Fix assign-to-agent model parameter — add coding_agent_model_selection feature flag

[Copilot]

The model parameter in assign-to-agent fails at runtime because the GraphQL API requires the coding_agent_model_selection feature flag to expose the model field on AgentAssignmentInput. Without this flag, the field is hidden and requests fail.

Changes

assign_agent_helpers.cjs

• Conditionally include coding_agent_model_selection in GraphQL-Features header when model parameter is provided
• Header with model: "issues_copilot_assignment_api_support,coding_agent_model_selection"
• Header without model: "issues_copilot_assignment_api_support" (unchanged)

assign_agent_helpers.test.cjs

• Verify header includes coding_agent_model_selection when model is provided
• Verify header excludes it when model is not provided

Verification

The GraphQL API behavior with/without the flag:

// With coding_agent_model_selection — model field visible
// GraphQL-Features: issues_copilot_assignment_api_support,coding_agent_model_selection
{
  "inputFields": [
    { "name": "targetRepositoryId" },
    { "name": "baseRef" },
    { "name": "customInstructions" },
    { "name": "customAgent" },
    { "name": "model" }  // ✓ visible
  ]
}

// Without coding_agent_model_selection — model field hidden
// GraphQL-Features: issues_copilot_assignment_api_support
{
  "inputFields": [
    { "name": "targetRepositoryId" },
    { "name": "baseRef" },
    { "name": "customInstructions" },
    { "name": "customAgent" }
    // model field missing
  ]
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/github/gh-aw/contents/.github%2Fworkflows%2Faudit-workflows.md
  • Triggering command: /opt/hostedtoolcache/node/24.13.0/x64/bin/node /opt/hostedtoolcache/node/24.13.0/x64/bin/node --conditions node --conditions development --experimental-import-meta-resolve --require /home/REDACTED/work/gh-aw/gh-aw/actions/setup/js/node_modules/vitest/suppress-warnings.cjs /home/REDACTED/work/gh-aw/gh-aw/actions/setup/js/node_modules/vitest/dist/workers/forks.js (http block)

If you need me to access, download, or install something from one of these locations, you can either:

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>assign-to-agent model parameter fails — missing coding_agent_model_selection GraphQL feature flag</issue_title>
<issue_description>## Problem

PR #16386 (fixing #16294) added model, custom-agent, and custom-instructions parameters to assign-to-agent. However, the model parameter fails at runtime because the GraphQL API requires the coding_agent_model_selection feature flag in the GraphQL-Features header to expose the model field on AgentAssignmentInput.

gh-aw currently sends:

GraphQL-Features: issues_copilot_assignment_api_support

It needs to send:

GraphQL-Features: issues_copilot_assignment_api_support,coding_agent_model_selection

Proof

With coding_agent_model_selection — model field is visible:

// gh api graphql -f query='{ __type(name: "AgentAssignmentInput") { inputFields { name } } }' \
//   -H 'GraphQL-Features: issues_copilot_assignment_api_support,coding_agent_model_selection'
{
  "inputFields": [
    { "name": "targetRepositoryId" },
    { "name": "baseRef" },
    { "name": "customInstructions" },
    { "name": "customAgent" },
    { "name": "model" }
  ]
}

Without coding_agent_model_selection — model field is hidden:

// gh api graphql -f query='{ __type(name: "AgentAssignmentInput") { inputFields { name } } }' \
//   -H 'GraphQL-Features: issues_copilot_assignment_api_support'
{
  "inputFields": [
    { "name": "targetRepositoryId" },
    { "name": "baseRef" },
    { "name": "customInstructions" },
    { "name": "customAgent" }
  ]
}

Fix

Add coding_agent_model_selection to the GraphQL-Features header in assign_agent_helpers.cjs (or wherever the GraphQL request headers are constructed) when the model parameter is provided — or unconditionally, since the flag is harmless when model is not used.

Notes

• customInstructions and customAgent do not require the extra flag — they work with just issues_copilot_assignment_api_support
• Only model is gated behind coding_agent_model_selection
• The Scout report on Feature request: Add model parameter to assign-to-agent safe output #16294 mentioned this header requirement but it wasn't incorporated into the PR implementation

Related

• Feature request: Add model parameter to assign-to-agent safe output #16294 — Original feature request (closed by PR Add model, custom_agent, and custom_instructions parameters to assign-to-agent (frontmatter configuration) #16386)
• PR Add model, custom_agent, and custom_instructions parameters to assign-to-agent (frontmatter configuration) #16386 — Implementation missing the header</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes assign-to-agent model parameter fails — missing coding_agent_model_selection GraphQL feature flag #16627

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[Copilot]

Pull request overview

This PR fixes a runtime failure in the assign-to-agent feature where the model parameter fails because the GraphQL API requires the coding_agent_model_selection feature flag to expose the model field on AgentAssignmentInput.

Changes:

• Updated the GraphQL-Features header to conditionally include coding_agent_model_selection when the model parameter is provided
• Added tests to verify the header is correctly set in both scenarios (with and without model)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
actions/setup/js/assign_agent_helpers.cjs	Modified GraphQL request to conditionally include coding_agent_model_selection feature flag when model parameter is provided
actions/setup/js/assign_agent_helpers.test.cjs	Added test assertions to verify the GraphQL-Features header is correctly set based on whether model is provided

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