diff --git a/REPORT-T1.md b/REPORT-T1.md
new file mode 100644
index 00000000..5ef8a7c2
--- /dev/null
+++ b/REPORT-T1.md
@@ -0,0 +1,94 @@
+# T1 report: canonical ungated Claude base and lease overlay
+
+## Changed
+
+- Replaced `packages/mosaic/framework/runtime/claude/settings.json` with the canonical ungated base. It retains the model, QA hooks, plugins, command allowlist, permissions, and `mcpServers.sequential-thinking`.
+- Added `packages/mosaic/framework/runtime/claude/lease-overlay.json`. It contains only `hooks` and the six removed lease hook entries.
+- Added the byte-identical pre-split source fixture at `packages/mosaic/src/runtime/fixtures/claude-settings.gated.pre-split.json`.
+- Added `packages/mosaic/src/runtime/claude-settings-base.spec.ts`.
+
+`framework-manifest.txt` already declares `runtime/**`, so the new overlay is framework-owned and shipped without a manifest change.
+
+## Lease-hook enumeration
+
+The actual template has six lease hook entries, matching fred's refined boundary:
+
+1. `PreToolUse` matcher `.*`: `mutator-gate.py`
+2. `Stop`: one combined command containing `receipt-observer-client.py` then `promote-complete.py`
+3. `UserPromptSubmit` matcher `^/mosaic-promote$`: `promote-begin.py`
+4. `PreCompact`: `revoke-lease.py --reason pre-compact`
+5. `SessionStart` matcher `compact`: `revoke-lease.py --reason session-start-compact`
+6. `SessionStart` matcher `resume|clear`: `revoke-lease.py --reason session-start-rollover --bump-generation`
+
+There is no delta from the refined six-entry enumeration. The Stop entry contains the receipt-observer and promote-complete commands together, rather than as two separate hook objects.
+
+## Tests and checks
+
+`pnpm install --frozen-lockfile` was run first because `node_modules` was absent. It completed successfully.
+
+Red-first run before artifacts existed:
+
+```text
+RUN  v2.1.9 .../packages/mosaic
+❯ src/runtime/claude-settings-base.spec.ts (4 tests | 4 failed)
+× keeps every lease command out of the ungated base
+  → mutator-gate: expected true to be false
+× reconstructs the pre-split gated hooks while retaining the canonical MCP correction
+  → ENOENT: .../lease-overlay.json
+× ships sequential-thinking in the base
+  → expected undefined to deeply equal { 'sequential-thinking': ... }
+× limits the overlay to lease hook entries
+  → ENOENT: .../lease-overlay.json
+```
+
+Final focused acceptance run:
+
+```text
+RUN  v2.1.9 .../packages/mosaic
+✓ src/runtime/claude-settings-base.spec.ts (4 tests) 19ms
+Test Files  1 passed (1)
+Tests  4 passed (4)
+```
+
+`pnpm --filter @mosaicstack/mosaic lint` passed:
+
+```text
+> @mosaicstack/mosaic@0.0.49 lint
+> eslint src
+```
+
+`pnpm --filter @mosaicstack/mosaic typecheck` failed on pre-existing workspace resolution and unrelated package errors. The new spec no longer appears in the error list. Initial failures include missing `@mosaicstack/{brain,forge,log,macp,memory,queue,storage,quality-rails,db,config,prdy,types}` declarations, followed by existing `fleet-backlog.ts`, `gateway-doctor.ts`, and TUI implicit-`any` errors. Exit status: 2.
+
+A focused legacy consumer run confirms an existing assumption that `settings.json` itself is gated:
+
+```text
+pnpm --filter @mosaicstack/mosaic exec vitest run src/mutator-gate/mutator-gate.acceptance.spec.ts
+❯ src/mutator-gate/mutator-gate.acceptance.spec.ts (20 tests | 6 failed)
+× non-dangerous parser residual is denied by the global all-tools hook without a lease
+  → expected all-tools mutator-gate command in settings.json
+× Claude and Pi compaction observer wiring is complete and fail-closed
+  → expected PreCompact/SessionStart revoke-lease hooks in settings.json
+```
+
+The other four failures in that focused run reported `STALE_GENERATION` where the test expected `MUTATOR_UNVERIFIED`, plus one successful-gate assertion. I did not redesign this legacy suite because the task explicitly says to report consumers that assume the base is gated.
+
+## Consumers found
+
+Direct `runtime/claude/settings.json` path consumers found by the required repository grep:
+
+- `packages/mosaic/framework/tools/_scripts/mosaic-link-runtime-assets`: copies the base to `~/.claude/settings.json`.
+- `packages/mosaic/src/commands/install-ordering-guard.ts` and `.spec.ts`: documentation and behavior assume the source embeds enforcement hooks.
+- `packages/mosaic/framework/tools/_scripts/test-install-ordering-guard.sh`: comments and assertions expect `mutator-gate.py` and `receipt-observer-client.py` in the base.
+- `packages/mosaic/src/mutator-gate/mutator-gate.acceptance.spec.ts`: reads the base and asserts mutator, promotion, and compaction lease wiring.
+- `packages/mosaic/src/lease-broker/promotion_trigger_unittest.py`: reads the base and asserts promotion wiring.
+- `packages/mosaic/src/lease-broker/recovery_runtime_unittest.py`: reads the base.
+- `packages/mosaic/src/runtime/update-checker.ts` and `.spec.ts`: references the path in settings wiring/update checks.
+- Documentation-only references: `docs/compaction-refresh/probes/p6_constrained_recovery.py`, `docs/plans/agent-reflection-loop-PRD.md`, `docs/tasks/544-agent-reflection-loop.md`, and the framework QA documentation/scripts found by grep.
+
+I did not change these consumers. The install/link and lease acceptance consumers must be taught to select and compose `lease-overlay.json` when a gated promotion seat is requested. That composition behavior is outside T1.
+
+## Ambiguity handled
+
+The exact pre-split template fixture has no `mcpServers` key (SHA-256 `44e74ea1e9d424fffa020ee666402662ac856b88bf6ae7f3b8931eed29dc75a4`). The task simultaneously requires a byte-for-byte pre-split fixture, `mcpServers.sequential-thinking` in the base, and `deep-merge(base, overlay) == original`. Those three conditions cannot all hold because a merge cannot remove the required MCP key.
+
+The acceptance test preserves the exact fixture and asserts that the normalized merge equals the pre-split template plus the required canonical `mcpServers.sequential-thinking` correction. It verifies all original hook content is reconstructed and the base carries the required MCP. Production three-layer merge semantics remain W-F1 work.
diff --git a/REPORT-T2.md b/REPORT-T2.md
new file mode 100644
index 00000000..f802fad5
--- /dev/null
+++ b/REPORT-T2.md
@@ -0,0 +1,102 @@
+# REPORT-T2
+
+Date: 2026-08-13 11:29 CDT
+Branch: `feat/wf-fleet-t2-launch`
+Base: `216cd722`
+Issue: #1209
+
+## What changed
+
+- Added `mosaic fleet launch <name> [--dry-run]` in `packages/mosaic/src/commands/fleet-launch-command.ts` and registered it on the existing fleet command.
+- Added strict schema-one parsing for the user-owned `~/.mosaic/fleet/agents/<name>/profile.json`:
+  - required `schema` and `harness`
+  - default bundle `primary`
+  - optional `model`, `overlay`, `plugins`, `skills`, and string-valued `env`
+  - unknown-key refusal naming the key
+  - dedicated `SCHEMA_TOO_NEW` code and upgrade guidance
+- Added the three-layer settings composer. Objects merge recursively, scalars use the higher layer, arrays replace, and `null` deletes a key. The selected agent overlay defaults to no overlay when the profile field is absent.
+- Writes canonical merged settings to `<agent-home>/settings.json` and the future harvest comparison snapshot to `<agent-dir>/settings.generated.json`.
+- Resolves `primary` to its named bundle, reads an optional account email, and reports forms such as `primary -> fred_example.com (fred@example.com)`.
+- Validates credential targets with `lstat`, rejects symlink credential files, resolves and checks containment under the harness auth root, and refuses a real credential file at the seat-link path as first-auth state.
+- Installs selected plugin and skill entries as seat-local symlinks, prunes stale symlinks, and refuses real objects instead of deleting them.
+- Builds a declared seat environment with the harness home variable, `MOSAIC_AGENT_NAME`, and profile environment entries. Mechanical values override conflicting profile entries.
+- Extended `launch.ts` so `harnessHome()` accepts fleet context and remains the home-resolution seam. The fleet launcher uses the existing runtime preflight, prompt, ledger, lease-gated, and process execution path over a minimal ambient environment.
+- Added deterministic dry-run output containing source layers, merged settings, output and snapshot paths, resolved bundle, symlink plans, declared environment, and harness argv.
+- Added 17 focused tests, including the required merge, schema, A3, dry-run snapshot, managed-link, command dry-run, execution-seam, and non-zero failure cases.
+
+## Reconciliation decisions and contradictions
+
+### Prominent contradiction: roster registries do not contain the frozen launch schema
+
+The existing code has two other profile/registry concepts:
+
+- `fleet-profiles.ts` models system-type YAML roster templates. Its `FleetProfile` has no harness bundle, overlay, plugin, skill, or seat environment fields.
+- roster-v2 models topology and lifecycle. It requires class, provider, reasoning, tool policy, working directory, lifecycle, and launch-yolo fields that schema-one `profile.json` does not contain.
+
+Deriving a complete roster-v2 member from the frozen per-agent profile is therefore not possible without inventing values. Launch now reads only the per-agent `profile.json` and does not require roster-v2 or the legacy v1 roster. roster-v2 remains the existing lifecycle/topology registry. No second launch registry was introduced.
+
+The pre-existing `resolveFleetIdentity()` path requires a legacy roster and a secure tmux helper whenever `MOSAIC_AGENT_NAME` is present during contract composition. For profile-backed launch, `launch.ts` excludes roster identity keys only from the contract-build environment, then exports the declared profile seat identity to the harness process. Legacy root runtime launches retain the existing roster-backed behavior. This is the smallest reconciliation that allows profile-only launch without fabricating roster-v2 fields.
+
+### Historical whole-store plugin link
+
+The prototype used a whole `plugins` directory symlink, while this task requires selected entry links and pruning. Launch refuses that historical shape with an explicit migration message. It does not delete or silently convert the whole-store link.
+
+### Existing `FleetProfile` name
+
+The system-type YAML `FleetProfile` remains unchanged. The new type is named `FleetAgentLaunchProfile` to keep the concepts separate while treating per-agent `profile.json` as the launch SSOT.
+
+## Ambiguities and bounded choices
+
+- The design does not freeze the generated snapshot filename. This implementation uses `settings.generated.json` in the agent directory, beside the hidden harness home.
+- The design explicitly identifies Claude `.credentials.json` and Pi `auth.json`. Codex and OpenCode use `auth.json` in the filename map, matching their harness-home composition shape, but no real credential launch was performed in this task.
+- Full interactive harvest-back disposition is not implemented. The task asks to store the generated snapshot for the future diff, and this change does that.
+- A machine descriptor file and content digests were not added. Dry-run and execution consume one resolved in-memory composition, and dry-run prints that composition.
+- No real harness process or real operator home was used. Every new filesystem test uses a temporary fixture root.
+
+## Test run
+
+Dependency install and build:
+
+```text
+$ pnpm install --frozen-lockfile
+Scope: all 28 workspace projects
+Lockfile is up to date, resolution step is skipped
+Done in 4.7s using pnpm v10.6.2
+
+$ pnpm --filter @mosaicstack/mosaic... build
+Scope: 13 of 28 workspace projects
+packages/mosaic build: Done
+```
+
+Focused and touched integration tests:
+
+```text
+$ pnpm --filter @mosaicstack/mosaic exec vitest run src/commands/fleet-launch-command.spec.ts src/commands/launch.spec.ts src/commands/fleet.spec.ts
+Test Files  3 passed (3)
+Tests       256 passed (256)
+```
+
+Typecheck and lint:
+
+```text
+$ pnpm --filter @mosaicstack/mosaic typecheck
+> tsc --noEmit
+(exit 0)
+
+$ pnpm exec eslint packages/mosaic/src/commands/fleet-launch-command.ts packages/mosaic/src/commands/fleet-launch-command.spec.ts packages/mosaic/src/commands/launch.ts packages/mosaic/src/commands/fleet.ts packages/mosaic/src/commands/fleet.spec.ts
+(exit 0)
+
+$ pnpm exec prettier --check packages/mosaic/src/commands/fleet-launch-command.ts packages/mosaic/src/commands/fleet-launch-command.spec.ts packages/mosaic/src/commands/launch.ts packages/mosaic/src/commands/fleet.ts packages/mosaic/src/commands/fleet.spec.ts
+Checking formatting...
+All matched files use Prettier code style!
+```
+
+Package-wide Vitest result:
+
+```text
+$ pnpm --filter @mosaicstack/mosaic exec vitest run
+Test Files  1 failed | 83 passed (84)
+Tests       4 failed | 1535 passed (1539)
+```
+
+All four failures are in `src/mutator-gate/mutator-gate.acceptance.spec.ts`. Three expected `MUTATOR_UNVERIFIED` but received `STALE_GENERATION`; one runtime-gate assertion expected status zero and received status two. An isolated rerun produced the same four failures. I did not confirm whether they predate this branch. The focused launch, fleet, and typecheck runs are green.
diff --git a/REPORT-T3.md b/REPORT-T3.md
new file mode 100644
index 00000000..6fb2ddd1
--- /dev/null
+++ b/REPORT-T3.md
@@ -0,0 +1,46 @@
+# T3 report: `mosaic fleet agent new`
+
+## Changed
+
+- Added `packages/mosaic/src/fleet/fleet-agent-scaffold.ts`.
+  - Creates user-owned seats at `~/.mosaic/fleet/agents/<name>` (test seam: `fleetDataHome`, environment default: `MOSAIC_DATA_HOME`).
+  - Writes schema-one `profile.json` with default `harness: "claude"`, `bundle: "primary"`, optional `model`, `overlay: "overlay.json"`, and mandatory `env.MOSAIC_AGENT_NAME`.
+  - Writes a positive `SOUL.md` identity and materializes that identity in `.claude/CLAUDE.md` or `.pi/AGENTS.md`.
+  - Writes `overlay.json` as `{}`. Claude homes get `.claude.json` with `hasCompletedOnboarding: true` and `theme: "dark"`. No settings file is composed.
+  - Creates the appropriate credential symlink (`.credentials.json` for Claude, `auth.json` for Pi), allowing an intentional dangling destination and reporting it at the command surface.
+  - Compares every existing object (including link targets as link text), succeeds only byte-identically, and otherwise refuses with the differing paths.
+- Added `packages/mosaic/src/commands/fleet-agent-scaffold-command.ts` and wired `fleet agent new <name> [--harness claude|pi] [--bundle B] [--model M]` in `packages/mosaic/src/commands/fleet.ts`.
+- Added `packages/mosaic/src/commands/fleet-agent-scaffold-command.spec.ts` with temp-root-only coverage: exact Claude/Pi layouts, literal quote/backtick/`$( )` handling, unsafe names and option failures, idempotence, changed-file refusal, and credential-link comparison.
+
+## Reconciliation
+
+`fleet-agent-crud-command.ts` currently registers roster-v2 `get/create/update/delete/plan` directly under `mosaic fleet`; it has no `agent new` command or profile schema. T3 adds an `agent` namespace for the profile-owned user-data scaffold and leaves roster-v2 CRUD unchanged.
+
+No roster projection is created. Current roster-v2 requires fields that cannot be derived from the new profile (`class`, provider, working directory, reasoning, tool policy, lifecycle), while no current `mosaic fleet launch <name>` consumes these profiles. Writing such a roster entry would create the forbidden second registry and invent semantics. The profile is therefore the sole state created here. When the launcher owns profile-to-roster projection, it must derive it there and emit the required actionable unscaffolded-name message.
+
+## Validation
+
+```text
+$ pnpm install --frozen-lockfile
+Done in 4.1s using pnpm v10.6.2
+
+$ pnpm --filter @mosaicstack/mosaic exec vitest run src/commands/fleet-agent-scaffold-command.spec.ts
+✓ src/commands/fleet-agent-scaffold-command.spec.ts (13 tests) 28ms
+Test Files  1 passed (1)
+Tests       13 passed (13)
+
+$ pnpm --filter @mosaicstack/mosaic exec eslint src/fleet/fleet-agent-scaffold.ts src/commands/fleet-agent-scaffold-command.ts src/commands/fleet-agent-scaffold-command.spec.ts src/commands/fleet.ts
+(exit 0)
+
+$ pnpm exec prettier --check packages/mosaic/src/fleet/fleet-agent-scaffold.ts packages/mosaic/src/commands/fleet-agent-scaffold-command.ts packages/mosaic/src/commands/fleet-agent-scaffold-command.spec.ts packages/mosaic/src/commands/fleet.ts
+All matched files use Prettier code style!
+
+$ git diff --check
+(exit 0)
+```
+
+`pnpm --filter @mosaicstack/mosaic typecheck` remains blocked by pre-existing unresolved workspace package entries (`@mosaicstack/brain`, `@mosaicstack/db`, `@mosaicstack/types`, and others). The typecheck output had no diagnostics naming T3 files. Running the pre-existing CRUD command spec is blocked by the same `@mosaicstack/db` Vite resolution failure through `fleet-backlog.ts`.
+
+## Skipped ambiguity
+
+The design asks for a generated harness-home `settings.json` as part of an earlier generic home-template description, but the task explicitly says composed settings are left to launch. T3 creates no `settings.json`; launch composition remains the owner.
diff --git a/packages/mosaic/framework/runtime/claude/lease-overlay.json b/packages/mosaic/framework/runtime/claude/lease-overlay.json
new file mode 100644
index 00000000..c2deaa11
--- /dev/null
+++ b/packages/mosaic/framework/runtime/claude/lease-overlay.json
@@ -0,0 +1,70 @@
+{
+  "hooks": {
+    "PreCompact": [
+      {
+        "matcher": ".*",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason pre-compact"
+          }
+        ]
+      }
+    ],
+    "SessionStart": [
+      {
+        "matcher": "compact",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason session-start-compact"
+          }
+        ]
+      },
+      {
+        "matcher": "resume|clear",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason session-start-rollover --bump-generation"
+          }
+        ]
+      }
+    ],
+    "UserPromptSubmit": [
+      {
+        "matcher": "^/mosaic-promote$",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ~/.config/mosaic/tools/lease-broker/promote-begin.py",
+            "timeout": 15
+          }
+        ]
+      }
+    ],
+    "PreToolUse": [
+      {
+        "matcher": ".*",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ~/.config/mosaic/tools/lease-broker/mutator-gate.py --runtime claude --recovery-command ~/.config/mosaic/tools/lease-broker/recover-context.py",
+            "timeout": 3
+          }
+        ]
+      }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ~/.config/mosaic/tools/lease-broker/receipt-observer-client.py --runtime claude --latest-entry; observer_status=$?; python3 ~/.config/mosaic/tools/lease-broker/promote-complete.py; exit $observer_status",
+            "timeout": 15
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/packages/mosaic/framework/runtime/claude/settings.json b/packages/mosaic/framework/runtime/claude/settings.json
index 0e6dcec1..bf79b5ba 100644
--- a/packages/mosaic/framework/runtime/claude/settings.json
+++ b/packages/mosaic/framework/runtime/claude/settings.json
@@ -1,60 +1,7 @@
 {
   "model": "opus",
   "hooks": {
-    "PreCompact": [
-      {
-        "matcher": ".*",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason pre-compact"
-          }
-        ]
-      }
-    ],
-    "SessionStart": [
-      {
-        "matcher": "compact",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason session-start-compact"
-          }
-        ]
-      },
-      {
-        "matcher": "resume|clear",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason session-start-rollover --bump-generation"
-          }
-        ]
-      }
-    ],
-    "UserPromptSubmit": [
-      {
-        "matcher": "^/mosaic-promote$",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "python3 ~/.config/mosaic/tools/lease-broker/promote-begin.py",
-            "timeout": 15
-          }
-        ]
-      }
-    ],
     "PreToolUse": [
-      {
-        "matcher": ".*",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "python3 ~/.config/mosaic/tools/lease-broker/mutator-gate.py --runtime claude --recovery-command ~/.config/mosaic/tools/lease-broker/recover-context.py",
-            "timeout": 3
-          }
-        ]
-      },
       {
         "matcher": "Write|Edit|MultiEdit",
         "hooks": [
@@ -91,11 +38,6 @@
     "Stop": [
       {
         "hooks": [
-          {
-            "type": "command",
-            "command": "python3 ~/.config/mosaic/tools/lease-broker/receipt-observer-client.py --runtime claude --latest-entry; observer_status=$?; python3 ~/.config/mosaic/tools/lease-broker/promote-complete.py; exit $observer_status",
-            "timeout": 15
-          },
           {
             "type": "command",
             "command": "~/.config/mosaic/tools/qa/reflect-stop-hook.sh",
@@ -315,5 +257,11 @@
     "cpan",
     "nohup"
   ],
-  "enableAllMcpTools": true
+  "enableAllMcpTools": true,
+  "mcpServers": {
+    "sequential-thinking": {
+      "command": "npx",
+      "args": ["-y", "@modelcontextprotocol/server-sequential-thinking"]
+    }
+  }
 }
diff --git a/packages/mosaic/src/commands/fleet-agent-scaffold-command.spec.ts b/packages/mosaic/src/commands/fleet-agent-scaffold-command.spec.ts
new file mode 100644
index 00000000..97da8aa3
--- /dev/null
+++ b/packages/mosaic/src/commands/fleet-agent-scaffold-command.spec.ts
@@ -0,0 +1,189 @@
+import { lstat, mkdtemp, readFile, readdir, readlink, rm, writeFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { Command } from 'commander';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { registerFleetAgentScaffoldCommand } from './fleet-agent-scaffold-command.js';
+
+let root: string | undefined;
+
+afterEach(async (): Promise<void> => {
+  vi.restoreAllMocks();
+  process.exitCode = undefined;
+  if (root) await rm(root, { recursive: true, force: true });
+  root = undefined;
+});
+
+async function fleetDataHome(): Promise<string> {
+  root = await mkdtemp(join(tmpdir(), 'mosaic-fleet-agent-new-'));
+  return join(root, '.mosaic');
+}
+
+function program(dataHome: string): Command {
+  const result = new Command();
+  result.exitOverride();
+  const fleet = result.command('fleet');
+  registerFleetAgentScaffoldCommand(fleet, { fleetDataHome: dataHome });
+  return result;
+}
+
+async function files(rootDir: string, prefix = ''): Promise<string[]> {
+  const result: string[] = [];
+  for (const entry of await readdir(join(rootDir, prefix), { withFileTypes: true })) {
+    const path = join(prefix, entry.name);
+    if (entry.isDirectory()) result.push(...(await files(rootDir, path)));
+    else result.push(path);
+  }
+  return result.sort();
+}
+
+describe('mosaic fleet agent new', (): void => {
+  it('creates the exact authored user-data scaffold under a temp ~/.mosaic root', async (): Promise<void> => {
+    const dataHome = await fleetDataHome();
+    await program(dataHome).parseAsync(['node', 'mosaic', 'fleet', 'agent', 'new', 'mira']);
+    const agent = join(dataHome, 'fleet', 'agents', 'mira');
+
+    expect(await files(agent)).toEqual([
+      '.claude/.claude.json',
+      '.claude/.credentials.json',
+      '.claude/CLAUDE.md',
+      'SOUL.md',
+      'overlay.json',
+      'profile.json',
+    ]);
+    expect(JSON.parse(await readFile(join(agent, 'profile.json'), 'utf8'))).toEqual({
+      schema: 1,
+      harness: 'claude',
+      bundle: 'primary',
+      overlay: 'overlay.json',
+      env: { MOSAIC_AGENT_NAME: 'mira' },
+    });
+    expect(await readFile(join(agent, 'SOUL.md'), 'utf8')).toContain('## Identity');
+    expect(await readFile(join(agent, '.claude', '.claude.json'), 'utf8')).toEqual(
+      `${JSON.stringify({ hasCompletedOnboarding: true, theme: 'dark' }, null, 2)}\n`,
+    );
+    expect(await readlink(join(agent, '.claude', '.credentials.json'))).toBe(
+      join(dataHome, 'auth', 'claude', 'primary', '.credentials.json'),
+    );
+  });
+
+  it('creates a Pi home without Claude onboarding state', async (): Promise<void> => {
+    const dataHome = await fleetDataHome();
+    await program(dataHome).parseAsync([
+      'node',
+      'mosaic',
+      'fleet',
+      'agent',
+      'new',
+      'pi-seat',
+      '--harness',
+      'pi',
+    ]);
+    expect(await files(join(dataHome, 'fleet', 'agents', 'pi-seat'))).toEqual([
+      '.pi/AGENTS.md',
+      '.pi/auth.json',
+      'SOUL.md',
+      'overlay.json',
+      'profile.json',
+    ]);
+  });
+
+  it('round-trips quotes, backticks, and shell-looking input literally', async (): Promise<void> => {
+    const dataHome = await fleetDataHome();
+    const name = 'seat"`$(literal)`';
+    const bundle = 'bundle"`$(literal)`';
+    const model = 'model"`$(literal)`';
+    await program(dataHome).parseAsync([
+      'node',
+      'mosaic',
+      'fleet',
+      'agent',
+      'new',
+      name,
+      '--harness',
+      'pi',
+      '--bundle',
+      bundle,
+      '--model',
+      model,
+    ]);
+    const agent = join(dataHome, 'fleet', 'agents', name);
+    expect(JSON.parse(await readFile(join(agent, 'profile.json'), 'utf8'))).toMatchObject({
+      harness: 'pi',
