morph-apply

• Fast file edits without reading entire file first
• Batch edits to a file (multiple changes in one operation)
• When you know what to change but file is large
• Large files where reading would consume too many tokens

Use // ... existing code ... (or language-appropriate comments) to mark where edits go:

```python

# ... existing code ...

try:

result = process()

except Exception as e:

log.error(e)

# ... existing code ...

```

The API intelligently places your edit in the right location.

Add error handling

```bash

uv run python -m runtime.harness scripts/mcp/morph_apply.py \

--file "src/auth.py" \

--instruction "Add error handling to login function" \

--code_edit "# ... existing code ...

try:

user = authenticate(credentials)

except AuthError as e:

log.error(f'Auth failed: {e}')

raise

# ... existing code ..."

```

Add logging

```bash

uv run python -m runtime.harness scripts/mcp/morph_apply.py \

--file "src/api.py" \

--instruction "Add debug logging" \

--code_edit "# ... existing code ...

logger.debug(f'Processing request: {request.id}')

# ... existing code ..."

```

TypeScript example

```bash

uv run python -m runtime.harness scripts/mcp/morph_apply.py \

--file "src/types.ts" \

--instruction "Add user validation" \

--code_edit "// ... existing code ...

if (!user) throw new Error('User not found');

if (!user.isActive) throw new Error('User inactive');

// ... existing code ..."

```

| Parameter | Description |

|-----------|-------------|

| --file | File path to edit (required) |

| --instruction | Human description of the change (required) |

| --code_edit | Code snippet with markers showing where to place edit (required) |

| Tool | Best For |

|------|----------|

| morph-apply | Fast edits, don't need to read file first, large files, batch edits |

| Claude Edit | Small precise edits when file is already in context |

Use morph-apply when:

• File is not in context and reading it would be expensive
• File is very large (>500 lines)
• Making multiple related edits at once
• You know the context of the change (function name, class, etc.)

Use Claude Edit when:

• File is already in context from prior Read
• Very precise edits requiring exact old/new string matching
• Small files (<200 lines)

Requires morph server in mcp_config.json with MORPH_API_KEY.

• Speed: 10,500 tokens/sec
• Accuracy: 98% correct placement
• Token savings: Don't need to read entire file first