[Bugfix][Parser] Fix streaming tool-call args truncated by schema coercion#48706
[Bugfix][Parser] Fix streaming tool-call args truncated by schema coercion#48706mahadrehmann wants to merge 1 commit into
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…rcion _safe_arg_prefix included completed middle-field values in streamed_json even for non-string-typed keys (integer/boolean/null/number). When _fix_arg_types coerced those values at flush time (e.g. "42" → 42, "true" → true, "null" → null), the already-sent prefix no longer matched the final JSON, causing _flush_arg_converter to silently return None and drop the closing brace and any remaining content. Fix: during the character scan in _safe_arg_prefix, record the position of the first non-string-typed key's value start. After the scan, clip the safe prefix there. This preserves the startswith invariant: the value arrives entirely as a single flush delta after coercion, so the client always accumulates valid, complete JSON. Affects all parsers that use stream_arg_deltas=True with an arg_converter (Qwen3, DeepSeek V4/V32, GLM47, MiniMax, Gemma4, Kimi K2). String-typed fields, already-native-typed values (e.g. unquoted integers), and schemas without a type annotation are unaffected. Co-authored-by: muhammadfawaz1 <135441198+muhammadfawaz1@users.noreply.github.com> Signed-off-by: mahadrehmann <mahadrehman04@gmail.com>
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Fixes #48702
Purpose
_safe_arg_prefixincluded completed middle-field values instreamed_jsoneven for non-string-typed keys (integer/boolean/null/number). When_fix_arg_typescoerced those values at flush time (e.g."42"→42,"true"→true,"null"→null), the already-sent prefix no longer matched the final JSON, causing_flush_arg_converterto silently returnNoneand drop the closing brace and any remaining content. Clients received truncated, invalid JSON with no error or log line indicating anything had gone wrong.Fix: during the character scan in
_safe_arg_prefix, record the position of the first non-string-typed key's value start (non_string_clip). After the scan, clip the safe prefix there instead of including it. This ensures the value arrives entirely as a single flush delta after coercion, preserving thestartswithinvariant so the client always accumulates valid, complete JSON.Affects all parsers using
stream_arg_deltas=Truewith anarg_converterthat cannot parse partial JSON (Qwen3, DeepSeek V4/V32, GLM47, MiniMax, Gemma4, Kimi K2). Parsers that resolve types during streaming itself (e.g. DeepSeek DSML) are structurally unaffected. String-typed fields, already-native-typed values (e.g. unquoted integers), and schemas without a type annotation are unaffected.This slots in cleanly on top of #46351 (merged). #46351 already protects trailing non-string fields via a dedicated branch in _safe_arg_prefix (the scan's last_key is always the trailing key, so that branch fully covers it) — non_string_clip is never consulted for trailing fields and only fires for middle (comma-terminated) non-string values, which #46351 didn't address. Verified empirically: a trailing non-string field already passes on main; middle non-string fields do not, and pass only with this patch.
Not a duplicate of:
deepseekv3_tool_parser.py).Nonecoercion incoerce_to_schema_type).<|"|>tokens #48678 — different file/mechanism (Gemma4 delimiter handling).Test Plan
python -m pytest tests/parser/engine/4 new deterministic regression tests added to
TestCoercionInstabilityRegressionintest_parser_engine.py, each constructing the exact chunk boundary that triggers the bug:test_integer_middle_field_not_truncated_by_coerciontest_boolean_middle_field_not_truncated_by_coerciontest_null_middle_field_not_truncated_by_coerciontest_qwen3_partial_xml_close_tag_not_included_in_valueEach test is verified to fail on
mainand pass with this fix. Also verified against:_safe_arg_prefixhas exactly one production callerTest Result
3678 passed, 0 failedFull
tests/parser/engine/suite, no regressions. No latency regression — the fix causes an earlier return in_safe_arg_prefix, making the non-string path measurably faster than baseline.Live end-to-end reproduction was also attempted against a running vLLM server (Qwen2.5-1.5B/0.5B-Instruct,
qwen3_xmlparser) across ~45 real generations. The malformation did not occur spontaneously, consistent with guided/structured decoding constraining generated tokens to match the declared schema in this configuration. The unit tests above isolate and prove the underlying invariant violation deterministically, independent of live reproducibility.