feat(mosaic): WI-2 mutator-class guard for directive-freshness (#837)

WI-2: mutator-class guard for the compaction directive-freshness mechanism — command-position parser (prefix x var-indirection unified) + primitive-anchored invariant backstop + all-tools-hook fail-close. Parser-complete on principle: realistic evasion matrix RED-regression-covered, residual exotic evasions proven backstop-caught (B-tests), lens-convergence reached.

closes #829

docs/architecture/lease-broker-protocol.md

@@ -12,7 +12,13 @@ Each connection carries exactly one UTF-8 JSON object followed by one newline, c
 - `authenticate`: `action`, broker-minted `session_id`, non-negative `runtime_generation`.
 - `mint_token`: authenticated identity plus `binding` containing exactly `compaction_epoch`, `request_epoch`, `h_source`, `h_payload`, and `schema_version`.
 - `consume_token`: authenticated identity plus `token`.
+- `begin_verification`: authenticated identity, runtime (`claude` or `pi`), cycle `binding`, and a TTL no greater than 300 seconds. The broker revokes existing authority first, enters `PENDING_VERIFICATION`, and returns a single-use promotion token.
+- `promote_lease`: authenticated identity plus the exact pending promotion token. The broker commits token consumption before making `VERIFIED` visible.
+- `revoke_lease`: authenticated observer signal; deletes pending tokens and makes the session `UNVERIFIED` immediately.
+- `authorize_tool`: authenticated identity, runtime, and exact runtime-reported tool name. The broker returns an explicit allow/deny decision from the whole-class policy and current lease.
 
-A higher generation for the same anchor atomically replaces the stored incarnation and deletes all prior tokens for that session. A lower generation is stale. Tokens are 256-bit values from the operating-system cryptographic RNG and are single use. At most 256 pending tokens may be persisted; another mint fails with `TOKEN_CAPACITY` before mutation. Successful consumption deletes the token, while a replay still fails with `TOKEN_REPLAY`. Live v1 token records retain the existing `consumed: false` schema. Their persisted binding is the WI-1 substrate for later receipt work; WI-1 does not implement receipts, promotion, hooks, payload builders, mutator gates, or recovery.
+A higher generation for the same anchor atomically replaces the stored incarnation and deletes all prior tokens and lease authority for that session. A lower generation is stale. Tokens are 256-bit values from the operating-system cryptographic RNG and are single use. At most 256 pending tokens may be persisted; another mint fails with `TOKEN_CAPACITY` before mutation. Successful consumption deletes the token, while a replay still fails with `TOKEN_REPLAY`. Live v1 token records retain the existing `consumed: false` schema.
+
+VERIFIED leases are volatile and monotonic-time bounded: broker restart, generation change, explicit observer revocation, or expiry returns the session to `UNVERIFIED`. `begin_verification` always revokes before minting a new prerequisite. `promote_lease` is valid only from the matching pending cycle; persistence failure rolls token and lease state back, while post-rename durability uncertainty terminates the broker. The WI-1 token is the atomic promotion prerequisite substrate. A later receipt implementation must satisfy that prerequisite but cannot replace the mechanical mutator gate as safety authority.
 
 State replacement serializes and enforces the 4 MiB maximum before opening a temporary file, then uses a mode-`0600` temporary file, `fsync`, atomic rename, and parent-directory `fsync`. Every broker mutation snapshots the prior v1 state. A commit failure before rename restores that snapshot and leaves durable state unchanged. A failure after rename makes durability uncertain, so the store is poisoned without rolling memory back and the daemon terminates rather than serving with divergent state. Existing state is opened without following symlinks, must be a bounded regular file at mode `0600`, and is fully schema- and invariant-validated before use. Persisted tokens must be unconsumed, match their session's current generation, and remain within the 256-token cap. Session identity is uniquely keyed by `(anchor_pid,anchor_starttime)`; duplicate logical sessions for one anchor refuse startup. State integrity or mode failures refuse startup. The daemon does not log session IDs or tokens.

