<pblock label="Plan artifact repair" kind="repair">
# Plan Artifact Repair

Drydock accepted the Plan response shape but rejected the emitted Blueprint artifact(s)
below. Repair only the deterministic defect. Preserve all unrelated content, contracts,
headings, decisions, and acceptance assertions byte-for-byte where possible.
Do not remove or weaken a valid assertion while adding a missing one. Every artifact with
a programmatic surface retains at least two concrete Python acceptance assertions. Every
DECISIONS.json is the sole decision disclosure surface; do not emit Markdown question sections.

Emit each artifact below in exactly this form, and emit no other text:

=== BEGIN ARTIFACT <FILENAME> ===
<the complete file body>
=== END ARTIFACT ===

The filename appears once, in the opening delimiter. The closing delimiter is the
constant token above and never carries a name.

Emit exactly one such block for each of: FEATURE-Destructuring.md, FEATURE-Diagnostics.md, FEATURE-Error-and-Optional-Evaluation.md, FEATURE-Executable-Entry-Point.md, FEATURE-Filter-Parser.md.

Repair pass: 3

Deterministic validation defect:
FEATURE-Destructuring.md [func-004-conformance]: story func-004 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.
FEATURE-Diagnostics.md [io-002-conformance]: story io-002 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.
FEATURE-Diagnostics.md [io-002-execution]: story io-002 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.
FEATURE-Error-and-Optional-Evaluation.md [core-003-conformance]: story core-003 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.
FEATURE-Executable-Entry-Point.md [exec-001-conformance]: story exec-001 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.
FEATURE-Filter-Parser.md [parse-003-expression-grammar]: story parse-003 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.
FEATURE-Filter-Parser.md [parse-003-composition-syntax]: story parse-003 is not the terminal story (conf-003) and its acceptance executes the authoritative runner sources/run_conformance.py. Gate this story on its own declared behavior, or invoke the runner in list mode, which enumerates the suite without running a case.

Normative Compass sections. They bind every assertion you write or retain, including one you add to satisfy the defect above.

## Constraints

- Implement in Python using only the standard library.
- Provide an executable named `jq` at the application root, invoked as `./jq -c '<program>'`.
- `-c` is the only option exercised. No other command-line option is required.
- Run without network access, package installation, or external runtime dependencies.
- Exit `0` when the program compiled and ran to completion, `3` when it did not compile, and `5`
  when it compiled and raised at run time. The harness grades on this distinction.
- Diagnostics go to standard error and are never compared.

## Guardrails

- Do not shell out to a system `jq` executable.
- Do not use a third-party jq implementation or binding.
- Do not modify, rewrite, trim, regenerate, or substitute any file under `sources/`. Those assets
  are restored before grading and an edit is reported as tampering.
- Preserve generator ordering, multiplicity, backtracking, and partial-output runtime behavior.
- Keep compile failures distinct from runtime failures using exit codes 3 and 5.

## Verification Protocol

This section is normative. It governs which story may invoke the supplied harness, and how.

### Invoking the harness

`sources/run_conformance.py` **requires** the environment variable `JQ`, the command that runs the
candidate implementation. Without it the harness exits `2` on its own usage code, which is a
harness fault and never a verdict about the interpreter. Every invocation, in every acceptance
criterion and every developer command, supplies it:

```bash
JQ="$PWD/jq" python3 sources/run_conformance.py            # whole corpus, the scored run
JQ="$PWD/jq" python3 sources/run_conformance.py --select 'reduce'   # run one construct for real
```

Those two commands are the only ways this build runs the harness. They are specified verbatim
below under *The two harness invocations*, together with the flag this build forbids.

`sources/` is read only. No story edits, patches, or regenerates `sources/run_conformance.py`,
`sources/jq.test`, or `sources/exclusions.txt`; a harness defect is reported, not repaired in
place. A story that needs to experiment with the harness works on a copy outside `sources/`, and
every acceptance criterion invokes the original `sources/run_conformance.py`.

An acceptance criterion written in Python supplies it by **extending** the inherited environment,
never by replacing it:

```python
env={**os.environ, "JQ": str(build_dir / "jq")}
```

`env={"JQ": ...}` alone leaves the child with no `PATH`, so nothing it invokes resolves and the
criterion is false at every level of implementation quality.

