fix(serve-app): bind the host's own opening call instead of re-posting a large tool result (#562) - #565
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…g a large tool result (#562) The serve-app page posted the seeded tool result back to POST /api/mcp/sessions/<id>/apps, so any opening result past the shared 64 KiB request-body bound (AB8010) dropped the App to the fallback panel — cargo-hauler's dashboard on a busy machine, for one. The host already made that call: McpAppRoutes gains an optional openingCall lookup, serve-app supplies its selection, and the page binds by tool name alone. A request that carries input and result (the Workbench) is unchanged; one that carries only one of them, names another tool, or another session is still AB8021.
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| Fix `agent-bundle serve-app` (and `serveApp`) dropping the App to the "ordinary tool result" fallback with `AB8010: Request body exceeds 64 KiB` when the opening tool's result is large: the host page now binds the tool call the host already made by tool name instead of re-sending the result through `POST /api/mcp/sessions/<id>/apps`. `McpAppRoutes` accepts an `openingCall` for that purpose; the Workbench's full-body shape is unchanged. (#562) |
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This changes user-facing behavior for agent-bundle serve-app and serveApp when an opening result exceeds 64 KiB, but neither the English nor Chinese standalone-App documentation is updated to describe the newly supported case. Update the matching pages under website/docs/en/** and website/docs/zh/** in this change.
AGENTS.md reference: AGENTS.md:L71-L77
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| "agent-bundle": patch | ||
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| Fix `agent-bundle serve-app` (and `serveApp`) dropping the App to the "ordinary tool result" fallback with `AB8010: Request body exceeds 64 KiB` when the opening tool's result is large: the host page now binds the tool call the host already made by tool name instead of re-sending the result through `POST /api/mcp/sessions/<id>/apps`. `McpAppRoutes` accepts an `openingCall` for that purpose; the Workbench's full-body shape is unchanged. (#562) |
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The second sentence turns this release note into an implementation note by naming the internal McpAppRoutes.openingCall, HTTP request shape, and Workbench behavior. Rewrite it around the consumer-visible serve-app/serveApp outcome so the published changeset remains user-facing.
AGENTS.md reference: AGENTS.md:L105-L106
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…ox, and surface-proxy iframes An inline iframe at height:100% inside a 100%-tall body overflows by its line-box descender, so the serve-app host page, the MCP App sandbox document, and the Runtime App surface proxy each grew a scrollbar around the App's own. Size the iframes as blocks and clip the framing documents' overflow.
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Closes #562.
Symptom
agent-bundle serve-app <server>/<app>shows the fallback panel — "MCP App preview failed: AB8010: Request body exceeds 64 KiB" over a JSON dump — whenever the opening tool's result is large. Reproduced with cargo-hauler'shauler dashboard(ScriptedAlchemy/cargo-hauler#83): on a machine with ~20 active tickets,hauler_statusreturns ~108 KB and the App never renders.Root cause
The host page round-tripped the result the host had just produced:
serve-mcp-app.tscalls the opening tool once and embeds the result in the page seed;serve-app-page.tsPOSTed{ host, input, previewProfile, result, toolName }back to/api/mcp/sessions/<id>/apps;mcp-app-routes.tsrequiredresultand reads bodies through the shared 64 KiBreadJsonBodybound.Fix
McpAppRoutesgains an optionalopeningCall(sessionId, toolName)lookup. A create request that carries neitherinputnorresultbinds that call; one that carries both is the Workbench's own tool run and is unchanged; one carrying only one of them, naming another tool, or another session is stillAB8021.serve-appsupplies its selection as the opening call; its page now posts{ host, previewProfile, toolName }only. The seed still carries the result for the fallback panel's display.Also: the host page, the MCP App sandbox document (
mcp-app-sandbox.ts), and the Runtime App surface proxy sized their iframes inline atheight: 100%, so each level overflowed by a line-box descender and grew its own scrollbar — three nested scrollbars around the App's. They now size the iframe as a block and clip their own overflow.Tests
tests/mcp-app-routes.test.ts: binds a >64 KiB opening result by tool name; rejects the half-shapes, another tool, and another session; without anopeningCallthe Workbench shape stays required.tests/serve-app.test.ts: binds the example App the way the page now does and asserts the page no longer postsseed.result.hauler dashboardon this branch binds a 107,694-bytehauler_statusresult and returns the 333 KB App resource plus sandbox frame.Self-review
Reviewer:
generalPurposesubagent on GPT-5.6 Sol (thechange-risk-reviewercould not run — TraceDecay's daemon is down and it has no shell fallback). Findings and disposition:tests/serve-app.test.ts) — dismissed with reasoning: the routes unit test binds a >64 KiB opening result through the exactcreateRequestpath that failed and rejects every half-shape; the integration test binds the example App the way the page now does and asserts the page no longer postsseed.result.examples/mcp-app'sshow-statuscannot produce a large result without a fixture change, and the live run in the description (107,694-bytehauler_status) is the end-to-end proof.packages/workbench/tests/mcp-app-real.e2e.test.tsnow asserts the sandbox proxy document does not scroll, clips its body, and renders the App frame as a block.(#565).No authorization, Workbench-compatibility, fallback-data, or stale-doc defects found (authorization precedes body parsing; the Workbench still sends
inputandresult).