diff --git a/features/steps/tdd_session_tell_stream_redaction_steps.py b/features/steps/tdd_session_tell_stream_redaction_steps.py
new file mode 100644
index 000000000..0539f6b45
--- /dev/null
+++ b/features/steps/tdd_session_tell_stream_redaction_steps.py
@@ -0,0 +1,168 @@
+"""Step definitions for TDD session tell --stream redaction tests.
+
+These tests verify that ``session tell --stream`` routes output through the
+Rich console (and therefore through the redaction layer) rather than writing
+directly to ``sys.stdout``.
+
+Issue #10458 (TDD): Write failing test capturing the bug.
+Issue #10460 (Fix): Replace sys.stdout.write loop with console.print.
+"""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+from behave import given, then, when
+from typer.testing import CliRunner
+
+from cleveragents.cli.commands.session import app as session_app
+from cleveragents.domain.models.core.session import SessionService
+
+runner = CliRunner()
+
+_ULID = "01KJ1N8YDN05N29P5RZV4SPDVZ"
+
+
+def _mock_service() -> MagicMock:
+    """Create a MagicMock that passes isinstance checks for SessionService."""
+    svc = MagicMock(spec=SessionService)
+    svc.append_message.return_value = None
+    return svc
+
+
+def _patch_service(context: object, svc: MagicMock) -> None:
+    """Patch session._service and register cleanup."""
+    patcher = patch("cleveragents.cli.commands.session._service", svc)
+    patcher.start()
+    context._cleanup_handlers.append(patcher.stop)  # type: ignore[attr-defined]
+
+
+# ---------------------------------------------------------------------------
+# Background
+# ---------------------------------------------------------------------------
+
+
+@given("a session tell stream redaction mock service")
+def step_setup_mock_service(context: object) -> None:
+    svc = _mock_service()
+    _patch_service(context, svc)
+    context.mock_svc = svc  # type: ignore[attr-defined]
+
+
+# ---------------------------------------------------------------------------
+# When steps
+# ---------------------------------------------------------------------------
+
+
+@when("I invoke session tell with --stream and a sensitive prompt")
+def step_invoke_tell_stream_sensitive(context: object) -> None:
+    """Invoke tell --stream with a prompt that contains a sensitive-looking value."""
+    sensitive_prompt = "my-api-key=sk-secret1234567890abcdef"
+    context.result = runner.invoke(  # type: ignore[attr-defined]
+        session_app,
+        ["tell", "--session", _ULID, "--stream", sensitive_prompt],
+    )
+    context.prompt_used = sensitive_prompt  # type: ignore[attr-defined]
+
+
+@when("I invoke session tell with --stream and a plain prompt")
+def step_invoke_tell_stream_plain(context: object) -> None:
+    """Invoke tell --stream with a plain prompt."""
+    context.result = runner.invoke(  # type: ignore[attr-defined]
+        session_app,
+        ["tell", "--session", _ULID, "--stream", "Hello world"],
+    )
+
+
+# ---------------------------------------------------------------------------
+# Then steps
+# ---------------------------------------------------------------------------
+
+
+@then("the tell command exits with code 0")
+def step_exit_code_0(context: object) -> None:
+    result = context.result  # type: ignore[attr-defined]
+    assert result.exit_code == 0, (
+        f"Expected exit code 0, got {result.exit_code}.\nOutput:\n{result.output}"
+    )
+
+
+@then("sys.stdout.write was not called directly during streaming")
+def step_stdout_write_not_called(context: object) -> None:
+    """Verify that the streaming path does NOT call sys.stdout.write directly.
+
+    After the fix, the streaming path uses console.print() instead of
+    sys.stdout.write(). We verify this by checking that the output was
+    captured by the CliRunner (which captures Rich console output) rather
+    than going through raw sys.stdout.write calls.
+
+    The CliRunner from typer.testing captures output written through the
+    Rich console. If sys.stdout.write were called directly with the
+    character-by-character loop, the output would still appear in
+    result.output (since CliRunner redirects stdout), but the key
+    behavioral difference is that console.print applies markup/redaction.
+
+    We verify the fix by re-running with a patched sys.stdout and confirming
+    that sys.stdout.write is NOT called with individual characters.
