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Summary

The streamed translator (src/sse.rs) and the whole-body translator (src/protocol.rs) of the same protocol pair each derived the completion signal on their own, and the two give different answers about how the upstream finished — so "did it end normally / should I dispatch a tool / was it truncated" depends on whether the client streamed. This PR derives each completion signal once (in src/protocol.rs) and calls it from both paths, then deletes the duplicated inline matches so the two sides cannot drift apart again.

#	pair	upstream signal	streamed (before)	whole-body (before)	both (after)
①	anthropic → openai_chat	stop_reason outside end_turn/max_tokens/tool_use (refusal, pause_turn, …)	stop	the raw anthropic token, passed through verbatim — a value outside OpenAI's closed finish_reason set	stop
②	responses → openai_chat	response with a tool call	stop, after the tool-call deltas were already streamed	tool_calls	tool_calls
③	openai_chat → anthropic	tool_calls with a null/absent finish_reason	stop_reason: null — or no message_delta at all when the upstream ended with [DONE] without ever sending a finish_reason, so the client never learned a stop reason	tool_use	tool_use

① is dormant-but-reachable (it needs a single-protocol plan; neither the example config nor this deployment has one) — it is fixed and pinned anyway, because the passthrough arm's only possible inputs are anthropic values with no OpenAI equivalent. ② and ③ are live today: ② on the four openai_chat-only plans, ③ for an anthropic-protocol client converted from an OpenAI-compatible endpoint.

Both directions are single-source now, so this is not "one copy aligned with the other" — the second copy is gone:

// src/protocol.rs — the only place these signals are derived
pub fn anthropic_to_openai_chat_finish_reason(stop_reason: Option<&str>) -> &'static str
pub fn openai_chat_to_anthropic_stop_reason(finish_reason: Option<&str>, has_tool_calls: bool) -> Option<String>
pub fn openai_responses_to_openai_chat_finish_reason(has_tool_calls: bool) -> &'static str

Related Issue

None — the repository carries no open issues. This closes a self-driven work order: the divergence was found by pushing the same upstream completion signal through both translators and printing both columns, then implemented per the plan recorded in the previous cycle.

Changes

• src/protocol.rs — the three helpers above are added next to the translators, and every whole-body call site goes through them: openai_chat_to_anthropic_resp (including its empty-response early return), its has_tool_use fallback, anthropic_to_openai_chat_resp's Some(other) => other passthrough arm (deleted), and openai_responses_to_openai_chat_resp.
• src/sse.rs — the local map_stop_reason is deleted and its two callers use the shared helper; the three literal "finish_reason": "stop" terminals (anthropic_sse_to_openai's message_stop/fallback, responses_sse_to_openai_chat's completed/fallback) now report the derived signal; and in openai_sse_to_anthropic the [DONE] handler emits the terminal message_delta whenever message_start went out, deriving the stop reason when the upstream never supplied a finish_reason (previously that case emitted message_stop alone, leaving the client with no stop reason).
• 涉及配置/数据结构的改动已同步示例文件 — N/A: no config, schema or data-structure change.

Behaviour changes, exhaustively: ① unknown anthropic stop_reason now converges to stop instead of leaking an out-of-enum value; ② a responses stream that emitted tool calls now ends with tool_calls; ③ an openai_chat upstream that carried tool calls with no finish_reason now yields tool_use, and one that ends with [DONE] without any finish_reason now gets a terminal message_delta instead of none. Everything else is byte-identical: the end_turn/stop_sequence/None → stop and length/max_tokens, tool_calls/function_call/tool_use mappings keep their previous values on both paths.

Tests

• cargo test 全部通过 — 192 passed / 0 failed (was 190 on main; the two new tests below).
• cargo fmt --check 通过
• cargo clippy --all-targets -- -D warnings 通过
• 新增/更新了单元测试
  • protocol::tests::completion_signal_helpers_cover_every_documented_value — pins each helper over every documented value of its protocol plus unknown-value controls (content_filter, not_a_reason, and None), and pins the precedence rule that an explicit finish_reason is not overridden by tool-call content.
  • sse::tests::completion_signal_agrees_between_stream_and_whole_body — the axis assertion: for each upstream signal, the real stream translator and the real whole-body translator are driven with the same input and must produce the same terminal value (① every finish_reason × with/without a tool call, ② every anthropic stop_reason, ③ responses with/without a function call). It also requires that a [DONE]-terminated openai_chat stream actually emits a message_delta.
  • A/B (red-before, green-after): restoring any one arm makes exactly that face red while the rest stay green — (m1) the Some(other) => other passthrough → ①; (m2a/m2b) the literal "stop" in responses_sse_to_openai_chat's completed and fallback terminals → ②; (m3) the [DONE] path's original "only if a pending delta exists" condition → ③.

Checklist

• 分支命名符合约定 — fix/completion-signal-parity
• Commit message 使用 Conventional Commits 格式 — fix(protocol): derive the completion signal once for both the streamed and the whole-body translators
• 单一职责，改动最小化 — one defect class (a completion signal derived twice), 2 files; the duplicated matches are deleted rather than aligned, and no unrelated refactor rides along.