Spec-Driven Rust: Process

Synopsis:

This thread follows the Rust implementation, the second of the four, written against documents that already existed.

One prompt record against the 14 the C++ thread carries. The five Rust documents were written in a single turn, so there was no buildup to record.
One 13-item audit covers the set, and it opens by saying these were the assistant's own drafts - a self-audit rather than an independent one.

Four resolutions changed the shape of the code, and Rust's type system drove three of them.

A thread_local! RefCell recovers the one-argument skip-list signature without unsafe and without a lock.
An exit code with no path at all, and an undecodable argument taking the code reserved for usage diagnostics.
One sink enforced, because two independent buffers over one stdout reorder the output under load.

The second implementation is where the parent specification gets tested, and three of the 13 answers landed there.

A rule generalized from Rust bound C++ and C++ did not satisfy it, which cost one C++ source file a rewrite.
The /p whitespace set is now named character by character, after Rust and C++ were about to trim differently by exactly one.
Section 5 states what this thread's evidence does and does not cover, including the turn that wrote the code and left no record at all.

1. What the Records Show

The Rust implementation carries one Prompts_*.md record, Prompts_Build_Rust_TextFinder.md, and Page_Structure.md §8 puts it on this page. That is one record against the 14 the C++ thread carries, and the difference is worth stating before the table rather than after it: the Rust specifications were written in a single turn from documents that already existed, so there was no seven-turn buildup to record.

Page	Records	What they cover
Process (this page)	1	The 13-item audit of the five Rust documents, the parent-specification changes it forced, and the C++ rebuild that followed
Structure	0	used C++ implementation as example instead of prompt
Entry	0	used C++ implementation as example instead of prompt
Cmdline	0	used C++ implementation as example instead of prompt
Dirnav	0	used C++ implementation as example instead of prompt
Output	0	used C++ implementation as example instead of prompt
Testing	0	used C++ implementation as example instead of prompt
Demonstration	0	used C++ implementation as example instead of prompt

Two turns are missing from this thread and each is missing for its own reason. The turn that created the Rust directory and wrote the five documents sits in Prompts_Pages.md, at the project level, and §8 decides a record's thread by the directory level it was produced at rather than by its subject, so that record belongs to the Process thread. The turn that wrote the four sources, the four suites, and the three runners has no record at all. Section 5 says what follows from that.

The record quotes user prompts verbatim and summarizes replies, noting tool calls as effects rather than transcribing them. It is a record, not an input to code: Constitution.md rule 1 names Spec*.md and *Structure.md and nothing else, which is what keeps a design conversation from becoming an unwritten requirement.

2. Questions the Specifications Had to Answer

One review covers the Rust set. It read all five documents against Spec_TextFinder.md and against each other, listed 13 items without editing, and opened by saying that these were the assistant's own drafts, so the review is a self-audit rather than an independent one. A reader weighing what follows needs that sentence.

The review found the substance consistent first, and named what it checked: the nine defaults match the §5 table, the engine is the regex crate and no other, the two-level block form and its two-space indent are fixed, the file and error announcement split and its /h gating are right, add_skip_directory extends the list rather than replacing it, the no-content case carries both accepted costs, and the three §5.3 listing cases resolve to one function.

Group	Items	The question that mattered most
Will not compile	1	The sink had no `flush`, and Entry §4 step 8 calls one
Contradictions	3	An undecodable argument exited 1, which §3.4's code-1 row reserves for a usage diagnostic, while exit code 2 had no path at all
Gaps	3	A root path's own separators were never normalized, so `-P src\sub` would emit `src\sub/file.rs`
A claim that does not hold	1	Cmdline §5 rule 1 justified counting characters rather than bytes, and the two produce identical diagnostics for every input
Minor	5	Nothing prevented a second `StdoutSink`, and two independent buffers over one stdout reorder the output under load

The user answered item by item and the answers were applied in one pass, which is the shape Constitution.md requires: an ambiguous specification is a question to ask, not a gap to fill from a sample implementation. Three of the 13 answers landed in Spec_TextFinder.md, where they bind all four implementations. Section 4 covers those.

