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Replay the phase of Responses assistant messages - #1231

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yorzi:fix/responses-assistant-phase-replay
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yorzi wants to merge 2 commits into
crmne:mainfrom
yorzi:fix/responses-assistant-phase-replay

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@yorzi

@yorzi yorzi commented Oct 17, 2026 •

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What this does

OpenAI labels each assistant message item with a phase (commentary or final_answer) and asks clients that send history back to keep it on every assistant message for gpt-5.3-codex and later. The Responses protocol kept a turn's raw output only for server tools, namespaced calls or several reasoning items, and otherwise rebuilt the assistant item without its phase. Since #1182 a turn with two reasoning items kept its phase while the common turn with one dropped it, sync and streamed alike.

The raw output is now kept when an output item carries a phase, the rule #1182 added for several reasoning items, so the turn replays as it came. A null phase keeps the portable replay.

The raw replay path this reuses is already accepted live: the recorded OpenAI and Azure compaction conversations send output message items back with their ids, and the xAI remote MCP history replays reasoning and message items; all answer 200. No cassette records a request that sends phase back, and I have no OpenAI key to record one, so that part rests on OpenAI's reference.

Checked: 3 new examples (sync, streamed, and the null-phase guard); the first two fail before. 2 of 2 mutations fail a spec. The recorded gpt-5.4, Azure and DeepSeek Responses cassettes replay unchanged (407 examples with CI=1, no cassette rewritten).

The second commit, from review: a turn replayed from its raw output now also sends the message's attachments in a user item after it, as portable turns have since #1130, and leaves the stored raw output untouched. 1 new example; it fails before, and 3 of 3 mutations fail a spec.

Type of change

  • Bug fix
  • New feature
  • Breaking change
  • Documentation
  • Performance improvement

Scope check

  • I read the Contributing Guide
  • This aligns with RubyLLM's focus on LLM communication
  • This isn't application-specific logic that belongs in user code
  • This benefits most users, not just my specific use case

Related issue

Fixes #1230

Quality check

  • I ran overcommit --install and all hooks pass (the RSpec hook ran with spec/ruby_llm/sandbox/mxc_spec.rb excluded: its gem install example fails on clean main on macOS with a Homebrew-linked Ruby, fixed separately)
  • I tested my changes thoroughly
    • For provider changes: Re-recorded VCR cassettes with bundle exec rake vcr:record[provider_name] (no request a cassette matches on changed; VCR matches method and URI)
    • All tests pass: bundle exec rspec (5,546 offline examples on the branch before its rebase onto Test with mxc 0.2 until code execution runs on Landlock #1225, which only pins mxc in the Gemfile; the commit hooks ran the suite again after the rebase; the two failures are spec/ruby_llm/generators/skill_generator_spec.rb:48 (macOS case-insensitive file system, fixed in its own PR) and spec/ruby_llm/sandbox/mxc_spec.rb:183 (macOS Homebrew-linked Ruby, fixed in its own PR), both also on main)
  • I updated documentation if needed (internal, no docs change)
  • I didn't modify auto-generated files manually (models.json, aliases.json)

Ownership

  • I understand every line of this change and can answer questions about it

API changes

  • Breaking change
  • New public methods/classes
  • Changed method signatures
  • No API changes

Summary by CodeRabbit

  • Bug Fixes
    • Phased assistant responses now retain their complete output, preserving phase information when responses are replayed.
    • Streaming responses also retain the full output when they include phased assistant messages.
    • Assistant attachments are now included when replaying responses with raw output, without replacing or losing that output.

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📥 Commits

Reviewing files that changed from the base of the PR and between 14f4dca and a44d982.

📒 Files selected for processing: 2
  • lib/ruby_llm/protocols/responses/chat.rb
  • spec/ruby_llm/protocols/responses/chat_spec.rb
🚧 Files skipped from review as they are similar to previous changes: 2
  • spec/ruby_llm/protocols/responses/chat_spec.rb
  • lib/ruby_llm/protocols/responses/chat.rb

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📝 Walkthrough

The Responses protocol now retains raw output when an output item has a phase field. Assistant replay uses retained raw content when available and appends attachments as a separate user item.

Changes: Responses phase replay

Layer / File(s) Summary
Phase-based raw output retention
lib/ruby_llm/protocols/responses/chat.rb, spec/ruby_llm/protocols/responses/chat_spec.rb, spec/ruby_llm/protocols/responses/streaming_spec.rb
keep_raw_output? now retains raw output when an item has a phase field. Specs check final_answer retention, behavior when phase is nil, and retention of streamed output.
Assistant replay and attachments
lib/ruby_llm/protocols/responses/chat.rb, spec/ruby_llm/protocols/responses/chat_spec.rb
Assistant replay uses raw content when available and appends attachments afterward. The spec checks that replay keeps raw output first and emits attachments in a separate user item.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: kieranklaassen

Merge Risk: ⚪ Minimal · up to a44d9

Phased assistant messages and their attachments appear to replay as intended. No identified issue blocks merging after normal checks.

