fix(host): gate the update module's callers for non-unix builds

The update module is `#[cfg(unix)]` (self-update replaces the running
program's file, which Windows forbids), but three commands in
`ledger-host` used `crate::update` unconditionally, so the server-only
Windows build could not resolve the module. GitHub's portable-windows
job failed on main 3aa1206a with nine E0433 errors in `ledger-host`.

Gate `update_waiting`, `check_for_updates` and `apply_update` with
`#[cfg(unix)]`, leaving their Unix bodies unchanged, and give non-unix
builds a stub of each: nothing is waiting, and checking for or accepting
an update is refused with "self-update isn't available on this platform"
(the same `Err` path a refused update takes). `UPDATE_WAIT` is gated with
the Unix `apply_update` it serves.

.github/workflows/scheduled.yml

@@ -33,7 +33,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        target: [fuzz_journal_line, fuzz_entry_validate, fuzz_op_sequence, fuzz_core_serde, fuzz_store_open, fuzz_store_replay, fuzz_settings_replay, fuzz_import_csv, fuzz_config_parse, fuzz_extract_pdf, fuzz_extract_xlsx]
+        target: [fuzz_journal_line, fuzz_entry_validate, fuzz_op_sequence, fuzz_core_serde, fuzz_store_open, fuzz_store_replay, fuzz_settings_replay, fuzz_import_csv, fuzz_config_parse, fuzz_extract_pdf, fuzz_extract_xlsx, fuzz_http_mcp_request, fuzz_upload_put]
     steps:
       - uses: actions/checkout@v4
       - uses: jdx/mise-action@v2

crates/ledger-host/src/commands.rs

@@ -1042,6 +1042,7 @@ pub struct UpdateWaiting {
 }
 
 /// The update waiting for the owner's accept, if there is one.
+#[cfg(unix)]
 pub fn update_waiting(common: &Common) -> Option<UpdateWaiting> {
     let found = ledger_store::root::Root::find(common.root.as_deref()).ok()?;
     let u = found.staged_update()?;
@@ -1058,9 +1059,16 @@ pub fn update_waiting(common: &Common) -> Option<UpdateWaiting> {
     })
 }
 
+/// Nothing waits on a platform the self-update isn't built for.
+#[cfg(not(unix))]
+pub fn update_waiting(_common: &Common) -> Option<UpdateWaiting> {
+    None
+}
+
 /// "Check for updates": look at the feed now, whatever the daily look
 /// last did, and stage a newer release if there is one (it never swaps
 /// the program: accepting is [`apply_update`]). What came of it.
+#[cfg(unix)]
 pub fn check_for_updates(common: &Common) -> Result<String, String> {
     let found =
         ledger_store::root::Root::find(common.root.as_deref()).map_err(|e| e.to_string())?;
@@ -1085,10 +1093,18 @@ pub fn check_for_updates(common: &Common) -> Result<String, String> {
     }
 }
 
+/// Checking for updates isn't built for this platform: say so, and
+/// change nothing.
+#[cfg(not(unix))]
+pub fn check_for_updates(_common: &Common) -> Result<String, String> {
+    Err(NO_SELF_UPDATE.into())
+}
+
 /// Accept the staged update: the books' host installs it and restarts
 /// onto it once no call is running, the books staying open meanwhile
 /// (the lease socket's apply_update). With no host running, it is
 /// installed here, since no call can be cut off. What came of it.
+#[cfg(unix)]
 pub fn apply_update(common: &Common) -> Result<String, String> {
     let found =
         ledger_store::root::Root::find(common.root.as_deref()).map_err(|e| e.to_string())?;
@@ -1111,10 +1127,23 @@ pub fn apply_update(common: &Common) -> Result<String, String> {
     }
 }
 
+/// Accepting an update isn't built for this platform: say so, and change
+/// nothing.
+#[cfg(not(unix))]
+pub fn apply_update(_common: &Common) -> Result<String, String> {
+    Err(NO_SELF_UPDATE.into())
+}
+
 /// The longest the host may take to install an accepted update (a copy
 /// and a health check of the new program).
+#[cfg(unix)]
 const UPDATE_WAIT: Duration = Duration::from_secs(90);
 
+/// What the app says when the self-update is asked for on a platform it
+/// isn't built for (Windows, today).
+#[cfg(not(unix))]
+const NO_SELF_UPDATE: &str = "self-update isn't available on this platform";
+
 /// The longest an agent's own command may take to add the books.
 const CONNECT_WAIT: Duration = Duration::from_secs(60);
 

crates/ledger-mcp/Cargo.toml

@@ -39,12 +39,18 @@ toml = "1"
 # The vault's TINs, decoded for the filing scan (tin_files.rs), are wiped
 # from memory when dropped, as the vault's own are.
 zeroize = "1"
+tempfile = { version = "3", optional = true }
 
 # The socket's peer credentials (SO_PEERCRED, getpeereid) for local.rs's
 # same-user check: std has no call for them.
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
 
+[features]
+# The door in-process, for fuzz/ (local.rs fuzz_door). Off in every build
+# but the fuzz workspace's.
+fuzzing = ["dep:tempfile"]
+
 [lints]
 workspace = true
 

crates/ledger-mcp/src/local.rs

@@ -1730,6 +1730,22 @@ async fn mcp(
     })
 }
 
+/// The one router both doors serve (the local socket and the tunnel).
+fn router(books: Arc<Books>) -> axum::Router {
+    axum::Router::new()
+        .route("/b/{book}/mcp", axum::routing::any(mcp))
+        .route("/b/{book}/u/{upload}", axum::routing::put(upload))
+        .route("/b/{book}/a/{attachment}", axum::routing::get(download))
+        .route("/b/{book}/x/{export}", axum::routing::get(export))
+        .fallback(not_found)
+        .with_state(books)
+}
+
+/// The door in-process, for the fuzz targets (P12): the same router, fed
+/// bytes without a socket. Not built unless asked for.
+#[cfg(feature = "fuzzing")]
+pub mod fuzz_door;
+
 /// Anything but `/b/{book}/mcp`.
 async fn not_found() -> (axum::http::StatusCode, &'static str) {
     (axum::http::StatusCode::NOT_FOUND, "not found")
@@ -2080,13 +2096,7 @@ async fn serve(
         }
     });
 
-    let app = axum::Router::new()
-        .route("/b/{book}/mcp", axum::routing::any(mcp))
-        .route("/b/{book}/u/{upload}", axum::routing::put(upload))
-        .route("/b/{book}/a/{attachment}", axum::routing::get(download))
-        .route("/b/{book}/x/{export}", axum::routing::get(export))
-        .fallback(not_found)
-        .with_state(books.clone());
+    let app = router(books.clone());
     // The HTTP side keeps answering (refusing, once closing) until the
     // close is done: a client is never cut off mid-request by it.
     let shut = CancellationToken::new();

crates/ledger-mcp/src/local/fuzz_door.rs

@@ -0,0 +1,187 @@
+//! The books server's HTTP door, in-process, for the fuzz targets
+//! (`fuzz_http_mcp_request`, `fuzz_upload_put`; P12). It is the very router
+//! `serve` mounts (`router`), over a real book in a folder of its own, fed
+//! requests by `tower::oneshot`: no socket, no port. Behind the `fuzzing`
+//! feature, which only the fuzz workspace turns on.
+//!
+//! Oracle: whatever the bytes, the door answers (no panic, no hang), and
+//! never lets in a request without a token live for the book (INVARIANT 8)
+//! or bytes that are not the ones declared (INVARIANT 9).
+
+use super::*;
+use tower::ServiceExt;
+
+/// One book `acme`, two tokens (`bearer`, `other`), and the router.
+pub struct FuzzDoor {
+    rt: tokio::runtime::Runtime,
+    books: Arc<Books>,
+    app: axum::Router,
+    bearer: String,
+    token_id: String,
+    other: String,
+    _home: tempfile::TempDir,
+}
+
+impl FuzzDoor {
+    /// A fresh book in a fresh folder.
+    pub fn new() -> Self {
+        let home = tempfile::tempdir().expect("a folder");
+        let (root, _) =
+            Root::setup(home.path(), Some(&home.path().join("root")), None).expect("a data root");
+        let books = Arc::new(Books {
+            root,
+            held: RwLock::new(BTreeMap::new()),
+            sessions: CancellationToken::new(),
+            closing: CancellationToken::new(),
+            in_flight: AtomicUsize::new(0),
+            finished: tokio::sync::Notify::new(),
+            last_arrival: std::sync::atomic::AtomicU64::new(0),
+            started: Instant::now(),
+            principals: RwLock::new(Err(String::new())),
+            session_tokens: Mutex::new(BTreeMap::new()),
+            backup_quiet: BACKUP_QUIET,
+            drill_first: DRILL_FIRST,
+            restoring: Mutex::new(()),
+            isolation: Isolation::SameUser,
+        });
+        let loaded = books.load_principals();
+        *books.principals.write().unwrap() = loaded;
+        match books.admin(Request::Create {
+            id: "acme".into(),
+            currency: "USD".into(),
+        }) {
+            Response::Created { problem: None, .. } => {}
+            other => panic!("{other:?}"),
+        }
+        let token = |name: &str| match books.admin(Request::TokenCreate {
+            book: "acme".into(),
+            name: name.into(),
+            scopes: ["read", "write", "post", "admin"]
+                .map(String::from)
+                .to_vec(),
+            replace: true,
+        }) {
+            Response::TokenCreated { token, text } => (token.id, text.0),
+            other => panic!("{other:?}"),
+        };
+        let (token_id, bearer) = token("fuzz");
+        let (_, other) = token("fuzz-other");
+        let app = router(books.clone());
+        let rt = tokio::runtime::Builder::new_multi_thread()
+            .worker_threads(2)
+            .enable_all()
+            .build()
+            .expect("a runtime");
+        FuzzDoor {
+            rt,
+            books,
+            app,
+            bearer,
+            token_id,
+            other,
+            _home: home,
+        }
+    }
+
+    /// The text of the token that is live for the book.
+    pub fn bearer(&self) -> &str {
+        &self.bearer
+    }
+
+    /// The text of a second live token (the one an upload is not its).
+    pub fn other_bearer(&self) -> &str {
+        &self.other
+    }
+
+    /// An upload granted to the live token: its id, or why not.
+    pub fn grant(&self, sha256: &str, size: u64) -> Result<String, String> {
+        let held = self.books.held();
+        let Some(Book::Open { uploads, .. }) = held.get("acme") else {
+            return Err("acme isn't open".into());
+        };
+        uploads
+            .grant(
+                &self.token_id,
+                sha256,
+                size,
+                "application/pdf",
+                "fuzz.pdf",
+                "document",
+                chrono::Utc::now().timestamp(),
+            )
+            .map(|g| g.id)
+            .map_err(|e| e.to_string())
+    }
+
+    /// Whether the door would take one of these headers as a bearer token
+    /// live for the book: the same check every request passes, so a target
+    /// never has to model the rule a second time.
+    pub fn carries_a_token(&self, headers: &[(Vec<u8>, Vec<u8>)]) -> bool {
+        let mut map = axum::http::HeaderMap::new();
+        for (name, value) in headers {
+            let (Ok(name), Ok(value)) = (
+                axum::http::HeaderName::from_bytes(name),
+                axum::http::HeaderValue::from_bytes(value),
+            ) else {
+                return false;
+            };
+            map.append(name, value);
+        }
+        self.books.bearer(&map).is_ok()
+    }
+
+    /// Send a request as the router receives it; the status and the body
+    /// of the answer, or `None` when the pieces do not make an HTTP request
+    /// at all (a method or header the HTTP types refuse never reaches the
+    /// door in life either).
+    pub fn send(
+        &self,
+        method: &[u8],
+        path: &str,
+        headers: &[(Vec<u8>, Vec<u8>)],
+        body: Vec<u8>,
+    ) -> Option<(u16, Vec<u8>)> {
+        let mut request = axum::http::Request::builder()
+            .method(axum::http::Method::from_bytes(method).ok()?)
+            .uri(
+                format!("http://localhost{path}")
+                    .parse::<axum::http::Uri>()
+                    .ok()?,
+            );
+        for (name, value) in headers {
+            request = request.header(
+                axum::http::HeaderName::from_bytes(name).ok()?,
+                axum::http::HeaderValue::from_bytes(value).ok()?,
+            );
+        }
+        let request = request.body(axum::body::Body::from(body)).ok()?;
+        let app = self.app.clone();
+        Some(self.rt.block_on(async move {
+            let response = app.oneshot(request).await.unwrap_or_else(|e| match e {});
+            let status = response.status().as_u16();
+            // An event stream never ends on its own: read what comes in a
+            // moment, as a client that hangs up would.
+            let bytes = tokio::time::timeout(
+                Duration::from_millis(200),
+                axum::body::to_bytes(response.into_body(), 1 << 20),
+            )
+            .await
+            .ok()
+            .and_then(Result::ok)
+            .unwrap_or_default();
+            (status, bytes.to_vec())
+        }))
+    }
+
+    /// Sessions the door has bound (they only grow, so the target starts
+    /// a fresh door now and then).
+    pub fn sessions(&self) -> usize {
+        self.books.session_tokens.lock().unwrap().len()
+    }
+}
+
+impl Default for FuzzDoor {
+    fn default() -> Self {
+        Self::new()
+    }
+}

