git:20261018.0fdf6be to git:20261019.2f1c8b3

2 added, 2 removed. Audit A to A.

---

name: execution

description: Phase execution methodology for orchestration workflows with error handling and completion protocols

---

# Execution Skill

Activate this skill during Phase 3 (Execution) of Maestro orchestration. This skill defines how Maestro executes implementation phases through native subagent delegation.

## Execution Mode Gate

### Step 0 — Express bypass (early return)

If `workflow_mode` is `express` in the current session, STOP HERE. Do not proceed

to the execution mode gate. Do not prompt the user. Do not resolve execution mode.

Express always dispatches sequentially. Return to the Express Workflow and continue

from the delegation step.

<HARD-GATE>

This gate MUST resolve before ANY delegation proceeds. Do not skip it. Do not defer it. Do not begin delegating to subagents until execution_mode is recorded in session state. If you reach a delegation step and execution_mode is not set, STOP and return here. Do not default to sequential.

</HARD-GATE>

### Recording the mode

If no session exists yet (orchestrate step 21, or `/maestro:execute` before session creation), pass `execution_mode` to `create_session`, which sets `execution_backend: 'native'` itself. If a session already exists (resume), call `update_session` with `{ execution_mode, execution_backend: 'native' }`.

### Step 1 — Read the configured mode

Read `MAESTRO_EXECUTION_MODE` (default: `ask`).

- If `parallel`: record `parallel` (see Recording the mode). Skip to delegation.

- If `sequential`: record `sequential` (see Recording the mode). Skip to delegation.

- If `ask`: proceed to Step 2.

### Step 2 — Analyze the implementation plan

Before prompting the user, analyze the approved plan to generate a recommendation:

1. Count total phases in the plan

2. Count phases marked `parallel: true` (parallelizable phases)

3. Count distinct parallel batches (groups of parallelizable phases at the same dependency depth)

4. Count sequential-only phases (phases with `blocked_by` dependencies that prevent parallelization)

5. Cross-check file ownership across all phases. If any two phases share a file in their `files` arrays, those phases CANNOT be parallel-eligible — subtract them from the parallelizable count. Report each overlap as an overlapping-file warning in the Step 4 question.

6. If `validate_plan` was called during planning and returned a `parallelization_profile`, use its `parallel_eligible` and `effective_batches` counts as the authoritative source for items 1-5 above. These are computed from actual dependency depths and override any manual flag-based counts. If `parallelization_profile` is not available, use the counts from items 1-5 as-is.

Record these counts — they feed into the prompt.

### Step 3 — Determine the recommendation

- If parallelizable phases ≤ 1 → auto-select **sequential**. Record `sequential` (see Recording the mode). Inform the user: "All phases are sequential — no parallel batches available." Skip to delegation. Do NOT prompt with a choice. Do NOT call `ask_user`. Do NOT present options. (Parallelism requires at least 2 phases at the same dependency depth; a single parallel-eligible phase has nothing to batch with.)

<ANTI-PATTERN>

WRONG — 1 parallel-eligible phase but user still prompted:

Parallel-eligible Phases: 1

→ Presented choice: "Sequential (Recommended)" / "Parallel"

When parallelizable phases ≤ 1, there is NO choice to make. Auto-select sequential

and skip directly to delegation. Do not show a picker.

</ANTI-PATTERN>

- If parallelizable phases > 50% of total phases → recommend **parallel**

- If parallelizable phases ≤ 50% but > 1 → recommend **sequential** (limited benefit)

- The recommended option appears first in the `ask_user` options list with "(Recommended)" appended to its label. The non-recommended option MUST NOT include "(Recommended)" in its label.

### Step 4 — Prompt the user

Call `ask_user` as a single-choice prompt using exactly one of these option sets:

**When recommending parallel:**

options:

- label: "Parallel (Recommended)"

description: "Spawn child agents for each ready batch where file ownership does not overlap."

- label: "Sequential (High Precision)"

description: "Spawn one child agent at a time in dependency order."

**When recommending sequential:**

options:

- label: "Sequential (Recommended)"

description: "Spawn one child agent at a time in dependency order."

- label: "Parallel"

description: "Spawn child agents for each ready batch where file ownership does not overlap."

<ANTI-PATTERN>

WRONG — Both options labeled "(Recommended)":

options:

- label: "Parallel (Recommended)"

- label: "Sequential (High Precision) (Recommended)"

Only ONE option receives the "(Recommended)" suffix. Never both.

</ANTI-PATTERN>

Prompt using the user-prompt tool from runtime context; in the question text, state the Step 2 counts (parallelizable phases out of total, number of batches) and any overlapping-file warnings.

