From 83f25e88b6dfb7cb20e32aca0867d1cf642dc13b Mon Sep 17 00:00:00 2001
From: Kit Langton <kit.langton@gmail.com>
Date: Tue, 7 Jul 2026 21:05:29 -0400
Subject: [PATCH] fix(core): continue after unavailable tool calls

---
 packages/core/src/session/runner/llm.ts   | 9 +++++++++
 packages/core/test/config/plugin.test.ts  | 4 ++--
 packages/core/test/session-runner.test.ts | 5 ++++-
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/packages/core/src/session/runner/llm.ts b/packages/core/src/session/runner/llm.ts
index 9f799ef6a3..e2cc611930 100644
--- a/packages/core/src/session/runner/llm.ts
+++ b/packages/core/src/session/runner/llm.ts
@@ -365,6 +365,15 @@ const layer = Layer.effect(
               return
             }
             needsContinuation = true
+            if (!advertisedTools.has(event.name)) {
+              yield* serialized(
+                publisher.failUnsettledTools({
+                  type: "tool.execution",
+                  message: `Tool is not available for this request: ${event.name}`,
+                }),
+              )
+              return
+            }
             const assistantMessageID = yield* publisher.assistantMessageID(event.id)
             ownedToolFibers.push(
               yield* Effect.uninterruptibleMask((restore) =>
diff --git a/packages/core/test/config/plugin.test.ts b/packages/core/test/config/plugin.test.ts
index dc1fbc72e7..2bfe1d6c74 100644
--- a/packages/core/test/config/plugin.test.ts
+++ b/packages/core/test/config/plugin.test.ts
@@ -273,9 +273,9 @@ function withLocation<A, E, R>(
 function mutablePlugin(description: string) {
   const plugin = pathToFileURL(path.join(import.meta.dir, "../../../plugin/src/v2/promise/index.ts")).href
   return `
-import { define } from ${JSON.stringify(plugin)}
+import { Plugin } from ${JSON.stringify(plugin)}
 
-export default EffectPlugin.define({
+export default Plugin.define({
   id: "mutable-plugin",
   setup: async (ctx) => {
     await ctx.agent.transform((agents) => {
diff --git a/packages/core/test/session-runner.test.ts b/packages/core/test/session-runner.test.ts
index 7705b1e486..282ed7cde0 100644
--- a/packages/core/test/session-runner.test.ts
+++ b/packages/core/test/session-runner.test.ts
@@ -2674,7 +2674,10 @@ describe("SessionRunnerLLM", () => {
             {
               type: "tool",
               id: "call-missing",
-              state: { status: "error", error: { message: "Unknown tool: missing" } },
+              state: {
+                status: "error",
+                error: { type: "tool.execution", message: "Tool is not available for this request: missing" },
+              },
             },
           ],
         },