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fix(mcp-apps): reconcile the show/defer contract — render results, remove show_ui #2774

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Merged
SamMorrowDrums merged 4 commits into from
Jun 26, 2026
Merged

fix(mcp-apps): reconcile the show/defer contract — render results, remove show_ui #2774

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d0ecf75
fix(ui): render success view when an MCP App tool executed up-front
SamMorrowDrums Jun 26, 2026
09a7a78
fix(ui): scope tool-result to the current invocation
SamMorrowDrums Jun 26, 2026
e2207ac
refactor(mcp-apps): remove show_ui — it can't suppress app rendering
SamMorrowDrums Jun 26, 2026
8b2363d
refactor(mcp-apps): centralize the show/defer decision (single source…
SamMorrowDrums Jun 26, 2026
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18 changes: 15 additions & 3 deletions ui/src/apps/issue-write/App.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ import {
} from "@primer/octicons-react";
import { AppProvider } from "../../components/AppProvider";
import { useMcpApp } from "../../hooks/useMcpApp";
import { completedToolResult } from "../../lib/toolResult";
import { MarkdownEditor } from "../../components/MarkdownEditor";

interface IssueResult {
Expand Down Expand Up @@ -435,10 +436,21 @@ function CreateIssueApp() {
const [repoSearchLoading, setRepoSearchLoading] = useState(false);
const [repoFilter, setRepoFilter] = useState("");

const { app, error: appError, toolInput, callTool, hostContext, setModelContext, openLink } = useMcpApp({
const { app, error: appError, toolInput, toolResult, callTool, hostContext, setModelContext, openLink } = useMcpApp({
appName: "github-mcp-server-issue-write",
});

// When the server created/updated the issue up-front instead of deferring to
// this form (e.g. the agent passed show_ui=false or parameters the form can't
// represent, such as labels/assignees/issue_fields), the host still renders
// this View and delivers the result via tool-result. Render that completed
// result as success so we never show a create/update form for an issue that
// is already done. The deferral sentinel (awaiting_user_submission) returns
// null here, keeping the form for the normal deferred flow.
// See github/copilot-mcp-core#1864.
const resultIssue = useMemo(() => completedToolResult<IssueResult>(toolResult), [toolResult]);
const shownIssue = successIssue ?? resultIssue;
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SamMorrowDrums marked this conversation as resolved.

// Get method and issue_number from toolInput
const method = (toolInput?.method as string) || "create";
const issueNumber = toolInput?.issue_number as number | undefined;
Expand Down Expand Up @@ -1210,10 +1222,10 @@ function CreateIssueApp() {
);
}

if (successIssue) {
if (shownIssue) {
return (
<SuccessView
issue={successIssue}
issue={shownIssue}
owner={owner}
repo={repo}
submittedTitle={title}
Expand Down
16 changes: 13 additions & 3 deletions ui/src/apps/pr-edit/App.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ import {
} from "@primer/octicons-react";
import { AppProvider } from "../../components/AppProvider";
import { useMcpApp } from "../../hooks/useMcpApp";
import { completedToolResult } from "../../lib/toolResult";
import { MarkdownEditor } from "../../components/MarkdownEditor";

interface PRResult {
Expand Down Expand Up @@ -267,14 +268,23 @@ function EditPRApp() {
const [reviewersLoading, setReviewersLoading] = useState(false);
const [reviewersFilter, setReviewersFilter] = useState("");

const { app, error: appError, toolInput, callTool, hostContext, setModelContext, openLink } = useMcpApp({
const { app, error: appError, toolInput, toolResult, callTool, hostContext, setModelContext, openLink } = useMcpApp({
appName: "github-mcp-server-edit-pull-request",
});

const owner = (toolInput?.owner as string) || "";
const repo = (toolInput?.repo as string) || "";
const pullNumber = asNumber(toolInput?.pullNumber);

// When the server updated the PR up-front instead of deferring to this form,
// the host still renders this View and delivers the updated PR via
// tool-result. Render that completed result as success so we never show an
// edit form for changes already applied. The deferral sentinel
// (awaiting_user_submission) returns null here, keeping the form for the
// normal deferred flow. See github/copilot-mcp-core#1864.
const resultPR = useMemo(() => completedToolResult<PRResult>(toolResult), [toolResult]);
const shownPR = successPR ?? resultPR;

Comment on lines +279 to +287

@SamMorrowDrums SamMorrowDrums Jun 26, 2026

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Good catch — fixed in 09a7a78. Rather than key the parsed result per app, I scoped it centrally in useMcpApp: toolResult is now reset to null whenever a new tool-input notification arrives. The MCP Apps 2026-01-26 spec guarantees tool-input is delivered before that invocation's tool-result, so a new invocation drops any prior result before its own arrives — closing the stale-success window for all three Views without per-app invocation keys.