docs/testing.md

@@ -622,6 +622,7 @@ scratch (`ledger-store` `backup.rs` and `root.rs`, `ledger-core`
 `settings.rs`, `ledger-mcp` `backup.rs`, `tools/backup.rs`, `local.rs`,
 `admin.rs`, `ledger-host` `commands.rs`, `ledger-cli`). The survivor lists
 are kept with the run's output, outside the repository.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: odd cents (2026-10-20)
 
@@ -729,6 +730,7 @@ parse; a tag that isn't text; the feature declaration);
 fields; `Currency::allocation_places`. P3's accept counts `ledger-core` and
 `ledger-import` (R-6); the store and MCP mutants above are for the whole
 pass.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: the IIF and as-of (2026-10-20)
 
@@ -934,6 +936,7 @@ condition and `receivable_payable`; `fonts.rs` and `theme.rs`
 `font_definitions`; the README's A/R and A/P sentence; `ledger-core`
 `parties.rs` `tin_separator`'s arms and `tin_invisible`, and the gap that
 doesn't count them.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: cash flow (defect 1, 2026-10-20)
 
@@ -1080,6 +1083,7 @@ the end.
 `export_cash_flow` and `settings_problems`; zero unexplained survivors
 (plan P3 accept). Likely equivalent, to adjudicate: `min` against `max`
 in `take` where both bounds coincide, and the kind order's tie-breaks.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: rename, defaults and tax categories (2026-10-20)
 
@@ -1267,6 +1271,7 @@ range, `export_journal`'s period, `described`, `uncategorized_warning`,
 `created_uncategorized`, the digest's `uncategorized_accounts`,
 `handbook::period_rule`. The viewer is not mutated (owner, 2026-10-18):
 `view_model.rs` and `show.rs` cover it.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: parties (defects 14, 24, 11; 2026-10-20)
 
@@ -1316,6 +1321,7 @@ cash, in_kind) and `update_party`'s creditor_of diff; the viewer's
 `party_what_for` and `share_text`. Expected equivalent:
 `Party::tin_last4`'s `or_else` order swapped (TIN facts and W-9 facts
 never disagree, parties INVARIANT 2a, enforced on replay).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: 1099s (defects 23, 12 and 18; 2026-10-20)
 
@@ -1375,6 +1381,7 @@ unchanged path, `set_vendor_w9_flag`, `add_instrument`,
 first, only when the flag changes); `ledger-package` `vendor_1099.rs` (the CSV columns, every note's
 guard, `may_file`, `missing_w9`'s suffix) and `package.rs` (tin_gaps, the
 README line). The viewer has no mutation job (its musts are tested).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: parties and 1099s landed together (2026-10-21)
 
@@ -1398,6 +1405,7 @@ fallback); the server's `vendor_1099` (`through`'s year check, the
 unknown-code check, the accounts passed) and `update_party`'s feature
 declaration; the bookspec loader's party, payee, decision and payment
 method setup.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: depreciation and schedules (defects 22 and 9, 2026-10-20)
 
@@ -1584,6 +1592,7 @@ version's journal format (rules.md B-27). Mutation testing waits for P12
 (`consent_now`, `upgrade_format`, `offer_upgrades`, `offer_upgrade`,
 `upgrade`, `book_line`, `upgraded_lines`, `upgrade_explained`,
 `ASKED_UPGRADES`). None run.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: asset basis and tax-basis capital (2026-10-20)
 
@@ -1715,6 +1724,7 @@ reversal's take-back) and
 `entry_property` (the mismatch branch, the unknown sum), the open-item
 conditions (`in_service`, the disposal window), and the reconciliation's
 signs.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: the seams between the pieces (2026-10-21)
 
@@ -1818,6 +1828,7 @@ before); the bookspec loader's exact-spelling filters and `check_k1`'s
 `cash_accounts` check; `documented_tools` (its own sample checks it).
 The earlier P3 sections' lists stand (one name corrected:
 `Ledger::depreciation_runs`, which was `depreciation_runs_ever`).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: projects (2026-10-21)
 
@@ -1957,6 +1968,7 @@ balance-sheet zero; `project_set_of` (newer vs corrupt);
 `set_project`'s unchanged short-cut; `subject_feature`; `check_link_to`'s
 feature check; the decision `projects` omit-when-empty;
 `late_tag_note`'s `is_over`; `remember_footer`'s threshold.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P3: the project snapshot (2026-10-22)
 
@@ -2068,6 +2080,7 @@ fail.
 **For P12 (mutation targets):** `contribution_margin_pct`'s `<=` and
 rounding strategy; `project_figures`' opening net and running sum;
 `profit_and_loss_counted`'s counts; `Standing::of`'s order.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## Invoices and bills take a project (2026-10-22)
 
@@ -2178,6 +2191,7 @@ order, the `contains` test); `add_document_parts`' tag index;
 `document_notes`' dedup and its `invoice` flag; `on_spec_invoice_note`'s
 kind test; `document_projects_rule`'s branch; the viewer's
 `document_of` (invoice before bill).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## After P3: the cutover review's open points 1 and 2 (2026-10-22)
 
@@ -2650,6 +2664,7 @@ amount match and one-line rule; `refresh_doc`'s settled sum;
 `doc_status`'s Overpaid and Unattached arms; the aging's `<= 0`;
 `ensure_payment_features`' comparison; `check_document_reversal`'s date
 check; `control_check`'s chain netting.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S1, part B: void, control check, and each payment's details (2026-10-24)
 
@@ -2702,6 +2717,7 @@ line and nothing needing attention, each field's mapping, the
 invoice/bill kind); `control_problems` (one message per unattached line
 and per document, both loops); the `digest` that includes it and the
 `verify` check that refuses a nonzero difference.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S2: reading documents, in the tools and in the viewer (2026-10-24)
 
@@ -2758,6 +2774,7 @@ Overdue's `overdue_days > 0`, Paid, Void, All), a document after the day
 shown only under All (`Ok(None)`), the list's `(due, date, name)` sort
 and the timeline's movement×reversal labels with their `(reversed later)`
 condition (`!t.reversal && !stands_on(t.entry, b.today)`).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S3: the invoice PDF (2026-10-24)
 
@@ -2811,6 +2828,7 @@ one does: `PartiallyPaid` (no sample is part paid and not yet due) and
 `Draft` (only S4's preview reaches it; the renderer's own test renders
 it but asserts only that it succeeds).
 ## P7: the TIN scanner's separators (2026-10-26)
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 rules.md B-26; plan 8.2 P7, with vault v2 closed by D-48 (nothing of
 HPKE, keyslots or human pages is built here). The scanner
@@ -2851,6 +2869,7 @@ Deleting any one of them leaves a TIN that the old scanner passed
 either readable or unmasked, which the truth table and the property
 catch.
 ## P13: bookspec, the checker crate and the runner (2026-10-26)
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 bookspec's example schema moved out of the loader into
 `bookspec/checker`, its own Cargo workspace inside the repository (P13
@@ -2918,6 +2937,7 @@ example" arm; the adapter's `event_of`, its `depreciation_schedule` month
 span (acquisition through as-of, 0.00 where the schedule reaches no month)
 and every `answer_*` figure against the loader's same check (the two must
 agree on all 56 examples).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P13 steps 4 and 5: the specification text, the laws, the derivation, GnuCash (2026-10-29)
 
@@ -2983,6 +3003,7 @@ condition), `Model::post`'s close (a debit-normal balance credits, the
 equity line's sign), `signed`'s date window and `closings` flag, and the
 accounting-equation check; the spec test's pin search (a mutant that skips
 the quote check passes only if `every_citation_resolves` has no bad pin).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## U0b: one attention engine over `PackageBooks` (2026-10-26)
 
@@ -3038,6 +3059,7 @@ negative-zero test; `filter(|a| a.tool.is_some()).take(12)` and
 intact-blob set (a damaged blob reported per attachment) and `Store::
 disk_check`'s snapshot load and `Unreadable` arm; the viewer wrapper's
 `Target` arms.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P9a: self-host, the move, and the static bearer over a tunnel (2026-10-26)
 
@@ -3118,6 +3140,7 @@ and `BooksServer::new`'s copy (a dropped field must fail
 `isolation_label_is_enforced_under_the_unit`); the host's `server_flags`
 extension and `parse_args`' passthrough of `--isolation` and its optional
 `--http` value.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S4.5: the issued PDF, the viewer and the handbook (2026-10-29)
 
@@ -3182,6 +3205,7 @@ arms and `InvoiceVersion::Current { as_of }`; the viewer's `details`
 number-else-id and `issued_copy`'s PDF-and-description match; the
 handbook's `documents_v2_rule` both arms and the server's `documents_v2`
 feature test.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S5: sent tracking (2026-10-27)
 
@@ -3246,6 +3270,7 @@ predicates in `ledger-package::attention`: `invoice.number.is_some()`
 `checked_add_days` `unsent_days` comparison (`>`), `overdue_days > 0`, the
 `sends.max()` last send, and the `reminder_days` comparison (`>`), plus
 each item's target (`Target::Invoice`) and `books.mark_sent` step args.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S6: paying on terms (2026-10-27)
 
@@ -3323,6 +3348,7 @@ arithmetic; `bills_due`'s `through` filter, the discount-window test and
 the running-total grouping; `aging_documents`'s outstanding filter and
 bucket; `aging_csv`'s tie-out columns and `aging_statement`'s totals; the
 viewer's `discount_by` and `days_overdue` flags.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4b S7: bad debts (write-offs), 2026-10-27
 
