capsule-runtime 0.3.0

//! Containment classes: what an operator *declares* versus what a host actually *achieves*.
//!
//! The two directions are deliberately kept apart:
//!
//! * The **declared floor** ([`murmur_artifact::ContainmentClass`]) is a requirement, combined
//!   from the manifest, the workspace config and `--containment` by taking the strongest (see
//!   [`murmur_artifact::effective_containment_floor`]).
//! * The **achieved class** starts from [`EnforcementTier`], which is host-probed at launch time.
//!   [`achieved_class_for_tier`] takes nothing else — not the manifest, not the grant set — so no
//!   declaration can ever talk a host into reporting a class it cannot back. Exactly one manifest
//!   property may then talk a *capsule* down from that ceiling, and only downwards:
//!   `capabilities.filesystem.workdir_exec: true` caps the result at
//!   [`ContainmentClass::Advisory`] (see [`achieved_containment_class`]), because a capsule whose
//!   own workdir is executable has given up the claim `scoped` makes. The cap is applied in a
//!   separate wrapper rather than inside [`achieved_class_for_tier`] precisely so the "no
//!   declaration raises a class" property stays a property of one small, pure function.
//!
//! [`ContainmentClass::Sealed`] is reachable exactly when [`EnforcementTier::KernelSealed`] is:
//! a Linux host with a usable Landlock ABI, AppArmor out of the way of unprivileged user
//! namespaces, and a namespace probe that really created one. See [`crate::sealed`] for the
//! mechanism and for the [`SealedBlocker`] taxonomy that turns "not sealed here" into a specific
//! command an operator can run.
//!
//! The shortfall reason for `sealed` is therefore *mechanism-specific*, not a fixed string: a
//! host missing the AppArmor profile and a container missing `CAP_SYS_ADMIN` both fail to reach
//! `sealed`, but they are fixed in completely different places, and a refusal that cannot tell
//! them apart is a refusal an operator cannot act on.

use murmur_artifact::{ContainmentClass, ExportMode, Exports, FileExport, PeerFilesExport};
use serde::Serialize;

use crate::{
    cgroup::{IoMaxReport, IoMaxStatus},
    errors::RuntimeError,
    sandbox::{detect_enforcement_tier, EnforcementTier},
    sealed::{SealedBlocker, UsernsGrant},
    types::CapabilityPolicy,
};

pub use crate::sandbox::{detect_sealed_blocker, detect_userns_grant};

/// The class a host in `tier` can actually back, and nothing stronger.
///
/// Pure — the host probe lives in [`detect_enforcement_tier`], mirroring the
/// `tier_from_probe`/`detect_enforcement_tier` split in `sandbox.rs` so this mapping stays
/// unit-testable on any OS.
pub(crate) fn achieved_class_for_tier(tier: EnforcementTier) -> ContainmentClass {
    match tier {
        // A private mount namespace pivoted onto a composed root: paths outside it are absent,
        // not merely denied — exactly the mechanism `sealed` names. Landlock and seccomp still
        // install inside it, so this arm is strictly stronger than `KernelFull`'s, never an
        // alternative to it.
        EnforcementTier::KernelSealed => ContainmentClass::Sealed,
        // Landlock mediates the filesystem and seccomp mediates exec/network: exactly the
        // mechanism `scoped` names.
        EnforcementTier::KernelFull => ContainmentClass::Scoped,
        // Seccomp alone leaves the filesystem scope convention-only, and `EnvironmentOnly` has
        // no kernel primitive at all. Neither can back a filesystem claim, so neither clears
        // `scoped`.
        EnforcementTier::KernelSeccompOnly | EnforcementTier::EnvironmentOnly => {
            ContainmentClass::Advisory
        }
    }
}

/// The class a session actually achieves: the host's ceiling from [`achieved_class_for_tier`],
/// capped by what the capsule's own `capabilities.filesystem.workdir_exec` leaves standing.
///
/// This is the one place a *manifest* property lowers an achieved class, and it does so by capping
/// rather than by deciding: [`achieved_class_for_tier`] above stays pure and tier-only, so no
/// declaration can talk a host up, and this wrapper can only ever talk a capsule *down*.
///
/// Why `workdir_exec` caps at [`ContainmentClass::Advisory`]: `scoped` (and `sealed` above it) both
/// claim that what runs inside the capsule is bounded by what the operator declared. With the
/// workdir's `Execute` right granted, a binary the agent compiles, downloads or renames inside its
/// own workdir runs whatever `capabilities.shell.allow` says — the allowlist stops being an
/// enforceable property. A host that could back `scoped` still cannot back a claim the capsule
/// itself has given up, so the honest report is `advisory`, on every tier.
pub(crate) fn achieved_containment_class(
    tier: EnforcementTier,
    workdir_exec: bool,
) -> ContainmentClass {
    let host_ceiling = achieved_class_for_tier(tier);
    if workdir_exec {
        host_ceiling.min(ContainmentClass::Advisory)
    } else {
        host_ceiling
    }
}

/// Probes this host and reports the strongest class it can actually provide.
///
/// Host-only, and deliberately still takes no capsule input: it answers "what can this machine
/// back?", which is what `mur doctor` and the escape-conformance harness ask. A *session* asks the
/// narrower question and must use [`achieved_containment_class`] with its own probed tier instead
/// — see `runtime::stage_session`, which probes the tier once and passes it to both that call and
/// [`scope_report_for_tier`].
pub fn detect_achieved_containment() -> ContainmentClass {
    achieved_class_for_tier(detect_enforcement_tier())
}

/// Why `achieved` falls short of `declared`, naming the missing *mechanism* rather than the
/// missing class. `None` when the floor is met.
///
/// Pure and host-independent: the caller supplies both classes *and* — for the `sealed` arm — the
/// already-probed [`SealedBlocker`], so this function still probes nothing and stays testable
/// without a kernel. `sealed_blocker` is `None` when the caller has not probed (or cannot: a
/// non-Linux host), in which case the arm falls back to naming the mechanism generically.
///
/// `workdir_exec` is the capsule's own `capabilities.filesystem.workdir_exec`. It is checked before
/// every host arm below, because it is the one shortfall an operator cannot fix by changing hosts:
/// no kernel backs `scoped` for a capsule that has declared its workdir executable. Naming a
/// missing Landlock ABI to someone whose real problem is a line in their own manifest sends them to
/// the wrong machine.
pub fn containment_shortfall_reason(
    declared: ContainmentClass,
    achieved: ContainmentClass,
    sealed_blocker: Option<SealedBlocker>,
    workdir_exec: bool,
) -> Option<String> {
    if achieved >= declared {
        return None;
    }

    if workdir_exec && declared > ContainmentClass::Advisory {
        return Some(WORKDIR_EXEC_SHORTFALL.to_string());
    }

    let reason = match declared {
        // Unreachable in practice — `Advisory` is the weakest class, so nothing is below it —
        // but stated rather than `unreachable!()` so a future variant reordering cannot panic
        // a launch path.
        ContainmentClass::Advisory => {
            "advisory is the weakest containment class and is satisfied by every host".to_string()
        }
        ContainmentClass::Scoped => {
            "scoped requires Landlock filesystem mediation (Linux 5.13+ with a usable Landlock \
             ABI); this host provides no kernel filesystem mediation, so paths outside the \
             workdir are constrained by convention only"
                .to_string()
        }
        // The mechanism exists now, so the reason names *which part of it* this host is missing
        // and how to fix that part — never the old blanket "no host can provide it today".
        ContainmentClass::Sealed => match sealed_blocker {
            Some(blocker) => blocker.reason(),
            None => "sealed requires a private mount namespace pivoted onto a composed root \
                     (unshare(CLONE_NEWUSER|CLONE_NEWNS) + pivot_root), which this host did not \
                     provide"
                .to_string(),
        },
    };

    Some(reason)
}

/// The reason a capsule that declared `capabilities.filesystem.workdir_exec: true` falls short of
/// any floor above `advisory`. Fixed text rather than a `match` arm per declared class: the
/// mechanism, the consequence and the remedy are identical for `scoped` and `sealed`, because both
/// rest on the claim this declaration gives up.
const WORKDIR_EXEC_SHORTFALL: &str =
    "capabilities.filesystem.workdir_exec: true keeps the Landlock Execute right on the session \
     workdir, so a binary the capsule compiles, downloads or renames inside it runs regardless of \
     capabilities.shell.allow — the allowlist stops being an enforceable property of this capsule. \
     No host can back a class above advisory for it. Either remove workdir_exec (the allowlist is \
     then enforced by the kernel on the resolved path) or lower the declared containment floor to \
     advisory";

/// The refusal gate: `Ok(())` when the host's `achieved` class meets or exceeds the `declared`
/// floor, [`RuntimeError::ContainmentFloorUnmet`] otherwise.
///
/// Pure — takes every input as an argument and probes nothing, so the whole decision is
/// testable without a kernel.
pub fn check_containment_floor(
    declared: ContainmentClass,
    achieved: ContainmentClass,
    sealed_blocker: Option<SealedBlocker>,
    workdir_exec: bool,
) -> Result<(), RuntimeError> {
    match containment_shortfall_reason(declared, achieved, sealed_blocker, workdir_exec) {
        None => Ok(()),
        Some(reason) => Err(RuntimeError::ContainmentFloorUnmet {
            declared,
            achieved,
            reason,
        }),
    }
}

/// The declared `exports.files` block as it appears in a [`ScopeReport`] — and therefore in
/// `mur run --explain-scope --json` and in `trace.jsonl`'s `session_start.effective_grants`.
///
/// A flattened copy rather than [`FileExport`] itself: this is a wire shape with a stable field
/// order and a `mode` that serializes as `"read-only"`, and it must not move whenever the
/// manifest type gains a field the report has no business publishing.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct ExportsFilesReport {
    /// `exports.files.root` verbatim, as declared.
    pub root: String,
    pub mode: ExportMode,
    /// The effective per-file read ceiling, with the default already applied.
    pub max_bytes: u64,
}

impl From<&FileExport> for ExportsFilesReport {
    fn from(export: &FileExport) -> Self {
        Self {
            root: export.root.clone(),
            mode: export.mode,
            max_bytes: export.max_bytes,
        }
    }
}

/// The declared `exports.peer_files` block as it appears in a [`ScopeReport`].
///
/// A flattened copy rather than [`PeerFilesExport`] itself, on the same terms as
/// [`ExportsFilesReport`]: a wire shape with a stable field order, which must not move whenever
/// the manifest type gains a field the report has no business publishing.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct PeerFilesReport {
    /// `exports.peer_files.root` verbatim, as declared.
    pub root: String,
    /// The effective handle-lifetime ceiling in seconds, with the ephemeral default already
    /// applied — so an operator reads the value the runtime will actually clamp to, not the
    /// absence of a declaration.
    pub max_ttl_secs: u64,
    /// The effective per-file ceiling on a redeemed read, with the default already applied.
    pub max_bytes: u64,
}

impl From<&PeerFilesExport> for PeerFilesReport {
    fn from(export: &PeerFilesExport) -> Self {
        Self {
            root: export.root.clone(),
            max_ttl_secs: export.effective_max_ttl_secs(),
            max_bytes: export.max_bytes,
        }
    }
}

/// One artifact's durable state grant as it appears in a [`ScopeReport`].
///
/// A grant rather than a disclosure, unlike [`ExportsFilesReport`] beside it — but reported on
/// exactly the same terms, and for the same reason: it opens a host path outside the workdir that
/// an operator reading `filesystem scope` alone would never see.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct StateStoreReport {
    /// The artifact whose entry declared `capabilities.state`.
    pub artifact: String,
    /// The store directory name, with the capsule-name default already applied — so an operator
    /// reads the directory that will actually be opened, not the absence of a declaration.
    pub store: String,
    /// Absolute host path of the store, `~/.murmur/state/<store>` with the home already resolved.
    /// Reported as a string rather than a path so the JSON shape does not vary by platform.
    pub host_path: String,
}

/// The filesystem surface one artifact's guest is preopened into, as a stable wire name.
///
/// The three values are the whole space: a WASI guest either holds a directory descriptor for the
/// accessible workdir, holds one for a subtree of it, or holds none at all. Which one an entry
/// resolves to is decided by its role and its `capabilities.filesystem.scope` in
/// [`crate::network_policy::preopen_reports`]; the baselines the two roles start from are
/// [`crate::network_policy::ToolCapabilityGrant`] and
/// [`crate::network_policy::HookCapabilityGrant`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
#[serde(rename_all = "kebab-case")]
pub enum PreopenSurface {
    /// The entire accessible workdir, preopened as `"."` with `DirPerms::all()` and
    /// `FilePerms::all()`. The wide default a `runtime: tool` or `runtime: driver` entry with no
    /// `capabilities.filesystem.scope` resolves to — see
    /// [`crate::network_policy::ToolCapabilityGrant`] for the threat that default is chosen
    /// against and the threat it is not.
    WholeWorkdir,
    /// `<accessible workdir>/<scope>` and nothing above it, preopened as `"."` with the same
    /// rights. What a declared `capabilities.filesystem.scope` resolves to, whatever the role.
    ScopedSubtree,
    /// No preopened directory of any kind, so the guest holds no `wasi:filesystem` descriptor. The
    /// default-deny baseline a `runtime: hook` entry with no `capabilities.filesystem.scope`
    /// resolves to — see [`crate::network_policy::HookCapabilityGrant`].
    Nothing,
}

impl PreopenSurface {
    /// The phrase [`PreopenReport::render`] names this surface with. Distinct per variant rather
    /// than a formatted path, because the point of the line is that an operator can tell the three
    /// apart without knowing the resolved workdir.
    fn summary(self) -> &'static str {
        match self {
            PreopenSurface::WholeWorkdir => "the whole accessible workdir",
            PreopenSurface::ScopedSubtree => "one subtree of the accessible workdir",
            PreopenSurface::Nothing => "nothing preopened",
        }
    }
}

