diff --git a/features/steps/tui_conversation_module_coverage_steps.py b/features/steps/tui_conversation_module_coverage_steps.py
new file mode 100644
index 000000000..80266c666
--- /dev/null
+++ b/features/steps/tui_conversation_module_coverage_steps.py
@@ -0,0 +1,284 @@
+"""Step definitions for direct coverage of cleveragents.tui.conversation."""
+
+from __future__ import annotations
+
+import json
+import tempfile
+from pathlib import Path
+
+from behave import then, when
+
+from cleveragents.tui.conversation import (
+    ConversationBlock,
+    ConversationSettings,
+    ConversationStream,
+    load_conversation_settings,
+)
+
+
+def _unescape(value: str) -> str:
+    return value.encode("utf-8").decode("unicode_escape")
+
+
+@when("I build default ConversationSettings")
+def step_build_default_settings(context):
+    context._conv_settings = ConversationSettings()
+
+
+@when(
+    "I build ConversationSettings with prune_low_mark {low:d} "
+    "prune_excess {excess:d} preserve_recent_lines {preserve:d}"
+)
+def step_build_explicit_settings(context, low, excess, preserve):
+    context._conv_settings = ConversationSettings(
+        prune_low_mark=low,
+        prune_excess=excess,
+        preserve_recent_lines=preserve,
+    )
+
+
+@then("conversation settings prune_low_mark should equal {expected:d}")
+def step_assert_settings_low(context, expected):
+    assert context._conv_settings.prune_low_mark == expected, (
+        f"expected prune_low_mark={expected}, "
+        f"got {context._conv_settings.prune_low_mark}"
+    )
+
+
+@then("conversation settings prune_excess should equal {expected:d}")
+def step_assert_settings_excess(context, expected):
+    assert context._conv_settings.prune_excess == expected, (
+        f"expected prune_excess={expected}, got {context._conv_settings.prune_excess}"
+    )
+
+
+@then("conversation settings preserve_recent_lines should equal {expected:d}")
+def step_assert_settings_preserve(context, expected):
+    assert context._conv_settings.preserve_recent_lines == expected, (
+        f"expected preserve_recent_lines={expected}, "
+        f"got {context._conv_settings.preserve_recent_lines}"
+    )
+
+
+@then("conversation settings trigger_line_count should equal {expected:d}")
+def step_assert_trigger(context, expected):
+    assert context._conv_settings.trigger_line_count == expected, (
+        f"expected trigger_line_count={expected}, "
+        f"got {context._conv_settings.trigger_line_count}"
+    )
+
+
+@then('a conversation block with text "{text}" should have line count {count:d}')
+def step_assert_block_lines(context, text, count):
+    decoded = _unescape(text)
+    block = ConversationBlock(text=decoded)
+    assert block.line_count() == count, (
+        f"expected line_count={count} for {decoded!r}, got {block.line_count()}"
+    )
+
+
+@then("a conversation block with empty text should have line count {count:d}")
+def step_assert_empty_block_lines(context, count):
+    block = ConversationBlock(text="")
+    assert block.line_count() == count, (
+        f"expected empty block line_count={count}, got {block.line_count()}"
+    )
+
+
+def _make_stream(settings: ConversationSettings | None = None) -> ConversationStream:
+    return ConversationStream(settings=settings)
+
+
+@when("a fresh ConversationStream with default settings")
+def step_fresh_stream_default(context):
+    context._conv_stream = _make_stream()
+
+
+# Behave does not support a "Given" decorator import alias mismatch; use when too.
