feat: add custom errors

Cargo.lock

@@ -80,7 +80,9 @@ dependencies = [
  "rand",
  "serde",
  "serde_json",
+ "sha2",
  "tempfile",
+ "thiserror",
  "tracing",
  "tracing-subscriber",
 ]
@@ -642,6 +644,26 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "thiserror"
+version = "2.0.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3467d614147380f2e4e374161426ff399c91084acd2363eaf549172b3d5e60c0"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "2.0.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c5e1be1c48b9172ee610da68fd9cd2770e7a4056cb3fc98710ee6906f0c7960"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "thread_local"
 version = "1.1.9"

Cargo.toml

@@ -17,6 +17,8 @@ glob = "0.3"
 rand = "0.8"                                                                # ed25519-dalek depends on rand_core v0.6
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+sha2 = "0.10.9"
+thiserror = "2.0"
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
 

src/host.rs

@@ -1,80 +1,191 @@
-use color_eyre::Result;
-use ed25519_dalek::{PUBLIC_KEY_LENGTH, SigningKey};
-use glob::Pattern;
-use rand::{Rng, SeedableRng, rngs::StdRng};
-use std::path::Path;
-use tracing::Level;
-
 use crate::{
     manifest::{CapabilityManifest, PRIME_MULTIPLIER},
-    trace::{TraceEvent, finalize_trace, log_trace_event, save_trace},
+    trace::{
+        CapEventSubtype, EventType, SignedTrace, TraceError, TraceEvent, finalize_trace,
+        log_trace_event, save_trace,
+    },
 };
+use ed25519_dalek::{PUBLIC_KEY_LENGTH, SigningKey, ed25519::signature::SignerMut};
+use glob::Pattern;
+use rand::{Rng, SeedableRng, rngs::StdRng};
+use sha2::{Digest, Sha256};
+use std::path::Path;
+use thiserror::Error;
+use tracing::Level;
 
 #[derive(Debug)]
 pub struct HostState {
-    pub manifest: CapabilityManifest,
-    pub trace: Vec<TraceEvent>,
-    pub seed: u64,
-    pub keypair: SigningKey,
-    pub pubkey: [u8; PUBLIC_KEY_LENGTH],
+    manifest: CapabilityManifest,
+    trace: Vec<TraceEvent>,
+    seed: u64,
+    keypair: SigningKey,
+    pubkey: [u8; PUBLIC_KEY_LENGTH],
+    run_id: String,
+    manifest_hash: String,
+}
+
+/// Errors from capability enforcement.
+#[derive(Debug, Error, PartialEq, Eq)]
+pub enum CapError {
+    #[error("No FS capability declared")]
+    NoFsCapability,
+
+    #[error("No read patterns defined")]
+    NoReadPatterns,
+
+    #[error("Path does not match any glob pattern")]
+    GlobMismatch,
+
+    #[error("Invalid path provided (empty or invalid UTF-8)")]
+    InvalidPath,
 }
 
 impl HostState {
     #[inline]
     #[must_use]
+    /// # Panics
+    ///
+    /// Should not panic
     pub fn new(manifest: CapabilityManifest, seed: u64, keypair: SigningKey) -> Self {
         let pubkey = keypair.verifying_key().to_bytes();
+        let run_id = format!("captra-run-{seed}");
+        let manifest_json = serde_json::to_string(&manifest).expect("Manifest serializes"); // Safe: validated earlier
+        let mut hashser = Sha256::default();
+        hashser.update(manifest_json.as_bytes());
+        let manifest_hash = format!("{:x}", hashser.finalize());
+
         Self {
             manifest,
             trace: Vec::new(),
             seed,
             keypair,
             pubkey,
+            run_id,
+            manifest_hash,
         }
     }
 