3. Ambiguities Found and Resolved

Four resolutions changed the shape of the code rather than a detail of it.

3.1 A Skip List Without unsafe and Without a Lock

Spec_TextFinder.md §3.5 fixes the extension point's signature as a function taking the directory name alone. A Rust function that mutates a process-wide list from that signature needs somewhere to reach the list, and the first draft had widened the signature to carry it - which would have made Rust the one implementation whose §3.5 call looks different from every other's.

RefCell recovers the one-argument form. It moves the borrow check from compile time to run time, at the cost of one integer comparison per call, and no unsafe block and no synchronization primitive appear. The declaration is a thread_local! rather than a plain static, and Spec_Rust_TextFinder_Entry.md §5 records why: a static must be Sync, and RefCell's borrow flag is an ordinary integer rather than an atomic one. The bound costs this binary nothing, since the list is finished before traversal begins and traversal runs on one thread.

One consequence reached the startup sequence. Step 7 takes the finished list out of the cell with RefCell::take into a local of main, so the Dirnav's borrow lasts the whole traversal rather than the body of a closure passed to with. The Entry page covers what that local does for the borrow checker.

3.2 An Exit Code With No Path

The draft exited 1 when an argument would not decode to a String, and §3.4 defines code 1 as the code that accompanies a §5.2 usage diagnostic. Nothing in §5.2 covers an undecodable argument, because the failure cannot arise in an implementation whose argument vector carries bytes. At the same time exit code 2 was unreachable: the sink's constructor could not fail, so the code §3.4 fixes for a failure that is not about the command line had no path in this implementation.

One decision settled both. The undecodable argument takes code 2, which makes code 2 reachable and retires the contradiction. Spec_Rust_TextFinder_Entry.md §6 records the reasoning rather than only the outcome: the binary cannot form the command line it would have to validate, so the failure precedes command-line validation rather than resulting from it.

3.3 One Sink, Because Two Buffers Reorder the Output

Nothing in the draft prevented a second StdoutSink. Two of them wrap the same stdout with two independent BufWriters, and their contents reach the stream in the order the buffers happen to fill rather than the order the lines were written - which breaks the emission order §3.4 fixes, silently and only under load.

StdoutSink::new therefore returns Option<Self>, yielding Some the first time and None after, behind a thread_local! Cell<bool> that Drop clears. Default came off the type in the same move, because Default::default must return Self and this type cannot promise one. That None is the second path to exit code 2 of Section 3.2, so the two resolutions met.

3.4 A Rule Generalized From Rust That Harmed C++

The review found a Rust entry name that is not valid UTF-8 handled two ways, neither of them matching §3.4. Settling it in the parent specification was the right move and it widened §3.4's cannot open row to cover a file carrying a name the implementation cannot render as text, with U+FFFD substituted for each unit that will not render.

Widening §3.4 bound C++ too, and C++ did not satisfy it. The record reports the analysis rather than the conclusion alone. On POSIX a std::filesystem::path holds raw bytes that pass through unchanged, so C++ searches such a file correctly today and conforming would mean adding code whose only effect is to refuse files it currently handles. On Windows path::generic_string() must convert UTF-16 to narrow, an unpaired surrogate has no UTF-8 encoding, and the conversion throws out of a traversal loop that no try surrounds.

The rule had been generalized from Rust, where String is validated UTF-8 and OsStr::to_str returns an Option on both platforms, so the constraint is symmetric there and is not in C++. The user kept the parent rule and added one requirement to it: rendering a name may not end the run. C++ answered with a helper that calls neither converting function, so there is nothing left to throw and nothing to catch. Section 4 covers what that cost.

4. What Rust Forced on the Parent and on C++

Three of the 13 answers landed in Spec_TextFinder.md, and §7 Non-Goals kept its number so that no citation broke.

