diff --git a/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md b/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md
index 8639cb4c..fa36ab21 100644
--- a/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md
+++ b/docs/development/current/main/01-JoinIR-Selfhost-INDEX.md
@@ -101,6 +101,8 @@ Phase 文書は歴史や検証ログも含むので、「JoinIR の現役設計
   - → `docs/development/current/main/phase131-2-summary.md`（要点）
 - LLVM（Python llvmlite）lowering の不具合切り分けで迷っているとき
   - → `docs/development/current/main/phase131-3-llvm-lowering-inventory.md`（再現ケース表 + 根本原因候補）
+  - → `docs/development/current/main/phase131-11-case-c-summary.md`（Case C: `loop(true)` + break/continue の本命計画）
+  - → `docs/development/current/main/case-c-infinite-loop-analysis.md`（Case C: 詳細調査ログ）
   - → `docs/development/current/main/phase131-5-taglink-fix-summary.md`（TAG-LINK: symbol 名の修正ログ）
   - → `docs/development/current/main/phase131-6-ssa-dominance-diagnosis.md`（TAG-RUN の初期診断ログ・歴史）
   - → `docs/development/current/main/phase87-selfhost-llvm-exe-line.md`（実行パイプラインのSSOT）
diff --git a/docs/development/current/main/10-Now.md b/docs/development/current/main/10-Now.md
index bf0aa18e..f0c4fd02 100644
--- a/docs/development/current/main/10-Now.md
+++ b/docs/development/current/main/10-Now.md
@@ -76,6 +76,9 @@
 - LLVM（Python llvmlite）lowering の棚卸し（Phase 131-3..10）:
   - `docs/development/current/main/phase131-3-llvm-lowering-inventory.md`
   - 状態: Case B（Pattern1/loop_min_while）は EMIT/LINK/RUN まで復旧済み。残りは Case C の JoinIR ループパターン穴。
+  - Case C の調査と実装計画:
+    - `docs/development/current/main/phase131-11-case-c-summary.md`
+    - `docs/development/current/main/case-c-infinite-loop-analysis.md`
 
 ---
 
diff --git a/docs/development/current/main/case-c-infinite-loop-analysis.md b/docs/development/current/main/case-c-infinite-loop-analysis.md
new file mode 100644
index 00000000..9aceb1a5
--- /dev/null
+++ b/docs/development/current/main/case-c-infinite-loop-analysis.md
@@ -0,0 +1,703 @@
+# Case C Analysis: loop(true) + break/continue Pattern
+
+**Date**: 2025-12-14
+**Phase**: 131-11 (Case C本命タスク)
+**Status**: 🔍 Root Cause Analysis Complete
+
+## Executive Summary
+
+**Problem**: `loop(true) { ... break ... continue }` fails JoinIR pattern matching
+**Root Cause**: Loop variable extraction expects comparison operators, not boolean literals
+**Pattern Gap**: Need a dedicated “infinite loop + early exit” pattern (avoid “Pattern5” naming collision with existing Trim/P5), or a carefully-scoped Pattern2 extension.
+
+---
+
+## Test Case
+
+**File**: `apps/tests/llvm_stage3_loop_only.hako`
+
+```nyash
+static box Main {
+  main() {
+    local counter = 0
+    loop (true) {
+      counter = counter + 1
+      if counter == 3 { break }
+      continue
+    }
+    print("Result: " + counter)
+    return 0
+  }
+}
+```
+
+**Error**:
+```
+❌ MIR compilation error: [joinir/freeze] Loop lowering failed:
+   JoinIR does not support this pattern, and LoopBuilder has been removed.
+Function: main
+Hint: This loop pattern is not supported. All loops must use JoinIR lowering.
+```
+
+---
+
+## Root Cause Analysis
+
+### 1. Pattern Detection Flow
+
+**Current Flow** (for `loop(true)`):
+```
+1. LoopPatternContext::new() extracts features from AST
+   ├─ has_break = true (✅ detected)
+   ├─ has_continue = true (✅ detected)
+   └─ pattern_kind = Pattern4Continue (❌ WRONG - should be Pattern2 or new Pattern5)
+
+2. Pattern 4 (Continue) detect function called
+   └─ Tries to extract loop variable from condition
+      └─ extract_loop_variable_from_condition(BoolLiteral(true))
+         └─ ❌ FAILS - expects BinaryOp comparison, not boolean literal
+
+3. Pattern falls through, no pattern matches
+   └─ Returns Ok(None) - "No pattern matched"
+      └─ Main router calls freeze() error
+```
+
+**Why it fails**:
+- **Location**: `src/mir/builder/control_flow/utils.rs:25-52`
+- **Function**: `extract_loop_variable_from_condition()`
+- **Expected**: Binary comparison like `i < 3`
+- **Actual**: Boolean literal `true`
+- **Result**: Error "Unsupported loop condition pattern"
+
+### 2. Pattern Classification Issue
+
+**Classification logic** (`src/mir/loop_pattern_detection/mod.rs:276-305`):
+
+```rust
+pub fn classify(features: &LoopFeatures) -> LoopPatternKind {
+    // Pattern 4: Continue (highest priority)
+    if features.has_continue {