+      bundle,
+      model,
+      env: { MOSAIC_AGENT_NAME: name },
+    });
+    expect(await readFile(join(agent, 'SOUL.md'), 'utf8')).toContain(`You are ${name},`);
+    expect(await readlink(join(agent, '.pi', 'auth.json'))).toBe(
+      join(dataHome, 'auth', 'pi', bundle, 'auth.json'),
+    );
+  });
+
+  it.each(['', '../outside', '/absolute', 'a/b', 'a\\b'])(
+    'rejects unsafe agent name %j with a non-zero outcome',
+    async (name: string): Promise<void> => {
+      const dataHome = await fleetDataHome();
+      const error = vi.spyOn(process.stderr, 'write').mockImplementation(() => true);
+      try {
+        await program(dataHome).parseAsync(['node', 'mosaic', 'fleet', 'agent', 'new', name]);
+      } catch {
+        // Commander rejects a missing positional before the action. That is also
+        // a non-zero CLI failure; all other unsafe names reach the scaffold.
+        process.exitCode = 1;
+      }
+      expect(process.exitCode).toBe(1);
+      if (name !== '')
+        expect(error).toHaveBeenCalledWith(expect.stringContaining('invalid-request'));
+    },
+  );
+
+  it.each([
+    ['--harness', 'codex'],
+    ['--bundle', '../outside'],
+    ['--model', ''],
+  ])(
+    'returns non-zero for invalid %s input',
+    async (option: string, value: string): Promise<void> => {
+      const dataHome = await fleetDataHome();
+      const error = vi.spyOn(process.stderr, 'write').mockImplementation(() => true);
+      await program(dataHome).parseAsync([
+        'node',
+        'mosaic',
+        'fleet',
+        'agent',
+        'new',
+        'mira',
+        option,
+        value,
+      ]);
+      expect(process.exitCode).toBe(1);
+      expect(error).toHaveBeenCalledWith(expect.stringContaining('invalid-request'));
+    },
+  );
+
+  it('is idempotent for byte-identical content and refuses a changed user file', async (): Promise<void> => {
+    const dataHome = await fleetDataHome();
+    const command = ['node', 'mosaic', 'fleet', 'agent', 'new', 'mira'];
+    await program(dataHome).parseAsync(command);
+    await program(dataHome).parseAsync(command);
+    expect(process.exitCode).toBeUndefined();
+
+    const soul = join(dataHome, 'fleet', 'agents', 'mira', 'SOUL.md');
+    await writeFile(soul, '# user-owned change\n');
+    const error = vi.spyOn(process.stderr, 'write').mockImplementation(() => true);
+    await program(dataHome).parseAsync(command);
+    expect(process.exitCode).toBe(1);
+    expect(error).toHaveBeenCalledWith(expect.stringContaining('SOUL.md'));
+    expect(await readFile(soul, 'utf8')).toBe('# user-owned change\n');
+  });
+
+  it('does not follow a managed credential link while comparing existing content', async (): Promise<void> => {
+    const dataHome = await fleetDataHome();
+    await program(dataHome).parseAsync(['node', 'mosaic', 'fleet', 'agent', 'new', 'mira']);
+    const credential = join(dataHome, 'fleet', 'agents', 'mira', '.claude', '.credentials.json');
+    expect((await lstat(credential)).isSymbolicLink()).toBe(true);
+    await program(dataHome).parseAsync(['node', 'mosaic', 'fleet', 'agent', 'new', 'mira']);
+    expect(process.exitCode).toBeUndefined();
+  });
+});
diff --git a/packages/mosaic/src/commands/fleet-agent-scaffold-command.ts b/packages/mosaic/src/commands/fleet-agent-scaffold-command.ts
new file mode 100644
index 00000000..64743237
--- /dev/null
+++ b/packages/mosaic/src/commands/fleet-agent-scaffold-command.ts
@@ -0,0 +1,56 @@
+import type { Command } from 'commander';
+import { FleetAgentScaffoldError, scaffoldFleetAgent } from '../fleet/fleet-agent-scaffold.js';
+
+export interface FleetAgentScaffoldCommandDeps {
+  /** Test seam for the user-owned ~/.mosaic root. */
+  readonly fleetDataHome?: string;
+}
+
+interface NewAgentOptions {
+  readonly harness?: string;
+  readonly bundle?: string;
+  readonly model?: string;
+}
+
+/** Registers the user-data seat scaffolder, distinct from roster-v2 CRUD. */
+export function registerFleetAgentScaffoldCommand(
+  fleetCommand: Command,
+  deps: FleetAgentScaffoldCommandDeps = {},
+): void {
+  const agent = fleetCommand
+    .command('agent')
+    .description('Manage user-owned fleet agent harness homes');
+
+  agent
+    .command('new <name>')
+    .description('Create an additive-or-refuse fleet agent harness home')
+    .option('--harness <harness>', 'Harness: claude or pi', 'claude')
+    .option('--bundle <bundle>', 'Auth bundle selector', 'primary')
+    .option('--model <model>', 'Optional harness-native model')
+    .action(async (name: string, options: NewAgentOptions): Promise<void> => {
+      try {
+        const result = await scaffoldFleetAgent({
+          name,
+          harness: options.harness,
+          bundle: options.bundle,
+          model: options.model,
+          ...(deps.fleetDataHome === undefined ? {} : { dataHome: deps.fleetDataHome }),
+        });
+        console.log(
+          result.idempotent
+            ? `Fleet agent "${name}" already matches the scaffold.`
+            : `Created fleet agent "${name}" at ${result.agentDir}.`,
+        );
+        if (!result.credentialTargetExists) {
+          console.log(
+            `Notice: credentials link is intentionally dangling until auth bundle "${result.profile['bundle']}" is enrolled: ${result.credentialTarget}`,
+          );
+        }
+      } catch (error: unknown) {
+        process.exitCode = 1;
+        const message = error instanceof Error ? error.message : String(error);
+        const code = error instanceof FleetAgentScaffoldError ? error.code : 'scaffold-failed';
+        process.stderr.write(`mosaic fleet agent new failed (${code}): ${message}\n`);
+      }
+    });
+}
diff --git a/packages/mosaic/src/commands/fleet-launch-command.spec.ts b/packages/mosaic/src/commands/fleet-launch-command.spec.ts
new file mode 100644
index 00000000..39007d66
--- /dev/null
+++ b/packages/mosaic/src/commands/fleet-launch-command.spec.ts
@@ -0,0 +1,440 @@
+import {
+  lstatSync,
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  rmSync,
+  symlinkSync,
+  writeFileSync,
+} from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { Command } from 'commander';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import {
+  applyFleetLaunchComposition,
+  deepMergeSettings,
+  FleetLaunchError,
+  formatFleetLaunchDryRun,
+  parseFleetAgentProfile,
+  registerFleetLaunchCommand,
+  resolveFleetLaunchComposition,
+} from './fleet-launch-command.js';
+
+const roots: string[] = [];
+
+afterEach(() => {
+  for (const root of roots.splice(0)) rmSync(root, { recursive: true, force: true });
+});
+
+function fixture(profile: Record<string, unknown> = { schema: 1, harness: 'claude' }): {
+  root: string;
+  systemHome: string;
+  userHome: string;
+  agentDir: string;
+  namedBundleDir: string;
+} {
+  const root = mkdtempSync(join(tmpdir(), 'mosaic-fleet-launch-'));
+  roots.push(root);
+  const systemHome = join(root, 'system');
+  const userHome = join(root, 'user');
+  const agentDir = join(userHome, 'fleet', 'agents', 'fred');
+  const namedBundleDir = join(userHome, 'auth', 'claude', 'fred_example.com');
+  mkdirSync(join(systemHome, 'runtime', 'claude'), { recursive: true });
+  mkdirSync(agentDir, { recursive: true });
+  mkdirSync(namedBundleDir, { recursive: true });
+  writeFileSync(join(systemHome, 'runtime', 'claude', 'settings.json'), '{}\n');
+  writeFileSync(join(agentDir, 'profile.json'), `${JSON.stringify(profile, null, 2)}\n`);
+  writeFileSync(join(namedBundleDir, '.credentials.json'), '{}\n', { mode: 0o600 });
+  writeFileSync(
+    join(namedBundleDir, 'account.json'),
+    '{"oauthAccount":{"emailAddress":"fred@example.com"}}\n',
+  );
+  symlinkSync('fred_example.com', join(userHome, 'auth', 'claude', 'primary'), 'dir');
+  return { root, systemHome, userHome, agentDir, namedBundleDir };
+}
+
+describe('fleet launch profile schema 1', () => {
+  it('rejects an unknown key and names it', () => {
+    expect(() =>
+      parseFleetAgentProfile('{"schema":1,"harness":"claude","pluigns":[]}'),
+    ).toThrowError(/unknown profile key "pluigns"/);
+  });
+
+  it('uses a dedicated SCHEMA_TOO_NEW error with an upgrade hint', () => {
+    try {
+      parseFleetAgentProfile('{"schema":2,"harness":"claude"}');
+      throw new Error('expected parse to fail');
+    } catch (error) {
+      expect(error).toBeInstanceOf(FleetLaunchError);
+      expect((error as FleetLaunchError).code).toBe('SCHEMA_TOO_NEW');
+      expect((error as Error).message).toMatch(/upgrade Mosaic/i);
+    }
+  });
+});
+
+describe('three-layer settings merge', () => {
+  it('keeps base-only settings', () => {
+    expect(deepMergeSettings({ base: { enabled: true } })).toEqual({ base: { enabled: true } });
+  });
+
+  it('uses the last layer for scalar conflicts', () => {
+    expect(deepMergeSettings({ model: 'base' }, { model: 'user' })).toEqual({ model: 'user' });
+  });
+
+  it('replaces arrays instead of appending', () => {
+    expect(deepMergeSettings({ hooks: ['base'] }, { hooks: ['user'] })).toEqual({
+      hooks: ['user'],
+    });
+  });
+
+  it('uses null as a key-deleting tombstone', () => {
+    expect(
+      deepMergeSettings({ nested: { keep: true, remove: true } }, { nested: { remove: null } }),
+    ).toEqual({ nested: { keep: true } });
+  });
+
+  it('concatenates hook event arrays so an overlay adds gating without erasing base hooks', () => {
+    const qaStop = { hooks: [{ type: 'command', command: 'qa-stop.sh' }] };
+    const leaseStop = { hooks: [{ type: 'command', command: 'receipt-observer.py' }] };
+    const qaPre = { matcher: 'Write', hooks: [{ type: 'command', command: 'qa-pre.sh' }] };
+    expect(
+      deepMergeSettings(
+        { hooks: { Stop: [qaStop], PreToolUse: [qaPre] } },
+        { hooks: { Stop: [leaseStop] } },
+      ),
+    ).toEqual({ hooks: { Stop: [qaStop, leaseStop], PreToolUse: [qaPre] } });
+  });
+
+  it('still deletes a whole hook event via the null tombstone', () => {
+    expect(
+      deepMergeSettings(
+        { hooks: { Stop: [{ hooks: [{ type: 'command', command: 'qa-stop.sh' }] }] } },
+        { hooks: { Stop: null } },
+      ),
+    ).toEqual({ hooks: {} });
+  });
+
+  it('keeps replace semantics for arrays outside the top-level hooks object', () => {
+    expect(
+      deepMergeSettings(
+        { plugins: ['base'], nested: { hooks: { Stop: ['base'] } } },
+        { plugins: ['user'], nested: { hooks: { Stop: ['user'] } } },
+      ),
+    ).toEqual({ plugins: ['user'], nested: { hooks: { Stop: ['user'] } } });
+  });
+
+  it('deep-merges all three layers in precedence order', () => {
+    expect(
+      deepMergeSettings(
+        { nested: { system: true, shared: 'system' }, list: [1] },
+        { nested: { user: true, shared: 'user' }, list: [2] },
+        { nested: { agent: true, shared: 'agent' }, list: [3] },
+      ),
+    ).toEqual({
+      nested: { system: true, user: true, agent: true, shared: 'agent' },
+      list: [3],
+    });
+  });
+});
+
+describe('profile-selected overlay', () => {
+  it('defaults to no overlay when the optional profile field is omitted', () => {
+    const fx = fixture();
+    writeFileSync(join(fx.agentDir, 'overlay.json'), '{"mustNotLoad":true}\n');
+
+    const plan = resolveFleetLaunchComposition('fred', {
+      systemHome: fx.systemHome,
+      userHome: fx.userHome,
+    });
+    expect(plan.settings.merged).toEqual({});
+    expect(plan.settings.layers[2]?.present).toBe(false);
+  });
+});
+
+describe('unscaffolded agent names', () => {
+  it('points an unscaffolded name at mosaic fleet agent new', () => {
+    const fx = fixture();
+    try {
+      resolveFleetLaunchComposition('ghost', {
+        systemHome: fx.systemHome,
+        userHome: fx.userHome,
+      });
+      throw new Error('expected resolution to fail');
+    } catch (error: unknown) {
+      const launchError = error as FleetLaunchError;
+      expect(launchError.code).toBe('AGENT_NOT_SCAFFOLDED');
+      expect(launchError.message).toContain("no such fleet agent 'ghost'");
+      expect(launchError.message).toContain('mosaic fleet agent new ghost');
+    }
+  });
+});
+
+describe('A3 credential validation', () => {
+  it('refuses a symlinked bundle credential file', () => {
+    const fx = fixture();
+    rmSync(join(fx.namedBundleDir, '.credentials.json'));
+    const outside = join(fx.root, 'outside-credentials.json');
+    writeFileSync(outside, '{}\n');
+    symlinkSync(outside, join(fx.namedBundleDir, '.credentials.json'));
+
+    expect(() =>
+      resolveFleetLaunchComposition('fred', {
+        systemHome: fx.systemHome,
+        userHome: fx.userHome,
+      }),
+    ).toThrowError(/real, non-symlink credential file/);
+  });
+
+  it('accepts a real credential file contained in the harness auth root', () => {
+    const fx = fixture();
+    const plan = resolveFleetLaunchComposition('fred', {
+      systemHome: fx.systemHome,
+      userHome: fx.userHome,
+    });
+
+    expect(plan.credential.target).toBe(join(fx.namedBundleDir, '.credentials.json'));
+    expect(plan.bundle.display).toBe('primary -> fred_example.com (fred@example.com)');
+  });
+
+  it('refuses first-auth state when a real file occupies the seat link', () => {
+    const fx = fixture();
+    const seatHome = join(fx.agentDir, '.claude');
+    mkdirSync(seatHome, { recursive: true });
+    writeFileSync(join(seatHome, '.credentials.json'), '{"private":true}\n');
+
+    expect(() =>
+      resolveFleetLaunchComposition('fred', {
+        systemHome: fx.systemHome,
+        userHome: fx.userHome,
+      }),
+    ).toThrowError(/first-auth.*refusing to delete or overwrite/i);
+    expect(lstatSync(join(seatHome, '.credentials.json')).isSymbolicLink()).toBe(false);
+  });
+});
+
+describe('managed plugin and skill links', () => {
+  it('installs listed entries and prunes only stale managed symlinks', () => {
+    const fx = fixture({
+      schema: 1,
+      harness: 'claude',
+      plugins: ['keep'],
+      skills: ['mosaic-tools'],
+    });
+    mkdirSync(join(fx.userHome, 'plugins', 'keep'), { recursive: true });
+    mkdirSync(join(fx.userHome, 'plugins', 'old'), { recursive: true });
+    mkdirSync(join(fx.userHome, 'skills', 'mosaic-tools'), { recursive: true });
+    const pluginHome = join(fx.agentDir, '.claude', 'plugins');
+    mkdirSync(pluginHome, { recursive: true });
+    symlinkSync(join(fx.userHome, 'plugins', 'old'), join(pluginHome, 'old'), 'dir');
+
+    const plan = resolveFleetLaunchComposition('fred', {
+      systemHome: fx.systemHome,
+      userHome: fx.userHome,
+    });
+    expect(plan.prune).toEqual([join(pluginHome, 'old')]);
+    applyFleetLaunchComposition(plan);
+
+    expect(() => lstatSync(join(pluginHome, 'old'))).toThrow();
+    expect(lstatSync(join(pluginHome, 'keep')).isSymbolicLink()).toBe(true);
+    expect(lstatSync(join(fx.agentDir, '.claude', 'skills', 'mosaic-tools')).isSymbolicLink()).toBe(
+      true,
+    );
+  });
+
+  it('tolerates harness metadata files in the install root and still refuses real directories', () => {
+    const fx = fixture({ schema: 1, harness: 'claude', plugins: [] });
+    const pluginHome = join(fx.agentDir, '.claude', 'plugins');
+    mkdirSync(pluginHome, { recursive: true });
+    writeFileSync(join(pluginHome, 'installed_plugins.json'), '{}\n');
+
+    const plan = resolveFleetLaunchComposition('fred', {
+      systemHome: fx.systemHome,
+      userHome: fx.userHome,
+    });
+    expect(plan.prune).toEqual([]);
+    expect(readFileSync(join(pluginHome, 'installed_plugins.json'), 'utf8')).toBe('{}\n');
+
+    mkdirSync(join(pluginHome, 'stray-plugin'), { recursive: true });
+    expect(() =>
+      resolveFleetLaunchComposition('fred', {
+        systemHome: fx.systemHome,
+        userHome: fx.userHome,
+      }),
+    ).toThrowError(/real plugin directory occupies managed install root.*refusing to prune/i);
+  });
+
+  it('surfaces a real directory at a managed link path without deleting it', () => {
+    const fx = fixture({ schema: 1, harness: 'claude', plugins: ['keep'] });
+    mkdirSync(join(fx.userHome, 'plugins', 'keep'), { recursive: true });
+    const occupied = join(fx.agentDir, '.claude', 'plugins', 'keep');
+    mkdirSync(occupied, { recursive: true });
+
+    expect(() =>
+      resolveFleetLaunchComposition('fred', {
+        systemHome: fx.systemHome,
+        userHome: fx.userHome,
+      }),
+    ).toThrowError(/real plugin directory.*refusing to delete/i);
+    expect(lstatSync(occupied).isDirectory()).toBe(true);
+  });
+});
+
+describe('fleet launch command outcomes', () => {
+  it('--dry-run prints without writing or invoking the launcher', () => {
+    const fx = fixture();
+    const program = new Command().exitOverride();
+    const fleet = program.command('fleet');
+    const launcher = vi.fn();
+    const stdout = vi.spyOn(process.stdout, 'write').mockImplementation(() => true);
+    registerFleetLaunchCommand(fleet, () => fx.systemHome, {
+      userHome: fx.userHome,
+      launcher,
+    });
+
+    try {
+      program.parse(['node', 'mosaic', 'fleet', 'launch', 'fred', '--dry-run']);
+      expect(stdout).toHaveBeenCalledWith(
+        expect.stringContaining('mosaic fleet launch fred --dry-run'),
+      );
+      expect(launcher).not.toHaveBeenCalled();
+      expect(() => lstatSync(join(fx.agentDir, '.claude'))).toThrow();
+    } finally {
+      stdout.mockRestore();
+    }
+  });
+
+  it('applies the plan and invokes the existing launch seam with declared values', () => {
+    const fx = fixture({
+      schema: 1,
+      harness: 'claude',
+      model: 'opus',
+      env: { SEAT_FLAG: 'yes' },
+    });
+    const program = new Command().exitOverride();
+    const fleet = program.command('fleet');
+    const launcher = vi.fn();
+    registerFleetLaunchCommand(fleet, () => fx.systemHome, {
+      userHome: fx.userHome,
+      launcher,
+    });
+
+    program.parse(['node', 'mosaic', 'fleet', 'launch', 'fred']);
+
+    expect(launcher).toHaveBeenCalledWith(
+      'claude',
+      ['--model', 'opus'],
+      {
+        CLAUDE_CONFIG_DIR: join(fx.agentDir, '.claude'),
+        MOSAIC_AGENT_NAME: 'fred',
+        SEAT_FLAG: 'yes',
+      },
+      { agentDir: fx.agentDir },
+    );
+    expect(lstatSync(join(fx.agentDir, '.claude', '.credentials.json')).isSymbolicLink()).toBe(
+      true,
+    );
+  });
+
+  it('sets a non-zero exit code and never invokes the launcher', () => {
+    const fx = fixture({ schema: 1, harness: 'claude', unknown: true });
+    const program = new Command().exitOverride();
+    const fleet = program.command('fleet');
+    const launcher = vi.fn();
+    const stderr = vi.spyOn(process.stderr, 'write').mockImplementation(() => true);
+    const priorExitCode = process.exitCode;
+    process.exitCode = 0;
+    registerFleetLaunchCommand(fleet, () => fx.systemHome, {
+      userHome: fx.userHome,
+      launcher,
+    });
+
+    try {
+      program.parse(['node', 'mosaic', 'fleet', 'launch', 'fred']);
+      expect(process.exitCode).toBe(1);
+      expect(launcher).not.toHaveBeenCalled();
+      expect(stderr).toHaveBeenCalledWith(expect.stringContaining('unknown profile key "unknown"'));
+    } finally {
+      process.exitCode = priorExitCode;
+      stderr.mockRestore();
+    }
+  });
+});
+
+describe('dry-run composition', () => {
+  it('renders a deterministic full composition and writes nothing', () => {
+    const fx = fixture({
+      schema: 1,
+      harness: 'claude',
+      bundle: 'primary',
+      model: 'opus',
+      overlay: 'overlay.json',
+      plugins: ['code-review'],
+      skills: ['mosaic-tools'],
+      env: { SEAT_FLAG: 'yes' },
+    });
+    writeFileSync(
+      join(fx.systemHome, 'runtime', 'claude', 'settings.json'),
+      '{"theme":"dark","hooks":["system"],"nested":{"system":true}}\n',
+    );
+    mkdirSync(join(fx.userHome, 'config', 'claude'), { recursive: true });
+    writeFileSync(
+      join(fx.userHome, 'config', 'claude', 'settings.json'),
+      '{"hooks":["user"],"nested":{"user":true}}\n',
+    );
+    writeFileSync(join(fx.agentDir, 'overlay.json'), '{"theme":null,"nested":{"agent":true}}\n');
+    mkdirSync(join(fx.userHome, 'plugins', 'code-review'), { recursive: true });
+    mkdirSync(join(fx.userHome, 'skills', 'mosaic-tools'), { recursive: true });
+
+    const plan = resolveFleetLaunchComposition('fred', {
+      systemHome: fx.systemHome,
+      userHome: fx.userHome,
+    });
+    const output = formatFleetLaunchDryRun(plan).replaceAll(fx.root, '<ROOT>');
+
+    expect(output).toMatchInlineSnapshot(`
+      "mosaic fleet launch fred --dry-run
+      profile: <ROOT>/user/fleet/agents/fred/profile.json (schema 1)
+      harness: claude
+      seat-home: <ROOT>/user/fleet/agents/fred/.claude
+      settings sources:
+        system: <ROOT>/system/runtime/claude/settings.json
+        user: <ROOT>/user/config/claude/settings.json
+        agent: <ROOT>/user/fleet/agents/fred/overlay.json
+        output: <ROOT>/user/fleet/agents/fred/.claude/settings.json
+        snapshot: <ROOT>/user/fleet/agents/fred/settings.generated.json
+      merged settings:
+      {
+        "hooks": [
+          "user"
+        ],
+        "nested": {
+          "agent": true,
+          "system": true,
+          "user": true
+        }
+      }
+      bundle: primary -> fred_example.com (fred@example.com)
+      symlinks:
+        credentials: <ROOT>/user/fleet/agents/fred/.claude/.credentials.json -> <ROOT>/user/auth/claude/fred_example.com/.credentials.json
+        plugin code-review: <ROOT>/user/fleet/agents/fred/.claude/plugins/code-review -> <ROOT>/user/plugins/code-review
+        skill mosaic-tools: <ROOT>/user/fleet/agents/fred/.claude/skills/mosaic-tools -> <ROOT>/user/skills/mosaic-tools
+      declared env:
+        CLAUDE_CONFIG_DIR=<ROOT>/user/fleet/agents/fred/.claude
+        MOSAIC_AGENT_NAME=fred
+        SEAT_FLAG=yes
+      argv: ["claude","--model","opus"]"
+    `);
+    expect(() => readFileSync(join(fx.agentDir, '.claude', 'settings.json'), 'utf8')).toThrow();
+
+    applyFleetLaunchComposition(plan);
+    expect(JSON.parse(readFileSync(plan.settings.output, 'utf8'))).toEqual({
+      hooks: ['user'],
+      nested: { agent: true, system: true, user: true },
+    });
+    expect(readFileSync(plan.settings.snapshot, 'utf8')).toBe(
+      readFileSync(plan.settings.output, 'utf8'),
+    );
+    expect(lstatSync(plan.credential.link).isSymbolicLink()).toBe(true);
+  });
+});
diff --git a/packages/mosaic/src/commands/fleet-launch-command.ts b/packages/mosaic/src/commands/fleet-launch-command.ts
new file mode 100644
index 00000000..42ebbe01
--- /dev/null
+++ b/packages/mosaic/src/commands/fleet-launch-command.ts
@@ -0,0 +1,744 @@
+import {
+  lstatSync,
+  mkdirSync,
+  readFileSync,
+  readlinkSync,
+  readdirSync,
+  realpathSync,
+  rmSync,
+  symlinkSync,
+  writeFileSync,
+  type Stats,
+} from 'node:fs';
+import { basename, dirname, isAbsolute, join, relative, resolve, sep } from 'node:path';
+import type { Command } from 'commander';
+import {
+  harnessHome,
+  launchFleetRuntime,
+  type FleetHarnessContext,
+  type RuntimeName,
+} from './launch.js';
+import { defaultFleetDataHome } from '../fleet/fleet-agent-scaffold.js';
+
+export const FLEET_AGENT_PROFILE_SCHEMA = 1;
+const PROFILE_KEYS = [
+  'schema',
+  'harness',
+  'bundle',
+  'model',
+  'overlay',
+  'plugins',
+  'skills',
+  'env',
+];
+const RUNTIMES: readonly RuntimeName[] = ['claude', 'codex', 'opencode', 'pi'];
+const AGENT_NAME = /^[A-Za-z0-9][A-Za-z0-9_.-]*$/;
+const STORE_ENTRY = /^[A-Za-z0-9][A-Za-z0-9_.@-]*$/;
+const BUNDLE_NAME = /^[A-Za-z0-9][A-Za-z0-9_.@-]*$/;
+const ENV_NAME = /^[A-Za-z_][A-Za-z0-9_]*$/;
+
+const CREDENTIAL_FILES: Record<RuntimeName, string> = {
+  claude: '.credentials.json',
+  pi: 'auth.json',
+  codex: 'auth.json',
+  opencode: 'auth.json',
+};
+
+export type FleetLaunchErrorCode =
+  | 'SCHEMA_TOO_NEW'
+  | 'PROFILE_INVALID'
+  | 'AGENT_NOT_SCAFFOLDED'
+  | 'COMPOSITION_FAILED'
+  | 'FIRST_AUTH_REFUSAL';
+
+export class FleetLaunchError extends Error {
+  constructor(
+    readonly code: FleetLaunchErrorCode,
+    message: string,
+  ) {
+    super(message);
+    this.name = 'FleetLaunchError';
+  }
+}
+
+export interface FleetAgentLaunchProfile {
+  readonly schema: 1;
+  readonly harness: RuntimeName;
+  readonly bundle: string;
+  readonly model?: string;
+  readonly overlay?: string;
+  readonly plugins: readonly string[];
+  readonly skills: readonly string[];
+  readonly env: Readonly<Record<string, string>>;
+}
+
+export interface FleetLaunchRoots {
+  readonly systemHome: string;
+  readonly userHome: string;
+}
+
+interface SettingsLayer {
+  readonly name: 'system' | 'user' | 'agent';
+  readonly path: string;
+  readonly present: boolean;
+  readonly value: Record<string, unknown>;
+}
+
+interface PlannedLink {
+  readonly kind: 'plugin' | 'skill';
+  readonly name: string;
+  readonly link: string;
+  readonly target: string;
+}
+
+export interface FleetLaunchComposition {
+  readonly name: string;
+  readonly profilePath: string;
+  readonly profile: FleetAgentLaunchProfile;
+  readonly agentDir: string;
+  readonly seatHome: string;
+  readonly settings: {
+    readonly layers: readonly SettingsLayer[];
+    readonly merged: Record<string, unknown>;
+    readonly output: string;
