Skip MCP App form when issue/PR write carries non-form params

[mattdholloway]

Problem

When MCP Apps are enabled and the client supports UI, issue_write and create_pull_request return a "Ready to create… click Submit" stub and route the call to an interactive form before parsing the rest of the parameters.

The form then rebuilt its submit payload from scratch and only re-sent the fields it collects. For issue_write the form only handles title/body (and issue_number on update), so any agent-supplied labels, assignees, milestone, type, state, state_reason, duplicate_of or issue_fields (e.g. priority) were silently dropped.

This was surfaced by a partner team testing the new issue-fields support: setting priority via the model never took effect when the UI form intercepted the call.

Fix

Two complementary layers so no agent-supplied parameter is ever lost:

1. Server: skip the form for non-form params (pkg/github)

Each tool declares an allowlist of the params its form collects/re-sends (issueWriteFormParams / pullRequestWriteFormParams). A helper returns true if the call carries any other non-nil param, and that is added to the interception condition so the call executes directly instead of being routed to the form.

• issue_write (both the issue_fields-enabled and legacy variants)
• create_pull_request

This generalizes the previous state-only guard (same behaviour preserved) and is allowlist-based, so it is robust to future parameters — any newly-added param that the form does not yet support automatically bypasses the form rather than being dropped.

Handler-only change — no tool schema changes, so toolsnaps and generated docs are unaffected.

2. UI: forward original params on submit (ui/src/apps)

The issue-write and pr-write forms now spread the original toolInput first and override only the edited fields (title/body/etc.), so any parameter the form does not render is preserved when the user submits. This is a safety net for any params that do reach the form (e.g. if the server guard is later relaxed, or for params the form renders only partially).

Tests

• Table-driven unit tests for both server-side helpers.
• Behavioral subtests asserting that a UI client passing issue_fields / labels (issue_write) or a non-form param (create_pull_request) skips the form and executes directly.
• UI changes type-check and build clean.

[Copilot]

Pull request overview

Fixes a data-loss bug where issue_write and create_pull_request MCP App UI form interception would silently drop agent-supplied parameters (e.g. labels, assignees, issue_fields) that the form does not collect or re-send. The fix introduces explicit allow-lists of form-collected params per tool and bypasses the UI form whenever any other parameter is present, generalizing the previous narrow state-only guard.

Changes:

• Add issueWriteFormParams / pullRequestWriteFormParams sets and *HasNonFormParams helpers; include them in the UI-interception condition.
• Simplify the issue_write update branch (state-specific guard removed; now subsumed by the general non-form-params check) in both the issue_fields variant and the legacy variant.
• Add table-driven helper tests and behavioral subtests verifying the bypass path for issue_fields/labels (issue_write) and a non-form param (create_pull_request).

Show a summary per file

File	Description
pkg/github/issues.go	Add form-param allow-list + helper; replace state-only bypass with general non-form-params bypass in both IssueWrite variants
pkg/github/issues_test.go	New helper unit tests and UI-gate behavioral tests for issue_fields and labels bypass
pkg/github/pullrequests.go	Add form-param allow-list + helper for create_pull_request; add to UI-interception guard
pkg/github/pullrequests_test.go	New helper unit tests and UI-gate behavioral test for non-form param bypass

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 0

[Copilot]

Copilot's findings

• Files reviewed: 6/6 changed files
• Comments generated: 0 new