§3.4 widened. The cannot open row now covers a name the implementation cannot render as text, with the case defined as bytes that are not valid UTF-8 on POSIX and unpaired surrogates on Windows, U+FFFD substitution fixed, and the two accepted costs stated.
§5 named its whitespace. The /p row now names six characters, so no two implementations trim a different set. Rust had been reaching for char::is_ascii_whitespace, which omits vertical tab, where C's isspace in the C locale includes it - one character's difference, and /p "cpp,\vrs" would have normalized differently in the two implementations.
§6.2 Verification arrived. Every implementation owes unit suites one per library component, one integration suite driving the built executable, one demonstration, and a runner per kind that announces each suite and exits with the failure count. A suite never built counts as a failure, and a dated capture is replaced rather than edited.

A fourth change came from a question about how far the parent should reach. Spec_TextFinder.md §2 now states what the document fixes - the blocks and announcements of §3.4, the §5.1 help text, the §5.3 listing, and the exit codes - and delegates the rest to each component specification in its own language's idiom, naming the argument vector, the skip-list signature, stderr wording, and the standard-library facilities behind each rule. §6 now scopes the consistency guarantee to stdout, so a cross-implementation test compares stdout and the exit code and leaves stderr alone.

§5.2 kept its table and changed status. Its seven reason lines are wording the document supplies, and an implementation adopting them unchanged is the expected case; what it still binds is the shape, the destination, exit code 1, and the stdout behavior of the invalid-regex row. Rust adopts the wording unchanged, and so does C++, so nothing either program emits moved. What moved is where a test looks to check it.

The C++ rebuild that followed changed exactly one source file, Cpp_TextFinder_Dirnav.ixx, and the C++ Dirnav page covers the helper it gained. Placing the new gate revealed a divergence in the opposite direction: C++ tested renderability before selection, while the Rust text had the extension filter reach it first, so the same tree and the same command line would have produced different stdout. §3.4 is written over every such file rather than over the selected ones, so C++ had it right and Rust now carries the identical rule in the identical position.

5. The State of the Record

Three things about this thread's evidence are worth naming rather than leaving to a reader who counts <details> blocks.

This thread took the sibling route. The Rust sources were written with the C++ implementation in view rather than from the Rust specifications alone, which is the second of the two routes Constitution.md rule 1 now permits, and the one it opens only where a user prompt asks for it. The table in Section 1 says so per page, and a note in the same rule is what obliges this page to carry the statement: which route a thread took is process evidence.

Rule 1 did not say that when the sources were written. It excluded "example code" without qualifying it, and the Constitution page covers the amendment that settled where the project's own implementations sit. Two limits came with the permission, and both bear on how this thread should be read: the specifications remain the authority, so a disagreement between the C++ implementation and a Rust specification is a defect in the code rather than a licence; and an ambiguity is still a question to ask rather than a gap to fill from what C++ did. Section 2's 13-item audit is what that second limit looks like when it is obeyed - it ran against the documents, not against the sibling.

The turn itself wrote no record. The one that produced the four Rust sources, the four suites, the three runners, and the first demonstration capture left no Prompts_*.md file. Page_Structure.md §8 lets a page stand without a block where a record was never produced, so the seven code pages of this thread carry none. The code those pages describe is checkable against the specifications it answers to; the conversation that produced it is not recoverable from this tree.

The record carries one disclosure of its own, at turn 18. A verification script globbed *_Structure.md across the tree and read archive/Page_Structure.md in passing, extracting link targets by regular expression. Constitution.md rule 2 bars reading an archive directory without an explicit request naming it. Nothing from it reached a decision, the context was discarded, and the re-run excluded archive explicitly. A rule that is only obeyed when obedience is convenient is not a rule, so the breach is recorded where the work it touched is recorded.

6. Prompt Records

The one record this thread carries. It runs from the RefCell decision through the 13-item audit and its answers, into the parent-specification changes those answers forced, the C++ specifications and source they in turn obliged, and the page updates that closed the session.

Prompts_Build_Rust_TextFinder.md

# Prompts and Replies — Rust Specifications and the C++ Rebuild

This file records turns 12 through 21 of the session of 2026-09-15, and the numbering is that session's. The turns run from the `RefCell` decision that settled the Rust skip list, through the review that audited the five Rust documents against [Spec_TextFinder.md](../Spec_TextFinder.md) and the thirteen fixes it produced, into the parent-specification changes those fixes forced, the C++ specifications and source they in turn obliged, and the page updates that closed the session. Turns 1 through 11 are recorded in [Prompts_Pages.md](../Prompts_Pages.md), which the tail of this file was moved out of; turn 11, where the five Rust documents were first written, is there.