@@ -3400,6 +3426,7 @@ the blob-before-journal order, the `File`/`Existing` link steps) and the
 feature gate; the MCP handler's amount default, the exactly-one evidence
 check, and the preview's clone; attention's year comparison and its
 `stands_on` filter; the bookspec loader's `may_refuse` arm.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P6: the evidence pipeline (2026-10-27)
 
@@ -3532,6 +3559,7 @@ arms, the 8 KiB cut, the 64 KiB hand-over threshold and `page - 1`.
 `ledger-package::attention`: the extraction `seq` comparison and the
 `Failed` filter, the owed-account name test, the credit side and the
 `settles_entry` skip.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P11a step 0: keyring stores for macOS and Windows (2026-10-29)
 
@@ -3556,6 +3584,7 @@ Secret Service run needs a desktop): the CI run is the evidence.
 **For P12 (mutation targets, none run, D-33):** `tokens.rs`'s `os` modules
 are not reachable by mutation testing (they need the real OS store); the
 `Items` logic they share is, through the file store.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## U0e: tokens in a file, the OS keyring removed (2026-10-29, D-63)
 
@@ -3594,6 +3623,7 @@ token" must die on `an_unreadable_token_file_is_an_error_never_no_token`),
 `Keeper::delete`'s `NotFound` arm, and `Account::key`'s three parts
 (`an_account_names_the_root_by_hash_and_the_book_and_token`);
 `bridge.rs::token_file_refusal`'s `holds_token` guard.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P4: draft states, the evidence gate, the preview digest (2026-10-29)
 
@@ -3669,6 +3699,7 @@ it); the digest's `since_seq` comparison (`>`), its `as_of` bound, the
 `zero_net_accounts` branch and the `never_reconciled` split;
 `report_status`'s three open conditions; the open-drafts refusal's
 `<= as_of` and its decision; the attention `awaiting_evidence` branch.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P11c: the native Windows port (2026-10-29, D-62)
 
@@ -3727,6 +3758,7 @@ arm; `Listener`'s `IDLE_INSTANCES` pool (a mutant that makes it 1 passes
 every test but `many_clients_at_once_all_connect`); `start.rs::host_env`'s
 list. None of the Windows arms is reachable by `cargo mutants` on Linux:
 they run on the Windows job only.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P11a steps 2 and 3: update, rollback, the Linux packages (2026-10-29)
 
@@ -3822,6 +3854,7 @@ covers the feature one; a case with a higher format number is a gap to
 add), `swap_in`'s temporary-then-rename (`update_is_atomic`), `healthy`
 (`failed_update_rolls_back`), `install_kind` (the marker test), and
 `parse_version`'s rejections.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P11a steps 4 and 6: the in-app accept, the viewer's notice, translocation (2026-11-05)
 
@@ -3954,6 +3987,7 @@ equal-source refusals and the empty-reason refusals; the three
 in `a_source_only_revision_is_journaled`); `books.start`'s fit order and
 `reconciliation` split (`reconciled_through.is_some()`).
 ## P8: audit and attestations (2026-10-29)
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 An audit run is a deterministic programme of checks over the books through
 a day, filed as a JSON and a PDF workpaper; attestations are claims by a
@@ -4044,6 +4078,7 @@ export gate (`cpa_audit_standing`'s four conditions and its feature test,
 the `refuse`/`warn` split, the reason's trim); `audit_items` in Needs
 attention (the declared test, the attested set, the last-ended fiscal
 year, the three year conditions).
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P10: the re-audit runbook's mirror
 
@@ -4074,6 +4109,7 @@ sign-off) is the owner's and has no CI equivalent.
 lines above it) and the scopes-line scan in `defect_20_*`. A mutant that
 widens the window or drops the `ignore` check survives only if no ignored
 or untested name is in the table; the table is the oracle.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
 