+    /// Get `pubkey`
+    #[must_use]
+    pub const fn pubkey(&self) -> &[u8; PUBLIC_KEY_LENGTH] {
+        &self.pubkey
+    }
+
+    /// Get `run_id`
+    #[inline]
+    #[must_use]
+    pub fn run_id(&self) -> &str {
+        &self.run_id
+    }
+
+    /// Get `trace`
+    #[inline]
+    #[must_use]
+    pub fn trace(&self) -> &[TraceEvent] {
+        &self.trace
+    }
+
     /// Simulate "plugin execution": check if path is allowed via FS read cap.
-    /// Returns `true` if allowed, `false` if denied.
-    #[must_use]
-    pub fn execute_plugin<P: AsRef<Path>>(&mut self, path: P) -> bool {
-        let Some(fs_cap) = &self.manifest.capabilities.fs else {
-            return false;
-        };
+    /// Logs to trace on success/error (outcome=false for errors).
+    ///
+    /// # Errors
+    ///
+    /// [`CapError`] if enforcement fails (e.g., no caps or mismatch).
+    pub fn execute_plugin<P: AsRef<Path>>(&mut self, path: P) -> Result<bool, CapError> {
+        let path_str = path.as_ref().to_string_lossy();
+        if path_str.is_empty() {
+            return Err(CapError::InvalidPath);
+        }
 
-        let Some(read_patterns) = &fs_cap.read else {
-            return false;
+        if self.manifest.capabilities.fs.is_none() {
+            self.log_cap_error(CapEventSubtype::NoFsCapability, "missing fs cap", &path_str);
+            return Err(CapError::NoFsCapability);
+        }
+
+        let read_patterns_ops = self
+            .manifest
+            .capabilities
+            .fs
+            .as_ref()
+            .and_then(|fs| fs.read.clone());
+
+        let read_patterns = match read_patterns_ops {
+            Some(v) if !v.is_empty() => v,
+            _ => {
+                self.log_cap_error(
+                    CapEventSubtype::NoReadPatterns,
+                    "empty read patterns",
+                    &path_str,
+                );
+                return Err(CapError::NoReadPatterns);
+            }
         };
 
         let seq = u64::try_from(self.trace.len()).map_or(1, |len| len + 1);
-        let path_str = path.as_ref().to_string_lossy();
 
         let mut rng = StdRng::seed_from_u64(self.seed.wrapping_mul(PRIME_MULTIPLIER + seq));
         let ts_seed = rng.r#gen();
 
         let is_allowed = read_patterns.iter().any(|pattern| {
-            Pattern::new(pattern)
-                .map(|p| p.matches(&path_str))
-                .unwrap_or(false)
+            Pattern::new(pattern).map_or_else(
+                |_| {
+                    self.log_cap_error(CapEventSubtype::InvalidGlob, pattern, &path_str);
+                    false
+                },
+                |p| p.matches(&path_str),
+            )
         });
 
+        if !is_allowed {
+            self.log_cap_error(
+                CapEventSubtype::GlobMismatch,
+                "no matching pattern",
+                &path_str,
+            );
+            return Err(CapError::GlobMismatch);
+        }
+
         log_trace_event(
             seq,
-            "cap.call",
+            EventType::CapCall,
             &path_str,
-            is_allowed,
+            true,
             ts_seed,
             &self.manifest.plugin,
         );
 
         self.trace.push(TraceEvent {
+            run_id: self.run_id.clone(),
             seq,
-            event_type: "cap.call".into(),
+            event_type: EventType::CapCall,
             input: path_str.into(),
             outcome: is_allowed,
             ts_seed,
         });
 
-        is_allowed
+        Ok(true)
+    }
+
+    /// Signs the current trace JSON with the host keypair.
+    /// Computes SHA256 hash of trace for integrity.
+    ///
+    /// # Errors
+    ///
+    /// [`TraceError`] (serialization).
+    pub fn sign_current_trace(&mut self) -> Result<SignedTrace, TraceError> {
+        let trace_json = finalize_trace(&self.trace);
+        let mut hasher = Sha256::default();
+        hasher.update(trace_json.as_bytes());
+        let trace_hash = format!("{:x}", hasher.finalize());
+
+        let signature = self.keypair.sign(trace_hash.as_bytes()).to_bytes().to_vec();
+
+        Ok(SignedTrace::new(
+            self.run_id.clone(),
+            self.manifest_hash.clone(),
+            trace_json,
+            signature,
+        ))
     }
 
