refactor(cache): extract filesystem fingerprinting into vt_fs_fingerprint crate

CLAUDE.md

@@ -9,6 +9,7 @@ A monorepo task runner (like Nx/Turbo) with intelligent caching and dependency r
 - `crates/vt_graph` — Task dependency graph construction and config loading
 - `crates/vt_plan` — Execution planning (resolves env vars, working dirs, commands)
 - `crates/vt_workspace` — Workspace detection and package dependency graph
+- `crates/vt_fs_fingerprint` — Filesystem fingerprinting for task caching (pre-run snapshot, traced-access judgment, cache-entry validation)
 - `crates/fspy*` — File system access tracing (9 crates: supervisor, preload libs, platform backends)
 - `crates/pty_terminal*` — Cross-platform headless terminal emulator (3 crates)
 - `crates/vt_path` — Type-safe absolute/relative path system

Cargo.toml

@@ -148,6 +148,7 @@ tui-term = "0.3.1"
 twox-hash = "2.1.1"
 uuid = "1.18.1"
 vec1 = "1.12.1"
+vt_fs_fingerprint = { path = "crates/vt_fs_fingerprint" }
 vt_glob = { path = "crates/vt_glob" }
 vt_graph_ser = { path = "crates/vt_graph_ser" }
 vt_path = { path = "crates/vt_path" }

crates/vt/Cargo.toml

@@ -19,12 +19,12 @@ wincode = { workspace = true, features = ["derive"] }
 clap = { workspace = true, features = ["derive"] }
 ctrlc = { workspace = true }
 derive_more = { workspace = true, features = ["debug", "from"] }
+fspy_shared = { workspace = true }
 futures-util = { workspace = true }
 once_cell = { workspace = true }
 owo-colors = { workspace = true }
 petgraph = { workspace = true }
 pty_terminal_test_client = { workspace = true }
-rayon = { workspace = true }
 rusqlite = { workspace = true, features = ["bundled"] }
 rustc-hash = { workspace = true }
 serde = { workspace = true, features = ["derive", "rc"] }
@@ -42,9 +42,9 @@ tokio = { workspace = true, features = [
 ] }
 tokio-util = { workspace = true }
 tracing = { workspace = true }
-twox-hash = { workspace = true }
 materialized_artifact = { workspace = true }
 uuid = { workspace = true, features = ["v4"] }
+vt_fs_fingerprint = { workspace = true }
 vt_glob = { workspace = true }
 vt_path = { workspace = true }
 vt_select = { workspace = true }
@@ -54,7 +54,6 @@ vt_ipc_shared = { workspace = true }
 vt_plan = { workspace = true }
 vt_server = { workspace = true }
 vt_workspace = { workspace = true }
-wax = { workspace = true }
 zstd = { workspace = true }
 
 # Artifact build-deps must be unconditional: cargo's resolver panics when

crates/vt/docs/task-cache.md

@@ -167,10 +167,11 @@ The cached execution result:
 
 ```rust
 pub struct CacheEntryValue {
-    pub post_run_fingerprint: PostRunFingerprint,
+    pub input_fingerprints: InputFingerprints,          // vt_fs_fingerprint (opaque)
+    pub tracked_env_fingerprints: TrackedEnvFingerprints,
     pub std_outputs: Arc<[StdOutput]>,
     pub duration: Duration,
-    pub globbed_inputs: BTreeMap<RelativePathBuf, u64>,
+    pub output_archive: Option<Str>,
 }
 ```
 
@@ -348,19 +349,20 @@ Cache entries are serialized using `bincode` for efficient storage.
 │    • Stop monitoring                                         │
 │         │                                                    │
 │         ▼                                                    │
-│  2. Generate Post-Run Fingerprint                           │
+│  2. Conclude the run (vt_fs_fingerprint)                        │
 │  ─────────────────────────────────                           │
-│    • Hash all accessed files                                 │
-│    • Record file system access patterns                     │
+│    • Judge traced accesses (read-write overlap check)        │
+│    • Fingerprint discovered inputs, collect outputs          │
 │         │                                                    │
 │         ▼                                                    │
 │  3. Create CacheEntryValue                                   │
 │  ────────────────────────────                                │
 │    CacheEntryValue {                                         │
-│        post_run_fingerprint,                                 │
+│        input_fingerprints,                                   │
+│        tracked_env_fingerprints,                             │
 │        std_outputs,                                          │
 │        duration,                                             │
-│        globbed_inputs,                                       │
+│        output_archive,                                       │
 │    }                                                         │
 │         │                                                    │
 │         ▼                                                    │
@@ -565,13 +567,21 @@ Each `&&` separated command is cached independently. If only terser config chang
 ### Core Cache Components
 
 ```
+crates/vt_fs_fingerprint/src/  # Filesystem fingerprinting (own crate)
+├── task_run.rs           # TaskFs (pre_run/post_run), Conclusion
+├── fingerprint.rs        # InputFingerprints, PathFingerprint, InputChange
+├── tracked_accesses.rs   # fspy access normalization
+├── glob.rs               # Glob walking + input hashing
+└── hash.rs               # Content hashing
+
 crates/vt/src/session/
 ├── cache/
 │   ├── mod.rs            # ExecutionCache, CacheEntryKey/Value, FingerprintMismatch
 │   └── display.rs        # Cache status display formatting
 ├── execute/
-│   ├── mod.rs            # execute_spawn, SpawnOutcome
-│   ├── fingerprint.rs    # PostRunFingerprint, PathFingerprint, DirEntryKind
+│   ├── mod.rs            # execute_spawn, SpawnOutcome, cache lookup
+│   ├── cache_update.rs   # Post-run cache update decision
+│   ├── post_run.rs       # TrackedEnvFingerprints (tracked env validation)
 │   └── spawn.rs          # spawn_with_tracking, fspy integration
 └── reporter/
     └── mod.rs            # Reporter traits for cache hit/miss display

crates/vt/src/lib.rs

@@ -1,5 +1,4 @@
 mod cli;
-mod collections;
 mod napi_client;
 pub mod session;
 

crates/vt/src/session/cache/display.rs

@@ -250,7 +250,7 @@ mod tests {
     fn inline_tracked_env_mismatch_preserves_kind() {
         let added = CacheStatus::Miss(CacheMiss::FingerprintMismatch(
             FingerprintMismatch::TrackedEnvQueryChanged {
-                query: crate::session::execute::fingerprint::TrackedEnvQuery::Glob(Str::from(
+                query: crate::session::execute::post_run::TrackedEnvQuery::Glob(Str::from(
                     "PROBE_*",
                 )),
                 mismatch: EnvMismatch::Added { name: Str::from("PROBE_C") },