fix: complete Cohere streaming Responses terminal events with the output array and reasoning payloads

[fus3r]

Summary

Streaming /v1/responses on Cohere never completed its terminal events: response.completed carried no output array at all ("output":null, every item type missing from the final snapshot) and no stop_reason, reasoning done events were empty shells (thinking deltas were never buffered, unlike text deltas since #3838), and citation annotation events carried no item_id. The non-streaming path returns the output array and the reasoning content correctly, and the Anthropic stream ingress already populates Output from per-item bookkeeping, so these were Cohere-only gaps. The streamed reasoning shape was also not replayable: it had neither the content blocks the request converter reads nor a filled summary, so conversations coming from streaming silently lost their thinking blocks on the next turn. Fixes #5385.

Changes

• Added output-item bookkeeping to CohereResponsesStreamState (OutputItems map fed by a small trackOutputItems helper wherever output_item.added/output_item.done are emitted) and populate response.completed.response.output from it, sorted by output index, mirroring the Anthropic ingress.
• Buffer thinking deltas in TextBuffers the way text deltas already are, and emit reasoning_summary_text.done, the reasoning content_part.done, and the reasoning output_item.done with the accumulated text. The done item carries the text as a reasoning content block, the exact shape the non-streaming converter produces, which is what convertBifrostReasoningToCohereThinking replays. The reasoning delta and done events also carry summary_index (0; Cohere thinking has a single summary part per item), which the official OpenAI event types require.
• Record citation annotations per output index, set item_id on output_text.annotation.added/done, include the already-streamed annotations in the text item's done events, and defensively fold annotations into the completed snapshot regardless of whether they arrive before or after content-end, with clone-on-write so already-emitted events are never mutated.
• Map delta.finish_reason on message-end (and finish_reason on the non-streaming Responses conversion) through the existing ConvertCohereFinishReasonToBifrost, so response.completed and the non-streaming response carry stop_reason the way the chat surface already does. This also fixes the Anthropic-format egress synthesizing end_turn for Cohere tool-use turns.
• Extracted the tool-plan close block (duplicated verbatim in content-start and tool-call-start) into a closeToolPlanItem helper and also call it on message-end, so a stream ending right after a tool plan completes the item before response.completed.
• Added a changelog entry.

Type of change

• Bug fix
• Feature
• Refactor
• Documentation
• Chore/CI

Affected areas

• Core (Go)
• Transports (HTTP)
• Providers/Integrations
• Plugins
• UI (React)
• Docs

How to test

cd core
go test ./providers/cohere/ -run 'TestCohere(ResponsesStream|NonStreamResponses)' -v
go test ./providers/cohere/

The nine new tests in streamterminalevents_test.go construct Cohere v2 stream event sequences (thinking deltas, text, tool plan, tool calls, citations arriving both during and after their content block) and drive them through ToBifrostResponsesStream, pinning: done events carrying the accumulated thinking text, response.completed carrying the full output array with the actual payloads and the mapped stop_reason, item_id on annotation events, citations present in the done events and the final snapshot, the tool-plan item completed at message-end, no state leakage across pooled-state recycling, a full replay chain (completed reasoning item JSON-echoed back through ConvertBifrostMessagesToCohereMessages recovers the thinking block), and the non-streaming stop_reason mapping. All nine fail on dev without the fix with the exact symptoms above.

Screenshots/Recordings

Not a UI change.

Breaking changes

• Yes
• No

Terminal events that previously carried empty payloads now carry the accumulated ones, and response.completed now includes the output array and stop_reason, matching the non-streaming path. The framework stream accumulator folds deltas and ignores done events, so logged messages are unchanged (verified). The Anthropic-format egress ignores the enriched done payloads and only gains the correct terminal stop_reason.

Related issues

Closes #5385

Security considerations

None. No new inputs are parsed; the change only carries already-received stream content through to the terminal events.

Checklist

• I read docs/contributing/README.md and followed the guidelines
• I added/updated tests where appropriate
• I updated documentation where needed
• I verified builds succeed (Go and UI)
• I verified the CI pipeline passes locally if applicable

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

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Run ID: 38ce85c6-d768-40b4-8970-544cdda6b510

📥 Commits

Reviewing files that changed from the base of the PR and between 329f840 and 1658e79.

📒 Files selected for processing (2)

• core/providers/cohere/responses.go
• core/providers/cohere/streamterminalevents_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• core/providers/cohere/responses.go

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Cohere streaming responses now include complete output items and stop reasons in response.completed.
  • Thinking terminal events now retain accumulated thinking text in the final reasoning-related payloads.
  • Citation annotations now include the associated text item ID and are reflected reliably in the final snapshot (including when citations arrive after content ends).
  • Tool plans are properly closed at message end and handled correctly when followed by content.
  • Non-streaming responses now correctly report the stop reason.
• Tests
  • Added streaming terminal-events coverage for completed payloads, ordering, citations, tool plans, and state recycling.