useEffect(() => {
setTitle("");
setBody("");
Expand Down Expand Up @@ -495,10 +505,10 @@ function EditPRApp() {
}
}, [title, body, owner, repo, pullNumber, baseBranch, initialValues, selectedReviewers, prState, isDraft, maintainerCanModify, callTool, setModelContext]);

if (successPR) {
if (shownPR) {
return (
<AppProvider hostContext={hostContext}>
<SuccessView pr={successPR} owner={owner} repo={repo} submittedTitle={submittedTitle} openLink={openLink} />
<SuccessView pr={shownPR} owner={owner} repo={repo} submittedTitle={submittedTitle} openLink={openLink} />
</AppProvider>
);
}
Expand Down
17 changes: 14 additions & 3 deletions ui/src/apps/pr-write/App.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ import {
} from "@primer/octicons-react";
import { AppProvider } from "../../components/AppProvider";
import { useMcpApp } from "../../hooks/useMcpApp";
import { completedToolResult } from "../../lib/toolResult";
import { MarkdownEditor } from "../../components/MarkdownEditor";

interface PRResult {
Expand Down Expand Up @@ -189,14 +190,24 @@ function CreatePRApp() {
const [repoSearchLoading, setRepoSearchLoading] = useState(false);
const [repoFilter, setRepoFilter] = useState("");

const { app, error: appError, toolInput, callTool, hostContext, setModelContext, openLink } = useMcpApp({
const { app, error: appError, toolInput, toolResult, callTool, hostContext, setModelContext, openLink } = useMcpApp({
appName: "github-mcp-server-create-pull-request",
});

const owner = selectedRepo?.owner || (toolInput?.owner as string) || "";
const repo = selectedRepo?.name || (toolInput?.repo as string) || "";
const [submittedTitle, setSubmittedTitle] = useState("");

// When the server executed up-front instead of deferring to this form (e.g.
// the agent passed show_ui=false or parameters the form can't represent), the
// host still renders this View and delivers the created PR via tool-result.
// Treat that completed result as a success so we never show a "Create pull
// request" form for a PR that already exists. The deferral sentinel
// (awaiting_user_submission) returns null here, keeping the form for the
// normal deferred flow. See github/copilot-mcp-core#1864.
const resultPR = useMemo(() => completedToolResult<PRResult>(toolResult), [toolResult]);
const shownPR = successPR ?? resultPR;

Comment thread
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// Reset all transient form/result state when toolInput changes (new invocation).
// Without this, the SuccessView from a previous submit stays visible and stale
// form values bleed through because the prefill effect below only sets when
Expand Down Expand Up @@ -440,10 +451,10 @@ function CreatePRApp() {
}
}, [title, body, owner, repo, baseBranch, headBranch, isDraft, maintainerCanModify, selectedReviewers, toolInput, callTool, setModelContext]);

if (successPR) {
if (shownPR) {
return (
<AppProvider hostContext={hostContext}>
<SuccessView pr={successPR} owner={owner} repo={repo} submittedTitle={submittedTitle} openLink={openLink} />
<SuccessView pr={shownPR} owner={owner} repo={repo} submittedTitle={submittedTitle} openLink={openLink} />
</AppProvider>
);
}
Expand Down
37 changes: 37 additions & 0 deletions ui/src/lib/toolResult.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
import type { CallToolResult } from "@modelcontextprotocol/sdk/types.js";

/**
* Returns the parsed JSON payload of a *completed* tool result, or `null` when
* the result is absent, an error, or the deferral sentinel (structured
* `status` of `"awaiting_user_submission"`, set by the server's
* `NewToolResultAwaitingFormSubmission`).
*
* Form-backed write Views (create_pull_request, issue_write,
* update_pull_request) use this to tell apart "the server deferred and is
* waiting for my form submission" from "the server already executed". Without
* it, a View renders its input form off in-app state alone and will show e.g. a
* "Create pull request" form for a PR that was already created up-front (when
* the agent passed `show_ui=false` or parameters the form can't represent).
*
* See github/copilot-mcp-core#1864 for the full show/defer state machine.
*/
export function completedToolResult<T = Record<string, unknown>>(
result: CallToolResult | null,
): T | null {
if (!result || result.isError) return null;

const status = (result.structuredContent as { status?: string } | undefined)
?.status;
if (status === "awaiting_user_submission") return null;

const textContent = result.content?.find((c) => c.type === "text");
if (!textContent || textContent.type !== "text" || !textContent.text) {
return null;
}

try {
return JSON.parse(textContent.text) as T;
} catch {
return null;
}
}
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