 ## P13 step 6: the specification in its own repository (2026-10-29)
 
@@ -4170,3 +4206,509 @@ brightening; `Session::resize`'s equality early return; the panel's
 open/closed ids (a remembered size must not leak between them);
 `Welcome::steps`' choice of `now` (each arm), the passphrase length and
 equality gates, the `agent_later` flag.
+*(Consolidated, with the other units' targets, in "P12: the checklists" at the end of this file.)*
+
+## P12: the checklists
+
+The **For P12** paragraphs above (kept where they were written, with their
+units' histories) consolidated into one checklist per crate, so the run
+(step 2 of P12, D-33) walks a crate at a time. Each item names a target and
+the mutants worth thinking about; its origin unit is in brackets. "None run"
+holds for all of them: every survivor is killed by a test or recorded below
+as equivalent, with its reason, when the run is made. The recipes are
+`just mutants`, `mutants-store`, `mutants-import`, `mutants-config`,
+`mutants-mcp`, and (P12 step 1) `mutants-host`, `mutants-package`,
+`mutants-vault`, `mutants-cli`: each runs the crate's own tests and
+`ledger-cli`'s end-to-end suites without the viewer, `-j 4` by default, one
+run at a time, local only (D-59). `ledger-gui` has no mutation run (its two
+musts are `tests/read_only.rs` and `tests/view_model.rs`). The `bookspec`
+items are for that repository's own check (D-34 step 6). The whole diff to mutate: from `168494b` (main before P2 slice 3).
+
+The fuzz targets P12 step 1 added: `fuzz_http_mcp_request` (arbitrary method,
+path, headers and body into the in-process router, `ledger-mcp`'s
+`local::fuzz_door`, behind its `fuzzing` feature: no token live for the book
+is never a 2xx, a valid one never makes the door fail) and `fuzz_upload_put`
+(bytes come in only if they are the declared ones, from the token the upload
+was granted to, once). `fuzz_op_sequence::Op` gained the invoice, bill,
+payment, settlement, write-off, void and draft-state ops and a control-check
+invariant (control accounts equal their documents).
+
+### ledger-core
+
+- [P2 slices 3 to 8] `settings.rs` from scratch.
+- [P3 odd cents] `kernel::apportion_cumulative` (length and range guards;
+  `checked_sub` for `checked_add`; the subtraction skipped);
+  `periods::allocate_cumulative` (the sign; `given` not negated for a loss;
+  `places` ignored; the exactness filter, zero products included);
+  `Ledger::members_regime` and `regime_where` (skip versus break at a close to
+  anything else; the order-free compare made ordered; `<=` for `<` in the date
+  filter; `given` added to the wrong member; the count's order);
+  `Regime::allocate` (the order); `Ledger::members_split` and
+  `close_period_to_steps` (the start check; the `posts` gate; the recorded
+  rule; the sweeps before the parts); `member_close_run`; `member_close_split`;
+  `reports::members_equity` (`allocate(C)` replaced by `given`; `places`;
+  "other"'s order); `k1::share_property`; `Currency::allocation_places`.
+  Accept counts for `ledger-core` and `ledger-import` are R-6.
+- [P3 cash flow] `cashflow.rs` (`cash_flow`, `analyse`, `pairs`, `label`,
+  `class_of`, `reconcile`, `warnings`, `bill_splits`, `role_problems`, `foot`,
+  `on_behalf`); `kernel.rs`'s `take`, `apply_cash`, `entry_flows`,
+  `constructive`, `exchanged`. Likely equivalent, to adjudicate: `min` against
+  `max` in `take` where both bounds coincide; the kind order's tie-breaks.
+- [P3 rename and defaults] `calendar::{fiscal_year_start_unclamped,
+  fiscal_year_unclamped, fiscal_year_start_on, period_defaults}`,
+  `PeriodDefaults::{statement, statement_range, as_of, calendar_year}`,
+  `PeriodKind::describe`, `Company::fiscal_year_containing`,
+  `ChartOfAccounts::set_name`, `Ledger::{add_account (its new-name checks),
+  add_control_account, check_account_name, rename_account,
+  check_rename_account, replay_rename_account, check_rename_reason,
+  check_tax_category_required, check_tax_category_kept}`,
+  `tax::{needs_category, account_needs_category, uncategorized_accounts,
+  on_form_4797}` and `tax_summary`'s Form 4797 section,
+  `Settings::require_tax_category`.
+- [P3 parties] `kernel::party_target` (each branch, the `!= 0` and `< 0`
+  tests, the property and money clamps, the neither-when-nothing-counts test),
+  `kernel::reverse_target`, `Direction::{flip, of}`; `shares::target` (the
+  closing check, the reversal arm and its parity, members_only, the equity
+  filter and the retained-earnings exclusion, the property test, the own
+  sums); `shares::split` (the member-order tie-break, the cash shortcut, the
+  zero sign); `parties::{flow, root_original, money_accounts, card_accounts,
+  MoneyAccounts::for_parties}` (the negation of what_for, the walk's guard,
+  cards and financing as money, the gift-card exclusion); `activity_with`
+  (the target before the split, the skip of nothing-counts, the bucket by side
+  and basis, the overflow checks); `Activity::totals`; `Basis::parse`;
+  `Ledger::{set_party_creditor, check_set_party_creditor, creditors_of,
+  is_closing_entry}`. Expected equivalent: `Party::tin_last4`'s `or_else`
+  order swapped (TIN and W-9 facts never disagree, parties INVARIANT 2a,
+  enforced on replay).
+- [P3 1099s] `form1099.rs` (`plan_decision`, `apply_decision`,
+  `check_new_decision`'s decided-before test, `in_force`/`in_force_before`
+  (`<` against `<=`), `vendor_1099_report`'s status branches (each `>=`, `<`,
+  `max(.,0)`, `min(.,0)`), the listing filter, the not-reportable and
+  undetermined routing, the R6 test (`< 0`, credit side, `refund_accounts` per
+  account type), `Roles::new` (which methods' accounts are financing, which a
+  card's), `split_share` (the floor corrections, the sign), `vendor_part`, the
+  unresolved fallback, `decisions_during`, `untagged_payments` (`> 0`, each
+  skip, each debit kind), `decision_changes`); `kernel.rs` (`payment_bucket`,
+  `split_payment`, `net_buckets`); `instruments.rs`,
+  `Ledger::check_add_instrument` (each refusal), `set_entry_instrument` (the
+  chain), the reversal step's copy, `set_vendor_w9_flag`.
+- [P3 parties and 1099s landed together] `parties::card_accounts` (the
+  recorded-cards branch, the gift and other-instruments exclusions).
+- [P3 asset basis] `kernel::basis_figures` (min for max, the sign of the gain,
+  purchase to a contribution); `Ledger::accumulated_posted` and
+  `assets::run_chain_entries` (`<=` for `<` on the entry and reversal dates,
+  the disposed-to-0 branch, the alternating sign); `live_depreciation_run`'s
+  reversal test; `check_depreciation_run`'s arms; the register filter
+  `acquired <= as_of` and `asset_acquired_date`'s min; `AssetBasis::check`,
+  `check_journaled`, `check_legacy_journaled`; the acquisition and in-service
+  date refusals; the disposal floor; `tax_capital::RunningSplit` (the sign, the
+  zero case, the snap to ten places, `unsplit`), `tax_capital::entry_parts`
+  (the member set, the date order, the reversal's take-back), `entry_property`
+  (the mismatch branch, the unknown sum); the open-item conditions
+  (`in_service`, the disposal window); the reconciliation's signs.
+- [P3 surface review] `kernel::entry_movements` and `kernel::flows_of` (the
+  split of `entry_flows`; the same mutants as before; the earlier P3 lists
+  stand, `Ledger::depreciation_runs` was `depreciation_runs_ever`).
+- [P3 projects] `check_set_project`'s arms (ended_on with active/paused, `<`
+  vs `<=` on the dates, the duplicate name's self-exception, case folding),
+  `ProjectFacts::check` (the link limit, whitespace, duplicates);
+  `kernel::unrecovered_cost` (`max`, the sign); `project_figures`' class
+  filter, 240-month window and closing-entry exclusion; `project_entries`'
+  normal-side sign and balance-sheet zero; `check_link_to`'s feature check.
+- [P3 project snapshot] `contribution_margin_pct`'s `<=` and rounding
+  strategy; `project_figures`' opening net and running sum;
+  `profit_and_loss_counted`'s counts; `Standing::of`'s order.
+- [Documents take a project] `document_parts` (first-appearance order, the
+  `contains` test); `ensure_document_lines`' `any`;
+  `parse_document_lines`' arms (null, absent, out of `u32`);
+  `document_projects_rule`'s branch.
+- [P4b S1 A] `stands_on`'s count and in-order `take_while`; `doc_state`'s
+  movement arms and `overdue_days`; `doc_status`'s order and its Overpaid and
+  Unattached arms; `check_hand_line`/`check_control_lines` (the
+  reversal-mirror exemption); `control_role_of`'s two clauses and the
+  exemption's even-depth test; `check_assign_role`'s SCENARIO 6 and its
+  `controls` filter; `standing_payments`' `!reversal`; `holds_role`'s type
+  check; `bounds_kept`'s `>`; `payment_room`'s `from`; `tag_replayed`'s side,
+  amount match and one-line rule; `refresh_doc`'s settled sum; the aging's
+  `<= 0`; `check_document_reversal`'s date check; `control_check`'s chain
+  netting.
+- [P4b S1 B] `PaymentDetails::check` (the newline test, the 200-character
+  bound, a blank reference as none); `PaymentDetails::description` (the
+  " (ref R)" suffix, the trim, a blank reference leaving the base).
+- [P4b S5] `Ledger::mark_sent`'s refusals (unknown invoice, a send dated
+  before it, `DocumentVoid`, empty `to`, each of the three `check_text` calls;
+  the note's check is stricter than the plan, to keep a full TIN out of the
+  journal); `SentVia::parse`'s arms and `other:` prefix; `SendKind::parse`;
+  `last_sent`'s `max`.
+- [P4b S6] `kernel::settle`'s length check, each negative check, the
+  fee-above-cash test and both checked adds; `Ledger::settlement_lines`'s
+  kind/party checks, duplicate-document check, per-application `cash +
+  discount` bound, discount window (`<= max`, `<= by`, "has a reason"),
+  asset-bill loop, fee-on-bill refusal and row order (payment lines,
+  discounts, fee, cash); `check_discount`'s `within` conjunction and `because`
+  arms; `replay_*_payment_at`'s line/amount/account/side match and the discount
+  line's tag; `bills_due`'s `through` filter, discount-window test and
+  running-total grouping; `aging_documents`'s outstanding filter and bucket.
+- [P4b S7] `Ledger::write_off_steps`' cash-basis comparison
+  (`eq_ignore_ascii_case`, the early return), order of checks (amount before
+  the day, the day before the room), the `amount > room` bound and its `room <
+  owed` message arm, the `WriteOff` tag, `least_owed_from`'s `max` and its
+  `min` over later days (shared with `payment_room`),
+  `replay_invoice_write_off`'s movement, `doc_state`'s `written_off` arm.
+- [P4] `evidence::requirement`'s exemption arms (reversal, closing, schedule
+  month, depreciation run, disposal origin, payroll remittance origin, a
+  tagged document line, a payroll run) and their order, the split-group branch
+  taken only for a `Draft`, `Policy::reason_for`'s three comparisons (required
+  account, `<=` the threshold, every code exempt); `Ledger::origin_exemption`;
+  the replay arms that note `AssetDisposal` and `PayrollRemittance`;
+  `Ledger::discard_draft`'s empty-reason and posted refusals and the side
+  tables it clears; `set_draft_state`'s `check_text`; `stamp_unstamped` and
+  `expect_posted_seq` (a mutant that stamps the wrong line shows in
+  `posted_seq_is_the_posting_lines_seq`).
+- [P6] `ledger-core::evidence`: `checked`'s trims, the zero number, the
+  negative amount and the empty-annotation refusal; `next_receipt_number`'s
+  `saturating_add`.
+- [P7] `parties.rs` `tin_gap` (the space-run arm, so four spaces count once;
+  `count <= MAX_TIN_GAP`; the invisible skip; the `grouped` arm), `tin_space`,
+  `grouped_tin_separator` (each of `,`, `(` and `)`), `grouped_tin_runs` (each
+  shape, the `n > 0` join, the nine-digit check), `full_tin_runs`'s
+  `extend(grouped_tin_runs(..))`.
+- [P3 IIF] `form1099.rs`'s `through` bound; `parties.rs` `tin_separator`'s
+  arms and `tin_invisible`, and the gap that doesn't count them (with [P7]'s
+  scanner items above).
+- [P13] the bookspec loader's party, payee, decision and payment-method
+  setup; its exact-spelling filters; `check_k1`'s `cash_accounts` check;
+  `documented_tools` (its own sample checks it); `may_refuse` for write-offs.
+
+### ledger-store
+
+- [P2 slices 3 to 8] its 34 triaged survivors; slices 7 and 8 from scratch:
+  `backup.rs`, `root.rs`.
+- [P3 odd cents] `close_to_from_journal` and `close_period_to` (the tag
+  mapping; `since_seq`'s parse; a tag that isn't text; the feature
+  declaration); `format::declared_knowing`.
+- [P3 rename and defaults] `Store::{ensure_feature, ensure_features,
+  journal_settings (its feature), add_account, add_account_with_tax,
+  journal_account_added, ensure_control_account, rename_account,
+  set_account_tax, journal_account_tax}`, the `account.renamed` replay and
+  projection arms, `format::setting_feature`, `ops::report_columns`.
+- [P3 parties] `Store::{set_party_creditor, ensure_feature}`.
+- [P3 1099s] `form1099.rs` (each decode check, `newer_content`), `store.rs`
+  (`ensure_feature`, `set_vendor_1099`'s unchanged path, `set_vendor_w9_flag`,
+  `add_instrument`, `set_entry_instrument`'s no-op, the replay and projection
+  arms, `sqlite_reversal_chain`).
+- [P3 format upgrade] `format.rs` (`current`, `upgrade_to`, `adds`,
+  `require_format`, `require_feature`), `store.rs` (`create_in_format`,
+  `ensure_format`, `ensure_feature`, `upgrade_format`), `root.rs` (adoption's
+  upgrade and its verify), `backup.rs` (`prove_archive`, `held_files`).
+- [P3 asset basis] `asset_basis_from_journal` (newer vs corrupt); the
+  projection loader's two key sets.
+- [P3 projects] `project_set_of` (newer vs corrupt); `Store::add_project`'s
+  "facts beyond the default" test (one line vs two); `set_project`'s unchanged
+  short-cut; `subject_feature`.
+- [Documents take a project] `add_document_parts`' tag index.
+- [P4b S6] the `documents_v2` condition (more than one application, any
+  discount, a fee) and the `line`/`discount_line`/`fee_line` arithmetic.
+- [P4b S7] `Store::write_off_invoice`'s evidence arms (the `check_linkable`
+  call, the already-linked-to-the-invoice check, the blob-before-journal
+  order, the `File`/`Existing` link steps) and the feature gate.
+- [P6] `attach`'s live-record lookup and link arms, `extract_and_journal`'s
+  text/blob branch and status mapping, `extraction_for`'s triple (attachment,
+  extractor, version), `withdraw_attachment_as`'s `duplicate_of` arm and
+  feature check, the `verify` text-blob loop, the projection arms' conflict
+  keys.
+- [P8] `Store::figure_head` (the `NOT_FIGURES` list: a type wrongly in it
+  lets a stale audit stand, a type wrongly out of it makes an audit stale at
+  its own filing), `find_audit_run`'s four equalities, `record_audit_run`'s
+  idempotence return, `attest_receipt`'s amount rule (the debit total or any
+  one line) and date equality, `run_for_period`'s `through_seq == head` and
+  `through >= period.end`; `Integrity::check`'s intact-blob set and
+  `Store::disk_check`'s snapshot load and `Unreadable` arm [U0b].
+
+### ledger-import
+
+- [P3 IIF and as-of] `iif.rs` (each `breaks` arm, the control, quote and
+  `None` arms of `each_piece`, the deunicode post-mapping, `segment`'s colon,
+  trim, cut and "?" fallback, `tag`, `with_tag`'s room, the clash loop's depth
+  bound, rounds and tag, `journal_to_iif`'s clash and length refusals, the
+  number rules, the memo cut, each `changes` comparison and its order,
+  `warnings`' grouping, order and masks, `shown`, DOCNUM, `EOL`); `pdf.rs`'s
+  fallback font; `iif_accounts`' type filter on parents and `apart_from`,
+  `parents_first`, the `AtTopLevel` change, the TIN note's condition and
+  `receivable_payable`; `fonts.rs`.
+- [P3 cash flow] `report::cash_flow`.
+- [P6] `extract`: the caps' comparisons (`MAX_BYTES`, `MAX_PAGES`,
+  `MAX_TEXT_BYTES`, the `cap_text` boundary walk), `extract`'s order (PDF by
+  type or magic, XLSX by type or extension, then plain text), `found`'s
+  blank-text arm; `pdf_lines`' page `take`, baseline rounding and
+  left-to-right sort; `page_png`'s scale floor and page bounds; `xlsx_text`'s
+  shared-string index, the `t="s"`/`inlineStr`/`b` arms and the sheet-name
+  filter.
+
+### ledger-config
+
+- No unit recorded a target for this crate since its 2026-10-14 run (55 caught
+  of 55 viable); the run (`just mutants-config`) confirms it still holds.
+
+### ledger-mcp
+
+- [P2 slices 3 to 8] `local.rs` (45 survivors) and `server.rs` (31); slices 7
+  and 8 from scratch: `backup.rs`, `tools/backup.rs`, `local.rs`, `admin.rs`.
+- [P3 odd cents] the MCP's `close_period` and `list_periods` fields.