     /// Serialize trace to pretty JSON string
@@ -89,9 +200,35 @@ impl HostState {
     /// # Errors
     ///
     /// If file write fails (e.g., I/O error) or JSON serialization fails.
-    pub fn save_current_trace<P: AsRef<Path>>(&self, path: P) -> Result<()> {
+    pub fn save_current_trace<P: AsRef<Path>>(&self, path: P) -> Result<(), TraceError> {
         save_trace(&self.trace, path)
     }
+
+    fn log_cap_error(&mut self, event_subtype: CapEventSubtype, reason: &str, path_str: &str) {
+        let seq = u64::try_from(self.trace.len()).map_or(1, |len| len + 1);
+        let mut rng = StdRng::seed_from_u64(self.seed.wrapping_mul(PRIME_MULTIPLIER + seq));
+        let ts_seed = rng.r#gen();
+
+        let event_type = EventType::from(event_subtype);
+
+        log_trace_event(
+            seq,
+            event_type,
+            path_str,
+            false,
+            ts_seed,
+            &self.manifest.plugin,
+        );
+
+        self.trace.push(TraceEvent {
+            run_id: self.run_id.clone(),
+            seq,
+            event_type,
+            input: format!("{event_subtype}: {reason}"),
+            outcome: false,
+            ts_seed,
+        });
+    }
 }
 
 pub fn init_tracing() {

src/lib.rs

@@ -1,111 +1,3 @@
 pub mod host;
 pub mod manifest;
 pub mod trace;
-
-#[cfg(test)]
-mod tests {
-    use crate::{
-        host::{HostState, init_tracing},
-        manifest::load_manifest,
-        trace::{TraceEvent, load_trace},
-    };
-    use claims::{assert_ok, assert_some};
-    use ed25519_dalek::SigningKey;
-    use rand::rngs::OsRng;
-    use tempfile::tempdir;
-
-    #[test]
-    fn tracing_init() {
-        init_tracing();
-    }
-
-    #[test]
-    fn manifest_loader() {
-        let manifest = assert_ok!(load_manifest("examples/manifest.json"), "Load failed");
-        assert_eq!(manifest.plugin, "formatter-v1");
-        assert_eq!(manifest.version, "0.1");
-        assert_eq!(manifest.issued_by, "dev-team");
-
-        let caps = manifest.capabilities;
-        let fs_cap = assert_some!(caps.fs);
-        let read_patterns = assert_some!(fs_cap.read);
-        assert_eq!(read_patterns, vec!["./workspace/*"]);
-        let write_patterns = assert_some!(fs_cap.write);
-        assert!(write_patterns.is_empty());
-    }
-
-    #[test]
-    fn host_enforcement_with_trace() {
-        init_tracing();
-
-        let manifest = assert_ok!(load_manifest("examples/manifest.json"), "Load failed");
-        let fixed_seed = 12345;
-        let mut csprng = OsRng;
-        let keypair = SigningKey::generate(&mut csprng);
-        let mut host = HostState::new(manifest, fixed_seed, keypair);
-
-        // allowed - expect a tracing event
-        let out1 = host.execute_plugin("./workspace/config.toml");
-        assert!(out1);
-        // denied - event + entry
-        let out2 = host.execute_plugin("/etc/passwd");
-        assert!(!out2);
-
-        assert_eq!(host.trace.len(), 2);
-
-        let trace1 = assert_some!(host.trace.first());
-        assert_eq!(trace1.seq, 1);
-        assert_eq!(trace1.event_type, "cap.call");
-        assert_eq!(trace1.input, "./workspace/config.toml");
-        assert!(trace1.outcome);
-        assert_eq!(trace1.ts_seed, 8_166_419_713_379_829_776);
-        assert_ne!(trace1.ts_seed, 0);
-
-        let trace2 = assert_some!(host.trace.get(1));
-        assert_eq!(trace2.seq, 2);
-        assert_eq!(trace2.input, "/etc/passwd");
-        assert!(!trace2.outcome);
-        assert_eq!(trace2.ts_seed, 10_553_447_931_939_622_718);
-        assert_ne!(trace1.ts_seed, trace2.ts_seed);
-
-        let tmp_dir = tempdir().expect("Temp dir failed");
-        let tmp_path = tmp_dir.as_ref().join("trace.json");
-
-        assert_ok!(host.save_current_trace(&tmp_path), "Save failed");
-
-        let loaded_trace = assert_ok!(load_trace(tmp_path), "Load failed");
-        assert_eq!(loaded_trace.len(), 2);
-
-        let loaded_trace1 = assert_some!(loaded_trace.first());
-        assert_eq!(trace1, loaded_trace1);
-
-        let loaded_trace2 = assert_some!(loaded_trace.get(1));
-        assert_eq!(trace2, loaded_trace2);
-    }
-
-    #[test]
-    fn trace_reproducibility() {
-        init_tracing();
-
-        let manifest = assert_ok!(load_manifest("examples/manifest.json"), "Load failed");
-
-        let fixed_seed = 12345;
-        let mut csprng1 = OsRng;
-        let keypair1 = SigningKey::generate(&mut csprng1);
-
-        let mut host1 = HostState::new(manifest.clone(), fixed_seed, keypair1);
-        assert!(!host1.execute_plugin("./allowed.txt"));
-        let trace1 = host1.get_trace_json();
-
-        let mut csprng2 = OsRng;
-        let keypair2 = SigningKey::generate(&mut csprng2);
-        let mut host2 = HostState::new(manifest, fixed_seed, keypair2);
-        assert!(!host2.execute_plugin("./allowed.txt"));
-        let trace2 = host2.get_trace_json();
-
-        let parsed1 = assert_ok!(serde_json::from_str::<Vec<TraceEvent>>(&trace1));
-        let parsed2 = assert_ok!(serde_json::from_str::<Vec<TraceEvent>>(&trace2));
-        assert_eq!(parsed1, parsed2);
-        assert_eq!(parsed1[0].ts_seed, parsed2[0].ts_seed);
-    }
-}

