This adds the UI but does not add it to the Settings sidebar. Until it's
actually functional and usable (which will come in future PRs) it will
remain hidden.
Next step is wiring this up to chats and actually testing the full flow
end-to-end, but we aren't there yet.
- Replace fixed `100vh` spacer at bottom of diff list with a dynamically
sized one
- Adds "X files changed" message to the bottom of the diff
> This PR was created with the help of Coder Agents, and was reviewed by several humans and robots. 🧑💻🤝🤖
There are 333 stories with play functions but no local way to run them.
CI uses Chromatic, which means broken play functions aren't caught until
after push. For agents, the feedback loop is even worse since they can't
open a browser.
This adds the `@storybook/addon-vitest` integration so play functions
can run locally via vitest + Playwright:
```sh
pnpm test:storybook
pnpm test:storybook src/path/to/component.stories.tsx
```
The vitest config is restructured into two projects (`unit` and
`storybook`).
The processChat defer at line 2464 catches panics on its main
goroutine and transitions the chat to error status. This was
previously untested.
The test wraps the database Store to panic during PersistStep's
InTx call, which runs synchronously on the processChat goroutine.
A tool-level panic wouldn't work because executeTools has its own
recover that converts panics into tool error results.
scheduleStreamReset() fired for every durable message event with
changed=true, including user messages (e.g. promoted queued messages).
When a batch contained trailing message_parts followed by a user
message event, the batch loop flushed the parts (building stream
state), then scheduleStreamReset cleared it immediately.
Restrict the reset to assistant messages, which are the only role
that ends a streaming turn.
Dynamic parameters supports ephemeral parameters. Updated the test to
use dynamic parameters.
Ephemeral params **require** a default value.
Closes https://github.com/coder/coder/issues/19065
## Problem
Anthropic rejects requests containing empty text content blocks with:
```
messages: text content blocks must be non-empty
```
Empty text parts (`""` or whitespace-only like `" "`) get persisted in
the database when a stream sends `TextStart`/`TextEnd` with no
`TextDelta` in between. On the next turn, these parts are loaded from
the DB and sent to Anthropic, which rejects them.
## Fix
Filter empty/whitespace-only text and reasoning parts at the two LLM
dispatch boundaries, without modifying persistence (the raw record is
preserved):
- **`partsToMessageParts()`** in `chatprompt.go` — filters when
converting persisted DB messages to fantasy message parts for LLM calls.
This is the last gateway before the Anthropic provider creates
`TextBlockParam` objects.
- **`toResponseMessages()`** in `chatloop.go` — filters when building
in-flight conversation messages between steps within a single turn.
Note: `flushActiveState()` (the interruption path) already had this
guard — the normal `TextEnd` streaming path did not, but since we're not
changing persistence, the fix is applied at the dispatch layer.
## Problem
When `Store: true` is set for OpenAI Responses API calls (the new
default), multi-turn conversations with reasoning models fail on the
second message:
```
stream response: bad request: Item 'rs_xxx' of type 'reasoning' was provided
without its required following item.
```
The fantasy library was reconstructing full `OfReasoning` input items
(with encrypted content and summary) when replaying assistant messages.
The API cannot pair these reconstructed reasoning items with the output
items that originally followed them because the output items are sent as
plain `OfMessage` without server-side IDs.
## Fix
Updates the fantasy dependency (`kylecarbs/fantasy@cj/go1.25`) to skip
reasoning parts during conversation replay in `toResponsesPrompt`. With
`Store` enabled, the API already has the reasoning persisted server-side
— it doesn't need to be replayed in the input.
Fantasy PR: https://github.com/charmbracelet/fantasy/pull/181
## Testing
Adds `TestOpenAIReasoningRoundTrip` integration test that:
1. Sends a query to `o4-mini` (reasoning model with `Store: true`)
2. Verifies reasoning content is persisted
3. Sends a follow-up message — this was the failing step
4. Verifies the follow-up completes successfully
Requires `OPENAI_API_KEY` env var to run.
Omit rehype-raw from the Streamdown rehype plugin list so
HTML-like syntax in LLM output is escaped as text instead of
being parsed by the HTML5 engine and stripped by rehype-sanitize.
When the LLM writes JSX fragments like <Component prop={val} />
outside code fences, remark-parse tags them as html nodes.
rehype-raw then feeds them to parse5, and rehype-sanitize strips
the unknown elements, silently destroying content. Without
rehype-raw, Streamdown auto-injects a remark plugin that converts
html nodes to text, preserving them as visible escaped text.