+- [P3 IIF and as-of] `server.rs` (the iif report, range and as_of checks,
+  `warnings`, the package note).
+- [P3 cash flow] `cash_flow_out`, `cash_flow_csv`, `export_cash_flow`,
+  `settings_problems`.
+- [P3 rename and defaults] `show` (the option refusals, the resolve, the
+  `shown` wording), `show_report_dates`, `rename_account` (its notes),
+  `add_account`, `import_chart_csv` (both loops), `profit_and_loss_by_class`'s
+  range, `export_journal`'s period, `described`, `uncategorized_warning`,
+  `created_uncategorized`, the digest's `uncategorized_accounts`,
+  `handbook::period_rule`.
+- [P3 parties] the server's `parse_basis`, `party_activity`,
+  `entry_parties_out` (direction, cash, in_kind) and `update_party`'s
+  creditor_of diff.
+- [P3 1099s] `tools/instruments.rs` (`decision_in`'s refusals,
+  `filed_year_warnings`' closed and due tests, `resolve_instrument`,
+  `add_instrument`'s warnings), `server.rs`'s `set_vendor_1099` (the W-9-only
+  path) and `set_w9` (the feature declared first, only when the flag changes).
+- [P3 parties and 1099s together] the server's `vendor_1099` (`through`'s
+  year check, the unknown-code check, the accounts passed) and `update_party`'s
+  feature declaration.
+- [P3 format upgrade] `backup.rs` (`upgrade_format`,
+  `UpgradeFailed::parts`), `local.rs` (`upgrade_format`, the List's
+  `format_upgrade`, `waiting`), `server.rs` (`with_store_mut`),
+  `tools/kept.rs` (the first next step, `format_upgrade`), `admin.rs`.
+- [P3 asset basis] the MCP `aliased` logic (both given and differing).
+- [P3 projects] the decision `projects` omit-when-empty; `late_tag_note`'s
+  `is_over`; `remember_footer`'s threshold.
+- [Documents take a project] `document_notes`' dedup and its `invoice` flag;
+  `on_spec_invoice_note`'s kind test; `document_line_json`'s `if let`.
+- [P4b S1 B] the server's `payment_details` (id or label resolution, an
+  unknown instrument refused); `payment_out` (as of the end of the books,
+  `remaining` from outstanding, `status` from `key()`); `doc_ref` (trim and
+  case, the two kinds, anything else refused); the `void_document` handler
+  (the status it answers, `map_or("void", ..)` after the day);
+  `control_check_out` (`agrees` as zero difference and no unattached line and
+  nothing needing attention, each field's mapping, the invoice/bill kind);
+  `control_problems` (one message per unattached line and per document, both
+  loops); the digest that includes it and the `verify` check that refuses a
+  nonzero difference.
+- [P4b S2] the `documents` handler's status arms (`"all"`; `"open"` as
+  `!st.outstanding.is_zero() && key != "void"`; `"overdue"` as
+  `st.overdue_days > 0`; `key == other`), the party compare, `due_by`'s `>`,
+  the `(due, id)` sort, the `outstanding_total` sum; the `document` handler's
+  `l.date <= as_of` timeline filter, `stands`/`reversal` from `stands_on`,
+  `movement_key`'s arms, `parse_doc_ref`'s split, parse and kind;
+  `DocStatus::key`'s arms.
+- [P4b S4.5] the handbook's `documents_v2_rule` both arms and the server's
+  `documents_v2` feature test.
+- [P4b S5] the handler's `kind` default (`original` when `sends` is empty,
+  `reminder` after), its `to` fallback (bill-to, then party, then refused) and
+  `by` fallback; `sent_via`'s arms and empty fallback; `send_kind`'s error
+  arm; `invoice_id`'s `invoice:` strip; the replay reader's `newer_content`
+  arms for an unknown channel or kind.
+- [P4b S6] `aging_csv`'s tie-out columns and `aging_statement`'s totals.
+- [P4b S7] the handler's amount default, exactly-one evidence check, and the
+  preview's clone.
+- [P6] `evidence`: `find_attachment`'s exactly-one selector, the hex check and
+  the text length floor; `consolidate_duplicates`' grouping (`< 2`), the
+  keep/dups split, the evidence `left == 0` gate, the keep `withdrawn` test,
+  the unlink dedup and the `withdrawn` count; the annotation amount/date parse
+  and the next number; `get_receipt`'s view arms, the 8 KiB cut, the 64 KiB
+  hand-over threshold and `page - 1`.
+- [P7] `tin_files::tin_shaped`'s comma in each rendering and
+  `holds_printed_tin`'s comma join; `access::masked`'s string arm. A deleted
+  arm leaves a TIN the old scanner passed readable or unmasked; the truth
+  table and the property catch it.
+- [P9a] `Isolation::parse`'s `same_user`/`advisory` and
+  `service_user`/`enforced` arms; `Isolation::label`'s two strings;
+  `start_out`'s `self.isolation.label()` (a mutant restoring a literal must
+  fail the two-door test); `local::tunnel_address`'s `is_loopback` test (must
+  fail `the_tunnel_door_binds_loopback_only`, in both halves); the `--http`
+  arm's `args.peek()` guard and default `127.0.0.1:7411`; `tunnel.is_some()`
+  and the bind failure path (ready after the try; a failed bind not fatal);
+  `open_with`'s `isolation` into `Served` and `BooksServer::new`'s copy (must
+  fail `isolation_label_is_enforced_under_the_unit`).
+- [P4] `Preview::operation` (the keys it drops: `confirmed`, `preview`,
+  nulls) and `Preview::check`'s three arms (missing, equal, different);
+  `post_entry`'s draft payload (each field); the digest's `since_seq`
+  comparison (`>`), its `as_of` bound, the `zero_net_accounts` branch and the
+  `never_reconciled` split; `report_status`'s three open conditions; the
+  open-drafts refusal's `<= as_of` and its decision.
+- [P5] `next_steps::apply`'s three branches (an error, a result without an
+  object, the normal path) and the `mutating` test that gives `head`;
+  `tool_steps`'s confirm branch (`!confirmed` and a `preview`), the
+  `receipt_missing` pair before it, each tool's arm; `attention_steps`'s
+  subject match (entry against invoice) and its `Problem` severity for
+  `required`; `subject_of`'s precedence; `guards::from_refusal`'s structured
+  and worded branches and `Guard::remedy_tool`'s table; `prompts::checked`'s
+  token test and each `Check` shape (month length and calendar, year length,
+  the word list); `prompt_get`'s extra-argument and missing-argument
+  refusals; `describe::subjects`'s per-prefix id choice, `describe`'s
+  `settings.set` key list and TIN mask, `history`'s `>` on `after_seq`, its
+  `limit` cut and `more`; `check_convention_source`'s three equalities,
+  `check_decision_source` and `check_open_item_source`'s equal-source and
+  empty-reason refusals; the three `apply_*_source` arms (a mutant that also
+  bumps `revision` or `seq` shows in `a_source_only_revision_is_journaled`);
+  `books.start`'s fit order and `reconciliation` split.
+- [P8] `audit::statements`' order of checks and `sort`; each `check_*`
+  predicate's comparison (`check_trial_balance`'s `balanced`,
+  `check_articulation`'s `!=`, `check_split`'s `> unit`, `check_register`'s two
+  conditions, `check_cash_flow`'s three arms, `check_control`'s `difference`,
+  unattached and `Overpaid` arms); `evidence`'s three arms (Required, the
+  reversal exemption and the policy test that lists it, the plain exemption)
+  and its receipt-set lookup; `closed_net`'s sign for revenue and expense;
+  `AttestationBar::counts` (each of the four conditions, `>=`, the `full`
+  branch, the `disagrees` early return) and `parse`; `Scope::full_bar` and
+  `serves_handoff`; `integrity_findings`'s eight arms; `backup_findings`'
+  three conditions; the export gate (`cpa_audit_standing`'s four conditions
+  and its feature test, the `refuse`/`warn` split, the reason's trim).
+- [P10] the `DEFECTS` table's file/name lookup (a `starts_with` on
+  `fn <name>(`; the `#[test]`/`#[ignore]` window of eight lines above it) and
+  the scopes-line scan in `defect_20_*`: a mutant that widens the window or
+  drops the `ignore` check survives only if no ignored or untested name is in
+  the table, so the table is the oracle.
+
+### ledger-package
+
+- [P3 IIF and as-of] `iif.rs` (`<=` in the as_of filter, the closes filter,
+  the FIXASSET date filter); `package.rs` (the cash and financing resolution,
+  the register's presence, the 1099 `through`, the README's IIF line, closes
+  sentence, warnings block and 1099 wording).
+- [P3 rename and defaults] `statement_range`, `as_of_date`, `pnl_statement`,
+  `bs_statement`, `cash_flow_statement`, `year_earnings`, `build_package`'s
+  fiscal year.
+- [P3 1099s] `vendor_1099.rs` (the CSV columns, every note's guard,
+  `may_file`, `missing_w9`'s suffix), `package.rs` (tin_gaps, the README line).
+- [P3 parties and 1099s together] `Settings::with_accounts` (each list's
+  fallback).
+- [P4b S4.5] `invoice::payment_methods` (the `qr` flag read, `link` appended
+  as a last line, the QR only when a link exists); `page_of`'s
+  snapshot-else-party choice for the bill-to, the contact, address, phone,
+  email order of the bill-to lines, the seller email's snapshot-else-company
+  fallback, the blank-footer filter; `invoice_document`'s stamp arms and
+  `InvoiceVersion::Current { as_of }`.
+- [P4b S3] `InvoiceStamp::text`'s five arms and `template_data`'s
+  `stamp_draft` test (`== Draft`); `invoice_document`'s stamp match (Void, then
+  Paid with `last_paid`, then `overdue_days > 0` before PartiallyPaid, then
+  none); the settled loop (`movement == Payment`, `!reversal`, `l.date >
+  as_of`, `!stands_on`, the negated amount, the method and " · ref " suffix
+  parsed back out of the description, `last_paid`); the re-created-copy branch
+  (`number: format!("Invoice {id}")`, `terms: None`, the `note` naming
+  `today`); `dollars`' sign handling and `format_amount`'s parenthesized
+  negatives; `template_data`'s no-lines refusal. Expect survivors in
+  `PartiallyPaid` (no sample is part paid and not yet due) and `Draft` (only
+  S4's preview reaches it) until a test asserts them.
+- [P4b S4.5] `invoice_pdf::dollars` (the negative arm) and `unit_price`
+  (`scale() <= 2`, the exact arm), `quantity_detail`'s both-or-neither match,
+  `note_text`'s three arms (re-created, both, note only).
+- [P4b S5] attention: `invoice.number.is_some()` (the legacy exemption),
+  `Open | Partial`, `sends.is_empty()`, the `checked_add_days` `unsent_days`
+  comparison (`>`), `overdue_days > 0`, the `sends.max()` last send, the
+  `reminder_days` comparison (`>`), each item's target (`Target::Invoice`) and
+  its `books.mark_sent` step args.
+- [P6] attention: the extraction `seq` comparison and the `Failed` filter, the
+  owed-account name test, the credit side and the `settles_entry` skip.
+- [U0b] `attention`: `origin`'s arm order (a reversal before its schedule, a
+  bill before its payment) and `entry_refs`' keys; `missing_receipt`'s
+  conjunction (the `Journal entry | Recurring` origin, `reversal_of` none, no
+  receipts, the policy); the `> 3` combine and its `try_fold`; `w9_missing`'s
+  three clauses (no W-9, files a 1099, the vendor not marked on file) and
+  `files_1099`'s `any`; `paid_this_year`'s `max` (today) and `min` (Dec 31) and
+  its `paid - received`; `depreciation_due`'s `in_effect` filter,
+  `period_month` (`1..=12`) and `!is_zero`; `period_month`'s split; the
+  severity arms (undetermined 1099, refuse tax category, parties require);
+  `dollars`' thousands grouping and negative-zero test.
+
+### ledger-host
+
+- [P2 slices 3 to 8] pass 2; `commands.rs`.
+- [P3 format upgrade] `host.rs` (`consent`, `consented`), `commands.rs`
+  (`consent_now`, `upgrade_format`, `offer_upgrades`, `offer_upgrade`,
+  `upgrade`, `book_line`, `upgraded_lines`, `upgrade_explained`,
+  `ASKED_UPGRADES`).
+- [P9a] the host's `server_flags` extension and `parse_args`' passthrough of
+  `--isolation` and its optional `--http` value.
+- [P11a step 0] `tokens.rs`'s `os` modules are not reachable by mutation
+  testing (they need the real OS store); the `Items` logic they share is,
+  through the file store.
+- [U0e] `tokens.rs`'s `Keeper::set` (the temporary file's mode and the
+  rename: a mutant that writes the final file directly or wider must die on
+  `a_token_file_is_owner_only`), `Keeper::get`'s `NotFound` arm (must die on
+  `an_unreadable_token_file_is_an_error_never_no_token`), `Keeper::delete`'s
+  `NotFound` arm, `Account::key`'s three parts
+  (`an_account_names_the_root_by_hash_and_the_book_and_token`);
+  `bridge.rs::token_file_refusal`'s `holds_token` guard.
+- [P11c] `winsec::is_private`'s three refusals (owner, missing DACL, an allow
+  entry for anyone else) and the ACE types it skips; `ipc::Endpoint::new`'s
+  hash input (a mutant that drops the lower-casing or the prefix strip splits
+  one root into two pipes: found only by two processes spelling the path
+  differently); the Windows `StdStream::read_some`'s deadline comparison and
+  `BROKEN_PIPE` arm; `Listener`'s `IDLE_INSTANCES` pool (a mutant making it 1
+  passes every test but `many_clients_at_once_all_connect`);
+  `start.rs::host_env`'s list. None of the Windows arms is reachable by
+  `cargo mutants` on Linux: they run on the Windows job only.
+- [P11a steps 2 and 3] `update.rs`'s `verify` (a mutant that drops the sha or
+  signature check must die on `unsigned_update_refused`'s sha and key cases),
+  `refuse_if_consented`'s two comparisons (the feature one is covered by
+  `rollback_refuses_after_a_book_consented_to_a_newer_format`; a case with a
+  higher format number is a gap to add), `swap_in`'s temporary-then-rename
+  (`update_is_atomic`), `healthy` (`failed_update_rolls_back`),
+  `install_kind` (the marker test), `parse_version`'s rejections.
+- [P11b] `commands::make_books_home_in` (the `!path.exists()` test that keeps
+  a person's `AGENTS.md`; the merge that dedupes the allow rule;
+  `BookId::parse` before any path is joined); `find_agent_in` (the order PATH
+  then the installer folders; `is_program`'s mode test); `start_agent_in` (the
+  `Missing` arm); `first_run_state`'s three fields; `set_first_passphrase`'s
+  already-set refusal.
+
+### ledger-vault
+
+- No target of its own was recorded by any unit. The recipe `mutants-vault`
+  runs the crate's `tests/vault.rs` and the `ledger-cli` suites that reach the
+  vault (`spec_vault.rs`, `tin_files.rs`); whatever survives is judged in the
+  run.
+
+### ledger-cli
+
+- [P2 slices 3 to 8] `ledger-cli` from scratch (the argument handling, the
+  server and bridge modes). The run is `just mutants-cli`.
+- [P9a] the `--isolation` and `--http` flags as the executable passes them on.
+
+### Not mutated
+
+- [P11b] `ledger-gui`: `dock::key_bytes` (the modifier parameter's arithmetic,
+  the Ctrl-letter byte, the app-cursor switch, the Alt escape), `dock::color`'s
+  cube and gray ramps and its bold brightening, `Session::resize`'s equality
+  early return, the panel's open/closed ids (a remembered size must not leak
+  between them), `Welcome::steps`' choice of `now` (each arm), the passphrase
+  length and equality gates, the `agent_later` flag. The viewer has no
+  mutation run (owner, 2026-10-18); these are for the viewer's own tests.
+- [P3 rename and defaults, P3 1099s, P3 IIF, P4b S2 to S4.5, P7] the viewer
+  items (`view_model.rs`, `show.rs`, `owed_to_member`, `party_what_for`,
+  `share_text`, `Filter::keeps` and its sorts and labels, `document_of`,
+  `details`, `invoice_name`, `issued_copy`, `viewer discount_by` and
+  `days_overdue`, `menu.rs`'s note, `theme.rs` `font_definitions`): covered by
+  `view_model.rs`, `show.rs` and `read_only.rs`, not mutated.
+
+### bookspec (its own repository since P13 step 6)
+
+- [P13] `rules::build`'s area ordinals; `RuleId::parse`'s prefix, area,
+  digit, leading-zero and zero checks; `rule_for_refusal`'s mapping arms;
+  `schema::is_exact_decimal`, `is_date`, `is_month`, `is_month_day`,
+  `check_amount`'s positivity; `Example::validate`'s closed-list arms, the
+  one-kind rule, `reverses < n`, shares summing to 1, `after` bounds, the
+  command's accepted-or-refused exclusivity, the `only` table;
+  `Query::is_complete`'s membership; `Refusal::of_reason`'s fallback; the
+  runner's `compare`, `Outcome`'s mapping and `run`'s "claimed but no example"
+  arm; the adapter's `event_of`, its `depreciation_schedule` month span and
+  every `answer_*` figure against the loader's same check (the two must agree
+  on all examples).
+- [P13 steps 4 and 5] the adapter's `refusal` arms (`UnbalancedEntry`,
+  `NegativeAmountLine`, `ZeroAmountLine`, `FinerThanMinorUnit`,
+  `ParentTypeMismatch`, `EntryAlreadyReversed`, `ClosedPeriod`), each pinned by
+  the example that expects it, and the `money` closure's positivity test;
+  `rule_for_refusal`'s new arms; `check_amount`'s `positive` flag; `derive`'s
+  `refusal_justified` arms, `Model::post`'s close, `signed`'s date window and
+  `closings` flag, the accounting-equation check; the spec test's pin search.