src/manifest.rs

@@ -1,6 +1,7 @@
-use color_eyre::eyre::Result;
+use glob::Pattern;
 use serde::{Deserialize, Serialize};
-use std::fs::read_to_string;
+use std::{fs::read_to_string, path::Path};
+use thiserror::Error;
 
 /// Prime for seq hashing to derive per-event RNG state
 pub const PRIME_MULTIPLIER: u64 = 314_159;
@@ -31,13 +32,80 @@ pub struct CapabilityManifest {
     // TODO: add signature
 }
 
-/// Loads a capability manifest from a JSON file.
+/// Errors from manifest loading/validation.
+#[derive(Debug, Error)]
+pub enum ManifestError {
+    #[error("IO error reading manifest: {0}")]
+    Io(#[from] std::io::Error),
+
+    #[error("JSON deserialization failed: {0}")]
+    Deserialize(#[from] serde_json::Error),
+
+    #[error("Invalid plugin name: must be non-empty")]
+    InvalidPlugin,
+
+    #[error("Invalid version: must be non-empty")]
+    InvalidVersion,
+
+    #[error("Invalid issuer: must be non-empty")]
+    InvalidIssuer,
+
+    #[error("Invalid glob pattern at index {idx}: {pattern} - {err}")]
+    InvalidGlob {
+        idx: usize,
+        pattern: String,
+        err: String,
+    },
+}
+
+impl CapabilityManifest {
+    /// Validates the manifest: non-empty fields and compilable glob patterns.
     ///
     /// # Errors
     ///
-/// - bubbles up `std::fs::read_to_string` and `serde_json::from_str` errors;
-pub fn load_manifest(path: &str) -> Result<CapabilityManifest> {
+    /// [`ManifestError`] if invalid.
+    pub fn validate(&self) -> Result<(), ManifestError> {
+        if self.plugin.is_empty() {
+            return Err(ManifestError::InvalidPlugin);
+        }
+        if self.version.is_empty() {
+            return Err(ManifestError::InvalidVersion);
+        }
+        if self.issued_by.is_empty() {
+            return Err(ManifestError::InvalidIssuer);
+        }
+        if let Some(fs_cap) = &self.capabilities.fs
+            && let Some(read_patterns) = &fs_cap.read
+        {
+            for (idx, pattern) in read_patterns.iter().enumerate() {
+                Pattern::new(pattern).map_err(|err| ManifestError::InvalidGlob {
+                    idx,
+                    pattern: pattern.clone(),
+                    err: err.to_string(),
+                })?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Loads a capability manifest from a JSON file and validates it.
+    ///
+    /// # Errors
+    ///
+    /// [`ManifestError`] (IO, JSON, or validation failures).
+    pub fn load<P: AsRef<Path>>(path: P) -> Result<Self, ManifestError> {
         let json_str = read_to_string(path)?;
-    let manifest = serde_json::from_str(&json_str)?;
+        let manifest = serde_json::from_str::<Self>(&json_str)?;
+        manifest.validate()?;
         Ok(manifest)
     }
+}
+
+/// A think wrapper around `CapabilityManifest::load()`
+///
+/// # Errors
+///
+/// [`ManifestError`] (IO, JSON, or validation failures).
+pub fn load_manifest<P: AsRef<Path>>(path: P) -> Result<CapabilityManifest, ManifestError> {
+    CapabilityManifest::load(path)
+}

