implement

name	implement
description	State-aware spec executor — read the active spec, run the next step's action, gate on its verification, retry once on fail, advance the scratchpad. Halts on any unrecoverable failure with full negative knowledge.
disable-model-invocation	false

Skill: /implement [check | auto] []

Triggered when the user types /implement (run next step), /implement check (verify current state without executing), or /implement auto (walk consecutive low-tier steps without re-prompting until a halt-worthy step). This is the physical-build engine of Spectre — it owns the action→verification→retry→advance cycle.

§6.0 Environment policy

Spectre owns the Python virtual environment. Specs must not declare PEP 668 strategy (system Python, venv path, --break-system-packages, pipx, etc.) — that is the executor's responsibility, not the spec author's.

At the start of every /implement session the runner calls ensure_venv (see bin/managed_venv.py) which creates state/.venv/ under the user's project root (mode 0700) on first use and is idempotent on subsequent calls. The resulting interpreter path is persisted to state/scratchpad.json as a top-level venv_python field so future sessions reuse it without re-running the venv check.

Every step's action: and verification: strings are passed through normalize_action before execution. This rewrites bare python, python3, pip, and pip3 tokens to use the venv interpreter — top-level shell tokens only (shlex-parsed), so absolute paths, heredoc blocks, and nested quoted strings are left untouched. If ensure_venv fails for any reason (missing python3-venv, out of disk, etc.), the skill HALTs with a clear error — it never falls back to system Python.

Hard rules (read every invocation)

• All paths are user-project-cwd-relative. Read specs/.active and state/scratchpad.json from the user's pwd, never from the plugin install dir (${CLAUDE_PLUGIN_ROOT} or ~/.claude/plugins/...). If pwd looks like a plugin cache, HALT and tell the user to restart from their project directory.
• Verification is the gate, not the action. A non-zero action: exit is a failure; a zero-exit action: followed by a non-zero verification: is also a failure. Both halt or retry per Option B.
• One step per invocation, except in auto mode. Plain /implement runs exactly one step. /implement auto chains consecutive steps that classify as silent or repo tier with no never-autonomous match, no resource-lock contention, no verification failure, and no drift trigger. The first step that fails any of those conditions halts auto mode and reverts to per-step.
• One retry, then halt. Option B retry policy (see Retry phase below).
• Hard halt on missing-binary errors. command not found, No such file or directory for the binary itself → halt without retry.
• Never edit the spec from /implement. If the spec is wrong, halt and tell the user to re-run /vision.
• Pre-flight check before executing Step N. Run Step N-1's verification first if scratchpad says it passed; halt with a "Root-State Desync" message if it now fails.

Protocol

Phase: Mode routing

Parse the args. Recognized invocations:

• /implement — run exactly one step.
• /implement check — verify current state (no execution, no advance).
• /implement auto — walk consecutive low-tier steps without re-prompting.
• /implement <track> / /implement auto <track> / /implement check <track> — same, scoped to a named track.

In auto mode, the runner repeats the Track through Drift phases in a loop until any of the following triggers a halt:

• Tier classifier returns host or network.
• Tier classifier returns a NEVER_AUTONOMOUS label.
• Resource-lock acquisition is queued (not granted on first try).
• Verification fails (Path B retry is per-step interactive — auto mode hands control back at the prompt).
• Drift checkpoint detects drift.
• Spec is complete (current_step > total_steps).

When auto mode halts, print one line summarizing what triggered the halt, then proceed exactly as plain /implement would for that step. The user's next /implement can re-enter auto mode by passing auto again. Auto is opt-in — never the default.

Phase: Track

/implement accepts an optional <track> argument. /implement (no arg) targets the default track. /implement <track> targets the named track; if the track does not yet exist in the v2 scratchpad's tracks: map, it is created with track_default() shape on first save.

Read the active spec from the per-track scratchpad: state/scratchpad.json["tracks"][<track>]["active_spec"]. If absent for that track, halt:

ERROR: track <name> has no active spec. Run /vision <track> first.

For backward compat: a v1 scratchpad is auto-migrated to v2 by the SessionStart hydrator. Plain /implement on the migrated default track works without further changes.

Phase: Tier 0 envelope

Before reading the spec or executing any step, validate the handoff envelope:

spectre handoff_validator check --project-path .

Stdout: RESULT envelope.check status=ok when valid, or WARN envelope.check status=missing detail=... / HALT envelope.check status=tampered detail=... for violations. Exit code: 0 on OK or warn-only findings, 1 on block-severity violations.

