checkpoint

name	checkpoint
description	Create a safety checkpoint marker before mutation or execution steps. Use when about to modify files, execute plans, or perform any irreversible action. Essential for the CAVR pattern.
argument-hint	[scope] [reason] [checkpoint_type]
disable-model-invocation	false
user-invocable	true
allowed-tools	Read, Bash, Edit
context	fork
agent	general-purpose
hooks	{"PreToolUse":[{"matcher":"Bash","hooks":[{"type":"prompt","prompt":"CHECKPOINT CREATION VALIDATION\n\nCheckpoint command: {{tool_input.command}}\n\nVerify checkpoint creation is appropriate:\n1. Scope includes all files that will be mutated\n2. No sensitive files (.env, credentials) being checkpointed\n3. Checkpoint reason is documented\n4. Checkpoint type matches the operation (git_stash, file_backup, etc.)\n\nReply ALLOW to create checkpoint.\nReply BLOCK if:\n- Scope is incomplete (missing files)\n- Sensitive data would be captured\n- Checkpoint storage location is invalid\n","once":false}]}],"PostToolUse":[{"matcher":"Bash","hooks":[{"type":"command","command":"# Log checkpoint creation for audit trail\nmkdir -p .checkpoints .audit 2>/dev/null || true\necho \"[CHECKPOINT] $(date -u +%Y-%m-%dT%H:%M:%SZ) | Command: {{tool_input.command}} | Exit: {{tool_output.exit_code}}\" >> .audit/checkpoint-operations.log\n# Record checkpoint metadata\nif [ \"{{tool_output.exit_code}}\" = \"0\" ]; then\n echo \"$(date -u +%Y-%m-%dT%H:%M:%SZ): Checkpoint created successfully\" >> .checkpoints/checkpoint-manifest.log\nfi\n"}]},{"matcher":"Edit","hooks":[{"type":"command","command":"echo \"[CHECKPOINT] $(date -u +%Y-%m-%dT%H:%M:%SZ) | Manifest updated: {{tool_input.file_path}}\" >> .audit/checkpoint-operations.log 2>/dev/null || true\n"}]}]}

Intent

Execute checkpoint to create a restorable state marker before any mutating operation. This is the foundation of safe agentic execution - enabling rollback if subsequent actions fail.

Success criteria:

• Checkpoint successfully created with unique identifier
• All files/state in scope are captured
• Restore command is documented and tested
• Expiry policy set if applicable

Compatible schemas:

• schemas/output_schema.yaml

Inputs

Parameter	Required	Type	Description
scope	Yes	string|array	Files, directories, or state keys to checkpoint
reason	No	string	Why this checkpoint is being created (for audit trail)
checkpoint_type	No	enum	Type: git_stash, file_backup, state_snapshot, database_savepoint
expiry	No	string	When checkpoint can be garbage collected (e.g., "24h", "never")

Procedure

1. Identify scope: Determine exactly what needs to be checkpointed

   • List all files that will be modified by upcoming mutation
   • Include related configuration or state files
   • Check for uncommitted git changes in scope

2. Select checkpoint type: Choose appropriate mechanism

   • git_stash: For git-tracked files (preferred for code changes)
   • file_backup: For non-git files, copy to .checkpoints/
   • state_snapshot: For in-memory or runtime state
   • database_savepoint: For database transactions

3. Capture pre-mutation state: Execute the checkpoint

   • For git: git stash push -m "checkpoint:<id>:<reason>"
   • For files: Copy to .checkpoints/<id>/ with manifest
   • Record hashes of all captured content
   • Verify checkpoint integrity immediately after creation

4. Generate restore command: Document how to rollback

   • Exact command(s) to restore state
   • Any prerequisites for restoration
   • Order of operations if multiple systems involved

5. Ground claims: Attach evidence of checkpoint creation

   • Format: tool:bash:<command>, file:<checkpoint_path>
   • Include hash verification output

6. Format output: Return checkpoint metadata per contract

Output Contract

Return a structured object:

checkpoint_created: boolean
checkpoint:
  id: string  # Unique identifier (e.g., "chk_20240115_143022_abc123")
  type: git_stash | file_backup | state_snapshot | database_savepoint
  created_at: string  # ISO timestamp
  scope:
    files: array[string]  # File paths included
    state_keys: array[string]  # State keys included (if applicable)
  restore_command: string  # Exact command to restore
  expiry: string | null  # When checkpoint expires
pre_mutation_state:
  hash: string | null  # Combined hash of all checkpointed content
  summary: string  # Human-readable state summary
next_safe_actions: array[string]  # What can now safely proceed
confidence: number  # 0.0-1.0
evidence_anchors: ["tool:bash:...", "file:..."]
assumptions: []

