fix(aws/ladder): report an exchange with an unknown accept outcome as unknown, not failed

providers/aws/go.mod

@@ -3,7 +3,7 @@ module github.com/LeanerCloud/cloud-commitments-go/providers/aws
 go 1.26.9
 
 require (
-	github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261016194019-89772cf80f67
+	github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261017020613-36d8b1100c05
 	github.com/aws/aws-sdk-go-v2 v1.41.5
 	github.com/aws/aws-sdk-go-v2/config v1.29.12
 	github.com/aws/aws-sdk-go-v2/credentials v1.17.65

providers/aws/go.sum

@@ -1,5 +1,5 @@
-github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261016194019-89772cf80f67 h1:zpr+lPSdlXeA9ySU7FqHtgn4ADinmRhfJ5Y6jm9ankw=
-github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261016194019-89772cf80f67/go.mod h1:SCDEgHG6evjPh0RsoXof+J3aMmGXNFMrwbJIle7rMpQ=
+github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261017020613-36d8b1100c05 h1:YtSRyJHVUTDnxykCGYpGX7Pt/z+mq4/sCphPmO6Pj5M=
+github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261017020613-36d8b1100c05/go.mod h1:SCDEgHG6evjPh0RsoXof+J3aMmGXNFMrwbJIle7rMpQ=
 github.com/aws/aws-sdk-go-v2 v1.41.5 h1:dj5kopbwUsVUVFgO4Fi5BIT3t4WyqIDjGKCangnV/yY=
 github.com/aws/aws-sdk-go-v2 v1.41.5/go.mod h1:mwsPRE8ceUUpiTgF7QmQIJ7lgsKUPQOUl3o72QBrE1o=
 github.com/aws/aws-sdk-go-v2/config v1.29.12 h1:Y/2a+jLPrPbHpFkpAAYkVEtJmxORlXoo5k2g1fa2sUo=

providers/aws/ladder/reshape.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"math"
 
+	"github.com/LeanerCloud/cloud-commitments-go/pkg/common"
 	"github.com/LeanerCloud/cloud-commitments-go/pkg/exchange"
 	"github.com/LeanerCloud/cloud-commitments-go/pkg/ladder"
 )
@@ -165,6 +166,8 @@ func summarizeExchangeResult(result *exchange.AutoExchangeResult) (ladder.Reshap
 			len(result.Completed)+len(result.Pending)+len(result.Failed)+len(result.Skipped)),
 	}
 
+	unknown := 0
+	firstUnknown := -1
 	for i := range result.Completed {
 		o := &result.Completed[i]
 		summary.Details = append(summary.Details, fmt.Sprintf(
@@ -179,9 +182,17 @@ func summarizeExchangeResult(result *exchange.AutoExchangeResult) (ladder.Reshap
 	}
 	for i := range result.Failed {
 		o := &result.Failed[i]
+		label := "failed"
+		if o.OutcomeUnknown {
+			unknown++
+			if firstUnknown < 0 {
+				firstUnknown = i
+			}
+			label = "outcome unknown, reconcile before retrying"
+		}
 		summary.Details = append(summary.Details, fmt.Sprintf(
-			"failed: %s (%s) -> %s: %s",
-			o.SourceRIID, o.SourceInstanceType, o.TargetInstanceType, o.Error))
+			"%s: %s (%s) -> %s: %s",
+			label, o.SourceRIID, o.SourceInstanceType, o.TargetInstanceType, o.Error))
 	}
 	for i := range result.Skipped {
 		s := &result.Skipped[i]
@@ -194,9 +205,16 @@ func summarizeExchangeResult(result *exchange.AutoExchangeResult) (ladder.Reshap
 		// summary.Analyzed: pending and skipped items were never attempted,
 		// and an inflated denominator would misread during an incident.
 		attempts := len(result.Completed) + len(result.Failed)
-		return summary, fmt.Errorf(
-			"ReshapeBuffer: %d of %d exchange attempt(s) failed (first: %s: %s); see summary details for the full list",
-			len(result.Failed), attempts, result.Failed[0].SourceRIID, result.Failed[0].Error)
+		const format = "ReshapeBuffer: %d of %d exchange attempt(s) failed (first: %s: %s)%s; see summary details for the full list"
+		if unknown == 0 {
+			first := &result.Failed[0]
+			return summary, fmt.Errorf(format, len(result.Failed), attempts, first.SourceRIID, first.Error, "")
+		}
+		// The unknown entry is the one needing reconciliation, so name it
+		// and wrap the sentinel for errors.Is.
+		first := &result.Failed[firstUnknown]
+		return summary, fmt.Errorf(format+": %w", len(result.Failed), attempts, first.SourceRIID, first.Error,
+			fmt.Sprintf("; %d with unknown outcome", unknown), common.ErrOutcomeUnknown)
 	}
 	return summary, nil
 }

