[oblomov-dev]

Behaviour fixes from four review passes, covering:

• the system mode
• the app client and the app tool handlers
• the two chat screens: MCP Apps and Adaptive Cards
• the build and browser tools

Every fix has a regression test, and each one was reproduced before it was fixed.

System mode (lib/system.mjs)

• Breaker race: a wrong password reaches the system once under parallel calls. Before, parallel calls each passed the breaker before the first 401 came back, and SAP locks a user after a few attempts.
• Password command: the command runs once for parallel first calls.
• Timeouts: system_status and app_list give up after 30 s.
• Startup: a malformed % in A2UI5_MCP_SYSTEM_URL no longer stops the server from starting.
• Credentials: a URL that does not parse no longer echoes its credentials.
• Redirects: a 3xx answer names its Location.

App client (lib/appclient.mjs, vendored by the playground, protocol and the VS Code extension)

• Queued acts: an act queued behind one in flight runs only if it still names what its caller saw. Before, two app_act a1 sent at once fired NEXT and then DELETE_ALL.
• Eviction: sessions are evicted least recently used first, and an evicted session does not come back.
• Event by name: without row, the screen action of that name wins over a row action.
• Error texts: breaker refusals pass through unchanged, a non-JSON body is sanitised, and errors echo at most 80 characters.

App tools (server.mjs, lib/args.mjs, lib/budget.mjs)

• Answer size: snapshot answers are fitted to ANSWER_BUDGET. Long values are cut and become read-only, then rows are dropped from the end, with a note saying what was cut.
• Card size: the Adaptive Card counts together with the snapshot.
• Arguments: an argument a tool does not declare is refused, and max_rows refuses booleans, arrays and blank strings.

Build and browser tools (lib/runtime.mjs, lib/npm-backend.mjs, lib/spawn.mjs)

• interact_app timing: each action waits for the roundtrip it started. Before, the frontend dropped an event fired during a roundtrip, and both clicks were reported as performed.
• Start during a build: a backend start while build_backend runs is refused. Before, it booted the old output, which the build then reported as built.
• Stop during a start: backend stop now stops a start in flight, and the start reports that it was stopped.
• Picture size: run_app and interact_app cut a page taller than 4096 px. screenshot_view leaves out pictures over 8000 px or past its image budget. Each call gets its own PNG file.
• Lint:
  • The JSON for the whole sandbox is read in full. Before, one app with many findings broke every later lint.
  • The first 100 findings are listed, counted per rule.
• Large answers:
  • read_app pages by lines (from_line).
  • A full run_unit_tests is counted per object.
  • migrate_report's files are named, not inlined, once they pass the budget.
• Framework classes: the npm build refuses a dev object named like a framework class, whichever tool wrote it.

Adaptive Card and MCP Apps (lib/adaptive-card.mjs, lib/mcp-app-view.mjs)

• Card rows: the card shows only the snapshot's rows, and hidden rows are no edits.
• Untouched inputs: untouched means "as rendered", so CRLF, newlines, multi-select order, choices and check boxes are no longer written back.
• Typing and focus survive a failed act.
• Refresh follows a session that moved on and keeps max_rows.
• Buttons that need a value only a browser computes are disabled.
• Height: the reported height shrinks again.

Snapshot (lib/viewxml.mjs, lib/snapshot.mjs)

• Character references: an out-of-range reference such as � no longer throws the snapshot.
• stripTags is linear.

Not in this PR

• Tool races, left as a follow-up:
  • a deploy during a build (the object list is read before the transpile, and read_app staleness is judged against it);
  • cancelling a build that other callers joined;
  • deploy_app erroring after it wrote the class when the lint config is missing;
  • remove_app leaving interfaces and tables behind;
  • add_agent_setup with a dangling .claude link.
• Password inputs: they are still shown in clear text in MCP Apps. Fixing this is a snapshot contract change.
• Re-vendoring: the playground and protocol re-vendor appclient/snapshot/viewxml, and this repo re-vendors the protocol renderer (Adaptive Cards: app text is never Markdown; linear htmlToText protocol#4, merged). Both come as follow-up PRs.

Checks

A2UI5_MCP_SKIP_NETWORK_TESTS=1 npm test (with Chromium): 439 passed, 16 skipped, 0 failed.

🤖 Generated with Claude Code

https://claude.ai/code/session_013nvd2W2zUT5ZyemG91n2oq