src/trace.rs

@@ -1,12 +1,14 @@
-use color_eyre::eyre::Result;
+use base64::{Engine, engine::general_purpose};
 use serde::{Deserialize, Serialize};
-use std::{fs, path::Path};
+use std::{fmt::Display, fs, path::Path, str::FromStr};
+use thiserror::Error;
 use tracing::info;
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub struct TraceEvent {
+    pub run_id: String,
     pub seq: u64,
-    pub event_type: String,
+    pub event_type: EventType,
     pub input: String,
     pub outcome: bool,
     pub ts_seed: u64,
@@ -20,12 +22,61 @@ pub struct SignedTrace {
     pub signature: String,
 }
 
+/// Errors from trace serialization/IO.
+#[derive(Debug, Error)]
+pub enum TraceError {
+    #[error("JSON serialization failed: {0}")]
+    Serialize(#[from] serde_json::Error),
+
+    #[error("IO error: {0}")]
+    Io(#[from] std::io::Error),
+
+    #[error("Base64 encoding failed: {0}")]
+    Base64(#[from] base64::DecodeError),
+}
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum EventType {
+    CapCall,
+    CapError,
+}
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum CapEventSubtype {
+    InvalidPath,
+    NoFsCapability,
+    NoReadPatterns,
+    GlobMismatch,
+    InvalidGlob,
+    // TODO: NetConnect, NetDeny, CpuQuotaExceeded
+}
+
+impl SignedTrace {
+    #[inline]
+    #[must_use]
+    pub fn new(
+        run_id: String,
+        manifest_hash: String,
+        trace_json: String,
+        signature: Vec<u8>,
+    ) -> Self {
+        Self {
+            run_id,
+            manifest_hash,
+            trace_json,
+            signature: general_purpose::STANDARD.encode(signature),
+        }
+    }
+}
+
 /// Save the current trace to a file as pretty JSON.
 ///
 /// # Errors
 ///
-/// If file write fails (e.g., I/O error) or JSON serialization fails.
-pub fn save_trace<P: AsRef<Path>>(trace: &[TraceEvent], path: P) -> Result<()> {
+/// [`TraceError`] (JSON or IO).
+pub fn save_trace<P: AsRef<Path>>(trace: &[TraceEvent], path: P) -> Result<(), TraceError> {
     let json_str = serde_json::to_string_pretty(trace)?;
     fs::write(path, json_str)?;
     Ok(())
@@ -35,8 +86,8 @@ pub fn save_trace<P: AsRef<Path>>(trace: &[TraceEvent], path: P) -> Result<()> {
 ///
 /// # Errors
 ///
-/// If file read fails (e.g., I/O error) or JSON parsing fails.
-pub fn load_trace<P: AsRef<Path>>(path: P) -> Result<Vec<TraceEvent>> {
+/// [`TraceError`] (JSON or IO).
+pub fn load_trace<P: AsRef<Path>>(path: P) -> Result<Vec<TraceEvent>, TraceError> {
     let json_str = fs::read_to_string(path)?;
     let trace = serde_json::from_str(&json_str)?;
     Ok(trace)
@@ -52,7 +103,7 @@ pub fn finalize_trace(trace: &[TraceEvent]) -> String {
 /// Log a trace event
 pub fn log_trace_event(
     seq: u64,
-    event_type: &str,
+    event_type: EventType,
     input: &str,
     outcome: bool,
     ts_seed: u64,
@@ -61,9 +112,66 @@ pub fn log_trace_event(
     info!(
         seq = seq,
         ts_seed = ts_seed,
-        event_type = event_type,
+        event_type = %event_type,
         input = %input,
         outcome = outcome,
         plugin = plugin,
     );
 }
+
+impl FromStr for EventType {
+    type Err = &'static str;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "cap.call" => Ok(Self::CapCall),
+            "cap.error" => Ok(Self::CapError),
+            _ => Err("Unknown event type"),
+        }
+    }
+}
+
+impl Display for EventType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = match self {
+            Self::CapCall => "cap.call",
+            Self::CapError => "cap.error",
+        };
+        f.write_str(s)
+    }
+}
+
+impl FromStr for CapEventSubtype {
+    type Err = &'static str;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "invalid_path" => Ok(Self::InvalidPath),
+            "no_fs_capability" => Ok(Self::NoFsCapability),
+            "no_read_patterns" => Ok(Self::NoReadPatterns),
+            "glob_mismatch" => Ok(Self::GlobMismatch),
+            "invalid_glob" => Ok(Self::InvalidGlob),
+            _ => Err("Unknown cap event subtype"),
+        }
+    }
+}
+
+impl Display for CapEventSubtype {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = match self {
+            Self::InvalidPath => "invalid_path",
+            Self::NoFsCapability => "no_fs_capability",
+            Self::NoReadPatterns => "no_read_patterns",
+            Self::GlobMismatch => "glob_mismatch",
+            Self::InvalidGlob => "invalid_glob",
+        };
+        f.write_str(s)
+    }
+}
+
+impl From<CapEventSubtype> for EventType {
+    fn from(subtype: CapEventSubtype) -> Self {
+        match subtype {
+            CapEventSubtype::GlobMismatch => Self::CapCall,
+            _ => Self::CapError,
+        }
+    }
+}