+        return LoopPatternKind::Pattern4Continue;  // ← Case C goes here
+    }
+
+    // Pattern 3: If-PHI (check before Pattern 1)
+    if features.has_if && features.carrier_count >= 1
+        && !features.has_break && !features.has_continue {
+        return LoopPatternKind::Pattern3IfPhi;
+    }
+
+    // Pattern 2: Break
+    if features.has_break && !features.has_continue {
+        return LoopPatternKind::Pattern2Break;
+    }
+
+    // Pattern 1: Simple While
+    if !features.has_break && !features.has_continue && !features.has_if {
+        return LoopPatternKind::Pattern1SimpleWhile;
+    }
+
+    LoopPatternKind::Unknown
+}
+```
+
+**Problem**: Case C has `has_continue = true`, so it routes to Pattern 4, but:
+- Pattern 4 expects a loop variable in condition (e.g., `i < 10`)
+- `loop(true)` has no loop variable - it's an infinite loop
+
+---
+
+## Pattern Coverage Gap
+
+### Current Patterns (4 total)
+
+| Pattern | Condition Type | Break | Continue | Notes |
+|---------|---------------|-------|----------|-------|
+| Pattern 1 | Comparison (`i < 3`) | ❌ | ❌ | Simple while loop |
+| Pattern 2 | Comparison (`i < 3`) | ✅ | ❌ | Loop with conditional break |
+| Pattern 3 | Comparison (`i < 3`) | ❌ | ❌ | Loop with if-else PHI |
+| Pattern 4 | Comparison (`i < 3`) | ❌ | ✅ | Loop with continue |
+
+### Missing Pattern: Infinite Loop with Early Exit
+
+**Case C characteristics**:
+- **Condition**: Boolean literal (`true`) - infinite loop
+- **Break**: ✅ Yes (exit condition inside loop)
+- **Continue**: ✅ Yes (skip iteration)
+- **Carrier**: Single variable (`counter`)
+
+**Pattern Gap**: None of the 4 patterns handle infinite loops!
+
+---
+
+## Implementation Options
+
+### Option A: Pattern 2 Extension (Break-First Variant)
+
+**Idea**: Extend Pattern 2 to handle both:
+- `loop(i < 3) { if cond { break } }` (existing)
+- `loop(true) { if cond { break } }` (new)
+
+**Changes**:
+1. Modify `extract_loop_variable_from_condition()` to handle boolean literals
+   - Return special token like `"__infinite__"` for `loop(true)`
+2. Update Pattern 2 to skip loop variable PHI when `loop_var == "__infinite__"`
+3. Use break condition as the only exit mechanism
+
+**Pros**:
+- Minimal code changes (1 file: `utils.rs`)
+- Reuses existing Pattern 2 infrastructure
+- Matches semantic similarity (both use `break` for exit)
+
+**Cons**:
+- Couples two different loop forms (finite vs infinite)
+- Special-case handling (`__infinite__` token) is a code smell
+- Pattern 2 assumes loop variable exists in multiple places
+
+---
+
+### Option B: New Pattern 5 (Infinite Loop with Early Exit)
+
+**Idea**: Create dedicated Pattern 5 for infinite loops
+
+**Structure**:
+```rust
+// src/mir/builder/control_flow/joinir/patterns/pattern5_infinite_break.rs
+
+/// Pattern 5: Infinite Loop with Early Exit
+///
+/// Handles:
+/// - loop(true) { ... break ... }
+/// - loop(true) { ... continue ... }
+/// - loop(true) { ... break ... continue ... }
+///
+/// Key differences from Pattern 2:
+/// - No loop variable in condition
+/// - Break condition is the ONLY exit mechanism
+/// - Continue jumps to top (no loop variable increment)
+pub fn can_lower(builder: &MirBuilder, ctx: &LoopPatternContext) -> bool {
+    // Check 1: Condition must be boolean literal `true`
+    matches!(ctx.condition, ASTNode::BoolLiteral { value: true, .. })
+    // Check 2: Must have break statement
+    && ctx.has_break
+}
+
+pub fn lower(builder: &mut MirBuilder, ctx: &LoopPatternContext)
+    -> Result<Option<ValueId>, String> {
+    // Similar to Pattern 2, but:
+    // - No loop variable PHI
+    // - Break condition becomes the only exit test
+    // - Continue jumps directly to loop header
+}
+```
+
+**Changes**:
+1. Add `pattern5_infinite_break.rs` (new file, ~200 lines)
+2. Register in `patterns/mod.rs` and `patterns/router.rs`
+3. Update `classify()` to add Pattern 5 before Pattern 4:
+   ```rust
+   // Pattern 5: Infinite loop (highest priority after continue)
+   if matches!(condition, ASTNode::BoolLiteral { value: true, .. })
+       && (features.has_break || features.has_continue) {
+       return LoopPatternKind::Pattern5InfiniteLoop;
+   }
+   ```
+
+**Pros**:
+- **Fail-Fast principle**: Clear separation of concerns
+- Independent testability (Pattern 5 doesn't affect Pattern 2)
+- Easy to extend for `loop(true)` without break (future Pattern 6?)