docs/architecture/lease-broker-security.md

@@ -6,6 +6,9 @@
 - Session IDs and cycle tokens use the OS cryptographic RNG. `Math.random` and model output are not token sources.
 - Framing and persistence failures fail closed. Sensitive tokens are not logged.
 - Built-in `0700`/`0600` filesystem modes provide same-principal hardening only, not socket authenticity against the same UID. WI-1 provides no distinct-principal isolation. That stronger deployment requires an external protected proxy, ACL, or service boundary, and the boundary must preserve authenticated client identity for the broker's `SO_PEERCRED` and ancestry authorization rather than substituting a shared proxy identity.
-- WI-2+ security surfaces—receipts, promotion transactions, mutator gates, hooks, payload construction, and recovery—are explicitly out of scope.
+- WI-2 whole-class authorization denies every consequential, unknown, and custom tool while UNVERIFIED; it does not inspect shell strings or trust wrapper selection. First-class Claude/Pi, both Claudex dispatch modes, PRDY, QA remediation, coord, orchestrator, and fleet starts converge on broker register-before-exec; Claudex additionally installs the mandatory all-tools hook inside its preserved isolated config and fails closed on unsafe settings.
+- The permanent `check-runtime-launches.py` suite/CI guard scans production source for direct literal, absolute-path, process-API, command-array, and dynamic Claude/Pi launches. It has no bypass allowlist: an unrecognized launch form fails CI until routed through the common boundary.
+- WI-2 promotion consumes a WI-1 cycle token before VERIFIED becomes visible. Observer revocation, runtime-generation replacement, broker restart, and monotonic TTL expiry remove authority.
+- Receipt observation, payload construction, compaction observers, and constrained recovery implementation remain later surfaces. A receipt can become a promotion prerequisite but is never the safety mechanism.
 
-Coordinator security review must rerun the real socket/peercred acceptance suite on an unrestricted Linux runner and obtain the mandated independent Opus-SECREV review before integration.
+Coordinator security review must rerun the real socket/peercred and mutator-gate acceptance suites on an unrestricted Linux runner and obtain the mandated independent Opus-SECREV review before integration.

