Finalize previous-session artifact documentation and restore-analyze continuity coverage

docs/cli.md

@@ -30,6 +30,7 @@ For config semantics, see [docs/config.md](./config.md). For operator lifecycle
 - `--config <path>`: optional explicit `pipeline.yml` path.
 - `--session <path>`: optional explicit `session.yml` path.
 - `--session-id <value>`: session template variable value.
+- `--previous-session-id <value>`: previous-session template variable value.
 - `--force`: force stage execution.
 - `--artifacts <names>`: analyze artifact keys to execute (repeatable or comma-separated).
 
@@ -38,6 +39,7 @@ For config semantics, see [docs/config.md](./config.md). For operator lifecycle
 - `--config <path>`
 - `--session <path>`
 - `--session-id <value>`
+- `--previous-session-id <value>`
 - `--force`
 
 ### `resume`
@@ -45,6 +47,7 @@ For config semantics, see [docs/config.md](./config.md). For operator lifecycle
 - `--config <path>`
 - `--session <path>`
 - `--session-id <value>`
+- `--previous-session-id <value>`
 - `--force`
 - `--artifacts <names>`: analyze artifact keys to execute (repeatable or comma-separated).
 
@@ -53,6 +56,7 @@ For config semantics, see [docs/config.md](./config.md). For operator lifecycle
 - `--config <path>`
 - `--session <path>`
 - `--session-id <value>`
+- `--previous-session-id <value>`
 - `--force`
 - `--artifacts <names>`: analyze artifact keys to execute (repeatable or comma-separated).
 - positional `<stage>`: required stage name.
@@ -74,6 +78,7 @@ Valid stage names:
 - `--config <path>`
 - `--session <path>`
 - `--session-id <value>`
+- `--previous-session-id <value>`
 - `--dry-run`: plan restore actions without writing local files.
 - `--force`: overwrite local conflicting files with remote archive files.
 - `--include-audio`: include durable archived `audio/**` files in restore scope.
@@ -92,7 +97,7 @@ Purpose:
 Syntax:
 
 ```bash
-narratio run [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--force] [--artifacts <name[,name...]>]
+narratio run [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--previous-session-id <id>] [--force] [--artifacts <name[,name...]>]
 ```
 
 Success output:
@@ -112,7 +117,7 @@ Purpose:
 Syntax:
 
 ```bash
-narratio plan [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--force]
+narratio plan [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--previous-session-id <id>] [--force]
 ```
 
 Success output includes:
@@ -132,7 +137,7 @@ Purpose:
 Syntax:
 
 ```bash
-narratio resume [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--force] [--artifacts <name[,name...]>]
+narratio resume [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--previous-session-id <id>] [--force] [--artifacts <name[,name...]>]
 ```
 
 Success output:
@@ -172,7 +177,7 @@ Purpose:
 Syntax:
 
 ```bash
-narratio run-stage [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--force] [--artifacts <name[,name...]>] <stage>
+narratio run-stage [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--previous-session-id <id>] [--force] [--artifacts <name[,name...]>] <stage>
 ```
 
 Success output:
@@ -191,12 +196,12 @@ Common failure cases:
 ### `restore`
 
 Purpose:
-- Restore durable session state (`manifest.json`, `transcripts/**`, `artifacts/**`, and optional `audio/**`) from the committed remote archive current state.
+- Restore durable session state (`manifest.json`, `transcripts/**`, `artifacts/**`, `previous/**`, and optional `audio/**`) from the committed remote archive current state.
 
 Syntax:
 
 ```bash
-narratio restore [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--dry-run] [--force] [--include-audio]
+narratio restore [--config <pipeline.yml>] [--session <session.yml>] [--session-id <id>] [--previous-session-id <id>] [--dry-run] [--force] [--include-audio]
 ```
 
 Success output (dry-run):
@@ -260,6 +265,12 @@ narratio restore --session-id 2026-04-04
 narratio run-stage --session-id 2026-04-04 --force analyze
 ```
 
+Rehydrate canonical previous-session inputs after artifact-input changes:
+
+```bash
+narratio run-stage --session-id 2026-04-04 --force prepare
+```
+
 ## Diagnostic / Recovery Commands
 
 Inspect stage status:

docs/config.md

@@ -48,9 +48,13 @@ Template behavior:
 - supported placeholders:
   - `{{session_id}}`
   - `{{ session_id }}`
+  - `{{previous_session_id}}`
+  - `{{ previous_session_id }}`
 - `--session-id <value>` supplies the placeholder value.
+- `--previous-session-id <value>` supplies the previous-session placeholder value.
 - unresolved placeholders fail load.
 - if rendered `session_id` mismatches `--session-id`, load fails.
+- if rendered `previous_session_id` mismatches `--previous-session-id`, load fails.
 
 ## 4. Minimal pipeline config
 
@@ -83,6 +87,23 @@ Usage:
 narratio run --config /path/to/pipeline.yml --session ./session.yml --session-id 2026-05-03
 ```
 
+Previous-session-enabled variant:
+
+```yaml
+session_id: "{{ session_id }}"
+previous_session_id: "{{ previous_session_id }}"
+campaign: sample-campaign
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./examples/speakers.yml
+  autocorrect_file: ./examples/autocorrect.yml
+  glossary_file: ./examples/glossary.yml
+```
+
+```bash
+narratio run --config /path/to/pipeline.yml --session ./session.yml --session-id 2026-05-03 --previous-session-id 2026-04-26
+```
+
 ## 6. Production-oriented config
 
 ```yaml
@@ -127,6 +148,9 @@ scriptorium:
         transcript:
           source: narratio.transcript.trimmed
           required: true
+        previous_recap:
+          source: narratio.previous_session.artifact.session_recap
+          required: false
 ```
 
 Operational notes:
@@ -243,13 +267,14 @@ Scriptorium artifact-key and dependency rules:
 
 Allowed `pipeline.scriptorium.artifacts.<name>.inputs.<key>.source` values:
 
-- `previous_session_artifact`
+- `narratio.previous_session.artifact.<configured_artifact_key>`
 - `narratio.transcript.merged`
 - `narratio.transcript.polished`
 - `narratio.transcript.full`
 - `narratio.transcript.trimmed`
 - `narratio.bounds.session`
 - `narratio.artifact.<configured_artifact_key>`
+- `previous_session_artifact` (legacy path-based source; uses `inputs.<key>.path`)
 
 `pipeline.archive.promote_artifacts[].source` values:
 
@@ -272,13 +297,14 @@ Archive promotion destination rules:
 Restore-related implications:
 
 - restore remote identity requires archive S3 identity to resolve (`pipeline.storage.s3.bucket` and session prefix derivation inputs).
-- restore scope considers only committed current state and durable paths (`manifest.json`, `transcripts/**`, `artifacts/**`, optional `audio/**`).
+- restore scope considers committed current state and durable paths (`manifest.json`, `transcripts/**`, `artifacts/**`, `previous/**`, optional `audio/**`).
 
 ## 8. Full session reference
 
 | Path | Type | Required | Default |
 | --- | --- | --- | --- |
 | `session.session_id` | string | Yes | none |
+| `session.previous_session_id` | string | No | empty |
 | `session.campaign` | string | Yes | none |
 | `session.date` | string | No | empty |
 | `session.title` | string | No | empty |
@@ -297,6 +323,11 @@ Audio-source rule:
   - `audio_s3.prefix`
 - `audio_s3` cannot be combined with local audio fields.
 
+Previous-session rule:
+
+- if `session.previous_session_id` is set, it must not equal `session.session_id`.
+- canonical previous-session sources (`narratio.previous_session.artifact.<name>`) are hydrated during `prepare` from archive current state when required by enabled configured artifacts.
+
 ## 9. Secrets
 
 Narratio supports filesystem-based secret injection via `pipeline.secrets.env_dir`.

docs/internal/artifacts.md

@@ -1,41 +1,35 @@
 # Internal: Artifacts
 
 ## Purpose
-Define Narratio's artifact identity and resolution model for built-in transcript/bounds artifacts and runtime-configured analyze artifacts.
+Define Narratio artifact identity, catalog, and source-resolution behavior for:
+- built-in session artifacts;
+- configured analyze artifacts;
+- canonical previous-session artifact sources.
 
 ## Inputs and outputs
 Inputs:
-- artifact sources from config/runtime (`pipeline.scriptorium.artifacts.*.inputs.*.source`)
+- configured input sources (`pipeline.scriptorium.artifacts.*.inputs.*.source`);
-- session paths and optional session manifest stage outputs
+- session paths and manifest inputs/outputs;
-- runtime artifact catalog state for configured artifact sources
+- runtime catalog state.
 
 Outputs:
-- resolved local artifact path and provenance (`ResolvedSessionArtifact`)
+- resolved artifact path + provenance (`ResolvedSessionArtifact`);
-- runtime catalog entries for planned/executable/available artifacts
+- runtime catalog entries for built-ins and configured artifacts;
-- validation errors for unsupported, missing, or invalid artifact sources
+- requirement sets for canonical previous-session inputs.
 
 ## Boundaries
 Owns:
-- built-in artifact registry and content validation rules
+- built-in source registry and validation;
-- runtime artifact catalog for configured artifact source IDs
+- configured artifact catalog identity (`narratio.artifact.<name>`);
-- source resolution behavior for built-in and configured artifact sources
+- canonical previous-session source parsing and resolution;
+- previous-session requirement collection (`CollectPreviousArtifactRequirements`).
 
 Does not own:
-- artifact generation (stages produce files)
+- prepare-stage remote hydration;
-- manifest transition policy
+- stage success/skip transitions;
-- archive promotion behavior
+- archive upload orchestration.
-
-## Config fields used
-- `pipeline.scriptorium.artifacts.<name>.enabled`
-- `pipeline.scriptorium.artifacts.<name>.output_path`
-- `pipeline.scriptorium.artifacts.<name>.inputs.<key>.source`
-
-## External adapters used
-- none
-
-## State and manifest behavior
-Built-in registry entries:
 
+## Built-in IDs
 | Artifact ID | Canonical file | Producer stage | Output kind |
 | --- | --- | --- | --- |
 | `narratio.transcript.merged` | `transcripts/merged.json` | `merge` | `transcript_merged` |
@@ -44,44 +38,58 @@ Built-in registry entries:
 | `narratio.transcript.trimmed` | `transcripts/trimmed.json` | `trim` | `transcript_trimmed` |
 | `narratio.bounds.session` | `artifacts/session_bounds.json` | `trim` | `session_bounds` |
 
-Runtime catalog entries include built-ins and configured `narratio.artifact.<name>` sources.
+## Source families
+- built-in: `narratio.transcript.*`, `narratio.bounds.session`
+- configured artifact: `narratio.artifact.<artifact_key>`
+- canonical previous-session artifact: `narratio.previous_session.artifact.<artifact_key>`
 
-Catalog states:
+## Runtime catalog model
-- `planned`: source is registered and known for this run
+Catalog entries track:
-- `executable`: configured artifact is selected for analyze execution
+- `planned`: source is registered for this run;
-- `available`: artifact has a usable file path (generated this run or reused from disk)
+- `executable`: configured artifact is selected for analyze execution;
+- `available`: usable local file exists (generated this run or reused from disk).
 
-Resolution behavior:
+Configured artifact provenance values include:
-- built-in sources resolve via manifest producer outputs first, then canonical fallback path
-- configured `narratio.artifact.<name>` sources resolve through runtime catalog availability
-- configured source lookup requires catalog context
-
-Configured artifact provenance values:
 - `generated.current_analyze_run`
 - `filesystem.disabled_artifact_output`
 
-Content validation:
+Previous-session canonical provenance values include:
-- transcript built-ins: JSON with top-level `segments` array
+- `manifest.inputs.previous_cache`
-- bounds built-in: valid JSON
+- `current_session.previous_cache`
-- configured artifacts: non-empty text file
 
-## Skip and resume behavior
+## Resolution behavior
-- resolver and catalog have no direct skip/resume decisions
+- Built-ins resolve via manifest producer outputs first, then canonical fallback paths.
-- stage/runner skip-resume behavior consumes catalog/resolver results
+- Configured `narratio.artifact.<name>` sources resolve through catalog availability.
+- Canonical previous-session sources resolve to current-session `previous/` cache candidates derived from configured artifact canonical output paths.
+- Previous-session canonical resolution prefers manifest-recorded input paths when present, then filesystem fallback under `previous/artifacts/**`.
+
+## Previous-session requirement scanning
+`CollectPreviousArtifactRequirements`:
+- scans enabled configured artifacts only;
+- includes canonical previous-session sources only;
+- deduplicates by artifact key;
+- merges required/optional references (`required` wins);
+- records deterministic sorted source locations for diagnostics.
+
+## Validation behavior
+- transcript built-ins: JSON with top-level `segments` array;
+- bounds built-in: valid JSON;
+- configured and previous-session artifact files: non-empty text content.
 
 ## Failure behavior
-- unsupported source -> source validation error
+- unsupported source or malformed canonical previous source: validation/resolution error;
-- known source unavailable -> `ErrSessionArtifactNotFound`
+- known source unavailable: `ErrSessionArtifactNotFound`;
-- configured source without catalog -> resolution error
+- configured/previous canonical source without catalog: error;
-- resolved file with invalid content -> validation error
+- resolved invalid file content: validation error.
 
 ## Tests to inspect before changing
 - `internal/artifacts/artifact_resolver_test.go`
 - `internal/artifacts/catalog_test.go`
+- `internal/artifacts/previous_requirements_test.go`
+- `internal/stage/prepare_previous_test.go`
 - `internal/stage/analyze_test.go`
-- `internal/config/scriptorium_test.go`
 
 ## Architectural invariants
-- built-in IDs are static and registry-backed
+- Built-in source IDs are static.
-- configured artifact IDs are runtime-derived (`narratio.artifact.<name>`) and catalog-backed
+- Configured and previous-session source IDs are artifact-key based and validation-gated.
-- built-in/source resolution remains deterministic and validation-gated
+- Resolution behavior remains deterministic and manifest-aware.

docs/internal/command-restore.md

@@ -1,11 +1,11 @@
 # Internal: Command Restore
 
 ## Purpose
-Define the implemented `narratio restore` command contract: committed remote-state discovery, deterministic planning, safe file installation, conflict policy, and restore reporting.
+Define the implemented `narratio restore` contract: committed remote-state discovery, deterministic plan classification, safe file install semantics, and restore reporting.
 
 ## Inputs and outputs
 Inputs:
-- CLI flags: `--config`, `--session`, `--session-id`, `--dry-run`, `--force`, `--include-audio`.
+- CLI flags: `--config`, `--session`, `--session-id`, `--previous-session-id`, `--dry-run`, `--force`, `--include-audio`.
 - Resolved/validated `pipeline.yml` and `session.yml`.
 - Configured remote object store.
 - Remote committed current-state markers (`current/run_id.txt`, `current/manifest.json`).
@@ -54,6 +54,21 @@ Does not own:
   - existing local manifest is preserved if restored manifest validation/install fails.
 - Non-dry-run report persists summary/action status metadata in `reports/restore-latest.json`.
 
+Restore path scope:
+- includes:
+  - `manifest.json`
+  - `transcripts/**`
+  - `artifacts/**`
+  - `previous/**`
+  - `audio/**` only when `--include-audio` is set
+- excludes:
+  - `runs/**`
+  - `logs/**`
+  - `reports/**`
+  - `config/**`
+  - `inputs/**`
+  - remote `current/**` pointer files as local restore targets
+
 ## Skip and resume behavior
 - Restore does not participate in stage skip/resume decisions.
 - Restore provides durable local state so subsequent stage commands can resume or rerun based on restored manifest state.
@@ -80,7 +95,7 @@ Does not own:
 - `current/run_id.txt` is the remote commit marker; restore must not infer committed state from incidental files.
 - Local path mapping is traversal-safe and constrained to session root.
 - Restore scope is deterministic and path-classified:
-  - include `manifest.json`, `transcripts/**`, `artifacts/**`
+  - include `manifest.json`, `transcripts/**`, `artifacts/**`, `previous/**`
   - include `audio/**` only with `--include-audio`
   - exclude `runs/**`, `logs/**`, `reports/**`, `config/**`, `inputs/**`
 - Command remains standalone; no implicit `run --restore` behavior.

docs/internal/stage-analyze.md

@@ -3,31 +3,36 @@
 ## Purpose
 Execute selected configured Scriptorium artifacts in deterministic dependency order and promote successful outputs to canonical session artifact paths.
 
-## Inputs and Outputs
+## Inputs and outputs
 Inputs:
-- configured artifact definitions from `pipeline.scriptorium.artifacts`
+- configured artifact definitions from `pipeline.scriptorium.artifacts`;
-- selected artifact filter from runtime (`--artifacts`) when provided
+- selected artifact filter (`--artifacts`) when provided;
-- resolved artifact input sources declared per artifact (`inputs.*.source`)
+- resolved artifact sources from resolver/catalog.
-- optional previous-session file inputs (`previous_session_artifact`)
+
+Source types used by analyze:
+- built-ins: `narratio.transcript.*`, `narratio.bounds.session`;
+- configured artifacts: `narratio.artifact.<artifact_key>`;
+- canonical previous-session artifacts: `narratio.previous_session.artifact.<artifact_key>`;
+- legacy path-based previous-session source: `previous_session_artifact` (uses `inputs.*.path`).
 
 Outputs:
-- one promoted output file per executed configured artifact at that artifact's configured `output_path`
+- promoted configured artifact files at each configured `output_path`;
-- stage metadata containing generated artifact entries and reused disabled-artifact entries
+- stage metadata (`generated_artifacts`, `reused_artifacts`, selected/order info).
 
 ## Boundaries
 Owns:
-- runtime artifact catalog construction for analyze execution
+- runtime artifact catalog construction;
-- selected-artifact planning and dependency ordering
+- selected-artifact planning and dependency ordering;
-- per-artifact input resolution, var resolution, timeout/render-debug resolution
+- per-input resolution and required/optional handling;
-- Scriptorium run/render invocation for each selected artifact
+- Scriptorium render/run invocation;
-- run-local output generation and canonical promotion
+- run-local output generation and canonical promotion.
 
 Does not own:
-- transcript generation/processing stages
+- prepare-time previous-session hydration;
-- archive promotion policy
+- object-store access for previous-session sources;
-- per-artifact resume semantics
+- archive promotion policy.
 
-## Config Fields Used
+## Config fields used
 - `session.session_id`
 - `session.campaign`
 - `pipeline.workspace.root`
@@ -36,49 +41,41 @@ Does not own:
 - `pipeline.scriptorium.timeout`
 - `pipeline.scriptorium.render_debug`
 - `pipeline.scriptorium.artifacts.<name>.*`
-  - `enabled`
-  - `depends_on`
-  - `prompt_id`
-  - `profile_id`
-  - `timeout`
-  - `output_path`
-  - `render_debug`
-  - `inputs`
-  - `vars`
 
-## External Adapters Used
+## External adapters used
 - Scriptorium adapter:
-  - optional `RenderArtifact` (render debug)
+  - optional `RenderArtifact` when render-debug is enabled;
-  - `RunArtifact` (artifact generation)
+  - `RunArtifact` for artifact generation.
 
-## State and Manifest Behavior
+## State and manifest behavior
-- If `pipeline.scriptorium` is absent, stage returns success metadata with `skipped=true`.
+- If Scriptorium config is absent, or no artifacts are executable after filtering, analyze returns success metadata with `skipped=true`.
-- If no artifacts are configured, stage returns success metadata with `skipped=true`.
+- Builds runtime catalog with built-ins and configured `narratio.artifact.<name>` entries.
-- If zero artifacts are executable after `enabled` + `--artifacts` filtering, stage returns success metadata with `skipped=true`.
+- Non-executable configured artifacts may still be marked available from existing canonical output files.
-- Builds runtime catalog with built-ins and configured artifacts.
+- Resolves canonical previous-session sources from local prepared `previous/` cache:
-- Non-executable configured artifacts are marked available only when their configured output file exists and is valid on disk.
+  - prefers manifest-backed previous input paths when present;
-- Executes selected configured artifacts in topological order with deterministic tie-breaking.
+  - may fall back to current-session `previous/` filesystem paths.
-- For each generated artifact, records metadata fields including `name`, `source_id`, `output_kind`, `path`, `prompt_id`, `profile_id`, and `provenance`.
+- Analyze does not call object storage for canonical previous-session source resolution.
-- Reused disabled artifacts are recorded separately in `reused_artifacts` with provenance `filesystem.disabled_artifact_output`.
+- Required canonical previous-session input missing:
+  - fails with guidance to run `narratio run-stage --force prepare`.
+- Optional missing sources are omitted from adapter input paths.
 
-## Skip and Resume Behavior
+## Skip and resume behavior
 - Runner-level skip applies when analyze is already `succeeded` and `--force` is not set.
-- Analyze remains stage-scoped for resume/skip; there is no per-artifact resume state.
+- Analyze is stage-scoped for resume; no per-artifact manifest resume state.
-- `--artifacts` filters which configured artifacts are executable when analyze runs; it does not imply `--force`.
+- `--artifacts` filters executable artifacts but does not imply force rerun.
 
-## Failure Behavior
+## Failure behavior
-- Fails on invalid dependency ordering, unavailable required configured inputs, invalid built-in input prerequisites, render/run adapter failures, validation-failed adapter results, or missing/empty outputs.
+- Fails on dependency-order violations, missing required inputs, resolver validation failures, adapter errors, and missing/empty generated outputs.
-- Required configured dependency missing from catalog availability fails clearly before invocation.
+- Required unavailable configured artifact source (`narratio.artifact.<name>`) fails before invocation.
-- Optional missing inputs are omitted.
+- Required canonical previous-session source fails with prepare-rerun guidance.
 
