diff --git a/src/openjarvis/optimize/llm_optimizer.py b/src/openjarvis/optimize/llm_optimizer.py
new file mode 100644
index 00000000..f4d1ec4c
--- /dev/null
+++ b/src/openjarvis/optimize/llm_optimizer.py
@@ -0,0 +1,382 @@
+"""LLM-based optimizer for OpenJarvis configuration tuning.
+
+Uses a cloud LLM to propose optimal OpenJarvis configs, inspired by DSPy's
+GEPA approach: textual feedback from execution traces rather than just scalar
+rewards guides the optimizer toward better configurations.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+import uuid
+from typing import Any, Dict, List, Optional
+
+from openjarvis.core.types import Trace
+from openjarvis.evals.core.backend import InferenceBackend
+from openjarvis.evals.core.types import RunSummary
+from openjarvis.optimize.types import SearchSpace, TrialConfig, TrialResult
+
+
+class LLMOptimizer:
+    """Uses a cloud LLM to propose optimal OpenJarvis configs.
+
+    Inspired by DSPy's GEPA: uses textual feedback from execution
+    traces rather than just scalar rewards.
+    """
+
+    def __init__(
+        self,
+        search_space: SearchSpace,
+        optimizer_model: str = "claude-sonnet-4-6",
+        optimizer_backend: Optional[InferenceBackend] = None,
+    ) -> None:
+        self.search_space = search_space
+        self.optimizer_model = optimizer_model
+        self.optimizer_backend = optimizer_backend
+
+    # ------------------------------------------------------------------
+    # Public API
+    # ------------------------------------------------------------------
+
+    def propose_initial(self) -> TrialConfig:
+        """Propose a reasonable starting config from the search space."""
+        if self.optimizer_backend is None:
+            raise ValueError(
+                "optimizer_backend is required to propose configurations"
+            )
+
+        prompt = self._build_initial_prompt()
+        response = self.optimizer_backend.generate(
+            prompt,
+            model=self.optimizer_model,
+            system="You are an expert AI systems optimizer.",
+            temperature=0.7,
+            max_tokens=2048,
+        )
+        return self._parse_config_response(response)
+
+    def propose_next(
+        self,
+        history: List[TrialResult],
+        traces: Optional[List[Trace]] = None,
+    ) -> TrialConfig:
+        """Ask the LLM to propose the next config to evaluate."""
+        if self.optimizer_backend is None:
+            raise ValueError(
+                "optimizer_backend is required to propose configurations"
+            )
+
+        prompt = self._build_propose_prompt(history, traces)
+        response = self.optimizer_backend.generate(
+            prompt,
+            model=self.optimizer_model,
+            system="You are an expert AI systems optimizer.",
+            temperature=0.7,
+            max_tokens=2048,
+        )
+        return self._parse_config_response(response)
+
+    def analyze_trial(
+        self,
+        trial: TrialConfig,
+        summary: RunSummary,
+        traces: Optional[List[Trace]] = None,
+    ) -> str:
+        """Ask the LLM to analyze a completed trial. Returns textual analysis."""
+        if self.optimizer_backend is None:
+            raise ValueError(
+                "optimizer_backend is required to analyze trials"
+            )
+
+        prompt = self._build_analyze_prompt(trial, summary, traces)
+        response = self.optimizer_backend.generate(
+            prompt,
+            model=self.optimizer_model,
+            system="You are an expert AI systems analyst.",
+            temperature=0.3,
+            max_tokens=2048,
+        )
+        return response.strip()
+
+    # ------------------------------------------------------------------
+    # Prompt builders
+    # ------------------------------------------------------------------
+
+    def _build_initial_prompt(self) -> str:
+        """Construct the prompt for the initial config proposal."""
+        lines: List[str] = []
+        lines.append(
+            "You are optimizing an OpenJarvis AI system configuration."
+        )
+        lines.append("")
+        lines.append(self.search_space.to_prompt_description())
+        lines.append("## Objective")
+        lines.append(
+            "Maximize accuracy while minimizing latency and cost."
+        )
+        lines.append("")
+        lines.append("## Your Task")
+        lines.append(
+            "Propose an initial configuration that is a reasonable starting "
+            "point for optimization. Choose sensible defaults that balance "
+            "accuracy, latency, and cost."
+        )
+        lines.append("")
+        lines.append(
+            "Return a JSON object inside a ```json code block with:"
+        )
+        lines.append(
+            '1. "params": dict of config params (dotted keys matching '
+            "the search space)"
+        )
+        lines.append(
+            '2. "reasoning": string explaining why this is a good '
+            "starting configuration"
+        )
+        return "\n".join(lines)
+
+    def _build_propose_prompt(
+        self,
+        history: List[TrialResult],
+        traces: Optional[List[Trace]] = None,
+    ) -> str:
+        """Construct the full prompt for propose_next."""