fuzz/Cargo.toml

@@ -24,6 +24,10 @@ path = "../crates/ledger-store"
 [dependencies.ledger-import]
 path = "../crates/ledger-import"
 
+[dependencies.ledger-mcp]
+path = "../crates/ledger-mcp"
+features = ["fuzzing"]
+
 [dependencies.ledger-config]
 path = "../crates/ledger-config"
 
@@ -105,3 +109,17 @@ path = "fuzz_targets/fuzz_settings_replay.rs"
 test = false
 doc = false
 bench = false
+
+[[bin]]
+name = "fuzz_http_mcp_request"
+path = "fuzz_targets/fuzz_http_mcp_request.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "fuzz_upload_put"
+path = "fuzz_targets/fuzz_upload_put.rs"
+test = false
+doc = false
+bench = false

fuzz/fuzz_targets/fuzz_http_mcp_request.rs

@@ -0,0 +1,169 @@
+// Fuzz target: the books server's HTTP door takes arbitrary requests.
+// Method, path, headers and body are all untrusted; the door is the very
+// router the server mounts (ledger-mcp local.rs `router`), in-process over a
+// real book, with no socket (`fuzz_door`). Whatever arrives: the door
+// answers (no panic, no hang), and a request that carries no token live
+// for the book is refused 4xx and never run (INVARIANT 8, local.rs); one
+// that carries it never makes the door fail (no 5xx on the MCP route).
+#![no_main]
+
+use arbitrary::Arbitrary;
+use ledger_mcp::local::fuzz_door::FuzzDoor;
+use libfuzzer_sys::fuzz_target;
+use std::cell::RefCell;
+
+#[derive(Arbitrary, Debug)]
+enum Auth {
+    None,
+    Valid,
+    Other,
+    /// `Authorization` with whatever text.
+    Raw(Vec<u8>),
+}
+
+#[derive(Arbitrary, Debug)]
+enum Body {
+    Raw(Vec<u8>),
+    /// A JSON-RPC message the server could understand.
+    Rpc {
+        method: u8,
+        id: u8,
+        params: String,
+    },
+    /// `tools/call` of a name picked from a few real ones, arguments as text.
+    Call {
+        tool: u8,
+        arguments: String,
+    },
+}
+
+#[derive(Arbitrary, Debug)]
+struct Request {
+    method: Vec<u8>,
+    verb: u8,
+    route: u8,
+    book: u8,
+    suffix: String,
+    auth: Auth,
+    session: Option<String>,
+    content_type: u8,
+    accept: bool,
+    extra: Vec<(Vec<u8>, Vec<u8>)>,
+    body: Body,
+}
+
+const METHODS: [&str; 6] = ["POST", "GET", "DELETE", "PUT", "OPTIONS", "PATCH"];
+const RPC: [&str; 8] = [
+    "initialize",
+    "notifications/initialized",
+    "tools/list",
+    "ping",
+    "resources/list",
+    "prompts/list",
+    "tools/call",
+    "logging/setLevel",
+];
+const TOOLS: [&str; 6] = [
+    "books.start",
+    "books.trial_balance",
+    "books.draft_entry",
+    "books.begin_upload",
+    "books.settings",
+    "books.handbook",
+];
+
+thread_local! {
+    /// The door, and how many requests it has had: a fresh book every so
+    /// often, because sessions and the access log only grow.
+    static DOOR: RefCell<Option<(FuzzDoor, u32)>> = const { RefCell::new(None) };
+}
+
+fn clean(s: &str) -> String {
+    s.chars()
+        .filter(|c| c.is_ascii_alphanumeric() || "-_.".contains(*c))
+        .take(40)
+        .collect()
+}
+
+fuzz_target!(|r: Request| {
+    DOOR.with(|cell| {
+        let mut cell = cell.borrow_mut();
+        if cell.as_ref().is_none_or(|(d, n)| *n > 3000 || d.sessions() > 500) {
+            *cell = Some((FuzzDoor::new(), 0));
+        }
+        let (door, n) = cell.as_mut().unwrap();
+        *n += 1;
+
+        let method: Vec<u8> = if r.verb % 4 == 0 {
+            r.method.clone()
+        } else {
+            METHODS[r.verb as usize % METHODS.len()].as_bytes().to_vec()
+        };
+        let book = match r.book % 4 {
+            0 | 1 => "acme".to_string(),
+            2 => "nobody".to_string(),
+            _ => clean(&r.suffix),
+        };
+        let path = match r.route % 6 {
+            0..=2 => format!("/b/{book}/mcp"),
+            3 => format!("/b/{book}/u/{}", clean(&r.suffix)),
+            4 => format!("/b/{book}/a/{}", clean(&r.suffix)),
+            _ => format!("/b/{book}/x/{}", clean(&r.suffix)),
+        };
+        let mut headers: Vec<(Vec<u8>, Vec<u8>)> = Vec::new();
+        match &r.auth {
+            Auth::None => {}
+            Auth::Valid => {
+                headers.push((b"authorization".to_vec(), format!("Bearer {}", door.bearer()).into_bytes()));
+            }
+            Auth::Other => {
+                headers.push((b"authorization".to_vec(), format!("Bearer {}x", door.other_bearer()).into_bytes()));
+            }
+            Auth::Raw(v) => {
+                headers.push((b"authorization".to_vec(), v.clone()));
+            }
+        }
+        if let Some(s) = &r.session {
+            headers.push((b"mcp-session-id".to_vec(), clean(s).into_bytes()));
+        }
+        headers.push((
+            b"content-type".to_vec(),
+            ["application/json", "text/plain", "application/octet-stream", ""][r.content_type as usize % 4]
+                .as_bytes()
+                .to_vec(),
+        ));
+        if r.accept {
+            headers.push((b"accept".to_vec(), b"application/json, text/event-stream".to_vec()));
+        }
+        headers.extend(r.extra.iter().take(4).cloned());
+        // The door's own rule, asked directly: any header (the authorization
+        // one, or a smuggled extra) can carry a token live for the book.
+        let live = door.carries_a_token(&headers);
+        let body = match &r.body {
+            Body::Raw(b) => b.clone(),
+            Body::Rpc { method, id, params } => {
+                let params = serde_json::from_str::<serde_json::Value>(params).unwrap_or_default();
+                serde_json::json!({"jsonrpc": "2.0", "id": id, "method": RPC[*method as usize % RPC.len()], "params": params})
+                    .to_string()
+                    .into_bytes()
+            }
+            Body::Call { tool, arguments } => {
+                let args = serde_json::from_str::<serde_json::Value>(arguments).unwrap_or_default();
+                serde_json::json!({"jsonrpc": "2.0", "id": 1, "method": "tools/call",
+                    "params": {"name": TOOLS[*tool as usize % TOOLS.len()], "arguments": args}})
+                .to_string()
+                .into_bytes()
+            }
+        };
+
+        let Some((status, _)) = door.send(&method, &path, &headers, body) else {
+            return; // not an HTTP request at all
+        };
+        if !live && book == "acme" && path.ends_with("/mcp") {
+            assert!((400..500).contains(&status), "no token, yet {status} for {path}");
+        }
+        if live && path.ends_with("/mcp") && book == "acme" {
+            assert!(status < 500, "a valid token made the door fail: {status}");
+        }
+    });
+});

