fix(core): recover malformed tool input

packages/ai/src/protocols/shared.ts

@@ -153,7 +153,21 @@ export const wrappedSystemUpdate = Effect.fn("ProviderShared.wrappedSystemUpdate
  * routes: `Invalid JSON input for <route> tool call <name>`.
  */
 export const parseToolInput = (route: string, name: string, raw: string) =>
-  parseJson(route, raw || "{}", `Invalid JSON input for ${route} tool call ${name}`)
+  Effect.try({
+    try: () => decodeJson(raw || "{}"),
+    catch: () =>
+      new LLMError({
+        module: "ProviderShared",
+        method: "stream",
+        reason: new InvalidProviderOutputReason({
+          route,
+          message: `Invalid JSON input for ${route} tool call ${name}`,
+          raw,
+          source: "tool-input",
+          toolName: name,
+        }),
+      }),
+  })
 
 export const IMAGE_MIMES = ["image/png", "image/jpeg", "image/gif", "image/webp"] as const
 export const VIDEO_MIMES = ["video/mp4", "video/webm", "video/quicktime"] as const

packages/ai/src/schema/errors.ts

@@ -106,6 +106,8 @@ export class InvalidProviderOutputReason extends Schema.Class<InvalidProviderOut
   message: Schema.String,
   route: Schema.optional(Schema.String),
   raw: Schema.optional(Schema.String),
+  source: Schema.optional(Schema.Literal("tool-input")),
+  toolName: Schema.optional(Schema.String),
   providerMetadata: Schema.optional(ProviderMetadata),
 }) {}
 

packages/ai/test/tool-stream.test.ts

@@ -64,6 +64,25 @@ describe("ToolStream", () => {
     }),
   )
 
+  it.effect("classifies malformed tool input with its raw arguments", () =>
+    Effect.gen(function* () {
+      const tools = ToolStream.start(ToolStream.empty<number>(), 0, {
+        id: "call_1",
+        name: "lookup",
+        input: '{"query":"partial',
+      })
+      const error = yield* ToolStream.finish(ADAPTER, tools, 0).pipe(Effect.flip)
+
+      expect(error).toBeInstanceOf(LLMError)
+      expect(error.reason).toMatchObject({
+        _tag: "InvalidProviderOutput",
+        source: "tool-input",
+        toolName: "lookup",
+        raw: '{"query":"partial',
+      })
+    }),
+  )
+
   it.effect("preserves providerExecuted and clears all tools", () =>
     Effect.gen(function* () {
       const first: ToolStream.State<number> = ToolStream.start(ToolStream.empty<number>(), 0, {

packages/client/src/promise/generated/types.ts

@@ -1839,6 +1839,7 @@ export type SessionMessageToolStateCompleted = {
 export type SessionMessageToolStateError = {
   status: "error"
   input: { [x: string]: JsonValue }
+  raw?: string
   content: Array<LLMToolContent>
   structured: { [x: string]: JsonValue }
   error: SessionStructuredError

packages/core/src/session/message-updater.ts

@@ -396,6 +396,7 @@ export function update(adapter: Adapter, event: SessionEvent.Event) {
                 status: "error",
                 error: event.data.error,
                 input: typeof match.state.input === "string" ? {} : match.state.input,
+                raw: typeof match.state.input === "string" ? match.state.input : undefined,
                 structured: match.state.status === "running" ? match.state.structured : {},
                 content: match.state.status === "running" ? match.state.content : [],
                 result: event.data.result,

packages/core/src/session/runner/llm.ts

@@ -243,6 +243,16 @@ const layer = Layer.effect(
           // already recorded from the stream. Terminal publication waits for owned tools.
           if (overflowFailure) yield* publish(overflowFailure)
           const llmFailure = streamFailure instanceof LLMError ? streamFailure : undefined
+          const malformedToolInput =
+            llmFailure?.reason._tag === "InvalidProviderOutput" && llmFailure.reason.source === "tool-input"
+          const recoveredMalformedToolInput = malformedToolInput
+            ? yield* serialized(
+                publisher.failUnsettledTools({
+                  type: "provider.invalid-output",
+                  message: "Tool call arguments were malformed JSON and were not executed. Retry with valid JSON.",
+                }),
+              )
+            : false
           if (llmFailure && !publisher.hasProviderError()) {
             const error = toSessionError(llmFailure)
             if (SessionRunnerRetry.isRetryable(llmFailure) && !publisher.hasRetryEvidence()) {
@@ -327,15 +337,15 @@ const layer = Layer.effect(
           if (stepFailure)
             yield* serialized(publisher.publishStepFailure(stepSettlement ? stepUsage(stepSettlement) : undefined))
 