+- Matches Box Theory modularization philosophy
+
+**Cons**:
+- More code (~200 lines new file)
+- Duplicates some logic from Pattern 2 (break condition extraction)
+
+---
+
+### Option C: Pattern Classification Fix (Recommended)
+
+**Idea**: Fix the classification logic to route `loop(true) + break` to Pattern 2, and add infinite loop support there
+
+**Changes**:
+
+1. **Step 1**: Add `is_infinite_loop` feature to `LoopFeatures`
+   ```rust
+   // src/mir/loop_pattern_detection/mod.rs
+   pub struct LoopFeatures {
+       pub has_break: bool,
+       pub has_continue: bool,
+       pub has_if: bool,
+       pub has_if_else_phi: bool,
+       pub carrier_count: usize,
+       pub break_count: usize,
+       pub continue_count: usize,
+       pub is_infinite_loop: bool,  // NEW: true for loop(true)
+       pub update_summary: Option<LoopUpdateSummary>,
+   }
+   ```
+
+2. **Step 2**: Detect infinite loop in `ast_feature_extractor.rs`
+   ```rust
+   // src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs
+   pub(crate) fn extract_features(
+       condition: &ASTNode,  // NEW: need condition for infinite loop detection
+       body: &[ASTNode],
+       has_continue: bool,
+       has_break: bool
+   ) -> LoopFeatures {
+       let is_infinite_loop = matches!(condition, ASTNode::BoolLiteral { value: true, .. });
+       // ... rest of extraction
+       LoopFeatures {
+           has_break,
+           has_continue,
+           // ... other fields
+           is_infinite_loop,
+           // ...
+       }
+   }
+   ```
+
+3. **Step 3**: Update classification priority
+   ```rust
+   // src/mir/loop_pattern_detection/mod.rs:classify()
+   pub fn classify(features: &LoopFeatures) -> LoopPatternKind {
+       // PRIORITY FIX: Infinite loop with break -> Pattern 2
+       // (check BEFORE Pattern 4 Continue)
+       if features.is_infinite_loop && features.has_break && !features.has_continue {
+           return LoopPatternKind::Pattern2Break;
+       }
+
+       // Pattern 4: Continue
+       if features.has_continue {
+           // Infinite loop with continue -> needs special handling
+           if features.is_infinite_loop {
+               // Option: Create Pattern6InfiniteLoopContinue
+               // For now: return Unknown to fail fast
+               return LoopPatternKind::Unknown;
+           }
+           return LoopPatternKind::Pattern4Continue;
+       }
+
+       // ... rest of classification
+   }
+   ```
+
+4. **Step 4**: Make Pattern 2 handle infinite loops
+   ```rust
+   // src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs
+
+   // In can_lower():
+   pub fn can_lower(builder: &MirBuilder, ctx: &LoopPatternContext) -> bool {
+       // Check if classified as Pattern 2
+       ctx.pattern_kind == LoopPatternKind::Pattern2Break
+   }
+
+   // In lower():
+   pub fn lower(builder: &mut MirBuilder, ctx: &LoopPatternContext)
+       -> Result<Option<ValueId>, String> {
+
+       // Check if infinite loop
+       let is_infinite = matches!(ctx.condition, ASTNode::BoolLiteral { value: true, .. });
+
+       if is_infinite {
+           // Infinite loop path: no loop variable extraction
+           // Use break condition as the only exit
+           return lower_infinite_loop_with_break(builder, ctx);
+       } else {
+           // Existing finite loop path
+           return lower_finite_loop_with_break(builder, ctx);
+       }
+   }
+
+   fn lower_infinite_loop_with_break(...) -> Result<Option<ValueId>, String> {
+       // Similar to existing Pattern 2, but:
+       // - Skip loop variable extraction
+       // - Skip loop variable PHI
+       // - Generate infinite loop header (always jump to body)
+       // - Break condition becomes the only exit test
+   }
+   ```
+
+**Pros**:
+- **Reuses Pattern 2 infrastructure** (break condition extraction, exit routing)
+- **Clear separation via helper function** (`lower_infinite_loop_with_break`)
+- **Fail-Fast for unsupported cases** (`loop(true) + continue` returns Unknown)
+- **Incremental implementation** (can add Pattern 6 for continue later)
+
+**Cons**:
+- Pattern 2 becomes more complex (2 lowering paths)
+- Need to update 3+ files (features, classifier, pattern2)
+
+---
+
+## Recommended Approach: Option C
+
+**Rationale**:
+1. **Semantic similarity**: `loop(true) { break }` and `loop(i < 3) { break }` both use break as the primary exit mechanism
+2. **Code reuse**: Break condition extraction, exit routing, boundary application all the same
+3. **Fail-Fast**: Explicitly returns Unknown for `loop(true) + continue` (Case C variant)
+4. **Incremental**: Can add Pattern 6 for `loop(true) + continue` in future phase
+
+**Implementation Steps** (next section)
+
+---
+
+## Implementation Plan (Option C)
+
+### Phase 131-11-A: Feature Detection
+
+**Files Modified**:
+1. `src/mir/loop_pattern_detection/mod.rs` - Add `is_infinite_loop` field
+2. `src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs` - Detect `loop(true)`
+3. `src/mir/builder/control_flow/joinir/patterns/router.rs` - Pass condition to extract_features
+
+**Changes**:
+```diff
+// LoopFeatures struct
+pub struct LoopFeatures {
+    pub has_break: bool,
+    pub has_continue: bool,
+    pub has_if: bool,
+    pub has_if_else_phi: bool,
+    pub carrier_count: usize,
+    pub break_count: usize,
+    pub continue_count: usize,
++   pub is_infinite_loop: bool,
+    pub update_summary: Option<LoopUpdateSummary>,
+}
+
+// extract_features signature
+- pub(crate) fn extract_features(body: &[ASTNode], has_continue: bool, has_break: bool) -> LoopFeatures
++ pub(crate) fn extract_features(condition: &ASTNode, body: &[ASTNode], has_continue: bool, has_break: bool) -> LoopFeatures
+
+// In LoopPatternContext::new()
+- let features = ast_features::extract_features(body, has_continue, has_break);
++ let features = ast_features::extract_features(condition, body, has_continue, has_break);
+```
+
+### Phase 131-11-B: Classification Priority Fix
+
+**File Modified**: `src/mir/loop_pattern_detection/mod.rs`
+
+**Change**:
+```rust
+pub fn classify(features: &LoopFeatures) -> LoopPatternKind {
+    // NEW: Infinite loop with break -> Pattern 2 (BEFORE Pattern 4 check!)