+    readonly snapshot: string;
+  };
+  readonly bundle: {
+    readonly requested: string;
+    readonly resolved: string;
+    readonly email?: string;
+    readonly display: string;
+  };
+  readonly credential: {
+    readonly link: string;
+    readonly target: string;
+  };
+  readonly installs: readonly PlannedLink[];
+  readonly prune: readonly string[];
+  readonly env: Readonly<Record<string, string>>;
+  readonly argv: readonly string[];
+}
+
+export interface FleetLaunchCommandDeps {
+  readonly userHome?: string;
+  readonly launcher?: (
+    runtime: RuntimeName,
+    args: string[],
+    declaredEnv: Readonly<Record<string, string>>,
+    context: FleetHarnessContext,
+  ) => void;
+}
+
+function requiredObject(value: unknown, label: string): Record<string, unknown> {
+  if (typeof value !== 'object' || value === null || Array.isArray(value)) {
+    throw new FleetLaunchError('PROFILE_INVALID', `${label} must be a JSON object.`);
+  }
+  return value as Record<string, unknown>;
+}
+
+function optionalString(value: unknown, label: string): string | undefined {
+  if (value === undefined) return undefined;
+  if (typeof value !== 'string' || value.trim() === '') {
+    throw new FleetLaunchError('PROFILE_INVALID', `${label} must be a non-empty string.`);
+  }
+  return value.trim();
+}
+
+function stringList(value: unknown, label: string): string[] {
+  if (value === undefined) return [];
+  if (!Array.isArray(value)) {
+    throw new FleetLaunchError(
+      'PROFILE_INVALID',
+      `${label} must be an array of store entry names.`,
+    );
+  }
+  return value.map((entry: unknown, index: number): string => {
+    if (typeof entry !== 'string' || !STORE_ENTRY.test(entry)) {
+      throw new FleetLaunchError(
+        'PROFILE_INVALID',
+        `${label}[${index}] must be a safe store entry name.`,
+      );
+    }
+    return entry;
+  });
+}
+
+/** Parse and strictly validate the frozen, user-facing per-agent profile schema. */
+export function parseFleetAgentProfile(source: string): FleetAgentLaunchProfile {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(source) as unknown;
+  } catch (error: unknown) {
+    const detail = error instanceof Error ? error.message : String(error);
+    throw new FleetLaunchError('PROFILE_INVALID', `profile.json is not valid JSON: ${detail}`);
+  }
+  const raw = requiredObject(parsed, 'profile.json');
+  if (!Number.isSafeInteger(raw['schema'])) {
+    throw new FleetLaunchError('PROFILE_INVALID', 'profile.json schema is required and must be 1.');
+  }
+  if ((raw['schema'] as number) > FLEET_AGENT_PROFILE_SCHEMA) {
+    throw new FleetLaunchError(
+      'SCHEMA_TOO_NEW',
+      `SCHEMA_TOO_NEW: profile schema ${String(raw['schema'])} is newer than supported schema ${FLEET_AGENT_PROFILE_SCHEMA}; upgrade Mosaic before launching this agent.`,
+    );
+  }
+  if (raw['schema'] !== FLEET_AGENT_PROFILE_SCHEMA) {
+    throw new FleetLaunchError(
+      'PROFILE_INVALID',
+      `profile.json schema ${String(raw['schema'])} is unsupported; expected schema 1.`,
+    );
+  }
+  const unknown = Object.keys(raw).filter((key: string): boolean => !PROFILE_KEYS.includes(key));
+  if (unknown.length > 0) {
+    throw new FleetLaunchError(
+      'PROFILE_INVALID',
+      `unknown profile key "${unknown[0]}" (schema ${String(raw['schema'])})`,
+    );
+  }
+  if (typeof raw['harness'] !== 'string' || !RUNTIMES.includes(raw['harness'] as RuntimeName)) {
+    throw new FleetLaunchError(
+      'PROFILE_INVALID',
+      `profile.json harness is required and must be one of: ${RUNTIMES.join(', ')}.`,
+    );
+  }
+  const bundle = optionalString(raw['bundle'], 'profile.json bundle') ?? 'primary';
+  if (!BUNDLE_NAME.test(bundle)) {
+    throw new FleetLaunchError(
+      'PROFILE_INVALID',
+      'profile.json bundle must be a safe bundle name.',
+    );
+  }
+  const overlay = optionalString(raw['overlay'], 'profile.json overlay');
+  if (overlay !== undefined && (isAbsolute(overlay) || overlay.split(/[\\/]/u).includes('..'))) {
+    throw new FleetLaunchError(
+      'PROFILE_INVALID',
+      'profile.json overlay must remain inside the agent directory.',
+    );
+  }
+  const rawEnv = raw['env'] === undefined ? {} : requiredObject(raw['env'], 'profile.json env');
+  const env: Record<string, string> = {};
+  for (const [key, value] of Object.entries(rawEnv)) {
+    if (!ENV_NAME.test(key) || typeof value !== 'string') {
+      throw new FleetLaunchError(
+        'PROFILE_INVALID',
+        `profile.json env entry "${key}" must have a valid name and string value.`,
+      );
+    }
+    env[key] = value;
+  }
+  const model = optionalString(raw['model'], 'profile.json model');
+  return {
+    schema: 1,
+    harness: raw['harness'] as RuntimeName,
+    bundle,
+    ...(model === undefined ? {} : { model }),
+    ...(overlay === undefined ? {} : { overlay }),
+    plugins: stringList(raw['plugins'], 'profile.json plugins'),
+    skills: stringList(raw['skills'], 'profile.json skills'),
+    env,
+  };
+}
+
+function isPlainObject(value: unknown): value is Record<string, unknown> {
+  return typeof value === 'object' && value !== null && !Array.isArray(value);
+}
+
+function cloneValue(value: unknown): unknown {
+  if (Array.isArray(value)) return value.map(cloneValue);
+  if (isPlainObject(value)) {
+    return Object.fromEntries(
+      Object.entries(value).map(([key, entry]) => [key, cloneValue(entry)]),
+    );
+  }
+  return value;
+}
+
+type MergeContext = 'root' | 'hooks' | 'nested';
+
+function mergeObject(
+  lower: Record<string, unknown>,
+  higher: Record<string, unknown>,
+  context: MergeContext = 'nested',
+): Record<string, unknown> {
+  const result = cloneValue(lower) as Record<string, unknown>;
+  for (const [key, highValue] of Object.entries(higher)) {
+    if (highValue === null) {
+      delete result[key];
+      continue;
+    }
+    const lowValue = result[key];
+    if (context === 'hooks' && Array.isArray(lowValue) && Array.isArray(highValue)) {
+      result[key] = [...(lowValue as unknown[]), ...(cloneValue(highValue) as unknown[])];
+      continue;
+    }
+    result[key] =
+      isPlainObject(lowValue) && isPlainObject(highValue)
+        ? mergeObject(
+            lowValue,
+            highValue,
+            context === 'root' && key === 'hooks' ? 'hooks' : 'nested',
+          )
+        : cloneValue(highValue);
+  }
+  return result;
+}
+
+/**
+ * Deep object merge. Scalars and arrays replace; null in a higher layer
+ * deletes. Exception: hook event arrays directly under the top-level `hooks`
+ * key concatenate (base entries first), so an overlay ADDS gating without
+ * erasing the base QA hooks that share an event — replacing them would make
+ * the gap-7 base/overlay split unimplementable without duplicating base
+ * hooks inside the lease overlay. Removing an event entirely still works via
+ * the null tombstone.
+ */
+export function deepMergeSettings(
+  ...layers: ReadonlyArray<Record<string, unknown> | undefined>
+): Record<string, unknown> {
+  return layers.reduce<Record<string, unknown>>(
+    (merged, layer) => (layer === undefined ? merged : mergeObject(merged, layer, 'root')),
+    {},
+  );
+}
+
+function lstatIfPresent(path: string): Stats | undefined {
+  try {
+    return lstatSync(path);
+  } catch (error: unknown) {
+    if ((error as NodeJS.ErrnoException).code === 'ENOENT') return undefined;
+    throw error;
+  }
+}
+
+function assertRealDirectory(path: string, label: string): void {
+  const info = lstatIfPresent(path);
+  if (!info?.isDirectory() || info.isSymbolicLink()) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `${label} must be a real, non-symlink directory: ${path}`,
+    );
+  }
+}
+
+function assertContained(root: string, candidate: string, label: string): void {
+  const rel = relative(resolve(root), resolve(candidate));
+  if (rel === '..' || rel.startsWith(`..${sep}`) || isAbsolute(rel)) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `${label} resolves outside ${root}: ${candidate}`,
+    );
+  }
+}
+
+function readSettingsLayer(
+  name: SettingsLayer['name'],
+  path: string,
+  required: boolean,
+): SettingsLayer {
+  const info = lstatIfPresent(path);
+  if (!info) {
+    if (required) {
+      throw new FleetLaunchError(
+        'COMPOSITION_FAILED',
+        `required ${name} settings missing: ${path}`,
+      );
+    }
+    return { name, path, present: false, value: {} };
+  }
+  if (!info.isFile() || info.isSymbolicLink()) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `${name} settings must be a real, non-symlink JSON file: ${path}`,
+    );
+  }
+  let value: unknown;
+  try {
+    value = JSON.parse(readFileSync(path, 'utf8')) as unknown;
+  } catch (error: unknown) {
+    const detail = error instanceof Error ? error.message : String(error);
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `${name} settings are invalid JSON: ${detail}`,
+    );
+  }
+  if (!isPlainObject(value)) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `${name} settings must contain a JSON object.`,
+    );
+  }
+  return { name, path, present: true, value };
+}
+
+function accountEmail(bundleDir: string): string | undefined {
+  const path = join(bundleDir, 'account.json');
+  const info = lstatIfPresent(path);
+  if (!info?.isFile() || info.isSymbolicLink()) return undefined;
+  try {
+    const account = JSON.parse(readFileSync(path, 'utf8')) as Record<string, unknown>;
+    const oauth = isPlainObject(account['oauthAccount']) ? account['oauthAccount'] : undefined;
+    for (const value of [oauth?.['emailAddress'], account['emailAddress'], account['email']]) {
+      if (typeof value === 'string' && value.trim() !== '') return value.trim();
+    }
+  } catch {
+    return undefined;
+  }
+  return undefined;
+}
+
+function resolveCredential(
+  profile: FleetAgentLaunchProfile,
+  userHome: string,
+  seatHome: string,
+): Pick<FleetLaunchComposition, 'bundle' | 'credential'> {
+  const authRoot = join(userHome, 'auth', profile.harness);
+  assertRealDirectory(authRoot, `${profile.harness} auth root`);
+  const bundlePath = join(authRoot, profile.bundle);
+  const bundleInfo = lstatIfPresent(bundlePath);
+  if (!bundleInfo) {
+    throw new FleetLaunchError('COMPOSITION_FAILED', `credential bundle not found: ${bundlePath}`);
+  }
+  if (bundleInfo.isSymbolicLink() && profile.bundle !== 'primary') {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `only the primary bundle may be an alias symlink: ${bundlePath}`,
+    );
+  }
+  let resolvedBundleDir: string;
+  try {
+    resolvedBundleDir = realpathSync(bundlePath);
+  } catch (error: unknown) {
+    const detail = error instanceof Error ? error.message : String(error);
+    throw new FleetLaunchError('COMPOSITION_FAILED', `credential bundle cannot resolve: ${detail}`);
+  }
+  assertContained(realpathSync(authRoot), resolvedBundleDir, 'credential bundle');
+  assertRealDirectory(resolvedBundleDir, 'resolved credential bundle');
+
+  const credentialTarget = join(resolvedBundleDir, CREDENTIAL_FILES[profile.harness]);
+  const credentialInfo = lstatIfPresent(credentialTarget);
+  if (!credentialInfo?.isFile() || credentialInfo.isSymbolicLink()) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `bundle credential must be a real, non-symlink credential file: ${credentialTarget}`,
+    );
+  }
+  const resolvedCredential = realpathSync(credentialTarget);
+  assertContained(realpathSync(authRoot), resolvedCredential, 'bundle credential');
+
+  const credentialLink = join(seatHome, CREDENTIAL_FILES[profile.harness]);
+  const seatInfo = lstatIfPresent(credentialLink);
+  if (seatInfo && !seatInfo.isSymbolicLink()) {
+    throw new FleetLaunchError(
+      'FIRST_AUTH_REFUSAL',
+      `first-auth state detected at ${credentialLink}; refusing to delete or overwrite the real credential file. Enroll or promote it explicitly.`,
+    );
+  }
+
+  const resolvedName = basename(resolvedBundleDir);
+  const email = accountEmail(resolvedBundleDir);
+  const display =
+    profile.bundle === resolvedName
+      ? `${resolvedName}${email ? ` (${email})` : ''}`
+      : `${profile.bundle} -> ${resolvedName}${email ? ` (${email})` : ''}`;
+  return {
+    bundle: {
+      requested: profile.bundle,
+      resolved: resolvedName,
+      ...(email === undefined ? {} : { email }),
+      display,
+    },
+    credential: { link: credentialLink, target: resolvedCredential },
+  };
+}
+
+function resolveManagedLinks(
+  kind: PlannedLink['kind'],
+  names: readonly string[],
+  userHome: string,
+  seatHome: string,
+): { installs: PlannedLink[]; prune: string[] } {
+  const plural = kind === 'plugin' ? 'plugins' : 'skills';
+  const storeRoot = join(userHome, plural);
+  const installRoot = join(seatHome, plural);
+  if (names.length > 0) assertRealDirectory(storeRoot, `${kind} store root`);
+
+  const installRootInfo = lstatIfPresent(installRoot);
+  if (installRootInfo?.isSymbolicLink() || (installRootInfo && !installRootInfo.isDirectory())) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `${kind} install root must be a real directory (the historical whole-store symlink requires explicit migration): ${installRoot}`,
+    );
+  }
+
+  const installs: PlannedLink[] = names.map((name: string): PlannedLink => {
+    const target = join(storeRoot, name);
+    const targetInfo = lstatIfPresent(target);
+    if (!targetInfo?.isDirectory() || targetInfo.isSymbolicLink()) {
+      throw new FleetLaunchError(
+        'COMPOSITION_FAILED',
+        `${kind} store entry must be a real, non-symlink directory: ${target}`,
+      );
+    }
+    assertContained(realpathSync(storeRoot), realpathSync(target), `${kind} store entry`);
+    const link = join(installRoot, name);
+    const linkInfo = lstatIfPresent(link);
+    if (linkInfo && !linkInfo.isSymbolicLink()) {
+      throw new FleetLaunchError(
+        'COMPOSITION_FAILED',
+        `real ${kind} directory occupies managed symlink path ${link}; refusing to delete it.`,
+      );
+    }
+    return { kind, name, link, target: realpathSync(target) };
+  });
+
+  const desired = new Set(names);
+  const prune: string[] = [];
+  if (installRootInfo?.isDirectory()) {
+    for (const entry of readdirSync(installRoot, { withFileTypes: true })) {
+      const path = join(installRoot, entry.name);
+      if (desired.has(entry.name)) continue;
+      if (!entry.isSymbolicLink()) {
+        // The harness writes its own metadata files (e.g. installed_plugins.json)
+        // beside the managed links; only a real directory is an unmanaged entry
+        // the pruner would orphan.
+        if (entry.isDirectory()) {
+          throw new FleetLaunchError(
+            'COMPOSITION_FAILED',
+            `real ${kind} directory occupies managed install root ${path}; refusing to prune it.`,
+          );
+        }
+        continue;
+      }
+      prune.push(path);
+    }
+  }
+  return { installs, prune };
+}
+
+function buildArgv(
+  profile: FleetAgentLaunchProfile,
+  seatHome: string,
+  passthrough: string[],
+): string[] {
+  const argv: string[] = [profile.harness];
+  if (profile.model) argv.push('--model', profile.model);
+  if (profile.harness === 'pi') {
+    for (const skill of profile.skills) argv.push('--skill', join(seatHome, 'skills', skill));
+  }
+  argv.push(...passthrough);
+  return argv;
+}
+
+/** Resolve and validate the complete launch without changing the filesystem. */
+export function resolveFleetLaunchComposition(
+  name: string,
+  roots: FleetLaunchRoots,
+  passthrough: string[] = [],
+): FleetLaunchComposition {
+  if (!AGENT_NAME.test(name)) {
+    throw new FleetLaunchError('PROFILE_INVALID', `invalid fleet agent name: ${name}`);
+  }
+  const agentDir = join(roots.userHome, 'fleet', 'agents', name);
+  if (lstatIfPresent(agentDir) === undefined) {
+    throw new FleetLaunchError(
+      'AGENT_NOT_SCAFFOLDED',
+      `no such fleet agent '${name}' — run: mosaic fleet agent new ${name}`,
+    );
+  }
+  assertRealDirectory(agentDir, 'fleet agent directory');
+  const profilePath = join(agentDir, 'profile.json');
+  const profileInfo = lstatIfPresent(profilePath);
+  if (!profileInfo?.isFile() || profileInfo.isSymbolicLink()) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `agent profile must be a real, non-symlink file: ${profilePath}`,
+    );
+  }
+  const profile = parseFleetAgentProfile(readFileSync(profilePath, 'utf8'));
+  const context: FleetHarnessContext = { agentDir };
+  const seatHome = harnessHome(profile.harness, context);
+  const seatHomeInfo = lstatIfPresent(seatHome);
+  if (seatHomeInfo && (!seatHomeInfo.isDirectory() || seatHomeInfo.isSymbolicLink())) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `agent harness home must be a real, non-symlink directory: ${seatHome}`,
+    );
+  }
+  const settingsOutput = join(seatHome, 'settings.json');
+  const settingsSnapshot = join(agentDir, 'settings.generated.json');
+  for (const [label, path] of [
+    ['generated settings', settingsOutput],
+    ['generated settings snapshot', settingsSnapshot],
+  ] as const) {
+    const info = lstatIfPresent(path);
+    if (info && (!info.isFile() || info.isSymbolicLink())) {
+      throw new FleetLaunchError(
+        'COMPOSITION_FAILED',
+        `${label} path must be a real file or absent: ${path}`,
+      );
+    }
+  }
+  const overlayPath = join(agentDir, profile.overlay ?? 'overlay.json');
+  assertContained(agentDir, overlayPath, 'agent overlay');
+  const layers: SettingsLayer[] = [
+    readSettingsLayer(
+      'system',
+      join(roots.systemHome, 'runtime', profile.harness, 'settings.json'),
+      true,
+    ),
+    readSettingsLayer(
+      'user',
+      join(roots.userHome, 'config', profile.harness, 'settings.json'),
+      false,
+    ),
+    profile.overlay === undefined
+      ? { name: 'agent', path: overlayPath, present: false, value: {} }
+      : readSettingsLayer('agent', overlayPath, false),
+  ];
+  const merged = deepMergeSettings(...layers.map((layer) => layer.value));
+  const credential = resolveCredential(profile, roots.userHome, seatHome);
+  const plugins = resolveManagedLinks('plugin', profile.plugins, roots.userHome, seatHome);
+  const skills = resolveManagedLinks('skill', profile.skills, roots.userHome, seatHome);
+  const homeEnvName: Record<RuntimeName, string> = {
+    claude: 'CLAUDE_CONFIG_DIR',
+    pi: 'PI_CODING_AGENT_DIR',
+    codex: 'CODEX_HOME',
+    opencode: 'XDG_CONFIG_HOME',
+  };
+  const env: Record<string, string> = {
+    ...profile.env,
+    [homeEnvName[profile.harness]]: seatHome,
+    MOSAIC_AGENT_NAME: name,
+  };
+  return {
+    name,
+    profilePath,
+    profile,
+    agentDir,
+    seatHome,
+    settings: {
+      layers,
+      merged,
+      output: settingsOutput,
+      snapshot: settingsSnapshot,
+    },
+    ...credential,
+    installs: [...plugins.installs, ...skills.installs],
+    prune: [...plugins.prune, ...skills.prune],
+    env,
+    argv: buildArgv(profile, seatHome, passthrough),
+  };
+}
+
+function ensureSymlink(link: string, target: string): void {
+  const info = lstatIfPresent(link);
+  if (info?.isSymbolicLink()) {
+    const current = resolve(dirname(link), readlinkSync(link));
+    if (current === target) return;
+    rmSync(link);
+  } else if (info) {
+    throw new FleetLaunchError(
+      'COMPOSITION_FAILED',
+      `real object occupies managed symlink path ${link}; refusing to delete it.`,
+    );
+  }
+  mkdirSync(dirname(link), { recursive: true });
+  symlinkSync(target, link, 'file');
+}
+
+function canonicalJson(value: unknown): unknown {
+  if (Array.isArray(value)) return value.map(canonicalJson);
+  if (!isPlainObject(value)) return value;
+  return Object.fromEntries(
+    Object.keys(value)
+      .sort((left, right) => left.localeCompare(right, 'en'))
+      .map((key) => [key, canonicalJson(value[key])]),
+  );
+}
+
+/** Apply a previously resolved plan. No caller should apply a dry-run plan. */
+export function applyFleetLaunchComposition(plan: FleetLaunchComposition): void {
+  mkdirSync(plan.seatHome, { recursive: true });
+  const settings = `${JSON.stringify(canonicalJson(plan.settings.merged), null, 2)}\n`;
+  writeFileSync(plan.settings.output, settings, { mode: 0o600 });
+  writeFileSync(plan.settings.snapshot, settings, { mode: 0o600 });
+  ensureSymlink(plan.credential.link, plan.credential.target);
+  for (const path of plan.prune) {
+    const info = lstatIfPresent(path);
+    if (info?.isSymbolicLink()) rmSync(path);
+    else if (info) {
+      throw new FleetLaunchError(
+        'COMPOSITION_FAILED',
+        `real object replaced managed symlink before prune: ${path}`,
+      );
+    }
+  }
+  for (const install of plan.installs) ensureSymlink(install.link, install.target);
+}
+
+/** Stable, auditable text representation used by --dry-run and snapshot tests. */
+export function formatFleetLaunchDryRun(plan: FleetLaunchComposition): string {
+  const lines = [
+    `mosaic fleet launch ${plan.name} --dry-run`,
+    `profile: ${plan.profilePath} (schema ${plan.profile.schema})`,
+    `harness: ${plan.profile.harness}`,
+    `seat-home: ${plan.seatHome}`,
+    'settings sources:',
+  ];
+  for (const layer of plan.settings.layers) {
+    lines.push(`  ${layer.name}: ${layer.path}${layer.present ? '' : ' (absent)'}`);
+  }
+  lines.push(`  output: ${plan.settings.output}`);
+  lines.push(`  snapshot: ${plan.settings.snapshot}`);
+  lines.push('merged settings:');
+  lines.push(JSON.stringify(canonicalJson(plan.settings.merged), null, 2));
+  lines.push(`bundle: ${plan.bundle.display}`);
+  lines.push('symlinks:');
+  lines.push(`  credentials: ${plan.credential.link} -> ${plan.credential.target}`);
+  for (const install of plan.installs) {
+    lines.push(`  ${install.kind} ${install.name}: ${install.link} -> ${install.target}`);
+  }
+  for (const path of plan.prune) lines.push(`  prune: ${path}`);
+  lines.push('declared env:');
+  for (const key of Object.keys(plan.env).sort()) lines.push(`  ${key}=${plan.env[key]}`);
+  lines.push(`argv: ${JSON.stringify(plan.argv)}`);
+  return lines.join('\n');
+}
+
+/** Register `mosaic fleet launch <name> [--dry-run]` on the fleet control plane. */
+export function registerFleetLaunchCommand(
+  fleetCommand: Command,
+  systemHomeFor: () => string,
+  deps: FleetLaunchCommandDeps = {},
+): Command {
+  return fleetCommand
+    .command('launch <name>')
+    .description('Compose and launch one per-agent harness home')
+    .option('--dry-run', 'Print the fully resolved composition without writing or launching')
+    .allowUnknownOption(true)
+    .allowExcessArguments(true)
+    .action((name: string, opts: { dryRun?: boolean }, command: Command): void => {
+      try {
+        const userHome = deps.userHome ?? defaultFleetDataHome();
+        const passthrough = command.args.slice(1);
+        const plan = resolveFleetLaunchComposition(
+          name,
+          { systemHome: systemHomeFor(), userHome },
+          passthrough,
+        );
+        if (opts.dryRun === true) {
+          process.stdout.write(`${formatFleetLaunchDryRun(plan)}\n`);
+          return;
+        }
+        applyFleetLaunchComposition(plan);
+        console.log(`[mosaic] bundle: ${plan.bundle.display}`);
+        const launcher = deps.launcher ?? launchFleetRuntime;
+        launcher(plan.profile.harness, plan.argv.slice(1), plan.env, { agentDir: plan.agentDir });
+      } catch (error: unknown) {
+        process.exitCode = 1;
+        const code = error instanceof FleetLaunchError ? `${error.code}: ` : '';
+        const message = error instanceof Error ? error.message : String(error);
+        process.stderr.write(`mosaic fleet launch failed: ${code}${message}\n`);
+      }
+    });
+}
diff --git a/packages/mosaic/src/commands/fleet.spec.ts b/packages/mosaic/src/commands/fleet.spec.ts
index 9aaaf055..c6e6b516 100644
--- a/packages/mosaic/src/commands/fleet.spec.ts
+++ b/packages/mosaic/src/commands/fleet.spec.ts
@@ -82,6 +82,7 @@ describe('registerFleetCommand', () => {
     expect(fleet).toBeDefined();
     expect(fleet!.commands.map((command) => command.name()).sort()).toEqual([
       'add',
+      'agent',
       'apply',
       'backlog',
       'create',
@@ -91,6 +92,7 @@ describe('registerFleetCommand', () => {
       'init',
       'install',
       'install-systemd',
+      'launch',
       'migrate-v1',
       'persona',
       'plan',
diff --git a/packages/mosaic/src/commands/fleet.ts b/packages/mosaic/src/commands/fleet.ts
index c344660a..03b840f9 100644
--- a/packages/mosaic/src/commands/fleet.ts
+++ b/packages/mosaic/src/commands/fleet.ts
@@ -38,6 +38,10 @@ import {
   registerFleetAgentCrudCommands,
   type FleetAgentCrudCommandDeps,
 } from './fleet-agent-crud-command.js';
+import {
+  registerFleetAgentScaffoldCommand,
+  type FleetAgentScaffoldCommandDeps,
+} from './fleet-agent-scaffold-command.js';
 import {
   registerFleetMigrationCommand,
   type FleetMigrationCommandDeps,
@@ -63,6 +67,7 @@ import { registerFleetBacklogCommand } from './fleet-backlog.js';
 import { registerFleetPersonaCommand } from './fleet-personas.js';
 import { registerFleetProfileCommand } from './fleet-profiles.js';
 import { registerFleetProvisionCommand } from './fleet-provision.js';
+import { registerFleetLaunchCommand, type FleetLaunchCommandDeps } from './fleet-launch-command.js';
 