fuzz/fuzz_targets/fuzz_op_sequence.rs

@@ -2,27 +2,112 @@
 // balanced pairs, foreign-currency lines, periods, and closes, with
 // amounts built from raw decimal bits (huge, tiny, odd scales). Refusals
 // are fine; panics, hangs, and broken books are not. After any sequence:
-// the trial balance balances, every posted entry validates, and no draft
-// sits in a closed period (the Lean invariant Inv).
+// the trial balance balances, every posted entry validates, no draft sits
+// in a closed period (the Lean invariant Inv), and the control accounts
+// equal their documents (control_check's difference is zero, B-38).
+//
+// The documents (invoices, bills), their settlements and payments, write-offs
+// and voids, and the draft-state ops (P12) run on the Ledger the store wraps:
+// the store adds the journal, the engine is the state machine fuzzed here.
 #![no_main]
 
 use arbitrary::Arbitrary;
 use chrono::NaiveDate;
-use ledger_core::{AccountType, Currency, EntryStatus, Ledger, Money, Side};
+use ledger_core::arap::{DocRef, DocumentLine};
+use ledger_core::{
+    AccountType, Application, Currency, DraftState, EntryStatus, Ledger, Money, PaymentDetails,
+    SettleParams, Side,
+};
 use libfuzzer_sys::fuzz_target;
 use rust_decimal::Decimal;
 
 #[derive(Arbitrary, Debug, Clone, Copy)]
 enum Op {
-    AddAccount { code: u8, typ: u8, placeholder: bool },
-    CreateEntry { day: u8 },
-    AddLine { entry: u8, account: u8, debit: bool, amount: Amount },
-    Pair { entry: u8, debit: u8, credit: u8, amount: Amount },
-    AddLineFx { entry: u8, account: u8, debit: bool, foreign: Amount, rate: Amount },
-    PostEntry { entry: u8 },
-    ReverseEntry { entry: u8, day: u8 },
-    CreatePeriod { start: u8, len: u8 },
-    ClosePeriod { period: u8 },
+    AddAccount {
+        code: u8,
+        typ: u8,
+        placeholder: bool,
+    },
+    CreateEntry {
+        day: u8,
+    },
+    AddLine {
+        entry: u8,
+        account: u8,
+        debit: bool,
+        amount: Amount,
+    },
+    Pair {
+        entry: u8,
+        debit: u8,
+        credit: u8,
+        amount: Amount,
+    },
+    AddLineFx {
+        entry: u8,
+        account: u8,
+        debit: bool,
+        foreign: Amount,
+        rate: Amount,
+    },
+    PostEntry {
+        entry: u8,
+    },
+    ReverseEntry {
+        entry: u8,
+        day: u8,
+    },
+    CreatePeriod {
+        start: u8,
+        len: u8,
+    },
+    ClosePeriod {
+        period: u8,
+    },
+    CreateInvoice {
+        day: u8,
+        terms: u8,
+        amount: Amount,
+    },
+    CreateBill {
+        day: u8,
+        terms: u8,
+        amount: Amount,
+    },
+    /// A payment on a document (mod the documents) from the bank or a
+    /// fuzzed account, with a reference or not.
+    Pay {
+        doc: u8,
+        day: u8,
+        amount: Amount,
+        from: u8,
+        reference: bool,
+    },
+    /// One payment settling two documents, the first with a discount.
+    Settle {
+        a: u8,
+        b: u8,
+        day: u8,
+        cash: Amount,
+        discount: Amount,
+    },
+    WriteOff {
+        doc: u8,
+        day: u8,
+        amount: Amount,
+    },
+    VoidDocument {
+        doc: u8,
+        day: u8,
+    },
+    SetDraftState {
+        entry: u8,
+        awaiting: bool,
+        note: u8,
+    },
+    DiscardDraft {
+        entry: u8,
+    },
 }
 
 /// A decimal from raw parts: any mantissa up to 96 bits, any scale 0-28.
@@ -42,7 +127,13 @@ impl Amount {
             // Mostly ordinary money, so entries balance and post.
             return Decimal::new(i64::from(self.lo % 1_000_000), 2);
         }
-        Decimal::from_parts(self.lo, self.mid, self.hi, self.negative, u32::from(self.scale % 29))
+        Decimal::from_parts(
+            self.lo,
+            self.mid,
+            self.hi,
+            self.negative,
+            u32::from(self.scale % 29),
+        )
     }
 }
 
@@ -63,34 +154,85 @@ fn day(d: u8) -> NaiveDate {
 fuzz_target!(|ops: Vec<Op>| {
     let mut l = Ledger::new(Currency::USD);
     let mut entries: Vec<u64> = Vec::new();
+    let mut docs: Vec<DocRef> = Vec::new();
+    // The books' fixed parts: the control accounts documents post to, a bank,
+    // a customer and a vendor.
+    let _ = (
+        l.add_control_account(&ledger_core::RECEIVABLES),
+        l.add_control_account(&ledger_core::PAYABLES),
+        l.add_control_account(&ledger_core::BAD_DEBTS),
+    );
+    let bank = l
+        .add_account("1900", "Bank", AccountType::Asset, None, false)
+        .ok();
+    let customer = l.add_customer("Fernhill Labs").ok();
+    let vendor = l.add_vendor("Tobin Harlow Supply").ok();
+    let doc_line = |a: Amount| {
+        vec![DocumentLine {
+            description: "work".into(),
+            amount: a.get(),
+            class_id: None,
+            account: None,
+            quantity: None,
+            unit_price: None,
+        }]
+    };
     let pick = |v: &[u64], i: u8| v.get(i as usize % v.len().max(1)).copied();
     for op in ops.into_iter().take(200) {
         let accounts: Vec<u64> = l.chart().all().map(|a| a.id).collect();
         match op {
-            Op::AddAccount { code, typ, placeholder } => {
-                let _ = l.add_account(&format!("{}", 1000 + u32::from(code % 40)), "f", account_type(typ), None, placeholder);
+            Op::AddAccount {
+                code,
+                typ,
+                placeholder,
+            } => {
+                let _ = l.add_account(
+                    &format!("{}", 1000 + u32::from(code % 40)),
+                    "f",
+                    account_type(typ),
+                    None,
+                    placeholder,
+                );
             }
             Op::CreateEntry { day: d } => {
                 if let Ok(id) = l.try_create_entry(day(d), "f") {
                     entries.push(id);
                 }
             }
-            Op::AddLine { entry, account, debit, amount } => {
+            Op::AddLine {
+                entry,
+                account,
+                debit,
+                amount,
+            } => {
                 if let (Some(e), Some(a)) = (pick(&entries, entry), pick(&accounts, account)) {
                     let side = if debit { Side::Debit } else { Side::Credit };
                     let _ = l.add_line(e, a, side, Money::new(amount.get(), Currency::USD));
                 }
             }
-            Op::Pair { entry, debit, credit, amount } => {
-                if let (Some(e), Some(a), Some(b)) =
-                    (pick(&entries, entry), pick(&accounts, debit), pick(&accounts, credit))
-                {
+            Op::Pair {
+                entry,
+                debit,
+                credit,
+                amount,
+            } => {
+                if let (Some(e), Some(a), Some(b)) = (
+                    pick(&entries, entry),
+                    pick(&accounts, debit),
+                    pick(&accounts, credit),
+                ) {
                     let m = Money::new(amount.get(), Currency::USD);
                     let _ = l.add_line(e, a, Side::Debit, m);
                     let _ = l.add_line(e, b, Side::Credit, m);
                 }
             }
-            Op::AddLineFx { entry, account, debit, foreign, rate } => {
+            Op::AddLineFx {
+                entry,
+                account,
+                debit,
+                foreign,
+                rate,
+            } => {
                 if let (Some(e), Some(a)) = (pick(&entries, entry), pick(&accounts, account)) {
                     let side = if debit { Side::Debit } else { Side::Credit };
                     let _ = l.add_line_fx(e, a, side, Currency::EUR, foreign.get(), rate.get());
@@ -111,6 +253,147 @@ fuzz_target!(|ops: Vec<Op>| {
             Op::CreatePeriod { start, len } => {
                 let _ = l.create_period("p", day(start), day(start.saturating_add(len % 60)));
             }
+            Op::CreateInvoice {
+                day: d,
+                terms,
+                amount,
+            } => {
+                if let Some(c) = customer
+                    && let Ok(id) = l.create_invoice_with(
+                        c,
+                        day(d),
+                        day(d) + chrono::Days::new(u64::from(terms)),
+                        doc_line(amount),
+                        Default::default(),
+                    )
+                {
+                    docs.push(DocRef::Invoice(id));
+                }
+            }
+            Op::CreateBill {
+                day: d,
+                terms,
+                amount,
+            } => {
+                if let Some(v) = vendor
+                    && let Ok(id) = l.create_bill_with(
+                        v,
+                        day(d),
+                        day(d) + chrono::Days::new(u64::from(terms)),
+                        doc_line(amount),
+                        Default::default(),
+                    )
+                {
+                    docs.push(DocRef::Bill(id));
+                }
+            }
+            Op::Pay {
+                doc,
+                day: d,
+                amount,
+                from,
+                reference,
+            } => {
+                if !docs.is_empty() {
+                    let cash = if from % 4 == 0 {
+                        pick(&accounts, from)
+                    } else {
+                        bank
+                    };
+                    let details = PaymentDetails {
+                        instrument: None,
+                        reference: reference.then(|| format!("trace {doc}{d}")),
+                    };
+                    if let Some(cash) = cash {
+                        let _ = match docs[doc as usize % docs.len()] {
+                            DocRef::Invoice(id) => {
+                                l.receive_payment_with(id, day(d), amount.get(), cash, &details)
+                            }
+                            DocRef::Bill(id) => {
+                                l.pay_bill_with(id, day(d), amount.get(), cash, &details)
+                            }
+                        };
+                    }
+                }
+            }
+            Op::Settle {
+                a,
+                b,
+                day: d,
+                cash,
+                discount,
+            } => {
+                if let (false, Some(cash_account)) = (docs.is_empty(), bank) {
+                    let first = docs[a as usize % docs.len()];
+                    let second = docs[b as usize % docs.len()];
+                    let party = match first {
+                        DocRef::Invoice(id) => l.get_invoice(id).map(|i| i.customer_id),
+                        DocRef::Bill(id) => l.get_bill(id).map(|v| v.vendor_id),
+                    };
+                    if let Some(party) = party {
+                        let _ = l.settle(SettleParams {
+                            date: day(d),
+                            description: "two documents, one payment".into(),
+                            cash_account,
+                            party,
+                            applications: vec![
+                                Application {
+                                    doc: first,
+                                    cash: cash.get(),
+                                    discount: discount.get(),
+                                    discount_reason: Some("fuzz".into()),
+                                },
+                                Application {
+                                    doc: second,
+                                    cash: cash.get(),
+                                    discount: Decimal::ZERO,
+                                    discount_reason: None,
+                                },
+                            ],
+                            fee: None,
+                            instrument: None,
+                            reference: None,
+                        });
+                    }
+                }
+            }
+            Op::WriteOff {
+                doc,
+                day: d,
+                amount,
+            } => {
+                if !docs.is_empty()
+                    && let DocRef::Invoice(id) = docs[doc as usize % docs.len()]
+                {
+                    let _ = l.write_off(id, day(d), amount.get(), "uncollectible");
+                }
+            }
+            Op::VoidDocument { doc, day: d } => {
+                if !docs.is_empty() {
+                    let _ = l.void_document(docs[doc as usize % docs.len()], day(d), "duplicate");
+                }
+            }
+            Op::SetDraftState {
+                entry,
+                awaiting,
+                note,
+            } => {
+                if let Some(e) = pick(&entries, entry) {
+                    let state = if awaiting {
+                        DraftState::AwaitingEvidence {
+                            note: format!("receipt {note}"),
+                        }
+                    } else {
+                        DraftState::Building
+                    };
+                    let _ = l.set_draft_state(e, state);
+                }
+            }
+            Op::DiscardDraft { entry } => {
+                if let Some(e) = pick(&entries, entry) {
+                    let _ = l.discard_draft(e, "fuzz");
+                }
+            }
             Op::ClosePeriod { period } => {
                 let ids: Vec<u64> = l.list_periods().iter().map(|p| p.id).collect();
                 if let Some(p) = pick(&ids, period) {
@@ -122,13 +405,34 @@ fuzz_target!(|ops: Vec<Op>| {
     let tb = ledger_core::reports::trial_balance(&l);
     assert_eq!(tb.total_debits, tb.total_credits, "trial balance broken");
     for e in l.posted_entries() {
-        assert!(e.validate(l.chart()).is_ok(), "posted entry {} invalid", e.id());
+        assert!(
+            e.validate(l.chart()).is_ok(),
+            "posted entry {} invalid",
+            e.id()
+        );
+    }
+    // The control accounts equal their documents, at any day (B-38): too
+    // large to compute is a refusal, never a difference.
+    for d in [0u8, 60, 199] {
+        if let Ok(checks) = l.control_check(day(d)) {
+            for c in checks {
+                assert_eq!(
+                    c.difference,
+                    Decimal::ZERO,
+                    "{} differs from its documents",
+                    c.role
+                );
+            }
+        }
     }
     for id in 1..l.next_entry_id() {
         if let Some(e) = l.get_entry(id)
             && e.status() == EntryStatus::Draft
         {
-            assert!(l.closed_period_containing(e.date()).is_none(), "draft in a closed period");
+            assert!(
+                l.closed_period_containing(e.date()).is_none(),
+                "draft in a closed period"
+            );
         }
     }
 });

