fix: responses stream events

[TejasGhatte]

Summary

output_text.done, content_part.done, and output_item.done stream events were being emitted with empty text content instead of the full accumulated text. This PR fixes that by introducing a TextBuffers map in each provider's stream state to accumulate text deltas as they arrive, then populating the done events with the complete text.

Additionally, tools with a nil or empty name are now skipped before being sent to Anthropic, which previously caused Anthropic to reject the request.

Changes

• Added TextBuffers map[int]string to the stream state structs for Anthropic, Bedrock, and Cohere providers, accumulating text deltas keyed by output index
• Updated output_text.done, content_part.done, and output_item.done events across all four providers (Anthropic, Bedrock, Cohere, Gemini) to include the full accumulated text in their payloads rather than empty strings
• Populated ContentBlocks in output_item.done messages with the actual text content block instead of an empty slice
• Cleaned up TextBuffers entries via delete after emitting done events to avoid stale state
• Ensured TextBuffers is properly initialized and cleared in pool acquire/flush paths
• Skipped Anthropic tool conversion when tool.Name is nil or empty to prevent Anthropic API rejections

Type of change

• Bug fix

Affected areas

• Core (Go)
• Providers/Integrations

How to test

go test ./...

Stream a response from each affected provider (Anthropic, Bedrock, Cohere, Gemini) using the Responses API and verify that:

• output_text.done events contain the full assembled text
• content_part.done events include a Part with the full text
• output_item.done events include a Content.ContentBlocks array with the complete text block
• Sending a tool with no name to Anthropic no longer causes a request rejection

Breaking changes

• Yes
• No

Security considerations

None.

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

Summary by CodeRabbit

• Bug Fixes
  • Streaming responses now accumulate per-output text and include full text in final completion events (avoids empty text/content blocks) across provider integrations.
  • Tool entries with missing or empty names are skipped during processing.
  • Stream state pooling lifecycle fixed to prevent cross-request text reuse by allocating, clearing, and releasing per-output text buffers between requests.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds per-output TextBuffers across Anthropic, Bedrock, Cohere, and Gemini stream converters to accumulate text deltas and emit the complete buffered text in final "done" events; Anthropic also skips tools with empty names.

Changes

Text buffering for accumulated text in done events

Layer / File(s)	Summary
Anthropic text accumulation and done event emission core/providers/anthropic/responses.go	AnthropicResponsesStreamState gains a TextBuffers map initialized and cleared through the pooling lifecycle. Text deltas are accumulated during streaming, and on ContentBlockStop for text the accumulated text populates output_text.done, content_part.done, and output_item.done. Tools with nil or empty names are skipped during conversion.
Bedrock text accumulation and done event emission core/providers/bedrock/responses.go	BedrockResponsesStreamState adds a TextBuffers map in the pool and acquisition flow. Text deltas are appended to buffers; when closing text outputs (before tool calls) or finalizing streams, converters emit output_text.done/content_part.done and conditionally include text ContentBlocks in output_item.done only when buffered text is non-empty, then delete buffers.
Cohere text accumulation for regular and tool-plan text core/providers/cohere/responses.go	CohereResponsesStreamState adds TextBuffers. Regular and tool-plan deltas are buffered; on content end or tool-call transitions the buffered text populates output_text.done, content_part.done, and output_item.done (text blocks added only when non-empty), and buffers are cleared after use.
Gemini text output in done events core/providers/gemini/responses.go	closeGeminiTextItem now uses the buffered fullText to set content_part.done text and populates output_item.done.content_blocks with a single text block containing the accumulated text instead of emitting empty payloads.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• maximhq/bifrost#3527: Modifies FinalizeBedrockStream; related to Bedrock finalization and output synthesis.

Suggested reviewers

• danpiths
• akshaydeo

"🐰 I buffered words through streaming light,
Chunks stitched gently into done-event sight,
No more empty shells where content should be,
Outputs now carry the full text you see,
Hooray for buffers—hop, munch, and delight!"