-## Tests to Inspect Before Changing
+## Tests to inspect before changing
 - `internal/stage/analyze_test.go`
 - `internal/artifacts/catalog_test.go`
 - `internal/artifacts/artifact_resolver_test.go`
-- `internal/adapters/scriptorium/subprocess_test.go`
+- `internal/app/restore_workflow_test.go`
 
-## Architectural Invariants
+## Architectural invariants
-- Configured artifacts are identified by `narratio.artifact.<name>` source IDs.
+- Canonical previous-session behavior is local-cache only during analyze.
-- Artifact-to-artifact references rely on explicit `depends_on` declarations validated in config.
+- Generated outputs are validated and promoted before stage success is recorded.
-- Generated analyze outputs are treated uniformly as Scriptorium artifacts.
+- Resolver/catalog decisions stay deterministic and validation-gated.
-- Successful outputs must exist and be non-empty before promotion.

docs/internal/stage-archive.md

@@ -1,17 +1,19 @@
 # Stage: archive
 
 ## Purpose
-Publish run records and promoted session artifacts to object storage, then atomically advance the remote current pointer.
+Publish durable run/session state to object storage, then atomically advance remote current state.
 
 ## Inputs and Outputs
 Inputs:
 - session manifest and prerequisite stage records
 - run root contents under `runs/{run_id}/`
 - promotion rules with artifact `source` IDs and archive `dest` paths (`archive.promote_artifacts`)
+- session-level `previous/**` cache files when present
 
 Outputs:
 - uploaded run files under `{session_prefix}/runs/{run_id}/...`
 - uploaded promoted artifacts under `{session_prefix}/...`
+- uploaded session previous-cache files under `{session_prefix}/previous/...` when present
 - `{session_prefix}/current/manifest.json`
 - `{session_prefix}/current/run_id.txt` written last
 
@@ -21,6 +23,7 @@ Owns:
 - Prerequisite stage success enforcement
 - Run file collection and upload (excluding `audio/`)
 - Promotion rule resolution and upload
+- Session previous-cache file collection/upload
 - Commit pointer publish order
 
 Does not own:
@@ -43,8 +46,10 @@ Does not own:
 ## State and Manifest Behavior
 - Requires `prepare`, `transcribe`, `merge`, `polish`, `normalize`, `trim`, and `analyze` status `succeeded`.
 - Resolves bucket/prefix from manifest identity first, then config fallback.
+- Uploads session `previous/**` files as durable session state when the local `previous/` directory exists.
 - Writes metadata including:
   - upload counts/paths
+  - `previous_files_uploaded` and `previous_uploaded_paths`
   - `current_manifest_key`
   - `current_run_id_key`
   - `current_pointer_written`
@@ -64,5 +69,6 @@ Does not own:
 
 ## Architectural Invariants
 - Run upload excludes `audio/` subtree.
+- Session `previous/**` is archiveable durable input/provenance state, not run-local output.
 - `current/manifest.json` uploads before `current/run_id.txt`.
 - `current/run_id.txt` is the remote publish commit marker.

docs/internal/stage-prepare.md

@@ -1,40 +1,49 @@
 # Stage: prepare
 
 ## Purpose
-Materialize all required session inputs into canonical local workspace paths and record input provenance in the session manifest.
+Materialize canonical current-session input state and provenance before downstream stages run.
 
-## Inputs and Outputs
+Prepare owns:
+- local input file materialization (`inputs/**`);
+- audio input materialization (`audio/**`);
+- previous-session cache hydration (`previous/**`) for canonical previous-session artifact sources.
+
+## Inputs and outputs
 Inputs:
-- `session.yml` (resolved session config)
+- resolved config/session (`pipeline.yml`, `session.yml`);
-- `pipeline.resolved.yml` (materialized from resolved pipeline config)
+- session-local input files (`speakers`, `autocorrect`, `glossary`);
-- `speakers.yml`
-- `autocorrect.yml`
-- `glossary.yml`
 - audio source:
-  - local (`session.inputs.audio_dir` or `session.inputs.audio_files`), or
+  - local: `session.inputs.audio_dir` or `session.inputs.audio_files`;
-  - S3 (`session.inputs.audio_s3.prefix`)
+  - S3: `session.inputs.audio_s3.prefix`;
+- configured enabled Scriptorium artifact inputs (for previous-session requirement scanning);
+- remote previous-session current archive state when previous hydration is required.
 
 Outputs:
-- `inputs/session.yml`
+- `inputs/session.yml`;
-- `inputs/pipeline.resolved.yml`
+- `inputs/pipeline.resolved.yml`;
-- `inputs/speakers.yml`
+- `inputs/speakers.yml`;
-- `inputs/autocorrect.yml`
+- `inputs/autocorrect.yml`;
-- `inputs/glossary.yml`
+- `inputs/glossary.yml`;
-- `audio/*.flac` in session workdir
+- `audio/*.flac` in canonical session `audio/`;
-- `manifest.Inputs` records with checksums and source metadata
+- optional `previous/manifest.json`;
+- optional `previous/artifacts/**`;
+- deterministic `manifest.Inputs` records with checksums and provenance metadata.
 
 ## Boundaries
 Owns:
-- Input path resolution and validation
+- input path resolution and materialization;
-- Local copy/materialization of configs and audio files
+- S3 audio list/download/copy flow;
-- S3 audio download to run-scoped spool, then copy into work audio dir
+- previous-session artifact requirement collection from enabled configured artifacts;
+- previous cache lifecycle when requirements exist (clear and rehydrate managed `previous/` state).
 
 Does not own:
-- Transcript generation/processing
+- transcript or artifact generation;
-- Archive publish behavior
+- analyze-stage source resolution;
+- archive commit behavior.
 
-## Config Fields Used
+## Config fields used
 - `session.session_id`
+- `session.previous_session_id`
 - `session.campaign`
 - `session.inputs.speakers_file`
 - `session.inputs.autocorrect_file`
@@ -46,29 +55,56 @@ Does not own:
 - `pipeline.spool.root`
 - `pipeline.storage.s3.bucket`
 - `pipeline.storage.s3.root_prefix`
+- `pipeline.scriptorium.artifacts.<name>.enabled`
+- `pipeline.scriptorium.artifacts.<name>.inputs.<key>.source`
+- `pipeline.scriptorium.artifacts.<name>.inputs.<key>.required`
 
-## External Adapters Used
+## External adapters used
-- Object storage backend (`env.ObjectStore`) for S3 audio list/download when `audio_s3` is configured.
+- `storage.ObjectStore` for:
+  - S3 audio listing/downloads;
+  - previous-session current pointer/manifest/artifact object checks and downloads.
 
-## State and Manifest Behavior
+## State and manifest behavior
 - Ensures workspace layout exists.
-- Writes resolved config and input files to canonical `inputs/` paths.
+- Materializes canonical input files and audio files.
-- Records all prepared inputs into `manifest.Inputs` (sorted deterministically by kind/path).
+- Scans enabled configured artifact inputs for canonical sources:
-- For S3 audio, records `S3Bucket`, `S3Key`, `S3Size`, `S3ETag`, and `SpoolPath` in each audio input record.
+  - `narratio.previous_session.artifact.<artifact_key>`
+- If one or more canonical previous-session requirements exist:
+  - clears managed `previous/` state;
+  - hydrates required/optional previous artifacts from the configured previous session’s committed archive current state;
+  - writes `previous/manifest.json` and hydrated `previous/artifacts/**`;
+  - records hydrated previous inputs in `manifest.Inputs` with source `previous_session_archive.current`.
+- If no canonical previous-session requirements exist, prepare does not manage `previous/`.
+- `manifest.Inputs` is sorted deterministically by `(kind, path)`.
 
-## Skip and Resume Behavior
+## Required and optional previous-session behavior
-- Runner-level skip applies when stage already `succeeded` and `--force` is not set.
+- `previous_session_id` unset:
-- Stage itself is deterministic/idempotent for unchanged inputs (`copyFileIfChanged`, `writeBytesIfChanged`).
+  - if any referenced previous artifact is required: fail;
+  - if all referenced previous artifacts are optional: continue and omit them.
+- Previous session archive current pointer or manifest missing:
+  - if any referenced previous artifact is required: fail;
+  - if all referenced previous artifacts are optional: continue and omit missing ones.
+- Missing required previous artifact object: fail.
+- Missing optional previous artifact object: omit.
+- Downloaded previous artifacts must validate as non-empty files.
 
-## Failure Behavior
+## Skip and resume behavior
-- Fails on missing required files, invalid audio source combinations, no discoverable `.flac` files, duplicate audio basenames, missing object store for S3 mode, or S3 list/download failures.
+- Runner-level skip remains authoritative:
+  - if `prepare` already succeeded and run is not forced, `prepare` does not run and no hydration/download occurs.
+- If `prepare` runs (including with `--force`), it owns managed `previous/` state for canonical previous-session inputs.
 
-## Tests to Inspect Before Changing
+## Failure behavior
+- Fails on missing required input files, invalid audio-source combinations, empty/duplicate audio inputs, missing object store for S3 modes, and remote access/download/validation errors.
+- For required canonical previous-session inputs, analyze-time missing-input guidance is to rerun:
+  - `narratio run-stage --force prepare`
+
+## Tests to inspect before changing
 - `internal/stage/prepare_test.go`
-- `internal/app/session_cli_test.go`
+- `internal/stage/prepare_previous_test.go`
-- `internal/config/load_validate_test.go`
+- `internal/artifacts/previous_requirements_test.go`
+- `internal/app/runner_test.go`
 
-## Architectural Invariants
+## Architectural invariants
 - `audio_dir`/`audio_files` and `audio_s3` are mutually exclusive.
-- Audio files must be `.flac`.
+- Storage keys are computed by callers using archive/path helpers; storage adapter receives explicit keys.
-- Canonical `inputs/*` and `audio/*` paths are the durable source for downstream stages.
+- `prepare` is the only stage that hydrates canonical previous-session cache state.

docs/internal/workspace.md

@@ -17,7 +17,8 @@ Outputs:
 
 ## Boundaries
 Owns:
-- Session-level path layout (`inputs/`, `audio/`, `transcripts/`, `artifacts/`, `reports/`, `logs/`, `config/`, `current/`, `runs/`)
+- Session-level path layout (`inputs/`, `audio/`, `transcripts/`, `artifacts/`, `reports/`, `logs/`, `config/`, `current/`, `runs/`, `previous/`)
+  - `previous/manifest.json` and `previous/artifacts/**` are reserved for prepared previous-session state
 - Run-local stage sandbox layout under `runs/{run_id}/{stage}/`
 - Session lock acquisition/release (`.lock`)
 
@@ -65,4 +66,5 @@ None directly in this subsystem. Stages may use object storage adapters and then
 - Session root is campaign-aware: `{workspace.root}/work/{campaign}/{session_id}`.
 - Run roots are always nested: `runs/{run_id}` under the session root.
 - Run-local output promotion must end in canonical session paths.
+- `previous/**` is session-durable state and must not be treated as run-local output scratch state.
 - Cleanup only targets run-scoped directories and must never delete configured root directories.

docs/operations.md

@@ -48,7 +48,7 @@ Restore source-of-truth:
 - remote current manifest: `current/manifest.json`
 
 Restore default scope:
-- includes `manifest.json`, `transcripts/**`, `artifacts/**`
+- includes `manifest.json`, `transcripts/**`, `artifacts/**`, `previous/**`
 - includes `audio/**` only with `--include-audio`
 - excludes `runs/**`, `logs/**`, `reports/**`, `config/**`, `inputs/**`, and `current/**` (except remote `current/manifest.json` as source)
 
@@ -67,6 +67,7 @@ Canonical session directories:
 - `audio/`
 - `transcripts/`
 - `artifacts/`
+- `previous/`
 - `reports/`
 - `logs/`
 - `config/`
@@ -99,6 +100,12 @@ Configured artifact source reuse:
 - accepted on `run`, `resume`, and `run-stage analyze`.
 - filters analyze execution only; does not force stage rerun.
 
+Canonical previous-session input behavior:
+- canonical sources use `narratio.previous_session.artifact.<artifact_key>`.
+- these inputs are hydrated by `prepare`, not `analyze`.
+- if analyze fails due to missing canonical previous cache, rerun:
+  - `narratio run-stage --session-id <id> --force prepare`
+
 ## Remote archive layout and publish contract
 
 When archive is enabled and run upload is enabled, archive publishes under:

docs/roadmap/previous.md

@@ -2,7 +2,7 @@
 
 ## Status
 
-Planned.
+Completed.
 
 This roadmap describes the implementation strategy for first-class previous-session artifact support in Narratio. It belongs under `docs/roadmap/previous.md` until the feature is implemented. After implementation, current behavior should be documented in the appropriate user-facing and internal documentation files, and this roadmap should be removed or marked complete according to the documentation policy.
 

examples/pipeline.full.annotated.yml

@@ -133,9 +133,7 @@ scriptorium:
           source: narratio.transcript.trimmed
           required: true
         previous_recap:
-          source: previous_session_artifact
+          source: narratio.previous_session.artifact.session_recap
-          artifact: session_recap
-          path: ""
           required: false
       vars:
         session_id: true

examples/pipeline.production.yml

@@ -81,8 +81,7 @@ scriptorium:
           source: narratio.transcript.trimmed
           required: true
         previous_recap:
-          source: previous_session_artifact
+          source: narratio.previous_session.artifact.session_recap
-          artifact: session_recap
           required: false
       vars:
         session_id: true

internal/app/plan.go

@@ -22,10 +22,12 @@ func Plan(ctx context.Context, args []string, out io.Writer) error {
 	var pipelinePath string
 	var sessionPath string
 	var sessionID string
+	var previousSessionID string
 	var force bool
 	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml (optional; defaults searched)")
 	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
 	fs.StringVar(&sessionID, "session-id", "", "session identifier for session.yml templates")
+	fs.StringVar(&previousSessionID, "previous-session-id", "", "previous session identifier for session.yml templates")
 	fs.BoolVar(&force, "force", false, "force stage execution (reserved for future behavior)")
 
 	if err := fs.Parse(args); err != nil {
@@ -45,6 +47,7 @@ func Plan(ctx context.Context, args []string, out io.Writer) error {
 
 	cfg, err := config.LoadWithSessionOptions(resolvedPipelinePath, resolvedSessionPath, config.SessionLoadOptions{
 		SessionID:         sessionID,
+		PreviousSessionID: previousSessionID,
 	})
 	if err != nil {
 		return fmt.Errorf("plan: %w", err)

internal/app/post_archive_cleanup_test.go

@@ -82,6 +82,7 @@ func TestPostArchiveCleanupWorkdirOnly(t *testing.T) {
 
 	assertExists(t, cfg.Pipeline.Workspace.Root)
 	assertExists(t, seed.otherRunDir)
+	assertExists(t, seed.previousCachePath)
 	assertMissing(t, seed.runWorkDir)
 	assertExists(t, seed.spoolAudioDir)
 }
@@ -98,6 +99,7 @@ func TestPostArchiveCleanupBothPolicies(t *testing.T) {
 	assertMissing(t, seed.spoolAudioDir)
 	assertMissing(t, seed.runWorkDir)
 	assertExists(t, seed.otherRunDir)
+	assertExists(t, seed.previousCachePath)
 }
 
 func TestPostArchiveCleanupNotRunWhenArchiveFails(t *testing.T) {
@@ -260,6 +262,7 @@ type cleanupSeed struct {
 	otherRunDir       string
 	spoolAudioDir     string
 	localSourceAudio  string
+	previousCachePath string
 	sessionPrefix     string
 }
 
@@ -274,11 +277,18 @@ func cleanupFixtureConfig(t *testing.T) (*config.Config, cleanupSeed) {
 	runWorkDir := artifacts.SessionRunRootForCampaign(cfg.Pipeline.Workspace.Root, cfg.Session.Campaign, cfg.Session.SessionID, runID)
 	otherRunDir := artifacts.SessionRunRootForCampaign(cfg.Pipeline.Workspace.Root, cfg.Session.Campaign, cfg.Session.SessionID, "20260516T010204Z-5e6f7a8b")
 	spoolAudioDir := artifacts.SessionSpoolAudioDir(cfg.Pipeline.Spool.Root, cfg.Session.Campaign, cfg.Session.SessionID, runID)
+	previousCachePath := artifacts.SessionPreviousArtifactPathForCampaign(
+		cfg.Pipeline.Workspace.Root,
+		cfg.Session.Campaign,
+		cfg.Session.SessionID,
+		"session_recap.md",
+	)
 
 	mustWriteFile(t, filepath.Join(runWorkDir, "manifest.json"), "{}\n")
 	mustWriteFile(t, filepath.Join(runWorkDir, "logs", "stage.log"), "log\n")
 	mustWriteFile(t, filepath.Join(otherRunDir, "logs", "stage.log"), "other\n")
 	mustWriteFile(t, filepath.Join(spoolAudioDir, "speaker.flac"), "flac\n")
+	mustWriteFile(t, previousCachePath, "# previous recap\n")
 
 	localSourceAudio := filepath.Join(filepath.Dir(cfg.SessionPath), "audio", "alice.flac")
 	mustWriteFile(t, localSourceAudio, "source\n")
@@ -305,6 +315,7 @@ func cleanupFixtureConfig(t *testing.T) (*config.Config, cleanupSeed) {
 		otherRunDir:       otherRunDir,
 		spoolAudioDir:     spoolAudioDir,
 		localSourceAudio:  localSourceAudio,
+		previousCachePath: previousCachePath,
 		sessionPrefix:     seed.S3SessionPrefix,
 	}
 }

internal/app/restore.go

@@ -28,17 +28,19 @@ func Restore(ctx context.Context, args []string, out io.Writer) error {
 	var pipelinePath string
 	var sessionPath string
 	var sessionID string
+	var previousSessionID string
 	var dryRun bool
 	var force bool
 	var includeAudio bool
 	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml (optional; defaults searched)")
 	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
 	fs.StringVar(&sessionID, "session-id", "", "session identifier for session.yml templates")
+	fs.StringVar(&previousSessionID, "previous-session-id", "", "previous session identifier for session.yml templates")
 	fs.BoolVar(&dryRun, "dry-run", false, "plan restore actions without writing local files")
 	fs.BoolVar(&force, "force", false, "overwrite local conflicts with remote state")
 	fs.BoolVar(&includeAudio, "include-audio", false, "include archived session-level audio objects")
 	fs.Usage = func() {
-		_, _ = fmt.Fprintln(out, "Usage: narratio restore [--config <path>] [--session <path>] [--session-id <value>] [--dry-run] [--force] [--include-audio]")
+		_, _ = fmt.Fprintln(out, "Usage: narratio restore [--config <path>] [--session <path>] [--session-id <value>] [--previous-session-id <value>] [--dry-run] [--force] [--include-audio]")
 		_, _ = fmt.Fprintln(out)
 		_, _ = fmt.Fprintln(out, "Flags:")
 		fs.PrintDefaults()
@@ -64,6 +66,7 @@ func Restore(ctx context.Context, args []string, out io.Writer) error {
 
 	cfg, err := config.LoadWithSessionOptions(resolvedPipelinePath, resolvedSessionPath, config.SessionLoadOptions{
 		SessionID:         sessionID,
+		PreviousSessionID: previousSessionID,
 	})
 	if err != nil {
 		return fmt.Errorf("restore: %w", err)

internal/app/restore_execution_test.go

@@ -87,6 +87,33 @@ func TestExecuteRestoreIncludeAudioRestoresAudio(t *testing.T) {
 	}
 }
 
+func TestExecuteRestoreRestoresPreviousCacheWhenPresent(t *testing.T) {
+	workspaceRoot := t.TempDir()
+	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)
+
+	fake := &storage.FakeBackend{}
+	cfg, sessionPrefix, _, _ := seedRestoreCommittedState(t, fake, pipelinePath, sessionPath)
+	seedRestoreObject(fake, sessionPrefix+"previous/manifest.json", []byte(`{"session_id":"2026-04-26"}`))
+	seedRestoreObject(fake, sessionPrefix+"previous/artifacts/session_recap.md", []byte("# previous recap\n"))
+
+	restoreWithStoreAndRealPhases(t, fake)
+
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	code := Execute([]string{"restore", "--config", pipelinePath, "--session", sessionPath}, &stdout, &stderr)
+	if code != 0 {
+		t.Fatalf("exit code = %d, want 0; stderr=%q", code, stderr.String())
+	}
+
+	sessionRoot := artifacts.SessionWorkDirForCampaign(workspaceRoot, cfg.Session.Campaign, cfg.Session.SessionID)
+	mustReadEquals(t, filepath.Join(sessionRoot, "previous", "manifest.json"), `{"session_id":"2026-04-26"}`)
+	mustReadEquals(t, filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md"), "# previous recap\n")
+	report := mustReadRestoreReport(t, filepath.Join(sessionRoot, "reports", "restore-latest.json"))
+	if report.Execution.Downloaded != 3 {
+		t.Fatalf("report execution.downloaded = %d, want 3", report.Execution.Downloaded)
+	}
+}
+
 func TestExecuteRestoreConflictWithoutForceDoesNotOverwrite(t *testing.T) {
 	workspaceRoot := t.TempDir()
 	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)
@@ -145,6 +172,28 @@ func TestExecuteRestoreForceOverwritesDifferingFile(t *testing.T) {
 	}
 }
 