Three of these turns reach past Rust. Turns 16 through 19 move the reason lines into the C++ specifications and rebuild `Cpp_TextFinder_Dirnav.ixx` from them, because a parent-specification change made for Rust binds C++ too, and turns 20 and 21 update the `Spec_Driven_Design_*.html` pages that the same changes made stale.

User prompts are quoted verbatim. Assistant replies are summarized from the actual responses; tool calls are noted as effects rather than transcribed.

---

## Turn 12

### User

> 1. ok
> 2. ok
> 3. I think use of a RefCell will fix this problem without unsafe or lock.
>
> edit the Project_Tree.md after finishing the Rust additions

### Assistant

Adopted the `RefCell`, which recovers §3.5's one-argument signature, and recorded why it must be a `thread_local!` rather than a plain `static`: a `static` must be `Sync` and `RefCell`'s borrow flag is an ordinary integer, not an atomic one, and the bound costs nothing because the list is finished before traversal starts and traversal is single-threaded. Step 7 takes the list out of the cell with `RefCell::take` into a local, so the `Dirnav`'s borrow lasts the whole traversal instead of the body of a `with` closure; §4's step 7 wording was updated to match.

`Project_Tree.md` gained the Rust subtree, the Cpp entry moving from `└──` to `├──` and its 50 subtree lines picking up the continuation bar, with one legend line noting the directory is at the specification stage. Verified both directions: every path drawn exists, and nothing under the project is missing except six files that predate the change, `Demo_9-14-2026.md`, `Page_Structure.md`, `Prompts_Page_Structure.md`, `Text_Tone.md`, `Prompts_Text_Tone.md`, and `README.md`. `Text_Tone.md` is absent by an earlier decision; the other five look like drift. All six left alone, the edit having been scoped to the Rust additions.

---

## Turn 13

### User

> are the rust specs consistent with the project spec and do they have any issues to address

### Assistant

Reviewed all five Rust documents against `Spec_TextFinder.md` and against each other without editing, and said plainly that these were the assistant's own drafts, so the review is a self-audit rather than an independent one. Found the substance consistent: the nine defaults match the §5 table, the engine is `regex` and no other, the two-level block form and two-space indent are fixed, the file and error announcement split and its `/h` gating are right, `addSkipDirectory` extends rather than replaces, the no-content case carries both accepted costs, and the three §5.3 listing cases are one function.

Then thirteen items, four of them behavioral. Will not compile: the sink has no `flush` but Entry §4 step 8 requires one. Contradictions: a non-UTF-8 entry name is handled two ways and neither announcement fits §3.4, which is a parent-spec gap C++ shares through `generic_string()`; `invalid argument encoding` exits 1, which §3.4's code-1 row forbids, with three ways out; and exit code 2 is unreachable, which the third of those ways would fix. Gaps: a root path's own separators are never normalized, so `-P src\sub` emits `src\sub/file.rs`; the skip-list comparison does not name its folding rule where the extension test does; and a failing flush in `Drop` is unspecified. A claim that does not hold: Cmdline §5 rule 1's char-counting justification is wrong, byte and char counting producing identical diagnostics for every input. Minor: `char::is_ascii_whitespace` excludes U+000B where C's `isspace` includes it, so `/p "cpp,\vrs"` normalizes differently in the two implementations; nothing prevents a second `StdoutSink`; Dirnav §4's interface block shows no dependency lines; a Structure wording slip; and nothing yet specifies the Rust suites or demonstration.

