mutate

name	mutate
description	Change persistent state with checkpoint and rollback support. Use when modifying files, updating databases, changing configuration, or any operation that permanently alters state.
argument-hint	[target] [operation] [checkpoint_id]
disable-model-invocation	false
user-invocable	true
allowed-tools	Read, Edit, Write, Bash
context	fork
agent	general-purpose
layer	EXECUTE

Intent

Make controlled changes to persistent state with safety guarantees. This is the primary capability for modifications and REQUIRES a checkpoint for rollback capability.

CRITICAL: This capability requires checkpoint to have been called first.

Success criteria:

• State change applied correctly
• Previous state captured for rollback
• Change is verifiable
• Audit trail recorded

Compatible schemas:

• schemas/output_schema.yaml

Inputs

Parameter	Required	Type	Description
target	Yes	string	What to modify (file path, resource identifier)
operation	Yes	object	The modification to apply
checkpoint_id	Yes	string	Checkpoint ID for rollback (from checkpoint capability)

Procedure

1. Verify checkpoint exists: Ensure recovery is possible

   • Confirm checkpoint_id references valid checkpoint
   • Verify checkpoint covers the target
   • STOP if no valid checkpoint

2. Capture previous state: Record what will change

   • Read current state of target
   • Store for comparison and rollback
   • Document what specifically will change

3. Apply mutation: Make the change

   • Execute the specified operation
   • Use appropriate tool (Edit for files, Bash for commands)
   • Capture any errors during modification

4. Verify change: Confirm mutation succeeded

   • Read new state
   • Compare to expected result
   • Note any unexpected side effects

5. Record mutation: Document what changed

   • Store diff between previous and new state
   • Record timestamp and operation details
   • Link to checkpoint for audit trail

6. Return result: Provide complete mutation record

   • Include success/failure status
   • Provide before/after state
   • Reference checkpoint for rollback

Output Contract

Return a structured object:

success: boolean  # Whether mutation completed
target: string  # What was modified
operation: string  # What was done
previous_state:
  snapshot: any  # State before mutation
  captured_at: string  # When captured
new_state:
  snapshot: any  # State after mutation
  verified_at: string  # When verified
diff:
  type: string  # unified, structural, summary
  content: string  # The actual diff
checkpoint_id: string  # For rollback reference
rollback_command: string  # How to undo this change
evidence_anchors: ["file:line", "command:output"]

Field Definitions

Field	Type	Description
success	boolean	Whether mutation completed successfully
target	string	Resource that was modified
operation	string	Description of the change
previous_state	object	State before modification
new_state	object	State after modification
diff	object	Difference between states
checkpoint_id	string	Reference for rollback
rollback_command	string	How to undo the change

Examples

Example 1: File Modification

Input:

target: "src/services/user_service.rb"
operation:
  type: "edit"
  description: "Add null check for user parameter"
  changes:
    - line: 42
      old: "user.email"
      new: "user&.email"
checkpoint_id: "chk-20240115-001"

Output:

success: true
target: "src/services/user_service.rb"
operation: "Added safe navigation operator for null user handling"
previous_state:
  snapshot: "def get_email(user)\n  user.email\nend"
  captured_at: "2024-01-15T10:30:00Z"
new_state:
  snapshot: "def get_email(user)\n  user&.email\nend"
  verified_at: "2024-01-15T10:30:01Z"
diff:
  type: "unified"
  content: |
    @@ -42 +42 @@
    -  user.email
    +  user&.email
checkpoint_id: "chk-20240115-001"
rollback_command: "git checkout src/services/user_service.rb"
evidence_anchors:
  - "src/services/user_service.rb:42"

Example 2: Database Mutation

Input:

target: "users table"
operation:
  type: "sql"
  description: "Add status column with default value"
  sql: "ALTER TABLE users ADD COLUMN status VARCHAR(20) DEFAULT 'active'"
checkpoint_id: "chk-20240115-002"

Output:

success: true
target: "users table"
operation: "Added status column with default 'active'"
previous_state:
  snapshot:
    columns: ["id", "email", "created_at"]
  captured_at: "2024-01-15T11:00:00Z"
new_state:
  snapshot:
    columns: ["id", "email", "created_at", "status"]
  verified_at: "2024-01-15T11:00:05Z"
diff:
  type: "structural"
  content: "+ status VARCHAR(20) DEFAULT 'active'"
checkpoint_id: "chk-20240115-002"
rollback_command: "ALTER TABLE users DROP COLUMN status"
evidence_anchors:
  - "command:psql:schema_after"

Example 3: Mutation Failure

Input:

target: "config/database.yml"
operation:
  type: "edit"
  description: "Update connection pool size"
checkpoint_id: "chk-20240115-003"

Output:

success: false
target: "config/database.yml"
operation: "Update connection pool size (FAILED)"
previous_state:
  snapshot: "pool: 5"
  captured_at: "2024-01-15T12:00:00Z"
new_state:
  snapshot: null
  verified_at: null
diff:
  type: "none"
  content: "Mutation failed: file locked by another process"
checkpoint_id: "chk-20240115-003"
rollback_command: "N/A - mutation did not complete"
evidence_anchors:
  - "error:file_locked"
error:
  message: "File locked by another process"
  recoverable: true
  suggestion: "Retry after process releases lock"

Verification

• Checkpoint exists and is valid
• Previous state captured before mutation
• New state verified after mutation
• Diff accurately reflects change
• Rollback command is correct

Verification tools: Read (to verify state changes)

Safety Constraints

• mutation: true
• requires_checkpoint: true
• requires_approval: true
• risk: high

Capability-specific rules:

• NEVER mutate without valid checkpoint
• Always capture previous state before modification
• Verify change matches intended operation
• Provide working rollback mechanism
• Stop immediately on unexpected errors
• Do not chain multiple mutations without intermediate checkpoints

Composition Patterns

Commonly follows:

• checkpoint - REQUIRED before any mutation
• plan - Mutations execute planned changes
• verify - Verify preconditions before mutating

Commonly precedes:

• verify - Verify mutation results
• audit - Record mutation for audit trail
• rollback - Undo mutation if verification fails

Anti-patterns:

• NEVER mutate without checkpoint
• Never combine multiple risky mutations
• Avoid mutation in exploratory workflows

Workflow references:

• See reference/workflow_catalog.yaml#debug_code_change for mutation in bug fixes
• See reference/workflow_catalog.yaml#digital_twin_sync_loop for mutation in sync loops