[docs] Self-healing documentation fix: byok-copilot COPILOT_MODEL default - 2026-04-20

[github-actions]

Self-Healing Documentation Fixes

This PR was automatically created by the Daily Documentation Healer workflow.

Gaps Fixed

• Bug bug: byok-copilot feature generates empty COPILOT_MODEL fallback, breaking BYOK mode #26565 fix undocumented: features.byok-copilot in docs/src/content/docs/reference/frontmatter.md described "three required behaviors" but the compiler actually implements four. The fourth behavior — setting COPILOT_MODEL to $\{\{ vars.GH_AW_MODEL_AGENT_COPILOT || 'claude-sonnet-4.6' }} — was added to fix bug bug: byok-copilot feature generates empty COPILOT_MODEL fallback, breaking BYOK mode #26565 (Copilot BYOK providers require a non-empty model), but was never reflected in the user-facing reference docs. The section now lists all four behaviors explicitly and documents how to override the model via the GH_AW_MODEL_AGENT_COPILOT repository variable.

Root Cause

DDUw skipped this gap twice:

• PR [docs] Update documentation for features from 2026-04-16 #26605 (2026-04-16): skipped because the code fix hadn't landed yet — reasonable at the time.
• PR [docs] Update documentation for features from 2026-04-18 #27017 (2026-04-18): skipped with "requires detailed knowledge of the Copilot CLI BYOK API surface that is not yet stable" — the code was already stable (CopilotBYOKDefaultModel = "claude-sonnet-4.6" was in pkg/constants/engine_constants.go), so this deferral was incorrect.

💡 DDUw Improvement Suggestions

DDUw Improvement Suggestions

Problem: DDUw deferred an already-fixed documentation gap by citing "API surface not yet stable" when in fact CopilotBYOKDefaultModel was committed and stable in pkg/constants/engine_constants.go.

Suggested heuristic to add to Step 1c or Step 2 in .github/workflows/daily-doc-updater.md:

After reviewing closed bug issues and their fix PRs, grep for the constant names mentioned in the fix commit in pkg/constants/. If the constant value is committed and the corresponding user-facing doc section (identified by feature name) does not mention the constant's effective behavior, treat this as a confirmed documentation gap — do not defer due to assumed instability.

Specifically: when a closed issue references a constants change (CopilotBYOK*), DDUw should cross-check whether the public-facing section that owns that feature (here features.byok-copilot) lists all compiler behaviors coded in pkg/workflow/copilot_engine_execution.go.

Related Issues

• Fixes bug: byok-copilot feature generates empty COPILOT_MODEL fallback, breaking BYOK mode #26565 (indirectly — the code fix landed, this PR documents it)
• Referenced by Daily Quality Report [Daily Report] Documentation Quality Report — April 16, 2026 #26592

References:

• §24663044850 — DDUw run that skipped this gap (PR [docs] Update documentation for features from April 20, 2026 #27309)
• §24603073517 — Earlier DDUw run that also skipped (PR [docs] Update documentation for features from 2026-04-18 #27017)
• §24668882876 — This doc-healer run

Generated by Daily Documentation Healer · ● 447.4K · ◷

• expires on Apr 23, 2026, 1:30 PM UTC

[Copilot]

Pull request overview

Updates the features.byok-copilot reference documentation to reflect the compiler’s actual BYOK wiring behavior, including the non-empty COPILOT_MODEL fallback added for bug #26565.

Changes:

• Expands the features.byok-copilot section from three to four required behaviors.
• Documents the default COPILOT_MODEL expression and its fallback (claude-sonnet-4.6) when GH_AW_MODEL_AGENT_COPILOT is unset.
• Adds guidance for overriding the model via the GH_AW_MODEL_AGENT_COPILOT GitHub Actions variable.

Show a summary per file

File	Description
docs/src/content/docs/reference/frontmatter.md	Updates BYOK Copilot feature-flag docs to include the COPILOT_MODEL default/fallback behavior and override mechanism.

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