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lets make the fanout match the max links from files and rename profile to `-wide` this will make it easier to discuss in ipfs/specs#499
Co-authored-by: Bumblefudge <bumblefudge@learningproof.xyz>
Import.* config params for controlling DAG width were added in: ipfs/kubo#10774
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Thank you for kicking this off, and filling initial state. I've incorporated specific "dag width" settings for Next:
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Co-authored-by: Christian Paul <info@jaller.de>
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include singularity as example showing balanced layout has implementation variants that affect CID determinism for large files: - document balanced-packed DAG layout variant (data-preservation-programs/singularity#525) - note boxo defaults for HAMT parameters - note rclone defaults for hidden files and symlinks
src/ipips/ipip-0499.md
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| This structural difference causes CID mismatches for files larger than `chunk_size * dag_width` (e.g., >1 GiB with 1 MiB chunks and 1024 links per node), even when all other parameters match. | ||
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| ### Divergence in current implementations |
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I've included Singularity as example showing that even among different "balanced" layout implementations we can see different variants that affect CID determinism for large files.
- documented
balancedandbalanced-packedDAG layout variants - noted implicit boxo defaults for HAMT parameters that the project seems to be using
- assumed it uses rclone's defaults for hidden files and symlinks
cc data-preservation-programs/singularity#525 @SethDocherty @parkan @2color to proofread if the "singularity" column here reflects reality or if there is more nuance to what Singularity does
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Nice addition with the balanced-packed section. What you've documented there sounds correct to me. I also believe one of the design reasons for Singularity going with a balanced-packed approach is to pack chunked content as best as possible to fit into Filecoin Sectors. Up to you, but it's some additional design context to consider if it would be worth noting
The table details for Singularity look correct, too.
add new --dereference-symlinks boolean flag that recursively resolves all symlinks to their target content during file collection. this works on symlinks inside directories, not just CLI arguments. the flag is wired through cli/parse.go to boxo's SerialFileOptions.DereferenceSymlinks. deprecate --dereference-args which only worked on symlinks passed directly as CLI arguments. the help text now indicates it is deprecated and directs users to use --dereference-symlinks instead. ref: ipfs/specs#499
add CLI flags for controlling file collection behavior during ipfs add: - `--dereference-symlinks`: recursively resolve symlinks to their target content (replaces deprecated --dereference-args which only worked on CLI arguments). wired through go-ipfs-cmds to boxo's SerialFileOptions. - `--empty-dirs` / `-E`: include empty directories (default: true) - `--hidden` / `-H`: include hidden files (default: false) these flags are CLI-only and not wired to Import.* config options because go-ipfs-cmds library handles input file filtering before the directory tree is passed to kubo. removed unused Import.UnixFSSymlinkMode config option that was defined but never actually read by the CLI. also: - wire --trickle to Import.UnixFSDAGLayout config default - update go-ipfs-cmds to v0.15.1-0.20260117043932-17687e216294 - add SYMLINK HANDLING section to ipfs add help text - add CLI tests for all three flags ref: ipfs/specs#499
add CLI flags for controlling file collection behavior during ipfs add: - `--dereference-symlinks`: recursively resolve symlinks to their target content (replaces deprecated --dereference-args which only worked on CLI arguments). wired through go-ipfs-cmds to boxo's SerialFileOptions. - `--empty-dirs` / `-E`: include empty directories (default: true) - `--hidden` / `-H`: include hidden files (default: false) these flags are CLI-only and not wired to Import.* config options because go-ipfs-cmds library handles input file filtering before the directory tree is passed to kubo. removed unused Import.UnixFSSymlinkMode config option that was defined but never actually read by the CLI. also: - wire --trickle to Import.UnixFSDAGLayout config default - update go-ipfs-cmds to v0.15.1-0.20260117043932-17687e216294 - add SYMLINK HANDLING section to ipfs add help text - add CLI tests for all three flags ref: ipfs/specs#499
add CLI flags for controlling file collection behavior during ipfs add: - `--dereference-symlinks`: recursively resolve symlinks to their target content (replaces deprecated --dereference-args which only worked on CLI arguments). wired through go-ipfs-cmds to boxo's SerialFileOptions. - `--empty-dirs` / `-E`: include empty directories (default: true) - `--hidden` / `-H`: include hidden files (default: false) these flags are CLI-only and not wired to Import.* config options because go-ipfs-cmds library handles input file filtering before the directory tree is passed to kubo. removed unused Import.UnixFSSymlinkMode config option that was defined but never actually read by the CLI. also: - wire --trickle to Import.UnixFSDAGLayout config default - update go-ipfs-cmds to v0.15.1-0.20260117043932-17687e216294 - add SYMLINK HANDLING section to ipfs add help text - add CLI tests for all three flags ref: ipfs/specs#499
| | DAG layout | balanced | | ||
| | DAG width (children per node) | 1024 | | ||
| | HAMTDirectory fanout | 256 blocks | | ||
| | HAMTDirectory threshold | 256KiB (block-bytes) | |
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I don't think Helia can currently do block-bytes. How much of a problem is this for making this the "modern" profile? Or does that just mean there's work to do.
