Default stacked PR runs to top-of-stack with configurable `on.pull_request.max-stack` by Copilot · Pull Request #49420 · github/gh-aw

Copilot · 2026-07-31T22:14:26Z

Agentic workflows currently run on every PR in a stack, which multiplies CI cost. This change adds stack-aware gating so workflows default to running only on the latest stack layer, with an explicit frontmatter override.

Frontmatter contract (on.pull_request)
- Added max-stack to workflow schema.
- Semantics:
  - default: 1 (run only top/latest PR in a stack)
  - N > 1: run on top N stack layers
  - -1: disable stack protection (run all layers)
Compiler behavior
- Added pull-request stack filter in workflow condition generation.
- Applied filter only when pull_request trigger is present.
- Condition allows non-stacked PRs and non-PR events unchanged.
Generated workflow readability
- Updated on: cleanup/commenting to mark max-stack as compiler-applied (like other derived trigger filters), so lock output remains clear about source-of-truth behavior.
Coverage updates
- Added focused tests for default behavior, custom max-stack, disable mode (-1), and trigger-shape handling (on: pull_request vs object form).

on:
pull_request:
types: [opened, synchronize]max-stack: 2# run only on top 2 PRs in a stack; use -1 to disable

Warning

threat detection engine error
The threat detection engine encountered an error and could not complete analysis. This is a tooling failure, not a security finding.

Details

The threat detection engine failed to produce results.

Review the workflow run logs for details.

run: https://github.com/github/gh-aw/actions/runs/30676859249

Generated by 👨‍🍳 PR Sous Chef · gpt54 · 12.7 AIC · ⊞ 5.7K · ◷
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Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot

Pull request overview

Adds configurable stack-aware gating for pull-request workflows, defaulting execution to the top PR.

Changes:

Adds the on.pull_request.max-stack schema and compiler filter.
Comments compiler-processed configuration in generated YAML.
Adds unit coverage and recompiles affected workflows.

Show a summary per file

File	Description
`pkg/workflow/frontmatter_on_section_cleanup.go`	Comments processed `max-stack` fields.
`pkg/workflow/filters.go`	Implements stack gating.
`pkg/workflow/filters_stack_test.go`	Tests stack-filter configurations.
`pkg/workflow/compiler_orchestrator_workflow.go`	Invokes stack filtering.
`pkg/parser/schemas/main_workflow_schema.json`	Defines `max-stack`.
`.github/workflows/visual-regression-checker.lock.yml`	Adds generated stack conditions.
`.github/workflows/test-quality-sentinel.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-update-cross-repo-pr.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-test-tools.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-temporary-id.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-project.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-pi.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-opencode.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-multi-pr.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-gemini.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-create-cross-repo-pr.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-copilot-arm.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-codex.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-claude.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-ci.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-call-workflow.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-antigravity.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-agent-scoped-approved.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-agent-public-none.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-agent-public-approved.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-agent-all-none.lock.yml`	Adds generated stack conditions.
`.github/workflows/smoke-agent-all-merged.lock.yml`	Adds generated stack conditions.
`.github/workflows/refiner.lock.yml`	Adds generated stack conditions.
`.github/workflows/pr-description-caveman.lock.yml`	Adds generated stack conditions.
`.github/workflows/pr-code-quality-reviewer.lock.yml`	Adds generated stack conditions.
`.github/workflows/mattpocock-skills-reviewer.lock.yml`	Adds generated stack conditions.
`.github/workflows/impeccable-skills-reviewer.lock.yml`	Adds generated stack conditions.
`.github/workflows/firewall-escape.lock.yml`	Adds generated stack conditions.
`.github/workflows/design-decision-gate.lock.yml`	Adds generated stack conditions.
`.github/workflows/changeset.lock.yml`	Adds generated stack conditions.
`.github/workflows/ai-moderator.lock.yml`	Adds generated stack conditions.