+func TestExecuteRestoreForceOverwritesDifferingPreviousCacheFile(t *testing.T) {
+	workspaceRoot := t.TempDir()
+	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)
+
+	fake := &storage.FakeBackend{}
+	cfg, sessionPrefix, _, _ := seedRestoreCommittedState(t, fake, pipelinePath, sessionPath)
+	seedRestoreObject(fake, sessionPrefix+"previous/artifacts/session_recap.md", []byte("# remote previous recap\n"))
+
+	sessionRoot := artifacts.SessionWorkDirForCampaign(workspaceRoot, cfg.Session.Campaign, cfg.Session.SessionID)
+	mustWriteTestFile(t, filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md"), "# local previous recap\n")
+
+	restoreWithStoreAndRealPhases(t, fake)
+
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	code := Execute([]string{"restore", "--config", pipelinePath, "--session", sessionPath, "--force"}, &stdout, &stderr)
+	if code != 0 {
+		t.Fatalf("exit code = %d, want 0; stderr=%q", code, stderr.String())
+	}
+	mustReadEquals(t, filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md"), "# remote previous recap\n")
+}
+
 func TestExecuteRestoreLockConflictFailsAndWritesNothing(t *testing.T) {
 	workspaceRoot := t.TempDir()
 	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)

internal/app/restore_plan.go

@@ -194,6 +194,9 @@ func restoreLocalRelativePathForKey(sessionPrefix, currentManifestKey, key strin
 	if cleanRel == config.PathArtifactsDirSegment || strings.HasPrefix(cleanRel, config.PathArtifactsDirSegment+"/") {
 		return cleanRel, true, nil
 	}
+	if cleanRel == config.PathPreviousDirSegment || strings.HasPrefix(cleanRel, config.PathPreviousDirSegment+"/") {
+		return cleanRel, true, nil
+	}
 	if includeAudio && (cleanRel == config.PathAudioDirSegment || strings.HasPrefix(cleanRel, config.PathAudioDirSegment+"/")) {
 		return cleanRel, true, nil
 	}

internal/app/restore_plan_test.go

@@ -58,6 +58,27 @@ func TestRestorePlanIncludeAudio(t *testing.T) {
 	}
 }
 
+func TestRestorePlanIncludesPreviousCacheByDefault(t *testing.T) {
+	cfg := restorePlanConfig(t)
+	current := restorePlanCurrentState(t, cfg)
+	store := &storage.FakeBackend{}
+
+	seedRestoreObject(store, current.CurrentManifestKey, []byte(`{"session_id":"2026-05-03"}`))
+	seedRestoreObject(store, current.SessionPrefix+"previous/manifest.json", []byte(`{"session_id":"2026-04-26"}`))
+	seedRestoreObject(store, current.SessionPrefix+"previous/artifacts/session_recap.md", []byte("# previous recap\n"))
+
+	plan, err := buildRestorePlan(context.Background(), cfg, current, store, RestorePlanOptions{})
+	if err != nil {
+		t.Fatalf("buildRestorePlan() error = %v", err)
+	}
+
+	got := actionRelPaths(plan.Actions)
+	want := []string{"manifest.json", "previous/artifacts/session_recap.md", "previous/manifest.json"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("action local paths = %#v, want %#v", got, want)
+	}
+}
+
 func TestRestorePlanClassifiesSameAndConflict(t *testing.T) {
 	cfg := restorePlanConfig(t)
 	current := restorePlanCurrentState(t, cfg)

internal/app/restore_workflow_test.go

@@ -155,6 +155,116 @@ func TestRestoreThenRunStageForceAnalyzeUsesRestoredDurableState(t *testing.T) {
 	}
 }
 
+func TestRestoreThenAnalyzeUsesRestoredPreviousCacheWithoutObjectStore(t *testing.T) {
+	workspaceRoot := t.TempDir()
+	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)
+	appendRestoreWorkflowScriptoriumConfig(t, pipelinePath, `
+scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        transcript:
+          source: narratio.transcript.trimmed
+          required: true
+        previous_recap:
+          source: narratio.previous_session.artifact.session_recap
+          required: true
+`)
+
+	fakeStore := &storage.FakeBackend{}
+	cfg, sessionPrefix, manifestKey, runIDKey := seedRestoreCommittedState(t, fakeStore, pipelinePath, sessionPath)
+	seedRestoreObject(fakeStore, runIDKey, []byte("20260519T010203Z-a1b2c3d4\n"))
+	seedRestoreObject(fakeStore, manifestKey, restoreWorkflowManifestJSON(t, cfg.Session.SessionID, cfg.Session.Campaign))
+	seedRestoreObject(fakeStore, sessionPrefix+"transcripts/trimmed.json", []byte(`{"segments":[]}`+"\n"))
+	seedRestoreObject(fakeStore, sessionPrefix+"previous/manifest.json", []byte(`{"session_id":"2026-04-26"}`))
+	seedRestoreObject(fakeStore, sessionPrefix+"previous/artifacts/session_recap.md", []byte("# previous recap\n"))
+
+	restoreWithStoreAndRealPhases(t, fakeStore)
+
+	var stdout bytes.Buffer
+	var stderr bytes.Buffer
+	restoreCode := Execute(
+		[]string{
+			"restore",
+			"--config", pipelinePath,
+			"--session", sessionPath,
+			"--session-id", cfg.Session.SessionID,
+		},
+		&stdout,
+		&stderr,
+	)
+	if restoreCode != 0 {
+		t.Fatalf("restore exit code = %d, want 0; stderr=%q", restoreCode, stderr.String())
+	}
+	if stderr.Len() != 0 {
+		t.Fatalf("restore stderr = %q, want empty", stderr.String())
+	}
+
+	sessionRoot := artifacts.SessionWorkDirForCampaign(workspaceRoot, cfg.Session.Campaign, cfg.Session.SessionID)
+	mustReadEquals(t, filepath.Join(sessionRoot, "transcripts", "trimmed.json"), `{"segments":[]}`+"\n")
+	mustReadEquals(t, filepath.Join(sessionRoot, "previous", "manifest.json"), `{"session_id":"2026-04-26"}`)
+	mustReadEquals(t, filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md"), "# previous recap\n")
+
+	scriptoriumFake := &scriptorium.FakeRunner{}
+	origExecuteStagesFn := executeStagesFn
+	origObjectStoreFn := newObjectStoreFromConfigFn
+	objectStoreConstructed := false
+	t.Cleanup(func() {
+		executeStagesFn = origExecuteStagesFn
+		newObjectStoreFromConfigFn = origObjectStoreFn
+	})
+	executeStagesFn = func(ctx context.Context, cfg *config.Config, stages []stage.Stage, opts RunOptions) (*RunSummary, error) {
+		if opts.Env == nil {
+			opts.Env = &Env{}
+		}
+		opts.Env.Scriptorium = scriptoriumFake
+		return executeStages(ctx, cfg, stages, opts)
+	}
+	newObjectStoreFromConfigFn = func(context.Context, *config.Config) (storage.ObjectStore, error) {
+		objectStoreConstructed = true
+		return nil, context.Canceled
+	}
+
+	stdout.Reset()
+	stderr.Reset()
+	runStageCode := Execute(
+		[]string{
+			"run-stage",
+			"--config", pipelinePath,
+			"--session", sessionPath,
+			"--session-id", cfg.Session.SessionID,
+			"--force",
+			"--artifacts", "session_recap",
+			"analyze",
+		},
+		&stdout,
+		&stderr,
+	)
+	if runStageCode != 0 {
+		t.Fatalf("run-stage exit code = %d, want 0; stderr=%q", runStageCode, stderr.String())
+	}
+	if stderr.Len() != 0 {
+		t.Fatalf("run-stage stderr = %q, want empty", stderr.String())
+	}
+	if objectStoreConstructed {
+		t.Fatal("analyze run-stage should not construct object store for previous-session input resolution")
+	}
+	if len(scriptoriumFake.RunRequests) != 1 {
+		t.Fatalf("scriptorium run requests = %d, want 1", len(scriptoriumFake.RunRequests))
+	}
+	req := scriptoriumFake.RunRequests[0]
+	if got := req.InputPaths["transcript"]; got != filepath.Join(sessionRoot, "transcripts", "trimmed.json") {
+		t.Fatalf("transcript input = %q, want trimmed transcript path", got)
+	}
+	if got := req.InputPaths["previous_recap"]; got != filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md") {
+		t.Fatalf("previous_recap input = %q, want restored previous cache path", got)
+	}
+}
+
 func restoreWorkflowManifestJSON(t *testing.T, sessionID, campaign string) []byte {
 	t.Helper()
 	store := &manifest.LocalStore{}
@@ -176,3 +286,15 @@ func restoreWorkflowManifestJSON(t *testing.T, sessionID, campaign string) []byt
 	}
 	return data
 }
+
+func appendRestoreWorkflowScriptoriumConfig(t *testing.T, pipelinePath, extra string) {
+	t.Helper()
+	f, err := os.OpenFile(pipelinePath, os.O_APPEND|os.O_WRONLY, 0)
+	if err != nil {
+		t.Fatalf("open pipeline config for append: %v", err)
+	}
+	defer f.Close()
+	if _, err := f.WriteString(extra); err != nil {
+		t.Fatalf("append pipeline config: %v", err)
+	}
+}

internal/app/resume.go

@@ -19,11 +19,13 @@ func Resume(ctx context.Context, args []string, out io.Writer) error {
 	var pipelinePath string
 	var sessionPath string
 	var sessionID string
+	var previousSessionID string
 	var force bool
 	var selectedArtifacts artifactSelectionFlag
 	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml (optional; defaults searched)")
 	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
 	fs.StringVar(&sessionID, "session-id", "", "session identifier for session.yml templates")
+	fs.StringVar(&previousSessionID, "previous-session-id", "", "previous session identifier for session.yml templates")
 	fs.BoolVar(&force, "force", false, "force stage execution")
 	fs.Var(&selectedArtifacts, "artifacts", "artifact names to execute during analyze (comma-separated or repeatable)")
 
@@ -44,6 +46,7 @@ func Resume(ctx context.Context, args []string, out io.Writer) error {
 
 	cfg, err := config.LoadWithSessionOptions(resolvedPipelinePath, resolvedSessionPath, config.SessionLoadOptions{
 		SessionID:         sessionID,
+		PreviousSessionID: previousSessionID,
 	})
 	if err != nil {
 		return fmt.Errorf("resume: %w", err)

internal/app/run.go

@@ -17,11 +17,13 @@ func Run(ctx context.Context, args []string, out io.Writer) error {
 	var pipelinePath string
 	var sessionPath string
 	var sessionID string
+	var previousSessionID string
 	var force bool
 	var selectedArtifacts artifactSelectionFlag
 	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml (optional; defaults searched)")
 	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
 	fs.StringVar(&sessionID, "session-id", "", "session identifier for session.yml templates")
+	fs.StringVar(&previousSessionID, "previous-session-id", "", "previous session identifier for session.yml templates")
 	fs.BoolVar(&force, "force", false, "force stage execution (reserved for future behavior)")
 	fs.Var(&selectedArtifacts, "artifacts", "artifact names to execute during analyze (comma-separated or repeatable)")
 
@@ -42,6 +44,7 @@ func Run(ctx context.Context, args []string, out io.Writer) error {
 
 	cfg, err := config.LoadWithSessionOptions(resolvedPipelinePath, resolvedSessionPath, config.SessionLoadOptions{
 		SessionID:         sessionID,
+		PreviousSessionID: previousSessionID,
 	})
 	if err != nil {
 		return fmt.Errorf("run: %w", err)

internal/app/run_stage.go

@@ -17,11 +17,13 @@ func RunStage(ctx context.Context, args []string, out io.Writer) error {
 	var pipelinePath string
 	var sessionPath string
 	var sessionID string
+	var previousSessionID string
 	var force bool
 	var selectedArtifacts artifactSelectionFlag
 	fs.StringVar(&pipelinePath, "config", "", "path to pipeline.yml (optional; defaults searched)")
 	fs.StringVar(&sessionPath, "session", "", "path to session.yml")
 	fs.StringVar(&sessionID, "session-id", "", "session identifier for session.yml templates")
+	fs.StringVar(&previousSessionID, "previous-session-id", "", "previous session identifier for session.yml templates")
 	fs.BoolVar(&force, "force", false, "force stage execution (reserved for future behavior)")
 	fs.Var(&selectedArtifacts, "artifacts", "artifact names to execute during analyze (comma-separated or repeatable)")
 
@@ -55,6 +57,7 @@ func RunStage(ctx context.Context, args []string, out io.Writer) error {
 
 	cfg, err := config.LoadWithSessionOptions(resolvedPipelinePath, resolvedSessionPath, config.SessionLoadOptions{
 		SessionID:         sessionID,
+		PreviousSessionID: previousSessionID,
 	})
 	if err != nil {
 		return fmt.Errorf("run-stage: %w", err)

internal/app/runner.go

@@ -555,6 +555,12 @@ func needsObjectStoreForRun(cfg *config.Config, stages []stage.Stage) bool {
 	if cfg.Session.Inputs.AudioS3 != nil && stageRequested("prepare") {
 		return true
 	}
+	if stageRequested("prepare") {
+		requirements := artifacts.CollectPreviousArtifactRequirements(configuredScriptoriumArtifacts(cfg))
+		if len(requirements) > 0 && strings.TrimSpace(cfg.Session.PreviousSessionID) != "" {
+			return true
+		}
+	}
 	if !stageRequested("archive") {
 		return false
 	}
@@ -569,3 +575,10 @@ func needsObjectStoreForRun(cfg *config.Config, stages []stage.Stage) bool {
 	}
 	return true
 }
+
+func configuredScriptoriumArtifacts(cfg *config.Config) map[string]config.ScriptoriumArtifactConfig {
+	if cfg == nil || cfg.Pipeline == nil || cfg.Pipeline.Scriptorium == nil {
+		return nil
+	}
+	return cfg.Pipeline.Scriptorium.Artifacts
+}

internal/app/runner_test.go

@@ -199,6 +199,55 @@ func TestExecuteStagesAnalyzeOutputsPersistAsScriptoriumArtifacts(t *testing.T)
 	}
 }
 
+func TestNeedsObjectStoreForRunPrepareWithPreviousRequirements(t *testing.T) {
+	tests := []struct {
+		name              string
+		previousSessionID string
+		want              bool
+	}{
+		{
+			name:              "previous session configured",
+			previousSessionID: "2026-05-10",
+			want:              true,
+		},
+		{
+			name:              "previous session missing",
+			previousSessionID: "",
+			want:              false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := &config.Config{
+				Pipeline: &config.PipelineConfig{
+					Scriptorium: &config.ScriptoriumConfig{
+						Artifacts: map[string]config.ScriptoriumArtifactConfig{
+							"session_recap": {
+								Enabled: true,
+								Inputs: map[string]config.ScriptoriumInputConfig{
+									"previous_recap": {
+										Source:   "narratio.previous_session.artifact.session_recap",
+										Required: true,
+									},
+								},
+							},
+						},
+					},
+				},
+				Session: &config.SessionConfig{
+					PreviousSessionID: tt.previousSessionID,
+				},
+			}
+
+			got := needsObjectStoreForRun(cfg, []stage.Stage{countingStage{name: "prepare", runs: new(int)}})
+			if got != tt.want {
+				t.Fatalf("needsObjectStoreForRun() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
 func TestExecuteStagesArchiveFailsWhenRequiredRecapPromotionMissingForSelectedArtifacts(t *testing.T) {
 	cfg := testConfig(t)
 	cfg.Pipeline.Storage.S3 = &config.StorageS3Config{

internal/app/session_cli_test.go

@@ -9,11 +9,12 @@ import (
 	"testing"
 )
 
-func TestPlanUsesDiscoveredSessionTemplateWithSessionID(t *testing.T) {
+func TestPlanUsesDiscoveredSessionTemplateWithSessionIDs(t *testing.T) {
 	workspaceRoot := t.TempDir()
 	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)
 
 	sessionTemplate := `session_id: "{{ session_id }}"
+previous_session_id: "{{ previous_session_id }}"
 campaign: sample-campaign
 inputs:
   audio_dir: ./audio
@@ -36,7 +37,11 @@ inputs:
 	t.Cleanup(func() { _ = os.Chdir(originalWD) })
 
 	var out bytes.Buffer
-	if err := Plan(context.Background(), []string{"--config", pipelinePath, "--session-id", "2026-04-04"}, &out); err != nil {
+	if err := Plan(context.Background(), []string{
+		"--config", pipelinePath,
+		"--session-id", "2026-04-04",
+		"--previous-session-id", "2026-03-28",
+	}, &out); err != nil {
 		t.Fatalf("Plan() error = %v", err)
 	}
 	if !strings.Contains(out.String(), "narratio plan: workdir prepared") {
@@ -58,6 +63,38 @@ func TestPlanFailsWhenSessionIDMismatchesConcreteSession(t *testing.T) {
 	}
 }
 
+func TestPlanFailsWhenPreviousSessionIDMismatchesConcreteSession(t *testing.T) {
+	workspaceRoot := t.TempDir()
+	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)
+
+	sessionYAML := `session_id: 2026-05-03
+previous_session_id: 2026-04-26
+campaign: sample-campaign
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`
+	if err := os.WriteFile(sessionPath, []byte(sessionYAML), 0o644); err != nil {
+		t.Fatalf("write session.yml: %v", err)
+	}
+
+	var out bytes.Buffer
+	err := Plan(context.Background(), []string{
+		"--config", pipelinePath,
+		"--session", sessionPath,
+		"--session-id", "2026-05-03",
+		"--previous-session-id", "2026-04-25",
+	}, &out)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "previous_session_id mismatch") {
+		t.Fatalf("error = %q, want mismatch context", err.Error())
+	}
+}
+
 func TestRunStageAcceptsSessionIDFlagAndParsesStageName(t *testing.T) {
 	workspaceRoot := t.TempDir()
 	pipelinePath, sessionPath := writeValidConfigFiles(t, workspaceRoot)

internal/artifacts/artifact_resolver.go

@@ -18,11 +18,15 @@ const (
 	ArtifactTranscriptFull     = "narratio.transcript.full"
 	ArtifactTranscriptTrimmed  = "narratio.transcript.trimmed"
 	ArtifactBoundsSession      = "narratio.bounds.session"
+
+	ArtifactProvenancePreviousCacheManifestInput = "manifest.inputs.previous_cache"
+	ArtifactProvenancePreviousCacheFilesystem    = "current_session.previous_cache"
 )
 
 // ErrSessionArtifactNotFound is returned when no readable artifact exists for a known ID.
 var ErrSessionArtifactNotFound = errors.New("session artifact not found")
 var configuredArtifactSourceRE = regexp.MustCompile(`^narratio\.artifact\.[a-z][a-z0-9_]*$`)
+var previousSessionArtifactSourceRE = regexp.MustCompile(`^narratio\.previous_session\.artifact\.([a-z][a-z0-9_]*)$`)
 
 type artifactContentKind string
 
@@ -118,6 +122,21 @@ func IsConfiguredArtifactSource(source string) bool {
 	return configuredArtifactSourceRE.MatchString(strings.TrimSpace(source))
 }
 
+// IsPreviousSessionArtifactSource returns true when source is narratio.previous_session.artifact.<name>.
+func IsPreviousSessionArtifactSource(source string) bool {
+	_, ok := PreviousSessionArtifactName(source)
+	return ok
+}
+
+// PreviousSessionArtifactName extracts <name> from narratio.previous_session.artifact.<name>.
+func PreviousSessionArtifactName(source string) (string, bool) {
+	matches := previousSessionArtifactSourceRE.FindStringSubmatch(strings.TrimSpace(source))
+	if len(matches) != 2 {
+		return "", false
+	}
+	return matches[1], true
+}
+
 // ResolveSessionArtifact resolves a symbolic source to a readable local session artifact path.
 // Resolution order is manifest producer outputs first, then canonical session path fallback.
 func ResolveSessionArtifact(paths SessionPaths, m *manifest.Manifest, source string) (ResolvedSessionArtifact, error) {
@@ -170,6 +189,9 @@ func ResolveSessionArtifact(paths SessionPaths, m *manifest.Manifest, source str
 // configured narratio.artifact.<name> sources through runtime catalog availability.
 func ResolveSessionArtifactWithCatalog(paths SessionPaths, m *manifest.Manifest, source string, catalog *ArtifactCatalog) (ResolvedSessionArtifact, error) {
 	normalized := strings.TrimSpace(source)
+	if IsPreviousSessionArtifactSource(normalized) {
+		return ResolvePreviousSessionArtifactWithCatalog(paths, m, normalized, catalog)
+	}
 	if !IsConfiguredArtifactSource(normalized) {
 		return ResolveSessionArtifact(paths, m, normalized)
 	}
@@ -195,6 +217,72 @@ func ResolveSessionArtifactWithCatalog(paths SessionPaths, m *manifest.Manifest,
 	}, nil
 }
 