/// One artifact's resolved WASI preopen as it appears in a [`ScopeReport`] — and therefore in
/// `mur run --explain-scope`, in `mur doctor`, and in `trace.jsonl`'s
/// `session_start.effective_grants`.
///
/// Per-artifact, like [`StateStoreReport`] beside it, and reported for the same reason: the
/// capsule-wide [`ScopeReport::filesystem_scope`] is joined into no guest preopen root, so an
/// operator reading that field alone learns nothing about what any tool, driver or hook can
/// actually see.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct PreopenReport {
    /// The artifact whose entry in the capsule operator's own manifest this describes.
    pub artifact: String,
    /// [`murmur_artifact::ArtifactRuntime::as_str`] verbatim, so the report and the manifest name
    /// a role with one vocabulary.
    pub role: String,
    /// The entry's declared `capabilities.filesystem.scope`, verbatim. `None` = undeclared, which
    /// is what [`Self::surface`] has already resolved against the role's own baseline.
    pub scope: Option<String>,
    /// What the guest is preopened into once the role's baseline and [`Self::scope`] are both
    /// applied.
    pub surface: PreopenSurface,
}

impl PreopenReport {
    /// The single line this preopen renders as, shared by [`ScopeReport::render`] and by
    /// `mur doctor` so the two cannot word the same grant differently.
    pub fn render(&self) -> String {
        let artifact = &self.artifact;
        let role = &self.role;
        let surface = self.surface.summary();
        match &self.scope {
            Some(scope) => {
                format!("{artifact} ({role}): {surface} — capabilities.filesystem.scope: {scope}")
            }
            None => format!(
                "{artifact} ({role}): {surface} — no capabilities.filesystem.scope declared"
            ),
        }
    }
}

/// What the filesystem mechanism this session installs restricts, as a stable wire name.
///
/// Keyed on [`crate::sandbox::applied_tier`] — the host tier capped by the declared containment
/// floor, which is the same value [`crate::sandbox::ShellEnforcement::resolve`] installs the
/// session's mechanisms from. The achieved containment class answers a different question ("what
/// can this host back"), and a capsule declaring less than `sealed` on a sealed-capable host is
/// where the two part company: it is reported `achieved: sealed` and runs Landlock-scoped.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
#[serde(rename_all = "kebab-case")]
pub enum FilesystemRestriction {
    /// No kernel mechanism mediates the filesystem, so a path outside the workdir is reachable.
    Advisory,
    /// Landlock refuses the open, and the path outside the granted set still exists.
    Enforced,
    /// A composed root, where the path outside the capsule is not there to open.
    Absent,
}

/// What the filesystem mechanism this session installs does *not* protect, in words an operator
/// can act on.
///
/// The counterpart to every grant beside it in a [`ScopeReport`]: those say what the capsule may
/// reach, and this says which of the restrictions an operator would read into them are not there.
///
/// [`Self::not_protected`] is empty at [`FilesystemRestriction::Absent`] and non-empty below it. It
/// is serialized either way — an absent key identifies a runtime that predates the field, never a
/// capsule with nothing to disclaim.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct FilesystemBoundaryReport {
    /// What the session's filesystem mechanism restricts.
    pub restriction: FilesystemRestriction,
    /// One statement per protection an operator would otherwise assume, empty at
    /// [`FilesystemRestriction::Absent`]. Rendered verbatim under `Not protected here`, so the JSON
    /// and the human report cannot word the same disclaimer differently.
    pub not_protected: Vec<String>,
}

/// What a session with no kernel filesystem mechanism leaves unrestricted.
///
/// Names the mechanism rather than the class, because "advisory" is the word an operator has
/// already read on the `achieved:` line and taken for a protection.
const ADVISORY_FILESYSTEM_NOT_PROTECTED: &str =
    "Filesystem restriction is advisory on this host: no kernel mechanism denies a read or a write \
     outside the session workdir, so capabilities.filesystem.scope bounds what the runtime hands a \
     subprocess rather than what that subprocess can reach. A Linux host with a usable Landlock \
     ABI installs a Landlock domain instead, where the kernel refuses the open.";

/// What a Landlock-scoped session leaves unrestricted.
///
/// Not the `advisory` sentence: Landlock really does mediate the filesystem here, and an operator
/// told otherwise goes and hardens something the kernel already holds. What Landlock does not do is
/// make a path absent — it mediates the operations that touch a file, not path resolution.
const ENFORCED_FILESYSTEM_NOT_PROTECTED: &str =
    "A path outside the granted set is denied rather than absent: Landlock refuses the open, and \
     stat, access and readlink on that path still succeed and still report the real file's \
     metadata, because Landlock mediates the operations that touch a file and not path resolution. \
     A probe that only asks whether a path exists therefore learns nothing about what was denied — \
     read the file to see the refusal. Declaring capabilities.containment: sealed on a host that \
     reaches the sealed tier composes a root the path is not in at all.";

/// What no mechanism protects, and the reason `--explain-scope` carries this block at all.
///
/// Identical wherever it prints, because the rewrite it describes is identical: `HOME` is replaced
/// with the session's synthetic home on every tier and every platform (see `crate::shell`), so the
/// obvious `~`-based containment probe answers *no such file* on a host that denies nothing.
const PATH_REWRITING_NOT_PROTECTED: &str =
    "Path rewriting is a convenience, not a boundary: HOME is set to <workdir>/.capsule-home on \
     every tier, so `cat ~/.ssh/id_rsa` answers \"No such file or directory\" whether or not \
     anything was denied — the tilde resolved into the workdir and the host file was never looked \
     for. A ~-based probe is therefore never evidence of containment; test with an absolute path \
     to a real file outside the workdir instead.";

/// The filesystem boundary the tier a session applies actually provides, and the protections it
/// does not.
///
/// Pure and derived from the applied tier alone, so `--explain-scope` and
/// `session_start.effective_grants` cannot word the same disclaimer differently: both go through
/// [`scope_report_for_tier`], which calls this once with the tier it has already resolved.
///
/// The argument is the *applied* tier, never the host tier and never the achieved class. A composed
/// root is what makes a host path absent, and a session composes one only when the host reaches
/// `KernelSealed` **and** the capsule declared a `sealed` floor; a Landlock domain is installed
/// whenever the applied tier is `KernelFull` or `KernelSealed`, including for a capsule whose
/// `capabilities.filesystem.workdir_exec` caps its achieved class at `advisory`.
pub(crate) fn filesystem_boundary(applied: EnforcementTier) -> FilesystemBoundaryReport {
    // The path-rewriting statement rides along with the mechanism-specific one rather than standing
    // on its own, so a composed root — where the paths outside it are absent, and the `~` rewrite
    // lands inside the only writable path in that root — discloses nothing at all.
    let (restriction, filesystem) = match applied {
        EnforcementTier::KernelSealed => (FilesystemRestriction::Absent, None),
        EnforcementTier::KernelFull => (
            FilesystemRestriction::Enforced,
            Some(ENFORCED_FILESYSTEM_NOT_PROTECTED),
        ),
        EnforcementTier::KernelSeccompOnly | EnforcementTier::EnvironmentOnly => (
            FilesystemRestriction::Advisory,
            Some(ADVISORY_FILESYSTEM_NOT_PROTECTED),
        ),
    };

    let not_protected = match filesystem {
        Some(filesystem) => vec![
            filesystem.to_string(),
            PATH_REWRITING_NOT_PROTECTED.to_string(),
        ],
        None => Vec::new(),
    };

