diff --git a/apps/backend/spec/compaction.py b/apps/backend/spec/compaction.py
index d74b377c..65365d34 100644
--- a/apps/backend/spec/compaction.py
+++ b/apps/backend/spec/compaction.py
@@ -141,7 +141,7 @@ def gather_phase_outputs(spec_dir: Path, phase_name: str) -> str:
         file_path = spec_dir / filename
         if file_path.exists():
             try:
-                content = file_path.read_text()
+                content = file_path.read_text(encoding="utf-8")
                 # Limit individual file size
                 if len(content) > 10000:
                     content = content[:10000] + "\n\n[... file truncated ...]"
diff --git a/apps/backend/spec/pipeline/agent_runner.py b/apps/backend/spec/pipeline/agent_runner.py
index d1ee2a78..b981a150 100644
--- a/apps/backend/spec/pipeline/agent_runner.py
+++ b/apps/backend/spec/pipeline/agent_runner.py
@@ -82,7 +82,7 @@ class AgentRunner:
             return False, f"Prompt not found: {prompt_path}"
 
         # Load prompt
-        prompt = prompt_path.read_text()
+        prompt = prompt_path.read_text(encoding="utf-8")
         debug_detailed(
             "agent_runner",
             "Loaded prompt file",
diff --git a/apps/backend/spec/validate_pkg/validators/spec_document_validator.py b/apps/backend/spec/validate_pkg/validators/spec_document_validator.py
index edf4a991..92a5f8ad 100644
--- a/apps/backend/spec/validate_pkg/validators/spec_document_validator.py
+++ b/apps/backend/spec/validate_pkg/validators/spec_document_validator.py
@@ -40,7 +40,12 @@ class SpecDocumentValidator:
             fixes.append("Create spec.md with required sections")
             return ValidationResult(False, "spec", errors, warnings, fixes)
 
-        content = spec_file.read_text()
+        try:
+            content = spec_file.read_text(encoding="utf-8")
+        except (OSError, UnicodeDecodeError) as e:
+            errors.append(f"Failed to read spec.md: {e}")
+            fixes.append("Ensure spec.md is a valid UTF-8 encoded file")
+            return ValidationResult(False, "spec", errors, warnings, fixes)
 
         # Check for required sections
         for section in SPEC_REQUIRED_SECTIONS:
diff --git a/apps/backend/spec/validation_strategy.py b/apps/backend/spec/validation_strategy.py
index cad467e2..fe71f8f1 100644
--- a/apps/backend/spec/validation_strategy.py
+++ b/apps/backend/spec/validation_strategy.py
@@ -171,9 +171,15 @@ def detect_project_type(project_dir: Path) -> str:
         # Try to detect API framework
         deps_text = ""
         if requirements.exists():
-            deps_text = requirements.read_text().lower()
+            try:
+                deps_text = requirements.read_text(encoding="utf-8").lower()
+            except (OSError, UnicodeDecodeError):
+                pass  # Skip if file is unreadable
         if pyproject.exists():
-            deps_text += pyproject.read_text().lower()
+            try:
+                deps_text += pyproject.read_text(encoding="utf-8").lower()
+            except (OSError, UnicodeDecodeError):
+                pass  # Skip if file is unreadable
 
         if "fastapi" in deps_text or "flask" in deps_text or "django" in deps_text:
             return "python_api"