SnapshotManager

The snapshot system provides content-addressable filesystem state capture with Merkle-committed integrity. Take a baseline before an agent runs, detect changes incrementally, and roll back to any previous state.

SnapshotManager(
    session_dir: str,
    tracked_paths: list[str],
    exclusion: ExclusionConfig | None = None,
    max_entries: int = 300_000,
    max_bytes: int = 2_147_483_648,
)

Parameter	Type	Default	Description
`session_dir`	`str`	required	Directory for session data (snapshots, objects)
`tracked_paths`	`list[str]`	required	Directories to track for changes
`exclusion`	`ExclusionConfig \| None`	`None`	File exclusion configuration
`max_entries`	`int`	`300,000`	Maximum files to track
`max_bytes`	`int`	2 GiB	Maximum total bytes to track

Each tracked path gets its own exclusion filter, so .gitignore rules are interpreted relative to their own root directory.

Methods

`create_baseline() -> SnapshotManifest`

Capture the initial filesystem state. Must be called before create_incremental().

`create_incremental() -> tuple[SnapshotManifest, list[Change]]`

Capture current state and return changes since the last snapshot. Uses mtime/size as a fast check, then hashes changed files.

`restore_to(snapshot_number: int) -> list[Change]`

Restore the filesystem to a previous snapshot. Retrieves file content from the object store, deletes files created after that snapshot. Returns the list of changes applied.

`compute_restore_diff(snapshot_number: int) -> list[Change]`

Dry-run: compute what restore_to() would change without modifying the filesystem.

`load_manifest(number: int) -> SnapshotManifest`

Load a snapshot manifest from disk by number.

`save_session_metadata(meta: SessionMetadata) -> None`

Save session metadata to the session directory.

`snapshot_count() -> int`

Number of snapshots taken (including resumed sessions).

`load_session_metadata(session_dir: str) -> SessionMetadata` (static)

Load session metadata from a session directory without creating a full manager.

Example

from nono_py import SnapshotManager, ExclusionConfig

mgr = SnapshotManager(
    session_dir="~/.nono/rollbacks/session-001",
    tracked_paths=["/workspace"],
    exclusion=ExclusionConfig(
        exclude_patterns=["node_modules", "__pycache__"],
        exclude_globs=["*.pyc"],
    ),
)

# Capture baseline
baseline = mgr.create_baseline()
print(f"Merkle root: {baseline.merkle_root.hex()}")

# ... agent modifies files ...

# Capture changes
manifest, changes = mgr.create_incremental()
for change in changes:
    print(f"{change.change_type}: {change.path}")

# Roll back
mgr.restore_to(snapshot_number=0)

Resuming Sessions

A new SnapshotManager pointed at an existing session_dir automatically loads the latest manifest from disk. This means create_incremental() works without calling create_baseline() again, and snapshot_count() returns the correct value.

# Later, or in a new process:
mgr = SnapshotManager(session_dir="~/.nono/rollbacks/session-001", tracked_paths=["/workspace"])
print(mgr.snapshot_count())  # Reflects snapshots already on disk
manifest, changes = mgr.create_incremental()

ExclusionConfig

ExclusionConfig(
    use_gitignore: bool = True,
    exclude_patterns: list[str] = [],
    exclude_globs: list[str] = [],
    force_include: list[str] = [],
)

Parameter	Type	Default	Description
`use_gitignore`	`bool`	`True`	Respect `.gitignore` files in tracked roots
`exclude_patterns`	`list[str]`	`[]`	Component-level or path-substring patterns
`exclude_globs`	`list[str]`	`[]`	Glob patterns matched against filenames
`force_include`	`list[str]`	`[]`	Patterns that override all exclusions

SnapshotManifest

A snapshot recording the state of all tracked files. Returned by create_baseline() and create_incremental().

Property	Type	Description
`number`	`int`	Snapshot sequence number (0 = baseline)
`timestamp`	`str`	ISO 8601 creation timestamp
`parent`	`int \| None`	Parent snapshot number
`merkle_root`	`ContentHash`	Cryptographic commitment to the entire state
`files`	`dict[str, FileState]`	Mapping of file paths to their state

ContentHash

SHA-256 content hash. Immutable and hashable.

Method	Returns	Description
`hex()`	`str`	64-character hex string

FileState

State of a single file within a snapshot.

Property	Type	Description
`hash`	`ContentHash`	SHA-256 of file content
`size`	`int`	File size in bytes
`mtime`	`int`	Modification time (seconds since epoch)
`permissions`	`int`	Unix permission bits

Change

A filesystem change detected between snapshots.

Property	Type	Description
`path`	`str`	Path of the changed file
`change_type`	`str`	`"created"`, `"modified"`, `"deleted"`, or `"permissions_changed"`
`size_delta`	`int \| None`	Size difference in bytes

SessionMetadata

Metadata for a sandboxed session. Ties together the snapshot chain, network audit trail, and execution context.

SessionMetadata(
    session_id: str,
    command: list[str],
    tracked_paths: list[str],
)

Constructor arguments (read-only after creation):

Property	Type	Description
`session_id`	`str`	Session identifier
`started`	`str`	ISO 8601 start time (set automatically)
`command`	`list[str]`	Command that was executed
`tracked_paths`	`list[str]`	Tracked directories

Mutable properties (set after the session runs):

Property	Type	Description
`ended`	`str \| None`	ISO 8601 end time
`snapshot_count`	`int`	Number of snapshots
`exit_code`	`int \| None`	Child process exit code
`merkle_roots`	`list[ContentHash]`	Chain of Merkle roots from each snapshot (read-only, use `add_merkle_root()`)
`network_events`	`list[dict]`	Network audit events (read-only, use `set_network_events()`)

Method	Description
`add_merkle_root(root)`	Append a Merkle root to the chain
`set_network_events(events)`	Set network events from a list of dicts
`to_json() -> str`	Serialize to JSON
`from_json(json) -> SessionMetadata`	Deserialize from JSON (static)

Security Properties

Merkle commitment: Single root hash commits to the entire filesystem state
Content-addressable dedup: Identical file content stored once
APFS clonefile: Copy-on-write on macOS for efficient snapshots
Atomic writes: Temp file + rename for all persistent state
TOCTOU protection: File content verified after storage

ProxyConfig - Network proxy configuration
Module Functions - start_proxy(), sandboxed_exec()

Getting Started

API Reference

Examples

SnapshotManager