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Oh, I see from your table that links-bytes is the most common across the implementations, so why not just use it? It's not precise, but it means that you don't need to change implementations as much to conform.
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@rvagg just mean there's work to do to implement block-bytes, but we will do it in Helia for parity with Kubo.
I hear you - standardizing on links-bytes sounds pragmatic at first. But the more I dug into this, the more I realized implementations aren't actually aligned on anything that feels solid:
- GO used
>=despite comments claiming>(just fixed in ipfs/boxo@6707376, JS uses>(imo correctly)) - but then JS hardcodes CID byte lengths assuming sha2-256 (link). Using longer hash function would produce incorrect estimation etc. Yes, this doesn't impact the default today, but it's not a solid foundation for a modern standard, it would backfire in the future when we switch away from
sha2-256
Both implementations need code changes to align on any method. There's no free lunch here.
Given that we're already introducing unixfs-v1-2025 with intentional breaking changes (1MiB chunks), this is our window to get it right, avoid ambiguity.
The goal of IPIP-499 is to create sensible modern profile that is implementable without poking your eyes out. I feel it needs block-bytes: it is unambiguous, precise, hash-agnostic, and future-proof. Legacy behavior stays in unixfs-v0-2015 for anyone who needs it, and modern software can just choose to not implement it.
(This is my "strong belief weakly held", I'm happy to be convinced otherwise :))
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reasonable, as long as there is people-budget to do all the work on this 👍
- add verification process for testing profile compliance - add test vectors for unixfs-v0-2015 profile (5 CIDs) - add test vectors for unixfs-v1-2025 profile (5 CIDs) - document HAMT threshold behavior (> not >=) - document balanced vs trickle DAG layout with ASCII diagrams - add trickle layout CID for reader compatibility testing - reference existing test vectors from UnixFS spec (empty dir, symlink)
Update (2026-01-24)Since the last update, we've made progress on multiple fronts: specs (this PR)
boxo
kubo
helia
Next stepsWe're planning to wait for kubo 0.40 to ship with the new profile built-in, and have both profiles explicitly implemented and tested in Helia as well, before ratifying this IPIP. Last call for feedback on
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I can tell you as a small but relatively popular developer which stores their program in IPFS and uses own ipns republisher/update system that this is very good! The most important thing that all 0.40 kubos should use the unixfs-v1-2025 by default, and everyone better comply to that. Determinism is very good, but determinism with different implementations is even better. It was very frustrating to see for the first time that Storacha and Pinata used different cid generation mechanism. Thank you very much for all the hard work, God bless you! |
add chunk size threshold test vectors for precise boundary testing: - file-at-chunk: file exactly at chunk size (single block) - file-over-chunk: file +1 byte over chunk size (2 blocks) update file-over-max-links CIDs to use +1 byte threshold instead of +1 chunk, enabling more precise DAG rebalancing boundary tests.