Field Definitions

Field	Type	Description
checkpoint_created	boolean	Whether checkpoint was successfully created
checkpoint.id	string	Unique identifier for this checkpoint
checkpoint.type	enum	Mechanism used for checkpointing
checkpoint.scope	object	What was included in the checkpoint
checkpoint.restore_command	string	Exact command to restore state
pre_mutation_state.hash	string	Integrity hash of captured state
next_safe_actions	array	Actions that can now safely proceed
confidence	number	0.0-1.0 based on checkpoint integrity verification
evidence_anchors	array	Proof of checkpoint creation
assumptions	array	Explicit assumptions (e.g., "git available")

Examples

Example 1: Git Stash Checkpoint

Input:

scope:
  - "src/api/handlers/*.py"
  - "tests/test_handlers.py"
reason: "Before refactoring API handlers"
checkpoint_type: git_stash

Output:

checkpoint_created: true
checkpoint:
  id: "chk_20240115_143022_a7b3c9"
  type: git_stash
  created_at: "2024-01-15T14:30:22Z"
  scope:
    files:
      - "src/api/handlers/user.py"
      - "src/api/handlers/auth.py"
      - "tests/test_handlers.py"
    state_keys: []
  restore_command: "git stash pop stash@{0}"
  expiry: null
pre_mutation_state:
  hash: "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
  summary: "3 files, 342 lines total, last modified 2024-01-15"
next_safe_actions:
  - "act-plan: Proceed with handler refactoring"
  - "edit: Modify files in scope"
confidence: 1.0
evidence_anchors:
  - "tool:bash:git stash push -m 'checkpoint:chk_20240115_143022_a7b3c9:Before refactoring API handlers'"
  - "tool:bash:git stash list | head -1"
assumptions:
  - "Git repository is initialized and clean"
  - "No merge conflicts in working tree"

Evidence pattern: Git stash creation command output, stash list verification.

---

Example 2: File Backup Checkpoint

Input:

scope: "config/production.yaml"
reason: "Before config migration"
checkpoint_type: file_backup
expiry: "24h"

Output:

checkpoint_created: true
checkpoint:
  id: "chk_20240115_150000_config"
  type: file_backup
  created_at: "2024-01-15T15:00:00Z"
  scope:
    files:
      - "config/production.yaml"
    state_keys: []
  restore_command: "cp .checkpoints/chk_20240115_150000_config/production.yaml config/production.yaml"
  expiry: "2024-01-16T15:00:00Z"
pre_mutation_state:
  hash: "sha256:abc123..."
  summary: "1 file, 89 lines, production database config"
next_safe_actions:
  - "act-plan: Apply config migration"
confidence: 0.95
evidence_anchors:
  - "file:.checkpoints/chk_20240115_150000_config/manifest.json"
  - "tool:bash:sha256sum config/production.yaml"
assumptions:
  - ".checkpoints directory exists and is writable"

Verification

Apply the following verification patterns:

• State Assertion: pre_mutation_state.hash can be recomputed and matches
• Restore Command Valid: restore_command executes without error (dry-run if possible)
• Scope Complete: All files in scope are captured in checkpoint
• Evidence Grounding: checkpoint.id appears in evidence_anchors

Verification tools: Bash (for hash verification), Read (for manifest)

Safety Constraints

• mutation: true (creates checkpoint artifacts)
• requires_checkpoint: false (this IS the checkpoint operation)
• requires_approval: false
• risk: medium

Capability-specific rules:

• NEVER skip checkpoint before act-plan (CRITICAL)
• NEVER delete checkpoints until explicitly requested
• ALWAYS verify checkpoint integrity immediately after creation
• Do not checkpoint sensitive files (.env, credentials) - warn and exclude
• Store checkpoint metadata in .checkpoints/ within workspace
• Include reason in checkpoint for audit trail

Composition Patterns

Commonly follows:

• plan - After creating a plan, checkpoint before execution
• critique - After reviewing risks, checkpoint before proceeding
• constrain - After policy check passes, checkpoint before mutation

Commonly precedes:

• act-plan - REQUIRED: Never act-plan without prior checkpoint (CAVR pattern)
• improve - Checkpoint before iterative improvement cycles
• send - Checkpoint before external communications

Anti-patterns:

• CRITICAL: Never call act-plan without prior checkpoint
• CRITICAL: Never call rollback without valid checkpoint reference
• Never checkpoint after mutation has started
• Never delete checkpoint before verify confirms success

Workflow references:

• See reference/composition_patterns.md#checkpoint-act-verify-rollback for CAVR pattern
• See reference/composition_patterns.md#debug-code-change for checkpoint placement
• See reference/composition_patterns.md#digital-twin-sync-loop for checkpoint in loops