feat(provider): add anthropic chat format for new provider#20
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📝 WalkthroughWalkthroughAdds an Anthropic gateway provider with OpenAI↔Anthropic request/response and SSE bridging, extends chat stream state to include response metadata, updates provider registry to register Changes
Sequence DiagramsequenceDiagram
participant Client
participant Gateway
participant AnthropicAPI as Anthropic API
Client->>Gateway: OpenAI ChatCompletionRequest
Note over Gateway: Transform request\n- Hoist system/developer into Anthropic system prompt\n- Convert messages & tools to Anthropic format\n- Map stop sequences / tool-choice
Gateway->>AnthropicAPI: AnthropicMessagesRequest
AnthropicAPI-->>Gateway: AnthropicMessagesResponse (id, model, created) / SSE events
Note over Gateway: Parse response/SSE\n- Capture response metadata into ChatStreamState\n- Map content blocks → assistant messages\n- Map tool_use → function/tool calls\n- Aggregate streaming deltas into ChatCompletionChunk(s)
Gateway->>Client: ChatCompletionResponse / streaming chunks
Estimated code review effort🎯 4 (Complex) | ⏱️ ~70 minutes Possibly related PRs
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✅ Passed checks (2 passed)
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Actionable comments posted: 1
🧹 Nitpick comments (4)
src/gateway/providers/anthropic/mod.rs (2)
201-206: Assertion can be simplified.The assertion
response.choices[0].message.content.as_ref().map(|_| true)just checks forSome. A cleaner approach would be to useis_some().✨ Suggested simplification
- assert_eq!( - response.choices[0].message.content.as_ref().map(|_| true), - Some(true) - ); + assert!(response.choices[0].message.content.is_some());🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@src/gateway/providers/anthropic/mod.rs` around lines 201 - 206, The test assertion that checks presence of content uses a convoluted map-to-true pattern; replace the expression response.choices[0].message.content.as_ref().map(|_| true) == Some(true) with a direct is_some() check (e.g., assert!(response.choices[0].message.content.as_ref().is_some())) to simplify and clarify the intent for the Content field on response.choices[0].message.
47-50: Consider documenting or making the Anthropic API version configurable.The
anthropic-versionheader is hardcoded to2023-06-01. While this is a stable version, Anthropic periodically releases new API versions with additional features. Consider adding a comment explaining this choice or making it configurable if version-specific features become necessary.🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@src/gateway/providers/anthropic/mod.rs` around lines 47 - 50, The Anthropic API version header is hardcoded in the headers.insert call (HeaderName::from_static("anthropic-version"), HeaderValue::from_static("2023-06-01")); update this to be configurable or at least documented: add a short comment explaining why this version is pinned and potential impacts, and refactor the HeaderValue to use a configurable constant or env var (e.g., ANTHROPIC_API_VERSION) so code paths that construct headers can reference that constant instead of the literal string; ensure the unique symbols headers.insert, HeaderName::from_static("anthropic-version"), and HeaderValue::from_static("2023-06-01") are updated to use the new constant or accompanied by the explanatory comment.src/gateway/providers/anthropic/transform.rs (2)
172-194: Tool call accumulator created viaor_default()may lack metadata ifContentBlockStartis missed.If a
ContentBlockDeltawithInputJsonDeltaarrives before its correspondingContentBlockStart(e.g., due to network issues or malformed streams), the accumulator will be created withoutid,kind, orname. Thebuild_stream_chunkwill still succeed, but the emittedChunkToolCallwill haveNonefor these fields.This is likely acceptable since a malformed stream from Anthropic would be an upstream issue, but consider adding a debug log or metric for this edge case.
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@src/gateway/providers/anthropic/transform.rs` around lines 172 - 194, ContentDelta::InputJsonDelta handling currently creates an accumulator with state.tool_call_accumulators.entry((0, index)).or_default() which can produce a tool-call accumulator missing metadata (id/kind/name) if the corresponding ContentBlockStart was missed; update this branch to detect when the entry is newly created or when accumulator.id/kind/name are None and emit a debug log or increment a metric before pushing partial_json and calling build_stream_chunk (referencing ContentDelta::InputJsonDelta, state.tool_call_accumulators, build_stream_chunk, ChunkToolCall, ChunkFunctionCall); ensure the log/metric includes the index and any context to diagnose malformed streams.
