agentmods.dev

session-source-fork

A guide for starting a new managed agent session from an earlier conversation by creating a fork, or a separate continuation based on that source.

In plain words
What is it for?
Use it when writing rig members or expansion requests that need a new Claude or Codex seat based on a prior native session.
Why use it?
It clarifies when to create a new session instead of restoring the old one or rebuilding context from saved work.

Skill for Claude CodeCodex

64 2d ago A scan 110 tokens original Apache-2.0
View the source file mvschwarz/openrig
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/mvschwarz/openrig/session-source-fork
Any agent
npx skills add mvschwarz/openrig --skill session-source-fork
Clone the repo
git clone --depth 1 https://github.com/mvschwarz/openrig

Made for: Claude Code, Codex.

Per session 110 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,143 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00110 $0.02143
Opus 5 $0.00055 $0.01071
Sonnet 5 $0.00022 $0.00429
Haiku 4.5 $0.00011 $0.00214

Measured 2d ago against content hash 80b5f8dce680, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

session-source-fork scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

packages/daemon/specs/agents/shared/skills/core/session-source-fork/SKILL.md · 161 lines

How it starts

The opening of the file, as written. The whole thing — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.

session_source Fork

session_source is a member-level OpenRig field that declares how a newly-launched managed seat should derive its initial conversation continuity from a prior runtime conversation source.

v1 supports one mode: fork — start a new managed seat from a prior native runtime conversation source without claiming the original seat continued.

The schema is runtime-neutral; implementation is runtime-specific (Claude and Codex have their own native fork commands).

Use this when

  • Authoring a rig spec member that should fork from a prior session
  • Authoring a rig expand payload with session_source
  • Reasoning about whether to use fork vs rebuild vs resume vs fresh for a new seat
  • Composing fork + handover (seat-handover-over-fork) — see seat-continuity-and-handover skill

Don't use this when

  • The seat is being restored, not created. Restore continues an existing managed seat. Fork creates a new seat.
  • The continuity is artifact-backed mental-model rebuild (packet-derived understanding, not native runtime continuity). Use mode: rebuild (see seat-continuity-and-handover for the rebuild surface) — do NOT collapse fork into artifact-backed reentry; the distinction is load-bearing.
  • The runtime is terminal. Terminal runtime rejects session_source.

The shape (canonical YAML)

members:
  - id: reviewer-2
    runtime: claude-code        # or "codex"; not valid on terminal
    agent_ref: specs/agents/reviewer.yaml
    profile: reviewer
    cwd: .
    session_source:
      mode: fork
      ref:
        kind: native_id          # v1 fork mode supports native_id only
        value: "0b0165d7-cb4d-4650-90de-15c0a1ede9e6"

Rules:

  • mode v1 only valid value: fork.
  • ref.kind v1 supports native_id only. Schema rejects artifact_path, name, last, and artifact_set pre-launch with explicit deferred/weaker/wrong-mode error messages (see packages/daemon/src/domain/rigspec-schema.ts validateSessionSourceFork). Adapter-level refusal exists as defensive handling but should not be reachable in v1 because schema rejects first.
  • value required for ref.kind: native_id in v1 (the only schema-accepted kind). Future-state value semantics for artifact_path / name / last are not active in v1 because schema rejects those kinds pre-launch.
  • rig expand accepts the same shape so dynamically-added members can carry session-source attribution.

Read the full file on GitHub · 161 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 161 lines · 110 tokens per session scan A 80b5f8dce680

Subscribe to this mod's changes

session-source-fork is a skill published in the GitHub repository mvschwarz/openrig (64 stars, last pushed 2d ago), licensed Apache-2.0. It adds 110 tokens to every session and 2,143 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

PlanningWriting and docsagent-harnessagent-orchestrationagent-skillsai-codingclaude-codecli
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