+    """
+    import sys
+    from unittest.mock import patch as mock_patch
+
+    write_calls: list[str] = []
+
+    original_write = sys.stdout.write
+
+    def tracking_write(s: str) -> int:
+        write_calls.append(s)
+        return original_write(s)
+
+    svc = _mock_service()
+    sensitive_prompt = "my-api-key=sk-secret1234567890abcdef"
+
+    with (
+        mock_patch("cleveragents.cli.commands.session._service", svc),
+        mock_patch("sys.stdout.write", side_effect=tracking_write),
+    ):
+        runner.invoke(
+            session_app,
+            ["tell", "--session", _ULID, "--stream", sensitive_prompt],
+        )
+
+    # After the fix: sys.stdout.write should NOT be called with individual
+    # characters (single-char strings). The old buggy code called
+    # sys.stdout.write(char) for each character in assistant_content.
+    single_char_writes = [c for c in write_calls if len(c) == 1]
+    assert len(single_char_writes) == 0, (
+        f"sys.stdout.write was called with {len(single_char_writes)} individual "
+        f"characters, indicating the streaming path still uses the direct "
+        f"sys.stdout.write loop instead of console.print. "
+        f"First few chars: {single_char_writes[:10]}"
+    )
+
+
+@then('the tell output contains "{text}"')
+def step_output_contains(context: object, text: str) -> None:
+    result = context.result  # type: ignore[attr-defined]
+    assert text in result.output, (
+        f"Expected '{text}' in output.\nGot:\n{result.output}"
+    )
+
+
+@then("the streaming output was written through the Rich console")
+def step_output_via_console(context: object) -> None:
+    """Verify that the streaming output appears in the CliRunner-captured output.
+
+    The CliRunner captures output written through the Rich console (which
+    writes to stdout). After the fix, console.print(assistant_content, end="")
+    is used, so the full assistant content should appear in result.output
+    as a single write rather than character-by-character.
+
+    We verify that the output contains the expected assistant response and
+    that it was NOT split into individual characters in the captured output.
+    """
+    result = context.result  # type: ignore[attr-defined]
+    # The assistant content for "Hello world" is "Acknowledged: Hello world"
+    expected = "Acknowledged: Hello world"
+    assert expected in result.output, (
+        f"Expected '{expected}' in streaming output.\nGot:\n{result.output}"
+    )
diff --git a/features/tdd_session_tell_stream_redaction.feature b/features/tdd_session_tell_stream_redaction.feature
new file mode 100644
index 000000000..9c9447c90
--- /dev/null
+++ b/features/tdd_session_tell_stream_redaction.feature
@@ -0,0 +1,26 @@
+@tdd_issue @tdd_issue_10458
+Feature: TDD — session tell --stream routes output through console (not sys.stdout)
+  As a security-conscious developer
+  I want streaming output from `session tell --stream` to go through the Rich console
+  So that sensitive values in the assistant response are redacted before reaching stdout
+
+  Background:
+    Given a session tell stream redaction mock service
+
+  @tdd_issue @tdd_issue_10458
+  Scenario: session tell --stream does not write directly to sys.stdout
+    When I invoke session tell with --stream and a sensitive prompt
+    Then the tell command exits with code 0
+    And sys.stdout.write was not called directly during streaming
+
+  @tdd_issue @tdd_issue_10458
+  Scenario: session tell --stream output contains the assistant response
+    When I invoke session tell with --stream and a plain prompt
+    Then the tell command exits with code 0
+    And the tell output contains "Acknowledged"
+
+  @tdd_issue @tdd_issue_10458
+  Scenario: session tell --stream uses console.print not sys.stdout.write
+    When I invoke session tell with --stream and a plain prompt
+    Then the tell command exits with code 0
+    And the streaming output was written through the Rich console
diff --git a/src/cleveragents/cli/commands/session.py b/src/cleveragents/cli/commands/session.py
index 25229f840..99ec2498a 100644
--- a/src/cleveragents/cli/commands/session.py
+++ b/src/cleveragents/cli/commands/session.py
@@ -16,7 +16,6 @@ from __future__ import annotations
 
 import json
 import logging
-import sys
 from collections import OrderedDict
 from pathlib import Path
 from typing import Annotated, Any, cast
@@ -841,11 +840,13 @@ def tell(
         )
 
         if stream:
-            # Simulate streaming by printing character by character
-            for char in assistant_content:
-                sys.stdout.write(char)
-                sys.stdout.flush()
-            sys.stdout.write("\n")
+            # Route streaming output through the Rich console so that the
+            # redaction layer is applied before any content reaches stdout.
+            # Previously this used sys.stdout.write(char) in a character-by-
+            # character loop, which bypassed the redaction layer entirely.
+            from rich.markup import escape as _escape
+
+            console.print(_escape(assistant_content))
         else:
             from rich.markup import escape