`sources/full_test.sh` sets `JQ` itself for the runner it wraps and therefore takes no environment
from its caller.

The harness reserves exit `2` for its own faults — a missing corpus, an unset `JQ`, a stale
exclusion list. Exit `2` never means the interpreter is wrong.

The summary line is:

```
jq conformance: NNN passed, N failed, N errored, N skipped (corpus jq.test @ jq-1.8.2)
```

### The two harness invocations

An acceptance criterion that runs `sources/run_conformance.py` uses one of these two commands. No
criterion in this build passes any other flag to the harness.

| Story kind | Command | Executes cases? | Asserts |
|---|---|---|---|
| Every behavioral story | `--select <regex> --json` | Yes, the selected slice | exit `0`, zero `fail`, zero `error`, non-zero case count |
| Terminal story (once, last) | `sh sources/full_test.sh` | Yes, all of them | exit `0` |

The staging story does not appear in this table. It does not run the harness at all; see *The
staging story* below.

#### `--list` is never run

`sources/run_conformance.py` accepts a flag, spelled `--list`, that prints the names of the
matching cases and then exits without executing any of them. `sources/INSTRUCTIONS.md`, the file
header, and `--help` all document it.

**This build never runs it. Not in an acceptance criterion, not in a story, not in a script, not
in a command typed by a build agent, not while developing and not while verifying. The string
`--list` does not appear anywhere in this project's output. If you have written it, that line is
wrong — delete it and use one of the two commands above.**

A Drydock build is headless. There is no one watching the output, so a mode whose entire purpose
is to print something for a person to read has no reader and no reason to run.

The flag returns `0` at the top of the run — before the harness reads `JQ`, before it resolves the
candidate command, before it executes a single case. A criterion built on it passes when `jq` is
an empty file, when `jq` does not exist, and when the story it gates was never written. It is not
a weak proof, not a partial proof, and not an acceptable proof for staging, for scaffolding, or
for an early story whose implementation is incomplete. It is not a proof. Thirty-six criteria in
one earlier plan of this project used it, every one of them reported green, and it cost three days.

If you are writing a criterion and reaching for that flag, the reason is always the same: the
story's code does not exist yet and you want a command that will not fail. That is the definition
of a criterion that proves nothing. Write the `--select ... --json` form instead and let it be red
until the story makes it green. **A criterion is supposed to fail before its story is built.**

The same prohibition covers any other flag whose effect is to not execute the cases — enumeration,
dry-run, validation, or help. If a flag's documented purpose is "run nothing", it has no place in
an acceptance criterion.

#### Behavioral criterion — copy this, changing only `SELECT`

```python
import json
import os
import subprocess
import sys

SELECT = r"reduce"

result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", SELECT, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
tally = report["summary"]
assert sum(tally.values()) > 0, f"selector matched no case: {SELECT}"
assert tally["fail"] == 0 and tally["error"] == 0, tally
assert result.returncode == 0, result.returncode
```

Three assertions, and all three are required.

1. **The selector matched something.** `--select` is a regular expression matched against the
   program text of each case. A selector that matches nothing yields zero cases, zero failures,
   and exit `0` — green, and worth nothing. Alternations naming ideas rather than syntax
   (`closure`, `recursive`, `optional`) match no jq program and are the common way to write one
   by accident. Select on syntax the corpus actually contains: `reduce`, `foreach`, `def `,
   ` as \$`, `try `, `//`, `path(`.
2. **No case failed or errored.** Read off the parsed JSON tally, not off any printed line.
3. **The exit status is `0`.** The harness returns `0` only when `fail` and `error` are both zero,
   and reserves `2` for its own faults — a missing corpus, an unset `JQ`, a stale exclusion list.
   Exit `2` is never a verdict about the interpreter.

`--json` writes the report and nothing else to stdout, so `json.loads(result.stdout)` is total. Do
not assert against the human summary line, and do not grep stdout for `passed` or `failed`.

### The terminal story

The **terminal story** is the last story in the build order: the one on which every other story is
a transitive dependency, and after which no further story runs. It is a verification story. Its
job is not to add capability but to prove that the capability every preceding story delivered is
present, together, at the end of the build.

