fix(ai): emit TOOL_CALL_START/ARGS during continuation re-executions by DiegoGBrisa · Pull Request #372 · TanStack/ai

DiegoGBrisa · 2026-03-13T08:08:18Z

Summary

Continuation re-executions (pending tool calls resumed from message history) only emit TOOL_CALL_END, skipping TOOL_CALL_START and TOOL_CALL_ARGS. This causes clients to store tool calls with empty
arguments, leading to infinite re-execution loops.

buildToolResultChunks now accepts an optional argsMap parameter
When provided (from checkForPendingToolCalls), emits the full START → ARGS → END sequence per tool call using the arguments from the original ToolCall objects
Normal flow (processToolCalls) is unaffected — the adapter stream already emits START/ARGS

Test plan

Commit 1 adds failing tests reproducing the issue (tests-first format)
Commit 2 applies the fix, all tests pass
Single pending tool call emits full START → ARGS → END sequence
Batch of pending tool calls each emit full START → ARGS → END sequence
Chunk ordering verified: START < ARGS < END per tool call
Existing 30 tests unaffected

Summary by CodeRabbit

Bug Fixes
- Pending tool calls now emit the full event sequence (start, arguments, and end) during continuations, ensuring complete tool call information is available downstream.
Tests
- Added tests covering single and batched pending tool call scenarios (including mixed server/client tools) to validate correct event ordering and completeness.

Continuation re-executions (pending tool calls from message history) only emit TOOL_CALL_END, skipping TOOL_CALL_START and TOOL_CALL_ARGS. This causes clients to store tool calls with empty arguments, leading to infinite re-execution loops. Two tests added: - Single pending tool call emits full START → ARGS → END sequence - Batch of pending tool calls each emit full START → ARGS → END sequence

…re-executions Pending tool calls resumed from message history only emit TOOL_CALL_END, causing clients to store empty arguments and triggering infinite re-execution loops. Emit the full START → ARGS → END sequence using the arguments from the original ToolCall objects.

changeset-bot · 2026-03-13T08:08:28Z

🦋 Changeset detected

Latest commit: ec66e30

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 29 packages

Name	Type
@tanstack/ai	Patch
@tanstack/ai-anthropic	Patch
@tanstack/ai-client	Patch
@tanstack/ai-devtools-core	Patch
@tanstack/ai-elevenlabs	Patch
@tanstack/ai-event-client	Patch
@tanstack/ai-fal	Patch
@tanstack/ai-gemini	Patch
@tanstack/ai-grok	Patch
@tanstack/ai-groq	Patch
@tanstack/ai-ollama	Patch
@tanstack/ai-openai	Patch
@tanstack/ai-openrouter	Patch
@tanstack/ai-preact	Patch
@tanstack/ai-react	Patch
@tanstack/ai-solid	Patch
@tanstack/ai-svelte	Patch
@tanstack/ai-vue	Patch
@tanstack/tests-adapters	Patch
@tanstack/smoke-tests-e2e	Patch
ts-svelte-chat	Patch
ts-vue-chat	Patch
@tanstack/ai-react-ui	Patch
@tanstack/ai-solid-ui	Patch
vanilla-chat	Patch
@tanstack/preact-ai-devtools	Patch
@tanstack/react-ai-devtools	Patch
@tanstack/solid-ai-devtools	Patch
@tanstack/ai-vue-ui	Patch

Not sure what this means? Click here to learn what changesets are.

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coderabbitai · 2026-03-13T08:08:41Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: de018ab7-b568-4b5a-ac72-a3fb8dc2c37d

📥 Commits

Reviewing files that changed from the base of the PR and between c2522b6 and ec66e30.

📒 Files selected for processing (1)

packages/typescript/ai/tests/chat.test.ts

🚧 Files skipped from review as they are similar to previous changes (1)

packages/typescript/ai/tests/chat.test.ts

📝 Walkthrough

Walkthrough

Adds emission of full tool-call chunks during continuation re-executions: an argsMap captures pending tool call arguments, and buildToolResultChunks now emits TOOL_CALL_START, TOOL_CALL_ARGS, then TOOL_CALL_END for pending/continuation tool executions so clients can reconstruct calls.

Changes

Cohort / File(s)	Summary
Changelog `.changeset/fix-continuation-chunk-emission.md`	New changelog entry documenting the patch release fix to emit `TOOL_CALL_START` and `TOOL_CALL_ARGS` during continuation tool executions.
Core Implementation `packages/typescript/ai/src/activities/chat/index.ts`	Adds an `argsMap` to collect pending tool call arguments and propagates it into `buildToolResultChunks`; updates chunk emission to optionally emit `TOOL_CALL_START` and `TOOL_CALL_ARGS` before `TOOL_CALL_END` for continuation/pending tool calls.
Tests `packages/typescript/ai/tests/chat.test.ts`	Adds tests verifying ordering and content of `TOOL_CALL_START` → `TOOL_CALL_ARGS` → `TOOL_CALL_END` for single and batched pending tool calls, including mixed server/client tool scenarios.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 I nibble at chunks where continuations sleep,
START then ARGS now wake what was deep,
END waits its turn, the sequence restored,
Tools sing their lines, no argument ignored,
Hooray — the stream hops clean and neat!

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main change: emitting TOOL_CALL_START and TOOL_CALL_ARGS during continuation re-executions, which directly addresses the core fix implemented in the changeset.
Description check	✅ Passed	The description comprehensively covers the problem, solution, and test plan. It follows the template structure with clear sections explaining the changes and includes test verification details, though the formal template checklist items are not explicitly marked.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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nx-cloud · 2026-03-13T08:10:17Z

View your CI Pipeline Execution ↗ for commit ec66e30

Command	Status	Duration	Result
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☁️ Nx Cloud last updated this comment at 2026-03-13 09:11:37 UTC

pkg-pr-new · 2026-03-13T08:12:42Z

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commit: 561b566

coderabbitai

🧹 Nitpick comments (2)

packages/typescript/ai/src/activities/chat/index.ts (1)
1027-1034: Populate args on the synthetic TOOL_CALL_ARGS chunk.

