feat: add rate limiting error handling

[bobrykov]

No description provided.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 280ae564-2b30-4274-8ae3-bb1ab4bfea5d

📥 Commits

Reviewing files that changed from the base of the PR and between 5d39fe0 and cae63bb.

📒 Files selected for processing (1)

• src/stream/handler.rs

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📝 Walkthrough

Walkthrough

This PR adds structured rate-limit handling across the API error and stream layers, including retry-after parsing, mid-stream detection, and rate-limit-aware retry backoff. It also adds an optional HTTP-date parser dependency, re-exports new stream types, and updates one dispatch comment.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: adding rate limiting error handling.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ 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 feat/rate-limit

Warning

Tools execution failed with the following error:

Failed to run tools: 13 INTERNAL: Received RST_STREAM with code 2 (Internal server error)

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[coderabbitai]

Actionable comments posted: 2

🤖 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 `@src/stream/handler.rs`:
- Around line 2261-2265: The parse_retry_after_http_date test in the stream
handler is hitting the httpdate-only path, so it needs to be aligned with the
providers feature gate. Update the test near parse_retry_after to either add
#[cfg(feature = "providers")] or ensure the providers feature is enabled in the
relevant test configuration, so it only runs when the httpdate branch is
available.
- Around line 1205-1214: The retry loop in stream_turn is ignoring
StreamOutcome::RateLimited, so DetectedRateLimit::detect and the rate-limit
config fields are not affecting sleep behavior. Update the StreamHandler
retry/fallback path to inspect
StreamHandlerError::StreamFailed(StreamOutcome::RateLimited { .. }) and, when
present, use the rate-limit-specific delay logic from RateLimitConfig (including
backoff and respect_retry_after) instead of always calling
retry_config.base_delay(attempt). Ensure the handling is wired through the
existing retry loop and fallback decision points so 429/503 responses follow the
server-advised policy.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: ee9b239a-d110-4c8e-8eed-57fc230989e7

📥 Commits

Reviewing files that changed from the base of the PR and between fae53fa and 5d39fe0.

📒 Files selected for processing (5)

• Cargo.toml
• src/api/error.rs
• src/engine/bare/stream.rs
• src/stream.rs
• src/stream/handler.rs