Behavior:

• status=missing (warn, exit 0) — pre-v0.6 locked spec; print the warning and continue. Re-run /vision to upgrade.
• status=tampered (block, exit 1) — spec/sidecar/contracts modified after lock. HALT. Tell the user to re-run /vision.
• no active spec (block, exit 1) — HALT. Tell the user to run /vision first.
• schema violation (block, exit 1) — HALT. The envelope file itself is malformed.

Phase: Context read

cat specs/.active   # → relative path to active spec
cat state/scratchpad.json   # → step, exit_code, failed_hypotheses (look under tracks.<track>)

If .active is missing or stale → halt: ERROR: no active spec. Run /vision first.

Parse the active spec's ## 6. Steps YAML block. Identify:

• total_steps = highest step: number in the YAML
• current_step = scratchpad.tracks.<track>.step
• current_action = the action: value at that step
• current_verification = the verification: value at that step
• current_resources = the optional resources: list at that step (default [])
• prev_verification = the verification: from step current_step - 1 (if any)

Terminal state check: if current_step > total_steps, halt:

SPEC COMPLETE: specs/<slug>.spec.md (all <N> steps verified).
To start a new mission, run /vision.

Do not execute anything further; do not modify the scratchpad.

Phase: Environment

After reading the active spec and before classifying the action, ensure the executor-owned venv exists and normalize the step's invocations.

Once per /implement session (skip if venv_python is already set in the scratchpad for this session):

spectre managed_venv ensure \
    --project-path . \
    --scratchpad state/scratchpad.json

Stdout: OK venv.ensure python=<absolute-path>. The CLI creates state/.venv/ (mode 0700) on first call, is idempotent on subsequent calls, and writes the interpreter path to state/scratchpad.json["tracks"][<track>]["venv_python"] via atomic write.

If this command exits non-zero → HALT immediately with its stderr. Do not fall back to system Python.

On every step, rewrite the step's action: and verification: strings through normalize_action before tier classification and before execution:

spectre managed_venv normalize \
    --action "<step action verbatim>" \
    --venv-python "<venv_python from scratchpad>"

The rewritten string (stdout) is what gets executed and verified. Original spec text is unchanged.

Phase: Pre-flight

If current_step > 1 and scratchpad.exit_code == 0:

• Run prev_verification.
• If it now fails, halt with:

  ROOT-STATE DESYNC: Step <N-1> verification no longer passes.
  Reason: <stderr>
  Action: investigate manually, then re-run /implement when state is restored.
  

Phase: Check mode

If the user invoked /implement check:

• Run current_verification (NOT the action).
• Print pass/fail + the verification command's output.
• Do NOT advance step. Do NOT modify scratchpad except for last_command/exit_code.
• Halt.

Phase: Tier classifier

Classify normalized_action (the post-rewrite string from the Environment phase — not the raw spec text) by tier before executing. Run:

spectre tier evaluate-action \
    --action "<normalized_action verbatim>" \
    --spec "specs/<active spec name>.spec.md"

The CLI wraps the tier orchestration in a single call: it invokes tier.classify, reads §8.1 locked paths from the spec via coverage_gate.parse_81_block, then runs tier.should_halt and emits the output. Pass --json instead to get a structured payload ({"tier","reasons","never_autonomous","halt","spec_locked_paths"}).

Stdout (no --json):

• RESULT tier.classify tier=<silent|repo|host|network> — exactly one line.
• RESULT tier.gate halt=<true|false> — exactly one line.
• RESULT tier.classify never_autonomous=<label> — present only when an intent-based override matched.

Exit codes: 0 success (parse stdout for the answer), 1 runtime error, 2 argparse error. Missing --spec or a missing spec file is not an error — locked paths default to empty.

bin/tier.py is the single source of truth for halt-vs-execute. Never substitute your own judgment about whether something is "safe enough" — if halt=true, halt. The should_halt semantics consult ~/.spectre/personal-rules.toml and respect §8.1 spec-locked paths (personal rules cannot override halts whose reason references a locked path).