Review details

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Files reviewed: 36/36 changed files
Comments generated: 3
Review effort level: Balanced

Copilot · 2026-08-01T01:44:44Z

+ "type": "integer",
+ "minimum": -1,
+ "description": "Maximum number of top stack layers to run on for stacked pull requests. Default is 1 (only the latest/top pull request in the stack). Set to -1 to disable stack protection and run on every pull request in the stack."


Fixed. Changed max-stack schema from {"type":"integer","minimum":-1} to an anyOf that accepts only const: -1 or minimum: 1, so 0, -2, and other invalid values are now rejected with a schema validation error. Schema tests covering rejection of 0 and -2 added in pkg/parser/schema_location_test.go.

Copilot · 2026-08-01T01:44:44Z

+	}
+
+	stackCondition := fmt.Sprintf(
+ "github.event_name != 'pull_request' || github.event.pull_request.stack == null || github.event.pull_request.stack.position + %d > github.event.pull_request.stack.size",


Fixed. GitHub Actions expressions don't support arithmetic operators, so the generated if: condition was rewritten:
max-stack: 1 (default): Uses github.event.pull_request.stack.position == github.event.pull_request.stack.size (equality only — always a supported operator). All 266 lock files have been recompiled with this corrected expression.
max-stack: N > 1: Instead of arithmetic in if:, injects a pre-steps bash step that computes size - position < N via shell arithmetic and exits 1 if the PR is not in the top-N layers. This keeps the job-level if: free of arithmetic.
Integration tests in pkg/workflow/filters_stack_integration_test.go (build-tagged integration) verify that no arithmetic operators appear in the compiled job-level if: conditions.

Copilot · 2026-08-01T01:44:45Z

+ "max-stack": {
+ "type": "integer",
+ "minimum": -1,
+ "description": "Maximum number of top stack layers to run on for stacked pull requests. Default is 1 (only the latest/top pull request in the stack). Set to -1 to disable stack protection and run on every pull request in the stack."


Added. A "Stacked PR Filtering (max-stack:)" subsection has been added to docs/src/content/docs/reference/triggers.md in the Pull Request Triggers section. It covers default behavior (run only the top PR), custom N (max-stack: 2), the disable mode (max-stack: -1), and explains why lower stack layers are skipped.

github-actions · 2026-08-01T01:03:02Z

test body

Generated by 🔧 PR Triage Agent · auto · 44.8 AIC · ⌖ 5.88 AIC · ⊞ 7.9K · ◷

github-actions · 2026-08-01T01:03:03Z

PR Triage

Category: feature
Risk: medium
Priority: 60/100
Action: fast_track

Generated by 🔧 PR Triage Agent · auto · 44.8 AIC · ⌖ 5.88 AIC · ⊞ 7.9K · ◷

gh-aw-bot · 2026-08-01T01:08:30Z

Warning

threat detection engine error
The threat detection engine encountered an error and could not complete analysis. This is a tooling failure, not a security finding.

Details

The threat detection engine failed to produce results.

Review the workflow run logs for details.

@copilot Please address the outstanding review feedback, refresh the branch, and run the pr-finisher skill before handing back for maintainer review.

Generated by 👨‍🍳 PR Sous Chef · gpt54 · 12.7 AIC · ⊞ 5.7K · ◷
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github-actions · 2026-08-01T01:26:37Z

Warning

threat detection engine error
The threat detection engine encountered an error and could not complete analysis. This is a tooling failure, not a security finding.

Details

The threat detection engine failed to produce results.

Review the workflow run logs for details.

Hey @pelikhan 👋 — Thanks for implementing stack-aware gating for agentic workflows! This addresses the real cost multiplier from workflows running on every layer of a PR stack. The feature is well-scoped, the schema contract is clear (max-stack: 1 by default, -1 to disable), and the compiler logic is clean.

✅ Tests are in place for default behavior, custom values, and disable mode.
✅ Description is thorough with a concrete YAML example.
✅ Lock files are properly generated (36 workflow artifacts updated).
✅ No new external dependencies.

This looks ready for review and merge.

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

patchdiff.githubusercontent.com

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
allowed:
- defaults
- "patchdiff.githubusercontent.com"

See Network Configuration for more information.