Markdown formatting (bold, italic, links, code blocks, tables)
is unaffected since those go through remark/rehype directly.
## Summary
- **Removed** `docs/install/cloud/ec2.md` — the standalone EC2 install
guide.
- **Renamed** `docs/install/cloud/aws-mktplc-ce.md` →
`docs/install/cloud/aws-marketplace.md` for a clearer, more discoverable
filename.
- **Updated** `docs/manifest.json`: replaced the "AWS EC2" entry with
"AWS Marketplace" pointing to the renamed file.
- **Updated** `docs/install/cloud/index.md`: fixed the internal link to
the renamed file.
* Adds a "molly-guard" to require users to type the workspace name
before the 'Archive & delete workspace' action fires. This prevents
accidental deletion of 'pet' workspaces.
* This is only shown for workspaces created *before* the chat was
created. The logic here is that any workspace that existed previous to
the chat *cannot* have been created by the chat.
Eliminates the timing flake in
`TestInterruptAutoPromotionIgnoresLaterUsageLimitIncrease` by making the
chatd worker loop clock-controllable.
## Changes
**`coderd/chatd/chatd.go`**
- Replace `time.NewTicker` calls in `Server.start()` with
`p.clock.NewTicker` using named quartz tags `("chatd", "acquire")` and
`("chatd", "stale-recovery")`.
**`coderd/chatd/chatd_test.go`**
- Inject `quartz.NewMock(t)` into the test via `newActiveTestServer`
config override.
- Trap the acquire ticker so the test controls exactly when pending
chats are reacquired.
- Rewrite the test flow as explicit clock-advance steps instead of
wall-clock polling.
**`AGENTS.md`**
- Document the PR title scope rule (scope must be a real path containing
all changed files).
## Validation
- `go test ./coderd/chatd -run
TestInterruptAutoPromotionIgnoresLaterUsageLimitIncrease -count=100` ✅
- `go test ./coderd/chatd` ✅
- `make lint` ✅
## Problem
The VS Code extension embeds the Coder agent chat UI in an iframe,
passing the session token via `postMessage`. HTTP requests use the
`Coder-Session-Token` header, but browser WebSocket connections **cannot
carry custom headers** — they rely on cookies. This causes all WebSocket
requests (e.g. streaming chat messages) to fail with authorization
errors in the embedded iframe.
## Solution
Add `POST /api/v2/users/me/session/token-to-cookie` — a lightweight
endpoint that converts the current (already-validated) session token
into a `Set-Cookie` response. The frontend embed bootstrap flow calls
this immediately after `API.setSessionToken(token)`, before any
WebSocket connections are opened.
### Backend (`coderd/userauth.go`, `coderd/coderd.go`)
- New handler `postSessionTokenCookie` behind `apiKeyMiddleware`.
- Reads the validated token via `httpmw.APITokenFromRequest(r)`.
- Sets an `HttpOnly` cookie with the API key's expiry, applying
site-wide cookie config (Secure, SameSite, host prefix) via
`HTTPCookies.Apply`.
- Returns `204 No Content`.
### Frontend (`site/src/pages/AgentsPage/EmbedContext.tsx`)
- `bootstrapChatEmbedSessionFn` now calls the new endpoint after setting
the header token and before fetching user/permissions.
- The cookie is in place before any WebSocket connections are opened.
## Security
- **No privilege escalation**: The token is already valid — this just
moves it from a header credential to a cookie credential.
- **POST only**: Avoids CSRF-via-navigation.
- **Same origin**: The iframe loads from the Coder server, so the cookie
applies to the correct domain.
- **HttpOnly**: The cookie is not accessible to JavaScript.
> Built with [Coder Agents](https://coder.com/agents) 🤖
LazyFileDiff memo comparator: ignore renderAnnotation reference
changes when the file has no lineAnnotations, preventing comment-box
interactions from re-rendering every file diff.
useGitWatcher stale socket guard: check socketRef.current against
the local socket variable in all event handlers. Stale close events
from superseded connections no longer clobber the active socket or
schedule spurious reconnects.
useGitWatcher field comparison guard: add a compile-time Record
type that errors when WorkspaceAgentRepoChanges gains a field not
covered by the bailout comparison.
Tests: stale close race, reference stability on duplicate messages,
per-field change detection (branch, remote_origin, unified_diff),
and no-op removal of unknown repos.