Interpret the output:

• tier=silent and no never_autonomous= → continue to Resource acquire silently.
• tier=repo and no never_autonomous= → continue to Resource acquire silently.
• tier=host, tier=network, OR any never_autonomous= → halt with:

TIER GATE Step <N>: <action>
Tier: <silent|repo|host|network>
Reasons:
  - <reason 1>
  - <reason 2>
Never autonomous: <label if any, else "n/a">
Reasoning: <one-line first-principles "why this halts — what state changes irreversibly or beyond the repo">
Proceed? (yes / halt / skip)

Record observation BEFORE accepting input: every TIER GATE halt — regardless of the user's answer — produces a fingerprint and an observation row. Run:

spectre observations record-halt \
    --action "<current_action>" \
    --label "<the first reason from the classifier output>" \
    --spec-slug "<active spec slug from .active>"

Stdout: OK observation.record fingerprint=<fp[:12]>.... The CLI computes the SHA-256 fingerprint, appends a JSONL record to ~/.spectre/observations.jsonl, and best-effort writes a CDLC ledger halt transition to <cwd>/state/cdlc-ledger.json. The fingerprint is what personal-rules.toml keys against.

Append to CDLC ledger. Every TIER GATE halt — regardless of yes/halt/skip — also records a halt transition:

spectre cdlc_ledger append --kind halt \
    --payload-kv "fingerprint=<fp from observation block>" \
    --payload-kv "label=<label>" \
    --payload-kv "action=<current_action>" \
    --payload-kv "user_answer=<yes|halt|skip>"

The CLI exits non-zero on JSON-corruption / disk-full / unwritable-state errors; capture stderr but DO NOT propagate the failure to the user. Ledger write is non-blocking.

• yes → continue to Resource acquire then Execute. After Path A succeeds, run the Post-halt-success prompt.
• halt → stop. No scratchpad change.
• skip → advance step by 1 (no execution, no verification). Use only when the step was already done out-of-band; rare.

Persist pending_adoption_prompt for durability.

spectre _scratchpad set-pending-adoption \
    --scratchpad state/scratchpad.json \
    --track "<active track from invocation, default 'default'>" \
    --fingerprint "<fp from tier classifier observation block>" \
    --label "<label from tier classifier observation block>" \
    --action "<current_action>"

Stdout: OK scratchpad.pending_adoption_set fingerprint=<fp[:12]>.... The CLI atomic-writes via _scratchpad.atomic_write, auto-promotes a v1 scratchpad to v2 if needed, and stamps recorded_at. This survives session restart and any mid-execution compact.

Post-halt-success prompt. After Path A (verification passes) completes successfully, READ pending_adoption_prompt from state/scratchpad.json for the active track. If None, skip this prompt entirely — no halt was queued. If present, fire the prompt using the persisted structured fields.

spectre _scratchpad get-pending-adoption \
    --scratchpad state/scratchpad.json \
    --track "<active track from invocation, default 'default'>"

Stdout (one of): OK scratchpad.no_pending_prompt (skip prompt entirely) or RESULT scratchpad.pending_prompt fingerprint=<fp[:12]> label=<label>. For the full structured prompt (action, recorded_at), pass --json and parse the result; null means no prompt is pending.

Clear pending_adoption_prompt FIRST. As soon as the prompt is read successfully and BEFORE running the adopt/once-only/never-ask-again branches, clear the field unconditionally:

spectre _scratchpad clear-pending-adoption \
    --scratchpad state/scratchpad.json \
    --track "<active track from invocation, default 'default'>"

Stdout: OK scratchpad.prompt_cleared (track existed and was cleared) or OK scratchpad.no_track_to_clear (track absent — no-op). Clearing FIRST means: if the adopt branch raises an exception during personal_rules.adopt, the field is already cleared. The user sees the adopt-write error and can fix their config, but next /implement will not re-prompt for the same halt.

After Path A completes successfully, emit:

The TIER GATE halted you on this action class. Adopt as personal-rule-skip going forward?
   adopt          — write to ~/.spectre/personal-rules.toml; future runs of this fingerprint will not halt.
   once-only      — no rule written. Same trigger halts again next time.
   never-ask-again — write a "user-declined" placeholder; this fingerprint never re-prompts (but still halts at TIER GATE).

If adopt: run

spectre personal_rules adopt \
    --label "<label>" \
    --fingerprint "<fp>" \
    --reason "<one-line user reason>" \
    --scratchpad state/scratchpad.json \
    --track "<active track, default 'default'>"

Stdout (one of): OK personal_rules.adopt session_count=N max=3 (TOML written, persistent counter bumped) or HALT personal_rules.brake session_count=N max=3 remediation=~/.spectre/personal-rules.toml (the brake — TOML untouched, counter not bumped). The CLI consults the persistent counter at tracks.<track>.session_adoption_count BEFORE writing.

If once-only: do nothing — the halt fires again on the next run.

If never-ask-again: treat as once-only for now. Print "Note: never-ask-again is pending; treating as once-only."

