fix(libsy): warn when Claude Code predates sub-agent identity headers - #696
linj-glitch wants to merge 5 commits into
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| fn parses_claude_code_versions_from_the_user_agent() { | ||
| assert_eq!( | ||
| claude_code_version("claude-cli/2.1.121 (external, cli)"), | ||
| Some([2, 1, 121]) | ||
| ); | ||
| assert_eq!(claude_code_version("claude-cli/2.1.139"), Some([2, 1, 139])); | ||
| assert_eq!( | ||
| claude_code_version("claude-cli/3.0.0-beta.1 (external, cli)"), | ||
| Some([3, 0, 0]) | ||
| ); | ||
| assert_eq!(claude_code_version("codex_cli_rs/0.120.0"), None); | ||
| assert_eq!(claude_code_version("claude-cli/nightly"), None); | ||
| assert_eq!(claude_code_version("claude-cli/2.1"), None); | ||
| } | ||
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| #[test] | ||
| fn flags_only_claude_code_older_than_the_identity_floor() { | ||
| let outdated = | ||
| |user_agent: &str| outdated_claude_code(claude_code(user_agent).metadata.as_ref()); | ||
| // A build without the headers is flagged with its version. | ||
| assert_eq!( | ||
| outdated("claude-cli/2.1.121 (external, cli)"), | ||
| Some([2, 1, 121]) | ||
| ); | ||
| assert_eq!(outdated("claude-cli/2.0.999"), Some([2, 0, 999])); | ||
| // The floor itself and anything newer are fine. | ||
| assert_eq!(outdated("claude-cli/2.1.139 (external, cli)"), None); | ||
| assert_eq!(outdated("claude-cli/2.1.211 (external, cli)"), None); | ||
| assert_eq!(outdated("claude-cli/3.0.0"), None); | ||
| // Other clients and requests without metadata are never flagged. | ||
| assert_eq!(outdated("codex_cli_rs/0.120.0"), None); | ||
| assert_eq!(outdated_claude_code(None), None); | ||
| assert_eq!(MIN_CLAUDE_CODE_VERSION, [2, 1, 139]); | ||
| } | ||
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| #[tokio::test] | ||
| async fn outdated_claude_code_still_routes_through_the_parent() -> crate::Result<()> { | ||
| let router = configured(Arc::new(ScriptedClassifier { | ||
| calls: AtomicUsize::new(0), | ||
| }))?; | ||
| let models = RuntimeModels::new([(Category::Any, vec![ModelId::from("parent")])].into()) | ||
| .with_subagent([(Category::Any, vec![ModelId::from("worker")])].into()); | ||
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| // Without child identity the request is indistinguishable from the parent's, so it | ||
| // keeps routing through the parent algorithm; the warning is emitted once. | ||
| for _ in 0..2 { | ||
| let request = claude_code("claude-cli/2.1.121 (external, cli)"); | ||
| let (selected, _) = | ||
| test_drive_with_models(router.clone(), request, models.clone(), echo()).await?; | ||
| assert_eq!(selected, "parent"); | ||
| } | ||
| assert!(router.outdated_claude_code_warned.load(Ordering::Relaxed)); | ||
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| let (selected, _) = test_drive_with_models( | ||
| configured(Arc::new(ScriptedClassifier { | ||
| calls: AtomicUsize::new(0), | ||
| }))?, | ||
| claude_code("claude-cli/2.1.139 (external, cli)"), | ||
| models, |
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@linj-glitch Can you please trim these tests down. I don't expect these many tests to be added. Usually a single test should be sufficient for this small fix.
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Done. The three tests are folded into one, outdated_claude_code_warns_once_and_routes_through_the_parent, in 4c6fc31. It checks the version floor, that an old build still routes to the parent, and that the warning fires once.
WalkthroughThe change records the caller User-Agent, detects Claude Code versions older than 2.1.139, warns once for affected sub-agent routes, and documents parent-route fallback behavior. ChangesSub-agent routing compatibility
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~15 minutes Merge Risk: 🔵 Low · up to Prerelease Claude Code clients and multi-route processes can miss or duplicate compatibility warnings, and downstream users may face a compile-breaking API update. Address these bounded compatibility issues before release. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
A rabbit trims the headers bright Comment |
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Actionable comments posted: 3
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Inline comments:
In `@crates/libsy/src/algorithms/subagent.rs`:
- Line 52: Update the version-check logic around split to preserve prerelease
identifiers and compare versions semantically, ensuring a prerelease such as
2.1.139-beta.1 is correctly evaluated as older than the 2.1.139 release floor;
otherwise conservatively flag prereleases at the floor.
- Line 108: Make the outdated Claude Code warning state process-wide by
replacing the per-SubagentRouter outdated_claude_code_warned AtomicBool
initialization with a shared static AtomicBool. Update the warning check and
mutation to use that static flag so only the first warning across all routes is
emitted.