+// ResolvePreviousSessionArtifactWithCatalog resolves one canonical previous-session source id
+// to the prepared current-session previous-cache path.
+func ResolvePreviousSessionArtifactWithCatalog(
+	paths SessionPaths,
+	m *manifest.Manifest,
+	source string,
+	catalog *ArtifactCatalog,
+) (ResolvedSessionArtifact, error) {
+	artifactName, ok := PreviousSessionArtifactName(source)
+	if !ok {
+		return ResolvedSessionArtifact{}, fmt.Errorf("unsupported previous-session artifact source %q", source)
+	}
+	if catalog == nil {
+		return ResolvedSessionArtifact{}, fmt.Errorf("previous-session artifact source %q requires runtime artifact catalog", source)
+	}
+
+	configuredSourceID := ConfiguredArtifactSourceID(artifactName)
+	entry, ok := catalog.Lookup(configuredSourceID)
+	if !ok {
+		return ResolvedSessionArtifact{}, fmt.Errorf("unsupported previous-session artifact source %q", source)
+	}
+	candidates := previousSessionCacheCandidatePaths(paths, entry.CanonicalRelPath)
+	if len(candidates) == 0 {
+		return ResolvedSessionArtifact{}, &SessionArtifactNotFoundError{ArtifactID: source}
+	}
+
+	manifestInputPaths := manifestInputPathSet(paths, m)
+	fallback := ""
+	for _, candidate := range candidates {
+		exists, isDir, statErr := pathExists(candidate)
+		if statErr != nil {
+			return ResolvedSessionArtifact{}, fmt.Errorf("stat %q: %w", candidate, statErr)
+		}
+		if !exists || isDir {
+			continue
+		}
+		if err := validateResolvedContent(candidate, contentText); err != nil {
+			return ResolvedSessionArtifact{}, fmt.Errorf("validate %q: %w", source, err)
+		}
+		if _, ok := manifestInputPaths[candidate]; ok {
+			return ResolvedSessionArtifact{
+				ID:            source,
+				Path:          candidate,
+				ProducerStage: "prepare",
+				OutputKind:    "previous_session_artifact",
+				Provenance:    ArtifactProvenancePreviousCacheManifestInput,
+			}, nil
+		}
+		if fallback == "" {
+			fallback = candidate
+		}
+	}
+
+	if fallback != "" {
+		return ResolvedSessionArtifact{
+			ID:            source,
+			Path:          fallback,
+			ProducerStage: "prepare",
+			OutputKind:    "previous_session_artifact",
+			Provenance:    ArtifactProvenancePreviousCacheFilesystem,
+		}, nil
+	}
+
+	return ResolvedSessionArtifact{}, &SessionArtifactNotFoundError{ArtifactID: source}
+}
+
 func manifestArtifactCandidates(paths SessionPaths, m *manifest.Manifest, spec artifactSpec) []ResolvedSessionArtifact {
 	if m == nil || len(m.Stages) == 0 || spec.ProducerStage == "" || spec.OutputKind == "" {
 		return nil
@@ -243,6 +331,50 @@ func dedupeResolvedArtifacts(values []ResolvedSessionArtifact) []ResolvedSession
 	return out
 }
 
+func previousSessionCacheCandidatePaths(paths SessionPaths, canonicalRelPath string) []string {
+	trimmed := strings.TrimSpace(canonicalRelPath)
+	if trimmed == "" {
+		return nil
+	}
+	normalized := filepath.ToSlash(filepath.Clean(filepath.FromSlash(trimmed)))
+	if normalized == "." || normalized == "" || normalized == ".." || strings.HasPrefix(normalized, "../") || strings.HasPrefix(normalized, "/") {
+		return nil
+	}
+
+	relCandidates := []string{normalized}
+	const artifactsPrefix = "artifacts/"
+	if strings.HasPrefix(normalized, artifactsPrefix) && len(normalized) > len(artifactsPrefix) {
+		relCandidates = append(relCandidates, strings.TrimPrefix(normalized, artifactsPrefix))
+	}
+
+	out := make([]string, 0, len(relCandidates))
+	seen := map[string]struct{}{}
+	for _, rel := range relCandidates {
+		abs := filepath.Clean(SessionPreviousArtifactPath(paths, rel))
+		if _, ok := seen[abs]; ok {
+			continue
+		}
+		seen[abs] = struct{}{}
+		out = append(out, abs)
+	}
+	return out
+}
+
+func manifestInputPathSet(paths SessionPaths, m *manifest.Manifest) map[string]struct{} {
+	if m == nil || len(m.Inputs) == 0 {
+		return nil
+	}
+	out := make(map[string]struct{}, len(m.Inputs))
+	for _, in := range m.Inputs {
+		resolved := filepath.Clean(ResolveSessionLocalPathForRead(paths, in.Path))
+		if strings.TrimSpace(resolved) == "" {
+			continue
+		}
+		out[resolved] = struct{}{}
+	}
+	return out
+}
+
 func pathExists(path string) (exists bool, isDir bool, err error) {
 	info, err := os.Stat(path)
 	if err == nil {

internal/artifacts/artifact_resolver_test.go

@@ -45,6 +45,58 @@ func TestNormalizeSessionArtifactSource(t *testing.T) {
 	}
 }
 
+func TestPreviousSessionArtifactSourceHelpers(t *testing.T) {
+	tests := []struct {
+		name      string
+		source    string
+		wantName  string
+		wantMatch bool
+	}{
+		{
+			name:      "valid",
+			source:    "narratio.previous_session.artifact.session_recap",
+			wantName:  "session_recap",
+			wantMatch: true,
+		},
+		{
+			name:      "valid with surrounding whitespace",
+			source:    "  narratio.previous_session.artifact.quest_log  ",
+			wantName:  "quest_log",
+			wantMatch: true,
+		},
+		{
+			name:      "missing name",
+			source:    "narratio.previous_session.artifact.",
+			wantMatch: false,
+		},
+		{
+			name:      "invalid key characters",
+			source:    "narratio.previous_session.artifact.session-recap",
+			wantMatch: false,
+		},
+		{
+			name:      "wrong prefix",
+			source:    "narratio.previous.artifact.session_recap",
+			wantMatch: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			name, ok := PreviousSessionArtifactName(tt.source)
+			if ok != tt.wantMatch {
+				t.Fatalf("PreviousSessionArtifactName(%q) ok = %t, want %t", tt.source, ok, tt.wantMatch)
+			}
+			if name != tt.wantName {
+				t.Fatalf("PreviousSessionArtifactName(%q) name = %q, want %q", tt.source, name, tt.wantName)
+			}
+			if got := IsPreviousSessionArtifactSource(tt.source); got != tt.wantMatch {
+				t.Fatalf("IsPreviousSessionArtifactSource(%q) = %t, want %t", tt.source, got, tt.wantMatch)
+			}
+		})
+	}
+}
+
 func TestResolveSessionArtifactPrefersManifestOutput(t *testing.T) {
 	workspace := t.TempDir()
 	paths := buildSessionPaths(workspace, "campaign", "session")
@@ -266,3 +318,120 @@ func TestResolveSessionArtifactWithCatalogUnsupportedConfiguredSourceFails(t *te
 		t.Fatalf("error = %q, want unsupported artifact source", err.Error())
 	}
 }
+
+func TestResolvePreviousSessionArtifactWithCatalogPrefersManifestInputRecord(t *testing.T) {
+	workspace := t.TempDir()
+	paths := buildSessionPaths(workspace, "campaign", "session")
+
+	manifestBackedPath := SessionPreviousArtifactPath(paths, "artifacts/session_recap.md")
+	fallbackPath := SessionPreviousArtifactPath(paths, "session_recap.md")
+	if err := os.MkdirAll(filepath.Dir(manifestBackedPath), 0o755); err != nil {
+		t.Fatalf("MkdirAll() error = %v", err)
+	}
+	if err := os.MkdirAll(filepath.Dir(fallbackPath), 0o755); err != nil {
+		t.Fatalf("MkdirAll() error = %v", err)
+	}
+	if err := os.WriteFile(manifestBackedPath, []byte("recap from manifest input\n"), 0o644); err != nil {
+		t.Fatalf("WriteFile() error = %v", err)
+	}
+	if err := os.WriteFile(fallbackPath, []byte("recap fallback\n"), 0o644); err != nil {
+		t.Fatalf("WriteFile() error = %v", err)
+	}
+
+	catalog := NewArtifactCatalog()
+	if err := catalog.RegisterConfiguredArtifacts(
+		map[string]ConfiguredArtifactDefinition{
+			"session_recap": {Enabled: true, OutputPath: "artifacts/session_recap.md"},
+		},
+		nil,
+	); err != nil {
+		t.Fatalf("RegisterConfiguredArtifacts() error = %v", err)
+	}
+
+	m := manifest.New("session", time.Now().UTC())
+	m.Inputs = []manifest.InputRecord{
+		{Kind: "previous_artifact", Path: manifestBackedPath},
+	}
+
+	resolved, err := ResolvePreviousSessionArtifactWithCatalog(
+		paths,
+		m,
+		"narratio.previous_session.artifact.session_recap",
+		catalog,
+	)
+	if err != nil {
+		t.Fatalf("ResolvePreviousSessionArtifactWithCatalog() error = %v", err)
+	}
+	if resolved.Path != manifestBackedPath {
+		t.Fatalf("resolved path = %q, want %q", resolved.Path, manifestBackedPath)
+	}
+	if resolved.Provenance != ArtifactProvenancePreviousCacheManifestInput {
+		t.Fatalf("provenance = %q, want %q", resolved.Provenance, ArtifactProvenancePreviousCacheManifestInput)
+	}
+}
+
+func TestResolvePreviousSessionArtifactWithCatalogFallsBackToPreparedCachePath(t *testing.T) {
+	workspace := t.TempDir()
+	paths := buildSessionPaths(workspace, "campaign", "session")
+
+	fallbackPath := SessionPreviousArtifactPath(paths, "session_recap.md")
+	if err := os.MkdirAll(filepath.Dir(fallbackPath), 0o755); err != nil {
+		t.Fatalf("MkdirAll() error = %v", err)
+	}
+	if err := os.WriteFile(fallbackPath, []byte("recap fallback\n"), 0o644); err != nil {
+		t.Fatalf("WriteFile() error = %v", err)
+	}
+
+	catalog := NewArtifactCatalog()
+	if err := catalog.RegisterConfiguredArtifacts(
+		map[string]ConfiguredArtifactDefinition{
+			"session_recap": {Enabled: true, OutputPath: "artifacts/session_recap.md"},
+		},
+		nil,
+	); err != nil {
+		t.Fatalf("RegisterConfiguredArtifacts() error = %v", err)
+	}
+
+	resolved, err := ResolvePreviousSessionArtifactWithCatalog(
+		paths,
+		nil,
+		"narratio.previous_session.artifact.session_recap",
+		catalog,
+	)
+	if err != nil {
+		t.Fatalf("ResolvePreviousSessionArtifactWithCatalog() error = %v", err)
+	}
+	if resolved.Path != fallbackPath {
+		t.Fatalf("resolved path = %q, want %q", resolved.Path, fallbackPath)
+	}
+	if resolved.Provenance != ArtifactProvenancePreviousCacheFilesystem {
+		t.Fatalf("provenance = %q, want %q", resolved.Provenance, ArtifactProvenancePreviousCacheFilesystem)
+	}
+}
+
+func TestResolvePreviousSessionArtifactWithCatalogMissingReturnsTypedError(t *testing.T) {
+	workspace := t.TempDir()
+	paths := buildSessionPaths(workspace, "campaign", "session")
+	catalog := NewArtifactCatalog()
+	if err := catalog.RegisterConfiguredArtifacts(
+		map[string]ConfiguredArtifactDefinition{
+			"session_recap": {Enabled: true, OutputPath: "artifacts/session_recap.md"},
+		},
+		nil,
+	); err != nil {
+		t.Fatalf("RegisterConfiguredArtifacts() error = %v", err)
+	}
+
+	_, err := ResolvePreviousSessionArtifactWithCatalog(
+		paths,
+		nil,
+		"narratio.previous_session.artifact.session_recap",
+		catalog,
+	)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !errors.Is(err, ErrSessionArtifactNotFound) {
+		t.Fatalf("errors.Is(err, ErrSessionArtifactNotFound)=false; err=%v", err)
+	}
+}

internal/artifacts/local.go

@@ -73,6 +73,8 @@ func (s *LocalStore) ensureLayout(paths SessionPaths) (SessionPaths, error) {
 		paths.LogsDir,
 		paths.CurrentDir,
 		paths.RunsDir,
+		paths.PreviousDir,
+		paths.PreviousArtifactsDir,
 	}
 
 	for _, dir := range dirs {

internal/artifacts/local_test.go

@@ -27,10 +27,15 @@ func TestEnsureLayoutCreatesExpectedDirectories(t *testing.T) {
 	checkDirExists(t, paths.LogsDir)
 	checkDirExists(t, paths.CurrentDir)
 	checkDirExists(t, paths.RunsDir)
+	checkDirExists(t, paths.PreviousDir)
+	checkDirExists(t, paths.PreviousArtifactsDir)
 
 	if filepath.Base(paths.ManifestPath) != "manifest.json" {
 		t.Fatalf("ManifestPath = %q, want basename manifest.json", paths.ManifestPath)
 	}
+	if filepath.Base(paths.PreviousManifestPath) != "manifest.json" {
+		t.Fatalf("PreviousManifestPath = %q, want basename manifest.json", paths.PreviousManifestPath)
+	}
 	if filepath.Base(paths.LockPath) != ".lock" {
 		t.Fatalf("LockPath = %q, want basename .lock", paths.LockPath)
 	}

internal/artifacts/paths.go

@@ -23,6 +23,9 @@ type SessionPaths struct {
 	LogsDir               string
 	CurrentDir            string
 	RunsDir               string
+	PreviousDir           string
+	PreviousManifestPath  string
+	PreviousArtifactsDir  string
 	ManifestPath          string
 	LockPath              string
 }
@@ -42,6 +45,29 @@ func SessionRunsDirForCampaign(rootDir, campaign, sessionID string) string {
 	return filepath.Join(SessionWorkDirForCampaign(rootDir, campaign, sessionID), config.PathRunsDirSegment)
 }
 
+// SessionPreviousDirForCampaign returns the canonical previous-session state directory.
+func SessionPreviousDirForCampaign(rootDir, campaign, sessionID string) string {
+	return filepath.Join(SessionWorkDirForCampaign(rootDir, campaign, sessionID), config.PathPreviousDirSegment)
+}
+
+// SessionPreviousManifestPathForCampaign returns the canonical previous-session manifest cache path.
+func SessionPreviousManifestPathForCampaign(rootDir, campaign, sessionID string) string {
+	return filepath.Join(SessionPreviousDirForCampaign(rootDir, campaign, sessionID), config.PathManifestFile)
+}
+
+// SessionPreviousArtifactsDirForCampaign returns the canonical previous-session artifact cache directory.
+func SessionPreviousArtifactsDirForCampaign(rootDir, campaign, sessionID string) string {
+	return filepath.Join(SessionPreviousDirForCampaign(rootDir, campaign, sessionID), config.PathArtifactsDirSegment)
+}
+
+// SessionPreviousArtifactPathForCampaign returns a path under previous/artifacts for one artifact.
+func SessionPreviousArtifactPathForCampaign(rootDir, campaign, sessionID, artifactRelativePath string) string {
+	return filepath.Join(
+		SessionPreviousArtifactsDirForCampaign(rootDir, campaign, sessionID),
+		filepath.FromSlash(artifactRelativePath),
+	)
+}
+
 // SessionRunRootForCampaign returns the canonical run root under runs/{run_id}.
 func SessionRunRootForCampaign(rootDir, campaign, sessionID, runID string) string {
 	return filepath.Join(SessionRunsDirForCampaign(rootDir, campaign, sessionID), runID)
@@ -62,6 +88,26 @@ func SessionSpoolAudioDir(spoolRoot, campaign, sessionID, runID string) string {
 	return filepath.Join(spoolRoot, campaign, sessionID, runID, config.PathAudioDirSegment)
 }
 
+// SessionPreviousDir returns the previous-session state directory for already-resolved session paths.
+func SessionPreviousDir(paths SessionPaths) string {
+	return paths.PreviousDir
+}
+
+// SessionPreviousManifestPath returns the previous-session manifest path for already-resolved session paths.
+func SessionPreviousManifestPath(paths SessionPaths) string {
+	return paths.PreviousManifestPath
+}
+
+// SessionPreviousArtifactsDir returns the previous-session artifact directory for already-resolved session paths.
+func SessionPreviousArtifactsDir(paths SessionPaths) string {
+	return paths.PreviousArtifactsDir
+}
+
+// SessionPreviousArtifactPath returns a path under previous/artifacts for already-resolved session paths.
+func SessionPreviousArtifactPath(paths SessionPaths, artifactRelativePath string) string {
+	return filepath.Join(paths.PreviousArtifactsDir, filepath.FromSlash(artifactRelativePath))
+}
+
 func buildSessionPaths(workspaceRoot, campaign, sessionID string) SessionPaths {
 	root := SessionWorkDirForCampaign(workspaceRoot, campaign, sessionID)
 	return buildSessionPathsFromRoot(workspaceRoot, campaign, sessionID, root)
@@ -84,6 +130,9 @@ func buildSessionPathsFromRoot(workspaceRoot, campaign, sessionID, root string)
 		LogsDir:               filepath.Join(root, config.PathLogsDirSegment),
 		CurrentDir:            filepath.Join(root, config.PathCurrentDirSegment),
 		RunsDir:               filepath.Join(root, config.PathRunsDirSegment),
+		PreviousDir:           filepath.Join(root, config.PathPreviousDirSegment),
+		PreviousManifestPath:  filepath.Join(root, config.PathPreviousDirSegment, config.PathManifestFile),
+		PreviousArtifactsDir:  filepath.Join(root, config.PathPreviousDirSegment, config.PathArtifactsDirSegment),
 		ManifestPath:          filepath.Join(root, config.PathManifestFile),
 		LockPath:              filepath.Join(root, config.PathLockFile),
 	}

internal/artifacts/paths_model_test.go

@@ -49,6 +49,52 @@ func TestSessionRunManifestPathForCampaign(t *testing.T) {
 	}
 }
 
+func TestSessionPreviousPathsForCampaign(t *testing.T) {
+	root := "/tmp/workspace"
+	previousDir := SessionPreviousDirForCampaign(root, "forsaken", "2026-04-19")
+	wantPreviousDir := filepath.Join(root, "work", "forsaken", "2026-04-19", "previous")
+	if previousDir != wantPreviousDir {
+		t.Fatalf("SessionPreviousDirForCampaign() = %q, want %q", previousDir, wantPreviousDir)
+	}
+
+	manifestPath := SessionPreviousManifestPathForCampaign(root, "forsaken", "2026-04-19")
+	wantManifestPath := filepath.Join(root, "work", "forsaken", "2026-04-19", "previous", "manifest.json")
+	if manifestPath != wantManifestPath {
+		t.Fatalf("SessionPreviousManifestPathForCampaign() = %q, want %q", manifestPath, wantManifestPath)
+	}
+
+	artifactsDir := SessionPreviousArtifactsDirForCampaign(root, "forsaken", "2026-04-19")
+	wantArtifactsDir := filepath.Join(root, "work", "forsaken", "2026-04-19", "previous", "artifacts")
+	if artifactsDir != wantArtifactsDir {
+		t.Fatalf("SessionPreviousArtifactsDirForCampaign() = %q, want %q", artifactsDir, wantArtifactsDir)
+	}
+
+	artifactPath := SessionPreviousArtifactPathForCampaign(root, "forsaken", "2026-04-19", "session_recap.md")
+	wantArtifactPath := filepath.Join(root, "work", "forsaken", "2026-04-19", "previous", "artifacts", "session_recap.md")
+	if artifactPath != wantArtifactPath {
+		t.Fatalf("SessionPreviousArtifactPathForCampaign() = %q, want %q", artifactPath, wantArtifactPath)
+	}
+}
+
+func TestSessionPreviousPathsFromSessionPaths(t *testing.T) {
+	paths := buildSessionPaths("/tmp/workspace", "forsaken", "2026-04-19")
+	if got := SessionPreviousDir(paths); got != paths.PreviousDir {
+		t.Fatalf("SessionPreviousDir() = %q, want %q", got, paths.PreviousDir)
+	}
+	if got := SessionPreviousManifestPath(paths); got != paths.PreviousManifestPath {
+		t.Fatalf("SessionPreviousManifestPath() = %q, want %q", got, paths.PreviousManifestPath)
+	}
+	if got := SessionPreviousArtifactsDir(paths); got != paths.PreviousArtifactsDir {
+		t.Fatalf("SessionPreviousArtifactsDir() = %q, want %q", got, paths.PreviousArtifactsDir)
+	}
+
+	got := SessionPreviousArtifactPath(paths, "quest_log.json")
+	want := filepath.Join(paths.PreviousArtifactsDir, "quest_log.json")
+	if got != want {
+		t.Fatalf("SessionPreviousArtifactPath() = %q, want %q", got, want)
+	}
+}
+
 func TestSessionSpoolAudioDir(t *testing.T) {
 	root := "/var/spool/narratio"
 	got := SessionSpoolAudioDir(root, "forsaken", "2026-04-19", "20260515T031522Z-a1b2c3d4")

