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fix(#1644): enforce Anthropic tool sequencing and filter sub-agent messages #1880

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03a585a
provider/anthropic: enforce tool sequencing, remove self-repair/valid…
rumpl Feb 10, 2026
237b006
fix(session): filter sub-agent messages in GetMessages to prevent too…
aheritier Feb 15, 2026
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116 changes: 0 additions & 116 deletions pkg/model/provider/anthropic/beta_client.go
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,14 +43,6 @@ func (c *Client) createBetaStream(
slog.Error("Failed to convert messages for Anthropic Beta request", "error", err)
return nil, err
}
if err := validateAnthropicSequencingBeta(converted); err != nil {
slog.Warn("Invalid message sequencing for Anthropic Beta API detected, attempting self-repair", "error", err)
converted = repairAnthropicSequencingBeta(converted)
if err2 := validateAnthropicSequencingBeta(converted); err2 != nil {
slog.Error("Failed to self-repair Anthropic Beta sequencing", "error", err2)
return nil, err
}
}
if len(converted) == 0 {
return nil, errors.New("no messages to send after conversion: all messages were filtered out")
}
Expand Down Expand Up @@ -149,114 +141,6 @@ func (c *Client) createBetaStream(
return ad, nil
}

// validateAnthropicSequencingBeta performs the same validation as standard API but for Beta payloads
func validateAnthropicSequencingBeta(msgs []anthropic.BetaMessageParam) error {
for i := range msgs {
m, ok := marshalToMapBeta(msgs[i])
if !ok || m["role"] != "assistant" {
continue
}

toolUseIDs := collectToolUseIDs(contentArrayBeta(m))
if len(toolUseIDs) == 0 {
continue
}

if i+1 >= len(msgs) {
slog.Warn("Anthropic (beta) sequencing invalid: assistant tool_use present but no next user tool_result message", "assistant_index", i)
return errors.New("assistant tool_use present but no subsequent user message with tool_result blocks (beta)")
}

next, ok := marshalToMapBeta(msgs[i+1])
if !ok || next["role"] != "user" {
slog.Warn("Anthropic (beta) sequencing invalid: next message after assistant tool_use is not user", "assistant_index", i, "next_role", next["role"])
return errors.New("assistant tool_use must be followed by a user message containing corresponding tool_result blocks (beta)")
}

toolResultIDs := collectToolResultIDs(contentArrayBeta(next))
missing := differenceIDs(toolUseIDs, toolResultIDs)
if len(missing) > 0 {
slog.Warn("Anthropic (beta) sequencing invalid: missing tool_result for tool_use id in next user message", "assistant_index", i, "tool_use_id", missing[0], "missing_count", len(missing))
return fmt.Errorf("missing tool_result for tool_use id %s in the next user message (beta)", missing[0])
}
}
return nil
}

// repairAnthropicSequencingBeta inserts a synthetic user message with tool_result blocks
// for any assistant tool_use blocks that don't have corresponding tool_result blocks
// in the immediate next user message.
func repairAnthropicSequencingBeta(msgs []anthropic.BetaMessageParam) []anthropic.BetaMessageParam {
if len(msgs) == 0 {
return msgs
}
repaired := make([]anthropic.BetaMessageParam, 0, len(msgs)+2)
for i := range msgs {
m, ok := marshalToMapBeta(msgs[i])
if !ok || m["role"] != "assistant" {
repaired = append(repaired, msgs[i])
continue
}

toolUseIDs := collectToolUseIDs(contentArrayBeta(m))
if len(toolUseIDs) == 0 {
repaired = append(repaired, msgs[i])
continue
}

// Check if the next message is a user message with tool_results
needsSyntheticMessage := true
if i+1 < len(msgs) {
if next, ok := marshalToMapBeta(msgs[i+1]); ok && next["role"] == "user" {
toolResultIDs := collectToolResultIDs(contentArrayBeta(next))
// Remove tool_use IDs that have corresponding tool_results
for id := range toolResultIDs {
delete(toolUseIDs, id)
}
// If all tool_use IDs have results, no synthetic message needed
if len(toolUseIDs) == 0 {
needsSyntheticMessage = false
}
}
}

// Append the assistant message first
repaired = append(repaired, msgs[i])

// If there are missing tool_results, insert a synthetic user message immediately after
if needsSyntheticMessage && len(toolUseIDs) > 0 {
slog.Debug("Inserting synthetic user message for missing tool_results",
"assistant_index", i,
"missing_count", len(toolUseIDs))

blocks := make([]anthropic.BetaContentBlockParamUnion, 0, len(toolUseIDs))
for id := range toolUseIDs {
slog.Debug("Creating synthetic tool_result", "tool_use_id", id)
blocks = append(blocks, anthropic.BetaContentBlockParamUnion{
OfToolResult: &anthropic.BetaToolResultBlockParam{
ToolUseID: id,
Content: []anthropic.BetaToolResultBlockParamContentUnion{
{OfText: &anthropic.BetaTextBlockParam{Text: "(tool execution failed)"}},
},
},
})
}
repaired = append(repaired, anthropic.BetaMessageParam{
Role: anthropic.BetaMessageParamRoleUser,
Content: blocks,
})
}
}
return repaired
}