providers/aws/ladder/reshape_test.go

@@ -260,6 +260,8 @@ func TestReshapeBuffer_PartialFailure_SummaryPlusError(t *testing.T) {
 	assert.Contains(t, err.Error(), "1 of 2 exchange attempt(s) failed",
 		"denominator must be completed+failed attempts, not Analyzed")
 	assert.Contains(t, err.Error(), "ri-bad")
+	assert.NotContains(t, err.Error(), "unknown outcome", "suffix only when K > 0")
+	require.NotErrorIs(t, err, common.ErrOutcomeUnknown, "definite failures must not claim an unknown outcome")
 
 	// The summary is still populated for audit alongside the error.
 	assert.Equal(t, 3, summary.Analyzed)
@@ -310,3 +312,41 @@ func TestReshapeBuffer_WrongScope_ReturnsError(t *testing.T) {
 	assert.Contains(t, err.Error(), "does not match configured account")
 	assert.Equal(t, 0, ex.calls)
 }
+
+func TestReshapeBuffer_UnknownOutcome_RenderedAsUnknownNotFailed(t *testing.T) {
+	ex := &fakeExchangeRunner{result: &exchange.AutoExchangeResult{
+		Mode: string(exchange.ExchangeModeAuto),
+		Failed: []exchange.ExchangeOutcome{
+			{SourceRIID: "ri-bad", SourceInstanceType: "m5.large", TargetInstanceType: "m5.xlarge", Error: "rejected"},
+			{SourceRIID: "ri-unk", SourceInstanceType: "c5.large", TargetInstanceType: "c5.xlarge", Error: "accept timed out", OutcomeUnknown: true},
+		},
+	}}
+	a := newWiredLadder(t, &fakePurchaser{}, &fakePurchaser{}, ex)
+
+	summary, err := a.ReshapeBuffer(context.Background(), testScope(), validReshapeCfg())
+	require.Error(t, err)
+	require.ErrorIs(t, err, common.ErrOutcomeUnknown)
+	assert.Contains(t, err.Error(), "2 of 2 exchange attempt(s) failed (first: ri-unk: accept timed out)",
+		"first: names the unknown entry even when a definite failure precedes it")
+	assert.Contains(t, err.Error(), "; 1 with unknown outcome")
+
+	require.Len(t, summary.Details, 2)
+	assert.Contains(t, summary.Details[0], "failed: ri-bad")
+	assert.NotContains(t, summary.Details[0], "outcome unknown")
+	assert.Contains(t, summary.Details[1], "outcome unknown, reconcile before retrying: ri-unk")
+	assert.NotContains(t, summary.Details[1], "failed:")
+}
+
+func TestReshapeBuffer_UnknownOnly_WrapsErrOutcomeUnknown(t *testing.T) {
+	ex := &fakeExchangeRunner{result: &exchange.AutoExchangeResult{
+		Mode: string(exchange.ExchangeModeAuto),
+		Failed: []exchange.ExchangeOutcome{
+			{SourceRIID: "ri-unk", SourceInstanceType: "c5.large", TargetInstanceType: "c5.xlarge", Error: "accept timed out", OutcomeUnknown: true},
+		},
+	}}
+	a := newWiredLadder(t, &fakePurchaser{}, &fakePurchaser{}, ex)
+
+	_, err := a.ReshapeBuffer(context.Background(), testScope(), validReshapeCfg())
+	require.ErrorIs(t, err, common.ErrOutcomeUnknown)
+	assert.Contains(t, err.Error(), "first: ri-unk: accept timed out")
+}