[keivenchang]

Summary

This PR suppresses truncated structured tool calls at the final response boundary for Chat Completions and Anthropic Messages. The Responses API retains the truncated function-call item and marks the terminal item status: "incomplete", while the terminal length signal remains visible.

Before / After

Chat Completions

Before: a stream ending with finish_reason: "length" and arguments: "{\"city\":\"San" returned the incomplete tool call, so a client could try to execute malformed arguments.

After: the final incomplete tool call is omitted, and the response keeps finish_reason: "length":

{
  "choices": [{
    "message": {"tool_calls": null},
    "finish_reason": "length"
  }]
}

A completed earlier call remains visible when only the final call is truncated. A completed call with finish_reason: "stop" and arguments: "{}" remains visible.

Anthropic Messages

Before: malformed or empty arguments could become input: {}, producing a runnable tool_use block even when generation stopped at max_tokens.

After: the incomplete terminal tool_use block is omitted. If every tool block is omitted, the response reports stop_reason: "end_turn" instead of "tool_use" with no runnable block. Completed calls still preserve input: {}.

For a truncated object such as {"city":"San","units":"c, the converter keeps only completed members, such as {"city":"San"}, and drops the unfinished member.

Responses API

Before: a length-limited response could mark every output item incomplete, including an earlier completed call.

After: only the terminal message or function-call item is marked status: "incomplete"; earlier output items remain status: "completed", and incomplete_details.reason is "max_output_tokens".

GLM47 recovery

Before: prose before an incomplete tool marker could be dropped or duplicated during streaming recovery, and a word-shaped marker could truncate ordinary prose such as functools.

After: emitted prose is preserved without duplication, incomplete markers are suppressed, and only punctuation-bearing markers trigger recovery.

Guided decoding validation

Before: conflicting guided-decoding options could pass request validation and fail later in the request path.

After: guided_json combined with guided_whitespace_pattern is accepted as a modifier combination, while guided_whitespace_pattern without a guided schema is rejected with HTTP 400.

Details

• Chat aggregation drops only the final call with invalid or empty arguments on finish_reason: length; earlier calls remain unchanged, and finished stop or tool_calls calls with {} remain valid.
• Anthropic unary and streaming conversion suppresses empty or malformed arguments at max_tokens, preserves {} for finished calls, and reports end_turn when all tool_use blocks were suppressed.
• Responses retains the truncated function-call item and marks the terminal item status: "incomplete"; Chat Completions and Anthropic omit the incomplete terminal call or block.
• Responses streaming closes each output item with its own terminal status, so output_item.done agrees with the final response.
• GLM47 recovery compacts already-emitted quote-free prose from its legacy jail buffer. Quote-bearing undecidable prose is retained because the legacy jail does not expose enough quote state for safe compaction.
• The ordinary Chat Completions stream remains outside this PR's dispatch changes. The opt-in tool_call_dispatch assembly mechanism is owned by fix(frontend): stop tool_call_dispatch handing harnesses truncated arguments #13986.
• The aggregator metadata and usage regression retains engine_data merging, choice count, and total-token assertions from the merge base.

Validation

• cargo fmt --all
• cargo test --locked -p dynamo-llm --lib (2616 passed, 5 ignored)
• Focused Chat aggregation, Anthropic unary and streaming, Responses streaming, GLM47 preprocessor, streaming tool parser, postprocessor, and guided-options tests passed.
• cargo test --locked -p dynamo-llm --test test_streaming_tool_parsers -- --nocapture (46 passed)
• cargo test --locked -p dynamo-llm --test postprocessor_parsing_stream -- --nocapture (92 passed)
• The GLM47 scaling-style tests preserve 400 chunks of prose. This is not a constant-memory claim for quote-bearing undecidable text in the legacy jail.

Where should the reviewer start?

lib/llm/src/protocols/openai/chat_completions/aggregator.rs

lib/llm/src/protocols/anthropic/types.rs

lib/llm/src/protocols/anthropic/stream_converter.rs

lib/llm/src/preprocessor.rs

lib/llm/src/protocols/openai/responses/stream_converter.rs

Related Issues

• Confirmed — no related issue

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[devin-ai-integration]

Devin Review found 1 potential issue.

[coderabbitai]

Walkthrough

The PR adds recovery for truncated Anthropic tool arguments. It centralizes OpenAI guided-decoding validation, classifies related errors, preserves terminal finish reasons, and adds regression coverage.

Changes

Anthropic tool-argument recovery

Layer / File(s)	Summary
Recover truncated tool arguments lib/llm/src/protocols/anthropic/types.rs	Tool-use conversion preserves completed members from truncated JSON objects and falls back to an empty object when recovery fails. Tests cover nested values, strings, escapes, and valid passthrough.

OpenAI protocol updates

Layer / File(s)	Summary
Centralize guided-decoding validation lib/llm/src/protocols/openai/validate.rs	validate_guided_decoding gathers guided-decoding fields and validates them through GuidedDecodingOptions::from_optional.
Apply request-boundary validation lib/llm/src/protocols/openai/chat_completions.rs, lib/llm/src/protocols/openai/completions.rs	Chat and completion request validation checks guided-decoding options before later validation. Tests cover conflicting and standalone options.
Classify guided-decoding errors lib/llm/src/preprocessor.rs, lib/llm/src/protocols/openai.rs	The invalid-argument helper is crate-visible. Guided-decoding conflicts now return typed invalid-argument errors.
Preserve terminal finish reasons lib/llm/src/protocols/openai/chat_completions/aggregator.rs	Tool calls change the finish reason only when it is absent or Stop. Length and ContentFilter remain unchanged.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: 🟡 Moderate · up to a77d6

The PR changes truncated Anthropic tool-call handling and request validation. At the current head, malformed Anthropic tool arguments can still be converted into partial input for non-length finishes, allowing an automatic client to treat an incomplete call as completed without the required truncation signal. This concrete correctness risk should be fixed or explicitly accepted before merge.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 7 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the main change: suppressing truncated structured tool calls. It is concise and specific.
Description check	✅ Passed	The description provides a detailed summary, implementation details, reviewer starting points, validation results, and a Related Issues section. It uses “Summary” instead of the template’s “Overview” …

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Actionable comments posted: 2

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Inline comments:
In `@lib/llm/src/protocols/anthropic/types.rs`:
- Line 668: Update tool_use_input and its call site in the Anthropic conversion
flow to accept the FinishReason, invoking recover_completed_members only for
FinishReason::Length; for Stop, ContentFilter, and other reasons, retain the
existing empty-object fallback when arguments are malformed.
- Line 2409: Rename the test module dis2780_tests to the neutral identifier
anthropic_types_tests, ensuring the internal ticket reference is removed from
the source.

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📥 Commits

Reviewing files that changed from the base of the PR and between 12fd94e and a77d64c.

📒 Files selected for processing (7)

• lib/llm/src/preprocessor.rs
• lib/llm/src/protocols/anthropic/types.rs
• lib/llm/src/protocols/openai.rs
• lib/llm/src/protocols/openai/chat_completions.rs
• lib/llm/src/protocols/openai/chat_completions/aggregator.rs
• lib/llm/src/protocols/openai/completions.rs
• lib/llm/src/protocols/openai/validate.rs

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[keivenchang]

Related PR: #13986 also addresses truncated tool-call arguments, at the opt-in streaming dispatch layer. This PR handles the final API response contract across Chat Completions, Responses, and Anthropic; #13986 assembles streaming deltas before dispatching a tool. The two changes overlap in the Chat Completions aggregation path and should be rebased together so the shared merge policy from #13986 remains compatible with this PR's terminal length filtering.