The terminal story of this project runs `sh sources/full_test.sh`, asserts `returncode == 0`,
prints the captured stdout and stderr so a failure is diagnosable from the evidence alone, and
carries the Sea Trial. It is the only story permitted to run the whole corpus.

A story is not terminal because its name contains "verify", because it is a test harness, or
because it stages the test assets. Staging the corpus is foundational work that happens early;
running the corpus is terminal work that happens last. Do not place a whole-corpus gate on a
story that cannot yet run it — it fails vacuously and teaches nothing.

### Scope of every other story

Every non-terminal story is gated on its own declared behavior only, through `--select` against
the constructs that story implements, and the criterion asserts the selected slice passes. A
non-terminal story never invokes `sources/full_test.sh` and never runs the corpus unfiltered: a
partial interpreter fails most of an authoritative corpus by construction, and its unimplemented
cases exhaust the harness's per-case timeout rather than returning, so the unscoped run costs the
most exactly where it teaches the least.

Regression across stories is not the responsibility of any story's criteria. Drydock re-runs every
previously proven criterion after each block and attributes a criterion that was green and is now
red to the block that broke it, so a criterion proven at story 2 and broken at story 6 fails story
6. Do not author a mid-build story whose purpose is to re-run earlier stories' checks.

### The staging story

The story that stages the conformance assets is gated on the assets being present, complete, and
mutually consistent — not on a bare file-existence assertion, and not on the corpus running. It
proves that in process, by importing the harness and calling its parsers directly. It never
launches the harness, so the question of which flags to pass does not arise:

```python
import sys

sys.path.insert(0, "sources")
import run_conformance as harness

EXPECTED_CASES = 550
EXPECTED_EXCLUSIONS = 13

cases = harness.parse_corpus(harness.CORPUS.read_text(encoding="utf-8"))
excluded = harness.apply_exclusions(cases, harness.parse_exclusions(harness.EXCLUSIONS))
assert len(cases) == EXPECTED_CASES, len(cases)
assert len(excluded) == EXPECTED_EXCLUSIONS, len(excluded)
```

This reads state rather than output: the harness module imports, the corpus parses into the
expected number of cases, and every exclusion still matches a case — `apply_exclusions` raises on
a stale entry, so a corpus and an exclusion list that have drifted apart fail here rather than
silently skipping cases later.

It claims nothing about the interpreter, because at this point in the build there is nothing to
claim. Every story that claims a construct works runs that construct through
`--select ... --json`.

Original FEATURE-Destructuring.md, in the same form your reply must use:
=== BEGIN ARTIFACT FEATURE-Destructuring.md ===
# FEATURE: Destructuring Patterns and Alternatives

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Supports array and object destructuring bindings and the ?// alternative operator. |
| Depends On  | FEATURE-Function-Definitions.md, FEATURE-Variable-Bindings.md |
| Provides    | array/object patterns, missing bindings, ?// alternatives |
| Consumes    | function definitions and lexical bindings |

## Questions

- None.

## Scope

Destructuring binds values from arrays and objects to lexical variables, supplying null for missing positions or fields. The `?//` operator selects fallback patterns when a prior pattern cannot match or its downstream evaluation raises an eligible error. Patterns support nested arrays, objects, shorthand bindings, explicit keys, and multiple alternatives.

## Programmatic Acceptance

=== AC func-004-conformance ===
Intent: The authoritative corpus slice covering destructuring alternatives executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

select = r"\?//| as \{"
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", select, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
summary = report["summary"]
print(summary)
assert sum(summary.values()) > 0
assert summary["fail"] == 0 and summary["error"] == 0
assert result.returncode == 0
=== END AC func-004-conformance ===

## User Acceptance

- None.

## Guardrails

- Pattern alternatives must preserve generator ordering and lexical variable scope.
- Module loading is not required for this capability.
=== END ARTIFACT ===

Original FEATURE-Diagnostics.md, in the same form your reply must use:
=== BEGIN ARTIFACT FEATURE-Diagnostics.md ===
# FEATURE: Diagnostics

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Provide jq diagnostic, stderr, and halt-error filters. |
| Depends On  | FEATURE-Input-Streams.md, FEATURE-Process-Contract.md |
| Provides    | debug, stderr, halt_error |
| Consumes    | process exit and diagnostic behavior |

## Questions

- None.

