fix(stella-pipeline): do not render an untracked file through both diff channels

[macanderson]

Follow-up to #2034, which merged before this landed on the same branch.

The problem #2034 introduced

#2034 made the probe half of the diff render an untracked file's content. The authored half (FileTouchPort::authored_diff) already rendered the same content for any file written through the file tools — and absorb_probe concatenates the two halves.

So after #2034, a file written with write_file that is also untracked — the single commonest shape of agent work — reached the verifier twice: once as a probe hunk, once as an authored chunk. That spends the diff budget twice to say one thing, and leaves a reader to wonder whether it is looking at one change or two.

The fix

DiffProbe now names the untracked paths whose content its text carries (untracked_rendered), and splice_authored drops those chunks from the authored half.

Reuses verify::strip_witness_hunks rather than writing a second chunk parser, so the two callers cannot come to disagree about where a chunk boundary is.

Which half survives is deliberate, and follows the precedence authored's own module docs already state — probe first, since on-disk state is the stronger claim where it exists. Only a hunk body claims the path: git's Binary files ... differ sentence is not content, so the authored channel still covers a binary file, and a path whose probe failed is likewise absent from the list.

This is the text-side analogue of the max (never a sum) that absorb_probe already applies to the two channels' line counts, for the same stated reason — they are two views of one change, not two changes.

Witness

a_file_the_probe_already_rendered_is_not_repeated_by_the_authored_half asserts the content appears exactly once (matches(...).count() == 1), which is the property that actually matters and which a "does it contain" assertion would not catch.

a_file_the_probe_did_not_render_is_still_spliced pins the other side: the drop is per path, and a file only the tools saw is still spliced — that being the entire reason the authored channel exists.

Gate

guards-fast (all 14), clippy -D warnings on stella-pipeline/stella-cli/stella-serve, and cargo test -p stella-pipeline — 605 pass, up from 603 by exactly these two tests.

Refs #2034

Summary by Sourcery

Prevent untracked files written by tools from having their contents rendered twice across probe and authored diff channels in the stella pipeline.

Bug Fixes:

• Avoid duplicate diff output for untracked files whose contents are present in both the probe and authored channels by dropping redundant authored chunks for those paths.

Tests:

• Add regression tests ensuring untracked files rendered by the probe are not repeated by the authored half, while files only seen by tools are still included in the final diff.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
stella-cli-docs	Ignored	Preview	Aug 7, 2026 4:53am

[sourcery-ai]

Reviewer's Guide

Ensures untracked files rendered by the diff probe are not redundantly rendered again in the authored diff, by tracking which untracked paths had their content emitted by the probe and dropping those chunks from the authored half while reusing shared chunk-parsing logic, plus tests to pin the new behavior.

Sequence diagram for combining probe and authored diffs without duplicate untracked content

sequenceDiagram
    participant Pipeline
    participant DiffProbe
    participant AuthoredChange
    participant authored as authored_module
    participant verify as verify_module

    Pipeline->>DiffProbe: gather_diff()
    DiffProbe-->>Pipeline: DiffProbe{text, available, untracked_rendered}

    Pipeline->>AuthoredChange: collect_authored_changes()
    AuthoredChange-->>Pipeline: AuthoredChange{text, ...}

    Pipeline->>authored: splice_authored(probe.text, &authored, &probe.untracked_rendered)
    activate authored
    authored->>verify: strip_witness_hunks(&authored.text, already_rendered)
    verify-->>authored: StripResult{diff}
    authored-->>Pipeline: combined_diff_text
    deactivate authored

    Pipeline->>Pipeline: verification_honest_diff(combined_diff_text)

Loading

File-Level Changes

Change	Details	Files
Make splice_authored aware of probe-rendered untracked paths and drop corresponding authored chunks while handling empty-text edge cases correctly.	Extend splice_authored to accept a slice of already-rendered untracked paths and pass authored.text through verify::strip_witness_hunks before splicing. Return probe_text alone when authored is empty or when all authored chunks for the listed paths are stripped resulting in empty content. Ensure that when only the authored side has content, the function returns the filtered authored_text without adding the authored section header; otherwise join probe and authored with the header using the filtered text.	crates/stella-pipeline/src/pipeline/authored.rs
Track which untracked files had their content rendered by the diff probe and propagate that metadata into splice_authored via DiffProbe.	Add an untracked_rendered: Vec field to DiffProbe, initialize it in all construction paths, and propagate it out of gather_diff. When rendering untracked file content in the probe, push the path into untracked_rendered only when a text hunk body is present (starts with "@@ "), excluding binary or failed probe cases. Update the verification path to pass probe.untracked_rendered into authored::splice_authored so redundant authored hunks are removed for those paths.	crates/stella-pipeline/src/pipeline/verify_probes.rs
Add tests to pin non-duplication of probe-rendered untracked files and preservation of authored-only files.	Add a test ensuring that when the probe already rendered an untracked file’s content, the spliced diff does not repeat that content and it appears exactly once. Add a test ensuring that if the probe rendered some other file, an authored-only file is still included in the spliced diff and the authored section header appears. Update existing tests for splice_authored to pass the new already_rendered parameter explicitly.	crates/stella-pipeline/src/pipeline/authored.rs

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