internal/artifacts/previous_requirements.go

@@ -0,0 +1,112 @@
+package artifacts
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
+)
+
+// PreviousArtifactRequirement describes one previous-session artifact dependency.
+type PreviousArtifactRequirement struct {
+	Name     string
+	Required bool
+	Sources  []string
+}
+
+// CollectPreviousArtifactRequirements scans enabled Scriptorium artifacts and returns
+// deduplicated previous-session artifact requirements in deterministic order.
+func CollectPreviousArtifactRequirements(
+	artifactsCfg map[string]config.ScriptoriumArtifactConfig,
+) []PreviousArtifactRequirement {
+	if len(artifactsCfg) == 0 {
+		return nil
+	}
+
+	artifactNames := sortedScriptoriumArtifactNames(artifactsCfg)
+	byName := map[string]PreviousArtifactRequirement{}
+
+	for _, artifactName := range artifactNames {
+		artifactCfg := artifactsCfg[artifactName]
+		if !artifactCfg.Enabled {
+			continue
+		}
+
+		inputNames := sortedScriptoriumInputKeys(artifactCfg.Inputs)
+		for _, inputName := range inputNames {
+			inputCfg := artifactCfg.Inputs[inputName]
+			previousName, ok := PreviousSessionArtifactName(inputCfg.Source)
+			if !ok {
+				continue
+			}
+
+			location := fmt.Sprintf(
+				"pipeline.scriptorium.artifacts.%s.inputs.%s.source",
+				artifactName,
+				inputName,
+			)
+			requirement := byName[previousName]
+			requirement.Name = previousName
+			requirement.Required = requirement.Required || inputCfg.Required
+			requirement.Sources = append(requirement.Sources, location)
+			byName[previousName] = requirement
+		}
+	}
+
+	if len(byName) == 0 {
+		return nil
+	}
+
+	requirements := make([]PreviousArtifactRequirement, 0, len(byName))
+	for _, requirement := range byName {
+		requirement.Sources = dedupeAndSortStrings(requirement.Sources)
+		requirements = append(requirements, requirement)
+	}
+	sort.Slice(requirements, func(i, j int) bool {
+		return requirements[i].Name < requirements[j].Name
+	})
+	return requirements
+}
+
+func sortedScriptoriumArtifactNames(artifactsCfg map[string]config.ScriptoriumArtifactConfig) []string {
+	names := make([]string, 0, len(artifactsCfg))
+	for name := range artifactsCfg {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}
+
+func sortedScriptoriumInputKeys(inputs map[string]config.ScriptoriumInputConfig) []string {
+	if len(inputs) == 0 {
+		return nil
+	}
+	names := make([]string, 0, len(inputs))
+	for name := range inputs {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}
+
+func dedupeAndSortStrings(values []string) []string {
+	if len(values) == 0 {
+		return nil
+	}
+	seen := map[string]struct{}{}
+	out := make([]string, 0, len(values))
+	for _, value := range values {
+		trimmed := strings.TrimSpace(value)
+		if trimmed == "" {
+			continue
+		}
+		if _, ok := seen[trimmed]; ok {
+			continue
+		}
+		seen[trimmed] = struct{}{}
+		out = append(out, trimmed)
+	}
+	sort.Strings(out)
+	return out
+}

internal/artifacts/previous_requirements_test.go

@@ -0,0 +1,190 @@
+package artifacts
+
+import (
+	"reflect"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
+)
+
+func TestCollectPreviousArtifactRequirements(t *testing.T) {
+	tests := []struct {
+		name         string
+		artifactsCfg map[string]config.ScriptoriumArtifactConfig
+		want         []PreviousArtifactRequirement
+	}{
+		{
+			name:         "no artifacts",
+			artifactsCfg: nil,
+			want:         nil,
+		},
+		{
+			name: "no previous inputs",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"session_recap": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"transcript": {Source: "narratio.transcript.trimmed", Required: true},
+					},
+				},
+			},
+			want: nil,
+		},
+		{
+			name: "one optional previous input",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"session_recap": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"previous_recap": {Source: "narratio.previous_session.artifact.session_recap", Required: false},
+					},
+				},
+			},
+			want: []PreviousArtifactRequirement{
+				{
+					Name:     "session_recap",
+					Required: false,
+					Sources:  []string{"pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source"},
+				},
+			},
+		},
+		{
+			name: "one required previous input",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"quest_log": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"previous_quest_log": {Source: "narratio.previous_session.artifact.quest_log", Required: true},
+					},
+				},
+			},
+			want: []PreviousArtifactRequirement{
+				{
+					Name:     "quest_log",
+					Required: true,
+					Sources:  []string{"pipeline.scriptorium.artifacts.quest_log.inputs.previous_quest_log.source"},
+				},
+			},
+		},
+		{
+			name: "duplicate references are deduped",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"a": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"x": {Source: "narratio.previous_session.artifact.session_recap", Required: false},
+					},
+				},
+				"b": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"y": {Source: "narratio.previous_session.artifact.session_recap", Required: false},
+					},
+				},
+			},
+			want: []PreviousArtifactRequirement{
+				{
+					Name:     "session_recap",
+					Required: false,
+					Sources: []string{
+						"pipeline.scriptorium.artifacts.a.inputs.x.source",
+						"pipeline.scriptorium.artifacts.b.inputs.y.source",
+					},
+				},
+			},
+		},
+		{
+			name: "required plus optional reference becomes required",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"a": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"x": {Source: "narratio.previous_session.artifact.session_recap", Required: false},
+					},
+				},
+				"b": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"y": {Source: "narratio.previous_session.artifact.session_recap", Required: true},
+					},
+				},
+			},
+			want: []PreviousArtifactRequirement{
+				{
+					Name:     "session_recap",
+					Required: true,
+					Sources: []string{
+						"pipeline.scriptorium.artifacts.a.inputs.x.source",
+						"pipeline.scriptorium.artifacts.b.inputs.y.source",
+					},
+				},
+			},
+		},
+		{
+			name: "disabled artifact references are ignored",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"disabled_artifact": {
+					Enabled: false,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"x": {Source: "narratio.previous_session.artifact.session_recap", Required: true},
+					},
+				},
+				"enabled_artifact": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"y": {Source: "narratio.previous_session.artifact.quest_log", Required: false},
+					},
+				},
+			},
+			want: []PreviousArtifactRequirement{
+				{
+					Name:     "quest_log",
+					Required: false,
+					Sources:  []string{"pipeline.scriptorium.artifacts.enabled_artifact.inputs.y.source"},
+				},
+			},
+		},
+		{
+			name: "deterministic ordering",
+			artifactsCfg: map[string]config.ScriptoriumArtifactConfig{
+				"zz": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"b_input": {Source: "narratio.previous_session.artifact.quest_log", Required: false},
+						"a_input": {Source: "narratio.previous_session.artifact.session_recap", Required: false},
+					},
+				},
+				"aa": {
+					Enabled: true,
+					Inputs: map[string]config.ScriptoriumInputConfig{
+						"c_input": {Source: "narratio.previous_session.artifact.session_recap", Required: false},
+					},
+				},
+			},
+			want: []PreviousArtifactRequirement{
+				{
+					Name:     "quest_log",
+					Required: false,
+					Sources:  []string{"pipeline.scriptorium.artifacts.zz.inputs.b_input.source"},
+				},
+				{
+					Name:     "session_recap",
+					Required: false,
+					Sources: []string{
+						"pipeline.scriptorium.artifacts.aa.inputs.c_input.source",
+						"pipeline.scriptorium.artifacts.zz.inputs.a_input.source",
+					},
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := CollectPreviousArtifactRequirements(tt.artifactsCfg)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Fatalf("CollectPreviousArtifactRequirements() = %#v, want %#v", got, tt.want)
+			}
+		})
+	}
+}

internal/config/config.go

@@ -28,6 +28,7 @@ type PipelineConfig struct {
 // SessionConfig contains per-session inputs and metadata.
 type SessionConfig struct {
 	SessionID         string              `yaml:"session_id"`
+	PreviousSessionID string              `yaml:"previous_session_id"`
 	Campaign          string              `yaml:"campaign"`
 	Date              string              `yaml:"date"`
 	Title             string              `yaml:"title"`

internal/config/defaults.go

@@ -56,6 +56,7 @@ const (
 	PathLogsDirSegment       = "logs"
 	PathCurrentDirSegment    = "current"
 	PathRunsDirSegment       = "runs"
+	PathPreviousDirSegment   = "previous"
 	PathManifestFile         = "manifest.json"
 	PathLockFile             = ".lock"
 	PathTranscriptMerged     = "transcripts/merged.json"

internal/config/load.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"sort"
 	"strings"
 
 	"gopkg.in/yaml.v3"
@@ -29,6 +30,7 @@ func LoadSession(path string) (*SessionConfig, error) {
 // SessionLoadOptions configures session template rendering behavior.
 type SessionLoadOptions struct {
 	SessionID         string
+	PreviousSessionID string
 }
 
 // LoadSessionWithOptions loads session configuration from a YAML file with
@@ -56,6 +58,16 @@ func LoadSessionWithOptions(path string, opts SessionLoadOptions) (*SessionConfi
 			strings.TrimSpace(cfg.SessionID),
 		)
 	}
+	if strings.TrimSpace(opts.PreviousSessionID) != "" &&
+		strings.TrimSpace(cfg.PreviousSessionID) != "" &&
+		strings.TrimSpace(cfg.PreviousSessionID) != strings.TrimSpace(opts.PreviousSessionID) {
+		return nil, fmt.Errorf(
+			"load session config: session file %q: previous_session_id mismatch: --previous-session-id %q does not match rendered previous_session_id %q",
+			path,
+			strings.TrimSpace(opts.PreviousSessionID),
+			strings.TrimSpace(cfg.PreviousSessionID),
+		)
+	}
 	return &cfg, nil
 }
 
@@ -114,24 +126,36 @@ var sessionTemplatePattern = regexp.MustCompile(`\{\{\s*([a-zA-Z_][a-zA-Z0-9_]*)
 
 func renderSessionTemplate(content string, opts SessionLoadOptions) (string, error) {
 	sessionID := strings.TrimSpace(opts.SessionID)
+	previousSessionID := strings.TrimSpace(opts.PreviousSessionID)
 	rendered := content
 	if sessionID != "" {
-		rendered = strings.ReplaceAll(rendered, "{{session_id}}", sessionID)
+		rendered = replaceTemplateVariable(rendered, "session_id", sessionID)
-		rendered = strings.ReplaceAll(rendered, "{{ session_id }}", sessionID)
+	}
+	if previousSessionID != "" {
+		rendered = replaceTemplateVariable(rendered, "previous_session_id", previousSessionID)
 	}
 
 	unresolved := sessionTemplatePattern.FindAllStringSubmatch(rendered, -1)
 	if len(unresolved) > 0 {
+		seenVars := map[string]struct{}{}
 		vars := make([]string, 0, len(unresolved))
 		for _, m := range unresolved {
 			if len(m) > 1 {
-				vars = append(vars, m[1])
+				name := m[1]
+				if _, ok := seenVars[name]; ok {
+					continue
+				}
+				seenVars[name] = struct{}{}
+				vars = append(vars, name)
 			}
 		}
+		sort.Strings(vars)
 		if len(vars) > 0 {
+			hints := unresolvedTemplateHints(vars)
 			return "", fmt.Errorf(
-				"session file template rendering failed: unresolved template variable(s): %s; pass --session-id when using {{ session_id }}",
+				"session file template rendering failed: unresolved template variable(s): %s%s",
 				strings.Join(vars, ", "),
+				hints,
 			)
 		}
 		return "", fmt.Errorf("session file template rendering failed: unresolved template placeholders remain")
@@ -140,6 +164,35 @@ func renderSessionTemplate(content string, opts SessionLoadOptions) (string, err
 	return rendered, nil
 }
 
+func replaceTemplateVariable(content, name, value string) string {
+	rendered := strings.ReplaceAll(content, "{{"+name+"}}", value)
+	rendered = strings.ReplaceAll(rendered, "{{ "+name+" }}", value)
+	return rendered
+}
+
+func unresolvedTemplateHints(vars []string) string {
+	seen := map[string]struct{}{}
+	flags := make([]string, 0, 2)
+	for _, name := range vars {
+		switch name {
+		case "session_id":
+			if _, ok := seen["--session-id"]; !ok {
+				seen["--session-id"] = struct{}{}
+				flags = append(flags, "--session-id")
+			}
+		case "previous_session_id":
+			if _, ok := seen["--previous-session-id"]; !ok {
+				seen["--previous-session-id"] = struct{}{}
+				flags = append(flags, "--previous-session-id")
+			}
+		}
+	}
+	if len(flags) == 0 {
+		return ""
+	}
+	return "; pass " + strings.Join(flags, " and ") + " when using those template variable(s)"
+}
+
 func shortName(path, fallback string) string {
 	base := filepath.Base(path)
 	if base == "." || base == string(filepath.Separator) {

internal/config/load_validate_test.go

@@ -187,6 +187,43 @@ inputs:
 `,
 			wantValidate: "session config \"session.yml\" invalid: session.session_id is required",
 		},
+		{
+			name: "valid previous_session_id passes",
+			pipelineYAML: `workspace:
+  root: /tmp/narratio
+whisperx:
+  transcribe_url: https://transcription.ai.rakestrawhome.com/transcribe
+seriatim:
+  binary: seriatim
+`,
+			sessionYAML: `session_id: 2026-05-03
+previous_session_id: 2026-04-26
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`,
+		},
+		{
+			name: "previous_session_id equal to session_id fails",
+			pipelineYAML: `workspace:
+  root: /tmp/narratio
+whisperx:
+  transcribe_url: https://transcription.ai.rakestrawhome.com/transcribe
+seriatim:
+  binary: seriatim
+`,
+			sessionYAML: `session_id: 2026-05-03
+previous_session_id: 2026-05-03
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`,
+			wantValidate: "session config \"session.yml\" invalid: session.previous_session_id must not equal session.session_id",
+		},
 		{
 			name: "missing transcribe_url fails",
 			pipelineYAML: `workspace:

internal/config/scriptorium_test.go

@@ -116,6 +116,75 @@ func TestScriptoriumLoadAndValidate(t *testing.T) {
         output_kind: session_recap
 `,
 		},
+		{
+			name: "canonical previous-session source is accepted",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        transcript:
+          source: narratio.transcript.polished
+          required: true
+        previous_recap:
+          source: narratio.previous_session.artifact.session_recap
+          required: false
+      vars:
+        session_id: true
+        output_kind: session_recap
+`,
+		},
+		{
+			name: "canonical previous-session source missing artifact key fails validation",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        previous_recap:
+          source: narratio.previous_session.artifact.
+          required: false
+`,
+			wantValidateErr: `pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source "narratio.previous_session.artifact." must reference configured artifact key matching ^[a-z][a-z0-9_]*$`,
+		},
+		{
+			name: "canonical previous-session source invalid artifact key fails validation",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        previous_recap:
+          source: narratio.previous_session.artifact.session-recap
+          required: false
+`,
+			wantValidateErr: `pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source "narratio.previous_session.artifact.session-recap" must reference configured artifact key matching ^[a-z][a-z0-9_]*$`,
+		},
+		{
+			name: "canonical previous-session source unknown artifact fails validation",
+			scriptoriumYAML: `scriptorium:
+  binary: scriptorium
+  artifacts:
+    session_recap:
+      enabled: true
+      prompt_id: dnd.session_recap
+      output_path: artifacts/session_recap.md
+      inputs:
+        previous_recap:
+          source: narratio.previous_session.artifact.quest_log
+          required: false
+`,
+			wantValidateErr: `pipeline.scriptorium.artifacts.session_recap.inputs.previous_recap.source "narratio.previous_session.artifact.quest_log" references unknown artifact "quest_log"`,
+		},
 		{
 			name: "canonical artifact source is accepted",
 			scriptoriumYAML: `scriptorium:

internal/config/session_template_test.go

@@ -55,6 +55,34 @@ inputs:
 	}
 }
 
+func TestLoadSessionWithOptionsRendersPreviousSessionPlaceholder(t *testing.T) {
+	dir := t.TempDir()
+	sessionPath := filepath.Join(dir, "session.yml")
+	sessionYAML := `session_id: "{{ session_id }}"
+previous_session_id: "{{ previous_session_id }}"
+campaign: sample-campaign
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`
+	if err := os.WriteFile(sessionPath, []byte(sessionYAML), 0o644); err != nil {
+		t.Fatalf("write session.yml: %v", err)
+	}
+
+	cfg, err := LoadSessionWithOptions(sessionPath, SessionLoadOptions{
+		SessionID:         "2026-04-04",
+		PreviousSessionID: "2026-03-28",
+	})
+	if err != nil {
+		t.Fatalf("LoadSessionWithOptions() error = %v", err)
+	}
+	if cfg.PreviousSessionID != "2026-03-28" {
+		t.Fatalf("PreviousSessionID = %q, want 2026-03-28", cfg.PreviousSessionID)
+	}
+}
+
 func TestLoadSessionWithOptionsUnresolvedPlaceholderFails(t *testing.T) {
 	dir := t.TempDir()
 	sessionPath := filepath.Join(dir, "session.yml")
@@ -82,6 +110,37 @@ inputs:
 	}
 }
 
+func TestLoadSessionWithOptionsUnresolvedPreviousSessionPlaceholderFails(t *testing.T) {
+	dir := t.TempDir()
+	sessionPath := filepath.Join(dir, "session.yml")
+	sessionYAML := `session_id: 2026-05-03
+previous_session_id: "{{ previous_session_id }}"
+campaign: sample-campaign
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`
+	if err := os.WriteFile(sessionPath, []byte(sessionYAML), 0o644); err != nil {
+		t.Fatalf("write session.yml: %v", err)
+	}
+
+	_, err := LoadSessionWithOptions(sessionPath, SessionLoadOptions{})
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "unresolved template variable") {
+		t.Fatalf("error = %q, want unresolved-variable context", err.Error())
+	}
+	if !strings.Contains(err.Error(), "previous_session_id") {
+		t.Fatalf("error = %q, want previous_session_id variable", err.Error())
+	}
+	if !strings.Contains(err.Error(), "--previous-session-id") {
+		t.Fatalf("error = %q, want previous-session-id guidance", err.Error())
+	}
+}
+
 func TestLoadSessionWithOptionsMismatchFails(t *testing.T) {
 	dir := t.TempDir()
 	sessionPath := filepath.Join(dir, "session.yml")
@@ -106,6 +165,34 @@ inputs:
 	}
 }
 
+func TestLoadSessionWithOptionsPreviousSessionMismatchFails(t *testing.T) {
+	dir := t.TempDir()
+	sessionPath := filepath.Join(dir, "session.yml")
+	sessionYAML := `session_id: 2026-05-03
+previous_session_id: 2026-04-26
+campaign: sample-campaign
+inputs:
+  audio_dir: ./audio
+  speakers_file: ./speakers.yml
+  autocorrect_file: ./autocorrect.yml
+  glossary_file: ./glossary.yml
+`
+	if err := os.WriteFile(sessionPath, []byte(sessionYAML), 0o644); err != nil {
+		t.Fatalf("write session.yml: %v", err)
+	}
+
+	_, err := LoadSessionWithOptions(sessionPath, SessionLoadOptions{
+		SessionID:         "2026-05-03",
+		PreviousSessionID: "2026-04-25",
+	})
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "previous_session_id mismatch") {
+		t.Fatalf("error = %q, want mismatch context", err.Error())
+	}
+}
+
 func TestLoadSessionWithOptionsUnknownFieldStillRejectedAfterRendering(t *testing.T) {
 	dir := t.TempDir()
 	sessionPath := filepath.Join(dir, "session.yml")

internal/config/validate.go

@@ -487,8 +487,14 @@ func validateScriptorium(cfg *ScriptoriumConfig) error {
 }
 
 func validateSession(cfg *SessionConfig) error {
-	if strings.TrimSpace(cfg.SessionID) == "" {
+	if err := validateSessionIdentifier("session.session_id", cfg.SessionID, true); err != nil {
-		return fmt.Errorf("session.session_id is required")
+		return err
+	}
+	if err := validateSessionIdentifier("session.previous_session_id", cfg.PreviousSessionID, false); err != nil {
+		return err
+	}
+	if strings.TrimSpace(cfg.PreviousSessionID) != "" && strings.TrimSpace(cfg.PreviousSessionID) == strings.TrimSpace(cfg.SessionID) {
+		return fmt.Errorf("session.previous_session_id must not equal session.session_id")
 	}
 	if strings.TrimSpace(cfg.Campaign) == "" {
 		return fmt.Errorf("session.campaign is required")
@@ -525,6 +531,16 @@ func validateSession(cfg *SessionConfig) error {
 	return nil
 }
 