    FilesystemBoundaryReport {
        restriction,
        not_protected,
    }
}

/// Read-only answer to "what would this capsule actually be allowed to do on this host?".
///
/// Built from the already-parsed [`CapabilityPolicy`] plus one host tier probe. Nothing here
/// stages artifacts, touches a registry, creates a workdir or resolves DNS — it is a diagnostic,
/// so it reports even when [`Self::floor_met`] is `false`.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct ScopeReport {
    /// Strongest class any source asked for (manifest / workspace config / `--containment`).
    pub declared_containment: ContainmentClass,
    /// Strongest class this host can actually back, derived from the tier probe alone.
    pub achieved_containment: ContainmentClass,
    /// `achieved_containment >= declared_containment`. `false` means `mur run` would refuse.
    pub floor_met: bool,
    /// The missing mechanism when `floor_met` is `false`; absent otherwise.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub shortfall_reason: Option<String>,
    /// The probed host tier, as a stable wire name.
    pub enforcement_tier: &'static str,
    /// Where this host's permission to create an unprivileged user namespace comes from, as
    /// [`UsernsGrant::wire_name`], or `null` off Linux, where AppArmor does not exist and the
    /// question has no answer.
    ///
    /// Always serialized, on the same terms as [`Self::workdir_exec`]: the key's absence
    /// identifies a runtime that predates it, not a host that was not asked. Reported because
    /// three very different hosts — no AppArmor, hardening switched off host-wide, and the shipped
    /// profile confining `mur` — otherwise produce byte-identical reports while differing enormously
    /// in what else on the machine can create a user namespace.
    pub userns_grant: Option<UsernsGrant>,
    /// `capabilities.filesystem.scope`, verbatim.
    pub filesystem_scope: Option<String>,
    /// `capabilities.filesystem.workdir_exec`. Always present (never skipped when `false`), so a
    /// consumer can tell "declared false" from "this runtime predates the key" by the field's
    /// presence rather than by its value.
    ///
    /// `true` is the only manifest declaration that lowers [`Self::achieved_containment`], which is
    /// why it is reported next to the grants rather than buried: reading `achieved: advisory` on a
    /// Landlock-capable host makes sense only alongside it.
    pub workdir_exec: bool,
    /// `capabilities.filesystem.read_only`, verbatim — the workdir subtrees the capsule may read
    /// but must not write. Empty when the capsule declares none, which is the whole workdir
    /// writable. Always serialized as an array (never skipped), on the same terms as
    /// [`Self::state_stores`]: an absent key identifies a runtime that predates the field, not a
    /// capsule that declared nothing.
    ///
    /// The one field here that subtracts rather than grants, which is why it is reported beside
    /// [`Self::read_only_advisory_for`] rather than alone: a protection stated without its
    /// qualification reads as a boundary the capsule does not have.
    pub read_only_paths: Vec<String>,
    /// The entries of [`Self::shell_allow`] that [`Self::read_only_paths`] is only advisory
    /// against — the same set `W-SEC-017` fires for, resolved by the same
    /// [`read_only_advisory_for`] both this report and `mur doctor` call.
    ///
    /// Empty means the declaration is enforced for every readable call. Non-empty names the
    /// binaries whose own file I/O the dispatch-time write-intent analyser cannot read, so the
    /// report cannot claim more than `W-SEC-017` already qualifies. Always serialized as an array
    /// (never skipped), on the same terms as [`Self::read_only_paths`], and always empty when
    /// that list is: nothing is advisory against a protection that was never declared.
    pub read_only_advisory_for: Vec<String>,
    /// The filesystem surface every guest-bearing artifact in this capsule is preopened into, one
    /// entry per `runtime: tool`, `runtime: driver` and `runtime: hook` entry, in manifest order.
    /// Empty when the capsule declares only skills. Always serialized as an array (never skipped),
    /// on the same terms as [`Self::state_stores`]: an absent key identifies a runtime that
    /// predates the field, not a capsule with no guest artifacts.
    ///
    /// This is the field that answers "what can this tool read and write?".
    /// [`Self::filesystem_scope`] above does not: it is the capsule-wide declaration, and it is
    /// joined into no preopen root.
    ///
    /// Copied through untouched, exactly as the reports beside it are — resolving a preopen
    /// changes no class, no floor and no tier.
    pub preopens: Vec<PreopenReport>,
    /// `capabilities.network.allow`, verbatim — declared destinations, not resolved IPs.
    pub network_allow: Vec<String>,
    /// `capabilities.network.unix_sockets`.
    pub unix_sockets: bool,
    /// `capabilities.shell.allow`, verbatim.
    pub shell_allow: Vec<String>,
    /// `capabilities.spawn.allow`, verbatim.
    pub spawn_allow: Vec<String>,
    /// `capabilities.env.allow`, verbatim.
    pub env_allow: Vec<String>,
    /// `capabilities.plan.submit` — whether the model is offered the `submit-plan` tool. Always
    /// serialized (never skipped when `false`), on the same terms as [`Self::workdir_exec`]: an
    /// absent key identifies a runtime that predates the grant, not a capsule that declined it.
    ///
    /// It opens no host resource of its own. It is reported beside the grants because it changes
    /// *how much* of every other grant one model turn can reach: a plan runs many steps against
    /// this capsule's own tools, shell allowlist and spawn grant without a turn in between.
    pub plan_submit: bool,
    /// Every host directory a `capabilities.shell.interpreter_runtime` grant opens, rendered as
    /// `<binary>: <dir>[ (list_dir)]`. These are the paths outside the workdir that stay
    /// reachable even at `scoped`.
    pub interpreter_runtime_grants: Vec<String>,
    /// The read-only file surface `exports.files` declares, or `null` when the capsule declares
    /// none. Always serialized (never skipped), so a consumer can tell "this runtime predates
    /// exports" from "this capsule declined to export anything" by the field's presence rather
    /// than by its value — the same terms [`Self::workdir_exec`] is reported on.
    ///
    /// An export is a *disclosure*, not a grant: it never appears in
    /// [`Self::achieved_containment`], and declaring one cannot change any other field of this
    /// report. It is printed beside the grants because it is the other direction of the same
    /// question — what crosses the capsule boundary, and which way.
    pub exports_files: Option<ExportsFilesReport>,
    /// The peer-handoff surface `exports.peer_files` declares, or `null` when the capsule
    /// declares none. Always serialized, on the same terms as [`Self::exports_files`].
    ///
    /// A separate authoriser from `exports.files`, over a separate subtree: a capsule may declare
    /// either, both or neither, and this field says nothing about the other. Like every export it
    /// is a disclosure rather than a grant, and declaring it cannot change
    /// [`Self::achieved_containment`], [`Self::enforcement_tier`] or [`Self::floor_met`].
    pub peer_files: Option<PeerFilesReport>,
    /// `capabilities.peer_fetch.allow`, verbatim — the peers this capsule may redeem a handle
    /// against. Empty when the block is absent, which is deny.
    ///
    /// A separate list from [`Self::network_allow`] and never an alias for it: a destination
    /// reachable by `send` is not redeemable unless it also appears here, because ingesting a
    /// peer's bytes into this workdir is a different question from being allowed to talk to it.
    pub peer_fetch_allow: Vec<String>,
    /// Every durable state store this session's artifacts declare, one entry per declaring
    /// artifact, empty when none does. Always serialized as an array (never skipped), on the same
    /// terms as [`Self::exports_files`]: an absent key identifies a runtime that predates state
    /// stores, not a capsule that declined one.
    ///
    /// Declaring a store cannot change [`Self::achieved_containment`], [`Self::floor_met`] or
    /// [`Self::enforcement_tier`] — it is copied through untouched, exactly as the export reports
    /// beside it are. It is reported because it is the one grant that opens a path *outside* every
    /// workdir, which nothing else in this block would reveal.
    pub state_stores: Vec<StateStoreReport>,
    /// Every artifact whose manifest entry declares a `config:` block, in manifest order, empty
    /// when none does. Always serialized as an array (never skipped), on the same terms as
    /// [`Self::state_stores`]: an absent key identifies a runtime that predates artifact config,
    /// not a capsule that declined it.
    ///
    /// Names only. What an artifact is configured *with* is operator-authored plaintext that
    /// belongs in the manifest and in nothing this report — or `trace.jsonl`, which carries this
    /// report verbatim — writes out.
    ///
    /// Declaring config cannot change [`Self::achieved_containment`], [`Self::floor_met`] or
    /// [`Self::enforcement_tier`]: it adds one environment variable to one guest and reaches no
    /// grant. Reported because a variable an artifact silently depends on is otherwise invisible
    /// to an operator reading the capsule's scope.
    pub configured_artifacts: Vec<String>,
    /// Every `capabilities.shell.staged_runtime` grant, rendered as
    /// `<binary>: <source_path> (pin: <pin>)`. These are host runtime trees a `sealed` capsule
    /// asks to have bind-mounted read-only into its composed root.
    ///
    /// Reported whatever the floor and whatever this host can back — a capsule that declares a
    /// staged runtime and cannot run here is exactly the case an operator is inspecting when they
    /// reach for `--explain-scope`, so hiding the grant behind a met floor would blank out the
    /// diagnostic in the one case it is for.
    pub staged_runtime_grants: Vec<String>,
    /// Every path the runtime itself writes inside the capsule's workdir, so a consumer for whom
    /// that workdir is the deliverable can subtract them and be left with what the *capsule*
    /// changed. Always serialized as an array (never skipped), on the same terms as
    /// [`Self::state_stores`]: an absent key identifies a runtime that predates the declaration,
    /// not a runtime that writes nothing.
    ///
    /// The one field here that describes what the runtime does rather than what the capsule may
    /// do. It is reported beside the grants because it answers the other half of "what is this
    /// workdir", and because a consumer that has to maintain its own list of runtime entries
    /// silently falls behind every time the set changes — enabling `sealed` being exactly that
    /// case.
    ///
    /// Keyed on the tier this session would install: [`Self::enforcement_tier`] capped by
    /// [`Self::declared_containment`], which is what decides whether a composed root is built at
    /// all. Reading `enforcement_tier: mountns+pivot_root+landlock+seccomp` next to a report with
    /// no `sealed` rows is that cap, not a disagreement — the host could seal and the capsule did
    /// not ask. See [`crate::workdir_writes`].
    pub runtime_writes: Vec<crate::workdir_writes::RuntimeWriteReport>,
    /// The declared `capabilities.resources.cgroup_io_bytes_per_sec` ceiling, and whether it is
    /// actually on this session's cgroup scope.
    ///
    /// Always serialized (never skipped), on the same terms as [`Self::workdir_exec`] and
    /// [`Self::state_stores`]: an absent key identifies a runtime that predates the field, not a
    /// host that was not asked. [`IoMaxStatus::NotProbed`] is what "not asked" looks like, and it
    /// is a value in the report rather than a missing key.
    ///
    /// The one field here filled from a *performed* operation rather than from the policy: at
    /// launch it carries the outcome of the real `io.max` write, established before `session_start`
    /// is written so `trace.jsonl` cannot claim a ceiling the kernel refused; under
    /// `--explain-scope` it carries the outcome of the same write against a throwaway cgroup that
    /// is created and removed. Declaring a ceiling that does not apply changes no class and refuses
    /// no launch — `io.max` is the one non-fatal cgroup limit — so this field is the only place
    /// the shortfall appears.
    pub io_max: IoMaxReport,
    /// What this session's filesystem mechanism does not restrict — the block `--explain-scope`
    /// prints as `Not protected here`, directly under `Containment`.
    ///
    /// Always serialized (never skipped), on the same terms as [`Self::state_stores`]: an absent
    /// key identifies a runtime that predates the field, and an empty
    /// [`FilesystemBoundaryReport::not_protected`] identifies a session with nothing to disclaim.
    ///
    /// Derived in [`filesystem_boundary`] from [`crate::sandbox::applied_tier`] — the same value
    /// [`Self::runtime_writes`] is keyed on — and from no [`CapabilityPolicy`] field. Not from
    /// [`Self::achieved_containment`], which reports the class this *host* can back: a capsule
    /// declaring less than `sealed` on a sealed-capable host reads `achieved: sealed` and composes
    /// no root, so a boundary keyed on the class would report an absence the capsule does not have.
    /// It stands beside the grants rather than among them because it qualifies every one at once.
    pub filesystem_boundary: FilesystemBoundaryReport,
}

impl ScopeReport {
    /// Human-readable rendering used by `mur run --explain-scope` without `--json`.
    pub fn render(&self) -> String {
        let mut out = String::new();
        out.push_str("Containment\n");
        out.push_str(&format!("  declared:  {}\n", self.declared_containment));
        out.push_str(&format!("  achieved:  {}\n", self.achieved_containment));
        out.push_str(&format!(
            "  floor met: {}\n",
            if self.floor_met { "yes" } else { "no" }
        ));
        if let Some(reason) = &self.shortfall_reason {
            out.push_str(&format!("  reason:    {reason}\n"));
        }
        out.push_str(&format!("  mechanism: {}\n", self.enforcement_tier));
        out.push_str(&format!(
            "  userns grant: {}\n",
            match self.userns_grant {
                Some(grant) => grant.wire_name(),
                None => "n/a",
            }
        ));

        out.push_str(&render_not_protected(&self.filesystem_boundary));

        out.push_str("\nEffective grants\n");
        out.push_str(&format!(
            "  filesystem scope: {}\n",
            self.filesystem_scope.as_deref().unwrap_or("<none>")
        ));
        out.push_str(&format!("  workdir exec:     {}\n", self.workdir_exec));
        out.push_str(&render_read_only(
            &self.read_only_paths,
            &self.read_only_advisory_for,
        ));
        push_list(
            &mut out,
            "preopens",
            &self
                .preopens
                .iter()
                .map(PreopenReport::render)
                .collect::<Vec<_>>(),
        );
        push_list(&mut out, "network allow", &self.network_allow);
        out.push_str(&format!("  unix sockets:     {}\n", self.unix_sockets));
        push_list(&mut out, "shell allow", &self.shell_allow);
        push_list(&mut out, "spawn allow", &self.spawn_allow);
        push_list(&mut out, "env allow", &self.env_allow);
        out.push_str(&format!("  plan submit:      {}\n", self.plan_submit));
        push_list(
            &mut out,
            "interpreter runtime",
            &self.interpreter_runtime_grants,
        );
        push_list(&mut out, "staged runtime", &self.staged_runtime_grants);
        push_list(
            &mut out,
            "state stores",
            &self
                .state_stores
                .iter()
                .map(|store| format!("{}: {} -> {}", store.artifact, store.store, store.host_path))
                .collect::<Vec<_>>(),
        );
        push_list(&mut out, "artifact config", &self.configured_artifacts);

        out.push_str("\nResource plane\n");
        match &self.exports_files {
            None => out.push_str("  exports.files: <none>\n"),
            Some(export) => {
                out.push_str(&format!("  exports.files root: {}\n", export.root));
                out.push_str(&format!("  mode:               {}\n", export.mode));
                out.push_str(&format!(
                    "  max bytes:          {} (per file)\n",
                    export.max_bytes
                ));
            }
        }

        out.push_str(&format!(
            "  io.max:        {} ({} bytes/s declared)\n",
            match self.io_max.status {
                IoMaxStatus::Enforced => "enforced",
                IoMaxStatus::Unavailable => "unavailable",
                IoMaxStatus::NotRequired => "not-required",
                IoMaxStatus::NotProbed => "not-probed",
            },
            self.io_max.declared_bytes_per_sec
        ));
        if let Some(reason) = &self.io_max.reason {
            out.push_str(&format!("    {reason}\n"));
        }

        out.push_str("\nPeer handoff\n");
        match &self.peer_files {
            None => out.push_str("  exports.peer_files: <none>\n"),
            Some(peer) => {
                out.push_str(&format!("  exports.peer_files root: {}\n", peer.root));
                out.push_str(&format!(
                    "  max handle ttl:          {}s\n",
                    peer.max_ttl_secs
                ));
                out.push_str(&format!(
                    "  max bytes:               {} (per file)\n",
                    peer.max_bytes
                ));
            }
        }
        push_list(&mut out, "peer_fetch allow", &self.peer_fetch_allow);

        out.push_str("\nRuntime writes\n");
        out.push_str(&crate::workdir_writes::render_runtime_writes(
            &self.runtime_writes,
        ));

        if !self.floor_met {
            out.push_str(
                "\nThis is a report only — `mur run` without --explain-scope would refuse to \
                 launch here.\n",
            );
        }
        out
    }
}

/// The allowlisted binaries a declared `capabilities.filesystem.read_only` is only advisory
/// against: those whose own file I/O the dispatch-time write-intent analyser cannot read, in
/// `shell_allow` order.
///
/// Exactly the set `W-SEC-017` fires one line for, resolved here so `--explain-scope`, `trace.jsonl`
/// and `mur doctor` cannot disagree with the warning printed beside them. Empty when nothing is
/// declared read-only: an interpreter is not advisory against a protection that does not exist.
#[must_use]
pub fn read_only_advisory_for(read_only_paths: &[String], shell_allow: &[String]) -> Vec<String> {
    if read_only_paths.is_empty() {
        return Vec::new();
    }
    shell_allow
        .iter()
        .filter(|binary| crate::protected_paths::is_advisory_interpreter(binary))
        .cloned()
        .collect()
}

/// The `read_only` block of the scope report: the declared paths, then one line saying whether the
/// protection is enforced for every readable call or advisory against a named binary.
///
/// Shared by [`ScopeReport::render`] and by `mur doctor` so the two cannot word the same grant
/// differently — the precedent [`PreopenReport::render`] sets. Ends with a newline; emits nothing
/// beyond the `<none>` line when no path is declared, because there is no enforcement question to
/// answer about a protection nobody asked for.
#[must_use]
pub fn render_read_only(read_only_paths: &[String], advisory_for: &[String]) -> String {
    let mut out = String::new();
    push_list(&mut out, "read_only", read_only_paths);
    if read_only_paths.is_empty() {
        return out;
    }
    if advisory_for.is_empty() {
        out.push_str(
            "  read_only enforcement: enforced for every tool call and every shell command the \
             dispatch check can read\n",
        );
    } else {
        out.push_str(&format!(
            "  read_only enforcement: advisory against {} — an interpreter's own file I/O is not \
             something the dispatch check can read; enforced for every tool call and for every \
             shell command it can read\n",
            advisory_for.join(", ")
        ));
    }
    out
}