tests/captra.rs

@@ -0,0 +1,176 @@
+use base64::{Engine, engine::general_purpose::STANDARD};
+use captra::{
+    host::{CapError, HostState, init_tracing},
+    manifest::{ManifestError, load_manifest},
+    trace::{EventType, TraceEvent, load_trace},
+};
+use claims::{assert_err, assert_matches, assert_ok, assert_some};
+use ed25519_dalek::SigningKey;
+use rand::rngs::OsRng;
+use std::{fs::File, io::Write};
+use tempfile::tempdir;
+
+#[test]
+fn tracing_init() {
+    init_tracing();
+}
+
+#[test]
+fn manifest_loader() {
+    let manifest = assert_ok!(load_manifest("examples/manifest.json"), "Load failed");
+    assert_eq!(manifest.plugin, "formatter-v1");
+    assert_eq!(manifest.version, "0.1");
+    assert_eq!(manifest.issued_by, "dev-team");
+
+    let caps = manifest.capabilities;
+    let fs_cap = assert_some!(caps.fs);
+    let read_patterns = assert_some!(fs_cap.read);
+    assert_eq!(read_patterns, vec!["./workspace/*"]);
+    let write_patterns = assert_some!(fs_cap.write);
+    assert!(write_patterns.is_empty());
+}
+
+#[test]
+fn manifest_validation_invalid() {
+    // Mock invalid manifest (empty plugin).
+    let invalid_json = r#"
+        {
+          "plugin": "",
+          "version": "0.1",
+          "capabilities": {
+            "fs": {
+              "read": []
+            }
+          },
+          "issued_by": "dev"
+        }
+    "#;
+    let tmp_dir = tempdir().expect("Temp dir failed");
+    let tmp_path = tmp_dir.as_ref().join("invalid.json");
+    {
+        let mut file = File::create(&tmp_path).expect("File creation failed");
+        file.write_all(invalid_json.as_bytes())
+            .expect("Write failed");
+    }
+
+    assert_err!(load_manifest(tmp_path), "Expected validation error");
+
+    let glob_invalid_json = r#"
+        {
+          "plugin": "test",
+          "version": "0.1",
+          "capabilities": {
+            "fs": {
+              "read": [
+                "["
+              ]
+            }
+          },
+          "issued_by": "dev"
+        }
+    "#;
+    let tmp_path2 = tmp_dir.as_ref().join("invalid.json");
+    {
+        let mut file = File::create(&tmp_path2).expect("File creation failed");
+        file.write_all(glob_invalid_json.as_bytes())
+            .expect("Write failed");
+    }
+    let err = assert_err!(load_manifest(tmp_path2), "Expected validation error");
+    assert_matches!(
+        &err,
+        ManifestError::InvalidGlob { .. },
+        "Expected InvalidGlob, got: {err:?}"
+    );
+}
+
+#[test]
+fn host_enforcement_with_trace() {
+    init_tracing();
+
+    let manifest = assert_ok!(load_manifest("examples/manifest.json"), "Load failed");
+    let fixed_seed = 12345;
+    let mut csprng = OsRng;
+    let keypair = SigningKey::generate(&mut csprng);
+    let mut host = HostState::new(manifest, fixed_seed, keypair);
+
+    assert_eq!(host.run_id(), "captra-run-12345");
+
+    // allowed - expect a tracing event
+    let out1 = assert_ok!(host.execute_plugin("./workspace/config.toml"));
+    assert!(out1);
