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[Bugfix][Parser] GLM-4.7: stray arg tags must not leak into tool-call argument keys - #54971
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Manny7717
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Verified locally on head 7fec1f39 vs base 41848ca — fix is correct and regression-proven.
Bug confirmed on base: both stray-tag shapes reproduce the reported leak exactly. _ARG_KEY replaced .*? (which backtracks across its own </arg_key> delimiter to reach a following <arg_value>) with a possessive non-<-crossing key group:
<arg_key>path</arg_key></arg_key><arg_value>/tmp/x</arg_value>→ base produced keypath</arg_key>(the exact production failure in the PR body); head →{"path": "/tmp/x"}.<arg_key><arg_key>path</arg_key><arg_value>...→ base produced key<arg_key>path; head correct.
Regression-proven: all 5 new tests FAIL on base (4 param converter tests + the streaming e2e test), PASS on head. Full file: 20/20 pass on head vs 5 failed/15 passed on base (teardown RuntimeError: Cannot access accelerator device errors are the known CUDA-less noise, identical on both).
No regressions on adjacent shapes — probed base-vs-head over 22 inputs: well-formed single/multi-arg, \s* whitespace variants, keys containing < (e.g. a<b), arg_key-like markup inside values, empty keys/values, newlines, trailing partial values, junk prefix. Byte-identical output everywhere except the corrupt-key cases. One deliberate delta on the malformed two-keys-one-value input: base merged a</arg_key><arg_key>b into one corrupt key; head drops the value-less a and keeps {"b": "1"} — cleaner fail behavior, not a regression.
Non-blocking note: vllm/tool_parsers/poolside_v1_tool_parser.py:82 uses the same <arg_key>(.*?)</arg_key>\s*<arg_value>(.*?)</arg_value> shape with stdlib re — same leak exists there (findall on <arg_key>path</arg_key></arg_key><arg_value>/tmp/x</arg_value> returns [('path</arg_key>', '/tmp/x')]). If poolside models can emit stray arg tags too, the same [^<]*+(?:<(?!/?arg_key>)[^<]*+)*+ key pattern would apply. Out of scope for this PR, just flagging the sibling.
Nice work — clear root-cause writeup, the _ARG_KEY comment explains the backtracking subtlety precisely, and the streaming e2e test is exactly the right level to prove the engine path.
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Thanks for the catch, @Manny7717 — |
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This pull request has merge conflicts that must be resolved before it can be |
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… argument keys
`_glm47_arg_converter` matched the argument key with an unbounded `.*?`
before `</arg_key>`. Because the group is non-greedy but unbounded, the
regex engine backtracks *past* the first `</arg_key>` whenever that is
what it takes to reach the following `<arg_value>` -- so a repeated or
stray tag in the model stream is absorbed into the key rather than
ignored.
Observed in production against a GLM server run with
`--tool-call-parser glm47`: an argument object came back as
`{"path</arg_key>": "/Users/user/Desktop/project"}`. The client rejected
the call ("must have required property 'path'"), and the model then
retried with an invented path.
Match runs of non-`<` text instead, so the key group cannot cross its own
delimiter, and accept a run of closing tags so the intended key survives.
Well-formed input is unaffected. The unrolled possessive form also avoids
the backtracking a tempered dot would add on the streaming path, which
re-runs the converter over the whole accumulated buffer on every chunk:
on an unterminated 20 KB buffer it is 1251 us -> 10 us.
Covers both `_ARG_RE` and `_PARTIAL_ARG_RE`, with a streaming test that
fails if only one of the two is fixed.
Signed-off-by: pctablet505 <55033230+pctablet505@users.noreply.github.com>
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…-call argument keys
PoolsideV1ToolParser.func_arg_regex captures the argument key with a plain
`.*?`:
r"<arg_key>(.*?)</arg_key>\s*<arg_value>(.*?)</arg_value>"
A non-greedy `.*?` only guarantees the *shortest match starting from the
left*, not that it stops at the first literal occurrence of `</arg_key>`
once the rest of the pattern is considered: if matching `\s*<arg_value>`
fails right after the first `</arg_key>`, the engine backtracks and lets
`.*?` cross that boundary to reach a later one, absorbing a stray
`<arg_key>`/`</arg_key>` tag into the key. Same defect class, same fix
shape, as the GLM-4.7 leak fixed in vllm-project#54971: bound the key to runs of
non-`<` text so the capture cannot cross its own delimiter.
r"<arg_key>([^<]*+(?:<(?!/?arg_key>)[^<]*+)*+)(?:</arg_key>\s*)+"
r"<arg_value>(.*?)</arg_value>"
Not a duplicate of vllm-project#54678, which fixes catastrophic backtracking (a timing
defect) in this file's `func_detail_regex` and adds a regex-timeout guard
around all three patterns in `extract_tool_calls`, including this one's
`.findall` call site -- but it leaves `func_arg_regex`'s pattern itself
unchanged, so the key-leak this PR fixes is still present after vllm-project#54678.