/// The `Not protected here` block: one line per statement in
/// [`FilesystemBoundaryReport::not_protected`], and nothing at all when that list is empty.
///
/// A heading with no entries under it would read as a disclaimer the reader had to interpret, so a
/// composed root prints no heading rather than an empty one. Every line is a statement from the report
/// verbatim, so the human rendering and `--explain-scope --json` say the same thing in the same
/// words.
fn render_not_protected(boundary: &FilesystemBoundaryReport) -> String {
    if boundary.not_protected.is_empty() {
        return String::new();
    }
    let mut out = String::from("\nNot protected here\n");
    for statement in &boundary.not_protected {
        out.push_str(&format!("  - {statement}\n"));
    }
    out
}

fn push_list(out: &mut String, label: &str, values: &[String]) {
    if values.is_empty() {
        out.push_str(&format!("  {label}: <none>\n"));
        return;
    }
    out.push_str(&format!("  {label}:\n"));
    for value in values {
        out.push_str(&format!("    - {value}\n"));
    }
}

/// Builds a [`ScopeReport`] for `policy` against this host, with `declared` as the already-
/// combined floor. Takes one [`crate::sandbox::HostProbe`], so the tier, the blocker and the
/// grant it reports all describe one host at one moment.
///
/// `state_stores`, `configured_artifacts` and `preopens` are resolved by the caller (from the
/// manifest's artifact entries, via [`crate::state_store::state_store_reports`],
/// [`crate::artifact_config::configured_artifact_names`] and
/// [`crate::network_policy::preopen_reports`]) rather than derived here, because all three are
/// per-artifact and `policy` is capsule-wide. No resolution creates anything, so this stays a
/// read-only diagnostic.
pub fn explain_scope(
    policy: &CapabilityPolicy,
    declared: ContainmentClass,
    exports: Option<&Exports>,
    state_stores: Vec<StateStoreReport>,
    configured_artifacts: Vec<String>,
    preopens: Vec<PreopenReport>,
    io_max: IoMaxReport,
) -> ScopeReport {
    let probe = crate::sandbox::HostProbe::probe();
    scope_report_for_tier(
        policy,
        declared,
        probe.tier(),
        probe.sealed_blocker(),
        probe.userns_grant(),
        exports,
        state_stores,
        configured_artifacts,
        preopens,
        io_max,
    )
}

/// [`explain_scope`] with the tier and the sealed blocker injected — the seam every test uses so
/// no test depends on the host it happens to run on.
#[allow(clippy::too_many_arguments)]
pub(crate) fn scope_report_for_tier(
    policy: &CapabilityPolicy,
    declared: ContainmentClass,
    tier: EnforcementTier,
    sealed_blocker: Option<SealedBlocker>,
    userns_grant: Option<UsernsGrant>,
    exports: Option<&Exports>,
    state_stores: Vec<StateStoreReport>,
    configured_artifacts: Vec<String>,
    preopens: Vec<PreopenReport>,
    io_max: IoMaxReport,
) -> ScopeReport {
    let achieved = achieved_containment_class(tier, policy.workdir_exec_allowed);
    // The tier this session would actually install: the host reading `enforcement_tier`
    // reports, capped by the declared floor, which is the same `sandbox::applied_tier`
    // `ShellEnforcement::resolve` runs. Two fields below are keyed on it rather than on
    // `achieved`, because both describe mechanisms rather than the class this host can back.
    let applied = crate::sandbox::applied_tier(tier, declared);
    let shortfall_reason = containment_shortfall_reason(
        declared,
        achieved,
        sealed_blocker,
        policy.workdir_exec_allowed,
    );

    ScopeReport {
        declared_containment: declared,
        achieved_containment: achieved,
        floor_met: shortfall_reason.is_none(),
        shortfall_reason,
        enforcement_tier: enforcement_tier_name(tier),
        userns_grant,
        // Copied straight through and never consulted above: `achieved` is already computed, and
        // no export or peer grant may reach it.
        exports_files: exports
            .and_then(|exports| exports.files.as_ref())
            .map(ExportsFilesReport::from),
        peer_files: exports
            .and_then(|exports| exports.peer_files.as_ref())
            .map(PeerFilesReport::from),
        peer_fetch_allow: policy.peer_fetch_allow.clone(),
        // Resolved by `state_store::state_store_reports` before this call and copied through on
        // the same terms as the export reports above: a grant that opens a path outside the
        // workdir still gets no say in what class this host is reported to back.
        state_stores,
        // Resolved by `artifact_config::configured_artifact_names` before this call and copied
        // through on the same terms: one environment variable delivered to one guest gets no say
        // in what class this host is reported to back.
        configured_artifacts,
        filesystem_scope: policy.filesystem_scope.clone(),
        workdir_exec: policy.workdir_exec_allowed,
        read_only_paths: policy.read_only_paths.clone(),
        read_only_advisory_for: read_only_advisory_for(
            &policy.read_only_paths,
            &policy.shell_allow,
        ),
        // Resolved by `network_policy::preopen_reports` before this call and copied through on the
        // same terms as the reports above: what one guest is preopened into gets no say in what
        // class this host is reported to back.
        preopens,
        network_allow: policy.network_allow.clone(),
        unix_sockets: policy.unix_sockets_allowed,
        shell_allow: policy.shell_allow.clone(),
        spawn_allow: policy.spawn_allow.clone(),
        env_allow: policy.env_allow.clone(),
        plan_submit: policy.plan_submit,
        interpreter_runtime_grants: policy
            .shell_interpreter_runtime
            .iter()
            .flat_map(|grant| {
                grant.dirs.iter().map(move |dir| {
                    let listable = if dir.list_dir { " (list_dir)" } else { "" };
                    format!("{}: {}{}", grant.binary, dir.path, listable)
                })
            })
            .collect(),
        staged_runtime_grants: policy
            .shell_staged_runtime
            .iter()
            .map(|grant| {
                format!(
                    "{}: {} (pin: {})",
                    grant.binary, grant.source_path, grant.pin
                )
            })
            .collect(),
        // A capsule declaring `scoped` on a sealed-capable host composes no root and writes no
        // `/tmp` store, so a declaration keyed on the bare host tier would name two directories
        // that never appear. Nothing here touches the filesystem: `--explain-scope` returns before
        // a workdir exists, and a diagnostic that created the directory it describes would be
        // answering a question it had changed.
        runtime_writes: crate::workdir_writes::runtime_writes(applied),
        // Established by performing the `io.max` write, never inferred: `prepare_scope` fills it
        // at launch and `cgroup::probe_io_max` fills it under `--explain-scope`. Like every field
        // above it, it reaches no class and no floor.
        io_max,
        // Derived here, from the `applied` tier already resolved above, rather than filled by
        // either caller: `--explain-scope --json` and `session_start.effective_grants` are the
        // same object, and a field either of them worded for itself would make them differ.
        filesystem_boundary: filesystem_boundary(applied),
    }
}

/// Stable wire name for a tier, so `--explain-scope --json` consumers see the mechanism rather
/// than a `Debug` rendering that is free to change.
fn enforcement_tier_name(tier: EnforcementTier) -> &'static str {
    match tier {
        EnforcementTier::KernelSealed => "mountns+pivot_root+landlock+seccomp",
        EnforcementTier::KernelFull => "landlock+seccomp",
        EnforcementTier::KernelSeccompOnly => "seccomp-only",
        EnforcementTier::EnvironmentOnly => "none",
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use murmur_artifact::{InterpreterRuntimeDir, InterpreterRuntimeGrant, StagedRuntimeGrant};

    /// Every tier, so a new variant cannot quietly escape a test that iterates "all of them".
    const ALL_TIERS: &[EnforcementTier] = &[
        EnforcementTier::KernelSealed,
        EnforcementTier::KernelFull,
        EnforcementTier::KernelSeccompOnly,
        EnforcementTier::EnvironmentOnly,
    ];

    #[test]
    fn kernel_full_achieves_scoped() {
        assert_eq!(
            achieved_class_for_tier(EnforcementTier::KernelFull),
            ContainmentClass::Scoped
        );
    }

    /// The sealed tier, and only the sealed tier, reports `sealed`.
    #[test]
    fn only_the_sealed_tier_achieves_sealed() {
        assert_eq!(
            achieved_class_for_tier(EnforcementTier::KernelSealed),
            ContainmentClass::Sealed
        );
        for tier in ALL_TIERS
            .iter()
            .filter(|t| **t != EnforcementTier::KernelSealed)
        {
            assert_ne!(achieved_class_for_tier(*tier), ContainmentClass::Sealed);
        }
    }

    #[test]
    fn tiers_without_landlock_achieve_only_advisory() {
        assert_eq!(
            achieved_class_for_tier(EnforcementTier::KernelSeccompOnly),
            ContainmentClass::Advisory
        );
        assert_eq!(
            achieved_class_for_tier(EnforcementTier::EnvironmentOnly),
            ContainmentClass::Advisory
        );
    }

    /// The whole tier × `workdir_exec` truth table, with both inputs supplied by the test and no
    /// kernel consulted — the seam `achieved_class_for_tier`/`achieved_containment_class` exists
    /// for. This is emphatically *not* a test of the security property (that a workdir binary
    /// cannot execute); it tests only the class arithmetic, which is all that can honestly be
    /// tested without a Landlock-capable host.
    #[test]
    fn workdir_exec_caps_the_achieved_class_at_advisory_on_every_tier() {
        // Without the declaration: the host ceiling, unchanged.
        assert_eq!(
            achieved_containment_class(EnforcementTier::KernelSealed, false),
            ContainmentClass::Sealed
        );
        assert_eq!(
            achieved_containment_class(EnforcementTier::KernelFull, false),
            ContainmentClass::Scoped
        );
        assert_eq!(
            achieved_containment_class(EnforcementTier::KernelSeccompOnly, false),
            ContainmentClass::Advisory
        );
        assert_eq!(
            achieved_containment_class(EnforcementTier::EnvironmentOnly, false),
            ContainmentClass::Advisory
        );

        // With it: advisory, whatever the host could otherwise back.
        for tier in ALL_TIERS {
            assert_eq!(
                achieved_containment_class(*tier, true),
                ContainmentClass::Advisory,
                "workdir_exec must cap tier {tier:?} at advisory"
            );
        }
    }

    /// The cap goes in the wrapper, never in the tier-only function — a regression here would mean
    /// a manifest key had leaked into the one mapping that must stay host-only.
    #[test]
    fn the_tier_only_mapping_is_unaffected_by_the_cap() {
        for tier in ALL_TIERS {
            assert_eq!(
                achieved_class_for_tier(*tier),
                achieved_containment_class(*tier, false),
                "the tier-only mapping and the uncapped wrapper must agree on tier {tier:?}"
            );
        }
    }

    /// The refusal an operator actually hits: `workdir_exec: true` plus
    /// `capabilities.containment: scoped`, on a host that could otherwise back `scoped`. It must
    /// refuse, and the reason must send them to their manifest rather than to another machine.
    #[test]
    fn workdir_exec_refuses_a_scoped_floor_even_on_a_landlock_capable_host() {
        let achieved = achieved_containment_class(EnforcementTier::KernelFull, true);
        assert_eq!(achieved, ContainmentClass::Advisory);

        let error = check_containment_floor(ContainmentClass::Scoped, achieved, None, true)
            .expect_err("workdir_exec + scoped must refuse");
        match error {
            RuntimeError::ContainmentFloorUnmet {
                declared,
                achieved,
                reason,
            } => {
                assert_eq!(declared, ContainmentClass::Scoped);
                assert_eq!(achieved, ContainmentClass::Advisory);
                assert!(
                    reason.contains("workdir_exec"),
                    "the reason must name the manifest key, got: {reason}"
                );
                assert!(
                    !reason.contains("this host provides no kernel filesystem mediation"),
                    "the reason must not blame the host for a manifest declaration: {reason}"
                );
            }
            other => panic!("expected ContainmentFloorUnmet, got {other:?}"),
        }
    }

    /// `sealed` gets the same manifest-side reason rather than a `SealedBlocker` one: a probed
    /// blocker is real but is not what is stopping *this* capsule, and reporting it would send the
    /// operator to install an AppArmor profile that changes nothing.
    #[test]
    fn workdir_exec_outranks_a_probed_sealed_blocker_in_the_reason() {
        let reason = containment_shortfall_reason(
            ContainmentClass::Sealed,
            ContainmentClass::Advisory,
            Some(SealedBlocker::AppArmorProfileMissing),
            true,
        )
        .expect("refusal");
        assert!(reason.contains("workdir_exec"));
        assert!(!reason.contains("apparmor_parser"));
    }

