diff --git a/README.md b/README.md
index d79d8b62..531d391e 100644
--- a/README.md
+++ b/README.md
@@ -202,6 +202,23 @@ Ralph only works if there are feedback loops:
 
 Frontend stories must include "Verify in browser using dev-browser skill" in acceptance criteria. Ralph will use the dev-browser skill to navigate to the page, interact with the UI, and confirm changes work.
 
+### Per-Story Model Selection (Claude Code)
+
+When using `--tool claude`, you can specify a model per story by adding a `model` field:
+
+```json
+{
+  "id": "US-005",
+  "title": "Complex table reconstruction",
+  "model": "opus",
+  "notes": "Requires opus for complex multi-column table logic"
+}
+```
+
+Ralph reads the `model` field from the next incomplete story and passes `--model` to the Claude CLI. Valid values: `sonnet`, `opus`, `haiku`, or full model IDs like `claude-opus-4-6`. Stories without a `model` field use the default model.
+
+This lets you use a cheaper model (sonnet) for straightforward stories and reserve opus for complex ones, optimizing cost across a run.
+
 ### Stop Condition
 
 When all stories have `passes: true`, Ralph outputs `<promise>COMPLETE</promise>` and the loop exits.
diff --git a/prd.json.example b/prd.json.example
index fbc40668..13148748 100644
--- a/prd.json.example
+++ b/prd.json.example
@@ -14,7 +14,8 @@
       ],
       "priority": 1,
       "passes": false,
-      "notes": ""
+      "notes": "",
+      "model": ""
     },
     {
       "id": "US-002",
diff --git a/ralph.sh b/ralph.sh
index baff052a..6ec7826b 100755
--- a/ralph.sh
+++ b/ralph.sh
@@ -87,12 +87,28 @@ for i in $(seq 1 $MAX_ITERATIONS); do
   echo "  Ralph Iteration $i of $MAX_ITERATIONS ($TOOL)"
   echo "==============================================================="
 
+  # Detect per-story model override from prd.json
+  # Reads the "model" field from the first story where passes is false
+  STORY_MODEL=""
+  STORY_ID=""
+  if [ -f "$PRD_FILE" ] && [[ "$TOOL" == "claude" ]]; then
+    STORY_MODEL=$(jq -r '[.userStories[] | select(.passes == false)] | sort_by(.priority) | first | .model // empty' "$PRD_FILE" 2>/dev/null || echo "")
+    STORY_ID=$(jq -r '[.userStories[] | select(.passes == false)] | sort_by(.priority) | first | .id // empty' "$PRD_FILE" 2>/dev/null || echo "")
+    if [ -n "$STORY_MODEL" ] && [ -n "$STORY_ID" ]; then
+      echo "  Story $STORY_ID requests model: $STORY_MODEL"
+    fi
+  fi
+
   # Run the selected tool with the ralph prompt
   if [[ "$TOOL" == "amp" ]]; then
     OUTPUT=$(cat "$SCRIPT_DIR/prompt.md" | amp --dangerously-allow-all 2>&1 | tee /dev/stderr) || true
   else
     # Claude Code: use --dangerously-skip-permissions for autonomous operation, --print for output
-    OUTPUT=$(claude --dangerously-skip-permissions --print < "$SCRIPT_DIR/CLAUDE.md" 2>&1 | tee /dev/stderr) || true
+    MODEL_FLAG=""
+    if [ -n "$STORY_MODEL" ]; then
+      MODEL_FLAG="--model $STORY_MODEL"
+    fi
+    OUTPUT=$(claude --dangerously-skip-permissions --print $MODEL_FLAG < "$SCRIPT_DIR/CLAUDE.md" 2>&1 | tee /dev/stderr) || true
   fi
   
   # Check for completion signal