 /**
  * A function that spawns a command with inherited stdio (TTY passthrough).
@@ -97,6 +102,10 @@ export interface FleetCommandDeps {
    */
   sleepFn?: SleepFn;
   mosaicHome?: string;
+  /** User-owned fleet/auth/config root. Defaults to ~/.mosaic. */
+  mosaicUserHome?: string;
+  /** Test/embedding seam for the final process-replacing fleet launch. */
+  fleetLauncher?: FleetLaunchCommandDeps['launcher'];
   frameworkRoot?: string;
   /**
    * Injectable TTY check for `fleet init` wizard. Defaults to process.stdin.isTTY.
@@ -104,6 +113,8 @@ export interface FleetCommandDeps {
    */
   isStdinTTY?: boolean;
   projectionApplier?: FleetAgentCrudCommandDeps['projectionApplier'];
+  /** Test-only user-data root for `fleet agent new` (production: ~/.mosaic). */
+  fleetDataHome?: FleetAgentScaffoldCommandDeps['fleetDataHome'];
   reconcileDeps?: FleetReconcilerCommandDeps['reconcileDeps'];
   migrationDeps?: Omit<FleetMigrationCommandDeps, 'mosaicHome'>;
 }
@@ -2041,6 +2052,14 @@ export function registerFleetCommand(program: Command, deps: FleetCommandDeps =
   // fleet/ directory as the roster and heartbeats.
   registerFleetBacklogCommand(cmd, () => cmd.opts<{ mosaicHome: string }>().mosaicHome);
 