    /// The declaration is not itself a refusal: a capsule that declares `workdir_exec` and asks
    /// for nothing above `advisory` launches normally on every host.
    #[test]
    fn workdir_exec_alone_refuses_nothing() {
        for tier in ALL_TIERS {
            let achieved = achieved_containment_class(*tier, true);
            assert!(
                check_containment_floor(ContainmentClass::Advisory, achieved, None, true).is_ok(),
                "workdir_exec at an advisory floor must launch on tier {tier:?}"
            );
        }
    }

    #[test]
    fn advisory_floor_is_met_on_every_tier() {
        for tier in ALL_TIERS {
            let achieved = achieved_class_for_tier(*tier);
            assert!(
                check_containment_floor(ContainmentClass::Advisory, achieved, None, false).is_ok()
            );
        }
    }

    #[test]
    fn scoped_floor_is_met_on_every_landlock_capable_tier() {
        for tier in [EnforcementTier::KernelFull, EnforcementTier::KernelSealed] {
            let achieved = achieved_class_for_tier(tier);
            assert!(
                check_containment_floor(ContainmentClass::Scoped, achieved, None, false).is_ok()
            );
        }

        for tier in [
            EnforcementTier::KernelSeccompOnly,
            EnforcementTier::EnvironmentOnly,
        ] {
            let achieved = achieved_class_for_tier(tier);
            let error = check_containment_floor(ContainmentClass::Scoped, achieved, None, false)
                .expect_err("scoped must refuse without Landlock");
            match error {
                RuntimeError::ContainmentFloorUnmet {
                    declared,
                    achieved,
                    reason,
                } => {
                    assert_eq!(declared, ContainmentClass::Scoped);
                    assert_eq!(achieved, ContainmentClass::Advisory);
                    assert!(
                        reason.contains("Landlock"),
                        "reason must name the missing mechanism, got: {reason}"
                    );
                }
                other => panic!("expected ContainmentFloorUnmet, got {other:?}"),
            }
        }
    }

    /// The edge case the new tier makes possible: a capsule declaring the *weaker* class on a
    /// sealed-capable host. The floor is met (a stronger host satisfies a weaker requirement),
    /// and the applied mechanism is the declared one — asserted next door in
    /// `sandbox::applied_tier`'s tests, since a careless `match` here could force sealed-only
    /// behaviour onto a `scoped` declaration.
    #[test]
    fn a_weaker_declaration_is_satisfied_by_a_sealed_host_without_being_upgraded() {
        let achieved = achieved_class_for_tier(EnforcementTier::KernelSealed);
        assert_eq!(achieved, ContainmentClass::Sealed);
        assert!(check_containment_floor(ContainmentClass::Advisory, achieved, None, false).is_ok());
        assert!(check_containment_floor(ContainmentClass::Scoped, achieved, None, false).is_ok());
        assert_eq!(
            containment_shortfall_reason(ContainmentClass::Scoped, achieved, None, false),
            None
        );
    }

    #[test]
    fn sealed_floor_is_met_only_on_the_sealed_tier() {
        assert!(check_containment_floor(
            ContainmentClass::Sealed,
            achieved_class_for_tier(EnforcementTier::KernelSealed),
            None,
            false
        )
        .is_ok());

        for tier in ALL_TIERS
            .iter()
            .filter(|t| **t != EnforcementTier::KernelSealed)
        {
            let achieved = achieved_class_for_tier(*tier);
            let error = check_containment_floor(
                ContainmentClass::Sealed,
                achieved,
                Some(SealedBlocker::NamespaceCreationDenied),
                false,
            )
            .expect_err("sealed must refuse on a host that cannot back it");
            match error {
                RuntimeError::ContainmentFloorUnmet {
                    declared, reason, ..
                } => {
                    assert_eq!(declared, ContainmentClass::Sealed);
                    assert!(
                        reason.contains("--cap-add SYS_ADMIN"),
                        "reason must name the blocking mechanism's remediation, got: {reason}"
                    );
                }
                other => panic!("expected ContainmentFloorUnmet, got {other:?}"),
            }
        }
    }

    /// The refusal text is mechanism-specific, not one fixed sentence: the same
    /// declared/achieved pair produces different, individually actionable reasons.
    #[test]
    fn the_sealed_refusal_names_the_specific_blocker() {
        let achieved = ContainmentClass::Scoped;

        let apparmor = containment_shortfall_reason(
            ContainmentClass::Sealed,
            achieved,
            Some(SealedBlocker::AppArmorProfileMissing),
            false,
        )
        .expect("refusal");
        assert!(apparmor.contains("mur-sealed"));
        assert!(apparmor.contains("apparmor_parser -r"));
        assert!(!apparmor.contains("--cap-add"));

        let container = containment_shortfall_reason(
            ContainmentClass::Sealed,
            achieved,
            Some(SealedBlocker::NamespaceCreationDenied),
            false,
        )
        .expect("refusal");
        assert!(container.contains("--cap-add SYS_ADMIN"));
        assert!(container.contains("outside the container"));
        assert!(!container.contains("apparmor_parser"));

        // A host that mounts and will not pivot is refused at launch with its own text, rather
        // than at the first subprocess with `E-RUN-014`.
        let pivot = containment_shortfall_reason(
            ContainmentClass::Sealed,
            ContainmentClass::Advisory,
            Some(SealedBlocker::PivotRootDenied),
            false,
        )
        .expect("refusal");
        assert!(pivot.contains("pivot_root(2)"), "reason was: {pivot}");
        assert_ne!(
            pivot,
            containment_shortfall_reason(
                ContainmentClass::Sealed,
                ContainmentClass::Advisory,
                Some(SealedBlocker::MountDenied),
                false,
            )
            .expect("refusal")
        );

        // Never the pre-mechanism blanket text again, under any blocker.
        for blocker in [
            SealedBlocker::NotLinux,
            SealedBlocker::AppArmorProfileMissing,
            SealedBlocker::NamespaceCreationDenied,
            SealedBlocker::MountDenied,
            SealedBlocker::PivotRootDenied,
            SealedBlocker::KernelUnsupported,
            SealedBlocker::LandlockUnavailable,
        ] {
            let reason = containment_shortfall_reason(
                ContainmentClass::Sealed,
                achieved,
                Some(blocker),
                false,
            )
            .expect("refusal");
            assert!(
                !reason.contains("no host can provide it today"),
                "got: {reason}"
            );
        }
    }

    /// A caller with no probe result still gets a reason naming the mechanism rather than an
    /// empty or misleading one.
    #[test]
    fn the_sealed_refusal_falls_back_to_naming_the_mechanism_without_a_probe() {
        let reason = containment_shortfall_reason(
            ContainmentClass::Sealed,
            ContainmentClass::Advisory,
            None,
            false,
        )
        .expect("refusal");
        assert!(reason.contains("pivot_root"));
        assert!(reason.contains("CLONE_NEWNS"));
    }

    #[test]
    fn shortfall_reason_is_absent_when_the_floor_is_met() {
        assert_eq!(
            containment_shortfall_reason(
                ContainmentClass::Advisory,
                ContainmentClass::Scoped,
                None,
                false
            ),
            None
        );
        assert_eq!(
            containment_shortfall_reason(
                ContainmentClass::Scoped,
                ContainmentClass::Scoped,
                None,
                false
            ),
            None
        );
        assert_eq!(
            containment_shortfall_reason(
                ContainmentClass::Sealed,
                ContainmentClass::Sealed,
                Some(SealedBlocker::NamespaceCreationDenied),
                false
            ),
            None,
            "a met floor must ignore a stale blocker rather than manufacture a refusal"
        );
    }

    fn sample_policy() -> CapabilityPolicy {
        CapabilityPolicy {
            network_allow: vec!["https://api.example.com".to_string()],
            unix_sockets_allowed: false,
            filesystem_scope: Some("workdir".to_string()),
            shell_allow: vec!["python3".to_string()],
            spawn_allow: vec!["helper".to_string()],
            env_allow: vec!["TZ".to_string()],
            shell_interpreter_runtime: vec![InterpreterRuntimeGrant {
                binary: "python3".to_string(),
                dirs: vec![InterpreterRuntimeDir {
                    path: "/usr/lib/python3.11".to_string(),
                    list_dir: true,
                }],
            }],
            ..CapabilityPolicy::default()
        }
    }

    #[test]
    fn scope_report_mirrors_the_policy_and_the_probed_tier() {
        let report = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );

        assert_eq!(report.declared_containment, ContainmentClass::Scoped);
        assert_eq!(report.achieved_containment, ContainmentClass::Scoped);
        assert!(report.floor_met);
        assert_eq!(report.shortfall_reason, None);
        assert_eq!(report.enforcement_tier, "landlock+seccomp");
        assert_eq!(report.filesystem_scope.as_deref(), Some("workdir"));
        assert_eq!(report.network_allow, vec!["https://api.example.com"]);
        assert!(!report.unix_sockets);
        assert_eq!(report.shell_allow, vec!["python3"]);
        assert_eq!(report.spawn_allow, vec!["helper"]);
        assert_eq!(report.env_allow, vec!["TZ"]);
        assert!(!report.workdir_exec);
        assert_eq!(
            report.interpreter_runtime_grants,
            vec!["python3: /usr/lib/python3.11 (list_dir)"]
        );
    }

    /// `--explain-scope` is where an operator finds out *why* a Landlock-capable host is reporting
    /// `advisory`, so the declaration and the class it produced have to appear together — in the
    /// struct, in the JSON, and in the rendered text.
    #[test]
    fn scope_report_surfaces_workdir_exec_and_the_advisory_it_forces() {
        let policy = CapabilityPolicy {
            shell_allow: vec!["gcc".to_string()],
            workdir_exec_allowed: true,
            ..CapabilityPolicy::default()
        };

        let report = scope_report_for_tier(
            &policy,
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );

        assert!(report.workdir_exec);
        assert_eq!(report.achieved_containment, ContainmentClass::Advisory);
        assert!(!report.floor_met);
        // The host is fully capable; the mechanism line must keep saying so, so the report does
        // not read as a broken host.
        assert_eq!(report.enforcement_tier, "landlock+seccomp");
        assert!(report
            .shortfall_reason
            .as_deref()
            .expect("refusal")
            .contains("workdir_exec"));

        let value: serde_json::Value = serde_json::to_value(&report).unwrap();
        assert_eq!(value["workdir_exec"], true);

        let rendered = report.render();
        assert!(rendered.contains("workdir exec:     true"));
        assert!(rendered.contains("achieved:  advisory"));
    }

    /// The key is always written, on the same terms `workdir_exec` and `state_stores` are: an
    /// absent `io_max` identifies a runtime that predates the field, not a host that was not
    /// asked. "Not asked" is a value — `not-probed` — inside the object.
    #[test]
    fn scope_report_json_always_carries_io_max() {
        let unprobed: serde_json::Value = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        assert_eq!(unprobed["io_max"]["status"], "not-probed");
        assert_eq!(unprobed["io_max"]["declared_bytes_per_sec"], 0);
        assert!(unprobed["io_max"].get("reason").is_none());

        let enforced: serde_json::Value = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport {
                declared_bytes_per_sec: 52_428_800,
                status: IoMaxStatus::Enforced,
                reason: None,
            },
        ))
        .unwrap();
        assert_eq!(enforced["io_max"]["status"], "enforced");
        assert_eq!(enforced["io_max"]["declared_bytes_per_sec"], 52_428_800);
    }

    /// A ceiling that did not apply has to be visible in the rendering an operator reads, not
    /// only in the JSON: this report is where the claim of an I/O bound would otherwise stand
    /// uncontradicted.
    #[test]
    fn the_rendered_resource_plane_states_what_became_of_the_io_ceiling() {
        let rendered = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport {
                declared_bytes_per_sec: 52_428_800,
                status: IoMaxStatus::Unavailable,
                reason: Some("the io controller is not delegated".to_string()),
            },
        )
        .render();

        assert!(rendered.contains("Resource plane"), "{rendered}");
        assert!(rendered.contains("io.max:"), "{rendered}");
        assert!(rendered.contains("unavailable"), "{rendered}");
        assert!(rendered.contains("52428800 bytes/s declared"), "{rendered}");
        assert!(
            rendered.contains("the io controller is not delegated"),
            "{rendered}"
        );
    }

    /// The field is always written, including `false`, so a consumer can distinguish "this capsule
    /// declared nothing" from "this runtime does not know the key".
    #[test]
    fn scope_report_json_always_carries_workdir_exec() {
        let value: serde_json::Value = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        assert_eq!(value["workdir_exec"], false);
    }

