test(dynamic-compression): cover tool-name substring exclusions for MCP tools

Add regression tests for disable_tool_name_substrings across config/env/CLI and runtime behavior, and document how to exclude optimized MCP families like fff from redundant compression.

Author: Mateusz

docs/user_guide/features/dynamic-tool-output-compression.md

@@ -107,6 +107,9 @@ dynamic_compression:
   # Specific tool exclusions
   disable_tools: []             # e.g., ["shell", "bash", "run_command"]
 
+  # Tool-name substring exclusions (match anywhere, case-insensitive)
+  disable_tool_name_substrings: []  # e.g., ["fff", "mcp_"]
+
   # Command prefix exclusions
   disable_command_prefixes: []  # e.g., ["git diff --stat", "pytest -v"]
 
@@ -153,8 +156,25 @@ dynamic_compression:
 | `--dynamic-compression-disable-categories CSV` | Comma-separated categories to bypass |
 | `--dynamic-compression-disable-methods CSV` | Comma-separated methods to disable |
 | `--dynamic-compression-disable-tools CSV` | Comma-separated tool names to bypass |
+| `--dynamic-compression-disable-tool-name-substrings CSV` | Comma-separated substrings matched anywhere in tool names |
 | `--dynamic-compression-disable-command-prefixes CSV` | Comma-separated command prefixes to bypass |
 
+### Excluding MCP Tool Families (for example `fff`)
+
+If a tool family already produces compact output, skip dynamic compression for it using `disable_tool_name_substrings`.
+
+```yaml
+dynamic_compression:
+  enabled: true
+  disable_tool_name_substrings: ["fff"]
+```
+
+This matches tool names case-insensitively and anywhere in the name, including:
+- `fff_grep`
+- `fff_find_files`
+- `fff_multi_grep`
+- `turbo_fff_grep`
+
 ### Compression Levels
 
 The `level` setting controls compression aggressiveness:

tests/unit/core/cli_support/applicators/test_dynamic_compression_applicator.py

@@ -37,6 +37,7 @@ def test_dynamic_compression_applicator_sets_overrides_and_resolution() -> None:
     args.dynamic_compression_per_output_evaluation_log_level = "off"
     args.dynamic_compression_file_detail_include_line_numbers = True
     args.dynamic_compression_disable_methods = "ansi_normalize,line_dedupe"
+    args.dynamic_compression_disable_tool_name_substrings = "fff,mcp_"
 
     overrides: dict[str, object] = {}
     resolution = ParameterResolution()
@@ -53,6 +54,7 @@ def test_dynamic_compression_applicator_sets_overrides_and_resolution() -> None:
     assert dc_typed.get("per_output_evaluation_log_level") == "off"
     assert dc_typed.get("file_detail_include_line_numbers") is True
     assert dc_typed.get("disable_methods") == ["ansi_normalize", "line_dedupe"]
+    assert dc_typed.get("disable_tool_name_substrings") == ["fff", "mcp_"]
 
     cli_paths = set(resolution.latest_by_source(ParameterSource.CLI))
     assert "dynamic_compression.enabled" in cli_paths
@@ -62,6 +64,7 @@ def test_dynamic_compression_applicator_sets_overrides_and_resolution() -> None:
     assert "dynamic_compression.per_output_evaluation_log_level" in cli_paths
     assert "dynamic_compression.file_detail_include_line_numbers" in cli_paths
     assert "dynamic_compression.disable_methods" in cli_paths
+    assert "dynamic_compression.disable_tool_name_substrings" in cli_paths
 
 
 def test_dynamic_compression_applicator_is_noop_when_no_args() -> None:

tests/unit/core/config/test_dynamic_compression_config.py

@@ -318,6 +318,7 @@ def test_dynamic_compression_env_is_loaded_and_tracked() -> None:
             "DYNAMIC_COMPRESSION_PER_OUTPUT_EVALUATION_LOG_LEVEL": "off",
             "DYNAMIC_COMPRESSION_FILE_DETAIL_INCLUDE_LINE_NUMBERS": "true",
             "DYNAMIC_COMPRESSION_DISABLE_METHODS": "ansi_normalize,line_dedupe",
+            "DYNAMIC_COMPRESSION_DISABLE_TOOL_NAME_SUBSTRINGS": "fff,mcp_",
         },
         resolution=resolution,
     )
@@ -332,6 +333,7 @@ def test_dynamic_compression_env_is_loaded_and_tracked() -> None:
         "ansi_normalize",
         "line_dedupe",
     ]
+    assert cfg.dynamic_compression.disable_tool_name_substrings == ["fff", "mcp_"]
 
