diff --git a/crates/pearlite-state/Cargo.toml b/crates/pearlite-state/Cargo.toml
index 244ac3b..a2edd35 100644
--- a/crates/pearlite-state/Cargo.toml
+++ b/crates/pearlite-state/Cargo.toml
@@ -12,3 +12,11 @@ repository.workspace = true
 workspace = true
 
 [dependencies]
+serde = { workspace = true }
+toml = { workspace = true }
+time = { workspace = true }
+uuid = { workspace = true }
+thiserror = { workspace = true }
+schemars = { workspace = true }
+# toml_edit lands in chunk M1-W1-E with the atomic-write implementation
+# that needs it for unknown-field preservation.
diff --git a/crates/pearlite-state/src/errors.rs b/crates/pearlite-state/src/errors.rs
new file mode 100644
index 0000000..d659696
--- /dev/null
+++ b/crates/pearlite-state/src/errors.rs
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2026 Mohamed Hammad
+
+//! Errors emitted by `pearlite-state`.
+
+use std::path::PathBuf;
+use thiserror::Error;
+
+/// Errors emitted while reading, writing, or migrating `state.toml`.
+#[derive(Debug, Error)]
+pub enum StateError {
+    /// The TOML failed to parse.
+    #[error("invalid TOML in state file: {0}")]
+    InvalidToml(#[from] toml::de::Error),
+    /// `state.toml` was not found at the expected path.
+    #[error("state file not found: {0}")]
+    NotFound(PathBuf),
+    /// I/O error while reading or writing the file.
+    #[error("I/O error on state file: {0}")]
+    Io(#[from] std::io::Error),
+    /// Unknown `schema_version` — the on-disk file is from a future
+    /// Pearlite release and cannot be read by this build.
+    #[error("unknown schema_version {found}; this build supports up to {supported}")]
+    UnsupportedSchemaVersion {
+        /// Version found in the file.
+        found: u32,
+        /// Highest version this build can read.
+        supported: u32,
+    },
+    /// `state.host` does not match the system `hostname()`.
+    #[error("state.host '{state_host}' does not match system hostname '{system_host}'")]
+    HostMismatch {
+        /// Host recorded in `state.toml`.
+        state_host: String,
+        /// Live `hostname(1)` value.
+        system_host: String,
+    },
+    /// TOML serialisation failed (should be unreachable for well-formed
+    /// `State` values).
+    #[error("could not serialize state: {0}")]
+    SerializeFailed(#[from] toml::ser::Error),
+}
diff --git a/crates/pearlite-state/src/failure.rs b/crates/pearlite-state/src/failure.rs
new file mode 100644
index 0000000..0b0e3cd
--- /dev/null
+++ b/crates/pearlite-state/src/failure.rs
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2026 Mohamed Hammad
+
+//! `[[failures]]` records — pointers to per-plan failure JSON files.
+
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+use time::OffsetDateTime;
+use uuid::Uuid;
+
+/// One entry in `state.toml`'s `[[failures]]` array.
+///
+/// The full forensic record (stderr, `investigate_commands`,
+/// `rollback_command`, …) lives in `/var/lib/pearlite/failures/<plan-id>.json`
+/// per PRD §11.4. This entry holds only the pointer plus enough metadata
+/// to render `pearlite gen list` without reading every JSON record.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+pub struct FailureRef {
+    /// Plan UUID this failure pertains to.
+    #[schemars(with = "String")]
+    pub plan_id: Uuid,
+    /// UTC timestamp the apply failed.
+    #[serde(with = "time::serde::iso8601")]
+    #[schemars(with = "String")]
+    pub failed_at: OffsetDateTime,
+    /// Failure class per PRD §8.5: 1 preflight, 2 plan, 3 recoverable,
+    /// 4 incoherent, 5 catastrophic.
+    pub class: u8,
+    /// Process exit code at failure.
+    pub exit_code: u8,
+    /// Path to the JSON record under `/var/lib/pearlite/failures/`.