+    if features.is_infinite_loop && features.has_break && !features.has_continue {
+        return LoopPatternKind::Pattern2Break;
+    }
+
+    // Pattern 4: Continue (existing)
+    if features.has_continue {
+        if features.is_infinite_loop {
+            // Fail-Fast: loop(true) + continue not supported yet
+            return LoopPatternKind::Unknown;
+        }
+        return LoopPatternKind::Pattern4Continue;
+    }
+
+    // ... rest of classification unchanged
+}
+```
+
+### Phase 131-11-C: Pattern 2 Infinite Loop Lowering
+
+**File Modified**: `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`
+
+**Changes**:
+1. Add `is_infinite_loop()` helper
+2. Split `lower()` into two paths
+3. Implement `lower_infinite_loop_with_break()`
+
+**Pseudo-code**:
+```rust
+pub fn lower(builder: &mut MirBuilder, ctx: &LoopPatternContext)
+    -> Result<Option<ValueId>, String> {
+
+    if is_infinite_loop(ctx.condition) {
+        lower_infinite_loop_with_break(builder, ctx)
+    } else {
+        lower_finite_loop_with_break(builder, ctx)  // existing code
+    }
+}
+
+fn is_infinite_loop(condition: &ASTNode) -> bool {
+    matches!(condition, ASTNode::BoolLiteral { value: true, .. })
+}
+
+fn lower_infinite_loop_with_break(
+    builder: &mut MirBuilder,
+    ctx: &LoopPatternContext
+) -> Result<Option<ValueId>, String> {
+    // Similar to existing Pattern 2, but:
+    // 1. Skip loop variable extraction (no loop_var_name)
+    // 2. Skip loop variable PHI (no counter increment)
+    // 3. Loop header unconditionally jumps to body (no condition check)
+    // 4. Break condition becomes the only exit test
+    // 5. Carriers are still tracked and merged at exit
+}
+```
+
+---
+
+## Test Strategy
+
+### Unit Tests
+
+**File**: `src/mir/loop_pattern_detection/mod.rs` (tests module)
+
+```rust
+#[test]
+fn test_classify_infinite_loop_with_break() {
+    let features = LoopFeatures {
+        has_break: true,
+        has_continue: false,
+        is_infinite_loop: true,
+        // ... other fields
+    };
+    assert_eq!(classify(&features), LoopPatternKind::Pattern2Break);
+}
+
+#[test]
+fn test_classify_infinite_loop_with_continue_unsupported() {
+    let features = LoopFeatures {
+        has_break: false,
+        has_continue: true,
+        is_infinite_loop: true,
+        // ... other fields
+    };
+    assert_eq!(classify(&features), LoopPatternKind::Unknown);
+}
+```
+
+### Integration Tests
+
+**Case C Variants**:
+
+1. **Minimal** (`/tmp/case_c_minimal.hako`):
+   ```nyash
+   static box Main {
+     main() {
+       local i = 0
+       loop (true) {
+         i = i + 1
+         if i == 3 { break }
+       }
+       print(i)
+       return 0
+     }
+   }
+   ```
+   Expected: Prints `3`
+
+2. **With Continue** (`apps/tests/llvm_stage3_loop_only.hako`):
+   ```nyash
+   static box Main {
+     main() {
+       local counter = 0
+       loop (true) {
+         counter = counter + 1
+         if counter == 3 { break }
+         continue
+       }
+       print("Result: " + counter)
+       return 0
+     }
+   }
+   ```
+   Expected: MIR compile error (Fail-Fast - not supported yet)
+
+3. **Multi-Carrier** (future test):
+   ```nyash
+   loop (true) {
+     i = i + 1
+     sum = sum + i
+     if sum > 10 { break }
+   }
+   ```
+
+---
+
+## Migration Path
+
+### Phase 131-11: Infinite Loop with Break (Priority 1)
+
+**Goal**: Make Case C (minimal) compile and run
+
+**Tasks**:
+1. ✅ Phase 131-11-A: Feature Detection (is_infinite_loop)
+2. ✅ Phase 131-11-B: Classification Priority Fix
+3. ✅ Phase 131-11-C: Pattern 2 Infinite Loop Lowering
+4. ✅ Unit tests for classification
+5. ✅ Integration test: `/tmp/case_c_minimal.hako`
+6. ✅ LLVM end-to-end test (EMIT + LINK + RUN)
+
+**Success Criteria**:
+- Case C (minimal) passes VM ✅
+- Case C (minimal) passes LLVM AOT ✅
+- Case C (with continue) fails with clear error ✅
+
+### Phase 131-12: Infinite Loop with Continue (Priority 2)
+
+**Goal**: Support `loop(true) + continue` (Case C full variant)
+
+**Approach**: Create Pattern 6 or extend Pattern 4
+
+**Not started yet** - pending Phase 131-11 completion
+
+---
+
+## SSOT Update
+
+**File**: `docs/development/current/main/phase131-3-llvm-lowering-inventory.md`
+
+**Section to Add**:
+
+```markdown
+### 4. TAG-EMIT: JoinIR Pattern Coverage Gap (Case C)
+
+**File**: `apps/tests/llvm_stage3_loop_only.hako`
+
+**Code**:
+```nyash
+static box Main {
+  main() {
+    local counter = 0
+    loop (true) {
+      counter = counter + 1
+      if counter == 3 { break }
+      continue
+    }
+    print("Result: " + counter)
+    return 0
+  }
+}
+```
+
+**MIR Compilation**: FAILURE
+```
+❌ MIR compilation error: [joinir/freeze] Loop lowering failed:
+   JoinIR does not support this pattern, and LoopBuilder has been removed.
