diff --git a/packages/core/src/session/model-request.ts b/packages/core/src/session/model-request.ts
index cbd27f531d2..ec1cede967a 100644
--- a/packages/core/src/session/model-request.ts
+++ b/packages/core/src/session/model-request.ts
@@ -53,7 +53,9 @@ export interface Prepared {
    * One request-scoped execution operation. Unknown and hook-removed calls
    * fail individually through the same seam.
    */
-  readonly executeTool: (input: Parameters<Tool.Snapshot["execute"]>[0]) => Effect.Effect<Tool.Result, ExecuteError>
+  readonly executeTool: (
+    input: Parameters<Tool.Snapshot["execute"]>[0],
+  ) => Effect.Effect<Tool.NormalizedResult, ExecuteError>
 }
 
 interface PrepareInput {
diff --git a/packages/core/src/session/runner/publish-llm-event.ts b/packages/core/src/session/runner/publish-llm-event.ts
index 46e9356fc2f..d7cc98d3ec6 100644
--- a/packages/core/src/session/runner/publish-llm-event.ts
+++ b/packages/core/src/session/runner/publish-llm-event.ts
@@ -4,7 +4,7 @@ import type { Model } from "@opencode-ai/schema/model"
 import type { RelativePath } from "@opencode-ai/schema/schema"
 import type { Snapshot } from "@opencode-ai/schema/snapshot"
 import { Effect, Fiber, Iterable } from "effect"
-import { isArrayNonEmpty, isReadonlyArrayNonEmpty } from "effect/Array"
+import { isReadonlyArrayNonEmpty } from "effect/Array"
 import { Bus } from "../../bus.js"
 import { SessionEvent } from "../event.js"
 import { SessionMessage } from "../message.js"
@@ -12,7 +12,7 @@ import { SessionSchema } from "../schema.js"
 import { SessionError } from "@opencode-ai/schema/session-error"
 import { Money } from "@opencode-ai/schema/money"
 import { SessionUsage } from "../usage.js"
-import { Tool } from "@opencode-ai/schema/tool"
+import type { Tool } from "../../tool.js"
 
 type Input = {
   readonly sessionID: SessionSchema.ID
@@ -557,20 +557,15 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
   })
 
   /** Publishes one canonical terminal event for a locally executed tool call. */
-  const toolExecution = Effect.fnUntraced(function* (id: string, name: string, result: Tool.Result) {
+  const toolExecution = Effect.fnUntraced(function* (id: string, name: string, result: Tool.NormalizedResult) {
     const tool = tools.get(id)
     if (!tool?.called) return yield* Effect.die(new Error(`Tool execution before call: ${id}`))
     if (tool.name !== name)
       return yield* Effect.die(new Error(`Tool execution name changed for ${id}: ${tool.name} -> ${name}`))
     if (tool.settled) return yield* Effect.die(new Error(`Duplicate tool execution: ${id}`))
     tool.settled = true
-    const content =
-      typeof result.content === "string"
-        ? [{ type: "text" as const, text: result.content }]
-        : result.content === undefined
-          ? []
-          : [...result.content]
-    if (!isArrayNonEmpty(content)) return yield* Effect.die(new Error(`Tool execution has no content: ${id}`))
+    const content = result.content
+    if (!isReadonlyArrayNonEmpty(content)) return yield* Effect.die(new Error(`Tool execution has no content: ${id}`))
     yield* bus.publish(SessionEvent.Tool.Success, {
       sessionID: input.sessionID,
       assistantMessageID,
diff --git a/packages/core/src/tool-output.ts b/packages/core/src/tool-output.ts
index f908cce6f38..53738be14be 100644
--- a/packages/core/src/tool-output.ts
+++ b/packages/core/src/tool-output.ts
@@ -1,7 +1,7 @@
 export * as ToolOutput from "./tool-output.js"
 
 import path from "path"
-import type { Tool } from "@opencode-ai/schema/tool"
+import type { Tool } from "./tool.js"
 import { Context, Duration, Effect, Layer, Schedule } from "effect"
 import { makeGlobalNode, makeLocationNode } from "@opencode-ai/util/effect/app-node"
 import { FSUtil } from "@opencode-ai/util/fs-util"
@@ -15,7 +15,7 @@ export const MAX_BYTES = 50 * 1024 // 50 KiB
 export const RETENTION = Duration.days(7)
 export const DIRECTORY = "tool-output"
 