+  // User-facing per-agent profile.json is the launch-composition SSOT. It is
+  // intentionally independent of roster-v2, whose lifecycle/topology registry
+  // does not model auth bundles, overlays, plugins, skills, or seat env.
+  registerFleetLaunchCommand(cmd, () => cmd.opts<{ mosaicHome: string }>().mosaicHome, {
+    ...(deps.mosaicUserHome === undefined ? {} : { userHome: deps.mosaicUserHome }),
+    ...(deps.fleetLauncher === undefined ? {} : { launcher: deps.fleetLauncher }),
+  });
+
   // System-type profiles (H2): declarative persona roster + topology, resolved
   // from <mosaicHome>/fleet/profiles/*.yaml using the same --mosaic-home flag.
   registerFleetProfileCommand(cmd, () => cmd.opts<{ mosaicHome: string }>().mosaicHome);
@@ -2054,6 +2073,10 @@ export function registerFleetCommand(program: Command, deps: FleetCommandDeps =
   // profile. DRY-RUN by default; --write persists under the same --mosaic-home.
   registerFleetProvisionCommand(cmd, () => cmd.opts<{ mosaicHome: string }>().mosaicHome);
 
+  // `fleet agent new` owns user-data harness homes under ~/.mosaic. The
+  // existing roster-v2 CRUD remains direct fleet control-plane CRUD, so there
+  // is one `agent` namespace but deliberately separate state authorities.
+  registerFleetAgentScaffoldCommand(cmd, { fleetDataHome: deps.fleetDataHome });
   // Roster-v2 desired-state mutations belong directly to the fleet control
   // plane; they do not share the root `mosaic agent` gateway-backed surface.
   registerFleetAgentCrudCommands(cmd, deps);
diff --git a/packages/mosaic/src/commands/launch.ts b/packages/mosaic/src/commands/launch.ts
index c4d8f3d2..0466a0f3 100644
--- a/packages/mosaic/src/commands/launch.ts
+++ b/packages/mosaic/src/commands/launch.ts
@@ -35,7 +35,12 @@ import { runLeaseEnforcementDoctorCheck } from './lease-doctor-check.js';
 const MOSAIC_HOME = process.env['MOSAIC_HOME'] ?? join(homedir(), '.config', 'mosaic');
 const MAX_INSTALLED_TOOLS_BYTES = 256 * 1024;
 
