Finalize open thinking blocks on messageStop for Bedrock Converse streaming

[mattwebbio]

Summary

• Bedrock's Converse stream doesn't reliably send a content_block_stop for every reasoning-content index before the stream ends — observed for a redacted thinking block immediately superseded by the next block's content_block_start with no stop in between.
• That left thinking.blocks empty for such turns, forcing replay onto format_thinking_blocks' lossy single-block reconstruction, which Anthropic rejects on the next request with Invalid \data` in `redacted_thinking` block`.
• messageStop now finalizes any block still open at that point, but only when it's structurally complete (has a signature or redacted-content marker present) — a genuinely truncated block with neither is still dropped, unchanged from existing behavior.

Test plan

• bundle exec rspec spec/ruby_llm/protocols/converse/streaming_spec.rb spec/ruby_llm/stream_accumulator_spec.rb — 18 examples, 0 failures (includes new regression test + the pre-existing truncation-drop test, both green)
• bundle exec rspec spec/ruby_llm/protocols/ — 309 examples, 0 failures
• bundle exec rubocop lib/ruby_llm/protocols/converse/streaming.rb spec/ruby_llm/protocols/converse/streaming_spec.rb — no offenses

🤖 Generated with Claude Code

[staging-supernova-dx-appf-io]

🤖 Supernova Code Review — View trace

[staging-supernova-dx-appf-io]

One bug found: the new finalize_remaining_thinking_blocks method calls .presence on an Array (line 234). This is an ActiveSupport method — it isn't part of Ruby core, and activesupport is not a declared runtime dependency of this gem. Tests pass only because spec/spec_helper.rb loads active_support/core_ext. In any non-Rails consumer, the call will raise NoMethodError at exactly the moment the fix is supposed to kick in (i.e., when messageStop arrives with an un-stopped thinking block).

See the inline comment for a drop-in fix.

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🔁 Re-run this review

[staging-supernova-dx-appf-io]

.presence is an ActiveSupport extension method — it isn't available in plain Ruby. The gem's gemspec has no activesupport runtime dependency, so any consumer using ruby_llm outside of a Rails context (or without manually loading ActiveSupport) will hit NoMethodError: undefined method 'presence' for Array the first time messageStop fires with leftover thinking state (i.e., exactly the scenario this fix is designed to handle).

Tests pass only because spec/spec_helper.rb explicitly require 'active_support/core_ext'.

Replace with an equivalent Ruby-native guard:

def finalize_remaining_thinking_blocks(thinking_state)
  blocks = thinking_state.keys.sort.filter_map do |index|
    state = thinking_state.delete(index)
    next unless state[:redacted] || state[:signature]

    finalize_thinking_block(state)
  end
  blocks.empty? ? nil : blocks
end