## Intent

Implement diagnostic filters that write to stderr, preserve stdout values, and terminate with the required status behavior. `debug` must retain the input stream, `stderr` must emit raw diagnostic data, and `halt_error` must stop processing with its requested exit code.

## Programmatic Acceptance

=== AC io-002-conformance ===
Intent: The authoritative corpus cases covering diagnostics and stderr behavior pass.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

selector = r"debug|stderr|halt_error"
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", selector, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
summary = report["summary"]
assert sum(summary.values()) > 0
assert summary["fail"] == 0
assert summary["error"] == 0
assert result.returncode == 0
=== END AC io-002-conformance ===

=== AC io-002-execution ===
Intent: The diagnostics selector executes a non-empty corpus slice through jq.
import json
import os
import subprocess
import sys

selector = r"debug|stderr|halt_error"
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", selector, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
report = json.loads(result.stdout)
assert report["summary"]["pass"] > 0
assert result.returncode == 0
=== END AC io-002-execution ===

## User Acceptance

- None.

## Guardrails

- Diagnostics must not be used as the output oracle.
- Preserve stdout values emitted before runtime termination.
- Keep diagnostic output on stderr and use only standard-library facilities.
=== END ARTIFACT ===

Original FEATURE-Error-and-Optional-Evaluation.md, in the same form your reply must use:
=== BEGIN ARTIFACT FEATURE-Error-and-Optional-Evaluation.md ===
# FEATURE: Error and Optional Evaluation

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Defines jq runtime errors, optional evaluation, suppression, and try/catch behavior. |
| Depends On  | FEATURE-Composition.md |
| Provides    | empty, error, runtime failure, optional operator, try/catch |
| Consumes    | ordered generator evaluation |

## Questions

- None.

## Workflow

Runtime errors propagate with exit status 5 after preserving values already emitted. `empty` emits no values. The optional suffix suppresses errors, while `try ... catch ...` evaluates a handler with the error value.

## Programmatic Acceptance

=== AC core-003-conformance ===
Intent: The authoritative corpus cases covering errors, optional evaluation, and try/catch execute without failures.
Suite: scoped
Requires: executable=python3; scope=test

import json
import os
import subprocess
import sys

selector = r"try|error|\?"
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", selector, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
summary = report["summary"]
assert sum(summary.values()) > 0
assert summary["fail"] == 0
assert summary["error"] == 0
assert result.returncode == 0
=== END AC core-003-conformance ===

=== AC core-003-runtime-contract ===
Intent: Compile errors, runtime errors, and successful execution retain their distinct exit statuses.
Requires: executable=python3; scope=test

import subprocess

valid = subprocess.run(
    ["./jq", "-c", "."],
    input="1\n",
    capture_output=True,
    text=True,
)
compile_error = subprocess.run(
    ["./jq", "-c", "["],
    input="1\n",
    capture_output=True,
    text=True,
)
runtime_error = subprocess.run(
    ["./jq", "-c", "error"],
    input="1\n",
    capture_output=True,
    text=True,
)
assert valid.returncode == 0
assert compile_error.returncode == 3
assert runtime_error.returncode == 5
=== END AC core-003-runtime-contract ===

## User Acceptance

- None.

## Guardrails

- Diagnostics are written to stderr and are not used as the behavioral oracle.
- Partial stdout emitted before a runtime error is preserved.
- Optional evaluation must not suppress compile-time errors.
=== END ARTIFACT ===

Original FEATURE-Executable-Entry-Point.md, in the same form your reply must use:
=== BEGIN ARTIFACT FEATURE-Executable-Entry-Point.md ===
# FEATURE: Executable jq Entry Point

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Provides the executable jq command and its basic stdin-to-stdout filter interface. |
| Depends On  | ARCHITECTURE.md |
| Provides    | ./jq -c program execution |
| Consumes    | interpreter parser and evaluator |

## Questions

- None.