+```
+
+**Root Cause**:
+- **Pattern Gap**: `loop(true)` (infinite loop) is not recognized by any of Patterns 1-4
+- **Loop Variable Extraction Fails**: `extract_loop_variable_from_condition()` expects binary comparison (`i < 3`), not boolean literal (`true`)
+- **Classification Priority Bug**: `has_continue = true` routes to Pattern 4, but Pattern 4 expects a loop variable
+
+**Solution** (Phase 131-11):
+- Add `is_infinite_loop` feature to `LoopFeatures`
+- Update classification priority: infinite loop + break → Pattern 2
+- Extend Pattern 2 to handle infinite loops (no loop variable PHI)
+
+**Location**:
+- Feature detection: `src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs`
+- Classification: `src/mir/loop_pattern_detection/mod.rs:classify()`
+- Lowering: `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`
+
+**Analysis**: [docs/development/current/main/case-c-infinite-loop-analysis.md](./case-c-infinite-loop-analysis.md)
+```
+
+---
+
+## Box Theory Alignment
+
+### Fail-Fast Principle ✅
+
+- **Unsupported patterns return Unknown** (not fallback to broken code)
+- **Clear error messages** ("JoinIR does not support this pattern")
+- **No silent degradation** (LoopBuilder removed, no hidden fallback)
+
+### Modular Boundaries ✅
+
+- **Feature extraction**: Pure function, no MirBuilder dependency
+- **Classification**: Centralized SSOT (`classify()` function)
+- **Pattern lowering**: Isolated modules (pattern2_with_break.rs)
+
+### Incremental Extension ✅
+
+- **Phase 131-11**: Add infinite loop with break (Pattern 2 extension)
+- **Phase 131-12**: Add infinite loop with continue (Pattern 6 new)
+- **No regression risk**: Existing patterns unchanged
+
+---
+
+## References
+
+### Related Files
+
+**Pattern Detection**:
+- `src/mir/loop_pattern_detection/mod.rs` - Classification logic
+- `src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs` - Feature extraction
+- `src/mir/builder/control_flow/joinir/patterns/router.rs` - Pattern routing
+
+**Pattern 2 Implementation**:
+- `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs` - Break pattern lowering
+- `src/mir/builder/control_flow/utils.rs` - Loop variable extraction
+
+**Testing**:
+- `apps/tests/llvm_stage3_loop_only.hako` - Case C test file
+- `apps/tests/loop_min_while.hako` - Case B (working reference)
+
+### Documentation
+
+- **Phase 131-3 Inventory**: `docs/development/current/main/phase131-3-llvm-lowering-inventory.md`
+- **JoinIR Architecture**: `docs/development/current/main/joinir-architecture-overview.md`
+- **Pattern Design**: `docs/private/roadmap2/phases/phase-188-joinir-loop-pattern-expansion/design.md`
+
+---
+
+## Appendix: AST Structure Comparison
+
+### Case B: `loop(i < 3)` (Working)
+
+```
+Loop {
+  condition: BinaryOp {
+    operator: Less,
+    left: Variable { name: "i" },
+    right: IntLiteral { value: 3 }
+  },
+  body: [...]
+}
+```
+
+**extract_loop_variable_from_condition()**: ✅ Returns `"i"`
+
+### Case C: `loop(true)` (Failing)
+
+```
+Loop {
+  condition: BoolLiteral { value: true },
+  body: [...]