-type Result = Tool.Result
+type Result = Tool.NormalizedResult
 
 type Limits = {
   maxLines: number
@@ -64,8 +64,7 @@ const layer = Layer.effect(
 
     const truncate = Effect.fnUntraced(function* (result: Result) {
       if (result.metadata?.truncated !== undefined) return result
-      const content =
-        typeof result.content === "string" ? [{ type: "text" as const, text: result.content }] : (result.content ?? [])
+      const content = result.content
       const text = content.flatMap((item) => (item.type === "text" ? [item.text] : [])).join("\n")
       const limits = state.get()
       const lines = text.split("\n")
diff --git a/packages/core/src/tool.ts b/packages/core/src/tool.ts
index 1137d047849..cc66732df8a 100644
--- a/packages/core/src/tool.ts
+++ b/packages/core/src/tool.ts
@@ -42,6 +42,11 @@ export interface Interface extends State.Transformable<Editor> {
   readonly snapshot: (permissions?: Permission.Ruleset) => Effect.Effect<Snapshot>
 }
 
+/** A local execution result after hooks and content normalization. */
+export interface NormalizedResult extends Tool.Result {
+  readonly content: ReadonlyArray<Tool.Content>
+}
+
 export interface Snapshot {
   readonly definitions: ReadonlyArray<ToolDefinition>
   readonly codeModeCatalog?: CodeModeCatalog.Inventory
@@ -53,7 +58,7 @@ export interface Snapshot {
     readonly progress?: (update: Tool.Metadata) => Effect.Effect<void>
     /** Surviving request definitions, keyed by the names advertised after session context hooks. */
     readonly definitions?: ReadonlyMap<string, ToolDefinition>
-  }) => Effect.Effect<Tool.Result & { readonly content: ReadonlyArray<Tool.Content> }, Tool.Error>
+  }) => Effect.Effect<NormalizedResult, Tool.Error>
 }
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/Tool") {}
diff --git a/packages/core/test/config/tool-output.test.ts b/packages/core/test/config/tool-output.test.ts
index a8cb7544130..81c1a76e6c3 100644
--- a/packages/core/test/config/tool-output.test.ts
+++ b/packages/core/test/config/tool-output.test.ts
@@ -26,7 +26,9 @@ describe("ConfigToolOutputPlugin.Plugin", () => {
           const plugins = yield* Plugin.Service
           yield* ConfigToolOutputPlugin.Plugin.effect(yield* PluginHost.make(plugins))
 
-          expect((yield* output.truncate({ content: "one\ntwo" })).metadata?.truncated).toBe(true)
+          expect((yield* output.truncate({ content: [{ type: "text", text: "one\ntwo" }] })).metadata?.truncated).toBe(
+            true,
+          )
 