### Step 5 — Record and proceed

1. Record the selected `execution_mode` (see Recording the mode)

2. Use the selected mode for the remainder of the session unless the user changes it

### Mode-specific behavior

- If `parallel` is selected and a ready batch has only one phase, execute it sequentially

- If `sequential` is selected, preserve plan order even when phases are parallel-safe

## Sequential Execution Protocol

For a sequential phase:

1. Verify all `blocked_by` dependencies are completed

2. Mark the phase `in_progress`

3. Update `current_phase`

4. Set `current_batch: null`

5. Update the progress-tracking tool (use the tool names from `get_runtime_context`) before delegation

6. Delegate to the assigned agent with the required header and full context

7. Parse the returned handoff

8. Update session state

9. Mark the phase `completed` or `failed`

10. Update the progress-tracking tool after the state update

## Native Parallel Execution Protocol

Use native parallel execution only for sibling phases at the same dependency depth with non-overlapping file ownership.

### Batch Rules

1. Verify all blocking phases for every phase in the batch are completed

2. Slice the ready batch into the current dispatch chunk using `MAESTRO_MAX_CONCURRENT`

3. Mark only the current chunk phases `in_progress`

4. Set `current_batch` in session state for that chunk

5. Write one in-progress todo item for the chunk

6. In the next turn, emit only agent tool calls for that chunk

7. Do not mix shell commands, validation commands, file writes, or narration between those agent calls

8. `MAESTRO_MAX_CONCURRENT=0` means emit the entire ready batch in one turn

### Native Constraints

- The runtime only parallelizes contiguous agent calls in one turn

- Native subagents currently run without user approval gates

- `ask_user` remains available; a batch may pause while waiting for user input

- If execution is interrupted, restart unfinished `in_progress` phases on resume instead of attempting to restore in-flight subagent interactions

## Error Handling Protocol

Record all errors in session state using the session-management Error Recording Format.

### Retry Logic

- Maximum retries per phase: `MAESTRO_MAX_RETRIES` (default `2`)

- First failure: analyze, adjust context/scope, retry automatically

- Subsequent failures up to the limit: continue retrying with clearer constraints

- Limit exceeded: mark the phase `failed` and escalate to the user

### Recovery Protocol

- When a subagent terminates early, times out, returns malformed output, or when `delegation.constraints.result_surface` is `deferred` and the agent's text cannot be retrieved:

+ When a subagent terminates early, times out, returns malformed output, or when `delegation.constraints.result_surface` is `deferred` or `notified` and the agent's text cannot be retrieved:

- 1. **Poll**: For deferred-result runtimes (Codex), call the runtime's wait tool (`wait_agent` equivalent) with a bounded timeout. For synchronous runtimes, the initial dispatch return IS the result.

+ 1. **Poll**: For deferred-result runtimes (Codex), call the runtime's wait tool (`wait_agent` equivalent) with a bounded timeout. For notified-result runtimes (Antigravity), the child's final response arrives as a message; there is nothing to poll, so if it never arrives, list the runtime's subagents (`manage_subagents` with `Action: "list"`) to check whether the child is still running. For synchronous runtimes, the initial dispatch return IS the result.

2. **Detect drift**: Call `scan_phase_changes(session_id, phase_id)`. If the returned `candidates.created` or `candidates.modified` arrays are non-empty, the agent produced filesystem output without a handoff.

3. **Ask the user to confirm**: Using the runtime's user-prompt tool, present the scan candidates and ask the user to confirm which files belong to this phase. For a parallel batch, include the `planned_files` from each phase's session state to assist attribution. If the scan surfaces files beyond any phase's `planned_files`, raise a blocker and surface the ambiguity to the user rather than silently attributing.

4. **Reconcile**: Call `reconcile_phase(session_id, phase_id, files_created, files_modified, files_deleted, downstream_context, reason)` with the user-confirmed manifest. This clears `requires_reconciliation`.

5. **Retry or advance**: If the user chose to retry the agent, re-delegate with the original scope plus the scan results as context. If the user accepted the work as delivered, advance to the next phase.

Record all recovery events in session state with `{agent, timestamp, type: 'recovery', resolution: 'retry'|'reconciled'|'aborted'}`.

### File Conflict Handling

When a subagent reports a file conflict:

1. Stop execution immediately

2. Record the conflicting files and phases

3. Do not attempt automatic merge resolution

4. Ask the user how to proceed

## Subagent Output Processing

Native subagent results are wrapped. Do not assume the handoff begins at byte 0.

### Parsing Rules

1. Locate `## Task Report` (or `# Task Report`) inside the returned text

2. Locate `## Downstream Context` (or `# Downstream Context`) inside the returned text

3. Parse:

- status

- files created / modified / deleted

- downstream context fields

- validation result

- reported errors

4. Persist the full raw output plus the parsed fields into session state

### State Update Sequence

After processing each handoff:

1. Update the phase file manifests

2. Update `downstream_context`

3. Append any errors

4. Aggregate token usage

5. If validation passed, mark the phase `completed`

6. If validation failed, trigger retry logic

7. Update `updated`

8. Advance or clear `current_batch` as each chunk finishes

## Completion Protocol

When all phases are completed:

1. Verify there are no `failed` or `pending` phases

2. Confirm plan deliverables are accounted for

3. Run the final code-review gate for non-documentation changes

4. Archive the session through `session-management`

5. Present a final summary with deliverables, files changed, token usage, deviations, and review status