Signed-off-by: pctablet505 <55033230+pctablet505@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Signed-off-by: pctablet505 <55033230+pctablet505@users.noreply.github.com>
Keep the one comment a reader needs; the bug narrative lives in the PR description. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Signed-off-by: pctablet505 <55033230+pctablet505@users.noreply.github.com>
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Brought this branch up to date with
I also trimmed the bug-narrative comments and test docstrings down to what a reader needs (the explanation stays in the description), and refreshed the related-PR list (#60842 and #58418 are new neighbours; neither changes the key pattern). @sfeng33, you last touched |
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Purpose
Fixes a tool-call corruption in the GLM-4.7 parser: stray
arg_keymarkup leaks into the parsed argument key, so the client rejects the call.Observed in production against a GLM server run with
--tool-call-parser glm47:The client rejects the call, the agent loses the step, and the model retries with an invented path.
Root cause.
_glm47_arg_convertermatched the key with an unbounded non-greedy group:r"<arg_key>(?P<key>.*?)</arg_key>\s*<arg_value>(?P<value>.*?)</arg_value>".*?is non-greedy but it is not bounded by the delimiter it is scanning for. If the stream contains a repeated or strayarg_keytag, the engine backtracks past the first</arg_key>because that is what it takes to reach the following<arg_value>, and the extra markup ends up inside the key. Onthe old code yields
{"path</arg_key>": "/tmp/x"}, reproducing the observed string exactly. The mirrored<arg_key><arg_key>path…case yields{"<arg_key>path": "/tmp/x"}.Fix. Match runs of non-
<text so the key group cannot cross its own delimiter, and accept a run of closing tags so a duplicate is skipped rather than shifting the key:Both
_ARG_REand_PARTIAL_ARG_REare built from it, so the streaming path gets the same guarantee.The unrolled possessive form is deliberate rather than the simpler tempered dot
(?:(?!</?arg_key>).)*._compute_arg_deltare-runs the converter over the whole accumulated buffer on every argument chunk, so the common streaming case is a failing match against a partial buffer — precisely where a tempered dot backtracks per character. Measured on an unterminated buffer:Equivalence was checked over 600,000 randomized tag-soup evaluations against both patterns: 0 differing results.
Test Plan
Three tests are added, CPU only:
test_arg_converter_ignores_stray_arg_tags— the non-streaming pattern (_ARG_RE), 3 cases.test_partial_arg_converter_ignores_stray_arg_tags— the streaming pattern (_PARTIAL_ARG_RE), 3 cases. These inputs deliberately omit the closing</arg_value>, which is what an in-flight stream feeds; with a closing tag they would never reach_PARTIAL_ARG_REat all.TestGlm47Streaming::test_stray_arg_key_tag— end-to-end throughextract_tool_calls_streaming, which is the only thing proving the stray tag survives the engine intoslot.args.Test Result
Re-run on 2026-10-10 on this branch merged with
mainat2bea22002(CPU only):Mutation-checked rather than just green — each variant was applied to this tree and the suite re-run:
main(revert_ARG_KEYentirely)_PARTIAL_ARG_RE, keep_ARG_REfixedpre-commit run --fileson the two touched files (ruff check/format, typos, mypy, SPDX, test-tethering): all passed.The third row is the one that matters. An earlier revision of this PR parametrized a single test over
partial=[False, True], but with a closing</arg_value>present both values take the_ARG_REpath — so half the production change had no coverage and the half-fix scored green. The three failures now aretest_partial_arg_converter_ignores_stray_arg_tags[repeated-closing-tag],[repeated-opening-tag], andTestGlm47Streaming::test_stray_arg_key_tag.No model evaluation is included: the change only affects recovery from malformed markup, and well-formed input is byte-identical, which the
well-formedparametrize case pins in both the streaming and non-streaming direction.Related work
Not a duplicate of the other open GLM-4.7 parser PRs (re-checked 2026-10-10) — each handles a different malformation in the same file:
<arg_key>(tool_namearg</arg_key>).<arg_value>.<tool_call>opens a phantom call._ARG_RE/_PARTIAL_ARG_RE, not the patterns).arg_keytag corrupting the key.They will conflict textually where they edit
_ARG_RE/_PARTIAL_ARG_RE. Happy to update this branch against whichever lands first.The possessive-quantifier approach follows #54678, which fixed catastrophic backtracking in the
poolside_v1anddotstool-call regexes.Scope note
The raw model stream that produced the production capture was not retained, so the exact upstream trigger for the stray tag is inferred from the corrupted output rather than replayed. The change is a strict improvement independently of what emitted the stray tag: it removes a way for the extraction to mis-key an argument, and leaves well-formed input byte-identical.
Two sibling parsers (
glm4_moe,dots1) carry structurally similar key patterns; they are left alone here to keep this reviewable, and neither has a reported corruption.AI assistance was used for this change. Every changed line was reviewed and the tests above were run locally before submission.