Walkthrough

Cohere Responses terminal events now preserve reasoning text, citations, output items, tool-plan completion, usage, and stop reasons. Non-streaming responses map stop reasons, with tests covering terminal snapshots, ordering, recycling, and replayability.

Changes

Cohere Responses terminal event handling

Layer / File(s)	Summary
Stream state tracking and shared helpers core/providers/cohere/responses.go	Tracks output items and annotations, resets pooled state, and centralizes tool-plan closure and tracked emission.
Streamed item and annotation events core/providers/cohere/responses.go	Preserves accumulated reasoning and text content, attaches citation metadata and item IDs, and tracks completed text, reasoning, and function-call items.
Completed response assembly core/providers/cohere/responses.go	Maps finish reasons, closes open tool plans, folds late citations, and builds an ordered response.completed output array. Non-streaming conversion also maps stop reasons.
Terminal behavior validation and changelog core/providers/cohere/streamterminalevents_test.go, core/changelog.md	Adds coverage for terminal output, reasoning, citations, tool plans, state recycling, replayability, and stop reasons, plus the changelog entry.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant CohereStreamEvent
  participant CohereResponsesStreamState
  participant response_completed
  CohereStreamEvent->>CohereResponsesStreamState: process streamed content and citations
  CohereStreamEvent->>CohereResponsesStreamState: process MessageEnd and FinishReason
  CohereResponsesStreamState->>CohereResponsesStreamState: close tool plan and fold annotations
  CohereResponsesStreamState->>response_completed: emit ordered output and stop reason

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Possibly related issues

• maximhq/bifrost#5259: Covers similar missing completed output and incomplete reasoning terminal events in a different provider implementation.

Suggested reviewers: akshaydeo, tejasghatte, pratham-mishra04, sammaji

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately summarizes the main Cohere streaming terminal-event fix.
Description check	✅ Passed	The PR description fills the required sections and clearly explains the change, testing, impact, and related issue.
Linked Issues check	✅ Passed	The code changes align with #5385 by fixing output snapshots, reasoning replay, citation item_ids, stop_reason mapping, and tool-plan completion.
Out of Scope Changes check	✅ Passed	The added changelog and tests are relevant to the fix; no unrelated code changes stand out.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[greptile-apps]

Confidence Score: 5/5

This looks safe to merge.

• The tool-plan index now advances the shared output counter, so later content cannot overwrite the plan item.
• Pending tool plans are tracked before the completed response is built.
• New pooled state is cleared between streams.
• No blocking issues remain in the changed code.

Important Files Changed

Filename	Overview
core/providers/cohere/responses.go	Completes Cohere terminal payloads and allocates distinct output indexes for tool plans and later content.
core/providers/cohere/streamterminalevents_test.go	Adds coverage for completed output, reasoning, citations, tool plans, replay, stop reasons, and pooled-state cleanup.
core/changelog.md	Documents the Cohere streaming terminal-event fix.

_{Reviews (2): Last reviewed commit: "fix: allocate the tool-plan output index..." | Re-trigger Greptile}

[coderabbitai]

🧹 Nitpick comments (1)

core/providers/cohere/streamterminalevents_test.go (1)

162-162: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Prefer a pointer helper over the address operator (&) for variables.

Based on learnings, prefer using a pointer helper function (like schemas.Ptr, which is heavily used in this file) instead of the address operator (&) when taking the address of a local variable. This improves readability and keeps the code consistent with the repository's preferred pattern.

• core/providers/cohere/streamterminalevents_test.go#L162-L162: Replace &document with schemas.Ptr(document).
• core/providers/cohere/streamterminalevents_test.go#L179-L179: Replace &finishReason with schemas.Ptr(finishReason).
• core/providers/cohere/streamterminalevents_test.go#L533-L533: Replace &finishReason with schemas.Ptr(finishReason).

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@core/providers/cohere/streamterminalevents_test.go` at line 162, Replace
direct address operators with schemas.Ptr for the local variables at
core/providers/cohere/streamterminalevents_test.go lines 162, 179, and 533: use
schemas.Ptr(document) and schemas.Ptr(finishReason) at the respective sites,
preserving the existing test data and behavior.

Source: Learnings

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@core/providers/cohere/streamterminalevents_test.go`:
- Line 162: Replace direct address operators with schemas.Ptr for the local
variables at core/providers/cohere/streamterminalevents_test.go lines 162, 179,
and 533: use schemas.Ptr(document) and schemas.Ptr(finishReason) at the
respective sites, preserving the existing test data and behavior.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 97437bd2-e1ce-4e52-a167-6a524a5f9198

📥 Commits

Reviewing files that changed from the base of the PR and between 4714e49 and 329f840.

📒 Files selected for processing (3)

• core/changelog.md
• core/providers/cohere/responses.go
• core/providers/cohere/streamterminalevents_test.go