// marshalToMapBeta is an alias for marshalToMap - shared with standard API.
// Kept as separate function for clarity in Beta-specific code paths.
var marshalToMapBeta = marshalToMap

// contentArrayBeta is an alias for contentArray - shared with standard API.
var contentArrayBeta = contentArray

// countAnthropicTokensBeta calls Anthropic's Count Tokens API for the provided Beta API payload
// and returns the number of input tokens.
func countAnthropicTokensBeta(
Expand Down
73 changes: 48 additions & 25 deletions pkg/model/provider/anthropic/beta_converter.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ import (
// blocks from the same assistant message MUST be grouped into a single user message.
func (c *Client) convertBetaMessages(ctx context.Context, messages []chat.Message) ([]anthropic.BetaMessageParam, error) {
var betaMessages []anthropic.BetaMessageParam
var pendingToolUseIDs map[string]struct{}

for i := 0; i < len(messages); i++ {
msg := &messages[i]
Expand Down Expand Up @@ -75,11 +76,15 @@ func (c *Client) convertBetaMessages(ctx context.Context, messages []chat.Messag

// Add tool calls
if len(msg.ToolCalls) > 0 {
pendingToolUseIDs = make(map[string]struct{}, len(msg.ToolCalls))
for _, toolCall := range msg.ToolCalls {
var inpts map[string]any
if err := json.Unmarshal([]byte(toolCall.Function.Arguments), &inpts); err != nil {
inpts = map[string]any{}
}
if toolCall.ID != "" {
pendingToolUseIDs[toolCall.ID] = struct{}{}
}
contentBlocks = append(contentBlocks, anthropic.BetaContentBlockParamUnion{
OfToolUse: &anthropic.BetaToolUseBlockParam{
ID: toolCall.ID,
Expand All @@ -88,6 +93,8 @@ func (c *Client) convertBetaMessages(ctx context.Context, messages []chat.Messag
},
})
}
} else {
pendingToolUseIDs = nil
}

if len(contentBlocks) > 0 {
Expand All @@ -102,38 +109,54 @@ func (c *Client) convertBetaMessages(ctx context.Context, messages []chat.Messag
// Collect consecutive tool messages and merge them into a single user message
// This is required by Anthropic API: all tool_result blocks for tool_use blocks
// from the same assistant message must be in the same user message
toolResultBlocks := []anthropic.BetaContentBlockParamUnion{
{
OfToolResult: &anthropic.BetaToolResultBlockParam{
ToolUseID: msg.ToolCallID,
Content: []anthropic.BetaToolResultBlockParamContentUnion{
{OfText: &anthropic.BetaTextBlockParam{Text: strings.TrimSpace(msg.Content)}},
},
},
},
if pendingToolUseIDs == nil {
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Beta converter silently drops orphan tool results while regular converter returns error

When pendingToolUseIDs == nil (indicating no preceding assistant tool_use in the current window), the beta converter silently skips tool messages without validation (lines 112-120). However, the regular converter in client.go:457-459 explicitly returns an error for this exact scenario:

if pendingToolUseIDs == nil {
    return nil, fmt.Errorf("unexpected tool result without preceding tool_use (tool_use_id=%q)", messages[i].ToolCallID)
}

Issue: This inconsistency violates the PR's stated goal of "strict enforcement" and "removing self-repair". Orphan tool results are a protocol violation per Anthropic's requirements — they should be caught and reported in both converters, not silently dropped in one.

Impact: Malformed message sequences (e.g., assistant with no tool calls followed by tool results) pass through undetected in the beta API path, potentially causing downstream issues or silent data loss.

Recommendation: Change the beta converter to return an error like the regular converter does, maintaining consistent strict validation across both API paths.

// Orphan tool results (no preceding assistant tool_use in this window): drop them.
j := i
for j < len(messages) && messages[j].Role == chat.MessageRoleTool {
j++
}
i = j - 1
continue
}

// Look ahead for consecutive tool messages and merge them
j := i + 1
toolResultBlocks := make([]anthropic.BetaContentBlockParamUnion, 0)
hadToolMessages := false
j := i
for j < len(messages) && messages[j].Role == chat.MessageRoleTool {
toolResultBlocks = append(toolResultBlocks, anthropic.BetaContentBlockParamUnion{
OfToolResult: &anthropic.BetaToolResultBlockParam{
ToolUseID: messages[j].ToolCallID,
Content: []anthropic.BetaToolResultBlockParamContentUnion{
{OfText: &anthropic.BetaTextBlockParam{Text: strings.TrimSpace(messages[j].Content)}},
},
},
})
hadToolMessages = true
id := messages[j].ToolCallID
if id != "" {
if _, ok := pendingToolUseIDs[id]; ok {
toolResultBlocks = append(toolResultBlocks, anthropic.BetaContentBlockParamUnion{
OfToolResult: &anthropic.BetaToolResultBlockParam{
ToolUseID: id,
Content: []anthropic.BetaToolResultBlockParamContentUnion{
{OfText: &anthropic.BetaTextBlockParam{Text: strings.TrimSpace(messages[j].Content)}},
},
},
})
delete(pendingToolUseIDs, id)
}
}
j++
}