Pre-merge checks: Passed 6 · Failed 1

Failed Failed checks: 1 warning

Check name Status Explanation Resolution
Docstring Coverage Warning Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 3 files. Write docstrings for the functions missing them to satisfy the coverage threshold.
Passed Passed checks: 6 passed
Check name Status Explanation
Linked Issues check Passed Issue #1230 requires assistant phase preservation for one-reasoning-item Responses turns in synchronous and streaming replay. The implementation retains raw output when an output item has a non-null…
Out of Scope Changes check Passed The implementation changes Responses replay selection and preserves attachment behavior when raw replay is used. The tests cover the new phase, null-phase, streaming, and attachment behavior. These ch…
Review Evidence Stays Out Of The Repository Passed The pull request changes only three Ruby source/spec files. The diff has no added files and no screenshots, captures, comparison pages, recordings, or other review-evidence artifacts.
Dependencies From Sources The Maintainer Controls Passed The pull request changes only lib/ruby_llm/protocols/responses/chat.rb and two Responses specs. No manifest, lockfile, or package-manager configuration changed, and no dependency source, git URL, pa…
Title check Passed The title clearly and concisely describes the main change: preserving the phase of Responses assistant messages during replay.
Description check Passed The description follows the required template, explains the change and scope, identifies the related issue, documents testing and known environment-specific failures, and confirms API impact.
Full details: Linked Issues check

Explanation

Issue #1230 requires assistant phase preservation for one-reasoning-item Responses turns in synchronous and streaming replay. The implementation retains raw output when an output item has a non-null phase. The added specs cover synchronous replay, streaming replay, and the null-phase portable path. The attachment spec verifies that raw replay also preserves assistant attachments without changing stored raw output.

Full details: Out of Scope Changes check

Explanation

The implementation changes Responses replay selection and preserves attachment behavior when raw replay is used. The tests cover the new phase, null-phase, streaming, and attachment behavior. These changes support the linked replay fix and do not show unrelated product behavior or public API changes.

Full details: Dependencies From Sources The Maintainer Controls

Explanation

The pull request changes only lib/ruby_llm/protocols/responses/chat.rb and two Responses specs. No manifest, lockfile, or package-manager configuration changed, and no dependency source, git URL, patch, override, replace, or alternate registry entry was introduced.

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OpenAI labels each assistant message item with a phase, commentary or
final_answer, and asks clients that send history back to keep it on
every assistant message for gpt-5.3-codex and later. The protocol kept
a turn's raw output only for server tools, namespaced calls or several
reasoning items, and otherwise rebuilt the assistant item without its
phase. Since crmne#1182 a turn with two reasoning items kept its phase while
the common turn with one dropped it, sync and streamed alike.

Keep the raw output when an output item carries a phase, the rule crmne#1182
added for several reasoning items, so the turn replays as it came.

Fixes crmne#1230
@yorzi
yorzi force-pushed the fix/responses-assistant-phase-replay branch from f22f526 to 14f4dca Compare October 17, 2026 11:49

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Actionable comments posted: 1


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Inline comments:
Review comments at @lib/ruby_llm/protocols/responses/chat.rb:
- Line 116: Update format_assistant_items so that when msg.raw_content is
present, it returns a copy with the assistant attachment item appended when
msg.attachments is nonempty, preserving the original raw output.

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Reviewing files that changed from the base of the PR and between 0d18ecd and 14f4dca.

📒 Files selected for processing: 3
  • lib/ruby_llm/protocols/responses/chat.rb
  • spec/ruby_llm/protocols/responses/chat_spec.rb
  • spec/ruby_llm/protocols/responses/streaming_spec.rb

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Comment thread lib/ruby_llm/protocols/responses/chat.rb
An assistant turn replayed from its raw output returned those items
alone, so attachments the message also carried never reached the next
request. Only portable turns sent them, in a user item after the turn,
since crmne#1130. Now that phased turns replay raw, that path is the common
one.

Append the attachment item to a copy of the raw items too, so the
stored output is left as it came. Raised in review on crmne#1231.
@crmne

crmne commented Oct 17, 2026

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Thank you so much for this, @yorzi, and for tracking down #1230 so carefully. I took your work in a slightly different direction in #1236: the message now keeps its phase and the protocol sends it back on the item it rebuilds from the local transcript, so edits to stored messages still reach the request and phased turns don't need the raw replay. The commit is yours, and new gpt-5.4 and DeepSeek cassettes show both APIs accepting the phase sent back. Closing this one in favour of it. Really appreciate it!

@crmne crmne closed this Oct 17, 2026
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[BUG] Responses replay drops the assistant phase of a turn with one reasoning item

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