Follow-up to #23243
Three changes that eliminate unnecessary re-renders cascading into
the FileDiff Shadow DOM components during chat/git-watcher updates:
useGitWatcher: compare repo fields before updating state, return
prev Map when nothing changed instead of always allocating a new one.
RemoteDiffPanel: remove dataUpdatedAt from parsedFiles memo deps,
replace it with a content-derived version counter. The memo now only
recomputes when the actual diff string changes.
DiffViewer: pre-compute per-file options and line annotations into
memoized Maps, wrap LazyFileDiff in React.memo so it skips renders
when props are reference-equal.
## Summary
Adds the database schema, API endpoints, SDK types, and encryption
wrappers for admin-managed MCP (Model Context Protocol) server
configurations that chatd can consume. This is the backend foundation
for allowing external MCP tools (Sentry, Linear, GitHub, etc.) to be
used during AI chat sessions.
## Database
Two new tables:
- **`mcp_server_configs`**: Admin-managed server definitions with URL,
transport (Streamable HTTP / SSE), auth config (none / OAuth2 / API key
/ custom headers), tool allow/deny lists, and an availability policy
(`force_on` / `default_on` / `default_off`). Includes CHECK constraints
on transport, auth_type, and availability values.
- **`mcp_server_user_tokens`**: Per-user OAuth2 tokens for servers
requiring individual authentication. Cascades on user/config deletion.
New column on `chats` table:
- **`mcp_server_ids UUID[]`**: Per-chat MCP server selection, following
the same pattern as `model_config_id` — passed at chat creation,
changeable per-message with nil-means-no-change semantics.
## API Endpoints
All routes are under `/api/experimental/mcp/servers/` and gated behind
the `agents` experiment.
**Admin endpoints** (`ResourceDeploymentConfig` auth):
- `POST /` — Create MCP server config
- `PATCH /{id}` — Update MCP server config (full-replace)
- `DELETE /{id}` — Delete MCP server config
**Authenticated endpoints** (all users, enabled servers only for
non-admins):
- `GET /` — List configs (admins see all, members see enabled-only with
admin fields redacted)
- `GET /{id}` — Get config by ID (with `auth_connected` populated
per-user)
**OAuth2 per-user auth flow:**
- `GET /{id}/oauth2/connect` — Initiate OAuth2 flow (state cookie CSRF
protection)
- `GET /{id}/oauth2/callback` — Handle OAuth2 callback, store tokens
- `DELETE /{id}/oauth2/disconnect` — Remove stored OAuth2 tokens
## Security
- **Secrets never returned**: `OAuth2ClientSecret`, `APIKeyValue`, and
`CustomHeaders` are never in API responses — only boolean indicators
(`has_oauth2_secret`, `has_api_key`, `has_custom_headers`).
- **Field redaction for non-admins**: `convertMCPServerConfigRedacted`
strips `OAuth2ClientID`, auth URLs, scopes, and `APIKeyHeader` from
non-admin responses.
- **dbcrypt encryption at rest**: All 5 secret fields use `dbcrypt_keys`
encryption with full encrypt-on-write / decrypt-on-read wrappers (11
dbcrypt method overrides + 2 helpers), following the same pattern as
`chat_providers.api_key`.
- **OAuth2 CSRF protection**: State parameter stored in `HttpOnly`
cookie with `HTTPCookies.Apply()` for correct `Secure`/`SameSite` behind
TLS-terminating proxies.
- **dbauthz authorization**: All 18 querier methods have authorization
wrappers. Read operations use `ActionRead`, write operations use
`ActionUpdate` on `ResourceDeploymentConfig`.