+func validateSessionIdentifier(fieldName, value string, required bool) error {
+	if strings.TrimSpace(value) == "" {
+		if required {
+			return fmt.Errorf("%s is required", fieldName)
+		}
+		return nil
+	}
+	return nil
+}
+
 func validateCrossConfig(pipeline *PipelineConfig, session *SessionConfig) error {
 	if pipeline == nil || session == nil {
 		return nil
@@ -563,12 +579,38 @@ var windowsAbsPathRE = regexp.MustCompile(`^[A-Za-z]:[\\/].*`)
 var envVarNameRE = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*$`)
 var scriptoriumArtifactKeyRE = regexp.MustCompile(`^[a-z][a-z0-9_]*$`)
 var narratioArtifactSourceRE = regexp.MustCompile(`^narratio\.artifact\.([a-z][a-z0-9_]*)$`)
+var narratioPreviousSessionArtifactSourceRE = regexp.MustCompile(`^narratio\.previous_session\.artifact\.([a-z][a-z0-9_]*)$`)
 
 func validateScriptoriumInputSource(artifactName, inputName, source string, configuredArtifacts map[string]struct{}) (string, error) {
-	if isStaticSupportedScriptoriumInputSource(source) {
+	trimmedSource := strings.TrimSpace(source)
+	if isStaticSupportedScriptoriumInputSource(trimmedSource) {
 		return "", nil
 	}
-	matches := narratioArtifactSourceRE.FindStringSubmatch(source)
+
+	if strings.HasPrefix(trimmedSource, "narratio.previous_session.artifact") {
+		matches := narratioPreviousSessionArtifactSourceRE.FindStringSubmatch(trimmedSource)
+		if len(matches) != 2 {
+			return "", fmt.Errorf(
+				"pipeline.scriptorium.artifacts.%s.inputs.%s.source %q must reference configured artifact key matching ^[a-z][a-z0-9_]*$",
+				artifactName,
+				inputName,
+				source,
+			)
+		}
+		referenced := matches[1]
+		if _, ok := configuredArtifacts[referenced]; !ok {
+			return "", fmt.Errorf(
+				"pipeline.scriptorium.artifacts.%s.inputs.%s.source %q references unknown artifact %q",
+				artifactName,
+				inputName,
+				source,
+				referenced,
+			)
+		}
+		return "", nil
+	}
+
+	matches := narratioArtifactSourceRE.FindStringSubmatch(trimmedSource)
 	if len(matches) != 2 {
 		return "", fmt.Errorf(
 			"pipeline.scriptorium.artifacts.%s.inputs.%s.source %q is unsupported",
@@ -591,7 +633,7 @@ func validateScriptoriumInputSource(artifactName, inputName, source string, conf
 }
 
 func isStaticSupportedScriptoriumInputSource(source string) bool {
-	switch strings.TrimSpace(source) {
+	switch source {
 	case "previous_session_artifact":
 		return true
 	case "narratio.transcript.merged":

internal/stage/analyze.go

@@ -631,6 +631,23 @@ func resolveScriptoriumInput(
 	runtimeCatalog *artifacts.ArtifactCatalog,
 ) (string, bool, *artifacts.ResolvedSessionArtifact, error) {
 	source := strings.TrimSpace(inputCfg.Source)
+	if artifacts.IsPreviousSessionArtifactSource(source) {
+		resolved, err := artifacts.ResolvePreviousSessionArtifactWithCatalog(paths, m, source, runtimeCatalog)
+		if err == nil {
+			copy := resolved
+			return resolved.Path, true, &copy, nil
+		}
+		if errors.Is(err, artifacts.ErrSessionArtifactNotFound) {
+			if inputCfg.Required {
+				return "", false, nil, fmt.Errorf(
+					"required previous-session input source %q is unavailable; run narratio run-stage --force prepare",
+					source,
+				)
+			}
+			return "", false, nil, nil
+		}
+		return "", false, nil, err
+	}
 	switch source {
 	case "previous_session_artifact":
 		if strings.TrimSpace(inputCfg.Path) == "" {

internal/stage/analyze_test.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"gitea.maximumdirect.net/eric/narratio/internal/adapters/scriptorium"
+	"gitea.maximumdirect.net/eric/narratio/internal/adapters/storage"
 	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
 	"gitea.maximumdirect.net/eric/narratio/internal/config"
 	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
@@ -717,6 +718,146 @@ func TestAnalyzeOmitsOptionalMissingConfiguredArtifactInput(t *testing.T) {
 	}
 }
 
+func TestAnalyzeRequiredPreviousSessionArtifactInputGuidesPrepareForce(t *testing.T) {
+	env, m, _ := setupAnalyzeEnv(t)
+
+	sessionRecap := env.Config.Pipeline.Scriptorium.Artifacts["session_recap"]
+	sessionRecap.Inputs["previous_recap"] = config.ScriptoriumInputConfig{
+		Source:   "narratio.previous_session.artifact.session_recap",
+		Required: true,
+	}
+	env.Config.Pipeline.Scriptorium.Artifacts["session_recap"] = sessionRecap
+
+	_, err := (analyzeStage{}).Run(context.Background(), env, m)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if !strings.Contains(err.Error(), "run narratio run-stage --force prepare") {
+		t.Fatalf("error = %q, want guidance to run force prepare", err.Error())
+	}
+}
+
+func TestAnalyzeResolvesCanonicalPreviousSessionArtifactFromManifestInput(t *testing.T) {
+	env, m, fake := setupAnalyzeEnv(t)
+	paths := sessionPathsForEnv(env, m.SessionID)
+	writeAnalyzeFile(t, filepath.Join(paths.TranscriptsDir, "trimmed.json"), `{"segments":[]}`)
+
+	previousPath := artifacts.SessionPreviousArtifactPath(paths, "artifacts/session_recap.md")
+	writeAnalyzeFile(t, previousPath, "previous recap\n")
+	m.Inputs = append(m.Inputs, manifest.InputRecord{
+		Kind: "previous_artifact",
+		Path: previousPath,
+	})
+
+	sessionRecap := env.Config.Pipeline.Scriptorium.Artifacts["session_recap"]
+	sessionRecap.Inputs["previous_recap"] = config.ScriptoriumInputConfig{
+		Source:   "narratio.previous_session.artifact.session_recap",
+		Required: true,
+	}
+	env.Config.Pipeline.Scriptorium.Artifacts["session_recap"] = sessionRecap
+
+	_, err := (analyzeStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if len(fake.RunRequests) != 1 {
+		t.Fatalf("run requests = %d, want 1", len(fake.RunRequests))
+	}
+	if got := fake.RunRequests[0].InputPaths["previous_recap"]; got != previousPath {
+		t.Fatalf("previous_recap input = %q, want %q", got, previousPath)
+	}
+}
+
+func TestAnalyzeOmitsOptionalMissingCanonicalPreviousSessionArtifact(t *testing.T) {
+	env, m, fake := setupAnalyzeEnv(t)
+	paths := sessionPathsForEnv(env, m.SessionID)
+	writeAnalyzeFile(t, filepath.Join(paths.TranscriptsDir, "trimmed.json"), `{"segments":[]}`)
+
+	sessionRecap := env.Config.Pipeline.Scriptorium.Artifacts["session_recap"]
+	sessionRecap.Inputs["previous_recap"] = config.ScriptoriumInputConfig{
+		Source:   "narratio.previous_session.artifact.session_recap",
+		Required: false,
+	}
+	env.Config.Pipeline.Scriptorium.Artifacts["session_recap"] = sessionRecap
+
+	_, err := (analyzeStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if len(fake.RunRequests) != 1 {
+		t.Fatalf("run requests = %d, want 1", len(fake.RunRequests))
+	}
+	if _, exists := fake.RunRequests[0].InputPaths["previous_recap"]; exists {
+		t.Fatalf("optional canonical previous_recap should be omitted when unavailable")
+	}
+}
+
+func TestAnalyzeRenderDebugWithCanonicalPreviousSessionInput(t *testing.T) {
+	env, m, fake := setupAnalyzeEnv(t)
+	paths := sessionPathsForEnv(env, m.SessionID)
+	writeAnalyzeFile(t, filepath.Join(paths.TranscriptsDir, "trimmed.json"), `{"segments":[]}`)
+	env.Config.Pipeline.Scriptorium.RenderDebug = true
+
+	previousPath := artifacts.SessionPreviousArtifactPath(paths, "artifacts/session_recap.md")
+	writeAnalyzeFile(t, previousPath, "previous recap\n")
+	m.Inputs = append(m.Inputs, manifest.InputRecord{
+		Kind: "previous_artifact",
+		Path: previousPath,
+	})
+
+	sessionRecap := env.Config.Pipeline.Scriptorium.Artifacts["session_recap"]
+	sessionRecap.Inputs["previous_recap"] = config.ScriptoriumInputConfig{
+		Source:   "narratio.previous_session.artifact.session_recap",
+		Required: true,
+	}
+	env.Config.Pipeline.Scriptorium.Artifacts["session_recap"] = sessionRecap
+
+	_, err := (analyzeStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if len(fake.RenderRequests) != 1 || len(fake.RunRequests) != 1 {
+		t.Fatalf("render/run requests = %d/%d, want 1/1", len(fake.RenderRequests), len(fake.RunRequests))
+	}
+	if got := fake.RenderRequests[0].InputPaths["previous_recap"]; got != previousPath {
+		t.Fatalf("render previous_recap input = %q, want %q", got, previousPath)
+	}
+	if got := fake.RunRequests[0].InputPaths["previous_recap"]; got != previousPath {
+		t.Fatalf("run previous_recap input = %q, want %q", got, previousPath)
+	}
+}
+
+func TestAnalyzeDoesNotCallObjectStoreForCanonicalPreviousSessionInput(t *testing.T) {
+	env, m, _ := setupAnalyzeEnv(t)
+	paths := sessionPathsForEnv(env, m.SessionID)
+	writeAnalyzeFile(t, filepath.Join(paths.TranscriptsDir, "trimmed.json"), `{"segments":[]}`)
+
+	previousPath := artifacts.SessionPreviousArtifactPath(paths, "artifacts/session_recap.md")
+	writeAnalyzeFile(t, previousPath, "previous recap\n")
+	m.Inputs = append(m.Inputs, manifest.InputRecord{
+		Kind: "previous_artifact",
+		Path: previousPath,
+	})
+
+	sessionRecap := env.Config.Pipeline.Scriptorium.Artifacts["session_recap"]
+	sessionRecap.Inputs["previous_recap"] = config.ScriptoriumInputConfig{
+		Source:   "narratio.previous_session.artifact.session_recap",
+		Required: true,
+	}
+	env.Config.Pipeline.Scriptorium.Artifacts["session_recap"] = sessionRecap
+
+	tracker := &analyzeObjectStoreTracker{}
+	env.ObjectStore = tracker
+
+	_, err := (analyzeStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if tracker.called {
+		t.Fatal("analyze should not call object store for previous-session input resolution")
+	}
+}
+
 func TestAnalyzeFailsWhenOutputPathMissing(t *testing.T) {
 	env, m, fake := setupAnalyzeEnv(t)
 	paths := sessionPathsForEnv(env, m.SessionID)
@@ -1145,3 +1286,27 @@ func mustArtifactEntryList(t *testing.T, metadata map[string]any, key string) []
 	}
 	return out
 }
+
+type analyzeObjectStoreTracker struct {
+	called bool
+}
+
+func (s *analyzeObjectStoreTracker) List(context.Context, string) ([]storage.ObjectInfo, error) {
+	s.called = true
+	return nil, errors.New("unexpected object store list call")
+}
+
+func (s *analyzeObjectStoreTracker) Download(context.Context, string, string) error {
+	s.called = true
+	return errors.New("unexpected object store download call")
+}
+
+func (s *analyzeObjectStoreTracker) Upload(context.Context, string, string, storage.UploadOptions) (storage.ObjectInfo, error) {
+	s.called = true
+	return storage.ObjectInfo{}, errors.New("unexpected object store upload call")
+}
+
+func (s *analyzeObjectStoreTracker) Exists(context.Context, string) (bool, error) {
+	s.called = true
+	return false, errors.New("unexpected object store exists call")
+}

internal/stage/archive.go

@@ -118,6 +118,10 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		return nil, fmt.Errorf("archive: collect run files: %w", err)
 	}
 	sessionPaths := archiveSessionPaths(env, m)
+	previousFiles, err := collectArchivePreviousFiles(sessionPaths.PreviousDir)
+	if err != nil {
+		return nil, fmt.Errorf("archive: collect previous files: %w", err)
+	}
 	runtimeCatalog, err := buildArchiveRuntimeArtifactCatalog(sessionPaths, env.Config.Pipeline.Scriptorium)
 	if err != nil {
 		return nil, fmt.Errorf("archive: build runtime artifact catalog: %w", err)
@@ -144,6 +148,15 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		promotedUploaded = append(promotedUploaded, promotion.Dest)
 	}
 
+	previousUploaded := make([]string, 0, len(previousFiles))
+	for _, file := range previousFiles {
+		key := artifacts.S3PromotedArtifactKey(sessionPrefix, file.RelativePath)
+		if _, err := env.ObjectStore.Upload(ctx, file.LocalPath, key, storage.UploadOptions{}); err != nil {
+			return nil, fmt.Errorf("archive: upload previous file %q to %q: %w", file.RelativePath, key, err)
+		}
+		previousUploaded = append(previousUploaded, file.RelativePath)
+	}
+
 	currentManifestKey, currentRunPointerKey := artifacts.ResolveArchiveCurrentStateKeys(sessionPrefix)
 	manifestTempPath, err := writeCurrentManifestSnapshot(m, archiveMetadataPreview(
 		bucket,
@@ -151,6 +164,7 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		sessionPrefix,
 		runUploaded,
 		promotedUploaded,
+		previousUploaded,
 		skippedOptional,
 		currentManifestKey,
 	))
@@ -187,6 +201,8 @@ func (archiveStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 			"run_uploaded_paths":          runUploaded,
 			"promoted_files_uploaded":     len(promotedUploaded),
 			"promoted_paths":              promotedUploaded,
+			"previous_files_uploaded":     len(previousUploaded),
+			"previous_uploaded_paths":     previousUploaded,
 			"skipped_optional_promotions": skippedOptional,
 			"current_manifest_key":        currentManifestKey,
 			"current_run_id_key":          currentRunPointerKey,
@@ -497,6 +513,51 @@ func collectArchiveRunFiles(runRoot, manifestPath string) ([]archiveUploadFile,
 	return files, nil
 }
 
+func collectArchivePreviousFiles(previousDir string) ([]archiveUploadFile, error) {
+	previousDir = filepath.Clean(strings.TrimSpace(previousDir))
+	if previousDir == "" {
+		return nil, fmt.Errorf("previous directory is required")
+	}
+	info, err := os.Stat(previousDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("stat %q: %w", previousDir, err)
+	}
+	if !info.IsDir() {
+		return nil, fmt.Errorf("previous path %q is not a directory", previousDir)
+	}
+
+	files := make([]archiveUploadFile, 0, 16)
+	err = filepath.WalkDir(previousDir, func(path string, d fs.DirEntry, walkErr error) error {
+		if walkErr != nil {
+			return walkErr
+		}
+		if d.IsDir() {
+			return nil
+		}
+		rel, err := filepath.Rel(previousDir, path)
+		if err != nil {
+			return fmt.Errorf("relative path from %q to %q: %w", previousDir, path, err)
+		}
+		rel = filepath.ToSlash(rel)
+		files = append(files, archiveUploadFile{
+			RelativePath: filepath.ToSlash(filepath.Join(config.PathPreviousDirSegment, rel)),
+			LocalPath:    path,
+		})
+		return nil
+	})
+	if err != nil {
+		return nil, fmt.Errorf("walk %q: %w", previousDir, err)
+	}
+
+	sort.Slice(files, func(i, j int) bool {
+		return files[i].RelativePath < files[j].RelativePath
+	})
+	return files, nil
+}
+
 func resolveArchiveRunManifestSource(runRoot string) (string, error) {
 	path := filepath.Join(filepath.Clean(runRoot), "manifest.json")
 	info, err := os.Stat(path)
@@ -600,6 +661,7 @@ func archiveMetadataPreview(
 	bucket, runPrefix, sessionPrefix string,
 	runUploaded []string,
 	promotedUploaded []string,
+	previousUploaded []string,
 	skippedOptional []string,
 	currentManifestKey string,
 ) map[string]any {
@@ -612,6 +674,8 @@ func archiveMetadataPreview(
 		"run_uploaded_paths":          append([]string(nil), runUploaded...),
 		"promoted_files_uploaded":     len(promotedUploaded),
 		"promoted_paths":              append([]string(nil), promotedUploaded...),
+		"previous_files_uploaded":     len(previousUploaded),
+		"previous_uploaded_paths":     append([]string(nil), previousUploaded...),
 		"skipped_optional_promotions": append([]string(nil), skippedOptional...),
 		"current_manifest_key":        currentManifestKey,
 		"current_run_id_key":          artifacts.S3CurrentRunPointerKey(sessionPrefix),

internal/stage/archive_test.go

@@ -130,6 +130,50 @@ func TestArchiveUploadsRunRecordPromotionsAndCurrentPointer(t *testing.T) {
 	if result.Metadata["promoted_files_uploaded"] != 2 {
 		t.Fatalf("metadata promoted_files_uploaded = %#v, want 2", result.Metadata["promoted_files_uploaded"])
 	}
+	if result.Metadata["previous_files_uploaded"] != 0 {
+		t.Fatalf("metadata previous_files_uploaded = %#v, want 0", result.Metadata["previous_files_uploaded"])
+	}
+}
+
+func TestArchiveUploadsPreviousCacheWhenPresent(t *testing.T) {
+	env, m, _ := archiveFixture(t)
+	fake := env.ObjectStore.(*storage.FakeBackend)
+	sessionRoot := artifacts.SessionWorkDirForCampaign(
+		env.Config.Pipeline.Workspace.Root,
+		env.Config.Session.Campaign,
+		env.Config.Session.SessionID,
+	)
+	writeStageTestFile(t, filepath.Join(sessionRoot, "previous", "manifest.json"), "{\"session_id\":\"2026-04-12\"}\n")
+	writeStageTestFile(t, filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md"), "# previous recap\n")
+
+	result, err := archiveStage{}.Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+
+	previousManifestKey := m.S3SessionPrefix + "previous/manifest.json"
+	previousRecapKey := m.S3SessionPrefix + "previous/artifacts/session_recap.md"
+	if _, ok := fake.Objects[previousManifestKey]; !ok {
+		t.Fatalf("missing archived previous manifest key %q", previousManifestKey)
+	}
+	if _, ok := fake.Objects[previousRecapKey]; !ok {
+		t.Fatalf("missing archived previous artifact key %q", previousRecapKey)
+	}
+	if result.Metadata["previous_files_uploaded"] != 2 {
+		t.Fatalf("metadata previous_files_uploaded = %#v, want 2", result.Metadata["previous_files_uploaded"])
+	}
+}
+
+func TestArchiveToleratesMissingPreviousCache(t *testing.T) {
+	env, m, _ := archiveFixture(t)
+
+	result, err := archiveStage{}.Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if result.Metadata["previous_files_uploaded"] != 0 {
+		t.Fatalf("metadata previous_files_uploaded = %#v, want 0", result.Metadata["previous_files_uploaded"])
+	}
 }
 
 func TestArchiveUsesCustomPromotionRules(t *testing.T) {

internal/stage/prepare.go

@@ -145,6 +145,20 @@ func (prepareStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 		}
 	}
 
+	previousRequirements := collectPreparePreviousRequirements(env.Config)
+	var previousHydration *previousSessionHydrationResult
+	if len(previousRequirements) > 0 {
+		if err := clearManagedPreviousState(paths); err != nil {
+			return nil, fmt.Errorf("prepare: clear previous-session cache: %w", err)
+		}
+		hydration, err := hydratePreviousSessionArtifacts(ctx, env, paths, previousRequirements)
+		if err != nil {
+			return nil, fmt.Errorf("prepare: hydrate previous-session artifacts: %w", err)
+		}
+		previousHydration = hydration
+		inputs = append(inputs, hydration.Inputs...)
+	}
+
 	sort.Slice(inputs, func(i, j int) bool {
 		if inputs[i].Kind != inputs[j].Kind {
 			return inputs[i].Kind < inputs[j].Kind
@@ -153,13 +167,27 @@ func (prepareStage) Run(ctx context.Context, env *Env, m *manifest.Manifest) (*S
 	})
 	m.Inputs = inputs
 
-	return &StageResult{
+	metadata := map[string]any{
-		Metadata: map[string]any{
 		"prepared":             true,
 		"stage":                "prepare",
 		"inputs_count":         len(inputs),
 		"audio_files_resolved": countAudioInputs(inputs),
-		},
+	}
+	if len(previousRequirements) > 0 {
+		metadata["previous_requirements_count"] = len(previousRequirements)
+		if previousHydration != nil {
+			metadata["previous_artifacts_hydrated"] = append([]string(nil), previousHydration.Hydrated...)
+			metadata["previous_artifacts_hydrated_count"] = len(previousHydration.Hydrated)
+			metadata["previous_artifacts_missing_optional"] = append([]string(nil), previousHydration.SkippedMissing...)
+			metadata["previous_artifacts_missing_optional_count"] = len(previousHydration.SkippedMissing)
+			if strings.TrimSpace(previousHydration.PreviousRunID) != "" {
+				metadata["previous_session_run_id"] = strings.TrimSpace(previousHydration.PreviousRunID)
+			}
+		}
+	}
+
+	return &StageResult{
+		Metadata: metadata,
 	}, nil
 }
 
@@ -354,6 +382,35 @@ func countAudioInputs(inputs []manifest.InputRecord) int {
 	return count
 }
 
