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feat(symphony): the structural tag derived from a table, for the JSON, GLM and DSML syntaxes - #2877
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…, GLM and DSML syntaxes A `Grammar` tree in the shape of the engines' structural-tag format (triggered_tags, tags_with_separator, tag, sequence, or, star, plus, optional, const_string, any_text, regex, json_schema), written as the engine reads it by `to_json()` and as a request carries it by `payload()`; and `Format::grammar(tools, at_least_one, reasoning_open)`, which derives the tag from the table's rows: the terminals that enter and leave the arguments state are the call markers, the ones around a wrapper state the block markers, the one that leaves the reasoning state closes the reasoning prefix. The JSON family wraps each tool's schema in the call markers; keyed arguments in GLM's spelling take the engines' `glm_xml` style; DSML gets the calls block, one invoke per tool and the typed parameter tag. The other syntaxes give `None` for now. Where the gateway's old parsers hand-write a tag for a format Symphony has, the derived tag is pinned to it literally: GLM's tag and reasoning prefix, and DeepSeek V4.1's DSML tag. Signed-off-by: Simo Lin <25425177+slin1237@users.noreply.github.com> Co-authored-by: Chang Su <8605658+CatherineSue@users.noreply.github.com>
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WalkthroughThe PR adds public grammar types and serialization. ChangesGrammar constraints
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~45 minutes Change: Feature Sequence Diagram(s)sequenceDiagram
participant Format
participant Tool
participant Grammar
participant Payload
Format->>Format: Read transition markers
Format->>Tool: Read name and parameter schema
Format->>Grammar: Derive call constraints
Grammar->>Payload: Serialize under format key
Merge Risk: ⚪ Minimal · up to This change adds grammar derivation types that the gateway does not use yet. No merge-blocking risk remains. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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Approving: no 🔴 issues found. I left 3 🟡 nits on crates/symphony/src/grammar.rs:
- with
reasoning_openset, a table with no reasoning row returnsNoneinstead of the plain tag marker()depends on the order rows were added, and the DSML reasoning prefix isn't tested- Ling gets GLM 4.7's no-newline tag although its template writes newlines
The PR description is also missing the template's headers (see the separate comment).
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Review comments at @crates/symphony/src/grammar.rs:
- Around line 226-246: Validate tool names against the selected assembler’s
accepted syntax before deriving keyed or DSML tags, so malformed names cannot be
emitted. Update the tool-name filtering in the grammar construction flow around
`json_calls`: reject quotes and angle brackets where keyed syntax disallows
them, and reject double quotes for DSML while allowing `>` there.
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crates/symphony/src/format.rscrates/symphony/src/grammar.rscrates/symphony/src/lib.rscrates/symphony/src/tagged/dsml.rs
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Rule-17 review of #2877 at 0dad743: request changes, for three of the four open threads. All three are right, and the code they point at is new behavior. What the PR claims to reproduce, it reproduces exactly. Rule 18 does not apply: there is no new CallSyntax. Rule 25: the merge is the maintainer's.
The derivation against the old builders. The unit tests pin literals. I compared the derived payloads against the old crate's builders themselves, from a throwaway test with tool-parser as a local dev-dependency:
- GLM:
Glm4MoeParser::build_structural_tag; - GLM on a thinking prompt: the same tag wrapped as the registry's
wrap_in_reasoning_prefixwraps it, withGlm4MoeParser::reasoning_prefix(); - DSML:
DeepSeekDsmlParser::build_v41_structural_tag.
I ran six tool sets with both at_least_one values: one tool; three tools, one taking no arguments; an unnamed tool beside a named one; a name with a quote and a backslash; a non-ASCII name; a nested schema with a nullable union and an array. All 36 payloads are equal to the old builders' output. The one difference is deliberate: with no named tool, grammar() gives None where the old builders give a tag with no tags, which cannot be satisfied when a call is required.
