLETE=bash_source pipenv)"
+Then reload your shell, and tab completions are enabled!
 
-Magic shell completions are now enabled!
+> **Note:** If you are upgrading from pipenv < 2026.5.0, the old
+> `_PIPENV_COMPLETE` environment variable method no longer works.
+> Replace it with the `register-python-argcomplete` commands above.
+> See the [Shell Completion docs](https://pipenv.pypa.io/en/latest/shell.html#shell-completion)
+> for details.
 
 Usage
 -------
diff --git a/docs/shell.md b/docs/shell.md
index 5ffd0bc14..602f3cb68 100644
--- a/docs/shell.md
+++ b/docs/shell.md
@@ -204,6 +204,35 @@ After reloading your shell, type `pipenv ` and press `Tab` — you should see th
 list of available subcommands. Pressing `Tab` again after a partial subcommand
 name (e.g. `pipenv ins<Tab>`) completes it to `pipenv install`.
 
+#### Git Bash (Windows)
+
+Git Bash supports bash completion. Add to your `~/.bashrc` (typically
+`C:\Users\<you>\.bashrc`):
+
+```bash
+eval "$(register-python-argcomplete pipenv)"
+```
+
+Then restart Git Bash or run `source ~/.bashrc`.
+
+### Migrating from pipenv < 2026.5.0
+
+In older versions of pipenv (before 2026.5.0), shell completion was powered by
+Click and activated with the `_PIPENV_COMPLETE` environment variable:
+
+```bash
+# OLD method — no longer works in pipenv >= 2026.5.0
+eval "$(_PIPENV_COMPLETE=bash_source pipenv)"    # bash
+eval "$(_PIPENV_COMPLETE=zsh_source pipenv)"     # zsh
+_PIPENV_COMPLETE=fish_source pipenv | source     # fish
+```
+
+Starting with pipenv 2026.5.0, shell completion uses
+[argcomplete](https://kislyuk.github.io/argcomplete/) instead. **Replace** the
+lines above with the `register-python-argcomplete` commands shown in the
+[Activation](#activation) section and make sure the `argcomplete` package is
+installed (`pip install "pipenv[completion]"`).
+
 ### Troubleshooting
 
 If completion is not working:
@@ -225,6 +254,10 @@ If completion is not working:
    ```
    It should print a shell function definition without errors.
 
+5. **If you see a migration message** about `_PIPENV_COMPLETE`, you are using
+   the old activation method. See [Migrating from pipenv < 2026.5.0](#migrating-from-pipenv--202650)
+   above.
+
 ## Best Practices for Shell Configuration
 
 ### Proper PATH Configuration
diff --git a/pipenv/cli/command.py b/pipenv/cli/command.py
index 13b4fd243..75ab7f693 100644
--- a/pipenv/cli/command.py
+++ b/pipenv/cli/command.py
@@ -627,6 +627,23 @@ def cli():
     from pipenv.utils.shell import system_which
     from pipenv.utils.virtualenv import do_where, warn_in_virtualenv
 
+    # Handle legacy _PIPENV_COMPLETE env var from the Click-based CLI.
+    # Since pipenv 2026.5.0, shell completion uses argcomplete instead.
+    # Detect the old mechanism and provide a helpful migration message.
+    if os.environ.get("_PIPENV_COMPLETE"):
+        print(
+            "Shell completion has changed in pipenv >= 2026.5.0.\n"
+            "The _PIPENV_COMPLETE environment variable is no longer supported.\n"
+            "\n"
+            "To enable shell completion, install the completion extra and use:\n"
+            "  pip install pipenv[completion]\n"
+            '  eval "$(register-python-argcomplete pipenv)"\n'
+            "\n"
+            "For more details, see: https://pipenv.pypa.io/en/latest/shell.html#shell-completion",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
     parser = build_parser()
 
     # Enable shell completion when argcomplete is installed.
diff --git a/pipenv/routines/audit.py b/pipenv/routines/audit.py
index 781d3c20a..6e4d71fd3 100644
--- a/pipenv/routines/audit.py
+++ b/pipenv/routines/audit.py
@@ -9,6 +9,7 @@
 import logging
 import subprocess
 import sys
+import tempfile
 
 from pipenv.utils import console, err
 from pipenv.utils.processes import run_command
@@ -115,9 +116,9 @@ def build_audit_options(
     if aliases:
         options.append("--aliases")
 
-    # Use lockfile (pyproject.toml / pylock.toml)
-    if use_lockfile:
-        options.append("--locked")
+    # Note: use_lockfile is handled in do_audit by generating a temporary
+    # requirements file from Pipfile.lock, since pip-audit's --locked flag
+    # does not support Pipfile.lock format.
 
     # Requirements file
     if requirements_file:
@@ -165,7 +166,7 @@ def do_audit(  # noqa: PLR0913
 
     Supports auditing from:
     - The current virtualenv (default)
-    - pyproject.toml / pylock.toml files (with --locked flag)
+    - Pipfile.lock (with --locked flag, converted to requirements format for pip-audit)
     """
     if not verbose:
         logging.getLogger("pipenv").setLevel(logging.ERROR if quiet else logging.WARN)
@@ -222,9 +223,35 @@ def do_audit(  # noqa: PLR0913
     python_path = project_python(project, system=system)
     cmd = [python_path, "-m", "pip_audit"] + options
 
-    # If using lockfile mode, add the project directory path
+    # If using lockfile mode, generate a temporary requirements file from
+    # Pipfile.lock and pass it via -r.  pip-audit's own --locked flag only
+    # recognises pylock.toml / poetry.lock / uv.lock — not Pipfile.lock.
+    tmp_requirements = None
     if use_lockfile:
-        cmd.append(project.project_directory)
+        if not project.lockfile_exists:
+            err.print(
+                "[red]Pipfile.lock not found. Run 'pipenv lock' first.[/red]"
+            )
+            sys.exit(1)
+
+        from pipenv.utils.requirements import requirements_from_lockfile
+
+        lockfile = project.load_lockfile(expand_env_vars=False)
+        deps = {}
+        deps.update(lockfile.get("default", {}))
+        deps.update(lockfile.get("develop", {}))
+
+        lines = requirements_from_lockfile(
+            deps, include_hashes=False, include_markers=True
+        )
+
+        tmp_requirements = tempfile.NamedTemporaryFile(
+            mode="w", suffix=".txt", prefix="pipenv-audit-", delete=False
+        )
+        tmp_requirements.write("\n".join(lines))
+        tmp_requirements.flush()
+        tmp_requirements.close()
+        cmd.extend(["-r", tmp_requirements.name])
 
     if not quiet and not project.s.is_quiet() and verbose:
         console.print(f"[dim]Running: {' '.join(cmd)}[/dim]")
@@ -240,3 +267,8 @@ def do_audit(  # noqa: PLR0913
     except Exception as e:
         err.print(f"[red]Error running pip-audit: {str(e)}[/red]")
         sys.exit(1)
+    finally:
+        if tmp_requirements is not None:
+            import os
+
+            os.unlink(tmp_requirements.name)