* feat: track token usage per conversation turn
Add token usage tracking to the streaming API so consumers can monitor
cost per turn without additional API calls.
Changes:
1. _serialize_message now includes usage_metadata for AI messages in
values events, exposing input_tokens/output_tokens/total_tokens
from LangChain's native metadata.
2. stream() accumulates token usage across all AI messages in a turn
and emits the cumulative totals in the end event:
{usage: {input_tokens: N, output_tokens: N, total_tokens: N}}
3. Each messages-tuple AI event with text content now includes a
per-message usage_metadata field for granular tracking.
This enables the frontend to display token consumption per turn,
support cost-aware UX, and let users monitor API spending.
10 tests added covering serialization passthrough and cumulative
aggregation logic.
Co-Authored-By: OpenClaw <noreply@openclaw.ai>
* fix: address Copilot review - use Mapping access for usage_metadata
- Replace getattr(usage, 'input_tokens', 0) with usage.get('input_tokens', 0)
since LangChain usage_metadata is a dict, not an object
- Remove unused 'import pytest' (fixes Ruff F401)
- Add proper stream() integration tests for cumulative usage in end event
and per-message usage_metadata in messages-tuple events
---------
Co-authored-by: Exploreunive <Exploreunive@users.noreply.github.com>
Co-authored-by: OpenClaw <noreply@openclaw.ai>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
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