+        lines: List[str] = []
+        lines.append(
+            "You are optimizing an OpenJarvis AI system configuration."
+        )
+        lines.append("")
+        lines.append(self.search_space.to_prompt_description())
+
+        lines.append("## Optimization History")
+        if history:
+            lines.append(self._format_history(history))
+        else:
+            lines.append("No trials have been run yet.")
+        lines.append("")
+
+        if traces:
+            lines.append("## Recent Execution Traces")
+            lines.append(self._format_traces(traces))
+            lines.append("")
+
+        lines.append("## Objective")
+        lines.append(
+            "Maximize accuracy while minimizing latency and cost."
+        )
+        lines.append("")
+        lines.append("## Your Task")
+        lines.append(
+            "Propose the next configuration to evaluate. Learn from "
+            "previous trials to improve results."
+        )
+        lines.append("")
+        lines.append(
+            "Return a JSON object inside a ```json code block with:"
+        )
+        lines.append(
+            '1. "params": dict of config params (dotted keys matching '
+            "the search space)"
+        )
+        lines.append(
+            '2. "reasoning": string explaining why this config should '
+            "improve results"
+        )
+        return "\n".join(lines)
+
+    def _build_analyze_prompt(
+        self,
+        trial: TrialConfig,
+        summary: RunSummary,
+        traces: Optional[List[Trace]] = None,
+    ) -> str:
+        """Construct the prompt for analyze_trial."""
+        lines: List[str] = []
+        lines.append("Analyze this OpenJarvis evaluation result.")
+        lines.append("")
+
+        lines.append("## Configuration")
+        for key, value in sorted(trial.params.items()):
+            lines.append(f"- {key}: {value}")
+        if trial.reasoning:
+            lines.append(f"\nOptimizer reasoning: {trial.reasoning}")
+        lines.append("")
+
+        lines.append("## Results")
+        lines.append(f"- accuracy: {summary.accuracy:.4f}")
+        lines.append(
+            f"- mean_latency_seconds: {summary.mean_latency_seconds:.4f}"
+        )
+        lines.append(f"- total_cost_usd: {summary.total_cost_usd:.4f}")
+        lines.append(f"- total_samples: {summary.total_samples}")
+        lines.append(f"- scored_samples: {summary.scored_samples}")
+        lines.append(f"- correct: {summary.correct}")
+        lines.append(f"- errors: {summary.errors}")
+        if summary.per_subject:
+            lines.append("\n### Per-Subject Breakdown")
+            for subject, metrics in sorted(summary.per_subject.items()):
+                metrics_str = ", ".join(
+                    f"{k}={v:.3f}" for k, v in sorted(metrics.items())
+                )
+                lines.append(f"- {subject}: {metrics_str}")
+        lines.append("")
+
+        if traces:
+            lines.append("## Sample Traces")
+            lines.append(self._format_traces(traces))
+            lines.append("")
+
+        lines.append(
+            "Provide a detailed textual analysis of what worked, what "
+            "failed, and what changes would likely improve results."
+        )
+        return "\n".join(lines)
+
+    # ------------------------------------------------------------------
+    # Helpers
+    # ------------------------------------------------------------------
+
+    def _format_history(self, history: List[TrialResult]) -> str:
+        """Render trial history as structured text for the LLM prompt."""
+        lines: List[str] = []
+        for i, result in enumerate(history, 1):
+            lines.append(f"### Trial {i} (id={result.trial_id})")
+            lines.append(f"Params: {json.dumps(result.config.params)}")
+            lines.append(f"Accuracy: {result.accuracy:.4f}")
+            lines.append(
+                f"Latency: {result.mean_latency_seconds:.4f}s"
+            )
+            lines.append(f"Cost: ${result.total_cost_usd:.4f}")
+            if result.analysis:
+                lines.append(f"Analysis: {result.analysis}")
+            if result.failure_modes:
+                lines.append(
+                    f"Failure modes: {', '.join(result.failure_modes)}"
+                )
+            lines.append("")
+        return "\n".join(lines)
+
+    def _format_traces(self, traces: List[Trace]) -> str:
+        """Render traces as structured text for the LLM prompt.
+
+        Limits to the last 10 traces and truncates long outputs to keep
+        the prompt manageable.