    /// `--explain-scope` is a diagnostic, not a launch: a capsule declaring `staged_runtime` on a
    /// host that cannot back `sealed` is exactly the case an operator inspects with it, so the
    /// grant must be reported on every tier — including the ones where `mur run` would refuse.
    #[test]
    fn staged_runtime_grants_are_reported_on_every_tier() {
        let policy = CapabilityPolicy {
            shell_allow: vec!["python3".to_string()],
            shell_staged_runtime: vec![StagedRuntimeGrant {
                binary: "python3".to_string(),
                source_path: "/opt/testbed/conda/envs/django__django".to_string(),
                pin: "conda-4.10.3/python-3.9.19".to_string(),
            }],
            ..CapabilityPolicy::default()
        };

        for tier in ALL_TIERS {
            let report = scope_report_for_tier(
                &policy,
                ContainmentClass::Sealed,
                *tier,
                Some(SealedBlocker::NamespaceCreationDenied),
                None,
                None,
                Vec::new(),
                Vec::new(),
                Vec::new(),
                IoMaxReport::default(),
            );
            assert_eq!(
                report.staged_runtime_grants,
                vec![
                    "python3: /opt/testbed/conda/envs/django__django \
                     (pin: conda-4.10.3/python-3.9.19)"
                ],
                "tier {tier:?} must still report the declared staged runtime"
            );
            assert!(
                report.render().contains("staged runtime"),
                "the rendered report must carry a staged runtime section on tier {tier:?}"
            );
        }
    }

    /// The absent case: no `staged_runtime` in the manifest leaves the section empty rather than
    /// inventing one, and `render` still names it as `<none>` like every other empty list.
    #[test]
    fn absent_staged_runtime_reports_nothing() {
        let report = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );
        assert!(report.staged_runtime_grants.is_empty());
        assert!(report.render().contains("staged runtime: <none>"));
    }

    /// A capsule that declares `scoped` *and* opens host paths through `interpreter_runtime`
    /// still achieves only `scoped` — the grant set is reported, never consulted to upgrade
    /// the achieved class.
    #[test]
    fn grant_set_never_raises_the_achieved_class() {
        let report = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Sealed,
            EnforcementTier::KernelFull,
            Some(SealedBlocker::NamespaceCreationDenied),
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );
        assert_eq!(report.achieved_containment, ContainmentClass::Scoped);
        assert!(!report.floor_met);
    }

    #[test]
    fn scope_report_still_reports_when_the_floor_is_unmet() {
        let report = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Sealed,
            EnforcementTier::EnvironmentOnly,
            Some(SealedBlocker::NotLinux),
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );

        assert_eq!(report.declared_containment, ContainmentClass::Sealed);
        assert_eq!(report.achieved_containment, ContainmentClass::Advisory);
        assert!(!report.floor_met);
        assert!(report.shortfall_reason.unwrap().contains("non-Linux"));
        assert_eq!(report.enforcement_tier, "none");
    }

    #[test]
    fn scope_report_names_the_sealed_mechanism_on_a_sealed_host() {
        let report = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Sealed,
            EnforcementTier::KernelSealed,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );
        assert_eq!(report.achieved_containment, ContainmentClass::Sealed);
        assert!(report.floor_met);
        assert_eq!(
            report.enforcement_tier,
            "mountns+pivot_root+landlock+seccomp"
        );
    }

    #[test]
    fn scope_report_json_uses_wire_names() {
        let report = scope_report_for_tier(
            &CapabilityPolicy::default(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelSeccompOnly,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );
        let value: serde_json::Value = serde_json::to_value(&report).unwrap();

        assert_eq!(value["declared_containment"], "advisory");
        assert_eq!(value["achieved_containment"], "advisory");
        assert_eq!(value["floor_met"], true);
        assert_eq!(value["enforcement_tier"], "seccomp-only");
        // Absent rather than null when the floor is met.
        assert!(value.get("shortfall_reason").is_none());
    }

    /// The grant is reported, and it never moves a class, a floor or a mechanism: the same tier
    /// with four different grants produces four reports that differ in exactly one field.
    #[test]
    fn the_userns_grant_is_reported_without_changing_any_verdict() {
        let baseline = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelSealed,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );

        for grant in UsernsGrant::ALL {
            let report = scope_report_for_tier(
                &sample_policy(),
                ContainmentClass::Advisory,
                EnforcementTier::KernelSealed,
                None,
                Some(*grant),
                None,
                Vec::new(),
                Vec::new(),
                Vec::new(),
                IoMaxReport::default(),
            );
            assert_eq!(report.achieved_containment, baseline.achieved_containment);
            assert_eq!(report.floor_met, baseline.floor_met);
            assert_eq!(report.enforcement_tier, baseline.enforcement_tier);
            assert_eq!(report.userns_grant, Some(*grant));

            let value: serde_json::Value = serde_json::to_value(&report).unwrap();
            assert_eq!(value["userns_grant"], grant.wire_name());
            assert!(report
                .render()
                .contains(&format!("userns grant: {}", grant.wire_name())));
        }

        // Off Linux the key is present and null — AppArmor does not exist there, which is not the
        // same statement as "the grant was withheld".
        let value: serde_json::Value = serde_json::to_value(&baseline).unwrap();
        assert!(value["userns_grant"].is_null());
        assert!(baseline.render().contains("userns grant: n/a"));
    }

    #[test]
    fn rendered_report_names_both_classes_and_the_refusal() {
        let rendered = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Sealed,
            EnforcementTier::KernelFull,
            Some(SealedBlocker::AppArmorProfileMissing),
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
        .render();

        assert!(rendered.contains("declared:  sealed"));
        assert!(rendered.contains("achieved:  scoped"));
        assert!(rendered.contains("floor met: no"));
        assert!(rendered.contains("mur-sealed"));
        assert!(rendered.contains("would refuse to launch"));
    }

    /// The invariant the whole design rests on: an export is a disclosure, not a grant. Declaring
    /// one must leave the achieved class — and everything else the report says about what the
    /// guest can reach — byte-identical.
    #[test]
    fn an_export_never_changes_what_the_report_says_about_containment() {
        let export = FileExport {
            root: "out/".to_string(),
            mode: ExportMode::ReadOnly,
            max_bytes: 10 * 1024 * 1024,
        };
        for tier in ALL_TIERS {
            for workdir_exec in [false, true] {
                let policy = CapabilityPolicy {
                    workdir_exec_allowed: workdir_exec,
                    ..sample_policy()
                };
                let without = scope_report_for_tier(
                    &policy,
                    ContainmentClass::Scoped,
                    *tier,
                    None,
                    None,
                    None,
                    Vec::new(),
                    Vec::new(),
                    Vec::new(),
                    IoMaxReport::default(),
                );
                let with = scope_report_for_tier(
                    &policy,
                    ContainmentClass::Scoped,
                    *tier,
                    None,
                    None,
                    Some(&Exports {
                        files: Some(export.clone()),
                        peer_files: None,
                    }),
                    Vec::new(),
                    Vec::new(),
                    Vec::new(),
                    IoMaxReport::default(),
                );
                assert_eq!(
                    with.achieved_containment, without.achieved_containment,
                    "tier {tier:?}, workdir_exec {workdir_exec}"
                );
                assert_eq!(with.enforcement_tier, without.enforcement_tier);
                assert_eq!(with.floor_met, without.floor_met);
                assert_eq!(with.shortfall_reason, without.shortfall_reason);
                // Everything but the one new field is identical, which is the strongest form of
                // "an export changes nothing else" this report can state.
                assert_eq!(
                    ScopeReport {
                        exports_files: None,
                        ..with.clone()
                    },
                    without
                );
                assert_eq!(
                    with.exports_files,
                    Some(ExportsFilesReport {
                        root: "out/".to_string(),
                        mode: ExportMode::ReadOnly,
                        max_bytes: 10 * 1024 * 1024,
                    })
                );
            }
        }
    }

    /// The same invariant for the peer-handoff grants, and stated separately because they are a
    /// separate authoriser: declaring either half must leave the achieved class, the tier and the
    /// floor verdict byte-identical, and must change no field of the report but its own.
    #[test]
    fn peer_handoff_never_changes_what_the_report_says_about_containment() {
        let peer_files = PeerFilesExport {
            root: "out/".to_string(),
            max_ttl_secs: Some(900),
            max_bytes: 10 * 1024 * 1024,
        };
        for tier in ALL_TIERS {
            for workdir_exec in [false, true] {
                let without_policy = CapabilityPolicy {
                    workdir_exec_allowed: workdir_exec,
                    ..sample_policy()
                };
                let with_policy = CapabilityPolicy {
                    peer_fetch_allow: vec!["localhost:41234".to_string()],
                    ..without_policy.clone()
                };
                let without = scope_report_for_tier(
                    &without_policy,
                    ContainmentClass::Scoped,
                    *tier,
                    None,
                    None,
                    None,
                    Vec::new(),
                    Vec::new(),
                    Vec::new(),
                    IoMaxReport::default(),
                );
                let with = scope_report_for_tier(
                    &with_policy,
                    ContainmentClass::Scoped,
                    *tier,
                    None,
                    None,
                    Some(&Exports {
                        files: None,
                        peer_files: Some(peer_files.clone()),
                    }),
                    Vec::new(),
                    Vec::new(),
                    Vec::new(),
                    IoMaxReport::default(),
                );
                assert_eq!(
                    with.achieved_containment, without.achieved_containment,
                    "tier {tier:?}, workdir_exec {workdir_exec}"
                );
                assert_eq!(with.enforcement_tier, without.enforcement_tier);
                assert_eq!(with.floor_met, without.floor_met);
                assert_eq!(with.shortfall_reason, without.shortfall_reason);
                assert_eq!(
                    ScopeReport {
                        peer_files: None,
                        peer_fetch_allow: Vec::new(),
                        ..with.clone()
                    },
                    without
                );
                assert_eq!(
                    with.peer_files,
                    Some(PeerFilesReport {
                        root: "out/".to_string(),
                        max_ttl_secs: 900,
                        max_bytes: 10 * 1024 * 1024,
                    })
                );
                assert_eq!(with.peer_fetch_allow, vec!["localhost:41234".to_string()]);
                // Declaring `peer_fetch` does not widen `network.allow`, on either side of the
                // report: the two lists are carried separately and neither is derived from the
                // other.
                assert_eq!(with.network_allow, without.network_allow);
            }
        }
    }

    /// Both peer fields are written whether or not they were declared, on the same terms as
    /// `exports_files`: an absent key identifies an older runtime, a `null`/`[]` identifies a
    /// capsule that declined.
    #[test]
    fn the_peer_fields_are_always_serialized() {
        let undeclared: serde_json::Value = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelSealed,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        assert_eq!(undeclared["peer_files"], serde_json::Value::Null);
        assert_eq!(undeclared["peer_fetch_allow"], serde_json::json!([]));

        let declared: serde_json::Value = serde_json::to_value(scope_report_for_tier(
            &CapabilityPolicy {
                peer_fetch_allow: vec!["localhost:41234".to_string()],
                ..sample_policy()
            },
            ContainmentClass::Advisory,
            EnforcementTier::KernelSealed,
            None,
            None,
            Some(&Exports {
                files: None,
                peer_files: Some(PeerFilesExport {
                    root: "out/".to_string(),
                    max_ttl_secs: None,
                    max_bytes: 10 * 1024 * 1024,
                }),
            }),
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        assert_eq!(
            declared["peer_files"],
            serde_json::json!({"root": "out/", "max_ttl_secs": 3600, "max_bytes": 10_485_760})
        );
        assert_eq!(
            declared["peer_fetch_allow"],
            serde_json::json!(["localhost:41234"])
        );
    }

    #[test]
    fn render_names_peer_handoff_in_both_directions() {
        let undeclared = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelSealed,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
        .render();
        assert!(undeclared.contains("Peer handoff"));
        assert!(undeclared.contains("exports.peer_files: <none>"));
        assert!(undeclared.contains("peer_fetch allow: <none>"));

        let declared = scope_report_for_tier(
            &CapabilityPolicy {
                peer_fetch_allow: vec!["localhost:41234".to_string()],
                ..sample_policy()
            },
            ContainmentClass::Advisory,
            EnforcementTier::KernelSealed,
            None,
            None,
            Some(&Exports {
                files: None,
                peer_files: Some(PeerFilesExport {
                    root: "out/".to_string(),
                    max_ttl_secs: Some(900),
                    max_bytes: 4096,
                }),
            }),
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
        .render();
        assert!(declared.contains("exports.peer_files root: out/"));
        assert!(declared.contains("max handle ttl:          900s"));
        assert!(declared.contains("max bytes:               4096 (per file)"));
        assert!(declared.contains("- localhost:41234"));
    }

    /// A declared state store is reported, and moves nothing else. Same discipline the export
    /// reports are held to: it is copied through, never consulted, so a durable directory grant
    /// cannot talk a host into reporting a class it does not back.
    #[test]
    fn a_state_store_is_reported_and_moves_no_other_field() {
        let policy = sample_policy();
        let stores = vec![StateStoreReport {
            artifact: "murmur-tool-corpus".to_string(),
            store: "shey".to_string(),
            host_path: "/home/dev/.murmur/state/shey".to_string(),
        }];

        let without = scope_report_for_tier(
            &policy,
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );
        let with = scope_report_for_tier(
            &policy,
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            stores.clone(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );

        assert_eq!(with.state_stores, stores);
        assert!(without.state_stores.is_empty());
        assert_eq!(with.achieved_containment, without.achieved_containment);
        assert_eq!(with.floor_met, without.floor_met);
        assert_eq!(with.enforcement_tier, without.enforcement_tier);
        assert_eq!(with.shortfall_reason, without.shortfall_reason);
        // The only field that moved is its own.
        assert_eq!(
            ScopeReport {
                state_stores: Vec::new(),
                ..with.clone()
            },
            without
        );

