cc-switch

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Jason 06ff5e211a fix(proxy/gemini): reconcile synthesized tool-call ids with later real ids + preserve thoughtSignature

Three related findings on `streaming_gemini.rs` for Gemini's cumulative
`streamGenerateContent` stream, all centered on `merge_tool_call_snapshots`:

1. (P1) Match upgraded tool-call IDs by position.
   When Gemini delivers a `functionCall` without an id on chunk 1
   (cc-switch synthesizes `gemini_synth_*`) and then upgrades it to a
   real id on chunk 2, the `Some(incoming_id)` branch only matched by
   id and missed the existing synthesized snapshot. A second entry
   would be pushed, yielding duplicate `tool_use` content blocks at
   stream end — one with the synthesized id, one with the real id —
   which could trigger duplicate tool execution and break tool_result
   correlation. Add a positional fallback: when no id match exists but
   the same-position slot holds a synthesized id, merge into it.
   `or(preserved_id)` already lets the real id win the merge.

2. (P2) Preserve prior thoughtSignature when merging snapshots.
   `tool_call_snapshots[index] = tool_call` overwrote the slot
   entirely, dropping any `thoughtSignature` captured on an earlier
   chunk if the current cumulative snapshot omitted it. Since
   `build_shadow_assistant_parts` writes `thoughtSignature` into the
   shadow turn from `tool_call.thought_signature`, a dropped signature
   would cause later replay requests to Gemini to be rejected with
   invalid-signature errors. Preserve the existing signature when the
   incoming chunk does not carry one.

3. (P2) Document the part-order streaming trade-off.
   All `tool_use` content blocks are emitted after the final text
   `content_block_stop`, so interleaved [text, functionCall, text,
   functionCall] parts arrive at the Anthropic client as [text(concat),
   tool_use, tool_use] — different from the non-streaming transformer,
   which preserves part order. This is intentional given the cumulative
   snapshot model and the consumers we target (claude-code-like clients
   don't depend on strict interleaving for tool execution correctness).
   Add a block comment at the flush site describing the trade-off and
   what a strict-order fix would entail, so this isn't rediscovered as
   a bug later.

Regression tests:
- upgraded_real_id_merges_into_existing_synthesized_snapshot
- thought_signature_preserved_when_later_chunk_omits_it

Test count: 868 -> 870. clippy 1.95 clean. fmt clean.

06ff5e211a · 2026-04-16 22:02:10 +08:00

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