## Governance Model
| Control | Implementation |
|---------|---------------|
| **Global kill switch** | `enabled` defaults to `false` |
| **Availability policy** | `force_on` (always injected), `default_on`
(pre-selected), `default_off` (opt-in) |
| **Per-chat selection** | `mcp_server_ids` on `CreateChatRequest` /
`CreateChatMessageRequest` |
| **Auth gate** | OAuth2 servers require per-user auth before tools are
injected |
| **Tool-level allow/deny** | Arrays on `mcp_server_configs` for
granular tool filtering |
| **Secrets encrypted at rest** | Uses `dbcrypt_keys` (same pattern as
`chat_providers.api_key`) |
## Tests
8 test functions covering:
- Full CRUD lifecycle (create, list, update, delete)
- Non-admin visibility filtering (enabled-only, field redaction)
- `auth_connected` population for OAuth2 vs non-OAuth2 servers
- Availability policy validation (valid values + invalid rejection)
- Unique slug enforcement (409 Conflict)
- OAuth2 disconnect idempotency
- Chat creation with `mcp_server_ids` persistence
## Known Limitations (Deferred)
These are documented and intentional for an experimental feature:
- **Audit logging** not yet wired — will add when feature stabilizes
- **Cross-field validation** (e.g., OAuth2 fields required when
`auth_type=oauth2`) — admin-only endpoint, will add when stabilizing
- **`force_on` auto-injection** — query exists but not yet wired into
chatd tool injection (follow-up)
- **Additional test coverage** — 403 auth tests, GET-by-ID tests,
callback CSRF tests planned for follow-up
## What's NOT in this PR
- Frontend UI (admin panel + chat picker)
- Actual MCP client connections (`chatd/chatmcp/` manager)
- Tool injection into `chatloop/`
Always deploy from main for now. We want to keep testing commits to main
as soon as they're merged, so we're going to disable the release
freezing behavior. We will test cut releases on a separate deployment,
upgraded manually.
Two issues caused the promoted message to never appear:
1. handlePromoteQueuedMessage discarded the ChatMessage returned by
the promote API, relying on the WebSocket to deliver it.
2. Even when the WebSocket did deliver it (via upsertDurableMessage),
the queue_update event in the same batch called
updateChatQueuedMessages, which mutated the React Query cache. This
gave chatMessagesList a new reference, triggering the message sync
effect. The effect found the promoted message in the store but not in
the REST-fetched data, classified it as a stale entry (the path
designed for edit truncation), and called replaceMessages, wiping it.
Fix (1): capture the ChatMessage from the promote response and upsert
it into the store, matching handleSend for non-queued messages.
Fix (2): track the fetched message array elements across effect runs
using element-level reference comparison. Only run the
hasStaleEntries/replaceMessages path when the message objects actually
changed (e.g. a refetch producing new objects from the server), not
when only an unrelated field like queued_messages caused the query
data reference to update. Element references work because
useMemo(flatMap) preserves object identity when only non-message
fields change in the page data.
Updates the `charm.land/fantasy` replace to the rebased `cj/go1.25`
branch on `kylecarbs/fantasy`, which now includes:
- **chore: downgrade to Go 1.25**
- **feat: anthropic computer use**
- **chore: use kylecarbs/openai-go fork for coder/coder compat**
Switches the `openai-go/v3` replace from `SasSwart/openai-go` →
`kylecarbs/openai-go`, which is the same SasSwart perf fork plus a fix
for `WithJSONSet` being clobbered by deferred body serialization.
Without the fix, `NewStreaming` silently drops `stream: true` from
requests. See https://github.com/kylecarbs/openai-go/pull/2 for details.
Updates the editing banner message in the agents chat input from:
> Editing message — all subsequent messages will be deleted
to:
> Editing will delete all subsequent messages and restart the
conversation here.
---
PR generated with Coder Agents
- Add `RequireExperimentWithDevBypass` middleware to
`/.well-known/oauth-authorization-server` and
`/.well-known/oauth-protected-resource` routes, matching the existing
`/oauth2` routes.
- Clients can now detect OAuth2 support via unauthenticated discovery
(404 = not available).
Fixes#21608
## Summary
- guard Agent pages against malformed model provider/model values before
trimming
- reuse a shared model-ref normalizer across Agent detail, sidebar,
list, and create flows
- add regression coverage for malformed catalog and config entries
## Validation
- `cd site && pnpm exec vitest run
src/pages/AgentsPage/modelOptions.test.ts
src/pages/AgentsPage/AgentDetail.test.ts`
- `cd site && pnpm lint:types`
## Problem
Scaletest follow-up storms showed that the chat stream path was doing a
same-replica DB reread for every durable message it had already
delivered locally.
In a 600-chat / 10-turn run, `/stream`-attributed
`GetChatMessagesByChatID` calls reached about 14.2k across 5,400
follow-up turns — roughly **2.63 rereads per turn**. The primary coderd
replicas saturated their DB pools at 60/60 open connections during the
storm window.
The root cause: when pubsub was active, `Subscribe()` suppressed local
durable `message` events and relied entirely on pubsub notify →
`GetChatMessagesByChatID` for catch-up. Same-replica subscribers paid
the full DB round-trip even though the persisting process was on the
same replica.
