Copilot routes through OpenAI-compatible endpoints that reject Anthropic's
thinking and redacted_thinking blocks. Previously the request would fail
upstream, burning one premium interaction, and only then trigger
thinking_rectifier to retry. This adds a proactive strip_thinking_blocks
pass in the Copilot optimization pipeline (step 3.5, after tool_result
merging). Signature fields and top-level thinking are left alone — those
are the reactive rectifier's job on the error path.
Also fixes a default-value inconsistency where CopilotOptimizerConfig's
Default impl used "gpt-4o-mini" while the serde default function returned
"gpt-5-mini" (aligned to gpt-5-mini, matching the reference implementation).
Aligned with yuegongzi/copilot-api's /v1/messages handler behavior.
- Fix request classification: treat messages containing tool_result as
agent continuation instead of user-initiated, preventing false premium
charges on every tool call
- Add subagent detection via __SUBAGENT_MARKER__ and metadata._agent_
fallback, setting x-interaction-type=conversation-subagent
- Add deterministic x-interaction-id derived from session ID to group
requests into a single billing interaction
- Add orphan tool_result sanitization to prevent upstream API errors
that could cause retries and duplicate billing
- Reorder pipeline: classify (on original body) → sanitize → merge →
warmup, ensuring classification sees raw tool_result semantics
- Enable warmup downgrade by default with gpt-5-mini model
- Enhance session ID extraction priority chain for Copilot cache keys
- Detect infinite whitespace bug in streaming tool call arguments
Implement request classification, tool result merging, compact detection,
deterministic request IDs, and warmup downgrade for Copilot proxy.
The root cause was x-initiator being hardcoded to "user", making Copilot
count every API request (including tool callbacks and agent continuations)
as a separate premium interaction. The optimizer dynamically classifies
requests as "user" or "agent" based on message content analysis.
Closes#1813
Jason