Add Restore function for agent checkpoint recovery
Restore loads a checkpoint from the store, resolves the agent from a registry, and re-enters coreLoop. Handles suspended, nested suspended (concurrent inner restore), and awaiting-approval states. Partial progress is saved when some inner agents complete while others remain suspended. Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
This commit is contained in:
Aurélien Sibiril
354
pkg/agent/restore.go
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354
pkg/agent/restore.go
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@@ -0,0 +1,354 @@
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// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice appear in all copies.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
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// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
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// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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// PERFORMANCE OF THIS SOFTWARE.
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package agent
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import (
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"context"
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"errors"
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"fmt"
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"sync"
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"go.gearno.de/kit/log"
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"go.probo.inc/probo/pkg/llm"
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)
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// Restore continues a previously suspended or approval-interrupted agent run
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// from its last persisted checkpoint. The registry must contain all agents
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// that may have been active (including handoff targets).
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func Restore(
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ctx context.Context,
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store CheckpointStore,
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runID string,
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registry AgentRegistry,
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) (*Result, error) {
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cp, err := store.Load(ctx, runID)
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if err != nil {
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return nil, fmt.Errorf("cannot load checkpoint: %w", err)
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}
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if cp == nil {
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return nil, fmt.Errorf("cannot restore: no checkpoint for run %s", runID)
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}
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if cp.Version != CheckpointVersion {
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return nil, fmt.Errorf("cannot restore: unsupported checkpoint version %d", cp.Version)
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}
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agent, err := registry.Agent(cp.AgentName)
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if err != nil {
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return nil, fmt.Errorf("cannot resolve agent %q: %w", cp.AgentName, err)
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}
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return restoreCheckpoint(ctx, agent, cp, store, runID, registry)
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}
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func restoreCheckpoint(
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ctx context.Context,
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agent *Agent,
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cp *Checkpoint,
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store CheckpointStore,
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runID string,
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registry AgentRegistry,
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) (*Result, error) {
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if cp.Version != CheckpointVersion {
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return nil, fmt.Errorf("cannot restore: unsupported checkpoint version %d", cp.Version)
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}
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emitHook(agent, func(h RunHooks) { h.OnRunRestore(ctx, agent, cp) })
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switch cp.Status {
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case CheckpointStatusSuspended:
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return restoreSuspended(ctx, agent, cp, store, runID, registry)
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case CheckpointStatusAwaitingApproval:
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return restoreAwaitingApproval(ctx, agent, cp, store, runID, registry)
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default:
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return nil, fmt.Errorf("cannot restore: unknown checkpoint status %q", cp.Status)
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}
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}
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func restoreSuspended(
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ctx context.Context,
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agent *Agent,
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cp *Checkpoint,
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store CheckpointStore,
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runID string,
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registry AgentRegistry,
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) (*Result, error) {
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if len(cp.InnerCheckpoints) > 0 {
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return restoreNestedSuspended(ctx, agent, cp, store, runID, registry)
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}
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return continueFromMessages(ctx, agent, cp.Messages, cp, store, runID)
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}
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func continueFromMessages(
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ctx context.Context,
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agent *Agent,
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messages []llm.Message,
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cp *Checkpoint,
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store CheckpointStore,
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runID string,
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) (*Result, error) {
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messagesCopy := make([]llm.Message, len(messages))
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copy(messagesCopy, messages)
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if cp.Turns >= agent.maxTurns {
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agent.logger.WarnCtx(
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ctx,
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"restored agent run has already reached max turns",
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log.String("agent", agent.name),
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log.Int("turns", cp.Turns),
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log.Int("max_turns", agent.maxTurns),
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)
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}
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return coreLoop(
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ctx,
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agent,
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messagesCopy,
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runOpts{
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callLLM: blockingCallLLM,
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onEvent: noopEvent,
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skipInputGuardrails: true,
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skipSessionLoad: true,
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initialUsage: cp.Usage,
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initialTurns: cp.Turns,
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checkpointStore: store,
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runID: runID,
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toolUsedInRun: cp.ToolUsedInRun,
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},
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)
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}
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func restoreNestedSuspended(
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ctx context.Context,
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agent *Agent,
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cp *Checkpoint,
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store CheckpointStore,
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runID string,
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registry AgentRegistry,
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) (*Result, error) {
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type nestedRestoreEntry struct {
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toolCall llm.ToolCall
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originalCheckpoint *Checkpoint
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suspendedCheckpoint *Checkpoint
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result ToolResult
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completed bool
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err error
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}
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completedByID := make(map[string]ToolResult, len(cp.CompletedCalls))
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for _, cc := range cp.CompletedCalls {
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completedByID[cc.ToolCallID] = cc.Result
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}
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entries := make([]nestedRestoreEntry, len(cp.AllToolCalls))
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var wg sync.WaitGroup
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for i, tc := range cp.AllToolCalls {
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entries[i].toolCall = tc
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result, ok := completedByID[tc.ID]
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if ok {
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entries[i].result = result
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entries[i].completed = true
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continue
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}
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innerCP, ok := cp.InnerCheckpoints[tc.ID]
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if !ok {
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entries[i].err = fmt.Errorf("cannot restore nested tool call %q: missing inner checkpoint", tc.ID)
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continue
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}
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entries[i].originalCheckpoint = innerCP
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innerAgent, err := registry.Agent(innerCP.AgentName)
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if err != nil {
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entries[i].err = fmt.Errorf("cannot resolve inner agent %q: %w", innerCP.AgentName, err)
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continue