+        """
+        max_traces = 10
+        max_result_len = 500
+        max_steps_per_trace = 10
+
+        recent = traces[-max_traces:]
+        lines: List[str] = []
+
+        for trace in recent:
+            lines.append(
+                f"### Trace {trace.trace_id} "
+                f"(agent={trace.agent}, model={trace.model})"
+            )
+            lines.append(f"Query: {trace.query}")
+            if trace.outcome:
+                lines.append(f"Outcome: {trace.outcome}")
+            if trace.feedback is not None:
+                lines.append(f"Feedback: {trace.feedback}")
+            lines.append(
+                f"Latency: {trace.total_latency_seconds:.3f}s, "
+                f"Tokens: {trace.total_tokens}"
+            )
+
+            # Show steps (limited)
+            steps = trace.steps[:max_steps_per_trace]
+            if steps:
+                lines.append("Steps:")
+                for step in steps:
+                    step_input = json.dumps(step.input)
+                    step_output = json.dumps(step.output)
+                    if len(step_input) > max_result_len:
+                        step_input = step_input[:max_result_len] + "..."
+                    if len(step_output) > max_result_len:
+                        step_output = step_output[:max_result_len] + "..."
+                    lines.append(
+                        f"  - {step.step_type.value}: "
+                        f"input={step_input}, "
+                        f"output={step_output} "
+                        f"({step.duration_seconds:.3f}s)"
+                    )
+                if len(trace.steps) > max_steps_per_trace:
+                    lines.append(
+                        f"  ... ({len(trace.steps) - max_steps_per_trace} "
+                        "more steps)"
+                    )
+
+            result_text = trace.result
+            if len(result_text) > max_result_len:
+                result_text = result_text[:max_result_len] + "..."
+            lines.append(f"Result: {result_text}")
+            lines.append("")
+
+        return "\n".join(lines)
+
+    def _parse_config_response(self, response: str) -> TrialConfig:
+        """Extract a TrialConfig from an LLM response.
+
+        Looks for a ```json ... ``` block first, then falls back to
+        finding a raw JSON object in the response text.
+        """
+        trial_id = uuid.uuid4().hex[:12]
+
+        # Try to extract from a ```json code block
+        json_block_match = re.search(
+            r"```json\s*\n?(.*?)\n?\s*```", response, re.DOTALL
+        )
+        if json_block_match:
+            raw_json = json_block_match.group(1).strip()
+            try:
+                data = json.loads(raw_json)
+                return self._config_from_dict(data, trial_id)
+            except json.JSONDecodeError:
+                pass
+
+        # Try to extract from a generic ``` code block
+        code_block_match = re.search(
+            r"```\s*\n?(.*?)\n?\s*```", response, re.DOTALL
+        )
+        if code_block_match:
+            raw_json = code_block_match.group(1).strip()
+            try:
+                data = json.loads(raw_json)
+                return self._config_from_dict(data, trial_id)
+            except json.JSONDecodeError:
+                pass
+
+        # Try to find a raw JSON object in the response by scanning
+        # for each '{' and attempting to parse from that position.
+        decoder = json.JSONDecoder()
+        for m in re.finditer(r"\{", response):
+            try:
+                data, _ = decoder.raw_decode(response, m.start())
+                if isinstance(data, dict):
+                    return self._config_from_dict(data, trial_id)
+            except json.JSONDecodeError:
+                continue
+
+        # Last resort: return empty config
+        return TrialConfig(
+            trial_id=trial_id,
+            params={},
+            reasoning="Failed to parse LLM response.",
+        )
+
+    def _config_from_dict(
+        self, data: Dict[str, Any], trial_id: str
+    ) -> TrialConfig:
+        """Build a TrialConfig from a parsed JSON dict."""
+        params = data.get("params", {})
+        reasoning = data.get("reasoning", "")
+        return TrialConfig(
+            trial_id=trial_id,
+            params=params,
+            reasoning=reasoning,
+        )
+
+
+__all__ = ["LLMOptimizer"]
diff --git a/tests/test_llm_optimizer.py b/tests/test_llm_optimizer.py
new file mode 100644
index 00000000..6baffd6e
--- /dev/null
+++ b/tests/test_llm_optimizer.py
@@ -0,0 +1,802 @@
+"""Tests for openjarvis.optimize.llm_optimizer module."""
+
+from __future__ import annotations
+
+import json
+from typing import Any, Dict
+from unittest.mock import MagicMock
+
+import pytest
+
+from openjarvis.core.types import StepType, Trace, TraceStep
+from openjarvis.evals.core.backend import InferenceBackend
+from openjarvis.evals.core.types import RunSummary
+from openjarvis.optimize.llm_optimizer import LLMOptimizer
+from openjarvis.optimize.types import (
+    SearchDimension,
+    SearchSpace,
+    TrialConfig,
+    TrialResult,
+)
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+
+def _make_search_space() -> SearchSpace:
+    """Build a small search space for testing."""