Generated by ✅ Contribution Check · auto · 60 AIC · ⊞ 8.7K · ◷

…ema, add docs Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>

Copilot · 2026-08-01T01:42:01Z

[!WARNING]
threat detection engine error
The threat detection engine encountered an error and could not complete analysis. This is a tooling failure, not a security finding....

Addressed all three review items in the latest commit:

Schema — reject max-stack: 0: Changed the max-stack schema definition from {"type": "integer", "minimum": -1} to an anyOf that accepts only const: -1 or minimum: 1, so 0 and negative integers other than -1 are now rejected. Tests added in schema_location_test.go.
Arithmetic operator fix: GitHub Actions expressions don't support +. Fixed by:
- max-stack: 1 (default) — uses position == size (equality, supported) in the job-level if:. All 266 lock files recompiled with this corrected expression.
- max-stack: N > 1 — injects a PreStep that uses bash arithmetic via env vars to compute the check. The step exits 1 if the PR is not in the top-N layers, blocking subsequent default-condition steps. Integration tests in filters_stack_integration_test.go verify no arithmetic appears in the job-level if:.
Documentation: Added a "Stacked PR Filtering (max-stack:)" subsection to docs/src/content/docs/reference/triggers.md under Pull Request Triggers, with examples for the default (max-stack: 1), custom N (max-stack: 2), and disable (max-stack: -1) cases.

github-actions · 2026-08-01T08:24:32Z

🎉 This pull request is included in a new release.

Release: v0.84.2

Add stacked PR max-stack trigger protection
f9181ad
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

CopilotAI assigned Copilot and pelikhan Jul 31, 2026

CopilotAI changed the title ~~Run stacked PR workflows on latest layer by default~~Default stacked PR runs to top-of-stack with configurable on.pull_request.max-stackJul 31, 2026

CopilotAI requested a review from pelikhan July 31, 2026 22:15

Copilotcreated this pull request from a session on behalf of pelikhan July 31, 2026 22:15 View session

Copilotfinished work on behalf of pelikhan July 31, 2026 22:15

pelikhan marked this pull request as ready for review August 1, 2026 00:49

CopilotAI review requested due to automatic review settings August 1, 2026 00:49

Copilotstarted reviewing on behalf of pelikhan August 1, 2026 00:50 View session

CopilotAI reviewed Aug 1, 2026
View reviewed changes

github-actionsBot added pr-action:fast_track pr-agent:copilot pr-priority:medium pr-risk:medium pr-type:feature labels Aug 1, 2026

github-actionsBot mentioned this pull request Aug 1, 2026
[PR Triage Report] PR Triage Report — 2026-08-01 (Run #30676648896) #49439
Closed

Merge branch 'main' into copilot/update-max-stack-on-pull-request
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github-actionsBot mentioned this pull request Aug 1, 2026
[pr-sous-chef] PR Sous Chef run report — 2026-08-01 00:15Z #49427
Closed

Copilotstarted work on behalf of gh-aw-bot August 1, 2026 01:09 View session

github-actionsBot mentioned this pull request Aug 1, 2026
[Contribution Check Report] Contribution Check — 2026-08-01 #49444
Closed

Fix max-stack: use equality for N=1, PreStep for N>1, reject 0 in sch…
75994d7
…ema, add docs Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>

Copilotfinished work on behalf of gh-aw-bot August 1, 2026 01:48

CopilotAI requested a review from gh-aw-bot August 1, 2026 01:48

pelikhan merged commit 184c9d1 into mainAug 1, 2026
29 checks passed

pelikhan deleted the copilot/update-max-stack-on-pull-request branch August 1, 2026 01:51

github-actionsBot mentioned this pull request Aug 1, 2026
Smoke Test: MAI-Code-1-Flash - 30689986700 #49532
Closed

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Default stacked PR runs to top-of-stack with configurable `on.pull_request.max-stack` - #49420

Default stacked PR runs to top-of-stack with configurable `on.pull_request.max-stack`#49420
pelikhan merged 3 commits into
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