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Kyle Carberry
385146000b
Records reasoning start and end times on persisted reasoning `ChatMessagePart`s so reasoning duration can be computed for stored chats. Backend-only: no SSE changes and no frontend rendering ship in this PR. The `created_at` field on `ChatMessagePart` is extended to also be present on `reasoning` parts (it previously appeared only on `tool-call` and `tool-result`), and a new `completed_at` field is added for `reasoning` parts. ### How timestamps are recorded - `StreamPartTypeReasoningStart`: stamp `startedAt = dbtime.Now()` on the active reasoning state. - `StreamPartTypeReasoningEnd`: stamp `completedAt = dbtime.Now()` and append both into parallel `[]time.Time` slices on `stepResult`. - Persistence reads the slices in occurrence order (reasoning has no provider-side ID) and applies them to the matching `ChatMessagePart` via `buildAssistantPartsForPersist`. The first reasoning block's stamps go onto the first reasoning part, and so on. - `flushActiveState` flushes partial reasoning interrupted before `StreamPartTypeReasoningEnd` with `startedAt` from the active state and `completedAt = dbtime.Now()` at the interruption. ### Why two fields, not one? Tool calls and results are point events. The frontend computes their duration by subtracting the call's `created_at` from the result's `created_at`. Reasoning is one assistant part that brackets a span, so we record both endpoints on the part itself. ### Why not stamp in `PartFromContent`? Same rationale as #24101: `PartFromContent` is called during both SSE publishing and persistence. Stamping there would yield incorrect persistence-time timestamps for reasoning blocks that finished much earlier in the step. Instead we capture in the chatloop and apply during persistence. <details><summary>Implementation plan</summary> - `codersdk/chats.go`: extend `CreatedAt`'s `variants` to include `reasoning?`; add `CompletedAt *time.Time` with `variants:"reasoning?"`. - `coderd/x/chatd/chatloop/chatloop.go`: extend `reasoningState` with `startedAt`; extend `stepResult` and `PersistedStep` with parallel `[]time.Time` reasoning slices; stamp on `ReasoningStart`/`ReasoningEnd`; thread the slices through all `PersistStep` call sites including the interrupt-safe path; record partial reasoning in `flushActiveState`. - `coderd/x/chatd/attachments.go`: walk reasoning parts in occurrence order and apply `step.ReasoningStartedAt[i]` to `part.CreatedAt` and `step.ReasoningCompletedAt[i]` to `part.CompletedAt`. ### Tests - `codersdk/chats_test.go` round-trips `created_at` + `completed_at` on reasoning parts and verifies omission when absent and partial interrupted parts. - `coderd/x/chatd/chatprompt/chatprompt_test.go` asserts `PartFromContent(ReasoningContent{})` does NOT stamp timestamps. - `coderd/x/chatd/chatloop/chatloop_test.go` `TestRun_ReasoningTimestamps` drives a stream with two reasoning blocks and verifies parallel slices, monotonicity, ordering, non-zero values, and content-block ordering. `TestRun_InterruptedReasoningFlushesTimestamps` cancels mid-reasoning and verifies `flushActiveState` records a non-zero pair. - `coderd/x/chatd/attachments_test.go` covers `buildAssistantPartsForPersist` for normal interleaved reasoning, partial (zero `completed_at`), and missing slices. </details> > Generated by Coder Agents. Co-authored-by: Coder Agent <agent@coder.com>