Sandbox-paradox brake. The CLI consults the persistent counter against DEFAULT_BRAKE_THRESHOLD (default 3) BEFORE writing the TOML; if the counter is already at threshold, the CLI prints the BRAKE message and exits 0 without bumping anything. The brake is session-scoped via state/scratchpad.json's tracks.<track>.session_adoption_count field — restarting Claude Code (or starting a new spec/track) resets it on the next /vision. The threshold is read dynamically from DEFAULT_BRAKE_THRESHOLD rather than hardcoded.

Exemplar context injection. When a spec declares **Spec-version:** 1.0 AND binds exemplars in any of §§9-13, Tier-3 (if enabled) automatically loads the bound exemplars' conventions list into its contradiction prompt's user message. The injection is view-level — every step in the spec is reviewed against the bound exemplars' conventions for that view. No skill action is required; the mechanism fires from bin/llm_judge._build_exemplar_context. Per-step satisfies: routing (where individual steps name which view contracts they fulfill) is deferred to v1.1 once dogfooding reveals how view-bound implementations fail.

Phase: Resource acquire

If current_resources is non-empty, acquire each Resource via the supervisor before executing. Run:

spectre track acquire \
    --track "<current track>" \
    --resources "<comma-joined current_resources, e.g. port:8080,db:postgres>"

Stdout: one OK track.acquire resource=<rid> line per granted lock, or HALT track.queue resource=<rid> position=N followed by exit code 1 on the first queued resource. A non-zero exit means the skill must halt with the RESOURCE QUEUED message below.

If any Resource is queued (not granted) → halt with:

RESOURCE QUEUED Step <N>: <track> waiting on <resource_id>
Position: <queued_position>
Action: another track holds this. Wait, then re-run /implement <track>.

Phase: Reasoning emit

Print the step's why: line BEFORE the action so it lands in conversation context AND in the next compact's additionalContext:

WHY: <why text from spec>

If the spec step is missing why:, halt with HALT: Step <N> has no why: field. Re-run /vision to add it. — do not fabricate a justification.

Phase: Execute

Print the action and run it via Bash:

EXECUTING Step <N>: <action>

The PostToolUse(Bash) hook will compact the result into Delta+Anchor automatically. Do not summarize stdout/stderr yourself.

Phase: Verify

Immediately after the action returns, run current_verification via Bash:

VERIFYING Step <N>: <verification>

State Auditor (informational). After verification passes but before the step advances, run the State Auditor for structural sanity. The auditor is informational on first pass — it does NOT block step advance:

spectre auditor audit-and-clear \
    --action "<current_action>" \
    --scratchpad state/scratchpad.json \
    --track "<current_track>"

If the active spec's current step declares a properties: YAML block, pass it as a JSON array via --properties '[{"kind":"type","target":"out.json","expected":"dict"}, ...]'. Otherwise omit the flag.

Stdout: RESULT audit.summary checks=N passed=<true|false>. Plus WARN audit.fail kind=... message=... per failed check. Pass --json instead to get {"kinds","passed","failures"} as a JSON object.

Phase: Branch on verification

Path A — verification exits 0:

• Print: VERIFICATION PASSED: Step <N>.
• Update scratchpad: increment step by 1, clear any retry state.

Append CDLC ledger transition. Record an implement transition for this successful step:

spectre cdlc_ledger append --kind implement \
    --payload-kv "step=<step number that just succeeded — the pre-increment value>" \
    --payload-kv "spec_slug=<active spec slug from .active>" \
    --payload-kv "action=<current_action>"

Failure here does NOT roll back the step increment — the step is the durable state.

• Run the Drift phase.
• Print: Ready for next /implement.
• Halt (do not auto-run Step N+1).

Path B — verification exits non-zero (Option B retry):

• This is the agent's ONE allowed retry.
• Read the verification's stderr.
• Diagnose: write a 1-line diagnosis to scratchpad explaining what likely went wrong.
• Propose a corrected action (NOT a corrected verification — the spec's verification is canonical).
• Print:

  VERIFICATION FAILED: Step <N>.
  Diagnosis: <one line>
  Retry action: <proposed corrected command>
  Run? (yes / halt)
  

• Wait for user. If yes, run the corrected action, then re-run the original verification.
  • If verification now passes → Path A.
  • If verification still fails → halt (no second retry):

    HALT: Step <N> verification failed twice. See state/scratchpad.json failed_hypotheses[].
    

• If halt, halt.

Hard halt without retry — when:

• The action's stderr matches command not found, No such file or directory: '<binary>', Permission denied for the binary itself.
• The verification command itself errors out structurally (unparseable, missing).
• Any spec field is missing for the current step.