The threads:
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?on the thought's close (grammar.rs:206): right. A table with no row leaving a reasoning state now givesNoneon a thinking prompt.qwen2_5()withreasoning_openis one. The old registry returns the plain tag there (if let (true, Some(prefix))).reasoning_opencomes from the tokenizer's template, not the table, so a mismatch silently drops the gateway onto the JSON-schema path. Returncallsunwrapped, or document it as a fourthNonecase. -
markertakes the first row (grammar.rs:351): right. DeepSeek V4.1's reasoning state has two exits, and only row order makes the prefix end at</think>rather than at the calls block. Preferring a row back to content makes that independent of order, as the thread suggests. Also, the DSML reasoning prefix is new behavior with no old builder behind it (the old registry registers none for DSML), so it wants a test of its own. -
Ling gets GLM 4.7's tag (grammar.rs:259): right. I found the same thing.
Tags::PLAINis the same for Ling and GLM, so the table cannot see the newline Ling's template writes after the name and after</arg_key>.- The old gateway gives the newline form (
glm45_moe) no structural tag at all, and the oldglm45regex requires that newline. - Unless xgrammar's
glm_xmlaccepts whitespace there, a forced call would push Ling off its own template.
Returning
Nonefor Ling until the newline is part of the table keeps "what is constrained is exactly what is parsed" true. The test that pins Ling's grammar equal to GLM's would then go, or invert. -
CodeRabbit's name check (grammar.rs:246): your call. The old builders insert the name unchecked too, which my comparison shows, so this is not a regression. Only the Kimi profile validates tool names in protocols. A quote in a DSML name, or
<,>or a quote in a keyed name, would let a forced call write a name its own assembler cannot read back. Filtering such tools out of the tag matches the PR's principle. Declining for parity, with that reason, is also fine.
Gates. I ran them at 0dad743 merged on main 21d5e44, with Rust 1.98.0, its own target dir and -j 2; each exited 0:
cargo +nightly fmt -p smg-symphony --checkcargo clippy -p smg-symphony --all-targets --all-features -- -D warningscargo test -p smg-symphony: 313 lib, 10 fixture, 7 contract and 5 README testsRUSTDOCFLAGS="-D warnings" cargo doc -p smg-symphony --no-deps
Rule 17:
- Fixture ids: none changed. The derivation is checked against the old builders above.
- Property tests: no new format.
- Protected paths:
grammar.rs,format.rs,lib.rsand DSML's marker constants, which this stream owns. - Trailers: the author's
Signed-off-by, then aCo-authored-by, and no AI trailer. - STATE.md: current.
- Threads: four open, as above.
…able, no prefix without a thought The review of the derived structural tag found three things. A table without a reasoning state dropped the whole tag when the prompt's reasoning was open: the tag now comes back as it is, as the old registry does when a parser has no prefix. The markers depended on the order of the rows: `marker(from, to)` names the two states instead, so the thought closes back to content and the call back to its block whichever row comes first; a test swaps DeepSeek V4.1's exits and gets the same grammar, and the DSML and JSON-family prefixes are pinned (the DSML one excludes the parameter tags too). Ling got GLM 4.7's compact tag though its template writes newlines: `keyed::Tags` now carries `between`, what the template writes after the name and after each `</arg_key>`, so `PLAIN` (nothing) derives the `glm_xml` tag and `LING` (a newline) returns `None` until that spelling has a derivation. Signed-off-by: Simo Lin <25425177+slin1237@users.noreply.github.com> Co-authored-by: Chang Su <8605658+CatherineSue@users.noreply.github.com>
…x, and Ling's newline has three places Two cases shared one `let … else`: a table without a thought, whose tag comes back as it is, and a table whose thought closes somewhere other than content, where a prefix ending anywhere else would force the call inside the thought. The second now gives `None` until it has a derivation, with a test whose thought closes into the calls block, as Kimi K3's closes into its message. The keyed tags' docs name every place Ling writes its newline: after the call's name, after each `</arg_key>` and before `</tool_call>`; the field tells the two spellings apart. Signed-off-by: Simo Lin <25425177+slin1237@users.noreply.github.com> Co-authored-by: Chang Su <8605658+CatherineSue@users.noreply.github.com>
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Rule-17 re-review of #2877 at d257234: approve. All six threads are answered and resolved: four from the first round and two from the second. My checks pass at this head.