-type RuntimeName = 'claude' | 'codex' | 'opencode' | 'pi';
+export type RuntimeName = 'claude' | 'codex' | 'opencode' | 'pi';
+
+/** Fleet context for the single harness-home resolution seam. */
+export interface FleetHarnessContext {
+  readonly agentDir: string;
+}
 
 const RUNTIME_LABELS: Record<RuntimeName, string> = {
   claude: 'Claude Code',
@@ -64,19 +69,19 @@ const HARNESS_HOME_ENV: Record<RuntimeName, string> = {
   opencode: 'XDG_CONFIG_HOME',
 };
 
-/** Dedicated mosaic-owned home for a runtime: ~/.config/mosaic/.<runtime> */
-function harnessHome(runtime: RuntimeName): string {
-  return join(MOSAIC_HOME, `.${runtime}`);
+/** Dedicated runtime home, optionally scoped to a user fleet agent. */
+export function harnessHome(runtime: RuntimeName, fleet?: FleetHarnessContext): string {
+  return join(fleet?.agentDir ?? MOSAIC_HOME, `.${runtime}`);
 }
 
 /**
  * Env overlay pointing a runtime at its mosaic-owned home. The directory is
  * created on demand so a first launch does not fail on a missing path.
  */
-function harnessEnv(runtime: RuntimeName): Record<string, string> {
+function harnessEnv(runtime: RuntimeName, fleet?: FleetHarnessContext): Record<string, string> {
   const key = HARNESS_HOME_ENV[runtime];
   if (!key) return {};
-  const home = harnessHome(runtime);
+  const home = harnessHome(runtime, fleet);
   mkdirSync(home, { recursive: true });
   return { [key]: home };
 }
@@ -162,7 +167,13 @@ function redactArgv(argv: string[]): string[] {
   );
 }
 
-function recordLaunch(runtime: RuntimeName, cliArgs: string[], yolo: boolean): void {
+function recordLaunch(
+  runtime: RuntimeName,
+  cliArgs: string[],
+  yolo: boolean,
+  fleet?: FleetHarnessContext,
+  launchEnv: NodeJS.ProcessEnv = process.env,
+): void {
   try {
     mkdirSync(LAUNCH_LEDGER_DIR, { recursive: true, mode: 0o700 });
     // Correlation id for the lease.register half. Set into process.env so it
@@ -180,13 +191,13 @@ function recordLaunch(runtime: RuntimeName, cliArgs: string[], yolo: boolean): v
       mode: yolo ? 'yolo' : 'normal',
       cwd: process.cwd(),
       cli_version: CLI_VERSION,
-      config_home: harnessHome(runtime),
+      config_home: harnessHome(runtime, fleet),
       config_home_isolated: true,
       config_home_env: HARNESS_HOME_ENV[runtime] ?? null,
       argv: redactArgv(cliArgs),
       normative_fragments: normativeFragmentDigests(runtime),
       // names only — values are never recorded
-      mosaic_env_present: Object.keys(process.env)
+      mosaic_env_present: Object.keys(launchEnv)
         .filter((k) => k.startsWith('MOSAIC_'))
         .sort(),
     };
@@ -262,9 +273,9 @@ interface SettingsAudit {
   warnings: string[];
 }
 
-function auditClaudeSettings(): SettingsAudit {
+function auditClaudeSettings(fleet?: FleetHarnessContext): SettingsAudit {
   const warnings: string[] = [];
-  const settingsPath = join(harnessHome('claude'), 'settings.json');
+  const settingsPath = join(harnessHome('claude', fleet), 'settings.json');
   const settings = readJson(settingsPath);
 
   if (!settings) {
@@ -483,7 +494,11 @@ function buildPrdBlock(): string {
  * `mosaicHome` is parameterized for testability; production callers use the
  * module-level default.
  */
-export function composeContract(runtime: RuntimeName, mosaicHome: string = MOSAIC_HOME): string {
+export function composeContract(
+  runtime: RuntimeName,
+  mosaicHome: string = MOSAIC_HOME,
+  env: NodeJS.ProcessEnv = process.env,
+): string {
   const runtimeContractPaths: Record<RuntimeName, string> = {
     claude: join(mosaicHome, 'runtime', 'claude', 'RUNTIME.md'),
     codex: join(mosaicHome, 'runtime', 'codex', 'RUNTIME.md'),
@@ -540,13 +555,13 @@ For required push/merge/issue-close/release actions, execute without routine con
     parts.push('\n\n## Operator Overlay (USER.local.md)\n\n' + userLocal);
   }
 
-  const fleetIdentity = resolveFleetIdentity(mosaicHome, process.env['MOSAIC_AGENT_NAME']);
+  const fleetIdentity = resolveFleetIdentity(mosaicHome, env['MOSAIC_AGENT_NAME']);
   if (!fleetIdentity.ok) {
     throw new Error(`Fleet communications contract unavailable: ${fleetIdentity.error}`);
   }
   const canonicalMember = fleetIdentity.identity?.member;
-  if (canonicalMember && process.env['MOSAIC_AGENT_CLASS']?.trim()) {
-    const ambientClass = canonicalizeRoleClass(process.env['MOSAIC_AGENT_CLASS']).canonicalClass;
+  if (canonicalMember && env['MOSAIC_AGENT_CLASS']?.trim()) {
+    const ambientClass = canonicalizeRoleClass(env['MOSAIC_AGENT_CLASS']).canonicalClass;
     if (ambientClass !== canonicalMember.className) {
       throw new Error(
         `Ambient MOSAIC_AGENT_CLASS resolves to "${ambientClass}" but canonical roster member "${canonicalMember.name}" resolves to "${canonicalMember.className}". Refusing split identity authority.`,
@@ -583,13 +598,13 @@ For required push/merge/issue-close/release actions, execute without routine con
   // Fleet launches derive every identity projection from the one canonical roster
   // member resolved above. Non-fleet launches retain the legacy ambient persona
   // and tool-policy behavior.
-  const personaClass = canonicalMember?.className ?? process.env['MOSAIC_AGENT_CLASS'];
+  const personaClass = canonicalMember?.className ?? env['MOSAIC_AGENT_CLASS'];
   const persona = readPersonaContractBlock(mosaicHome, personaClass);
   if (persona) parts.push('\n\n' + persona);
 
   const toolPolicyName = canonicalMember
     ? canonicalMember.toolPolicy
-    : process.env['MOSAIC_AGENT_TOOL_POLICY'];
+    : env['MOSAIC_AGENT_TOOL_POLICY'];
   const toolPolicy = readFleetToolPolicyBlock(toolPolicyName);
   if (toolPolicy) parts.push('\n\n' + toolPolicy);
 
@@ -613,8 +628,8 @@ function readFleetToolPolicyBlock(policy: string | undefined): string {
 }
 
 /** @deprecated internal alias — use composeContract. Retained for call-site clarity. */
-function buildRuntimePrompt(runtime: RuntimeName): string {
-  return composeContract(runtime);
+function buildRuntimePrompt(runtime: RuntimeName, env: NodeJS.ProcessEnv = process.env): string {
+  return composeContract(runtime, MOSAIC_HOME, env);
 }
 
 // ─── Session lock ────────────────────────────────────────────────────────────
@@ -695,8 +710,12 @@ function checkResumableSession(): void {
 
 // ─── Write config for runtimes that read from fixed paths ────────────────────
 
-function ensureRuntimeConfig(runtime: RuntimeName, destPath: string): void {
-  const prompt = buildRuntimePrompt(runtime);
+function ensureRuntimeConfig(
+  runtime: RuntimeName,
+  destPath: string,
+  env: NodeJS.ProcessEnv = process.env,
+): void {
+  const prompt = buildRuntimePrompt(runtime, env);
   mkdirSync(dirname(destPath), { recursive: true });
   const existing = readOptional(destPath);
   if (existing !== prompt) {
@@ -889,7 +908,38 @@ function getMissionPrompt(): string {
   return `Active mission detected: ${mission.name}. Read the mission state files and report status.`;
 }
 
-function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): never {
+interface RuntimeLaunchContext {
+  readonly fleet?: FleetHarnessContext;
+  readonly declaredEnv?: Readonly<Record<string, string>>;
+}
+
+function minimalLaunchEnv(declared: Readonly<Record<string, string>>): NodeJS.ProcessEnv {
+  const env: NodeJS.ProcessEnv = {};
+  for (const name of [
+    'PATH',
+    'HOME',
+    'USER',
+    'LOGNAME',
+    'SHELL',
+    'TERM',
+    'COLORTERM',
+    'LANG',
+    'LC_ALL',
+    'TMPDIR',
+    'XDG_RUNTIME_DIR',
+  ]) {
+    const value = process.env[name];
+    if (value !== undefined) env[name] = value;
+  }
+  return { ...env, ...declared };
+}
+
+function launchRuntime(
+  runtime: RuntimeName,
+  args: string[],
+  yolo: boolean,
+  context: RuntimeLaunchContext = {},
+): never {
   checkMosaicHome();
   checkFile(join(MOSAIC_HOME, 'AGENTS.md'), 'AGENTS.md');
   checkSoul();
@@ -909,14 +959,32 @@ function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): nev
   const missionStr = hasMissionNoArgs ? ' (active mission detected)' : '';
 
   writeSessionLock(runtime);
+  const launchEnv =
+    context.declaredEnv === undefined ? process.env : minimalLaunchEnv(context.declaredEnv);
+  // A per-agent profile is the launch SSOT and intentionally does not require a
+  // second roster registry. Keep roster-v1 identity composition for legacy
+  // launches, but remove its identity keys from the contract-build environment
+  // for a profile-backed seat. The declared identity is still exported to the
+  // harness process below.
+  const contractEnv =
+    context.declaredEnv === undefined
+      ? launchEnv
+      : Object.fromEntries(
+          Object.entries(launchEnv).filter(
+            ([name]) =>
+              name !== 'MOSAIC_AGENT_NAME' &&
+              name !== 'MOSAIC_AGENT_CLASS' &&
+              name !== 'MOSAIC_AGENT_TOOL_POLICY',
+          ),
+        );
 
   switch (runtime) {
     case 'claude': {
       // Audit Claude Code settings and warn about missing hooks/plugins
-      const settingsAudit = auditClaudeSettings();
+      const settingsAudit = auditClaudeSettings(context.fleet);
       printSettingsWarnings(settingsAudit);
 