        // Rendered under the grants, one line per declaring artifact; `<none>` when empty.
        assert!(with
            .render()
            .contains("- murmur-tool-corpus: shey -> /home/dev/.murmur/state/shey"));
        assert!(without.render().contains("state stores: <none>"));

        // Always an array in JSON, never skipped: an absent key means an older runtime, not a
        // capsule that declined a store.
        let json = serde_json::to_value(&without).unwrap();
        assert_eq!(json["state_stores"], serde_json::json!([]));
        assert_eq!(
            serde_json::to_value(&with).unwrap()["state_stores"],
            serde_json::json!([{
                "artifact": "murmur-tool-corpus",
                "store": "shey",
                "host_path": "/home/dev/.murmur/state/shey",
            }])
        );
    }

    /// The preopen set is reported and moves nothing else, on the same terms the state-store
    /// report beside it is held to. It is also the field that answers what `filesystem_scope`
    /// does not: a capsule-wide scope is joined into no guest preopen root, so both can be
    /// present and disagree without either being wrong.
    #[test]
    fn preopens_are_reported_and_move_no_other_field() {
        let policy = sample_policy();
        let preopens = vec![
            PreopenReport {
                artifact: "notes-tool".to_string(),
                role: "tool".to_string(),
                scope: None,
                surface: PreopenSurface::WholeWorkdir,
            },
            PreopenReport {
                artifact: "cache-tool".to_string(),
                role: "tool".to_string(),
                scope: Some("cache".to_string()),
                surface: PreopenSurface::ScopedSubtree,
            },
            PreopenReport {
                artifact: "telemetry-hook".to_string(),
                role: "hook".to_string(),
                scope: None,
                surface: PreopenSurface::Nothing,
            },
        ];

        let without = scope_report_for_tier(
            &policy,
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );
        let with = scope_report_for_tier(
            &policy,
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            preopens.clone(),
            IoMaxReport::default(),
        );

        assert_eq!(with.preopens, preopens);
        assert!(without.preopens.is_empty());
        // The only field that moved is its own.
        assert_eq!(
            ScopeReport {
                preopens: Vec::new(),
                ..with.clone()
            },
            without
        );

        // Three visibly different lines under `Effective grants`; `<none>` when empty.
        let rendered = with.render();
        assert!(rendered.contains(
            "- notes-tool (tool): the whole accessible workdir — no capabilities.filesystem.scope \
             declared"
        ));
        assert!(rendered.contains(
            "- cache-tool (tool): one subtree of the accessible workdir — \
             capabilities.filesystem.scope: cache"
        ));
        assert!(rendered.contains(
            "- telemetry-hook (hook): nothing preopened — no capabilities.filesystem.scope declared"
        ));
        assert!(without.render().contains("preopens: <none>"));

        // Always an array in JSON, never skipped, with an undeclared scope as `null`.
        assert_eq!(
            serde_json::to_value(&without).unwrap()["preopens"],
            serde_json::json!([])
        );
        assert_eq!(
            serde_json::to_value(&with).unwrap()["preopens"],
            serde_json::json!([
                {
                    "artifact": "notes-tool",
                    "role": "tool",
                    "scope": null,
                    "surface": "whole-workdir",
                },
                {
                    "artifact": "cache-tool",
                    "role": "tool",
                    "scope": "cache",
                    "surface": "scoped-subtree",
                },
                {
                    "artifact": "telemetry-hook",
                    "role": "hook",
                    "scope": null,
                    "surface": "nothing",
                },
            ])
        );
    }

    /// `exports_files` is written whether or not it was declared, on the same terms as
    /// `workdir_exec`: an absent key identifies an older runtime, a `null` a capsule that
    /// exported nothing.
    #[test]
    fn exports_files_is_always_serialized() {
        let undeclared = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        assert_eq!(undeclared["exports_files"], serde_json::Value::Null);

        let declared = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelFull,
            None,
            None,
            Some(&Exports {
                files: Some(FileExport {
                    root: "out/".to_string(),
                    mode: ExportMode::ReadOnly,
                    max_bytes: 10_485_760,
                }),
                peer_files: None,
            }),
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        assert_eq!(
            declared["exports_files"],
            serde_json::json!({"root": "out/", "mode": "read-only", "max_bytes": 10_485_760})
        );
    }

    #[test]
    fn render_names_the_resource_plane_in_both_directions() {
        let undeclared = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
        .render();
        assert!(
            undeclared.contains("Resource plane") && undeclared.contains("exports.files: <none>"),
            "{undeclared}"
        );

        let declared = scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Advisory,
            EnforcementTier::KernelFull,
            None,
            None,
            Some(&Exports {
                files: Some(FileExport {
                    root: "out/".to_string(),
                    mode: ExportMode::ReadOnly,
                    max_bytes: 10_485_760,
                }),
                peer_files: None,
            }),
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
        .render();
        assert!(declared.contains("exports.files root: out/"), "{declared}");
        assert!(
            declared.contains("mode:               read-only"),
            "{declared}"
        );
        assert!(
            declared.contains("max bytes:          10485760 (per file)"),
            "{declared}"
        );
    }

    // ── read_only reporting ───────────────────────────────────────────────────

    fn report_for(read_only: &[&str], shell_allow: &[&str]) -> ScopeReport {
        let policy = CapabilityPolicy {
            read_only_paths: read_only.iter().map(|p| (*p).to_string()).collect(),
            shell_allow: shell_allow.iter().map(|b| (*b).to_string()).collect(),
            ..CapabilityPolicy::default()
        };
        scope_report_for_tier(
            &policy,
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
    }

    /// With no allowlisted interpreter the declaration holds everywhere the check can reach, and
    /// the report says exactly that and nothing stronger.
    #[test]
    fn declared_read_only_with_no_interpreter_reports_as_enforced() {
        let report = report_for(&["tests", "bench/fixtures"], &["git"]);
        assert_eq!(
            report.read_only_paths,
            vec!["tests".to_string(), "bench/fixtures".to_string()]
        );
        assert!(report.read_only_advisory_for.is_empty());

        let rendered = report.render();
        assert!(rendered.contains("  read_only:\n    - tests\n    - bench/fixtures\n"));
        assert!(rendered.contains(
            "read_only enforcement: enforced for every tool call and every shell command the \
             dispatch check can read"
        ));
        assert!(!rendered.contains("advisory against"));
    }

    /// An allowlisted interpreter is named, and the enforcement line is qualified — the report
    /// must never claim more than `W-SEC-017` already withdraws.
    #[test]
    fn an_allowlisted_interpreter_is_named_as_advisory() {
        let report = report_for(&["tests"], &["git", "python3"]);
        assert_eq!(report.read_only_advisory_for, vec!["python3".to_string()]);

        let rendered = report.render();
        assert!(rendered.contains("read_only enforcement: advisory against python3"));
        assert!(rendered
            .contains("enforced for every tool call and for every shell command it can read"));
    }

    /// The report's advisory set is the set `W-SEC-017` fires for, because both call one
    /// resolver. Asserted through the resolver rather than by re-listing interpreters, so adding
    /// one to `protected_paths::ADVISORY_INTERPRETERS` cannot make the two disagree.
    #[test]
    fn the_reported_advisory_set_is_the_set_the_warning_fires_for() {
        let shell_allow: Vec<String> = ["git", "python3", "node", "make", "bash"]
            .iter()
            .map(|b| (*b).to_string())
            .collect();
        let declared = vec!["tests".to_string()];
        assert_eq!(
            report_for(&["tests"], &["git", "python3", "node", "make", "bash"])
                .read_only_advisory_for,
            read_only_advisory_for(&declared, &shell_allow)
        );
        // Nothing is advisory against a protection that was never declared, whatever is allowed.
        assert!(read_only_advisory_for(&[], &shell_allow).is_empty());
    }

    /// Both keys are always arrays, including for a capsule with no `capabilities.filesystem`
    /// block at all: an absent key must identify a runtime that predates the field, never a
    /// capsule that declared nothing.
    #[test]
    fn both_read_only_keys_are_always_serialized_arrays() {
        let json = serde_json::to_value(report_for(&[], &["python3"])).unwrap();
        assert_eq!(json["read_only_paths"], serde_json::json!([]));
        assert_eq!(json["read_only_advisory_for"], serde_json::json!([]));

        let json = serde_json::to_value(report_for(&["tests"], &["python3"])).unwrap();
        assert_eq!(json["read_only_paths"], serde_json::json!(["tests"]));
        assert_eq!(
            json["read_only_advisory_for"],
            serde_json::json!(["python3"])
        );
    }

    /// An undeclared `read_only` renders one `<none>` line and asks no enforcement question,
    /// because there is no protection to qualify.
    #[test]
    fn an_undeclared_read_only_renders_none_and_no_enforcement_line() {
        let rendered = report_for(&[], &["python3"]).render();
        assert!(rendered.contains("  read_only: <none>\n"));
        assert!(!rendered.contains("read_only enforcement:"));
    }

    // ── Grant coverage ────────────────────────────────────────────────────────

    /// Every `pub` field of [`CapabilityPolicy`] is either reported by [`ScopeReport`] or
    /// exempted here with a written reason.
    ///
    /// The field list is derived from `types.rs`'s own source text rather than written out, so a
    /// grant added later fails this test until someone decides which it is.
    ///
    /// The mapping is checked in both directions — every policy field is accounted for, *and*
    /// every report key the mapping names is really present in a serialized report — so the
    /// table cannot claim coverage it does not have.
    #[test]
    fn every_capability_policy_field_is_reported_or_exempted() {
        /// Policy fields deliberately absent from the scope report, each with the reason.
        const EXEMPT: &[(&str, &str)] = &[
            (
                "shell_strip_env",
                "Names host variables removed from the shell child's environment on top of the \
                 credential patterns the runtime always strips. It subtracts from what the \
                 capsule sees and can open nothing, so reporting it beside the grants would pad \
                 the list an operator audits for reach.",
            ),
            (
                "shell_baseline_env",
                "The fixed variables the shell child starts with (PATH, HOME, …). It shapes the \
                 environment of a subprocess the capsule was already granted, and names no host \
                 resource `shell allow` and `env allow` do not already account for.",
            ),
            (
                "limits",
                "Execution ceilings for a WASM guest — memory, table elements, instance count, \
                 deadline. A bound on how much the capsule may consume, never a reach it gains.",
            ),
            (
                "resources",
                "The same, for native subprocesses: rlimits, the Linux cgroup v2 scope and the \
                 workdir size ceiling. A ceiling, not a grant, on exactly `limits`' terms.",
            ),
            (
                "declared_deadline_seconds",
                "The undefaulted form of `limits.deadline_seconds`, retained only so hook calls \
                 can apply a lower default. Reporting it would report one ceiling twice.",
            ),
            (
                "state_declared",
                "Records that a capsule-wide `capabilities.state` block was declared where \
                 nothing reads it, which `W-SEC-014` says in words. The stores that actually \
                 exist are reported per artifact in `state_stores`.",
            ),
            (
                "conversation_declared",
                "Records a capsule-wide `capabilities.conversation` block that reaches no \
                 artifact, on `state_declared`'s terms; `W-SEC-016` is what an operator needs, \
                 and the grant itself is per artifact.",
            ),
        ];

        /// Policy field → the key it is reported under in a serialized [`ScopeReport`].
        const REPORTED: &[(&str, &str)] = &[
            ("network_allow", "network_allow"),
            ("peer_fetch_allow", "peer_fetch_allow"),
            ("unix_sockets_allowed", "unix_sockets"),
            ("filesystem_scope", "filesystem_scope"),
            ("workdir_exec_allowed", "workdir_exec"),
            ("read_only_paths", "read_only_paths"),
            ("shell_allow", "shell_allow"),
            ("spawn_allow", "spawn_allow"),
            ("shell_interpreter_runtime", "interpreter_runtime_grants"),
            ("shell_staged_runtime", "staged_runtime_grants"),
            ("env_allow", "env_allow"),
            ("plan_submit", "plan_submit"),
            ("containment_floor", "declared_containment"),
        ];

        let declared = capability_policy_field_names(include_str!("types.rs"));
        assert!(
            declared.len() > 10,
            "failed to read CapabilityPolicy's fields out of types.rs (found {declared:?})"
        );

        for field in &declared {
            let reported = REPORTED.iter().any(|(policy, _)| policy == field);
            let exempt = EXEMPT.iter().any(|(policy, _)| policy == field);
            assert!(
                reported || exempt,
                "CapabilityPolicy::{field} is a grant no --explain-scope report mentions. Either \
                 add it to ScopeReport and to this test's REPORTED table, or add it to EXEMPT \
                 with a written reason for why an operator does not need to see it."
            );
            assert!(
                !(reported && exempt),
                "CapabilityPolicy::{field} is listed as both reported and exempt"
            );
        }

        for (policy_field, _) in REPORTED.iter().chain(EXEMPT.iter()) {
            assert!(
                declared.iter().any(|field| field == policy_field),
                "the table names CapabilityPolicy::{policy_field}, which types.rs no longer \
                 declares — remove the stale row"
            );
        }

