The Parallel Trials of Mythos

[!NOTE] Status: Content ready · Media: Generated cover and original SVG illustration · Last verified: 2026-09-05
Primary capability: Coordinating independent agents

[!TIP] Download this learner kit and use the extraction and setup guide. Keep the original starter untouched.

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flowchart TD
    accTitle: The Parallel Trials of Mythos capability map
    accDescr: Parallel execution is useful only when dependencies and ownership permit it. A failed task remains visible in the evidence.
    V["Validate all tasks"] --> A["Task 0"]
    V --> B["Task 1"]
    V --> C["Task 2"]
    A --> R["Collect settled results"]
    B --> R
    C --> R
    R --> O["Return in input order"]

Legend. The fan-out denotes independent starts; the fan-in collects outcomes without changing assignment order.

Explanation. Parallel execution is useful only when dependencies and ownership permit it. A failed task remains visible in the evidence.

Official references

These official sources are the authority for product behavior and availability. Recheck them when using a different surface or after a product update.

• Run subagents
• Manage agent sessions
• Git branches and worktrees

Story

Mythos offers three trials at once, but echoes punish parties that send multiple heroes down the same corridor.

The fantasy is a memory aid; the engineering lesson requires observable, reproducible evidence.

Learning objectives

• Start independent task functions before awaiting completion.
• Preserve input order while recording successful and failed results separately.
• Validate every task before starting any and distinguish process concurrency from isolated agent ownership.

Prerequisites

For tools and personal accounts, complete the prerequisites guide. For terminal-only study, follow the extracted-kit CLI route; VS Code-specific evidence remains separate.

Evidence boundary: JavaScript task concurrency is not proof of isolated agent sessions or worktrees. Those require separate ownership and environment evidence.

Estimated session: 45–75 minutes after prerequisites; actual duration varies. Never use production secrets or customer data.

Concept explanation

Parallel agents are appropriate when tasks are independent, inputs and outputs are clear, and workers do not edit the same files or repeat the same investigation. No speedup is assumed. A coordinator owns decomposition, shared constraints, dependency order, integration, and final verification. Workers return evidence and unresolved questions, not confidence alone.

Concrete use case

Three runes can begin together even if the middle rune fails. The report still follows the original assignment order, so a reviewer can attribute each result.

Vocabulary checkpoint

• Role: Ask, Plan, Agent, or a custom agent.
• Harness/surface: the runtime or product surface in which a role operates.
• Target: the selected session destination, such as Local, Copilot, or Cloud where exposed.
• Environment: the folder, worktree, local machine, Codespace, or remote environment.
• Instructions: automatically applied durable context.
• Prompt: a manually invoked task template.
• Skill: reusable expertise loaded when relevant.
• Custom agent: a role with instructions, tools, and optional handoffs.
• MCP: Model Context Protocol.
• Evidence: a path, diff, command result, trace, or review decision.

Ask → Plan → Agent workflow

Ask — investigate

1. Identify the real user outcome and current source of truth.
2. Inspect relevant files, instructions, tools, permissions, and existing checks.
3. Cite concrete paths or platform evidence for every important finding.
4. Record uncertainty and do not infer unavailable capabilities.

Gate: No implementation until the current state and evidence are understood.

Plan — design

1. State scope, non-goals, assumptions, risks, and trust boundaries.
2. Select the minimum role, tools, authority, and environment.
3. Define acceptance criteria, verification commands, review, and reset.
4. Mark any Preview or experimental dependency and provide a fallback.

Gate: Another learner should be able to predict completion from the plan.

Agent — execute

1. Make the smallest reversible change or produce the planned artifact.
2. Use short inspect → change → verify loops.
3. Preserve command output, exit status, diffs, traces, or platform records.
4. Stop when acceptance criteria are met; do not perform unrelated cleanup.

Review — challenge

1. Inspect the complete diff or artifact.
2. Compare each result with the plan and acceptance criteria.
3. Run the narrowest relevant existing check, broadening only when justified.
4. Record limitations and unresolved risks.
5. Score the work with rubric.md.

Guided mission

1. Prepare one isolated copy

1. Download and extract the mythos-parallel kit into a new work-drive directory.
2. Read KIT-START.md at its root. Open starter/ as the VS Code workspace when testing discovery, but run the verifier from the kit root.
3. Inspect starter/parallel.js, verify.js before editing.
4. From the extracted kit root, run node verify.js.
5. Record the documented starter rejection. A missing runtime or unrelated crash is not the expected exercise result.

2. Investigate and plan

Copyable baseline command, from the extracted kit root:

node verify.js

In Ask, request a trace of the inspected files and what the verifier actually observes. Challenge any claim about live execution that is not supported by output.

Use this planning prompt:

Validate the whole task list before invoking any function. Define fulfilled/rejected result records, start all tasks and preserve original indexes in the final array.
Do not implement yet. Identify affected files, the negative case and a safe reset.

3. Implement the reviewed slice

1. Approve only the named starter artifact and necessary focused tests.
2. Ask Agent to implement one slice; inspect proposed commands before execution.
3. Run node verify.js again from the kit root, or node ../verify.js from starter/.
4. Compare the exact result with the checkpoint below and review the complete diff.
5. Record host discovery or live activity separately when available. Do not enable extra services to manufacture a passing result.

[!IMPORTANT] Checkpoint: All three tasks start before the release gate; a failed task is represented without losing successful results. JavaScript task concurrency is not proof of isolated agent sessions or worktrees. Those require separate ownership and environment evidence.

4. Prove a check can reject a mistake

Await each task inside the start loop and observe the verifier reject sequential startup. Restore concurrent startup.

Finish with the adventure-specific capability evidence in the rubric, not just the presence of a file.

Intentional failure: The Echoing Corridor

Perform this only in a disposable environment:

Assign two agents to the same file and goal. Duplicate findings and conflicting edits add coordination cost without planned independent replication.

Recovery

Return to Ask, identify the violated boundary, narrow the plan, remove unnecessary authority or context, and repeat the smallest relevant verification. Document the causal lesson rather than merely stating that the attempt failed.

Independent challenge

Design a three-worker plan with one dependency edge, one parallel pair, and a final integration gate.

Constraints:

• Do not copy the guided mission verbatim.
• Do not add tools, permissions, or cloud resources without a stated need.
• Do not claim quality, performance, compatibility, or availability without executed evidence.
• Keep fantasy language subordinate to technical clarity.

Evidence checklist

• Source-grounded Ask findings.
• Approved plan with scope, non-goals, risks, checks, and reset.
• Agent diff or artifact limited to the declared scope.
• Verification output with command, status, or platform record.
• Intentional-failure root cause and recovery.
• Independent challenge result.
• Explicit limitations and feature-status notes.
• Completed rubric.md.

Reset instructions

1. Save your diff, command output and limitations from the disposable kit.
2. Stop only the process or learning session you started. Do not stop other projects.
3. If you initialized Git in the kit, inspect git status --short there and restore only your named exercise files from its local baseline.
4. Otherwise, extract the original ZIP into a new unused directory for another attempt; do not overwrite your current work.
5. Remove only exercise-owned configurations, worktrees or remote resources after reviewing anything worth preserving.

The curriculum source and other projects must remain unchanged. A reset of the copied kit is not a repository-wide hard reset.

Next adventure

The Cloud Citadel