+func collectPreparePreviousRequirements(cfg *config.Config) []artifacts.PreviousArtifactRequirement {
+	if cfg == nil || cfg.Pipeline == nil || cfg.Pipeline.Scriptorium == nil {
+		return nil
+	}
+	return artifacts.CollectPreviousArtifactRequirements(cfg.Pipeline.Scriptorium.Artifacts)
+}
+
+func clearManagedPreviousState(paths artifacts.SessionPaths) error {
+	previousDir := filepath.Clean(paths.PreviousDir)
+	sessionRoot := filepath.Clean(paths.Root)
+	if strings.TrimSpace(previousDir) == "" || strings.TrimSpace(sessionRoot) == "" {
+		return fmt.Errorf("previous/session root paths are required")
+	}
+	if previousDir == sessionRoot {
+		return fmt.Errorf("refusing to clear session root as previous cache: %q", previousDir)
+	}
+	prefix := sessionRoot + string(filepath.Separator)
+	if !strings.HasPrefix(previousDir, prefix) {
+		return fmt.Errorf("refusing to clear path outside session root: %q", previousDir)
+	}
+	if filepath.Base(previousDir) != config.PathPreviousDirSegment {
+		return fmt.Errorf("refusing to clear non-previous path %q", previousDir)
+	}
+	if err := os.RemoveAll(previousDir); err != nil {
+		return err
+	}
+	return os.MkdirAll(previousDir, 0o755)
+}
+
 func pathsWorkDirForManifest(env *Env, m *manifest.Manifest, sessionID string) string {
 	if env == nil || env.Config == nil || env.Config.Pipeline == nil || env.Config.Session == nil {
 		return ""

internal/stage/prepare_previous.go

@@ -0,0 +1,475 @@
+package stage
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
+	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
+)
+
+const (
+	preparePreviousInputKindManifest = "previous_manifest"
+	preparePreviousInputKindArtifact = "previous_artifact"
+	preparePreviousInputSource       = "previous_session_archive.current"
+)
+
+// previousSessionHydrationResult captures prepare-time previous-session cache materialization.
+type previousSessionHydrationResult struct {
+	Inputs         []manifest.InputRecord
+	Hydrated       []string
+	SkippedMissing []string
+	PreviousRunID  string
+}
+
+func hydratePreviousSessionArtifacts(
+	ctx context.Context,
+	env *Env,
+	paths artifacts.SessionPaths,
+	requirements []artifacts.PreviousArtifactRequirement,
+) (*previousSessionHydrationResult, error) {
+	if len(requirements) == 0 {
+		return &previousSessionHydrationResult{}, nil
+	}
+	if env == nil || env.Config == nil || env.Config.Session == nil || env.Config.Pipeline == nil {
+		return nil, fmt.Errorf("resolved config with session/pipeline is required")
+	}
+	if env.ArtifactStore == nil {
+		return nil, fmt.Errorf("artifact store is required")
+	}
+
+	orderedRequirements := append([]artifacts.PreviousArtifactRequirement(nil), requirements...)
+	sort.Slice(orderedRequirements, func(i, j int) bool {
+		return orderedRequirements[i].Name < orderedRequirements[j].Name
+	})
+
+	requiredNames := requiredPreviousArtifactNames(orderedRequirements)
+	optionalNames := optionalPreviousArtifactNames(orderedRequirements)
+	previousSessionID := strings.TrimSpace(env.Config.Session.PreviousSessionID)
+	if previousSessionID == "" {
+		if len(requiredNames) > 0 {
+			return nil, fmt.Errorf(
+				"previous_session_id is required for required previous-session artifacts: %s",
+				strings.Join(requiredNames, ", "),
+			)
+		}
+		return &previousSessionHydrationResult{SkippedMissing: optionalNames}, nil
+	}
+
+	if env.ObjectStore == nil {
+		return nil, fmt.Errorf("previous-session artifact hydration requires object store backend")
+	}
+	if env.Config.Pipeline.Storage.S3 == nil {
+		return nil, fmt.Errorf("pipeline.storage.s3 configuration is required for previous-session artifact hydration")
+	}
+	campaign := strings.TrimSpace(env.Config.Session.Campaign)
+	if campaign == "" {
+		return nil, fmt.Errorf("session campaign is required for previous-session artifact hydration")
+	}
+	bucket := strings.TrimSpace(env.Config.Pipeline.Storage.S3.Bucket)
+	if bucket == "" {
+		return nil, fmt.Errorf("pipeline.storage.s3.bucket is required for previous-session artifact hydration")
+	}
+
+	previousSessionPrefix := artifacts.S3SessionPrefix(
+		env.Config.Pipeline.Storage.S3.RootPrefix,
+		campaign,
+		previousSessionID,
+	)
+	currentManifestKey, currentRunIDKey := artifacts.ResolveArchiveCurrentStateKeys(previousSessionPrefix)
+
+	result := &previousSessionHydrationResult{}
+
+	runPointerExists, err := env.ObjectStore.Exists(ctx, currentRunIDKey)
+	if err != nil {
+		return nil, fmt.Errorf("check previous-session current run pointer %q: %w", currentRunIDKey, err)
+	}
+	if !runPointerExists {
+		if len(requiredNames) > 0 {
+			return nil, fmt.Errorf("required previous-session artifacts unavailable: remote current run pointer missing: %q", currentRunIDKey)
+		}
+		result.SkippedMissing = optionalNames
+		return result, nil
+	}
+
+	runIDTemp, err := downloadObjectToTempStage(ctx, env.ObjectStore, currentRunIDKey, "narratio-prepare-previous-run-id-*.txt")
+	if err != nil {
+		return nil, fmt.Errorf("download previous-session current run pointer %q: %w", currentRunIDKey, err)
+	}
+	defer func() { _ = os.Remove(runIDTemp) }()
+
+	runIDBytes, err := os.ReadFile(runIDTemp)
+	if err != nil {
+		return nil, fmt.Errorf("read previous-session current run pointer %q: %w", currentRunIDKey, err)
+	}
+	previousRunID := strings.TrimSpace(string(runIDBytes))
+	if previousRunID == "" {
+		return nil, fmt.Errorf("previous-session current run pointer %q is empty", currentRunIDKey)
+	}
+	result.PreviousRunID = previousRunID
+
+	manifestExists, err := env.ObjectStore.Exists(ctx, currentManifestKey)
+	if err != nil {
+		return nil, fmt.Errorf("check previous-session current manifest %q: %w", currentManifestKey, err)
+	}
+	if !manifestExists {
+		if len(requiredNames) > 0 {
+			return nil, fmt.Errorf("required previous-session artifacts unavailable: remote current manifest missing: %q", currentManifestKey)
+		}
+		result.SkippedMissing = optionalNames
+		return result, nil
+	}
+
+	if err := os.MkdirAll(filepath.Dir(paths.PreviousManifestPath), 0o755); err != nil {
+		return nil, fmt.Errorf("create previous manifest directory: %w", err)
+	}
+	if err := env.ObjectStore.Download(ctx, currentManifestKey, paths.PreviousManifestPath); err != nil {
+		return nil, fmt.Errorf("download previous-session current manifest %q: %w", currentManifestKey, err)
+	}
+
+	manifestStore := &manifest.LocalStore{}
+	previousManifest, err := manifestStore.Load(ctx, paths.PreviousManifestPath)
+	if err != nil {
+		return nil, fmt.Errorf("decode downloaded previous-session manifest %q: %w", currentManifestKey, err)
+	}
+	if strings.TrimSpace(previousManifest.SessionID) != previousSessionID {
+		return nil, fmt.Errorf(
+			"previous-session manifest session_id %q does not match configured previous_session_id %q",
+			strings.TrimSpace(previousManifest.SessionID),
+			previousSessionID,
+		)
+	}
+	if strings.TrimSpace(previousManifest.Campaign) != campaign {
+		return nil, fmt.Errorf(
+			"previous-session manifest campaign %q does not match current campaign %q",
+			strings.TrimSpace(previousManifest.Campaign),
+			campaign,
+		)
+	}
+	if strings.TrimSpace(previousManifest.RunID) == "" {
+		return nil, fmt.Errorf("previous-session manifest run_id is required")
+	}
+	if strings.TrimSpace(previousManifest.RunID) != previousRunID {
+		return nil, fmt.Errorf(
+			"previous-session current run pointer %q references run %q but current manifest run_id is %q",
+			currentRunIDKey,
+			previousRunID,
+			strings.TrimSpace(previousManifest.RunID),
+		)
+	}
+
+	manifestChecksum, err := env.ArtifactStore.Checksum(paths.PreviousManifestPath)
+	if err != nil {
+		return nil, fmt.Errorf("checksum downloaded previous-session manifest: %w", err)
+	}
+	result.Inputs = append(result.Inputs, manifest.InputRecord{
+		Kind:     preparePreviousInputKindManifest,
+		Path:     paths.PreviousManifestPath,
+		Checksum: manifestChecksum,
+		Source:   preparePreviousInputSource,
+		S3Bucket: bucket,
+		S3Key:    currentManifestKey,
+	})
+
+	for _, requirement := range orderedRequirements {
+		candidates := previousArtifactRelativePathCandidates(requirement.Name, previousManifest, env.Config)
+		if len(candidates) == 0 {
+			if requirement.Required {
+				return nil, fmt.Errorf(
+					"required previous-session artifact %q is unavailable in previous-session manifest/archive",
+					requirement.Name,
+				)
+			}
+			result.SkippedMissing = append(result.SkippedMissing, requirement.Name)
+			continue
+		}
+
+		selectedRel := ""
+		selectedKey := ""
+		for _, candidate := range candidates {
+			remoteKey := artifacts.S3PromotedArtifactKey(previousSessionPrefix, candidate)
+			exists, err := env.ObjectStore.Exists(ctx, remoteKey)
+			if err != nil {
+				return nil, fmt.Errorf("check previous-session artifact object %q: %w", remoteKey, err)
+			}
+			if !exists {
+				continue
+			}
+			selectedRel = candidate
+			selectedKey = remoteKey
+			break
+		}
+		if selectedRel == "" {
+			if requirement.Required {
+				return nil, fmt.Errorf(
+					"required previous-session artifact %q object missing from archive candidate keys",
+					requirement.Name,
+				)
+			}
+			result.SkippedMissing = append(result.SkippedMissing, requirement.Name)
+			continue
+		}
+
+		localPath := artifacts.SessionPreviousArtifactPath(paths, selectedRel)
+		if err := os.MkdirAll(filepath.Dir(localPath), 0o755); err != nil {
+			return nil, fmt.Errorf("create previous-session artifact directory for %q: %w", localPath, err)
+		}
+		if err := env.ObjectStore.Download(ctx, selectedKey, localPath); err != nil {
+			return nil, fmt.Errorf("download previous-session artifact %q from %q: %w", requirement.Name, selectedKey, err)
+		}
+		if err := requireNonEmptyFile(localPath, "previous-session artifact "+requirement.Name); err != nil {
+			return nil, err
+		}
+		checksum, err := env.ArtifactStore.Checksum(localPath)
+		if err != nil {
+			return nil, fmt.Errorf("checksum previous-session artifact %q: %w", requirement.Name, err)
+		}
+
+		result.Inputs = append(result.Inputs, manifest.InputRecord{
+			Kind:     preparePreviousInputKindArtifact,
+			Path:     localPath,
+			Checksum: checksum,
+			Source:   preparePreviousInputSource,
+			S3Bucket: bucket,
+			S3Key:    selectedKey,
+		})
+		result.Hydrated = append(result.Hydrated, requirement.Name)
+	}
+
+	sort.Strings(result.Hydrated)
+	sort.Strings(result.SkippedMissing)
+	sort.Slice(result.Inputs, func(i, j int) bool {
+		if result.Inputs[i].Kind != result.Inputs[j].Kind {
+			return result.Inputs[i].Kind < result.Inputs[j].Kind
+		}
+		return result.Inputs[i].Path < result.Inputs[j].Path
+	})
+	return result, nil
+}
+
+func requiredPreviousArtifactNames(requirements []artifacts.PreviousArtifactRequirement) []string {
+	names := make([]string, 0, len(requirements))
+	for _, requirement := range requirements {
+		if requirement.Required {
+			names = append(names, strings.TrimSpace(requirement.Name))
+		}
+	}
+	sort.Strings(names)
+	return names
+}
+
+func optionalPreviousArtifactNames(requirements []artifacts.PreviousArtifactRequirement) []string {
+	names := make([]string, 0, len(requirements))
+	for _, requirement := range requirements {
+		if requirement.Required {
+			continue
+		}
+		names = append(names, strings.TrimSpace(requirement.Name))
+	}
+	sort.Strings(names)
+	return names
+}
+
+func previousArtifactRelativePathCandidates(
+	artifactName string,
+	previousManifest *manifest.Manifest,
+	cfg *config.Config,
+) []string {
+	candidates := []string{}
+	appendCandidate := func(v string) {
+		normalized, err := normalizeArchiveRelativePath(v)
+		if err != nil {
+			return
+		}
+		candidates = append(candidates, normalized)
+	}
+
+	sourceID := artifacts.ConfiguredArtifactSourceID(artifactName)
+	if rel, ok := previousManifestArtifactRelativePathBySourceID(previousManifest, sourceID); ok {
+		appendCandidate(rel)
+		base := path.Base(rel)
+		for _, promoted := range previousManifestPromotedPaths(previousManifest) {
+			if path.Base(promoted) == base {
+				appendCandidate(promoted)
+			}
+		}
+	}
+
+	if cfg != nil && cfg.Pipeline != nil && cfg.Pipeline.Scriptorium != nil {
+		if artifactCfg, ok := cfg.Pipeline.Scriptorium.Artifacts[artifactName]; ok {
+			appendCandidate(artifactCfg.OutputPath)
+		}
+	}
+
+	return dedupeOrderedStrings(candidates)
+}
+
+func previousManifestArtifactRelativePathBySourceID(previousManifest *manifest.Manifest, sourceID string) (string, bool) {
+	if previousManifest == nil || len(previousManifest.Stages) == 0 {
+		return "", false
+	}
+	sourceID = strings.TrimSpace(sourceID)
+	if sourceID == "" {
+		return "", false
+	}
+
+	stageNames := make([]string, 0, len(previousManifest.Stages))
+	if _, ok := previousManifest.Stages["analyze"]; ok {
+		stageNames = append(stageNames, "analyze")
+	}
+	for stageName := range previousManifest.Stages {
+		if stageName == "analyze" {
+			continue
+		}
+		stageNames = append(stageNames, stageName)
+	}
+	start := 0
+	if len(stageNames) > 0 && stageNames[0] == "analyze" {
+		start = 1
+	}
+	sort.Strings(stageNames[start:])
+
+	for _, stageName := range stageNames {
+		sr := previousManifest.Stages[stageName]
+		if sr == nil {
+			continue
+		}
+		for _, out := range sr.Outputs {
+			if strings.TrimSpace(out.SourceID) != sourceID {
+				continue
+			}
+			rel, ok := derivePreviousManifestRelativePath(previousManifest, out.LocalPath)
+			if ok {
+				return rel, true
+			}
+		}
+	}
+	return "", false
+}
+
+func derivePreviousManifestRelativePath(previousManifest *manifest.Manifest, localPath string) (string, bool) {
+	trimmed := strings.TrimSpace(localPath)
+	if trimmed == "" {
+		return "", false
+	}
+	if !filepath.IsAbs(trimmed) {
+		normalized, err := normalizeArchiveRelativePath(filepath.ToSlash(trimmed))
+		if err != nil {
+			return "", false
+		}
+		return normalized, true
+	}
+
+	sessionRoot, ok := previousManifestSessionRoot(previousManifest)
+	if !ok {
+		return "", false
+	}
+	rel, err := filepath.Rel(sessionRoot, trimmed)
+	if err != nil {
+		return "", false
+	}
+	normalized, err := normalizeArchiveRelativePath(filepath.ToSlash(rel))
+	if err != nil {
+		return "", false
+	}
+	return normalized, true
+}
+
+func previousManifestSessionRoot(previousManifest *manifest.Manifest) (string, bool) {
+	if previousManifest == nil {
+		return "", false
+	}
+	runRoot := filepath.Clean(strings.TrimSpace(previousManifest.LocalWorkDir))
+	runID := strings.TrimSpace(previousManifest.RunID)
+	if runRoot == "" || runID == "" {
+		return "", false
+	}
+	if filepath.Base(runRoot) != runID {
+		return "", false
+	}
+	runsDir := filepath.Dir(runRoot)
+	if filepath.Base(runsDir) != config.PathRunsDirSegment {
+		return "", false
+	}
+	return filepath.Dir(runsDir), true
+}
+
+func previousManifestPromotedPaths(previousManifest *manifest.Manifest) []string {
+	if previousManifest == nil || len(previousManifest.Stages) == 0 {
+		return nil
+	}
+	sr := previousManifest.Stages["archive"]
+	if sr == nil || sr.Metadata == nil {
+		return nil
+	}
+	raw, ok := sr.Metadata["promoted_paths"]
+	if !ok {
+		return nil
+	}
+	values, ok := raw.([]any)
+	if !ok {
+		return nil
+	}
+	out := make([]string, 0, len(values))
+	for _, value := range values {
+		asString, ok := value.(string)
+		if !ok {
+			continue
+		}
+		normalized, err := normalizeArchiveRelativePath(asString)
+		if err != nil {
+			continue
+		}
+		out = append(out, normalized)
+	}
+	return dedupeOrderedStrings(out)
+}
+
+func dedupeOrderedStrings(values []string) []string {
+	if len(values) == 0 {
+		return nil
+	}
+	seen := map[string]struct{}{}
+	out := make([]string, 0, len(values))
+	for _, value := range values {
+		trimmed := strings.TrimSpace(value)
+		if trimmed == "" {
+			continue
+		}
+		if _, ok := seen[trimmed]; ok {
+			continue
+		}
+		seen[trimmed] = struct{}{}
+		out = append(out, trimmed)
+	}
+	return out
+}
+
+func downloadObjectToTempStage(
+	ctx context.Context,
+	store interface {
+		Download(context.Context, string, string) error
+	},
+	key, pattern string,
+) (string, error) {
+	tmp, err := os.CreateTemp("", pattern)
+	if err != nil {
+		return "", fmt.Errorf("create temp file: %w", err)
+	}
+	path := tmp.Name()
+	if err := tmp.Close(); err != nil {
+		_ = os.Remove(path)
+		return "", fmt.Errorf("close temp file: %w", err)
+	}
+	if err := store.Download(ctx, key, path); err != nil {
+		_ = os.Remove(path)
+		return "", err
+	}
+	return path, nil
+}

