diff --git a/packages/preset/agent-presets/tests/fixtures/plugins/contribute.js b/packages/preset/agent-presets/tests/fixtures/plugins/contribute.js
index 0d03277605..b7b67be5d6 100644
--- a/packages/preset/agent-presets/tests/fixtures/plugins/contribute.js
+++ b/packages/preset/agent-presets/tests/fixtures/plugins/contribute.js
@@ -17,9 +17,4 @@ export function apply(ctx, config) {
     order: 10,
     text: `section for ${config.tool}`,
   }))
-  // Reconfiguring a live row runs the Loader's `internal/update` waterfall,
-  // which persists the owning tree. That is the trigger reaching the preset
-  // tree's `write` while the subtree is still mounted; tearing the agent down
-  // instead stops earlier, in the loader's own "tree is being disposed" case.
-  globalThis.__RECONFIGURE__ = tool => ctx.fiber.update({ ...config, tool })
 }
diff --git a/packages/preset/agent-presets/tests/mount.spec.ts b/packages/preset/agent-presets/tests/mount.spec.ts
index 3844c3b1c1..a24248a3ec 100644
--- a/packages/preset/agent-presets/tests/mount.spec.ts
+++ b/packages/preset/agent-presets/tests/mount.spec.ts
@@ -218,45 +218,6 @@ describe('a roster with nothing in it', () => {
   })
 })
 
-describe('attributing a service to a subtree', () => {
-  it('never writes the preset file back, however the subtree changes', async () => {
-    delete (globalThis as { __RECONFIGURE__?: unknown }).__RECONFIGURE__
-    const handle = await ctx.agents.create({
-      sessionId: SessionId('sess-write'),
-      setup: async (agentCtx: Context) => void await ctx.agentPresets.mount(agentCtx, 'standard'),
-    })
-    const file = join(FIXTURES, 'system', 'standard', 'agent.cordis.yml')
-    const before = await readFile(file, 'utf8')
-
-    // The inherited `write()` persists the whole tree whenever the Loader
-    // decides a row's config moved, so one row reconfiguring itself would
-    // rewrite the shipped composition — here, with the row's new tool name.
-    const reconfigure = (globalThis as { __RECONFIGURE__?: (tool: string) => Promise<void> }).__RECONFIGURE__
-    expect(reconfigure).toBeTypeOf('function')
-    await reconfigure!('rewritten')
-
-    expect(toolNames(ctx, handle.agent)).toContain('rewritten')
-    expect(await readFile(file, 'utf8')).toBe(before)
-
-    await handle.dispose()
-  })
-
-  it('attributes nothing to a subtree that is already torn down', async () => {
-    const handle = await ctx.agents.create({
-      sessionId: SessionId('sess-torn'),
-      setup: async (agentCtx: Context) => void await ctx.agentPresets.mount(agentCtx, 'standard'),
-    })
-    const [mount] = livePresetMounts().filter(entry => entry.presetId === 'standard')
-    expect(mount).toBeDefined()
-
-    await handle.dispose()
-
-    // A disposed subtree owns nothing, so it can never be blamed for a service
-    // some other subtree published under the same name afterwards.
-    expect(leakedServices(ctx, mount!.fiber)).toEqual([])
-  })
-})
-
 describe('the preset file is an input, never a persistence target', () => {
   it('survives a row that disposes itself, which makes the Loader persist a tree', async () => {
     // The preset lives in a temp root, not under `fixtures/`: without the
@@ -310,6 +271,23 @@ describe('the preset file is an input, never a persistence target', () => {
   })
 })
 
+describe('attributing a service to a subtree', () => {
+  it('attributes nothing to a subtree that is already torn down', async () => {
+    const handle = await ctx.agents.create({
+      sessionId: SessionId('sess-torn'),
+      setup: async (agentCtx: Context) => void await ctx.agentPresets.mount(agentCtx, 'standard'),
+    })
+    const [mount] = livePresetMounts().filter(entry => entry.presetId === 'standard')
+    expect(mount).toBeDefined()
+
+    await handle.dispose()
+
+    // A disposed subtree owns nothing, so it can never be blamed for a service
+    // some other subtree published under the same name afterwards.
+    expect(leakedServices(ctx, mount!.fiber)).toEqual([])
+  })
+})
+
 describe('replacing a composition', () => {
   it('swaps the agent\'s tools without touching another session', async () => {
     const keeper = await agentOn(ctx, 'sess-keeper', 'standard')