+    return SearchSpace(
+        dimensions=[
+            SearchDimension(
+                name="agent.type",
+                dim_type="categorical",
+                values=["simple", "orchestrator", "native_react"],
+                description="Agent architecture",
+                pillar="agent",
+            ),
+            SearchDimension(
+                name="intelligence.temperature",
+                dim_type="continuous",
+                low=0.0,
+                high=1.0,
+                description="Generation temperature",
+                pillar="intelligence",
+            ),
+            SearchDimension(
+                name="agent.max_turns",
+                dim_type="integer",
+                low=1,
+                high=30,
+                description="Maximum reasoning turns",
+                pillar="agent",
+            ),
+        ],
+        fixed={"engine": "ollama"},
+        constraints=["SimpleAgent should only have max_turns = 1"],
+    )
+
+
+def _make_mock_backend(response: str) -> MagicMock:
+    """Create a mock InferenceBackend that returns the given response."""
+    backend = MagicMock(spec=InferenceBackend)
+    backend.backend_id = "mock"
+    backend.generate.return_value = response
+    return backend
+
+
+def _make_trial_result(
+    trial_id: str = "t1",
+    params: Dict[str, Any] | None = None,
+    accuracy: float = 0.75,
+    latency: float = 1.5,
+    cost: float = 0.02,
+    analysis: str = "Decent results",
+    failure_modes: list[str] | None = None,
+) -> TrialResult:
+    """Create a TrialResult for testing."""
+    if params is None:
+        params = {
+            "agent.type": "orchestrator",
+            "intelligence.temperature": 0.5,
+        }
+    config = TrialConfig(
+        trial_id=trial_id,
+        params=params,
+        reasoning="Test reasoning",
+    )
+    return TrialResult(
+        trial_id=trial_id,
+        config=config,
+        accuracy=accuracy,
+        mean_latency_seconds=latency,
+        total_cost_usd=cost,
+        analysis=analysis,
+        failure_modes=failure_modes or [],
+    )
+
+
+def _make_trace(
+    trace_id: str = "trace-001",
+    query: str = "What is 2+2?",
+    agent: str = "orchestrator",
+    model: str = "qwen3:8b",
+    outcome: str = "success",
+    result: str = "4",
+    total_latency: float = 0.5,
+    total_tokens: int = 100,
+    num_steps: int = 2,
+) -> Trace:
+    """Create a Trace for testing."""
+    steps = []
+    for i in range(num_steps):
+        step_type = StepType.GENERATE if i % 2 == 0 else StepType.TOOL_CALL
+        steps.append(
+            TraceStep(
+                step_type=step_type,
+                timestamp=float(i),
+                duration_seconds=0.1,
+                input={"prompt": f"step {i} input"},
+                output={"content": f"step {i} output"},
+            )
+        )
+    return Trace(
+        trace_id=trace_id,
+        query=query,
+        agent=agent,
+        model=model,
+        steps=steps,
+        result=result,
+        outcome=outcome,
+        total_latency_seconds=total_latency,
+        total_tokens=total_tokens,
+    )
+
+
+def _make_run_summary(
+    accuracy: float = 0.80,
+    latency: float = 1.2,
+    cost: float = 0.03,
+) -> RunSummary:
+    """Create a RunSummary for testing."""
+    return RunSummary(
+        benchmark="supergpqa",
+        category="reasoning",
+        backend="ollama",
+        model="qwen3:8b",
+        total_samples=100,
+        scored_samples=95,
+        correct=76,
+        accuracy=accuracy,
+        errors=5,
+        mean_latency_seconds=latency,
+        total_cost_usd=cost,
+        per_subject={"math": {"accuracy": 0.85, "count": 20.0}},
+    )
+
+
+# ---------------------------------------------------------------------------
+# TestLLMOptimizer.__init__
+# ---------------------------------------------------------------------------
+
+
+class TestInit:
+    """Tests for LLMOptimizer.__init__."""
+
+    def test_stores_search_space(self) -> None:
+        space = _make_search_space()
+        opt = LLMOptimizer(search_space=space)
+        assert opt.search_space is space
+
+    def test_stores_optimizer_model(self) -> None:
+        space = _make_search_space()
+        opt = LLMOptimizer(search_space=space, optimizer_model="gpt-4o")
+        assert opt.optimizer_model == "gpt-4o"
+
+    def test_default_optimizer_model(self) -> None:
+        space = _make_search_space()
+        opt = LLMOptimizer(search_space=space)
+        assert opt.optimizer_model == "claude-sonnet-4-6"
+
+    def test_stores_optimizer_backend(self) -> None:
+        space = _make_search_space()
+        backend = _make_mock_backend("")
+        opt = LLMOptimizer(
+            search_space=space, optimizer_backend=backend
+        )
+        assert opt.optimizer_backend is backend
+
+    def test_default_backend_is_none(self) -> None:
+        space = _make_search_space()
+        opt = LLMOptimizer(search_space=space)
+        assert opt.optimizer_backend is None
+
+
+# ---------------------------------------------------------------------------
+# TestProposeInitial
+# ---------------------------------------------------------------------------
+
+
+class TestProposeInitial:
+    """Tests for LLMOptimizer.propose_initial."""