+    pub record_path: PathBuf,
+}
diff --git a/crates/pearlite-state/src/history.rs b/crates/pearlite-state/src/history.rs
new file mode 100644
index 0000000..8e006d8
--- /dev/null
+++ b/crates/pearlite-state/src/history.rs
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2026 Mohamed Hammad
+
+//! `[[history]]` and snapshot-reference records.
+
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use time::OffsetDateTime;
+use uuid::Uuid;
+
+/// One entry in `state.toml`'s `[[history]]` array — a summary of one
+/// successful `apply`. The full plan and per-action breakdown live in
+/// `/var/lib/pearlite/plans/<plan-id>.json`, referenced by `plan_id`.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+pub struct HistoryEntry {
+    /// Plan UUID (canonical persistent identifier).
+    #[schemars(with = "String")]
+    pub plan_id: Uuid,
+    /// Host-scoped monotonic generation number.
+    pub generation: u64,
+    /// UTC timestamp the apply completed successfully.
+    #[serde(with = "time::serde::iso8601")]
+    #[schemars(with = "String")]
+    pub applied_at: OffsetDateTime,
+    /// Wall-clock duration of the apply, in milliseconds.
+    pub duration_ms: u64,
+    /// Pre-apply snapshot reference.
+    pub snapshot_pre: SnapshotRef,
+    /// Post-apply snapshot reference.
+    pub snapshot_post: SnapshotRef,
+    /// Number of actions executed in this apply.
+    pub actions_executed: u32,
+    /// Git revision of the config repo at apply time, if available.
+    #[serde(default)]
+    pub git_revision: Option<String>,
+    /// Whether the config repo had uncommitted changes at apply time.
+    #[serde(default)]
+    pub git_dirty: bool,
+    /// One-line summary, e.g. `"+8 -2 ~4 (8 installs, 2 removals, 4 config updates)"`.
+    pub summary: String,
+}
+
+/// Reference to a Snapper snapshot.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+pub struct SnapshotRef {
+    /// Snapper snapshot ID.
+    pub id: u64,
+    /// Snapper snapshot label.
+    pub label: String,
+    /// UTC creation timestamp.
+    #[serde(with = "time::serde::iso8601")]
+    #[schemars(with = "String")]
+    pub created_at: OffsetDateTime,
+}
diff --git a/crates/pearlite-state/src/lib.rs b/crates/pearlite-state/src/lib.rs
index a48b36b..90b3689 100644
--- a/crates/pearlite-state/src/lib.rs
+++ b/crates/pearlite-state/src/lib.rs
@@ -2,3 +2,23 @@
 // Copyright (C) 2026 Mohamed Hammad
 
 //! Persistent Pearlite state: atomic read/write, migrations, history.
+//!
+//! [`State`] is the in-memory mirror of `/var/lib/pearlite/state.toml` —
+//! the load-bearing artifact in PRD §7. The `read` / `write_atomic` /
+//! `append_*` operations land in chunk M1-W1-E; this scaffold defines the
+//! types and errors only.
+
+mod errors;
+mod failure;
+mod history;
+mod reconciliation;
+mod schema;
+
+pub use errors::StateError;
+pub use failure::FailureRef;
+pub use history::{HistoryEntry, SnapshotRef};
+pub use reconciliation::{ReconciliationAction, ReconciliationEntry};
+pub use schema::{
+    Adopted, ConfigFileRecord, KernelRecord, Managed, SCHEMA_VERSION, ServicesState, State,
+    UserEnvRecord,
+};
diff --git a/crates/pearlite-state/src/reconciliation.rs b/crates/pearlite-state/src/reconciliation.rs
new file mode 100644
index 0000000..12b052e
--- /dev/null
+++ b/crates/pearlite-state/src/reconciliation.rs
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2026 Mohamed Hammad
+
+//! `[[reconciliations]]` records — one per `pearlite reconcile --commit`.