        // The other direction: a report key the table claims must really be in the JSON, so no
        // row can cover a field with a key that does not exist.
        let json = serde_json::to_value(scope_report_for_tier(
            &sample_policy(),
            ContainmentClass::Scoped,
            EnforcementTier::KernelFull,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        ))
        .unwrap();
        let object = json.as_object().expect("a scope report is a JSON object");
        for (policy_field, report_key) in REPORTED {
            assert!(
                object.contains_key(*report_key),
                "the table maps CapabilityPolicy::{policy_field} to a report key \
                 '{report_key}' that a serialized ScopeReport does not carry"
            );
        }
    }

    /// A report off [`sample_policy`] at a chosen host tier and declared floor, so the mechanism
    /// this session would install is the only thing that varies between the cases below.
    fn boundary_report(declared: ContainmentClass, tier: EnforcementTier) -> ScopeReport {
        scope_report_for_tier(
            &sample_policy(),
            declared,
            tier,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        )
    }

    /// A host that mediates nothing says so, in the block an operator reads before the grants.
    #[test]
    fn a_session_with_no_kernel_mechanism_reports_what_it_does_not_protect() {
        let report = boundary_report(ContainmentClass::Advisory, EnforcementTier::EnvironmentOnly);

        assert_eq!(report.achieved_containment, ContainmentClass::Advisory);
        assert_eq!(
            report.filesystem_boundary.restriction,
            FilesystemRestriction::Advisory
        );
        assert_eq!(report.filesystem_boundary.not_protected.len(), 2);

        let filesystem = &report.filesystem_boundary.not_protected[0];
        assert!(filesystem.contains("advisory"), "{filesystem}");
        assert!(
            filesystem.contains("denies a read or a write outside the session workdir"),
            "{filesystem}"
        );

        let rewriting = &report.filesystem_boundary.not_protected[1];
        assert!(rewriting.contains("not a boundary"), "{rewriting}");
        assert!(rewriting.contains("HOME"), "{rewriting}");

        let rendered = report.render();
        let heading = rendered
            .find("\nNot protected here\n")
            .expect("a session that composes no root prints the block");
        assert!(
            heading > rendered.find("Containment\n").unwrap(),
            "the block belongs under Containment:\n{rendered}"
        );
        assert!(
            heading < rendered.find("\nEffective grants\n").unwrap(),
            "the block belongs ahead of the grants an operator reads it against:\n{rendered}"
        );
        for statement in &report.filesystem_boundary.not_protected {
            assert!(rendered.contains(statement.as_str()), "{rendered}");
        }
    }

    /// A Landlock domain really does mediate the filesystem, so its statement says what Landlock
    /// leaves open rather than repeating the advisory one.
    #[test]
    fn a_landlock_session_reports_denial_rather_than_absence() {
        let report = boundary_report(ContainmentClass::Advisory, EnforcementTier::KernelFull);

        assert_eq!(report.achieved_containment, ContainmentClass::Scoped);
        assert_eq!(
            report.filesystem_boundary.restriction,
            FilesystemRestriction::Enforced
        );
        assert_eq!(report.filesystem_boundary.not_protected.len(), 2);

        let filesystem = &report.filesystem_boundary.not_protected[0];
        assert!(
            !filesystem.contains("advisory"),
            "Landlock mediates the filesystem here: {filesystem}"
        );
        assert!(
            filesystem.contains("denied rather than absent"),
            "{filesystem}"
        );
        for probe in ["stat", "access", "readlink"] {
            assert!(filesystem.contains(probe), "{filesystem}");
        }
    }

    /// A capsule that declares less than `sealed` composes no root on a sealed-capable host: it
    /// runs Landlock-scoped, and the block must say so rather than claim the paths outside its
    /// grants are absent. This is the configuration `achieved_containment` cannot distinguish —
    /// it reads `sealed` on both sides of this test.
    #[test]
    fn a_sealed_capable_host_still_discloses_landlock_for_a_capsule_that_declared_less() {
        let report = boundary_report(ContainmentClass::Advisory, EnforcementTier::KernelSealed);

        assert_eq!(
            report.achieved_containment,
            ContainmentClass::Sealed,
            "the host can back sealed, which is what `achieved` answers"
        );
        assert_eq!(
            report.filesystem_boundary.restriction,
            FilesystemRestriction::Enforced,
            "no composed root is installed for a capsule that did not declare one"
        );
        assert_eq!(
            report.filesystem_boundary.not_protected,
            boundary_report(ContainmentClass::Advisory, EnforcementTier::KernelFull)
                .filesystem_boundary
                .not_protected,
            "the same mechanism gets the same statements on either host"
        );
        assert!(report.render().contains("Not protected here"));
    }

    /// The half of the block that is genuinely mechanism-independent: `HOME` is rewritten on every
    /// tier, so the statement about it is one string, not one per mechanism.
    #[test]
    fn the_path_rewriting_statement_is_identical_wherever_it_is_carried() {
        let advisory =
            boundary_report(ContainmentClass::Advisory, EnforcementTier::EnvironmentOnly);
        let enforced = boundary_report(ContainmentClass::Advisory, EnforcementTier::KernelFull);

        assert_eq!(
            advisory.filesystem_boundary.not_protected[1],
            enforced.filesystem_boundary.not_protected[1]
        );
        assert!(
            advisory.filesystem_boundary.not_protected[1]
                .contains(crate::shell::SYNTHETIC_HOME_DIR_NAME),
            "the statement must name the directory `shell::build_shell_env` really sets HOME to"
        );
    }

    /// A composed root prints no heading — not a heading with an empty list under it — and still
    /// carries the key, because an absent key must identify a runtime that predates the field.
    #[test]
    fn a_composed_root_carries_the_key_with_nothing_to_disclaim() {
        let report = boundary_report(ContainmentClass::Sealed, EnforcementTier::KernelSealed);

        assert_eq!(report.achieved_containment, ContainmentClass::Sealed);
        assert_eq!(
            report.filesystem_boundary.restriction,
            FilesystemRestriction::Absent
        );
        assert!(report.filesystem_boundary.not_protected.is_empty());
        assert!(
            !report.render().contains("Not protected here"),
            "{}",
            report.render()
        );

        let json = serde_json::to_value(&report).unwrap();
        assert_eq!(json["filesystem_boundary"]["restriction"], "absent");
        assert_eq!(
            json["filesystem_boundary"]["not_protected"],
            serde_json::json!([]),
            "the key is present and empty at absent, never missing"
        );
    }

    /// `capabilities.filesystem.workdir_exec` caps the achieved *class* at `advisory` and leaves
    /// the *mechanism* alone: Landlock is still installed, so the block prints the Landlock
    /// statement rather than claiming the host denies nothing.
    #[test]
    fn workdir_exec_caps_the_class_without_changing_the_mechanism() {
        let policy = CapabilityPolicy {
            workdir_exec_allowed: true,
            ..CapabilityPolicy::default()
        };

        let report = scope_report_for_tier(
            &policy,
            ContainmentClass::Advisory,
            EnforcementTier::KernelSealed,
            None,
            None,
            None,
            Vec::new(),
            Vec::new(),
            Vec::new(),
            IoMaxReport::default(),
        );

        assert_eq!(
            report.enforcement_tier,
            "mountns+pivot_root+landlock+seccomp"
        );
        assert_eq!(report.achieved_containment, ContainmentClass::Advisory);
        assert_eq!(
            report.filesystem_boundary.restriction,
            FilesystemRestriction::Enforced
        );
        assert_eq!(report.filesystem_boundary.not_protected.len(), 2);
        assert!(report.render().contains("Not protected here"));
    }

    /// The restriction follows the tier the session applies, at every combination of host tier and
    /// declared floor — which is what `runtime_writes` beside it is already keyed on.
    #[test]
    fn the_restriction_follows_the_tier_the_session_would_install() {
        for tier in ALL_TIERS {
            for declared in [
                ContainmentClass::Advisory,
                ContainmentClass::Scoped,
                ContainmentClass::Sealed,
            ] {
                let report = boundary_report(declared, *tier);
                let expected = match crate::sandbox::applied_tier(*tier, declared) {
                    EnforcementTier::KernelSealed => FilesystemRestriction::Absent,
                    EnforcementTier::KernelFull => FilesystemRestriction::Enforced,
                    EnforcementTier::KernelSeccompOnly | EnforcementTier::EnvironmentOnly => {
                        FilesystemRestriction::Advisory
                    }
                };
                assert_eq!(
                    report.filesystem_boundary.restriction, expected,
                    "{tier:?} / {declared:?}"
                );
                assert_eq!(
                    report.filesystem_boundary.not_protected.is_empty(),
                    expected == FilesystemRestriction::Absent,
                    "{tier:?} / {declared:?}"
                );
                let wire = match expected {
                    FilesystemRestriction::Advisory => "advisory",
                    FilesystemRestriction::Enforced => "enforced",
                    FilesystemRestriction::Absent => "absent",
                };
                assert_eq!(
                    serde_json::to_value(report.filesystem_boundary.restriction).unwrap(),
                    serde_json::Value::String(wire.to_string())
                );
            }
        }
    }

    /// The one assertion the report cannot satisfy by agreeing with itself: what a subprocess in a
    /// real session actually gets back when it probes a host file outside its workdir, compared
    /// against the `restriction` the report prints for that same session.
    ///
    /// Runs on whatever tier this host reaches, and asserts against the restriction it observes
    /// rather than against a tier it assumes. `bash` reads the file with a redirect and tests its
    /// existence with `[[ -e ]]` — both are syscalls the shell makes itself, so nothing here needs
    /// a second binary on the exec allowlist.
    ///
    /// Driving `execute_shell` needs an egress network namespace, so it stands down where the host
    /// withholds one rather than failing: a host that restricts unprivileged user namespaces
    /// refuses the uid_map write every spawn goes through, whatever the filesystem tier.
    #[test]
    fn the_reported_restriction_matches_what_a_subprocess_actually_reaches() {
        if crate::network_namespace::skip_without_egress_namespace(
            "the_reported_restriction_matches_what_a_subprocess_actually_reaches",
        ) {
            return;
        }
        if crate::sandbox::find_on_path("bash").is_none() {
            eprintln!(
                "[SKIP-HOST] the_reported_restriction_matches_what_a_subprocess_actually_reaches: \
                 no bash on PATH"
            );
            return;
        }
        let outside = tempfile::tempdir().expect("a temp directory outside the workdir");
        let secret = outside.path().join("host-file");
        std::fs::write(&secret, "PROBE-CONTENTS\n").unwrap();
        let secret = secret.to_str().unwrap().to_string();

        for declared in [ContainmentClass::Advisory, ContainmentClass::Sealed] {
            let workdir = tempfile::tempdir().unwrap();
            let policy = CapabilityPolicy {
                shell_allow: vec!["bash".to_string()],
                ..CapabilityPolicy::default()
            };
            let probe = crate::sandbox::HostProbe::probe();
            let enforcement =
                crate::sandbox::ShellEnforcement::resolve(&policy, declared, probe).unwrap();
            let report = scope_report_for_tier(
                &policy,
                declared,
                probe.tier(),
                None,
                None,
                None,
                Vec::new(),
                Vec::new(),
                Vec::new(),
                IoMaxReport::default(),
            );

            let command = format!(
                "if read -r line < '{secret}' 2>/dev/null; then echo \"read=$line\"; \
                 else echo read=refused; fi; \
                 if [[ -e '{secret}' ]]; then echo exists=yes; else echo exists=no; fi"
            );
            let result = crate::shell::execute_shell(
                "bash",
                &["-c", &command],
                &[],
                workdir.path(),
                workdir.path(),
                &policy,
                &enforcement,
            )
            .unwrap_or_else(|error| panic!("declared {declared:?}: {error}"));
            let seen = result.stdout;

            match report.filesystem_boundary.restriction {
                FilesystemRestriction::Advisory => assert!(
                    seen.contains("read=PROBE-CONTENTS"),
                    "reported advisory, so nothing denies the read: {seen}"
                ),
                FilesystemRestriction::Enforced => assert!(
                    seen.contains("read=refused") && seen.contains("exists=yes"),
                    "reported enforced, so the read is denied and the path still exists: {seen}"
                ),
                FilesystemRestriction::Absent => assert!(
                    seen.contains("read=refused") && seen.contains("exists=no"),
                    "reported absent, so the path is not in the composed root: {seen}"
                ),
            }
        }
    }

    /// The `pub` field names of `CapabilityPolicy`, read out of `types.rs`'s own text.
    fn capability_policy_field_names(source: &str) -> Vec<String> {
        source
            .split_once("pub struct CapabilityPolicy {")
            .expect("types.rs declares CapabilityPolicy")
            .1
            .split_once("\n}")
            .expect("CapabilityPolicy's declaration is closed at column 0")
            .0
            .lines()
            .filter_map(|line| {
                line.strip_prefix("    pub ")
                    .and_then(|rest| rest.split_once(':'))
                    .map(|(name, _)| name.to_string())
            })
            .collect()
    }
}