fix(slack-gateway): preserve ACP reply whitespace

.github/workflows/go-tests.yml

@@ -3,6 +3,7 @@ name: go-tests
 on:
   pull_request:
     paths:
+      - "integrations/acptext/**"
       - "api/**"
       - "operator/**"
       - "integrations/github-app/**"
@@ -12,6 +13,7 @@ on:
     branches:
       - main
     paths:
+      - "integrations/acptext/**"
       - "api/**"
       - "operator/**"
       - "integrations/github-app/**"
@@ -25,6 +27,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - name: acptext
+            working-directory: integrations/acptext
           - name: api
             working-directory: api
           - name: operator
@@ -44,7 +48,24 @@ jobs:
         uses: actions/setup-go@v5
         with:
           go-version-file: ${{ matrix.working-directory }}/go.mod
-          cache-dependency-path: ${{ matrix.working-directory }}/go.sum
+          cache-dependency-path: ${{ matrix.working-directory }}/go.*
 
       - name: Test
         run: go test ./...
+
+  docker-build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: api
+            dockerfile: api/Dockerfile
+          - name: integrations-slack-gateway
+            dockerfile: integrations/slack-gateway/Dockerfile
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Build image
+        run: docker build -f "${{ matrix.dockerfile }}" . -t "spritz-${{ matrix.name }}-ci"

api/Dockerfile

@@ -1,12 +1,17 @@
+# Build with the repository root as context so the shared local Go modules are available.
 FROM golang:1.25-alpine AS build
 
 WORKDIR /src
+COPY integrations/acptext/go.mod ./integrations/acptext/go.mod
 COPY api/go.mod api/go.sum ./api/
 COPY operator/go.mod operator/go.sum ./operator/
 WORKDIR /src/api
 RUN go mod download
-COPY api/ /src/api/
+WORKDIR /src
+COPY integrations/acptext/ /src/integrations/acptext/
 COPY operator/ /src/operator/
+COPY api/ /src/api/
+WORKDIR /src/api
 RUN CGO_ENABLED=0 go build -o /out/spritz-api .
 RUN CGO_ENABLED=0 go build -o /out/spritz-shared-syncer ./cmd/shared-syncer
 

api/acp_prompt.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"strings"
 	"time"
+
+	"spritz.sh/acptext"
 )
 
 type acpPromptResult struct {
@@ -156,50 +158,5 @@ func assistantTextFromACPUpdates(updates []map[string]any) string {
 		}
 		chunks = append(chunks, update["content"])
 	}
-	return joinACPTextChunks(chunks)
-}
-
-func joinACPTextChunks(values []any) string {
-	var builder strings.Builder
-	for _, value := range values {
-		builder.WriteString(extractACPText(value))
-	}
-	return builder.String()
-}
-
-func extractACPText(value any) string {
-	switch typed := value.(type) {
-	case nil:
-		return ""
-	case string:
-		return typed
-	case []any:
-		parts := make([]string, 0, len(typed))
-		for _, item := range typed {
-			text := extractACPText(item)
-			if text == "" {
-				continue
-			}
-			parts = append(parts, text)
-		}
-		return strings.Join(parts, "\n")
-	case map[string]any:
-		if text, ok := typed["text"].(string); ok {
-			return text
-		}
-		if content, ok := typed["content"]; ok {
-			return extractACPText(content)
-		}
-		if resource, ok := typed["resource"].(map[string]any); ok {
-			if text, ok := resource["text"].(string); ok {
-				return text
-			}
-			if uri, ok := resource["uri"].(string); ok {
-				return uri
-			}
-		}
-		return ""
-	default:
-		return fmt.Sprint(typed)
-	}
+	return acptext.JoinChunks(chunks)
 }

api/go.mod

@@ -14,6 +14,7 @@ require (
 	k8s.io/apimachinery v0.35.0
 	k8s.io/client-go v0.35.0
 	sigs.k8s.io/controller-runtime v0.22.4
+	spritz.sh/acptext v0.0.0-00010101000000-000000000000
 	spritz.sh/operator v0.0.0-00010101000000-000000000000
 )
 
@@ -77,4 +78,6 @@ require (
 	sigs.k8s.io/yaml v1.6.0 // indirect
 )
 
+replace spritz.sh/acptext => ../integrations/acptext
+
 replace spritz.sh/operator => ../operator

docs/2026-03-24-slack-channel-gateway-implementation-plan.md

@@ -445,6 +445,29 @@ The gateway should also not mark delivery success just because session exchange
 returned `resolved`. Success means the prompt has actually been handed off to
 the runtime and the normal reply path can continue.
 
+## ACP Reply Text Integrity
+
+The Slack gateway must treat ACP assistant text as lossless content, not as
+display text that may be normalized.
+
+That means:
+
+- `agent_message_chunk` text must be assembled without trimming individual
+  chunks
+- spaces and newlines at chunk boundaries are part of the payload and must be
+  preserved
+- the gateway may trim only for emptiness checks at the final boundary, not as
+  part of text extraction or chunk joining
+- channel adapters should reuse one shared ACP text extraction and chunk-join
+  helper instead of reimplementing their own whitespace rules
+
+If this contract is violated, the provider-visible reply can silently corrupt
+content even when the runtime output is correct. Typical failures are:
+
+- merged words across chunk boundaries
+- lost paragraph breaks
+- flattened lists or code blocks
+
 ## Threading Defaults
 
 Phase 1 should keep channel behavior predictable:
@@ -519,6 +542,8 @@ Before calling Phase 1 done, verify:
 16. Duplicate Slack webhook deliveries converge on the same pending delivery.
 17. The first recovered Slack turn is not marked successful until the prompt is
     actually accepted by ACP.
+18. Multiline assistant replies preserve spaces and newlines across ACP chunk
+    boundaries.
 
