diff --git a/packages/opencode/src/cli/tui/worker.ts b/packages/opencode/src/cli/tui/worker.ts
index 4cf6b2d446b3..ba0541c0be94 100644
--- a/packages/opencode/src/cli/tui/worker.ts
+++ b/packages/opencode/src/cli/tui/worker.ts
@@ -9,7 +9,7 @@ import { writeHeapSnapshot } from "node:v8"
 import { Heap } from "@/cli/heap"
 import { AppRuntime } from "@/effect/app-runtime"
 import { Effect } from "effect"
-import { disposeAllInstancesAndEmitGlobalDisposed } from "@/server/global-lifecycle"
+import { awaitSessionsIdle, disposeAllInstancesAndEmitGlobalDisposed } from "@/server/global-lifecycle"
 
 Heap.start()
 
@@ -26,6 +26,7 @@ GlobalBus.on("event", (event) => {
 })
 
 let server: Awaited<ReturnType<typeof Server.listen>> | undefined
+let reloading: Promise<void> | undefined
 
 export const rpc = {
   async fetch(input: { url: string; method: string; headers: Record<string, string>; body?: string }) {
@@ -61,13 +62,23 @@ export const rpc = {
     await upgrade().catch(() => {})
   },
   async reload() {
-    await AppRuntime.runPromise(
-      Effect.gen(function* () {
-        const cfg = yield* Config.Service
-        yield* cfg.invalidate()
-        yield* disposeAllInstancesAndEmitGlobalDisposed({ swallowErrors: true })
-      }),
-    )
+    // SIGUSR2 arrives from desktop environments on theme changes, so a reload
+    // can land mid-run. Swapping config in disposes every instance, which
+    // cancels the session that is currently working — wait for it to finish
+    // instead. Signals that arrive while waiting join the pending reload.
+    if (!reloading) {
+      reloading = AppRuntime.runPromise(
+        Effect.gen(function* () {
+          yield* awaitSessionsIdle()
+          const cfg = yield* Config.Service
+          yield* cfg.invalidate()
+          yield* disposeAllInstancesAndEmitGlobalDisposed({ swallowErrors: true })
+        }),
+      ).finally(() => {
+        reloading = undefined
+      })
+    }
+    await reloading
   },
   async shutdown() {
     await InstanceRuntime.disposeAllInstances()
diff --git a/packages/opencode/src/project/instance-store.ts b/packages/opencode/src/project/instance-store.ts
index 720549ddaff7..c9188d9b0e0b 100644
--- a/packages/opencode/src/project/instance-store.ts
+++ b/packages/opencode/src/project/instance-store.ts
@@ -19,6 +19,7 @@ export interface LoadInput {
 
 export interface Interface {
   readonly load: (input: LoadInput) => Effect.Effect<InstanceContext>
+  readonly list: () => Effect.Effect<InstanceContext[]>
   readonly reload: (input: LoadInput) => Effect.Effect<InstanceContext>
   readonly dispose: (ctx: InstanceContext) => Effect.Effect<void>
   readonly disposeDirectory: (directory: string) => Effect.Effect<void>
@@ -123,6 +124,13 @@ const layer: Layer.Layer<Service, never, Project.Service | InstanceBootstrap.Ser
       ).pipe(Effect.withSpan("InstanceStore.load"))
     }
 
+    const list = Effect.fn("InstanceStore.list")(function* () {
+      const exits = yield* Effect.forEach([...cache.values()], (entry) =>
+        Deferred.await(entry.deferred).pipe(Effect.exit),
+      )
+      return exits.filter(Exit.isSuccess).map((exit) => exit.value)
+    })
+
     const reload = (input: LoadInput): Effect.Effect<InstanceContext> => {
       const directory = FSUtil.resolve(input.directory)
       return Effect.uninterruptibleMask((restore) =>
@@ -193,6 +201,7 @@ const layer: Layer.Layer<Service, never, Project.Service | InstanceBootstrap.Ser
 
     return Service.of({
       load,
+      list,
       reload,
       dispose,
       disposeDirectory,
diff --git a/packages/opencode/src/server/global-lifecycle.ts b/packages/opencode/src/server/global-lifecycle.ts
index 12b7687bfe08..8beda3e64f80 100644
--- a/packages/opencode/src/server/global-lifecycle.ts
+++ b/packages/opencode/src/server/global-lifecycle.ts
@@ -1,5 +1,7 @@
 import { GlobalBus } from "@/bus/global"
+import { InstanceRef } from "@/effect/instance-ref"
 import { InstanceStore } from "@/project/instance-store"
+import { SessionStatus } from "@/session/status"
 import { Effect } from "effect"
 import { Event } from "./event"
 
@@ -25,4 +27,24 @@ export const disposeAllInstancesAndEmitGlobalDisposed = Effect.fn("Server.dispos
   },
 )
 
