Scope Migrator shell to dry-run and scratch-copy execution

run_shell is dry-run/scratch-copy ONLY: never execute the forward migration against live state, no background shells (shell_collect unmounted; foreground with timeouts only). Scratch copies live under tmp/, are cleaned up afterwards, and the scratch path is reported in the delivery. Rename the registry leaf test to dry-run-scoped and raise the migrator prompt budgets to 12800 chars / 13900 bytes (measured-max + 2000/+3000, ceiling 100).

Author: TheGreatAxios

src/agent/directors/migrator/package.test.ts

@@ -43,6 +43,29 @@ describe("migratorPackage", () => {
     expect(p).toMatch(/do not ship it/);
   });
 
+  test("systemPrompt scopes run_shell to dry-run/scratch-only, forbids live execution", () => {
+    const p = migratorPackage.systemPrompt;
+    expect(p).toMatch(/dry-run and scratch-copy execution ONLY/);
+    expect(p).toMatch(/never execute the forward migration/);
+    expect(p).toMatch(/live state/);
+  });
+
+  test("systemPrompt forbids background shells — foreground with timeouts only", () => {
+    const p = migratorPackage.systemPrompt;
+    expect(p).toMatch(/Background shells are forbidden/);
+    expect(p).toMatch(/background: true/);
+    expect(p).toMatch(/shell_collect/);
+    expect(p).toMatch(/foreground/);
+    expect(p).toMatch(/timeouts only/);
+  });
+
+  test("systemPrompt makes scratch auditable under tmp/ with reported path", () => {
+    const p = migratorPackage.systemPrompt;
+    expect(p).toMatch(/tmp\//);
+    expect(p).toMatch(/clean them up afterwards/);
+    expect(p).toMatch(/scratch path in the delivery/);
+  });
+
   test("systemPrompt states the report shape", () => {
     const p = migratorPackage.systemPrompt;
     expect(p).toMatch(

src/agent/directors/migrator/package.ts

@@ -26,5 +26,5 @@ export const migratorPackage: DirectorPackage = {
   modelRole: "plan",
   systemPrompt: `PRIMARY INTENT: Ship reversible data migrations with dry-run evidence and a tested rollback path.
 
-You are Migrator, the reversible-migration leaf. You own settings-schema, config-key, run.json, and context-store-layout data changes ONLY — never bulk renames, never features. Every change ships three artifacts: (1) dry-run output showing exactly what would change, (2) the forward migration path, (3) the rollback path back to the prior shape. State what happens to in-flight sessions on both paths. Verify the rollback by executing it in a scratch copy (temporary test, cleaned up afterwards), not by inspection. If a change cannot be rolled back, say so plainly and stop — do not ship it. Report: dry-run output, forward path, rollback path, in-flight impact.`,
+You are Migrator, the reversible-migration leaf. You own settings-schema, config-key, run.json, and context-store-layout data changes ONLY — never bulk renames, never features. Every change ships three artifacts: (1) dry-run output showing exactly what would change, (2) the forward migration path, (3) the rollback path back to the prior shape. State what happens to in-flight sessions on both paths. Verify the rollback by executing it in a scratch copy (temporary test, cleaned up afterwards), not by inspection. run_shell is for dry-run and scratch-copy execution ONLY — never execute the forward migration (or anything else) against live state. Background shells are forbidden (background: true starts are uncollectable without shell_collect, which is deliberately not mounted) — use foreground calls with timeouts only. Keep scratch copies under tmp/, clean them up afterwards, and report the scratch path in the delivery. If a change cannot be rolled back, say so plainly and stop — do not ship it. Report: dry-run output, forward path, rollback path, in-flight impact.`,
 };

src/agent/directors/registry.test.ts

@@ -133,14 +133,16 @@ describe("director registry", () => {
     expect(packageToProfile(g).orchestrator).toBe(true);
   });
 
-  test("migrator is a read-only leaf with no fleet verbs (CL-7671)", () => {
+  test("migrator is a dry-run-scoped leaf with no fleet verbs (CL-7671)", () => {
     const m = DIRECTOR_REGISTRY.migrator;
     expect(m.id).toBe("migrator");
     expect(m.tier).toBe("leaf");
     expect(m.spawn.maySpawn).toBe(false);
     expect(m.modelRole).toBe("plan");
     expect(m.tools?.allow).toEqual(["read_file", "grep", "lsp", "run_shell"]);
     expect(packageToProfile(m).orchestrator).toBe(false);
+    expect(m.systemPrompt).toMatch(/dry-run and scratch-copy execution ONLY/);
+    expect(m.systemPrompt).toMatch(/Background shells are forbidden/);
     const r = resolveDirector({ agentId: "migrator" });
     expect(r.ok).toBe(true);
     if (r.ok) expect(r.package.id).toBe("migrator");

src/agent/prompt-sizes.test.ts

@@ -33,7 +33,9 @@ const CHAR_BUDGET: Record<DirectorId, number> = {
   shakespeare: 54700,
   testsmith: 16200,
   tester: 13900,
-  migrator: 12300,
+  // CL-7671 scope-honesty sentences grew migrator past the 12300-char
+  // placeholder: measured-max + 2000 allowance, ceiling to 100.
+  migrator: 12800,
 };
 
 const BYTE_BUDGET: Record<DirectorId, number> = {
@@ -55,7 +57,9 @@ const BYTE_BUDGET: Record<DirectorId, number> = {
   shakespeare: 55900,
   testsmith: 17200,
   tester: 15000,
-  migrator: 13400,
+  // CL-7671 scope-honesty sentences grew migrator past the 13400-byte
+  // placeholder: measured-max + 3000 allowance, ceiling to 100.
+  migrator: 13900,
 };
 
 function budgetMessage(