+    // denied - event + entry
+    let out2 = assert_err!(host.execute_plugin("/etc/passwd"));
+    assert_eq!(out2, CapError::GlobMismatch);
+
+    {
+        assert_eq!(host.trace().len(), 2); // Both allowed/denied log to trace.
+
+        let trace1 = assert_some!(host.trace().get(0));
+        assert_eq!(trace1.seq, 1);
+        assert_eq!(trace1.event_type, EventType::CapCall);
+        assert_eq!(trace1.input, "./workspace/config.toml");
+        assert!(trace1.outcome);
+        assert_eq!(trace1.ts_seed, 8_166_419_713_379_829_776);
+        assert_ne!(trace1.ts_seed, 0);
+
+        let trace2 = assert_some!(host.trace().get(1));
+        assert_eq!(trace2.run_id, "captra-run-12345");
+        assert_eq!(trace2.seq, 2);
+        assert_eq!(trace2.event_type, EventType::CapCall);
+        assert!(!trace2.outcome);
+        assert!(trace2.input.starts_with("glob_mismatch: "));
+        assert_eq!(trace2.ts_seed, 10_553_447_931_939_622_718);
+        assert_ne!(trace1.ts_seed, trace2.ts_seed);
+    }
+
+    let signed = assert_ok!(host.sign_current_trace());
+    assert_eq!(signed.run_id, "captra-run-12345");
+
+    let sig_bytes = STANDARD.decode(&signed.signature).expect("Base64 decode");
+    assert_eq!(sig_bytes.len(), 64);
+    assert!(!signed.trace_json.is_empty()); // Nonempty JSON
+
+    // Save/load roundtrip
+    let tmp_dir = tempdir().expect("Temp dir failed");
+    let tmp_path = tmp_dir.as_ref().join("trace.json");
+    assert_ok!(host.save_current_trace(&tmp_path), "Save failed");
+
+    let loaded_trace = assert_ok!(load_trace(tmp_path), "Load failed");
+    assert_eq!(loaded_trace.len(), 2);
+
+    let trace1_refetched = assert_some!(host.trace().get(0));
+    let trace2_refetched = assert_some!(host.trace().get(1));
+    let loaded_trace1 = assert_some!(loaded_trace.get(0));
+    let loaded_trace2 = assert_some!(loaded_trace.get(1));
+
+    assert_eq!(trace1_refetched, loaded_trace1);
+    assert_eq!(trace2_refetched, loaded_trace2);
+}
+
+#[test]
+fn trace_reproducibility() {
+    init_tracing();
+
+    let manifest = assert_ok!(load_manifest("examples/manifest.json"), "Load failed");
+
+    let fixed_seed = 12345;
+    let mut csprng1 = OsRng;
+    let keypair1 = SigningKey::generate(&mut csprng1);
+
+    let mut host1 = HostState::new(manifest.clone(), fixed_seed, keypair1);
+    let out1 = assert_err!(host1.execute_plugin("./allowed.txt"));
+    assert_eq!(out1, CapError::GlobMismatch);
+    let trace1 = host1.get_trace_json();
+
+    let mut csprng2 = OsRng;
+    let keypair2 = SigningKey::generate(&mut csprng2);
+    let mut host2 = HostState::new(manifest, fixed_seed, keypair2);
+    let out2 = assert_err!(host2.execute_plugin("./allowed.txt"));
+    assert_eq!(out2, CapError::GlobMismatch);
+    let trace2 = host2.get_trace_json();
+
+    let parsed1 = assert_ok!(serde_json::from_str::<Vec<TraceEvent>>(&trace1));
+    let parsed2 = assert_ok!(serde_json::from_str::<Vec<TraceEvent>>(&trace2));
+    assert_eq!(parsed1, parsed2);
+    assert_eq!(parsed1[0].ts_seed, parsed2[0].ts_seed);
+}