+
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use time::OffsetDateTime;
+use uuid::Uuid;
+
+/// One entry in `state.toml`'s `[[reconciliations]]` array.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+pub struct ReconciliationEntry {
+    /// Plan UUID generated for this reconciliation.
+    #[schemars(with = "String")]
+    pub plan_id: Uuid,
+    /// UTC timestamp when the reconciliation committed.
+    #[serde(with = "time::serde::iso8601")]
+    #[schemars(with = "String")]
+    pub committed_at: OffsetDateTime,
+    /// Resolution chosen for the drift items at commit time.
+    pub action: ReconciliationAction,
+    /// Number of packages classified during this reconciliation.
+    pub package_count: u32,
+}
+
+/// How a reconciliation resolved its detected drift.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize, JsonSchema)]
+#[serde(rename_all = "snake_case")]
+pub enum ReconciliationAction {
+    /// Non-interactive `--adopt-all`: every drift item moved to `adopted`.
+    AdoptAll,
+    /// Interactive prompt path: per-package decisions taken.
+    Interactive,
+    /// Reconciliation aborted before any state was written.
+    Skipped,
+}
diff --git a/crates/pearlite-state/src/schema.rs b/crates/pearlite-state/src/schema.rs
new file mode 100644
index 0000000..332f955
--- /dev/null
+++ b/crates/pearlite-state/src/schema.rs
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2026 Mohamed Hammad
+
+//! Top-level [`State`] struct and the `[managed.*]` / `[adopted.*]` records
+//! it owns.
+
+use crate::failure::FailureRef;
+use crate::history::HistoryEntry;
+use crate::reconciliation::ReconciliationEntry;
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+use time::OffsetDateTime;
+
+/// Current `schema_version` written by this build.
+///
+/// Incremented when the on-disk shape changes incompatibly. Migration
+/// from older versions lands in `migrate.rs` (chunk M1-W1-F).
+pub const SCHEMA_VERSION: u32 = 1;
+
+/// In-memory mirror of `/var/lib/pearlite/state.toml`.
+///
+/// The full schema is specified in PRD §7.2. `State` is mutated only by
+/// `pearlite-engine`; every other crate consumes it read-only.
+///
+/// `Eq` is intentionally **not** derived: the `reserved` field carries a
+/// `toml::Value` map for forward-compatibility, and `toml::Value::Float`
+/// wraps an `f64` that is not `Eq`. Use `PartialEq` (which is derived)
+/// for equality checks in tests.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize, JsonSchema)]
+pub struct State {
+    /// Schema version of the file at last write.
+    pub schema_version: u32,
+    /// Hostname this state belongs to. Mismatch with `hostname()` is
+    /// preflight Class 1.
+    pub host: String,
+    /// Pearlite version that last wrote the file.
+    pub tool_version: String,
+    /// Path to the user's Pearlite config repository at last apply.
+    pub config_dir: PathBuf,
+    /// Timestamp of the last successful `apply`.
+    #[serde(with = "time::serde::iso8601::option", default)]
+    #[schemars(with = "Option<String>")]
+    pub last_apply: Option<OffsetDateTime>,
+    /// Timestamp of the last write of any kind.
+    #[serde(with = "time::serde::iso8601::option", default)]
+    #[schemars(with = "Option<String>")]
+    pub last_modified: Option<OffsetDateTime>,
+    /// Pearlite-managed packages, configs, services, kernel, and user envs.
+    #[serde(default)]
+    pub managed: Managed,
+    /// User-flagged "leave alone" packages.
+    #[serde(default)]
+    pub adopted: Adopted,
+    /// Append-only log of successful applies.
+    #[serde(default)]
+    pub history: Vec<HistoryEntry>,
+    /// Log of `pearlite reconcile --commit` invocations.
+    #[serde(default)]
+    pub reconciliations: Vec<ReconciliationEntry>,
+    /// Pointers to `/var/lib/pearlite/failures/<plan-id>.json` records.