+
+    def test_returns_trial_config(self) -> None:
+        response = json.dumps({
+            "params": {
+                "agent.type": "native_react",
+                "intelligence.temperature": 0.3,
+            },
+            "reasoning": "Balanced starting point",
+        })
+        response = f"```json\n{response}\n```"
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        config = opt.propose_initial()
+        assert isinstance(config, TrialConfig)
+        assert config.params["agent.type"] == "native_react"
+        assert config.params["intelligence.temperature"] == 0.3
+        assert config.reasoning == "Balanced starting point"
+        assert len(config.trial_id) == 12
+
+    def test_calls_backend_generate(self) -> None:
+        response = '```json\n{"params": {}, "reasoning": "test"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        opt.propose_initial()
+        backend.generate.assert_called_once()
+        call_kwargs = backend.generate.call_args
+        assert call_kwargs.kwargs["model"] == "claude-sonnet-4-6"
+        assert call_kwargs.kwargs["temperature"] == 0.7
+
+    def test_prompt_contains_search_space(self) -> None:
+        response = '```json\n{"params": {}, "reasoning": "ok"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        opt.propose_initial()
+        prompt = backend.generate.call_args.args[0]
+        assert "Search Space" in prompt
+        assert "agent.type" in prompt
+        assert "intelligence.temperature" in prompt
+        assert "Objective" in prompt
+
+    def test_raises_without_backend(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        with pytest.raises(ValueError, match="optimizer_backend"):
+            opt.propose_initial()
+
+
+# ---------------------------------------------------------------------------
+# TestProposeNext
+# ---------------------------------------------------------------------------
+
+
+class TestProposeNext:
+    """Tests for LLMOptimizer.propose_next."""
+
+    def test_returns_trial_config_with_history(self) -> None:
+        response = json.dumps({
+            "params": {
+                "agent.type": "native_react",
+                "intelligence.temperature": 0.2,
+                "agent.max_turns": 15,
+            },
+            "reasoning": "Lower temp for better accuracy",
+        })
+        response = f"```json\n{response}\n```"
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        history = [_make_trial_result()]
+        config = opt.propose_next(history)
+        assert config.params["agent.type"] == "native_react"
+        assert config.params["intelligence.temperature"] == 0.2
+        assert config.reasoning == "Lower temp for better accuracy"
+
+    def test_prompt_includes_history(self) -> None:
+        response = '```json\n{"params": {}, "reasoning": "ok"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        history = [
+            _make_trial_result(
+                trial_id="t1",
+                accuracy=0.75,
+                analysis="Good but slow",
+            ),
+        ]
+        opt.propose_next(history)
+        prompt = backend.generate.call_args.args[0]
+        assert "Optimization History" in prompt
+        assert "Trial 1" in prompt
+        assert "0.75" in prompt
+        assert "Good but slow" in prompt
+
+    def test_prompt_includes_traces(self) -> None:
+        response = '```json\n{"params": {}, "reasoning": "ok"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        traces = [_make_trace()]
+        opt.propose_next([], traces=traces)
+        prompt = backend.generate.call_args.args[0]
+        assert "Execution Traces" in prompt
+        assert "trace-001" in prompt
+        assert "What is 2+2?" in prompt
+
+    def test_empty_history(self) -> None:
+        response = '```json\n{"params": {"agent.type": "simple"}, "reasoning": "start simple"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        config = opt.propose_next([])
+        prompt = backend.generate.call_args.args[0]
+        assert "No trials have been run yet" in prompt
+        assert config.params["agent.type"] == "simple"
+
+    def test_raises_without_backend(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        with pytest.raises(ValueError, match="optimizer_backend"):
+            opt.propose_next([])
+
+    def test_prompt_includes_failure_modes(self) -> None:
+        response = '```json\n{"params": {}, "reasoning": "fix failures"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        history = [
+            _make_trial_result(
+                failure_modes=["timeout on long inputs", "JSON parse error"],
+            ),
+        ]
+        opt.propose_next(history)
+        prompt = backend.generate.call_args.args[0]
+        assert "timeout on long inputs" in prompt
+        assert "JSON parse error" in prompt
+
+
+# ---------------------------------------------------------------------------
+# TestAnalyzeTrial
+# ---------------------------------------------------------------------------
+
+
+class TestAnalyzeTrial:
+    """Tests for LLMOptimizer.analyze_trial."""