     env_paths = set(resolution.latest_by_source(ParameterSource.ENVIRONMENT))
     assert "dynamic_compression.enabled" in env_paths
@@ -341,3 +343,4 @@ def test_dynamic_compression_env_is_loaded_and_tracked() -> None:
     assert "dynamic_compression.per_output_evaluation_log_level" in env_paths
     assert "dynamic_compression.file_detail_include_line_numbers" in env_paths
     assert "dynamic_compression.disable_methods" in env_paths
+    assert "dynamic_compression.disable_tool_name_substrings" in env_paths

tests/unit/core/services/test_tool_output_compression_service.py

@@ -1553,11 +1553,9 @@ async def test_service_skips_tool_matching_tool_name_substring() -> None:
 
     result = await service.compress_messages(messages=messages, config=cfg)
 
-    assert result.records[0].applied is False, (
-        f"Expected applied=False, got {result.records[0].applied}. "
-        f"Identity: {result.records[0].identity}"
-    )
-    assert "tool_name_substring_disabled" in result.records[0].warnings
+    assert result.records[0].applied is False
+    assert result.messages[1].content == messages[1].content
+    assert result.records[0].methods == []
 
 
 @pytest.mark.asyncio
@@ -1593,7 +1591,8 @@ async def test_service_skips_tool_matching_substring_anywhere_in_name() -> None:
     result = await service.compress_messages(messages=messages, config=cfg)
 
     assert result.records[0].applied is False
-    assert "tool_name_substring_disabled" in result.records[0].warnings
+    assert result.messages[1].content == messages[1].content
+    assert result.records[0].methods == []
 
 
 @pytest.mark.asyncio
@@ -1620,7 +1619,7 @@ async def test_service_does_not_skip_tool_not_matching_substring() -> None:
             CompressionRule(
                 name="default",
                 priority=1,
-                when=CompressionRulePredicate(tool_category="search"),
+                when=CompressionRulePredicate(),
                 pipeline=["half_trim"],
             )
         ],
@@ -1629,6 +1628,7 @@ async def test_service_does_not_skip_tool_not_matching_substring() -> None:
     result = await service.compress_messages(messages=messages, config=cfg)
 
     assert result.records[0].applied is True
+    assert result.messages[1].content != messages[1].content
 
 
 @pytest.mark.asyncio
@@ -1664,4 +1664,44 @@ async def test_tool_name_substring_is_case_insensitive() -> None:
     result = await service.compress_messages(messages=messages, config=cfg)
 
     assert result.records[0].applied is False
-    assert "tool_name_substring_disabled" in result.records[0].warnings
+    assert result.messages[1].content == messages[1].content
+    assert result.records[0].methods == []
+
+
+@pytest.mark.asyncio
+async def test_tool_name_substring_appears_in_effective_config_diagnostics() -> None:
+    registry = CompressionStrategyRegistry()
+    registry.register("half_trim", _HalfTrimStrategy())
+    service = ToolOutputCompressionService(
+        strategy_registry=registry,
+        identity_resolver=ToolIdentityResolver(),
+        selector=RuleBasedStrategySelector(),
+    )
+    messages = _build_messages_for_tool(
+        tool_name="grep_tool",
+        arguments='{"pattern":"target","path":"src"}',
+        output="src/a.py:10:def target()\n" * 100,
+    )
+    cfg = DynamicCompressionConfig(
+        enabled=True,
+        min_bytes=0,
+        marker=CompressionMarkerConfig(enabled=False),
+        methods={"half_trim": True},
+        disable_tool_name_substrings=["fff"],
+        rules=[
+            CompressionRule(
+                name="default",
+                priority=1,
+                when=CompressionRulePredicate(),
+                pipeline=["half_trim"],
+            )
+        ],
+    )
+
+    result = await service.compress_messages(messages=messages, config=cfg)
+
+    assert result.effective_config is not None
+    assert (
+        "dynamic_compression.disable_tool_name_substrings.fff"
+        in result.effective_config.active_controls
+    )