---

## Turn 14

### User

> 1. use pub fn flush(&mut self)
> 2. settle in 3.4 for all implementations
> 3. use exit code 2
> 5. fix
> 6. Rust Spec uses the same rule
> 7. fix
> 8. the sentence should go
> 9. can you make Cmdline 7 language agnostic?
> 10. fix so there is only one StdoutSink
> 11. can you fix by referencing Cargo deps?
> 12. fix
> 13. fix in project spec by specifying creation of both

### Assistant

All thirteen applied, three of them in `Spec_TextFinder.md`, which binds all four implementations, with §7 Non-Goals keeping its number so no citation broke. §3.4's `cannot open` row now also covers a file that "carries a name the implementation cannot render as text", with a paragraph defining the case as bytes that are not valid UTF-8 on POSIX and unpaired surrogates on Windows, fixing U+FFFD substitution, and stating the two accepted costs. The §5 `/p` row now names six whitespace characters, so no two implementations trim a different set. And a new §6.2 Verification requires unit suites per library component, one integration suite, one demonstration, and a runner per kind that announces each suite and exits with the failure count, a suite never built counting as a failure, with dated captures replaced rather than edited.

On the Rust side: `flush` added and called at step 8; the undecodable argument moved to exit 2, which makes code 2 reachable and retires item 4; root path separators normalized; the skip-list comparison bound to the same function as the extension test; a failing `Drop` flush now writing the one notice; the spurious char-counting sentence deleted; `new() -> Option<Self>` behind a `thread_local!` `Cell` with `Default` dropped, since it cannot promise a `Self`; `use` lines added to the Dirnav interface block keyed to §9's Cargo dependencies; and the Structure wording corrected. Two stray citations of "Entry §4 step 7" for regex compilation were fixed to step 8, the C++ numbering having been carried across.

One consequence raised for decision: widening §3.4 binds C++ too, and C++ does not satisfy it, `Spec_Cpp_TextFinder_Dirnav.md` saying nothing about an unrenderable name and `displayPath` calling `generic_string()`, which on Windows can throw. Neither the C++ spec nor its code was touched, a code change starting with a spec change.

---

## Turn 15

### User

> I want the outputs (no errors) to match as long as any fixes don't over-complicate the specs.  I don't intend to specify exactly matching error messages.  That can be an implementation decision.  Fix 7 for rust, and change the parent to require the parts specs to use language specific needs or idioms.

### Assistant

Put the line at stdout. A new parent §2 paragraph states what the document fixes, the blocks and announcements of §3.4, the §5.1 help text, the §5.3 listing, and the exit codes, and delegates the rest to each component spec in its own language's idiom, naming the argument vector, the skip-list signature, stderr wording, and the standard-library facilities behind each rule. §6 Consistency now says the guarantee is over stdout, so a cross-implementation test compares stdout and the exit code and leaves stderr alone.

§5.2 kept its table but changed status: the seven reason lines are the wording the document supplies and an implementation adopting them unchanged is the expected case, while what it still binds is the shape, the destination, exit code 1, and the stdout behavior of the invalid-regex row. Four downstream sentences that asserted byte-identical diagnostics were softened. `/H` help and the `/v` listing were untouched, both being stdout.

On the Rust side, Cmdline §6 now carries the six parse-time reason lines as its own table and says it adopts §5.2's wording unchanged, and Entry §6 fixes the seventh and the two code-2 strings. The Entry spec's reason for not printing the `regex` crate's own error was rewritten, the old justification having rested on the parent binding the text, where the reason that outlives the change is that a crate upgrade would otherwise alter this program's output with no document recording it. Left undone deliberately: three C++ passages still attribute their wording to a document that no longer claims it.

---

## Turn 16

### User

> move the changes to Cpp as well.  fix the reason lines for Cpp.  Can you fix 3.4 for C++?

### Assistant

Moved the wording into the C++ specs, `Spec_Cpp_TextFinder_Cmdline.md` §6 carrying the six parse-time reason lines and `Spec_Cpp_TextFinder_Entry.md` §6 the seventh plus `cannot initialize output`, both stopping short of attributing them to the parent, and §4 step 3 gaining the reason `std::regex_error::what()` is not written. Also updated Cmdline §7, which still defined whitespace locally, to defer to §5's six characters, noting that `std::isspace` in the C locale reports exactly those six and calling out the `unsigned char` cast, since a path byte above 0x7F makes the unguarded call undefined. No C++ code changed; only the authority moved.