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Title check	❓ Inconclusive	The title 'fix: responses stream events' is vague and generic, referring to 'responses' and 'stream events' without specifying which aspect of the stream events is being fixed.	Consider a more specific title such as 'fix: populate stream done events with accumulated text' or 'fix: include full text in output_text.done and related events'.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description is comprehensive with clear sections covering summary, changes, type, affected areas, testing instructions, and checklist items that mostly align with the template.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 05-28-fix_responses_stream_events

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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[TejasGhatte]

• fix: default Anthropic tool_use input to {} when arguments are absent #3880
• fix: responses stream events #3838 👈 (View in Graphite)
• dev

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Confidence Score: 5/5

Safe to merge; the changes are targeted streaming-state fixes with no broad interface changes and correct pool lifecycle handling across all four providers.

The text-buffer accumulation pattern is applied consistently, pool acquire and flush paths both reset the new map field, the delete-after-done approach avoids stale state within a stream, and the nil-tool guard in convertBifrostToolToAnthropic is handled correctly by its caller. No new concurrency concerns are introduced.

core/providers/cohere/responses.go — the two ToolPlan output_item.done paths unconditionally emit a content block even when accumulated text is empty (noted in a prior review thread).

Important Files Changed

Filename	Overview
core/providers/anthropic/responses.go	Adds TextBuffers map[int]*strings.Builder to stream state for text accumulation; properly initializes in pool acquire, nils in flush; correctly populates output_text.done, content_part.done, and output_item.done with accumulated text; nil return from convertBifrostToolToAnthropic is checked by its sole caller at line 5035
core/providers/bedrock/responses.go	TextBuffers added and integrated into both text-delta accumulation paths (new-block and regular-delta); done events in ToBifrostResponsesStream and FinalizeBedrockStream both read and delete from TextBuffers correctly; flush clears instead of nils (minor inconsistency with Anthropic) but functionally sound
core/providers/cohere/responses.go	TextBuffers integrated into text and tool-plan delta paths; non-ToolPlan non-reasoning output_item.done correctly guards with if accText != ""; ToolPlan output_item.done unconditionally emits a content block even when accText is empty (flagged in prior review thread)
core/providers/gemini/responses.go	closeGeminiTextItem extended to populate content_part.done and output_item.done using the already-accumulated fullText from state.TextBuffer; no new buffer management needed since Gemini already had a single TextBuffer field; change is straightforward and correct

_{Reviews (6): Last reviewed commit: "fix: responses stream events" | Re-trigger Greptile}

[coderabbitai]

Actionable comments posted: 3

🤖 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.

Inline comments:
In `@core/providers/anthropic/responses.go`:
- Around line 5239-5242: The guard that skips tools currently checks only for
nil or empty string (tool.Name == nil || *tool.Name == "") but should also treat
whitespace-only names as missing; update the check in the skip-tools block to
use strings.TrimSpace on *tool.Name (e.g., if tool.Name == nil ||
strings.TrimSpace(*tool.Name) == "" { return nil }) and add the strings import
if not already present so whitespace-only names are rejected before sending tool
definitions upstream.
- Around line 1345-1349: The code is unconditionally persisting fallback
doneItem into state.OutputItems which can pollute response.completed; wrap the
cloning/storage (the block that clones doneItem, clones doneItem.Content, sets
cloned.Content and assigns state.OutputItems[outputIndex] = &cloned) with a
guard that ensures the synthesized fallback is a text-only item (e.g., check
doneItem.Content is non-nil and that the content type/mime or text field
indicates plain text — use the project's canonical field such as Content.Type or
Content.Mime or presence of Content.Text). Only when that text-only check passes
perform the clone/store; otherwise skip modifying state.OutputItems so non-text
reasoning/MCP paths do not get persisted.