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}
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wg.Add(1)
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go func(i int, tc llm.ToolCall, innerAgent *Agent, innerCP *Checkpoint) {
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defer wg.Done()
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result, err := restoreCheckpoint(ctx, innerAgent, innerCP, nil, "", registry)
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if err != nil {
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if se, ok := errors.AsType[*SuspendedError](err); ok {
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if se.Checkpoint == nil {
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entries[i].err = fmt.Errorf("cannot restore nested tool call %q: missing suspension checkpoint", tc.ID)
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return
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}
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entries[i].suspendedCheckpoint = se.Checkpoint
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return
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}
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entries[i].err = fmt.Errorf("cannot restore nested tool call %q: %w", tc.ID, err)
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return
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}
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entries[i].result = ToolResult{Content: result.FinalMessage().Text()}
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entries[i].completed = true
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}(i, tc, innerAgent, innerCP)
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}
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wg.Wait()
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messages := make([]llm.Message, len(cp.Messages))
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copy(messages, cp.Messages)
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completedCalls := make([]CompletedCall, 0, len(cp.AllToolCalls))
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remainingInner := make(map[string]*Checkpoint)
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var restoreErr error
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for _, entry := range entries {
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switch {
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case entry.err != nil:
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if entry.originalCheckpoint != nil {
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remainingInner[entry.toolCall.ID] = entry.originalCheckpoint
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}
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if restoreErr == nil {
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restoreErr = entry.err
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}
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continue
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case entry.suspendedCheckpoint != nil:
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remainingInner[entry.toolCall.ID] = entry.suspendedCheckpoint
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continue
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case !entry.completed:
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if restoreErr == nil {
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restoreErr = fmt.Errorf("cannot restore nested tool call %q: no result", entry.toolCall.ID)
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}
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continue
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}
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completedCalls = append(
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completedCalls,
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CompletedCall{
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ToolCallID: entry.toolCall.ID,
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Result: entry.result,
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},
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)
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messages = append(
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messages,
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llm.Message{
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Role: llm.RoleTool,
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ToolCallID: entry.toolCall.ID,
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Parts: []llm.Part{llm.TextPart{Text: entry.result.Content}},
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},
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)
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}
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saveProgress := func() (*Checkpoint, error) {
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next := *cp
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next.InnerCheckpoints = remainingInner
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next.CompletedCalls = completedCalls
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if store != nil && runID != "" {
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if err := store.Save(ctx, runID, &next); err != nil {
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return nil, fmt.Errorf("cannot save nested restore progress: %w", err)
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}
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}
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return &next, nil
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}
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if restoreErr != nil {
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if _, err := saveProgress(); err != nil {
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return nil, errors.Join(restoreErr, err)
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}
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return nil, restoreErr
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}
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if len(remainingInner) > 0 {
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next, err := saveProgress()
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if err != nil {
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return nil, err
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}
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return nil, &SuspendedError{RunID: runID, Checkpoint: next}
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}
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return continueFromMessages(ctx, agent, messages, cp, store, runID)
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}
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func restoreAwaitingApproval(
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ctx context.Context,
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agent *Agent,
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cp *Checkpoint,
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store CheckpointStore,
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runID string,
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registry AgentRegistry,
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) (*Result, error) {
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// Reconstruct an InterruptedError from the checkpoint.
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ie := &InterruptedError{
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ToolCalls: cp.PendingToolCalls,
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PendingApprovals: cp.PendingApprovals,
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Agent: agent,
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Messages: cp.Messages,
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Usage: cp.Usage,
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Turns: cp.Turns,
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}
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// Reconstruct outerState if this was a nested interruption.
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if len(cp.InnerCheckpoints) > 0 {
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if len(cp.InnerCheckpoints) > 1 {
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return nil, fmt.Errorf("cannot restore approval checkpoint: expected one inner checkpoint, got %d", len(cp.InnerCheckpoints))
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}
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for toolCallID, innerCP := range cp.InnerCheckpoints {
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innerAgent, err := registry.Agent(innerCP.AgentName)
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if err != nil {
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return nil, fmt.Errorf("cannot resolve inner agent %q: %w", innerCP.AgentName, err)
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}
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innerIE := &InterruptedError{
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ToolCalls: innerCP.PendingToolCalls,
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PendingApprovals: innerCP.PendingApprovals,
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Agent: innerAgent,
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Messages: innerCP.Messages,
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Usage: innerCP.Usage,
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Turns: innerCP.Turns,
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}
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ie.Agent = innerAgent
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ie.Messages = innerCP.Messages
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ie.Usage = innerCP.Usage
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ie.Turns = innerCP.Turns
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ie.ToolCalls = innerCP.PendingToolCalls
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ie.PendingApprovals = innerCP.PendingApprovals
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ie.outerState = &outerLoopState{
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agent: agent,
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messages: cp.Messages,
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usage: cp.Usage,
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turns: cp.Turns,
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allToolCalls: cp.AllToolCalls,
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toolCallID: toolCallID,
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completedCalls: cp.CompletedCalls,
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innerInterrupt: innerIE,
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}
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break
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}
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}
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if len(cp.ApprovalInput) > 0 {
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return resumeWithOpts(
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ctx,
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ie,
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ResumeInput{Approvals: cp.ApprovalInput},
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runOpts{
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callLLM: blockingCallLLM,
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onEvent: noopEvent,
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checkpointStore: store,
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runID: runID,
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toolUsedInRun: cp.ToolUsedInRun,
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},
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)
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}
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return nil, ie
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}
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