- move HAMT sharding history to Motivation, add HAMT switch comparison to profiles - rename Divergence section to Divergences across ecosystem - merge Observed differences into balanced-packed, promote subsections to h3 - move Why sections under Compatibility
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| - 2026-01: [boxo#1088](https://github.com/ipfs/boxo/pull/1088) fixed threshold comparison from `>=` to `>`, aligning with JS implementation and documentation. Shipped in Kubo 0.40. | ||
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| Timeline of JavaScript implementation changes: |
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@achingbrain added timelines for GO and JS to show all permutations. This is my understanding of the JS timeline (only included things that actually shipped).
TLDR: js-ipfs did link counting and then switched to link-bytes to be better aligned with GO, is this accurate?
👍 / 👎 if I got this right.
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@lidel sounds like we're going to need to do some work to make singularity compliant with this (ref data-preservation-programs/singularity#525) yes? |
#315) * feat: add --dereference-symlinks flag for recursive symlink resolution add new --dereference-symlinks boolean flag that recursively resolves all symlinks to their target content during file collection. this works on symlinks inside directories, not just CLI arguments. the flag is wired through cli/parse.go to boxo's SerialFileOptions.DereferenceSymlinks. deprecate --dereference-args which only worked on symlinks passed directly as CLI arguments. the help text now indicates it is deprecated and directs users to use --dereference-symlinks instead. ref: ipfs/specs#499 * fix: make --dereference-symlinks resolve CLI arg symlinks too --dereference-symlinks is now a superset of --dereference-args: - resolves symlinks passed as CLI arguments (like --dereference-args) - ALSO resolves symlinks found during directory traversal (new behavior) this allows users to use just --dereference-symlinks instead of needing to pass both flags for full symlink resolution. * chore: update to rebased boxo PR updates github.com/ipfs/boxo to 56cf0aecdc1a (feat/ipip-499-unixfs-2025 rebased on main) * fix: reuse derefSymlinks variable, fix typo in deprecation notice * chore: update boxo to f188f79fd412 switches to boxo@main after merging ipfs/boxo#1088
* feat(config): Import.* and unixfs-v1-2025 profile implements IPIP-499: add config options for controlling UnixFS DAG determinism and introduces `unixfs-v1-2025` and `unixfs-v0-2015` profiles for cross-implementation CID reproducibility. changes: - add Import.* fields: HAMTDirectorySizeEstimation, SymlinkMode, DAGLayout, IncludeEmptyDirectories, IncludeHidden - add validation for all Import.* config values - add unixfs-v1-2025 profile (recommended for new data) - add unixfs-v0-2015 profile (alias: legacy-cid-v0) - remove deprecated test-cid-v1 and test-cid-v1-wide profiles - wire Import.HAMTSizeEstimationMode() to boxo globals - update go.mod to use boxo with SizeEstimationMode support ref: https://specs.ipfs.tech/ipips/ipip-0499/ * feat(add): add --dereference-symlinks, --empty-dirs, --hidden CLI flags add CLI flags for controlling file collection behavior during ipfs add: - `--dereference-symlinks`: recursively resolve symlinks to their target content (replaces deprecated --dereference-args which only worked on CLI arguments). wired through go-ipfs-cmds to boxo's SerialFileOptions. - `--empty-dirs` / `-E`: include empty directories (default: true) - `--hidden` / `-H`: include hidden files (default: false) these flags are CLI-only and not wired to Import.