The threads, checked:
- No reasoning exit: the tag now comes back unwrapped.
qwen2_5().grammar(…, true, true)givesSomein my probe, anda_table_without_a_thought_has_no_prefix_to_wrappins it. - The markers come from the states, not the row order:
marker(from, to)names both states. The test that builds DeepSeek V4.1's rows with both pairs of exits swapped gets the same grammar. The DSML and JSON-family prefixes are pinned too. - Ling:
keyed::Tagsgainsbetween, andLINGisPLAINwith a newline. OnlyPLAINderives theglm_xmltag. So Ling givesNone(my probe confirms), as the old gateway's JSON-schema path does forglm45. IQuest gets the compact tag under its own markers (<iquest_tool_call>get_weather,glm_xml,</iquest_tool_call>). The keyed assembler never readsbetween, which I grepped for: Ling's parsing is unchanged, so no replay is needed. - CodeRabbit's name filter: kept at parity with the old builders, with the reason given. Fine by me.
- Two cases apart (second round): a table with no reasoning state gives the tag as it is. One whose thought does not close straight to content gives
None, since a prefix ending anywhere else would force the call inside the thought.a_thought_that_closes_somewhere_other_than_content_has_no_prefix_yetpins it with a thought that closes into the calls block, as Kimi K3's closes into its message. between's places: the docs ofTagsandLINGnow name all three: after the name, after each</arg_key>, and before</tool_call>.
Parity, re-run at d257234: the same throwaway comparison with the old builders. GLM, GLM wrapped with its reasoning prefix as the registry wraps it, and DSML v4.1, over six tool sets and both at_least_one values: 36 of 36 payloads equal.
Gates. I ran them at d257234 merged on main 21d5e44, with Rust 1.98.0, its own target dir and -j 2; each exited 0:
cargo +nightly fmt -p smg-symphony --checkcargo clippy -p smg-symphony --all-targets --all-features -- -D warningscargo test -p smg-symphony: 318 lib, 10 fixture, 7 contract and 5 README testsRUSTDOCFLAGS="-D warnings" cargo doc -p smg-symphony --no-deps
Rule 18: keyed::Tags is the data inside CallSyntax::Keyed, and it gains a public field. So this now touches what a Format carries, and the merge is the maintainer's, as rule 25 already has it.
Rule 17:
- Fixture ids: none changed; parsing is unchanged.
- Property tests: no new format.
- Protected paths: the crate's grammar, format and keyed spelling, which this stream owns.
- Trailers: the author's
Signed-off-by, then aCo-authored-by, and no AI trailer. - STATE.md: current.
- Threads: six, all answered and resolved.
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| #[test] | ||
| fn a_thought_that_closes_somewhere_other_than_content_has_no_prefix_yet() { | ||
| // A thought that closes into the calls block, as Kimi K3's closes into its message: the |
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🟡 Nit: Kimi K3 is the example here, but its real table doesn't hit this guard, so the comment (and the module doc at L25-26) promises more than the code does.
The guard only gives None when no row goes from a reasoning state to a content state. Kimi K3's reasoning state does have one (crates/symphony/src/formats/kimi_k3.rs:58-59):
reasoning + think_close = message (Wrapper)
reasoning + response_open = content (Content)
So for Kimi K3:
has_state(Reasoning)is true.marker(Reasoning, Content)returns<|open|>response<|sep|>, notNone.- The prefix would end at the response opener instead of at the thought's close.
You can't reach this today, because Xtml returns None earlier. But the stated rule, "a thought that closes somewhere other than content gives None", only holds when the reasoning state has no other exit to content. Any table with both kinds of exit gets a prefix that ends at the wrong terminal.
Two ways to fix it:
- Narrow the wording: the test's table closes into the block and has no other way back to content, and drop the Kimi K3 comparison (or say Kimi K3 needs more than this guard).
- Or tighten the guard: give
Nonewhen any row leaves the reasoning state to a non-content state that isn't the call block (DeepSeek V4.1's and MiniMax M3'sreasoning + calls_open = callswould still need to pass).