+// Disposing an instance cancels every session runner it owns, so a config
+// reload that lands while the model is streaming aborts the run. Callers that
+// reload on an external trigger (SIGUSR2, config writes) wait here first so the
+// reload is deferred rather than dropped.
+export const awaitSessionsIdle = Effect.fn("Server.awaitSessionsIdle")(function* () {
+  while (yield* sessionsBusy) {
+    yield* Effect.sleep(IDLE_POLL_INTERVAL)
+  }
+})
+
+const IDLE_POLL_INTERVAL = "250 millis"
+
+const sessionsBusy = Effect.gen(function* () {
+  const store = yield* InstanceStore.Service
+  const status = yield* SessionStatus.Service
+  const instances = yield* store.list()
+  const active = yield* Effect.forEach(instances, (ctx) => status.list().pipe(Effect.provideService(InstanceRef, ctx)))
+  return active.some((sessions) => sessions.size > 0)
+})
+
 export * as GlobalLifecycle from "./global-lifecycle"
diff --git a/packages/opencode/test/project/instance.test.ts b/packages/opencode/test/project/instance.test.ts
index f78b99ef7d9b..90335908e325 100644
--- a/packages/opencode/test/project/instance.test.ts
+++ b/packages/opencode/test/project/instance.test.ts
@@ -50,6 +50,19 @@ describe("InstanceStore", () => {
     }),
   )
 
+  it.live("lists loaded instance contexts", () =>
+    Effect.gen(function* () {
+      const first = yield* tmpdirScoped({ git: true })
+      const second = yield* tmpdirScoped({ git: true })
+      const store = yield* InstanceStore.Service
+
+      yield* store.load({ directory: first })
+      yield* store.load({ directory: second })
+
+      expect((yield* store.list()).map((ctx) => ctx.directory).toSorted()).toEqual([first, second].toSorted())
+    }),
+  )
+
   it.live("runs bootstrap with InstanceRef provided", () =>
     Effect.gen(function* () {
       const dir = yield* tmpdirScoped({ git: true })
diff --git a/packages/opencode/test/server/global-lifecycle.test.ts b/packages/opencode/test/server/global-lifecycle.test.ts
new file mode 100644
index 000000000000..fd146f8b74d3
--- /dev/null
+++ b/packages/opencode/test/server/global-lifecycle.test.ts
@@ -0,0 +1,54 @@
+import { describe, expect } from "bun:test"
+import { LayerNode } from "@opencode-ai/core/effect/layer-node"
+import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
+import { Effect, Layer } from "effect"
+import { InstanceRef } from "../../src/effect/instance-ref"
+import { InstanceBootstrap } from "../../src/project/bootstrap-service"
+import { InstanceStore } from "../../src/project/instance-store"
+import { SessionID } from "../../src/session/schema"
+import { SessionStatus } from "../../src/session/status"
+import { awaitSessionsIdle } from "../../src/server/global-lifecycle"
+import { tmpdirScoped } from "../fixture/fixture"
+import { awaitWithTimeout, testEffect } from "../lib/effect"
+
+const noopBootstrap = Layer.succeed(InstanceBootstrap.Service, InstanceBootstrap.Service.of({ run: Effect.void }))
+
+const it = testEffect(
+  LayerNode.compile(LayerNode.group([InstanceStore.node, SessionStatus.node, CrossSpawnSpawner.node]), [
+    [InstanceStore.bootstrapNode, noopBootstrap],
+  ]),
+)
+
+const sessionID = SessionID.make("ses_global_lifecycle")
+
+describe("awaitSessionsIdle", () => {
+  it.live("resolves when no instance has a busy session", () =>
+    Effect.gen(function* () {
+      const dir = yield* tmpdirScoped({ git: true })
+      const store = yield* InstanceStore.Service
+      yield* store.load({ directory: dir })
+
+      yield* awaitWithTimeout(awaitSessionsIdle(), "awaitSessionsIdle blocked while idle")
+    }),
+  )
+
+  it.live("waits for a busy session to go idle", () =>
+    Effect.gen(function* () {
+      const dir = yield* tmpdirScoped({ git: true })
+      const store = yield* InstanceStore.Service
+      const ctx = yield* store.load({ directory: dir })
+      const status = yield* SessionStatus.Service
+
+      yield* status.set(sessionID, { type: "busy" }).pipe(Effect.provideService(InstanceRef, ctx))
+
+      const blocked = yield* awaitSessionsIdle().pipe(
+        Effect.as(false),
+        Effect.timeoutOrElse({ duration: "500 millis", orElse: () => Effect.succeed(true) }),
+      )
+      expect(blocked).toBe(true)
+
+      yield* status.set(sessionID, { type: "idle" }).pipe(Effect.provideService(InstanceRef, ctx))
+      yield* awaitWithTimeout(awaitSessionsIdle(), "awaitSessionsIdle did not resolve after the session went idle")
+    }),
+  )
+})