* config options because go-ipfs-cmds library handles input file filtering before the directory tree is passed to kubo. removed unused Import.UnixFSSymlinkMode config option that was defined but never actually read by the CLI. also: - wire --trickle to Import.UnixFSDAGLayout config default - update go-ipfs-cmds to v0.15.1-0.20260117043932-17687e216294 - add SYMLINK HANDLING section to ipfs add help text - add CLI tests for all three flags ref: ipfs/specs#499 * test(add): add CID profile tests and wire SizeEstimationMode add comprehensive test suite for UnixFS CID determinism per IPIP-499: - verify exact HAMT threshold boundary for both estimation modes: - v0-2015 (links): sum(name_len + cid_len) == 262144 - v1-2025 (block): serialized block size == 262144 - verify HAMT triggers at threshold + 1 byte for both profiles - add all deterministic CIDs for cross-implementation testing also wires SizeEstimationMode through CLI/API, allowing Import.UnixFSHAMTSizeEstimation config to take effect. bumps boxo to ipfs/boxo@6707376 which aligns HAMT threshold with JS implementation (uses > instead of >=), fixing CID determinism at the exact 256 KiB boundary. * feat(add): --dereference-symlinks now resolves all symlinks Previously, resolving symlinks required two flags: - --dereference-args: resolved symlinks passed as CLI arguments - --dereference-symlinks: resolved symlinks inside directories Now --dereference-symlinks handles both cases. Users only need one flag to fully dereference symlinks when adding files to IPFS. The deprecated --dereference-args still works for backwards compatibility but is no longer necessary. * chore: update boxo and improve changelog - update boxo to ebdaf07c (nil filter fix, thread-safety docs) - simplify changelog for IPIP-499 section - shorten test names, move context to comments * chore: update boxo to 5cf22196 * chore: apply suggestions from code review Co-authored-by: Andrew Gillis <11790789+gammazero@users.noreply.github.com> * test(add): verify balanced DAG layout produces uniform leaf depth add test that confirms kubo uses balanced layout (all leaves at same depth) rather than balanced-packed (varying depths). creates 45MiB file to trigger multi-level DAG and walks it to verify leaf depth uniformity. includes trickle subtest to validate test logic can detect varying depths. supports CAR export via DAG_LAYOUT_CAR_OUTPUT env var for test vectors. * chore(deps): update boxo to 6141039ad8ef switches to ipfs/boxo@6141039 changes since 5cf22196ad0b: - refactor(unixfs): use arithmetic for exact block size calculation - refactor(unixfs): unify size tracking and make SizeEstimationMode immutable - feat(unixfs): optimize SizeEstimationBlock and add mode/mtime tests also clarifies that directory sharding globals affect both `ipfs add` and MFS. * test(cli): improve HAMT threshold tests with exact +1 byte verification - add UnixFSDataType() helper to directly check UnixFS type via protobuf - refactor threshold tests to use exact +1 byte calculations instead of +1 file - verify directory type directly (ft.TDirectory vs ft.THAMTShard) instead of inferring from link count - clean up helper function signatures by removing unused cidLength parameter * test(cli): consolidate profile tests into cid_profiles_test.go remove duplicate profile threshold tests from add_test.go since they are fully covered by the data-driven tests in cid_profiles_test.go. changes: - improve test names to describe what threshold is being tested - add inline documentation explaining each test's purpose - add byte-precise helper IPFSAddDeterministicBytes for threshold tests - remove ~200 lines of duplicated test code from add_test.go - keep non-profile tests (pinning, symlinks, hidden files) in add_test.go * chore: update to rebased boxo and go-ipfs-cmds PRs * docs: add HAMT threshold fix details to changelog * feat(mfs): use Import config for CID version and hash function make MFS commands (files cp, files write, files mkdir, files chcid) respect Import.CidVersion and Import.HashFunction config settings when CLI options are not explicitly provided. also add tests for: - files write respects Import.UnixFSRawLeaves=true - single-block file: files write produces same CID as ipfs add - updated comments clarifying CID parity with ipfs add * feat(files): wire Import.UnixFSChunker and UnixFSDirectoryMaxLinks to MFS `ipfs files` commands now respect these Import.