## Solution
Add a bounded per-chat **durable message cache** to `chatStreamState` so
that same-replica subscribers can catch up from memory instead of the
database.
### How it works
1. `publishMessage()` caches the SDK event in `chatStreamState` before
local fanout and pubsub notify.
2. `publishEditedMessage()` replaces the cache with only the edited
message, then publishes `FullRefresh`.
3. `Subscribe()` handles ordinary `AfterMessageID` notifies by first
consulting the per-chat durable cache and only falling back to
`GetChatMessagesByChatID` on cache miss.
4. `FullRefresh` always forces a DB reread (cache is bypassed).
### Safety properties
- If the cache misses (e.g. message expired or remote replica), the DB
catch-up still runs — no silent message loss.
- `FullRefresh` (edits) always rereads from the database.
- Remote replicas still use the pubsub + DB path unchanged.
- The cache is bounded (`maxDurableMessageCacheSize = 256`) and scoped
per chat — no unbounded memory growth.
## Impact
This change removes the entire same-replica portion of the stream
rereads. Based on the 600-chat follow-up run, the upper bound on saved
work is the same-replica share of about 14.2k `GetChatMessagesByChatID`
rereads, with the observed total stream reread rate at about 2.63
rereads per follow-up turn.
React's [Why You Might Not Need An
Effect](https://react.dev/learn/you-might-not-need-an-effect) article
describes several antipatterns and footguns you might encounter when
working with useEffect, so I fed it to an agent and let it determine
some low hanging fruit to fix:
Replace useEffect+setState patterns with direct computations where the
values are purely derived from props, state, or query data:
- useWebpushNotifications: derive `enabled` inline from query data
instead of setting it via useEffect
- ProxyContext: replace `proxy` state + updateProxy callback + useEffect
with a single useMemo over its three inputs
- useSyncFormParameters: replace ref-sync useEffect with direct
assignment during render
- AgentsSidebar (LoadMoreSentinel): replace two ref-sync useEffects with
direct assignments during render
Co-authored by Coder Agent 🤖
- Adds a new API endpoint `GET /api/v2/users/oidc-claims` that returns
only the **merged claims** (not the separate id_token/userinfo
breakdown). Scoped exclusively to the authenticated user's own identity
— no user parameter, so users cannot view each other's claims.
- Adds a new CLI command:** `coder users oidc-claims` that hits the
above endpoint.
- The existing owner-only debug endpoint is preserved unchanged for
admins who need the full claim breakdown.
> 🤖 This PR was created with the help of Coder Agents, and will be
reviewed by my human. 🧑💻
Added new AWS install documentation and screenshots to support
deployment of AWS Marketplace Coder Community Edition, as the
primary/recommended method on AWS for POCs and experimenting with Coder.
This PR fixes a bug where if a tool result contained binary data it
wouldn't be persisted to the database.
`jsonb` in Postgres is unable to store null bytes which are sometimes
output by tool results. This change makes it so that we encode them with
a special escape sequence before saving them to the database, and decode
them on read.
<img width="808" height="637" alt="Screenshot 2026-03-11 at 13 14 06"
src="https://github.com/user-attachments/assets/9be353eb-ff26-40ec-9f0a-195022b11f43"
/>
## Problem
The `/agents/settings/insights` page had several issues:
1. **Duplicate PRs** in "Recent Pull Requests" — multiple chats
referencing the same PR URL each produced a row
2. **Wildly wrong costs** — the cost subquery summed ALL messages across
the entire chat *tree* (`GROUP BY root_chat_id`), so every chat in a
tree got the same inflated total. When aggregated, the same tree cost
was counted N× per PR in that tree
3. **UI clutter** — too many stat cards, too many table columns, mixed
naming conventions
## Fix
### Backend (SQL)
- **Deduplicate by PR URL** using `DISTINCT ON (COALESCE(cds.url,
c.id::text))` across all 4 queries
- **Fix cost computation**: use two CTEs — `pr_costs` sums cost from ALL
chats that reference a PR (so review chats contribute), `deduped` picks
one row per PR for state/additions/deletions via DISTINCT ON
- **Tests**: 3 subtests covering multi-chat cost summing, different PRs
no duplication, and duplicate URL counted once
### Frontend
- **3 stat cards** (down from 5): Merged, Merge rate, Cost / merge
- **2-line chart** (down from 3): created (dashed) + merged (solid)
- **4-column model table** (down from 7): Model, Merged, Merge rate,
Cost/merge
- **4-column recent table** (down from 7): Title, Status, Cost, Created
— with `table-fixed` to prevent overflow
- **Consistent naming**: no mixed PR/PRs abbreviation, contextual labels
since page title establishes context
- coderd: Wires `options.WorkspaceUsageTracker` into the chatd config.