docs/architecture/mutator-class-gate.md

@@ -0,0 +1,72 @@
+# Whole mutator-class lease gate
+
+WI-2 adds the framework-native authorization boundary for Claude (including the supported Claudex overlay) and Pi. Every runtime-reported tool name reaches the lease broker before execution. The gate classifies capabilities by the whole tool class; it never parses a Bash command to decide whether that particular string looks read-only.
+
+## Default-deny policy
+
+While a session is not VERIFIED, only these exact classes are allowed:
+
+- Claude: `Read`, `Grep`, `Glob`, `Ls`, `Find`
+- Pi: `read`, `grep`, `find`, `ls`
+- Both runtimes: the fixed `mosaic_context_recover` primitive
+
+Every other built-in, unknown tool, and custom/MCP tool is consequential by default and is denied. This includes Claude `Bash`, `Edit`, `Write`, and `NotebookEdit`, plus Pi `bash`, `edit`, and `write`. A compromised model therefore cannot bypass Mosaic wrappers by selecting raw `git`, `curl`, `kubectl`, provider, deployment, or filesystem commands inside a generic mutator—the generic mutator itself is blocked before its input executes.
+
+## Broker-owned transition order
+
+The authenticated broker is the sole lease writer:
+
+1. `begin_verification` revokes existing authority and pending tokens first, then records `PENDING_VERIFICATION` and mints one WI-1 single-use promotion token bound to the exact cycle.
+2. `promote_lease` accepts only that session/generation/binding/token combination.
+3. Token consumption commits before the volatile lease becomes VERIFIED. Promotion is last and cannot be reached directly from UNVERIFIED.
+4. `revoke_lease`, a runtime-generation increase, broker restart, or monotonic expiry removes mutator authority.
+
+The initial TTL is capped at the ratified 300-second maximum. A caller may request a shorter positive TTL but cannot lengthen the maximum. Dual compaction-hook miss within an unexpired lease remains the ratified bounded T-A residual; once either observer revokes or TTL expires, the next consequential tool is denied.
+
+A receipt is only a future promotion prerequisite. It is not an obedience, residency, or safety proof and never replaces this mechanical gate.
+
+## Runtime adapters
+
+`launch-runtime.py` registers itself with the broker and then `exec`s Claude or Pi so PID/starttime remain the authenticated parent anchor. It exports only the broker-minted session ID and current generation to descendants.
+
+- Claude installs `mutator-gate.py` as an all-tools (`.*`) `PreToolUse` hook.
+- `mosaic claudex` and `mosaic yolo claudex` preserve their isolated `CLAUDE_CONFIG_DIR`, merge the mandatory hook into that isolated `settings.json`, and use the same register-before-exec launcher. Malformed or symlinked isolated settings deny launch.
+- Pi invokes the same executable from its `tool_call` handler.
+
+The executable submits the runtime's actual tool name to `authorize_tool`. Missing identity, malformed input/reply, timeout, broker unavailability, or denial exits with status 2 and blocks fail-closed.
+
+## Runtime-launch choke-point and permanent guard
+
+Every repository-owned Claude/Pi launch entry converges on `launch-runtime.py`, either directly or through `mosaic` → `execLeaseGatedRuntime`. PRDY init/update and QA remediation invoke the wrapper directly so their existing prompts, dangerous-permission behavior, working directory, and environment survive without skipping broker registration. The raw Claude `--dangerously-skip-permissions` primitive is owned only by `launch-runtime.py`; callers request semantic `--dangerous` mode, and the wrapper validates Claude before injecting the primitive. `@mosaicstack/coord` rewrites direct Claude commands to `mosaic claude` and rejects unknown custom Claude launchers.
+
+`check-runtime-launches.py` is the permanent completeness guard. It scans production shell, TypeScript/JavaScript, Python, and data launch definitions under `packages/`, `apps/`, `plugins/`, and `tools/`; direct literal, absolute-path, process-API, dynamic, command-substitution, `eval`, and variable-execution runtime launches fail. Shell comments are stripped with quote awareness, wrapper prefixes are tokenized with `shlex`, and only an invocation in command position with `--runtime` before the command separator is gated. Literal and tracked-variable command tokens use one terminal resolver after any nesting of `exec`, `command`, `nohup`, or `env` plus assignments. A direct command always wins over an inert marker on the same line. Independently, the raw dangerous primitive anywhere outside the choke-point is RED.
+
+The command parser is a best-effort CI defense, not a complete shell interpreter. Alias/function redefinition, sourced commands, generated scripts, and encoded pipelines are intentionally residual rather than an invitation to chase an unbounded shell language. Two runtime controls backstop that residual surface: primitive ownership rejects a dangerous launch even when command identity is alias-indirected, and Claude's global `.*` `PreToolUse` hook invokes the broker gate for non-dangerous launches. Without `MOSAIC_LEASE_SESSION_ID`, representative read, mutator, and custom/MCP tools all fail closed with `GATE_UNAVAILABLE`. Hook absence or replacement remains in the documented T-C boundary.
+
+### Parser stopping criterion
+
+- **A — realistic parser matrix:** comments, inert strings/assignments, heredocs, continuations, chained commands, command substitution, `eval`, bare tracked variables, and quoted/unquoted tracked variables behind `exec`, `command`, `nohup`, or `env` are permanent RED regressions. Prefix-variable forms are covered in both multiline and same-line assignment shapes.
+- **B — residual backstops:** a dangerous alias-indirected launch is RED solely through primitive anchoring; a parser-missed non-dangerous alias launch is paired with an acceptance test proving the global all-tools hook denies every representative tool class as `GATE_UNAVAILABLE` without a lease.
+- **C — independent fresh review:** the parser class is considered complete only when reviewers find no new non-overlapping realistic evasion on the exact head. A and B are repository evidence; C is supplied by the fresh review round.
+
+All three layers are load-bearing and complementary. The guard is mandatory in `@mosaicstack/mosaic`'s test script, so root CI fails on a future realistic bypass. Real-socket tests separately prove PRDY init/update and QA receive broker sessions and deny an unverified mutator.
+
+The live inventory is emitted by:
+
+```bash
+python3 packages/mosaic/framework/tools/lease-broker/check-runtime-launches.py --root . --json
+```
+
+| Production launch family                               | Gated entries |
+| ------------------------------------------------------ | ------------: |
+| `@mosaicstack/coord` default/configured Claude command |             2 |
+| Fleet runtime start                                    |             1 |
+| QA remediation + generated QA command                  |             2 |
+| Orchestrator command construction/session launches     |             3 |
+| PRDY init/update                                       |             2 |
+| Mosaic Claude/Pi/Claudex adapter and wrapper boundary  |             4 |
+| **Total**                                              |   **14 / 14** |
+
+## Assurance boundary
+
+This closes T-A after an observer fires or lease expiry and T-B for in-runtime tool calls. Hook/extension absence, a runtime executing outside the gated launcher, ptrace/same-UID broker replacement, and other fully rotted behavior remain T-C. Server-side branch protection and required PR review/CI remain the irreducible line for protected repository mutations.