On §3.4 the answer was yes with a catch. The Windows half is worth having, `path::generic_string()` being permitted to fail and MSVC's throwing `std::system_error`, which nothing catches, so a file with an unpaired surrogate terminates the program mid-traversal. The POSIX half is the problem: a `path` there holds raw bytes that pass through unchanged, so C++ searches such a file correctly today, and conforming would mean adding code whose only effect is to refuse files it currently handles. Offered two ways out, A keeping §3.4 as approved at the cost of the POSIX regression, and B narrowing it so the file is searched and only its reported path is lossy, and recommended B.

---

## Turn 17

### User

> explain why the unimplemented changes make C++ worse

### Assistant

Traced it through the code rather than from memory. `displayPath` calls `path::generic_string()` and `baseName` calls `path::filename().string()`, and the two behave differently by platform because `path::value_type` does. On POSIX, `value_type` is `char` and the native format already uses `/`, so `generic_string()` is effectively an identity copy that does not validate and cannot fail: a file named `caf\xE9.cpp`, a `café.cpp` from a Latin-1 editor, flows through the whole pipeline intact and its matches are reported. On Windows, `value_type` is `wchar_t`, both calls must convert UTF-16 to narrow, and an unpaired surrogate has no UTF-8 encoding, so the conversion throws.

The harm on POSIX is that the rule turns `src/caf\xE9.cpp` into `cannot open src/caf<U+FFFD>.cpp`: a legitimate source file with valid UTF-8 contents drops out of the results and is reported as a failure, and the only new code is code that refuses files the program handles correctly. Explained the origin honestly, the rule having been generalized from Rust, where `String` is validated UTF-8 and `OsStr::to_str` returns `Option` on both platforms, so the constraint is symmetric there and is not in C++.

The Windows defect turned out worse than stated the turn before: `selected()` calls `baseName` for every file whenever `/p` is non-empty and `pruned()` calls it for every directory, so the conversion runs during selection, before anything is emitted, and `main.cpp:79` runs the traversal loop outside any `try`, so the throw escapes `main` and terminates the process with partial output and no diagnostic. Closed with the honest case for A: it keeps every path on stdout usable, where B admits a path line containing U+FFFD that looks like a path and is not one.

---

## Turn 18

### User

> Use option A.  If Posix throws in this case, catch and emit a brief error explanation but continue processing

### Assistant

Put the catch-and-continue requirement in the parent, since it binds every implementation: rendering a name may not end the run, a failure that would propagate out of the walk is contained where it arises, the entry draws its announcement, traversal continues, and the run still exits 0.

C++ Dirnav stops using `path::generic_string()` and `filename().string()` for rendering, both being the wrong tool because one platform never reports the condition and the other reports it by throwing out of the walk. In their place is a helper that behaves identically on both and cannot throw, producing the generic form with U+FFFD per unrenderable unit and a flag saying whether it substituted: POSIX walks the bytes reusing the same `validUtf8` test applied to file contents, Windows walks the UTF-16 units and substitutes for each unpaired surrogate. Calling neither converting function, it leaves nothing to throw and nothing to catch, which is a stronger guarantee than catching. That flag drives a new §5 rule 6, Unrenderable names, with Failed opens renumbered to 7.

Placing the gate revealed a divergence: C++ now tests renderability before selection, so an unrenderable name draws `cannot open` whatever `/p` holds, while Rust's text had the extension filter reach it first and emitted nothing under a non-empty `/p`. Same tree, same command line, different stdout. §3.4 is written over every such file rather than over the selected ones, so C++ had it right and Rust now carries the identical rule in the identical position. One deliberate asymmetry survives in both: a symbolic link is tested before rule 6, so a link with an unrenderable name stays silent.

Two notes. The C++ code did not yet match its spec, so the Windows crash was still live. And a disclosure: a verification script globbed `*_Structure.md` across the tree and read `archive/Page_Structure.md` in passing, extracting link targets by regex; nothing from it reached any decision, Constitution rule 2 bars it, the context was discarded, and the re-run excluded `archive` explicitly.