-      const prompt = buildRuntimePrompt('claude');
+      const prompt = buildRuntimePrompt('claude', contractEnv);
       const cliArgs: string[] = [];
       cliArgs.push('--append-system-prompt', prompt);
       if (hasMissionNoArgs) {
@@ -925,13 +993,20 @@ function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): nev
         cliArgs.push(...args);
       }
       console.log(`[mosaic] Launching ${label}${modeStr}${missionStr}...`);
-      recordLaunch('claude', cliArgs, yolo);
-      execLeaseGatedRuntime('claude', cliArgs, process.env, yolo);
+      recordLaunch('claude', cliArgs, yolo, context.fleet, launchEnv);
+      if (process.env['MOSAIC_LAUNCH_ID']) {
+        launchEnv['MOSAIC_LAUNCH_ID'] = process.env['MOSAIC_LAUNCH_ID'];
+      }
+      execLeaseGatedRuntime('claude', cliArgs, launchEnv, yolo, context.fleet);
       break;
     }
 
     case 'codex': {
-      ensureRuntimeConfig('codex', join(harnessHome('codex'), 'instructions.md'));
+      ensureRuntimeConfig(
+        'codex',
+        join(harnessHome('codex', context.fleet), 'instructions.md'),
+        contractEnv,
+      );
       const cliArgs = yolo ? ['--dangerously-bypass-approvals-and-sandbox'] : [];
       if (hasMissionNoArgs) {
         cliArgs.push(missionPrompt);
@@ -939,22 +1014,38 @@ function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): nev
         cliArgs.push(...args);
       }
       console.log(`[mosaic] Launching ${label}${modeStr}${missionStr}...`);
-      recordLaunch('codex', cliArgs, yolo);
-      execRuntime('codex', cliArgs, { ...process.env, ...harnessEnv('codex') });
+      recordLaunch('codex', cliArgs, yolo, context.fleet, launchEnv);
+      execRuntime('codex', cliArgs, {
+        ...launchEnv,
+        ...harnessEnv('codex', context.fleet),
+        ...(process.env['MOSAIC_LAUNCH_ID']
+          ? { MOSAIC_LAUNCH_ID: process.env['MOSAIC_LAUNCH_ID'] }
+          : {}),
+      });
       break;
     }
 
     case 'opencode': {
       // opencode follows XDG, so its config resolves to $XDG_CONFIG_HOME/opencode.
-      ensureRuntimeConfig('opencode', join(harnessHome('opencode'), 'opencode', 'AGENTS.md'));
+      ensureRuntimeConfig(
+        'opencode',
+        join(harnessHome('opencode', context.fleet), 'opencode', 'AGENTS.md'),
+        contractEnv,
+      );
       console.log(`[mosaic] Launching ${label}${modeStr}...`);
-      recordLaunch('opencode', args, yolo);
-      execRuntime('opencode', args, { ...process.env, ...harnessEnv('opencode') });
+      recordLaunch('opencode', args, yolo, context.fleet, launchEnv);
+      execRuntime('opencode', args, {
+        ...launchEnv,
+        ...harnessEnv('opencode', context.fleet),
+        ...(process.env['MOSAIC_LAUNCH_ID']
+          ? { MOSAIC_LAUNCH_ID: process.env['MOSAIC_LAUNCH_ID'] }
+          : {}),
+      });
       break;
     }
 
     case 'pi': {
-      const prompt = buildRuntimePrompt('pi');
+      const prompt = buildRuntimePrompt('pi', contractEnv);
       const cliArgs = ['--append-system-prompt', prompt];
       cliArgs.push(...buildPiSkillArgs(args));
       cliArgs.push(...discoverPiExtension());
@@ -964,8 +1055,11 @@ function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): nev
         cliArgs.push(...args);
       }
       console.log(`[mosaic] Launching ${label}${modeStr}${missionStr}...`);
-      recordLaunch('pi', cliArgs, yolo);
-      execLeaseGatedRuntime('pi', cliArgs);
+      recordLaunch('pi', cliArgs, yolo, context.fleet, launchEnv);
+      if (process.env['MOSAIC_LAUNCH_ID']) {
+        launchEnv['MOSAIC_LAUNCH_ID'] = process.env['MOSAIC_LAUNCH_ID'];
+      }
+      execLeaseGatedRuntime('pi', cliArgs, launchEnv, false, context.fleet);
       break;
     }
   }
@@ -993,6 +1087,7 @@ function execLeaseGatedRuntime(
   args: string[],
   baseEnv: NodeJS.ProcessEnv = process.env,
   dangerous = false,
+  fleet?: FleetHarnessContext,
 ): void {
   const launcher = resolveTool('lease-broker', 'launch-runtime.py');
   const dangerousArgs = dangerous ? ['--dangerous'] : [];
@@ -1001,13 +1096,23 @@ function execLeaseGatedRuntime(
     [launcher, ...dangerousArgs, '--runtime', runtime, '--', runtime, ...args],
     {
       ...baseEnv,
-      ...harnessEnv(runtime),
+      ...harnessEnv(runtime, fleet),
       MOSAIC_LEASE_BROKER_SOCKET: defaultLeaseBrokerSocket(baseEnv),
       MOSAIC_RUNTIME_GENERATION: baseEnv['MOSAIC_RUNTIME_GENERATION'] ?? '1',
     },
   );
 }
 
+/** Fleet entry point reusing the normative runtime launch and exec path. */
+export function launchFleetRuntime(
+  runtime: RuntimeName,
+  args: string[],
+  declaredEnv: Readonly<Record<string, string>>,
+  fleet: FleetHarnessContext,
+): never {
+  return launchRuntime(runtime, args, false, { fleet, declaredEnv });
+}
+
 /** exec into the runtime, replacing the current process. */
 function execRuntime(cmd: string, args: string[], env: NodeJS.ProcessEnv = process.env): void {
   try {
diff --git a/packages/mosaic/src/fleet/fleet-agent-scaffold.ts b/packages/mosaic/src/fleet/fleet-agent-scaffold.ts
new file mode 100644
index 00000000..fbb4dbaa
--- /dev/null
+++ b/packages/mosaic/src/fleet/fleet-agent-scaffold.ts
@@ -0,0 +1,270 @@
+import { lstat, mkdir, readFile, readdir, readlink, symlink, writeFile } from 'node:fs/promises';
+import { homedir } from 'node:os';
+import { isAbsolute, join, relative, resolve } from 'node:path';
+
+export type FleetAgentHarness = 'claude' | 'pi';
+
+export interface FleetAgentScaffoldOptions {
+  readonly dataHome?: string;
+  readonly name: string;
+  readonly harness?: string;
+  readonly bundle?: string;
+  readonly model?: string;
+}
+
+export interface FleetAgentScaffoldResult {
+  readonly agentDir: string;
+  readonly profile: Readonly<Record<string, unknown>>;
+  readonly idempotent: boolean;
+  readonly credentialTarget: string;
+  readonly credentialTargetExists: boolean;
+}
+
+export class FleetAgentScaffoldError extends Error {
+  readonly code: 'invalid-request' | 'agent-exists-different';
+
+  constructor(code: FleetAgentScaffoldError['code'], message: string) {
+    super(message);
+    this.name = 'FleetAgentScaffoldError';
+    this.code = code;
+  }
+}
+
+/** User-owned data root, deliberately distinct from the update-owned mosaic home. */
+export function defaultFleetDataHome(): string {
+  return process.env['MOSAIC_DATA_HOME'] ?? join(homedir(), '.mosaic');
+}
+
+/**
+ * Materialize one fleet seat from authored, deterministic template content.
+ * Settings composition intentionally does not happen here: launch owns the
+ * three-layer settings merge and writes the generated settings.json then.
+ */
+export async function scaffoldFleetAgent(
+  options: FleetAgentScaffoldOptions,
+): Promise<FleetAgentScaffoldResult> {
+  const name = requireSafeName(options.name);
+  const harness = requireHarness(options.harness ?? 'claude');
+  const bundle = requireBundle(options.bundle ?? 'primary');
+  const model = optionalNonEmpty(options.model, '--model');
+  const dataHome = resolve(options.dataHome ?? defaultFleetDataHome());
+  const agentDir = join(dataHome, 'fleet', 'agents', name);
+  const homeName = harness === 'claude' ? '.claude' : '.pi';
+  const credentialName = harness === 'claude' ? '.credentials.json' : 'auth.json';
+  const credentialTarget = join(dataHome, 'auth', harness, bundle, credentialName);
+  const profile: Record<string, unknown> = {
+    schema: 1,
+    harness,
+    bundle,
+    overlay: 'overlay.json',
+    ...(model === undefined ? {} : { model }),
+    env: { MOSAIC_AGENT_NAME: name },
+  };
+  const entries: [string, ExpectedFile][] = [
+    ['profile.json', { type: 'file', content: json(profile) }],
+    ['SOUL.md', { type: 'file', content: soul(name) }],
+    ['overlay.json', { type: 'file', content: '{}\n' }],
+    [
+      join(homeName, harness === 'claude' ? 'CLAUDE.md' : 'AGENTS.md'),
+      { type: 'file', content: identityBootstrap(name) },
+    ],
+    [join(homeName, credentialName), { type: 'symlink', target: credentialTarget }],
+  ];
+  if (harness === 'claude') {
+    entries.push([
+      join(homeName, '.claude.json'),
+      { type: 'file', content: json(onboardingState()) },
+    ]);
+  }
+  const files = new Map<string, ExpectedFile>(entries);
+
+  const differences = await findDifferences(agentDir, files);
+  if (differences.length > 0) {
+    throw new FleetAgentScaffoldError(
+      'agent-exists-different',
+      `Agent "${name}" already exists with different user-owned file(s): ${differences.join(', ')}. Refusing to overwrite.`,
+    );
+  }
+
+  const idempotent = await pathExists(agentDir);
+  if (!idempotent) {
+    for (const [file, expected] of files) {
+      const path = join(agentDir, file);
+      await mkdir(join(path, '..'), { recursive: true, mode: 0o700 });
+      if (expected.type === 'file') {
+        await writeFile(path, expected.content, { encoding: 'utf8', mode: 0o600, flag: 'wx' });
+      } else {
+        // A dangling link is intentional before enrollment. It makes absent auth
+        // visible at launch instead of silently selecting another account.
+        await symlink(expected.target, path);
+      }
+    }
+  }
+
+  return {
+    agentDir,
+    profile,
+    idempotent,
+    credentialTarget,
+    credentialTargetExists: await pathExists(credentialTarget),
+  };
+}
+
+type ExpectedFile =
+  | { readonly type: 'file'; readonly content: string }
+  | { readonly type: 'symlink'; readonly target: string };
+
+async function findDifferences(
+  agentDir: string,
+  expected: ReadonlyMap<string, ExpectedFile>,
+): Promise<string[]> {
+  let root;
+  try {
+    root = await lstat(agentDir);
+  } catch (error: unknown) {
+    if (isMissing(error)) return [];
+    throw error;
+  }
+  if (!root.isDirectory() || root.isSymbolicLink()) return ['.'];
+
+  const actual = await listRelativeEntries(agentDir);
+  const expectedDirs = new Set<string>();
+  for (const path of expected.keys()) {
+    const parent = relative('.', join(path, '..'));
+    if (parent !== '') expectedDirs.add(parent);
+  }
+  const paths = new Set([
+    ...expected.keys(),
+    ...actual.filter((path: string): boolean => !expectedDirs.has(path)),
+  ]);
+  const differences: string[] = [];
+  for (const path of [...paths].sort()) {
+    const required = expected.get(path);
+    if (!required) {
+      differences.push(path);
+      continue;
+    }
+    try {
+      const info = await lstat(join(agentDir, path));
+      if (required.type === 'file') {
+        if (
+          !info.isFile() ||
+          info.isSymbolicLink() ||
+          (await readFile(join(agentDir, path), 'utf8')) !== required.content
+        ) {
+          differences.push(path);
+        }
+      } else if (
+        !info.isSymbolicLink() ||
+        (await readlink(join(agentDir, path))) !== required.target
+      ) {
+        differences.push(path);
+      }
+    } catch (error: unknown) {
+      if (isMissing(error)) differences.push(path);
+      else throw error;
+    }
+  }
+  return differences;
+}
+
+async function listRelativeEntries(root: string, prefix = ''): Promise<string[]> {
+  const result: string[] = [];
+  for (const entry of await readdir(join(root, prefix), { withFileTypes: true })) {
+    const path = join(prefix, entry.name);
+    if (entry.isDirectory() && !entry.isSymbolicLink()) {
+      result.push(path, ...(await listRelativeEntries(root, path)));
+    } else {
+      result.push(path);
+    }
+  }
+  return result;
+}
+
+function requireSafeName(value: string): string {
+  if (
+    typeof value !== 'string' ||
+    value.length === 0 ||
+    value === '.' ||
+    value === '..' ||
+    value.includes('/') ||
+    value.includes('\\') ||
+    value.includes('\0') ||
+    isAbsolute(value)
+  ) {
+    throw new FleetAgentScaffoldError(
+      'invalid-request',
+      'Agent name must be one non-empty path component (not absolute or traversal).',
+    );
+  }
+  return value;
+}
+
+function requireHarness(value: string): FleetAgentHarness {
+  if (value === 'claude' || value === 'pi') return value;
+  throw new FleetAgentScaffoldError('invalid-request', '--harness must be claude or pi.');
+}
+
+function requireBundle(value: string): string {
+  if (
+    typeof value !== 'string' ||
+    value.length === 0 ||
+    value === '.' ||
+    value === '..' ||
+    value.includes('/') ||
+    value.includes('\\') ||
+    value.includes('\0') ||
+    isAbsolute(value)
+  ) {
+    throw new FleetAgentScaffoldError(
+      'invalid-request',
+      '--bundle must be one non-empty auth-bundle path component.',
+    );
+  }
+  return value;
+}
+
+function optionalNonEmpty(value: string | undefined, option: string): string | undefined {
+  if (value === undefined) return undefined;
+  if (value.length === 0 || value.includes('\0')) {
+    throw new FleetAgentScaffoldError('invalid-request', `${option} must be a non-empty string.`);
+  }
+  return value;
+}
+
+function onboardingState(): Record<string, unknown> {
+  return { hasCompletedOnboarding: true, theme: 'dark' };
+}
+
+function soul(name: string): string {
+  return `# SOUL\n\n## Identity\n\nYou are ${name}, a Mosaic fleet agent seat.\n\nRole: _Describe this seat's role._\n`;
+}
+
+/** Identity is materialized by value so restricted harness modes never need to read SOUL.md. */
+function identityBootstrap(name: string): string {
+  return `# Mosaic Fleet Agent Identity\n\nYou are ${name}, a Mosaic fleet agent seat.\n\nYour mechanical identity is ${name} (MOSAIC_AGENT_NAME). Keep this identity when working in repositories with other personas.\n`;
+}
+
+function json(value: unknown): string {
+  return `${JSON.stringify(value, null, 2)}\n`;
+}
+
+async function pathExists(path: string): Promise<boolean> {
+  try {
+    await lstat(path);
+    return true;
+  } catch (error: unknown) {
+    if (isMissing(error)) return false;
+    throw error;
+  }
+}
+
+function isMissing(error: unknown): boolean {
+  return (error as NodeJS.ErrnoException).code === 'ENOENT';
+}
+
+/** Guardrail kept explicit for callers that construct paths from untrusted text. */
+export function isContainedInFleetDataHome(dataHome: string, path: string): boolean {
+  const rel = relative(resolve(dataHome), resolve(path));
+  return rel === '' || (!rel.startsWith('..') && !isAbsolute(rel));
+}
diff --git a/packages/mosaic/src/lease-broker/promotion_trigger_unittest.py b/packages/mosaic/src/lease-broker/promotion_trigger_unittest.py
index 3f5deff1..0026f457 100644
--- a/packages/mosaic/src/lease-broker/promotion_trigger_unittest.py
+++ b/packages/mosaic/src/lease-broker/promotion_trigger_unittest.py
@@ -23,6 +23,7 @@ COMPLETE_PATH = TOOLS / "promote-complete.py"
 OBSERVER_CLIENT_PATH = TOOLS / "receipt-observer-client.py"
 RECEIPT_CHALLENGE_PATH = TOOLS / "receipt_challenge.py"
 CLAUDE_SETTINGS = FRAMEWORK / "runtime/claude/settings.json"
+CLAUDE_LEASE_OVERLAY = FRAMEWORK / "runtime/claude/lease-overlay.json"
 CLAUDE_COMMAND = FRAMEWORK / "runtime/claude/commands/mosaic-promote.md"
 SESSION_ID = "a" * 64
 CHALLENGE = "b" * 64
@@ -569,8 +570,15 @@ class PromotionCompleteTest(PromotionHookFixture):
 
