Fix non-deterministic map iteration in EngineRegistry by Copilot · Pull Request #21474 · github/gh-aw

Copilot · 2026-03-17T23:45:32Z

GetSupportedEngines() and GetEngineByPrefix() iterated r.engines map[string]CodingAgentEngine directly, producing random ordering due to Go's map iteration randomization. GetEngineByPrefix() returned the first match found, meaning the same prefix string could resolve to different engines across runs.

Changes

GetSupportedEngines() — sorts the result slice before returning
GetEngineByPrefix() — collects all matching candidates, sorts by engine ID, returns the first deterministically

func (r *EngineRegistry) GetEngineByPrefix(prefix string) (CodingAgentEngine, error) {
    type engineCandidate struct{ id string; engine CodingAgentEngine }
    var candidates []engineCandidate
    for id, engine := range r.engines {
        if strings.HasPrefix(prefix, id) {
            candidates = append(candidates, engineCandidate{id, engine})
        }
    }
    if len(candidates) == 0 {
        return nil, fmt.Errorf("no engine found matching prefix: %s", prefix)
    }
    sort.Slice(candidates, func(i, j int) bool { return candidates[i].id < candidates[j].id })
    return candidates[0].engine, nil
}

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

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

Copilot

Pull request overview

Fixes non-deterministic behavior in engine lookup APIs caused by Go’s randomized map iteration order, ensuring stable results across runs.

Changes:

Sorts the result of EngineRegistry.GetSupportedEngines() before returning.
Makes EngineRegistry.GetEngineByPrefix() deterministic by collecting matches, sorting, and returning a consistent winner.
Updates the generated changeset.lock.yml workflow file by removing app_token_minting_failed output/env wiring.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
pkg/workflow/agentic_engine.go	Adds sorting to stabilize engine ID listing and prefix-based resolution.
.github/workflows/changeset.lock.yml	Removes app token minting failure-related env/outputs from the changeset workflow lockfile.

Comments suppressed due to low confidence (1)

pkg/workflow/agentic_engine.go:497

GetEngineByPrefix() now deterministically picks the first candidate after sorting, but there’s no test ensuring deterministic/consistent selection when multiple engines match a given string. Add a unit test that registers two engines with IDs that both match the same input (e.g., "co" and "copilot") and asserts the chosen engine is stable and follows the intended tie-break rule.

func (r *EngineRegistry) GetEngineByPrefix(prefix string) (CodingAgentEngine, error) {
	type engineCandidate struct {
		id     string
		engine CodingAgentEngine
	}
	var candidates []engineCandidate
	for id, engine := range r.engines {
		if strings.HasPrefix(prefix, id) {
			candidates = append(candidates, engineCandidate{id, engine})
		}
	}
	if len(candidates) == 0 {
		return nil, fmt.Errorf("no engine found matching prefix: %s", prefix)
	}
	sort.Slice(candidates, func(i, j int) bool { return candidates[i].id < candidates[j].id })
	return candidates[0].engine, nil

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pkg/workflow/agentic_engine.go

 func (r *EngineRegistry) GetSupportedEngines() []string {
 	var engines []string
 	for id := range r.engines {
 		engines = append(engines, id)
 	}
+	sort.Strings(engines)
 	return engines


.github/workflows/changeset.lock.yml

          GH_AW_CHECKOUT_PR_SUCCESS: ${{ needs.agent.outputs.checkout_pr_success }}
          GH_AW_CODE_PUSH_FAILURE_ERRORS: ${{ needs.safe_outputs.outputs.code_push_failure_errors }}
          GH_AW_CODE_PUSH_FAILURE_COUNT: ${{ needs.safe_outputs.outputs.code_push_failure_count }}
-          GH_AW_SAFE_OUTPUTS_APP_TOKEN_MINTING_FAILED: ${{ needs.safe_outputs.outputs.app_token_minting_failed }}
-          GH_AW_CONCLUSION_APP_TOKEN_MINTING_FAILED: ${{ steps.safe-outputs-app-token.outcome == 'failure' }}
          GH_AW_GROUP_REPORTS: "false"
          GH_AW_FAILURE_REPORT_AS_ISSUE: "true"


Initial plan

9829c4d

Copilot AI assigned Copilot and pelikhan Mar 17, 2026

Copilot started work on behalf of pelikhan March 17, 2026 23:45 View session

Copilot AI linked an issue Mar 17, 2026 that may be closed by this pull request

[plan] Fix non-deterministic map iteration in EngineRegistry #21473

Closed

5 tasks

Copilot AI and others added 2 commits March 17, 2026 23:49

plan: fix non-deterministic map iteration in EngineRegistry

accee9e

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

fix: deterministic map iteration in EngineRegistry GetSupportedEngine…

04e8238

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

Copilot AI changed the title ~~[WIP] [plan] Fix non-deterministic map iteration in EngineRegistry~~ Fix non-deterministic map iteration in EngineRegistry Mar 17, 2026

Copilot AI requested a review from pelikhan March 17, 2026 23:55

Copilot finished work on behalf of pelikhan March 17, 2026 23:55

pelikhan marked this pull request as ready for review March 18, 2026 00:09

Copilot AI review requested due to automatic review settings March 18, 2026 00:09

Copilot started reviewing on behalf of pelikhan March 18, 2026 00:10 View session

github-actions bot mentioned this pull request Mar 18, 2026

Smoke Test: Claude - 23222225233 #21489

Closed

Copilot AI reviewed Mar 18, 2026

View reviewed changes

pelikhan merged commit 4b15992 into main Mar 18, 2026
115 checks passed

pelikhan deleted the copilot/plan-fix-map-iteration branch March 18, 2026 00:46

This was referenced Mar 18, 2026

Smoke Test: Claude - 23223776723 #21495

Closed

Smoke Test: Copilot - 23224312109 #21503

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[Daily Report] 2026-03-18 — Daily Status Report #21544

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Fix non-deterministic map iteration in EngineRegistry#21474

Fix non-deterministic map iteration in EngineRegistry#21474
pelikhan merged 3 commits intomainfrom
copilot/plan-fix-map-iteration

Copilot AI commented Mar 17, 2026 •

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Copilot AI commented Mar 17, 2026 •

edited

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