+}
+```
+
+**extract_loop_variable_from_condition()**: ❌ Error "Unsupported loop condition pattern"
+
+---
+
+## Timeline Estimate
+
+**Phase 131-11-A (Feature Detection)**: 30 minutes
+- Add `is_infinite_loop` field to LoopFeatures
+- Update extract_features signature
+- Update callers (LoopPatternContext)
+
+**Phase 131-11-B (Classification Fix)**: 15 minutes
+- Update classify() priority order
+- Add unit tests
+
+**Phase 131-11-C (Pattern 2 Extension)**: 2-3 hours
+- Implement `is_infinite_loop()` helper
+- Implement `lower_infinite_loop_with_break()`
+- Handle carriers without loop variable PHI
+- Integration testing
+
+**Total**: 3-4 hours to complete Phase 131-11
+
+---
+
+**Last Updated**: 2025-12-14
+**Author**: Claude (Analysis Phase)
+**Next Step**: Get user confirmation on Option C approach
diff --git a/docs/development/current/main/phase131-11-case-c-summary.md b/docs/development/current/main/phase131-11-case-c-summary.md
new file mode 100644
index 00000000..851ebb92
--- /dev/null
+++ b/docs/development/current/main/phase131-11-case-c-summary.md
@@ -0,0 +1,312 @@
+# Phase 131-11: Case C 本命タスク - 調査完了レポート
+
+**Date**: 2025-12-14
+**Status**: ✅ Root Cause Analysis Complete - Ready for Implementation
+
+---
+
+## 🎯 Task Summary
+
+**Goal**: Make `loop(true) { ... break ... continue }` compile and run in JoinIR
+
+**Test File**: `apps/tests/llvm_stage3_loop_only.hako`
+
+---
+
+## 🔍 Root Cause (完全解明済み)
+
+### 問題の核心
+
+**Case C fails because**:
+1. **Pattern Gap**: `loop(true)` (infinite loop) is NOT recognized by any of Patterns 1-4
+2. **Loop Variable Extraction Fails**: `extract_loop_variable_from_condition()` expects binary comparison (`i < 3`), not boolean literal (`true`)
+3. **Classification Priority Bug**: `has_continue = true` routes to Pattern 4, but Pattern 4 expects a loop variable
+
+### Failure Flow (5 Steps)
+
+```
+1. LoopPatternContext::new()
+   └─ has_continue=true, has_break=true (✅ detected correctly)
+
+2. classify(features)
+   └─ Returns Pattern4Continue (❌ WRONG - should be Pattern2 or new Pattern5)
+
+3. Pattern4::can_lower()
+   └─ Tries extract_loop_variable_from_condition(BoolLiteral(true))
+
+4. extract_loop_variable_from_condition()
+   └─ ❌ Error: "Unsupported loop condition pattern"
+   └─ Expected: BinaryOp comparison (i < 3)
+   └─ Actual: BoolLiteral(true)
+
+5. Pattern falls through
+   └─ No pattern matches → freeze() error
+```
+
+### 現在のパターン対応表
+
+| Pattern | Condition Type | Break | Continue | Supported? |
+|---------|---------------|-------|----------|------------|
+| Pattern 1 | Comparison (`i < 3`) | ❌ | ❌ | ✅ |
+| Pattern 2 | Comparison (`i < 3`) | ✅ | ❌ | ✅ |
+| Pattern 3 | Comparison (`i < 3`) | ❌ | ❌ | ✅ |
+| Pattern 4 | Comparison (`i < 3`) | ❌ | ✅ | ✅ |
+| **Case C** | **Boolean (`true`)** | ✅ | ✅ | ❌ **GAP!** |
+
+---
+
+## 💡 Recommended Solution: Dedicated “InfiniteEarlyExit” pattern (recommended)
+
+**Approach**: Add `is_infinite_loop` feature + fix classification, then add a dedicated JoinIR loop pattern module for `loop(true)` with early-exit.
+
+### Why this approach?
+
+1. **Correctness-first**: `has_break && has_continue` must not route to Pattern 4 (Pattern 4 assumes a loop variable in the condition).
+2. **No naming collision**: Existing “Trim/P5” already exists; avoid calling this “Pattern 5”.
+3. **Minimal + Fail-Fast**: Support exactly the Case C skeleton first, reject everything else.
+4. **Keeps Pattern2 invariants**: Pattern2 is “break but no continue”; extending it to include continue blurs its contract.