fuzz/fuzz_targets/fuzz_upload_put.rs

@@ -0,0 +1,130 @@
+// Fuzz target: a file's bytes come in only by `PUT /b/{book}/u/{upload}`
+// (ledger-mcp local.rs INVARIANT 9), through the same in-process router as
+// fuzz_http_mcp_request. The body, the declared size and hash, the upload
+// id and the token are all arbitrary. Whatever arrives: the door answers,
+// and bytes are taken only if they are exactly the declared ones, from the
+// token the upload was granted to, once: a 200 for anything else is a bug.
+#![no_main]
+
+use arbitrary::Arbitrary;
+use ledger_mcp::local::fuzz_door::FuzzDoor;
+use libfuzzer_sys::fuzz_target;
+use std::cell::RefCell;
+
+#[derive(Arbitrary, Debug)]
+enum Declared {
+    Honest,
+    /// The size off by this much (never 0).
+    SizeOff(i8),
+    /// The hash of other bytes.
+    HashOf(Vec<u8>),
+    /// A hash that is not 64 hex digits.
+    BadHash(String),
+}
+
+#[derive(Arbitrary, Debug)]
+enum Who {
+    Owner,
+    Other,
+    Nobody,
+}
+
+#[derive(Arbitrary, Debug)]
+struct Put {
+    body: Vec<u8>,
+    declared: Declared,
+    who: Who,
+    /// Use an id that was never granted (this text, cleaned).
+    unknown_id: Option<String>,
+    /// Send it a second time too.
+    again: bool,
+    /// And a body of another length the second time.
+    second: Vec<u8>,
+}
+
+thread_local! {
+    static DOOR: RefCell<Option<(FuzzDoor, u32)>> = const { RefCell::new(None) };
+}
+
+fuzz_target!(|p: Put| {
+    DOOR.with(|cell| {
+        let mut cell = cell.borrow_mut();
+        if cell.as_ref().is_none_or(|(_, n)| *n > 1500) {
+            *cell = Some((FuzzDoor::new(), 0));
+        }
+        let (door, n) = cell.as_mut().unwrap();
+        *n += 1;
+
+        let sha = ledger_store::journal::sha256_hex(&p.body);
+        let (grant_sha, grant_size) = match &p.declared {
+            Declared::Honest => (sha.clone(), p.body.len() as u64),
+            Declared::SizeOff(d) => {
+                let d = if *d == 0 { 1 } else { i64::from(*d) };
+                (sha.clone(), (p.body.len() as i64 + d).max(0) as u64)
+            }
+            Declared::HashOf(other) => (
+                ledger_store::journal::sha256_hex(other),
+                p.body.len() as u64,
+            ),
+            Declared::BadHash(s) => (s.clone(), p.body.len() as u64),
+        };
+        let size_ok = grant_size == p.body.len() as u64 && grant_sha == sha;
+
+        let granted = door.grant(&grant_sha, grant_size);
+        let id = match (&p.unknown_id, &granted) {
+            (Some(s), _) => {
+                let s: String = s
+                    .chars()
+                    .filter(|c| c.is_ascii_alphanumeric() || *c == '_')
+                    .take(40)
+                    .collect();
+                if s.is_empty() { "up_x".to_string() } else { s }
+            }
+            (None, Ok(id)) => id.clone(),
+            (None, Err(_)) => "up_none".to_string(),
+        };
+        let real = p.unknown_id.is_none() && granted.is_ok();
+        let bearer = match p.who {
+            Who::Owner => Some(door.bearer().to_string()),
+            Who::Other => Some(door.other_bearer().to_string()),
+            Who::Nobody => None,
+        };
+        let mut headers = Vec::new();
+        if let Some(b) = &bearer {
+            headers.push((
+                b"authorization".to_vec(),
+                format!("Bearer {b}").into_bytes(),
+            ));
+        }
+        let path = format!("/b/acme/u/{id}");
+        let Some((status, text)) = door.send(b"PUT", &path, &headers, p.body.clone()) else {
+            return;
+        };
+        let may_succeed = real && matches!(p.who, Who::Owner) && size_ok;
+        if status == 200 {
+            assert!(
+                may_succeed,
+                "bytes taken that should not be: {:?} {:?}",
+                p.who, p.declared
+            );
+            let said = String::from_utf8_lossy(&text);
+            assert!(
+                said.contains(&sha),
+                "the answer doesn't name the bytes' hash: {said}"
+            );
+        } else if may_succeed {
+            // Everything lined up: the only way not to be taken is a
+            // failure of the door itself.
+            panic!(
+                "honest upload by its owner refused: {status} {}",
+                String::from_utf8_lossy(&text)
+            );
+        }
+        if status == 200 && p.again {
+            let Some((again, _)) = door.send(b"PUT", &path, &headers, p.second.clone()) else {
+                return;
+            };
+            assert_ne!(again, 200, "an upload taken twice");
+        }
+    });
+});

justfile

@@ -209,6 +209,38 @@ mutants-mcp shard="0/1": sweep-test-tmp
     MCP_CASES=16 PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-mcp --test-package ledger-mcp --test-package ledger-cli --no-default-features -j 4 --timeout-multiplier 3 --minimum-test-timeout 600 --shard {{shard}} -o mutants-mcp
     @just sweep-test-tmp
 
+# Mutation testing of the host (the books home, the lease, the update channel, the bridge): every mutant runs its own tests and the
+# suites that drive a real books server (ledger-cli's, D-44), built without
+# the viewer, as for the MCP server. A local run, never CI (D-59).
+mutants-host shard="0/1": sweep-test-tmp
+    mkdir -p {{mutants_tmp}}
+    PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-host --test-package ledger-host --test-package ledger-cli --no-default-features -j 4 --timeout-multiplier 3 --minimum-test-timeout 300 --shard {{shard}} -o mutants-host
+    @just sweep-test-tmp
+
+# Mutation testing of the CPA package and the 1099 worksheet: every mutant runs its own tests and the
+# suites that drive a real books server (ledger-cli's, D-44), built without
+# the viewer, as for the MCP server. A local run, never CI (D-59).
+mutants-package shard="0/1": sweep-test-tmp
+    mkdir -p {{mutants_tmp}}
+    PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-package --test-package ledger-package --test-package ledger-cli --no-default-features -j 4 --timeout-multiplier 3 --minimum-test-timeout 300 --shard {{shard}} -o mutants-package
+    @just sweep-test-tmp
+
+# Mutation testing of the TIN vault: every mutant runs its own tests and the
+# suites that drive a real books server (ledger-cli's, D-44), built without
+# the viewer, as for the MCP server. A local run, never CI (D-59).
+mutants-vault shard="0/1": sweep-test-tmp
+    mkdir -p {{mutants_tmp}}
+    PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-vault --test-package ledger-vault --test-package ledger-cli --no-default-features -j 4 --timeout-multiplier 3 --minimum-test-timeout 120 --shard {{shard}} -o mutants-vault
+    @just sweep-test-tmp
+
+# Mutation testing of the one executable (its argument handling, the server and bridge modes): every mutant runs its own tests and the
+# suites that drive a real books server (ledger-cli's, D-44), built without
+# the viewer, as for the MCP server. A local run, never CI (D-59).
+mutants-cli shard="0/1": sweep-test-tmp
+    mkdir -p {{mutants_tmp}}
+    PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-cli --test-package ledger-cli --no-default-features -j 4 --timeout-multiplier 3 --minimum-test-timeout 600 --shard {{shard}} -o mutants-cli
+    @just sweep-test-tmp
+
 # No mutation runs on the viewer (owner, 2026-10-18: they crushed the
 # machine, and for the GUI it's "not as critical"). Its two musts are
 # tested directly instead: it never writes the books (tests/read_only.rs)