Phase: Drift

After advancing step, check if a drift audit is due:

• Read last_drift_check_step from scratchpad (default 0).

• Let new_step = scratchpad.step (after the increment in Path A).

• If (new_step - last_drift_check_step) >= 5 AND new_step <= total_steps:

  1. Re-read the spec's ## 1. Hard Problem section verbatim.
  2. Read the action: and why: for steps new_step .. min(new_step + 4, total_steps).
  3. Self-audit silently: "Do these remaining actions still serve the Hard Problem? Articulate one reason yes and one reason no."
  4. If you can articulate any plausible "no" — e.g. the actions have drifted into a different subsystem, scope expanded, the Hard Problem is no longer being addressed — halt with:

     DRIFT DETECTED at Step <N>.
     Hard Problem: <quoted from spec>
     Concern: <one-line — what drifted, in first-principles terms>
     Options: (continue / edit-spec)
     

     • continue → update last_drift_check_step to new_step. Do NOT modify the spec.
     • edit-spec → halt. Tell the user to re-run /vision with current scratchpad context so the new spec inherits accumulated state.
  5. If clean (no drift) → silently update last_drift_check_step to new_step and proceed.

• If less than 5 steps since last check → no audit, no scratchpad write to last_drift_check_step.

Phase: Resource release

If current_resources is non-empty AND verification passed (Path A) OR the step halted permanently (no further retries possible), release every Resource the step acquired:

spectre track release \
    --track "<current track>" \
    --resources "<comma-joined current_resources>"

Stdout: OK track.release resource=<rid> per resource. The CLI is idempotent — releasing a resource the track does not own is a no-op on the supervisor side. Do NOT call this on retry-mid-flight (Path B retry pending) — the track still owns the lock. Only release on terminal step state (advance OR halt).

Phase: Failure log

Whether the failure halts or retries, the compact.py hook already appends to failed_hypotheses[]. The /implement skill doesn't write to scratchpad directly except to advance step on success or store diagnosis on retry.

Phase: Finding capture

Triggered when Path B retry succeeded — verification failed on the first run, the agent diagnosed and proposed a corrected action, the user said yes, and verification passed on the corrected action. This signal pattern reliably identifies "the spec author didn't anticipate something about the runtime environment."

Prompt:

FINDING: <one-line summary of what the corrected action revealed>
Detected: verification-fail-recover
Category? (project / spectre)
  - project → decisions/<NNNN>-<slug>.md in the active project
  - spectre → gh issue comment 1 --repo Joncik91/Spectre with auto-drafted body

Default category is spectre because the trigger is an invocation correction, not a design choice.

On spectre:

gh issue comment 1 --repo Joncik91/Spectre --body "$(cat <<EOF
## Finding from /implement (auto-captured)

**Spec:** <slug>
**Step:** <N>
**Original action:** <action from spec>
**Corrected action:** <agent's diagnosis-driven retry>
**Diagnosis:** <one-line>

Captured from a real /implement run where Path B retry succeeded — i.e. the
spec author's invocation didn't account for the runtime quirk surfaced here.
EOF
)"

If gh is unavailable or the command fails, write the draft to decisions/<NNNN>-DRAFT-<slug>.md with a # DRAFT: TO-BE-FILED-UPSTREAM header banner, AND append a record to scratchpad's pending_findings: [] queue so the user can file later. Never lose a finding to a network/auth blip.

On project:

spectre adr write \
    --dir decisions \
    --title "<title>" \
    --body "<body with finding>"

Stdout: OK adr.write path=decisions/<NNNN>-<slug>.md. The slug is auto-derived from the title via adr.slugify(); no need to pass it separately.

Skip this phase entirely on silent/repo-tier steps that pass on first try — those have no signal worth capturing.

Output contract

On success:

EXECUTING Step <N>: <action>
VERIFYING Step <N>: <verification>
VERIFICATION PASSED: Step <N>.
Ready for next /implement.

On /implement check:

CHECK Step <N>: <verification>
RESULT: PASS | FAIL — <stderr if fail>

On halt:

HALT: <reason>
<actionable next step for the user>

Why this shape

The action-verification split forces intellectual honesty: the spec author commits, in writing, to what "this step worked" means before any code runs. The agent cannot retroactively redefine success. Option B retry catches typos and missing-flag mistakes (one bounded chance to self-correct) without thrashing on real bugs. The pre-flight re-verification of step N-1 catches "user manually deleted a file" desyncs before they snowball.