 class PromotionTemplateWiringTest(unittest.TestCase):
     def test_gated_claude_template_wires_begin_and_ordered_stop_chain(self) -> None:
-        settings = json.loads(CLAUDE_SETTINGS.read_text(encoding="utf-8"))
-        hooks = settings["hooks"]
+        base = json.loads(CLAUDE_SETTINGS.read_text(encoding="utf-8"))
+        overlay = json.loads(CLAUDE_LEASE_OVERLAY.read_text(encoding="utf-8"))
+        # A launched seat composes base + lease overlay; hook event arrays
+        # concatenate with base entries first, so wiring is asserted against
+        # the composed view rather than either file alone.
+        hooks: dict[str, list] = {}
+        for layer in (base["hooks"], overlay["hooks"]):
+            for event, groups in layer.items():
+                hooks.setdefault(event, []).extend(groups)
         submit_commands = [
             hook["command"]
             for group in hooks["UserPromptSubmit"]
diff --git a/packages/mosaic/src/mutator-gate/mutator-gate.acceptance.spec.ts b/packages/mosaic/src/mutator-gate/mutator-gate.acceptance.spec.ts
index f2f48e2e..dbc27b41 100644
--- a/packages/mosaic/src/mutator-gate/mutator-gate.acceptance.spec.ts
+++ b/packages/mosaic/src/mutator-gate/mutator-gate.acceptance.spec.ts
@@ -6,6 +6,7 @@ import { spawn, spawnSync, type ChildProcess } from 'node:child_process';
 import { afterEach, describe, expect, test } from 'vitest';
 
 import { launchClaudex, type ClaudexHarnessAdapter } from '../commands/claudex.js';
+import { deepMergeSettings } from '../commands/fleet-launch-command.js';
 import {
   observeAndPromoteReceiptChallenge,
   requestBrokerReply,
@@ -42,6 +43,19 @@ const launcherPath = join(frameworkRoot, 'tools/lease-broker/launch-runtime.py')
 const revokerPath = join(frameworkRoot, 'tools/lease-broker/revoke-lease.py');
 const compactionThreatPath = join(repositoryRoot, 'docs/architecture/compaction-revocation.md');
 const claudeSettingsPath = join(frameworkRoot, 'runtime/claude/settings.json');
+const claudeLeaseOverlayPath = join(frameworkRoot, 'runtime/claude/lease-overlay.json');
+
+// The gated seat contract is the COMPOSITION of the ungated base and the
+// lease overlay (gap-7 split); assertions about lease wiring must read that
+// composed view, produced by the same merge the launcher uses.
+async function readGatedClaudeSettings(): Promise<Record<string, unknown>> {
+  const base = JSON.parse(await readFile(claudeSettingsPath, 'utf8')) as Record<string, unknown>;
+  const overlay = JSON.parse(await readFile(claudeLeaseOverlayPath, 'utf8')) as Record<
+    string,
+    unknown
+  >;
+  return deepMergeSettings(base, overlay);
+}
 const piExtensionPath = join(frameworkRoot, 'runtime/pi/mosaic-extension.ts');
 const piLifecyclePath = join(frameworkRoot, 'runtime/pi/lease-lifecycle.ts');
 const prdyInitPath = join(frameworkRoot, 'tools/prdy/prdy-init.sh');
@@ -364,7 +378,7 @@ describe('whole mutator-class lease gate', () => {
     expect(parserResult.status).toBe(0);
     expect(JSON.parse(parserResult.stdout)).toMatchObject({ gated: 0, total: 0 });
 
-    const settings = JSON.parse(await readFile(claudeSettingsPath, 'utf8')) as {
+    const settings = (await readGatedClaudeSettings()) as unknown as {
       hooks: { PreToolUse: Array<{ matcher: string; hooks: Array<{ command: string }> }> };
     };
     const allToolsHook = settings.hooks.PreToolUse.find((hook) => hook.matcher === '.*');
@@ -660,7 +674,7 @@ describe('whole mutator-class lease gate', () => {
   });
 
   test('Claude and Pi compaction observer wiring is complete and fail-closed', async () => {
-    const settings = JSON.parse(await readFile(claudeSettingsPath, 'utf8')) as {
+    const settings = (await readGatedClaudeSettings()) as unknown as {
       hooks: Record<string, Array<{ matcher?: string; hooks: Array<{ command: string }> }>>;
     };
     expect(
@@ -956,7 +970,7 @@ raise SystemExit(0 if len(session_id) == 64 and hook_present and observers_prese
     await promote(socket, sessionId, pending.receipt_challenge!);
     expect(runRuntimeGate(socket, sessionId, 'claude', 'Bash').status).toBe(0);
 
-    const settings = JSON.parse(await readFile(claudeSettingsPath, 'utf8')) as {
+    const settings = (await readGatedClaudeSettings()) as unknown as {
       hooks: { PreToolUse: Array<{ matcher?: string; hooks: Array<{ command: string }> }> };
     };
     expect(
diff --git a/packages/mosaic/src/runtime/claude-settings-base.spec.ts b/packages/mosaic/src/runtime/claude-settings-base.spec.ts
new file mode 100644
index 00000000..71cf7c95
--- /dev/null
+++ b/packages/mosaic/src/runtime/claude-settings-base.spec.ts
@@ -0,0 +1,131 @@
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { describe, expect, it } from 'vitest';
+
+type Json = null | boolean | number | string | Json[] | { [key: string]: Json };
+type JsonObject = { [key: string]: Json };
+
+const frameworkRoot = fileURLToPath(new URL('../../framework/', import.meta.url));
+const basePath = `${frameworkRoot}runtime/claude/settings.json`;
+const overlayPath = `${frameworkRoot}runtime/claude/lease-overlay.json`;
+const gatedFixturePath = fileURLToPath(
+  new URL('./fixtures/claude-settings.gated.pre-split.json', import.meta.url),
+);
+
+function readJson(path: string): JsonObject {
+  return JSON.parse(readFileSync(path, 'utf8')) as JsonObject;
+}
+
+function isObject(value: unknown): value is JsonObject {
+  return typeof value === 'object' && value !== null && !Array.isArray(value);
+}
+
+// This fixture contract composes hook event arrays additively. It is deliberately
+// limited to verifying that the split is lossless; production launch merge
+// semantics remain owned by W-F1.
+function deepMerge(base: Json, overlay: Json): Json {
+  if (Array.isArray(base) && Array.isArray(overlay)) {
+    const merged = [...base];
+    for (const entry of overlay) {
+      if (!isObject(entry) || !Array.isArray(entry['hooks'])) {
+        merged.push(entry);
+        continue;
+      }
+      const matchingIndex = merged.findIndex(
+        (candidate) =>
+          isObject(candidate) &&
+          Array.isArray(candidate['hooks']) &&
+          candidate['matcher'] === entry['matcher'],
+      );
+      if (matchingIndex === -1) merged.push(entry);
+      else merged[matchingIndex] = deepMerge(merged[matchingIndex]!, entry);
+    }
+    return merged;
+  }
+  if (isObject(base) && isObject(overlay)) {
+    const merged: JsonObject = { ...base };
+    for (const [key, value] of Object.entries(overlay)) {
+      merged[key] = key in merged ? deepMerge(merged[key]!, value) : value;
+    }
+    return merged;
+  }
+  return overlay;
+}
+
+function normalize(value: Json): Json {
+  if (Array.isArray(value)) {
+    return value
+      .map(normalize)
+      .sort((left, right) => JSON.stringify(left).localeCompare(JSON.stringify(right)));
+  }
+  if (isObject(value)) {
+    return Object.fromEntries(
+      Object.entries(value)
+        .sort(([left], [right]) => left.localeCompare(right))
+        .map(([key, nested]) => [key, normalize(nested)]),
+    );
+  }
+  return value;
+}
+
+function hookCommands(settings: JsonObject): string[] {
+  const hooks = settings['hooks'];
+  if (!isObject(hooks)) return [];
+
+  return Object.values(hooks).flatMap((event) => {
+    if (!Array.isArray(event)) return [];
+    return event.flatMap((entry) => {
+      if (!isObject(entry) || !Array.isArray(entry['hooks'])) return [];
+      return entry['hooks'].flatMap((hook) =>
+        isObject(hook) && typeof hook['command'] === 'string' ? [hook['command']] : [],
+      );
+    });
+  });
+}
+
+const sequentialThinking: JsonObject = {
+  command: 'npx',
+  args: ['-y', '@modelcontextprotocol/server-sequential-thinking'],
+};
+
+describe('canonical Claude base and lease-promotion overlay', () => {
+  it('keeps every lease command out of the ungated base', () => {
+    const base = readJson(basePath);
+    const commands = hookCommands(base);
+
+    for (const marker of ['mutator-gate', 'receipt-observer', 'promote-', 'revoke-lease']) {
+      expect(
+        commands.some((command) => command.includes(marker)),
+        marker,
+      ).toBe(false);
+    }
+  });
+
+  it('reconstructs the pre-split gated hooks while retaining the canonical MCP correction', () => {
+    const base = readJson(basePath);
+    const overlay = readJson(overlayPath);
+    const preSplit = readJson(gatedFixturePath);
+    const expected: JsonObject = {
+      ...preSplit,
+      mcpServers: { 'sequential-thinking': sequentialThinking },
+    };
+
+    expect(normalize(deepMerge(base, overlay))).toEqual(normalize(expected));
+  });
+
+  it('ships sequential-thinking in the base', () => {
+    const base = readJson(basePath);
+    expect(base['mcpServers']).toEqual({ 'sequential-thinking': sequentialThinking });
+  });
+
+  it('limits the overlay to lease hook entries', () => {
+    const overlay = readJson(overlayPath);
+    expect(Object.keys(overlay)).toEqual(['hooks']);
+
+    const commands = hookCommands(overlay);
+    expect(commands).toHaveLength(6);
+    for (const command of commands) {
+      expect(command).toMatch(/mutator-gate|receipt-observer|promote-|revoke-lease/);
+    }
+  });
+});
diff --git a/packages/mosaic/src/runtime/fixtures/claude-settings.gated.pre-split.json b/packages/mosaic/src/runtime/fixtures/claude-settings.gated.pre-split.json
new file mode 100644
index 00000000..0e6dcec1
--- /dev/null
+++ b/packages/mosaic/src/runtime/fixtures/claude-settings.gated.pre-split.json
@@ -0,0 +1,319 @@
+{
+  "model": "opus",
+  "hooks": {
+    "PreCompact": [
+      {
+        "matcher": ".*",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason pre-compact"
+          }
+        ]
+      }
+    ],
+    "SessionStart": [
+      {
+        "matcher": "compact",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason session-start-compact"
+          }
+        ]
+      },
+      {
+        "matcher": "resume|clear",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 \"$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py\" --runtime claude --reason session-start-rollover --bump-generation"
+          }
+        ]
+      }
+    ],
+    "UserPromptSubmit": [
+      {
+        "matcher": "^/mosaic-promote$",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ~/.config/mosaic/tools/lease-broker/promote-begin.py",
+            "timeout": 15
+          }
+        ]
+      }
+    ],
+    "PreToolUse": [
+      {
+        "matcher": ".*",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ~/.config/mosaic/tools/lease-broker/mutator-gate.py --runtime claude --recovery-command ~/.config/mosaic/tools/lease-broker/recover-context.py",
+            "timeout": 3
+          }
+        ]
+      },
+      {
+        "matcher": "Write|Edit|MultiEdit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.config/mosaic/tools/qa/prevent-memory-write.sh",
+            "timeout": 10
+          }
+        ]
+      }
+    ],
+    "PostToolUse": [
+      {
+        "matcher": "Edit|MultiEdit|Write",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.config/mosaic/tools/qa/qa-hook-stdin.sh",
+            "timeout": 60
+          }
+        ]
+      },
+      {
+        "matcher": "Edit|MultiEdit|Write",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.config/mosaic/tools/qa/typecheck-hook.sh",
+            "timeout": 30
+          }
+        ]
+      }
+    ],
+    "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 ~/.config/mosaic/tools/lease-broker/receipt-observer-client.py --runtime claude --latest-entry; observer_status=$?; python3 ~/.config/mosaic/tools/lease-broker/promote-complete.py; exit $observer_status",
+            "timeout": 15
+          },
+          {
+            "type": "command",
+            "command": "~/.config/mosaic/tools/qa/reflect-stop-hook.sh",
+            "timeout": 15
+          }
+        ]
+      }
+    ]
+  },
+  "enabledPlugins": {
+    "frontend-design@claude-plugins-official": true,
+    "feature-dev@claude-plugins-official": true,
+    "code-review@claude-plugins-official": true,
+    "pr-review-toolkit@claude-plugins-official": true
+  },
+  "skipDangerousModePermissionPrompt": true,
+  "allowedCommands": [
+    "npm",
+    "npm install",
+    "npm run",
+    "npm test",
+    "npm build",
+    "npm start",
+    "npm run dev",
+    "npm run build",
+    "npm run lint",
+    "npm run typecheck",
+    "npm run test:ci",
+    "npm run test:e2e",
+    "npm run test:unit",
+    "npm run test:integration",
+    "npm run test:cov",
+    "npm run test:security",
+    "npm run security:scan",
+    "npm run security:audit",
+    "npm run performance:benchmark",
+    "npm run build:dev",
+    "npm run build:prod",
+    "npm run test",
+    "npm run test:watch",
+    "npm run migrate",
+    "npm run migrate:rollback",
+    "npm run db:seed",
+    "npm run db:reset",
+    "node",
+    "yarn",
+    "pnpm",
+    "npx",
+    "npx tsc",
+    "npx eslint",
+    "npx prettier",
+    "npx jest",
+    "npx vitest",
+    "git",
+    "git add",
+    "git commit",
+    "git push",
+    "git pull",
+    "git status",
+    "git diff",
+    "git log",
+    "git branch",
+    "git checkout",
+    "git merge",
+    "git init",
+    "git remote",
+    "git fetch",
+    "git reset",
+    "git rebase",
+    "git stash",
+    "git tag",
+    "git show",
+    "git config",
+    "gh",
+    "gh issue",
+    "gh pr",
+    "gh repo",
+    "gh api",
+    "docker",
+    "docker build",
+    "docker run",
+    "docker ps",
+    "docker logs",
+    "docker exec",
+    "docker stop",
+    "docker start",
+    "docker pull",
+    "docker push",
+    "docker-compose",
+    "docker-compose up",
+    "docker-compose down",
+    "docker-compose build",
+    "docker-compose logs",
+    "docker-compose ps",
+    "docker-compose exec",
+    "kubectl",
+    "kubectl get",
+    "kubectl describe",
+    "kubectl logs",
+    "kubectl apply",
+    "kubectl delete",
+    "kubectl port-forward",
+    "mkdir",
+    "touch",
+    "chmod",
+    "chown",
+    "ls",
+    "cd",
+    "pwd",
+    "cp",
+    "mv",
+    "rm",
+    "cat",
+    "echo",
+    "head",
+    "tail",
+    "grep",
+    "grep -E",
+    "grep -r",
+    "find",
+    "find -name",
+    "find -type",
+    "find -path",
+    "find -exec",
+    "find . -type f",
+    "find . -type d",
+    "wc",
+    "sort",
+    "uniq",
+    "curl",
+    "wget",
+    "ping",
+    "netstat",
+    "ss",
+    "lsof",
+    "psql",
+    "pg_dump",
+    "pg_restore",
+    "sqlite3",
+    "jest",
+    "vitest",
+    "playwright",
+    "cypress",
+    "artillery",
+    "lighthouse",
+    "tsc",
+    "eslint",
+    "prettier",
+    "snyk",
+    "semgrep",
+    "tar",
+    "gzip",
+    "unzip",
+    "zip",
+    "which",
+    "whoami",
+    "id",
+    "env",
+    "export",
+    "source",
+    "sleep",
+    "date",
+    "uptime",
+    "df",
+    "du",
+    "free",
+    "top",
+    "htop",
+    "ps",
+    "tree",
+    "jq",
+    "sed",
+    "awk",
+    "xargs",
+    "tee",
+    "test",
+    "true",
+    "false",
+    "basename",
+    "dirname",
+    "realpath",
+    "readlink",
+    "stat",
+    "file",
+    "make",
+    "cmake",
+    "gcc",
+    "g++",
+    "clang",
+    "python",
+    "python3",
+    "pip",
+    "pip3",
+    "pip install",
+    "poetry",
+    "pipenv",
+    "go",
+    "go build",
+    "go test",
+    "go run",
+    "go mod",
+    "cargo",
+    "rustc",
+    "ruby",
+    "gem",
+    "bundle",
+    "rake",
+    "java",
+    "javac",
+    "mvn",
+    "gradle",
+    "dotnet",
+    "msbuild",
+    "php",
+    "composer",
+    "perl",
+    "cpan",
+    "nohup"
+  ],
+  "enableAllMcpTools": true
+}