Removes OpenAI Responses "chain mode" from chatd. Closes CODAGT-445.
- Deletes `chatopenai/responses.go` (chain detection, activation, prompt filtering, response ID extraction) and its tests.
- Deletes the `ChainBroken` classification in `chaterror` and the chatloop retry bookkeeping that disabled chain mode mid-generation.
- Drops the `chain_broken` label from the `coderd_chatd_stream_retries_total` metric.
- Stops reading and writing `chat_messages.provider_response_id`
- Deletes the dead `ClearChatMessageProviderResponseIDsByChatID` query. Dropping the column is a follow-up migration.
- Deletes three chatloop hooks no caller sets (`ReloadMessages`, `DisableChainMode`, `PrepareMessages`), the dead `const AgentChatContextSentinelPath`, and stale chain-mode comments.
🤖 Generated by Coder Agents on behalf of @johnstcn.
## Problem
Local tool results were persisted and replayed to the model verbatim,
with no size cap. A single oversized result, most often a multi-megabyte
response from an MCP tool, overflows the prompt on the next request.
Every retry rebuilds the same history and fails the same way, leaving
the chat wedged in `error`. Auto-compaction is reactive (token usage is
only known after a response), so it can't catch a single result that
blows the very next request.
## Fix
Cap every locally-executed tool result at its single choke point,
`executeSingleTool` in `chatloop`, so the cap covers built-in tools,
**global (deployment-pinned) MCP**, **workspace MCP**, and provider
runners uniformly. Because this runs before the result is published to
the live stream and before it is committed, the SSE preview, the
persisted message, and the model replay all see the same bounded output.
The budget is token-aware: a single tool result may use at most half the
model's context window (`~4 bytes/token`), with a `16KB` floor and a
`64KB` default when the window is unknown. Truncation keeps the head and
tail of the output and replaces the middle with a marker telling the
model how much was removed and to narrow its query; it is UTF-8 safe and
never exceeds the budget. Binary media `Data` is passed through
untouched (only the text payload is bounded).
A `coderd_chatd_tool_result_truncated_total{provider,model,tool_name}`
counter and a warning log record each truncation.
## Out of scope
- Provider-executed results (e.g. web search) arrive via the stream, not
`executeSingleTool`.
- Dynamic/external tool results submitted through the `/tool-results`
API are validated as JSON elsewhere.
- Cumulative growth across many results is still handled by context
compaction; this change only bounds any single result.
<details>
<summary>Implementation notes</summary>
- New `coderd/x/chatd/chatloop/tooltruncate.go`:
`toolResultByteBudget(contextLimitTokens)` and
`truncateToolResultText(text, maxBytes)` (pure, unit-tested).
- `chatloop.go`: added `ContextLimit` to `ExecuteLocalToolsOptions`;
threaded a computed byte budget through `executeTools` into
`executeSingleTool`, where `resp.Content` is capped for the text,
media-text, and error branches.
- `generation.go`: passes `ContextLimit: prepared.ContextLimitFallback`
(the model's configured context limit).
- `metrics.go`: new `ToolResultTruncatedTotal` counter +
`RecordToolResultTruncated`.
- Tunable knobs live as constants in `tooltruncate.go`
(`toolResultContextDivisor = 2`, `bytesPerTokenEstimate`,
`minToolResultBytes`, `defaultToolResultBytes`).
Verified: `go build ./coderd/x/chatd/...`, `go test
./coderd/x/chatd/chatloop/...`, and the `chatd` test binary compiles.
</details>
---
Resolves CODAGT-678
Generated by Coder Agents on behalf of @kylecarbs.
When OpenAI's Responses API returns `Previous response with id ... not
found` for a chained turn, classify it as a `ChainBroken` retry, clear
`previous_response_id`, exit chain mode, reload full history, and let
`chatretry` retry. Self-heals chats whose anchor was poisoned before
#25074 stopped truncated streams from being persisted as a successful
turn with a stored response id.
The new state is exposed via the existing
`coderd_chatd_stream_retries_total` counter as a
`chain_broken="true"|"false"` label. Aggregating queries (`sum`, `rate`
over `provider`/`model`/`kind`) keep working without changes; raw-series
matchers without aggregation will now see two series per `(provider,
model, kind)` where they previously saw one. The metric is internal-only
so the blast radius should be small, but if you have dashboards that
index by exact label matchers without aggregation they will need an
extra `sum` or an explicit `chain_broken` selector.
> 🤖 This PR was created with the help of Coder Agents, and was reviewed by a human 🧑💻
Moves the chat error kind taxonomy from `coderd/x/chatd/chaterror` into
`codersdk.ChatErrorKind` and types `ChatError.Kind` /
`ChatStreamRetry.Kind` so generated TypeScript exposes an SDK-owned
union, including `usage_limit`. Backend chat classification now
references the SDK constants directly while preserving the existing JSON
string values.
Keeps chat usage-limit admission failures on their existing 409 response
shape. The frontend maps structured usage-limit responses to the
SDK-owned `usage_limit` kind, uses generated `TypesGen.ChatErrorKind`
directly, and removes the local string union and alias.
Adds production-observability metrics to coderd/x/chatd/ for
model-level correlation and a chatStreams memory-leak investigation.
- Label per-request chatd metrics (steps_total, message_count,
prompt_size_bytes, tool_result_size_bytes, ttft_seconds,
compaction_total) with `model` and enrich the per-turn logger
with provider/model.
- Add `coderd_chatd_stream_retries_total{provider, model, kind}`
counter incremented in chatloop before OnRetry.
- Register a prometheus.Collector exposing `streams_active`,
`stream_buffer_size_max`, `stream_buffer_events`,
`stream_subscribers` from p.chatStreams.
- Add `coderd_chatd_stream_buffer_dropped_total` counter,
incremented per publishToStream drop independently of the
existing log-rate-limited bufferDropCount.
- Snapshot logger/model before the title-generation goroutine to
avoid a data race with the logger/model rebind below it.
> 🤖
The `coderd_chatd_message_count` histogram's current max bucket of 128
is being hit in production. This increases the exponential bucket count
from 8 to 11, extending coverage from `1..128` to `1..1024`.
Before: `1, 2, 4, 8, 16, 32, 64, 128`
After: `1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024`
Co-authored-by: blink-so[bot] <211532188+blink-so[bot]@users.noreply.github.com>
Cian Johnston