internal/stage/prepare_previous_test.go

@@ -0,0 +1,415 @@
+package stage
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/adapters/storage"
+	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
+	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
+)
+
+func TestHydratePreviousSessionArtifactsDownloadsManifestAndRequiredArtifact(t *testing.T) {
+	env, sessionPaths, fake := previousHydrationFixture(t)
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: true},
+	}
+	seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeArtifactObject:   true,
+		artifactBody:            "# previous recap\n",
+	})
+
+	result, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err != nil {
+		t.Fatalf("hydratePreviousSessionArtifacts() error = %v", err)
+	}
+	if result == nil {
+		t.Fatal("result is nil")
+	}
+	if len(result.Inputs) != 2 {
+		t.Fatalf("inputs len = %d, want 2", len(result.Inputs))
+	}
+	if !containsString(result.Hydrated, "session_recap") {
+		t.Fatalf("hydrated = %#v, want session_recap", result.Hydrated)
+	}
+	if len(result.SkippedMissing) != 0 {
+		t.Fatalf("skipped missing = %#v, want none", result.SkippedMissing)
+	}
+
+	if _, err := os.Stat(sessionPaths.PreviousManifestPath); err != nil {
+		t.Fatalf("previous manifest missing: %v", err)
+	}
+	recapPath := artifacts.SessionPreviousArtifactPath(sessionPaths, "artifacts/session_recap.md")
+	if _, err := os.Stat(recapPath); err != nil {
+		t.Fatalf("previous artifact missing: %v", err)
+	}
+
+	manifestInput := findInputByKind(result.Inputs, preparePreviousInputKindManifest)
+	if manifestInput == nil {
+		t.Fatalf("missing input kind %q", preparePreviousInputKindManifest)
+	}
+	if manifestInput.Source != preparePreviousInputSource {
+		t.Fatalf("manifest input source = %q, want %q", manifestInput.Source, preparePreviousInputSource)
+	}
+
+	artifactInput := findInputByKind(result.Inputs, preparePreviousInputKindArtifact)
+	if artifactInput == nil {
+		t.Fatalf("missing input kind %q", preparePreviousInputKindArtifact)
+	}
+	if artifactInput.Source != preparePreviousInputSource {
+		t.Fatalf("artifact input source = %q, want %q", artifactInput.Source, preparePreviousInputSource)
+	}
+	if artifactInput.Path != recapPath {
+		t.Fatalf("artifact input path = %q, want %q", artifactInput.Path, recapPath)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsSkipsMissingOptionalArtifact(t *testing.T) {
+	env, sessionPaths, fake := previousHydrationFixture(t)
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: false},
+	}
+	seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeManifestObject:   true,
+		includeArtifactObject:   false,
+	})
+
+	result, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err != nil {
+		t.Fatalf("hydratePreviousSessionArtifacts() error = %v", err)
+	}
+	if result == nil {
+		t.Fatal("result is nil")
+	}
+	if !containsString(result.SkippedMissing, "session_recap") {
+		t.Fatalf("skipped missing = %#v, want session_recap", result.SkippedMissing)
+	}
+	if len(result.Hydrated) != 0 {
+		t.Fatalf("hydrated = %#v, want none", result.Hydrated)
+	}
+	manifestInput := findInputByKind(result.Inputs, preparePreviousInputKindManifest)
+	if manifestInput == nil {
+		t.Fatalf("missing input kind %q", preparePreviousInputKindManifest)
+	}
+	if findInputByKind(result.Inputs, preparePreviousInputKindArtifact) != nil {
+		t.Fatalf("unexpected %q input for missing optional artifact", preparePreviousInputKindArtifact)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsFailsMissingRequiredArtifact(t *testing.T) {
+	env, sessionPaths, fake := previousHydrationFixture(t)
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: true},
+	}
+	seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeArtifactObject:   false,
+	})
+
+	_, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err == nil || !strings.Contains(err.Error(), "required previous-session artifact") {
+		t.Fatalf("error = %v, want required artifact failure", err)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsFailsRequiredWhenPreviousSessionIDUnset(t *testing.T) {
+	env, sessionPaths, _ := previousHydrationFixture(t)
+	env.Config.Session.PreviousSessionID = ""
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: true},
+	}
+
+	_, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err == nil || !strings.Contains(err.Error(), "previous_session_id is required") {
+		t.Fatalf("error = %v, want previous_session_id required failure", err)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsOptionalWithNoPreviousSessionID(t *testing.T) {
+	env, sessionPaths, _ := previousHydrationFixture(t)
+	env.Config.Session.PreviousSessionID = ""
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: false},
+	}
+
+	result, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err != nil {
+		t.Fatalf("hydratePreviousSessionArtifacts() error = %v", err)
+	}
+	if result == nil {
+		t.Fatal("result is nil")
+	}
+	if len(result.Inputs) != 0 {
+		t.Fatalf("inputs len = %d, want 0", len(result.Inputs))
+	}
+	if !containsString(result.SkippedMissing, "session_recap") {
+		t.Fatalf("skipped missing = %#v, want session_recap", result.SkippedMissing)
+	}
+	if _, err := os.Stat(sessionPaths.PreviousManifestPath); !os.IsNotExist(err) {
+		t.Fatalf("previous manifest should not be created, stat err = %v", err)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsRespectsCurrentCommitMarker(t *testing.T) {
+	env, sessionPaths, fake := previousHydrationFixture(t)
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: true},
+	}
+	seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: false,
+		includeArtifactObject:   true,
+		artifactBody:            "# previous recap\n",
+	})
+
+	_, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err == nil || !strings.Contains(err.Error(), "remote current run pointer missing") {
+		t.Fatalf("error = %v, want current run pointer missing failure", err)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsDoesNotUseLocalPreviousWorkspaceState(t *testing.T) {
+	env, sessionPaths, fake := previousHydrationFixture(t)
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: true},
+	}
+	seed := seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeManifestObject:   true,
+		includeArtifactObject:   false,
+	})
+	// Write a local previous-session workspace file that should be ignored.
+	writeFile(t, filepath.Join(seed.PreviousSessionRoot, "artifacts", "session_recap.md"), "# local stale recap\n")
+
+	_, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err == nil || !strings.Contains(err.Error(), "object missing from archive") {
+		t.Fatalf("error = %v, want remote-object-missing failure", err)
+	}
+}
+
+func TestHydratePreviousSessionArtifactsUsesExplicitStorageKeys(t *testing.T) {
+	env, sessionPaths, fake := previousHydrationFixture(t)
+	requirements := []artifacts.PreviousArtifactRequirement{
+		{Name: "session_recap", Required: true},
+	}
+	seed := seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeArtifactObject:   true,
+		artifactBody:            "# previous recap\n",
+	})
+
+	capture := &preparePreviousCaptureStore{delegate: fake}
+	env.ObjectStore = capture
+
+	_, err := hydratePreviousSessionArtifacts(context.Background(), env, sessionPaths, requirements)
+	if err != nil {
+		t.Fatalf("hydratePreviousSessionArtifacts() error = %v", err)
+	}
+
+	if !containsString(capture.existsKeys, seed.RunPointerKey) {
+		t.Fatalf("exists keys = %#v, want %q", capture.existsKeys, seed.RunPointerKey)
+	}
+	if !containsString(capture.existsKeys, seed.ManifestKey) {
+		t.Fatalf("exists keys = %#v, want %q", capture.existsKeys, seed.ManifestKey)
+	}
+	if !containsString(capture.existsKeys, seed.ArtifactKey) {
+		t.Fatalf("exists keys = %#v, want %q", capture.existsKeys, seed.ArtifactKey)
+	}
+	if !containsString(capture.downloadKeys, seed.RunPointerKey) {
+		t.Fatalf("download keys = %#v, want %q", capture.downloadKeys, seed.RunPointerKey)
+	}
+	if !containsString(capture.downloadKeys, seed.ManifestKey) {
+		t.Fatalf("download keys = %#v, want %q", capture.downloadKeys, seed.ManifestKey)
+	}
+	if !containsString(capture.downloadKeys, seed.ArtifactKey) {
+		t.Fatalf("download keys = %#v, want %q", capture.downloadKeys, seed.ArtifactKey)
+	}
+}
+
+type previousStateSeedResult struct {
+	PreviousSessionPrefix string
+	PreviousSessionRoot   string
+	ManifestKey           string
+	RunPointerKey         string
+	ArtifactKey           string
+}
+
+type previousStateSeedOptions struct {
+	includeRunPointerObject bool
+	includeManifestObject   bool
+	includeArtifactObject   bool
+	artifactBody            string
+}
+
+func seedPreviousCurrentState(
+	t *testing.T,
+	env *Env,
+	fake *storage.FakeBackend,
+	options previousStateSeedOptions,
+) previousStateSeedResult {
+	t.Helper()
+
+	if !options.includeRunPointerObject && !options.includeManifestObject && !options.includeArtifactObject {
+		// Keep default behavior deterministic when caller omits explicit flags.
+		options.includeRunPointerObject = true
+		options.includeManifestObject = true
+	}
+	if options.includeManifestObject == false && options.includeArtifactObject {
+		options.includeManifestObject = true
+	}
+
+	previousSessionID := strings.TrimSpace(env.Config.Session.PreviousSessionID)
+	campaign := strings.TrimSpace(env.Config.Session.Campaign)
+	rootPrefix := strings.TrimSpace(env.Config.Pipeline.Storage.S3.RootPrefix)
+	previousSessionPrefix := artifacts.S3SessionPrefix(rootPrefix, campaign, previousSessionID)
+	manifestKey, runPointerKey := artifacts.ResolveArchiveCurrentStateKeys(previousSessionPrefix)
+
+	previousRunID := "20260510T010203Z-a1b2c3d4"
+	previousSessionRoot := filepath.Join(t.TempDir(), "work", campaign, previousSessionID)
+	artifactLocalPath := filepath.Join(previousSessionRoot, "artifacts", "session_recap.md")
+	previousManifest := buildPreviousManifestForSeed(
+		t,
+		previousSessionID,
+		campaign,
+		previousRunID,
+		filepath.Join(previousSessionRoot, "runs", previousRunID),
+		artifactLocalPath,
+	)
+
+	if options.includeRunPointerObject || (!options.includeRunPointerObject && !options.includeManifestObject && !options.includeArtifactObject) {
+		fake.SeedObject(storage.FakeObject{
+			Key:  runPointerKey,
+			Data: []byte(previousRunID + "\n"),
+		})
+	}
+	if options.includeManifestObject || options.includeArtifactObject {
+		fake.SeedObject(storage.FakeObject{
+			Key:  manifestKey,
+			Data: previousManifest,
+		})
+	}
+
+	artifactKey := artifacts.S3PromotedArtifactKey(previousSessionPrefix, "artifacts/session_recap.md")
+	if options.includeArtifactObject {
+		body := options.artifactBody
+		if body == "" {
+			body = "# previous recap\n"
+		}
+		fake.SeedObject(storage.FakeObject{
+			Key:  artifactKey,
+			Data: []byte(body),
+		})
+	}
+
+	return previousStateSeedResult{
+		PreviousSessionPrefix: previousSessionPrefix,
+		PreviousSessionRoot:   previousSessionRoot,
+		ManifestKey:           manifestKey,
+		RunPointerKey:         runPointerKey,
+		ArtifactKey:           artifactKey,
+	}
+}
+
+func previousHydrationFixture(t *testing.T) (*Env, artifacts.SessionPaths, *storage.FakeBackend) {
+	t.Helper()
+	env, m := setupPrepareEnv(t)
+	env.Config.Session.Campaign = "forsaken"
+	env.Config.Session.PreviousSessionID = "2026-05-10"
+	env.Config.Pipeline.Storage.S3 = &config.StorageS3Config{
+		Bucket:     "my-dnd-archive",
+		RootPrefix: "dnd",
+	}
+	env.Config.Pipeline.Scriptorium = &config.ScriptoriumConfig{
+		Artifacts: map[string]config.ScriptoriumArtifactConfig{
+			"session_recap": {
+				Enabled:    true,
+				OutputPath: "artifacts/session_recap.md",
+			},
+		},
+	}
+	fake := &storage.FakeBackend{}
+	env.ObjectStore = fake
+
+	paths, err := ensureLayoutForEnv(env, m.SessionID)
+	if err != nil {
+		t.Fatalf("ensureLayoutForEnv() error = %v", err)
+	}
+	return env, paths, fake
+}
+
+func buildPreviousManifestForSeed(
+	t *testing.T,
+	sessionID, campaign, runID, runRoot, artifactPath string,
+) []byte {
+	t.Helper()
+	now := time.Date(2026, 5, 19, 22, 0, 0, 0, time.UTC)
+	m := manifest.New(sessionID, now)
+	m.Campaign = campaign
+	m.RunID = runID
+	m.LocalWorkDir = runRoot
+	m.MarkStageSucceeded("analyze", now, []manifest.ArtifactRecord{
+		{
+			Kind:      "scriptorium_artifact",
+			SourceID:  artifacts.ConfiguredArtifactSourceID("session_recap"),
+			LocalPath: artifactPath,
+		},
+	})
+	m.MarkStageSucceeded("archive", now, nil)
+	m.Stages["archive"].Metadata = map[string]any{
+		"promoted_paths": []string{"artifacts/session_recap.md"},
+	}
+	data, err := json.MarshalIndent(m, "", "  ")
+	if err != nil {
+		t.Fatalf("marshal manifest: %v", err)
+	}
+	return append(data, '\n')
+}
+
+type preparePreviousCaptureStore struct {
+	delegate     storage.ObjectStore
+	existsKeys   []string
+	downloadKeys []string
+}
+
+func (s *preparePreviousCaptureStore) List(ctx context.Context, prefix string) ([]storage.ObjectInfo, error) {
+	return s.delegate.List(ctx, prefix)
+}
+
+func (s *preparePreviousCaptureStore) Download(ctx context.Context, key, localPath string) error {
+	s.downloadKeys = append(s.downloadKeys, key)
+	return s.delegate.Download(ctx, key, localPath)
+}
+
+func (s *preparePreviousCaptureStore) Upload(ctx context.Context, localPath, key string, opts storage.UploadOptions) (storage.ObjectInfo, error) {
+	return s.delegate.Upload(ctx, localPath, key, opts)
+}
+
+func (s *preparePreviousCaptureStore) Exists(ctx context.Context, key string) (bool, error) {
+	s.existsKeys = append(s.existsKeys, key)
+	return s.delegate.Exists(ctx, key)
+}
+
+func findInputByKind(inputs []manifest.InputRecord, kind string) *manifest.InputRecord {
+	for i := range inputs {
+		if inputs[i].Kind == kind {
+			return &inputs[i]
+		}
+	}
+	return nil
+}
+
+func containsString(values []string, target string) bool {
+	for _, value := range values {
+		if value == target {
+			return true
+		}
+	}
+	return false
+}

internal/stage/prepare_test.go

@@ -284,6 +284,188 @@ func TestPrepareStageAudioSourceConflictFails(t *testing.T) {
 	}
 }
 
+func TestPrepareStageWithoutPreviousRequirementsDoesNotTouchPreviousState(t *testing.T) {
+	env, m := setupPrepareEnv(t)
+	root := filepath.Dir(env.Config.SessionPath)
+	writeFile(t, filepath.Join(root, "audio", "a.flac"), "a")
+	env.Config.Session.Inputs.AudioFiles = []string{"./audio/a.flac"}
+
+	paths := sessionPathsForEnv(env, m.SessionID)
+	stalePath := filepath.Join(paths.PreviousDir, "stale.txt")
+	writeFile(t, stalePath, "stale")
+
+	_, err := (prepareStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("prepare.Run() error = %v", err)
+	}
+	if _, err := os.Stat(stalePath); err != nil {
+		t.Fatalf("expected previous stale file to remain untouched: %v", err)
+	}
+}
+
+func TestPrepareStageOptionalPreviousArtifactWithoutPreviousSessionIDSucceeds(t *testing.T) {
+	env, m := setupPrepareEnv(t)
+	root := filepath.Dir(env.Config.SessionPath)
+	writeFile(t, filepath.Join(root, "audio", "a.flac"), "a")
+	env.Config.Session.Inputs.AudioFiles = []string{"./audio/a.flac"}
+	configurePreparePreviousArtifactSource(env, false)
+	env.Config.Session.PreviousSessionID = ""
+
+	paths := sessionPathsForEnv(env, m.SessionID)
+	writeFile(t, filepath.Join(paths.PreviousArtifactsDir, "stale.txt"), "stale")
+
+	result, err := (prepareStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("prepare.Run() error = %v", err)
+	}
+	if result.Metadata["previous_requirements_count"] != 1 {
+		t.Fatalf("metadata previous_requirements_count = %#v, want 1", result.Metadata["previous_requirements_count"])
+	}
+	if result.Metadata["previous_artifacts_hydrated_count"] != 0 {
+		t.Fatalf("metadata previous_artifacts_hydrated_count = %#v, want 0", result.Metadata["previous_artifacts_hydrated_count"])
+	}
+	if result.Metadata["previous_artifacts_missing_optional_count"] != 1 {
+		t.Fatalf("metadata previous_artifacts_missing_optional_count = %#v, want 1", result.Metadata["previous_artifacts_missing_optional_count"])
+	}
+	if _, err := os.Stat(filepath.Join(paths.PreviousArtifactsDir, "stale.txt")); !os.IsNotExist(err) {
+		t.Fatalf("expected stale previous state to be cleared, stat err = %v", err)
+	}
+	for _, in := range m.Inputs {
+		if in.Kind == preparePreviousInputKindManifest || in.Kind == preparePreviousInputKindArtifact {
+			t.Fatalf("unexpected previous input record: %#v", in)
+		}
+	}
+}
+
+func TestPrepareStageRequiredPreviousArtifactWithoutPreviousSessionIDFails(t *testing.T) {
+	env, m := setupPrepareEnv(t)
+	root := filepath.Dir(env.Config.SessionPath)
+	writeFile(t, filepath.Join(root, "audio", "a.flac"), "a")
+	env.Config.Session.Inputs.AudioFiles = []string{"./audio/a.flac"}
+	configurePreparePreviousArtifactSource(env, true)
+	env.Config.Session.PreviousSessionID = ""
+
+	_, err := (prepareStage{}).Run(context.Background(), env, m)
+	if err == nil || !strings.Contains(err.Error(), "previous_session_id is required") {
+		t.Fatalf("error = %v, want previous_session_id required failure", err)
+	}
+}
+
+func TestPrepareStageHydratesRequiredPreviousArtifactAndRecordsInputs(t *testing.T) {
+	env, m := setupPrepareEnv(t)
+	root := filepath.Dir(env.Config.SessionPath)
+	writeFile(t, filepath.Join(root, "audio", "a.flac"), "a")
+	env.Config.Session.Inputs.AudioFiles = []string{"./audio/a.flac"}
+	env.Config.Session.Campaign = "forsaken"
+	env.Config.Session.PreviousSessionID = "2026-05-10"
+	env.Config.Pipeline.Storage.S3 = &config.StorageS3Config{Bucket: "my-dnd-archive", RootPrefix: "dnd"}
+	configurePreparePreviousArtifactSource(env, true)
+
+	fake := &storage.FakeBackend{}
+	env.ObjectStore = fake
+	seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeArtifactObject:   true,
+		artifactBody:            "# prior recap\n",
+	})
+
+	paths := sessionPathsForEnv(env, m.SessionID)
+	result, err := (prepareStage{}).Run(context.Background(), env, m)
+	if err != nil {
+		t.Fatalf("prepare.Run() error = %v", err)
+	}
+
+	if _, err := os.Stat(paths.PreviousManifestPath); err != nil {
+		t.Fatalf("expected previous manifest: %v", err)
+	}
+	recapPath := artifacts.SessionPreviousArtifactPath(paths, "artifacts/session_recap.md")
+	if _, err := os.Stat(recapPath); err != nil {
+		t.Fatalf("expected previous artifact: %v", err)
+	}
+
+	var hasPreviousManifest, hasPreviousArtifact bool
+	for _, in := range m.Inputs {
+		if in.Kind == preparePreviousInputKindManifest {
+			hasPreviousManifest = true
+		}
+		if in.Kind == preparePreviousInputKindArtifact {
+			hasPreviousArtifact = true
+		}
+	}
+	if !hasPreviousManifest || !hasPreviousArtifact {
+		t.Fatalf("manifest inputs missing previous provenance: %#v", m.Inputs)
+	}
+	if result.Metadata["previous_artifacts_hydrated_count"] != 1 {
+		t.Fatalf("metadata previous_artifacts_hydrated_count = %#v, want 1", result.Metadata["previous_artifacts_hydrated_count"])
+	}
+}
+
+func TestPrepareStageRerunOverwritesPreviousCache(t *testing.T) {
+	env, m := setupPrepareEnv(t)
+	root := filepath.Dir(env.Config.SessionPath)
+	writeFile(t, filepath.Join(root, "audio", "a.flac"), "a")
+	env.Config.Session.Inputs.AudioFiles = []string{"./audio/a.flac"}
+	env.Config.Session.Campaign = "forsaken"
+	env.Config.Session.PreviousSessionID = "2026-05-10"
+	env.Config.Pipeline.Storage.S3 = &config.StorageS3Config{Bucket: "my-dnd-archive", RootPrefix: "dnd"}
+	configurePreparePreviousArtifactSource(env, true)
+
+	fake := &storage.FakeBackend{}
+	env.ObjectStore = fake
+	seed := seedPreviousCurrentState(t, env, fake, previousStateSeedOptions{
+		includeRunPointerObject: true,
+		includeArtifactObject:   true,
+		artifactBody:            "# old recap\n",
+	})
+
+	paths := sessionPathsForEnv(env, m.SessionID)
+	if _, err := (prepareStage{}).Run(context.Background(), env, m); err != nil {
+		t.Fatalf("first prepare run error = %v", err)
+	}
+	recapPath := artifacts.SessionPreviousArtifactPath(paths, "artifacts/session_recap.md")
+	firstBytes, err := os.ReadFile(recapPath)
+	if err != nil {
+		t.Fatalf("read first hydrated artifact: %v", err)
+	}
+	if strings.TrimSpace(string(firstBytes)) != "# old recap" {
+		t.Fatalf("first hydrated content = %q, want %q", strings.TrimSpace(string(firstBytes)), "# old recap")
+	}
+
+	writeFile(t, filepath.Join(paths.PreviousArtifactsDir, "stale.txt"), "stale")
+	fake.SeedObject(storage.FakeObject{Key: seed.ArtifactKey, Data: []byte("# new recap\n")})
+
+	if _, err := (prepareStage{}).Run(context.Background(), env, m); err != nil {
+		t.Fatalf("second prepare run error = %v", err)
+	}
+	secondBytes, err := os.ReadFile(recapPath)
+	if err != nil {
+		t.Fatalf("read second hydrated artifact: %v", err)
+	}
+	if strings.TrimSpace(string(secondBytes)) != "# new recap" {
+		t.Fatalf("second hydrated content = %q, want %q", strings.TrimSpace(string(secondBytes)), "# new recap")
+	}
+	if _, err := os.Stat(filepath.Join(paths.PreviousArtifactsDir, "stale.txt")); !os.IsNotExist(err) {
+		t.Fatalf("expected stale previous cache file to be removed, stat err = %v", err)
+	}
+}
+
+func configurePreparePreviousArtifactSource(env *Env, required bool) {
+	env.Config.Pipeline.Scriptorium = &config.ScriptoriumConfig{
+		Artifacts: map[string]config.ScriptoriumArtifactConfig{
+			"session_recap": {
+				Enabled:    true,
+				OutputPath: "artifacts/session_recap.md",
+				Inputs: map[string]config.ScriptoriumInputConfig{
+					"previous_recap": {
+						Source:   "narratio.previous_session.artifact.session_recap",
+						Required: required,
+					},
+				},
+			},
+		},
+	}
+}
+
 func setupPrepareEnv(t *testing.T) (*Env, *manifest.Manifest) {
 	t.Helper()
 	workspace := t.TempDir()

internal/stage/run_local.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
 	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
 )
 
@@ -99,6 +100,9 @@ func runLocalPathForCanonical(layout runStageLayout, sessionPaths artifacts.Sess
 	if rel == "." || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
 		return "", fmt.Errorf("canonical path %q is outside session root %q", cleanCanonical, sessionPaths.Root)
 	}
+	if rel == config.PathPreviousDirSegment || strings.HasPrefix(rel, config.PathPreviousDirSegment+string(filepath.Separator)) {
+		return cleanCanonical, nil
+	}
 	localPath := filepath.Join(layout.OutputsDir, rel)
 	if err := os.MkdirAll(filepath.Dir(localPath), 0o755); err != nil {
 		return "", fmt.Errorf("create run-local output parent for %q: %w", localPath, err)

internal/stage/run_local_test.go

@@ -33,3 +33,24 @@ func TestRunLocalPathForCanonicalCreatesParentDirectories(t *testing.T) {
 		t.Fatalf("expected run-local parent directory to exist: %v", err)
 	}
 }
+
+func TestRunLocalPathForCanonicalKeepsPreviousStateSessionDurable(t *testing.T) {
+	root := t.TempDir()
+	sessionRoot := filepath.Join(root, "work", "dilfs", "2026-05-17")
+	layout := runStageLayout{
+		Enabled:    true,
+		OutputsDir: filepath.Join(sessionRoot, "runs", "run-1", "prepare", "outputs"),
+	}
+	if err := os.MkdirAll(layout.OutputsDir, 0o755); err != nil {
+		t.Fatalf("mkdir outputs dir: %v", err)
+	}
+
+	canonical := filepath.Join(sessionRoot, "previous", "artifacts", "session_recap.md")
+	got, err := runLocalPathForCanonical(layout, artifacts.SessionPaths{Root: sessionRoot}, canonical)
+	if err != nil {
+		t.Fatalf("runLocalPathForCanonical() error = %v", err)
+	}
+	if got != canonical {
+		t.Fatalf("runLocalPathForCanonical() = %q, want canonical %q", got, canonical)
+	}
+}