feat(harnesses): shared-variables/v1 context + workflow-script/v1 composite (WF-COMP-31, WV-19) (03878b12-86b5-4b88-86d5-7182ae1c471f)

harnesses/composites/workflow-script/v1/harness.yaml

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+kind: composite
+name: workflow-script
+version: 1
+description: "Internal composite for the flag-on kind: script path (typed-workflows WF-COMP-31 / workflow-variables WV-19). Brings the shared-variables filesystem context AND the AU-51 CP write credential (cp-service-token/v1 sets CP_SERVICE_TOKEN_FILE in the entrypoint process env before shell_runner runs). NOT a model-bearing composite — the kind: script compiled shape is cli=\"shell\", params.cmd=<cmd>; this composite provides the harness layers that path needs and nothing else."
+
+# Order matters only for HC-6 env last-writer-wins / HC-8 git identity. The two
+# layers here have disjoint env vars (shared-variables sets WORKFLOW_VARIABLES_*
+# paths, cp-service-token sets CP_SERVICE_TOKEN_FILE) and no overlapping git
+# identity, so the listed order has no observable merge effect — both layers
+# reach the script-node container either way.
+layers:
+  # spec/workflow-variables.md WV-19 / spec/harness.md HD-14 — agent-facing
+  # /variables/ context (CLAUDE.md mounted at /opt/harness/context/shared-variables/CLAUDE.md)
+  # plus WORKFLOW_VARIABLES_ROOT=/variables and templated WORKFLOW_VARIABLES_SELF=<step_path>.
+  # Provides the [shared-variables] tag used by the dispatcher's extra_layers injection.
+  - context: shared-variables/v1
+  # spec/typed-workflows.md WF-COMP-31 "AU-51 credential env seam" — this layer's
+  # init.sh restages the ESO-mounted CP-service-token secret (root-owned mode 0400)
+  # to an agent-owned 0600 copy at /run/agent/cp-service-token/token and exports
+  # CP_SERVICE_TOKEN_FILE pointing at it. Verified: env.CP_SERVICE_TOKEN_FILE is set
+  # on the entrypoint process environment before shell_runner runs (entrypoint reads
+  # os.environ via env=os.environ.copy() in subprocess.run at entrypoint/runners/shell.py:73,
+  # so the same credential channel an agent node gets reaches a script node unchanged).
+  - context: cp-service-token/v1