In `@crates/protocol/src/metadata.rs`:
- Line 194: Document the compatibility break in the public
switchyard_protocol::metadata::Metadata API caused by adding the user_agent
field, noting that downstream Metadata struct literals omitting this field no
longer compile.
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CHANGELOG.mdcrates/libsy/src/algorithms/subagent.rscrates/protocol/src/metadata.rsdocs/routing_algorithms/subagent_routing.md
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| const MIN_CLAUDE_CODE_VERSION: [u64; 3] = [2, 1, 139]; | ||
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| /// Parses the version out of a Claude Code `User-Agent` such as | ||
| /// `claude-cli/2.1.139 (external, cli)`. Returns `None` for any other client. | ||
| fn claude_code_version(user_agent: &str) -> Option<[u64; 3]> { | ||
| let version = user_agent | ||
| .strip_prefix("claude-cli/")? | ||
| .split([' ', '-', '+']) | ||
| .next()?; | ||
| let mut parts = version.split('.').map(|part| part.parse::<u64>().ok()); | ||
| Some([parts.next()??, parts.next()??, parts.next()??]) | ||
| } | ||
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| /// The Claude Code version behind `metadata` when it predates child identity headers. | ||
| fn outdated_claude_code(metadata: Option<&Metadata>) -> Option<[u64; 3]> { | ||
| let version = claude_code_version(metadata?.user_agent.as_deref()?)?; | ||
| (version < MIN_CLAUDE_CODE_VERSION).then_some(version) | ||
| } | ||
|
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Do we need to warn about outdated claude ? I feel backward compatibility is also important. So we should be supporting both here.
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Below 2.1.139 a child request is identical to a parent request on the wire: same session header, same body metadata, same User-Agent. The only differences are the system prompt and the first user message, and any heuristic on those misroutes the parent after compaction or on side-queries, which is worse than routing the child through the parent. Codex has carried lineage for a long time, so this only affects Claude Code.
I'd propose we set the supported Claude Code floor to 2.1.139 (released May 11; the benchmark already pins 2.1.211) and keep this warning so the gap is visible instead of silent.
| { | ||
| return; | ||
| } | ||
| let [min_major, min_minor, min_patch] = MIN_CLAUDE_CODE_VERSION; |
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@linj-glitch I don't think libsy should be aware of agent versions. This feels like something that belongs in translation / normalization. Perhaps in crates/protocol/src/metadata.rs. And then SubagentRouter can read a bool like: subagent_identity_unsupported.
I would also say we don't need to call out specific versions. We could just detect when no recognized child entity and warn harness upgrade may be required.
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Done in 5a1c562. Version knowledge now lives in crates/protocol/src/metadata.rs next to the other Claude Code header handling: claude_lacks_child_identity reads the User-Agent during normalization and sets a new Metadata::subagent_identity_unsupported bool. SubagentRouter only reads that bool and warns once per route that the harness does not send sub-agent identity and an upgrade may be required, with no version named. The user_agent field is gone. One test per crate.
Signed-off-by: Lin Jia <linj@nvidia.com>
Signed-off-by: Lin Jia <linj@nvidia.com>
Signed-off-by: Lin Jia <linj@nvidia.com>
Signed-off-by: Lin Jia <linj@nvidia.com>
…header normalization Signed-off-by: Lin Jia <linj@nvidia.com>
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Looks good. Please merge once Ryan approves the PR. Thanks
3 participants
What
Sub-agent routing detects Claude Code children only through the
x-claude-code-agent-idheader. Claude Code started sending that header in 2.1.139. Older builds, such as the 2.1.121 QA used, send only the session id, so their sub-agent requests look like the parent's and silently route through the parent route.This PR:
subagent_identity_unsupportedflag toswitchyard_protocol::Metadata, set during header normalization when the calling harness build is known not to send child identity (today: Claude Code before 2.1.139, read from itsUser-Agent);SubagentRouterlog one warning per sub-agent route, without naming versions, when such a request reaches a route with asubagentstable;Routing behavior is unchanged. Below 2.1.139 the parent and its children send identical headers and the body carries no stable child marker, so a heuristic fallback would risk misrouting parent turns.
Why
Fixes SWITCH-1437 (NvBug 6771746). QA ran Claude Code 2.1.121 against v0.3.0-rc.1 with a Composite route and a
subagentspassthrough. The child target recorded zero calls with no error or warning. The header floor comes from the Claude Code 2.1.139 release notes: "API requests from subagents now carry x-claude-code-agent-id / x-claude-code-parent-agent-id headers."Notes for reviewers
Harness and version knowledge lives in
crates/protocol/src/metadata.rs(claude_lacks_child_identity), next to the other Claude Code header handling.libsyonly reads the resulting bool inSubagentRouter::warn_if_subagent_identity_unsupported. The Claude CodeUser-Agenthas the formclaude-cli/<version> (...). One test in each crate: the protocol test covers the version floor and prerelease handling, the libsy test covers the once-only warning on the parent path.cargo clippy --workspace --all-targets -- -D warningsis clean.