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Preserve inline sub-agent frontmatter during extraction#39577

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pelikhan merged 9 commits into
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copilot/fix-sub-agent-model-override
Jun 16, 2026
Merged

Preserve inline sub-agent frontmatter during extraction#39577
pelikhan merged 9 commits into
mainfrom
copilot/fix-sub-agent-model-override

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Copilot AI commented Jun 16, 2026 •
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Inline sub-agents can declare their own frontmatter, including model: overrides and additional engine-specific fields. The extraction path should preserve that frontmatter exactly as authored instead of filtering unsupported keys or corrupting nested YAML.

  • Runtime extractor fix

    • Stop filtering inline sub-agent frontmatter during extraction.
    • Preserve the entire authored frontmatter block as-is in the emitted sub-agent file.

  • Regression coverage

    • Add JS regression coverage for an inline sub-agent frontmatter block where tools: appears between description: and model:.
    • Assert that the emitted sub-agent file preserves the full frontmatter exactly as written.

  • Parser coverage

    • Add a Go parser test that verifies inline sub-agent extraction preserves the full frontmatter exactly in the extracted agent content.
    • Update parser validation coverage so inline sub-agent frontmatter is accepted as long as it remains parseable.
---
description: Helper
tools:
  github:
    toolsets: [issues]
model: claude-haiku-4.5
engine: copilot
---
Prompt.

Now extracts as:

---
description: Helper
tools:
  github:
    toolsets: [issues]
model: claude-haiku-4.5
engine: copilot
---
Prompt.

Copilot AI and others added 2 commits June 16, 2026 15:52
@pelikhan
Plan inline sub-agent model tests
a98dc5c 
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
@pelikhan
Add inline sub-agent model extraction tests
a6f2f30 
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Copilot AI changed the title [WIP] Fix sub-agent model frontmatter being ignored Preserve inline sub-agent model: frontmatter during extraction Jun 16, 2026
Copilot AI requested a review from pelikhan June 16, 2026 15:59
@pelikhan

pelikhan commented Jun 16, 2026

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@copilot the entire frontmatter should be preserved as is

Copilot AI and others added 3 commits June 16, 2026 16:21
@pelikhan
Preserve inline sub-agent frontmatter
244b428 
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
@pelikhan
Preserve full inline sub-agent frontmatter
0f863af 
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
@pelikhan
Clarify preserved sub-agent frontmatter flow
2e7478c 
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot AI commented Jun 16, 2026

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@copilot the entire frontmatter should be preserved as is

Addressed in 952be38. Inline sub-agent extraction now preserves the entire authored frontmatter as-is, and the JS/Go coverage was updated to lock in that behavior.

Copilot AI changed the title Preserve inline sub-agent model: frontmatter during extraction Preserve inline sub-agent frontmatter during extraction Jun 16, 2026
@pelikhan pelikhan marked this pull request as ready for review June 16, 2026 16:42
Copilot AI review requested due to automatic review settings June 16, 2026 16:42
Copilot AI reviewed Jun 16, 2026
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Pull request overview

This PR updates inline sub-agent handling so authored YAML frontmatter blocks are preserved (rather than filtered) during extraction, and adjusts validation/tests to accept arbitrary sub-agent frontmatter as long as it remains parseable.

Changes:

  • Remove runtime filtering of inline sub-agent frontmatter and keep emitted agent content intact.
  • Relax Go sub-agent frontmatter validation to only warn on parse/extraction errors (not unknown keys).
  • Add Go + JS regression tests to ensure nested YAML and field ordering are preserved.
Show a summary per file
File Description
pkg/parser/sub_agent_validation_test.go Updates validation expectations to allow arbitrary sub-agent frontmatter and adds a malformed-frontmatter warning test.
pkg/parser/sub_agent_extractor.go Removes unknown-field validation and validates only frontmatter parseability for inline sub-agents.
pkg/parser/sub_agent_extractor_test.go Adds a regression test asserting extracted sub-agent content preserves the authored frontmatter block.
actions/setup/js/extract_inline_sub_agents.test.cjs Updates JS tests to assert frontmatter is preserved (including order and nested YAML).
actions/setup/js/extract_inline_sub_agents.cjs Removes frontmatter filtering logic and preserves agent content when writing extracted agent files.

Copilot's findings

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  • Files reviewed: 5/5 changed files
  • Comments generated: 3

Comment thread pkg/parser/sub_agent_validation_test.go
Comment on lines 199 to 203
"---",
"engine: copilot",
"on:",
" workflow_dispatch:",
"---",
`description: "unterminated string`,
"model: claude-haiku-4.5",
"Do work.",
}, "\n")
Comment thread pkg/parser/sub_agent_extractor.go Outdated
// - description: Human-readable description of the sub-agent's role.
// - model: AI model to use. Default is "inherited" (uses the parent
// workflow's model when not set).
// Sub-agent frontmatter is preserved exactly as authored.
Comment thread actions/setup/js/extract_inline_sub_agents.cjs Outdated
// description Human-readable description of the sub-agent's role.
// model AI model to use. Default is "inherited" (uses the parent
// workflow's model when not set).
// Sub-agent frontmatter is preserved exactly as authored.
@pelikhan

pelikhan commented Jun 16, 2026

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@copilot run pr-finisher skill

@pelikhan
Address review feedback: fix ParseError fixture, soften frontmatter c…
94fd8fe 
…omments

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot AI commented Jun 16, 2026

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@copilot run pr-finisher skill

Done. Addressed all three open review threads in the latest commit:

  • ParseError fixture (sub_agent_validation_test.go) — added the missing closing --- delimiter so the test now exercises a real YAML parse error (unterminated string) rather than "frontmatter not properly closed".
  • Comment wording (sub_agent_extractor.go and extract_inline_sub_agents.cjs) — softened "preserved exactly as authored" to "keys and order are preserved without filtering; boundary whitespace is trimmed" in both files.

Local make agent-report-progress (build + fmt + lint + test-unit) passes cleanly.

@pelikhan pelikhan merged commit c90da21 into main Jun 16, 2026
37 checks passed
@pelikhan pelikhan deleted the copilot/fix-sub-agent-model-override branch June 16, 2026 17:42
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