coder/fantasy now fails closed when Anthropic or OpenAI Responses
streams close before their provider terminal events instead of yielding
a successful finish.
This bumps the fantasy replacement to coder/fantasy#33 and teaches chat
error classification to treat those failures as retryable timeout errors
with explicit stream-closed messages.
<img width="875" height="311" alt="image"
src="https://github.com/user-attachments/assets/69c6f7b5-c885-46d2-a88b-b7a2b111bd55"
/>
Modifies chatloop error classification behaviour to treat the following as retryable:
* HTTP/2 `force closed`
* GOAWAY
* use of closed network connection
* Modfies user-facing retry banner to show "<provider> is temporarily
unavailable."
Relates to CODAGT-212.
> 🤖
> **PR Stack**
> 1. **#23351** ← `#23282` *(you are here)*
> 2. #23282 ← `#23275`
> 3. #23275 ← `#23349`
> 4. #23349 ← `main`
---
## Summary
`chatretry.Retry()` used pure exponential backoff (1 s, 2 s, 4 s, …) and
never consulted provider `Retry-After` headers. Fantasy's
`ProviderError` carries `ResponseHeaders` including `Retry-After`, but
`chaterror.Classify()` only parsed error text and silently dropped the
structured transport metadata.
This makes `Retry-After` a first-class signal in the classification →
retry pipeline.
<img width="853" height="346" alt="image"
src="https://github.com/user-attachments/assets/65f012b6-8173-43d2-957e-ab9faddea525"
/>
## Changes
### `coderd/chatd/chaterror/classify.go`
- Added `RetryAfter time.Duration` field to `ClassifiedError` — a
normalized minimum retry delay derived from provider response metadata.
- `Classify()` now calls `extractProviderErrorDetails()` before falling
back to text heuristics. Structured `ProviderError.StatusCode` takes
priority over regex extraction.
- `normalizeClassification()` preserves and clamps `RetryAfter`.
### `coderd/chatd/chaterror/provider_error.go` (new)
Provider-specific extraction, isolated from the text-based
classification logic:
- `extractProviderErrorDetails()` unwraps `*fantasy.ProviderError` from
the error chain via `errors.As`.
- `retryAfterFromHeaders()` parses headers in priority order:
1. `retry-after-ms` (OpenAI-specific, millisecond precision)
2. `retry-after` (standard HTTP — integer seconds or HTTP-date)
- Case-insensitive header key lookup.
### `coderd/chatd/chatretry/chatretry.go`
- `effectiveDelay(attempt, classified)` computes `max(Delay(attempt),
classified.RetryAfter)` — the provider hint acts as a floor without
weakening the local exponential backoff.
- `Retry()` now uses `effectiveDelay` and passes the effective delay to
both `onRetry(...)` and the sleep timer, so downstream payloads, logs,
and the frontend countdown stay aligned automatically.
### Tests
- `classify_test.go`: Structured provider status + `Retry-After`
extraction, `retry-after-ms` priority, HTTP-date parsing, invalid header
fallback, `WithProvider` preservation.
- `chatretry_test.go`: Retry-after-as-floor semantics — longer hint
wins, shorter hint keeps base delay.
## Design notes
- **No SDK/API/frontend changes needed.** `codersdk.ChatStreamRetry`
already carries `DelayMs` and `RetryingAt`, and the frontend already
consumes them. The fix is purely in the server-side delay computation.
- **Existing retryability rules unchanged.** This fixes *when* we sleep,
not *whether* an error is retryable.
- **Provider hint is a floor:** `max(baseDelay, RetryAfter)` ensures we
never retry earlier than the provider asks, and never weaken our own
backoff curve.
> **PR Stack**
> 1. #23351 ← `#23282`
> 2. #23282 ← `#23275`
> 3. **#23275** ← `#23349` *(you are here)*
> 4. #23349 ← `main`
---
## Summary
Extracts a structured error classification subsystem for agent chat
(`chatd`) so that retry and error payloads carry machine-readable
metadata — error kind, provider name, HTTP status code, and retryability
— instead of raw error strings.
This is the **backend half** of the error-handling work. The frontend
counterpart is in #23282.
## Changes
### New package: `coderd/chatd/chaterror/`
Canonical error classification — extracts error kind, provider, status
code, and user-facing message from raw provider errors. One source of
truth that drives both retry policy and stream payloads.
- **`kind.go`**: Error kind enum (`rate_limit`, `timeout`, `auth`,
`config`, `overloaded`, `unknown`).
- **`signals.go`**: Signal extraction — parses provider name, HTTP
status code, and retryability from error strings and wrapped types.
- **`classify.go`**: Classification logic — maps extracted signals to an
error kind.
- **`message.go`**: User-facing message templates keyed by kind +
signals.
- **`payload.go`**: Projectors that build `ChatStreamError` and
`ChatStreamRetry` payloads from a classified error.
### Modified
- **`codersdk/chats.go`**: Added `Kind`, `Provider`, `Retryable`,
`StatusCode` fields to `ChatStreamError` and `ChatStreamRetry`.
- **`coderd/chatd/chatretry/`**: Thinned to retry-policy only;
classification logic moved to `chaterror`.
- **`coderd/chatd/chatloop/`**: Added per-attempt first-chunk timeout
(60 s) via `guardedStream` wrapper — produces retryable
`startup_timeout` errors instead of hanging forever.
- **`coderd/chatd/chatd.go`**: Publishes normalized retry/error payloads
via `chaterror` projectors.
- Moves `coderd/chatd/`, `coderd/gitsync/`, `enterprise/coderd/chatd/`
under `x/` parent directories to signal instability
- Adds `Experimental:` glue code comments in `coderd/coderd.go`
> 🤖 This PR was created with the help of Coder Agents, and was
reviewed by my human. 🧑💻
Ethan