 ## Follow-ups
 

e2e/acp-smoke-lib.mjs

@@ -186,10 +186,10 @@ export function extractACPText(value) {
     return value.map((item) => extractACPText(item)).filter(Boolean).join('\n');
   }
   if (typeof value !== 'object') return String(value);
-  if (typeof value.text === 'string') return value.text;
+  if (typeof value.text === 'string' && value.text !== '') return value.text;
   if (value.content !== undefined) return extractACPText(value.content);
   if (value.resource) {
-    if (typeof value.resource.text === 'string') return value.resource.text;
+    if (typeof value.resource.text === 'string' && value.resource.text !== '') return value.resource.text;
     if (typeof value.resource.uri === 'string') return value.resource.uri;
   }
   return '';

e2e/acp-smoke-lib.test.mjs

@@ -113,6 +113,13 @@ test('extractACPText flattens nested content blocks', () => {
   );
 });
 
+test('extractACPText falls back to resource uri when text is empty', () => {
+  assert.equal(
+    extractACPText({ resource: { text: '', uri: 'file://smoke-fallback.txt' } }),
+    'file://smoke-fallback.txt',
+  );
+});
+
 test('joinACPTextChunks preserves chunked tokens without inserted separators', () => {
   assert.equal(joinACPTextChunks([{ text: 'spr' }, { text: 'itz-smoke-openclaw' }]), 'spritz-smoke-openclaw');
 });

integrations/acptext/go.mod

@@ -0,0 +1,3 @@
+module spritz.sh/acptext
+
+go 1.25.0

integrations/acptext/text.go

@@ -0,0 +1,53 @@
+package acptext
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Extract returns the readable text content represented by one ACP payload
+// without trimming or normalizing whitespace.
+func Extract(value any) string {
+	switch typed := value.(type) {
+	case nil:
+		return ""
+	case string:
+		return typed
+	case []any:
+		parts := make([]string, 0, len(typed))
+		for _, item := range typed {
+			text := Extract(item)
+			if text == "" {
+				continue
+			}
+			parts = append(parts, text)
+		}
+		return strings.Join(parts, "\n")
+	case map[string]any:
+		if text, ok := typed["text"].(string); ok && text != "" {
+			return text
+		}
+		if content, ok := typed["content"]; ok {
+			return Extract(content)
+		}
+		if resource, ok := typed["resource"]; ok {
+			return Extract(resource)
+		}
+		if uri, ok := typed["uri"].(string); ok {
+			return uri
+		}
+		return ""
+	default:
+		return fmt.Sprint(typed)
+	}
+}
+
+// JoinChunks concatenates ACP chunk payloads without injecting separators or
+// trimming whitespace at chunk boundaries.
+func JoinChunks(values []any) string {
+	var builder strings.Builder
+	for _, value := range values {
+		builder.WriteString(Extract(value))
+	}
+	return builder.String()
+}

integrations/acptext/text_test.go

@@ -0,0 +1,40 @@
+package acptext
+
+import "testing"
+
+func TestExtractPreservesWhitespaceInTextBlocks(t *testing.T) {
+	got := Extract([]any{
+		map[string]any{"text": "hello"},
+		map[string]any{"text": " world"},
+		map[string]any{"text": "\nagain"},
+	})
+	want := "hello\n world\n\nagain"
+	if got != want {
+		t.Fatalf("expected %q, got %q", want, got)
+	}
+}
+
+func TestExtractSupportsResourceBlocks(t *testing.T) {
+	if got := Extract(map[string]any{"resource": map[string]any{"text": "resource text"}}); got != "resource text" {
+		t.Fatalf("expected resource text, got %q", got)
+	}
+	if got := Extract(map[string]any{"resource": map[string]any{"uri": "file://workspace/report.txt"}}); got != "file://workspace/report.txt" {
+		t.Fatalf("expected resource uri, got %q", got)
+	}
+	if got := Extract(map[string]any{"resource": map[string]any{"text": "", "uri": "file://workspace/fallback.txt"}}); got != "file://workspace/fallback.txt" {
+		t.Fatalf("expected resource uri fallback, got %q", got)
+	}
+}
+
+func TestJoinChunksPreservesChunkBoundaryWhitespaceAndNewlines(t *testing.T) {
+	got := JoinChunks([]any{
+		[]any{map[string]any{"text": "I'll "}},
+		[]any{map[string]any{"text": "spawn a dedicated agent for you using the"}},
+		[]any{map[string]any{"text": "\nSpritz controls.\n\nThe"}},
+		[]any{map[string]any{"text": " Slack account could not be resolved.\n"}},
+	})
+	want := "I'll spawn a dedicated agent for you using the\nSpritz controls.\n\nThe Slack account could not be resolved.\n"
+	if got != want {
+		t.Fatalf("expected %q, got %q", want, got)
+	}
+}

integrations/slack-gateway/Dockerfile

@@ -1,11 +1,16 @@
+# Build with the repository root as context so the shared local Go modules are available.
 FROM golang:1.25-alpine AS build
 
 WORKDIR /src
+COPY integrations/acptext/go.mod ./integrations/acptext/go.mod
 COPY integrations/slack-gateway/go.mod ./integrations/slack-gateway/go.mod
 COPY integrations/slack-gateway/go.sum ./integrations/slack-gateway/go.sum
 WORKDIR /src/integrations/slack-gateway
 RUN go mod download
+WORKDIR /src
+COPY integrations/acptext/ /src/integrations/acptext/
 COPY integrations/slack-gateway/ /src/integrations/slack-gateway/
+WORKDIR /src/integrations/slack-gateway
 RUN CGO_ENABLED=0 go build -o /out/spritz-slack-gateway .
 
 FROM alpine:3.20