- chatd: Adds `UsageTracker` and calls `UsageTracker.Add(workspaceID)`
on each heartbeat tick
- chatd: adds tests to verify `last_used_at` bump behaviour
> 🤖 This PR was created with the help of Coder Agents, and will be
reviewed by my human. 🧑💻
ChatMessagePart uses a flat struct with omitempty on all fields,
but some fields are required in their TypeScript variant (no ?
suffix in the variants struct tag). When Go omits a zero-valued
required field, the frontend receives undefined where it expects
a concrete value.
Remove omitempty from fields that are required in at least one
variant: Text, URL, MediaType, FileName, StartLine, EndLine,
Content. Fields where all variants use ? keep omitempty.
Add a sub-test to TestChatMessagePartVariantTags that enforces
this invariant via reflection so future additions cannot
reintroduce the mismatch.
Supersedes #23249
Adds a `deleted` boolean column to the `chat_messages` table. Messages
are never physically deleted from the database — instead they are marked
as deleted so that usage and cost data is preserved.
## Changes
### Migration
- New migration (000444) adds `deleted boolean NOT NULL DEFAULT false`
to `chat_messages`
### SQL queries
- `DeleteChatMessagesAfterID` → `SoftDeleteChatMessagesAfterID` (UPDATE
SET deleted=true instead of DELETE)
- New `SoftDeleteChatMessageByID` query for single-message soft-delete
- All read queries now filter `deleted = false`:
- `GetChatMessageByID`
- `GetChatMessagesByChatID`
- `GetChatMessagesByChatIDDescPaginated`
- `GetChatMessagesForPromptByChatID` (both CTE and main query)
- `GetLastChatMessageByRole`
- Cost/usage queries (`GetChatCostSummary`, `GetChatCostPerModel`, etc.)
intentionally still include deleted messages to preserve accurate spend
tracking
### EditMessage behavior
- Previously: updated the message content in-place + hard-deleted
subsequent messages
- Now: soft-deletes the original message + soft-deletes subsequent
messages + inserts a new message with the updated content
- This preserves the original message data (tokens, cost, content) in
the database
- Adds a wrapper script at `/usr/local/bin/gh` in the dogfood image that
ensures the GitHub CLI stays authenticated even when tokens expire
during long-running workspace sessions.
Requested by @johnstcn, based on suggestion from @kylecarbs.
Co-authored-by: blink-so[bot] <211532188+blink-so[bot]@users.noreply.github.com>
## Problem
Uploading a file on the `/agents` chat page fails with:
```
Failed to execute 'setRequestHeader' on 'XMLHttpRequest': String contains non ISO-8859-1 code point.
```
This happens when the image filename contains non-ASCII characters (e.g.
CJK characters from macOS screenshots like `スクリーンショット.png`, accented
characters, emoji, etc.). HTTP headers only support ISO-8859-1 code
points, and the filename was being interpolated directly into the
`Content-Disposition` header.
## Fix
Use [RFC 5987](https://datatracker.ietf.org/doc/html/rfc5987)
`filename*=UTF-8''` encoding so the percent-encoded name is always valid
in the header. A static ASCII `filename="file"` fallback is included for
older clients.
The server already uses Go's `mime.ParseMediaType` which decodes
`filename*` automatically, so no backend changes are needed.
### Before
```ts
"Content-Disposition": `attachment; filename="${file.name}"`
```
### After
```ts
"Content-Disposition": `attachment; filename="file"; filename*=UTF-8''${encodeURIComponent(file.name)}`
```
## Testing
Added a server-side test (`TestGetChatFile/UnicodeFilename`) that
uploads with a Japanese filename and verifies it round-trips correctly
through the `Content-Disposition` header.
Go serializes ChatMessagePart.Text with omitempty, so empty
reasoning text (from reasoning_start with no delta) is omitted
from JSON. The frontend receives {type: "reasoning"} with text
as undefined, crashing on .trim() calls.
Mark Text as optional in the reasoning variant via the variants
struct tag. This generates ChatReasoningPart with text?: string
and the frontend falls back to "" via nullish coalescing.
Closes#23245
Kyle Carberry