diff --git a/aai_cli/environments.py b/aai_cli/environments.py
index 3739edc9..ded6260d 100644
--- a/aai_cli/environments.py
+++ b/aai_cli/environments.py
@@ -66,10 +66,15 @@ def get(name: str) -> Environment:
     """The named environment, or a clean CLIError if it's unknown."""
     env = ENVIRONMENTS.get(name)
     if env is None:
+        # The bad name can arrive via --env, AAI_ENV, or a profile's stored env, so
+        # the suggestion points at all three rather than assuming the flag.
         raise CLIError(
             f"Unknown environment {name!r}. Known: {', '.join(ENVIRONMENTS)}.",
             error_type="invalid_environment",
             exit_code=2,
+            suggestion=(
+                f"Pass --env with one of: {', '.join(ENVIRONMENTS)}, or unset AAI_ENV if it's set."
+            ),
         )
     return env
 
diff --git a/aai_cli/main.py b/aai_cli/main.py
index cc367828..8e0f5838 100644
--- a/aai_cli/main.py
+++ b/aai_cli/main.py
@@ -11,7 +11,7 @@
     # context type, not the upstream click.Context. Imported for typing only.
     from typer._click.core import Context as ClickContext
 
-from aai_cli import __version__, environments, help_panels, stdio
+from aai_cli import __version__, environments, help_panels, output, stdio
 from aai_cli.commands import (
     account,
     agent,
@@ -108,14 +108,17 @@ def main(
         env = "sandbox000"
     state = AppState(profile=profile, env=env)
     ctx.obj = state
+    # The command's own --json flag isn't parsed yet, so fall back to auto-detection
+    # (JSON when piped/agentic) — the same default run_command uses for its errors.
+    json_mode = output.resolve_json(explicit=False)
     try:
         environments.set_active(resolve_environment(state))
     except CLIError as err:
-        typer.echo(err.message, err=True)
+        output.emit_error(err, json_mode=json_mode)
         raise typer.Exit(code=err.exit_code) from None
     warning = env_override_warning(state)
     if warning:
-        typer.echo(warning, err=True)
+        output.error_console.print(output.warn(warning))
 
 
 # Help-panel grouping: named sub-typers carry their panel on `add_typer`; merged
diff --git a/tests/test_environments.py b/tests/test_environments.py
index ee7bfe6f..d4a36026 100644
--- a/tests/test_environments.py
+++ b/tests/test_environments.py
@@ -21,6 +21,9 @@ def test_get_unknown_raises_cli_error():
     with pytest.raises(CLIError) as exc:
         environments.get("nope")
     assert exc.value.exit_code == 2
+    # Carries a recovery hint covering all three sources of the name (flag/env/profile).
+    assert exc.value.suggestion is not None
+    assert "unset AAI_ENV" in exc.value.suggestion
 
 
 def test_resolve_precedence(monkeypatch):
diff --git a/tests/test_login.py b/tests/test_login.py
index 67aece52..9f80d227 100644
--- a/tests/test_login.py
+++ b/tests/test_login.py
@@ -202,8 +202,27 @@ def test_root_callback_sandbox_overrides_profile_env():
 
 
 def test_unknown_env_exits_2():
+    import json
+
     result = runner.invoke(app, ["--env", "bogus", "whoami"])
     assert result.exit_code == 2
+    # Routed through the standard error path: JSON shape (piped/agentic) + a suggestion,
+    # not a bare echo of the message.
+    payload = json.loads(result.output.strip().splitlines()[-1])
+    assert payload["error"]["type"] == "invalid_environment"
+    assert "unset AAI_ENV" in payload["error"]["suggestion"]
+
+
+def test_unknown_env_human_output_when_interactive():
+    # For an interactive human (not piped/agentic) the callback emits the human
+    # "Error:" + "Suggestion:" pair, not JSON — pinning that resolve_json(explicit=False)
+    # actually consults the auto-detection rather than always forcing JSON.
+    with patch("aai_cli.output._is_agentic", return_value=False):
+        result = runner.invoke(app, ["--env", "bogus", "whoami"])
+    assert result.exit_code == 2
+    assert "Error:" in result.output
+    assert "Suggestion:" in result.output
+    assert '"error"' not in result.output  # not the JSON shape
 
 
 def test_env_override_prints_warning_to_stderr():