In `@core/providers/bedrock/responses.go`:
- Around line 816-818: The TextBuffers accumulation currently does repeated
string concatenation (state.TextBuffers[outputIndex] += text) causing quadratic
copies; change TextBuffers from map[int]string (or []string) to
map[int]*strings.Builder (or []*strings.Builder), initialize per-output builders
where outputs are created, replace every place that appends (e.g., where
state.TextBuffers[outputIndex] += text and similar at line ~845) with
builder.WriteString(text), and when emitting the done event (where accText :=
state.TextBuffers[outputIndex] around ~1289) call accText := builder.String()
(and delete the builder entry if needed). Update references to state.ItemIDs and
outputIndex accordingly so you locate the correct builder for each output.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: c422b722-aee0-48e8-a3b7-34abd22a6f29

📥 Commits

Reviewing files that changed from the base of the PR and between d5e2ea4 and 8bf07c3.

📒 Files selected for processing (4)

• core/providers/anthropic/responses.go
• core/providers/bedrock/responses.go
• core/providers/cohere/responses.go
• core/providers/gemini/responses.go

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

core/providers/bedrock/responses.go (1)

392-460: 🧹 Nitpick | 🔵 Trivial | ⚡ Quick win

Add table-driven coverage for both text close paths.

This behavior now exists in two separate branches: closing text before a tool block starts, and closing text during FinalizeBedrockStream. Please add focused table-driven tests for both so regressions don't bring back empty output_text.done / output_item.done payloads or miss buffer cleanup.

As per coding guidelines, "Apply standard Go review practices: small interfaces, clear error wrapping, context propagation, race-safe shared state, goroutine/channel cleanup, and table-driven tests for behavior changes."

Also applies to: 1289-1357

🤖 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/bedrock/responses.go` around lines 392 - 460, Add table-driven
tests that exercise both code paths that close buffered text: (1) the branch
that emits output_text.done/output_item.done when closing text before a tool
block starts and (2) the branch exercised by FinalizeBedrockStream. For each
table case, set up state.TextBuffers with a variety of
prevOutputIndex/prevAccText values (including empty and non-empty), call the
code-path (the handler that emits output_text.done / content_part.done /
output_item.done and FinalizeBedrockStream), and assert that responses contain
non-empty Text and ContentBlocks when prevAccText is non-empty, that no empty
output_text.done or output_item.done payloads are emitted, and that the
corresponding entry is removed from state.TextBuffers after the call;
parameterize cases for empty vs non-empty buffers and for invoking the close
logic directly vs via FinalizeBedrockStream to prevent regressions.

🤖 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.

Outside diff comments:
In `@core/providers/bedrock/responses.go`:
- Around line 392-460: Add table-driven tests that exercise both code paths that
close buffered text: (1) the branch that emits output_text.done/output_item.done
when closing text before a tool block starts and (2) the branch exercised by
FinalizeBedrockStream. For each table case, set up state.TextBuffers with a
variety of prevOutputIndex/prevAccText values (including empty and non-empty),
call the code-path (the handler that emits output_text.done / content_part.done
/ output_item.done and FinalizeBedrockStream), and assert that responses contain
non-empty Text and ContentBlocks when prevAccText is non-empty, that no empty
output_text.done or output_item.done payloads are emitted, and that the
corresponding entry is removed from state.TextBuffers after the call;
parameterize cases for empty vs non-empty buffers and for invoking the close
logic directly vs via FinalizeBedrockStream to prevent regressions.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 1834ff66-08e4-426a-9a9f-3090434e9b00

📥 Commits

Reviewing files that changed from the base of the PR and between 8bf07c3 and ea20dcd.

📒 Files selected for processing (4)

• core/providers/anthropic/responses.go
• core/providers/bedrock/responses.go
• core/providers/cohere/responses.go
• core/providers/gemini/responses.go

[coderabbitai]

Actionable comments posted: 1

♻️ Duplicate comments (1)

core/providers/anthropic/responses.go (1)

5249-5255: ⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Reject whitespace-only tool names too.