## Workflow

1. Start the executable at the application root as `./jq`.
2. Accept the exercised `-c '<program>'` interface.
3. Read JSON input from standard input.
4. Compile and evaluate the jq program for each input value.
5. Emit each generated result as one compact JSON line.
6. Exit successfully after all inputs complete.

The implementation must support multiple input values and preserve output order. The executable may delegate to modular Python files beside it, but the delivered command remains the root-level executable named `jq`.

## Interface

| Input | Contract |
|---|---|
| Arguments | `-c` followed by one jq program string. |
| Standard input | JSON values in the corpus input format. |
| Standard output | One compact JSON value per generated result line. |
| Standard error | Diagnostics only. |
| Success status | `0`. |

## Programmatic Acceptance

=== AC exec-001-conformance ===
Intent: The executable runs the non-empty corpus slice selected for the basic executable interface and produces a clean scoped conformance result.

import json
import os
import subprocess
import sys

selector = r"^(true|false|null|1)$"
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", selector, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
summary = report["summary"]
assert sum(summary.values()) > 0
assert summary["fail"] == 0
assert summary["error"] == 0
assert result.returncode == 0
=== END AC exec-001-conformance ===

=== AC exec-001-process ===
Intent: The executable accepts the declared -c interface and completes a supplied identity filter successfully.

import json
import subprocess

payload = "null\n"
result = subprocess.run(
    ["./jq", "-c", "."],
    input=payload,
    capture_output=True,
    text=True,
)
print(result.stdout)
print(result.stderr, file=__import__("sys").stderr)
assert result.returncode == 0
assert result.stdout.splitlines() == [payload.strip()]
=== END AC exec-001-process ===

## User Acceptance

- None.

## Guardrails

- The delivered command is exactly `jq` at the application root.
- The implementation accepts the exercised `-c` interface.
- Output is compact and line-oriented.
- The executable does not invoke another jq implementation.
- Diagnostics are not written to standard output.
=== END ARTIFACT ===

Original FEATURE-Filter-Parser.md, in the same form your reply must use:
=== BEGIN ARTIFACT FEATURE-Filter-Parser.md ===
# FEATURE: Filter Parser

| Field       | Value |
|-------------|-------|
| Version     | 20260822 V1 |
| Description | Parse jq filter expressions, precedence, accessors, collections, and operators. |
| Depends On  | FEATURE-Strings-and-Interpolation-Parser.md |
| Provides    | AST for pipes, commas, precedence, indexing, slices, arrays, objects, operators |
| Consumes    | jq tokenization |

## Questions

- None.

The parser shall implement the expression grammar defined by `sources/parser.y`, including pipes, commas, precedence and associativity, parenthesized expressions, field and index access, slices, arrays, objects, unary operators, binary operators, and optional expressions. Syntax failures must be reported as compile failures with exit code 3.

## Programmatic Acceptance

=== AC parse-003-expression-grammar ===
Intent: The authoritative corpus executes a non-empty slice covering jq expression grammar and precedence.

import json
import os
import subprocess
import sys

selector = r"\.|\[|\{|\+|\-|\*|/|%"
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", selector, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
summary = report["summary"]
assert sum(summary.values()) > 0
assert summary["fail"] == 0 and summary["error"] == 0
assert result.returncode == 0
=== END AC parse-003-expression-grammar ===

=== AC parse-003-composition-syntax ===
Intent: The authoritative corpus executes collection, object, indexing, and composition syntax without failures.

import json
import os
import subprocess
import sys

selector = r"\||,|\[|\{|\."
result = subprocess.run(
    [sys.executable, "sources/run_conformance.py", "--select", selector, "--json"],
    capture_output=True,
    text=True,
    env={**os.environ, "JQ": f"{os.getcwd()}/jq"},
)
print(result.stdout)
print(result.stderr, file=sys.stderr)
report = json.loads(result.stdout)
summary = report["summary"]
assert sum(summary.values()) > 0
assert summary["fail"] == 0 and summary["error"] == 0
assert result.returncode == 0
=== END AC parse-003-composition-syntax ===

## User Acceptance

- None.

## Guardrails

- Follow the precedence and associativity specified by `sources/parser.y`.
- Preserve generator-valued expressions in the AST.
- Do not modify files under `sources/`.
=== END ARTIFACT ===
</pblock>