diff --git a/packages/core/src/session/runner/llm.ts b/packages/core/src/session/runner/llm.ts
index 23cbfa049d..3da43acd8c 100644
--- a/packages/core/src/session/runner/llm.ts
+++ b/packages/core/src/session/runner/llm.ts
@@ -315,10 +315,25 @@ const layer = Layer.effect(
             }
             yield* publish(event)
             if (event.type !== "tool-call" || event.providerExecuted) return
-            if (!toolMaterialization || !advertisedTools.has(event.name)) {
+            if (!toolMaterialization) {
               yield* serialized(
                 publisher.failUnsettledTools({
                   type: "tool.execution",
+                  message: "Tools are disabled after the maximum agent steps",
+                }),
+              )
+              return
+            }
+            // A request hook hid this registered tool from the current request. Fail only
+            // this call durably and continue so the model can react, instead of executing
+            // a tool that was not advertised. Unregistered tools flow through settle, which
+            // durably fails them as unknown.
+            if (!advertisedTools.has(event.name) && availableTools.has(event.name)) {
+              needsContinuation = true
+              yield* publish(
+                LLMEvent.toolError({
+                  id: event.id,
+                  name: event.name,
                   message: `Tool is not available for this request: ${event.name}`,
                 }),
               )
diff --git a/packages/core/test/lib/tool.ts b/packages/core/test/lib/tool.ts
index 3692e5476e..c09d1e6296 100644
--- a/packages/core/test/lib/tool.ts
+++ b/packages/core/test/lib/tool.ts
@@ -6,6 +6,7 @@ import { Tool } from "@opencode-ai/core/tool/tool"
 import { Tools } from "@opencode-ai/core/tool/tools"
 import type { Context as PluginContext } from "@opencode-ai/plugin/v2/effect/plugin"
 import { Effect, type Scope } from "effect"
+import { host } from "../plugin/host"
 
 export const toolIdentity = {
   agent: AgentV2.ID.make("build"),
@@ -48,7 +49,7 @@ export const registerToolPlugin = <R>(plugin: {
 }): Effect.Effect<void, never, R | Tools.Service | Scope.Scope> =>
   Effect.gen(function* () {
     const tools = yield* Tools.Service
-    const context: Pick<PluginContext, "tool"> = {
+    const context = host({
       tool: {
         transform: (callback) =>
           Effect.gen(function* () {
@@ -71,8 +72,8 @@ export const registerToolPlugin = <R>(plugin: {
           }),
         hook: () => Effect.die("registerToolPlugin does not support tool hooks"),
       },
-    }
-    yield* plugin.effect(context as PluginContext)
+    })
+    yield* plugin.effect(context)
   })
 
 export const settleTool = (registry: ToolRegistry.Interface, input: ToolRegistry.ExecuteInput, model = testModel) =>
diff --git a/packages/core/test/location-layer.test.ts b/packages/core/test/location-layer.test.ts
index 6b7ba5654c..c538d1151f 100644
--- a/packages/core/test/location-layer.test.ts
+++ b/packages/core/test/location-layer.test.ts
@@ -290,6 +290,7 @@ describe("LocationServiceMap", () => {
             "edit",
             "glob",
             "grep",
+            "patch",
             "question",
             "read",
             "shell",
@@ -307,6 +308,7 @@ describe("LocationServiceMap", () => {
             "edit",
             "glob",
             "grep",
+            "patch",
             "question",
             "read",
             "shell",
diff --git a/packages/core/test/plugin/host.ts b/packages/core/test/plugin/host.ts
index c5dc96c384..659ec40f86 100644
--- a/packages/core/test/plugin/host.ts
+++ b/packages/core/test/plugin/host.ts
@@ -83,7 +83,9 @@ export function host(overrides: Overrides = {}): PluginContext {
       prompt: () => Effect.die("unused session.prompt"),
       command: () => Effect.die("unused session.command"),
       interrupt: () => Effect.die("unused session.interrupt"),
-      hook: () => Effect.die("unused session.hook"),
+      // Plugins register session hooks during setup, so a bare host accepts the
+      // registration; the callback only runs when a test triggers the request pipeline.
+      hook: () => Effect.succeed({ dispose: Effect.void }),
     },
   }
 }
diff --git a/packages/core/test/tool-subagent.test.ts b/packages/core/test/tool-subagent.test.ts
index 9f7bf8c7b9..92dc0e833b 100644
--- a/packages/core/test/tool-subagent.test.ts
+++ b/packages/core/test/tool-subagent.test.ts
@@ -107,6 +107,11 @@ const withSubagent = (location: Location.Ref) =>
     const locations = yield* LocationServiceMap.Service
     yield* AgentV2.Service.use((agents) =>
       agents.transform((draft) => {
+        // The caller identity used by executeTool; subagent permission asserts against it.
+        draft.update(toolIdentity.agent, (agent) => {
+          agent.mode = "primary"
+          agent.permissions.push({ action: "*", resource: "*", effect: "allow" })
+        })
         draft.update(AgentV2.ID.make("reviewer"), (agent) => {
           agent.mode = "subagent"
           agent.model = childModel