+from behave import given  # noqa: E402
+
+
+@given("a fresh ConversationStream with default settings")
+def step_given_fresh_stream_default(context):
+    context._conv_stream = _make_stream()
+
+
+@given(
+    "a fresh ConversationStream with low_mark {low:d} excess {excess:d} "
+    "preserve_recent_lines {preserve:d}"
+)
+def step_given_fresh_stream_custom(context, low, excess, preserve):
+    context._conv_stream = _make_stream(
+        ConversationSettings(
+            prune_low_mark=low,
+            prune_excess=excess,
+            preserve_recent_lines=preserve,
+        )
+    )
+
+
+@when('I bootstrap the stream with welcome text "{text}"')
+def step_bootstrap_stream(context, text):
+    context._conv_stream.bootstrap(welcome_text=text)
+
+
+@when("I clear the stream")
+def step_clear_stream(context):
+    context._conv_stream.clear()
+
+
+@when("I extend the stream with {count:d} plain message blocks")
+def step_extend_stream(context, count):
+    blocks = [
+        ConversationBlock(text=f"extend-block-{idx}") for idx in range(1, count + 1)
+    ]
+    context._conv_stream.extend(blocks)
+
+
+@when('I add a plain block "{text}" to the stream')
+def step_add_plain_block(context, text):
+    context._conv_stream.add_block(text)
+
+
+@when("I add an empty plain block to the stream")
+def step_add_empty_plain_block(context):
+    context._conv_stream.add_block("")
+
+
+@when('I add a markup block "{text}" to the stream')
+def step_add_markup_block(context, text):
+    context._conv_stream.add_block(text, markup=True)
+
+
+@when("I deliver {count:d} plain blocks of {lines:d} lines each through add_block")
+def step_deliver_blocks(context, count, lines):
+    for idx in range(1, count + 1):
+        payload = "\n".join(f"plain-{idx}-line-{line}" for line in range(1, lines + 1))
+        context._conv_stream.add_block(payload)
+
+
+@then("the stream should have exactly {count:d} block")
+@then("the stream should have exactly {count:d} blocks")
+def step_assert_block_count(context, count):
+    assert len(context._conv_stream.blocks) == count, (
+        f"expected {count} blocks, got {len(context._conv_stream.blocks)}"
+    )
+
+
+@then("the stream total_lines should be zero")
+def step_assert_zero_lines(context):
+    assert context._conv_stream.total_lines == 0, (
+        f"expected total_lines=0, got {context._conv_stream.total_lines}"
+    )
+
+
+@then("the stream total_lines should be greater than zero")
+def step_assert_positive_lines(context):
+    assert context._conv_stream.total_lines > 0, (
+        f"expected positive total_lines, got {context._conv_stream.total_lines}"
+    )
+
+
+@then("the stream total_lines should be less than or equal to {limit:d}")
+def step_assert_lines_bound(context, limit):
+    assert context._conv_stream.total_lines <= limit, (
+        f"expected total_lines<={limit}, got {context._conv_stream.total_lines}"
+    )
+
+
+@then('the stream rendered text should contain "{text}"')
+def step_assert_render_contains(context, text):
+    rendered = context._conv_stream.render()
+    assert text in rendered, f"expected {text!r} in render, got {rendered!r}"
+
+
+@then('the stream rendered text should not contain "{text}"')
+def step_assert_render_not_contains(context, text):
+    decoded = _unescape(text)
+    rendered = context._conv_stream.render()
+    assert decoded not in rendered, (
+        f"unexpected {decoded!r} in render, got {rendered!r}"
+    )
+
+
+@then('the stream rendered text should equal "{text}"')
+def step_assert_render_equals(context, text):
+    rendered = context._conv_stream.render()