+    #[serde(default)]
+    pub failures: Vec<FailureRef>,
+    /// Forward-compat namespace; arbitrary unknown keys preserved on
+    /// round-trip via the toml_edit-based atomic writer. Excluded from
+    /// the JSON Schema because its values are untyped by design.
+    #[serde(default)]
+    #[schemars(skip)]
+    pub reserved: BTreeMap<String, toml::Value>,
+}
+
+/// `[managed.*]` namespace: everything Pearlite has installed or written.
+#[derive(Clone, Debug, PartialEq, Eq, Default, Serialize, Deserialize, JsonSchema)]
+pub struct Managed {
+    /// pacman/AUR packages installed via Pearlite.
+    #[serde(default)]
+    pub pacman: Vec<String>,
+    /// Cargo crates installed via Pearlite.
+    #[serde(default)]
+    pub cargo: Vec<String>,
+    /// Per-file metadata for managed `/etc` config files.
+    #[serde(default)]
+    pub config_files: Vec<ConfigFileRecord>,
+    /// systemd unit state at last apply.
+    #[serde(default)]
+    pub services: ServicesState,
+    /// Per-user Home Manager generation and config hash.
+    #[serde(default)]
+    pub user_env: Vec<UserEnvRecord>,
+    /// Kernel package, version, cmdline, modules at last apply.
+    #[serde(default)]
+    pub kernel: Option<KernelRecord>,
+}
+
+/// One managed `/etc` config file's record.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+pub struct ConfigFileRecord {
+    /// Absolute destination path on the host.
+    pub target: PathBuf,
+    /// Source path within the user's config repo.
+    pub source_in_repo: PathBuf,
+    /// SHA-256 of the file contents at last successful write, hex-encoded.
+    pub sha256: String,
+    /// File mode (`stat(2).st_mode & 0o7777`).
+    pub mode: u32,
+    /// Owning user.
+    pub owner: String,
+    /// Owning group.
+    pub group: String,
+}
+
+/// systemd-unit state recorded by Pearlite at apply time.
+#[derive(Clone, Debug, PartialEq, Eq, Default, Serialize, Deserialize, JsonSchema)]
+pub struct ServicesState {
+    /// Units enabled (and started) by Pearlite.
+    #[serde(default)]
+    pub enabled: Vec<String>,
+    /// Units disabled by Pearlite.
+    #[serde(default)]
+    pub disabled: Vec<String>,
+    /// Units masked by Pearlite.
+    #[serde(default)]
+    pub masked: Vec<String>,
+}
+
+/// One user's Home Manager generation pointer.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, JsonSchema)]
+pub struct UserEnvRecord {
+    /// Login name.
+    pub user: String,
+    /// Home Manager generation number at last apply.
+    pub generation: u64,
+    /// SHA-256 of the user's HM config directory at last apply.
+    pub config_hash: String,
+}
+
+/// Kernel record: package, version, cmdline, modules at last apply.
+#[derive(Clone, Debug, PartialEq, Eq, Default, Serialize, Deserialize, JsonSchema)]
+pub struct KernelRecord {
+    /// Kernel package name (e.g. `linux-cachyos`).
+    pub package: String,
+    /// Installed kernel version string.
+    pub version: String,
+    /// Kernel command-line as last applied.
+    #[serde(default)]
+    pub cmdline: Vec<String>,
+    /// Loaded modules as last applied.
+    #[serde(default)]
+    pub modules: Vec<String>,
+}
+
+/// `[adopted.*]` namespace: drift items the user has explicitly told
+/// Pearlite to leave alone.
+#[derive(Clone, Debug, PartialEq, Eq, Default, Serialize, Deserialize, JsonSchema)]
+pub struct Adopted {
+    /// Adopted pacman/AUR packages.
+    #[serde(default)]
+    pub pacman: Vec<String>,
+    /// Adopted cargo crates.
+    #[serde(default)]
+    pub cargo: Vec<String>,
+}