// Add the merged user message with all tool results
betaMessages = append(betaMessages, anthropic.BetaMessageParam{
Role: anthropic.BetaMessageParamRoleUser,
Content: toolResultBlocks,
})
if hadToolMessages && len(toolResultBlocks) == 0 {
return nil, fmt.Errorf("tool_result messages present but none match pending tool_use ids (beta converter)")
}
if len(pendingToolUseIDs) > 0 {
for id := range pendingToolUseIDs {
return nil, fmt.Errorf("missing tool_result for tool_use id %s (beta converter)", id)
}
}

// Skip the messages we've already processed
if len(toolResultBlocks) > 0 {
betaMessages = append(betaMessages, anthropic.BetaMessageParam{
Role: anthropic.BetaMessageParamRoleUser,
Content: toolResultBlocks,
})
}
pendingToolUseIDs = nil
i = j - 1
continue
}
Expand Down
61 changes: 41 additions & 20 deletions pkg/model/provider/anthropic/beta_converter_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package anthropic

import (
"encoding/json"
"testing"

"github.com/stretchr/testify/assert"
Expand All @@ -10,6 +11,39 @@ import (
"github.com/docker/cagent/pkg/tools"
)

func marshalToMapBeta(t *testing.T, v any) map[string]any {
t.Helper()
b, err := json.Marshal(v)
require.NoError(t, err)
var m map[string]any
require.NoError(t, json.Unmarshal(b, &m))
return m
}

func contentArrayBeta(m map[string]any) []any {
if a, ok := m["content"].([]any); ok {
return a
}
return nil
}

func collectToolResultIDsBeta(content []any) map[string]struct{} {
ids := make(map[string]struct{})
for _, c := range content {
cb, ok := c.(map[string]any)
if !ok {
continue
}
if cb["type"] != "tool_result" {
continue
}
if id, _ := cb["tool_use_id"].(string); id != "" {
ids[id] = struct{}{}
}
}
return ids
}

func TestConvertBetaMessages_MergesConsecutiveToolMessages(t *testing.T) {
// Simulates the roast battle scenario where:
// - Assistant message has 2 tool_use blocks (transfer_task calls)
Expand Down Expand Up @@ -65,27 +99,22 @@ func TestConvertBetaMessages_MergesConsecutiveToolMessages(t *testing.T) {

require.Len(t, betaMessages, 4, "Should have 4 messages after conversion")

msg0Map, _ := marshalToMapBeta(betaMessages[0])
msg1Map, _ := marshalToMapBeta(betaMessages[1])
msg2Map, _ := marshalToMapBeta(betaMessages[2])
msg3Map, _ := marshalToMapBeta(betaMessages[3])
msg0Map := marshalToMapBeta(t, betaMessages[0])
msg1Map := marshalToMapBeta(t, betaMessages[1])
msg2Map := marshalToMapBeta(t, betaMessages[2])
msg3Map := marshalToMapBeta(t, betaMessages[3])
assert.Equal(t, "user", msg0Map["role"])
assert.Equal(t, "assistant", msg1Map["role"])
assert.Equal(t, "user", msg2Map["role"])
assert.Equal(t, "assistant", msg3Map["role"])

userMsg2Map, ok := marshalToMapBeta(betaMessages[2])
require.True(t, ok)
userMsg2Map := marshalToMapBeta(t, betaMessages[2])
content := contentArrayBeta(userMsg2Map)
require.Len(t, content, 2, "User message should have 2 tool_result blocks")

toolResultIDs := collectToolResultIDs(content)
toolResultIDs := collectToolResultIDsBeta(content)
assert.Contains(t, toolResultIDs, "tool_call_1")
assert.Contains(t, toolResultIDs, "tool_call_2")

// Most importantly: validate that the sequence is valid for Anthropic API
err = validateAnthropicSequencingBeta(betaMessages)
require.NoError(t, err, "Converted messages should pass Anthropic sequencing validation")
}

func TestConvertBetaMessages_SingleToolMessage(t *testing.T) {
Expand Down Expand Up @@ -123,10 +152,6 @@ func TestConvertBetaMessages_SingleToolMessage(t *testing.T) {
betaMessages, err := testClient().convertBetaMessages(t.Context(), messages)
require.NoError(t, err)
require.Len(t, betaMessages, 4)

// Validate sequence
err = validateAnthropicSequencingBeta(betaMessages)
require.NoError(t, err)
}

func TestConvertBetaMessages_NonConsecutiveToolMessages(t *testing.T) {
Expand Down Expand Up @@ -181,10 +206,6 @@ func TestConvertBetaMessages_NonConsecutiveToolMessages(t *testing.T) {
},
}

betaMessages, err := testClient().convertBetaMessages(t.Context(), messages)
_, err := testClient().convertBetaMessages(t.Context(), messages)
require.NoError(t, err)

// Validate the entire sequence
err = validateAnthropicSequencingBeta(betaMessages)
require.NoError(t, err, "Messages with non-consecutive tool calls should still validate")
}
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