+    assert rendered == text, f"expected render=={text!r}, got {rendered!r}"
+
+
+@then("the stream rendered plain segment should be backslash escaped")
+def step_assert_plain_escaped(context):
+    rendered = context._conv_stream.render()
+    assert "\\[red]plain\\[/]" in rendered, (
+        f"expected escaped plain markup in render, got {rendered!r}"
+    )
+
+
+@then("the stream should have exactly {count:d} note block")
+@then("the stream should have exactly {count:d} note blocks")
+def step_assert_note_count(context, count):
+    notes = [b for b in context._conv_stream.blocks if b.block_type == "note"]
+    assert len(notes) == count, (
+        f"expected {count} note blocks, got {len(notes)}: {notes!r}"
+    )
+
+
+def _temp_dir(context) -> Path:
+    if not hasattr(context, "_conv_tmp"):
+        context._conv_tmp = tempfile.mkdtemp(prefix="conv-settings-")
+    return Path(context._conv_tmp)
+
+
+@when("I load conversation settings from a missing config path")
+def step_load_missing(context):
+    missing = _temp_dir(context) / "absent.json"
+    context._loaded_settings = load_conversation_settings(missing)
+
+
+@when("I load conversation settings from a malformed JSON config")
+def step_load_malformed(context):
+    path = _temp_dir(context) / "malformed.json"
+    path.write_text("{not valid json", encoding="utf-8")
+    context._loaded_settings = load_conversation_settings(path)
+
+
+@when(
+    "I load conversation settings from a config with low_mark {low:d} excess {excess:d}"
+)
+def step_load_valid(context, low, excess):
+    path = _temp_dir(context) / "valid.json"
+    payload = {"ui": {"prune_low_mark": low, "prune_excess": excess}}
+    path.write_text(json.dumps(payload), encoding="utf-8")
+    context._loaded_settings = load_conversation_settings(path)
+
+
+@when("I load conversation settings from a config with non-numeric values")
+def step_load_bad_numeric(context):
+    path = _temp_dir(context) / "non_numeric.json"
+    payload = {"ui": {"prune_low_mark": "not-a-number", "prune_excess": {}}}
+    path.write_text(json.dumps(payload), encoding="utf-8")
+    context._loaded_settings = load_conversation_settings(path)
+
+
+@when("I load conversation settings from a list-valued JSON config")
+def step_load_list_root(context):
+    path = _temp_dir(context) / "list.json"
+    path.write_text(json.dumps(["this", "is", "a", "list"]), encoding="utf-8")
+    context._loaded_settings = load_conversation_settings(path)
+
+
+@then("loaded settings prune_low_mark should equal {expected:d}")
+def step_assert_loaded_low(context, expected):
+    assert context._loaded_settings.prune_low_mark == expected, (
+        f"expected loaded prune_low_mark={expected}, "
+        f"got {context._loaded_settings.prune_low_mark}"
+    )
+
+
+@then("loaded settings prune_excess should equal {expected:d}")
+def step_assert_loaded_excess(context, expected):
+    assert context._loaded_settings.prune_excess == expected, (
+        f"expected loaded prune_excess={expected}, "
+        f"got {context._loaded_settings.prune_excess}"
+    )
diff --git a/features/tui_conversation_module_coverage.feature b/features/tui_conversation_module_coverage.feature
new file mode 100644
index 000000000..754d91a75
--- /dev/null
+++ b/features/tui_conversation_module_coverage.feature
@@ -0,0 +1,132 @@
+Feature: TUI conversation module coverage
+  Directly exercises the cleveragents.tui.conversation module to cover
+  pruning hysteresis, settings clamping, persistence loading, and edge
+  cases that the high-level TUI scenarios do not reach.