+
+    def test_returns_analysis_text(self) -> None:
+        backend = _make_mock_backend(
+            "The configuration showed strong accuracy at 0.80 "
+            "but latency could be improved."
+        )
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        trial = TrialConfig(
+            trial_id="t1",
+            params={"agent.type": "orchestrator"},
+            reasoning="Test",
+        )
+        summary = _make_run_summary()
+        result = opt.analyze_trial(trial, summary)
+        assert "accuracy" in result.lower()
+        assert isinstance(result, str)
+
+    def test_prompt_contains_config(self) -> None:
+        backend = _make_mock_backend("Analysis here.")
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        trial = TrialConfig(
+            trial_id="t1",
+            params={
+                "agent.type": "orchestrator",
+                "intelligence.temperature": 0.5,
+            },
+            reasoning="Testing mid-range temperature",
+        )
+        summary = _make_run_summary()
+        opt.analyze_trial(trial, summary)
+        prompt = backend.generate.call_args.args[0]
+        assert "agent.type" in prompt
+        assert "orchestrator" in prompt
+        assert "0.5" in prompt
+        assert "Testing mid-range temperature" in prompt
+
+    def test_prompt_contains_results(self) -> None:
+        backend = _make_mock_backend("Analysis here.")
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        trial = TrialConfig(trial_id="t1", params={})
+        summary = _make_run_summary(accuracy=0.85, latency=2.1, cost=0.05)
+        opt.analyze_trial(trial, summary)
+        prompt = backend.generate.call_args.args[0]
+        assert "0.8500" in prompt
+        assert "2.1000" in prompt
+        assert "0.0500" in prompt
+
+    def test_prompt_contains_per_subject(self) -> None:
+        backend = _make_mock_backend("Analysis here.")
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        trial = TrialConfig(trial_id="t1", params={})
+        summary = _make_run_summary()
+        opt.analyze_trial(trial, summary)
+        prompt = backend.generate.call_args.args[0]
+        assert "Per-Subject" in prompt
+        assert "math" in prompt
+
+    def test_prompt_contains_traces(self) -> None:
+        backend = _make_mock_backend("Analysis with traces.")
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        trial = TrialConfig(trial_id="t1", params={})
+        summary = _make_run_summary()
+        traces = [_make_trace()]
+        opt.analyze_trial(trial, summary, traces=traces)
+        prompt = backend.generate.call_args.args[0]
+        assert "Sample Traces" in prompt
+        assert "trace-001" in prompt
+
+    def test_raises_without_backend(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        trial = TrialConfig(trial_id="t1", params={})
+        summary = _make_run_summary()
+        with pytest.raises(ValueError, match="optimizer_backend"):
+            opt.analyze_trial(trial, summary)
+
+    def test_uses_low_temperature(self) -> None:
+        backend = _make_mock_backend("Analysis.")
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_backend=backend,
+        )
+        trial = TrialConfig(trial_id="t1", params={})
+        summary = _make_run_summary()
+        opt.analyze_trial(trial, summary)
+        call_kwargs = backend.generate.call_args
+        assert call_kwargs.kwargs["temperature"] == 0.3
+
+
+# ---------------------------------------------------------------------------
+# TestParseConfigResponse
+# ---------------------------------------------------------------------------
+
+
+class TestParseConfigResponse:
+    """Tests for LLMOptimizer._parse_config_response."""
+
+    def _make_optimizer(self) -> LLMOptimizer:
+        return LLMOptimizer(search_space=_make_search_space())
+
+    def test_json_code_block(self) -> None:
+        opt = self._make_optimizer()
+        response = (
+            "Here is my suggestion:\n\n"
+            "```json\n"
+            '{"params": {"agent.type": "native_react"}, '
+            '"reasoning": "Best for tool use"}\n'
+            "```\n\n"
+            "This should improve results."
+        )
+        config = opt._parse_config_response(response)
+        assert config.params["agent.type"] == "native_react"
+        assert config.reasoning == "Best for tool use"
+
+    def test_generic_code_block(self) -> None:
+        opt = self._make_optimizer()
+        response = (
+            "```\n"
+            '{"params": {"intelligence.temperature": 0.1}, '
+            '"reasoning": "Low temp"}\n'
+            "```"
+        )
+        config = opt._parse_config_response(response)
+        assert config.params["intelligence.temperature"] == 0.1
+
+    def test_raw_json(self) -> None:
+        opt = self._make_optimizer()
+        response = (
+            'I suggest: {"params": {"agent.max_turns": 10}, '
+            '"reasoning": "More turns"}'
+        )
+        config = opt._parse_config_response(response)
+        assert config.params["agent.max_turns"] == 10
+        assert config.reasoning == "More turns"
+
+    def test_unparseable_response(self) -> None:
+        opt = self._make_optimizer()
+        response = "I cannot produce a valid configuration right now."
+        config = opt._parse_config_response(response)
+        assert config.params == {}
+        assert "Failed to parse" in config.reasoning
+
+    def test_trial_id_is_12_chars(self) -> None:
+        opt = self._make_optimizer()
+        response = '```json\n{"params": {}, "reasoning": ""}\n```'
+        config = opt._parse_config_response(response)
+        assert len(config.trial_id) == 12
+
+    def test_missing_reasoning_key(self) -> None:
+        opt = self._make_optimizer()
+        response = '```json\n{"params": {"agent.type": "simple"}}\n```'
+        config = opt._parse_config_response(response)
+        assert config.params["agent.type"] == "simple"
+        assert config.reasoning == ""
+
+    def test_missing_params_key(self) -> None:
+        opt = self._make_optimizer()
+        response = '```json\n{"reasoning": "just thinking"}\n```'
+        config = opt._parse_config_response(response)
+        assert config.params == {}
+        assert config.reasoning == "just thinking"
+
+    def test_json_with_surrounding_text(self) -> None:
+        opt = self._make_optimizer()
+        response = (
+            "Based on the analysis, I propose:\n\n"
+            "```json\n"
+            "{\n"
+            '  "params": {\n'
+            '    "agent.type": "orchestrator",\n'
+            '    "intelligence.temperature": 0.4,\n'
+            '    "agent.max_turns": 20\n'
+            "  },\n"
+            '  "reasoning": "Multi-line\\nreasoning here"\n'
+            "}\n"
+            "```\n\n"
+            "Let me know if you'd like to adjust anything."
+        )
+        config = opt._parse_config_response(response)
+        assert config.params["agent.type"] == "orchestrator"
+        assert config.params["intelligence.temperature"] == 0.4
+        assert config.params["agent.max_turns"] == 20
+
+    def test_invalid_json_in_code_block_falls_through(self) -> None:
+        """If ```json block has invalid JSON, fall back to raw search."""
+        opt = self._make_optimizer()
+        # Invalid JSON in ```json block, but valid JSON later
+        response = (
+            "```json\n{invalid json}\n```\n\n"
+            'Actually: {"params": {"agent.type": "simple"}, "reasoning": "fallback"}'
+        )
+        config = opt._parse_config_response(response)
+        # Should find the valid JSON via raw search
+        assert config.params.get("agent.type") == "simple"
+
+
+# ---------------------------------------------------------------------------
+# TestFormatHistory
+# ---------------------------------------------------------------------------
+
+
+class TestFormatHistory:
+    """Tests for LLMOptimizer._format_history."""
+
+    def test_single_trial(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        history = [_make_trial_result(trial_id="abc")]
+        result = opt._format_history(history)
+        assert "Trial 1" in result
+        assert "abc" in result
+        assert "0.7500" in result
+        assert "Decent results" in result
+
+    def test_multiple_trials(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        history = [
+            _make_trial_result(trial_id="t1", accuracy=0.7),
+            _make_trial_result(trial_id="t2", accuracy=0.85),
+        ]
+        result = opt._format_history(history)
+        assert "Trial 1" in result
+        assert "Trial 2" in result
+        assert "t1" in result
+        assert "t2" in result
+
+    def test_includes_failure_modes(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        history = [
+            _make_trial_result(
+                failure_modes=["timeout", "parse_error"],
+            ),
+        ]
+        result = opt._format_history(history)
+        assert "timeout" in result
+        assert "parse_error" in result
+
+    def test_includes_params(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        history = [
+            _make_trial_result(
+                params={"agent.type": "native_react"},
+            ),
+        ]
+        result = opt._format_history(history)
+        assert "native_react" in result
+
+    def test_empty_history(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        result = opt._format_history([])
+        assert result == ""
+
+
+# ---------------------------------------------------------------------------
+# TestFormatTraces
+# ---------------------------------------------------------------------------
+
+
+class TestFormatTraces:
+    """Tests for LLMOptimizer._format_traces."""
+
+    def test_single_trace(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        traces = [_make_trace()]
+        result = opt._format_traces(traces)
+        assert "trace-001" in result
+        assert "What is 2+2?" in result
+        assert "orchestrator" in result
+        assert "success" in result
+
+    def test_limits_to_last_10(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        traces = [
+            _make_trace(trace_id=f"trace-{i:03d}")
+            for i in range(20)
+        ]
+        result = opt._format_traces(traces)
+        # Should only include the last 10 (indices 10-19)
+        assert "trace-010" in result
+        assert "trace-019" in result
+        # The first traces should not appear
+        assert "trace-000" not in result
+        assert "trace-009" not in result
+
+    def test_truncates_long_outputs(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        long_result = "x" * 1000
+        traces = [_make_trace(result=long_result)]
+        result = opt._format_traces(traces)
+        # Should be truncated and end with "..."
+        assert "..." in result
+        # Should NOT contain the full 1000 chars
+        assert long_result not in result
+
+    def test_includes_steps(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        traces = [_make_trace(num_steps=3)]
+        result = opt._format_traces(traces)
+        assert "Steps:" in result
+        assert "generate" in result
+        assert "tool_call" in result
+
+    def test_shows_feedback(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        trace = _make_trace()
+        trace.feedback = 0.9
+        result = opt._format_traces([trace])
+        assert "0.9" in result
+
+    def test_empty_traces(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        result = opt._format_traces([])
+        assert result == ""
+
+    def test_truncates_long_step_data(self) -> None:
+        opt = LLMOptimizer(search_space=_make_search_space())
+        trace = _make_trace(num_steps=0)
+        # Add a step with very long input/output
+        trace.steps.append(
+            TraceStep(
+                step_type=StepType.GENERATE,
+                timestamp=0.0,
+                duration_seconds=0.1,
+                input={"prompt": "a" * 1000},
+                output={"content": "b" * 1000},
+            )
+        )
+        result = opt._format_traces([trace])
+        # The full 1000-char strings should not appear verbatim
+        assert ("a" * 1000) not in result
+        assert ("b" * 1000) not in result
+        assert "..." in result
+
+
+# ---------------------------------------------------------------------------
+# Integration-style tests
+# ---------------------------------------------------------------------------
+
+
+class TestIntegration:
+    """End-to-end tests with mocked backend."""
+
+    def test_propose_initial_then_next(self) -> None:
+        """Simulate a two-step optimization loop."""
+        space = _make_search_space()
+        initial_response = (
+            '```json\n'
+            '{"params": {"agent.type": "orchestrator", '
+            '"intelligence.temperature": 0.5, "agent.max_turns": 10}, '
+            '"reasoning": "Balanced start"}\n'
+            '```'
+        )
+        next_response = (
+            '```json\n'
+            '{"params": {"agent.type": "native_react", '
+            '"intelligence.temperature": 0.2, "agent.max_turns": 15}, '
+            '"reasoning": "Switch to ReAct for better tool use"}\n'
+            '```'
+        )
+        backend = MagicMock(spec=InferenceBackend)
+        backend.backend_id = "mock"
+        backend.generate.side_effect = [initial_response, next_response]
+
+        opt = LLMOptimizer(
+            search_space=space, optimizer_backend=backend
+        )
+
+        # Step 1: initial proposal
+        config1 = opt.propose_initial()
+        assert config1.params["agent.type"] == "orchestrator"
+
+        # Step 2: build history and ask for next
+        result1 = TrialResult(
+            trial_id=config1.trial_id,
+            config=config1,
+            accuracy=0.72,
+            mean_latency_seconds=2.0,
+            analysis="Accuracy needs improvement",
+        )
+        config2 = opt.propose_next([result1])
+        assert config2.params["agent.type"] == "native_react"
+        assert config2.params["intelligence.temperature"] == 0.2
+
+    def test_full_loop_with_analysis(self) -> None:
+        """Simulate propose -> evaluate -> analyze."""
+        space = _make_search_space()
+        propose_response = (
+            '```json\n'
+            '{"params": {"agent.type": "orchestrator"}, '
+            '"reasoning": "Start with orchestrator"}\n'
+            '```'
+        )
+        analysis_response = (
+            "The orchestrator agent achieved moderate accuracy. "
+            "The main bottleneck is latency due to multi-turn reasoning. "
+            "Reducing max_turns or switching to native_react may help."
+        )
+        backend = MagicMock(spec=InferenceBackend)
+        backend.backend_id = "mock"
+        backend.generate.side_effect = [
+            propose_response,
+            analysis_response,
+        ]
+
+        opt = LLMOptimizer(
+            search_space=space, optimizer_backend=backend
+        )
+
+        config = opt.propose_initial()
+        summary = _make_run_summary()
+        analysis = opt.analyze_trial(config, summary)
+        assert "orchestrator" in analysis
+        assert "latency" in analysis
+
+    def test_custom_optimizer_model(self) -> None:
+        """Verify custom model is passed to backend."""
+        response = '```json\n{"params": {}, "reasoning": "ok"}\n```'
+        backend = _make_mock_backend(response)
+        opt = LLMOptimizer(
+            search_space=_make_search_space(),
+            optimizer_model="gpt-4o",
+            optimizer_backend=backend,
+        )
+        opt.propose_initial()
+        call_kwargs = backend.generate.call_args
+        assert call_kwargs.kwargs["model"] == "gpt-4o"