+
+### Implementation Strategy (3 Phases)
+
+#### Phase 131-11-A: Feature Detection (30 min)
+
+**Add `is_infinite_loop` field to LoopFeatures**
+
+```rust
+// src/mir/loop_pattern_detection/mod.rs
+pub struct LoopFeatures {
+    pub has_break: bool,
+    pub has_continue: bool,
+    pub has_if: bool,
+    pub has_if_else_phi: bool,
+    pub carrier_count: usize,
+    pub break_count: usize,
+    pub continue_count: usize,
++   pub is_infinite_loop: bool,  // NEW: true for loop(true)
+    pub update_summary: Option<LoopUpdateSummary>,
+}
+```
+
+**Update extract_features to detect loop(true)**
+
+```rust
+// src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs
+pub(crate) fn extract_features(
++   condition: &ASTNode,  // NEW: need condition for infinite loop detection
+    body: &[ASTNode],
+    has_continue: bool,
+    has_break: bool
+) -> LoopFeatures {
++   let is_infinite_loop = matches!(condition, ASTNode::BoolLiteral { value: true, .. });
+    // ... rest
+}
+```
+
+**Update callers**
+
+```rust
+// src/mir/builder/control_flow/joinir/patterns/router.rs (LoopPatternContext::new)
+- let features = ast_features::extract_features(body, has_continue, has_break);
++ let features = ast_features::extract_features(condition, body, has_continue, has_break);
+```
+
+#### Phase 131-11-B: Classification Fix (15 min)
+
+**Fix classify() so break+continue does not misroute to Pattern 4**
+
+```rust
+// src/mir/loop_pattern_detection/mod.rs
+pub fn classify(features: &LoopFeatures) -> LoopPatternKind {
++   // NEW: Case C core: infinite loop + break + continue → dedicated pattern kind
++   if features.is_infinite_loop && features.has_break && features.has_continue {
++       return LoopPatternKind::InfiniteEarlyExit;
++   }
+
+    // Pattern 4: Continue (existing)
+    if features.has_continue && !features.has_break {
+        return LoopPatternKind::Pattern4Continue;
+    }
+
+    // ... rest unchanged
+}
+```
+
+#### Phase 131-11-C: InfiniteEarlyExit lowering (2-3 hours)
+
+**Add a dedicated pattern module and keep Pattern2 untouched**
+
+```rust
+// src/mir/builder/control_flow/joinir/patterns/pattern_infinite_early_exit.rs
+pub fn can_lower(ctx: &LoopPatternContext) -> bool {
+    matches!(ctx.pattern_kind, LoopPatternKind::InfiniteEarlyExit)
+}
+
+pub fn lower(builder: &mut MirBuilder, ctx: &LoopPatternContext) -> Result<Option<ValueId>, String> {
+    // Shape guard (Fail-Fast):
+    // - condition must be `true` literal
+    // - exactly one break site and one continue site
+    // - no nested loop / nested break/continue
+    // Lowering outline:
+    // - header: unconditional enter step
+    // - step: body core → break-check → continue (tailcall to step) / exit
+    unimplemented!()
+}
+```
+
+---
+
+## 📋 Modified Files Summary
+
+**Total**: 5–6 files modified (+1 new pattern module)
+
+1. **`src/mir/loop_pattern_detection/mod.rs`**
+   - Add `is_infinite_loop: bool` field to `LoopFeatures` struct
+   - Add `LoopPatternKind::InfiniteEarlyExit`
+   - Update `classify()` (infinite+break+continue must not route to Pattern4)
+
+2. **`src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs`**
+   - Update `extract_features()` signature (add `condition: &ASTNode` param)
+   - Detect `loop(true)` in condition
+
+3. **`src/mir/builder/control_flow/joinir/patterns/router.rs`**
+   - Pass condition into `extract_features()`
+   - Ensure `LOOP_PATTERNS` table routes `InfiniteEarlyExit`
+
+4. **`src/mir/builder/control_flow/joinir/patterns/mod.rs`**
+   - `pub(in crate::mir::builder) mod pattern_infinite_early_exit;` (new module export)
+
+5. **`src/mir/builder/control_flow/joinir/patterns/pattern_infinite_early_exit.rs`** (NEW)
+   - Shape guard + lowering implementation for Case C
+
+---
+
+## 🧪 Test Strategy
+
+### Unit Tests
+
+**File**: `src/mir/loop_pattern_detection/mod.rs` (tests module)
+
+```rust
+#[test]
+fn test_classify_infinite_loop_with_break() {
+    let features = LoopFeatures {
+        has_break: true,
+        has_continue: false,
+        is_infinite_loop: true,
+        // ... other fields
+    };
+    assert_eq!(classify(&features), LoopPatternKind::Pattern2Break);
+}
+
+#[test]
+fn test_classify_infinite_loop_with_continue_unsupported() {
+    let features = LoopFeatures {
+        has_break: false,
+        has_continue: true,
+        is_infinite_loop: true,
+        // ... other fields
+    };
+    assert_eq!(classify(&features), LoopPatternKind::Unknown);
+}
+```
+
+### Integration Tests
+
+**Case C Minimal** (`/tmp/case_c_minimal.hako`):
+```nyash
+static box Main {
+  main() {
+    local i = 0
+    loop (true) {
+      i = i + 1
+      if i == 3 { break }
+    }
+    print(i)
+    return 0
+  }
+}
+```
+Expected: Prints `3`
+
+**Case C Full** (`apps/tests/llvm_stage3_loop_only.hako`):
+```nyash
+loop (true) {
+  counter = counter + 1
+  if counter == 3 { break }
+  continue
+}
+```
+Expected: MIR compile error (Fail-Fast - not supported yet)
+
+### End-to-End Test
+
+```bash
+# VM test
+./target/release/hakorune /tmp/case_c_minimal.hako
+# Expected output: 3
+
+# LLVM test (after Phase 131-11 complete)
+tools/build_llvm.sh /tmp/case_c_minimal.hako -o /tmp/case_c_exe
+/tmp/case_c_exe
+# Expected output: 3
+echo $?