At continuation time you already have the full serialized arguments, so emitting only delta makes these synthetic chunks a little less expressive than the adapter-emitted ones. Setting args too keeps raw stream consumers from needing a continuation-only code path.
💡 Suggested change
         const args = argsMap.get(result.toolCallId) ?? '{}'
         chunks.push({
           type: 'TOOL_CALL_ARGS',
           timestamp: Date.now(),
           model: finishEvent.model,
           toolCallId: result.toolCallId,
           delta: args,
+          args,
         })
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@packages/typescript/ai/src/activities/chat/index.ts` around lines 1027 -
1034, The synthetic TOOL_CALL_ARGS chunk currently only sets delta and omits the
full args; update the chunk created in the continuation path (the block using
argsMap.get(result.toolCallId) and pushing into chunks) to also set an args
property with the serialized arguments (the same value you pull from argsMap,
e.g., args or parsed equivalent) so consumers see the full arguments on the
synthetic chunk alongside delta, model, toolCallId, and timestamp.
packages/typescript/ai/tests/chat.test.ts (1)

722-801: Add one regression for the mixed pending/wait branch too.

These cases cover the path where pending server tools finish and the engine proceeds to the next model call. The new argsMap plumbing is also used when continuation pauses again for needsClientExecution or needsApproval, so I’d add one assertion there that TOOL_CALL_START and TOOL_CALL_ARGS are still emitted for the completed server tool.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@packages/typescript/ai/src/activities/chat/index.ts`:
- Around line 1027-1034: The synthetic TOOL_CALL_ARGS chunk currently only sets
delta and omits the full args; update the chunk created in the continuation path
(the block using argsMap.get(result.toolCallId) and pushing into chunks) to also
set an args property with the serialized arguments (the same value you pull from
argsMap, e.g., args or parsed equivalent) so consumers see the full arguments on
the synthetic chunk alongside delta, model, toolCallId, and timestamp.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 09507dd7-efca-4f4a-8822-f6c0d6ef6b33

📥 Commits

Reviewing files that changed from the base of the PR and between 570c9f6 and c2522b6.

📒 Files selected for processing (3)

.changeset/fix-continuation-chunk-emission.md
packages/typescript/ai/src/activities/chat/index.ts
packages/typescript/ai/tests/chat.test.ts

DiegoGBrisa · 2026-03-13T09:02:20Z

🧹 Nitpick comments (2)
packages/typescript/ai/src/activities/chat/index.ts (1)> 1027-1034: Populate args on the synthetic TOOL_CALL_ARGS chunk.
At continuation time you already have the full serialized arguments, so emitting only delta makes these synthetic chunks a little less expressive than the adapter-emitted ones. Setting args too keeps raw stream consumers from needing a continuation-only code path.

💡 Suggested change
         const args = argsMap.get(result.toolCallId) ?? '{}'
         chunks.push({
           type: 'TOOL_CALL_ARGS',
           timestamp: Date.now(),
           model: finishEvent.model,
           toolCallId: result.toolCallId,
           delta: args,
+          args,
         })
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@packages/typescript/ai/src/activities/chat/index.ts` around lines 1027 -
1034, The synthetic TOOL_CALL_ARGS chunk currently only sets delta and omits the
full args; update the chunk created in the continuation path (the block using
argsMap.get(result.toolCallId) and pushing into chunks) to also set an args
property with the serialized arguments (the same value you pull from argsMap,
e.g., args or parsed equivalent) so consumers see the full arguments on the
synthetic chunk alongside delta, model, toolCallId, and timestamp.
packages/typescript/ai/tests/chat.test.ts (1)> 722-801: Add one regression for the mixed pending/wait branch too.

These cases cover the path where pending server tools finish and the engine proceeds to the next model call. The new argsMap plumbing is also used when continuation pauses again for needsClientExecution or needsApproval, so I’d add one assertion there that TOOL_CALL_START and TOOL_CALL_ARGS are still emitted for the completed server tool.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@packages/typescript/ai/src/activities/chat/index.ts`:
- Around line 1027-1034: The synthetic TOOL_CALL_ARGS chunk currently only sets
delta and omits the full args; update the chunk created in the continuation path
(the block using argsMap.get(result.toolCallId) and pushing into chunks) to also
set an args property with the serialized arguments (the same value you pull from
argsMap, e.g., args or parsed equivalent) so consumers see the full arguments on
the synthetic chunk alongside delta, model, toolCallId, and timestamp.
ℹ️ Review info

Intentionally omitting args — adapter-emitted TOOL_CALL_ARGS chunks only use delta, so the synthetic chunks match the same shape. Adding a non-standard field would require consumers to handle continuation chunks differently from regular ones.

DiegoGBrisa added 2 commits March 13, 2026 08:42

ci: apply automated fixes

c2522b6

coderabbitai bot reviewed Mar 13, 2026

View reviewed changes

DiegoGBrisa and others added 2 commits March 13, 2026 10:04

test(ai): add test for mixed pending batch with server and client tools

99af6f8

ci: apply automated fixes

ec66e30

AlemTuzlak requested a review from jherr March 13, 2026 09:34

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fix(ai): emit TOOL_CALL_START/ARGS during continuation re-executions#372

fix(ai): emit TOOL_CALL_START/ARGS during continuation re-executions#372
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