harnesses/contexts/shared-variables/v1/CLAUDE.md

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+# Shared Variables Context
+
+Your container is running with the **shared variables filesystem** mounted at `/variables/`.
+This is the only way you read a step's inputs and return its outputs to the control
+plane — there is no API to call, no credential to hold, no env var to substitute.
+You write plain files under your own step folder; the CP picks them up.
+
+Normative source: `spec/workflow-variables.md` (WV-1..6a). This document summarises
+the contract; when in doubt, the spec wins.
+
+## What is where
+
+```
+/variables/
+  workflow/                       # run inputs, frozen at dispatch time (WV-8)
+    run-id
+    template
+    item.uuid
+    item.title
+    item.label
+    item.flow-state
+    artifacts.<key>               # per WorkflowInput.required_artifacts
+  <step>/                         # this step's OWN folder — write outputs here
+  <loop-id>_<n>/<step>/           # loop body node in iteration n (n is 1-based)
+  .self                           # path to your own step folder (read-only)
+  .done                           # completion marker, written by the entrypoint
+```
+
+You only write under your OWN folder. The pack sidecar walks that folder after you
+exit and returns its contents to the CP. Earlier loop iterations' results and your
+direct `depends_on` dependencies' outputs are also under `/variables/`, pre-filled
+when your container started — you only READ those.
+
+## Two env vars are set for you
+
+- `WORKFLOW_VARIABLES_ROOT` — always `/variables`.
+- `WORKFLOW_VARIABLES_SELF` — the path to your own step folder
+  (e.g. `/variables/judge` for a top-level node named `judge`, or
+  `/variables/review-loop_2/judge` for loop iteration 2's `judge` node).
+
+Neither ever contains a value. Both are paths only. Treat both as read-only inputs.
+
+## Key naming (the contract you'll be checked against)
+
+- A variable's key is the joined, lowercased path from `/variables/` to the leaf
+  file, with `.` as the separator.
+  `/variables/judge/VERDICT` ↔ `judge.verdict`.
+  `/variables/review-loop_2/judge/findings/HIGH` ↔ `review-loop_2.judge.findings.high`.
+- **Leaf files are UPPERCASE** on disk by convention; folders stay lowercase.
+  Lookup via the helpers and the CP API is case-insensitive.
+- Each path segment, after lowercasing, must match `^[a-z0-9][a-z0-9_-]{0,63}$`.
+  Maximum depth is 8 segments. Dotfiles, symlinks, FIFOs, sockets, and devices are
+  skipped with a warning (never read or followed).
+- Two leaf files at the same level whose names lowercase to the same key → both
+  rejected at pack time as `invalid_output_key`.
+- **Reserved names** that cannot be used as step or loop ids (case-insensitive):
+  `workflow`, `while`, `for`, `foreach`, `loop`, `until`, `do`, `repeat`, `if`,
+  `else`, `elif`, `elseif`, `then`, `switch`, `case`, `default`, `when`, `break`,
+  `continue`, `return`, `goto`, `yield`, `try`, `catch`, `except`, `finally`,
+  `raise`, `throw`, `and`, `or`, `not`, `xor`, `in`, `is`, `true`, `false`,
+  `null`, `none`, `nil`, `yes`, `no`, `on`, `off`. The full list lives in
+  `controlplane/typed_workflows/reserved_ids.py` and may grow by spec amendment.
+- Step/loop ids are restricted to lowercase letters, digits, `-` and `_`, starting
+  with a letter; no trailing `_<digits>` (reserved for loop-iteration suffixes).
+
+## What you can see (visibility)
+
+- `workflow.*` — always. These are the run inputs, frozen for the life of the run
+  (later item changes are not reflected here; pass them on through step outputs).
+- The outputs of each of your **direct** `depends_on` nodes (the same set the
+  manifest DAG wires you to) — not transitive.
+- Inside a loop body, **every prior iteration's** outputs for **every** step in
+  the loop — not just the immediately preceding one. So iteration 2 sees what
+  iterations 1, 2, … of every loop body node wrote. Iteration 1 sees only its
+  direct dependencies.
+- Nothing else. Your own folder is always created, even if empty.
+
+## Declared outputs
+
+If your node's template declares `outputs: [<key>, ...]`, those are the keys you
+are expected to write. Any file actually present under your step folder is
+accepted regardless — `outputs:` is for policy and tooling, not an allowlist.
+A missing declared output produces a warning by default (configurable per-project
+to fail the step with `variables_missing_output`).
+
+## Values
+
+- **Strings only.** JSON is supported as a string value — you parse it yourself;
+  the CP never interprets a value's structure.
+- Per-value cap is configurable (`max_value_bytes`, default 1 MiB). Per-step cap
+  (`max_step_bytes`) and per-step file count (`max_step_files`) also apply.
+- Values are data — never substituted into prompts, commands, or environment
+  variables by the CP. Don't put values in shell; read them through the helpers
+  or the CLI.
+
+## Helpers (use these, not shell)
+
+A Python package is pre-installed in your image at `/opt/agent/variables/` and a
+CLI at `/usr/local/bin/wfvar`. Both are stdlib-only.
+
+```python
+from variables import load, save, keys
+
+value = load("verdict")                    # load from your own folder
+save("verdict", "CLEAN")                   # write into your own folder
+keys()                                     # list keys under your own folder
+keys(prefix="judge.")                      # narrow by prefix (read-only access)
+```
+
+```bash
+wfvar get VERDICT                 # print the value, NO trailing newline
+wfvar set VERDICT CLEAN           # write into your own folder
+wfvar list                        # list your own keys
+wfvar path                        # print your own step folder (same as $WORKFLOW_VARIABLES_SELF)
+wfvar get judge.findings.high     # read another step's output (visibility permitting)
+```
+
+Exit codes: `0` ok, `1` not found (key is valid but absent), `2` invalid key or
+usage, `3` value exceeds per-value limit, `4` write attempted outside your own
+step. Do not wrap `wfvar get` with extra shell that strips newlines — it prints
+exactly the stored bytes.
+
+**Don't write plan-like content with `wfvar set <key> <body>`** — argv breaks on
+shell quoting and truncates at ARG_MAX. For multi-line / quoting-sensitive bodies
+(e.g. the decompose plan files at `/variables/<node>/items/<local_id>`), use your
+file-write tool or a heredoc with a terminator that cannot occur in the body,
+writing directly into `/variables/<node>/...`.
+
+## Safety
+
+The pack sidecar reads your step folder with strict traversal protections
+(`O_NOFOLLOW`, `S_ISREG` checks, size caps, 4 KiB marker cap). It does not follow
+symlinks you might drop in. A symlink at any level is silently skipped with a
+warning — never assume it will be read.
+
+## What you must NOT do
+
+- Do not read or write outside your own step folder under `/variables/`.
+- Do not call out to the CP API directly — the helpers and the pack sidecar
+  handle all variable transport.
+- Do not assume `/variables/` exists in an unstamped container — it doesn't.
+- Do not write to `/variables/.done` — the entrypoint owns that marker; it is
+  written for you after `run_finalize_phase` returns, whether you exited 0, non-zero,
+  or via SIGTERM.
+- Do not store values in env vars, command lines, or prompts — values are data,
+  and data doesn't go there.

harnesses/contexts/shared-variables/v1/harness.yaml

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+kind: context
+name: shared-variables
+version: 1
+description: "Workflow variables filesystem contract — /variables/ layout, key naming, helpers and CLI for CP-held step inputs/outputs (spec/workflow-variables.md WV-19; injected per-task via HD-14 extra_layers)"
+requires: []
+provides: [shared-variables]
+
+# WV-20: both env vars are set by THIS harness layer (not the entrypoint, not
+# the container backend). WORKFLOW_VARIABLES_ROOT is static; WORKFLOW_VARIABLES_SELF
+# is templated by the composer at harness-composition time on the dispatcher,
+# substituting the node's resolved step_path (the SAME value WV-15 derives at mint
+# time). A task with no shared-variables/v1 layer (unstamped) has neither env var
+# set, and /variables does not exist for it at all.
+env:
+  WORKFLOW_VARIABLES_ROOT: /variables
+  WORKFLOW_VARIABLES_SELF: "{{ step_path }}"
+
+context_files:
+  - source: ./CLAUDE.md
+    target: /opt/harness/context/shared-variables/CLAUDE.md