diff --git a/packages/core/src/session/runner/publish-llm-event.ts b/packages/core/src/session/runner/publish-llm-event.ts
index 9116e32091a7..755fbd71c918 100644
--- a/packages/core/src/session/runner/publish-llm-event.ts
+++ b/packages/core/src/session/runner/publish-llm-event.ts
@@ -1,5 +1,6 @@
 import { type LLMEvent, type ProviderMetadata, type ToolResultValue } from "@opencode-ai/ai"
 import { Clock, Effect, Iterable } from "effect"
+import { isArrayNonEmpty, isReadonlyArrayNonEmpty } from "effect/Array"
 import { Bus } from "../../bus.js"
 import { Model } from "../../model.js"
 import { SessionEvent } from "../event.js"
@@ -45,9 +46,6 @@ export interface StepRecord {
 /** Derives canonical model content from a provider-hosted tool result. */
 type NonEmptyContent = readonly [Tool.Content, ...Tool.Content[]]
 
-const nonEmpty = (content: ReadonlyArray<Tool.Content>): NonEmptyContent | undefined =>
-  content.length > 0 ? (content as NonEmptyContent) : undefined
-
 const stringify = (value: unknown) => {
   if (typeof value === "string") return value
   try {
@@ -58,10 +56,7 @@ const stringify = (value: unknown) => {
 }
 
 const hostedContent = (result: ToolResultValue): NonEmptyContent => {
-  if (result.type === "content") {
-    const content = nonEmpty(result.value)
-    if (content !== undefined) return content
-  }
+  if (result.type === "content" && isReadonlyArrayNonEmpty(result.value)) return result.value
   return [{ type: "text", text: stringify(result.value) }]
 }
 
@@ -563,12 +558,12 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
         : result.content === undefined
           ? []
           : [...result.content]
-    if (content.length === 0) return yield* Effect.die(new Error(`Tool execution has no content: ${id}`))
+    if (!isArrayNonEmpty(content)) return yield* Effect.die(new Error(`Tool execution has no content: ${id}`))
     yield* bus.publish(SessionEvent.Tool.Success, {
       sessionID: input.sessionID,
       assistantMessageID,
       id,
-      content: [content[0], ...content.slice(1)],
+      content,
       ...(result.metadata === undefined ? {} : { metadata: result.metadata }),
       executed: tool.providerExecuted,
     })
diff --git a/packages/core/src/session/transfer.ts b/packages/core/src/session/transfer.ts
index 4a9b11b6f8ba..1cfcb7ef72a2 100644
--- a/packages/core/src/session/transfer.ts
+++ b/packages/core/src/session/transfer.ts
@@ -5,6 +5,7 @@ import { Tool } from "@opencode-ai/schema/tool"
 import { Skill } from "@opencode-ai/schema/skill"
 import { eq } from "drizzle-orm"
 import { Context, DateTime, Effect, Layer, Schema } from "effect"
+import { map } from "effect/Array"
 import path from "path"
 import { makeGlobalNode } from "@opencode-ai/util/effect/app-node"
 import { App } from "../app.js"
@@ -309,21 +310,13 @@ function sanitizeToolState(id: string, state: SessionMessage.ToolState): Session
     return {
       ...state,
       input: { redacted: `tool-input:${id}` },
-      content: [
-        sanitizeToolContent(id, state.content[0]),
-        ...state.content.slice(1).map((item) => sanitizeToolContent(id, item)),
-      ],
+      content: map(state.content, (item) => sanitizeToolContent(id, item)),
       metadata: meta,
     }
   return {
     ...state,
     input: { redacted: `tool-input:${id}` },
-    content: state.content
-      ? [
-          sanitizeToolContent(id, state.content[0]),
-          ...state.content.slice(1).map((item) => sanitizeToolContent(id, item)),
-        ]
-      : undefined,
+    content: state.content ? map(state.content, (item) => sanitizeToolContent(id, item)) : undefined,
     metadata: meta,
   }
 }
diff --git a/packages/util/src/cross-spawn-spawner.ts b/packages/util/src/cross-spawn-spawner.ts
index 920fcf2223a9..0ca2cb156fc6 100644
--- a/packages/util/src/cross-spawn-spawner.ts
+++ b/packages/util/src/cross-spawn-spawner.ts
@@ -1,4 +1,4 @@
-import type { NonEmptyReadonlyArray } from "effect/Array"
+import { isArrayNonEmpty } from "effect/Array"
 import * as NodeSink from "@effect/platform-node/NodeSink"
 import * as NodeStream from "@effect/platform-node/NodeStream"
 import { Deferred, Effect, Exit, FileSystem, Layer, Path, PlatformError, Predicate, Sink, Stream } from "effect"
@@ -60,10 +60,9 @@ const flatten = (command: ChildProcess.Command) => {
   }
 
   walk(command)
-  if (commands.length === 0) throw new Error("flatten produced empty commands array")
-  const [head, ...tail] = commands
+  if (!isArrayNonEmpty(commands)) throw new Error("flatten produced empty commands array")
   return {
-    commands: [head, ...tail] as NonEmptyReadonlyArray<ChildProcess.StandardCommand>,
+    commands,
     opts,
   }
 }