fix: cap percentage displays at 100% in stats, gateway, and memory tool (#3599)

Salvage of PR #3533 (binhnt92). Follow-up to #3480 — applies min(100, ...) to 5 remaining unclamped percentage display sites in context_compressor, cli /stats, gateway /stats, and memory tool. Defensive clamps now that the root cause (estimation heuristic) was already removed in #3480.

Co-Authored-By: binhnt92 <binhnt92@users.noreply.github.com>

tests/test_percentage_clamp.py

@@ -0,0 +1,154 @@
+"""Tests for percentage clamping at 100% across display paths.
+
+PR #3480 capped context pressure percentage at 100% in agent/display.py
+but missed the same unclamped pattern in 4 other files. When token counts
+overshoot the context length (possible during streaming or before
+compression fires), users see >100% in /stats, gateway status, and
+memory tool output.
+"""
+
+import pytest
+
+
+class TestContextCompressorUsagePercent:
+    """agent/context_compressor.py — get_status() usage_percent"""
+
+    def test_usage_percent_capped_at_100(self):
+        """Tokens exceeding context_length should still show max 100%."""
+        from agent.context_compressor import ContextCompressor
+
+        comp = ContextCompressor.__new__(ContextCompressor)
+        comp.last_prompt_tokens = 210_000  # exceeds context_length
+        comp.context_length = 200_000
+        comp.threshold_tokens = 160_000
+        comp.compression_count = 0
+
+        status = comp.get_status()
+        assert status["usage_percent"] <= 100
+
+    def test_usage_percent_normal(self):
+        """Normal usage should show correct percentage."""
+        from agent.context_compressor import ContextCompressor
+
+        comp = ContextCompressor.__new__(ContextCompressor)
+        comp.last_prompt_tokens = 100_000
+        comp.context_length = 200_000
+        comp.threshold_tokens = 160_000
+        comp.compression_count = 0
+
+        status = comp.get_status()
+        assert status["usage_percent"] == 50.0
+
+    def test_usage_percent_zero_context_length(self):
+        """Zero context_length should return 0, not crash."""
+        from agent.context_compressor import ContextCompressor
+
+        comp = ContextCompressor.__new__(ContextCompressor)
+        comp.last_prompt_tokens = 1000
+        comp.context_length = 0
+        comp.threshold_tokens = 0
+        comp.compression_count = 0
+
+        status = comp.get_status()
+        assert status["usage_percent"] == 0
+
+
+class TestMemoryToolPercentClamp:
+    """tools/memory_tool.py — _success_response and _render_block pct"""
+
+    def test_over_limit_clamped_at_100(self):
+        """Percentage should be capped at 100 even if current > limit."""
+        # Simulate the calculation directly
+        current = 5500
+        limit = 5000
+        pct = min(100, int((current / limit) * 100)) if limit > 0 else 0
+        assert pct == 100
+
+    def test_normal_percentage(self):
+        current = 2500
+        limit = 5000
+        pct = min(100, int((current / limit) * 100)) if limit > 0 else 0
+        assert pct == 50
+
+    def test_zero_limit_returns_zero(self):
+        current = 100
+        limit = 0
+        pct = min(100, int((current / limit) * 100)) if limit > 0 else 0
+        assert pct == 0
+
+
+class TestCLIStatsPercentClamp:
+    """cli.py — /stats command percentage"""
+
+    def test_over_context_clamped_at_100(self):
+        """Tokens exceeding context_length should show max 100%."""
+        last_prompt = 210_000
+        ctx_len = 200_000
+        pct = min(100, (last_prompt / ctx_len * 100)) if ctx_len else 0
+        assert pct == 100
+
+    def test_normal_context(self):
+        last_prompt = 100_000
+        ctx_len = 200_000
+        pct = min(100, (last_prompt / ctx_len * 100)) if ctx_len else 0
+        assert pct == 50.0
+
+    def test_zero_context_length(self):
+        last_prompt = 1000
+        ctx_len = 0
+        pct = min(100, (last_prompt / ctx_len * 100)) if ctx_len else 0
+        assert pct == 0
+
+
+class TestGatewayStatsPercentClamp:
+    """gateway/run.py — _format_usage_stats percentage"""
+
+    def test_over_context_clamped_at_100(self):
+        last_prompt_tokens = 210_000
+        context_length = 200_000
+        pct = min(100, last_prompt_tokens / context_length * 100) if context_length else 0
+        assert pct == 100
+
+    def test_normal_context(self):
+        last_prompt_tokens = 150_000
+        context_length = 200_000
+        pct = min(100, last_prompt_tokens / context_length * 100) if context_length else 0
+        assert pct == 75.0
+
+
+class TestSourceLinesAreClamped:
+    """Verify the actual source files have min(100, ...) applied."""
+
+    @staticmethod
+    def _read_file(rel_path: str) -> str:
+        import os
+        base = os.path.dirname(os.path.dirname(__file__))
+        with open(os.path.join(base, rel_path)) as f:
+            return f.read()
+
+    def test_context_compressor_clamped(self):
+        src = self._read_file("agent/context_compressor.py")
+        assert "min(100," in src, (
+            "context_compressor.py usage_percent is not clamped with min(100, ...)"
+        )
+
+    def test_gateway_run_clamped(self):
+        src = self._read_file("gateway/run.py")
+        # Check that the stats handler has min(100, ...)
+        assert "min(100, ctx.last_prompt_tokens" in src, (
+            "gateway/run.py stats pct is not clamped with min(100, ...)"
+        )
+
+    def test_cli_clamped(self):
+        src = self._read_file("cli.py")
+        assert "min(100, (last_prompt" in src, (
+            "cli.py /stats pct is not clamped with min(100, ...)"
+        )
+
+    def test_memory_tool_clamped(self):
+        src = self._read_file("tools/memory_tool.py")
+        # Both _success_response and _render_block should have min(100, ...)
+        count = src.count("min(100, int((current / limit)")
+        assert count >= 2, (
+            f"memory_tool.py has only {count} clamped pct lines, expected >= 2"
+        )