+# Expected exit code: 0
+```
+
+---
+
+## ⏱️ Timeline Estimate
+
+**Phase 131-11-A**: 30 minutes (Feature Detection)
+**Phase 131-11-B**: 15 minutes (Classification Fix)
+**Phase 131-11-C**: 2-3 hours (Pattern 2 Extension)
+
+**Total**: 3-4 hours to complete Phase 131-11
+
+---
+
+## ✅ Success Criteria
+
+**Phase 131-11 Complete** when:
+1. ✅ Case C (minimal) compiles to MIR successfully
+2. ✅ Case C (minimal) passes VM execution (prints `3`)
+3. ✅ Case C (minimal) passes LLVM AOT (EMIT + LINK + RUN)
+4. ✅ Case C (with continue) fails with clear error message (Fail-Fast)
+5. ✅ No regression in Cases A, B, B2 (all still pass)
+6. ✅ Unit tests for classification pass
+
+---
+
+## 📚 References
+
+**Detailed Analysis**: [case-c-infinite-loop-analysis.md](./case-c-infinite-loop-analysis.md) (13KB, complete investigation)
+
+**SSOT**: [phase131-3-llvm-lowering-inventory.md](./phase131-3-llvm-lowering-inventory.md) (updated with root cause)
+
+**Related Files**:
+- Pattern Detection: `src/mir/loop_pattern_detection/mod.rs`
+- Feature Extraction: `src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs`
+- Pattern Router: `src/mir/builder/control_flow/joinir/patterns/router.rs`
+- Pattern 2 Lowering: `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs`
+
+---
+
+## 🚦 Next Steps
+
+**For ChatGPT** (Implementation):
+1. Start with Phase 131-11-A (Feature Detection) - 30 min
+2. Proceed to Phase 131-11-B (Classification Fix) - 15 min
+3. Implement Phase 131-11-C (Pattern 2 Extension) - 2-3 hours
+4. Run unit tests + integration tests
+5. Verify end-to-end LLVM AOT path
+
+**For Claude** (Review):
+- Review implementation for Box Theory alignment (Fail-Fast, modular boundaries)
+- Verify no regression in existing patterns
+- Check for code duplication opportunities (Pattern 2 finite vs infinite)
+
+---
+
+**Last Updated**: 2025-12-14
+**Phase**: 131-11 (Case C本命タスク)
+**Status**: 🎯 Ready for Implementation
diff --git a/docs/development/current/main/phase131-3-llvm-lowering-inventory.md b/docs/development/current/main/phase131-3-llvm-lowering-inventory.md
index 73ad1688..b58f8720 100644
--- a/docs/development/current/main/phase131-3-llvm-lowering-inventory.md
+++ b/docs/development/current/main/phase131-3-llvm-lowering-inventory.md
@@ -175,7 +175,7 @@ RC: 0
 
 ---
 
-### 4. TAG-EMIT: JoinIR Pattern Mismatch (Case C)
+### 4. TAG-EMIT: JoinIR Pattern Coverage Gap (Case C) - ✅ ROOT CAUSE IDENTIFIED
 
 **File**: `apps/tests/llvm_stage3_loop_only.hako`
 
@@ -203,10 +203,36 @@ Function: main
 Hint: This loop pattern is not supported. All loops must use JoinIR lowering.
 ```
 
-**Diagnosis**:
-- `loop(true)` with `break`/`continue` doesn't match Pattern 1-4
-- LoopBuilder fallback was removed (Phase 33 cleanup)
-- JoinIR Pattern coverage gap: needs Pattern 5 or Pattern variant for infinite loops with early exit
+**Root Cause** (Phase 131-11 Analysis):
+1. **Pattern Gap**: `loop(true)` (infinite loop) not recognized by Patterns 1-4
+2. **Loop Variable Extraction Fails**: `extract_loop_variable_from_condition()` expects binary comparison (`i < 3`), not boolean literal (`true`)
+3. **Classification Priority Bug**: `has_continue = true` routes to Pattern 4, but Pattern 4 expects a loop variable
+
+**Failure Flow**:
+```
+1. LoopPatternContext::new() detects has_continue=true, has_break=true
+2. classify() returns Pattern4Continue (because has_continue)
+3. Pattern4::can_lower() tries extract_loop_variable_from_condition(BoolLiteral(true))
+4. ❌ Fails: "Unsupported loop condition pattern"
+5. No pattern matches → freeze() error
+```
+
+**Solution** (Phase 131-11 Recommended):
+- Add `is_infinite_loop: bool` feature to `LoopFeatures` (detect `loop(true)`).
+- Fix classification so `has_break && has_continue` does not route to Pattern 4.
+- Introduce a dedicated pattern kind + lowerer for **infinite loop + early-exit (+ optional continue)**:
+  - Example name: `InfiniteEarlyExit` (avoid “Pattern5” naming collision with existing Trim/P5).
+  - Scope (minimum): `loop(true)` with exactly one `break` site and one `continue` site (Fail-Fast outside this).
+
+**Files to Modify**:
+1. `src/mir/loop_pattern_detection/mod.rs` - Add `is_infinite_loop` field, update classify()
+2. `src/mir/builder/control_flow/joinir/patterns/ast_feature_extractor.rs` - Detect `loop(true)` in condition
+3. `src/mir/builder/control_flow/joinir/patterns/router.rs` - Pass condition to extract_features()
+4. `src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs` - Add infinite loop lowering path
+
+**Docs (Phase 131-11)**:
+- Detailed analysis: `docs/development/current/main/case-c-infinite-loop-analysis.md`
+- Implementation summary: `docs/development/current/main/phase131-11-case-c-summary.md`
 
 **Location**: `src/mir/builder/control_flow/joinir/router.rs` - pattern matching logic