119-160: Hardcoded choice index 0 may limit future extensibility.The tool call accumulator key uses a hardcoded choice index of
0(line 127:(0, index)). While Anthropic's current API doesn't support multiple choices (n > 1), this assumption is baked into multiple places. If Anthropic adds multi-choice streaming in the future, this would need refactoring.This is acceptable for now given Anthropic's current API constraints, but worth noting in a comment.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Inline comments:
In `@src/gateway/providers/anthropic/transform.rs`:
- Around line 395-408: The crate uses if-let chain syntax (see
normalize_anthropic_content and its if let [...] && cache_control.is_none()
usage) which requires Rust 1.76; update Cargo.toml's [package] section to
declare the MSRV by adding rust-version = "1.76" so the minimum supported Rust
version is explicitly documented.
---
Nitpick comments:
In `@src/gateway/providers/anthropic/mod.rs`:
- Around line 201-206: The test assertion that checks presence of content uses a
convoluted map-to-true pattern; replace the expression
response.choices[0].message.content.as_ref().map(|_| true) == Some(true) with a
direct is_some() check (e.g.,
assert!(response.choices[0].message.content.as_ref().is_some())) to simplify and
clarify the intent for the Content field on response.choices[0].message.
- Around line 47-50: The Anthropic API version header is hardcoded in the
headers.insert call (HeaderName::from_static("anthropic-version"),
HeaderValue::from_static("2023-06-01")); update this to be configurable or at
least documented: add a short comment explaining why this version is pinned and
potential impacts, and refactor the HeaderValue to use a configurable constant
or env var (e.g., ANTHROPIC_API_VERSION) so code paths that construct headers
can reference that constant instead of the literal string; ensure the unique
symbols headers.insert, HeaderName::from_static("anthropic-version"), and
HeaderValue::from_static("2023-06-01") are updated to use the new constant or
accompanied by the explanatory comment.
In `@src/gateway/providers/anthropic/transform.rs`:
- Around line 172-194: ContentDelta::InputJsonDelta handling currently creates
an accumulator with state.tool_call_accumulators.entry((0, index)).or_default()
which can produce a tool-call accumulator missing metadata (id/kind/name) if the
corresponding ContentBlockStart was missed; update this branch to detect when
the entry is newly created or when accumulator.id/kind/name are None and emit a
debug log or increment a metric before pushing partial_json and calling
build_stream_chunk (referencing ContentDelta::InputJsonDelta,
state.tool_call_accumulators, build_stream_chunk, ChunkToolCall,
ChunkFunctionCall); ensure the log/metric includes the index and any context to
diagnose malformed streams.
🪄 Autofix (Beta)
Fix all unresolved CodeRabbit comments on this PR:
- Push a commit to this branch (recommended)
- Create a new PR with the fixes
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📒 Files selected for processing (5)
docs/internals/llm-types.mdsrc/gateway/providers/anthropic/mod.rssrc/gateway/providers/anthropic/transform.rssrc/gateway/providers/mod.rssrc/gateway/traits/chat_format.rs
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Pull request overview
Adds a first-class Anthropic provider implementation to the gateway’s new provider stack, including request/response bridging between the hub (OpenAI Chat Completions) types and Anthropic Messages, plus streaming adaptation.
Changes:
- Extend
ChatStreamStateto carry streamed response metadata (id,model,created) needed by provider SSE adapters. - Register a new
AnthropicDefprovider and expose it via the default provider registry. - Implement OpenAI↔Anthropic transform logic (including SSE stream event conversion) and document the new provider layering.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| src/gateway/traits/chat_format.rs | Adds response metadata fields to shared streaming state. |
| src/gateway/providers/mod.rs | Registers and exports the new Anthropic provider definition. |
| src/gateway/providers/anthropic/mod.rs | Implements ProviderMeta/ChatTransform and native Anthropic Messages support wiring. |
| src/gateway/providers/anthropic/transform.rs | Implements request/response and SSE streaming conversions between OpenAI hub types and Anthropic Messages. |
| docs/internals/llm-types.md | Documents stream-state metadata and Anthropic provider positioning in the new stack. |
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This was referenced Apr 7, 2026
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As the 6th part of the major refactoring of the provider, add the Anthropic provider.
Summary by CodeRabbit
New Features
Bug Fixes / Improvements
Documentation