           yield* config.setEntries([
             new Document({
@@ -38,7 +40,7 @@ describe("ConfigToolOutputPlugin.Plugin", () => {
           ])
           yield* bus.publish(Event.Updated, {})
           for (let attempt = 0; attempt < 200; attempt++) {
-            const result = yield* output.truncate({ content: "one\ntwo" })
+            const result = yield* output.truncate({ content: [{ type: "text", text: "one\ntwo" }] })
             if (result.metadata?.truncated === false) return
             yield* Effect.sleep("10 millis")
           }
diff --git a/packages/core/test/session-step.test.ts b/packages/core/test/session-step.test.ts
index 063ade46afa..9170c4b97b7 100644
--- a/packages/core/test/session-step.test.ts
+++ b/packages/core/test/session-step.test.ts
@@ -111,7 +111,7 @@ for (const fixture of [
             executeTool: () =>
               Effect.sync(() => {
                 executions++
-                return { content: "Completed tool" }
+                return { content: [{ type: "text", text: "Completed tool" }] }
               }),
           },
           retry: (_cause, _error, retry) =>
diff --git a/packages/core/test/tool-output.test.ts b/packages/core/test/tool-output.test.ts
index 35e47d19c1b..35dfef6a3c2 100644
--- a/packages/core/test/tool-output.test.ts
+++ b/packages/core/test/tool-output.test.ts
@@ -4,6 +4,7 @@ import { Effect } from "effect"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { LayerNode } from "@opencode-ai/util/effect/layer-node"
 import { ToolOutput } from "@opencode-ai/core/tool-output"
+import type { Tool } from "@opencode-ai/core/tool"
 import { FSUtil } from "@opencode-ai/util/fs-util"
 import { Global } from "@opencode-ai/util/global"
 import { Identifier } from "@opencode-ai/core/id/id"
@@ -36,7 +37,7 @@ describe("ToolOutput", () => {
       (service, fs) =>
         Effect.gen(function* () {
           const output = { items: [1, 2, 3] }
-          const result = yield* service.truncate({ output, content: "one\ntwo\nthree" })
+          const result = yield* service.truncate({ output, content: [{ type: "text", text: "one\ntwo\nthree" }] })
           expect(result.output).toBe(output)
           expect(result.metadata).toMatchObject({ truncated: true })
           const outputPath = result.metadata?.outputPath
@@ -56,7 +57,7 @@ describe("ToolOutput", () => {
     withStore(
       (output) =>
         Effect.gen(function* () {
-          const result = yield* output.truncate({ content: "one\ntwo" })
+          const result = yield* output.truncate({ content: [{ type: "text", text: "one\ntwo" }] })
           expect(result.content).toEqual([
             { type: "text", text: "one" },
             {
@@ -91,8 +92,9 @@ describe("ToolOutput", () => {
   it.live("skips results that report a truncation state", () =>
     withStore((output) =>
       Effect.gen(function* () {
-        const truncated = { content: "one\ntwo", metadata: { truncated: true, source: "tool" } }
-        const retained = { content: "one\ntwo", metadata: { truncated: false, source: "tool" } }
+        const content: Tool.NormalizedResult["content"] = [{ type: "text", text: "one\ntwo" }]
+        const truncated = { content, metadata: { truncated: true, source: "tool" } }
+        const retained = { content, metadata: { truncated: false, source: "tool" } }
         expect(yield* output.truncate(truncated)).toBe(truncated)
         expect(yield* output.truncate(retained)).toBe(retained)
       }),
@@ -112,8 +114,8 @@ describe("ToolOutput", () => {
     withStore(
       (output) =>
         Effect.gen(function* () {
-          expect(yield* output.truncate({ content: "one\ntwo\n" })).toEqual({
-            content: "one\ntwo\n",
+          expect(yield* output.truncate({ content: [{ type: "text", text: "one\ntwo\n" }] })).toEqual({
+            content: [{ type: "text", text: "one\ntwo\n" }],
             metadata: { truncated: false },
           })
         }),
@@ -125,7 +127,7 @@ describe("ToolOutput", () => {
     withStore(
       (output) =>
         Effect.gen(function* () {
-          const result = yield* output.truncate({ content: "one\n" })
+          const result = yield* output.truncate({ content: [{ type: "text", text: "one\n" }] })
           expect(result.content).toEqual([
             { type: "text", text: "one" },
             { type: "text", text: expect.stringMatching(/^\.\.\. 1 byte truncated; full content saved to /) },
diff --git a/packages/core/test/tool-registry.test.ts b/packages/core/test/tool-registry.test.ts
index ef6397e72b1..f7d7c761db9 100644
--- a/packages/core/test/tool-registry.test.ts
+++ b/packages/core/test/tool-registry.test.ts
@@ -3,11 +3,13 @@ import { Agent } from "@opencode-ai/core/agent"
 import type { Permission } from "@opencode-ai/core/permission"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { Image } from "@opencode-ai/core/image"
+import { PluginHooks } from "@opencode-ai/core/plugin/hooks"
 import { Session } from "@opencode-ai/core/session"
 import { SessionMessage } from "@opencode-ai/core/session/message"
 import { State } from "@opencode-ai/core/state"
 import { Tool } from "@opencode-ai/core/tool"
 import type { Info } from "@opencode-ai/schema/tool"
+import { LayerNode } from "@opencode-ai/util/effect/layer-node"
 import { codeModeListings, executeTool, toolDefinitions } from "./lib/tool"
 import { Deferred, Effect, Exit, Fiber, Layer, Logger, Schema, SchemaGetter, SchemaIssue, Scope } from "effect"
 import { z } from "zod"
@@ -35,7 +37,9 @@ const imageStore = Layer.mock(Image.Service, {
     })
   },
 })
-const registryLayer = AppNodeBuilder.build(Tool.node, [Image.node.replace(imageStore)])
+const registryLayer = AppNodeBuilder.build(LayerNode.group([Tool.node, PluginHooks.node]), [
+  Image.node.replace(imageStore),
+])
 const it = testEffect(registryLayer)
 const identity = {
   agent: Agent.ID.make("build"),
@@ -843,6 +847,36 @@ describe("Tool", () => {
       ])
     }),
   )
+  ;[
+    { name: "string", content: "hooked", text: "hooked" },
+    { name: "empty string", content: "", text: "" },
+    { name: "missing content", content: undefined, text: '{"text":"hooked"}' },
+    { name: "empty content array", content: [], text: '{"text":"hooked"}' },
+  ].forEach((input) => {
+    it.effect(`normalizes ${input.name} after the final tool hook`, () =>
+      Effect.gen(function* () {
+        const service = yield* Tool.Service
+        const hooks = yield* PluginHooks.Service
+        yield* transform(service, { echo: make() }, { codemode: false })
+        yield* hooks.register("tool", "execute.after", (event) =>
+          Effect.sync(() => {
+            if (event.status !== "completed") return
+            event.result = {
+              output: { text: "hooked" },
+              content: input.content,
+              metadata: { source: "hook" },
+            }
+          }),
+        )
+        const snapshot = yield* service.snapshot()
+        expect(yield* snapshot.execute(call("echo"))).toEqual({
+          output: { text: "hooked" },
+          content: [{ type: "text", text: input.text }],
+          metadata: { source: "hook" },
+        })
+      }),
+    )
+  })
 
   it.effect("normalizes image tool output once and drops unresizable images", () =>
     Effect.gen(function* () {