* config options: - UnixFSChunker: configures chunk size for `files write` - UnixFSDirectoryMaxLinks: triggers HAMT sharding in `files mkdir` - UnixFSHAMTDirectorySizeEstimation: controls size estimation mode previously, MFS used hardcoded defaults ignoring user config. changes: - config/import.go: add UnixFSSplitterFunc() returning chunk.SplitterGen - core/node/core.go: pass chunker, maxLinks, sizeEstimationMode to mfs.NewRoot() via new boxo RootOption API - core/commands/files.go: pass maxLinks and sizeEstimationMode to mfs.Mkdir() and ensureContainingDirectoryExists(); document that UnixFSFileMaxLinks doesn't apply to files write (trickle DAG limitation) - test/cli/files_test.go: add tests for UnixFSDirectoryMaxLinks and UnixFSChunker, including CID parity test with `ipfs add --trickle` related: boxo@54e044f1b265 * feat(files): wire Import.UnixFSHAMTDirectoryMaxFanout and UnixFSHAMTDirectorySizeThreshold wire remaining HAMT config options to MFS root: - Import.UnixFSHAMTDirectoryMaxFanout via mfs.WithMaxHAMTFanout - Import.UnixFSHAMTDirectorySizeThreshold via mfs.WithHAMTShardingSize add CLI tests: - files mkdir respects Import.UnixFSHAMTDirectoryMaxFanout - files mkdir respects Import.UnixFSHAMTDirectorySizeThreshold - config change takes effect after daemon restart add UnixFSHAMTFanout() helper to test harness update boxo to ac97424d99ab90e097fc7c36f285988b596b6f05 * fix(mfs): single-block files in CIDv1 dirs now produce raw CIDs problem: `ipfs files write` in CIDv1 directories wrapped single-block files in dag-pb even when raw-leaves was enabled, producing different CIDs than `ipfs add --raw-leaves` for the same content. fix: boxo now collapses single-block ProtoNode wrappers (with no metadata) to RawNode in DagModifier.GetNode(). files with mtime/mode stay as dag-pb since raw blocks cannot store UnixFS metadata. also fixes sparse file writes where writing past EOF would lose data because expandSparse didn't update the internal node pointer. updates boxo to v0.36.1-0.20260203003133-7884ae23aaff updates t0250-files-api.sh test hashes to match new behavior * chore(test): use Go 1.22+ range-over-int syntax * chore: update boxo to c6829fe26860 - fix typo in files write help text - update boxo with CI fixes (gofumpt, race condition in test) * chore: update go-ipfs-cmds to 192ec9d15c1f includes binary content types fix: gzip, zip, vnd.ipld.car, vnd.ipld.raw, vnd.ipfs.ipns-record * chore: update boxo to 0a22cde9225c includes refactor of maxLinks check in addLinkChild (review feedback). * ci: fix helia-interop and improve caching skip '@helia/mfs - should have the same CID after creating a file' test until helia implements IPIP-499 (tracking: ipfs/helia#941) the test fails because kubo now collapses single-block files to raw CIDs while helia explicitly uses reduceSingleLeafToSelf: false changes: - run aegir directly instead of helia-interop binary (binary ignores --grep flags) - cache node_modules keyed by @helia/interop version from npm registry - skip npm install on cache hit (matches ipfs-webui caching pattern) * chore: update boxo to 1e30b954 includes latest upstream changes from boxo main * chore: update go-ipfs-cmds to 1b2a641ed6f6 * chore: update boxo to f188f79fd412 switches to boxo@main after merging ipfs/boxo#1088 * chore: update go-ipfs-cmds to af9bcbaf5709 switches to go-ipfs-cmds@master after merging ipfs/go-ipfs-cmds#315 --------- Co-authored-by: Andrew Gillis <11790789+gammazero@users.noreply.github.com>
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@parkan Not for me to say, it is up to the project. The difference ( Whether matching future Kubo 1.0 CIDs (the |
Currently, CIDs can be generated with a variety of settings and optimizations for chunking, DAG width, and more. This means the same file can yield multiple, different CIDs depending on which tools and settings are used, and it is not possible to reliably reproduce or verify the CID.
This proposal introduces profiles for IPFS CIDs. Profiles explicitly define CID version, hash algorithm, chunk size, DAG width, layout, and other parameters. They can be used to verify data across implementations, provide recommended settings depending on retrieval performance goals, and more.