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diff --git a/openspec/changes/add-toc-depth/design.md b/openspec/changes/archive/2026-09-28-add-toc-depth/design.md
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diff --git a/openspec/changes/add-toc-depth/specs/toc-depth/spec.md b/openspec/changes/archive/2026-09-28-add-toc-depth/specs/toc-depth/spec.md
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diff --git a/openspec/changes/add-toc-depth/tasks.md b/openspec/changes/archive/2026-09-28-add-toc-depth/tasks.md
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diff --git a/openspec/specs/toc-depth/spec.md b/openspec/specs/toc-depth/spec.md
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+# toc-depth Specification
+
+## Purpose
+
+Lets the user limit the generated TOC to headings up to a given level, e.g. only `#` and
+`##`, for any input.
+
+## Requirements
+
+### Requirement: TOC limited by heading level
+
+With `--depth <NUM>` where `NUM` is greater than 0, the TOC SHALL contain entries only for
+headings whose level is less than or equal to `NUM` (`#` is level 1, `######` is level
+6). The level is absolute: it does not depend on the highest level present in the
+document. The remaining entries SHALL be the same as without `--depth`: same text, same
+anchor, same order, same indentation of `(level - 1) * indent` spaces. This SHALL apply
+to every input: stdin, a local file, a remote URL, several inputs, and `--insert`.
+
+`--depth <NUM>` SHALL be accepted after `--indent <NUM>` (when given) and before `-`,
+`--insert`, `--no-backup`, `--hide-footer`, `--skip-header` and the inputs.
+
+#### Scenario: Local file
+
+- **WHEN** the user runs `gh-md-toc --depth 2 "tests/test directory/test_depth.md"`,
+  where the file has the headings `# Title one`, `## Section`, `### Subsection`,
+  `#### Deep`, `# Title two`
+- **THEN** the TOC entries are `* [Title one](#title-one)`, `   * [Section](#section)`,
+  `* [Title two](#title-two)`, followed by
+  `<!-- Created by https://github.com/ekalinin/github-markdown-toc -->`
+
+#### Scenario: Stdin
+
+- **WHEN** the user runs
+  `cat "tests/test directory/test_depth.md" | gh-md-toc --depth 1 -`
+- **THEN** the output is `* [Title one](#title-one)` and `* [Title two](#title-two)`
+
+### Requirement: No limit by default
+
+Without `--depth`, or with `--depth 0`, the TOC SHALL contain an entry for every heading
+of the document, as before this change.
+
+#### Scenario: Without the option
+
+- **WHEN** the user runs `gh-md-toc "tests/test directory/test_depth.md"`
+- **THEN** the TOC entries are `* [Title one](#title-one)`, `   * [Section](#section)`,
+  `      * [Subsection](#subsection)`, `         * [Deep](#deep)`,
+  `* [Title two](#title-two)`
+
+#### Scenario: Zero depth
+
+- **WHEN** the user runs `gh-md-toc --depth 0 "tests/test directory/test_depth.md"`
+- **THEN** the TOC entries are the same as without the option
+
+### Requirement: Help lists the option
+
+`--help` SHALL list `--depth <NUM>` in the "Options" section right after
+`--indent <NUM>`.
+
+#### Scenario: Help output
+
+- **WHEN** the user runs `gh-md-toc --help`
+- **THEN** the line after `  --indent <NUM>      Set indent size. Default: 3.` is
+  `  --depth <NUM>       Max heading level to include into TOC. Default: 0 (all levels).`