---

## Turn 19

### User

> rebuild the C++ from it's modified specs (no other source or example used), build, and run the unit, integration and demonstration tests and show me the output

### Assistant

Exactly one source file changed, `Cpp_TextFinder_Dirnav.ixx`, the Cmdline and Entry spec edits having moved authority for text the code already emitted. Wrote `renderPath(path, lossy)` from §5 rule 6 and §8 alone, producing the generic form and substituting U+FFFD per unrenderable unit, with Windows walking the UTF-16 native string and POSIX walking the native bytes; factored `utf8Sequence` out of `validUtf8` so the two share one definition, as §8 requires; and gated `walk` after the symlink test and `search` for the root through `renderable()`, with `baseName` and `displayPath` routing through `renderPath`.

All four suites passed, 50 Cmdline, 28 Dirnav, 9 Output, and 49 integration, 136 assertions with every driver exiting 0, and the demonstration ran all eight invocations and exited 0. Two build notes: the first attempt failed on `io.h: no include path set`, this shell lacking the MSVC include paths that the Output module's global fragment needs, and the rebuild through `vcvars64.bat` succeeded.

Three things reported. The new code path is untested, no suite creating a name that cannot be rendered, so what the 136 assertions prove is that `renderPath` is byte-identical to `generic_string()` for ordinary names, which is the regression risk, not that the substitution branch is right. The demonstration counts moved because the five Rust specs joined the tree that day, five of eight numbers changing, which makes `Spec_Driven_Design_Cpp_Demonstration.html` stale and, under `Page_Structure.md` §7.5, due a full recapture. And one capture is self-referential: invocation 3 reports `Cpp_TextFinder_Dirnav.ixx` line 255 where the earlier capture said 167, the 88-line shift being the new helpers, so the demonstration is measuring the change just made.

---

## Turn 20

### User

> update the Spec_Driven_*.html pages

### Assistant

Inventoried what the pages claimed that the specs no longer said, then worked through the Behavior Overview, Contracts, Process Specification, C++, and Traversal pages and began recapturing the Demonstration page per `Page_Structure.md` §7.5. The turn ended part way through, the API returning a usage-limit error rather than a reply.

---

## Turn 21

### User

> continue

### Assistant

Finished the remaining pages. Ten of the 18 were updated and all 18 still verify structurally, with balanced tags, resolving section anchors, contiguous `<h3>` numbering, and good internal links.

In the Behavior thread: CommandLine's §4 now says §5.2 binds the shape, destination, exit code, and stdout behavior but not the wording, and §6 was retitled from "Why the Text Is Fixed Byte for Byte" to "Where the Line Falls: stdout, Not stderr" and rewritten around the point that relaxing §5.2 retired a claim the project could not keep. Overview widened the `cannot open` row and gained the unrenderable-name case and the rule that rendering may not end the run. Traversal placed the gate after the symlink test. Contracts scoped consistency to stdout and gained a new section on §6.2, pushing Non-Goals to 7.

In the Process thread, Specification now distinguishes the two blocks that stayed binding from the one that did not. In the C++ thread, Cmdline and Entry record that the reason lines moved into the C++ specs with nothing emitted moving; Dirnav took the largest revision, with the gate, the `generic_string()` rejection, `renderPath`, and the source re-embedded at 342 lines; Testing names §6.2 and adds a paragraph on the coverage gap; and Demonstration was recaptured in full, all ten blocks replaced from a fresh run, four prose counts corrected, and a paragraph added explaining that five of eight numbers moved within a day with nothing about the program changing. The Introduction's Rust row now reads "Specifications written … No code, and no pages yet".

Two things left deliberately. The Rust thread's eight pages do not exist, so the Rust entry in every header row stays disabled, §2.4 disabling a thread only while it has no pages and §6 requiring a language thread be created whole. And the prompt records embedded in `<details>` blocks still carry the old §5.2 language, including a verbatim quote of "fixed text, identical across implementations"; those are history and stay as written, §8 treating them as process evidence.