" " still passes this guard and gets forwarded as a custom tool name, which Anthropic will reject the same way it rejects an empty name. Trim before the emptiness check.

💡 Suggested fix

-	if tool.Name == nil || *tool.Name == "" {
+	if tool.Name == nil || strings.TrimSpace(*tool.Name) == "" {
 		return nil
 	}

As per coding guidelines, validate untrusted input before provider calls.

🤖 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/anthropic/responses.go` around lines 5249 - 5255, The guard
that skips tools with empty names only checks for nil or exact empty string, but
does not reject whitespace-only names; update the validation in the code that
inspects tool.Name (before constructing AnthropiсTool) to trim the string and
treat it as empty if all whitespace (e.g., call strings.TrimSpace on *tool.Name)
so that whitespace-only names are rejected the same way as "" — ensure this
change is applied where tool.Name is read and before creating/setting
anthropicTool.Name.

🤖 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.

Inline comments:
In `@core/providers/cohere/responses.go`:
- Around line 340-341: When closing a synthetic tool-plan item you clear
state.ToolPlanOutputIndex but leave state.ContentIndexToOutputIndex[0] pointing
to that output index; update both tool-plan close sites (the blocks that delete
from state.TextBuffers and set state.ToolPlanOutputIndex = nil) to also delete
state.ContentIndexToOutputIndex[0] so the mapping is removed, preventing
getOrCreateOutputIndex() from reusing a closed output index; apply the same
deletion in both locations mentioned and ensure any code relying on
ContentIndexToOutputIndex checks for existence after this cleanup.

---

Duplicate comments:
In `@core/providers/anthropic/responses.go`:
- Around line 5249-5255: The guard that skips tools with empty names only checks
for nil or exact empty string, but does not reject whitespace-only names; update
the validation in the code that inspects tool.Name (before constructing
AnthropiсTool) to trim the string and treat it as empty if all whitespace (e.g.,
call strings.TrimSpace on *tool.Name) so that whitespace-only names are rejected
the same way as "" — ensure this change is applied where tool.Name is read and
before creating/setting anthropicTool.Name.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 280b84b6-9f5b-435a-88d3-f92e52fc45a9

📥 Commits

Reviewing files that changed from the base of the PR and between ea20dcd and 0a83eca.

📒 Files selected for processing (4)

• core/providers/anthropic/responses.go
• core/providers/bedrock/responses.go
• core/providers/cohere/responses.go
• core/providers/gemini/responses.go

[coderabbitai]

Actionable comments posted: 1

🤖 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.

Inline comments:
In `@core/providers/cohere/responses.go`:
- Around line 340-344: When closing the synthetic tool-plan item, don’t just
delete state.ContentIndexToOutputIndex[0] and state.TextBuffers[outputIndex];
you must reserve/advance the global output counter so the next
getOrCreateOutputIndex() cannot re-use the same output index. Update the
tear-down in the block that currently sets state.ToolPlanOutputIndex = nil to
also advance state.CurrentOutputIndex past the released outputIndex (or set
CurrentOutputIndex = max(CurrentOutputIndex, outputIndex+1)) and then clear
state.ToolPlanOutputIndex, ensuring getOrCreateOutputIndex() will allocate a new
unique index for subsequent real content/tool items.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: 7ad85204-be16-46b3-b52d-118162ccdd38

📥 Commits

Reviewing files that changed from the base of the PR and between 0a83eca and 9a60961.

📒 Files selected for processing (4)

• core/providers/anthropic/responses.go
• core/providers/bedrock/responses.go
• core/providers/cohere/responses.go
• core/providers/gemini/responses.go

[akshaydeo]

Merge activity

• May 29, 12:30 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• May 29, 12:31 PM UTC: @akshaydeo merged this pull request with Graphite.