-          if (stream._tag === "Failure") return yield* Effect.failCause(stream.cause)
+          if (stream._tag === "Failure" && !recoveredMalformedToolInput) return yield* Effect.failCause(stream.cause)
           if (userDeclined) return yield* Effect.interrupt
           if ((toolsInterrupted || infraError !== undefined) && settledFailure)
             return yield* Effect.failCause(settledFailure)
           if (toolsInterrupted && settled._tag === "Failure") return yield* Effect.failCause(settled.cause)
-          if (stepFailure) return yield* new StepFailedError({ error: stepFailure })
+          if (stepFailure && !recoveredMalformedToolInput) return yield* new StepFailedError({ error: stepFailure })
           return {
             _tag: "Completed",
-            needsContinuation,
+            needsContinuation: needsContinuation || recoveredMalformedToolInput,
             step: currentStep,
           } as const
         }),

packages/core/test/session-runner.test.ts

@@ -4125,27 +4125,69 @@ describe("SessionRunnerLLM", () => {
     }),
   )
 
-  it.effect("settles malformed streamed tool input before the provider failure", () =>
+  it.effect("continues after malformed streamed tool input without executing it", () =>
     Effect.gen(function* () {
       const session = yield* setup
       yield* admit(session, "Call a malformed tool")
       const failure = new LLMError({
         module: "test",
         method: "stream",
-        reason: new InvalidProviderOutputReason({ message: "Invalid JSON input for tool call echo" }),
+        reason: new InvalidProviderOutputReason({
+          message: "Invalid JSON input for tool call echo",
+          raw: '{"text":"partial',
+          source: "tool-input",
+          toolName: "echo",
+        }),
       })
-      responseStream = Stream.fromIterable([
-        LLMEvent.stepStart({ index: 0 }),
-        LLMEvent.toolInputStart({ id: "call-malformed", name: "echo" }),
-        LLMEvent.toolInputDelta({ id: "call-malformed", name: "echo", text: '{"text":"partial' }),
-      ]).pipe(Stream.concat(Stream.fail(failure)))
+      responseStreams = [
+        Stream.fromIterable([
+          LLMEvent.stepStart({ index: 0 }),
+          LLMEvent.toolInputStart({ id: "call-malformed", name: "echo" }),
+          LLMEvent.toolInputDelta({ id: "call-malformed", name: "echo", text: '{"text":"partial' }),
+        ]).pipe(Stream.concat(Stream.fail(failure))),
+        Stream.fromIterable(reply.stop()),
+      ]
 
-      expect(yield* session.resume(sessionID).pipe(Effect.flip)).toBe(failure)
+      yield* session.resume(sessionID)
       const assistant = requireAssistant(yield* session.context(sessionID))
 
-      response = reply.stop()
-      yield* admit(session, "Continue")
-      yield* session.resume(sessionID)
+      expect(requests).toHaveLength(2)
+      expect(assistant.content).toMatchObject([
+        {
+          type: "tool",
+          id: "call-malformed",
+          executed: false,
+          state: {
+            status: "error",
+            input: {},
+            raw: '{"text":"partial',
+            error: {
+              message: "Tool call arguments were malformed JSON and were not executed. Retry with valid JSON.",
+            },
+          },
+        },
+      ])
+      expect(requests[1].messages).toMatchObject([
+        { role: "user" },
+        { role: "assistant", content: [{ type: "tool-call", id: "call-malformed", input: {} }] },
+        {
+          role: "tool",
+          content: [
+            {
+              type: "tool-result",
+              id: "call-malformed",
+              result: {
+                type: "error",
+                value: {
+                  error: {
+                    message: "Tool call arguments were malformed JSON and were not executed. Retry with valid JSON.",
+                  },
+                },
+              },
+            },
+          ],
+        },
+      ])
 
       expect(yield* recordedStepSettlementEvents(sessionID, assistant.id)).toMatchObject([
         { type: "session.step.started.1" },
@@ -4153,7 +4195,10 @@ describe("SessionRunnerLLM", () => {
           type: "session.tool.failed.1",
           data: {
             callID: "call-malformed",
-            error: { type: "provider.invalid-output", message: "Invalid JSON input for tool call echo" },
+            error: {
+              type: "provider.invalid-output",
+              message: "Tool call arguments were malformed JSON and were not executed. Retry with valid JSON.",
+            },
           },
         },
         {

packages/schema/src/session-message.ts

@@ -127,6 +127,7 @@ export interface ToolStateError extends Schema.Schema.Type<typeof ToolStateError
 export const ToolStateError = Schema.Struct({
   status: Schema.tag("error"),
   input: Schema.Record(Schema.String, Schema.Unknown),
+  raw: Schema.String.pipe(optional),
   content: ToolContent.pipe(Schema.Array),
   structured: Schema.Record(Schema.String, Schema.Unknown),
   error: SessionError.Error,