diff --git a/apps/backend/cli/utils.py b/apps/backend/cli/utils.py
index 23df3561..25b92ca2 100644
--- a/apps/backend/cli/utils.py
+++ b/apps/backend/cli/utils.py
@@ -29,7 +29,7 @@ from ui import (
 )
 
 # Configuration - uses shorthand that resolves via API Profile if configured
-DEFAULT_MODEL = "opus"
+DEFAULT_MODEL = "sonnet"  # Changed from "opus" (fix #433)
 
 
 def setup_environment() -> Path:
diff --git a/apps/backend/ideation/config.py b/apps/backend/ideation/config.py
index 0d76113b..0f56a893 100644
--- a/apps/backend/ideation/config.py
+++ b/apps/backend/ideation/config.py
@@ -25,7 +25,7 @@ class IdeationConfigManager:
         include_roadmap_context: bool = True,
         include_kanban_context: bool = True,
         max_ideas_per_type: int = 5,
-        model: str = "opus",
+        model: str = "sonnet",  # Changed from "opus" (fix #433)
         thinking_level: str = "medium",
         refresh: bool = False,
         append: bool = False,
diff --git a/apps/backend/ideation/generator.py b/apps/backend/ideation/generator.py
index 61d685ac..dcd34704 100644
--- a/apps/backend/ideation/generator.py
+++ b/apps/backend/ideation/generator.py
@@ -56,7 +56,7 @@ class IdeationGenerator:
         self,
         project_dir: Path,
         output_dir: Path,
-        model: str = "opus",
+        model: str = "sonnet",  # Changed from "opus" (fix #433)
         thinking_level: str = "medium",
         max_ideas_per_type: int = 5,
     ):
diff --git a/apps/backend/ideation/runner.py b/apps/backend/ideation/runner.py
index b46e4167..c20d41f8 100644
--- a/apps/backend/ideation/runner.py
+++ b/apps/backend/ideation/runner.py
@@ -41,7 +41,7 @@ class IdeationOrchestrator:
         include_roadmap_context: bool = True,
         include_kanban_context: bool = True,
         max_ideas_per_type: int = 5,
-        model: str = "opus",
+        model: str = "sonnet",  # Changed from "opus" (fix #433)
         thinking_level: str = "medium",
         refresh: bool = False,
         append: bool = False,
diff --git a/apps/backend/ideation/types.py b/apps/backend/ideation/types.py
index 2310a274..c2c391d6 100644
--- a/apps/backend/ideation/types.py
+++ b/apps/backend/ideation/types.py
@@ -31,6 +31,6 @@ class IdeationConfig:
     include_roadmap_context: bool = True
     include_kanban_context: bool = True
     max_ideas_per_type: int = 5
-    model: str = "opus"
+    model: str = "sonnet"  # Changed from "opus" (fix #433)
     refresh: bool = False
     append: bool = False  # If True, preserve existing ideas when merging
diff --git a/apps/backend/phase_config.py b/apps/backend/phase_config.py
index bbcebc95..3fc9ba74 100644
--- a/apps/backend/phase_config.py
+++ b/apps/backend/phase_config.py
@@ -47,10 +47,10 @@ SPEC_PHASE_THINKING_LEVELS: dict[str, str] = {
     "complexity_assessment": "medium",
 }
 
-# Default phase configuration (matches UI defaults)
+# Default phase configuration (fallback, matches 'Balanced' profile)
 DEFAULT_PHASE_MODELS: dict[str, str] = {
     "spec": "sonnet",
-    "planning": "opus",
+    "planning": "sonnet",  # Changed from "opus" (fix #433)
     "coding": "sonnet",
     "qa": "sonnet",
 }
diff --git a/apps/backend/runners/ideation_runner.py b/apps/backend/runners/ideation_runner.py
index c81a061d..4e74f683 100644
--- a/apps/backend/runners/ideation_runner.py
+++ b/apps/backend/runners/ideation_runner.py
@@ -94,7 +94,7 @@ def main():
     parser.add_argument(
         "--model",
         type=str,
-        default="opus",
+        default="sonnet",  # Changed from "opus" (fix #433)
         help="Model to use (haiku, sonnet, opus, or full model ID)",
     )
     parser.add_argument(
diff --git a/apps/backend/runners/roadmap/models.py b/apps/backend/runners/roadmap/models.py
index 2fd41341..377f5cfa 100644
--- a/apps/backend/runners/roadmap/models.py
+++ b/apps/backend/runners/roadmap/models.py
@@ -23,6 +23,6 @@ class RoadmapConfig:
 
     project_dir: Path
     output_dir: Path
-    model: str = "opus"
+    model: str = "sonnet"  # Changed from "opus" (fix #433)
     refresh: bool = False  # Force regeneration even if roadmap exists
     enable_competitor_analysis: bool = False  # Enable competitor analysis phase
diff --git a/apps/backend/runners/roadmap/orchestrator.py b/apps/backend/runners/roadmap/orchestrator.py
index 5d67ad35..b49ca2c1 100644
--- a/apps/backend/runners/roadmap/orchestrator.py
+++ b/apps/backend/runners/roadmap/orchestrator.py
@@ -27,7 +27,7 @@ class RoadmapOrchestrator:
         self,
         project_dir: Path,
         output_dir: Path | None = None,
-        model: str = "opus",
+        model: str = "sonnet",  # Changed from "opus" (fix #433)
         thinking_level: str = "medium",
         refresh: bool = False,
         enable_competitor_analysis: bool = False,
diff --git a/apps/backend/runners/roadmap_runner.py b/apps/backend/runners/roadmap_runner.py
index ebb1b8c4..4a31c025 100644
--- a/apps/backend/runners/roadmap_runner.py
+++ b/apps/backend/runners/roadmap_runner.py
@@ -55,7 +55,7 @@ def main():
     parser.add_argument(
         "--model",
         type=str,
-        default="opus",
+        default="sonnet",  # Changed from "opus" (fix #433)
         help="Model to use (haiku, sonnet, opus, or full model ID)",
     )
     parser.add_argument(