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Improve agent file missing error message with actionable frontmatter guidance #19966

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Improve agent file missing error message with actionable frontmatter guidance #19966

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Copilot Mar 7, 2026
e57109d
fix: improve agent file validation error message with explicit frontm…
Copilot Mar 7, 2026
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2 changes: 1 addition & 1 deletion pkg/workflow/agent_validation.go
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,7 @@ func (c *Compiler) validateAgentFile(workflowData *WorkflowData, markdownPath st
if _, err := os.Stat(fullAgentPath); err != nil {
if os.IsNotExist(err) {
return formatCompilerError(markdownPath, "error",
fmt.Sprintf("agent file '%s' does not exist. Ensure the file exists in the repository and is properly imported.", agentPath), nil)
fmt.Sprintf("agent file '%s' does not exist. Check your workflow frontmatter: the 'agent:' field should reference a valid file path (e.g., '.github/agents/custom.agent.md')", agentPath), nil)
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Copilot AI Mar 7, 2026

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The error message refers to "the 'agent:' field" in the workflow frontmatter, but there is no top-level agent: frontmatter field. The AgentFile is actually populated through the imports: frontmatter field when a file under .github/agents/ is imported (see pkg/parser/import_bfs.go:180-198 and pkg/workflow/frontmatter_types.go:164). The engine.agent field in frontmatter (pkg/workflow/engine.go:206-212) is for specifying an agent identifier string, not a file path.

The message should reference the imports: field instead, and the example should show the imports syntax (e.g., imports: ['.github/agents/custom.agent.md']). The current wording will mislead users into looking for a non-existent agent: frontmatter key.

Suggested change
fmt.Sprintf("agent file '%s' does not exist. Check your workflow frontmatter: the 'agent:' field should reference a valid file path (e.g., '.github/agents/custom.agent.md')", agentPath), nil)
fmt.Sprintf("agent file '%s' does not exist. Check your workflow frontmatter: ensure the 'imports:' field includes a valid agent file path (for example: imports: ['.github/agents/custom.agent.md'])", agentPath), nil)

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}
// Other error (permissions, etc.)
return formatCompilerError(markdownPath, "error",
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