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: Default ConversationSettings derive trigger_line_count from low_mark and excess
+    When I build default ConversationSettings
+    Then conversation settings prune_low_mark should equal 1500
+    And conversation settings prune_excess should equal 1000
+    And conversation settings trigger_line_count should equal 2500
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationSettings clamps prune_low_mark below the minimum
+    When I build ConversationSettings with prune_low_mark 10 prune_excess 200 preserve_recent_lines 50
+    Then conversation settings prune_low_mark should equal 100
+    And conversation settings prune_excess should equal 200
+    And conversation settings preserve_recent_lines should equal 50
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationSettings clamps prune_low_mark above the maximum
+    When I build ConversationSettings with prune_low_mark 99999 prune_excess 200 preserve_recent_lines 50
+    Then conversation settings prune_low_mark should equal 10000
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationSettings clamps prune_excess below the minimum
+    When I build ConversationSettings with prune_low_mark 500 prune_excess 1 preserve_recent_lines 50
+    Then conversation settings prune_excess should equal 10
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationSettings clamps prune_excess above the maximum
+    When I build ConversationSettings with prune_low_mark 500 prune_excess 99999 preserve_recent_lines 50
+    Then conversation settings prune_excess should equal 5000
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationSettings clamps preserve_recent_lines below zero
+    When I build ConversationSettings with prune_low_mark 500 prune_excess 100 preserve_recent_lines -25
+    Then conversation settings preserve_recent_lines should equal 0
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationBlock line_count counts trailing newlines and empty text
+    Then a conversation block with text "alpha" should have line count 1
+    And a conversation block with text "alpha\nbeta" should have line count 2
+    And a conversation block with empty text should have line count 0
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream bootstrap installs a protected welcome block
+    Given a fresh ConversationStream with default settings
+    When I bootstrap the stream with welcome text "Hello world"
+    Then the stream should have exactly 1 block
+    And the stream total_lines should be greater than zero
+    And the stream rendered text should contain "Hello world"
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream clear empties blocks and resets total_lines
+    Given a fresh ConversationStream with default settings
+    When I bootstrap the stream with welcome text "Hello"
+    And I clear the stream
+    Then the stream should have exactly 0 blocks
+    And the stream total_lines should be zero
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream extend appends multiple blocks
+    Given a fresh ConversationStream with default settings
+    When I extend the stream with 3 plain message blocks
+    Then the stream should have exactly 3 blocks
+    And the stream rendered text should contain "extend-block-2"
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream renders markup blocks verbatim and escapes plain blocks
+    Given a fresh ConversationStream with default settings
+    When I add a plain block "[red]plain[/]" to the stream
+    And I add a markup block "[red]styled[/]" to the stream
+    Then the stream rendered text should contain "[red]styled[/]"
+    And the stream rendered plain segment should be backslash escaped
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream skips empty-text blocks during render
+    Given a fresh ConversationStream with default settings
+    When I add an empty plain block to the stream
+    And I add a plain block "after-empty" to the stream
+    Then the stream rendered text should equal "after-empty"
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream pruning preserves protected blocks
+    Given a fresh ConversationStream with low_mark 200 excess 50 preserve_recent_lines 100
+    When I bootstrap the stream with welcome text "Protected welcome"
+    And I deliver 4 plain blocks of 200 lines each through add_block
+    Then the stream rendered text should contain "Protected welcome"
+    And the stream total_lines should be less than or equal to 350
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream pruning updates the note in place rather than re-inserting
+    Given a fresh ConversationStream with low_mark 200 excess 50 preserve_recent_lines 100
+    When I deliver 8 plain blocks of 200 lines each through add_block
+    Then the stream should have exactly 1 note block
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: ConversationStream pruning with preserve_recent_lines zero allows full prune
+    Given a fresh ConversationStream with low_mark 200 excess 50 preserve_recent_lines 0
+    When I deliver 6 plain blocks of 200 lines each through add_block
+    Then the stream total_lines should be less than or equal to 250
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: load_conversation_settings returns defaults when the config file is absent
+    When I load conversation settings from a missing config path
+    Then loaded settings prune_low_mark should equal 1500
+    And loaded settings prune_excess should equal 1000
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: load_conversation_settings returns defaults when the config file is malformed JSON
+    When I load conversation settings from a malformed JSON config
+    Then loaded settings prune_low_mark should equal 1500
+    And loaded settings prune_excess should equal 1000
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: load_conversation_settings honours explicit ui values
+    When I load conversation settings from a config with low_mark 800 excess 400
+    Then loaded settings prune_low_mark should equal 800
+    And loaded settings prune_excess should equal 400
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: load_conversation_settings returns defaults when ui values are non-numeric
+    When I load conversation settings from a config with non-numeric values
+    Then loaded settings prune_low_mark should equal 1500
+    And loaded settings prune_excess should equal 1000
+
+  @tdd_issue @tdd_issue_6350
+  Scenario: load_conversation_settings returns defaults when payload is not a dict
+    When I load conversation settings from a list-valued JSON config
+    Then loaded settings prune_low_mark should equal 1500
+    And loaded settings prune_excess should equal 1000