2 participants
What
The design decides that
tool_choiceis Symphony's: the constraint an engine takes for a forced or required call comes from the same table the parser reads, so what is constrained is exactly what is parsed. This PR builds the first step of that, insidecrates/symphony/only:Grammar(src/grammar.rs): Symphony's own tree in the shape of the engines' structural-tag format (xgrammar's, which vLLM and SGLang accept):TriggeredTags,TagsWithSeparator,Tag,Sequence,Or,Star,Plus,Optional,ConstString,AnyText { excludes },Regex,JsonSchema { schema, style }.to_json()writes it as the engine reads it;payload()wraps it underformatas a request carries it. No new dependency (rule 27; design Q3, own serialisable type).Format::grammar(tools, at_least_one, reasoning_open) -> Option<Grammar>: derived from the rows, not written per table. The terminals that enter and leave the arguments state are the call markers; the ones around a wrapper state are the block markers; the one that leaves the reasoning state closes the reasoning prefix (free text that can write none of the table's terminals, nor the keyed tags). The request's tools give each call its name and schema; nameless tools are skipped; no named tool, or no derivation for the syntax, givesNone.{"name": <name>, "arguments":around the tool's schema, closed by}and the call close.glm_xmlstyle of each schema, the shape of xgrammar's built-in GLM tag. Ling's template writes newlines the compact style does not, so its table now records them and it returnsNoneuntil that spelling has a derivation.keyed::Tags::between: the template's newline, written after the call's name, after each</arg_key>and before the call's close (LING: Ling, GLM 4.5 and 4.6), or nothing anywhere (PLAIN: GLM 4.7 and later, IQuest;HY4). The field tells the two spellings apart; the assembler reads a call either way, and the grammar spells the one the template writes.dsml::PARAMETER_OPENandPARAMETER_CLOSEbecome public (the index constants are renamedOPEN/CLOSE), andFormat::transitions()gives the rows at crate level.Parity
The gateway's old parsers hand-write a tag per parser. Where one exists for a format Symphony has, the derived tag is pinned to it literally in the unit tests, read from
crates/tool_parser/src/parsers/:Glm4MoeParser::build_structural_tagformats::glm()at_least_oneboth waysGlm4MoeParser::reasoning_prefix+wrap_in_reasoning_prefixformats::glm()withreasoning_openDeepSeekDsmlParser::build_v41_structural_tagformats::deepseek_v4_1()The JSON family has no old structural tag (the gateway takes the JSON-schema path for it), so its test pins the shape the template writes; so do the DSML and JSON-family reasoning prefixes, which no old builder wrote. A test swaps DeepSeek V4.1's reasoning and invoke exits and gets the same grammar, so the markers come from the states, not the order of the rows. A table without a thought (Qwen 2.5) returns its tag unwrapped when the prompt's reasoning is open, as the old registry does without a prefix; a table whose thought closes somewhere other than content (as Kimi K3's closes into its message) gives
Noneinstead of a tag the model could write inside its thought. Every node's serialisation is tested once.Gates
By exit code (
.claude/symphony/gates.sh): fmt, clippy-D warnings, test (318 lib, 10 fixture, 7 contract, 5 README), doc, width, codespell, all 0.Not in this PR
grammar()still answersNonefor: the tagged syntax (Qwen 3.5 and later, Seed-OSS), keyed arguments in Ling's newline spelling and in Hy4's, MiniMax M3's XML, Kimi K3's XTML (its old builder is the next parity oracle), the pythonic tables, xLAM's list. The gateway takes its JSON-schema path for them, as today.Constrainedadapter (feat(symphony): the constrained format for a forced or required tool choice #2806, parked on bellwether Extracttool-parsercrate #19): the gateway still calls its own builders; nothing outsidecrates/symphony/changes.Merge
Squash under rule 25. Rule 18: no new
CallSyntax, butkeyed::Tags(the dataCallSyntax::Keyedcarries) gains a public field, so the merge is the maintainer's. Subject: the PR title plus(#<n>). Body: