diff --git a/src/skillspector/llm_analyzer_base.py b/src/skillspector/llm_analyzer_base.py
index aa3e7e9..b6be791 100644
--- a/src/skillspector/llm_analyzer_base.py
+++ b/src/skillspector/llm_analyzer_base.py
@@ -33,7 +33,7 @@
 from typing import Literal
 
 from langchain_core.messages import BaseMessage
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, field_validator
 
 from skillspector.llm_utils import get_chat_model
 from skillspector.logging_config import get_logger
@@ -62,12 +62,35 @@ class LLMFinding(BaseModel):
     rule_id: str = Field(description="Identifier for the type of finding")
     message: str = Field(description="Short description of the finding")
     severity: Literal["LOW", "MEDIUM", "HIGH", "CRITICAL"] = Field(description="Severity level")
-    start_line: int = Field(ge=1, description="Starting line number")
+    # start_line and confidence carry no ge/le Field bounds on purpose. Pydantic
+    # bounds emit JSON-schema minimum/maximum, which some OpenAI-compatible
+    # structured-output / tool-calling endpoints reject when they validate the
+    # response schema, failing the whole call. The ranges are enforced by the
+    # validators below instead, so the guarantee holds without those keywords in
+    # the emitted schema. start_line stays required (no default), so a finding
+    # with no location is still rejected rather than materialised at line 1;
+    # only the numeric bound is removed, not the requiredness.
+    start_line: int = Field(description="Starting line number (>= 1)")
     end_line: int | None = Field(default=None, description="Ending line number (optional)")
-    confidence: float = Field(ge=0.0, le=1.0, default=0.5, description="Confidence score")
+    confidence: float = Field(default=0.5, description="Confidence score between 0.0 and 1.0")
     explanation: str = Field(default="", description="Why this is a finding (2-3 sentences)")
     remediation: str = Field(default="", description="Actionable steps to fix the issue")
 
+    @field_validator("start_line")
+    @classmethod
+    def _clamp_start_line(cls, v: int) -> int:
+        # Clamp rather than raise: an LLM occasionally returns 0 for a
+        # whole-file finding, and normalising to the first line is better than
+        # dropping the finding over an off-by-one.
+        return v if v >= 1 else 1
+
+    @field_validator("confidence")
+    @classmethod
+    def _clamp_confidence(cls, v: float) -> float:
+        # Clamp into [0.0, 1.0] so a slightly out-of-range model value
+        # normalises instead of failing the structured-output parse.
+        return min(1.0, max(0.0, v))
+
     def to_finding(self, file: str) -> Finding:
         """Convert to a :class:`Finding` for the graph state."""
         return Finding(
diff --git a/src/skillspector/nodes/meta_analyzer.py b/src/skillspector/nodes/meta_analyzer.py
index 8f2b541..c1ae287 100644
--- a/src/skillspector/nodes/meta_analyzer.py
+++ b/src/skillspector/nodes/meta_analyzer.py
@@ -63,7 +63,10 @@ class MetaAnalyzerFinding(BaseModel):
         description="The end line number from the finding's Location, if available.",
     )
     is_vulnerability: bool = Field(description="Whether this is a true vulnerability")
-    confidence: float = Field(ge=0.0, le=1.0, description="Confidence score between 0.0 and 1.0")
+    # No ge/le bound on purpose: Pydantic bounds emit JSON-schema
+    # minimum/maximum, which some OpenAI-compatible structured-output endpoints
+    # reject. The range is enforced by the validator below instead.
+    confidence: float = Field(description="Confidence score between 0.0 and 1.0")
     intent: Literal["malicious", "negligent", "benign"] = Field(
         description="Likely intent behind the finding"
     )
@@ -73,6 +76,13 @@ class MetaAnalyzerFinding(BaseModel):
     explanation: str = Field(default="", description="Why this is dangerous (2-3 sentences)")
     remediation: str = Field(default="", description="How to fix the issue (actionable steps)")
 
+    @field_validator("confidence")
+    @classmethod
+    def _clamp_confidence(cls, v: float) -> float:
+        # Clamp into [0.0, 1.0] so a slightly out-of-range model value
+        # normalises instead of failing the structured-output parse.
+        return min(1.0, max(0.0, v))
+
 
 class OverallAssessment(BaseModel):
     """Overall risk assessment for the analyzed file."""
diff --git a/tests/nodes/test_llm_analyzer_base.py b/tests/nodes/test_llm_analyzer_base.py
index c1fabca..5b42db1 100644
--- a/tests/nodes/test_llm_analyzer_base.py
+++ b/tests/nodes/test_llm_analyzer_base.py
@@ -566,15 +566,13 @@ def test_valid_finding(self) -> None:
         assert len(result.findings) == 1
         assert result.findings[0].confidence == 0.9
 
-    def test_confidence_validation(self) -> None:
-        with pytest.raises(ValueError):
-            LLMFinding(
-                rule_id="X",
-                message="x",
-                severity="LOW",
-                start_line=1,
-                confidence=1.5,
-            )
+    def test_confidence_is_clamped(self) -> None:
+        """Out-of-range confidence is clamped, not rejected, so a slightly off
+        model value does not fail the whole structured-output parse."""
+        hi = LLMFinding(rule_id="X", message="x", severity="LOW", start_line=1, confidence=1.5)
+        lo = LLMFinding(rule_id="X", message="x", severity="LOW", start_line=1, confidence=-0.3)
+        assert hi.confidence == 1.0
+        assert lo.confidence == 0.0
 
     def test_severity_validation(self) -> None:
         with pytest.raises(ValueError):
@@ -660,15 +658,25 @@ def test_valid_finding(self) -> None:
         assert len(result.findings) == 1
         assert result.findings[0].confidence == 0.9
 
-    def test_confidence_validation(self) -> None:
-        with pytest.raises(ValueError):
-            MetaAnalyzerFinding(
-                pattern_id="E1",
-                is_vulnerability=True,
-                confidence=1.5,
-                intent="malicious",
-                impact="high",
-            )
+    def test_confidence_is_clamped(self) -> None:
+        """Out-of-range confidence is clamped, not rejected, so a slightly off
+        model value does not fail the whole structured-output parse."""
+        high = MetaAnalyzerFinding(
+            pattern_id="E1",
+            is_vulnerability=True,
+            confidence=1.5,
+            intent="malicious",
+            impact="high",
+        )
+        low = MetaAnalyzerFinding(
+            pattern_id="E1",
+            is_vulnerability=True,
+            confidence=-0.2,
+            intent="malicious",
+            impact="high",
+        )
+        assert high.confidence == 1.0
+        assert low.confidence == 0.0
 
     def test_intent_validation(self) -> None:
         with pytest.raises(ValueError):
@@ -719,6 +727,54 @@ def test_model_dump(self) -> None:
         assert d["start_line"] is None
 
 
+class TestStructuredOutputSchema:
+    """The response schemas must stay portable across structured-output backends.
+
+    Pydantic ge/le bounds emit JSON-schema ``minimum`` / ``maximum``, which some
+    OpenAI-compatible structured-output / tool-calling endpoints reject when they
+    validate the response schema. The ranges are enforced by runtime validators
+    instead, so these keywords must not appear in the emitted schema.
+    """
+
+    @staticmethod
+    def _numeric_keywords(schema: dict) -> set[str]:
+        found: set[str] = set()
+
+        def walk(node: object) -> None:
+            if isinstance(node, dict):
+                found.update(k for k in ("minimum", "maximum") if k in node)
+                for value in node.values():
+                    walk(value)
+            elif isinstance(node, list):
+                for value in node:
+                    walk(value)
+
+        walk(schema)
+        return found
+
+    def test_llm_finding_schema_has_no_numeric_bounds(self) -> None:
+        assert self._numeric_keywords(LLMFinding.model_json_schema()) == set()
+
+    def test_meta_finding_schema_has_no_numeric_bounds(self) -> None:
+        assert self._numeric_keywords(MetaAnalyzerFinding.model_json_schema()) == set()
+
+    def test_llm_finding_clamps_confidence(self) -> None:
+        hi = LLMFinding(rule_id="R", message="m", severity="LOW", start_line=1, confidence=1.5)
+        lo = LLMFinding(rule_id="R", message="m", severity="LOW", start_line=1, confidence=-0.3)
+        assert hi.confidence == 1.0
+        assert lo.confidence == 0.0
+
+    def test_llm_finding_clamps_start_line(self) -> None:
+        assert LLMFinding(rule_id="R", message="m", severity="LOW", start_line=0).start_line == 1
+        assert LLMFinding(rule_id="R", message="m", severity="LOW", start_line=42).start_line == 42
+
+    def test_llm_finding_start_line_is_required(self) -> None:
+        """start_line stays required: a finding with no location is rejected,
+        not materialised at line 1."""
+        with pytest.raises(ValueError):
+            LLMFinding(rule_id="R", message="m", severity="LOW")
+
+
 # ---------------------------------------------------------------------------
 # LLMMetaAnalyzer.get_batches
 # ---------------------------------------------------------------------------